# Patent

## Title
Signal acquisition in a multimode environment

## Abstract

A transmitter comprises a symbol mapper operable to map a frame of bits to a frame of symbols, where the symbols correspond to a determined modulation scheme, and circuitry operable to convert the frame of symbols to a physical layer signal and transmit the physical layer signal onto a communication medium. The circuitry is operable to process the physical layer signal such that a first portion of the physical layer signal is a first type of signal (e.g., a linear signal and/or non-ISC signal) and a second portion of the physical layer signal is a second type of signal (e.g., nonlinear signal and/or ISC signal). The first portion of the physical layer signal may comprise a header, a preamble, and/or a payload of the frame. The second portion of the physical layer signal may comprise a header, a preamble, and/or a payload of the frame.

## Background
PRIORITY CLAIM
This application claims priority to the following application(s), each of which is hereby incorporated herein by reference:
U.S. provisional patent application 61/989,122 titled “Signal Acquisition in a Multimode Environment” filed on May 6, 2014.


INCORPORATION BY REFERENCE
Each of the following applications is hereby incorporated herein by reference:
United States patent application publication 2014/0133540 titled “Low-Complexity, Highly-Spectrally-Efficient Communications;”
U.S. Pat. No. 8,831,124 titled “Multi-Mode Orthogonal Frequency Division Multiplexing Transmitter for Highly-Spectrally-Efficient Communications;”
U.S. Pat. No. 8,681,889 titled “Multi-Mode Orthogonal Frequency Division Multiplexing Receiver for Highly-Spectrally-Efficient Communications;”
United States patent application publication 2015/0070089 titled “Adaptive Nonlinear Model Learning;” and
U.S. patent application Ser. No. 14/600,310 titled “Communication Methods and Systems for Nonlinear Multi-User Environments.”
BACKGROUND
Conventional communications systems suffer from degraded performance in the presence of nonlinear distortion. Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.
BRIEF SUMMARY
System and methods are provided for signal acquisition in a multimode environment, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
These and other advantages, aspects and novel features of the present invention, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.



BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 is a diagram illustrating a communication network in which some devices communicate using non-intersymbol-correlated signals and some devices communicate using intersymbol-correlated signals.
FIG. 2 depicts an example frame format for communications between devices which communicate using non-intersymbol-correlated signals in a multimode environment.
FIG. 3A depicts a first example frame format for communications between devices which communicate using intersymbol-correlated signals in a multimode environment.
FIG. 3B depicts a second example frame format for communications between devices which communicate using intersymbol-correlated signals in a multimode environment.
FIG. 3C depicts a third example frame format for communications between devices which communicate using intersymbol-correlated signals in a multimode environment.
FIG. 3D depicts a fourth example frame format for communications between devices which communicate using intersymbol-correlated signals in a multimode environment.
FIG. 4 depicts a flowchart for communication using the frame format of FIG. 2.
FIG. 5 depicts a flowchart for communication using the frame format of FIG. 3A.
FIG. 6 depicts a flowchart for communication using the frame format of FIG. 3B.
FIG. 7 depicts an example frame format for communications between or among devices using linear signals in a multimode environment.
FIG. 8A depicts a first example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment.
FIG. 8B depicts a second example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment.
FIG. 8C depicts a third example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment.
FIG. 8D depicts a fourth example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment.
FIG. 9 depicts a flowchart for an example communication using the frame format of FIG. 7.
FIG. 10 depicts a flowchart for an example communication using the frame format of FIG. 8A.
FIG. 11 depicts a flowchart for example communication using the frame format of FIG. 8B.



