System and method for nonlinearity estimation with reference signals

A transmitter may be configured to generate a reference signal having a non-constant envelope for nonlinearity estimation by a receiver. The transmitter may transmit the reference signal. A receiver may be configured to receive, from the transmitter, the reference signal having the non-constant envelope. The receiver may estimate at least one nonlinearity characteristic based on the reference signal having the non-constant envelope. The receiver may transmit feedback based on the at least one nonlinearity characteristic and/or perform at least one digital post distortion (DPoD) operation based on the at least one nonlinearity characteristic.

BACKGROUND

Technical Field

The present disclosure relates generally to communication systems, and more particularly, to a transmitter configured to generate a reference signal having a non-constant envelope that may be used for nonlinearity estimation.

INTRODUCTION

SUMMARY

In various wireless communications system, a transmitter may include various nonlinear components, such as high power amplifiers with limit linear dynamic range. Some nonlinear components may distort a transmitted signal due to high peak to average power ratio (PAPR). In order to reduce this distortion, a back off may be applied (e.g., to the transmission power). However, the back off may reduce power efficiency.

The efficiency of radiated power may be influential in the design of a radio frequency (RF) transmitter. In order to improve efficiency, at least one digital pre-distortion (DPD) operation and/or digital post-distortion (DPoD) operations may be performed based on non-linearity estimations from the transmission of the signal. For example, a transmitter may apply DPD operations and/or a receiver may apply DPoD operations. In order perform DPD and/or DPoD operations, the non-linearity characteristics of various components in the transmitter and/or the receiver (e.g., amplifiers, signal converters, etc.) may be estimated.

The present disclosure may provide approaches to estimation of nonlinearity characteristics of various components of the transmitter and/or receiver. Various approaches described herein may avoid data-driven nonlinearity estimation, which may use iterative decoding for signals having a relatively high signal-to-noise ratio (SNR) and with a modulation scheme of 16 quadrature amplitude modulation (QAM) or a higher modulation scheme. In various approaches, various portions of a transmitted signal may be used for nonlinearity estimation, such as a preamble. The dynamic range of a transmitted reference signal may be modified using non-constant envelope constellations in order to cover many (potentially all) dynamic ranges of nonlinear components. Some approaches described in the present disclosure may differ from some protocols, which may use signal preambles with a constant (or approximately constant, due to some shaping pulse) envelope in order to avoid nonlinearity effects (e.g., for a high-power amplifier). Signal preambles with a constant (or nearly constant) envelope may prevent nonlinearity estimation by a receiver.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a transmitter. The apparatus may generate a reference signal having a non-constant envelope for nonlinearity estimation by a receiver. The apparatus may transmit the reference signal, e.g., to a receiver. In an aspect, the reference signal includes a primary synchronization signal. In an aspect, the primary synchronization signal is based on a Zadoff-Chu sequence. In an aspect, the reference signal includes one of a short training sequence (STS) or a guard interval (GI). In an aspect, the reference signal includes a preamble having the non-constant envelope. In an aspect, the generation of the reference signal having the non-constant envelope includes modulation of the reference signal to have a first dynamic range, the first dynamic range being higher than a second dynamic range of another signal having a constant envelope. The apparatus may further receive, from the receiver, feedback associated with the nonlinearity estimation, and perform at least one DPD operation based on the feedback. In an aspect, the performance of the at least one DPD operation based on the feedback comprises adjusting one or more coefficients associated with at least one of a high-power amplifier (HPA) or a digital to analog converter (DAC).

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a receiver. The apparatus may receive a reference signal having a non-constant envelope. The apparatus may estimate at least one nonlinearity characteristic based on the reference signal having the non-constant envelope. The apparatus may at least one of: transmit feedback based on the at least one nonlinearity characteristic, or perform at least one DPoD operation based on the at least one nonlinearity characteristic. In an aspect, the reference signal includes a primary synchronization signal. In an aspect, the primary synchronization signal is based on a Zadoff-Chu sequence. In an aspect, the reference signal includes one of a STS or a GI. In an aspect, the reference signal includes a preamble having the non-constant envelope. In an aspect, the estimation of the at least one nonlinearity characteristic based on the reference signal having the non-constant envelope is based on a least-squares algorithm. In an aspect, the performance of the at least one DPoD operation based on the at least one nonlinearity characteristic comprises adjusting one or more coefficients associated with at least one of a low-noise amplifier (LNA) or an analog to digital converter (ADC).

