U.S. patent application number 11/608550 was filed with the patent office on 2007-04-05 for power line communications device and method of use.
Invention is credited to Kevin P. Barrett, William O. Radtke.
Application Number | 20070076505 11/608550 |
Document ID | / |
Family ID | 36228242 |
Filed Date | 2007-04-05 |
United States Patent
Application |
20070076505 |
Kind Code |
A1 |
Radtke; William O. ; et
al. |
April 5, 2007 |
Power Line Communications Device and Method of Use
Abstract
A method of providing communications over a medium voltage power
line having a plurality of segments is provided. In one embodiment,
the method comprises the steps of determining a first amplification
for data signals, receiving a first data signal from a first
segment of the power line, amplifying said first data signal via
the first amplification, coupling the amplified first data signal
to a second segment of the power line with a first amplification
power, receiving user data; and transmitting the user data over the
second segment of the power line with a transmission power
substantially the same as the first amplification power. In
addition, the step of determining may comprises receiving a signal
from the first segment of the power line, determining a target
amplification based on the received signal, determining a maximum
amplification; and wherein said first amplification is
substantially equal to the lesser of the target amplification and
the maximum amplification.
Inventors: |
Radtke; William O.;
(Ellicott City, MD) ; Barrett; Kevin P.;
(Adamstown, MD) |
Correspondence
Address: |
CAPITAL LEGAL GROUP, LLC
5323 POOKS HILL ROAD
BETHESDA
MD
20814
US
|
Family ID: |
36228242 |
Appl. No.: |
11/608550 |
Filed: |
December 8, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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10973493 |
Oct 26, 2004 |
|
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11608550 |
Dec 8, 2006 |
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Current U.S.
Class: |
365/222 ;
379/399.01 |
Current CPC
Class: |
H04B 3/58 20130101; H04J
14/0232 20130101; H04J 14/0246 20130101; H04J 14/025 20130101; H04J
14/02 20130101; H04J 14/0247 20130101; H04J 14/0282 20130101; H04L
27/2601 20130101; H04J 14/0226 20130101; H04J 14/028 20130101; H04J
14/0227 20130101; H04J 14/0252 20130101; H04J 14/0283 20130101 |
Class at
Publication: |
365/222 ;
379/399.01 |
International
Class: |
G11C 7/00 20060101
G11C007/00 |
Claims
1. A method of providing communications over a power line having a
plurality of segments and carrying a power signal having a voltage
greater than one thousand volts, comprising: determining a first
amplification for data signals; receiving a first data signal from
a first segment of the power line; amplifying said first data
signal via the first amplification; coupling the amplified first
data signal to a second segment of the power line with a first
amplification power; receiving user data; and transmitting the user
data over the second segment of the power line with a transmission
power substantially the same as the first amplification power.
2. The method of claim 1, wherein said determining comprises:
receiving a signal from the first segment of the power line;
determining a target amplification based on the received signal;
determining a maximum amplification; and wherein said first
amplification is substantially equal to the lesser of the target
amplification and the maximum amplification.
3. The method of claim 1, further comprising determining a second
amplification for data signals; receiving a second data signal from
the second segment of the power line; amplifying said second data
signal via the second amplification; and coupling the amplified
second data signal to the first segment of the power line.
4. The method of claim 3, further comprising: demodulating the
second data signal to provide user data; and transmitting the user
data over a low voltage power line.
5. The method of claim 1, further comprising: receiving a second
data signal from the second segment of the power line; demodulating
the second data signal to provide second data; and transmitting the
second data over a low voltage power line.
6. The method of claim 5, further comprising routing the second
data prior to said transmitting the second data.
7. The method claim 6, further comprising receiving the second data
at one or more of a plurality of user devices communicatively
coupled to the low voltage power line.
8. The method of claim 1, wherein receiving user data comprises
receiving a plurality of user data packets from a plurality of
customer premises.
9. The method of claim 8, further comprising routing the user data
packets prior to said transmitting.
10. The method of claim 1, wherein said determining comprises
setting the first amplification based, at least in part, on the
power level of a received signal.
11. A method of providing communications over a power line having a
plurality of segments and carrying a power signal having a voltage
greater than one thousand volts, comprising: receiving a signal via
the first segment of the power line; determining a target
amplification for amplifying data signals based, at least in part,
on the power of the received signal; determining whether the target
amplification exceeds a maximum amplification; receiving first data
signals via the first segment of the power line; amplifying first
data signals with the target amplification if said target
amplification does not exceed the maximum amplification; amplifying
first data signals with the maximum amplification if said target
amplification exceeds the maximum amplification; and coupling the
amplified first data signals to the second segment of the power
line with a first amplification power.
12. The method of claim 11, further comprising transmitting data
signals over the second segment of the power line with a
transmission power substantially the same as the first
amplification power.
13. The method of claim 11, wherein the signal comprises a
multi-carrier signal.
14. The method of claim 11, further comprising setting a
transmission power for data signals over the second segment of the
power line to be substantially the same power as the first
amplification power.
15. The method of claim 11, wherein the maximum amplification is
based, at least in part, on the attenuation of data signals between
the first and second segments of the power line.
16. The method of claim 11, further comprising determining a second
amplification for data signals; receiving a second data signal from
the second segment of the power line; amplifying said second data
signal via the second amplification; and coupling the amplified
second data signal to the first segment of the power line.
17. The method of claim 16, further comprising: demodulating the
second data signal to provide user data; and transmitting the user
data over a low voltage power line.
18. The method of claim 11, further comprising: receiving a second
data signal from the second segment of the power line; demodulating
the second data signal to provide second data; and transmitting the
second data over a low voltage power line.
19. The method of claim 18, further comprising routing the second
data prior to said transmitting the second data.
20. The method claim 19, further comprising receiving the second
data at one or more of a plurality of user devices communicatively
coupled to the low voltage power line.
21. The method of claim 11, wherein the maximum amplification
corresponds to a maximum power.
22. The method of claim 21, wherein the maximum power corresponds
to the isolation between the first and second segments of the power
line.
23. The method of claim 11, wherein the received signal comprises a
training signal that does not comprise data communicated to or from
data a user device.
24. A method of providing communications over a power line having a
plurality of segments and carrying a power signal having a voltage
greater than one thousand volts, comprising: receiving a signal via
the first segment of the power line; determining a target
amplification for amplifying data signals based on the power of the
received signal; determining a maximum amplification; setting a
first segment amplification substantially equal to the lesser of
the maximum amplification and the target amplification; receiving
data signals from the first segment of the power line; amplifying
the data signals with the first segment amplification; and coupling
the data signals to the second segment of the power line with a
first amplification power.
25. The method of claim 24, wherein the maximum amplification is
based, at least in part, on the attenuation of data signals between
the first and second segments of the power line.
26. The method of claim 24, wherein determining the maximum
amplification comprises retrieving data of the maximum
amplification from memory.
27. The method of claim 24, further comprising: receiving user
data; and transmitting the user data over the second segment of the
power line with a transmission power substantially the same as the
first amplification power.
28. The method of claim 24, further comprising determining a second
amplification for data signals; receiving a second data signal from
the second segment of the power line; amplifying said second data
signal via the second amplification; and coupling the amplified
second data signal to the first segment of the power line.
29. The method of claim 28, further comprising: demodulating the
second data signal to provide user data; and transmitting the user
data over a low voltage power line.
30. The method of claim 24, further comprising: receiving a second
data signal from the second segment of the power line; demodulating
the second data signal to provide second data; and transmitting the
second data over a low voltage power line.
31. The method claim 30, further comprising receiving the second
data at one or more of a plurality of user devices communicatively
coupled to the low voltage power line.
32. A method of providing communications over a power line having a
plurality of segments and carrying a power signal having a voltage
greater than one thousand volts, comprising: determining a first
amplification for data signals; receiving a first data signal from
a first segment of the power line; amplifying said first data
signal via the first amplification; and coupling the amplified
first data signal to a second segment of the power line with a
first amplification power.
33. The method of claim 32, wherein said determining comprises
setting a first amplification based, at least in part, on the power
of a received signal.
34. The method of claim 33, wherein the received signal comprises a
training signal that does not comprise data communicated to or from
data a user device.
35. The method of claim 32, further comprising: receiving a second
data signal from the second segment of the power line; demodulating
the second data signal to provide second data; and transmitting the
second data over a low voltage power line.
36. The method of claim 35, further comprising: receiving user
data; and transmitting the user data over the second segment of the
power line with a transmission power substantially the same as the
first amplification power.
37. A method of using a plurality of communication device to
provide communications over a power line having a plurality of
segments of differing lengths that cause differing attenuations at
communication frequencies, the power line carrying a power signal
having a voltage greater than one thousand volts and the plurality
of communication devices each being coupled to two segments of the
power line, the method comprising at each of the plurality of
communication devices: determining a first amplification for data
signals; receiving a first data signal from one of the two segments
of the power line; amplifying the first data signal via the first
amplification; coupling the amplified first data signal to the
second of the two segments of the power line with a first
amplification power; and wherein the first amplification power is
different for at least some of the plurality power line
communication devices.
38. The method of claim 37, further comprising at each of the
plurality of communication devices: receiving user data; and
transmitting the user data over the second of the two segments of
the power line with a transmission power substantially the same as
the first amplification power of that device.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of, and claims
priority to, U.S. patent application Ser. No. 10/973,493 filed Oct.
26, 2004, which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention generally relates to data
communications over a power distribution system and more
particularly, to a power line communication system, device and
method of using the same.
BACKGROUND OF THE INVENTION
[0003] Well-established power distribution systems exist throughout
most of the United States, and other countries, which provide power
to customers via power lines. With some modification, the
infrastructure of the existing power distribution systems can be
used to provide data communication in addition to power delivery,
thereby forming a power line communication system (PLCS). In other
words, existing power lines, that already have been run to many
homes and offices, can be used to carry data signals to and from
the homes and offices. These data signals are communicated on and
off the power lines at various points in the power line
communication system, such as, for example, near homes, offices,
Internet service providers, and the like.
[0004] While the concept may sound simple, there are many
challenges to overcome in order to use power lines for data
communication. Power lines are not designed to provide high speed
data communications, are susceptible to interference, and are very
lossy at the frequencies used for data communications.
Additionally, federal regulations limit the amount of radiated
energy of a power line communication system, which therefore limits
the power of the data signal that can be injected onto power
lines.
[0005] Power distribution systems include numerous sections, which
transmit power at different voltages. The transition from one
section to another typically is accomplished with a transformer.
The sections of the power distribution system that are connected to
the customers premises typically are low voltage (LV) sections
having a voltage between 100 volts (Vrms, 60 Hz, or "V"). and 240V,
depending on the system. In the United States, the LV section
typically is about 120V. The sections of the power distribution
system that provide the power to the LV sections are referred to as
the medium voltage (MV) sections. The voltage of the MV section is
in the range of 1,000V to 100,000V. The transition from the MV
section to the LV section of the power distribution system
typically is accomplished with a distribution transformer, which
converts the higher voltage of the MV section to the lower voltage
of the LV section.
[0006] Power system transformers are one obstacle to using power
distribution lines for data communication. Transformers act as a
low-pass filter, passing the low frequency signals (e.g., the 50 or
60 Hz) power signals and impeding the high frequency signals (e.g.,
frequencies typically used for data communication). As such, power
line communication systems face the challenge of communicating the
data signals around, or through, the distribution transformers.
[0007] Furthermore, up to ten (and sometimes more) customer
premises will typically receive power from one distribution
transformer via their respective LV power lines. However, all of
the customer premises LV power lines typically are electrically
connected at the transformer. Consequently, a power line
communications system must be able to tolerate the interference
produced by many customers. In addition, the power line
communication system should provide bus arbitration and router
functions for numerous customers who share a LV subnet (i.e., the
customer premises LV power lines that are all electrically
connected to the LV power line extending from the LV side of the
transformer) and a MV power line.
[0008] In addition, components of the power line communication
system, such as the distribution transformer bypass device (PLB),
must electrically isolate the MV power signal from the LV power
lines and the customer premises. Furthermore, a communication
device of the system should be designed to facilitate bidirectional
communication and to be installed without disrupting power to
customers. These and other advantages are provided by various
embodiments of the present invention.
SUMMARY OF THE INVENTION
[0009] The present invention provides a method of providing
communications over a medium voltage power line having a plurality
of segments. In one embodiment, the method comprises the steps of
determining a first amplification for data signals, receiving a
first data signal from a first segment of the power line,
amplifying said first data signal via the first amplification,
coupling the amplified first data signal to a second segment of the
power line with a first amplification power, receiving user data;
and transmitting the user data over the second segment of the power
line with a transmission power substantially the same as the first
amplification power. In addition, the step of determining may
comprises receiving a signal from the first segment of the power
line, determining a target amplification based on the received
signal, determining a maximum amplification; and wherein said first
amplification is substantially equal to the lesser of the target
amplification and the maximum amplification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention is further described in the detailed
description that follows, by reference to the noted drawings by way
of non-limiting illustrative embodiments of the invention, in which
like reference numerals represent similar parts throughout the
drawings. As should be understood, however, the invention is not
limited to the precise arrangements and instrumentalities shown. In
the drawings:
[0011] FIG. 1 is a diagram of an exemplary power distribution
system with which the present invention may be employed;
[0012] FIG. 2 is a diagram of the exemplary power distribution
system of FIG. 1 modified to operate as a power line communication
system, in accordance with an embodiment of the present
invention;
[0013] FIG. 3 is a schematic of a power line communication system
in accordance with an embodiment of the present invention;
[0014] FIG. 4 is a block diagram of an example PLCS, in accordance
with an embodiment of the present invention;
[0015] FIG. 5 is a block diagram of a portion of an example PLCS,
in accordance with an embodiment of the present invention;
[0016] FIG. 6 is a block diagram of a portion of an example PLCS,
in accordance with an embodiment of the present invention;
[0017] FIG. 7 is a block diagram of another example PLCS, in
accordance with an embodiment of the present invention;
[0018] FIG. 8 is a block diagram of still another example PLCS, in
accordance with an embodiment of the present invention;
[0019] FIG. 9 is a block diagram of a portion of an example PLCS,
in accordance with an embodiment of the present invention;
[0020] FIG. 10 is a block diagram of an example optical termination
point, in accordance with an embodiment of the present
invention;
[0021] FIG. 11 is a block diagram of another example optical
termination point, in accordance with an embodiment of the present
invention;
[0022] FIG. 12A is a block diagram of a portion of an example PLB,
in accordance with an embodiment of the present invention;
[0023] FIG. 12B is a flow chart of an example power line
communication procedure, in accordance with an embodiment of the
present invention;
[0024] FIG. 13 is a block diagram of a portion of an example PLB,
in accordance with an embodiment of the present invention; and
[0025] FIGS. 14a-c are functional block diagrams of a portion of a
PLB, in accordance with various embodiments of the present
invention.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0026] In the following description, for purposes of explanation
and not limitation, specific details are set forth, such as
particular networks, communication systems, computers, terminals,
devices, components, techniques, data and network protocols,
software products and systems, operating systems, development
interfaces, hardware, etc. in order to provide a thorough
understanding of the present invention.
[0027] However, it will be apparent to one skilled in the art that
the present invention may be practiced in other embodiments that
depart from these specific details. Detailed descriptions of
well-known networks, communication systems, computers, terminals,
devices, components, techniques, data and network protocols,
software products and systems, operating systems, development
interfaces, and hardware are omitted so as not to obscure the
description of the present invention.
System Architecture and General Design Concepts
[0028] Power distribution systems typically include components for
power generation, power transmission, and power delivery. A
transmission substation typically is used to increase the voltage
from the power generation source to high voltage (HV) levels for
long distance transmission on HV transmission lines to a
substation. Typical voltages found on HV transmission lines range
from 69 kilovolts (kV) to in excess of 800 kV.
[0029] As shown in FIG. 1, in addition to HV transmission lines,
power distribution systems include MV power lines and LV power
lines. As discussed, MV typically ranges from about 1000 V to about
100 kV and LV typically ranges from about 100 V to about 600 V.
Transformers are used to convert between the respective voltage
portions, e.g., between the HV section and the MV section and
between the MV section and the LV section. Transformers have a
primary side for connection to a first voltage (e.g., the MV
section) and a secondary side for outputting another (usually
lower) voltage (e.g., the LV section). Such transformers are often
referred to as distribution transformers or a step down
transformers, because they "step down" the voltage to some lower
voltage. Transformers, therefore, provide voltage conversion for
the power distribution system. Thus, power is carried from
substation transformer to a distribution transformer over one or
more MV power lines. Power is carried from the distribution
transformer to the customer premises via one or more LV power
lines.
[0030] In addition, a distribution transformer (DT) may function to
distribute one, two, three, or more phase voltages to the customer
premises, depending upon the demands of the user. In the United
States, for example, these local distribution transformers
typically feed anywhere from one to ten homes, depending upon the
concentration of the customer premises in a particular area.
