The present invention generally relates to communications systems and, more particularly, to cable television systems.
Current cable television (TV) systems offer a number of services to customers such as TV programming (both network and local), pay-per-view programming and Internet access. One example of a cable TV system is a hybrid fiber/coax based network that has a bandwidth capacity of 750 MHz (millions of hertz), or more, for delivering these services to their subscribers. This bandwidth capacity is typically divided between a down stream channel and an upstream channel. The downstream channel conveys not only the TV programming but also the downstream Internet data communications to each subscriber; while the upstream channel conveys the upstream Internet data communications from each subscriber.
The above described distribution of cable TV bandwidth into a downstream channel and an upstream channel is fixed. As a result, this makes it difficult for cable operators to extend the capabilities of their cable networks or to offer new types of services that require additional bandwidth. However, we have realized that it is possible for a cable system to manage the bandwidth the bandwidths of the upstream and downstream channels—thus enabling the cable system to offer new capabilities and services. In particular, and in accordance with the principles of the invention, a cable system manages bandwidth by selecting a bandwidth in accordance with a selected one of a plurality of cable network bandwidth configurations, each cable network bandwidth configuration allocating bandwidth differently between upstream communications and downstream communications over at least a portion of the cable network; and filtering at least one signal (e.g., a downstream signal or an upstream signal of the cable network or both of these signals) in accordance with the selected bandwidth.
In an illustrative embodiment of the invention, a portion of a cable network includes an apparatus, e.g., a tap, comprising a first port for coupling to an upstream portion of a cable network and for receiving a downstream signal; a second port for coupling to a downstream portion of the cable network and for receiving an upstream signal; and a filter for filtering at least one of the downstream signal and the upstream signal; wherein the filter has a bandwidth that is adjustable in accordance with a plurality of cable network bandwidth configurations, each cable network bandwidth configuration allocating bandwidth differently between upstream communications and downstream communications over at least a portion of the cable network.
Other than the inventive concept, the elements shown in the figures are well known and will not be described in detail. Also, familiarity with television broadcasting and receivers in the context of terrestrial, satellite and cable is assumed and is not described in detail herein. For example, other than the inventive concept, familiarity with current and proposed recommendations for TV standards such as NTSC (National Television Systems Committee), PAL (Phase Alternation Lines), SECAM (SEquential Couleur Avec Memoire) ATSC (Advanced Television Systems Committee) (ATSC) and ITU-T J.83 “Digital multi-programme systems for television, sound and data services for cable distribution” is assumed. Likewise, other than the inventive concept, familiarity with satellite transponders, cable head-ends, set-top boxes, downlink signals and transmission concepts such as eight-level vestigial sideband (8-VSB), Quadrature Amplitude Modulation (QAM), out-of-band control channels and receiver components such as a radio-frequency (RF) front-end, or receiver section, such as a low noise block, tuners, and demodulators is assumed. Similarly, formatting and encoding methods (such as Moving Picture Expert Group (MPEG)-2 Systems Standard (ISO/IEC 13818-1)) for generating transport bit streams are well-known and not described herein. It should also be noted that the inventive concept may be implemented using conventional programming techniques, which, as such, will not be described herein. Finally, like-numbers on the figures represent similar elements.
Turning now to PIG. 1, an illustrative cable system 100 in accordance with the principles of the invention is shown. Illustratively, cable system 100 is a hybrid-fiber coax (HFC) system. For simplicity, the fiber portion is not described herein. It should be noted that although the inventive concept is described in the context of coaxial cable (coax), the inventive concept is not so limited and can be extended to the processing of fiber optic signals. A plurality of stations, as represented by stations 120-1 to 120-6, are connected to a common head-end 105 by a tree and branch cable network. Each station is associated with a cable subscriber. Each station includes, e.g., a set top box for receiving video programming and a cable modem for bi-directional data communications to, e.g., the Internet. Head-end 105 is a stored-program-processor based system and includes at least one processor (e.g., a microprocessor) with associated memory, along with a transmitter and receiver coupled to the cable network (for simplicity, theses elements are not shown). Ignoring for the moment element 200, the cable network comprises a main coaxial cable 106 having a plurality of taps 110-1, 110-2 to 110-N. Each of these taps serves a corresponding feeder cable. For example, tap 110-1 serves feeder cable 111-1. Each feeder cable in turn serves one, or more, stations via a tap and a drop. For example, feeder cable 111-1 serves station 120-1 via tap 115-1 and drop 116-1. For the purposes of this description, it is assumed that the devices of cable network 100, e.g., taps, drops, etc., are addressable and controllable by head-end 105 via an out-of-band signaling channel (not shown in
In cable system 100, communications between head-end 105 and the various stations occurs in both an upstream direction and a downstream direction. The upstream direction is towards head-end 105 as represented by the direction of arrow 101 and the downstream direction is towards the stations as represented by the direction of arrow 102. In accordance with the principles of the invention, cable system 100 includes at least one device that includes a programmable bandwidth (PBW) function (referred to herein as a PBW device). One, or more, of these PBW devices are used to manage the bandwidth in the cable system. This is further illustrated in
Referring now to
Turning now to
As described above, the bandwidth of each variable bandwidth filter of PBW 200 is set to conform to a bandwidth configuration selected by the head-end. In this regard, illustrative embodiments of variable bandwidth filter 210 and variable bandwidth filter 260 are shown in
Similar comments apply to variable bandwidth filter 260 shown in
As noted above, a cable system may have one, or more, PBW devices located in one, or more, portions of the cable network. Illustratively,
As described above, the inventive concept provides the ability to extend the capabilities of cable networks by increasing symmetry in the network and distributing serving capability throughout the network. Illustratively, the cable spectrum is divided into multiple bands, and band direction (upstream or downstream) can be electronically selected by a device of the cable network such as, but not limited to, a tap. This enables the cable network to better adapt to the traffic demands of upstream and downstream services, and allow for new distribution of local services. For example, downstream bandwidth can be increased at the expense of upstream bandwidth. It should be noted that although the inventive concept was described in the context of a fixed downstream band (B3), a fixed upstream band (B0) and a number of programmable bands (B1 and B2), the inventive concept is not so limited. For example, all of the bands can be programmable. Further, although the inventive concept was described in the context of application to a traditional cable system, the inventive concept is not so limited and is applicable to any form of network, even, e.g., a home network, campus network, etc.
