U.S. patent application number 14/337424 was filed with the patent office on 2014-11-06 for dynamically configurable frequency band selection device between catv distribution system and catv user.
This patent application is currently assigned to PPC Broadband, Inc.. The applicant listed for this patent is PPC Broadband, Inc.. Invention is credited to David Kelma, Joseph Lai, Thomas A. Olson, Steven K. Shafer.
Application Number | 20140331270 14/337424 |
Document ID | / |
Family ID | 42109661 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140331270 |
Kind Code |
A1 |
Olson; Thomas A. ; et
al. |
November 6, 2014 |
DYNAMICALLY CONFIGURABLE FREQUENCY BAND SELECTION DEVICE BETWEEN
CATV DISTRIBUTION SYSTEM AND CATV USER
Abstract
A frequency band selection device that can be inserted into a
signal transmission line of a CATV system on the premise of a user
includes at least two signal path sets between a tap side and a
premise side. Each signal path set includes two discrete signal
paths, a high frequency signal path for a downstream bandwidth and
a low frequency signal path for an upstream bandwidth. The high
frequency signal path and the low frequency signal path are
separated by a cut-off transition frequency that is different for
each signal path set. The device further includes a switch
controller having at least two discrete switch positions. The
switch controller chooses one of the switch positions as a result
of an information signal. Each of the switch positions corresponds
to a respective one of the signal path sets.
Inventors: |
Olson; Thomas A.;
(Maryville, TN) ; Kelma; David; (Madisonville,
TN) ; Lai; Joseph; (Los Angeles, CA) ; Shafer;
Steven K.; (Chittenango, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
PPC Broadband, Inc. |
East Syracuse |
NY |
US |
|
|
Assignee: |
PPC Broadband, Inc.
East Syracuse
NY
|
Family ID: |
42109661 |
Appl. No.: |
14/337424 |
Filed: |
July 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12252907 |
Oct 16, 2008 |
8832767 |
|
|
14337424 |
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Current U.S.
Class: |
725/149 |
Current CPC
Class: |
H04L 12/2801 20130101;
H04N 7/102 20130101; H04N 21/4104 20130101; H04N 21/643 20130101;
H04N 21/6168 20130101 |
Class at
Publication: |
725/149 |
International
Class: |
H04N 21/41 20060101
H04N021/41; H04N 21/643 20060101 H04N021/643; H04N 21/61 20060101
H04N021/61 |
Claims
1. A frequency band selection device that can be inserted into a
signal transmission line of a CATV system on the premise of a user,
the device comprising: at least two signal path sets between a tap
side and a premise side, each signal path set comprising two
discrete signal paths, a high frequency signal path allowing a
downstream bandwidth to pass from the tap side to the premise side
and a low frequency signal path allowing an upstream bandwidth to
pass from the premise side to the tap side, the high frequency
signal path and the low frequency signal path being separated by a
cut-off transition frequency that is different for each signal path
set; and a switch controller having at least two discrete switch
positions, the switch controller choosing one of the switch
positions as a result of an information signal, each of the switch
positions corresponding to a respective one of the signal path
sets.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of, and claims the
benefit and priority of, U.S. patent application Ser. No.
12/252,907, filed on Oct. 16, 2008. The entire contents of which
are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The use of a cable television ("CATV") system to provide
internet, voice over internet protocol ("VOIP") telephone,
television, and radio services is well known in the art. In
providing these services, a downstream bandwidth (i.e., radio
frequency ("RF") signals, digital signals, optical signals, etc.)
is passed from a supplier of the services to a user and an upstream
bandwidth is passed from the user to the supplier. The downstream
bandwidth is passed, for example, within relatively higher
frequencies from within a total bandwidth of the CATV system while
the upstream bandwidth is passed within relatively lower
frequencies.
[0003] Traditionally, the size of the downstream bandwidth far
exceeds the size of the upstream bandwidth due to nature of the
services provided. For example, while the downstream bandwidth must
accommodate all of the television and radio programming along with
internet and VOIP downloading, the upstream bandwidth is only
required to accommodate internet, system control signals, and VOIP
uploading. Problems are arising, however, due to an increase in
upstream bandwidth usage caused by an increasing demand for higher
speed internet uploads and the increasing demand for the VOIP
telephone services.
[0004] VOIP telephone services places significant demands on the
upstream bandwidth. When a user uploads a large image file to a
photo sharing website, the image file will be parsed into a number
of data packets that can be intermixed with other data packets
being passed through a particular portion of the upstream bandwidth
by other users located on a particular signal transmission line
within the CATV system. To optimize a total data throughput on the
particular signal transmission line, the data packets may be
significantly delayed and/or reorganized without any knowledge of
or inconvenience to the user. When a user uses VOIP telephone
services, their voice is converted into data packets that are
similar in form to the data packets used to upload the image file.
Because a typical conversation is carried out in real time, meaning
that a contiguous and unbroken flow of data packets is required,
any person with whom the user is talking will quickly notice
significant delays in the delivery of the data packets and/or
reorganization of the data packets that results in audio distortion
of the user's voice. Any such reorganization and/or delay in the
uploading of data packets carrying VOIP telephone services are
measured in terms of jitter, and are closely monitored because of
the significant service quality characteristics it represents.
[0005] Jitter experienced between the user and their caller is a
direct result of network congestion within the upstream bandwidth.
Because the upstream bandwidth is shared by all users on the
particular signal transmission line, each user is competing with
the other users for packet data space within the upstream
bandwidth. Even further, each of the users can unknowingly inject
interference signals, such as noise, spurious signals, and other
undesirable signals, into the upstream bandwidth through the use of
common household items and poor quality wiring in the user's
premise, the interference signals causing errors that force a slow
down and an additional amount of jitter in the upstream flow of
packets.