DETAILED DESCRIPTION
As used herein, a non-intersymbol-correlated (non-ISC) signal is a signal transmitted at a symbol rate that is less than twice the baseband bandwidth of the signal. Conversely, an intersymbol-correlated (ISC) signal is a signal transmitted at a symbol rate that is more than twice the baseband bandwidth of the signal. Another way of characterizing an ISC signal is that, even after: (1) sampling the signal at a sample rate at least two times its symbol rate; and (2) appropriately filtering it (e.g., a fixed root-raised-cosine (RRC) filter or equalizer configured such that an overall response of the transmitter and receiver is a raised cosine response), correlation of some or all of the resulting filtered samples is still above a threshold for two or more transmitted symbols of the signal. Attempts to recover the transmitted symbols through symbol-by-symbol slicing of the filtered samples of the ISC signal at fixed intervals will thus result in an expected error rate above a determined threshold.
As used herein, a nonlinear signal is a signal which is nonlinearly distorted to a significant degree such that the expected error rate in the receiver cannot be below a determined threshold unless the receiver compensates for the nonlinear distortion (e.g., through use of a nonlinear distortion compensation circuit that adaptively models the nonlinear distortion). A linear signal, on the other hand, is a signal for which the same receiver can achieve an expected error rate below the determined threshold even without compensating for the nonlinear distortion. The determined threshold for the expected error rate may correspond to a determined limit on nonlinear distortion which may be set by an applicable standard (e.g., promulgated by a regulatory body) and/or network operator. For example, the LTE standard specifies a maximum error vector magnitude (EVM) of 17.5% when using QPSK and 12.5% when using 16-QAM. Thus, in an example 16-QAM LTE implementation, a nonlinear signal is a signal having EVM greater than 12.5% and a linear signal is a signal having EVM of 12.5% or less.
FIG. 1 is a diagram illustrating a communication network in which some devices communicate using non-intersymbol-correlated (non-ISC) signals and some devices communicate using intersymbol-correlated (ISC) signals. Shown are two user equipment devices (UEs) 1021 and 1023 and an access point device 1022. Each of the UEs 1021 and 1023 may be, for example, a smartphone, a tablet computer, a laptop computer, a router, a network switch, a network gateway, or the like. The AP 1022 may be, for example, a cellular basestation, an 802.11 compatible access point, and/or the like. In some instances, the AP 1022 may be the same device as a UE device but configured into an access point mode.
The device 1021 comprises user interface circuitry 120 (e.g., touchscreen, buttons, speakers, etc. and their associated drivers), CPU 122, system memory 124 (e.g., flash, DRAM, SRAM, ROM, HDD, and/or the like), a receiver 126, and a transmitter 132. The receiver 126 comprises a filter 130 and a symbol slicer 128. The filter 130 may comprise, for example, a fixed-configuration filter or an equalizer that is configurable to achieve a desired response (e.g., a root-raised cosine (RRC) response, or other response such that the composite response of a transmitter and the filter 130 is a raised cosine response). The slicer 128 may be configured to sample a received signal at a fixed interval to generate pairs of in-phase and quadrature phase samples, and then determine the constellation point that is closest each such sample pair. The transmitter 132 comprises a filter 136 and a mapper 134. Each of the receiver 126 and transmitter 132 may communicate using single carrier and/or multi-carrier protocols. Where device 1021 is an LTE handset, for example, transmitter 132 may transmit in accordance with an SCFDMA scheme and receiver 126 may receive in accordance with an OFDM scheme.
The device 1022 comprises CPU 1222, system memory 1242, a receiver 140, and a transmitter 152. The receiver 140 comprises a filter 142 configured for processing non-ISC signals (e.g., configured to have an RRC response), a slicer 144, a filter 146 configured for processing intersymbol-correlated (ISC) signals, nonlinear distortion compensation circuit 148, and reduced state sequence estimation (RSSE) circuit 150. In an example implementation, the filter 142 and the filter 146 may be implemented with shared, reconfigurable circuitry. For example, an equalizer may be configurable into a first configuration which provides an RRC response and into a second configuration which provides a response such that the composite response of a transmitter and the filter 146 has desired inter-symbol correlation. In an example implementation, the ISC filter 146 (or the equalizer configured to have an ISC response) may be the same as the filter 109 in the above-incorporated U.S. patent application Ser. No. 14/074,878. The slicer 144 may be the same as slicer 128. In an example implementation, the RSSE circuit 130 may be the same as the sequence estimation circuit 210 of the above-incorporated United States Patent Application Publication 2014/0133540. In an example implementation, the RSSE circuit 130 may be part of the decoding circuit 218 of the above-incorporated U.S. Pat. No. 