Reference signal sequence identification in wireless communications

Methods, systems, and devices for wireless communications are described in which a base station may provide an indication of a reference signal to be used in demodulation of a π/2 BPSK modulation scheme for communications between a UE and the base station. The base station may indicate whether a first type of reference signal or a second type of reference signal is to be transmitted. The second type of reference signal may be a π/2 BPSK DMRS that has a reference signal sequence that has a lower PAPR. The second type of reference signal sequence may be a power deboosted version of the first reference signal sequence. The indication from the base station of the type of reference signal may be provided via RRC signaling, such as a cell-specific RRC transmission or a UE-specific RRC transmission.

BACKGROUND

The following relates generally to wireless communications, and to reference signal sequence identification in wireless communications.

SUMMARY

The described techniques relate to improved methods, systems, devices, and apparatuses that support reference signal sequence identification in wireless communications. Various described techniques provide for indicating a reference signal to be used in demodulation of a π/2 binary phase shift keying (BPSK) modulation scheme for communications between a user equipment (UE) and a base station. In some cases, the base station may indicate a first type of reference signal or a second type of reference signal that is to be transmitted. The indication from the base station of the type of reference signal may be provided via radio resource control (RRC) signaling, such as a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE in a cell served by the base station (e.g., a system information block (SIB) transmission, an other system information (OSI) transmission, or a remaining minimum system information (RMSI) transmission), or a UE-specific RRC transmission provided to each UE.

The first type of reference signal may be based on a Zadoff-Chu (ZC) sequence, in some examples, that is usable by all UEs served by the base station, and the second type of reference signal may be usable by fewer than all UEs served by the base station (e.g., UEs that are capable of operating according to a newer release of a wireless communications standard). In some cases, the second type of reference signal has a reference signal sequence that has a lower peak to average power ratio (PAPR) than the first type of reference signal. In other cases, the second type of reference signal sequence may be a power deboosted version of the first reference signal sequence (e.g., a power deboosted ZC sequence).

A method of wireless communication at a UE is described. The method may include establishing a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station, receiving, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, generating a reference signal based on the indication of the type of reference signal sequence, and transmitting the reference signal within communications that use the π/2 BPSK modulation scheme.

An apparatus for wireless communication at a UE is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station, receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, generate a reference signal based on the indication of the type of reference signal sequence, and transmit the reference signal within communications that use the π/2 BPSK modulation scheme.

Another apparatus for wireless communication at a UE is described. The apparatus may include means for establishing a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station, receiving, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, generating a reference signal based on the indication of the type of reference signal sequence, and transmitting the reference signal within communications that use the π/2 BPSK modulation scheme.

A non-transitory computer-readable medium storing code for wireless communication at a UE is described. The code may include instructions executable by a processor to establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station, receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, generate a reference signal based on the indication of the type of reference signal sequence, and transmit the reference signal within communications that use the π/2 BPSK modulation scheme.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence indicates a first type of reference signal sequence or a second type of reference signal sequence. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second type of reference signal sequence may have a lower PAPR than the first type of reference signal. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second type of reference signal sequence may be a power deboosted version of the first sequence. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first type of reference signal sequence may be a ZC sequence and the second type of reference signal sequence may be a power deboosted ZC sequence or a π/2 BPSK demodulation reference signal (DMRS) sequence. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence indicates the power deboosted ZC sequence and an amount of power deboosting to apply relative to data transmissions that use the π/2 BPSK modulation scheme.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication from the base station may be received via RRC signaling. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the RRC signaling may be a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE in a cell served by the base station. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the cell-specific RRC transmission includes a SIB transmission, an OSI transmission, or an RMSI transmission from the base station. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the RRC signaling may be a UE-specific RRC transmission that indicates the type of reference signal sequence to be used by the UE.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a capability indication to the base station that indicates supported types of reference signals at the UE, and where the indication of the type of reference signal may be received responsive to the capability indication. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence provides an initial type of reference signal sequence, and where the UE may further may perform or include features, means, or instructions for transmitting a capability indication to the base station that indicates supported types of reference signals at the UE, receiving, responsive to the capability indication, a second indication of the type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, and generating a reference signal based on the second indication of the type of reference signal sequence.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the generating the reference signal may include operations, features, means, or instructions for identifying a set of allocated resource blocks and a number of the allocated resource blocks for at least a first transmission using the π/2 BPSK modulation scheme, determining a bit sequence length for the reference signal corresponding to the number of allocated resource blocks, and generating the reference signal based on a bit sequence having the bit sequence length.