Distribution transformers may be pole-top transformers located on a
utility pole, pad-mounted transformers located on the ground, or
transformers located under ground level.
[0031] FIG. 1 discloses a representative underground residential
distribution (URD) system comprising a high voltage (HV) power line
that is connected to a plurality of high voltage transformers (HVT)
that steps down the high voltage to medium voltage.
[0032] The HVT steps down the high voltage to medium voltage for
distribution on the medium voltage (MV) power lines which are
connected to one or more distribution transformers (DTs). Each DT
further steps down the medium voltage to low voltage (LV) and
typically is connected to one or more LV power lines, each of which
may extend to a separate customer premises (not shown in FIG.
1).
[0033] The URD network of FIG. 1 includes two types of
topographies. The first type is commonly referred to as a ring or
"U" topology as represented by networks 1 and 2. The ring network
may be U shaped with each leg of the U being connected to a HVT. In
addition, the ring network may include a switch SW that connects
both sides of the ring together (as in network 1). Consequently,
should either HVT fail (or a break in the MV power line occur) the
switch may be closed so that the entire MV network receives power.
Other such networks may not include a switch (as in network 2).
[0034] Another type of topology is referred to as a radial or star
network as shown in network 3 in which one or more MV power lines
extend away from a single HVT. While the illustrations of these
networks depict a single MV power line, a radial or ring network
configuration may include multiple MV power lines extending from
each HVT (e.g., one or more sets of three cables with each cable of
each set carrying one phase of the three phases in a three phase
system).
[0035] As is known to those skilled in the art, each DT in the URD
network may be electrically connected to the adjacent DTs via a
length of URD cable. The URD cables typically may be terminated
(e.g., on each end) via an elbow that plugs into a bushing on the
DT. The two cables typically are electrically connected to each
other inside the transformer enclosure and are also connected to
the primary of the distribution transformer itself. As discussed,
the secondary of the DT is connected to the LV power lines
supplying power to the customer premises. Thus, the series of URD
cables, and transformers connecting them, form a first (MV) segment
of the URD power distribution network and the LV power lines
connected to the DTs form a plurality of low voltage segments.
[0036] The URD network may be connected to, and receive power from,
an overhead MV power line. Referring to FIG. 2, a URD cable may
extend up a utility pole and terminate with a pothead connector
(not shown) for connection to an overhead MV power line (known as a
Riser-Pole). At the other end, the URD cable may terminate with an
elbow to be plugged into a bushing at a transformer. As discussed,
the URD cables extending between URD transformers typically will
terminate with an elbow to be plugged in the transformer on both
ends. Typically, the URD cable will include a center conductor, an
insulator surrounding the center conductor, a concentric neutral
conductor surrounding the insulator, and an external insulator
surrounding the concentric neutral conductor. In addition, the
cable may include one or more sheaths such as a semi-conductive
sheath around the insulator.
Power Line Communication System
[0037] FIG. 3 provides a schematic of one embodiment of the present
invention, which includes an aggregation point (AP) that may be
co-located with a point of presence (POP) for connection to the
Internet and/or other network. The AP 100 may include a
conventional Internet Protocol (IP) data packet router and may be
directly connected to an Internet backbone thereby providing access
to the Internet. Alternatively, the AP 100 may be connected to a
core router (not shown), which provides access to the Internet, or
other communication network.
[0038] The AP 100 may route voice traffic to and from a voice
service provider and route Internet traffic to and from an Internet
service provider. The routing of packets to the appropriate
provider may be determined by any suitable means such as by
including information in the data packets to determine whether a
packet is voice. If the packet is voice, the packet may be routed
to the voice service provider and, if not, the packet may be routed
to the Internet service provider. Similarly, the packet may include
information (which may be a portion of the address) to determine
whether a packet is Internet data. If the packet is Internet data,
the packet may be routed to the Internet service provider and, if
not, the packet may be routed to the voice service provider.
[0039] The AP 100 may be communicatively coupled to one or more
distribution points (DPs) 200. Each DP 200 may be communicatively
coupled to one or more MV interface devices (MVID) 300. Each MVID
300 may be in communication with one or more power line bridges
(PLBs) 400, via the URD medium voltage power line(s). The PLBs 400
may be in communication with one or more user devices that reside
in one or more customer premises CP via the low voltage power lines
or via a wireless link. As will be evident from the discussion
below, communications over the power distribution network occur
between the MVID 300 and the customer premises user devices (e.g.,
via the PLBs). Communications upstream from the MVID 300--such as
between the MVIDs 300 and their DPs 200 or between the DPs 200 and
the AP 100--may be fiber optic, wireless, coaxial cable, T-carrier,
Synchronous Optical Network (SONET), any other suitable medium, or
any combination thereof. As will be evident to one skilled in the
art, each network element (e.g., MVID 300, DP 200, or AP 100),
would include a transceiver appropriate for communicating over the
selected medium (e.g., a wireless transceiver for a wireless
link).
[0040] The PLCS also may include a power line server (PLS) (not
shown) that is a computer system with memory for storing a database
of information about the PLCS and includes a network element
manager (NEM) that monitors and controls the PLCS. The PLS allows
network operations personnel to provision users and network
equipment, manage customer data, and monitor system status,
performance and usage. The PLS may reside at a remote operations
center to oversee a group of communication devices via the
Internet. The PLS may provide an Internet identity to the network
devices by assigning the devices (e.g., user devices, PLBs 400,
(e.g., the LV modems and MV modems of PLBs), repeaters, MVIDs 300,
DPs 200, and AP 100 if necessary) an IP address and storing the IP
address and other device identifying information (e.g., the
device's location, address, serial number, etc.) in its memory. In
addition, the PLS may approve or deny user device authorization
requests, command status reports and measurements from the PLBs,
repeaters, and MVIDs, and provide application software upgrades to
the communication devices (e.g., PLBs, MVIDs (if necessary),
repeaters, and other devices). The PLS, by collecting electric
power distribution information and interfacing with utilities'
back-end computer systems may provide enhanced distribution
services such as automated meter reading, outage detection, load
balancing, distribution automation, Volt/Volt-Amp Reactance
(Volt/VAr) management, and other similar functions. The PLS also
may be connected to one or more APs 100 directly or through the
Internet and therefore can communicate with any of the PLBs,
repeaters, user devices, and other devices through the respective
AP 100.
[0041] FIG. 4 illustrates example underground PLCS subnets that
employ an embodiment of the present invention. In FIG. 4 each
distribution transformer is indicated by small square box and
labeled DT. Referring to network 1, a MVID 300 is installed at two
distribution transformers and a PLB 400 is installed at the
remaining distribution transformers. For ease of illustration, the
PLB 400 and MVIDs 300 in FIG. 4 are not shown separately from the
DTs. In network 1, each PLB 400 is in communication with the
closest MVID 300 via the MV power line with which it is
communicatively coupled and provides communications to the customer
premises via the LV power lines. Thus, the PLBs 400 are
communicatively coupled to the MV power line and the LV power
lines. The PLB 400 may communicate with the MVID 300 directly, or
the data from the PLB 400 may be repeated (e.g., demodulated,
source decoded, channel decoded, error decoded, decrypted. and then
encrypted, error encoded, channel encoded, source encoded and
modulated) and/or amplified by one or more of the PLBs 400 between
the PLB 400 and the MVID.
[0042] The MVIDs 300 may be configured to communicate upstream via
a wireless communications link, twisted pair, coaxial cable, other
conductor, or via fiber optic link. In this example, the MVIDs 300
of network 1 are in communication with a wireless repeater, which
is in wireless communication with DP 200, which is in communication
with the AP 100 via a fiber optic link. In other embodiments, the
link between the DP 200 and AP 100 may be wireless as well. One or
more wireless repeaters may be used between the MVIDs 300 and DP
200 and/or between the DP 200 and AP 100 in the embodiments herein.
The repeaters may be daisy-chained together for bidirectional
communications via time division multiplexing and/or frequency
division multiplexing (e.g., a separate upstream and downstream
frequency band) and may use any suitable licensed or unlicensed
bands. Such frequencies may include the much used 2.4 GHz, 5 GHz,
24 GHz, and/or 60 GHz wireless bands, for example. Protocols (and
therefore frequency bands) used may comprise 802.11a, b, or g,
802.16, and/or 802.21. Thus, the MVID 300 may comprise an antenna
that is attached to a tower, transformer enclosure, or other
structure that facilitates wireless communications.
[0043] Network 3 includes three DTs with two having a PLB 400. Each
PLB 400 is configured to communicate with the MVID 300 of that
network. The MVID 300 of network 3 is in communication with its DP
200 via a fiber optic link and wireless link as shown.
[0044] In networks 1 and 3, the PLBs 400 communicate with user
devices in the customer premises via the low voltage power lines
or, alternately, via a wireless link.
[0045] In this embodiment, the PLBs 400 provide communication
services for the users, which services may include security
management, routing of Internet protocol (IP) packets, filtering
data, access control, service level monitoring, signal processing
and modulation/demodulation of signals transmitted over the power
lines.
[0046] At the user end of the PLCS, data flow originates from a
user device, which may provide the data to a power line modem
(PLM), which is well-known in the art.
[0047] Various electrical circuits within the customer's premises
distribute power and data signals within the customer premises. The
customer draws power on demand by plugging a device into a power
outlet. In a similar manner, the customer may plug the PLM into a
power outlet to digitally connect user devices to communicate data
signals carried by the power wiring. The PLM thus serves as an
interface for user devices to access the PLCS. The PLM can have a
variety of interfaces for customer data appliances. For example, a
PLM may include a RJ-11 Plain Old Telephone Service (POTS)
connector, an RS-232 connector, a USB connector, a 10 Base-T
connector, RJ-45 connector, and the like. In this manner, a
customer may connect a variety of user devices to the PLCS.
Further, multiple PLMs may be plugged into power outlets throughout
the customer premises, with each PLM communicating over the same
wiring internal to the customer premises.
[0048] The user device connected to the PLM may be any device
capable of supplying data for transmission (or for receiving such
data) including, but not limited to a computer, a telephone, a
telephone answering machine, a fax, a digital cable box (e.g., for
processing digital audio and video, which may then be supplied to a
conventional television and for transmitting requests for video
programming), a video game, a stereo, a videophone, a television
(which may be a digital television), a video recording device, a
home network device, a utility meter, or other device. The PLM
transmits the data received from the user device through the
customer LV power line to a PLB 400 and provides data received from
the LV power line to the user device. The PLM also may be
integrated with the user device, which may be a computer. In
addition, the functions of the PLM may be integrated into a smart
utility meter such as a gas meter, electric meter, water meter, or
other utility meter to thereby provide automated meter reading
(AMR) and control.
[0049] The PLB 400 typically transmits the data to the MVID, which,
in turn, transmits the data to the DP 200, which transmits the data
to the AP 100. The AP 100 then transmits the data to the
appropriate destination, which may be a network destination (such
as an Internet address) in which case the packets are transmitted
to, and pass through, numerous routers (herein routers are meant to
include both network routers and switches) in order to arrive at
the desired destination.
[0050] System
[0051] Referring to FIG. 5, one example of an embodiment of the
system of the present invention includes an aggregation point 100
including a cable modem termination system (CMTS) 110 and an
optical multiplexer/demultiplexer system. As shown, the aggregation
point 100 that may be co-located with a point of presence (POP).
The aggregation point 100 may be in communication with one or more
distribution points 200 via one or more fiber optic cables 140. In
other embodiments, this link may be a wireless link, a T1 link, a
coaxial cable, or any other suitable link. Each distribution point
200 may be in communication with one or more MVIDs 300 via one or
more fiber optic conductors 240. Each MVID 300 may be in
communication with one or more power line bridges 400 via the URD
medium voltage power line(s). The PLBs 400 may be in communication
with one or more user devices that reside in the customer premises
via the low voltage power lines or via a wireless link.
[0052] In this embodiment, a Frequency Division Multiplexed (FDM)
channel plan may be used for allocating multiple downstream and
multiple upstream communication channels. Upstream channels also
may be multiplexed in the time domain (Time Division Multiple
Access or TDMA) to accommodate the large number of PLBs 400 that
may exist in large neighborhoods or daisy-chained MVIDs 300. For
example, the PLBs 400 coupled to a URD MV cable may be configured
to transmit to an MVID 300 using time division multiplexing, but in
the same frequency channel (which may be different than the
downstream frequency channel). Other embodiments may use other
schemes, such as purely FDM for upstream channels, or Code Division
Multiple Access (CDMA) which may include Synchronous CDMA (SDMA),
or Time Division SCDMA (TD-SCDMA).
[0053] In this embodiment, the downstream channels (e.g., as
transmitted from the MVID 300, amplified by the PLBs 400, and
repeated by any repeaters) may be approximately six megahertz (6
MHz) wide. Three such channels may be used between 30 MHz and 50
MHz on the URD power lines, which has been found to be less noisy
than frequencies below 30 MHz. In addition, this frequency band may
be orthogonal from the frequency band (e.g., the HomePlug frequency
band) used to communicate over the LV power lines with the user
devices in the customer premises in this embodiment. Consequently,
any communications signals that unintentionally bleed through the
transformer (either from the LV side to the MV or from the MV side
to the LV side) will not interfere with communications.
[0054] The downstream communications may be 256 Quadrature
Amplitude Modulation (QAM) or 64 QAM, Quadrature Phase Shift Keying
(QPSK), Binary Phase Shift Keying (BPSK), or any other appropriate
modulation format, where spectrally efficient formats are
preferred. In the case of 256 QAM, the communications may have 8
bits per symbol while if 64 QAM is used, the communications may
have 6 bits per symbol. In each case, the communications may use
differential encoding and have a symbol rate of more than 5
Baud.
[0055] Upstream communications such as those transmitted by the
PLBs 400 toward the MVID 300, may be both FDM and TDMA or FDM and
SCDMA or simply SCDMA. Many of the communications parameters of the
PLBs 400 are configured under the direction of the CMTS 110 via the
MAC layer control specification. Most of these parameters are
normally negotiated between CMTS 110 and the PLB MV modem (which
may be a cable modem). In one embodiment, a first upstream channel
has a bandwidth of approximately 1.6 MHz and may employ any of
QPSK, 16 QAM, or 64 QAM. The communications may employ differential
encoding and have a symbol rate of 1.28 MBaud. For QPSK
communications may be at two bits per symbol, for 16 QAM four bits
per symbol, and for 64 QAM six bits per symbol may be used.
[0056] A second and third upstream channel may also be 1.6 MHz
wide, or alternately, may be 800 KHz wide with each having a symbol
rate of 640 KBaud (and otherwise having the parameters listed above
for the first upstream channel).
[0057] Depending on the layout of the network, the system may
employ one upstream and one downstream channel for each URD MV
cable. In other implementations, such as where more than one
channel is needed due to capacity or other reasons, two, three, or
more channels (upstream and/or downstream) may be used for
communications over one URD MV cable. As will be evident to those
skilled in the art, the MVIDs 300 may need to communicate data in
all of the channels, while the PLBs may need to communicate data in
all, or some subset, of the communication channels. In this
embodiment, the channels (frequencies) for communications and
amplification by the PLBs may be remotely controlled via a command
from the PLS. There need not be the same number of upstream and
downstream channels. Other embodiments of the present invention may
use more or fewer channels and/or completely different
communications schemes.
[0058] Aggregation Point
[0059] Referring to FIGS. 5 and 6, this example embodiment includes
an aggregation point 100 that includes a CMTS 110 having a
plurality of ports. The CMTS 110 may be a large CMTS or a plurality
of smaller CMTSs. As is known to those skilled in the art, the
output of a CMTS typically is a radio frequency electrical signal.
The CMTS 110 also may serve as a master controller, providing
instructions and granting requests to/from downstream devices (DPs
200, MVIDs 300, and PLBs 400). Such commands typically relate to
the physical layer and may comply with MAC layer control
specification of DOCSIS (Data Over Cable System Interface
Specification) (e.g., DOCSIS 2.0). In other words, the commands and
status requests transmitted to the network elements, and responses
thereto, may substantially or fully comply with the format and
protocol (e.g., the bit sequence) defined by the DOCSIS
specification.
[0060] Each port of the CMTS 110 may be communicatively coupled to
an Electrical-to-Optical converter (EO converter) 130. This
embodiment includes a plurality of groups of EO converters 130,
with each group of EO converters 130 communicating with an optical
multiplexer/demultiplexer 135. All of the EO converters 130 in a
group may communicate with the multiplexer/demultiplexer 135 via a
different wavelength. The Optical Multiplexer/Demultiplexer 135 may
include an Arrayed Waveguide Grating (AWG) or Thin Film Filter
(TFF) and/or Fiber Bragg Grating (FBG). Each optical
multiplexer/demultiplexer 135 receives optical signals from its
corresponding EO converters 130 and multiplexes the signals onto
one or more optical conductors 140. In this example embodiment, the
optical multiplexer/demultiplexer 135 transmits to each
distribution point 200 on one fiber conductor and receives from
each distribution point on another optical fiber conductor. The
output of the optical multiplexer 135 may be amplified prior to
transmission onto the optical conductor. Thus, the downstream (DS)
transmission from the optical multiplexer/demultiplexer 135 (or
optical amplifier (OA)) may comprise a plurality of different
wavelengths and the communications may be amplitude modulated and
be a dense wave division multiplexed (DWDM) or coarse wave division
multiplexed (CWDM) signal. In other embodiments, this link may be
digital. In addition, or instead of wave division multiplexing,
additional fiber conductors may be used. Thus, the AP 100 may
include one or more ports for fiber optic communications and could
include one or more fiber optic transceivers--although the
transceiver(s) may not necessarily communicate over the same fiber
optic conductor.