DETAILED DESCRIPTION

The small cell102′ may operate in a licensed and/or an unlicensed frequency spectrum. When operating in an unlicensed frequency spectrum, the small cell102′ may employ NR and use the same 5 GHz unlicensed frequency spectrum as used by the Wi-Fi AP150. The small cell102′, employing NR in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. A base station102, whether a small cell102′ or a large cell (e.g., macro base station), may include an eNB, gNodeB (gNB), or other type of base station. Some base stations, such as gNB180may operate in a traditional sub 6 GHz spectrum, in millimeter wave (mmW) frequencies, and/or near mmW frequencies in communication with the UE104. When the gNB180operates in mmW or near mmW frequencies, the gNB180may be referred to as an mmW base station. Extremely high frequency (EHF) is part of the RF in the electromagnetic spectrum. EHF has a range of 30 GHz to 300 GHz and a wavelength between 1 millimeter and 10 millimeters. Radio waves in the band may be referred to as a millimeter wave. Near mmW may extend down to a frequency of 3 GHz with a wavelength of 100 millimeters. The super high frequency (SHF) band extends between 3 GHz and 30 GHz, also referred to as centimeter wave. Communications using the mmW/near mmW radio frequency band (e.g., 3 GHz-300 GHz) has extremely high path loss and a short range. The mmW base station180may utilize beamforming182with the UE104to compensate for the extremely high path loss and short range.

Referring again toFIG. 1, in certain aspects, the base station180may be configured to generate a reference signal198having a non-constant envelope. The base station180may transmit the reference signal198having the non-constant envelope to the UE104. The UE104may be configured to receive the reference signal198having the non-constant envelope from the base station180. The UE104may estimate one or more nonlinearity characteristics based on the reference signal198. Thereafter, the UE104may (1) transmit, to the base station180, feedback based on the one or more nonlinearity characteristics, (2) perform at least one digital post distortion (DPoD) operation based on the one or more nonlinearity characteristics, or (3) both transmit feedback based on the one or more nonlinearity characteristics and perform the at least one DPoD operation based on the one or more nonlinearity characteristics. When the UE104transmits feedback based on the one or more nonlinearity characteristics to the base station180, the base station180may perform at least one digital pre-distortion (DPD) operation based on the feedback. In this way, the UE104and/or the base station180may improve the response, throughput, and/or capacity of one or more channels on which the UE104and the base station180communicate.

In various wireless communications system, a transmitter may include various nonlinear components, such as high power amplifiers with limit linear dynamic range. Some nonlinear components may distort a transmitted signal due to high peak to average power ratio (PAPR). In order to reduce this distortion, a back off may be applied (e.g., to the transmission power). However, the back off may reduce power efficiency.

The efficiency of radiated power may be influential in the design of a radio frequency (RF) transmitter. In order to improve efficiency, at least one DPD and/or at least one DPoD operation(s) may be performed based on non-linearity estimations from the transmission of the signal. For example, a transmitter may apply at least one DPD operation and/or a receiver may apply at least one DPoD operation. In order perform at least one DPD operation and/or at least one DPoD operation, the non-linearity characteristics of various components in the transmitter and/or the receiver (e.g., amplifiers, signal converters, etc.) may be estimated.

The present disclosure may provide approaches to estimation of nonlinearity characteristics of various components of the transmitter and/or receiver. Various approaches described herein may avoid data-driven nonlinearity estimation, which may use iterative decoding for signals having a relatively high signal-to-noise ratio (SNR) and with a modulation scheme of 16 quadrature amplitude modulation (QAM) or a higher modulation scheme. In various approaches, various portions of a transmitted signal may be used for nonlinearity estimation, such as a preamble. The dynamic range of a transmitted reference signal may be modified using non-constant envelope constellations in order to cover many (potentially all) dynamic ranges of nonlinear components. Some approaches described in the present disclosure may differ from some protocols, which may use signal preambles with a constant (or approximately constant, due to some shaping pulse) envelope in order to avoid nonlinearity effects (e.g., for a high-power amplifier). Signal preambles with a constant (or nearly constant) envelope may prevent nonlinearity estimation by a receiver.

FIG. 4is a call flow diagram of a wireless communications system400. The wireless communications system400may include at least one transmitter402and at least one receiver404. The transmitter402and the receiver404are illustrated as a base station and a UE, respectively (e.g., for uplink communication); however, this arrangement is to be regarded as illustrative and the transmitter402and/or the receiver404may be any apparatuses configured for wireless communication.

The transmitter402and the receiver404may be configured to communicate on one or more channels according to at least one standard. For example, the transmitter402and the receiver404may be configured to communicate according to one or more 3GPP standards (e.g., 5G NR, LTE, etc.). In another example, the transmitter402and the receiver404may be configured to communicate according to one or more IEEE standards (e.g., 802.11). The aforementioned examples are intended to be illustrative, and the aspects described herein may be applicable to any standard and/or protocol for wireless communication.

