U.S. patent application number 14/538425 was filed with the patent office on 2015-03-05 for non-beacon network communications using frequency subbands.
The applicant listed for this patent is Texas Instruments Incorporated. Invention is credited to Anand G. Dabak, Badri N. Varadarajan, Ramanuja Vedantham, Kumaran Vijayasankar.
Application Number | 20150063285 14/538425 |
Document ID | / |
Family ID | 47067826 |
Filed Date | 2015-03-05 |
United States Patent
Application |
20150063285 |
Kind Code |
A1 |
Vedantham; Ramanuja ; et
al. |
March 5, 2015 |
Non-Beacon Network Communications Using Frequency Subbands
Abstract
Systems and methods for designing, using, and/or implementing
non-beacon network communications using frequency subbands are
described. In various implementations, these systems and methods
may be applicable to Power Line Communications (PLC). For example,
a method may include transmitting a beacon request message over a
given one of a plurality of frequency subbands, receiving a
plurality of beacons in response to having transmitted the beacon
request message, each of the plurality of beacons received over a
respective one of the plurality of frequency subbands, and
calculating a downlink quality report based, at least in part, upon
the received beacons. The method may also include transmitting the
downlink quality report over each of the plurality of frequency
subbands and receiving a subband allocation command in response to
having transmitted the downlink quality report, the subband
allocation command indicating a downlink subband assignment and an
uplink subband assignment.
Inventors: |
Vedantham; Ramanuja; (Allen,
TX) ; Vijayasankar; Kumaran; (Dallas, TX) ;
Dabak; Anand G.; (Plano, TX) ; Varadarajan; Badri
N.; (Mountain View, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Texas Instruments Incorporated |
Dallas |
TX |
US |
|
|
Family ID: |
47067826 |
Appl. No.: |
14/538425 |
Filed: |
November 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13457590 |
Apr 27, 2012 |
8885505 |
|
|
14538425 |
|
|
|
|
61480028 |
Apr 28, 2011 |
|
|
|
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
Y04S 40/00 20130101;
H04B 3/544 20130101; Y04S 40/162 20130101; H04L 41/0833 20130101;
H04W 72/0453 20130101; H04W 72/1231 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/04 20060101
H04W072/04; H04W 72/12 20060101 H04W072/12 |
Claims
1-20. (canceled)
21. A method comprising: performing, using a communication device,
transmitting a beacon request message over a given one of a
plurality of frequency subbands; receiving a plurality of beacons
in response to having transmitted the beacon request message, each
of the plurality of beacons received over a respective one of the
plurality of frequency subbands; calculating a downlink quality
report based, at least in part, upon the received beacons;
transmitting the downlink quality report over each of the plurality
of frequency subbands; and receiving a subband allocation command
in response to having transmitted the downlink quality report, the
subband allocation command indicating a downlink subband assignment
and an uplink subband assignment.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. Nonprovisional
patent application Ser. No. 13/457,590, filed Apr. 27, 2012 (now
U.S. Pat. No. 8,885,505), which claims the benefit of the filing
date of U.S. Provisional Patent Application No. 61/480,028 titled
"Non Beacon Mode Multi Tone Mask MAC Protocol for MV-LV PLC
Networks" and filed Apr. 28, 2011, the disclosure of which is
hereby incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] This specification is directed, in general, to network
communications, and, more specifically, to systems and methods for
designing, using, and/or implementing non-beacon network
communications using frequency subbands.
BACKGROUND
[0003] There are several different types of network communications
available today. For example, power line communications (PLC)
include systems for communicating data over the same medium (i.e.,
a wire or conductor) that is also used to transmit electric power
to residences, buildings, and other premises. Once deployed, PLC
systems may enable a wide array of applications, including, for
example, automatic meter reading and load control (i.e.,
utility-type applications), automotive uses (e.g., charging
electric cars), home automation (e.g., controlling appliances,
lights, etc.), and/or computer networking (e.g., Internet access),
to name only a few.
[0004] For each different type of communications network, different
standardizing efforts are commonly undertaken throughout the world.
For instance, in the case of PLC communications may be implemented
differently depending upon local regulations, characteristics of
local power grids, etc. Examples of competing PLC standards include
the IEEE 1901, HomePlug AV, and ITU-T G.hn (e.g., G.9960 and
G.9961) specifications. Another PLC standardization effort
includes, for example, the Powerline-Related Intelligent Metering
Evolution (PRIME) standard designed for OFDM-based (Orthogonal
Frequency-Division Multiplexing) communications.
SUMMARY
[0005] Systems and methods for designing, using, and/or
implementing non-beacon network communications using frequency
subbands are described. In an illustrative, non-limiting
embodiment, a method may include transmitting a beacon request
message over a given one of a plurality of frequency subbands,
receiving a plurality of beacons in response to having transmitted
the beacon request message, each of the plurality of beacons
received over a respective one of the plurality of frequency
subbands, and calculating a downlink quality report based, at least
in part, upon the received beacons. The method may also include
transmitting the downlink quality report over each of the plurality
of frequency subbands and receiving a subband allocation command in
response to having transmitted the downlink quality report, the
subband allocation command indicating a downlink subband assignment
and an uplink subband assignment.
[0006] In some implementations, the beacon request message may
indicate a sequence of frequency subbands over which the plurality
of beacons is transmitted by other devices that are already a part
of the network (e.g., including a data concentrator or the like)
and/or a sequence of frequency subbands over which the downlink
quality report is transmitted. The downlink quality report may
include a downlink channel quality indicator for each of the
plurality of subbands (which may be usable by other devices to
estimate an uplink quality in each of the plurality of subbands)
and/or it may indicate a downlink subband chosen by the
communication device among the plurality of plurality of
subbands.
[0007] Moreover, receiving the subband allocation command may
include receiving the allocation command over the chosen downlink
subband. For example, the subband allocation command may identify
uplink subbands chosen by other devices. Additionally or
alternatively, allocated downlink subband assignment may identify
an assigned downlink subband that is the same or different than the
chosen downlink subband. The method may also include communicating
with a PLC device using the downlink subband assignment and the
uplink subband assignment.