8,681,889. In an example implementation, the slicer 144 and the RSSE circuit 150 may be implemented with shared, reconfigurable circuitry. In an example implementation, the nonlinear distortion compensation circuit 148 may comprise one or more feedback loops and nonlinear distortion modeling circuitry operable to model/reproduce nonlinear distortion introduced by the transmitter, the communication medium, and/or the receiver front-end. The transmitter 152 comprises a symbol mapper 154, a filter 156, nonlinear distorter 158, and ISC generator 158. The nonlinear distorter 155 represents circuitry (e.g., a power amplifier and/or a predistortion circuit) that may introduce nonlinear distortion to signals transmitted by the transmitter 152. In an example implementation, the ISC generator 158 may be a filter (e.g., the filter 104 in the above-incorporated United States Patent Application Publication 2014/0133540) that introduces intersymbol correlation to the signal. In such an implementation, the ISC generator 158 and the filter 156 may be implemented with shared, reconfigurable circuitry. In another example implementation, the ISC generator 158 may introduce intersymbol correlation by predistorting the signal to be transmitted. In such an implementation, the ISC generator 158 may merge with the nonlinear distorter 155. Each of the receiver 126 and transmitter 132 may communicate using single carrier and/or multi-carrier protocols. Where device 1022 is an LTE basestation, for example, transmitter 152 may transmit in accordance with an OFDM scheme and receiver 140 may receive in accordance with an SCFDMA scheme.
The device 1023 comprises UI circuitry 1203, CPU 1223, system memory 1243, a receiver 160, and a transmitter 172. The receiver 160 comprises a filter 162 (the same as or similar to filter 142 described above), a filter 166 (the same as or similar to the filter 146 described above), nonlinear distortion compensation circuit 168 (the same as or similar to the nonlinear distortion compensation circuit 148 described above), slicer 164 (the same as or similar to slicer 144 described above), and RSSE circuit 170 (the same as or similar to the RSSE circuit 150 described above). The transmitter 172 comprises a mapper 174, a filter 176, nonlinear distorter 175, and ISC generator 178. The nonlinear distorter 155 represents circuitry (e.g., a power amplifier and/or a predistortion circuit) that may introduce nonlinear distortion to signals transmitted by the transmitter 172. In an example implementation, the ISC generator 178 may be a filter (e.g., the filter 104 in the above-incorporated United States Patent Application Publication 2014/0133540) that introduces intersymbol correlation to the signal. In such an implementation, the ISC generator 178 and the filter 176 may be implemented with shared, reconfigurable circuitry. In another example implementation, the ISC generator 178 may introduce intersymbol correlation by predistorting the signal to be transmitted. In such an implementation, the ISC generator 178 may merge with the nonlinear distorter 178. Each of the receiver 160 and transmitter 172 may communicate using single carrier and/or multi-carrier protocols. Where device 1021 is an LTE handset, for example, transmitter 172 may transmit in accordance with an SCFDMA scheme and receiver 160 may receive in accordance with an OFDM scheme.
FIG. 2 depicts an example frame format for communications among devices using non-intersymbol-correlated signals in a multimode environment. The frame 200 comprises a non-ISC preamble, a non-ISC header, and a non-ISC payload.
FIG. 3A depicts a first example frame format for communications among devices using ISC signals and non-ISC signals in a multimode environment. The frame 300 comprises a non-ISC preamble, a non-ISC header, and an ISC payload as compared to the non-ISC payload of frame 200.
FIG. 3B depicts a second example frame format for communications among devices using ISC signals and non-ISC in a multimode environment. The frame 320 comprises a non-ISC preamble and non-ISC header. A frame length field of the non-ISC header may indicate the length of ISC preamble plus the ISC payload. The frame 320 also comprises an ISC payload. In an example implementation, the ISC preamble may be formatted for use in initializing the state of RSSE circuitry (e.g., 150 or 170) and/or nonlinear distortion compensation circuitry (e.g., 148 and 168).
FIG. 3C depicts a third example frame format for communications among devices using ISC signals and non-ISC signals in a multimode environment. The frame 340 comprises a non-ISC preamble, non-ISC header, ISC header, and ISC payload. In an example implementation, the frame length field of the non-ISC header of frame 340 may indicate the overall length of the ISC header plus ISC payload, and a frame length field of the ISC header may indicate the length of the ISC payload.
FIG. 3D depicts a fourth example frame format for communications among devices using ISC signals and non-ISC signals in a multimode environment. The frame 360 comprises a non-ISC preamble, an ISC preamble, a non-ISC header, an ISC header, and an ISC payload. In an example implementation, the frame length field of the non-ISC header of frame 360 may indicate the overall length of the ISC preamble plus ISC header plus ISC payload, and the ISC header may indicate the length of the ISC payload.