In order to improve communication between the transmitter402and the receiver404, it may be beneficial to estimate one or more nonlinearity characteristics (or coefficients) associated with the transmitter/receiver path (e.g., channel). Estimation of the one or more nonlinearity characteristics may allow the transmitter402to perform at least one DPD operation based on feedback from the receiver404and/or may allow the receiver404to perform at least one DPoD operation based on the estimation of the one or more nonlinearity characteristics by the receiver404. In so performing at least one DPD operation and/or at least one DPoD operation, the transmitter402and/or the receiver404may improve throughput, capacity, and/or response of a channel while also improving efficiency of radiated power.

The transmitter402may include one or more nonlinear components, for example, as part of the transmit chain corresponding to generation of signals for transmission. Examples of such nonlinear components include a high-power amplifier (HPA) (e.g., an HPA with limited linear dynamic range), a digital-to-analog converter (DAC), and so forth. The nonlinear components may distort signals transmitted by the transmitter402—e.g., an HPA with limited linear dynamic range may distort transmitted signals due to a relatively high peak-to-average-power ratio (PAPR).

Complementary to the transmit chain, the receiver404may include a receive chain. The receive chain may include one or more nonlinear components. Examples of such nonlinear components include a low-noise amplifier (LNA), an analog-to-digital converter (ADC), and so forth.

Such nonlinear components may be adjusted before transmission (e.g., at least one DPD operation by the transmitter402) and/or after reception (e.g., at least one DPoD operation by the receiver404), e.g., by adjusting one or more coefficients of one or more nonlinear components in order to reduce or cancel distortion. In order to reduce or cancel the distortion through at least one DPD operation and/or at least one DPoD operation, the receiver404may determine (e.g., estimate) one or more nonlinearity characteristics based on a signal having a non-constant envelope from the transmitter402.

According to aspects, the transmitter402may generate420a reference signal422having a non-constant envelope for nonlinearity estimation by the receiver404. In aspects, an envelope of a signal may outline variation of amplitude (e.g., over a period of time). A signal having a constant envelope may have an approximately constant amplitude, e.g., so that the absolute value of the signal is approximately one (1). Consequently, a signal having a non-constant envelope may be a signal that may not have an approximately constant amplitude, e.g., so that the absolute value of the signal is not approximately one (1). For example, the transmitter402may refrain from attempting to constrain the absolute value of the reference signal422to approximately one (1), which may result in the reference signal422having a non-constant envelope.

In one aspect, the transmitter402may set the modulation of the reference signal422to have a relatively higher dynamic range (e.g., a higher dynamic range relative to a signal modulated to have a dynamic range corresponding to a constant envelope). For example, the transmitter402may set the modulation of the reference signal422to have the highest possible dynamic range achievable by the transmit chain (e.g., HPA, DAC, etc.), which may enable the receiver404to estimate an approximately full set of nonlinearity characteristic(s).

By way of example, the reference signal422may be illustrated as a plurality of samples as shown inFIG. 4. In one aspect, the transmitter402may modulate the reference signal422using QAM. For example, the reference signal422may be a 16 QAM constellation, a 64 QAM constellation, a 256 QAM constellation, and so forth (n.b., the reference signal422may be a constellation of any order QAM, and the preceding 16, 64, and 256 orders are to be regarded as illustrative). In another aspect, the transmitter402may modulate the reference signal422using another modulation scheme.

In one example, the reference signal422may include at least a portion of a downlink signal or an uplink signal (e.g., the reference signal422may be included as part of a frame, subframe, or another transmission time interval (TTI)). In one example, the reference signal422may include an individual signal (e.g., the reference signal422may include an individual burst of bursty communication). In one example, the reference signal422may include a single-carrier signal.

In various aspects, the reference signal422may include a known reference signal, e.g., as defined in one or more standards and/or protocols for wireless communication. For example, a known reference signal may be modulated using phase-shift keying according to one or more standards and/or protocols, such as binary phase-shift keying (BPSK). However, as indicated supra, the transmitter402may modulate the reference signal422so that the reference signal422has a non-constant envelope. Thus, while the reference signal422may be known, the reference signal422may not have a constant envelope (e.g., the reference signal422would otherwise have a constant envelope when defined by one or more known standards and/or protocols). In some aspects, the reference signal422having the non-constant envelope may have the approximately the same average power as a known reference signal having a constant envelope.

