U.S. patent application number 10/869578 was filed with the patent office on 2005-12-22 for wideband node in a cable tv network.
This patent application is currently assigned to XTEND Networks, Ltd.. Invention is credited to Dounaevski, Oleg, Strull, Yeshayahu, Weinstein, Hillel.
Application Number | 20050283816 10/869578 |
Document ID | / |
Family ID | 35482062 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050283816 |
Kind Code |
A1 |
Weinstein, Hillel ; et
al. |
December 22, 2005 |
Wideband node in a cable TV network
Abstract
A novel node device enables transmission of a wideband signal,
in compliance with various acceptable transmission standards and
protocols. The signal consists of the legacy spectrum of about
5-860 MHz as well as a new downstream spectrum of about 1000-2000
MHz and a new upstream spectrum of about 2000-3000 MHz or about
930-1100 MHz. The novel device enables transfer of additional data
in the upstream direction employing multiple upstream bands without
making substantial investment in upstream physical node splitting,
thus providing networking services to residential subscribers as
well as to small and medium-sized businesses (SMB), which may
operate under existing DOCSIS protocols and controlled by standard
DOCSIS routers (CMTSs).
Inventors: |
Weinstein, Hillel; (Haifa,
IL) ; Strull, Yeshayahu; (Tel Aviv, IL) ;
Dounaevski, Oleg; (Netanya, IL) |
Correspondence
Address: |
PEARL COHEN ZEDEK, LLP
10 ROCKEFELLER PLAZA
SUITE 1001
NEW YORK
NY
10020
US
|
Assignee: |
XTEND Networks, Ltd.
Tel Aviv
IL
|
Family ID: |
35482062 |
Appl. No.: |
10/869578 |
Filed: |
June 16, 2004 |
Current U.S.
Class: |
725/129 ;
725/126 |
Current CPC
Class: |
H04N 7/102 20130101;
H04N 7/17309 20130101; H04N 7/104 20130101 |
Class at
Publication: |
725/129 ;
725/126 |
International
Class: |
H04N 007/173 |
Claims
1. In a hybrid fiber cable signal distribution network, a node
apparatus for the division, frequency conversion and multiplexing
of at least four signal sub-bands included in a high frequency band
signal of a wideband signal of about 5 to 3000 MHz, the apparatus
comprising the elements of: a triplexer device to separate in an
upstream direction the wideband signal into the high frequency band
signal and a CATV signal of about 5 to 860 MHz; an amplifier device
to amplify the high frequency band signal in the upstream
direction; a splitter device to split the amplified high frequency
band signal into at least four reproduced signals in the upstream
direction; a first frequency converter device to down-convert the
first frequency sub-band of the first reproduced signal into a
first down-converted signal of about 12 to 42 MHz in the upstream
direction; a second frequency converter device to down-convert the
second frequency sub-band of the second reproduced signal into a
second down-converted signal in the upstream direction; a third
frequency converter device to down-convert the third frequency
sub-band of the third reproduced signal into a third down-converted
signal in the upstream direction; a fourth frequency converter
device to down-convert the fourth frequency sub-band of the fourth
reproduced signal into a fourth down-converted signal in the
upstream direction; and a multiplexer device to multiplex the first
down-converted signal, the second down-converted signal, the third
down-converted signal and the fourth down-converted signal into a
combined signal in the upstream direction.
2. The node apparatus as claimed in claim 1 wherein the high
frequency upstream band signal is of about 2000 to 3000 MHz.
3. The node apparatus as claimed in claim 1 wherein the high
frequency upstream band signal is of about 860 to 1100 MHz.
4. The node apparatus as claimed in claim 2 wherein the high
frequency band signal further comprises a plurality of channels,
which may be operating under the DOCSIS standards and
protocols.
5. The node apparatus as claimed in claim 3 wherein the high
frequency band signal further comprises a plurality of channels,
which may be operating under the DOCSIS standards and
protocols.
6. The node apparatus as claimed in claim 1 wherein the first or
second or third or fourth frequency sub bands are about 30 MHz
wide, which may be operating under the DOCSIS standards and
protocols.
7. The node apparatus as claimed in claim 1 wherein the first
frequency sub-band is in the about 2250 to 2280 MHz or in the about
900 to 930 MHz frequency range.
8. The node apparatus as claimed in claim 1 wherein the second
frequency sub-band is in the about 2300 to 2330 MHz or in the about
931 to 960 MHz frequency range.
9. The node apparatus as claimed in claim 1 wherein the third
frequency sub-band is in the about 2350 to 2380 MHz or in the about
961 to 990 MHz frequency range.
10. The node apparatus as claimed in claim 1 wherein the fourth
frequency sub-band is in the about 2400 to 24300 MHz or in the
about 991 to 1100 MHz frequency range.
