Source: http://www.google.com/patents/US7089478?dq=7,403,220
Timestamp: 2014-03-14 18:59:30
Document Index: 38439945

Matched Legal Cases: ['art 500', 'art 400', 'art 400', 'art 500', 'art 400', 'art 400', 'art 400', 'art 400', 'art 400', 'art 500', 'art 500', 'art 500', 'art 500', 'art 900', 'art 800', 'art 1300', 'art 1300']

Patent US7089478 - FEC block reconstruction system, method and computer program product for ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA system, method and computer program product is provided for mitigating the effects of burst noise on packets transmitted in a communications system. A transmitting device applies an outer code, which may include, for example, a block code, an exclusive OR (XOR) code, or a repetition code, to one or...http://www.google.com/patents/US7089478?utm_source=gb-gplus-sharePatent US7089478 - FEC block reconstruction system, method and computer program product for mitigating burst noise in a communications systemAdvanced Patent SearchPublication numberUS7089478 B2Publication typeGrantApplication numberUS 10/175,346Publication dateAug 8, 2006Filing dateJun 20, 2002Priority dateJun 22, 2001Fee statusPaidAlso published asUS20030002499Publication number10175346, 175346, US 7089478 B2, US 7089478B2, US-B2-7089478, US7089478 B2, US7089478B2InventorsScott Cummings, Joel Danzig, Stephen Hughey, Thomas L. JohnsonOriginal AssigneeBroadcom CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (14), Non-Patent Citations (2), Referenced by (11), Classifications (14), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetFEC block reconstruction system, method and computer program product for mitigating burst noise in a communications systemUS 7089478 B2Abstract A system, method and computer program product is provided for mitigating the effects of burst noise on packets transmitted in a communications system. A transmitting device applies an outer code, which may include, for example, a block code, an exclusive OR (XOR) code, or a repetition code, to one or more packets prior to adaptation of the packets for transmission over the physical (PHY) layer of the communications system, wherein the PHY layer adaptation may include FEC encoding of individual packets. The outer coded packets are then separately transmitted over a channel of the communications system. A receiving device receives the outer coded packets, performs PHY level demodulation and optional FEC decoding of the packets, and then applies outer code decoding to the out6r coded packets in order to restore packets that were erased during transmission due to burst noise or other impairments on the channel.
adapting each of said plurality of information segments and said at least one parity segment for transmission over a channel of a communications system, wherein said adapting includes forward error correction (FEC) encoding each of said plurality of information segments and said at least one parity segment, thereby dividing each of said plurality of information segments and said at least one parity segment into a corresponding plurality of FEC blocks; and
separately transmitting each of said plurality of FEC blocks over said channel.
separately receiving a plurality of information segments and at least one parity segment over a channel of a communications system, wherein each of said plurality of information segments and said at least one parity segment comprises a plurality of FEC codewords;
forward error correction (FEC) decoding each of said plurality of information segments and said at least one parity segment, wherein said FEC decoding comprises FEC decoding each of a plurality of FEC blocks within each of said plurality of information segments and said at least one parity segment;
identifying one of said plurality of FEC blocks within one of said plurality of information segments as erased, wherein said erased FEC block includes more errors than can be corrected by said FEC decoding;
restoring said erased FEC block by decoding non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with a block code; and
10. The method of claim 8, wherein said decoding non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with a block code comprises decoding non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with a Hamming code.