[0006] In an effort to increase the upstream flow of packets,
several suppliers have a plan to increase the size of the upstream
bandwidth from 5-42 Mhz to 5-85 Mhz to allow a greater flow of the
upstream content. Along with such an increase, the downstream
bandwidth must be correspondingly decreased in size because the
total bandwidth is relatively fixed. Such a change is, however,
very difficult to implement.
[0007] Traditional practices would require that every drop
amplifier and two way (diplex) filter in network amplifiers and
nodes of the CATV system to be changed as part of the increasing
the size of the upstream bandwidth. Compounding the difficulty of
implementing such a change, all of the changes must be implemented
at various locations throughout the CATV system at a single,
particular time. Accordingly, such an implementation is time
consuming, costly, and difficult to coordinate.
[0008] Further, while increasing the size of the upstream bandwidth
may incrementally increase the flow of upstream data packets, the
upstream bandwidth remains susceptible to reliability/congestion
issues since it is based on an inherent, system wide flaw that
leaves the upstream bandwidth open and easily impacted by any
single user. For example, while the downstream bandwidth is
constantly monitored and serviced by skilled network engineers, the
upstream bandwidth is created and passed using an infrastructure
within a user's premise that is maintained by the user without the
skill or knowledge required to reduce the creation and passage of
interference signals into the upstream bandwidth. This issue is
further compounded by the fact that over 500 premises can be
connected together such that interference signals generated by one
of the 500 premises can easily impact all of the remaining
premises. It is common in the art for the supplier to add physical
filters between the user's premise and a tap from of the main
signal distribution system near the users premise to reduce the
impact of the interference signals generated on the user's premise,
but such a physical filter must be installed manually and does not
account for significant, transient interference sources such as
garbage disposals, vacuum cleaners, welders, powered hand tools,
etc.
[0009] Even further, increasing the size of the upstream bandwidth
forces suppliers to push their downstream content into increasingly
higher frequency portions of the downstream bandwidth.
Unfortunately, these higher frequencies are much more susceptible
to parasitic losses in signal strength caused by the signal
transmission lines, connectors on the user's premise, devices
connected to the signal transmission lines on the user's premise,
etc. In the past many users have added relatively low-tech drop
amplifiers on their premise to account for such losses. Because of
the changes to increase the size of the upstream bandwidth, all of
these drop amplifiers must be removed and or replaced.
Additionally, because of the increased demands placed on the
downstream content (e.g., high definition television, increased
compression, etc.) the signal strength (i.e., level) of the
downstream bandwidth must be maintained to closer tolerances than
can typically be provided by the typical low-tech drop amplifier.
Accordingly, as a result of increasing the size of the upstream
bandwidth, the quality of the content moved to the higher
frequencies within the downstream bandwidth may be significantly
lessened causing a decrease in customer satisfaction and an
increase in costly service calls.
[0010] In light of the forgoing, increasing the size of the
upstream bandwidth: (i) may require a significant amount of capital
expenditure in terms new filter devices and the manpower to install
the devices; (ii) may not result in the expected large increases in
upstream data throughput because of the interference signals
injected from within each user's premise; (iii) may result in lower
quality downstream content, and (iv) may inject additional
interference signals that now fall within the additional upstream
bandwidth, which would have otherwise been filtered out.
[0011] Therefore, there is a need to overcome, or otherwise lessen
the effects of, the disadvantages and shortcomings described
above.
SUMMARY OF THE INVENTION
[0012] The present invention helps to reduce the complexity and
cost involved with changing the size of an upstream bandwidth.
Specifically, the present invention allows a CATV supplier to
implement such a change in the size at a common, specific time to
all users of the CATV services.
[0013] Further, the present invention can be added to a variety of
other devices that require a defined separation between the
upstream bandwidth and the downstream bandwidth. The incorporation
of the present invention allows such other devices to remain
relevant after a change in the size of the upstream bandwidth.
[0014] In accordance with one embodiment of the present invention,
a frequency band selection device is provided that can be inserted
into a signal transmission line of a CATV system on the premise of
a user. The device includes at least two signal path sets between a
tap side and a premise side. Each signal path set includes two
discrete signal paths, a high frequency signal path allowing a
downstream bandwidth to pass from the tap side to the premise side
and a low frequency signal path allowing an upstream bandwidth to
pass from the premise side to the tap side. The high frequency
signal path and the low frequency signal path are separated by a
cut-off transition frequency that is different for each signal path
set. The device further includes a switch controller having at
least two discrete switch positions. The switch controller chooses
one of the switch positions as a result of an information signal.
Each of the switch positions corresponds to a respective one of the
signal path sets.
[0015] In accordance with one embodiment of the present invention,
a dynamically configurable CATV system is provided. The system
includes a plurality of frequency band selection devices, each of
the devices being located on a premise of a user. Each device
includes at least two signal path sets between a tap side and a
premise side. Each signal path set includes two discrete signal
paths, a high frequency signal path allowing a downstream bandwidth
to pass from the tap side to the premise side and a low frequency
signal path allowing an upstream bandwidth to pass from the premise
side to the tap side. The high frequency signal path and the low
frequency signal path are separated by a cut-off transition
frequency that is different for each signal path set. Each device
further includes a switch controller having at least two discrete
switch positions. The switch controller chooses one of the switch
positions as a result of an information signal. Each of the switch
positions corresponds to a respective one of the signal path sets.
The system further includes a head end transmitter being connected
to each of the plurality of devices via a main distribution line,
the head end transmitter providing the information signal to the
switch controller in each of the devices.