A method of wireless communication at a base station is described. The method may include establishing a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE, transmitting an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, receiving a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence, and demodulating the transmission based on the reference signal.

An apparatus for wireless communication at a base station is described. The apparatus may include a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE, transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence, and demodulate the transmission based on the reference signal.

Another apparatus for wireless communication at a base station is described. The apparatus may include means for establishing a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE, transmitting an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, receiving a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence, and demodulating the transmission based on the reference signal.

A non-transitory computer-readable medium storing code for wireless communication at a base station is described. The code may include instructions executable by a processor to establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE, transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence, and demodulate the transmission based on the reference signal.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence indicates a first type of reference signal sequence or a second type of reference signal sequence. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second type of reference signal sequence may have a lower PAPR than the first type of reference signal. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the second type of reference signal sequence may be a power deboosted version of the first sequence. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the first type of reference signal sequence may be a ZC sequence and the second type of reference signal sequence may be a power deboosted ZC sequence or a π/2 BPSK DMRS sequence. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence indicates the power deboosted ZC sequence and an amount of power deboosting to apply relative to data transmissions that use the π/2 BPSK modulation scheme.

In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence may be transmitted via RRC signaling. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the RRC signaling may be a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE in a cell served by the base station. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the cell-specific RRC transmission includes a SIB transmission, an OSI transmission, or a RMSI transmission. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the RRC signaling may be a UE-specific RRC transmission that indicates the type of reference signal sequence to be used by the first UE, and where one or more other UEs use a different type of reference signal sequence for transmissions that use the π/2 BPSK modulation scheme.

Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the first UE, a capability indication that indicates supported types of reference signals at the UE, and where the indication of the type of reference signal sequence may be transmitted to the first UE responsive to the capability indication. In some examples of the method, apparatuses, and non-transitory computer-readable medium described herein, the indication of the type of reference signal sequence provides an initial type of reference signal sequence, and the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving, from the first UE, a capability indication that indicates supported types of reference signals at the UE; selecting, responsive to the capability indication, the type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme and transmitting a second indication to the first UE of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, where one or more subsequent communications with the first UE may be based on the second indication.

DETAILED DESCRIPTION

In some wireless communications systems, a transmitter, such as a UE or a base station, may transmit one or more reference signals to provide a receiver, such as a UE or a base station, with an amplitude and a phase reference for performing channel estimation of a wireless channel. The receiver may use the channel estimate to remove amplitude and/or phase distortion to a signal caused by transmission of the signal via the wireless channel. In some LTE and NR systems, for example, a transmitter may generate a reference signal by performing quadrature phase shift keying (QPSK) modulation on a Zadoff-Chu (ZC) sequence. pilot tones that transport a QPSK-based reference signal may have a large peak to average power ratio (PAPR), and may not be suitable for use in some NR systems. Moreover, such reference signals may cause tones that transport reference signals to have a PAPR that may exceed a PAPR of tones that transport data.

In some cases, larger PAPRs or large differences in PAPRs between reference signal tones and data tones may cause a power amplifier (PA) at a UE to have a gain that is set according to the higher PAPR of the reference signal, which may result in data tones with lower gain. Further, in some 5G or NR systems, a π/2 binary phase shift keying (BPSK) modulation scheme may be implemented from some communications between a UE and a base station, in which the BPSK constellation of alternating tones is phase shifted by 90 degrees. Such techniques provide a lower PAPR relative to standard BPSK modulation. However, in cases where a reference signal that uses the ZC sequence is included with transmissions, the PAPR of the reference signal may result in reduced PA gain.

In some examples, in order to allow a receiving device to have higher PA gain, a second type of reference signal may be implemented in addition or alternatively to a first type of reference signal that includes a ZC sequence that is transmitted at a same power level as data tones. Thus, implementing the second type of reference signal may enhance reliability for transmissions of data tones due to being transmitted at higher gains. In some cases, different UEs may have different capabilities for transmitting and receiving the second type of reference signal. For example, UEs deployed in some NR systems may be capable of transmitting and receiving the first type of reference signal and not the second type of reference signal, while other UEs may be capable of transmitting and receiving both the first type of reference signal and the second type of reference signal.

Various aspects of the present disclosure provide techniques for indicating a reference signal to be used in demodulation of a π/2 BPSK modulation scheme for communications between the UE and the base station. In some cases, the base station may indicate whether the first type of reference signal or the second type of reference signal is to be transmitted. In some cases, the second type of reference signal may be a π/2 BPSK demodulation reference signal (DMRS) that has a reference signal sequence with a lower PAPR than the first type of reference signal (e.g., a ZC sequence). In other cases, the second type of reference signal sequence may be a power deboosted version of the first reference signal sequence (e.g., a power deboosted ZC sequence). The indication from the base station of the type of reference signal may be provided via radio resource control (RRC) signaling, such as a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE in a cell served by the base station (e.g., a system information block (SIB) transmission, an other system information (OSI) transmission, or a remaining minimum system information (RMSI) transmission), or a UE-specific RRC transmission provided to each UE.