[0061] In the upstream direction (i.e., data transmitted from the
DP 200 to the AP 100), data is received by the optical
multiplexer/demultiplexer 135 and demultiplexed (based on the
wavelengths of the signals in this embodiment). The demultiplexed
outputs are communicated to the respective OE converter 130 which
then converts the optical signal to an electrical signal. The
output of the OE converter 130 is provided to the CMTS 110, which
communicates the signal via the POP to the appropriate network such
as the Internet or a voice network.
[0062] While this figure discloses only two distribution points
200, any number of distribution points 200 may be communicatively
coupled to the aggregation point 100 provided the aggregation point
100 is suitable to handle the information capacity. In addition,
while the AP 100 of FIGS. 5 and 6 utilize optical links to
communicate with their DPs 200, other systems may in addition to,
or instead, employ wireless, coaxial, T1, SONET, or any other
suitable link, and therefore, will have the appropriate transceiver
for providing such communications.
Distribution Point
[0063] The distribution point 200 receives the downstream optical
signals (e.g., via an optical conductor 140) from the optical
multiplexer/demultiplexer 135 of the aggregation point 100. The
distribution point 200 includes a multiplexer/demultiplexer 235
that operates substantially similar to the
multiplexer/demultiplexer 135 of the aggregation point 100. The DP
200 also may include a plurality of downstream ports. Thus, the DP
200 may include one or more ports for fiber optic communications
and could include one or more fiber optic transceivers--although
the transceiver(s) may not necessarily communicate over the same
fiber optic conductor.
[0064] The multiplexer/demultiplexer 235 of the DP 200 may
demultiplex the received optical signals (based on wavelength in
this embodiment) and output each demultiplexed signal via one of
its downstream ports. In this example embodiment, each downstream
port is communicatively coupled to a MVID 300 via one or more fiber
optic conductors 240. In addition, the DP 200 may convert the
optical signals to optical digital signals and modulate the signals
onto an optical carrier of the same, or different, wavelength. In
this embodiment, each downstream port of the DP 200 communicates
with the associated MVID 300 via a different wavelength, and
therefore, the system uses wavelength division multiplexing.
[0065] The DP 200 also may include a cable modem (e.g., a CableLabs
Certified Cable Modem) and central processing unit in order to
receive and process control commands and status requests. Control
and status of DPs may be accomplished by means of an in-band
channel. Such signals may be transmitted from the AP 100 (e.g.,
from the CMTS 110 therein and may be DOCSIS commands) or PLS.
[0066] Upstream optical signals may be received from each MVID 300
via a separate port. Each upstream optical signal may be
multiplexed by the DP's multiplexer/demultiplexer and communicated
upstream to the aggregation point 100. The signals received from
the MVID 300 by the DP 200 may be converted to optical digital
signals and modulated onto an optical carrier of the same, or
different, wavelength.
[0067] MVID
[0068] Each MVID 300 receives the downstream data signals from the
DP 200 and converts the optical signals to electrical signals. The
communications between the DP 200 and the MVIDs 300 (and between
the AP 100 and DPs 200) may be amplitude modulated (AM) fiber optic
signals. At the MVID 300, DOCSIS compliant RF signals (e.g.,
optical signals) may be converted to a frequency channel plan which
is more compatible with the URD MV cable/coupler power line
communications infrastructure. Thus, one function of the MVID 300
may be to shift the channels from their CATV spectral assignments
to those in the URD channel plan. The MVID 300 also may serve as
the optical/electrical interface device by converting downstream AM
fiber signals into electrical RF signals and vice-versa for
upstream signals.
[0069] As shown in FIG. 6, the MVID 300 may be communicatively
coupled to one or more URD medium voltage power lines for example,
at a riser pole (where the underground power line traverses up a
pole to connect to an overhead power line) or at an URD transformer
such as the first transformer connected to the riser pole in the
URD system. In this example, the MVID 300 is coupled to all three
phases (phase A, B, and C) of the three phase URD power
distribution system. As shown, the MVID 300 may be in communication
with one or more PLBs 400 via each URD MV power line. The URD
transformers, and their associated PLBs, are connected together by
a length of URD cable that typically may be up to 1000 feet in
length, but may sometimes be longer.
[0070] In some embodiments, the MVID 300 may perform routing and
transmit the data signals over the appropriate MV power line.
Alternately, and as in this example embodiment, the MVID 300 simply
converts the incoming signal from an optical signal (or a wireless
signal in alternate embodiment) to an electrical signal and
transmits the electrical signals down all (or some) of the URD MV
power lines. As will be evident to those skilled in the art, the
less processing that the MVID 300 (and other network elements)
perform, the faster the network will communicate data (i.e., the
system will have less latency), which is important for voice,
video, and other latency sensitive applications.
[0071] PLB
[0072] The PLB 400 may include a processing section and a through
section. Each PLB 400 receives the downstream data signals via the
MV power line. In this example embodiment, each PLB 400 receives
all the data transmitted from the MVID 300 on the MV power line to
which the PLB 400 is connected. The processing section of the PLB
400 demodulates all the data signals to determine whether the data
should be processed by the PLB 400 (e.g. as a command) or
transmitted to the user devices on the PLB's LV subnet. If the data
signals include appropriate address information (as discussed in
detail below), the PLB 400 may process the data or transmit the
data via the LV subnet to be received by a user device in a
customer premises (not shown). If the data signals do not include
the appropriate address information, the data signals may be
ignored. In addition to demodulating and processing the data, the
through section of the PLB 400 may amplify, filter and transmit all
the data signals it receives for reception by the downstream PLBs
400.
[0073] Upstream data signals received by the PLBs 400 on the MV
power line may be amplified, filtered and transmitted by the
through section of the PLB 400 toward the MVID 300. Thus, each PLB
400 may include a bidirectional amplifier to amplify all the
downstream (and upstream) data signals that may be attenuated as
they propagate through the URD MV cable. In this embodiment, there
is no need to demodulate and process the upstream data. Other
embodiments, which may operate in a noise environment, may provide
demodulation and modulation of MV power line upstream data at the
PLB to thereby repeat the data. Also, the input and output filter
of the amplifiers may be tunable in that the PLB 400 may filter for
data signals from the first segment in the first frequency band.
However, upon receiving a command to filter for data signals in a
second frequency band (for receiving and/or transmitting); and
subsequently filtering for data signals in the second frequency
band (for receiving and/or transmitting) in response to receiving
the command.
[0074] The PLB 400 also receives upstream data via the LV power
line from the user device(s) at the customer premises (not shown).
This data may be processed and transmitted upstream by the
processing section of the PLB 400 to the MVID 300. In other
embodiments, the PLB 400 may communicate with devices at the
customer premises via another link such as a fiber optic cable, a
coaxial cable, a twisted pair, or a wireless link. (e.g., an IEEE
802.11).
[0075] System Variations
[0076] While the above described embodiment includes a DP 200,
other embodiments may not include a DP 200. For example, FIG. 7
depicts a PLCS that does not employ a DP 200. The embodiment
depicted in FIG. 7 may be suitable for single phase URD power
distribution segments. The aggregation point 100 communicates
directly with a plurality of MVIDs 300, which may be located in the
pit of, or adjacent to, a URD transformer (instead of at the riser
pole) such as the first URD transformer or the URD transformer that
is most directly connected to the pole riser. In other words, the
MVIDs 300 in the embodiment may be co-located with a PLB 400 and
may communicate with the adjacent PLB 400 over a conventional
telecommunications medium such as a coaxial cable or Ethernet
cable.
[0077] The aggregation point 100 of FIG. 7 remains substantially
similar to the aggregation point 100 of FIG. 5 except that there
may be no multiplexer/demultiplexer present. Instead, the optical
output of each OE converter 130 of the AP 100 may communicate with
an associated MVID 300 via an upstream optical fiber conductor 140a
and a downstream optical fiber conductor 140b using amplitude
modulated fiber optic signals.
[0078] FIG. 8 depicts another example system in which a DP 200 is
not present and in which the AP 100 is providing communications for
three different MVIDs 300. The MVIDs 300 may be located in the pit
of, or adjacent to, a URD transformer (instead of at the riser
pole) such as the first URD transformer or the URD transformer that
is most directly connected to the pole riser. In other words, the
MVIDs 300 in the embodiment may be co-located with a PLB 400 and
may communicate over a conventional telecommunications medium such
as a coaxial cable or Ethernet cable. The embodiment depicted in
FIG. 8 may be suitable for single phase URD power distribution
segments. In this example embodiment, a single EO converter 130
provides communications to multiple MVIDs 300. As shown in FIG. 8,
the downstream fiber optic link 140b between the AP 100 and the
MVIDs 300 may be connected to splitters that split the signals so
that all three MVIDs 300 receive all downstream communications from
the AP 100. The upstream links 140a of the MVIDs 300 are chained
together as shown and, therefore, are all combined on one fiber
optic cable. Specifically, the upstream link 140a from MVID 300a is
coupled to MVID 300b where the signals of MVID 300a and 300b may be
combined (electrically). The upstream link from MVID 300b is
coupled to MVID 300c where the data signals from MVID 300b (which
may include signals from MVID 300a and 300b) and MVID 300c may be
combined (electrically). The combined signals are then communicated
to the EO converter 130 of the AP 100, where they may be converted
to electrical signals and demodulated. The fiber optic signals
employed in this embodiment may be amplitude modulated fiber optic
signals.
[0079] FIG. 9 depicts a DP 200 that communicates with its
associated MVIDs 300 in substantially the same manner as the AP 100
of FIG. 8. The embodiment depicted in FIG. 9 also may be suitable
for single or multi-phase URD power distribution segments. The
MVIDs 300 may be located in the pit of, or adjacent to, a URD
transformer (instead of at the riser pole) such as at the first URD
transformer or the URD transformer that is most directly connected
to the pole riser. Thus, the MVIDs 300 in the embodiment may be
co-located with a PLB 400 and may communicate with that PLB 400
over a conventional telecommunications medium such as a coaxial
cable or Ethernet cable. Data communicated between the MVIDs 300
and other downstream PLBs 400 may traverse through (and be
amplified by) the PLB 400 with which the MVID 300 is
co-located.
[0080] The DP 200 of FIG. 9 includes an analog-to-digital converter
(ADC) for the upstream communications from the MVIDs 300. The ADC
converts the analog optical signals from the MVIDs 300 (i.e., the
amplitude modulated optical signals) to digital optical signals for
upstream transmissions to the AP 100. As will be evident to those
skilled in the art, the other DPs 200 and MVIDs 300 disclosed
herein might also include an ADC and operate accordingly. As shown
in FIG. 9, the downstream fiber optic link 140b between the DP 200
and the MVIDs 300 may be connected to splitters that split the
signals so that all three MVIDs 300 receive all downstream
communications form the DP 200 and, if desirable, may transmit all
received data downstream to the PLBs 400. The upstream links 140a
of the MVIDs 300 may be chained together as shown and discussed
above and, therefore, may be combined on one fiber optic cable by
the MVID 300 with which the DP 200 is most directly communicatively
coupled.
[0081] MVID
[0082] FIG. 10 depicts an example embodiment of a MVID 300 that is
coupled to one MV power line for communications to one or more
PLBs. The MVID 300 may be installed at, or on, a utility pole at a
pole riser. The MVID 300 also may be communicatively coupled to
fiber optic conductors 140 for communications with an upstream
device such as a DP 200 or AP 100. Such fiber optic signals may
include modulated fiber optic signals, which may be amplitude
modulated (as in the embodiment) or digitally modulated (i.e., be
digital optical signals). In other embodiments, the MVID 300, which
may be mounted at the riser pole, may include a wireless
transceiver for communication with the DP 200 or AP 100 in the
licensed or unlicensed frequency bands. As shown in FIG. 10,
downstream data signals are received via a fiber optic cable 140b
and converted from an optical to an electrical signal via an OE
converter 330a. The output of the OE converter 330a is supplied to
a tuner 331 or other band pass filter that may filter out and shift
the channel center frequency for all but the frequency band
containing the desired information. The output of the tuner 331 may
be supplied to a pre-emphasis filter. The pre-emphasis filter 332
may attenuate the signal so that certain frequencies may be
transmitted with more power than other frequencies. Because higher
frequencies may be attenuated more than lower frequencies by the
URD cable, the pre-emphasis filter 332 may attenuate the lower
frequencies more than the higher frequencies (e.g., providing a
slope across the frequency band) to compensate for the anticipated
loss of the URD cable or URD Couplers. Thus, the pre-emphasized
signal may be received at the other end of the URD cable as a more
flat signal (e.g., having more uniform power spectrum) across the
carrier frequency band than if the signal had not been
pre-emphasized. In other embodiments, pre-emphasis may be performed
via a pre-emphasis amplifier in addition to, or instead of, the
pre-emphasis filter.
[0083] The output of the pre-emphasis filter 332 is supplied to a
line amplifier 333. The signal amplified by the line amplifier 333
is supplied to a diplexer 334, which is communicatively coupled to
coupler 420. An alternate embodiment, could use an a power splitter
or a directional coupler or any device configured to separate the
downstream and upstream signals (e.g., via frequency for FDM),
which couples the downstream frequencies to the MV coupler and onto
the URD MV power line for reception by the PLBs 400 instead of a
diplexer. It is worth noting that this example embodiment of the
MVID 300 does not route or demodulate and modulate the downstream
signals and, therefore, has a lower latency than might be provided
from a MVID 300 that does route, demodulate and/or modulate the
signals (which would also be within the scope of the present
invention).
[0084] The upstream data signals are coupled from the MV power line
to the diplexer 334 (or any other device that can separate the
downstream and upstream signals) via the MV coupler 420. The
diplexer 334 couples the upstream frequencies to the low noise
amplifier (LNA) 340, which may be connected to an input band pass
filter (or image filter) 341. The amplified and filtered signals
are supplied to a first intermediate frequency (IF) converter 342
(e.g., a mixer that receives an input from the local oscillator
(Lo) synthesizer 345 to shift the frequency) and then to an IF
filter 343. Thus, the amplified and filtered signal is frequency
shifted, filtered, and then supplied to a second frequency
converter 344 (e.g., a mixer that receives an input from the local
oscillator (Lo) synthesizer 345 to shift the frequency) which
converts the data signals to the appropriate frequency for upstream
transmission. In an alternate embodiment, an equalization filter
may also be connected to the output of the LNA amplifier 340 that
has the inverse frequency response of different lengths of the URD
cable.
[0085] The output of the second frequency converter 344 is supplied
to a programmable gain amplifier (PGA) 346. Data signals from
downstream MVIDs 300 are received by OE converter 330b and
converted to electrical signals. The amplified output of the PGA
346 may be combined by combiner 347 with the upstream data signals
of the other downstream MVIDs 300 (that converted to electrical
signals by OE converter 330b), and then provided to the upstream EO
converter 330c for conversion to an optical signal for transmission
upstream to a DP 200 or AP 100 (as depicted by MVID 300c shown in
FIGS. 8 and 9 or the MVIDs shown in FIG. 7) or to another MVID 300
(as depicted by MVIDs 300a and 300b of FIGS. 8 and 9).
[0086] The MVID 300 also may include a cable modem (e.g., a
CableLabs Certified Cable Modem) and central processing unit in
order to receive and process control commands and status requests.
Control and status of MVIDs (and PLBs) may be accomplished by means
of an in-band channel. Such signals may be transmitted from the AP
100 (e.g., the CMTS 110 therein in the case of DOCSIS commands) or
PLS.
[0087] In this embodiment the communications (both upstream and
downstream) that are upstream from the MVID 300 (e.g., between the
MVID 300 and DP 200 and between the DP 200 and AP 100) may employ a
substantially DOCSIS (e.g. DOCSIS 2.0) (Data Over Cable System
Interface Specification) compliant protocol. format, and physical
layer. This is indicated by the vertical dotted line in FIGS. 7, 8,
and 9. While the protocol and physical layer may be substantially
DOCSIS 2.0 compliant, the mediums (e.g., fiber) and hardware (e.g.,
DP 200) may not be consistent with a conventional DOCSIS system. Of
course, variations of DOCSIS and protocols and physical layers that
are not similar to DOCSIS may be suitable as well in some
embodiments. For example, a system substantially compliant with a
Digital Audio Visual Council (DAVIC) specification alternately may
be employed (i.e., protocol, format, commands and/or status
requests thereof).