[0008] In another illustrative, non-limiting embodiment, a method
may include transmitting, to a PLC data concentrator, a beacon
request message over a given one of a plurality of frequency
subbands and receive a plurality of beacons from the PLC data
concentrator in response to having transmitted the beacon request
message, each of the plurality of beacons received over a
respective one of the plurality of frequency subbands. The method
may also include calculating a downlink quality report based, at
least in part, upon the received beacons, and transmitting an
uplink scan initiation request to the PLC data concentrator over
the given one of the plurality of frequency subbands, the uplink
scan initiation request indicating a chosen one of the plurality of
frequency subbands.
[0009] In some implementations, the method may include receiving an
uplink scan initiation command from the PLC data concentrator in
response to the uplink scan initiation request over the chosen one
of the plurality of frequency subbands, the uplink scan initiation
request indicating a downlink subband assignment to be used in
subsequent communications. The method may also include transmitting
the downlink quality report to the PLC data concentrator over each
of the plurality of frequency subbands in response to the uplink
scan initiation command. The method may further include receiving a
subband allocation command from the PLC data concentrator in
response to having transmitted the downlink quality report, the
subband allocation command received over the downlink subband
assignment, the subband allocation command indicating an uplink
subband assignment to be used in subsequent communications.
[0010] Additionally or alternatively, in response to not receiving
an uplink scan initiation command from the PLC data concentrator,
the method may include transmitting another beacon request message
to the PLC data concentrator over each of the plurality of
subbands, the PLC data concentrator configured to select an uplink
subband based, at least in part, upon the other beacon
requests.
[0011] In yet another illustrative, non-limiting embodiment, a
method may include receiving, from a PLC device, a beacon request
message over a given one of a plurality of frequency subbands,
transmitting a plurality of beacons to the PLC device, each of the
plurality of beacons transmitted over a respective one of the
plurality of frequency subbands, and receiving a downlink quality
report from the PLC device over each of the plurality of frequency
subbands. The method may also include transmitting a subband
allocation command to the PLC device, the subband allocation
command indicating an uplink subband assignment to be used in
subsequent communications with the PLC device.
[0012] In some implementations, prior to having received the
downlink quality report, the method may include receiving an uplink
scan initiation request from the PLC device over the given one of
the plurality of frequency subbands, the uplink scan initiation
request indicating a chosen one of the plurality of frequency
subbands suitable for subsequent downlink communications. The
method may also include transmitting an uplink scan initiation
command to the PLC device in response to the uplink scan initiation
request over the chosen one of the plurality of frequency subbands,
the uplink scan initiation request indicating a downlink subband
assignment to be used in subsequent communications.
[0013] In some embodiments, one or more communication devices or
computer systems may perform one or more of the techniques
described herein. In other embodiments, a tangible
computer-readable or electronic storage medium may have program
instructions stored thereon that, upon execution by one or more
communication devices or computer systems, cause the one or more
communication devices or computer systems to execute one or more
operations disclosed herein. In yet other embodiments, a
communication system (e.g., a device or modem) may include at least
one processor and a memory coupled to the at least one processor.
Examples of a processor include, but are not limited to, a digital
signal processor (DSP), an application specific integrated circuit
(ASIC), a system-on-chip (SoC) circuit, a field-programmable gate
array (FPGA), a microprocessor, or a microcontroller. The memory
may be configured to store program instructions executable by the
at least one processor to cause the system to execute one or more
operations disclosed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Having thus described the invention(s) in general terms,
reference will now be made to the accompanying drawings,
wherein:
[0015] FIG. 1 is a block diagram of a power line communication
(PLC) environment according to some embodiments.
[0016] FIG. 2 is a block diagram of a PLC device or modem according
to some embodiments.
[0017] FIG. 3 is a block diagram of an integrated circuit according
to some embodiments.
[0018] FIGS. 4-6 are block diagrams illustrating connections
between a PLC transmitter and/or receiver circuitry to three-phase
power lines according to some embodiments.
[0019] FIG. 7 is a block diagram of a hierarchical PLC
communications network according to some embodiments.
[0020] FIG. 8 is a diagram illustrating operation of an MV device
using frequency subbands according to some embodiments.
[0021] FIGS. 9A and 9B are flowcharts of a first method of scanning
frequency subbands in connection with discovery operations from the
perspectives of an LV and an MV device, respectively, according to
some embodiments.
[0022] FIG. 10 is a diagram illustrating the first method of
scanning frequency subbands according to some embodiments.
[0023] FIGS. 11A and 11B are flowcharts of a second method of
scanning frequency subbands in connection with discovery operations
from the perspectives of an LV and an MV device, respectively,
according to some embodiments.
[0024] FIG. 12 is a diagram illustrating the second method of
scanning frequency subbands according to some embodiments.
[0025] FIG. 13 is a block diagram of a computing system configured
to implement certain systems and methods described herein according
to some embodiments.
DETAILED DESCRIPTION
[0026] The invention(s) now will be described more fully
hereinafter with reference to the accompanying drawings. The
invention(s) may, however, be embodied in many different forms and
should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention(s) to a person of ordinary skill in the art.
A person of ordinary skill in the art may be able to use the
various embodiments of the invention(s).
[0027] In various embodiments, the systems and methods described
herein may be used to design and/or non-beacon network
communications using frequency subbands. Generally speaking, these
systems and methods may be applicable to a wide variety of
communication environments, including, but not limited to, those
involving wireless communications (e.g., cellular, Wi-Fi, WiMax,
etc.), wired communications (e.g., Ethernet, etc.), power line
communications (PLC), or the like. For ease of explanation, several
examples discussed below are described specifically in the context
of PLC. As a person of ordinary skill in the art will recognize in
light of this disclosure, however, certain techniques and
principles disclosed herein may also be applicable to other
communication environments.
[0028] Turning now to FIG. 1, an electric power distribution system
is depicted according to some embodiments. Medium voltage (MV)
power lines 103 from substation 101 typically carry voltage in the
tens of kilovolts range. Transformer 104 steps the MV power down to
low voltage (LV) power on LV lines 105, carrying voltage in the
range of 100-240 VAC. Transformer 104 is typically designed to
operate at very low frequencies in the range of 50-60 Hz.