11. The method of claim 8, wherein said decoding non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with a block code comprises decoding non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with an exclusive or (XOR) code.
adapting each of said plurality of information segments and said at least one parity segment for transmission over a channel of a communications system, said adapting including forward error correction (FEC) encoding each of said plurality of information segments and said at least one parity segment, thereby dividing each of said plurality of information segments and said at least one parity segment into a corresponding plurality of FEC blocks;
separately transmitting each of said plurality of FEC blocks over said channel;
receiving and FEC decoding each of said plurality of FEC blocks associated with each of said plurality of information segments and said at least one parity segment;
identifying one of said plurality of FEC blocks associated with one of said plurality of information segments as erased, wherein said erased FEC block includes more errors than can be corrected by said FEC decoding;
restoring said erased FEC block by decoding non-erased FEC blocks associated with said plurality of information segments and said at least one parity segment in accordance with said block code; and
physical layer logic coupled to said media access control, said physical layer logic configured to adapt each of said plurality of information segments and said at least one parity segment for transmission over a channel of a communications system, said adapting including forward error correction (FEC) encoding each of said plurality of information segments and said at least one parity segment, thereby dividing each of said plurality of information segments and said at least one parity segment into a corresponding plurality of FEC blocks; and
a transmitter coupled to said physical layer logic, said transmitter configured to separately transmit each of said plurality of FEC blocks over said channel.
a receiver configured to separately receive a plurality of information segments and at least one parity segment over a channel of a communications system wherein each of said plurality of information segments and said at least one parity segment comprises a plurality of forward error correction (FEC) codewords;
physical layer logic coupled to said receiver, said physical layer logic configured to FEC decode each of said plurality of information segments and said at least one parity segment, wherein said FEC decoding comprises FEC decoding each of a plurality of FEC blocks within each of said plurality of information segments and said at least one parity segment, and to identify one of said plurality of FEC blocks within one of said plurality of information segments as erased, wherein said erased FEC block includes more errors than can be corrected by said FEC decoding; and
a media access control coupled to said physical layer logic, said media access control configured to restore said erased FEC block by decoding non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with a block code and to organize said plurality of information segments into one or more packets.
25. The device of claim 23, wherein said media access control is configured to decode non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with a Hamming code.
26. The device of claim 23, wherein said media access control is configured to decode non-erased FEC blocks in said plurality of information segments and said at least one parity segment in accordance with an exclusive or (XOR) code.
first physical layer logic coupled to said first media access control, said first physical layer logic configured to adapt each of said plurality of information segments and said at least one parity segment for transmission over a channel of a communications system, said adapting including forward error correction (FEC) encoding each of said plurality of information segments and said at least one parity segment, thereby dividing each of said plurality of information segments and said at least one parity segment into a corresponding plurality of FEC blocks, and
a transmitter coupled to said physical layer logic, said transmitter configured to separately transmit each of said plurality of FEC blocks over said channel; and
a receiver configured to receive said plurality of FEC blocks over said channel,
second physical layer logic coupled to said receiver, said second physical layer logic configured to FEC decode each of said plurality FEC blocks associated with each of said plurality of information segments and said at least one parity segment, and to identify one of said plurality of FEC blocks associated with one of said plurality of information segments as erased, wherein said erased FEC block includes more errors than can be corrected by said FEC decoding, and
a second media access control coupled to said second physical layer logic, said second media access control configured to restore said erased FEC block by decoding non-erased FEC blocks associated with said plurality of information segments and said at least one parity segment in accordance with a block code and to organize said plurality of information segments into said one or more packets.
CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to the following provisional applications: U.S. application Ser. No. 60/299,768, entitled �Method, System and Computer Program Product for Mitigating Burst Noise,� filed Jun. 22, 2001, and U.S. application Ser. No. 60/308,101, entitled �FEC Block Reconstruction Method, System and Computer Program Product for Mitigating BurstNoise,� filed Jul. 30, 2001. Each of these provisional applications is incorporated by reference in its entirety as if set forth fully herein.
This application is related to co-pending non-provisional application entitled �System, Method and Computer Program Product for Mitigating Burst Noise in a Communications System,� application Ser. No. 10/175,330, filed Jun. 20, 2002, filed concurrently herewith and incorporated by reference herein in its entirety.