[0088] In addition, in this embodiment the communications (both
upstream and downstream) that are downstream from the MVID 300
(e.g., between the MVID 300 and PLBs) may employ a substantially
DOCSIS (Data Over Cable System Interface Specification) compliant
protocol and physical layer and a frequency scheme that is
consistent with DOCSIS.
[0089] This example embodiment uses a first frequency band for
upstream communications from the PLBs 400 to their MVID 300 and a
second frequency band for upstream communications from the MVIDs
300 to their upstream devices (DP 200 or AP 100). Thus, frequency
translation is required by MVID 300 in this example. For example,
the first frequency band (between the PLBs 400 and the MVID 300)
may be from approximately 54 MHz to 100 MHz and the second
frequency band (between the MVIDs 300 and the DP 200 or AP 100) may
be from 5 MHz to 50 MHz. In this example embodiment, the downstream
communications to the MVID 300 (from a DP 200 or AP 100) may use
the same frequency as the downstream communications from the MVID
300 to its PLBs 400. Consequently, frequency translation is not
required in this example embodiment. In other embodiments the
downstream channels may be frequency translated (i.e., frequency
shifted) by MVID 300.
[0090] FIG. 11 depicts another example embodiment of a MVID 300,
which also may be installed at, or on, a utility pole at a pole
riser. The MVID 300 also may be communicatively coupled to fiber
optic conductors for communications with an upstream device such as
a DP 200 or AP 100. Such fiber optic signals may comprise amplitude
modulated fiber optic signals, but could also be digital optical
signals. In this example embodiment, the downstream communications
to the MVID 300 (from a DP 200 or AP 100) use a different frequency
than the downstream communications from the MVID 300 to its PLBs
400. In addition, the upstream communications from the PLBs 400 to
the MVID 300 employ different frequencies than the upstream
communications from the MVID 300 to its upstream device (DP 200 or
AP 100). Consequently, frequency translation may be required in
both the upstream and downstream directions.
[0091] Thus, downstream data received by the MVID 300 from its
upstream device will be converted to an electrical signal by the OE
converter 330a and converted to an IF frequency by the first IF
converter 350 (e.g., a mixer that receives an input from the Lo
synthesizer 351 to shift the frequency). The output of the
converter 350 may be band pass filtered by band pass filter 352 and
supplied to a second frequency converter 353, which converts the
signals to the frequencies used on the MV power line. The output of
the second converter 353 is image filtered by image filter 354 and
amplified by a line amplifier 355. The amplified signal is supplied
to a diplexer 334 that couples the downstream frequencies to the MV
power line via the MV coupler 420 and circuit protection circuitry
356.
[0092] Upstream data signals received from the PLBs 400 are coupled
from the MV coupler 420 to the LNA 357 by the diplexer 334 and
circuit protection circuitry 356. The LNA 357 amplifies the
signals, which are provided to a bandpass filter 358, which filters
for the band of frequencies used for upstream communications on the
URD MV power line. The output of the filter 358 is supplied to a
PGA 359, which amplifies the signal. The amplified signals are then
supplied to a frequency converter 360 that converts the frequency
band received to the frequency band used for upstream
communications. Data signals from downstream MVIDs 300 are received
by OE converter 330b and converted to electrical signals. The
output of the frequency converter 360 may pass through an image
rejection filter (not shown) before being combined with the
upstream data signals of other MVIDs 300 (if any) by combiner 361
before being converted to amplitude modulated optical signals by
the EO converter 330c and transmitted to the upstream device (DP
200 or AP 100).
[0093] It is worth noting that these example embodiments of the
MVID 300 may not employ a modulator or demodulator for upstream or
downstream communications, thereby ensuring low latency through the
MVID 300.
[0094] This embodiment of the MVID 300 also may include a cable
modem (e.g., a CableLabs Certified Cable Modem) and central
processing unit in order to receive and process control commands
and status requests as discussed above.
[0095] PLB
[0096] FIG. 12A depicts a portion of an example embodiment of a PLB
400. In particular, FIG. 12A depicts the through portion of the PLB
400, which amplifies both the upstream and downstream
communications frequencies. As will be discussed in more detail
below, in this embodiment, communications via the MV power line use
separate frequencies for upstream transmissions (from the PLB 400
to the MVID 300) and downstream transmissions (from the MVID 300 to
the PLBs 400). Thus, referring to the left side of FIG. 12A, the
downstream frequency band is coupled to a first diplexer 410a (or
any other device capable of isolating the downstream signals from
the upstream signals) from the MV power line via the first MV
coupler 420a. The first diplexer 410a couples the downstream
frequencies to the LNA 411, which amplifies the signals that are
then supplied to a bandpass filter 412. The bandpass filter filters
for the downstream frequencies. The output of the bandpass filter
412 (which may be programmable by controller) is supplied to both a
demodulator 480 and an automatic level control (ALC) amplifier 413
(implemented in hardware or a combination of hardware and
software). The output of the ALC amplifier 413 is supplied to a
second diplexer 410b (or any other device capable of combining the
downstream and upstream signals), which couples the amplified data
signals of the downstream frequencies to the MV power line via the
second MV coupler 420b. The demodulator 480 and other process
related portions of the PLB 400 are discussed below.
[0097] Referring to the right side of FIG. 12A, the upstream
frequency band is coupled to the second diplexer 410b (or any other
device capable of isolating the upstream signals from the
downstream signals) from the MV power line via the second MV
coupler 420b. The second diplexer 410b couples the data
communicated in the upstream frequency band(s) to the upstream low
noise amplifier 415, which amplifies the upstream signals. Thus,
each PLB 400 may be equipped with bi-directional linear amplifiers.
A form of "soft" automatic gain control (AGC) may be used,
providing gain/power level control for downstream and upstream
directions at each amplifier PLB 400. Control of this system
function is under the direction of the CMTS 110 via a downstream
control channel. Repeaters may also be deployed to regenerate the
modulated signal on extremely long/lossy channels.
[0098] The output of the upstream low noise amplifier 415 is
combined with the amplified output (amplified by amplifier 417) of
the modulator 481 (e.g., via time division multiplexing, code
division multiplexing, and/or as specified by DOCSIS 2.0) via
combiner 416. Instead of amplifier 417, the output power of the
modulator 417 could be set high (or simply be higher than permitted
by federal regulations) in which case amplifier 417 may be replaced
with an adjustable attenuator. The DOCSIS 2.0 specification is
hereby incorporated by reference in its entirety. The amplified
signal may be supplied to the first diplexer 410a (or any other
device capable of combining the upstream and downstream signals),
which couples the upstream frequencies to the MV power line via the
first MV coupler 420a for reception by the MVID 300.
[0099] Thus, the through section of the PLB 400 amplifies both the
upstream and downstream data signals (based on their frequency)
without demodulating and modulating the data, thereby reducing
latency (compared to if the signal was demodulated and modulated)
and increasing the distance of communications via the
amplification. It is has been found that the URD MV power line
cables are very lossy at frequencies used to provide broadband
communications. In addition, government regulations limit the
amount of power that can be used to transmit such signals.
Consequently, in comparison to other communications mediums, the
transmitted signals will travel only relatively short distance on
the URD MV power lines. Other embodiments of the PLB 400 may
include demodulating and re-modulating the data signals to permit
communicating long distances over the URD MV cables. However, the
increased latency of the PLB 400 may reduce the quality of the time
sensitive applications (e.g., voice and video delivery) to a point
where such applications are precluded. In contrast, the example
embodiment of the PLB 400 disclosed provides amplification of the
signal in both directions without a significant latency
increase.
[0100] After transmission of the data signals toward a PLB 400
(e.g., from another PLB or the MVID), the data signals will be
attenuated by the URD cable, the MV couplers (e.g., the MV couplers
on each end of the URD cable), and other power distribution
elements (e.g., taps). The attenuation (or loss) caused by the URD
MV cable is related to its length. While the loss of the MV coupler
may be substantially predetermined, the distance to the PLB, and
length of the URD cable, typically will vary between URD
transformers. In other words, the channel loss between each PLB is
not the same because the distance between each PLB, and length of
the URD cable, is not the same. Consequently, even if the data
signals are transmitted at the same power level toward each PLB,
the data signals may be received at a different power levels at
each PLB 400 due to the variances in the loss of the channel
associated with each PLB 400 (i.e., variances in the lengths of the
URD cables that the data signals must traverse to reach each PLB
400).
[0101] The transmit level may be defined as the average RF power
spectral density (PSD) at the center frequency of the channel
transmitted during the data symbols of a burst, assuming equally
likely QAM symbols, and measured at the output of the PLB 400. The
maximum output power levels (for both the transmissions from the
PLB modem and PLB amplifiers) and associated radiated emissions
must always be less than or equal to the appropriate Federal
Communications Commission's Part 15 limits (i.e.,
.ltoreq.P.sub.FCC.sub.--.sub.Limit).
[0102] As discussed below, the MV coupler provides isolation to
thereby attenuate signals that might otherwise traverse through the
URD transformer where they could be undesirably received by the MV
coupler on the other side of the transformer and create a feedback
loop. Thus, the transmit levels may also (or instead) be limited by
the isolation provided by the MV couplers. In summary, there is a
ceiling to the output power levels of the PLB's bi-directional
amplifiers (i.e., amplification power) and modem (i.e., transmit
power).
[0103] As discussed, for data signals transmitted at the same power
levels, the power levels of those signals when received may vary
from PLB to PLB. For those PLBs receiving data signals via a short
URD cable, the data signals typically will be received at higher
power levels than those PLBs receiving data signals via a long URD
cable. Consequently, an amplifier providing the same amplification
at each PLB may not suffice, because the higher power level signals
may be amplified above the FCC power limits (or above the isolation
limits of the MV couplers) and/or the lower power level data
signals may not be amplified enough to allow the signals to be
reliably received by the next PLB 400 (or the MVID 300).
[0104] In some embodiments, an automated gain control or automatic
level control amplifier may be used. However, transmissions in the
upstream direction are often bursts, which do not allow enough time
for an AGC or ALC amplifier to adjust the amplification.
Consequently, the present invention provides a method of gain
control to compensate for receiving signals of varying power levels
for upstream communications. For downstream communications, in
which transmissions are more constant, an ALC amplifier may be used
to adjust the amplification.
[0105] Gain Alignment is the task of adjusting the gains of each
PLB 400 upstream amplifier to achieve a desired overall cascaded
gain. In addition, the output of the PLB 400 transmitter (e.g.,
transmitting data from the PLB such as user data) may also be
adjusted accordingly. In this embodiment, the desirable overall
cascaded gain may be .gtoreq.60 dB (<60 dB loss) from the
furthest PLB 400 to the MVID 300 input. A net loss may be
acceptable and may result from the accumulation of long single-URD
spans that attenuate the signal more than a single upstream
amplifier at a PLB 400 is capable of compensating. The 60 dB max
cascaded loss is determined by the minimum carrier-to-noise (C/N)
objective of this example embodiment.
[0106] While the upstream amplifiers, like the downstream
amplifiers, may be gain limited (e.g., due to limited isolation
between URD MV couplers), the MVID 300 gain is not limited in this
manner, and may be capable of much higher gains, which will be used
for additional signal level alignment.
[0107] In an example system shown in FIG. 9, there are four spans,
S.sub.0, S.sub.1, S.sub.2, and S.sub.3. Each span will consist of
two URD MV couplers and a length of URD Cable. Other spans, such as
those that traverse tap-pits may have three or more MV Couplers and
two or more cable spans. The variables S.sub.0 . . . S.sub.3
represent the total equivalent power loss in dB for each span.
[0108] There are also four gain stages, A.sub.MVID, A.sub.1,
A.sub.2, and A.sub.3. Gains A.sub.1, A.sub.2, and A.sub.3 represent
the gain in PLBs 400a, b, and c, respectively. The fourth gain
stage, A.sub.4, is not used in this case, as PLB 400d is the last
PLB 400 in the cascade. A.sub.MVID is the amplifier incorporated in
the MVID 300c, and is not gain limited as in the PLBs 400.
A.sub.MVID, A.sub.1 . . . A.sub.3 are gains expressed in dB. These
gains could be used, for example, to determine the amplification of
adjustable (or programmable) upstream amplifier 415 in FIG. 12A for
example.
[0109] P.sub.1, P.sub.2, P.sub.3, and P.sub.4 are the output power
spectral densities of the PLB's transmitter (e.g., data transmitted
from the MV modem) for PLB 400a, b, c, and d, respectively. They
are measured in units of dBm/Hz and are controlled in the PLBs 400
by a software programmable amplifier/attenuator, which the level of
the output of the transmitter (or cable modem (e.g., a CableLabs
Certified Cable Modem) in this example). As discussed, these power
levels must always be .ltoreq.P.sub.FCC.sub.--.sub.Limit. These
power outputs, for example, could be used to set the amplification
of adjustable (or programmable) amplifier 417 of FIG. 12A, or an
attenuator may be replace amplifier 417 in some embodiments.
[0110] The gain and transmit PSD settings for any PLB upstream
amplifier/transmitter may be determined from the following rules:
[0111] P.sub.n.ltoreq.P.sub.FCC.sub.--.sub.Limit (expressed in
dBm/Hz) [0112] A.sub.n.ltoreq.A.sub.max (maximum upstream gain)
[0113] No amplifier output level can exceed
P.sub.FCC.sub.--Limit
[0114] In this example embodiment, the following system design
objectives may be: (1) the desired cascaded system gain, including
A.sub.MVID, is 0 dB; (2) the entire PLB-MVID cascaded gain is
bounded by: -60 dB.ltoreq.A.sub.total.ltoreq.0 dB; and (3) any
intermediate cumulative loss be .ltoreq.50 dB.
[0115] For a cascaded chain of N PLBs the following formulas may be
used to compute the upstream amplifier gains and maximum upstream
transmitter power spectral densities.
[0116] The upstream gain of the n.sup.th PLB 400 is:
A.sub.n=[S.sub.n+.SIGMA.(S.sub.k-A.sub.k) , A.sub.max].sub.min
[0117] The maximum transmit PSD for the n.sup.th PLB 400 is:
P.sub.n=P.sub.FCC.sub.--.sub.Limit-.SIGMA.(S.sub.k-A.sub.k)
[0118] Based on these equations, the gains may be computed starting
at the furthest PLB 400 from the MVID 300, PLB.sub.N-1 followed by
PLB.sub.N-2 and so on until reaching the MVID 300. Also, the output
power level P.sub.n of PLB.sub.n is computed after figuring the
gain A.sub.n of PLB.sub.n.
[0119] For the example of FIG. 9, the gains and transmission powers
may be computed as follows: P.sub.4=P.sub.FCC.sub.--.sub.Limit
A.sub.3=[S.sub.3+(S.sub.4-A.sub.4), A.sub.max].sub.min (S.sub.4 and
A.sub.4 are 0, end of line)
P.sub.3=P.sub.FCC.sub.--.sub.Limit-(S.sub.3-A.sub.3)
[0120] Using A.sub.3 from above, A.sub.2 and P.sub.2 can be
calculated below as:
A.sub.2=[S.sub.2+(S.sub.3-A.sub.3)+(S.sub.4-A.sub.4),
A.sub.max].sub.min
P.sub.2=P.sub.FCC.sub.--.sub.Limit-(S.sub.2-A.sub.2)-(S.sub.3-A.sub.3)
[0121] Using A.sub.2 and A.sub.3 from above, A.sub.1 and P.sub.1
can be calculated below as:
A.sub.1=[S.sub.1+(S.sub.2-A.sub.2)+(S.sub.3-A.sub.3)+(S.sub.4-A.sub.4),
A.sub.max].sub.min
P.sub.1=P.sub.FCC.sub.--.sub.Limit-(S.sub.1-A.sub.1)-(S.sub.2-A.sub.2)-(S-
.sub.3-A.sub.3)
[0122] Using A.sub.1, A.sub.2 and A.sub.3 from above, AMVID can be
calculated below as:
A.sub.MVID=[S.sub.0+(S.sub.1-A.sub.1)+(S.sub.2-A.sub.2)+(S.sub.3-A.sub.3)-
+(S.sub.4-A.sub.4), A.sub.max].sub.min
[0123] The output power of the amplifier or transmitter may be
adjusted up or down or, alternately, the output power may be set at
a fixed predetermined level and attenuated to provide the desired
output power.
[0124] The loss of a span (S.sub.n) may be determined in any
suitable manner. For example, the PLB 400 may transmit a tone, or
range of tones (e.g. across all or a portion of the communications
channel), at a predetermined power level (e.g. at the
P.sub.FCC.sub.--.sub.Limit or MV coupler limit). Based on the power
level(s) of the received signal, the receiving device (e.g., a PLB
400 or MVID 300) may then determine the loss of the span. After
determining the loss of the span, the software program stored in
the memory of the controller of the PLB 400 may then execute the
algorithms above in order to set the output gain and power of the
amplifier and transmitter. The tone(s) may be transmitted at
installation, periodically, when the error rate exceeds a
predetermined threshold, or upon receiving a command from the CMTS
110 (of the AP 100) or PLS.