11. The node apparatus as claimed in claim 1 wherein the first or
second or third or fourth down-converted signal is in the about 12
to 42 MHz.
12. The node apparatus as claimed in claim 1 further comprises an
RF-to-optical converter in the upstream direction and an
Optical-to-RF converter in the downstream direction.
13. The node apparatus as claimed in claim 1 further comprises an
optical transmitter device in the upstream and an optical receiver
in the downstream direction.
14. The node apparatus as claimed in claim 1 wherein the triplexer
device combines into the wideband signal a low frequency
signal.
15. The node apparatus as claimed in claim 1 further comprises a
fifth frequency converter device to up-convert a downstream signal
to a low frequency band signal in a downstream direction.
16. The node apparatus as claimed in claim 15 wherein the low
frequency downstream band signal is in the about 1000 to 2000
MHz.
17. The node apparatus as claimed in claim 15 wherein the low
frequency downstream band signal is in the about 1000 to 2000
MHz.
18. The node apparatus as claimed in claim 15 wherein the
downstream signal is in the about 150-860 MHz.
19. In a hybrid fiber cable signal distribution network, a method
for the division, frequency conversion and multiplexing of at least
four signal sub-bands included in a high frequency upstream band
signal of a wideband signal of about 5 to 3000 MHz, the method
comprising the steps of: separating in an upstream direction the
wideband signal into the high frequency band signal and a CATV
signal of about 50 to 860 MHz; amplifying the high frequency band
signal in the upstream direction; splitting the amplified high
frequency band signal into at least four reproduced signals in the
upstream direction; down-converting the first frequency sub-band of
the first reproduced signal into a first down-converted signal in
the upstream direction; down-converting the second frequency
sub-band of the second reproduced signal into a second
down-converted signal in the upstream direction; down-converting
the third frequency sub-band of the third reproduced signal into a
third down-converted signal in the upstream direction;
down-converting the fourth frequency sub-band of the fourth
reproduced signal into a fourth down-converted signal in the
upstream direction; and multiplexing the first down-converted
signal, the second down-converted signal, the third down-converted
signal and the fourth down-converted signal into a combined signal
in the upstream direction.
20. The method as claimed in claim 19 wherein the high frequency
band signal is of about 2000 to 3000 MHz.
21. The method as claimed in claim 19 wherein the first frequency
sub-band is in the about 2250 to 2280 MHz or in the about 900 to
931 MHz frequency range.
22. The method as claimed in claim 19 wherein the second frequency
sub-band is in the about 2300 to 2330 MHz or in the about 931 to
960 MHz frequency range.
23. The method as claimed in claim 19 wherein the third frequency
sub-band is in the about 2350 to 2380 MHz or in the about 961 to
990 MHz frequency range.
24. The method as claimed in claim 19 wherein the fourth frequency
sub-band is in the about 2400 to 2430 MHz or in the about 991 to
1100 MHz frequency range.
25. The method as claimed in claim 19 wherein the first or second
or third or fourth down-converted signal is in the about 12 to 42
MHz.
26. The method as claimed in claim 19 further comprising the step
of combining into the wideband signal a low frequency signal.
27. The method as claimed in claim 19 further comprises the step of
up-converting a downstream signal to a low frequency band signal in
a downstream direction.
28. The method as claimed in claim 26 wherein the low frequency
band signal is in the about 1000 to 2000 MHz.
29. The method as claimed in claim 25 wherein the low frequency
band signal is in the about 1000 to 2000 MHz.
30. The method as claimed in claim 26 wherein the low frequency
band signal further comprises a plurality of channels.
31. The method as claimed in claim 27 wherein the low frequency
band signal further comprises a plurality of channels.
32. The method as claimed in claim 27 wherein the downstream signal
is in the about 150-860 MHz.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is generally related to co-pending
PCT application No. PCT/IL00/00655 entitled SYSTEM AND METHOD FOR
EXPANDING THE OPERATIONAL BANDWIDTH OF A COMMUNICATION SYSTEM,
filed Nov. 16, 2000, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to cable television
("CATV") distribution networks. More particularly, the present
invention relates to a node in a HFC infrastructure-based CATV
network utilized as an advanced interfacing device between the
fiber optic segment and the coaxial segment of the CATV
infrastructure.
[0004] 2. Discussion of the Related Art
[0005] In CATV distribution networks based on a Hybrid Fiber Coax
(HFC) plant infrastructure, the fiber optic trunk and the coaxial
trunk of the network are connected via specific devices typically
referred to as fiber nodes. In the downstream, the fiber node
receives optical signals from the head-end via fiber optic cables,
converting the optical signals to an RF signal and feeding the RF
signal to the network subscribers via the coaxial portion which
typically includes the distribution and drop cables and associated
amplifiers and splitters. In the upstream, the fiber node receives
an RF signal from subscribers via the coaxial portion of the
network, converts the RF signal to optical signals and feeds the
optical signals via the fiber optic portion of the network back to
the head-end.