Communications systems maybe subject to intermittent, random bursts of noise, often referred to as burst noise or impulse noise. This burst noise can result in the introduction of errors into the electronic information transmitted over the communications system. For example, in a communications system in which voice, data and/or other electronic information is transmitted in packets, the presence of burst noise can cause packets to become corrupted. Packet errors must be detected in order for a communications system to operate reliably. Where packet errors are detected but cannot be corrected, bad packets must be dropped and re-transmitted, resulting in a net loss of transmission speed and network bandwidth. If the dropped packets include voice information, the result may be a loss in overall quality of service (QOS).
BRIEF SUMMARY OF THE INVENTION The present invention addresses the above problems by providing novel techniques for preventing the loss of packets due to burst noise in a communications system. In accordance with embodiments of the invention, a transmitting device applies a layer of coding, which may be termed an �outer code,� to one or more packets prior to transmitting the packets over a communication channel. The outer coding of the packets enables a receiving device to restore packets corrupted by burst noise in instances where the packet errors could not otherwise be corrected by conventional PHY layer Forward Error Correction (FEC) and interleaving techniques.
a. Hamming Block Coding b. Exclusive OR (XOR) Coding c. Alternative Outer Block Coding Embodiments 2. Repetition Coding
4. Block Reconstruction
a. FEC Block Reconstruction and Outer Block Coding b. FEC Block Reconstruction and Repetition Coding c. Alternative FEC Block Reconstruction Embodiments 5. Outer Coding and Packet Header Suppression
FIG. 1 is a high-level block diagram of an example cable modem system 100 in which embodiments of the present invention may operate. The example cable modem system 100 enables voice communications, video and data services based on a bidirectional transfer of packet-based traffic, such as Internet Protocol (IP) traffic, between a cable system head end 102 and a plurality of cable modems 108 a�108 n over a hybrid fiber-coaxial (HFC) cable network 106.
The cable headend 102 is comprised of at least one cable modem termination system (CMTS) 104. The CMTS 104 is the portion of the cable headend 102 that manages the upstream and downstream transfer of data between the cable headend 102 and the cable modems 108 a�108 n, which are located at the customer premises. The CMTS 104 broadcasts information downstream to the cable modems 108 a�108 n as a continuous transmitted signal in accordance with a time division multiplexing (TDM) technique. Additionally, the CMTS 104 receives data from the cable modems 108 a�108 n over a plurality of shared upstream channels. Data from the cable modems 108 a�108 n may be transmitted upstream in accordance with a time domain multiple access (TDMA) technique or a synchronous code division multiple access (S-CDMA) technique. In accordance with TDMA, each cable modem 108 a�108 n may only send information upstream as short burst signals during a transmission opportunity allocated to it by the CMTS 104.
As shown in FIG. 1, the CMTS 104 further serves as an interface between the HFC network 106 and a packet-switched network 112, transferring IP packets received from the cable modems 108 a�108 n to the packet-switched network 112 and transferring IP packets received from the packet-switched network 112 to the cable modems 108 a�108 n when appropriate. The packet-switched network 112 may include, for example, the Internet.
The HFC network 106 provides a point-to-multipoint topology for the high-speed, reliable, and secure transport of data between the cable headend 102 and the cable modems 108 a�108 n at the customer premises. As will be appreciated by persons skilled in the relevant art(s), the HFC network 106 may include coaxial cable, fiberoptic cable, or a combination of coaxial cable and fiberoptic cable linked via one or more fiber nodes.
Each of the cable modems 108 a�108 n operates as an interface between the HFC network 106 and at least one attached user device. In particular, the cable modems 108 a�108 n convert downstream signals received over the HFC network 106 into IP data packets for receipt by an attached user device. Additionally, the cable modems 108 a�108 n convert IP data packets received from the attached user device into upstream burst signals suitable for transfer over the HFC network 106.
In the example cable modem system 100, each cable modem 108 a�108 n is shown supporting only a single user device for clarity. In general, each cable modem 108 a�108 n is capable of supporting a plurality of user devices for communication over the cable modem system 100. User devices may include personal computers, data terminal equipment, telephony devices, broadband media players, network-controlled appliances, or any other device capable of transmitting or receiving data over a packet-switched network.