[0125] In one example embodiment the PLB 400 may implement a UGA
(Upstream Gain Alignment) process. The upstream amplifier 415,
shown in FIG. 12A, of a given PLB 400 may be adjustable or
programmable to adjust the gain of upstream communications and be
set according to the UGA process before the communication of data.
FIG. 12B shows a process 500 for setting the gain for each upstream
amplifier 415 among a series of PLB 400 devices coupled to a URD
cable for communications with an MVID 300. Such a configuration,
for example, is illustrated by the series of PLBs 400a-400d coupled
to various segments of the URD cable for communications with a MVID
300c depicted in FIG. 9. The process also may be applied for other
embodiments wherein one device is amplifying data for another
device and may also be transmitting data as well.
[0126] In one embodiment the CMTS 110 of an AP 100 or a PLS may
transmit a command to a given PLB 400 (e.g., a PLB 400 at the end
of a MV URD cable) to commence an upstream gain alignment
procedure. In another embodiment, a specific PLB 400 may make a
determination to perform the process by executing program code
(e.g., at boot up or at other programmed times or events). In one
example, the most remote PLB 400d relative to a given MVID 300 may
determine to (or be commanded to) transmit a tone upstream to a
next PLB 400c. In this embodiment a multi-carrier tone signal is
transmitted. The multiple carriers may encompass each carrier among
the frequency band used for upstream communications. In turn, each
PLB 400 performs the process 500.
[0127] As discussed, in some embodiments the PLBs 400 may amplify
data signals received from more PLBs more distant from the MVID
300. However, the length of the URD cable segment between each PLB
will vary and therefore the loss suffered by data signals over each
cable segment will often vary. The amplification that each PLB 400
can provide may be limited by the isolation that can be provided by
its couplers 420. In other words, if a PLB 400 were to amplify a
data signal too much (i.e., with more power than can be isolated by
the PLB's couplers 420), the data signal may bleed through the
distribution transformer from the upstream coupler and be received
by the downstream coupler causing an undesirable feedback loop. In
other embodiments, the amplification also (or instead) may be
limited by government (FCC) regulations and/or the capabilities of
the amplification circuitry. In many instances, the upstream data
signal may be too bursty to rely on conventional AGC circuitry.
Thus, the UGA process allows the system to set the amplification
gain or one or more PLBs.
[0128] Referring to FIG. 12b, at step 502 a given PLB 400 may
receive the multi-carrier tone signal from the downstream segment
of the power line. The signal may be transmitted from an adjacent
PLB 400 that is more distant along the URD cable. The receiving PLB
400 may perform a plurality of steps (e.g., steps 504-508) to set
the gain of its upstream amplifier 415. At step 504, a target
amplification for the received signal is determined. For example,
the target amplification may be the gain which would increase the
power of the received signal up to, or approximating, a maximum
communication signal power level permitted by government
regulations (e.g., the FCC). At step 506, a maximum amplification
is determined. For example, the maximum amplification may be
determined by a maximum isolation (i.e., the minimum attenuation)
of data signals between the first and second segments of the power
line, which is largely dependent on the isolation that can be
provided by the couplers 420 (i.e., the attenuation between the
input of the two couplers 420 from the transformer side). In
another embodiment, the maximum amplification may be based on the
amplification that can by provided by the amplifier circuitry or
based on other factors. The maximum amplification may be stored in
memory and retrieved by the controller 470 to perform step 506.
This value may be changed via commands and data received from the
PLS or other remote computer system. At step 508, the amplification
gain for amplifier 415 is set to equal the lesser of the target
amplification and the maximum amplification. The amplified
multi-carrier signal (amplified to an amplifier output power) then
may be coupled to the upstream segment of the power line for
reception by the next upstream PLB 400, which in turn performs the
procedure 500. Eventually each of the PLB 400 devices in a series
of devices performs the steps 502-508 of procedure 500. The gain
alignment procedure thus ensures that the series of PLB 400 devices
may effectively communicate data within regulatory and system
constraints.
[0129] As discussed, the amplified tone signal will have an
amplified output power, which is the power of the amplified tone
signal (and subsequently the power of the data signals) that is
coupled to the upstream segment of the power line. Generally, this
power will approximate the transmission power of the signal (from
the transmitting PLB) minus the cable loss of the segment (and
coupler loss) plus the amplification power added by amplifier 415.
At step 509, the transmission power of the PLB 400 is set to be
substantially equal to the power of the amplified output power (as
set by the UGA process). Referring to FIG. 12a, the transmission
power may be set to the amplified output power by adjusting the
gain of amplifier 417 or, in another embodiment, by determining the
attenuation to apply to a transmission signal. In another
embodiment, the data signals are coupled back onto the same power
line segment and permitted to traverse through the transformer to
the other segment. This embodiment may also translate the frequency
(i.e., shift the carriers used to communicate the data) so that the
received signals are in a different band than the amplified and
transmitted data signals.
[0130] At step 510, user data may be received at a given PLB 400
from a LV power line (e.g., received from the LV power line via
coupler 440, conditioner 460, and LV modem 450 shown in FIG. 13).
At step 512 the user data may be transmitted upstream to a next PLB
400, or to an MVID 300, using the transmission power set at step
509.
[0131] Thus, upstream communications may be received from a
downstream PLB 400 via a downstream segment of a URD cable or from
customer premises via a LV power line. The communications from a
customer premises may be modulated by the QAM modulator 481 (see
FIG. 12A), then amplified by amplifier 417 before being coupled to
the URD cable for upstream communication. Because the amplification
gain of amplifier 417 is adjusted to achieve a transmission power
approximating the amplified output power of data signals amplified
by amplifier 415, amplified data signals and transmitted data
signals typically will be coupled to the upstream segment of the
power line, and received by the next upstream PLB 400 (or MVID
300), with substantially the same power.
[0132] One might expect a system would be designed so that the
transmission power (e.g., output of amplifier 417) would be the
maximum allowable by government regulations. However, in many
instances the amplified output power (output from amplifier 415)
may be set to be less than the maximum allowable by government
regulations by the UGA process. If the transmission power and
amplified output power were different, the next upstream PLB would
be amplifying data signals that are received with different power
levels, which would be undesirable. It is worth noting that
although the amplifiers 415 and 417 among the series of PLB 400
devices have their gains set, the gain for each respective
amplifier 415 and amplifier 417 may vary among the PLBs 400 (e.g.,
due to the varying lengths of URD cable segments connecting the PLB
devices).
[0133] In some embodiments, a downstream gain alignment to set the
gain of amplifier 413 may be used that includes substantially the
same steps as those of the UGA shown in FIG. 12b. After the
downstream gain alignment, there typically would be no need to set
a transmission power because, in this embodiment, the PLB devices
do not transmit communications downstream (i.e., they only amplify
data signals downstream). In another embodiment the results of the
upstream gain alignment for a given PLB 400 may be used to
determine the gain for the downstream amplifier 413 of the PLB or
of another PLB 400. As will be to those skilled in the art, some
carrier frequencies may be amplified more or less than other
frequencies.
[0134] As shown in FIG. 13, in addition to the through section
shown in FIG. 12A, the PLB 400 also includes a processing section
that includes a MV modem 480, a controller/router 470, a LV power
line coupler 440, a LV signal conditioner 460, and a LV modem
450.
[0135] Upstream data from the user devices will be supplied to the
through section via the modulator 480 as discussed below. In this
embodiment, all the downstream data from the URD cable may be
filtered, and demodulated for processing by the PLB 400. If the
data signals are successfully demodulated, they may be transmitted
to the appropriate user device.
[0136] The PLB 400 is controlled by a programmable processor and
associated peripheral circuitry, which form part of the controller
470. The controller 470 includes memory that stores, among other
things, program code, which controls the operation of the
processor. The controller and modem may be integrated. In this
embodiment, the controller may executes the steps for implementing
the UGA process.
[0137] The router forms part of the controller 470 and performs
routing functions. The router may perform routing functions using
layer 3 data (e.g., IP addresses), layer 2 data (e.g., MAC
addresses), or a combination of layer 2 and layer 3 data (e.g., a
combination of MAC and IP addresses). In addition to routing, the
controller 470 may perform other functions including controlling
the operation of the modems. A more complete description of the
controller 470 and its functionality is described below. (A router
as used herein may include a bridge or switch unless otherwise
indicated expressly or by the context of surrounding text.)
[0138] The controller 470 may receive and respond to commands
originating from the PLS. The MV modem 480, which may be a cable
modem (e.g., a CableLabs Certified Cable Modem), may receive and
respond to DOCSIS commands that may originate from the CMTS 110 of
the AP 100. For example, the CMTS may transmit a command (e.g.,
using the format and protocol defined by a DOCSIS specification)
directing the MV modem 480 of the PLB 400 to use a particular
upstream channel (e.g., frequency band). In response to the
command, the MV modem 480 may send and an acknowledgment (and/or
otherwise respond according to the DOCSIS specification) and use
the designated upstream channel for future communications. The MV
modem 480 may receive and process, and respond as appropriate, any
of the DOCSIS commands that may be useful for the application. In
some embodiments, the MV modem 480 need not be able to process
every DOCSIS command defined in the DOCSIS specification. The
commands processed by the controller 470 are described below.
Communications between the PLS and the controller 470 of the PLB
400 may employ Simple Network Management Protocol (SNMP). In
addition, the PLS may transmit a command to the controller 470 of
the PLB 400 instructing the controller 470 to control or modify the
operation of the MV modem 480. For example, the PLS may transmit an
instruction to the controller 470 to cause the MV modem 480 to
transmit the tone(s) described above in order to set the output
gain and transmission power levels.
[0139] As discussed, this embodiment of the present invention
provides bi-directional communications to thereby provide a first
communications path from the LV power line to the MV power line and
a second path from the MV power line to the LV power line. For ease
of understanding, the processing, and functional components of a
communication path from the LV power line to the MV power line (the
LV to MV path) will be described first. Subsequently, the
processing and functional components of the communication path from
the MV power line to the LV power line (the MV to LV path) will be
described.
[0140] As will be evident to those skilled in the art, the two
paths are logical paths. The LV to MV path and the MV to LV path
may be separate physical electrical paths at certain functional
blocks and may be the same physical path in other functional
blocks. However, other embodiments of the present invention may
provide for a completely, or substantially complete, separate
physical path for the LV to MV and the MV to LV paths.
LV Power Line to MV Power Line Path
[0141] In the United States, the LV power line typically includes a
neutral conductor and two conductors carrying current ("energized")
conductors. In the United States, the two energized conductors
typically carry about 120V alternating current (AC) at a frequency
of 60 Hz and are 180 degrees out of phase with each other. The
present invention is suitable for LV power line cables having
conductors that are spaced apart or that are coupled together
(e.g., in a twisted pair or via the conductor insulation).
[0142] LV Coupler
[0143] The LV power line coupler 440 couples data to and from the
LV power line and may include a transducer. The coupler 440 also
may couple power from the LV power line, which is used to power at
least a portion of the PLB 400. In this embodiment, the electronics
of much of the PLB 400 is housed in an enclosure with first and
second PLB 400 cables extending from the enclosure. The first PLB
400 cable includes a twisted pair of conductors including a signal
conductor and neutral conductor. The first conductor of the first
PLB 400 cable is connected to one of the energized LV conductors
extending from the transformer and the second conductor of the
first PLB 400 cable is connected to the neutral conductor extending
from the transformer. In this embodiment, clamping the PLB 400
conductors to the LV power line conductors makes the
connection.
[0144] The second PLB 400 cable extending from the enclosure is
also a twisted pair comprised of a first and second conductor. The
first conductor of the second PLB 400 cable is connected to the
neutral conductor extending from the transformer and the second
conductor of the second PLB 400 cable is connected to the second
(other) energized LV conductor extending from the transformer.
[0145] The third PLB 400 cable is a ground conductor that may be
connected to an earth ground, which typically is an earth ground
conductor that connects the transformer housing to a ground rod.
The neutral conductor of the LV power line may also be connected to
the earth ground of the power line system (by the electric power
company). However, there may be an intrinsic RF impedance between
the PLB 400 ground conductor connection and the LV neutral
conductor connections of the PLB 400 (i.e., the second conductor of
the first PLB 400 cable and the first conductor of the second PLB
400 cable). Additionally, it may be desirable to add an RF
impedance (e.g., an RF choke) between the connections.
[0146] In other embodiments, the LV coupler 410 may include a
transducer and may be an inductive coupler such as toroid coupling
transformer or a capacitive coupler, for coupling data to and/or
from the LV power line and/or for coupling power from the LV power
line.
[0147] In this embodiment, the signals entering the PLB 400 via the
first and second PLB 400 cables (hereinafter the first signal and
second signal respectively) are processed with conventional
transient protection circuitry, which is well-known to those
skilled in the art. Next, the first signal and second signal are
processed with voltage translation circuitry. The data signals in
this embodiment, which are in the 4.5 to 21 MHz HomePlug 1.0 band,
"ride on" (i.e., are additive of) the low frequency power signal
(the 120V 60 Hz voltage signal). Consequently, in this embodiment,
it is desirable to remove the low frequency power signal, but to
keep the data signals for processing, which is accomplished by the
voltage translation circuitry. The voltage translation circuitry
may include a high pass filter to remove the low frequency power
signal and may also (or instead) include other conventional voltage
translation circuitry.
[0148] Next, the first and second signals may be processed with
impedance translation circuitry, which is well-known in the art. In
this embodiment, it is desirable to substantially match the
impedance of the LV power line. One method of matching the
impedance of the LV power line is to separately terminate the PLB
400 LV conductors of the first and second PLB 400 cables through a
termination resistor to ground. The value of the termination
resistor may be selected to match the characteristic impedance of
the LV power line.
[0149] The electronics of the PLB 400 may be powered by power
received from the LV power line. Thus, this embodiment of the PLB
400 includes a power supply for powering much of the PLB 400
electronics. The power supply may include its own transient
protection circuitry, which may be in addition to, or instead of,
the transient protection circuitry that processes the data signals
described above. Thus, the power supply may receive power from the
PLB 400 LV conductor of the first (or second) PLB 400 cable after
the power signal passes through the transient protection
circuitry.
[0150] In addition to the power supply, the PLB 400 may include a
battery backup for operating the PLB 400 during power outages.
Thus, a backup power system (which may include a battery) may allow
the device to detect a power outage and communicate information
relating to the outage to the utility company and/or PLS. In
practice, information of the outage may be transmitted to the PLS,
which communicates the location, time, and/or other information of
the outage to the power utility (e.g., the utility's computer
system). The backup power system also may allow the PLB 400 to
communicate certain data packets during a power outage. For
example, during an outage, the PLB 400 may be programmed to
communicate all voice data, only emergency voice transmissions
(e.g., phone calls dialed to 911), or a notice of the power
outage.
[0151] LV Signal Conditioner
[0152] The data signals are received via the transmit/receive
circuitry, examples of which (as well as other circuitry) are shown
in FIGS. 14b and c and are discussed below. As shown in FIG. 14a,
after passing through the transmit/receive circuitry and LV
transmit/receive switch 426 (which would be in receive mode) the
first signal (comprising data signals from the PLB 400 LV conductor
of the first cable) is supplied to a first filter 421a that has a
pass band of approximately 4.0 to 10 MHz. The second signal
(comprising data signals from the PLB 400 LV conductor of the
second PLB 400 cable) is supplied to a second filter 421b that has
a pass band of approximately 10-21 MHz. Each of these filters 421
provides pass band filtering and may also provide anti-aliasing
filtering for their respective frequency bands, and noise
filtering.
[0153] The outputs of the first and second filters 421a-b are
supplied to a first amplifier 422a and second amplifier 422b,
respectively. The outputs of the first and second amplifiers 422a-b
are coupled to a first feedback device 423a and a second feedback
device 423b, respectively. Each feedback device 423 measures the
power over time and supplies the power measurement to the
controller 470. Based on the power measurement, the controller 470
increases, decreases, or leaves the gain of the associated
amplifiers the same to provide automatic gain control (AGC). The
outputs of the first and second amplifiers 422 are also supplied to
a summation device 424 that sums the two pass band, amplified
signals to provide a single data signal.
[0154] Thus, the gain of the second amplifier 422b, which receives
signals in the 10-21 MHz band, may be greater (or may be
dynamically made greater) than the gain of the first amplifier
422a, which receives signals in the 4.5 to 10 MHz band. The higher
gain of the second amplifier filter 422b can thus compensate for
the greater loss of the transmission channel at the higher
frequencies.