Transformer 104 does not typically allow high frequencies, such as
signals greater than 100 KHz, to pass between LV lines 105 and MV
lines 103. LV lines 105 feed power to customers via meters 106a-n,
which are typically mounted on the outside of residences 102a-n.
(Although referred to as "residences," premises 102a-n may include
any type of building, facility or location where electric power is
received and/or consumed.) A breaker panel, such as panel 107,
provides an interface between meter 106n and electrical wires 108
within residence 102n. Electrical wires 108 deliver power to
outlets 110, switches 111 and other electric devices within
residence 102n.
[0029] The power line topology illustrated in FIG. 1 may be used to
deliver high-speed communications to residences 102a-n. In some
implementations, power line communications modems or gateways
112a-n may be coupled to LV power lines 105 at meter 106a-n. PLC
modems/gateways 112a-n may be used to transmit and receive data
signals over MV/LV lines 103/105. Such data signals may be used to
support metering and power delivery applications (e.g., smart grid
applications), communication systems, high speed Internet,
telephony, video conferencing, and video delivery, to name a few.
By transporting telecommunications and/or data signals over a power
transmission network, there is no need to install new cabling to
each subscriber 102a-n. Thus, by using existing electricity
distribution systems to carry data signals, significant cost
savings are possible.
[0030] An illustrative method for transmitting data over power
lines may use, for example, a carrier signal having a frequency
different from that of the power signal. The carrier signal may be
modulated by the data, for example, using an orthogonal frequency
division multiplexing (OFDM) scheme or the like.
[0031] PLC modems or gateways 112a-n at residences 102a-n use the
MV/LV power grid to carry data signals to and from PLC data
concentrator 114 without requiring additional wiring. Concentrator
114 may be coupled to either MV line 103 or LV line 105. Modems or
gateways 112a-n may support applications such as high-speed
broadband Internet links, narrowband control applications, low
bandwidth data collection applications, or the like. In a home
environment, for example, modems or gateways 112a-n may further
enable home and building automation in heat and air conditioning,
lighting, and security. Also, PLC modems or gateways 112a-n may
enable AC or DC charging of electric vehicles and other appliances.
An example of an AC or DC charger is illustrated as PLC device 113.
Outside the premises, power line communication networks may provide
street lighting control and remote power meter data collection.
[0032] One or more data concentrators 114 may be coupled to control
center 130 (e.g., a utility company) via network 120. Network 120
may include, for example, an IP-based network, the Internet, a
cellular network, a WiFi network, a WiMax network, or the like. As
such, control center 130 may be configured to collect power
consumption and other types of relevant information from gateway(s)
112 and/or device(s) 113 through concentrator(s) 114. Additionally
or alternatively, control center 130 may be configured to implement
smart grid policies and other regulatory or commercial rules by
communicating such rules to each gateway(s) 112 and/or device(s)
113 through concentrator(s) 114.
[0033] In some embodiments, each concentrator 114 may be seen as a
base node for a PLC domain, each such domain comprising downstream
PLC devices that communicate with control center 130 through a
respective concentrator 114. For example, in FIG. 1, device 106a-n,
112a-n, and 113 may all be considered part of the PLC domain that
has data concentrator 114 as its base node; although in other
scenarios other devices may be used as the base node of a PLC
domain. In a typical situation, multiple nodes may be deployed in a
given PLC network, and at least a subset of those nodes may be tied
to a common clock through a backbone (e.g., Ethernet, digital
subscriber loop (DSL), etc.). Further, each PLC domain may be
coupled to MV line 103 through its own distinct transformer similar
to transformer 104.
[0034] Still referring to FIG. 1, meter 106, gateways 112, PLC
device 113, and data concentrator 114 may each be coupled to or
otherwise include a PLC modem or the like. The PLC modem may
include transmitter and/or receiver circuitry to facilitate the
device's connection to power lines 103, 105, and/or 108.
[0035] FIG. 2 is a block diagram of PLC device or modem 113
according to some embodiments. As illustrated, AC interface 201 may
be coupled to electrical wires 108a and 108b inside of premises
112n in a manner that allows PLC device 113 to switch the
connection between wires 108a and 108b off using a switching
circuit or the like. In other embodiments, however, AC interface
201 may be connected to a single wire 108 (i.e., without breaking
wire 108 into wires 108a and 108b) and without providing such
switching capabilities. In operation, AC interface 201 may allow
PLC engine 202 to receive and transmit PLC signals over wires
108a-b. As noted above, in some cases, PLC device 113 may be a PLC
modem. Additionally or alternatively, PLC device 113 may be a part
of a smart grid device (e.g., an AC or DC charger, a meter, etc.),
an appliance, or a control module for other electrical elements
located inside or outside of premises 112n (e.g., street lighting,
etc.).
[0036] PLC engine 202 may be configured to transmit and/or receive
PLC signals over wires 108a and/or 108b via AC interface 201 using
a particular channel or frequency band. In some embodiments, PLC
engine 202 may be configured to transmit OFDM signals, although
other types of modulation schemes may be used. As such, PLC engine
202 may include or otherwise be configured to communicate with
metrology or monitoring circuits (not shown) that are in turn
configured to measure power consumption characteristics of certain
devices or appliances via wires 108, 108a, and/or 108b. PLC engine
202 may receive such power consumption information, encode it as
one or more PLC signals, and transmit it over wires 108, 108a,
and/or 108b to higher-level PLC devices (e.g., PLC gateways 112n,
data concentrators 114, etc.) for further processing. Conversely,
PLC engine 202 may receive instructions and/or other information
from such higher-level PLC devices encoded in PLC signals, for
example, to allow PLC engine 202 to select a particular frequency
band in which to operate.