In the example cable modem system 100, cable modems 108 a�108 n and CMTS 104 represent DOCSIS-compliant cable modem equipment. In other words, cable modems 108 a�108 n and CMTS 104 communicate in accordance with protocols and formats set forth in the DOCSIS specification. The term DOCSIS (Data Over Cable System Interface Specification) generally refers to a group of specifications published by CableLabs that define industry standards for cable headend and cable modem equipment. In part, DOCSIS sets forth requirements and objectives for various aspects of cable modem systems including operations support systems, management, data interfaces, as well as network layer, data link layer, and physical layer transport for data over cable systems.
The receiver portion includes an optical-to-coax stage 204, an RF input 206, a splitter 214, and a plurality of burst receivers 216. Reception begins with the receipt of upstream burst signals originating from one or more cable modems by the optical-to-coax stage 204 via the optical fiber 202. The optical-to-coax stage 204 routes the received burst signals to the radio frequency (RF) input 206 via coaxial cable 205. These upstream burst signals have spectral characteristics within the frequency range of roughly 5�42 MHz.
The modulated carrier signal output by the downstream modulator 226 is input to the SAW filter 228 which passes only spectral components of the signal that are within a desired bandwidth. The filtered signal is then output to an amplifier 230 which amplifies it and outputs it to the IF output 212. The IF output 212 routes the signal to the RF upconverter 210, which upconverts the signal. The upconverted signal has spectral characteristics in the frequency range of approximately 54�860 MHz. The upconverted signal is then output to the optical-to-coax stage 204 over the coaxial cable 208. The optical-to-coax stage 204 broadcasts the signal via the optical fiber 202 of the HFC network 106.
The receiver portion includes a diplex filter 302, an RF tuner 304, a SAW filter 306, an amplifier 308, and a downstream receiver 310. Reception begins with the receipt of a downstream signal originating from the CMTS 104 by the diplex filter 302. The diplex filter 302 operates to isolate the downstream signal and route it to the RF tuner 304. In embodiments, the downstream signal has spectral characteristics in the frequency range of roughly 54�860 MHz. The RF tuner 304 downconverts the signal and outputs it to the SAW filter 306, which passes only spectral components of the downconverted signal that are within a desired bandwidth. The filtered signal is output to the amplifier 308 which amplifies it and passes it to the downstream receiver 310. Automatic gain controls are provided from the downstream receiver 310 to the RF tuner 304.
The upstream burst modulator 326 outputs the modulated carrier signal to the low pass filter 328 which passes signals with spectral characteristics in a desired bandwidth within the frequency range of approximately 5�42 MHz. The filtered signals are then introduced to the power amplifier 330 which amplifies the signal and provides it to the diplex filter 302. The gain in the power amplifier 330 is regulated by the burst modulator 326. The diplex filter 302 isolates the amplified signal and transmits it upstream over the HFC network 106 during a scheduled burst opportunity.
The outer block code applied in step 406 may be any of the many block codes available in the literature, such as an (n, k) binary code, and in particular may be an (n, k) Hamming code. In an embodiment in which the outer code is an (n, k) binary code, each row includes a single bit from each of the k segments and parity check equations are used to compute n�k additional parity bits for each row. These n�k parity bits are arranged to form an additional n�k columns, or parity segments. Thus, the parity checks for each row provide a row of bits for the newly created n�k parity segments. If there are m bits in each of the original k segments, then there will be m parity check rows processed, and the newly created n�k parity segments will each have m bits.
Step 408 is an optional processing step in which identification bits are added to each of the k information segments and n�k parity segments. The identification bits may be used to uniquely identify information segments and parity check segments as originating from the same set of n encoded segments. The identification bits may also be used as a counter that establishes the order in which the information segments and parity check segments were originally encoded. In an embodiment, the identification bits may be repeated or otherwise placed in each column with redundancy to increase their robustness beyond the normal data bits in each segment.