[0006] Presently, signals transmitted across a standard cable
television infrastructure, from a head-end to a network subscriber
and back from the network subscriber to the head-end, are modulated
such as to have a bandwidth with a frequency range of about 5 MHz
to about 860 MHz. The signals carry diverse encoded information
units representing content, services and applications. Logically
related and physically grouped information units are suitably
modulated into distinct specifically allocated transmission
channels. The channels are distributed across the available
frequency range according to a predefined frequency plan. The
number of potentially available downstream channels from the
head-end to the subscriber and upstream channels from the
subscriber to the head-end for the subscribers depends directly on
the available bandwidth of the signal. The currently utilized
signal with an about 5 to 860 MHz transmission bandwidth limits the
number of available downstream and upstream channels. In many
applications, the 5-42 MHz portion of the signal is used for
upstream transmission, and the 50-860 MHz portion of the signal is
used for the downstream or forward portion.
[0007] The Data Over Cable Services Interface Specification
(DOCSIS) protocol has proven itself a successful product for
broadband Internet access to the residential subscribers. Some
Multi-system Operators (MSOs) are beginning to provide DOCSIS to
small and medium businesses as a best effort connection for
Internet access. However, DOCSIS over existing HFC networks can not
be used as an alternative to existing high-speed data services, as
the existing HFC networks do not have the transmission spectrum to
carry the high speed data for the small and medium businesses
(SMB), which require substantial data throughput in the upstream as
well as in the downstream direction. The transmission spectrum
problem is particularly acute in the upstream where, out of the
about 15 to 42 MHz portion of the signal used, less than 20 MHz are
usable. In addition, equipment which is based on the DOCSIS
standard, such as the so-called CMTS routers, located in the
head-end of the HFC networks is now suitable for broadcast and
reception of a signal ranging between about 5-860 MHz.
[0008] The current solution for increasing the upstream capacity,
which is referred to as node splitting, involves costly investment
as well as only 80 MHz of the 100 MHz available since some of the
spectrum is dedicated to common service for all nodes. The
co-pending related PCT patent application PCT/IL00/00655 describes
and teaches a system and method of a CATV network having a
bandwidth of about 5 to about 3000 MHz for the transmission of
upstream and downstream wideband signals within. The CATV network
could be a standard coaxial media-based plant or an
HFC-infrastructure. The system and method proposed by the
above-mentioned related patent application involves the
installation and/or modification of a set of active and passive
components along the signal transport path of the network in order
to enable the transmission of a wideband signal with a frequency
range of about 5 to 3000 MHz and higher.
[0009] It is, however, desirable to continue use of the equipment
presently operative in the head-end of the CATV network, such as
but not limited to DOCSIS CMTS routers, while providing a bandwidth
in excess of 860 MHz. It is also desirable to make use of the
DOCSIS protocol for transfer of data in the upstream direction
employing multiple upstream bands without making substantial
investment in upstream physical node splitting thus providing
networking services to subscribers, small and medium-sized
businesses.
SUMMARY OF THE INVENTION
[0010] Currently operating CATV systems are inherently asymmetric,
as constrains and limitations exist regarding the size and speed of
the upstream traffic. The asymmetry arises as a result of a limited
upstream frequency band of about 5 to 42 MHz. It is an objective of
the present invention to alleviate the problem of asymmetry by
providing additional upstream frequency bands and by delivering
additional high-speed channels within the additional frequency
band, as well as additional downstream channels.
[0011] One aspect of the present invention regards a hybrid fiber
cable signal distribution network, a node apparatus for the
division, frequency conversion and multiplexing of at least four
signal sub-bands included in a high frequency band signal of a
wideband signal of about 5 to 3000 MHz. The apparatus comprises the
elements of: a triplexer device to separate in an upstream
direction the wideband signal into the high frequency band signal
and a CATV signal of about 5 to 860 MHz, an amplifier device to
amplify the high frequency band signal in the upstream direction, a
splitter device to split the amplified high frequency band signal
into at least four reproduced signals in the upstream direction, a
first frequency converter device to down-convert the first
frequency sub-band of the first reproduced signal into a first
down-converted signal of about 12 to 42 MHz in the upstream
direction, a second frequency converter device to down-convert the
second frequency sub-band of the second reproduced signal into a
second down-converted signal in the upstream direction, a third
frequency converter device to down-convert the third frequency
sub-band of the third reproduced signal into a third down-converted
signal in the upstream direction, a fourth frequency converter
device to down-convert the fourth frequency sub-band of the fourth
reproduced signal into a fourth down-converted signal in the
upstream direction; and a multiplexer device to multiplex the first
down-converted signal, the second down-converted signal, the third
down-converted signal and the fourth down-converted signal into a
combined signal in the upstream direction.