[0037] In various embodiments, PLC device 113 may be implemented at
least in part as an integrated circuit. FIG. 3 is a block diagram
of such an integrated circuit. In some cases, one or more of meter
106, gateway 112, PLC device 113, or data concentrator 114 may be
implemented similarly as shown in FIG. 3. For example, integrated
circuit 302 may be a digital signal processor (DSP), an application
specific integrated circuit (ASIC), a system-on-chip (SoC) circuit,
a field-programmable gate array (FPGA), a microprocessor, a
microcontroller, or the like. As such, integrated circuit 302 may
implement, at least in part, at least a portion of PLC engine 202
shown in FIG. 2. Integrated circuit 302 is coupled to one or more
peripherals 304 and external memory 303. Further, integrated
circuit 302 may include a driver for communicating signals to
external memory 303 and another driver for communicating signals to
peripherals 304. Power supply 301 is also provided which supplies
the supply voltages to integrated circuit 302 as well as one or
more supply voltages to memory 303 and/or peripherals 304. In some
embodiments, more than one instance of integrated circuit 302 may
be included (and more than one external memory 303 may be included
as well).
[0038] Peripherals 304 may include any desired circuitry, depending
on the type of PLC device or system. For example, in some
embodiments, peripherals 304 may implement, at least in part, at
least a portion of a PLC modem (e.g., portions of AC interface 210
shown in FIG. 2). Peripherals 304 may also include additional
storage, including RAM storage, solid-state storage, or disk
storage. In some cases, peripherals 304 may include user interface
devices such as a display screen, including touch display screens
or multi-touch display screens, keyboard or other input devices,
microphones, speakers, etc. External memory 303 may include any
type of memory. For example, external memory 303 may include SRAM,
nonvolatile RAM (NVRAM, such as "flash" memory), and/or dynamic RAM
(DRAM) such as synchronous DRAM (SDRAM), double data rate (DDR,
DDR2, DDR3, etc.) SDRAM, etc. External memory 303 may include one
or more memory modules to which the memory devices are mounted,
such as single inline memory modules (SIMMs), dual inline memory
modules (DIMMs), etc.
[0039] In various implementations, PLC device or modem 113 may
include transmitter and/or receiver circuits configured to connect
to power lines 103, 105, and/or 108. FIG. 4 illustrates a
connection between the power line communication transmitter and/or
receiver circuitry to the power lines according to some
embodiments. PLC transmitter/receiver 401 may function as the
transmitter and/or receiver circuit. When PLC transmitter/receiver
401 operates as a transmitter, it may generate pre-coded signals
for transmission over the power line network. Each output signal,
which may be a digital signal, may be provided to a separate line
driver circuit 402A-C. Line drivers 402A-C may comprise, for
example, digital-to-analog conversion circuitry, filters, and/or
line drivers that couple signals from PLC transmitter/receiver 401
to power lines 403A-C. Transformer 404 and coupling capacitor 405
link each analog circuit/line driver 402 to its respective power
line 403A-C. Accordingly, in the embodiment illustrated in FIG. 4,
each output signal is independently linked to a separate, dedicated
power line. Conversely, when PLC transmitter/receiver 401 operates
as a receiver, coded signals may be received on power lines 403A-C,
respectively. In an embodiment, each of these signals may be
individually received through coupling capacitors 405, transformers
404, and line drivers 402 to PLC transmitter/receiver 401 for
detection and receiver processing of each signal separately.
Alternatively, the received signals may be routed to summing filter
406, which combines all of the received signals into one signal
that is routed to PLC transmitter/receiver 401 for receiver
processing.
[0040] FIG. 5 illustrates an alternative embodiment in which PLC
transmitter/receiver 501 is coupled to a single line driver 502,
which is in turn coupled to power lines 503A-C by a single
transformer 504. All of the output signals are sent through line
driver 502 and transformer 504. Switch 506 selects which power line
503A-C receives a particular output signal. Switch 506 may be
controlled by PLC transmitter/receiver 501. Alternatively, switch
506 may determine which power line 503A-C should receive a
particular signal based upon information, such as a header or other
data, in the output signal. Switch 506 links line driver 502 and
transformer 504 to the selected power line 503A-C and associated
coupling capacitor 505. Switch 506 also may control how received
signals are routed to PLC transmitter/receiver 501.
[0041] FIG. 6 is similar to FIG. 5 in which PLC
transmitter/receiver 601 is coupled to a single line driver 602.
However, in the embodiment of FIG. 6, power lines 603A-C are each
coupled to a separate transformer 604 and coupling capacitor 605.
Line driver 602 is coupled to the transformers 604 for each power
line 603 via switch 606. Switch 606 selects which transformer 604,
coupling capacitor 605, and power line 603A-C receives a particular
signal. Switch 606 may be controlled by PLC transmitter/receiver
601, or switch 606 may determine which power line 603A-C should
receive a particular signal based upon information, such as a
header or other data, in each signal. Switch 606 also may control
how received signals are routed to PLC transmitter/receiver
601.
[0042] Turning to FIG. 7 a block diagram of a hierarchical PLC
communications network 700 is depicted. In the embodiment shown,
medium-voltage (MV) devices or modems MV1, MV2, and MV3 (e.g., PLC
data concentrators, routers, etc.) are coupled to an MV power line
(e.g., 103 in FIG. 1). First-level low-voltage (LV) devices
LV1.sub.1, LV2.sub.1, LV3.sub.1, and LV4.sub.1 (e.g., a PLC
charger, a PLC meter, a PLC modem, etc.) are coupled to an LV power
line (e.g., 105 in FIG. 1) through transformers 705a and 705b
(e.g., 104 in FIG. 1). Second-level LV devices LV1.sub.2 and
LV2.sub.2 are coupled to device LV1.sub.1. Third-level device
LV1.sub.3 is coupled to device LV2.sub.2, and fourth-level device
LV1.sub.4 is coupled to device LV1.sub.3 (second-, third-, and
fourth-level devices may be referred to as "lower-level" devices).
It should be noted that network 700 is presented for sake of
illustration only, and that in any given implementation may include
an arbitrary number of MV and/or LV devices coupled in different
ways under a different hierarchy. As illustrated, at least three
different types of communication take place in network 700; namely,
between MV devices (the "MV-MV network"), between MV devices and
first-level LV devices (the "MV-LV network"), and among LV devices
(the "LV-LV network").