In some cases, cell-specific RRC signaling may be used to establish an initial type of reference signal (e.g., the first type of reference signal) that is to be used by a UE and, after the UE reports a capability for different types of reference signals (e.g., via a physical uplink shared channel (PUSCH) transmission), the base station may transmit UE-specific RRC signaling that indicates a type of reference signal to use for one or more subsequent transmissions (e.g., an RRC reconfiguration may indicate which type of reference signal is to be used, a semi-persistent scheduling (SPS) grant may indicate a type of reference signal to use for SPS transmissions, etc.). If the indication from the UE-specific RRC is different than the initial type of reference signal, the indication from the UE-specific RRC may override the initial type of reference signal.

Aspects of the disclosure are initially described in the context of a wireless communications system. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to reference signal sequence identification in wireless communications.

In some cases, a base station105may provide an indication of a reference signal to be used in demodulation of π/2 BPSK modulation scheme for communications between a UE115and the base station105. In some cases, the base station105may indicate whether a first type of reference signal or a second type of reference signal is to be transmitted. In some cases, the second type of reference signal may be a specified π/2 BPSK DMRS that has a reference signal sequence that has a lower PAPR than the first type of reference signal (e.g., a ZC sequence). In other cases, the second type of reference signal sequence may be a power deboosted version of the first reference signal sequence (e.g., a power deboosted ZC sequence). The indication from the base station105of the type of reference signal may be provided via RRC signaling, such as a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE115in a cell served by the base station105(e.g., a SIB, OSI, or RMSI transmission), or a UE-specific RRC transmission provided to each UE115. In some cases, an initial type of reference signal may be indicated by the base station105in cell-specific RRC signaling, which may be overridden for one or more UEs115using UE-specific RRC signaling.

FIG. 2illustrates an example of a wireless communications system200that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. In some examples, wireless communications system200may implement aspects of wireless communications system100. In this example, wireless communications system200includes UE115-aand base station105-a, which may be respective examples of a UE115and a base station105as described herein. UE115-aand base station105-amay communicate via a communication link205. The communication link205may be configured for uplink and downlink transmissions.

UE115-aand base station105-amay implement techniques for π/2 BPSK modulation, which may enable transmission of reference signals and data using a common modulation scheme to achieve a desired PAPR (e.g., a low PAPR or a PAPR that is less than a PAPR threshold). In some examples, UE115-aand base station105-amay use π/2 BPSK modulation and the base station105-amay indicate a reference signal that the UE115-ais to use for π/2 BPSK transmissions. As described above, in some cases the base station105-amay indicate that a first type of reference signal or a second type of reference signal is to be used for DMRS transmissions.

In some examples, base station105-amay allocate one or more resource blocks to the UE115-afrom a system bandwidth for an uplink or downlink transmission. The system bandwidth may be divided into a set of resource blocks that may be allocated for uplink and/or downlink transmission. A time duration of the resource block may correspond to a transmission time interval (TTI) (e.g., a mini-slot, a slot, a subframe, a frame, or the like), and the base station105-amay allocate the resource blocks to one or more UEs115of the wireless communications system100in each TTI. In some examples, a resource block may correspond to a defined number of symbol periods and a defined number of subcarriers of a carrier. A resource block may correspond to a set of resource elements, and a resource element may include one subcarrier and one symbol period. Each subcarrier may be a radio frequency used for symbol modulation and may be spaced apart from one another in frequency by a fixed amount. In some examples, a resource block may be the smallest set of time-frequency resources that may be allocated to a UE115.

Base station105-amay determine a resource block allocation210for UE115-a. Base station105-amay determine which resource blocks, and corresponding REs and subcarriers, within the system bandwidth to allocate to UE115-afor carrying a reference signal and an uplink or downlink data transmission. In some examples, the resource block allocation210may include a small number of resource blocks, for example including two, three, or four resource blocks, or any number of resource blocks less than or equal to a threshold number of resource blocks (e.g., that satisfies a resource block threshold). In some examples, the techniques described herein may be used for small length π/2 BPSK DMRS sequence.