In one example, the reference signal422may include a preamble that begins a signal. In one example, the reference signal422may be another part of a signal besides the preamble, such as a guard period (GP) or guard interval (GI). In one example, the reference signal422may include a pilot signal (e.g., LTE pilot signal, 5G pilot signal, WiFi pilot signal, etc.). In one example, the reference signal422may include a preamble having the non-constant envelope, and the non-constant envelope may be absent from a second portion of the reference signal422that is separate from the preamble.

In the context of IEEE standard(s), including 802.11, the reference signal422may include a short training sequence (STS), channel estimation sequence (CES), GI (e.g., for 802.11.ad/802.11.ay), or another sequence. In the context of 3GPP standard(s), including 5G and/or LTE, the reference signal422may include a synchronization signal (e.g., PSS), a Zadoff-Chu sequence, or another sequence.

As illustrated inFIG. 4, the transmitter402may transmit the reference signal422for nonlinearity estimation by the receiver404. The receiver404may receive the reference signal422having the non-constant envelope.

Because the reference signal422may be defined by one or more standards and/or protocols, the reference signal422may be known by the receiver404. Upon reception, the receiver404may estimate424one or more nonlinearity characteristics (e.g., coefficients) based on the reference signal422having the non-constant envelope.

In one aspect, the receiver404may estimate424the one or more nonlinearity characteristics based on an algorithm that employs the least squares method. By way of example, the receiver404may estimate the nonlinearity characteristic(s) as kNL=(xNLHxNL)−1xNLHy. In the preceding equation, x may denote the transmitted reference signal422having the non-constant envelope. Correspondingly, y may denote the received reference signal422, which may be modeled as y=kNLxNL+n (where n is noise). The nonlinearity kernels may be denoted as xNL=[x, x|x|2, x|x|4]H(although any order of nonlinearity estimation can be achieved by adding additional kernels). The nonlinearity coefficients to be estimated may be denoted as kNL=[k1, k3, k5]. Therefore, as shown supra, the receiver404may estimate424nonlinearity characteristic(s) or coefficient(s) as kNL=(xNLHxNL)−1xNLHy. The preceding examples are to be regarded as illustrative and, therefore, the receiver404may employ any suitable algorithm(s) in order to estimate424the one or more nonlinearity characteristic(s).

Based on estimation424of the one or more nonlinearity characteristic(s), the receiver404may perform one or more operations in order to reduce (or cancel) nonlinearity by at least one of the transmitter402and/or the receiver404.

In one aspect, the receiver404may generate feedback426that indicates at least one of the one or more nonlinearity characteristics. For example, the receiver404may identify the non-constant envelope of the reference signal422, which may include identifying or detecting distortion present in the reference signal422. The receiver404may generate the feedback426to indicate the non-constant envelope (e.g., to indicate distortion present in the received reference signal422). The receiver404may transmit the generated feedback426to the transmitter402.

Responsively, the transmitter402may attempt to reduce (e.g., cancel) nonlinearity based on the received feedback426. For example, the transmitter402may identify the non-constant envelope (e.g., distortion in the reference signal422received by the receiver404) indicated by the feedback426, and the transmitter402may perform one or more operations to improve reduce distortion of transmitted signals based on the non-constant envelope indicated by the feedback426. The transmitter402may perform428at least one DPD operation based on the feedback426. In one example, the transmitter402may adjust one or more coefficients or parameters of one or more components of the transmit chain of the transmitter402. For example, the transmitter402may adjust one or more coefficients associated with at least one of an HPA and/or a DAC based on the received feedback426.

In one aspect, the receiver404may attempt to reduce (e.g., cancel) nonlinearity based on the estimated nonlinearity characteristic(s). For example, the receiver404may perform430at least one DPoD operation based on the estimated nonlinearity characteristic(s). In one example, the receiver404may adjust one or more coefficients or parameters of one or more components of the receive chain of the receiver404. For example, the receiver404may adjust one or more coefficients associated with at least one of an LNA and/or an ADC based on the estimated nonlinearity characteristic(s).

In one aspect, the receiver404and transmitter402may attempt to reduce (e.g., cancel) nonlinearity at both the receiver404and the transmitter402. Accordingly, the receiver404may both transmit the feedback426based on the nonlinearity characteristic(s) so that the transmitter402may perform428at least one DPD operation based on the feedback426, and may perform430at least one DPoD operation based on the nonlinearity characteristic(s).

With the operations described supra, nonlinearity may be reduced or canceled. The reduction or cancellation of nonlinearity may improve communication between the transmitter402and the receiver404, e.g., by improving throughput, capacity, and/or response of at least one channel on which the transmitter402and the receiver404communicate in the wireless communications system400.