[0043] Within network 700, communications may be achieved between
or among devices using one or more different frequency subbands
(also referred to as "tone masks" or "channels") in the downlink
and uplink directions. Generally speaking, the term "downlink"
refers to a communication in a direction that is received by a
given device, and the term "uplink" refers to a communication in a
direction that is transmitted by that same device. In the case of
MV-LV communications, however, the term "downlink" refers to links
or communications taking place from an MV device to an LV device,
and the term "uplink" refers to links or communications taking
place from an LV device to an MV device.
[0044] In a typical case, the frequency subband over which an MV
device can communicate with an LV device (downlink) may be
different from the subband that the LV device may used to
communicate with an MV device (uplink). Also, the uplink and
downlink subbands may be different between different LV devices
communicating with the same MV device. As such, each PLC device
involved in a communication may select (or allow another device to
select) good or best communication channels or subbands, for
example, based upon a determination of channel conditions (e.g.,
signal-to-noise ratio (SNR) measurements, congestion indicators,
etc.) or the like.
[0045] In various embodiments, the PLC devices described above
(and/or the computer system shown in FIG. 13) may be configured to
implement one or more communication techniques through
modifications to the network's MAC protocol. Generally speaking, a
MAC protocol is a sub-layer of a data link layer specified in a
seven-layer Open Systems Interconnection (OSI) model. Particularly,
a MAC protocol may provide addressing and channel access control
mechanisms that enable terminals or network nodes (e.g., PLC
modems, etc.) to communicate over a shared medium (i.e., a power
line). To facilitate communications among the devices described
above, each device may implement a MAC protocol configured to
coordinate communications according to one or more of the
techniques illustrated in FIGS. 8-12.
[0046] For example, in some implementations, communications between
MV1 and MV2 may be performed using poll-based data transfer with
carrier sense multiple access (CSMA) or other carrier access (CA)
technique. Communications between MV1 and MV3 may be performed
using beacon mode CSMA/CA during an allocated time. Communications
between MV devices and first-level LV devices may be performed
using poll-based Contention Free Period(s) (CFP) over a given
frequency subband. Communications between first- and second-level
LV devices may be performed using wideband CSMA/CA operations
blocked out for periods of time for subband operation, and
communications between lower-level LV devices may be performed
using wideband CSMA/CA operational at all times. These and other
operations are discussed below.
[0047] MV Operation
[0048] FIG. 8 is a diagram illustrating operation of an MV device
using frequency subbands. In some embodiments, one or more MV
devices may employ a master-slave approach to poll individual nodes
connected to the network. For example, a given MV device may be
configured with a maximum number of poll attempts
("aMAXPollAttempts") so that it does not poll the same node more
than that maximum number of times over a preselected amount of time
(e.g., one second). There may be portions of time during which the
MV device does not poll any node, and therefore it remains idle,
for example, in wideband ("all"). The MV device may also ensure
that it does not stay in a single frequency subband for more than a
predetermined period of time ("aMAXSubBandTime").
[0049] Accordingly, an MV device may tune its receiver to different
subbands over a period of time, as shown in FIG. 8 for N frequency
subbands. As illustrated, the MV device is configured to operate
over frequency subbands 805a-n. Block 810 indicates that the MV
device is operating over frequency subband 805a for a given period
of time, block 815 indicates that the MV device is subsequently
operating over frequency subband 805b over a longer period of time,
and block 820 shows the MV device operating over frequency subband
805a for a shorter period of time. Block 825 shows the MV device
operating over frequency band 805n for the "aMAXSubBandTime," and
then it operates over wideband in block 830, also for the maximum
allowed amount of time.
[0050] In some implementations, the MV device's switching among
frequency subbands (e.g., 805a-805b-805a- . . . -805n), as well as
their durations, may be random. Additionally or alternatively, it
may follow a selected pattern or sequence of frequency subbands
and/or durations. In some cases, the MV device may be capable of
tuning its receiver to two or more distinct frequency subbands at
the same time (e.g., subbands 805a and 805b), in addition or as an
alternative to being able to operate in wideband (i.e., subbands
805a through 805n).
[0051] LV-MV Scanning
[0052] With respect to LV-MV scanning or discovery, an LV node
(e.g., LV1.sub.1 shown in FIG. 7) may send a beacon request
message, packet, and/or frame over a randomly selected frequency
subband. Therefore, an MV device receives the beacon request if it
is actually listening on that same randomly selected subband, if
the subband is a good or other viable option for communications in
the uplink direction, if no collision occurs during the beacon
request, and if there is no error otherwise (e.g., due to noise in
the channel). In some implementations, the beacon request message
or frame may carry information about a sequence of tone masks to be
followed during an initial tone mask scanning or discovery
operation ("LV tone mask sequence"). Once an MV device receives the
beacon request, a tone mask scanning procedure may continue to take
place as shown in FIGS. 9 and/or 11.
[0053] FIGS. 9A and 9B are flowcharts of a first method of scanning
frequency subbands in connection with discovery operations, and
FIG. 10 is a diagram illustrating such a method over three
frequency subbands, according to some embodiments. Particularly,
method 900A illustrates scanning operations from the perspective of
an LV device, and method 900B illustrates counterpart scanning
operations from the perspective of an MV device. At block 905, the
LV device may transmit a beacon request message, packet, or frame
1005 over a randomly selected frequency subband--in this example,
subband 1. The beacon request may include an LV tone mask
sequence--in this example, the sequence is 1-2-3. As explained
above, given that certain receiver and channel conditions are
satisfied, the MV device may receive beacon request 1005 at block
910. Thereafter, in response to beacon request 1005, the MV device
may transmit a beacon over each of frequency subbands 1010 in the
order specified by the beacon request (i.e., 1-2-3) at block 915.
At block 920, the LV device may switch its receiver to those same
subbands in the same order and may therefore receive beacons
1010.