FIG. 4 depicts a flowchart for an example communication using the frame format of FIG. 2. The process begins with block 402. In block 402, the device 1022 transmits frame 200 using mapper 154 and filter 156.
In block 404, the device 1021 receives the non-ISC preamble and non-ISC header of frame 200 via filter 130. In block 406, the device 1021 synchronizes its circuitry and trains its equalizer (as necessary), using the non-ISC preamble of frame 200. In block 408, the device 1021 processes the non-ISC header using the slicer 128. In block 410, the device 1021 receives the non-ISC payload via filter 130. In block 412, the device 1021 processes non-ISC payload using slicer 128.
In block 414, the device 1023 receives the non-ISC preamble and the non-ISC header via filter 162. In block 416, the device 1023 synchronizes its circuitry, trains its equalizer (as necessary), and trains its nonlinear distortion compensation circuit 168 (e.g., determines a type of nonlinear model to use and/or parameters of a selected nonlinear model to use for processing the frame 200) using the non-ISC preamble. In block 418, the device 1023 processes the non-ISC header using a receive path configured for non-ISC signals. In an example implementation, such a receive path may comprise slicer 164. In another example implementation, such a receive path may comprise the RSSE circuit 170 configured into a mode in which it operates equivalently to slicer 164. Such a mode may, for example, be characterized by a memory depth of the sequence estimation being set to zero (e.g., it may be a parameter stored in a configuration register). In an example implementation, non-ISC preambles and/or headers may be demodulated without the aid of the nonlinear distortion compensation circuit 168 (e.g., it may be in a low power state), while in another example implementation the nonlinear distortion compensation circuit 168 may aid demodulation of non-ISC preambles and/or headers.
In block 420, the device 1023 receives the non-ISC payload via filter 162. In block 422, the device 1023 processes non-ISC payload using a receive path configured for non-ISC signals. In an example implementation, such a receive path may comprise slicer 164. In another example implementation, such a receive path may comprise the RSSE circuit 170 configured into a mode in which it operates equivalently to slicer 164. Such a mode may, for example, be characterized by a memory depth of the sequence estimation being set to zero (e.g., it may be a parameter stored in a configuration register). In an example implementation, non-ISC payloads may be demodulated without the aid of the nonlinear distortion compensation circuit 168 (e.g., it may be in a low power state), while in another example implementation the nonlinear distortion compensation circuit 168 may aid demodulation of non-ISC payloads.
FIG. 5 depicts a flowchart for an example communication using the frame format of FIG. 3A. The process begins with block 502. In block 502, the device 1022 transmits frame 300. In an example implementation, the non-ISC preamble and the non-ISC header are transmitted using mapper 154 and filter 156 configured to have an RRC response, while the ISC payload is transmitted using mapper 154 and ISC generator 158 configured to generate desired inter-symbol correlation. Thus, different portions of the frame 300 experience different signal paths through the transmitter 152. In another example implementation, each of the non-ISC preamble, non-ISC header, and ISC payload may be transmitted via the mapper 154, ISC generator 158, and filter 156, but with the ISC generator 158 and/or filter 156 being in a first configuration for the non-ISC preamble and non-ISC header and a second configuration for the ISC payload.
In block 504, the device 1021 receives the non-ISC preamble and non-ISC header via filter 130. In block 506, device 1021 synchronizes its circuitry and trains its equalizer (as necessary) using the non-ISC preamble. In block 508, the device 1021 processes the non-ISC header using slicer 128. In block 510, device 1021 either fails to detect the payload, or discards the payload after detecting, based on the header, that the payload will be an ISC signal, which the device 1021 is not configured to support. Where the device 1021 fails to detect the payload it may nonetheless retain synchronization with the device 1022 based on the frame length field detected in the non-ISC header.
In block 512, device 1023 receives the non-ISC preamble and the non-ISC header via filter 162. In block 514, device 1023 synchronizes its circuitry, trains its equalizer (as necessary), and trains its nonlinear distortion compensation circuit 168 using the non-ISC preamble. In block 516, the device 1023 processes the non-ISC header using a receive path configured for non-ISC signals. In an example implementation, such a receive path may comprise slicer 164. In another example implementation, such a receive path may comprise the RSSE circuit 170 configured into a mode in which it operates equivalently to slicer 164. Such a mode may, for example, be characterized by a memory depth of the sequence estimation being set to zero (e.g., it may be a parameter stored in a configuration register). In an example implementation, non-ISC payloads may be demodulated without the aid of the nonlinear distortion compensation circuit 168 (e.g., it may be in a low power state), while in another example implementation the nonlinear distortion compensation circuit 168 may aid demodulation of non-ISC payloads.
