Patent Description:
A UE may identify multiple waveforms (e.g., data or reference signals) to transmit to a base station, and the UE may modulate the waveforms and map the modulated symbols to a set of frequency resources. In some cases, modulated symbols associated with each waveform may be interleaved over a set of frequency resources. However, interleaving modulated symbols associated with different waveforms may increase the peak-to-average power ratio of an uplink transmission, and this may be detrimental to communication in a wireless communications system.

Document "<NPL>) discusses OFDMA, several variants of precoded OFDMA and SC-FDMA in its frequency-domain implementations and compares them for uplink transmission.

Document "<NPL>) discusses the impact of radio resource allocation and pulse shaping on the PAPR of SC-FDMA signals, especially for localized FDMA (LFDMA) signals. It is shown that distributed FDMA (DFDMA) signals with raised cosine filtering experience reduced PAPR as α increases. However, for LFDMA signals the PAPR increases with increasing alpha and further varies according to the allocated resource unit.

<CIT> relates to methods for peak-to-average power ratio (PAPR) reduction of a transmission signal in a single carrier frequency division multiple access (SC-FDMA) system.

<CIT> relates to a transmitter and to a receiver and methods thereof wherein the PAPR is reduced by applying a set of different phase rotations to the output of each DFT of the transmitter.

Further embodiments of the invention are defined in the dependent claims.

The described techniques relate to improved methods, systems, devices, or apparatuses that support time domain phase ramping for interlacing of multiple discrete Fourier transform (DFT) spread waveforms. A user equipment (UE) may be configured with a transmission stream processor used to maintain a lower peak-to-average power ratio (PAPR) for uplink transmissions. In some cases, a UE may map modulated symbols of different signals (or waveforms) to interleaved subsets of frequency resources, and this form of frequency division multiplexing (FDM) may increase the PAPR of an uplink transmission. In order to reduce the PAPR of uplink transmissions, a transmission stream processor at the UE may support techniques for phase ramping modulated symbols in the time domain prior to mapping the symbols to the frequency resources. These techniques may help to ensure that the signals to be included in an uplink transmission are aligned in such a way that the PAPR of the uplink transmission is reduced.

A wireless communications system may support communication between a base station and a user equipment (UE). Specifically, a wireless communications system may support downlink transmissions from a base station to a UE and uplink transmissions from a UE to a base station. Uplink transmissions from a UE to a base station may include data, control signals, reference signals (e.g., demodulation reference signals (DMRSs), etc., and different streams may be multiplexed over a set of frequency resources (i.e., frequency division multiplexing (FDM)) for an uplink transmission. In some cases, the different waveforms may be mapped to interleaved subsets of the set of resources, and the subcarrier indices occupied by a specific waveform may be offset (e.g., one stream may be mapped to subcarriers <NUM>, <NUM>, <NUM>, etc.). In such cases, the peak-to-average power ratio of the uplink transmission may be high, and this may result in reduced throughput in a wireless communications system.

Some UEs may support efficient techniques for reducing the peak-to-average power ratio (PAPR) of an uplink transmission to a base station. A UE may identify multiple streams associated with different signals (e.g., data, control, or reference signals) for an uplink transmission to a base station, and the UE may modulate the streams based on one or more modulation schemes (e.g., indicated by the base station in a control message). Subsequently, the UE may apply a time domain phase ramp to at least one of the sets of modulated symbols. The UE may then transform the time domain modulated symbols for the streams to the frequency domain using a discrete Fourier transform (DFT) (e.g., DFT spreading). Alternatively, at least one stream may be a set of symbols in the frequency domain that already have a low PAPR property (e.g., a reference signal sequence, such as a DMRS sequence). The UE may then map the modulated symbols to a set of frequency resources, and transform the frequency domain symbols back to the time domain using an inverse DFT (IDFT). The time domain phase ramp applied to the modulated symbols of a specific signal may depend on the amount of the DFT spreading. Afterwards, the UE may perform additional processes to prepare the signals for transmission to the base station. The time delay introduced by the time domain phase ramp may help to reduce the PAPR of the uplink transmission, thus resulting in more efficient communication. The techniques for uplink transmission described herein may be used for other transmissions such as UE-to-UE direct communication (e.g., sidelink communications, etc.), or other types of transmissions where a low PAPR may be desired.

Aspects of the disclosure introduced above are further described below with reference to a wireless communications system. These and other features are further illustrated by and then described with reference to apparatus diagrams and system diagrams that relate to supporting time domain phase ramping for interlacing of multiple DFT spread waveforms.

<FIG> illustrates an example of a wireless communications system <NUM> that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. The wireless communications system <NUM> includes base stations <NUM>, UEs <NUM>, and a core network <NUM>. In some examples, the wireless communications system <NUM> may be a Long Term Evolution (LTE) (or LTE-Advanced (LTE-A)) network, or a New Radio (NR) network. In some cases, wireless communications system <NUM> may support enhanced broadband communications, ultra-reliable (i.e., mission critical) communications, low latency communications, and communications with low-cost and low-complexity devices.

Each base station <NUM> may provide communication coverage for a respective geographic coverage area <NUM>. Communication links <NUM> shown in the wireless communications system <NUM> may include uplink transmissions from a UE <NUM> to a base station <NUM>, or downlink transmissions, from a base station <NUM> to a UE <NUM>. Control information may be multiplexed on an uplink channel (e.g., physical uplink control channel (PUCCH)) or downlink channel (e.g., physical downlink control channel (PDCCH)) according to various techniques. Similarly, data may be multiplexed on an uplink channel (e.g., physical uplink shared channel (PUSCH)) or downlink channel (e.g., physical downlink shared channel (PDSCH)) according to various techniques. Control information and data may be multiplexed on a downlink channel, for example, using time division multiplexing (TDM) techniques, FDM techniques, or hybrid TDM-FDM techniques.

A UE <NUM> may also be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. A UE <NUM> may be a cellular phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a wireless local loop (WLL) station, an Internet of things (IoT) device, an Internet of Everything (IoE) device, a machine type communication (MTC) device, an appliance, an automobile, or the like.

At least some of the network devices, such as base station <NUM> may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with a number of UEs <NUM> through a number of other access network transmission entities, each of which may be an example of a smart radio head, or a transmission/reception point (TRP).

A frame structure may be used to organize physical resources used for communication between a base station <NUM> and a UE <NUM>. A frame may be a <NUM> interval that may be further divided into <NUM> equally sized sub-frames. Each sub-frame may include two consecutive time slots. Each slot may include <NUM> or <NUM> OFDMA symbol periods. A resource element consists of one symbol period and one subcarrier (a <NUM> frequency range). A resource block may contain <NUM> consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each orthogonal frequency-division multiplexing (OFDM) symbol, <NUM> consecutive OFDM symbols in the time domain (<NUM> slot), or <NUM> resource elements. Some resource elements may include downlink reference signals (DL-RS). The DL-RS may include a cell-specific reference signal (CRS) and a UE-specific RS (UE-RS). UE-RS may be transmitted on the resource blocks associated with PDSCH. The number of bits carried by each resource element may depend on the modulation scheme (the configuration of symbols that may be selected during each symbol period). Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate may be.