[0054] At block 925, the LV device may calculate a downlink quality
report based, at least in part, upon the received beacons. For
example, such a report may include a measured or estimated channel
or link quality metric (e.g., signal-to-noise ratio or SNR, etc.)
for each frequency subband. Still at block 925, the LV device may
select one of the frequency subbands suitable for subsequent
downlink communications--e.g., it may select the subband with
highest SNR or the like, according to the report. In this example,
assume that the selected downlink subband is subband 2. Then, at
block 930, the LV device may transmit the downlink quality report
and/or the selected downlink subband as messages, packets, or
frames 1015 over each of the frequency subbands in the same order
as the LV tone mask sequence. Alternatively, the LV device may
transmit beacon requests over each of the plurality of
subbands.
[0055] At block 935, the MV device may receive the downlink quality
reports 1015 (or beacon requests), and may create an uplink quality
report based on those signals. The MV device may also select or
assign a downlink subband (based on the downlink quality report or
beacon requests), as well as an uplink subband (based on the uplink
quality report) to the LV device. As such, at block 940, the MV
device may transmit subband allocation command 1020 indicating
those assignments to the LV device over the downlink frequency
subband chosen by the LV device. At block 945, the LV device may
tune its receiver to the chosen subband and it may receive subband
allocation command 1020. The LV device may then conduct subsequent
communications with the MV device using the assigned downlink and
uplink frequency subbands.
[0056] In some cases, the MV device may assign a downlink frequency
subband to the LV device that is different from the subband chosen
by the LV device at block 925. For example, the chosen downlink
subband may be subband 2 (over which the mask allocation command is
received), but the assigned subband may be subband 1 or 3.
Generally speaking, the LV device may select what it perceives to
be a good or best downlink subband based on the measured or
estimated channel quality metrics. However, the MV device may take
other criteria into account such as, for example, the level of
congestion in the downlink direction (i.e., whether or how many
other devices are already using that subband, etc.), when assigning
a downlink subband for future communications. In other words,
although the downlink subband assigned by the MV device may be
"sub-optimal" from the perspective of the LV device in terms of
channel or link quality, it may nonetheless result in better
overall network performance.
[0057] Typically, when employing the techniques shown in FIGS. 9
and 10, the LV device performs the downlink scan for beacons 1010
regardless of whether the MV device actually receives the beacon
request. Similarly, the LV device may also perform the uplink
transmission of tone mask reports 1015 even when it does not
receive beacons 1010. In some cases, this may cause additional
overhead, particularly as the number of frequency subbands
increases (along with the duration of the scans). To address these
and other concerns, a handshake procedure may be introduced as
shown in FIGS. 11 and 12.
[0058] Specifically, FIGS. 11A and 11B are flowcharts of a second
method of scanning frequency subbands in connection with discovery
operations and FIG. 12 is a diagram illustrating such a method over
three frequency subbands, according to some embodiments. Similarly
as before, here methods 1100A and 1100B illustrate scanning
operations from the perspectives of an LV device and an MV device,
respectively. At block 1105, the LV device may transmit a beacon
request message, packet, or frame 1205 over a randomly selected
frequency subband--in this case, subband 1. The beacon request may
include an LV tone mask sequence--in this example, the sequence is
again 1-2-3. Then, the MV device may receive beacon request 1205 at
block 1110. In response to beacon request 1205, the MV device may
transmit a beacon over each of frequency subbands 1210 in the order
specified by the beacon request (e.g., 1-2-3) at block 1115. At
block 1120, the LV device may switch its receiver to those same
subbands in the same order and may therefore receive transmitted
beacons 1210. At block 1125, the LV device may calculate a downlink
quality report based, at least in part, upon the received beacons.
The LV device may also select one of the frequency subbands
suitable for subsequent downlink communications--in this case, the
selected downlink subband is again subband 2.
[0059] In contrast with the techniques illustrated in FIGS. 9 and
10, however, methods 1100A and 1100B may include a handshake
procedure. At block 1130, the LV device may transmit uplink
initiation request 1215 over the same subband used by beacon
request 1205 (i.e., subband 1). In some cases, the uplink scan
initiation request may inform the MV device that the LV device will
be sending the tone mask reports, and it may also inform the MV
device about the LV device's chosen downlink subband (i.e., subband
2). At block 1135, the MV device may receive uplink initiation
request 1215, and at block 1040 the MV device may transmit uplink
scan initiation command 1220 over the LV device's chosen downlink
subband (i.e., subband 2). Uplink scan initiate command 1220 may
inform the LV device of a downlink subband assignment made by the
MV device--in this case, subband 3. As explained above, the
downlink subband assignment may be the same or different from the
selected downlink subband.
[0060] At block 1145, the LV device may receive uplink scan
initiate command 1220 and it may transmit the downlink quality
report as messages, packets, or frames 1225 over each of the
frequency subbands in the same order as the LV tone mask sequence
at block 1150. (Similarly as above, the LV device may transmit
beacon requests instead of downlink quality reports over each of
subband.) At block 1155, the MV device may receive the downlink
quality reports 1225 (or beacon requests), and may create an uplink
quality report based on those signals. The MV device may also
select or assign an uplink subband (based on the uplink quality
report) to the LV device. As such, at block 1160, the MV device may
transmit subband allocation command 1230 indicating the uplink
subband assignment to the LV device over the downlink frequency
subband previously assigned via uplink scan initiation command 1220
(in some cases, subband allocation command 1230 may include both
the uplink and the downlink assignments). At block 1165, the LV
device may tune its receiver to the assigned the downlink frequency
subband and it may receive subband allocation command 1230. The LV
device may then conduct subsequent communications with the MV
device using the assigned downlink and uplink frequency
subbands.
[0061] Again, compared with the methods described in FIGS. 9 and
10, the methods of FIGS. 11 and 12 may be more suited for
communications employing a larger number of subbands. Particularly,
the operations shown in block 1235 need not be performed, for
example, if the MV and LV devices do not receive the uplink scan
initiation request 1215 or uplink scan initiation command 1220,
respectively. In that case, the LV device may return to block 1105
and transmit another beacon request (e.g., in another frequency
subband). The higher the number of subbands over which tone mask
reports 1225 would otherwise have to be transmitted, the better the
efficiency of the scanning operations due to the introduction of
the handshake procedure. In other words, the relatively small
overhead introduced by the handshake procedure may be compensated
by the savings in unnecessary uplink scanning time as the number of
available frequency subbands increases. It is noted, however, that
such a handshake may also be considered "overhead," for example,
when the number of subbands is small or when at least one of the
beacons usually reaches the LV node in the network.
