# US 7,609,614 B2 · Uplink modulation and receiver structures for asymmetric OFDMA systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,609,614 B2 - Document ID: US7609614B2 - Status: Granted - Kind: B2 - Application number: 11/374,217 - Filed: 2006-03-14 - Published: 2007-05-24 - Granted: 2009-10-27 - Earliest claimed: 2005-10-20 - Assignees: Trellis Phase Communications, LP - Inventors: John P. Fonseka; Eric Morgan Dowling - Web page: https://patentgrep.com/patent/US7609614B2 ## CPC - H04L 1/0054: {Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) ## Abstract The present invention centers upon uplink communication protocols for use primarily with orthogonal frequency division multiple access (OFDMA) communication systems. Aspects of the invention relate to narrow band frequency division multiplexed (NBFDM) modulation protocols primarily for uplink usage in asymmetric OFDMA communication systems. In particular, NBFDM uplinks that use quadrature multiplexed continuous phase modulation are detailed and noncoherent detection schemes are developed to process the uplink channel signals without the need to transmit uplink phase reference signals. Other aspects of the invention relate to burst mode uplink communications in OFDMA systems such as those involving opportunistic beamforming. ## Claims ### Claim 1 A demodulator apparatus for use in a wireless multiple-access communication system where a headend communicates with a plurality of wireless subscriber stations, and the plurality of wireless subscriber stations use frequency division multiplexing to share an uplink frequency bandwidth, the demodulator apparatus comprising: a channelizing filter bank that separates a collection of frequency division multiplexed uplink signals into a plurality of noncoherently demodulated channel signals including a particular noncoherently demodulated channel signal, wherein the noncoherently demodulated channel signals are noncoherently demodulated complex-valued channel signals and the particular noncoherently demodulated channel signal is a particular noncoherently demodulated complex-valued channel signal; a noncoherent detector configured to detect information from the particular noncoherently demodulated channel signal, the noncoherent detector including an I/Q demodulator that noncoherently extracts first and second real-valued baseband signals respectively from an in-phase carrier signal and a quadrature-phase carrier signal, and the particular noncoherently demodulated complex-valued channel signal comprises the first and second real-valued baseband signals; and a trellis decoder responsive to the particular noncoherently demodulated complex-valued channel signal, wherein the trellis decoder includes: a set of composite states including a first composite state that represents information related to first and second simple states, wherein the first simple state corresponds to a first state of a first real-valued trellis path of a first real-valued message signal and the second simple state corresponds to a first state of a second real-valued trellis path of a second real-valued message signal; and a branch metric calculator that calculates a respective branch metric for each of a plurality of composite state transitions, wherein each composite state transition of the plurality of composite state transitions respectively leads from the first composite state to a respective second composite state, and each respective second composite state represents information related to third and fourth simple states, wherein the third simple state corresponds to a next state after the first state of the first real-valued trellis path and the fourth simple state corresponds to a next state after the first state of the second real-valued trellis path; and wherein the particular noncoherently demodulated complex-valued channel signal corresponds to a quadrature-multiplexed continuous phase modulation (QM-CPM) signal, and the first and second real-valued message signals are related to respective first and second continuous-phase baseband signals though a complex-to-real mapping function. ### Claim 2 A demodulator apparatus for use in a wireless multiple-access communication system where a headend communicates with a plurality of wireless subscriber stations, and the plurality of wireless subscriber stations use frequency division multiplexing to share an uplink frequency bandwidth, the demodulator apparatus, comprising: a channelizing filter bank that separates a collection of frequency division multiplexed uplink signals into a plurality of noncoherently demodulated channel signals including a particular noncoherently demodulated channel signal, wherein the noncoherently demodulated channel signals are noncoherently demodulated complex-valued channel signals and the particular noncoherently demodulated channel signal is a particular noncoherently demodulated complex-valued channel signal; a noncoherent detector configured to detect information from the particular noncoherently demodulated complex-valued channel signal, wherein the noncoherent detector includes: an I/Q demodulator that noncoherently extracts from an in-phase carrier signal and a quadrature-phase carrier signal first and second real-valued baseband signals; an envelope estimator that computes from the first and second real-valued baseband signals one or more envelope measurements per symbol interval; and a differential phase detector that computes from the first and second real-valued baseband signals one or more differential phase measurements per symbol interval; and a trellis decoder responsive to the particular noncoherently demodulated complex-valued channel signal, wherein the trellis decoder includes: a set of composite states including a first composite state that represents information related to first and second simple states, wherein the first simple state corresponds to a first state of a first real-valued trellis path of a first real-valued message signal and the second simple state corresponds to a first state of a second real-valued trellis path of a second real-valued message signal; and a branch metric calculator that calculates a respective branch metric for each of a plurality of composite state transitions, wherein each composite state transition of the plurality of composite state transitions respectively leads from the first composite state to a respective second composite state, and each respective second composite state represents information related to third and fourth simple states, wherein the third simple state corresponds to a next state after the first state of the first real-valued trellis path and the fourth simple state corresponds to a next state after the first state of the second real-valued trellis path; wherein the branch metric calculator calculates the respective branch metric for each of a plurality of composite state transitions using the one or more envelope measurements per symbol interval and the one or more differential phase measurements per symbol interval, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements. ### Claim 3 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a quadrature-modulate signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, the demodulator apparatus comprising: an I/Q demodulator that noncoherently extracts from an in-phase carrier signal and a quadrature-phase carrier signal first and second real-valued baseband signals; an envelope estimator that computes from the first and second real-valued baseband signals one or more envelope measurements per symbol interval; a differential phase detector that computes from the first and second real-valued baseband signals one or more differential phase measurements per symbol interval; and a trellis decoder which includes: a set of composite states including a first composite state that comprises information related to a first pair of information values that were respectively modulated onto an in-phase carrier and a quadrature-phase carrier by an I/Q modulator, and second composite states that each respectively comprise information related to a respective second pair of information values that were respectively modulated onto the in-phase carrier and the quadrature-phase carrier by the I/Q modulator; and a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements, wherein each composite state transition of the plurality of composite state transitions respectively leads from the first composite state to a respective one of the second composite states. ### Claim 4 An apparatus for use in a wireless multiple-access communication system where a headend communicates with a plurality of wireless subscriber stations, and the plurality of wireless subscriber stations use frequency division multiplexing to share an uplink frequency bandwidth, the demodulator apparatus comprising: a channelizing filter bank that separates a collection of frequency division multiplexed uplink signals into a plurality of noncoherently demodulated complex-valued channel signals including a particular noncoherently demodulated complex-valued channel signal that corresponds to a quadrature-multiplexed continuous phase modulation (QM-CPM) signal, wherein the QM-CPM signal has encoded therein first and second real-valued message signals that are related to respective first and second continuous-phase baseband signals through a complex-to-real mapping function; a trellis decoder responsive to the particular noncoherently demodulated complex-valued channel signal, wherein the trellis decoder includes: a set of composite states including a first composite state that represents information related to first and second simple states, wherein the first simple state corresponds to a first state of a first real-valued trellis path of a first real-valued message signal and the second simple state corresponds to a first state of a second real-valued trellis path of a second real-valued message signal; and a branch metric calculator that calculates a respective branch metric for each of a plurality of composite state transitions, wherein each composite state transition of the plurality of composite state transitions respectively leads from the first composite state to a respective second composite state, and each respective second composite state represents information related to third and fourth simple states, wherein the third simple state corresponds to a next state after the first state of the first real-valued trellis path and the fourth simple state corresponds to a next state after the first state of the second real-valued trellis path. ### Claim 5 (depends on 4) The apparatus of claim 4, further comprising: a transmitter apparatus that simultaneously transmits in a downlink direction a plurality of downlink information signals to the plurality of wireless subscriber stations using an orthogonal frequency division multiplexed (OFDM) communication protocol; wherein the frequency-division multiplexed uplink signals are transmitted from respective ones of the plurality of wireless subscriber stations and are modulated onto respective uplink tones of a non-orthogonal narrow band frequency division multiplexed uplink signal, and respective ones of the frequency-division multiplexed uplink signals are substantially confined to respective sub-band portions of the uplink frequency bandwidth. ### Claim 6 (depends on 5) The apparatus of claim 5, wherein the channelizing filter bank performs frequency-domain filtering to isolate respective uplink component signals contained in the respective sub-band portions to separate each respective frequency-division multiplexed uplink signal. ### Claim 7 (depends on 6) The apparatus of claim 6, wherein uplink component signals have a frequency spacing drawn from a range of [0.8/T, 1.2/T], where T is the narrow band frequency division multiplexed signal's symbol duration, and wherein each of the respective sub-band portions of the uplink frequency bandwidth are equal to or less than the frequency spacing. ### Claim 8 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a modulated signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, wherein the modulated signal is used to carry information in a communication system, the demodulator apparatus comprising: an I/O demodulator that noncoherently extracts from the modulated signal a first real-valued baseband signal and a second real-valued baseband signal; an envelope estimator that computes one or more envelope measurements per symbol interval based on the first and second real-valued baseband signals; a differential phase detector that computes one or more differential phase measurements per symbol interval based on the first and second real-valued baseband signals; and a trellis decoder which includes a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, wherein each such composite state transition respectively leads from a respective first composite state to a respective second composite state, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements; wherein the modulated signal does not include pilot symbols that carry carrier phase reference information embedded therein, and the demodulator apparatus does not perform carrier phase recovery to phase-align the first and second real-valued baseband signals with respect to any carrier phase reference. ### Claim 9 (depends on 8) The demodulator apparatus of claim 8, further comprising: a transmitter apparatus that simultaneously transmits in a downlink direction a plurality of downlink information signals to the plurality of wireless subscriber stations using an orthogonal frequency division multiplexed (OFDM) communication protocol; wherein the frequency-division multiplexed uplink signals are transmitted from respective ones of the plurality of wireless subscriber stations and are modulated onto respective uplink tones of a non-orthogonal narrow band frequency division multiplexed uplink signal, and respective ones of the frequency-division multiplexed uplink signals are substantially confined to respective sub-band portions of the uplink frequency bandwidth. ### Claim 10 (depends on 9) The demodulator apparatus of claim 9, wherein the channelizing filter bank performs frequency-domain filtering to isolate respective uplink component signals contained in the respective sub-band portions to separate each respective frequency-division multiplexed