This approach to reduction or cancellation of nonlinearity may reduce the overhead commensurate with existing approaches to nonlinearity reduction or cancellation. For example, existing approaches to nonlinearity reduction or cancellation may be data-driven, may involve iterative decoding, may be effective only for a relatively high SNR, and may be possible only for QAM modulation of an order that is sixteen (16) or higher. Advantageously, operations for nonlinearity reduction or cancellation as described herein may be more power efficient, less computationally expensive (e.g., less complex, reduce or remove iterative decoding, etc.), more robust (e.g., effective for a larger SNR range, effective for more and/or other order modulation schemes, etc.), and/or faster than existing approaches to nonlinearity reduction or cancellation.

FIG. 5is a diagram of a HPA characteristics500, modeled using two (2) parameters. InFIG. 5, amplitude-to-amplitude (AM/AM) modeling of a memoryless HPA is illustrated, using feedback of a sharpness factor, and similar modeling may be done for amplitude-to-phase (AM/PM).

In aspects, ρ may denote a coefficient, such as a voltage coefficient. In one example, ρ may be a coefficient adjusted by the transmitter402in the transmit chain (e.g., a coefficient of an HPA), e.g., in order to reduce or cancel nonlinearity. Psatmay denote power, e.g., when an HPA is saturated. Vccmay denote voltage (e.g., power supply voltage, which may be positive). Accordingly, F(ρ) may denote the output of a component of a transmit chain of the transmitter402, such as an HPA.

InFIG. 5, a first graph520illustrates an example for a solid state power amplifier (SSPA) AM/AM model with Vcc=3. A first curve522illustrates ρ=2.5. A second curve524illustrates ρ=2.1. A third curve526illustrates ρ=1.7. A fourth curve528illustrates ρ=1.4. A fifth curve530illustrates ρ=1.1. A sixth curve532illustrates ρ=0.7. A seventh curve534illustrates ρ=0.5.

A second graph540illustrates an example of an AM/AM model that may be measured. A measured curve542may illustrate a measured F(ρ). A modeled curve544may illustrate a modeled F(ρ), with ρ=2.2 and Vcc=1.4. As illustrated, the modeled curve544approximates the measured curve542.

FIG. 6is a flowchart illustrating a method600of wireless communication, in accordance with various aspects of the present disclosure. The method600may be implemented by a transmitter, such as the transmitter402ofFIG. 4, the base station310ofFIG. 3, and/or the base station180ofFIG. 1. In various aspects, one or more operations may be optional (e.g., as denoted by dashed lines). Further, one or more operations may be omitted, transposed, and/or contemporaneously performed.

Beginning at operation602, the transmitter may generate a reference signal having a non-constant envelope for nonlinearity estimation by a receiver. In one aspect, the reference signal may include a PSS. In one aspect, the reference signal may be based on a sequence, such as a Zadoff-Chu sequence. In one aspect, the reference signal may include at least one of an STS or a GI. In an aspect, the reference signal includes a preamble having the non-constant envelope, and the non-constant envelope may be absent from a second portion of the reference signal that is separate from the preamble. In the context ofFIG. 4, the transmitter402may generate the reference signal422having a non-constant envelope for nonlinearity estimation by the receiver404.

In one aspect, operation602includes operation620. At operation620, the transmitter may modulate the reference signal to have a first dynamic range, and the first dynamic range may be relatively higher than a second dynamic range of another signal having a constant envelope. For example, the second dynamic range may correspond to the dynamic range of a known reference signal having a constant envelope. In the context ofFIG. 4, the transmitter402may modulate the reference signal422to have a first dynamic range, which may be relatively higher than a second dynamic range of another reference signal having a constant envelope.

At operation604, the transmitter may transmit the reference signal. In one aspect, the transmitter may broadcast the reference signal. In another aspect, the transmitter may unicast or multicast the reference signal to the receiver. In the context ofFIG. 4, the transmitter402may transmit the reference signal422.

At operation606, the transmitter may receive, from the receiver, feedback associated with the nonlinearity estimation. For example, the feedback may indicate one or more nonlinearity characteristics or coefficients estimated by the receiver based on the reference signal having the non-constant envelope. In the context ofFIG. 4, the transmitter402may receive, from the receiver404, the feedback426associated with the estimation424of the one or more nonlinearity characteristics by the receiver404.