[0016] In accordance with one embodiment of the present invention,
a method is provided for varying CATV frequency bands on a premise
of a user of CATV services. The method includes providing a
frequency band selection device on the premise. The device includes
at least two signal path sets between a tap side and a premise
side. Each signal path set includes two discrete signal paths, a
high frequency signal path allowing a downstream bandwidth to pass
from the tap side to the premise side and a low frequency signal
path allowing an upstream bandwidth to pass from the premise side
to the tap side. The high frequency signal path and the low
frequency signal path are separated by a cut-off transition
frequency that is different for each signal path set. The device
further includes a switch controller having at least two discrete
switch positions. The switch controller chooses one of the switch
positions as a result of an information signal. Each of the switch
positions corresponds to a respective one of the signal path sets.
The method further includes actuating the switch controller as a
result of the information signal.
[0017] In accordance with one embodiment of the present invention,
the device further includes a tap side filter set including at
least two frequency band splitting devices selectable by a tap side
switch set, and a premise side filter set including at least two
frequency band splitting devices selectable by a premise side
switch set. Preferably, the tap side switch set and the premise
side switch set are actuated by the switch controller.
[0018] In accordance with one embodiment of the present invention,
the tap side switch set includes a tap side downstream switch and a
tap side upstream switch, and the premise side switch set includes
a premise side downstream switch and a premise side upstream
switch.
[0019] In accordance with one embodiment of the present invention,
the information signal is a continuous tone.
[0020] In accordance with one embodiment of the present invention,
the information signal contains a coded operational signal.
[0021] In accordance with one embodiment of the present invention,
one of the frequency band splitting devices in each of the tap side
filter set and the premise side filter set is configured to
separate the upstream bandwidth from the downstream bandwidth
according to DOCSIS-1 and DOCSIS-2 standards.
[0022] In accordance with one embodiment of the present invention,
one of the frequency band splitting devices in each of the tap side
filter set and the premise side filter set is configured to
separate the upstream bandwidth from the downstream bandwidth
according to a DOCSIS-3 standard.
[0023] In accordance with one embodiment of the present invention,
the device includes three or more signal path sets and three or
more discrete switch positions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] For a further understanding of the nature and objects of the
invention, references should be made to the following detailed
description of a preferred mode of practicing the invention, read
in connection with the accompanying drawings in which:
[0025] FIG. 1 is a graphical representation of a CATV system
arranged in accordance with an embodiment of the present
invention;
[0026] FIG. 2 is a graphical representation of a user's premise
arranged in accordance with an embodiment of the present
invention;
[0027] FIG. 3 is a partial circuit diagram of a premise device made
in accordance with an embodiment of the present invention;
[0028] FIG. 4 is a partial circuit diagram of the premise device
represented in FIG. 3;
[0029] FIG. 5 is a circuit diagram representing a premise device
including a configurable frequency band selection device made in
accordance with another embodiment of the present invention;
[0030] FIG. 6a is a circuit diagram representing a premise device
including an upstream bandwidth conditioning device made in
accordance with another embodiment of the present invention;
[0031] FIG. 6b is a circuit diagram representing a premise device
including an upstream bandwidth conditioning device made in
accordance with another embodiment of the present invention;
[0032] FIG. 7 is a flow chart representing an signal level
adjustment setting routine performed by the circuit of FIGS. 6a and
6b;
[0033] FIG. 8 is a circuit diagram representing a premise device
including an automatic downstream bandwidth output level and/or
output level tilt compensation device made in accordance with
another embodiment of the present invention; (NOTE: manually
inserted compensation devices have been common for years)
[0034] FIG. 9 is a graphical representation of an interpolated gain
curve determined in accordance with the device represented in FIG.
8.
[0035] FIG. 10 is a graphical representation of a gain curve
determined in accordance with the device represented in FIG. 8;
[0036] FIG. 11 is a graphical representation of a gain curve
determined in accordance with the device represented in FIG. 8;
[0037] FIG. 12 is a graphical representation of a gain curve
determined in accordance with the device represented in FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
[0038] As shown in FIG. 1, a cable television ("CATV") system
typically includes a supplier 20 that transmits downstream signals,
such as radio frequency ("RF") signals, digital signals, optical
signals, etc., to a user through a main signal distribution system
30 and receives upstream signals from a user through the same main
signal distribution system 30. A tap 90 is located at the main
signal distribution system 30 to allow for the passage of the
downstream\upstream signals from\to the main signal distribution
system 30. A drop transmission line 120 is then used to connect the
tap 90 to a house 10, 60, an apartment building 50, 70, a coffee
shop 80, and so on. A premise device 100 of the present invention
is connected in series or in parallel between the drop transmission
line 120 and a user's premise distribution system 130.
[0039] Referring still to FIG. 1, is should be understood that the
premise device 100 can be placed at any location between the tap 90
and the user's premise distribution system 130. This location can
be conveniently located within the building 10, or exterior to the
building 60. Similarly, the premise device 100 can be located
within individual apartments of the apartment building 70 or
exterior to the apartment building 50. It should be understood that
the premise device 100 can be placed at any location, such as the
coffee shop 80 or other business, where CATV services, including
internet, VOIP, or other unidirectional\bidirectional services are
being used.
[0040] As shown in FIG. 2, the user's premise distribution system
130 can then be split using a splitter 190 so that
upstream/downstream signals can pass to a television 150 and a
modem 140 in accordance with practices well known in the art. The
modem 140 can include voice over internet protocol ("VOIP")
capabilities affording telephone 170 services and can include a
router affording internet services to a desktop computer 160 and a
laptop computer 180, for example.
[0041] Additionally, it is common practice to provide a "set-top
box" ("STB") or "set-top unit" ("STU") for use directly with the
television 150. For the sake of clarity, however, there is no
representation of an STB or STU included in FIG. 2. The STB and STU
are mentioned here in light of the fact that many models utilize
the upstream bandwidth to transmit information relating to
"pay-per-view" purchases, billing, etc. Accordingly, it should be
understood that even though FIG. 2 explicitly shows that there is
only one premise device 100 used for each device generating
upstream data packets, each premises device 100 can be used with
two or more devices (e.g. a modem, a STB, a STU, a dedicated VOIP
server, etc.) that transmit upstream data packets via the upstream
bandwidth.