In block 518, the device 1023 receives ISC payload via ISC filter 166. In block 520, device 1023 process the ISC payload using nonlinear distortion compensation circuit 168 and RSSE circuit 170. Because the payload is ISC, the RSSE 170 may operate in a mode in which the payload is filtered by the filter 176 configured for ISC signals and/or demodulated by the RSSE circuit 170 configured into a mode in which it operable to account for intersymbol correlation better than can be done with a symbol-by-symbol slicing (for an ISC signal, the intersymbol correlation is unlikely to have minimums, let alone zeros, at regular intervals). Such a mode may be characterized by, for example, a memory depth of the sequence estimation being set to a non-zero value.
FIG. 6 depicts a flowchart for example communication using the frame format of FIG. 3B. The process begins with block 602. In block 602, the device 1022 transmits frame 320. In an example implementation, the non-ISC preamble and the non-ISC header are transmitted using mapper 154 and filter 156 configured for non-ISC signals (e.g., configured to have an RRC response), while the ISC preamble and ISC payload are transmitted using mapper 154 and ISC generator 158. Thus, different portions of the frame 320 experience different signal paths through the transmitter 152. In another example implementation, each of the non-ISC preamble, non-ISC header, ISC preamble, and ISC payload may be transmitted via the mapper 154, ISC generator 158, and filter 156, but with the ISC generator 158 and/or filter 156 being in a first configuration for the non-ISC preamble and non-ISC header and a second configuration for the ISC preamble and ISC payload.
In block 604, the device 1021 receives the non-ISC preamble and the non-ISC header via filter 130. In block 606, the device 1021 synchronizes its circuitry and trains its equalizer (as necessary) based on the non-ISC preamble. In block 608, the device 1021 processes the non-ISC header using slicer 128. In block 610, device 1021 either fails to detect the payload or discards the payload after detecting, based on the header, that the payload will be transmitted as an ISC signal, which the device 1021 is not configured to support. Where the device 1021 fails to detect the payload it may nonetheless retain synchronization with the device 1022 based on the frame length field detected in the non-ISC header.
In block 612, the device 1023 receives the non-ISC preamble and the non-ISC header via filter 162 (e.g., configured to have an RRC response). In block 614, the device 1023 synchronizes its circuitry and trains its equalizer (as necessary) based on the non-ISC preamble. In block 616, the device 1023 processes the non-ISC header using a receive path configured for non-ISC signals. In an example implementation, such a receive path may comprise slicer 164. In another example implementation, such a receive path may comprise the RSSE circuit 170 configured into a mode in which it operates equivalently to slicer 164. Such a mode may, for example, be characterized by a memory depth of the sequence estimation being set to zero (e.g., it may be a parameter stored in a configuration register). In block 618, the device 1023 receives the ISC preamble via filter 166. In block 620, the device 1023 trains its nonlinear distortion compensation circuitry 168, and (optionally) initializes the state of the RSSE circuit 170 using the ISC preamble. In block 622, the device 1023 process the ISC payload using the trained nonlinear distortion compensation circuit 168 and (initialized) RSSE circuit 170. Because the payload is ISC, the RSSE 170 may operate in a mode in which the payload is filtered with the filter 146 and/or demodulated by the RSSE circuit 170 configured into a mode in which it operable to account for intersymbol correlation better than can be done with a symbol-by-symbol slicing (for an ISC signal, the intersymbol correlation is unlikely to have minimums, let alone zeros, at well-defined intervals). Such a mode may be characterized by, for example, a memory depth of the sequence estimation being set to a non-zero value.
FIG. 7 depicts an example frame format for communications between or among devices using linear signals in a multimode environment. The frame 700 comprises a linear preamble, a linear header, and a linear payload.
FIG. 8A depicts a first example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment. The frame 800 comprises a linear preamble, a linear header, and a nonlinear payload as compared to the linear payload of frame 200.
FIG. 8B depicts a second example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment. The frame 820 comprises a linear preamble and linear header. A frame length field of the linear header may indicate the length of the nonlinear preamble plus the nonlinear payload. The frame 820 also comprises a nonlinear payload. In an example implementation, the nonlinear preamble may be formatted for use in initializing the state of RSSE circuitry (e.g., 150 or 170) and/or nonlinear distortion compensation circuitry (e.g., 148 and 168).