[0012] A second aspect of the present invention regards within a
hybrid fiber cable signal distribution network, a method for the
division, frequency conversion and multiplexing of at least four
signal sub-bands included in a high frequency upstream band signal
of a combined wideband signal of about 5 to 3000 MHz. The method
comprises the steps of: separating in an upstream direction the
wideband signal into the high frequency band signal and a CATV
signal of about 50 to 860 MHz, amplifying the high frequency band
signal in the upstream direction, splitting the amplified high
frequency band signal into at least four reproduced signals in the
upstream direction, down-converting the first frequency sub-band of
the first reproduced signal into a first down-converted signal in
the upstream direction, down-converting the second frequency
sub-band of the second reproduced signal into a second
down-converted signal in the upstream direction, down-converting
the third frequency sub-band of the third reproduced signal into a
third down-converted signal in the upstream direction,
down-converting the fourth frequency sub-band of the fourth
reproduced signal into a fourth down-converted signal in the
upstream direction; and multiplexing the first down-converted
signal, the second down-converted signal, the third down-converted
signal and the fourth down-converted signal into a combined signal
in the upstream direction.
[0013] According to the teachings of the present invention,
existing CATV data protocols and standards, such as DOCSIS, and
their associated routers, such as the so-called CMTS, can be
readily used, thus utilizing and preserving the investments made by
various MSOs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present invention will be understood and appreciated
more fully from the following detailed description taken in
conjunction with the drawings in which:
[0015] FIG. 1 is a schematic illustration of a CATV distribution
plant, as known in the art;
[0016] FIG. 2A is a schematic illustration of the structure of the
wideband node device installed in the CATV network, in accordance
with a preferred embodiment of the present invention;
[0017] FIG. 2B is a schematic illustration of the structure of an
alternative extended node device, in accordance with a preferred
embodiment of the present invention;
[0018] FIG. 3 shows an exemplary allocation of the transmission
spectrum of the wideband signal in the upstream and downstream, in
accordance with a preferred embodiment of the present
invention;
[0019] FIG. 4 shows another exemplary allocation of the
transmission spectrum of the wideband signal in the upstream and
downstream, in accordance with a preferred embodiment of the
present invention; and
[0020] FIGS. 5 and 6 show the detailed exemplary structure of the
wideband node device installed in the CATV network, in accordance
with a preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] A new and novel node device is disclosed which enables
transmission of a wideband signal consisting of the legacy spectrum
of about 5-860 MHz as well as a new downstream spectrum of about
1000-2000 MHz and a new upstream spectrum of about 2000-3000 MHz,
which enables transfer of data in the upstream direction employing
multiple upstream bands without making substantial investment in
upstream physical node splitting thus providing networking services
to residential subscribers, as well as to small and medium-sized
businesses (SMB).
[0022] FIG. 1 illustrates a simplified structure of an existing
CATV network. Signals from a network head-end 8 are transmitted and
received via the fiber trunk section 10 of the network to a
conventional CATV node device 12. The head-end may include one or
more DOCSIS or other Cable Modem Termination System (CMTS) devices
9. The CATV node device 12 is connected to network subscribers 32
via one or more ports where each port connected to a distinct
distribution coax cable 14. The distribution cable 14 includes one
or more line extender amplifiers (LEX) 20, 26 to maintain the
signal levels and several splitters and tap devices 16, 18, 22, 24,
28, 30. The tap devices 28, 30 are linked via specific drop cables
32 to the Customer Premises Equipment (CPE) of the network
subscribers 34. At the network subscriber the outlet 40 is
connected to a cable modem 42 and a CPE such as a computing device
44 and to Set Top Box 46 connected to CPE such as a television set
48.
[0023] The transmission path over the cable system can be realized
at the head-end by the CMTS 9, and at each subscriber location by a
cable modem (not shown). At the head-end or hub (not shown), the
interface to the data-over-cable system is called the Cable Modem
Termination System--Network-Side Interface (CMTS-NSI), which may be
specified in DOCSIS protocol. At the subscriber locations, the
interface is called the cable-modem-to-customer-premises-equipment
interface (CMCI) and may also be specified in DOCSIS protocol.
[0024] Operators desire to transparently transfer data between
these interfaces. The CMTS 9 may be connected to a data network 11,
such as the Internet or other wide or local networks. Presently, at
the head-end 8, the CMTS 9 receives data from the data network 11.
The data is modulated by the CMTS 9 to the CMTS downstream RF
interface (not shown) and is combined and sent downstream in the
50-860 MHz signal band. In the upstream direction, data is sent
from the node 12 via the fiber trunk cable to the head-end 8 in the
5-42 MHz signal band. The CMTS upstream RF interface (not shown)
receives the data signal from the upstream splitter (not shown) and
demodulates the signal to data signals sent to the data network 11.