In an embodiment, each of the above steps 404 through 408 is performed by the MAC 314 of the cable modem 108 a. At step 410, each of the k information segments and n�k parity check segments is adapted for transmission over the physical (PHY) layer of a cable modem system. In a DOCSIS cable modem system, this step includes prepending a MAC header to each segment, optionally performing FEC encoding on the MAC header and the payload, and then prepending a preamble for subsequent burst transmission. As a result, each segment becomes the payload of a separate upstream burst. This step may also include interleaving of the upstream burst. In an embodiment, the prepending of a MAC header to each segment is performed by the MAC 314 of the cable modem 108 a, while FEC encoding, prepending of a preamble, and interleaving is performed by PHY layer logic (not shown in FIG. 3) that resides between the MAC 314 and the upstream burst modulator 326 in the cable modem 108 a. At step 412, the cable modem 108 a separately transmits each burst generated in step 410 over an upstream communication channel of the cable modem system to the CMTS 104. In accordance with a DOCSIS cable modem system, the cable modem 108 a must request a transmission opportunity from the CMTS for each burst it wishes to transmit over the upstream channel. Burst transmission includes the conversion of each burst into analog form and modulation onto a carrier signal by the upstream burst modulator 326 of the cable modem 108 a for transmission during an appropriate time slot.
The method of flowchart 500 begins at step 502, in which the CMTS 104 receives the upstream bursts transmitted from the cable modem 108 a during step 412 of flowchart 400. At step 504, a segment is recovered from each upstream burst. This step includes demodulation of each burst and conversion to digital form by the burst receiver 216 of CMTS 104. This step may also include deinterleaving and FEC decoding of the burst data by PHY layer logic within the CMTS that resides between the burst receiver 216 and the headend MAC 218 (not shown in FIG. 2).
An example of the methods of flowchart 400 and flowchart 500 in which the outer block code is an extended (8, 4) Hamming code will now be described. For the purposes of this example, it is assumed that a queue of four m length data packets is collected at the cable modem for upstream transmission and organized as four information segments, so through s4, respectively, in accordance with steps 402 and 404 of flowchart 400. As depicted in FIG. 6, the four information segments are arranged as a series of columns 602. In accordance with step 406 of flowchart 400, parity equations for an (8, 4) Hamming code are then applied to each row of four information bits created by the arrangement of columns 602 to calculate four parity bits for each row. For example, with continued reference to FIG. 6, parity check equations are applied to the row of four information bits s1d1, s2d1, s3d1, and s4d1, to generate the four parity bits s5d1, s6d1, s7d1 and s8d1. Each resulting row of information and parity bits 606 a through 606 m represents a separate (8, 4) Hamming codeword.
The generation of four parity bits for each row results in the creation of four new columns 604. These four new columns 604 correspond to four new parity segments, s5 through s8 In accordance with step 408 of flowchart 400, identification bits may be added to each segment s1�s8 to uniquely identify the segments as originating from the same set of encoded segments and/or to establish the order in which the segments were originally encoded. FIG. 7 illustrates the prepending of sequential identification bits 706 to the information segments s1 through s4 and the parity segments s5 through s8, which results in extended information segments 702 and parity segments 704. These identification bits identify the encoding order of each of the segments. Although not shown in FIG. 7, a unique identification number identifying the set of packets may also be added to each segment. Note that the rows created by the addition of the identification bits 706 do not represent (8, 4) Hamming codewords.
Each of the segments s1�s8 is then adapted for transmission over the PHY layer of a cable modem system in accordance with step 410 of flowchart 400. As discussed above, this includes prepending a MAC header to each segment, optionally performing FEC encoding on the MAC header and the payload, and then prepending a preamble for subsequent burst transmission. Where FEC is performed, it may be used to encode the identification bits as well as the data included in each segment. Each segment is then transmitted upstream in one of eight separate bursts of upstream transmission using the DOCSIS PHY, in accordance with step 412 of the flowchart 400.