[0042] Referring to FIG. 3, the premise device 100 includes a main
circuit 200 that is positioned along with a tuner circuit 600 and a
microprocessor circuit 800. Preferably, the combination of circuits
200, 600, 800 forms a configurable frequency band selection device
1 (represented separately in FIG. 5), an upstream bandwidth
conditioning device 2 (represented separately in FIGS. 6a and 6b)
and a downstream output level and/or output level tilt compensation
device 3 (represented separately in FIG. 8), each of which will be
discussed separately in greater detail below. It should be
understood, however, that circuits 200, 600, 800 of the premise
device 100 can be configured to form any combination of the devices
such that the premise device 100 may include any one of the
devices, any two the devices, or all three of the devices.
Preferably, each of the circuits are positioned within a single
enclosure, but it should be understood that circuits 200, 600, 800
could be arranged within multiple enclosures to account for space,
cost, better resultant performance, or other environmental
considerations.
[0043] Because a diagram of a premise device 100 including all
three devices is too complex to be clearly represented in one
figure, a circuit 205 of the main circuit 200, as it is represented
in FIG. 3, is represented in FIG. 4 with inputs and outputs between
itself and the remaining positions of the circuit 200 in FIG. 3
labeled similarly.
[0044] Along these lines, alternate embodiments of the premise
device 100 are represented in FIGS. 5, 6a, 6b and 8. FIG. 5
represents an embodiment of the premise device 100 including only
the configurable frequency band selection device 1. FIGS. 6a and 6b
represent an embodiment of the premise device 100 including only
the upstream bandwidth conditioning device 2. FIG. 8 represents an
embodiment of the premise device 100 including only the downstream
output level and/or output level tilt compensation device 3. It
should be understood that the embodiments shown in FIGS. 5, 6a, 6b
and 8 are presented to help clarify the components specific to the
particular device, and that other embodiments including
combinations of these are envisioned.
[0045] Individual components that are similar between the
embodiments represented in FIGS. 3, 4, 5, 6a, 6b, and 8 are
identified using the similar reference numbers. For example, the
microprocessor represented in each of the embodiments is referenced
using the number 810. One skilled in the art should know that the
microprocessor could be the same or different across the
embodiments depending on the requirements placed thereon.
[0046] As shown in FIG. 3, the main circuit 200 of the premise
device 100 includes a supplier side 210 and a premise side 220. The
supplier side 210 is positioned to receive the downstream bandwidth
from the supplier 20 (FIG. 1) and to send the upstream bandwidth to
the supplier 20. The premise side 220 is positioned to send the
downstream bandwidth to the user and to receive the upstream
bandwidth from the user. Each of the supplier side 210 and the
premise side 220 can include a traditional threaded 75 ohm
connector so that the premise device 100 can be easily placed in
series with the drop transmission line 120 and the premise
distribution system 130. Alternatively, each of the supplier side
210 and the premise side 220 may include a proprietary connecter to
hinder attempts at tampering with or theft of the premise device
100. Other connectors may also be used depending on the type and/or
size of the drop transmission line 120, the premise distribution
system 130, or a system impedance other than 75 ohms.
[0047] The premise device 100 preferably includes a lightening
protection device 230 positioned near the supplier side 210 and a
lightening protection device 240 positioned near the premise side
220. Having two lightening protection devices 230, 240 attempts to
protect the premise device 100 from energy passing from the drop
transmission line 120 from a lighting strike and from energy
passing from the premise distribution system 130 from a lighting
strike. It should be understood that the lightening protection
devices may not be necessary if/when the premise device 100 is
configured to be placed in a CATV system that utilizes
non-conductive signal transmission lines. Any of the high quality,
commercially available lightning protection devices will function
well within the specified locations within the premise device
100.
[0048] The premise device 100 preferably includes two power bypass
failure switches 250, 260 that route all of the upstream\downstream
signals through a bypass signal path 270 (e.g. a coaxial cable, an
optical cable, a microstrip, a stripline, etc.) in the event of a
power outage. The bypass failure switches 250, 260 are preferably
located near the supplier end 210 and premise end 220,
respectively. In an effort to protect the bypass failure switches
250, 260 from damage due to lightening energy, they are preferably
placed between the lightening protection devices 230, 240 and the
supplier end 210 and premise end 220.
[0049] Each of the bypass failure switches 250, 260 includes a
default position bypassing the upstream/downstream signals through
the bypass signal path 270 at any time power is removed from the
premise device 100. When power is applied, each of the bypass
failure switches 250, 260 actuate to a second position that
disconnects the bypass signal path 270 and passes all of the
upstream\downstream signal transmissions along another path through
the circuit 205 (FIG. 4) within the main circuit 200. The switches
may also be controlled such that when there is a fault detected in
the premise device 100 that could abnormally hinder the flow of the
upstream\downstream bandwidths through the circuit 205 (FIG. 4),
the switches 250, 260 are moved to their default position sending
the upstream/downstream signal transmissions through the bypass
signal path 270. Any of the high quality, commercially available
signal transmission switches will function well within the
specified locations within the premise device 100. The bypass
signal path 270 can be any suitable coaxial cable or optical cable
depending on the CATV system configuration.