The CATV node device 12 converts the fiber optic signal into an RF
signal to be transmitted downstream on the distribution coax cable
14.
[0025] The DOCSIS defines the interface requirements for cable
modems operative in high-speed data distribution over cable
television system networks. The current DOCSIS protocol enables the
handling of data transmission in the downstream direction at speeds
up to about 30 Mbps per 6 MHz channel at quadrature amplitude
modulation (QAM) 64, as well as up to about 10 Mbps per 3.2 MHz
channel at QAM 16 for the upstream or return direction. The node 12
is the frequency conversion element, which may be implemented by
having a multi port hub to interface with a multi port fiber node.
However, the current upstream data speeds are much lower, due to
the inherent asymmetry of the cable network spectrum. The apparatus
and method proposed by the present invention provide substantially
higher upstream data speeds in order to alleviate the problem.
[0026] In accordance with the present invention, the downstream
signal of between about 100-800 MHz is converted to a first high
frequency signal of about 1250-1950 MHz band. The fiber node of the
present invention further receives the upstream signal carried in a
second high frequency signal band of about 2250-2950 MHz band. In
the preferred embodiment of the present invention, the first and
second high frequency signal bands are divided into channels
carrying data according to the DOCSIS protocol, which can provide
up to 100 new 6 MHz channels each carrying 30 Mbps with QAM 64
metrics in the downstream direction and 100 new 3.2 MHz channels
each carrying 10 Mbps with QAM 16 metrics in the upstream
direction. The creation of these additional upstream channels,
according to the teachings of this invention, enables the
transmission of substantially more high-speed data to and from the
subscribers and particularly in the upstream direction. Because
DOCSIS is a Layer 2 protocol, Virtual Private Networks may be
implemented in association with the present invention in order to
replace costly leased line services.
[0027] Refer now to FIG. 2A where the node device 200 of the
present invention is installed in an HFC infrastructure-based CATV
network between the fiber trunk and the distribution cable of the
network. The node device 200 is connected to at least one
distribution line in the downstream and to a fiber node (not shown)
in the upstream where the fiber node is connected via the fiber
optic lines 84, 86 to a network head-end 82. The device 200
comprises a triplexer device 74, an amplifier device 73, a signal
splitter device 76, at least four frequency conversion devices 78',
78", 78'", 78"", and a Wavelength Division Multiplexing (WDM)
multiplexer device 80.
[0028] In FIG. 2A, the device 74 receives an upstream wideband
signal 72 of about 5 to about 3000 MHz from the distribution
segment of the CATV network. A node may receive one or more
downstream wideband signal from one or more distribution cables.
Typically, a node will receive 3 distribution cables in the
upstream direction. The wideband signal 72 is fed to the triplexer
device 74. The triplexer device 74 comprises three frequency
selective circuits in order to select from the wideband signal 72
three separate frequency bands. The CATV frequency selective
circuit 74'" separates the signal 90 of about 5 to about 860 MHz
band from the wideband signal. The signal 90 carries the standard
CATV channels in the downstream and upstream from the network
head-end 82 through the fiber node to the network subscribers and
vice versa. A fiber transceiver 101 converts the RF signal to optic
signal in the upstream direction and from the fiber optic to RF
signal in the downstream or forward direction.
[0029] In the upstream direction, the X-High frequency selective
circuit 74' separates from the wideband signal 72 a high frequency
signal 91 of about 2250 to 3000 MHz band of the wideband signal 72.
The separated high frequency signal 91 carries upstream data
submitted by the network subscribers in order to be sent to the
head-end 82 via an upstream fiber optic trunk 84. In the example of
the present embodiment, the high frequency signal 91 may be divided
into about 100 3.2 MHz channels each carrying DOCSIS compliant data
at about 10 Mbps in the upstream direction. The signal 91 includes
at least four frequency sub-bands in between 2250 and 3000 MHz
where each sub-band carries 30 MHz of upstream band. The four
sub-bands may be collected from one to four different distribution
lines. In one example, the signal 91 includes a first sub-band of
an about 2250 to about 2280 MHz frequency range that carries
upstream data, a second sub-band of an about 2300 to about 2330 MHz
frequency range that carries upstream data, a third sub-band of
about 2350 to about 2380 MHz that carries upstream data, and a
fourth sub-band of about 2400 to about 2430 MHz that carries
upstream data. The first, second, third and fourth sub-bands may be
received from one to four different distribution lines.
[0030] Note should be taken that the limiting values of the above
described sub-band limits could be different. Other sub bands could
be selected for operation and additional nodes of the present
invention may be cascaded in parallel to create additional upstream
channels. In one example, eight or even sixteen upstream channels
can be maintained in accordance with the teaching of the present
invention. Each sub band may comprise nine channels of about 3.2
MHz or eighteen channels of about 1.6 MHz carrying data at 10 Mbps
and 5 Mbps respectively.