In accordance with steps 502 and 504 of flowchart 500, the eight upstream bursts are received by the CMTS, which recovers the eight segments s -s through the demodulation and optional de-interleaving and FEC decoding of the bursts. Due to an impairment in the upstream channel, one or more of these segments are marked as erased pursuant to step 506 of flowchart 500.
In accordance with step 508 of the flowchart 500, the CMTS then uses the prepended identification bits 706 in each segment to re-assemble the segments s1�s8 in the column arrangement depicted in FIG. 7. Any erased segments in the matrix are identified at this stage. The CMTS then decodes each row of the assembled matrix using the same (8,4) Hamming code scheme implemented in the cable modem to recover lost information segments. Because an (8, 4) Hamming code has been used, as long as (a) three or fewer segments are erased, or (b) at most one segment is erased and at most one bit error occurs in any row of the remaining seven columns, then the original information segments can be recovered. In 54 out of 70 cases, four of the eight segments can be erased and the original four information segments can still be restored.
At the CMTS, in decoding step 510 of flowchart 500, matrix assembly includes examining the total number of information segments described in the identification bits of each successfully received segment. If the majority of the segments indicate that N information segments were encoded, and N is less than 4, then 4−N filler columns of zero data are assembled beginning with column 4−N+1 and ending at column 4. Decoding then proceeds as if a fall eight segments had been received.
In accordance with a DOCSIS cable modem system, to ensure that repeated packets have allocated minislots (i.e., grants) for upstream transmission, either the cable modem 108 a must request additional minislots from the CMTS 104, or the CMTS must automatically make the necessary additional grants at some point later in time for repeated packets. The time delay between grants for a given repeated packet may be constant, or random, based on efficiently filling the available DOCSIS MAP space. Alternatively, the time delay may be based on avoiding periodic impulse noise. For example, in a case of repetition coding where N=3, the spacing between the first and second grant may be different from the spacing between the second and third grant. This prevents the case of periodic impulses obliterating all three packets due to a synchronization between the periodic impulses and the repeated packets. The optimal spacing between repeated packets will depend on the assumed impulse interarrival time statistics. For CMTS systems which sample, detect, and classify impulse events, this information may be used by the CMTS to determine the optimal spacing of repeated grants. Such a system is disclosed in commonly-owned patent application Ser. No. 09/988,065, entitled �Method and Apparatus for the Detection and Classification of Impairments on an RF Modulated Network,� filed Nov. 16, 2001, incorporated by reference in its entirety herein.
The method of flowchart 900 begins at step 902, in which the CMTS 104 receives the upstream bursts transmitted from the cable modem 108 a during step 808 of flowchart 800. At step 904, a packet is recovered from each upstream burst. This step includes demodulation of each burst and conversion to digital form by the burst receiver 216 of CMTS 104. This step may also include deinterleaving and FEC decoding of the burst data by PHY layer logic within the CMTS that resides between the burst receiver 216 and the headend MAC 218 (not shown in FIG. 2).
In accordance with the method of flowchart 1300, the cable modem 108 a transmits a packet over an upstream channel to the CMTS 104 at step 1302. At step 1304, the cable modem 108 a waits for a predetermined amount of time to receive a NACK message from the CMTS 104 over a downstream channel that indicates that the packet transmitted in step 1302 has not been received successfully. If a NACK message is not received within the predetermined amount of time, then the transmission of the packet is complete, as indicated at step 1306. However, if a NACK message is received within the predetermined amount of time, then the cable modem 108 a retransmits the packet, which is indicated by the arrow returning to step 1302 from step 1304 in flowchart 1300. The packet may be continually retransmitted until such time as a NACK message is not received, or may be retransmitted only a fixed number of times.
Embodiments of the present invention may take advantage of the fact that packets are often transmitted as two or more FEC encoded blocks, or �FEC blocks.� For example, in a DOCSIS cable modem system, a cable modem may encode a packet using Reed Solomon (RS) techniques to produce two or more FEC blocks, each of which form part of the same upstream burst. During transmission, burst noise on the upstream channel may interfere with some, but not all, of the FEC blocks. Consequently, the CMTS may recover some of the FEC blocks, while erasing others. As will be described in more detail below, the ability of the CMTS to recover at least a portion of a plurality of FEC blocks in a burst permits the CMTS to restore lost information in a manner that is more efficient than if the entire packet were erased.