[0155] In this embodiment, the amplification by the amplifiers 422
is accomplished by amplifying the signal a first predetermined
amount, which may be the same or different (e.g., such as
proportional to the anticipated loss of the channel) for each
amplifier. The amplified signal is then attenuated so that the
resultant amplified and subsequently attenuated signal is at the
appropriate amplification with respect to the original signal,
which may be determined by controller 470 from information received
by the feedback devices 423. The feedback device 423 may be
implemented with suitable feedback architecture, well-known to
those skilled in the art. For example, the feedback devices 423 may
use both hardware (such as feedback that may be provided by an
analog to digital converter) and software (such as in modifying the
reference voltage supplied to an operational amplifier that is
implementing the amplifier 422).
[0156] Other embodiments may not include filtering the inputs of
the two PLB 400 LV conductors at separate pass bands and separately
amplifying the filtered signals. Instead, the signal may be
filtered and amplified across the entire LV power line
communication pass band (e.g., from 4.5 to 21 MHz). Similarly,
while this embodiment divides the LV power line communication
channel into two bands (for filtering, amplifying and summing),
other embodiments may similarly divide the LV power line
communication channel into three, four, five or more bands (for
filtering, amplifying and summing). In another embodiment the LV
signal conditioning could be implemented using an equalizer with a
slope of attenuation/gain versus frequency that is the inverse of
the cable loss (i.e. cable equalization).
[0157] LV Modem
[0158] The LV modem 450 may include a modulator and demodulator.
The LV modem 450 also may include one or more additional functional
submodules such as an Analog-to-Digital Converter (ADC),
Digital-to-Analog Converter (DAC), a memory, source
encoder/decoder, error encoder/decoder, channel encoder/decoder,
MAC (Media Access Control) controller, encryption module, and
decryption module. These functional submodules may be omitted in
some embodiments, may be integrated into a modem integrated circuit
(chip or chip set), or may be peripheral to a modem chip. In the
present example embodiment, the LV modem 450 is formed, at least in
part, by part number INT5130, which is an integrated power line
transceiver circuit incorporating most of the above-identified
submodules, and which is manufactured by Intellon, Inc. of Ocala,
Fla. Thus, the modem may be a HomePlug compatible (1.0 or AV)
modem.
[0159] The incoming signal is supplied to an ADC to convert the
incoming analog signal to a digital signal. The digital signal is
then demodulated. The LV modem 450 then provides decryption, source
decoding, error decoding, channel decoding, and media access
control (MAC) all of which are known in the art and, therefore, not
explained in detail here.
[0160] With respect to MAC, however, the LV modem 450 may examine
information in the packet to determine whether the packet should be
ignored or passed to the router. For example, the modem 450 may
compare the destination MAC address of the packet with the MAC
address of the LV modem 450 (which is stored in the memory of the
LV modem 450). If there is a match, the LV modem 450 removes the
MAC header of the packet and passes the packet to the router. If
there is not a match, the packet may be ignored.
[0161] Router
[0162] The data packets from the LV modem 450 may be supplied to
the router, which forms part of the controller 470. The router
performs prioritization, filtering, packet routing, access control,
and encryption. The router of this example embodiment of the
present invention uses a table (e.g., a routing table) and
programmed routing rules stored in memory to determine the next
destination of a data packet. The table is a collection of
information and may include information relating to which interface
(e.g., LV or MV) leads to particular groups of addresses (such as
the addresses of the user devices connected to the customer LV
power lines), priorities for connections to be used, and rules for
handling both routine and special cases of traffic (such as voice
packets and/or control packets).
[0163] The router will detect routing information, such as the
destination address (e.g., the destination IP address) and/or other
packet information (such as information identifying the packet as
voice data), and match that routing information with rules (e.g.,
address rules) in the table. The rules may indicate that packets in
a particular group of addresses should be transmitted in a specific
direction such as through the LV power line (e.g., if the packet
was received from the MV power line and the destination IP address
corresponds to a user device connected to the LV power line),
repeated on the MV line (e.g., if the PLB 400 is acting as a
repeater), or be ignored (e.g., if the address does not correspond
to a user device connected to the LV power line or to the PLB 400
itself).
[0164] As an example, the table may include information such as the
IP addresses (and potentially the MAC addresses) of the user
devices on the PLB's LV subnet, the MAC addresses of the power line
modems on the PLB's LV subnet, the MV subnet mask (which may
include the MAC address and/or IP address of the PLBs 400, DP 200
(if any) or AP 100 (if any)), and the IP address of the LV modem
450 and MV modem 480. Based on the destination IP address of the
packet (e.g., an IP address), the router may pass the packet to the
MV modem 480 for transmission on the MV power line. Alternately, if
the IP destination address of the packet matches the IP address of
the PLB, the PLB 400 may process the packet as a request for
data.
[0165] In other instances, such as if the user device is not
provisioned and registered, the router may prevent packets from
being transmitted to any destination other than a DNS server or
registration server of the PLCS operator. In addition, if the user
device is not registered, the router may replace any request for a
web page received from that user device with a request for a web
page on the registration server (the address of which is stored in
the memory of the router) of the operator of the PLCS.
[0166] The router may also prioritize transmission of packets. For
example, data packets determined to be voice packets may be given
higher priority for transmission through the PLB 400 than data
packets so as to reduce delays and improve the voice connection
experienced by the user. Routing and/or prioritization may be based
on IP addresses, MAC addresses, subscription level, or a
combination thereof (e.g., the MAC address of the power line modem
or IP address of the user device).
[0167] MV Modem
[0168] Similar to the LV modem 450, the MV modem 480 receives data
from the router and includes a modulator and demodulator. In
addition, the MV modem 280 also may include one or more additional
functional submodules such as an ADC, DAC, memory, source
encoder/decoder, error encoder/decoder, channel encoder/decoder,
MAC controller, encryption module, and decryption module. These
functional submodules may be omitted in some embodiments, may be
integrated into a modem integrated circuit (chip or chip set), or
may be peripheral to a modem chip. In this example embodiment the
MV modem may be comprised of a DOCSIS compliant modem (e.g., DOCSIS
2.0), which may be a cable modem (e.g., a CableLabs Certified Cable
Modem).
[0169] The modem may employ QAM digital modulation such as QPSK,
16, 64, and/or 256-QAM. Different digital modulation formats may be
used for downstream and upstream channels. Downstream channels may
use 64 or 256 QAM, while upstream channels may use QPSK, or 16 or
64 QAM. In one embodiment, and as discussed above, three downstream
channels may be used, with each having a bandwidth of approximately
6 MHz and located in the 30-50 MHz band. The band has been found to
have less noise from consumer appliances and less interference from
higher frequency television bands. One channel may centered at
approximately 32.7 MHz which as been found to have a lower cable
loss than some other frequencies. The upstream channels, which may
comprise three or more channels, may be in the available spectrum
between 72 MHz and 76 MHz.
[0170] In another embodiment, the MV modem 480 is formed, at least
in part, by part number INT5130, which is an integrated power line
transceiver circuit incorporating most of the identified submodules
and which is manufactured by Intellon, Inc. of Ocala, Fla.
[0171] The incoming signal from the router (i.e., the controller)
is supplied to the MV modem 480, which may provide MAC processing,
for example, by adding a MAC header that includes the MAC address
of the MV modem 480 as the source address and the MAC address of
the upstream device as the destination MAC address. In addition,
the MV modem 480 also may provide channel encoding, source
encoding, error encoding, and encryption. The data is then
modulated and provided to the DAC to convert the digital data to an
analog signal.
[0172] First MV Signal Conditioner
[0173] The modulated analog signal from the MV modem 480 is
provided to first MV signal conditioner (not shown), which may
provide filtering (anti-alias, noise, and/or band pass filtering)
and amplification. In addition, the MV signal conditioner 260 may
provide frequency translation. In this embodiment, translation of
the frequency is accomplished through the use of a local oscillator
and a conversion mixer. This method and other methods of frequency
translation are well known in the art and, therefore, not described
in detail.
[0174] As is known in the art, frequency translation may result in
a first and second image of the original frequency although in some
instances, such as in the present embodiment, only one of the two
images is desired. Thus, the frequency translation circuitry may
include an image rejection filter to filter out the undesired image
leaving only the desired frequency bandwidth, which in this
embodiment is the higher frequency band of the MV power line.
[0175] The output of the MV signal conditioning circuitry is
supplied to the through portion of the PLB 400 shown in FIG. 12A.
In summary, the output of the MV signal conditioning circuitry may
be supplied to an amplifier and combiner and then coupled onto the
URD MF power line to conduction to the MVID 300 (perhaps via other
PLB 400 through portions).
[0176] MV Power Line Coupler
[0177] The coupling device couples the data onto the URD MV power
line. The coupling device may be inductive, capacitive, conductive,
a combination thereof, or any suitable device for communicating
data signals to and/or from the MV power line. In this example
embodiment, the MV coupler is a three port device, with a first
port coupling data to the PLB 400, a second port coupling power
signals to or from the distribution transformer (while impeding or
filtering data signals), and a third port coupling both data and
power to the URD MV power line. Thus, the first port may include a
high pass filter to permit the data signals to pass, but to impede
the lower frequency power signals. The second port may comprise a
low pass filter (or high frequency attenuator) to allow the low
frequency power signals to pass substantially unimpeded. Thus, the
two URD MV power cables connected to the transformer may be
considered separate communication channels. One example of such a
coupler is described in U.S. application Ser. No. 10/947,929 filed
Sep. 23, 2004, entitled "Power Line Coupling Device and Method of
Using the Same," which is hereby incorporated by reference in its
entirety.
[0178] Path from MV Power Line to LV Power Line
[0179] As discussed the MV power line coupler also receives data
signals from the MV power line via a coupling device, which may
take the form of any of those coupling devices described above. The
data signals from the MV coupler may pass through transient
suppression circuitry, and impedance translation circuitry. In
addition, the signals traverse the diplexer 410a, the LNA, the
bandpass filter, and the splitter of the thru section of the PLB
400 to be received by the MV modem 480 as shown in FIG. 12A.
[0180] MV Modem
[0181] The MV modem 480 and LV modem 450 provide a bidirectional
path and form part of the MV to LV path and the LV to MV path. The
components of the MV modem 480 have been described above in the
context of the LV to MV path and are therefore not repeated here.
The incoming signal may be supplied to the ADC to convert the
incoming analog signal to a digital signal. The digital signal is
then demodulated. The modem then provides decryption, source
decoding, error decoding, and channel decoding all of which are
known in the art and, therefore, not explained in detail here.
[0182] The MV modem 480 also provides MAC processing through the
use of MAC addresses. In one embodiment employing the present
invention, the MAC address is used to direct data packets to the
appropriate device. The MAC addresses may provide a unique
identifier for one or more of the devices on the PLC network
including, for example, user devices, PLBs, power line modems,
repeaters (if any), MVIDs 300, DPs 200, and APs 100. However, in
some implementation, some of these network elements may not have an
address (e.g., a MVID).
[0183] The routing upstream device (e.g., a MVID, DP 200 or AP 100)
may determine the MAC address of the MV modem 480 of the PLB 400
servicing the user device. The information for making this
determination may be stored in a table in the memory of the
upstream device. The upstream device may remove the MAC header of
the packet and add a new header that includes the MAC address of
the transmitting device (as the source address) and the MAC address
of the PLB 400 (the destination address)--or more specifically, the
MAC address of the MV modem 280 of the destination PLB.
[0184] Thus, in this embodiment, packets destined for a user device
on a LV subnet of a PLB 400 (or to the PLB) are addressed to the
MAC address of the MV modem 480 of the PLB 400 and may include
additional information (e.g., the destination IP address of the
user device) for routing the packet to devices on the PLB's LV
subnet.
[0185] If the destination MAC address of the received packet does
not match the MAC address of the MV modem 480, the packet may be
discarded (ignored). If the destination MAC address of the received
packet does match the MAC address of the MV modem 480, the MAC
header may be removed from the packet and the packet is supplied to
the router for further processing.
[0186] There may be a different MAC sublayer for each physical
device type such as for user devices and PLCS network elements
(which may include any subset of devices such as MVIDs 300, PLBs
400, repeaters, DPs 200, and aggregation points 100).
[0187] Router
[0188] As discussed above, upon reception of a data packet, the MV
modem 480 of a PLB 400 will determine if the destination MAC
address of the packet matches the MAC address of the MV modem 480
and, if there is a match, the packet is passed to the router. If
there is no match, the packet is discarded.
[0189] In this embodiment, the router analyzes packets having a
destination IP address to determine the destination of the packet
which may be a user device or the PLB 400 itself. This analysis
includes comparing the information in the packet (e.g., a
destination IP address) with information stored in memory, which
may include the IP addresses of the user devices on the PLB 400 LV
subnet. If a match is found, the router routes the packet through
to the LV modem 450 for transmission on the LV power line. If the
destination IP address matches the IP address of the PLB, the
packet is processed as a command or data intended for the PLB 400
(e.g., by the Command Processing software described below) and may
not be passed to the LV modem 450.
[0190] The term "router" is sometimes used to refer to a device
that routes data at the IP layer (e.g., using IP addresses). The
term "switch" is sometimes used to refer to a device that routes at
the MAC layer (e.g., using MAC addresses). Herein, however, the
terms "router", "routing", "routing functions" and the like are
meant to include both routing at the IP layer and MAC layer.
Consequently, the router of the present invention may use MAC
addresses instead of, or in addition to, IP addresses to perform
routing functions.
[0191] For many networks, the MAC address of a network device will
be different from the IP address. Transmission Control Protocol
(TCP)/IP includes a facility referred to as the Address Resolution
Protocol (ARP) that permits the creation of a table that maps IP
addresses to MAC addresses. The table is sometimes referred to as
the ARP cache. Thus, the router may use the ARP cache or other
information stored in memory to determine IP addresses based on MAC
addresses (and/or vice versa). In other words, the ARP cache and/or
other information may be used with information in the data packet
(such as the destination IP address) to determine the routing of a
packet (e.g., to determine the MAC address of the power line modem
communicating with the user device having the destination IP
address).
[0192] In an alternate embodiment using IP address to route data
packets, all packets received by the MV modem 480 may be supplied
to the router. The router may determine whether the packet includes
a destination IP address that corresponds to a device on the PLB's
LV subnet (e.g., an address corresponding to a user device address
or the PLB's address). Specifically, upon determining the
destination IP address of an incoming packet, the router may
compare the identified destination address with the addresses of
the devices on the subnet, which are stored in memory. If there is
a match between the destination address and the IP address of a
user device stored in memory, the data is routed to the LV power
line for transmission to the user device. If there is a match
between the destination address and the IP address of the PLB 400
stored in memory, the data packet is processed as a command or
information destined for the PLB.
[0193] In addition, the router may also compare the destination
address with the IP address of the upstream device, other PLBs. If
there is no match between the destination address and an IP address
stored in memory, the packet is discarded (ignored).
[0194] According to any of these router embodiments, if the data is
addressed to an address on the PLB's LV, the router may perform any
or all of prioritization, packet routing, access control,
filtering, and encryption.
[0195] As discussed, the router of this example embodiment of the
present invention may use a routing table to determine the
destination of a data packet. Based on information in the routing
table and possibly elsewhere in memory, the router routes the
packets. For example, voice packets may be given higher priority
than data packets so as to reduce delays and improve the voice
connection experienced by the user. The router supplies data
packets intended for transmission along the LV power line to the LV
modem 450.
[0196] LV Modem
[0197] The functional components of the LV Modem 450 have been
described above in the context of the LV to MV path and, therefore,
are not repeated here. After receiving the data packet from the
router, the LV modem 450 provides MAC processing, which may
comprise adding a MAC header that includes the source MAC address
(which may be the MAC address of the LV modem 450) and the
destination MAC address (which may be the MAC address of the power
line modem corresponding to the user device identified by the
destination IP address of the packet).
[0198] To determine the MAC address of the power line modem that
provides communications for the user device identified by the
destination IP address of the packet, the LV modem 450 first
determines if the destination IP address of the packet is an IP
address stored in its memory (e.g., stored in its bridging table).
If the IP address is stored in memory, the LV modem 450 retrieves
the MAC address for communicating with the destination IP address
(e.g., the MAC address of the power line modem) from memory, which
will also be stored therein. If the IP address is not stored in
memory, the LV modem 450 transmits a request to all the devices to
which it is coupled via the low voltage power line (e.g., all the
power line modems). The request is a request for the MAC address
for communicating with the destination IP address of the packet.
The device (e.g., the power line modem) that has the MAC address
for communicating with the destination IP address will respond by
providing its MAC address. The LV modem 450 stores the received MAC
address and the IP address for which the MAC address provides
communications in its memory (e.g., in its bridging table). The LV
modem 450 then adds the received MAC address as the destination MAC
address for the packet.
[0199] The packet is then channel encoded, source encoded, error
encoded, and encrypted. The data is then modulated and provided to
the DAC to convert the digital data to an analog signal.
[0200] LV Signal Conditioner
[0201] The output of the LV modem 450 is provided to the LV signal
conditioner 460, which conditions the signal for transmission.
Knowing (or determining) the frequency response (or loss) of the LV
power line transmission channel allows the device to predistort or
pre-emphasize signals prior to transmission to compensate for
anticipated losses at certain frequencies or frequency ranges.