[0031] Consequent to the separation, the signal 91 is fed to the
amplifier device 73 and amplified in order to maintain appropriate
signal level. Subsequently, the amplified signal 91 is fed to a
signal splitter device 76. The splitter device 76 splits the signal
91 into at least four identical or near identical reproduced
signals 91', 91", 91'", and 91"". The reproduced signals 91', 91",
91", 91"" are fed into a set of frequency selective block
conversion devices 78', 78", 78'", 78"" respectively. In the
example of the present invention, the first reproduced signal 91'
is down-converted by the frequency conversion device 78' from the
about 2250 to 2280 MHz to about 12-42 MHz. The second reproduced
signal 91" is down-converted by the frequency conversion device 78"
from the about 2300 to 2330 MHz to about 12-42 MHz. The third
reproduced signal 91'" is down-converted by the frequency
conversion device 78'" from the about 2350 to 2380 MHz to about
12-42 MHz. The fourth reproduced signal 91"" is down-converted by
the frequency conversion device 78"" from the about 2400 to 2430
MHz to about 12 to 42 MHz. The output of the frequency conversion
devices the first down-converted signal 78', the second
down-converted signal 78", the third down-converted signal 78'",
and the fourth down-converted signal 78"" are four distinct signals
at the about 12 to 42 MHz frequency band where each distinct signal
carries sub-band and or distribution line-specific upstream
data.
[0032] Subsequently, the signals are either converted into optical
format by an RF-to-Optical converter (not shown) or converted into
digital format by an Analog-to-Digital converter device (not
shown). The converted signals are fed to a multiplexer device 80.
The device 80 could be a Wavelength Division Multiplexing (WDM or
DWDM) device or any other multiplexer device in accordance with the
network configuration. The multiplexer device 80 generates a
multiplexed output signal 84 that is transmitted across the trunk
segment of the CATV network to the network head-end 82 via an
optical transmitter device. The multiplexed signal 84 is received
by the network head-end 82. The signal is separated into at least
four distinct signals 95', 95", 95'", 95"" and the separated
signals are transmitted to separate CMTS ports in order to be
suitably handled by the CMTS device 88.
[0033] As shown in FIG. 2B, instead of multiplexing the
down-converted signals into a combined signal, the at least four
down-converted signals could be converted to optical format by
RF-to-Optical converters 104', 104", 104'", 104"" and fed into at
least four separate fiber optic lines 102', 102", 102'", 102"" that
could carry the at least four signals separately to the network
head-end 82 via the fiber trunk segment of the CATV network. The
four optical signals transmitted through the optical fibers 102',
102", 102'", 102"" are received by the network head-end 82 and are
transmitted to separate CMTS ports in order to be suitably handled
by the CMTS device 88.
[0034] In the downstream, a signal carrying data generated through
CMTS ports 88 of about 100 to about 800 MHz is transmitted from the
head-end 82 to the extended node device 72 via the fiber trunk
segment 86 of the CATV network. This signal is non-legacy and
includes new data and information. In accordance with the
configuration of the network, the signal 86 is suitably converted
from optical format to RF analog format via a fiber receiver 100.
The signal 86 is then up-converted by the frequency conversion
device 93 to signal 92 from the about 150-860 MHz to the about
1250-1950 MHz signal band. The X-low frequency selective circuit
74" combines the low frequency signal 92 of about 1250 MHz to about
1950 MHz to the wideband signal 72. The signal 92 carries a
plurality of additional channels in the downstream from the network
head-end 82 to network subscribers. In the example of the present
embodiment, the low frequency signal 92 may be divided into about
one hundred 6 MHz channels, each carrying DOCSIS compliant data at
about 30 Mbps per channel in the downstream or forward direction.
The triplexer device 74 combines the signal 92 with the CATV signal
legacy signal 90 into a wideband signal that is transmitted to the
distribution lines in the downstream or forward direction.
[0035] Referring now to FIG. 3, the transmission spectrum spans a
frequency range of about 5 to 3000 MHz. The spectrum includes an
about 5 to 42 MHz legacy upstream band 114, an about 54 to 880 MHz
legacy downstream band 116, an about 1250 to 1950 MHz additional
(or extended) downstream band 118, and an about 2250 to 3000 MHz
additional upstream region 120. The legacy region spans a frequency
range of about 5 to 860 MHz. The legacy upstream band 114 is
allocated within the legacy region, and carries information units
introduced by the network subscribers from the subscribers to the
head-end in the upstream. The legacy downstream band 116 is
allocated within the legacy region and it is utilized to transmit
legacy channels from the head-end to the network subscribers in the
downstream. The additional bandwidth region spans a frequency range
of about 1250 to 3000 MHz. The additional downstream band 118 is
allocated within the additional frequency region, and said band is
used in the transmission of a plurality of channels from the
head-end to the subscribers in the downstream. The additional
upstream band 120 is allocated to carry information units generated
by the subscribers from the subscribers to the head-end in the
upstream.