uplink signal. ### Claim 11 (depends on 10) The demodulator apparatus of claim 10, wherein uplink component signals have a frequency spacing drawn from a range of [0.8/T, 1.2/T], where T is the narrow band frequency division multiplexed signal's symbol duration, and wherein each of the respective sub-band portions of the uplink frequency bandwidth are equal to or less than the frequency spacing. ### Claim 12 (depends on 8) The demodulator apparatus of claim 8, wherein the communication system is a wireless multiple-access communication system where a headend communicates with a plurality of wireless subscriber stations, and the plurality of wireless subscriber stations use frequency division multiplexing to share an uplink frequency bandwidth. ### Claim 13 (depends on 12) The demodulator apparatus of claim 12, further comprising: a channelizing filter bank that separates a collection of frequency division multiplexed uplink signals into a plurality of noncoherently demodulated complex-valued channel signals including a particular noncoherently demodulated complex-valued channel signal. ### Claim 14 (depends on 8) The demodulator apparatus of claim 8, wherein the modulated signal has information embedded into both its amplitude envelope and its phase components. ### Claim 15 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a modulated signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, wherein the modulated signal is used to carry information in a communication system, the demodulator apparatus comprising: an envelope estimator that computes one or more envelope measurements per symbol interval; a differential phase detector that computes one or more differential phase measurements per symbol interval; and a trellis decoder which includes a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, wherein each such composite state transition respectively leads from a respective first composite state to a respective second composite state, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements; wherein the particular noncoherently demodulated complex-valued channel signal corresponds to a quadrature-multiplexed continuous phase modulation (QM-CPM) signal. ### Claim 16 (depends on 15) The demodulator apparatus of claim 15, wherein the QM-CPM signal has encoded therein first and second real-valued message signals that are related to respective first and second continuous-phase baseband signals through a complex-to-real mapping function. ### Claim 17 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a modulated signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, wherein the modulated signal is used to carry information in a communication system, the demodulator apparatus comprising: an envelope estimator that computes one or more envelope measurements per symbol interval; a differential phase detector that computes one or more differential phase measurements per symbol interval; and a trellis decoder which includes a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, wherein each such composite state transition respectively leads from a respective first composite state to a respective second composite state, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements; wherein the branch metric calculator includes means for computing a branch metric and the means for computing a branch metric computes a function that is at least a component of a member of the group consisting of joint probability density function, and a natural logarithm of the joint probability density function. ### Claim 18 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a modulated signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, wherein the modulated signal is used to carry information in a communication system, the demodulator apparatus comprising: an envelope estimator that computes one or more envelope measurements per symbol interval; a differential phase detector that computes one or more differential phase measurements per symbol interval; and a trellis decoder which includes a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, wherein each such composite state transition respectively leads from a respective first composite state to a respective second composite state, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements; wherein the branch metric calculator includes means for computing a branch metric and the means for computing a branch metric computes a function that is at least an approximation of a component of a member of the group consisting of joint probability density function, and a natural logarithm of the joint probability density function. ### Claim 19 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a modulated signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, wherein the modulated signal is used to carry information in a communication system, the demodulator apparatus comprising: an envelope estimator that computes one or more envelope measurements per symbol interval; a differential phase detector that computes one or more differential phase measurements per symbol interval; and a trellis decoder which includes a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, wherein each such composite state transition respectively leads from a respective first composite state to a respective second composite state, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements; wherein the branch metric calculator computes a function that is at least an approximation of a component of a member of the group consisting of joint probability density function, and a natural logarithm of the joint probability density function. ### Claim 20 (depends on 19) The demodulator apparatus of claim 19, wherein the modulated signal has information embedded into both its amplitude envelope and its phase components. ### Claim 21 (depends on 19) The demodulator apparatus of claim 19, wherein the modulated signal does not include pilot symbols that carry carrier phase reference information embedded therein, and the demodulator apparatus does not perform carrier phase recovery. ### Claim 22 A demodulator apparatus for use in noncoherently detecting a sequence of information symbols encoded into a modulated signal, wherein each information symbol in the sequence of information symbols has a duration of one symbol interval, wherein the modulated signal is used to carry information in a communication system, the demodulator apparatus comprising: an envelope estimator that computes one or more envelope measurements per symbol interval; a differential phase detector that computes one or more differential phase measurements per symbol interval; and a trellis decoder which includes a branch metric calculator that uses the one or more envelope measurements and the one or more differential phase measurements to calculate a set of branch metrics for each of a plurality of composite state transitions, wherein each such composite state transition respectively leads from a respective first composite state to a respective second composite state, and the values of the branch metrics are substantially dependent on both the one or more envelope measurements and the one or more differential phase measurements.