[0050] The premise device 100 preferably includes circuit
components creating the frequency band selection device 1 (FIG. 5
and represented but not referenced in FIGS. 3 and 4). The frequency
band selection device 1 is configured to automatically switch
between a configuration corresponding to earlier Data Over Cable
Service Interface Specification ("DOCSIS") specifications and a
configuration corresponding to a later generation specification,
such as DOCSIS 3.0. While this feature may be advantageous by
itself in the premise device 100, this feature allows for other
devices, such as the upstream bandwidth conditioning device 2 and
the downstream bandwidth output level and/or output level tilt
compensation device 3, to remain relevant after a change between
specifications. In particular, because each of these devices
requires an accurate separation of signals between the upstream
bandwidth and the downstream bandwidth, any necessary change in the
upstream/downstream bandwidths would render these specific devices
inoperable. It should be understood that even though the DOCSIS
specifications are referenced above and below, the
upstream/downstream bandwidth configurations may be maintained and
changed according to any specifications.
[0051] A simplified version of the of the frequency band selection
device 1 is shown in FIG. 5 while all of the components are also
present in the embodiment of FIGS. 3 and 4. The selection device 1
includes a plurality of switches 280, 290, 300, 310, 320, 330 that
define a first signal path set 910 and second signal path set 920.
Each signal path set includes two discrete signal paths, a high
frequency signal path 930 and a low frequency signal path 940. The
first signal path set 910 is formed using a pair of first frequency
band splitting devices 340, 345, and the second signal path set 920
is formed using a pair of second frequency band splitting device
350, 355. A cutoff frequency set by the first pair of frequency
band splitting devices 340, 345 corresponds to DOCSIS
specifications having a narrower upstream bandwidth, and a cutoff
frequency set by the second set pair of frequency band splitting
devices 350, 355 corresponds to the later DOCSIS specifications,
which include a broader upstream bandwidth than the earlier DOCSIS
standards. It should be understood that the cutoff frequencies can
be changed to accommodate even newer DOCSIS standards or other
standards by the mere replacement of the first pair of frequency
band splitting devices 340, 345 and/or the second pair of frequency
band splitting devices 350, 355. Any of the high quality,
commercially available switches and frequency band splitting
devices will function well within the specified locations within
the premise device 100.
[0052] Each of the switches 280, 290, 300, 310, 320, 330 is
controlled either directly or indirectly by a microprocessor 810
(FIG. 3). The microprocessor 810 determines whether to actuate the
switches 280, 290, 300, 310, 320, 330 to the first signal path set
910 or to the second signal path set 920 based on an information
transmission signal preferably sent by the supplier 20. A signal
coupler 360 allows for a receiver to 820 to receive the information
transmission signal, such as a tone, a coded operational signal, or
other well known information transmission, that can be understood
by the microprocessor 810 to indicate the switch position. For
example, the presence of an information signal can be used to
indicate that the microprocessor 810 should select the second
signal path set 920, whereas no information signal could indicate
that microprocessor 810 should select the first signal path set
910. For example, the presence of a continuous tone at 900 MHz can
be identified by passing a signal carrying such a tone through a
band pass filter 830 to eliminate unnecessary signals and a
comparator 840, which only provides a tone to the microprocessor
when/if the tone is stronger than a predetermined threshold
determined by a voltage source 850 and a resistive voltage divider
860. The frequency can be selected by the microprocessor 810 and
can be tuned by a phase-locked loop control system 880 and an
amplifier 870 in a manner well known in the art. Any of the high
quality, commercially available microprocessors, signal couplers
and receivers will function well within the specified locations
with the premise device 100.
[0053] The premise device 100 preferably further includes circuit
components creating the upstream bandwidth conditioning device 2,
which automatically increases the signal to noise ratio of the
upstream bandwidth created on the user's premise and passed into
the upstream bandwidths on the main signal distribution system 30.
It should be understood that with VOIP telephone service, the
consistent flow of upstream data packets that lasts as long as the
telephone call can appear to be noise (i.e., interference signals).
Before VOIP, such continuous upstream flow data of data packets was
not likely. Accordingly, the present device purposefully includes
logic and structure that will halt the addition of attenuation once
the maximum output of the cable modem is sensed even if the
upstream data flow is consistent enough to be interpreted as
noise.
[0054] As shown in FIGS. 3, 4, and 6a, the upstream bandwidth
conditioning device 2 of one embodiment of the premise device 100
includes a variable attenuator 400 and an amplifier 410. The amount
of signal level adjustment used to condition the upstream bandwidth
is determined by the microprocessor 810 based on inputs from a
signal level detector 390. The signal level detector 390 measures
and maintains a contemporary peak signal strength of the upstream
bandwidth via a tap 370 and a filter 380. The microprocessor 810
includes a counting circuit, a threshold comparison circuit and a
level comparison circuit. It should be understood that even though
a microprocessor 810 is used in the present embodiment, it is
envisioned to control the variable attenuator 400 in the manner
described using a traditional logic circuit.
[0055] As shown in FIG. 6b, another embodiment of the upstream
bandwidth conditioning device 2 includes a variable amplifier 415,
which is connected and controlled by the 810. According to this
embodiment, an attenuator 405 is present and is not controlled by
the microprocessor. Other embodiments are envisioned that include
both a variable amplifier 415 and a variable attenuator 405.
Further, the variable signal level adjustment device could also be
an automatic gain control circuit ("AGC") and function well in the
current device. In other words, it should also be understood that
the amount of signal level adjustment and any incremental amount of
additional signal level adjustment can be accomplished through any
of a wide variety of amplification and/or attenuation devices.
[0056] In light of the forgoing, the term "variable signal level
adjustment device" used herein should be understood to include not
only a variable attenuation device, but also circuits containing a
variable amplifier, AGC circuits, other variable
amplifier/attenuation circuits, and related optical circuits that
can be used to reduce the signal strength on the upstream
bandwidth.
[0057] It should be noted that the term contemporary signal
strength is intended to describe a current or present signal
strength as opposed to a signal strength measured at a time in the
past (i.e., a previous signal strength) such as prior to an
application of signal level adjustment or an application of an
additional amount of signal level adjustment. The reason for this
point should be clear based on the following.
