# US 7,609,757 B2 · DSL rate adaptation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,757 B2 - Document ID: US7609757B2 - Status: Granted - Kind: B2 - Application number: 11/080,100 - Filed: 2005-03-15 - Published: 2005-07-21 - Granted: 2009-10-27 - Earliest claimed: 1998-12-23 - Assignees: Broadcom Corporation - Inventors: David Jones - Web page: https://patentgrep.com/patent/US7609757B2 ## CPC - H04L 5/0064: {Rate requirement of the data, e.g. scalable bandwidth, data priority} - H04L 5/0046: {Determination of the number of bits transmitted on different sub-channels} - H04L 5/006: {Quality of the received signal, e.g. BER, SNR, water filling} - H04L 5/023: {Multiplexing of multicarrier modulation signals, e.g. multi-user orthogonal frequency division multiple access [OFDMA] (multicarrier modulation H04L27/2601)} - H04L 5/143: {for modulated signals (H04L5/1469 takes precedence)} - H04L 5/0007: {the frequencies being orthogonal, e.g. OFDM(A) or DMT} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract A method for enhancing the bit rate and/or margin at which quadrature amplitude modulation (QAM) communication is performed includes the steps of varying a spectral allocation and constellation size with which communication is performed, so as to define a combination of spectral allocation and constellation size at which the bit rate and/or margin are enhanced. The spectral allocation can be varied by varying a stop frequency thereof, while maintaining a substantially constant start frequency, so as to mitigate undesirable high frequency content of the bandwidth. Alternatively, both start and stop frequencies may be varied. ## Claims ### Claim 1 A method for data communication over a transmission channel, comprising: (a) evaluating, by a communications transceiver, a channel response characteristic with respect to a constellation size and a single carrier having an adjustable center frequency of a transmission signal; (b) varying, by the communications transceiver, the adjustable center frequency of the transmission signal; (c) determining, by the communications transceiver, a maximum spectral allocation for the transmission channel for which a signal-to-noise ratio is less than a predetermined value; (d) re-evaluating, by the communications transceiver, the channel response characteristic with respect to the varied center frequency; and (e) determining, by the communications transceiver, an optimal constellation size and optimal center frequency responsive to at least one of an optimum bit rate and an optimum noise margin. ### Claim 2 (depends on 1) The method of claim 1, wherein step (b) comprises: (b)(i) varying a stop frequency of a spectral allocation of the transmission signal while maintaining a substantially constant start frequency of the spectral allocation. ### Claim 3 (depends on 1) The method of claim 1, wherein the transmission channel is a single QAM channel. ### Claim 4 (depends on 1) The method of claim 1, further comprising: (f) varying the constellation size by encoding a signal in conformance with a plurality of discrete constellation sizes and determining a maximum constellation size at which a single QAM communication occurs without exceeding a predetermined bit error rate. ### Claim 5 (depends on 4) The method of claim 4, wherein step (f) comprises: (f)(i) varying the constellation size while maintaining a substantially constant spectral allocation; and repeating the constellation size varying step at a plurality of different discrete spectral allocations. ### Claim 6 (depends on 1) The method of claim 1, wherein step (b) comprises: (b)(i) varying the spectral allocation while maintaining a constant constellation size; and (b)(ii) repeating the center frequency varying step for a plurality of different discrete constellation sizes. ### Claim 7 A method for enhancing a potential channel response characteristic of a transmission channel, comprising: (a) varying, by a communications transceiver, a center frequency and a constellation size of the transmission channel; (b) determining, by the communications transceiver, the potential channel response characteristic associated with the center frequency and the constellation size; and (c) defining, by the communications transceiver, a combination of the center frequency and the constellation size at which the potential channel response characteristic is enhanced. ### Claim 8 (depends on 7) The method of claim 7, wherein step (a) comprises: (a)(i) varying a start frequency and a stop frequency thereof. ### Claim 9 (depends on 8) The method of claim 8, wherein step (a)(i) comprises: (a)(i)(A) varying the start frequency and the stop frequency in discrete increments. ### Claim 10 (depends on 8) The method of claim 8, wherein step (a)(i) comprises: (a)(i)(A) sweeping the start frequency and the stop frequency in a continuous manner. ### Claim 11 (depends on 7) The method of claim 7, wherein the channel performs quadrature amplitude modulated (QAM) communication. ### Claim 12 (depends on 7) The method of claim 7, wherein step (c) comprises: (c)(i) defining the combination of the center frequency and the constellation size at which a bit rate is enhanced. ### Claim 13 (depends on 7) The method of claim 7, wherein step (c) comprises: (c)(i) defining the combination of the center frequency and the constellation size at which a margin at which quadrature amplitude modulated (QAM) communication is performed is enhanced. ### Claim 14 (depends on 7) The method of claim 7, wherein step (a) comprises: (a)(i) utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs. ### Claim 15 (depends on 7) The method of claim 7, wherein step (a) comprises: (a)(i) utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs without exceeding a predetermined bit error rate (BER). ### Claim 16 (depends on 7) The method of claim 7, wherein step (a) comprises: (a)(i) varying the constellation size while maintaining a constant center frequency and repeating this step for a plurality of different center frequencies. ### Claim 17 (depends on 7) The method of claim 7, wherein step (a) comprises: (a)(i) varying the center frequency while maintaining a constant constellation size for a plurality of different constellation sizes. ### Claim 18 A system for data communication over a transmission channel, comprising: means for evaluating a channel response characteristic with respect to a constellation size and a single carrier having an adjustable center frequency of a transmission signal; means for varying the adjustable center frequency of the transmission signal; means for determining a maximum spectral allocation for the transmission channel for which a signal-to-noise ratio is less than a predetermined value; means for re-evaluating the channel response characteristic with respect to the varied center frequency; and means for determining an optimal constellation size and an optimal center frequency responsive to at least one of an optimum bit rate and an optimum noise margin. ### Claim 19 (depends on 18) The system of claim 18, wherein means for varying the adjustable center frequency comprises: means for varying a stop frequency of spectral allocation of the transmission signal while maintaining a substantially constant start frequency of the spectral allocation. ### Claim 20 (depends on 18) The system of claim 18, further comprising: means for varying the constellation size by encoding a signal in conformance with a plurality of discrete constellation sizes; and means for determining a maximum constellation size at which a single QAM communication occurs without exceeding a predetermined bit error rate. ### Claim 21 (depends on 20) The system of claim 20, wherein the means for varying the constellation size comprises: means for varying the constellation size while maintaining a substantially constant spectral allocation; and means for repeating the varying of the constellation size at a plurality of different discrete spectral allocations. ### Claim 22 (depends on 18) The system of claim 18, means for varying the adjustable center frequency of the transmission signal comprises: means for varying the spectral allocation while maintaining a constant constellation size; and means for repeating the center frequency varying step for a plurality of different discrete constellation sizes. ### Claim 23 A system for enhancing a potential channel response characteristic of a transmission channel, comprising: means for varying a center frequency and a constellation size of the transmission channel; means for determining the potential channel response characteristic associated with the center frequency and the constellation size; and means for defining a combination of the center frequency and the constellation size at which the channel response characteristic is enhanced. ### Claim 24 (depends on 23) The system of claim 23, wherein the means for varying the center frequency and constellation size comprises: means for varying a start frequency and a stop frequency thereof. ### Claim 25 (depends on 24) The system of claim 24, wherein the means for varying the center frequency and constellation size comprises: means for varying the start frequency and the stop frequency in discrete increments. ### Claim 26 (depends on 24) The system of claim 24, wherein the means for varying the center frequency and the constellation size comprises: means for sweeping the start frequency and the stop frequency in a continuous manner. ### Claim 27 (depends on 23) The system of claim 23, wherein the channel performs quadrature amplitude modulated (QAM) communication. ### Claim 28 (depends on 23) The system of claim 23, wherein the means for defining the combination of the center frequency and the constellation size comprises: means for defining the combination of the center frequency and the constellation size at which a bit rate is enhanced. ### Claim 29 (depends on 23) The system of claim 23, wherein the means for defining the combination of the center frequency and the constellation size comprises: means for defining the combination of the center frequency and the constellation size at which a margin at which quadrature amplitude modulated (QAM) communication is performed is enhanced. ### Claim 30 (depends on 23) The system of claim 23, wherein the means for varying the center frequency and the constellation size comprises: means for utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs. ### Claim 31 (depends on 23) The system of claim 23, wherein the means for varying the center frequency and the constellation size comprises: means for utilizing a plurality of different constellation sizes so as to determine a maximum constellation size at which communication occurs without exceeding a predetermined bit error rate (BER). ### Claim 32 (depends on 23) The system of claim 23, wherein the means for varying the center frequency and the constellation size comprises: means for varying the constellation size while maintaining a constant center frequency and repeating this step for a plurality of different center frequencies. ### Claim 33 (depends on 23) The system of claim 23, wherein the means for varying the center frequency and the constellation size comprises: means for varying the center frequency while maintaining a constant constellation size for a plurality of different constellation sizes.