FIG. 8C depicts a third example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment. The frame 840 comprises a linear preamble, linear header, nonlinear header, and nonlinear payload. In an example implementation, the frame length field of the linear header of frame 840 may indicate the overall length of the nonlinear header plus nonlinear payload, and a frame length field of the nonlinear header may indicate the length of the nonlinear payload.
FIG. 8D depicts a fourth example frame format for communications between or among devices using linear and nonlinear signals in a multimode environment. The frame 860 comprises a linear preamble, a nonlinear preamble, a linear header, a nonlinear header, and a nonlinear payload. In an example implementation, the frame length field of the linear header of frame 860 may indicate the overall length of the nonlinear preamble plus nonlinear header plus nonlinear payload, and the nonlinear header may indicate the length of the nonlinear payload.
FIG. 9 depicts a flowchart for an example communication using the frame format of FIG. 7. The process begins with block 902. In block 902, the device 1022 transmits frame 700. The frame 700 may be transmitted with the nonlinear distorter 155 disabled and/or configured for linear operation (e.g., a power amplifier biased in its linear region).
In block 904, the device 1021 receives the linear preamble and linear header of frame 200 via filter 130. In block 906, the device 1021 synchronizes its circuitry and trains its equalizer (as necessary), using the linear preamble of frame 200. In block 908, the device 1021 processes the linear header using the slicer 128. In block 910, the device 1021 receives the linear payload via filter 130. In block 912, the device 1021 processes linear payload using slicer 128.
In block 914, the device 1023 receives the linear preamble and the linear header via filter 162. In block 916, the device 1023 synchronizes its circuitry and trains its equalizer using the linear preamble. In block 918, the device 1023 processes the linear header using a receive path configured for linear signals. Such a mode may, for example, be characterized the nonlinear distortion compensation circuit 168 being disabled or bypassed.
In block 920, the device 1023 receives the linear payload via filter 162. In block 922, the device 1023 processes the linear payload using a receive path configured for linear signals. Such a mode may, for example, be characterized by the nonlinear distortion compensation circuit 168 being disabled or bypassed.
FIG. 10 depicts a flowchart for an example communication using the frame format of FIG. 8A. The process begins with block 1002. In block 1002, the device 1022 transmits frame 300. In an example implementation, the linear preamble and the linear header are transmitted using nonlinear distorter 155 configured to generate a linear signal (e.g., predistortion reduced, bypassed, or disabled, and power amplifier biased in linear region), while the nonlinear payload is transmitted using nonlinear distorter 155 configured to generate a nonlinear signal (e.g., predistortion enabled or increased, and/or power amplifier biased in nonlinear region).
In block 1004, the device 1021 receives the linear preamble and linear header via filter 130. In block 1006, device 1021 synchronizes its circuitry and trains its equalizer (as necessary) using the linear preamble. In block 1008, the device 1021 processes the linear header using slicer 128. In block 1010, device 1021 either fails to detect the payload, or discards the payload after detecting, based on the header, that the payload will be a nonlinear signal, which the device 1021 is not configured to support. Where the device 1021 fails to detect the payload it may nonetheless retain synchronization with the device 1022 based on the frame length field detected in the linear header.
In block 1012, device 1023 receives the linear preamble and the linear header via filter 162. In block 1014, device 1023 synchronizes its circuitry and trains its equalizer (as necessary). In block 1016, the device 1023 processes the linear header using a receive path configured for linear signals. Such a receive path may, for example, bypass the NL compensation circuit 168, or the NL compensation circuit 168 may be in the receive path but be powered down and/or have its parameters set such that the response of its model of nonlinearity reduces to a linear response. In block 1018, the device 1023 receives nonlinear payload via nonlinear filter 166. In block 1020, the NL compensation circuit 168 trains its model of the nonlinear distortion present in the payload based on the payload itself (e.g., predetermined portions of the payload and/or using iterative decision feedback). In block 1022, the device 1023 process the nonlinear payload using a receive path configured for nonlinear signals. Such a receive path may comprise the NL compensation circuit 168 trained in block 1020.
FIG. 11 depicts a flowchart for example communication using the frame format of FIG. 8B. The process begins with block 1102. In block 1102, the device 1022 transmits frame 320. In an example implementation, the linear preamble and the linear header are transmitted using nonlinear distorter 155 configured to generate a linear signal (e.g., predistortion reduced, bypassed, or disabled, and/or power amplifier biased in linear region), while the nonlinear preamble and nonlinear payload are transmitted using nonlinear distorter 155 configured to generate a nonlinear signal (e.g., predistortion enabled or increased, and/or power amplifier biased in nonlinear region).