In some cases, UE115-amay transmit or receive a reference signal215and a data transmission220within resource block allocation210, where the reference signal215may be communicated using a first subset of the resource elements of the resource block allocation210and the data transmission220may be communicated using a second subset of the resource elements of the resource block allocation210. The reference signal215may be used to generate a channel estimate to enable a receiver to correct amplitude and/or phase distortion of the data transmission220caused by the wireless channel.

For an uplink data transmission, UE115-amay transmit, to the base station105-a, a reference signal215and the uplink data transmission within resource block allocation210, where the reference signal215may be communicated using a first subset of the resource elements of the resource block allocation210and the uplink data transmission may be communicated using a second subset of the resource elements of the resource block allocation210.

For a downlink data transmission, UE115-amay receive, from the base station105-a, a reference signal215and the downlink data transmission within resource block allocation210, where the reference signal215may be communicated using a first subset of the resource elements of the resource block allocation210and the downlink data transmission may be communicated using a second subset of the resource elements of the resource block allocation210.

Base station105-amay transmit, to UE115-a, a grant indicating the resource block allocation210. A grant may identify which resource blocks within the available system bandwidth are allocated to UE115-afor an uplink and/or downlink data transmission. In some examples, the grant may indicate a bit sequence length of a bit sequence used to generate the reference signal215. In another example, UE115-amay determine a length of the bit sequence based on the number of allocated resource blocks.

In cases where the reference signal215is based on a ZC sequence transmitted at a same power as data transmission220, the base station105-amay indicate to the UE115-a, and to other UEs115within the coverage area of the base station105-a, that a first type of reference signal is to be transmitted for π/2 BPSK transmissions. In some cases, the UE115-amay transmit a capability indication that indicates whether the UE115-ais capable of using other types of reference signals, such as a π/2 BPSK DMRS or a power deboosted reference signal based on a ZC sequence. Based on the capability indication, the base station105-amay indicate to the UE115-athat the first type of reference signal or the second type of reference signal is to be transmitted. If the UE115-ais signaled (e.g., via a modulation and coding scheme (MCS) indication in a downlink control information (DCI) transmission) that a resource allocation is associated with π/2 BPSK transmissions, the UE115-amay then generate the reference signal215according to the indicated first type of reference signal or second type of reference signal.

In some examples, the second type of reference signal may be based on a π/2 BPSK DMRS sequence. In other examples, the second type of reference signal may be based on a same ZC sequence of the first type of reference signal, but the transmission power of the reference signal215may be deboosted by X dB (e.g., X=1, where the value of X may also be indicated with the indication of the second type of reference signal) with respect to data transmissions220.

In some cases, as described above, the base station105-amay use RRC signaling to indicate to the UE115-awhether the first type of reference signal or the second type of reference signal is to be used for shared channel transmissions (e.g., PUSCH transmissions). Such RRC signaling may be, in some cases, a cell-specific RRC transmission such as SIB transmissions or either of an OSI or RMSI transmission. For example, the base station105-amay use a SIB, OSI, or RMSI transmission to indicate to UE115-a(and all other UEs115served by the base station105-a) that the first type of reference signal is to be used. In such cases, even though the UE115-amay be capable of using the second type of reference signal, the UE115-amay use the first type of reference signal for π/2 BPSK transmissions. In some cases, if one or more UEs115served by the base station105-aare not capable of using the second type of reference signal, the base station105-amay signal to all served UEs115to use the first type of reference signal. In other cases, after the UE115-areports its capability, the base station105-amay use UE-specific RRC to indicate that the second type of reference signal is to be used by the UE115-a. In such UE-specific signaling cases, the base station105-amay configure some UEs115to use the first type of reference signal and other UEs115to use the second type of reference signal. In some cases, if the UE115-ais capable of using the first type of reference signal (e.g., and not capable of using the second type of reference signal), the base station105-amay not send any RRC signaling that indicates a type of reference signal, such that the UE115-amay use the first type of reference signal.

In some cases, cell-specific RRC may be used to establish an initial type of reference signal (e.g., the first type of reference signal) that is to be used by UE115-aand, after the UE115-areports a capability for different types of reference signals (e.g., via a PUSCH transmission), the base station105-amay transmit UE-specific RRC signaling that indicates which type of reference signal to use for one or more subsequent transmissions (e.g., an RRC reconfiguration may indicate which type of reference signal is to be used, a SPS grant may indicate a type of reference signal to use for SPS transmissions, etc.). If the indication from the UE-specific RRC is different than the initial type of reference signal, the indication from the UE-specific RRC may override the initial type of reference signal.