In some cases, a base station <NUM> or UE <NUM> may modulate a digital signal by modifying the properties of a periodic waveform (e.g., frequency, amplitude and phase) prior to transmitting to a receiving device. A modulated waveform may be divided into time units known as symbols. Each symbol may be modulated separately. In a wireless communications system that uses narrow frequency subcarriers to transmit distinct symbols, the modulation is accomplished by varying the phase and amplitude of each symbol. For example, a binary phase shift keying (BPSK) modulation scheme conveys information by alternating between waveforms that are transmitted with no phase offset or with a <NUM>° offset (i.e., each symbol conveys a single bit of information). In a quadrature amplitude modulation (QAM) scheme, two carrier signals (known as the in-phase component, I, and the quadrature component, Q) may be transmitted with a phase offset of <NUM>°, and each signal may be transmitted with specific amplitude selected from a finite set. The number of amplitude bins determines the number of bits that are conveyed by each symbol. For example, in a <NUM> QAM scheme, each carrier signal may have one of four amplitudes (e.g., -<NUM>, -<NUM>, <NUM>, <NUM>), which results in <NUM> possible combinations (i.e., <NUM> bits). The various possible combinations may be represented in a graph known as a constellation map, where the amplitude of the I component is represented on the horizontal axis and the Q component is represented on the vertical axis.

Elements of wireless communications system <NUM> (e.g., UE <NUM> and base station <NUM>) may utilize digital signal processors (DSPs) implementing Fourier transforms. A DFT may transform discrete time data sets into a discrete frequency representation. The discrete frequency representation may be used to map information to subcarriers in the frequency domain. Further, an IDFT may be used to transform a discrete frequency representation (e.g., information represented in subcarriers) into a discrete time representation (e.g., a signal carrying information in the time domain). For example, a transmitter may perform a DFT to map information to subcarriers, and subsequently perform an IDFT to transform the information contained in subcarriers into a signal varying in time to convey the original information.

In some cases, a UE <NUM> may identify information to transmit to a base station <NUM> in an uplink transmission. Specifically, a UE <NUM> may identify a set of signals (e.g., data signals associated with different data streams or data types, control signals, reference signals) to transmit to a base station <NUM>. Prior to transmitting the signals, the UE may process the signals using a transmission stream processor that is used to, for example, modulate, map, and multiplex the signals on a set of resources. Different waveforms associated with different signals may be multiplexed over a set of frequency resources (i.e., FDM) for an uplink transmission. In some cases, the different waveforms may be mapped to interleaved subsets of the set of resources, and the subcarrier indices occupied by frequency domain information for a specific stream may be offset (e.g., subcarrier <NUM>, <NUM>, <NUM>). In such cases, the PAPR of the uplink transmission may be high, and a transmitter at the UE <NUM> may not be able to correctly transmit the uplink transmission with the high PAPR. As a result, a base station <NUM> may not be able to decode the signals of the uplink transmission, and this may result in reduced throughput in a wireless communications system.

Some UEs may support efficient techniques for reducing the PAPR of an uplink transmission to a base station. A UE may identify multiple waveforms associated with different signals (e.g., data, control, or reference signals) for an uplink transmission to a base station, and the UE may modulate the signals based on a modulation scheme indicated by the base station in a control message. Subsequently, the UE may apply a time domain phase ramp to the modulated symbols to induce a time delay. The UE may then transform the time domain modulated symbols to the frequency domain using a DFT (e.g., DFT spreading), map the modulated symbols to a set of frequency resources, and transform the frequency domain symbols back to the time domain using an IDFT. The time domain phase ramp applied to the modulated symbols of a specific signal may depend on the amount of the DFT spreading. Afterwards, the UE may perform additional processes to prepare the signals for transmission to the base station. The time delay introduced by the time domain phase ramp may help to reduce the PAPR of the uplink transmission, thus resulting in more efficient communication.

<FIG> illustrates an example of a wireless communications system <NUM> that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. Wireless communications system <NUM> includes base station <NUM>-a, which may be an example of a base station <NUM> as described with reference to <FIG>. Wireless communications system also includes UE <NUM>-a, which may be an example of a UE <NUM> as described with reference to <FIG>. UE <NUM>-a may be configured with a transmitter <NUM> used to transmit signals prior to base station <NUM>-a, and base station <NUM>-a may be configured with a receiver <NUM> used to receive signals from UE <NUM>-a. The transmitter <NUM> may communicate with a transmission stream processor <NUM> to process uplink signals prior to transmission. The receiver <NUM> may communicate with a reception stream processor <NUM> to process received uplink signals after reception.

In some cases, UE <NUM>-a may identify information for an uplink transmission <NUM> to base station <NUM>-a. For example, UE <NUM>-a may identify three (<NUM>) uplink information streams to transmit to base station <NUM>-a, where the uplink information streams may include, for example, data, control information, or reference signal information (e.g., DMRS information). As described with reference to <FIG>, a mapper at UE <NUM>-a may map the different streams to different subsets of a set of frequency resources. For example, the UE <NUM>-a may interleave the streams such that the tones associated with a single stream are offset from each other by at least two (<NUM>) tones (e.g., a first stream mapped to tones <NUM>, <NUM>, and <NUM>, a second stream mapped to tones <NUM>, <NUM>, and <NUM>). Additionally, a UE <NUM>-a may interleave more than two streams, in which case the tones associated with each stream may be offset from each other by a number of tones determined by the number of streams.

However, multiplexing or mapping different streams to interleaved frequency resources (e.g., as described with reference to <FIG>) may result in an increased PAPR associated with an uplink transmission (i.e., the probability of a higher PAPR is increased). In some cases, however, due to cost constraints, transmitter <NUM> may have transmission limitations regarding PAPR of transmitted signals. As such, uplink transmissions having PAPR above a threshold may be distorted and it may be difficult for receiver <NUM> to process and decode the streams of the uplink transmission <NUM>. This may result in, for example, a relatively higher block error rate (BLER), etc. Wireless communications system <NUM> may support efficient techniques to reduce the PAPR associated with uplink transmission <NUM>. Specifically, UE <NUM>-a may support additional techniques to align signals in a symbol period mapped to multiplexed frequency resources for an uplink transmission so that the PAPR of the uplink transmission is reduced.

<FIG> illustrates an example diagram <NUM> of a transmission stream processor <NUM>-a that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, transmission stream processor <NUM>-a may be an example of a transmission stream processor <NUM> of a UE <NUM> as described with reference to <FIG>. Transmission stream processor <NUM>-a may include a mapper <NUM>, inverse Fourier transform component <NUM>, and a cyclic prefix component <NUM>. These components may be used to process signals <NUM> for an uplink transmission from a UE <NUM>.

In some cases, signals <NUM>-a, <NUM>-b, and <NUM>-c may each be frequency domain signals associated with low PAPR waveforms. Mapper <NUM> may map these signals to interleaved frequency resources, and IDFT component <NUM> may transform the signals <NUM> from the frequency domain to the time domain. Once transformed, cyclic prefix component <NUM> may append a cyclic prefix to the time domain signals. Subsequently, the signals may be further processed and transmitted over a set of resources allocated for the uplink transmission (e.g., via a transmitter <NUM>). However, due to the mapping of the modulated symbols associated with different signals to interleaved frequency resources, the PAPR associated with the uplink transmission may be high, even though the PAPR of the individual signals, if transmitted independently, may be low. Accordingly, the uplink transmission from the UE <NUM> may be distorted, and a receiver (e.g., at a base station) may not be able to correctly decode the signals <NUM>. In some examples, transmission stream processor <NUM>-a may support efficient techniques for reducing the PAPR associated with an uplink transmission that includes uplink signals mapped to interleaved subsets of a set of frequency resources.

<FIG> illustrates an example diagram <NUM> of a transmission stream processor <NUM>-b that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, transmission stream processor <NUM>-b may be an example of a transmission stream processor <NUM> of a UE <NUM> as described with reference to <FIG>. Transmission stream processor <NUM>-b may include a phase ramper <NUM>, Fourier transformer <NUM>, mapper <NUM>, inverse Fourier transformer <NUM>, and a cyclic prefix adder <NUM>. These components may be used to process signals <NUM> for an uplink transmission from a UE <NUM>.