[0036] In the preferred embodiment of the invention, the upstream
band 120 is divided into at least four sub-bands 122, 124, 126, and
128 where each sub-band spans a frequency rage of about 30 MHz. The
frequency allocation of the sub-bands is as follows: an about 2250
to 2280 MHz sub-band 122, an about 2300 to 2330 MHz sub-band 124,
an about 2350 to 2380 MHz sub-band 126, and an about 2400 to 2430
MHz sub-band 128. Each of the sub-bands 122, 124, 126, 128 includes
about 10 upstream channels assigned for subscriber traffic under
the current DOCSIS protocols. The bandwidth of each of the upstream
channels is about 3 MHz.
[0037] As described above, the four sub-bands may be collected from
one to four different distribution lines. The wideband node
extracts the four sub-bands 122, 124, 126, 128 from the additional
upstream band 120. From the extracted sub-bands 122, 124, 126, 128
four separate signals, such as an about 2250 to 2280 MHz signal
130, an about 2300 to 2330 MHz signal 132, an about 2350 to 3280
MHz signal 134, and an about 2400 to 2430 MHz signal 136, are
created. Each of signals 130, 132, 134, 136 has a 30 MHz bandwidth.
Consequently, the four signals 130, 132, 134, 136 are
down-converted separately to four signals 138, 140, 142, 144 where
each of the down-converted signals has the same about 30 MHz
bandwidth and the same about 12 to 42 MHz frequency range but
carrying different content.
[0038] Referring now to FIG. 4, the wideband node proposed by the
present invention can be modified to allow substantially increased
upstream data transmission without the need to replace passive
elements in upgraded legacy CATV networks if the spectrum used will
be confined up to about 1100 MHz. In the proposed wideband node of
FIG. 3, provision is made for about four upstream channels in the
2250 to 3000 MHz frequency range. The above mentioned frequency
allocation will require the replacement of existing CATV passive
elements. In order to prevent the necessity of replacing the
passives, a frequency range of about 860 MHz to 1100 MHz could be
dedicated to the additional upstream data traffic. In FIG. 4, the
transmission spectrum includes an about 5 to 42 MHz legacy upstream
band 148, an about 54 to 880 MHz legacy downstream band 150, and an
about 880 to 1100 MHz additional upstream region. The additional
upstream band 152 is allocated to carry information units generated
by the subscribers from the subscribers to the head-end in the
upstream.
[0039] In the preferred embodiment of the invention, the upstream
band 152 is divided into at least four sub-bands 154, 156, 158, and
160 where each sub-band spans a frequency rage of about 30 MHz. The
frequency allocation of the sub-bands is as follows: an about 900
to 930 MHz sub-band 154, an about 931 960 MHz sub-band 156, an
about 961 to 990 MHz sub-band 158, and an about 991 to 1100 MHz
sub-band 160. Each of the sub-bands 154, 156, 158, 160 includes
about 10 upstream channels assigned for subscriber traffic. The
bandwidth of each of the upstream channels is about 3 MHz, all
operating under DOCSIS protocols.
[0040] As described above the four sub-bands may be collected from
one to four different distribution lines. The wideband node
extracts the four sub-bands 154, 156, 158, 160 from the additional
upstream band 120. From the extracted sub-bands 154, 156, 158, 160
four separate signals, such as an about 900 to 930 MHz signal 162,
about 931 to 960 MHz signal 164, an about 961 to 990 MHz signal
166, and an about 991 to 1100 MHz signal 168 are created. Each of
signals 162, 164, 166, 168 has a 30 MHz bandwidth. Consequently,
the at least four signals 162, 164, 166, 168 are down-converted
separately to four signals 170, 172, 174, 176 where each of the
down-converted signals has the same about 30 MHz bandwidth and the
same about 12 to 42 MHz frequency range.
[0041] The operating procedures and associated components of the
wideband node device were described hereinabove in association with
FIGS. 2A and 2B. An exemplary detailed structure of the wideband
node device and the components is shown in FIGS. 5, 6. In general,
FIG. 5 shows the components for the handling of the signals with an
allocated frequency band of about 2250 to 3000 MHz in the upstream,
while in general FIG. 6 shows the components used in the handling
of the signals with a frequency band of about 1250 to 1950 MHz in
the downstream. Several values concerning the limits of various
frequency ranges are different from the values provided herein
above. In other preferred embodiments of the invention, still more
different values could be used, as amply demonstrated in the
relevant value differences between FIGS. 2A and 2B.