FIG. 3illustrates an example of a wireless communications system300that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. In some examples, wireless communications system300may implement aspects of wireless communications system100. In this example, wireless communications system300includes a first UE115-b, a second UE115-b, and a base station105-b, which may be respective examples of a UE115and a base station105as described herein. First UE115-band base station105-bmay communicate via a communication link305and second UE115-cand base station105-bmay communicate via a communication link310. Similarly as discussed with respect toFIG. 2, communication links305and310may be configured for uplink and downlink transmission.

In this example, the base station105-bmay use UE-specific RRC signaling to indicate a first type of reference signal and a second type of reference signal that is to be used by UEs115-band115-cfor π/2 BPSK transmissions. In this case, communication link305with the first UE115-bmay use a first type of reference signal315, which may have a higher PAPR relative to data transmissions320of resource block allocation210-a. Communication link310with the second UE115-cmay use a second type of reference signal325, which may have a similar or lower PAPR as data transmissions320of resource block allocation210-b. In some examples, UEs115-band115-cand base station105-bmay use π/2 BPSK modulation and the base station105-bmay signal a reference signal that the UE115-cis to use for π/2 BPSK transmissions. As indicated above, in some cases the second UE115-cmay transmit a capability indication to the base station105-b, indicating a capability with reference to the second type of reference signal325, and the base station105-bmay provide an indication via RRC signaling that the second UE115-cis to use the first type of reference signal or the second type of reference signal. Also, as indicated above, in some cases the base station105-bmay provide an initial indication to the second UE115-cthat the first type of reference signal315is to be used and, upon receiving capability information that the second UE115-cis capable of using the second type of reference signal325, may transmit UE-specific signaling to the second UE115-c, indicating for the UE115-cto use the second type of reference signal325.

As discussed above, in some cases the base station105-bmay transmit an indication to use a second type of reference signal325. Such reference signals may provide lower power transmissions, or lower PAPR. In some cases, the second reference signal325may be a power deboosted version of the first reference signal315. In other cases, the second reference signal325may be π/2 BPSK DMRS in which a length of a bit sequence of the second reference signal325may correspond to a number of allocated resource blocks within which data and the reference signal are to be transmitted. In such examples, base station105-band second UE115-cmay each store a set of tables that each includes sets of bit sequences that may be used to generate the second reference signal325, and the second reference signal325may be generated based on a table of the set of tables that corresponds to the resource block allocation210-b.

FIG. 4illustrates an example of a process flow400that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. In some examples, process flow400may implement aspects of wireless communications system100,200, or300. Process flow400may include UE115-dand base station105-c, which may be respective examples of a UE115and a base station105as described herein. Process flow400may implement techniques for signaling an uplink reference signal using π/2 BPSK modulation.

At405, UE115-dand base station105-cmay establish communications (e.g., establish a connection). In some cases, during connection establishment (e.g., RRC connection establishment or RRC connection reconfiguration), base station105-cmay semi-statically configure UE115-dwith a type of reference signal for use in π/2 BPSK modulation communications. In some cases, an initial type of reference signal may be configured via cell-specific RRC signaling.

At410, UE115-dmay, in some cases, transmit a capability indication to the base station105-cthat may indicate whether the UE115-dis capable of using different types of reference signals for π/2 BPSK transmissions. In some cases, the capability indication may be provided via RRC signaling as part of the connection establishment. In some cases, the base station105-cmay transmit a separate capability request to the UE115-d, and the capability indication may be provided responsive to the capability request (e.g., via PUSCH). The capability indication may be an explicit indication provided by the UE115-d, or may be an implicit indication based on one or more other capabilities of the UE115-d(e.g., a capability of the UE115-dto perform one or more advanced features, such as those associated with a newer release of a radio communications standard).

At415, the base station105-cmay transmit a reference signal type indication to the UE115-d. In some cases, the reference signal type indication may indicate whether the UE115-dis to use a first type of reference signal or a second type of reference signal. The first type of reference signal may be based on a ZC sequence and may be transmitted at a same power level as data transmissions. In some cases, the second type of reference signal may be a power deboosted reference signal that is based on the ZC sequence that is transmitted at a lower power level than the data transmissions. In such cases, the reference signal type indication may also indicate an amount of power deboosting that is to be used (e.g., a 1 dB power reduction for DMRS transmissions). In some cases, the second type of reference signal may be based on π/2 BPSK DMRS sequence that has a lower PAPR than the ZC sequence, which may have a similar PAPR to data transmissions within a resource allocation.