As described with reference to <FIG>, the mapping of modulated symbols associated with different streams to frequency multiplexed subsets of a set of frequency resources may increase the PAPR of an uplink transmission. This is a result of a frequency domain offset between tones of a given stream. Transmission stream processor <NUM>-b may support efficient techniques for compensating for the frequency domain offset. Specifically, transmission stream processor <NUM>-a may include a phase ramper <NUM> that introduces a phase ramp in the time domain to compensate for the frequency domain offset. That is, prior to transforming at least one of the streams to the frequency domain, the transmission stream processor <NUM>-b may introduce a phase ramp in the time domain.

The phase ramp is determined based on the tone offset associated with the tones to be mapped to a specific signal. For example, first waveform <NUM>-d may be mapped to tones k+<NUM>, k+<NUM>, k+<NUM>, etc. and, as a result, first waveform <NUM>-d may be phase ramped based on the tone offset of <NUM>. Similarly, second waveform <NUM>-e may be mapped to tones k+<NUM>, k+<NUM>, k+<NUM>, etc. and, as a result, second waveform <NUM>-e may be phase ramped based on the tone offset of <NUM>. Finally, third waveform <NUM>-f may be mapped to tones k, k+<NUM>, k+<NUM>, etc., and, as a result, third waveform <NUM>-f may not be phase ramped based on a tone offset. The phase ramp for a given time domain symbol depends on a time index associated with the symbol (e.g., within a DFT spreading block, etc.). Each symbol for a given stream is phase ramped according to the tone offset of the stream (e.g., <NUM>, <NUM>, <NUM>, etc.) and the time index for the symbol within the DFT block.

Thus, for multiplexing of a given number of waveforms <NUM>, some waveforms may be phase ramped while other waveforms are not phase ramped, or all waveforms may be phase ramped. By using this time domain phase ramping technique, after the symbols of the stream are converted to the frequency domain (e.g., by Fourier transformer <NUM>) and back to the time domain (e.g., by inverse Fourier transformer <NUM>), the signals may have a known alignment that reduces the PAPR of the uplink transmission.

<FIG> illustrates an example diagram <NUM> of a transmission stream processor <NUM>-c that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, transmission stream processor <NUM>-c may be an example of a transmission stream processor <NUM> of a UE <NUM> as described with reference to <FIG>. Transmission stream processor <NUM>-c may include a modulator <NUM>, phase ramper <NUM>, Fourier transformer <NUM>, mapper <NUM>, inverse Fourier transformer <NUM>, and a cyclic prefix adder <NUM>. These components may be used to process bit streams <NUM> for an uplink transmission from a UE <NUM>.

As described with reference to <FIG>, the mapping of modulated symbols associated with different signals to interleaved subsets of a set of frequency resources may increase the PAPR of an uplink transmission. This may be due to the phase ramp introduced by the frequency domain offset between tones of a specific signal. Transmission stream processor <NUM>-c may support efficient techniques for compensating for the phase ramp introduced by the frequency domain offset. Specifically, transmission stream processor <NUM>-c may include a phase ramper <NUM> that introduces a phase ramp in the time domain to compensate for the frequency domain offset.

In some cases, UE <NUM> may identify a first bit stream <NUM>-g and a second bit stream <NUM>-h for transmission in an uplink transmission (e.g., in a given symbol period of the uplink transmission). In this example, modulator <NUM> modulates the first bit stream <NUM>-g according to a BPSK modulation scheme, and modulator <NUM> modulates the second bit stream <NUM>-h according to a rotated BPSK modulation scheme. Phase ramper <NUM> then phase ramps the modulated symbols of the first bit stream <NUM>-g in the time domain. That is, prior to transforming the signals to the frequency domain, the transmission stream processor <NUM>-c may introduce a phase ramp in the time domain. By applying a phase ramp to modulated symbols of the first bit stream in combination with using different modulation schemes for the different waveforms, transmission stream processor <NUM>-c may produce signals that have a known alignment in the time domain after further processing, such that the PAPR of the final uplink transmission is reduced. For reference signal sequences with a low inherent PAPR (e.g., when mapped directly in the frequency domain), the transmission stream processor <NUM>-c may convert the signal to the time domain (e.g., via an IDFT) prior to performing the phase ramp, in order to maintain the low PAPR property of the signal.

The phase ramp may be determined based on various equations to reduce the PAPR of an uplink transmission. For example, the phase ramp may be calculated based on the following equation: <MAT> where DFT size corresponds to the size of the DFT spreading, the tone offset corresponds to the offset between the tones of a waveform and a reference (e.g., non-offset) waveform as discussed above, and the time index is the time index within the block being input into the Fourier transformer <NUM>. In some cases, the time index may not be used in the above equation (i.e., time index = <NUM>).

In the example of <FIG>, the different waveforms are modulated according to a BPSK modulation scheme and a rotated BPSK modulation scheme. However, in other examples, the different waveforms may be modulated according to different modulation schemes. In some cases, the condition for applying the above techniques to signals modulated according to different modulation schemes may be that there may be no zero crossing between modulated symbols of different waveforms (e.g., no null symbol energy level crossings between corresponding symbols of the different modulation schemes). That is, if the modulated symbols of the first bit stream <NUM> are superimposed over the modulated symbols of the second bit stream <NUM>, each modulated symbol of the first bit stream may share the same quadrant as a modulated symbol of the second bit stream.

Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) streams for an uplink transmission. In some cases, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams. For example, three streams using BPSK modulation schemes may be rotated by <NUM>, pi/<NUM>, and <NUM>*pi/<NUM>, respectively.

<FIG> illustrates an example diagram <NUM> of a transmission stream processor <NUM>-d that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, transmission stream processor <NUM>-d may be an example of a transmission stream processor <NUM> of a UE <NUM> as described with reference to <FIG>. Transmission stream processor <NUM>-d may include a modulator <NUM>, phase ramper <NUM>, Fourier transformer <NUM>, mapper <NUM>, inverse Fourier transformer <NUM>, and a cyclic prefix adder <NUM>. These components may be used to process bit streams <NUM> for an uplink transmission from a UE <NUM>. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) streams for an uplink transmission.

As described with reference to <FIG>, the mapping of modulated symbols associated with different signals to interleaved subsets of a set of frequency resources may increase the PAPR of an uplink transmission. This may be due to the phase ramp introduced by the frequency domain offset between tones of a specific signal. Transmission stream processor <NUM>-d may support efficient techniques for compensating for the phase ramp introduced by the frequency domain offset. Specifically, transmission stream processor <NUM>-d may include a phase ramper <NUM> that introduces a phase ramp in the time domain to compensate for the frequency domain offset.

In some cases, UE <NUM> may identify a first bit stream <NUM>-i and a second bit stream <NUM>-j for transmission in an uplink transmission (e.g., in a given symbol period of the uplink transmission). In this example, modulator <NUM> modulates the first bit stream <NUM>-g according to a quadrature phase-shift keying (QPSK) modulation scheme, and modulator <NUM> modulates the second bit stream <NUM>-h according to a rotated QPSK modulation scheme. Phase ramper <NUM> then phase ramps the modulated symbols of the first bit stream <NUM>-i in the time domain. That is, prior to transforming the signals to the frequency domain, the transmission stream processor <NUM>-d may introduce a phase ramp in the time domain. By applying a phase ramp to modulated symbols of the first bit stream in combination with using different modulation schemes for the different waveforms, transmission stream processor <NUM>-d may produce signals that have a known alignment in the time domain after further processing, such that the PAPR of the final uplink transmission is reduced. The phase ramp may be determined based on various equations to reduce the PAPR of an uplink transmission. For example, the phase ramp may be calculated according to equation <NUM> given above.