[0058] In operation, the microprocessor 810 within the upstream
bandwidth conditioning device 2 performs a signal level setting
routine 1000 (FIG. 7) to determine an appropriate amount of signal
level adjustment to apply to the upstream bandwidth via the
variable attenuator 400, the variable amplifier 415 or other
suitable variable signal level adjustment device. The signal level
setting routine can be run continuously, at predetermined
intervals, and/or on command as a result of an information signal
transmitted by the supplier 20. Once initiated, the microprocessor
810 or logic circuit performs the signal level setting routine in
accordance with the flow chart shown in FIG. 7.
[0059] Referring now to FIG. 7, upon initialization 1010 of the
signal level setting routine 1000, the counting circuit in the
microprocessor 810 is reset to zero (0), for example, in step 1020.
Next, the microprocessor 810 iteratively performs steps 1030, 1040,
1050, 1060, 1070, 1080 and 1090 until the counter reaches a
predetermined number (e.g. 25) or the answer to step 1080 is
negative.
[0060] Specifically, in step 1030 the microprocessor 810 reads a
contemporary signal strength from the signal level detector 390,
and the counter is incremented by a predetermined increment, such
as one (1) in step 1040. The microprocessor 810 then looks to see
if the counter is greater than the predetermined number (i.e., 25).
If so, the microprocessor 810 ends the routine, but if not, the
microprocessor 810 proceeds to step 1060. In step 1060, the
microprocessor 810 compares the contemporary signal strength to a
predetermined threshold. If the contemporary signal strength is
greater than the predetermined threshold, the microprocessor 810
instructs the variable attenuator 400 to add an amount of
additional signal level adjustment (e.g. 1 dB), but if the
contemporary signal strength is lower than the predetermined
threshold, the microprocessor 810 returns to step 1030.
[0061] After adding the amount of additional signal level
adjustment, the microprocessor 810 reads a new contemporary signal
strength in step 1080 while saving the previously read contemporary
signal strength (i.e., from step 1030) as a previous signal
strength in preparation for step 1090. In step 1090, the
microprocessor 810 compares the contemporary signal strength
measured in step 1080 and the previous signal strength measured in
step 1030 to one another. If the contemporary signal strength is
equal to the previous signal strength then the microprocessor 810
returns to step 1030, but if the contemporary signal strength is
less than the previous signal strength the microprocessor 810
proceeds to step 1100 where it instructs the variable attenuator
400 to reduce the amount of signal level adjustment by a
predetermined amount (e.g. the amount of additional signal level
adjustment added in step 1070 or an amount greater than the
additional signal level adjustment added in step 1070). After step
1100, the microprocessor 810 saves the total amount of signal level
adjustment in step 1110 and stops the routine at step 1120. Again,
it should be understood that the amount of additional signal level
adjustment may be added/removed by the variable amplifier 415, or
by the AGC discussed above.
[0062] As mentioned above, an important aspect of the present
signal level setting routine is the comparison step conducted in
step 1090. A traditional cable modem 140 (FIG. 2) used in CATV
systems can adjust its output level based on information signals
received from the suppler in the downstream bandwidth. In
particular, if the modem signal received by the supplier 20 is
weak, the supplier 20 instructs the modem 140 to increase its
transmission signal level. As this relates to the current
invention, the modem 140 will continually increase signal level as
a result of increased amounts of upstream bandwidth signal level
adjustment until the modem 140 can no longer increase its
transmission signal strength. Accordingly, the contemporary signal
strength measured in step 1080 after the addition of additional
signal level adjustment in step 1070 should be equal to the
previous signal strength if the modem 140 is able to compensate for
the additional signal level adjustment. However, if the modem 140
is already producing its maximum signal strength, the contemporary
signal strength will be less than the previous signal strength when
an additional amount of upstream bandwidth signal level adjustment
is applied.
[0063] Because problems could result in the modem 140 from
operating it at its maximum output (i.e., signal distortion may be
high when the modem 140 is operating at or near a maximum level
and/or the durability of the modem 140 may be sacrificed when the
modem 140 is operating at or near a maximum level), the amount of
signal level adjustment may be reduced by a sufficient amount in
step 1100 to ensure quality of the output signal generated by the
modem 140 and the durability of the modem 140 once the maximum
output strength of the modem 140 is identified.
[0064] It is noted that in a system with more than one device
passing data packets into the upstream bandwidth, the premise
device 100 may identify the maximum output strength of one device
and not the other. In other words, the premise device 100 may
identify the first device achieving its maximum output strength
without proceeding to identify the maximum output strength of any
other devices. If the premise device 100 fails to identify the
first observed maximum output strength, that device may continue to
operate at its maximum output strength until another determination
cycle is initiated.
[0065] The predetermined number compared in 1050 can be related
directly to the amount of signal level adjustment. For example, if
the variable signal level adjustment device is a step attenuator
including 25 steps of 1 dB attenuation, as is the case in the
embodiment represented in FIG. 6a, the predetermined number can be
set to 25 to allow for the finest resolution (i.e., 1 dB) and the
broadest use of the particular step attenuator's range (i.e., 25
dB). It should be understood that the number of steps could be
reduced and the resolution could be decreased (i.e., 5 steps of 5
dB) if faster overall operation is desired. It is also foreseeable
that the predetermined number could be increased if a variable
signal level adjustment device having a finer resolution (i.e.,
less than 1 dB) or a broader range (i.e., greater than 25 dB) is
utilized. The incremented amount discussed here relating the
counter and the predetermined number is one (1) such that there are
25 iterations (i.e., 25 steps) when the predetermined number is 25.
The increment could easily be any number (i.e., 1, 5, 10, -1, -10,
etc.) depending on the predetermined number and the total number of
steps desired, which, as discussed above, is based on the desired
resolution and the desired range of signal level adjustment.