[0042] The wideband signal of about 5 to 3000 MHz is fed from the
network subscribers to the head-end in the upstream. As shown in
FIG. 6, the wideband signal is received via a connection point J4
and fed into a triplexer device 212. The device 212 divides the
signal into three distinct bands; a legacy (CATV) frequency band of
about 5 to 860 MHz, a downstream frequency band of about 1250 to
1950 MHz, and an upstream frequency band of about 2250 to 3000 MHz.
The upstream band of about 2250 to 3000 MHz is fed through
amplifiers, and split in two stages by splitter devices 214, 215,
217 into four identical signals having a frequency bandwidth of
about 2250 to 3000 MHz. As was described in association with FIGS.
2A and 2B, each of the identical signals is processed separately by
distinct groups of components. The groups of components are
represented on FIG. 5 electrical symbols successively located in
four processing sections leading to the connection points J7, J6,
J5, and J2, respectively. Each of the component groups extracts a
specific sub-band from the original wideband signal, in the
conversion of the extracted specific sub-band into a different
frequency band and in the down-converting of the frequency band
into a pre-defined lower frequency band. Since the principles of
the operation were already described in association with FIGS. 2A
and 2B, and since the components associated with the processing
sections illustrated are substantially similar, only the operation
of one processing section will be described. Other sections operate
in a similar manner.
[0043] The signal that is fed through the component group that is
suitably arranged in the processing section leading to connection
point J7 is converted from a frequency band of about 2250 to 2280
MHz to a first IF of about 700 MHz to 900 MHz by a mixer 20 in
association with a PLL 240. Consequently, the signal is filtered by
filter 222, amplified by amplifier 224 and attenuated by variable
attenuator 226. The signal is down-converted by mixer 228
controlled by PLL 238 to a frequency range of about 12 to 42 MHz.
Then, the signal is fed through the connection point J7 via several
filtering devices 230, 234, and an amplifier device 232. The three
other signals pass through three similar processing sections
leading respectively to connection points J6, J5, and J2. From the
connection points J7, J6, J5, and J2 the four separate signals
having the same frequency band of about 12 to 42 MHz are fed to the
head-end through the optical trunk segment of the network. As
described in FIGS. 2A and 2B, the four signals are either
multiplexed by a WDM device or converted separately into optical
format by a RF-to-Optical converter sent to the head-end via four
separate optical fiber lines.
[0044] The legacy (CATV) frequency band of the signal is sent from
the triplexer 212 to the head-end via connection point J3. The
downstream frequency band of the signal is fed from the head-end to
connection point J1 to a diplexer 252. The diplexer 252 separates
the about 100 to 800 MHz frequency band and feds the separated
portion of the signal to the triplexer 212 device via a downstream
processing section. The downstream processing section up-converts
the about 100 to 800 MHz frequency band into an about 1250 to 1950
MHz band. The signal is passed through an amplifier 253, a variable
equalizer 255 and a mixer unit 254. The mixer unit 254 up-converts
the signal in accordance with conversion values supplied by a
pre-programmed microprocessor 270. A pilot signal of 1910 MHz (271)
controlled by a pilot control AGC circuit 272 is inserted into the
signal in order to maintain signal coherence. The up-converted
downstream signal is passed through a filtering device 256, an
attenuator device controlled by an AGC circuit 273, several
amplifier devices 274, 275, a tilt up equalizer device 278 and fed
into the triplexer device 212. The triplexer device 212 combines
the legacy band, the downstream band and the upstream band to a
wideband signal having a frequency range of about 5 to 3000 MHz and
feeds the wideband signal downstream through the distribution
segment of the network to the network subscribers.
[0045] Note should be taken that the operational values illustrated
in the discussed drawings are in accordance with a preferred
embodiment of the present invention. In other embodiments,
different values could be used. Furthermore, the details of the
implementation could differ among different embodiments.
[0046] As a result of the operation of the wideband node device,
the low frequency signal carries data in the downstream direction
and the high frequency carries data in the upstream direction
utilizing an additional bandwidth of above 1 GHz and up to about 3
GHz while presently currently used head-end equipment, and the
DOCSIS protocol is fully exploited to carry up to about 9 channels
of 3.2 MHz per channel 10 Mbps at data streams in the upstream
direction.
[0047] Moreover, the multiple upstream signals transmitted over the
high frequency range enable to render a DOCSIS system in the SMB
market, as well as for other markets requiring symmetric data
transfers into a high-throughput system in the upstream as well as
the downstream direction.
[0048] Persons skilled in the art will appreciate that the low and
high frequency signal band assignments may be altered and that
various other signal bands may be used in association with the
teaching of the present invention. It will be appreciated by
persons skilled in the art that the present invention is not
limited to what has been particularly shown and described
hereinabove. Rather the scope of the present invention is defined
only by the claims, which follow.
* * * * *