In the example of <FIG>, the different waveforms are modulated according to a QPSK modulation scheme and a rotated QPSK modulation scheme. However, in other examples, the different waveforms may be modulated according to different modulation schemes and may, in some cases, have different modulation orders. In some cases, the condition for applying the above techniques to signals modulated according to different modulation schemes may be that there may be no zero crossing between modulated symbols of different waveforms. That is, if the modulated symbols of the first bit stream <NUM> is superimposed over the modulated symbols of the second bit stream <NUM>, each modulated symbol of the first bit stream may share the same quadrant as a modulated symbol of the second bit stream. For two or more streams, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams.

<FIG> illustrates an example diagram <NUM> of a transmission stream processor <NUM>-e that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, transmission stream processor <NUM>-e may be an example of a transmission stream processor <NUM> of a UE <NUM> as described with reference to <FIG>. Transmission stream processor <NUM>-e may include a modulator <NUM>, time domain phase ramper <NUM>, Fourier transformer <NUM>, mapper <NUM>, frequency domain phase ramper <NUM>, inverse Fourier transformer <NUM>, and a cyclic prefix adder <NUM>. These components may be used to process bit streams <NUM> for an uplink transmission from a UE <NUM>. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) streams for an uplink transmission.

As described with reference to <FIG>, the mapping of modulated symbols associated with different signals to interleaved subsets of a set of frequency resources may increase the PAPR of an uplink transmission. This may be due to the phase ramp introduced by the frequency domain offset between tones of a specific signal. Transmission stream processor <NUM>-e may support efficient techniques for compensating for the phase ramp introduced by the frequency domain offset. Specifically, transmission stream processor <NUM>-e may include a phase ramper <NUM> that introduces a phase ramp in the time domain and a phase ramper <NUM> that introduces a phase ramp in the frequency domain to compensate for the frequency domain offset.

In some cases, UE <NUM> may identify a first bit stream <NUM>-k and a second bit stream <NUM>-<NUM>. In this example, modulator <NUM> modulates the first bit stream <NUM>-k according to a BPSK modulation scheme, and modulator <NUM> modulates the second bit stream <NUM>-<NUM> according to a rotated BPSK modulation scheme. Time domain phase ramper <NUM> then phase ramps the modulated symbols of the first bit stream <NUM>-k in the time domain. That is, prior to transforming the signals to the frequency domain, the transmission stream processor <NUM>-e may introduce a phase ramp in the time domain. By applying a phase ramp to modulated symbols of the first bit stream in combination with using different modulation schemes for the different waveforms, transmission stream processor <NUM>-e may produce signals that align in the time domain after further processing, such that the PAPR of the final uplink transmission is reduced. The phase ramp may be determined based on various equations to reduce the PAPR of an uplink transmission. For example, the phase ramp may be calculated according to equation <NUM> given above.

Additionally, transmission stream processor <NUM>-e may phase ramp the modulated symbols after Fourier transformer <NUM> converts the time domain signals into frequency domain signals and mapper <NUM> maps the frequency domain signals to tones. Specifically, frequency domain phase ramper <NUM> may introduce a frequency domain phase ramp to the mapped frequency domain signals. In addition, prior to mapping the modulated symbols to the frequency resources, mapper <NUM> may repeat the first and second frequency domain signals in the frequency domain (i.e., upsample the signals in the time domain). Subsequently, frequency domain phase ramper <NUM> may apply a frequency domain phase ramp to one or more of the first or second frequency domain signals to introduce a time domain offset between the two (<NUM>) waveforms. This additional phase ramp may further help to reduce the PAPR of the uplink transmission. The frequency domain phase ramp may be determined based on various equations to reduce the PAPR of an uplink transmission. In some examples, the phase ramp may have an inverse direction to the phase ramp used in the time domain for one or more streams. For example, the phase ramp may be calculated based on the following equation: <MAT> where DFT size corresponds to the size of the DFT spreading, and the tone index is associated with the tones to which the modulated symbols are to be mapped for transmission in the symbol period.

In the example of <FIG>, the different waveforms are modulated according to a BPSK modulation scheme and a rotated BPSK modulation scheme. However, in other examples, the different waveforms may be modulated according to different modulation schemes. In some cases, the condition for applying the above techniques to signals modulated according to different modulation schemes may be that there may be no zero crossing between modulated symbols of different bit streams. That is, if the modulated symbols of the first bit stream <NUM> is superimposed over the modulated symbols of the second bit stream <NUM>, each modulated symbol of the first bit stream may share the same quadrant as a modulated symbol of the second bit stream. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) streams for an uplink transmission. For two or more streams, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams.

<FIG> illustrates an example diagram <NUM> of a transmission stream processor <NUM>-f that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, transmission stream processor <NUM>-f may be an example of a transmission stream processor of a UE <NUM> as described with reference to <FIG>. Transmission stream processor <NUM>-f may include a modulator <NUM>, time domain phase ramper <NUM>, Fourier transformer <NUM>, mapper <NUM>, frequency domain phase ramper <NUM>, inverse Fourier transformer <NUM>, and a cyclic prefix adder <NUM>. These components may be used to process bit streams <NUM> for an uplink transmission from a UE <NUM>. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) streams for an uplink transmission.

As described with reference to <FIG>, the mapping of modulated symbols associated with different signals to interleaved subsets of a set of frequency resources may increase the PAPR of an uplink transmission. This may be due to the phase ramp introduced by the frequency domain offset between tones of a specific signal. Transmission stream processor <NUM>-f may support efficient techniques for compensating for the phase ramp introduced by the frequency domain offset. Specifically, transmission stream processor <NUM>-f may include a phase ramper <NUM> that introduces a phase ramp in the time domain and a phase ramper <NUM> that introduces a phase ramp in the frequency domain to compensate for the frequency domain offset.

In some cases, UE <NUM> may identify a first bit stream <NUM>-m and a second bit stream <NUM>-n. In this example, modulator <NUM> modulates the first bit stream <NUM>-m according to a QPSK modulation scheme, and modulator <NUM> modulates the second bit stream <NUM>-n according to a rotated QPSK modulation scheme. Time domain phase ramper <NUM> then phase ramps the modulated symbols of the first bit stream <NUM>-m in the time domain. That is, prior to transforming the signals to the frequency domain, phase ramper <NUM> may introduce a phase ramp in the time domain. By applying a phase ramp to modulated symbols of the first bit stream in combination with using different modulation schemes for the different waveforms, transmission stream processor <NUM>-f may produce signals that align in the time domain after further processing, such that the PAPR of the final uplink transmission is reduced. For example, the phase ramp may be calculated according to equation <NUM> given above.