In block 1104, the device 1021 receives the linear preamble and the linear header via filter 130. In block 1106, the device 1021 synchronizes its circuitry and trains its equalizer (as necessary) based on the linear preamble. In block 1108, the device 1021 processes the linear header using slicer 128. In block 1110, device 1021 either fails to detect the payload or discards the payload after detecting, based on the header, that the payload will be transmitted as an nonlinear signal, which the device 1021 is not configured to support. Where the device 1021 fails to detect the payload it may nonetheless retain synchronization with the device 1022 based on the frame length field detected in the linear header.
In block 1112, the device 1023 receives the linear preamble and the linear header via filter 1112. In block 1114, the device 1023 synchronizes its circuitry and trains its equalizer (as necessary) based on the linear preamble. In block 1116, the device 1023 processes the linear header using a receive path configured for linear signals. Such a receive path may, for example, bypass the NL compensation circuit 168, or the NL compensation circuit 168 may be in the receive path but powered down and/or have its parameters set such that the response of its model of nonlinearity reduces to a linear response. In block 1118, the device 1023 receives the nonlinear preamble via filter 166. In block 1120, the device 1023 trains its nonlinear distortion compensation circuitry 168 such that a nonlinear distortion model maintained by the nonlinear distortion compensation circuitry 168 can predict/reproduce (with desired accuracy) the nonlinear distortion present in the nonlinear signals from device 1022, and (optionally) initializes the state of the RSSE circuit 170 using the nonlinear preamble. In block 1122, the device 1023 process the nonlinear payload using the trained nonlinear distortion compensation circuit 168 and (initialized) RSSE circuit 170.
In accordance with various aspects of this disclosure, a transmitter (e.g., 152) comprises a symbol mapper (e.g., 154) operable to map a frame of bits to a frame of symbols, where the symbols correspond to a determined modulation scheme, and circuitry (e.g., 155, 156, and/or 158) operable to convert the frame of symbols to a physical layer signal and transmit the physical layer signal onto a communication medium. The circuitry is operable to process the physical layer signal such that a first portion of the physical layer signal is a first type of signal (e.g., a linear signal and/or non-ISC signal) and a second portion of the physical layer signal is a second type of signal (e.g., nonlinear signal and/or ISC signal). The first portion of the physical layer signal may comprise a header, a preamble, and/or a payload of the frame. The second portion of the physical layer signal may comprise a header, a preamble, and/or a payload of the frame.
As utilized herein the terms “circuits” and “circuitry” refer to physical electronic components (i.e. hardware) and any software and/or firmware (“code”) which may configure the hardware, be executed by the hardware, and or otherwise be associated with the hardware. As used herein, for example, a particular processor and memory may comprise a first “circuit” when executing a first one or more lines of code and may comprise a second “circuit” when executing a second one or more lines of code. As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y”. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y and z”. As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “e.g.,” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, circuitry is “operable” to perform a function whenever the circuitry comprises the necessary hardware and code (if any is necessary) to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, etc.).
Other embodiments of the invention may provide a non-transitory computer readable medium and/or storage medium, and/or a non-transitory machine readable medium and/or storage medium, having stored thereon, a machine code and/or a computer program having at least one code section executable by a machine and/or a computer, thereby causing the machine and/or computer to perform the processes as described herein.
Accordingly, the present invention may be realized in hardware, software, or a combination of hardware and software. The present invention may be realized in a centralized fashion in at least one computing system, or in a distributed fashion where different elements are spread across several interconnected computing systems. Any kind of computing system or other apparatus adapted for carrying out the methods described herein is suited. A typical combination of hardware and software may be a general-purpose computing system with a program or other code that, when being loaded and executed, controls the computing system such that it carries out the methods described herein. Another typical implementation may comprise an application specific integrated circuit or chip.
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.