At operation608, the transmitter may perform at least one DPD operation based on the received feedback. In one aspect, the at least one DPD operation may include an algorithm that is to be applied to one or more components (e.g., RF frontend components). For example, transmitter may identify one or more coefficients associated with a component of the transmitter. The component may include, e.g., an amplifier, a converter, or another component that may affect, transform, adjust, etc. a signal that is to be transmitted. The transmitter may apply a DPD algorithm in order to reduce distortion introduced to the signal by the component, reduce nonlinearity of the component, and/or otherwise improve signal fidelity during signal transmission. In application of the algorithm, the transmitter may calculate one or more coefficients of the component that may affect the signal. The calculated coefficients may be used for transmission of one or more signals, e.g., after the signal having the non-constant envelope. In the context ofFIG. 4, the transmitter402may perform428at least one DPD operation based on the received feedback426.

In one aspect, operation608includes operation622. At operation622, the transmitter may adjust one or more coefficients associated with one or more components of the transmit chain of the transmitter. For example, the transmitter may identify at least one coefficient of an HPA and/or a DAC that contributes to the nonlinearity based on the feedback, and the transmitter may set the at least one coefficient to a value based on the received feedback in order to reduce or cancel nonlinearity (e.g., in order to improve signal fidelity). In the context ofFIG. 4, the transmitter402may adjust one or more coefficients associated with at least one of an HPA or a DAC based on the received feedback426.

FIG. 7is a flowchart illustrating a method700of wireless communication, in accordance with various aspects of the present disclosure. The method700may be implemented by a receiver, such as the receiver404ofFIG. 4, the UE350ofFIG. 3, and/or the UE104ofFIG. 1. In various aspects, one or more operations may be optional (e.g., as denoted by dashed lines). Further, one or more operations may be omitted, transposed, and/or contemporaneously performed.

Beginning with operation702, the receiver may receive a reference signal having a non-constant envelope. In one aspect, the reference signal may include a PSS. In one aspect, the reference signal may be based on a sequence, such as a Zadoff-Chu sequence. In one aspect, the reference signal may include at least one of an STS or a GI. In an aspect, the reference signal includes a preamble having the non-constant envelope, and the non-constant envelope may be absent from a second portion of the reference signal that is separate from the preamble. In the context ofFIG. 4, the receiver404may receive the reference signal422from the transmitter402.

At operation704, the receiver may estimate at least one nonlinearity characteristic based on the reference signal having the non-constant envelope. In one aspect, the receiver may estimate the at least one nonlinearity characteristic using an algorithm that is based on a least squares method. In the context ofFIG. 4, the receiver404may estimate424at least one nonlinearity characteristic based on the reference signal422having the non-constant envelope.

At operation706, the receiver may transmit, to the transmitter, feedback based on the at least one nonlinearity characteristic. For example, the receiver may select one or more values indicative of the one or more nonlinearity characteristics, and the receiver may include the one or more values in a message to be transmitted to the transmitter so that the transmitter may perform at least one DPD operation to reduce or cancel nonlinearity. In the context ofFIG. 4, the receiver404may transmit, to the transmitter402, the feedback426that is based on the estimation424of the one or more nonlinearity characteristics.

At operation708, the receiver may perform at least one DPoD operation based on the at least one nonlinearity characteristic estimated by the receiver. In one aspect, the at least one DPoD operation may include an algorithm that is to be applied to one or more components (e.g., RF frontend components). For example, receiver may identify one or more coefficients associated with a component of the receiver. The component may include, e.g., an amplifier, a converter, or another component that may affect, transform, adjust, etc. a signal that is to be received. The receiver may apply a DPoD algorithm in order to reduce distortion introduced to the signal by the component, reduce nonlinearity of the component, and/or otherwise improve signal fidelity during signal reception. In application of the algorithm, the receiver may calculate one or more coefficients of the component that may affect the signal. The calculated coefficients may be used for reception of one or more signals, e.g., after the signal having the non-constant envelope. In the context ofFIG. 4, the receiver404may perform430at least one DPoD operation based on the estimation424of the at least one nonlinearity characteristic.

In one aspect, operation708includes operation720. At operation720, the receiver may adjust one or more coefficients associated with one or more components of the receive chain of the receiver. For example, the receiver may identify at least one coefficient of an LNA and/or an ADC that contributes to the nonlinearity based on the estimated nonlinearity characteristic(s), and the receiver may set the at least one coefficient to a value based on the estimated nonlinearity characteristic(s) in order to reduce or cancel nonlinearity. In the context ofFIG. 4, the receiver404may adjust one or more coefficients associated with at least one of an LNA or an ADC based on the estimated nonlinearity characteristic(s).