At420, base station105-cmay determine a DMRS sequence for π/2 BPSK modulation transmissions. In some cases, as discussed above, the base station105-cmay determine to use a power deboosted version of a reference signal based on a ZC sequence, and the DMRS sequence may be the power deboosted version of ZC sequence. In other cases, the base station105-cmay determine a bit sequence length corresponding to the number of allocated resource blocks, identify a bit sequence table from the set of bit sequence tables based on the determined bit sequence length, and select a bit sequence from a set of bit sequences in the identified bit sequence table.

At425, base station105-cmay transmit control information to UE115-dindicating the number of allocated resource blocks. In some cases, the control information may indicate a type of reference signal to be used for DMRS transmissions of the UE115-d. In an example, the control information may include a grant allocating a set of resource blocks to the UE115-dfor transmitting a reference signal and an uplink data transmission to the base station105-c. In some cases, the control information may include the index value for the identified bit sequence table to indicate which bit sequence of the set of bit sequences to use from the bit sequence table for the π/2 BPSK DMRS sequence. In some cases, base station105-cmay signal the bit sequence length to UE115-d(e.g., in the grant or other DCI), or UE115-dmay determine the bit sequence length based on the number of allocated resource blocks (e.g., a bit sequence length may be a function of the number of allocated resource blocks).

At430, UE115-dmay determine the DMRS sequence. In cases where the base station105-cindicates that a power deboosted reference signal is to be transmitted, the UE may determine the DMRS sequence based on a ZC sequence. In cases where the base station105-cindicates that π/2 BPSK DMRS sequence is to be used, the UE115-dmay identify a π/2 BPSK DMRS sequence. In some cases, the UE115-dmay identify the π/2 BPSK DMRS sequence based on a resource block allocation and an index value provided with the control information. In an example, the UE115-dmay process the control information to identify the set of allocated resource blocks and the number of allocated resource blocks and UE115-dmay determine the bit sequence length corresponding to the number of allocated resource blocks.

At435, UE115-dmay generate the reference signal. In some cases, the reference signal may be generated by modulating the identified reference signal sequence according to π/2 BPSK modulation scheme. In cases where the base station105-cprovides an initial type of reference signal, if the reference signal type indication is different than the initial type reference signal, the UE115-dmay switch the type of reference signal in accordance with the reference signal type indication.

At440, UE115-dmay transmit the reference signal and the uplink data transmission to base station105-cwithin the allocated resource blocks. The reference signal may be, for example a DMRS. In cases where the second type of reference signal is a π/2 BPSK DMRS, a PAPR of tones of the uplink data transmission transporting the modulated data bit sequence within the allocated resource blocks may satisfy a PAPR threshold, and a PAPR of tones transporting the reference signal within the allocated resource blocks may have a similar or lower PAPR. Therefore, the reference signal and data may use a same modulation scheme resulting in a low PAPR for both the reference signal and the uplink data transmission.

At445, base station105-cmay monitor the allocated resource blocks for the reference signal and the uplink data transmission. Base station105-cmay receive the reference signal within the allocated resource blocks for estimating amplitude and/or phase distortion introduced to the uplink data transmission by the wireless channel. Base station105-cmay remove the amplitude and/or phase distortion during decoding of the uplink data transmission based on the received reference signal. In some cases, the wireless channel may introduce delay to the reference signal, and each bit sequence used to generate the reference signal may be orthogonal to at least one delayed version of the same bit sequence to distinguish multipath interference.

The receiver510may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to reference signal sequence identification in wireless communications, etc.). Information may be passed on to other components of the device505. The receiver510may be an example of aspects of the transceiver820described with reference toFIG. 8. The receiver510may utilize a single antenna or a set of antennas.

The communications manager515may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station, receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, generate a reference signal based on the indication of the type of reference signal sequence, and transmit the reference signal within communications that use the π/2 BPSK modulation scheme. The communications manager515may be an example of aspects of the communications manager810described herein.

FIG. 6shows a block diagram600of a device605that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. The device605may be an example of aspects of a device505or a UE115as described herein. The device605may include a receiver610, a communications manager615, and a transmitter635. The device605may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

The communications manager615may be an example of aspects of the communications manager515as described herein. The communications manager615may include a connection establishment component620, a reference signal component625, and a π/2 BPSK modulation component630. The communications manager615may be an example of aspects of the communications manager810described herein.

The connection establishment component620may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station.

The reference signal component625may receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme and generate a reference signal based on the indication of the type of reference signal sequence.

The π/2 BPSK modulation component630may transmit the reference signal within communications that use the π/2 BPSK modulation scheme.

The transmitter635may transmit signals generated by other components of the device605. In some examples, the transmitter635may be collocated with a receiver610in a transceiver module. For example, the transmitter635may be an example of aspects of the transceiver820described with reference toFIG. 8. The transmitter635may utilize a single antenna or a set of antennas.