Other illustrative embodiments of a PBW device in accordance with the principles of the invention are shown in
Likewise, in
Turning now to
An upstream signal 401 is applied to splitter 405, which splits the signal into signals 406 and 491 for application to bypass filter 410 and input filter 415, respectively. Bypass filter 410 is a low pass filter for upstream use and, e.g., has a pass band of B0 (conversely, bypass filter 410 would be a high pass filter for downstream use). As a result, bypass filter 410 provides a signal 411 restricted to the frequency region B0. The input filter 415 has a bandwidth corresponding to one, or more, of the above-described programmable bands and is used to restrict downstream signal 491 to the corresponding frequency range. For example, input filter 415 may have a bandwidth equal to B1+B2 with the result that output signal 416 from input filter 415 represents any upstream components present in that frequency range. The output signal 416, along with a sinusoidal signal 421 from variable oscillator 420, is applied to multiplier (mixer) 425. The later frequency shifts output signal 416 as a function of the frequency of sinusoidal signal 421 to provide a signal 426 to selection filter 430. Signal 426 is also referred to herein as the “conversion image” of signal 416. As a result, by changing the frequency of variable oscillator 420 the frequency range of signal 426 can be shifted such that selection filter 430 filters some, all, or none of the signal components in output signal 416. The selection filter can be low pass, high pass, or band pass. All that matters is that the conversion image, either inverted or non-inverted spectrum, can be frequency shifted before application to selection filter 430 to, in effect, change the bandwidth of the system. The output signal (if any) from selection filter 430 is re-mixed down to the original frequency range, via mixer 435, and applied to output filter 440. The latter has a bandwidth similar to input filter 415 and is used to reject any undesired images as a result of the second mixing, or conversion, process. The output signals from bypass filter 411 and output filter 440 are formed back into an upstream signal 451 via combiner 445 and amplifier 450.
As a more concrete example of PBW 400, a programmable upstream filter enabling the selection of the 42 to 108 MHz range comprises: a bypass filter 410 having a pass band in the range of 5-42 MHz; an input filter 415 having a pass band in the range of 42 to 108 MHz; a selection filter 430 having a 72 MHz bandwidth centered at 140 MHz (similar to a commercially available Sawtek 856314 filter) (also, ideally, the center frequency would be slightly higher to avoid oscillator leakage to the output); an output filter 440 having cutoff frequency above 108 MHz; and a variable oscillator 420 that can be set to 212 MHz to shift the inverted image to the pass band of selection filter 430. As the frequency of variable oscillator 420 is decreased (e.g., via control signal 299) the spectrum of the inverted image signal 426) will decrease in frequency, shifting what was the high end of the 42 to 108 MHz band out of the pass band of selection filter 430, and, by the time the frequency reaches 146 MHz, selection filter 430, in effect, blocks the entire pass band.
Other illustrative embodiments are shown in
As such, the foregoing merely illustrates the principles of the invention and it will thus be appreciated that those skilled in the art will be able to devise numerous alternative arrangements which, although not explicitly described herein, embody the principles of the invention and are within its spirit and scope. For example, although illustrated in the context of separate functional elements, these functional elements may be embodied in one or more integrated circuits (ICs). Similarly, although shown as separate elements, any or all of the elements may be implemented in a stored-program-controlled processor, e.g., a digital signal processor (DSP) or microprocessor that executes associated software, e.g., corresponding to one or more of the steps shown in
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2006/021051 | 5/31/2006 | WO | 00 | 4/9/2008 |
Number | Date | Country | |
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60725795 | Oct 2005 | US |