Additionally, transmission stream processor <NUM>-f may phase ramp the modulated symbols after Fourier transformer <NUM> converts the time domain signals into frequency domain signals. Specifically, frequency domain phase ramper <NUM> may introduce a frequency domain phase ramp to the mapped frequency domain signals. In addition, prior to mapping the modulated symbols to the frequency resources, mapper <NUM> may repeat the first and second frequency domain signals in the frequency domain (i.e., upsample the signals in the time domain). In some cases, mapper <NUM> may repeat a frequency domain signal (e.g., either the first frequency domain signal, the second frequency domain signal, or any other frequency domain signal received by mapper <NUM>) in the frequency domain by mapping each frequency domain symbol included in the frequency domain signal to more than one subcarrier. For example, Fourier transformer <NUM> may generate the frequency domain signal as comprising N frequency domain symbols indexed <NUM>, <NUM>, <NUM>. Mapper <NUM> may map each of the N frequency domain symbols to a first subset of a set of subcarriers and also map each of the N frequency domain symbols (that is, a duplicate set of the N frequency domain symbols) to a second subset of the set of subcarriers. Thus, mapper <NUM> may map a given one of the N frequency domain symbols to more than one subcarrier (e.g., one subcarrier in the first subset of the set of subcarriers and one subcarrier in the second subset of the set of subcarriers). In some cases, mapper <NUM> may repeat the frequency domain symbols included in the frequency domain signal in indexed order (e.g., map frequency domain symbols <NUM>, <NUM>, <NUM>. N to a first subset of subcarriers of increasing frequency and also map frequency domain symbols <NUM>, <NUM>, <NUM>. N to a second subset of subcarriers of increasing frequency, where the lowest-frequency subcarrier in the second subset of carriers is higher in frequency than the highest-frequency subcarrier in the first subset. It is to be understood that mapper <NUM> may repeat the frequency domain signal any number of times in the frequency domain-e.g., may map the frequency domain signal to any number of subsets of the set of subcarriers, and thus a subset of the set of subcarriers to which mapper <NUM> maps the frequency domain signal may in fact comprise any number of subsets of subcarriers, each carrying a complete representation of the frequency domain signal. It is further to be understood that any mapper in accordance with the improved techniques described herein (e.g., mapper <NUM>, mapper <NUM>, mapper <NUM>, mapper <NUM>, mapper <NUM>) may similarly repeat one or more frequency domain signals in the frequency domain. Subsequently, frequency domain phase ramper <NUM> may apply a frequency domain phase ramp to the one or more of the mapped first or second frequency domain signals to introduce a time domain offset between the two (<NUM>) waveforms. This additional phase ramp may further help to reduce the PAPR of the uplink transmission. The frequency domain phase ramp may be determined based on various equations to reduce the PAPR of an uplink transmission. For example, the phase ramp may be calculated according to equation <NUM> given above.

In the example of <FIG>, the different waveforms are modulated according to a QPSK modulation scheme and a rotated QPSK modulation scheme. However, in other examples, the different waveforms may be modulated according to different modulation schemes. In some cases, the condition for applying the above techniques to signals modulated according to different modulation schemes may be that there may be no zero crossing between modulated symbols of different bit streams. That is, if the modulated symbols of the first bit stream <NUM> is superimposed over the modulated symbols of the second bit stream <NUM>, each modulated symbol of the first bit stream may share the same quadrant as a modulated symbol of the second bit stream. For two or more streams, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams.

<FIG> illustrates a diagram of a system <NUM> including a device <NUM> that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. Device <NUM> may be an example of or include the components of a UE <NUM> as described with reference to <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, transmission stream processor <NUM>, and I/O controller <NUM>. These components may be in electronic communication via one or more busses (e.g., bus <NUM>). Device <NUM> may communicate wirelessly with one or more UEs <NUM>.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting time domain phase ramping for interlacing of multiple DFT spread waveforms).

Software <NUM> may include code to implement aspects of the present disclosure, including code to support time domain phase ramping for interlacing of multiple DFT spread waveforms. Software <NUM> may be stored in a non-transitory computer-readable medium such as system memory or other memory. In some cases, the software <NUM> may not be directly executable by the processor but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

However, in some cases, the device may have more than one antenna <NUM>, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

Transceiver <NUM> may coordinate with a transmission stream processor <NUM> to process signals for an uplink transmission. Transmission stream processor <NUM> may include aspects of transmission stream processors <NUM> as described with reference to <FIG>. In some cases, transmission stream processor <NUM> may apply a phase ramp in the time domain to a first set of symbols to obtain a set of phase-ramped time domain symbols, the first set of symbols being modulated according to a first symbol constellation for a transmission in a symbol period, perform frequency domain spreading of the set of phase-ramped time domain symbols to obtain a first frequency domain signal, map the first frequency domain signal to a first subset of a set of subcarriers for the transmission and a second frequency domain signal to a second subset of the set of subcarriers, where the second frequency domain signal is based at least in part on a second set of symbols modulated according to a second symbol constellation, generate a time domain waveform for the transmission based on a frequency to time domain transform of the mapped first and second frequency domain signals to the set of subcarriers, and transmit the time domain waveform to a receiver.

In some cases, the transmission stream processor <NUM> may apply a second phase ramp in the time domain to the second set of symbols, and perform frequency domain spreading of the phase-ramped second set of symbols to obtain the second frequency domain signal. In some cases, the mapping comprises mapping a third frequency domain signal to a third subset of the set of subcarriers, and the third frequency domain signal is based at least in part on a third set of symbols modulated according to a third symbol constellation. In some cases, the transmission stream processor <NUM> may apply a third phase ramp in the time domain to the third set of symbols and perform freqeuncy domain spreading of the phase-ramped third set of symbols to obain the third frequency domain signal.

In some cases, the second symbol constellation may be different from the first symbol constellation. In some cases the second symbol constellation corresponds to the first symbol constellation with a symbol rotation. In some cases the symbol rotation is based on a modulation order of the first symbol constellation. In some cases, the second symbol constellation has a different modulation order than the first symbol constellation. In some cases, the first symbol constellation and the second symbol constellation are a same symbol constellation. In some cases, the phase ramp for the first set of symbols is based on respective subcarrier mapping indexes for the mapping of the first frequency domain signal.

In some cases, the phase ramp for the first set of symbols is based on a spreading length of the frequency domain spreading. In some cases, the phase ramp for the first set of symbols is based on a size of the frequency to time domain transform. In some cases, the first subset and the second subset of the set of subcarriers comprise interleaved subsets of the set of subcarriers. In some cases, each symbol within the first symbol constellation has a corresponding symbol in the second symbol constellation, and a translation from the each symbol to the corresponding symbol does not cross a null symbol energy level. In some cases, the first symbol constellation is a BPSK constellation, a QPSK constellation, or a QAM constellation. In some cases, the first set of symbols comprise a first type of information and the second set of symbols comprise a second, different type of information. In some cases, the second frequency domain signal comprises a frequency domain reference signal sequence.

I/O controller <NUM> may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, Processor <NUM> may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/<NUM>®, UNIX®, LINUX®, or another known operating system. In some cases, I/O controller <NUM> may be implemented as part of processor <NUM>.

<FIG> illustrates a diagram of a system <NUM> including a device <NUM> that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. Device <NUM> may be an example of or include the components of base station <NUM> as described above, e.g., with reference to <FIG>. Device <NUM> may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including processor <NUM>, memory <NUM>, software <NUM>, transceiver <NUM>, antenna <NUM>, network communications manager <NUM>, and base station communications manager <NUM>. These components may be in electronic communication via one or more busses (e.g., bus <NUM>). Device <NUM> may communicate wirelessly with one or more UEs <NUM>. Specifically, device <NUM> may include a reception stream processor <NUM> having components corresponding to the inverse functions (e.g., cyclic prefix removal, DFT, de-mapping, de-spreading, phase ramp removal) to the functions of a transmission stream processor <NUM> as described with reference to <FIG>. Reception stream processor <NUM> may be an example of the reception stream processors as described with reference to <FIG>. Although illustrated as implemented in a device <NUM> including the components of a base station <NUM>, a reception stream processor <NUM> may be implemented in any wireless communication device such as an access point, repeater, relay station, or UE <NUM>.

Processor <NUM> may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, processor <NUM> may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into processor <NUM>. Processor <NUM> may be configured to execute computer-readable instructions stored in a memory to perform various functions (e.g., functions or tasks supporting time domain phase ramping for interlacing of multiple DFT spread waveforms).