FIG. 7shows a block diagram700of a communications manager705that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. The communications manager705may be an example of aspects of a communications manager515, a communications manager615, or a communications manager810described herein. The communications manager705may include a connection establishment component710, a reference signal component715, a π/2 BPSK modulation component720, a sequence generation component725, an RRC component730, a capability indication component735, and a resource allocation component740. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The connection establishment component710may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station.

The reference signal component715may receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme. In some examples, the reference signal component715may generate a reference signal based on the indication of the type of reference signal sequence. In some examples, the reference signal component715may determine a bit sequence length for the reference signal corresponding to the number of allocated resource blocks. In some examples, the reference signal component715may generate the reference signal based on a bit sequence having the bit sequence length.

In some cases, the indication of the type of reference signal sequence indicates a first type of reference signal sequence or a second type of reference signal sequence. In some cases, the second type of reference signal sequence has a lower PAPR than the first type of reference signal sequence. In some cases, the second type of reference signal sequence is a power deboosted version of the first sequence. In some cases, the indication of the type of reference signal sequence indicates the power deboosted ZC sequence and an amount of power deboosting to apply relative to data transmissions that use the π/2 BPSK modulation scheme.

The π/2 BPSK modulation component720may transmit the reference signal within communications that use the π/2 BPSK modulation scheme.

The sequence generation component725may generate a reference signal sequence. In some cases, the first type of reference signal sequence is a ZC sequence. In some cases, the second type of reference signal sequence is a power deboosted ZC sequence. In other cases, the second type of reference signal sequence is a π/2 BPSK DMRS sequence.

The RRC component730may transmit and receive RRC signaling from a base station. In some cases, the indication of a type of reference signal to use for π/2 BPSK DMRS transmissions is received via RRC signaling. In some cases, the RRC signaling is a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE in a cell served by the base station. In some cases, the cell-specific RRC transmission includes a SIB transmission or either an OSI or RMSI transmission from the base station. In some cases, the RRC signaling is a UE-specific RRC transmission that indicates the type of reference signal sequence to be used by the UE.

The capability indication component735may transmit a capability indication to the base station that indicates supported types of reference signals at the UE, and where the indication of the type of reference signal is received responsive to the capability indication.

The resource allocation component740may identify a set of allocated resource blocks and a number of the allocated resource blocks for at least a first transmission using the π/2 BPSK modulation scheme.

The communications manager810may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station, receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme, generate a reference signal based on the indication of the type of reference signal sequence, and transmit the reference signal within communications that use the π/2 BPSK modulation scheme.

The memory830may include random access memory (RAM) and read only memory (ROM). The memory830may store computer-readable, computer-executable code835including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory830may contain, among other things, a basic I/O system (BIOS) which may control basic hardware or software operation such as the interaction with peripheral components or devices.

The communications manager915may establish a connection with at least a first UE that uses π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE, transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence, and demodulate the transmission based on the reference signal. The communications manager915may be an example of aspects of the communications manager1210described herein.

The communications manager1015may be an example of aspects of the communications manager915as described herein. The communications manager1015may include a connection establishment component1020, a reference signal component1025, and a π/2 BPSK modulation component1030. The communications manager1015may be an example of aspects of the communications manager1210described herein.

The connection establishment component1020may establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE.

The reference signal component1025may transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme and receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence.

The π/2 BPSK modulation component1030may demodulate the transmission based on the reference signal.

The transmitter1035may transmit signals generated by other components of the device1005. In some examples, the transmitter1035may be collocated with a receiver1010in a transceiver module. For example, the transmitter1035may be an example of aspects of the transceiver1220described with reference toFIG. 12. The transmitter1035may utilize a single antenna or a set of antennas.

FIG. 11shows a block diagram1100of a communications manager1105that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. The communications manager1105may be an example of aspects of a communications manager915, a communications manager1015, or a communications manager1210described herein. The communications manager1105may include a connection establishment component1110, a reference signal component1115, a π/2 BPSK modulation component1120, an RRC component1125, and a capability indication component1130. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The connection establishment component1110may establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE.

The reference signal component1115may transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme. In some examples, the reference signal component1115may receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence.

In some cases, the indication of the type of reference signal sequence indicates a first type of reference signal sequence or a second type of reference signal sequence. In some cases, the second type of reference signal sequence has a lower PAPR than the first type of reference signal. In some cases, the second type of reference signal sequence is a power deboosted version of the first sequence. In some cases, the first type of reference signal sequence is a ZC sequence. In some cases, the second type of reference signal sequence is a power deboosted ZC sequence or a π/2 BPSK DMRS sequence. In some cases, the indication of the type of reference signal sequence indicates the power deboosted ZC sequence and an amount of power deboosting to apply relative to data transmissions that use the π/2 BPSK modulation scheme.