[0062] LV-LV and MV-MV Scanning
[0063] In various embodiments, LV-LV scanning (e.g., between two LV
devices of the same or different levels) may be performed on
wideband (i.e., using all available frequency subbands). A new LV
node may send a beacon request on wideband (e.g., periodically)
using CSMA/CA or the like. An LV switch node or coordinator (e.g.,
a first-level LV device) may then respond to beacon request with
beacon so long as the LV switch node or coordinator is listening on
wideband (in some implementations, first-level devices only), no
collision occurred on the beacon request frame, and there is no
frame error due to noise in the channel.
[0064] The MV-MV scanning procedure may be similar to LV-LV
scanning procedure. Specifically, a new MV node may send a beacon
request on wideband periodically. An MV coordinator may then
respond to beacon requests if: the MV coordinator is listening on
wideband, no collision occurred on the beacon request frame, and no
frame error due to noise in the channel. In some implementations,
MV-MV scanning may always take place over wideband.
[0065] Data Transfers (Steady State)
[0066] After tone mask selection, a first-level LV device (e.g.,
LV1.sub.1) may listen on its assigned downlink tone mask for poll
and/or downlink data, as well as wideband for uplink data from
lower-level nodes (e.g., LV2.sub.2). For example, LV1.sub.1 may use
poll-based CFP for uplink data transmissions. An MV device may send
a poll command using LV1.sub.1's assigned downlink tone mask and,
it may switch to LV1.sub.1's assigned uplink tone mask for any
potential reception (e.g., after starting a timer). Prior to
responding to the MV device's poll requests, LV1.sub.1 may transmit
a clear-to-send-to-self ("CTS-2-Self") frame in order to block
lower-level devices from transmitting on wideband for the duration
of LV1.sub.1's uplink transmission. Moreover, LV1.sub.1 may respond
to the poll request with uplink data on the assigned uplink tone
mask. If LV1.sub.1 does not have uplink data to transmit, the MV
device may time out, and then it may poll other LV devices.
[0067] In some implementations, the MV device may transmit data to
LV1.sub.1 over the assigned downlink tone mask. For example, the MV
node may transmit a poll with a time indication for downlink data
transmission, so that LV1.sub.1 may forward this information in a
CTS-2-Self frame to block lower-level LV nodes from transmitting on
wideband. Also, because LV1.sub.1 is listening on the assigned
downlink tone mask by default, it may be able to receive the
downlink data following the MV's poll. For uplink acknowledgement
("ACK") transmissions, LV may switch to its assigned uplink tone
mask after a downlink data reception to transmit the ACK.
Conversely, for downlink ACK transmissions, the MV device may
switch to LV1.sub.1's assigned downlink tone mask after an uplink
data reception. ACK packets may be transmitted immediately or as
block ACK, which may be negotiated during connection setup. In some
embodiments, LV1.sub.1 may also listen on wideband for any uplink
transmissions from lower-level LV devices. If a lower-level LV
device transmits while there are no poll-CFP packets, its receiver
may be tuned to the wideband.
[0068] MV-MV communications may take place similarly as described
above. Specifically, MV-MV communication may occur on wideband when
there is no polling for MV-LV1.sub.1 communication. It may also
employ CSMA/CA--based communication on wideband when first-level LV
nodes communicate with lower-level LV nodes. Furthermore, the MV
coordinator may prevent unnecessary transmissions on wideband when
polling for first-level LV nodes by transmitting CTS-2-Self frames
for the desired duration (e.g., when operating on a tone-mask).
LV-LV communications may also be similar. First-level LV nodes may
prevent any unnecessary transmissions on wideband when
communicating with MV node by transmitting CTS-2-Self frames for
the desired duration (when operating on a tone-mask). At all other
times and at third-level and below, communications may employ
CSMA/CA-based communication on wideband.
[0069] As previously noted, in certain embodiments, systems and
methods for designing, using, and/or non-beacon network
communications using frequency subbands may be executed, at least
in part, by one or more communication devices and/or computer
systems. One such computer system is illustrated in FIG. 13. In
various embodiments, system 1300 may be implemented as a
communication device, modem, data concentrator, server, a mainframe
computer system, a workstation, a network computer, a desktop
computer, a laptop, mobile device, or the like. In different
embodiments, these various systems may be configured to communicate
with each other in any suitable way, such as, for example, via a
local area network or the like.
[0070] As illustrated, system 1300 includes one or more processors
1310 coupled to a system memory 1320 via an input/output (I/O)
interface 1330. Computer system 1300 further includes a network
interface 1340 coupled to I/O interface 1330, and one or more
input/output devices 1325, such as cursor control device 1360,
keyboard 1370, display(s) 1380, and/or mobile device 1390. In
various embodiments, computer system 1300 may be a single-processor
system including one processor 1310, or a multi-processor system
including two or more processors 1310 (e.g., two, four, eight, or
another suitable number). Processors 1310 may be any processor
capable of executing program instructions. For example, in various
embodiments, processors 1310 may be general-purpose or embedded
processors implementing any of a variety of instruction set
architectures (ISAs), such as the x86, POWERPC.RTM., ARM.RTM.,
SPARC.RTM., or MIPS.RTM. ISAs, or any other suitable ISA. In
multi-processor systems, each of processors 1310 may commonly, but
not necessarily, implement the same ISA. Also, in some embodiments,
at least one processor 1310 may be a graphics processing unit (GPU)
or other dedicated graphics-rendering device.