Reception stream processor <NUM> may receive a time domain waveform from a transmitter. Reception stream processor <NUM> may generate a frequency domain waveform based on a time to frequency domain transform of the received time domain waveform to obtain a first frequency domain signal mapped to a first subset of a set of subcarriers and a second frequency domain signal mapped to a second subset of the set of subcarriers. Reception stream processor <NUM> may perform a frequency to time domain transform on the first frequency domain signal to obtain a first set of phase-ramped time domain symbols. Reception stream processor <NUM> may apply an inverse phase ramp in the time domain to obtain a first set of time domain symbols. Reception stream processor <NUM> may identify, based on the first set of time domain symbols, a first set of symbols modulated according to a first symbol constellation. Reception stream processor <NUM> may identify, based on the second frequency domain signal, a second set of symbols modulated according to a second symbol constellation.

In some cases, the second frequency domain signal includes a frequency domain reference signal sequence. In some cases, the second symbol constellation is different from the first symbol constellation. In some cases, the symbol rotation is based on a modulation order of the first symbol constellation. In some cases, the second symbol constellation has a different modulation order than the first symbol constellation. In some cases, the first symbol constellation and the second symbol constellation are a same symbol constellation. In some cases, each symbol within the first symbol constellation has a corresponding symbol in the second symbol constellation, and where a translation from the each symbol to the corresponding symbol does not cross a null symbol energy level. In some cases, the phase-ramped time domain symbols have a phase ramp that is based on at least one of a respective subcarrier mapping indexes for the mapping of the first frequency domain signal, a spreading length of the frequency domain spreading, a size of the frequency to time domain transform, or a combination thereof. In some cases, the first set of symbols include a first type of information and the second set of symbols include a second, different type of information. In some cases, the second symbol constellation corresponds to the first symbol constellation with a symbol rotation.

Base station communications manager <NUM> may manage communications with other base stations <NUM>, and may include a controller or scheduler for controlling communications with UEs <NUM> in cooperation with other base stations <NUM>. For example, the base station communications manager <NUM> may coordinate scheduling for transmissions to UEs <NUM> for various interference mitigation techniques such as beamforming or joint transmission. In some examples, base station communications manager <NUM> may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations <NUM>.

<FIG> illustrates an example diagram <NUM> of a reception stream processor <NUM>-a that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, reception stream processor <NUM>-a may be an example of a reception stream processor <NUM> of a base station <NUM> as described with reference to <FIG>. Reception stream processor <NUM>-b may include a cyclic prefix remover <NUM>, a Fourier transformer <NUM>, a demapper <NUM>, an inverse Fourier transformer <NUM>, and a phase deramper <NUM>. These components may be used to process signals and generate bit streams <NUM> from an uplink transmission received from a UE <NUM>.

As described with reference to <FIG>, the mapping of modulated symbols associated with different streams to frequency multiplexed subsets of a set of frequency resources (e.g., subcarriers) may increase the PAPR of an uplink transmission. A transmission stream processor may introduce a phase ramp to the transmission stream to compensate for the frequency domain offset, as described with reference to <FIG>. Reception stream processor <NUM>-a may correspondingly deramp the transmission stream to obtain the resulting bit streams <NUM>.

In some cases, signals received from a transmitter may be one or more time domain waveforms. In some cases, the received signals may each have a cyclic prefix appended to the time domain signal. Cyclic prefix remover <NUM> may remove this appended cyclic prefix from the time domain signal. After removing the cyclic prefix, Fourier transformer <NUM> may transform the signal from the time domain to the frequency domain, to identify information mapped to interleaved frequency domain resources (e.g., subcarriers). Then, demapper <NUM> may perform a demapping operation to deinterleave the interleaved frequency domain resources to obtain frequency domain signals. The frequency domain signals then be input into inverse Fourier transformer <NUM> to perform a frequency to time domain transform on the frequency domain signals to obtain sets of time domain symbols. These time domain symbols may have a phase ramp applied to them (e.g., these time domain symbols may be phase-ramped). Then, based on whether or not the sets of time domain symbols have a phase ramp applied, phase deramper <NUM> may apply phase deramping (e.g., may apply an inverse phase ramp) to obtain the resulting bit stream <NUM> modulated according to a particular symbol constellation (e.g., BPSK, QPSK, etc.).

Thus, for multiplexing of a given number of waveforms, some waveforms may have been phase ramped while other waveforms were not phase ramped, or all waveforms may be phase ramped. By applying this phase deramping technique, as described above, reception stream processor may efficiently decode signals that may have a known alignment that reduces the PAPR of the uplink transmission.

<FIG> illustrates an example diagram <NUM> of a reception stream processor <NUM>-b that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, reception stream processor <NUM>-b may be an example of a reception stream processor <NUM> of a base station <NUM> as described with reference to <FIG>. Reception stream processor <NUM>-b may include a cyclic prefix remover <NUM>, a Fourier transformer <NUM>, a demapper <NUM>, an inverse Fourier transformer <NUM>, a phase deramper <NUM>, and a demodulator <NUM>. These components may be used to process signals and generate bit streams <NUM> from an uplink transmission received from a UE <NUM>.

As described with reference to <FIG>, the mapping of modulated symbols associated with different streams to frequency multiplexed subsets of a set of frequency resources may increase the PAPR of an uplink transmission. A transmission stream processor may introduce a phase ramp to the transmission stream to compensate for the frequency domain offset, as described with reference to <FIG>. Reception stream processor <NUM>-b may correspondingly deramp the transmission stream to obtain the resulting bit streams <NUM>.

In some cases, signals received from a transmitter may be one or more time domain waveforms. In some cases, the received signals may each have a cyclic prefix appended to the time domain signal. Cyclic prefix remover <NUM> may remove this appended cyclic prefix from the time domain signal. After removing the cyclic prefix, Fourier transformer <NUM> may transform the signal from the time domain to the frequency domain, to identify information mapped to interleaved frequency domain resources. Then, demapper <NUM> may perform a demapping operation to deinterleave the interleaved frequency domain resources to obtain frequency domain signals. The frequency domain signals may then be input into inverse Fourier transformer <NUM> to perform a frequency to time domain transform on the frequency domain signals to obtain sets of time domain symbols. These time domain symbols may have a phase ramp applied to them (e.g., these time domain symbols may be phase-ramped). Then, based on whether or not the sets of time domain symbols have a phase ramp applied, phase deramper <NUM> may apply phase deramping (e.g., may apply an inverse phase ramp) to obtain the resulting bit stream <NUM> modulated according to a particular symbol constellation.

In the example of <FIG>, the different waveforms are modulated according to a BPSK modulation scheme and a rotated BPSK modulation scheme. Demodulator <NUM> accordingly applies a BPSK demodulation scheme and a rotated BPSK demodulation scheme to identify bit information for bits streams <NUM> (e.g., hard-bit values, soft-bit values, LLRs, etc.) based on the respective sets of modulated symbols. However, in other examples, the different waveforms may be modulated according to different modulation schemes.

Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) received transmission streams. In some cases, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams. For example, three streams using BPSK modulation schemes may be rotated by <NUM>, pi/<NUM>, and <NUM>*pi/<NUM>, respectively.

<FIG> illustrates an example diagram <NUM> of a reception stream processor <NUM>-c that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, reception stream processor <NUM>-c may be an example of a reception stream processor <NUM> of a base station <NUM> as described with reference to <FIG>. Reception stream processor <NUM>-c may include a cyclic prefix remover <NUM>, a Fourier transformer <NUM>, a demapper <NUM>, an inverse Fourier transformer <NUM>, a phase deramper <NUM>, and a demodulator <NUM>. These components may be used to process signals and generate bit streams <NUM> from an uplink transmission received from a UE <NUM>. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) received transmission streams.