[0066] The amount of additional attenuation added in step 1070, and
the predetermined amount of attenuation reduced in step 1100 are
all variables that are currently based, at least partially, on
hardware design limitations and can, depending on the hardware, be
adjusted by one skilled in the art based on the conditions
experienced in a particular CATV system and with particular CATV
equipment. As discussed above, the variable signal level adjustment
device in one embodiment of the present invention is a step
attenuator having a resolution of 1 dB and a range of 25 dB.
Accordingly, the amount of additional attenuation added in step
1070 using the present hardware could be 1 dB or multiples of 1 dB.
Similarly, the predetermined amount of attenuation reduced in step
1100 can be 1 dB or multiples of 1 dB. It should be understood that
if the amount of additional attenuation added in step 1070 is a
multiple of 1 dB, such as 5 dB, the amount of attenuation reduced
in step 1100 can be a lesser amount, such as 2 dB or 4 dB. The
amount of attenuation reduced in step 1100 can also be greater than
the amount of additional attenuation added in step 1070 for the
reasons stated above relating to maintaining the quality of the
output from the modem 140 and the and durability of the modem
140.
[0067] The predetermined threshold compared in step 1060 is a
signal level sufficient to distinguish the presence of upstream
data packets in the upstream bandwidth from interference signals.
This value will vary depending on the output power of any cable
modem 140, STB, STU, etc. in the system and the average observed
level of interference signals. A goal is, for example, to determine
if a device is present that sends upstream data packets via the
upstream bandwidth. If the predetermined threshold is set too low,
the interference signals may appear to be upstream data packets,
but if the predetermined threshold is set too high, the upstream
data packets may appear as interference signals.
[0068] Any of the high quality, commercially available signal
couplers, signal level detectors, variable attenuation devices,
filters, amplifiers, and microprocessors will function well within
the specified locations within the premise device 100.
[0069] Referring now to FIGS. 3, 4, and 8, the premise device 100
preferably includes circuit components creating the downstream
bandwidth output level and/or output level tilt compensation device
3, which helps to maintain a desired signal quality in transmitted
signals using relatively high frequencies within the downstream
bandwidth, which are much more susceptible to traditional parasitic
losses. At a simplistic level, the microprocessor 810 observes
channel data obtained from the tuner circuit 600, compares the
observed channel data to a known parasitic loss curve, and then
adjusts a pair of variable output level compensation devices 440,
450 and a variable slope adjusting circuit 460 located in the
circuit 200 to create an output having a desired gain curve (i.e.,
a curve representative of transmitted signal strengths) across the
downstream bandwidth. While each of the variable output level
compensation devices 440, 450 are depicted in FIGS. 4 and 8 as a
variable attenuator, it should be understood that the term
"variable output level compensation device" used herein should be
understood to include not only a variable attenuation device, but
also circuits containing a variable amplifier, AGC circuits, other
variable amplifier/attenuation circuits, and related optical
circuits that can be used to alter the signal strength of signals
in the downstream bandwidth. Each of these steps will be discussed
in further detail below.
[0070] The tuner circuit 600 obtains the downstream bandwidth from
a coupler 420 drawing the downstream bandwidth off of the high
frequency signal path 930 (FIG. 5). Please note that these signals
will be referred to herein as the coupled downstream bandwidth. The
coupled downstream bandwidth is passed through a resistor 430 prior
to being passed into a tuner 610.
[0071] Through instructions provided by the microprocessor 810, the
tuner 610 scans the coupled downstream bandwidth in an effort to
locate and identify a channel having a low frequency, referred to
herein as a low band signal channel 1250 (FIG. 9), and a channel
having a high frequency, referred to herein as a high band signal
channel 1260 (FIG. 9). In the present instance, the microprocessor
810 instructs the tuner 610 to begin at the lowest frequency in the
downstream bandwidth and scan toward higher frequencies until the
low band signal channel 1250 is found. Similarly, the
microprocessor 810 instructs the tuner 610 to begin at the highest
frequency in the coupled downstream bandwidth and scan toward lower
frequencies until the high band signal channel 1260 is found.
Accordingly, the low band signal channel 1250 is a channel located
near the lowest frequency within the coupled downstream bandwidth
while the high band channel 1260 is a channel located near the
highest frequency within the coupled downstream bandwidth. Even
though the low band signal channel 1250 and the high band signal
channel 1260 are depicted in FIG. 9 as a single frequency for
clarity, it should be understood that a channel is typically a
range of frequencies. It should also be understood that the low
band signal channel 1250 and the high band signal channel 1260 do
not need to be the lowest or highest frequency channels,
respectively. It is beneficial, however that the two channels be
spaced as far apart from one another as practical to better
estimate the amount of parasitic loss experiences across the entire
downstream bandwidth.
[0072] During the scanning process to locate and identify the low
and high band signal channels 1250, 1260, the tuner circuit 600
provides the microprocessor 810 with three types of information.
First, a signal indicating that a channel has been identified is
provided to the microprocessor 810 through input line 640. Second,
a signal indicating signal strength of the identified channel is
provided to the microprocessor 810 through input line 630. Third, a
signal indicating the format of the identified channel is provided
to the microprocessor 810 through input line 620.
[0073] The signal indicating that a channel has been identified is
created by passing the coupled downstream bandwidth though a band
pass filter 650 to remove extraneous noise, a signal level detector
660 to convert signal into a voltage, and another signal level
detector 670. The signal leaving the signal level detector 670 is
compared to a predetermined threshold voltage using comparator 680.
The predetermined threshold voltage is created using a voltage
source 690 and an resistive divider 700, and is set such that if
the voltage associated with the coupled downstream bandwidth at the
tuner frequency is greater than the threshold voltage, it is likely
a channel in use by the supplier 20, whereas if the voltage
associated with the coupled downstream bandwidth at the tuner
frequency is less than the threshold voltage, it is likely
interference signals.