As described, supra, the receiver may perform at least one of operation706and operation708. Accordingly, at least one of the transmitter or the receiver may attempt to reduce or cancel nonlinearity by performing at least one DPD operation and/or at least one DPoD operation, respectively. Thus, in one aspect, operation706may be performed and operation708may be omitted. In another aspect, operation706may be omitted and operation708may be performed. In a third aspect, both operation706and operation708may be performed (n.b., operation706and operation708may be transposed in one aspect).

FIG. 8is a conceptual data flow diagram800illustrating the data flow between different means/components in an exemplary apparatus802. The apparatus may be a transmitter, such as a base station. The apparatus802includes a reception component804for receiving signals from a UE850. The apparatus802includes a transmission component810for transmitting signals to the UE850.

A signal component806may generate a reference signal having a non-constant envelope. The signal may be generated for nonlinearity estimation by the UE850. In one aspect, the reference signal may include a PSS. In one aspect, the PSS may be based on a Zadoff-Chu sequence. The signal component806may generate the reference signal to include one of a STS and/or a GI. The signal component806may generate the reference signal so that the non-constant envelope is applied to a preamble of the reference signal.

The signal component806may generate the reference signal to have the non-constant envelope by modulating the reference signal to have a first dynamic range. The first dynamic range may be higher than a second dynamic range of another signal having a constant envelope, which may also be generated by the signal component806.

The signal component806may provide the reference signal to the transmission component810for transmission to the UE850. The UE850may receive the signal, and the UE850may transmit feedback associated with nonlinearity estimation based on the reference signal.

The reception component804may receive the feedback and provide the feedback to the feedback component808. The feedback component808may perform at least one DPD operation based on the received feedback. For example, the feedback component808may adjust one or more coefficients associated with at least one of an HPA and/or a DAC of the apparatus802. The adjusted coefficients may be used for the transmission of additional signals.

FIG. 9is a diagram900illustrating an example of a hardware implementation for an apparatus802′ employing a processing system914. The processing system914may be implemented with a bus architecture, represented generally by the bus924. The bus924may include any number of interconnecting buses and bridges depending on the specific application of the processing system914and the overall design constraints. The bus924links together various circuits including one or more processors and/or hardware components, represented by the processor904, the components804,806,808,810and the computer-readable medium/memory906. The bus924may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system914may be coupled to a transceiver910. The transceiver910is coupled to one or more antennas920. The transceiver910provides a means for communicating with various other apparatus over a transmission medium. The transceiver910receives a signal from the one or more antennas920, extracts information from the received signal, and provides the extracted information to the processing system914, specifically the reception component804. In addition, the transceiver910receives information from the processing system914, specifically the transmission component810, and based on the received information, generates a signal to be applied to the one or more antennas920. The processing system914includes a processor904coupled to a computer-readable medium/memory906. The processor904is responsible for general processing, including the execution of software stored on the computer-readable medium/memory906. The software, when executed by the processor904, causes the processing system914to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory906may also be used for storing data that is manipulated by the processor904when executing software. The processing system914further includes at least one of the components804,806,808. The components may be software components running in the processor904, resident/stored in the computer readable medium/memory906, one or more hardware components coupled to the processor904, or some combination thereof. The processing system914may be a component of the base station310and may include the memory376and/or at least one of the TX processor316, the RX processor370, and the controller/processor375.

In one configuration, the apparatus802/802′ for wireless communication includes means for generating, by the apparatus802/802′, a reference signal having a non-constant envelope for nonlinearity estimation by a receiver. The apparatus802/802′ may include means for transmitting, by the apparatus, the reference signal. In one aspect, the reference signal comprises a primary synchronization signal. In one aspect, the primary synchronization signal is based on a Zadoff-Chu sequence. In one aspect, the reference signal comprises one of a STS or a GI. In an aspect, the reference signal comprises a preamble having the non-constant envelope. In an aspect, the means for generating the reference signal having the non-constant envelope is configured to modulate the reference signal to have a first dynamic range, the first dynamic range being higher than a second dynamic range of another signal having a constant envelope. In one aspect, the apparatus802/802′ further includes means for receiving, from the receiver, feedback associated with the nonlinearity estimation, and means for performing at least one DPD operation based on the feedback. In one aspect, the means for performing at least one DPD operation based on the feedback is configured to adjust one or more coefficients associated with at least one of a HPA or a DAC.

The aforementioned means may be one or more of the aforementioned components of the apparatus802and/or the processing system914of the apparatus802′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system914may include the TX Processor316, the RX Processor370, and the controller/processor375. As such, in one configuration, the aforementioned means may be the TX Processor316, the RX Processor370, and the controller/processor375configured to perform the functions recited by the aforementioned means.