During and/or prior to transmission, the amount of amplification
necessary for particular frequency ranges may be periodically
determined according to methods known in the art to provide dynamic
predistortion (i.e., changing the amount of amplification of all or
portions (e.g., frequencies or frequency ranges) of the signal over
time of the transmitted signal. The determination of the desired
amount of amplification may, for example, be determined and/or
relate to the amount of amplification performed by amplifiers in
the LV to MV path. Alternately, the amplification may be
characteristic for a particular type of channel (e.g., overhead or
underground), or measured for a channel, and the predistortion thus
may be fixed (preprogrammed and/or hardwired into the device).
[0202] In this embodiment, signals at higher frequencies are
amplified more than signals at lower frequencies to compensate for
the anticipated greater loss at the higher frequencies. As shown in
FIG. 14a, the signal to be transmitted is amplified with an
amplifier that provides greater amplification at higher frequencies
of the 4.5 to 21 MHz band. Such amplifiers are well-known to those
skilled in the art. The amplifier may have a transfer function
substantially inverse to the frequency response of the LV
transmission channel. Once amplified and filtered, the signal is
conducted through switch 426 to the LV power line coupler 440 for
transmission on the energized LV conductors of the LV power line.
Of course, in alternate embodiments the transmission may not be
predistorted and may be filtered and amplified substantially the
same across the transmission channel.
[0203] FIG. 14b illustrates the transmit circuit used to drive the
data signal (indicated by Vs). Components to the left of the dashed
line in FIG. 14b may be inside the PLB 400 enclosure and those to
the right may be outside the PLB 400 enclosure. The transmit
circuit of this embodiment includes a transformer that drives the
two conductor pairs 436 and 437. Each conductor pair 436, 437 is
coupled to ground by impedance Z3, which may be resistive. In
addition, each conductor 436a,b and 437a,b includes a series
impedance Z1, which may be capacitive (e.g., providing a high pass
filter) and/or resistive.
[0204] As discussed, the first and second PLB 400 cables 436, 437
are each comprised of a twisted pair of conductors 436a,b and
437a,b. As will be evident to those skilled in the art, each
twisted pair cable 436, 437 will have an impedance (determined by
the geometry of the cable) as represented by Z2 in FIG. 14b. This
impedance Z2 may be modeled by a resistive component and an
inductive component. The inductive component also may cause
coupling between the two twisted conductors of each cable.
[0205] LV Power Line Coupler
[0206] In addition to the above, the LV power line coupler 410 may
include the impedance matching circuitry and transient protection
circuitry. The coupler 410 couples the data signal onto the LV
power line as described above for reception by a user device
communicatively coupled to the LV power line via a power line
modem.
[0207] After the LV energized conductors enter the customer
premises, typically only one LV energized conductor will be present
at each wall socket where a power line modem might be installed
(e.g., plugged in). Given this fact regarding the internal customer
premises wiring, there is no way to know to which LV energized
conductor the power line modem (and user device) will be connected.
In addition, the subscriber may move the power line modem and user
device to another socket to access the PLCS and the new socket may
be coupled to the second (different) LV energized conductor. Given
these facts, the network designer must supply communications on
both LV energized conductors and, therefore, would be motivated to
simultaneously transmit the PLC RF data signal on each LV energized
conductor referenced to the neutral conductor. However, in
comparison to transmitting the RF data signals on both energized
conductors referenced to the neutral, the following method of
providing communications on the LV energized has been found to
provide improved performance.
[0208] As shown in FIG. 14b, the first PLB 400 cable 436 is coupled
to the LV power line so that the data signal is applied to the
first LV energized conductor referenced to the LV neutral
conductor. The second PLB 400 cable 437 is coupled to the LV power
line so that the data signal (Vs) is applied to the neutral
conductor referenced to the second LV energized conductor. As a
result, the data signal is applied to the first and second LV
energized conductors differentially. In other words, with reference
to the neutral conductor, the voltage signal (representing the
data) on the second LV energized conductor is equal in magnitude
and opposite in polarity of the voltage on the first LV energized
conductor. Similarly, the current flow representing the data on the
second LV energized conductor will be the opposite of the current
flow on the first LV energized conductor in magnitude and
direction. It has been found that differentially driving the LV
energized conductors as described provides significant performance
improvements over methods, which may result from reduced
reflections, improved signal propagation, and impedance matching
among other things. It is worth noting the transmit circuit of this
and the following embodiments may transmit data signals with
multiple carriers (e.g., eighty or more) such as with using an
Orthogonal Frequency Division Multiplex (OFDM) modulation
scheme.
[0209] FIG. 14c illustrates another embodiment of a transmit
circuit for transmitting the data signal. Components to the left of
the dashed line in FIG. 14c may be inside the PLB 400 enclosure and
those to the right may be outside the PLB 400 enclosure. The
transmit circuit of this embodiment is comprised of a transformer
that drives one conductor pair 436, which traverse through a common
mode choke. The common mode choke provides a very low impedance to
differential currents in the two conductors 436a,b, but provides a
significant or high impedance to common mode currents (i.e.,
currents traveling in the same direction such as in or out). The
two conductors 436a,b may also be coupled to ground by an impedance
Z3, which may be a resistive impedance. In addition, each conductor
436a, b includes a series impedance Z1, which may be a capacitive
impedance, or other high pass filter component(s), for impeding the
60 Hz power signal and permitting the RF data signal to pass
unimpeded. Such impedances may be on either side of the common mode
choke, but are preferably on the LV power line side of the
choke.
[0210] In either embodiment, each conductor may also include a
surge protection circuit, which in FIG. 14c are shown as S1 and S2.
Finally, the cable 436 may be comprised of a twisted pair of
conductors between the PLB 400 enclosure and LV power line. As will
be evident to those skilled in the art, the twisted pair cable 436
may have an impedance (determined by the geometry of the cable) as
represented by Z2. This impedance Z2 may be modeled by a resistive
component and an inductive component. The inductive component also
may cause coupling between the two twisted wired conductors.
[0211] While not shown in the figures, the transmit circuit of
either embodiment may also include a fuse in series with each
conductor and a voltage limiting device, such as a pair of
oppositely disposed zener diodes, coupled between the pair of
conductors and may be located between the common mode choke and the
transformer. Finally, one of the conductors of the PLB 400 cable(s)
436 or 437 may used to supply power to the power supply of the PLB
400 to power the PLB.
[0212] It is worth noting that these embodiments of the present
invention drive the first and second LV energized conductors
differentially to transmit the data signal (e.g., using OFDM).
However, the power line modem transmits data signals from the
customer premises to the PLB 400 by applying the data signal to one
conductor (e.g., one energized conductor) referenced to the other
conductor such as a ground and/or neutral.
[0213] While in this embodiment the two energized conductors are
opposite in magnitude, other embodiments may phase shift the data
signal on one conductor (relative to the data signal on the other
conductor) by forty-five degrees, ninety degrees, one hundred
twenty degrees, one hundred eighty degrees, or some other value, in
addition to or instead of differentially driving the two
conductors.
[0214] Controller
[0215] As discussed, the controller 470 includes the hardware and
software for managing communications and control of the PLB. In
this embodiment, the controller 470 may include an IDT 32334 RISC
microprocessor for running the embedded application software and
also includes flash memory for storing the boot code, device data
and configuration information (serial number, MAC addresses, subnet
mask, and other information), the application software, routing
table, and the statistical and measured data. This memory includes
the program code stored therein for operating the processor to
perform the routing functions described herein. Other processors
may be used as well. In another embodiment, the controller may be
formed by the central processing unit of the cable modem.
[0216] This embodiment of the controller also includes random
access memory (RAM) for running the application software and
temporary storage of data and data packets. This embodiment of the
controller 470 also includes an Analog-to-Digital Converter (ADC)
for taking various measurements, which may include measuring the
temperature inside the PLB 400 (through a temperature sensor such
as a varistor or thermistor), for taking power quality
measurements, detecting power outages, measuring the outputs of
feedback devices, and others. The embodiment also includes a
"watchdog" timer for resetting the device should a hardware glitch
or software problem prevent proper operation to continue.
[0217] This embodiment of the controller 470 also includes an
Ethernet adapter, an optional on-board MAC and physical (PHY) layer
Ethernet chipset that can be used for converting peripheral
component interconnect (PCI) to Ethernet signals for communicating
with the backhaul side of the PLB. Thus, an RJ45 connector may
provide a port for a wireless transceiver (which may be a 802.11
compliant transceiver) for communicating wirelessly.
[0218] The PLB 400 also may have a debug port, such as a debug port
that can be used to connect serially to a portable computer. The
debug port preferably connects to any computer that provides
terminal emulation to print debug information at different
verbosity levels and can be used to control the PLB 400 in many
respects such as sending commands to extract all statistical,
fault, and trend data.
[0219] In addition to storing a real-time operating system, the
memory of controller 470 of the PLB 400 also includes various
program code sections such as a software upgrade handler, software
upgrade processing software, the PLS command processing software
(which receives commands from the PLS, and processes the commands,
and may return a status back to the PLS), the ADC control software,
the power quality monitoring software, the error detection and
alarm processing software, the data filtering software, the traffic
monitoring software, the network element provisioning software, and
a dynamic host configuration protocol (DHCP) Server for
auto-provisioning user devices (e.g., user computers) and
associated power line modems.
[0220] The router in this embodiment is not physically located
between the two modems, but instead all three devices--the router,
LV modem 450, and MV modem 280--are communicatively coupled
together via the bus. Consequently, in some instances (e.g., at the
occurrence of a particular event) the router may be programmed to
allow the LV modem 450 to pass data directly to the MV modem 280
and vice versa, without performing data filtering and/or the other
functions performed by the router which are described above.
[0221] This embodiment of the PLB 400 may only receive or transmit
data over the LV power line at any one instant. However, as will be
evident to those skilled in the art, the PLB 400 may transmit or
receive over the LV power line, while simultaneously transmitting
or receiving data over the MV power line and, depending on the
specific implementation, may be able to receive and transmit on the
MV side simultaneously (because those communications may use
different frequency bands). Upstream communications from each PLB
400 may be time division multiplexed, while downstream
communications may be broadcast (e.g., point to multi-point).
[0222] Any suitable frequency scheme may be used for communications
over the MV power line. For example, if only one downstream channel
is used (for communications from the MVID 300 to the PLBs), the
system may use a six megahertz (MHz) channel from 29.7 MHz to 35.7
MHz and employ 256 QAM. If additional channels are used, such
channels also may be six megahertz and be located between 36.85 MHz
to 42.85 MHz and another from 44 MHz to 50 MHz. The upstream power
line channel may be larger or smaller than the downstream channels.
For example, the upstream communications (from PLBs 400 to the
MVID) may be from 71.965 MHz to 74.835 MHz.
[0223] PLS Command Processing Software
[0224] The PLS and PLB 400 (or repeater) may communicate with each
other through two types of communications: 1) PLS Commands and PLB
400 responses, and 2) PLB 400 Alerts and Alarms. TCP packets are
used to communicate commands and responses. The commands typically
are initiated by the NEM portion of the PLS. Responses sent by the
PLB 400 (or repeater) may be in the form of an acknowledgement
(ACK) or negative acknowledgement (NACK), or a data response
depending on the type of command received by the PLB 400 (or
repeater).
[0225] Commands
[0226] The PLS may transmit any number of commands to the PLB 400
to support system control of PLB 400 functionality. As will be
evident to those skilled in the art, most of these commands are
equally applicable for repeaters. For ease of discussion, however,
the description of the commands will be in the context of a PLB 400
only. These commands may include altering configuration
information, synchronizing the time of the PLB 400 with that of the
PLS, controlling measurement intervals (e.g., voltage measurements
of the ADC), requesting measurement or data statistics, requesting
the status of user device activations, and requesting reset or
other system-level commands. Any or all of these commands may
require a unique response from the PLB, which is transmitted by the
PLB 400 (or repeater) and received and stored by the PLS.
[0227] Alerts
[0228] In addition to commands and responses, the PLB 400 (or
repeater) has the ability to send Alerts and Alarms to the PLS (the
NEM) via User Datagram Protocol (UDP), which does not require an
established connection but also does not guarantee message
delivery.
[0229] Alerts typically are either warnings or informational
messages transmitted to the NEM in light of events detected or
measured by the PLB. Alarms typically are error conditions detected
by the PLB. Due to the fact that UDP messages may not be guaranteed
to be delivered to the PLS, the PLB 400 may repeat Alarms and/or
Alerts that are critically important to the operation of the
device.
[0230] One example of an Alarm is an Out-of-Limit Alarm that
indicates that an out-of-limit condition and has been detected at
the PLB, which may indicate a power outage on the LV power line, a
temperature measurement inside the PLB 400 is too high, and/or
other out-of-limit condition. Information of the Out-of-Limit
condition, such as the type of condition (e.g., a LV voltage
measurement, a PLB 400 temperature), the Out-of-Limit threshold
exceeded, the time of detection, the amount (e.g., over, under,
etc.) the out of limit threshold has been exceeded, is stored in
the memory of the PLB 400 and may be retrieved by the PLS.
[0231] Software Upgrade Handler
[0232] The Software Upgrade Handler software may be started by the
PLS Command Processing software in response to a PLS command.
Information needed to download the upgrade, including for example
the remote file name and PLS IP address, may be included in the
parameters passed to this software module (or task) from the
Software Command Handler.
[0233] Upon startup, this task may open a file transfer program
such as Trivial File Transfer Protocol (TFTP) to provide a
connection to the PLS and request the file. The requested file is
then downloaded to the PLB. For example, the PLS may transmit the
upgrade through the Internet, through the backhaul point 10,
through the MV power line to the PLB 400 where the upgrade may be
stored in a local RAM buffer and validated (e.g., error checked)
while the PLB 400 continues to operate (i.e., continues to
communicate packets to and from power line modems and the backhaul
point 10). Finally, the task copies the downloaded software into a
backup boot page, and transmits an Alert indicating successful
installation to the PLS. A separate command transmitted from the
PLS, processed by the Command Processing software of the PLB, may
make the newly downloaded and validated program code the primary
software operating the PLB. If an error occurs, the PLB 400 issues
an Alert indicating the download was not successful.
[0234] ADC Scheduler
[0235] The ADC Scheduler software, in conjunction with the
real-time operating system, creates ADC scheduler tasks to perform
ADC sampling according to configurable periods for each sample
type. Each sample type corresponds with an ADC channel. The ADC
Scheduler software creates a scheduling table in memory with
entries for each sampling channel according to default
configurations or commands received from the PLS. The table
contains timer intervals for the next sample for each ADC channel,
which are monitored by the ADC scheduler.
[0236] Based on the measured voltages, the PLS may also determine
the location and/or area of a power outage. Periodically, the PLS
may ping each (or some subset of) network element. The
determination of a power outage may be made by a failure of a
network element to respond to the periodic ping (or other command
or request) transmitted by the PLS. If the network element has an
alternate power source such as a battery backup, the network
element may transmit a notification of the power outage (e.g.,
based on a low voltage measurement by the network element).
[0237] Based on the network element(s) serial number(s), the PLS
can retrieve the network element's physical location (such as its
pole number, which may be mapped to a longitude and latitude and/or
street address) from memory to determine the location of the power
outage. Thus, by determining that a number of network elements are
not responsive, the PLS may map an area without power. Information
of the power outage, such as the location(s) time, etc., may then
be transmitted to the utility company.
[0238] ADC Measurement Software
[0239] The ADC Measurement Software, in conjunction with the
real-time operating system, creates ADC measurement tasks that are
responsible for monitoring and measuring data accessible through
the ADC 330. Each separate measurable parameter may have an ADC
measurement task. Each ADC measurement task may have configurable
rates for processing, recording, and reporting for example.
[0240] An ADC measurement task may wait on a timer (set by the ADC
scheduler). When the timer expires the task may retrieve all new
ADC samples for that measurement type from the sample buffer, which
may be one or more samples. The raw samples are converted into a
measurement value. The measurement is given the timestamp of the
last ADC sample used to make the measurement. The measurement may
require further processing. If the measurement (or processed
measurement) exceeds limit values, an alarm condition may be
generated. Out of limit Alarms may be transmitted to the PLS and
repeated at the report rate until the measurement is back within
limits. An out of limit recovery Alert may be generated (and
transmitted to the PLS) when the out of limit condition is cleared
(i.e., the measured value falls back within limit conditions).
[0241] The measurements performed by the ADC 330, each of which has
a corresponding ADC measurement task, may include PLB 400 inside
temperature, LV power line voltage, LV power line current (e.g.,
the voltage across a resistor), AGC1 (corresponding to Feedback
device 423a), and AGC2 (corresponding to Feedback device 423a) for
example.
[0242] As discussed, the PLB 400 includes value limits for most of
these measurements stored in memory with which the measured value
may be compared. If a measurement is below a lower limit or above
an upper limit (or otherwise out of an acceptable range), the PLB
400 may transmit an Out-of-Limit Alarm, which is received and
stored by the PLS. In some instances, one or more measured values
are processed to convert the measured value(s) to a standard or
more conventional data value.