[0071] System memory 1320 may be configured to store program
instructions and/or data accessible by processor 1310. In various
embodiments, system memory 1320 may be implemented using any
suitable memory technology, such as static random access memory
(SRAM), synchronous dynamic RAM (SDRAM), nonvolatile/Flash-type
memory, or any other type of memory. As illustrated, program
instructions and data implementing certain operations such as, for
example, those described in the figures above, may be stored within
system memory 1320 as program instructions 1325 and data storage
1335, respectively. In other embodiments, program instructions
and/or data may be received, sent or stored upon different types of
computer-accessible media or on similar media separate from system
memory 1320 or computer system 1300. Generally speaking, a
computer-accessible medium may include any tangible storage media
or memory media such as magnetic or optical media--e.g., disk or
CD/DVD-ROM coupled to computer system 1300 via I/O interface 1330.
Program instructions and data stored on a tangible
computer-accessible medium in non-transitory form may further be
transmitted by transmission media or signals such as electrical,
electromagnetic, or digital signals, which may be conveyed via a
communication medium such as a network and/or a wireless link, such
as may be implemented via network interface 1340.
[0072] In one embodiment, I/O interface 1330 may be configured to
coordinate I/O traffic between processor 1310, system memory 1320,
and any peripheral devices in the device, including network
interface 1340 or other peripheral interfaces, such as input/output
devices 1350. In some embodiments, I/O interface 1330 may perform
any necessary protocol, timing or other data transformations to
convert data signals from one component (e.g., system memory 1320)
into a format suitable for use by another component (e.g.,
processor 1310). In some embodiments, I/O interface 1330 may
include support for devices attached through various types of
peripheral buses, such as a variant of the Peripheral Component
Interconnect (PCI) bus standard or the Universal Serial Bus (USB)
standard, for example. In some embodiments, the function of I/O
interface 1330 may be split into two or more separate components,
such as a north bridge and a south bridge, for example. In
addition, in some embodiments some or all of the functionality of
I/O interface 1330, such as an interface to system memory 1320, may
be incorporated directly into processor 1310.
[0073] Network interface 1340 may be configured to allow data to be
exchanged between computer system 1300 and other devices attached
to a network, such as other computer systems, or between nodes of
computer system 1300. In various embodiments, network interface
1340 may support communication via wired or wireless general data
networks, such as any suitable type of Ethernet network, for
example; via telecommunications/telephony networks such as analog
voice networks or digital fiber communications networks; via
storage area networks such as Fibre Channel SANs, or via any other
suitable type of network and/or protocol.
[0074] Input/output devices 1350 may, in some embodiments, include
one or more display terminals, keyboards, keypads, touchpads,
scanning devices, voice or optical recognition devices, mobile
devices, or any other devices suitable for entering or retrieving
data by one or more computer system 1300. Multiple input/output
devices 1350 may be present in computer system 1300 or may be
distributed on various nodes of computer system 1300. In some
embodiments, similar input/output devices may be separate from
computer system 1300 and may interact with one or more nodes of
computer system 1300 through a wired or wireless connection, such
as over network interface 1340.
[0075] As shown in FIG. 13, memory 1320 may include program
instructions 1325, configured to implement certain embodiments
described herein, and data storage 1335, comprising various data
accessible by program instructions 1325. In an embodiment, program
instructions 1325 may include software elements of embodiments
illustrated in the above figures. For example, program instructions
1325 may be implemented in various embodiments using any desired
programming language, scripting language, or combination of
programming languages and/or scripting languages (e.g., C, C++, C#,
JAVA.RTM., JAVASCRIPT.RTM., PERL.RTM., etc.). Data storage 1335 may
include data that may be used in these embodiments (e.g., recorded
communications, profiles for different modes of operations, etc.).
In other embodiments, other or different software elements and data
may be included.
[0076] A person of ordinary skill in the art will appreciate that
computer system 1300 is merely illustrative and is not intended to
limit the scope of the disclosure described herein. In particular,
the computer system and devices may include any combination of
hardware or software that can perform the indicated operations. In
addition, the operations performed by the illustrated components
may, in some embodiments, be performed by fewer components or
distributed across additional components. Similarly, in other
embodiments, the operations of some of the illustrated components
may not be provided and/or other additional operations may be
available. Accordingly, systems and methods described herein may be
implemented or executed with other computer system
configurations.
[0077] It will be understood that various operations discussed
herein may be executed simultaneously and/or sequentially. It will
be further understood that each operation may be performed in any
order and may be performed once or repetitiously. In various
embodiments, the operations discussed herein may represent sets of
software routines, logic functions, and/or data structures that are
configured to perform specified operations. Although certain
operations may be shown as distinct logical blocks, in some
embodiments at least some of these operations may be combined into
fewer blocks. Conversely, any given one of the blocks shown herein
may be implemented such that its operations may be divided among
two or more logical blocks. Moreover, although shown with a
particular configuration, in other embodiments these various
modules may be rearranged in other suitable ways.
[0078] Many of the operations described herein may be implemented
in hardware, software, and/or firmware, and/or any combination
thereof. When implemented in software, code segments perform the
necessary tasks or operations. The program or code segments may be
stored in a processor-readable, computer-readable, or
machine-readable medium. The processor-readable, computer-readable,
or machine-readable medium may include any device or medium that
can store or transfer information. Examples of such a
processor-readable medium include an electronic circuit, a
semiconductor memory device, a flash memory, a ROM, an erasable ROM
(EROM), a floppy diskette, a compact disk, an optical disk, a hard
disk, a fiber optic medium, etc. Software code segments may be
stored in any volatile or non-volatile storage device, such as a
hard drive, flash memory, solid state memory, optical disk, CD,
DVD, computer program product, or other memory device, that
provides tangible computer-readable or machine-readable storage for
a processor or a middleware container service. In other
embodiments, the memory may be a virtualization of several physical
storage devices, wherein the physical storage devices are of the
same or different kinds. The code segments may be downloaded or
transferred from storage to a processor or container via an
internal bus, another computer network, such as the Internet or an
intranet, or via other wired or wireless networks.
[0079] Many modifications and other embodiments of the invention(s)
will come to mind to one skilled in the art to which the
invention(s) pertain having the benefit of the teachings presented
in the foregoing descriptions, and the associated drawings.
Therefore, it is to be understood that the invention(s) are not to
be limited to the specific embodiments disclosed. Although specific
terms are employed herein, they are used in a generic and
descriptive sense only and not for purposes of limitation.
* * * * *