FIG. 10is a conceptual data flow diagram1000illustrating the data flow between different means/components in an exemplary apparatus1002. The apparatus may be a transmitter, such as a UE. The apparatus1002may include a reception component1004, e.g., to receive signals from a base station1050. The apparatus1002may include a transmission component1010, e.g., to transmit signals to the base station1050.

The reception component1004may receive, from the base station1050, a reference signal having a non-constant envelope. The reception component1004may provide the reference signal to a signal component1008. In one aspect, the reference signal may include a PSS. In one aspect, the PSS may be based on a Zadoff-Chu sequence. In one aspect, the reference signal includes at least one of an STS and/or a GI. In one aspect, the reference signal comprises a preamble having the non-constant envelope.

The signal component1008may estimate at least one nonlinearity characteristic based on the reference signal having the non-constant envelope. In one aspect, the signal component1008may estimate the at least one nonlinearity characteristic based on a least-squares algorithm.

The signal component1008may provide the at least one nonlinearity characteristic to the feedback component1006. In one aspect, the feedback component1006may generate feedback based on the at least one nonlinearity characteristic. The feedback component1006may provide the feedback to the transmission component1010for transmission to the base station1050.

In one aspect, the feedback component1006may perform at least one DPoD operation based on the at least one nonlinearity characteristic. The feedback component1006may perform at least one DPoD operation by adjusting one or more coefficients associated with at least one of an LNA and/or an ADC. The adjusted coefficients may be used for receiving additional signals from the base station1050.

FIG. 11is a diagram1100illustrating an example of a hardware implementation for an apparatus1002′ employing a processing system1114. The processing system1114may be implemented with a bus architecture, represented generally by the bus1124. The bus1124may include any number of interconnecting buses and bridges depending on the specific application of the processing system1114and the overall design constraints. The bus1124links together various circuits including one or more processors and/or hardware components, represented by the processor1104, the components1004,1006,1008,1010and the computer-readable medium/memory1106. The bus1124may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system1114may be coupled to a transceiver1110. The transceiver1110is coupled to one or more antennas1120. The transceiver1110provides a means for communicating with various other apparatus over a transmission medium. The transceiver1110receives a signal from the one or more antennas1120, extracts information from the received signal, and provides the extracted information to the processing system1114, specifically the reception component1004. In addition, the transceiver1110receives information from the processing system1114, specifically the transmission component1010, and based on the received information, generates a signal to be applied to the one or more antennas1120. The processing system1114includes a processor1104coupled to a computer-readable medium/memory1106. The processor1104is responsible for general processing, including the execution of software stored on the computer-readable medium/memory1106. The software, when executed by the processor1104, causes the processing system1114to perform the various functions described supra for any particular apparatus. The computer-readable medium/memory1106may also be used for storing data that is manipulated by the processor1104when executing software. The processing system1114further includes at least one of the components1004,1006,1008,1010. The components may be software components running in the processor1104, resident/stored in the computer readable medium/memory1106, one or more hardware components coupled to the processor1104, or some combination thereof. The processing system1114may be a component of the UE350and may include the memory360and/or at least one of the TX processor368, the RX processor356, and the controller/processor359.

In one configuration, the apparatus1002/1002′ for wireless communication includes means for receiving, from a receiver, feedback associated with the nonlinearity estimation. The apparatus1002/1002′ may include means for receiving a reference signal having a non-constant envelope. The apparatus1002/1002′ may include means for estimating at least one nonlinearity characteristic based on the reference signal having the non-constant envelope. The apparatus1002/1002′ may include at least one of: means for transmitting feedback based on the at least one nonlinearity characteristic, or means for performing at least one DPoD operation based on the at least one nonlinearity characteristic. In an aspect, the reference signal comprises a primary synchronization signal. In an aspect, the primary synchronization signal is based on a Zadoff-Chu sequence. In an aspect, the reference signal comprises one of a STS or a GI. In an aspect, the reference signal comprises a preamble having the non-constant envelope. In an aspect, the estimating the at least one nonlinearity characteristic based on the reference signal having the non-constant envelope is based on a least-squares algorithm. In an aspect, means for performing the at least one DPoD operation based on the at least one nonlinearity characteristic is configured to adjust one or more coefficients associated with at least one of a LNA or an ADC.

The aforementioned means may be one or more of the aforementioned components of the apparatus1002and/or the processing system1114of the apparatus1002′ configured to perform the functions recited by the aforementioned means. As described supra, the processing system1114may include the TX Processor368, the RX Processor356, and the controller/processor359. As such, in one configuration, the aforementioned means may be the TX Processor368, the RX Processor356, and the controller/processor359configured to perform the functions recited by the aforementioned means.