[0243] The measured data (or measured and processed data) is stored
in the memory of the PLB. This memory area contains a circular
buffer for each ADC measurement and time stamp. The buffers may be
read by the PLS Command Processing software task in response to a
request for a measurement report. The measurement data may be
backed up to flash memory by the flash store task.
[0244] The LV power line voltage measurement may be used to provide
various information. For example, the measurement may be used to
determine a power outage, or measure the power used by a consumer
or by all of the consumers connected to that distribution
transformer. In addition, it may be used to determine the power
quality of the LV power line by measuring and processing the
measured values over time to provide frequency, harmonic content,
and other power line quality characteristics.
[0245] Traffic Monitoring Software
[0246] The Traffic Monitoring software may collect various data
packet traffic statistics, which may be stored in memory including
the amount of data (i.e., packets and/or bytes) communicated (i.e.,
transmitted and received) through the MV power line, and/or through
the LV power line; the amount of data (packets and/or bytes)
communicated (transmitted and received) to and/or from the PLS; the
number of Alerts and Alarms sent to the PLS; the number of DHCP
requests from user devices; the number of failed user device
authentications; the number of failed PLS authentications; and the
number of packets and bytes received and/or transmitted from/to
each user device (or power line modem 50).
[0247] Data Filtering Software
[0248] The Data Filtering software provides filtering of data
packets transmitted to and/or from a user device (or power line
modem). The filtering criteria may be supplied from the PLS (which
may be based on requests received from the user) and is stored in
memory of the PLB 400 and may form part of the routing table. The
Data Filtering software may analyze the data packets and may
prevent the transmission of data packets through the PLB:1) that
are transmitted to the user device from a particular source (e.g.,
from a particular person, user, domain name, email address, or IP
or MAC source address); 2) that are transmitted from the user
device to a particular destination (e.g., to a particular person,
email address, user, domain name, or IP or MAC destination
address); 3) that have particular content (e.g., voice data or
video data); 4) based on the time of transmission or reception
(e.g., times of the day and/or days of the week); 5) that surpass a
threshold quantity of data (either transmitted, received, or
combination thereof) for a predetermined window of time (e.g., a
day, week, month, year, or subscription period); or 7) some
combination thereof.
[0249] Auto-Provision and Activation of Network Components
[0250] "Auto-Provisioning" is the term used that may be used to
refer to the steps performed to get a new network element (e.g., a
PLB, repeater, or backhaul point 10) onto the PLCS network. While
skilled in working with power lines, personnel installing the PLBs
400 (linemen) often have little or no experience in working with
communication networks. Consequently, it is desirable to have a
system that permits easy installation of the PLBs 400 without the
need to perform network configuration or other network installation
procedures.
[0251] In the present example embodiment, each network element
includes a unique identifier, which may be a serial number. In this
embodiment, the enclosure of the PLB 400 has a barcode that the
installer scans to record the serial number. The installer also
records the location of the installed device. This information (the
identifying information and location) is provided to a network
administrator to input the information into the PLS. Alternately,
the installer may wirelessly transmit the information to the PLS
for reception and storage by the PLS.
[0252] In one example embodiment, after being physically installed
and powered up, the PLB 400 transmits a request, such as a dynamic
host configuration protocol (DHCP) request, to the BP 10 with whom
the communication device is physically or functionally connected.
In response to the request, the BP 10 assigns and transmits an IP
address to the MV interface 200 (i.e., assigns an IP address to be
used to communicate with the MV modem 280), and the MV subnet mask.
In addition, the BP transmits the IP address of the BP 10 to be
used as the PLB's network gateway address, and the IP address for
the PLS. The PLB 400 receives the information from the BP 10 and
stores it in its non-volatile memory.
[0253] The PLB 400 then transmits an Alive Alert to the PLS (using
the IP address received in response to the DHCP request) indicating
that the PLB 400 is running and connected to the network. The Alive
Alert may include information identifying the PLB, network
configurations of the PLB 400 (e.g., MAC addresses of the LV modem
450 and MV modem 280), the IP address of the MV Interface (i.e.,
the IP address assigned to the MV modem 280 received from the BP
10) and MV subnet mask for use by the communication device's
backhaul interface (much of which was received from the BP 10).
This information is stored by the PLS in the network elements
database.
[0254] In response, the PLS may activate the PLB 400 by assigning
and transmitting the PLB 400 a LV subnet mask and a LV Interface IP
address (i.e., the IP address used to communicate with the LV modem
450). If there are customers present on the LV subnet, the PLS will
transmit customer information to the PLB, which may include such
information as data filtering information, keys (e.g., encryption
keys), user device IP addresses, and subscription levels for the
various users and/or user devices. In addition, the PLS may
configure the PLB 400 by transmitting DNS addresses (e.g., a first
and second DNS address), and a registration server IP address. This
information is stored by the PLS (in the network elements database)
and the PLB. As discussed below, until a user device is registered,
the PLB 400 may be programmed to allow the user device to access
only the domain name servers and registration server.
[0255] Provisioning a New User Device
[0256] Similarly, when a user installs a new user device on the LV
subnet attached to the PLB, the user device may need to be
provisioned to identify itself on the network. To do so in this
embodiment, the new user device transmits a DHCP request, which is
received and routed by the PLB 400 to a DHCP server running in the
controller 470 of the PLB. In response to the request, the PLB 400
may respond by transmitting to the user device the IP address and
subnet mask for the user device, the gateway IP address for the
device's network interface to be used as the network gateway (e.g.,
the IP address of the LV modem 450 of the PLB), and the IP
addresses of the Domain Name Servers (DNS) all of which are stored
in memory by the user device. In addition, the PLB 400 may transmit
a new user device Alert to the PLS.
[0257] After provisioning, it may be necessary to register the user
device with the network, which may require providing user
information (e.g., name, address, phone number, etc.), payment
information (e.g., credit card information or power utility account
information), and/or other information to the registration server.
The registration server may correlate this information with
information of the utility company or Internet service provider.
The registration server may form part of, or be separate from, the
PLS. Until registered, the PLB 400 prevents the user device
(through its power line modem 50) from communicating with
(receiving data from or transmitting data to) any computer other
than the registration server or the two DNSs. Thus, until the user
device is registered, the PLB 400 may filter data packets
transmitted to and/or from the user device that are not from or to
the registration server or a DNS. In addition, requests (such as
HTTP requests) for other Internet web pages may be redirected and
transmitted as a request for the registration web page on the
registration server, which responds by transmitting the
registration web page. Control of access of the user device may be
performed by limiting access based on the IP address of the user
device to the IP addresses of the registration server and DNSs.
[0258] After registration is successfully completed, the
registration server communicates with the PLS to provide
registration information of the user device to the PLS. The PLS
transmits an activation message for the user device (or power line
modem) to the PLB. In response, the PLB 400 removes communication
restrictions and permits the user device (and power line modem 50)
to communicate through the PLCS to all parts of the Internet. As
will be evident to those skilled in the art, filtering of data and
controlling access of the user device may be performed by limiting
access based on the IP address of the user device (or depending on
the network communication protocol, the MAC address of the user
device) or the MAC address of the power line modem 50 to which the
user device is connected. Thus, the PLB 400 may compare the source
IP address (or MAC address) with information in its memory to
determine if the IP address (or MAC address) is an address that has
been granted access to the PLCS. If the source address is not an
address that has been granted access to the PLCS (e.g., by
registering, which results in an activation message from the PLS to
the PLB), the PLB 400 may replace the destination IP address of the
packet with the IP address of the registration server and transmit
the packet to the backhaul point. The procedure above, or portions
of the procedure, with respect to provisioning user devices may be
used to provision a power line modem instead of or in addition to a
user device.
ALTERNATE EMBODIMENTS
[0259] As discussed, the PLB 400 of the above embodiment
communicates data signals to user devices via the LV power line.
Rather than communicating data signals to the power line modem
and/or user devices via the LV power line, the PLB 400 may use
other communication mediums. For example, the PLB 400 may convert
the data signals to a format for communication via a telephone
line, fiber optic, cable, or coaxial cable line. Such communication
may be implemented in a similar fashion to the communication with
LV power line as would be well known to those skilled in the
art.
[0260] In addition, the PLB 400 may convert the data signal to
radio signals for communication over a wireless communication link
to the user device. In this case, user device may be coupled to a
radio transceiver for communicating through the wireless
communication link. The wireless communication link may be a
wireless local area network implementing a network protocol in
accordance with an IEEE 802.11 (e.g., a, b, or g) standard.
[0261] Alternatively, the PLB 400 may communicate with the user
device via a fiber optic link. In this alternative embodiment, the
PLB 400 may convert the data signals to light signals for
communication over the fiber optic link. In this embodiment, the
customer premises may have a fiber optic cable for carrying data
signals, rather than using the internal wiring of customer
premise.
[0262] In addition to or instead of a wired connection or fiber
connection, the MVID 300 may include a transceiver such as a
wireless transceiver for communicating with the AP 100 or DP 200
wirelessly (e.g., an 802.11 wireless link) and/or the PLBs.
Likewise, the CMTS may alternately communicate with the DP 200 via
a wireless connection.
[0263] Thus, the AP 100 may communicate with the DP 200 or MVID 300
via a Wireless Modem Termination System (WMTS) and a hub
transceiver antenna at the base station, and a transceiver antenna
at the DP 200 or MVID. Preferably, the system uses
DOCSIS-compatible protocols and offers scalability and measurable
Quality of Service (QoS). Such a system commercially available from
Arcwave located at 910 Campisi Way #1C, Campbell, Calif. 95008 in
there ARCXtend.TM. Wireless Plant Extension Solution, which
includes their ARCell products. The wireless link may be in the
license-free 5 GHz bands or in a different and licensed band.
[0264] In another embodiment, the wireless link is provided via the
ARCXtend Wireless Plant Extension solution by Arcwave. In another
embodiment, the DL-5800 by Wireless Bypass, Inc., which also
wirelessly communicates with DOCSIS protocols may be use for
bidirectional communications.
[0265] In addition, the controller 470 of this embodiment may
include substantially the same software and functionality as that
described with respect to the PLB 400 and modifications thereto
would be readily apparent to one skilled in the art.
[0266] Miscellaneous
[0267] As discussed, the functions of the power line modem may be
integrated into a smart utility meter such as a gas meter, electric
meter, or water meter. The meter may be assigned an IP address by
the PLCS (e.g., by the PLS) and, upon receiving a request or at
predetermined intervals, transmit data such as consumption data to
the PLB, the PLS, and/or a utility computer system in a manner
described herein, thereby eliminating the need to have utility
personnel physically travel to read the meter. In addition, one or
more addressable switches, which may form part of a utility meter,
may be controlled via the PLCS (e.g., with commands transmitted
from the PLB, the PLS, and/or utility computer system) to permit
connection and disconnection of gas, electricity, and/or water to
the customer premises.
[0268] Similarly, the PLCS may be used to control MV power line
switches. The addressable MV power line switch may be a motorized
switch and assigned an IP address by the PLS, which is also
provided to the utility computer system to thereby operate the
switch. When a power outage is detected, the utility company may
remotely operate one or more addressable MV power line switches to
provide power to the area where the outage is detected by
transmitting commands to the IP addresses of the switches.
[0269] Likewise, the PLCS may be used to operate a capacitor switch
that inserts or removes a capacitor (or capacitor bank) into the
power distribution system. Capacitor banks are used to improve the
efficiency of the power distribution network by providing Volt/VAr
management (e.g., modifying the reactance of the power distribution
network). Thus, the PLS may assign an IP address to one or more
capacitor switches, which is also provided to the utility computer
system to thereby operate the switch. Based on power quality
measurements taken and received from one or more PLBs, the utility
company may insert or remove one or more capacitor banks by
remotely actuating one or more capacitor bank switches by
transmitting commands to the IP addresses of the switches.
[0270] The capacitor switch and the MV power line switch may be
controlled by an embodiment of the present invention that includes
a MV interface and controller. In addition, in some embodiments a
LV interface may also be employed.
[0271] The power line modem in the above embodiments has been
described as a device that is separate from the user device.
However, the power line modem may also be integrated into and form
part of the user device.
[0272] While the above described embodiments utilize a single modem
in the LV interface and the in the MV interface, alternate
embodiments may use two modems in the LV interface and/or two
modems in the MV interface. For example, the LV interface may
comprise a receive path (for receiving data from the LV power
lines) that includes a LV modem and signal conditioning circuitry
and a transmit path (for transmitting data through the LV power
lines) that includes a second LV modem and signal conditioning
circuitry. Each LV modem may have a separate address (MAC and IP
address) and operate at a separate frequency band. Thus, the
receive or transmit LV interfaces may also include frequency
translation circuitry.
[0273] Likewise, as another example the MV interface may comprise a
receive path (for receiving data from the MV power line) that
includes a MV modem and signal conditioning circuitry and a
transmit path (for transmitting data through the MV power line)
that includes a second MV modem and associated signal conditioning
circuitry. Each MV modem may have a separate address (MAC and IP
address) and operate at a separate frequency band. Thus, the
receive or transmit MV interfaces may also include frequency
translation circuitry. A repeater may also be constructed with
multiple MV modems in both of its MV interfaces or in its only MV
interface as the case may be.
[0274] While the described embodiments may apply the data signals
to one MV conductor (and the data signals may couple to other
conductors), other embodiments may apply the data signals
differently. For example, a first MV coupler (and an associated MV
interface) may be coupled to a first MV conductor for transmitting
data on the MV conductor and a second MV coupler may be coupled to
a second MV conductor for receiving the return current of the
transmitted data. The two couplers may thus share a signal MV
modem. Similarly, the first and second couplers (coupled to the
first and second MV power line conductors) may transmit (and
receive) the data signals differentially as described above in the
context of the LV power line transmissions and shown in FIGS. 6b
and 6c. Thus, the same data signal may be transmitted down multiple
MV conductors with the signal on each conductor being phase shifted
(e.g., 120 degrees or 180 degrees) with respect to the signal(s) on
the other conductor(s). Alternately, in any of these embodiments,
the neutral conductor may be used (e.g., as a return path or
separate transmission path) instead of one or more of the MV
conductors.
[0275] The PLBs 400 may communicate with the user devices via low
voltage repeater. An example of such a repeater is described in
U.S. patent application Ser. No. 10/434,024 filed May 8, 2003,
entitled "Power Line Communication Device and Method of Using the
Same," which is hereby incorporated by reference in its
entirety.
[0276] As will be evident to those skilled in the art, the MVIDs
300 and power line modem for communicating with these alternate
embodiments of the bypass device (or repeater) would also require
similar circuitry for transmitting and receiving with multiple
modems and in the different frequency bands. More specifically, the
modified power line modem would also require a first and second
modem for transmitting and receiving, respectively, and designed to
operate in the appropriate frequency bands for establishing
communications. Such a system would permit full duplex
communications through the power lines.
[0277] In the above embodiment, the processor performs routing
functions and may act as a router in some instances and perform
other functions at other times depending on the software that is
presently being executed. The router may also be a chip, chip set,
or circuit board (e.g., such as an off the shelf circuit card)
specifically designed for routing, any of which may include memory
for storing, for example, routing information (e.g., the routing
table) including MAC addresses, IP addresses, and address
rules.
[0278] While the above description describes communications between
the MVIDs 300 and DPs to be via optical, wireless, T1, or coaxial
cable communication medium, the communications may also be
accomplished by using over a MV power line or neutral conductor
using conductive electrical signals or surface waves.
[0279] Finally, the type of data signal coupled by the coupling
device may be any suitable type of data signal. The type of signal
modulation used can be any suitable signal modulation used in
communications (Code Division Multiple Access (CDMA), Time Division
Multiple Access (TDMA), Frequency Division Multiplex (FDM),
Orthogonal Frequency Division Multiplex (OFDM), and the like). OFDM
may be used on one or both of the LV and MV power lines. In
addition, DOCSIS signals may be used on the MV power lines and over
the fiber optic conductors in the above described embodiments. A
modulation scheme producing a wideband signal such as OFDM or CDMA
that is relatively flat in the spectral domain may be used to
reduce radiated interference to other systems while still
delivering high data communication rates.
[0280] It is to be understood that the foregoing illustrative
embodiments have been provided merely for the purpose of
explanation and are in no way to be construed as limiting of the
invention. Words used herein are words of description and
illustration, rather than words of limitation. In addition, the
advantages and objectives described herein may not be realized by
each and every embodiment practicing the present invention.
Further, although the invention has been described herein with
reference to particular structure, materials and/or embodiments,
the invention is not intended to be limited to the particulars
disclosed herein. Rather, the invention extends to all functionally
equivalent structures, methods and uses, such as are within the
scope of the appended claims. Those skilled in the art, having the
benefit of the teachings of this specification, may affect numerous
modifications thereto and changes may be made without departing
from the scope and spirit of the invention.
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