[0074] The signal indicating signal strength is created similarly
to the signal indicating that a channel has been identified. The
signal indicating signal strength passes through comparator 720
when it is greater than a threshold voltage created by a voltage
source 730 and a resistive divider 740. To clarify the differences,
the signal indicating that a channel has been identified may not
have any direct relation to the actual signal strength, whereas the
signal indicating signal strength is directly proportional to the
actual signal strength of the identified channel.
[0075] The signal indicating the format of the identified channel
is created when the coupled downstream bandwidth passes through a
channel analyzer, which includes the band pass filter 650, the
signal level detector 660, a synch detector 750, a low pass filter
760, and a signal level detector 770. The resulting signal
identifies whether the identified channel is an analog format
channel or another type of signal format.
[0076] According to current signal transmission specifications,
digital format channels have a signal strength that is typically 6
dB less than a corresponding analog channel. Accordingly, the
microprocessor 810 must include a level offset calculation that can
account for this 6 dB difference when comparing the relative signal
strengths of the low and high band signal channels 1250, 1260. If
this inherent difference is not accounted for, any resulting
comparisons of the two channels 1250, 1260 for the purpose of
determining relative signal strengths would necessarily be flawed.
For example, if the high band channel 1260 is digital while the low
band channel 1250 is analog, the additional, inherent 6 dB
difference would incorrectly indicate that there is more parasitic
losses than there actually is. Similarly, if the high band channel
1260 is analog and the low band channel 1250 is digital, any
resulting comparison would incorrectly indicate that there is less
parasitic loss that there actually is. Therefore, it should be
understood that it does not matter whether the 6 dB offset is added
to the signal strength of a digital format channel or the 6 dB
offset is subtracted from the signal strength of an analog format
channel. Further, it should be understood that the 6 dB offset can
be added to the signal strength of both the low and high band
channels 1250, 1260 if they are both digital or the 6 dB offset can
be subtracted from the signal strength of both the low and high
band channels 1250, 1260 if they are both analog. Even further, it
should be understood that the offset value is dictated by the
standards observed by a particular supplier and can be, therefore,
a value other than 6 dB.
[0077] After completing the scanning process and the process of
adding/removing any offsets, the microprocessor 810 now has a low
band signal strength (including any offset), a low band channel
frequency, a high band signal strength (including any offset), and
a high band channel frequency. The known information (i.e., the
strength and frequency) of the low and high band channels 1250,
1260 are now compared, by the microprocessor 810, to a
predetermined signal strength loss curve (i.e., a gain loss curve),
which corresponds to the known parasitic losses associated with the
type of coaxial/optical cables used, as shown in FIG. 9. This step
beneficially allows the known information to be interpolated across
the entire downstream bandwidth. Using the interpolated curve, the
microprocessor 810 determines how much signal level adjustment to
apply and in what manner to apply the level adjustment across the
entire downstream bandwidth such that the a resulting gain curve
across the entire bandwidth is nearly linear and preferably with a
slight increase in gain toward the higher frequencies in
anticipation of parasitic losses that will occur downstream from
the premise device 100. For example, the amount of level is
determined by the high band signal strength (i.e., high band gain)
including any interpolation to the highest frequency, and the
amount of level reduction is determined by the low band signal
strength (i.e., low band level) including any interpolation to the
lowest frequency.
[0078] It should be understood that parasitic losses affect higher
frequencies more than lower frequencies. Accordingly, if a known
signal having a -10 dB signal strength, for example, is transmitted
at various frequencies across the entire downstream bandwidth and
across a length of coaxial/optical cable, a plot of the resulting
gain curve would result in a curve, which is known. Because the end
goal is to have a gain curve that is a straight line near the
original signal strengths or to have a gain curve that has an
increasing slope versus frequency, the microprocessor 810 directly
controls the variable slope adjustment circuit to adjust the
downstream signal transmission in curve such that the lower
frequencies are lower in amplitude than the higher frequencies.
[0079] For example, as shown in FIG. 9, using the known frequency
and signal strength for each of the low band channel 1250 and the
high band channel 1260, a gain curve 1210 can be plotted across the
entire downstream bandwidth, which is shown, for example, as being
from 50 MHz to 1000 MHz. The microprocessor 810 then determines a
total amount of level adjustment to be added by the amplifier 490
and/or the amplifier 500 that will at least replace the loss at the
highest frequency. In the present example, the amount of level
adjustment would be at least +38 dB, resulting in a gain curve 1220
that is shown in FIG. 10. Based on the interpolated gain curve
shown in FIG. 9, the microprocessor 810 instructs the variable
slope circuit 460 to apply a similar, but inversely curved amount
of correction to result in a relatively flat gain curve 1230 shown
in FIG. 10. It may be desirable to increase the amount of level
adjustment applied and increase the curvature of the slope
adjustment to result in a gain curve 1240, as shown in FIG. 8,
which has an increasing slope toward the higher frequencies.
[0080] As with the other devices discussed above, the downstream
bandwidth output level and/or output level tilt compensation device
3 can be activated automatically upon initialization of the premise
device 100, a set intervals, upon the occurrence of a particular
event, and/or upon receipt of an information signal (e.g. a tone, a
coded operating signal, etc.) from the supplier 20.
[0081] While the present invention has been particularly shown and
described with reference to certain exemplary embodiments, it will
be understood by one skilled in the art that various changes in
detail may be effected therein without departing from the spirit
and scope of the invention as defined by claims that can be
supported by the written description and drawings. Further, where
exemplary embodiments are described with reference to a certain
number of elements it will be understood that the exemplary
embodiments can be practiced utilizing either less than or more
than the certain number of elements.
* * * * *