The outer coding techniques described above may have an adverse effect on network capacity. Indeed, where the outer coding technique is a repetition code, sending a single packet several times reduces the overall capacity of the network by the same amount as the repetition factor. For example, sending a packet two times will consume twice as much capacity as sending it a single time, reducing network capacity to 50%. One way to mitigate this reduction in capacity is to utilize packet header suppression technology in conjunction with such outer coding techniques to reduce the size of each packet. For example, Broadcom's Propane� header suppression technology may be used to offset the bandwidth-consuming effect of repetition coding. Propane� is an advanced transport technology for DOCSIS-based cable modem systems that is available from Broadcom Corporation of Irvine, Calif.
In the case of small packets, a large percentage of the total packet consists of protocol headers. These headers are highly structured and can be coded to a much smaller size in most cases. Application of Propane� packet header suppression in a DOCSIS environment results in a 50% capacity savings over uncompressed packets. When used in conjunction with outer coding for small packets, Propane� transport technology completely mitigates the capacity effects of repetition coding where the repetition factor is N=2. Where the repetition factor is N=3, using Propane� transport technology results in network capacity of 66% as opposed to 33% for uncompressed packets.
To use Propane� transport technology in conjunction with outer coding in accordance with embodiments of the present invention, a transmitting device preferably encodes a packet to be transmitted by the Propane� coding process prior to the application of outer coding (e.g., outer block coding or repetition coding). At the receiving device, the outer code decoding process preferably reassembles the packet and corrects errors as needed prior to decoding of the packet by the Propane� process, which results in the full-size original packet. Alternately, packet header suppression may be applied by the transmitting device after application of outer coding and by the receiving device prior to outer code decoding.
Relevant packet header suppression techniques for cable modem systems are also set forth in the following commonly owned, co-pending patent applications: �Cable Modem System and Method for Supporting Extended Protocols,� U.S. patent Ser. No. 09/973,875, filed Oct. 11, 2001 by Bunn et al., �Cable Modem System and Method for Dynamically Mixing Protocol Specific Header Suppression Techniques,� U.S. patent Ser. No. 09/973,781, filed Oct. 11, 2001 by Bunn et al., �Efficiently Transmitting RTP Protocol in a Network that Guarantees In Order Delivery of Packets,� U.S. patent Ser. No. 09/973,872, filed Oct. 11, 2001 by Bunn et al., and �Dynamic Delta Encoding for Cable Modem Header Suppression,� U.S. patent Ser. No. 09/973,871, filed Oct. 11, 2001 by Bunn et al. Each of these applications is incorporated by reference as if set forth herein in their entirety.
The computer system 1800 includes one or more processors, such as processor 1804. The processor 1804 is connected to a communication infrastructure 1806. Also connected to the communication infrastructure 1806 is a display interface 1802 that facilitates bidirectional communication with a display 1830. The computer system 1800 also includes a main memory 1808, preferably random access memory (RAM), and may also include a secondary memory 1810. The secondary memory 1810 may include, for example, a hard disk drive 1812 and/or a removable storage drive 1814, representing a floppy disk drive, a magnetic tape drive, an optical disk drive, etc. The removable storage drive 1814 reads from and/or writes to a removable storage unit 1816 in a well-known manner. Removable storage unit 1816, represents a floppy disk, magnetic tape, optical disk, etc., which is read by and written to by removable storage drive 1814. As will be appreciated, the removable storage unit 1816 includes a computer usable storage medium having stored therein computer software and/or data.
In this document, the term �computer program product� refers to removable storage units 1816, 1822, and signals 1828. These computer program products are means for providing software to computer system 1800. The invention is directed to such computer program products.
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