## Claims

1. A transmitter comprising:
a symbol mapping circuit configured to map a frame of bits to a frame of symbols, said symbols corresponding to a determined modulation scheme; and
circuitry configured to convert said frame of symbols to a physical layer signal and transmit said physical layer signal onto a communication medium,
wherein:
said circuitry comprises a nonlinear distorter circuit configured to process said physical layer signal such that a first portion of said physical layer signal not including payload data is a linear signal and a second portion of said physical layer signal including payload data is a nonlinear signal.

2. The transmitter of claim 1, wherein said first portion of said physical layer signal comprises a header of said frame and said second portion of said physical layer signal comprises a payload of said frame.

3. The transmitter of claim 2, wherein:
said nonlinear distorter circuit comprises a predistortion circuit;
said predistortion circuit introduces more nonlinear distortion to said payload of said frame than to said header of said frame.

4. The transmitter of claim 2, wherein:
said nonlinear distorter circuit comprises a power amplifier;
said power amplifier operates in a linear response region during processing of said header of said frame; and
said power amplifier operates in a nonlinear response region during processing of said payload of said frame.

5. The transmitter of claim 1, wherein said first portion of said physical layer signal comprises a header of said frame and said second portion of said physical layer signal comprises a preamble of said frame.

6. The transmitter of claim 5, wherein:
said nonlinear distorter circuit comprises a predistortion circuit;
said predistortion circuit introduces more nonlinear distortion to said preamble of said frame than to said header of said frame.

7. The transmitter of claim 5, wherein:
said nonlinear distorter circuit comprises a power amplifier;
said power amplifier operates in a linear response region during processing of said header of said frame; and
said power amplifier operates in a nonlinear response region during processing of said preamble of said frame.

8. The transmitter of claim 1, wherein said first portion of said physical layer signal comprises a header of said frame, and said second portion of said physical layer signal comprises a preamble of said frame and a payload of said frame.

9. The transmitter of claim 8, wherein:
said nonlinear distorter circuit comprises a predistortion circuit;
said predistortion circuit introduces more nonlinear distortion to said preamble of said frame and said payload of said frame than to said header of said frame.

10. The transmitter of claim 8, wherein:
said nonlinear distorter circuit comprises a power amplifier;
said power amplifier operates in a linear response region during processing of said header of said frame; and
said power amplifier operates in a nonlinear response region during processing of said payload of said frame and said preamble of said frame.

11. The transmitter of claim 1, wherein said first portion of said physical layer signal comprises a first preamble of said frame and a header of said frame, and said second portion of said physical layer signal comprises a second preamble of said frame and a payload of said frame.

12. The transmitter of claim 11, wherein:
said nonlinear distorter circuit comprises a predistortion circuit;
said predistortion circuit introduces more nonlinear distortion to said second preamble of said frame and said payload of said frame than to said header of said frame and said first preamble of said frame.

13. The transmitter of claim 11, wherein:
said nonlinear distorter circuit comprises a power amplifier;
said power amplifier operates in a linear response region during processing of said header of said frame and said first preamble of said frame; and
said power amplifier operates in a nonlinear response region during processing of said payload of said frame and said second preamble of said frame.

14. The transmitter of claim 1, wherein said second portion of said physical layer signal is an inter-symbol correlated signal.

15. A transmitter comprising:
a symbol mapping circuit configured to map a frame of bits to a frame of symbols, said symbols corresponding to a determined modulation scheme; and
circuitry operable to convert said frame of symbols to a physical layer signal and transmit said physical layer signal onto a communication medium,
wherein:
said circuitry comprises an inter-symbol correlated (ISC) signal generator configured to process said physical layer signal such that a first portion of said physical layer signal not including payload data is a non-ISC signal and a second portion of said physical layer signal including payload data is an ISC signal.

16. The transmitter of claim 15, wherein said first portion of said physical layer signal comprises a header of said frame and said second portion of said physical layer signal comprises a payload of said frame.

17. The transmitter of claim 15, wherein said first portion of said physical layer signal comprises a header of said frame and said second portion of said physical layer signal comprises a preamble of said frame.

18. The transmitter of claim 15, wherein said first portion of said physical layer signal comprises a header of said frame, and said second portion of said physical layer signal comprises a preamble of said frame and a payload of said frame.

19. The transmitter of claim 15, wherein said first portion of said physical layer signal comprises a first preamble of said frame and a header of said frame, and said second portion of said physical layer signal comprises a second preamble of said frame and a payload of said frame.

20. The transmitter of claim 15, wherein said second portion of said physical layer signal is a nonlinear signal.