As described with reference to <FIG>, the mapping of modulated symbols associated with different streams to frequency multiplexed subsets of a set of frequency resources (e.g., subcarriers) may increase the PAPR of an uplink transmission. A transmission stream processor may introduce a phase ramp to the transmission stream to compensate for the frequency domain offset, as described with reference to <FIG>. Reception stream processor <NUM>-c may correspondingly deramp the transmission stream to obtain the resulting bit streams <NUM>.

In the example of <FIG>, the different waveforms are modulated according to a QPSK modulation scheme and a rotated QPSK modulation scheme. Demodulator <NUM> accordingly applies a QPSK demodulation scheme and a rotated QPSK demodulation scheme to identify bit information for bit streams <NUM> (e.g., hard-bit values, soft-bit values, LLRs, etc.) based on the respective sets of modulated symbols. However, in other examples, the different waveforms may be modulated according to different modulation schemes and may, in some cases, have different modulation orders. For two or more streams, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams.

<FIG> illustrates an example diagram <NUM> of a reception stream processor <NUM>-d that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, reception stream processor <NUM>-d may be an example of a reception stream processor <NUM> of a base station <NUM> as described with reference to <FIG>. Reception stream processor <NUM>-d may include a cyclic prefix remover <NUM>, a Fourier transformer <NUM>, a phase deramper <NUM>, a demapper <NUM>, an inverse Fourier transformer <NUM>, a phase deramper <NUM>, and a demodulator <NUM>. These components may be used to process signals and generate bit streams <NUM> from an uplink transmission received from a UE <NUM>. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) received transmission streams.

As described with reference to <FIG>, the mapping of modulated symbols associated with different streams to frequency multiplexed subsets of a set of frequency resources (e.g., subcarriers) may increase the PAPR of an uplink transmission. A transmission stream processor may introduce a phase ramp to the transmission stream to compensate for the frequency domain offset, as described with reference to <FIG>. In some cases, as described in <FIG>, one or more of the transmission streams may have a phase ramp applied in the time domain and in the frequency domain. Reception stream processor <NUM>-d may correspondingly deramp the transmission stream to obtain the resulting bit streams <NUM>.

In some cases, signals received from a transmitter may be one or more time domain waveforms. In some cases, the received signals may each have a cyclic prefix appended to the time domain signal. Cyclic prefix remover <NUM> may remove this appended cyclic prefix from the time domain signal. After removing the cyclic prefix, Fourier transformer <NUM> may transform the signal from the time domain to the frequency domain, to identify information mapped to interleaved frequency domain resources (e.g., subcarriers). These frequency domain resources may have a phase ramp applied to them in the frequency domain (e.g., these frequency domain symbols may be phase-ramped). Based on whether or not the sets of frequency domain resources have a phase ramp applied, phase deramper <NUM> may apply phase deramping (e.g., may apply an inverse phase ramp) to un-phase ramp the sets of frequency domain resources. Then, demapper <NUM> may perform a demapping operation to deinterleave the interleaved frequency domain resources to obtain frequency domain signals. The frequency domain signals may then be input into inverse Fourier transformer <NUM> to perform a frequency to time domain transform on the frequency domain signals to obtain sets of time domain symbols. These time domain symbols may have a phase ramp applied to them in the time domain (e.g., these time domain symbols may be phase-ramped). Based on whether or not the sets of time domain symbols have such a phase ramp applied, phase deramper <NUM> may apply phase deramping (e.g., may apply an inverse phase ramp) to obtain the resulting bit stream <NUM> modulated according to a particular symbol constellation.

In the example of <FIG>, the different waveforms are modulated according to a BPSK modulation scheme and a rotated BPSK modulation scheme. Demodulator <NUM> accordingly applies a BPSK demodulation scheme and a rotated BPSK demodulation scheme to identify bit information for bits streams <NUM> (e.g., hard-bit values, soft-bit values, LLRs, etc.) based on the respective sets of modulated symbols. However, in other examples, the different waveforms may be modulated according to different modulation schemes. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) streams for an uplink transmission. For two or more streams, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams.

<FIG> illustrates an example diagram <NUM> of a reception stream processor <NUM>-e that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. In some examples, reception stream processor <NUM>-e may be an example of a reception stream processor of a base station <NUM> as described with reference to <FIG>. Reception stream processor <NUM>-e may include a cyclic prefix remover <NUM>, a Fourier transformer <NUM>, a phase deramper <NUM>, a demapper <NUM>, an inverse Fourier transformer <NUM>, a phase deramper <NUM>, and a demodulator <NUM>. These components may be used to process signals and generate bit streams <NUM> from an uplink transmission received from a UE <NUM>. Although <FIG> illustrates an example including two (<NUM>) streams, it should be understood that the techniques described herein also apply to processing more than two (<NUM>) received transmission streams.

As described with reference to <FIG>, the mapping of modulated symbols associated with different streams to frequency multiplexed subsets of a set of frequency resources (e.g., subcarriers) may increase the PAPR of an uplink transmission. A transmission stream processor may introduce a phase ramp to the transmission stream to compensate for the frequency domain offset, as described with reference to <FIG>. In some cases, as described in <FIG>, one or more of the transmission streams may have a phase ramp applied in the time domain and in the frequency domain. Reception stream processor <NUM>-e may correspondingly deramp the transmission stream to obtain the resulting bit streams <NUM>.

In some cases, signals received from a transmitter may be one or more time domain waveforms. In some cases, the received signals may each have a cyclic prefix appended to the time domain signal. Cyclic prefix remover <NUM> may remove this appended cyclic prefix from the time domain signal. After removing the cyclic prefix, Fourier transformer <NUM> may transform the signal from the time domain to the frequency domain, to identify information mapped to interleaved frequency domain resources (e.g., subcarriers). These frequency domain resources may have a phase ramp applied to them in the frequency domain (e.g., these frequency domain symbols may be phase-ramped). Based on whether or not the frequency domain resources have a phase ramp applied, phase deramper <NUM> may apply phase deramping (e.g., may apply an inverse phase ramp) to un-phase ramp the sets of frequency domain resources. Then, demapper <NUM> may perform a demapping operation to deinterleave the interleaved frequency domain resources to obtain frequency domain signals. In some cases, a frequency domain signal may have been repeated in the frequency domain (i.e., upsampled in the time domain). For example, each frequency domain symbol may have been mapped to more than one subcarrier, as described herein (e.g., in reference to <FIG>). Demapper <NUM> may identify repeated instances of a frequency domain symbol included in the frequency domain signal (e.g., based on configuration information or other information demapper <NUM> may have received indicative of a repetitive mapping process used by a transmitting device) and may combine repeated instances of the frequency domain symbol to generate a combined version of the frequency domain symbol. Thus, demapper <NUM> may in some cases obtain a frequency domain signal based on obtaining multiple instances of the frequency domain signal, each instance mapped to a distinct subset of a set of subcarriers, and combining each instance of the frequency domain signal. It is to be understood that any demapper in accordance with the improved techniques described herein (e.g., demapper <NUM>, demapper <NUM>, demapper <NUM>, demapper <NUM>, demapper <NUM>) may perform similar demapping operations and thus may similarly combine repeated instances of one or more frequency domain signals. The frequency domain signals may then be input into inverse Fourier transformer <NUM> to perform a frequency to time domain transform on the frequency domain signals to obtain sets of time domain symbols. These time domain symbols may have a phase ramp applied to them in the time domain (e.g., these time domain symbols may be phase-ramped). Based on whether or not the sets of time domain symbols have such a phase ramp applied, phase deramper <NUM> may apply phase deramping (e.g., may apply an inverse phase ramp) to obtain the resulting bit stream <NUM> according to a particular symbol constellation.

In the example of <FIG>, the different waveforms are modulated according to a QPSK modulation scheme and a rotated QPSK modulation scheme. Demodulator <NUM> accordingly applies a QPSK demodulation scheme and a rotated QPSK demodulation scheme to identify bit information for bits streams <NUM> (e.g., hard-bit values, soft-bit values, LLRs, etc.) based on the respective sets of modulated symbols. However, in other examples, the different waveforms may be modulated according to different modulation schemes. For two or more streams, the phase rotation of the modulation schemes for the streams may depend on the number of streams and the modulation orders of the streams.

<FIG> shows a flowchart illustrating a method <NUM> that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a UE <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a transmission stream processor as described with reference to <FIG>. Alternatively, and while the operations are described as performed by a UE <NUM>, it should be understood that the operations of method <NUM> may similarly be implemented by a transmitter at a base station <NUM> or its components as described herein. In some examples, a UE <NUM> may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE <NUM> may perform aspects of the functions described below using special-purpose hardware.

At <NUM> the UE <NUM> may apply a phase ramp in the time domain to the first set of symbols to obtain a set of phase-ramped time domain symbols, where the first set of symbols may be modulated according to a first symbol constellation for a transmission in a symbol period. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a transmission stream processor as described with reference to <FIG>.

At <NUM> the UE <NUM> may perform frequency domain spreading on the set of phase-ramped time domain symbols to obtain a first frequency domain signal. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a transmission stream processor as described with reference to <FIG>.

At <NUM> the UE <NUM> may map the first frequency domain signal to a first subset of a set of subcarriers for the transmission and a second frequency domain signal to a second subset of the set of subcarriers, wherein the second frequency domain signal is based at least in part on a second set of symbols modulated according to a second symbol constellation. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a transmission stream processor as described with reference to <FIG>.

At <NUM> the UE <NUM> may generate a time domain waveform for the transmission based on a frequency to time domain transform of the mapped first and second frequency domain signals to the set of subcarriers. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a transmission stream processor as described with reference to <FIG>.

At <NUM> the UE <NUM> may transmit the time domain waveform to a receiver. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a transmission stream processor as described with reference to <FIG>.

<FIG> shows a flowchart illustrating a method <NUM> that supports time domain phase ramping for interlacing of multiple DFT spread waveforms in accordance with various aspects of the present disclosure. The operations of method <NUM> may be implemented by a base station <NUM> or its components as described herein. For example, the operations of method <NUM> may be performed by a reception stream processor as described with reference to <FIG>. Alternatively, and while the operations are described as performed by a base station <NUM>, it should be understood that the operations of method <NUM> may similarly be implemented by a receiver at a UE <NUM> or its components as described herein. In some examples, a base station <NUM> may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the base station <NUM> may perform aspects of the functions described below using special-purpose hardware.

At <NUM> the base station <NUM> may receive a time domain waveform from a transmitter. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a reception stream processor as described with reference to <FIG>.

At <NUM> the base station <NUM> may generate a frequency domain waveform based on a time to frequency domain transform of the received time domain waveform to obtain a first frequency domain signal mapped to a first subset of a set of subcarriers and a second frequency domain signal mapped to a second subset of the set of subcarriers. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a reception stream processor as described reference to <FIG>.

At <NUM> the base station <NUM> may perform a frequency to time domain transform on the first frequency domain signal to obtain a first set of phase-ramped time domain symbols. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a reception stream processor as described with reference to <FIG>.

At <NUM> the base station <NUM> may apply an inverse phase ramp in the time domain to obtain a first set of time domain symbols. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a reception stream processor as described reference to <FIG>.

At <NUM> the base station <NUM> may identify, based on the first set of time domain symbols, a first set of symbols modulated according to a first symbol constellation. The operations of <NUM> may be performed according to the methods described herein. In certain examples, aspects of the operations of <NUM> may be performed by a reception stream processor as described reference to <FIG>.

In some examples, aspects from two or more of the methods may be combined. It should be noted that the methods are just example implementations, and that the operations of the methods may be rearranged or otherwise modified such that other implementations are possible.

The terms "system" and "network" are often used interchangeably.

An orthogonal frequency division multiple access (OFDMA) system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) <NUM>. <NUM> (Wi-Fi), IEEE <NUM>. <NUM> (WiMAX), IEEE <NUM>, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications system (UMTS). 3GPP LTE and LTE-A are releases of UMTS that use E-UTRA. While aspects an LTE or an NR system may be described for purposes of example, and LTE or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE or NR applications.

In LTE/LTE-A networks, including such networks described herein, the term evolved node B (eNB) may be generally used to describe the base stations. The wireless communications system or systems described herein may include a heterogeneous LTE/LTE-A or NR network in which different types of evolved node B (eNBs) provide coverage for various geographical regions. For example, each eNB, gNB or base station may provide communication coverage for a macro cell, a small cell, or other types of cell. The term "cell" may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on context.

Base stations may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, eNodeB (eNB), next generation NodeB (gNB), Home NodeB, a Home eNodeB, or some other suitable terminology. The geographic coverage area for a base station may be divided into sectors making up only a portion of the coverage area. The wireless communications system or systems described herein may include base stations of different types (e.g., macro or small cell base stations). The UEs described herein may be able to communicate with various types of base stations and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like. There may be overlapping geographic coverage areas for different technologies.

Each communication link described herein-including, for example, wireless communications system <NUM> and <NUM> as described with reference to <FIG> and <FIG>-may include one or more carriers, where each carrier may be a signal made up of multiple subcarriers (e.g., waveform signals of different frequencies).

Features implementing functions may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations. Also, as used herein, including in the claims, "or" as used in a list of items (for example, a list of items prefaced by a phrase such as "at least one of" or "one or more of') indicates an inclusive list such that, for example, a phrase referring to "at least one of" a list of items refers to any combination of those items, including single members. As an example, "at least one of: A, B, or C" is intended to cover A, B, C, A-B, A-C, B-C, and A-B-C. , as well as any combination with multiples of the same element (e.g., A-A A-A-A, A-A-B, A-A-C, A-B-B, A-C-C, B-B, B-B-B, B-B-C, C-C, and C-C-C or any other ordering of A, B, and C).

As used herein, the phrase "based on" shall not be construed as a reference to a closed set of conditions. For example, an exemplary feature that is described as "based on condition A" may be based on both a condition A and a condition B without departing from the scope of the present disclosure.

By way of example, and not limitation, non-transitory computer-readable media can comprise RAM, ROM, electrically erasable programmable read only memory (EEPROM), compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

Claim 1:
A method for wireless communication, comprising:
applying (<NUM>) a phase ramp in a time domain to a first set of symbols to obtain a set of phase-ramped time domain symbols, the first set of symbols being modulated according to a first symbol constellation for a transmission in a symbol period;
performing (<NUM>) frequency domain spreading on the set of phase-ramped time domain symbols to obtain a first frequency domain signal;
mapping (<NUM>) the first frequency domain signal to a first subset of a set of subcarriers for the transmission and a second frequency domain signal to a second subset of the set of subcarriers, wherein the first subset and the second subset are interleaved subsets, wherein the second frequency domain signal is based at least in part on a frequency domain spread second set of symbols modulated according to a second symbol constellation;
generating (<NUM>) a time domain waveform for the transmission based at least in part on a frequency to time domain transform of the mapped first and second frequency domain signals to the set of subcarriers; and
transmitting (<NUM>) the time domain waveform to a receiver;
wherein for each symbol of the first set of symbols the phase ramp is based at least in part on a time index associated with the symbol and a tone offset of the first subset of the set of subcarriers.