The π/2 BPSK modulation component1120may demodulate the transmission based on the reference signal.

The RRC component1125may transmit and receive RRC signaling. In some cases, the indication of the type of reference signal sequence is transmitted via RRC signaling. In some cases, the RRC signaling is a cell-specific RRC transmission that indicates the type of reference signal sequence to be used by each UE in a cell served by the base station. In some cases, the cell-specific RRC transmission includes a SIB transmission, an OSI transmission, or an RMSI transmission. In some cases, the RRC signaling is a UE-specific RRC transmission that indicates the type of reference signal sequence to be used by the first UE, and where one or more other UEs use a different type of reference signal sequence for transmissions that use the π/2 BPSK modulation scheme.

The capability indication component1130may receive, from the first UE, a capability indication that indicates supported types of reference signals at the UE, and where the indication of the type of reference signal sequence is transmitted to the first UE responsive to the capability indication.

FIG. 12shows a diagram of a system1200including a device1205that supports reference signal sequence identification in wireless communications in accordance with aspects of the present disclosure. The device1205may be an example of or include the components of device905, device1005, or a base station105as described herein. The device1205may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager1210, a network communications manager1215, a transceiver1220, an antenna1225, memory1230, a processor1240, and an inter-station communications manager1245. These components may be in electronic communication via one or more buses (e.g., bus1250).

The communications manager1210may establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE, transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme, receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence, and demodulate the transmission based on the reference signal.

The memory1230may include RAM, ROM, or a combination thereof. The memory1230may store computer-readable code1235including instructions that, when executed by a processor (e.g., the processor1240) cause the device to perform various functions described herein. In some cases, the memory1230may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

At1305, the UE may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station. The operations of1305may be performed according to the methods described herein. In some examples, aspects of the operations of1305may be performed by a connection establishment component as described with reference toFIGS. 5 through 8.

At1310, the UE may receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme. The operations of1310may be performed according to the methods described herein. In some examples, aspects of the operations of1310may be performed by a reference signal component as described with reference toFIGS. 5 through 8.

At1315, the UE may generate a reference signal based on the indication of the type of reference signal sequence. The operations of1315may be performed according to the methods described herein. In some examples, aspects of the operations of1315may be performed by a reference signal component as described with reference toFIGS. 5 through 8.

At1320, the UE may transmit the reference signal within communications that use the π/2 BPSK modulation scheme. The operations of1320may be performed according to the methods described herein. In some examples, aspects of the operations of1320may be performed by a π/2 BPSK modulation component as described with reference toFIGS. 5 through 8.

At1405, the UE may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station. The operations of1405may be performed according to the methods described herein. In some examples, aspects of the operations of1405may be performed by a connection establishment component as described with reference toFIGS. 5 through 8.

At1410, the UE may transmit a capability indication to the base station that indicates supported types of reference signals at the UE. The operations of1410may be performed according to the methods described herein. In some examples, aspects of the operations of1410may be performed by a capability indication component as described with reference toFIGS. 5 through 8.

At1415, the UE may receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme. The operations of1415may be performed according to the methods described herein. In some examples, aspects of the operations of1415may be performed by a reference signal component as described with reference toFIGS. 5 through 8. In some cases, the indication of the type of reference signal is responsive to the capability indication transmitted by the UE.

At1420, the UE may generate a reference signal based on the indication of the type of reference signal sequence. The operations of1420may be performed according to the methods described herein. In some examples, aspects of the operations of1420may be performed by a reference signal component as described with reference toFIGS. 5 through 8.

At1425, the UE may transmit the reference signal within communications that use the π/2 BPSK modulation scheme. The operations of1425may be performed according to the methods described herein. In some examples, aspects of the operations of1425may be performed by a π/2 BPSK modulation component as described with reference toFIGS. 5 through 8.

At1505, the UE may establish a connection with a base station that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the base station. The operations of1505may be performed according to the methods described herein. In some examples, aspects of the operations of1505may be performed by a connection establishment component as described with reference toFIGS. 5 through 8.

At1510, the UE may receive, from the base station, an indication of a type of reference signal sequence to be included within transmissions that use the π/2 BPSK modulation scheme. The operations of1510may be performed according to the methods described herein. In some examples, aspects of the operations of1510may be performed by a reference signal component as described with reference toFIGS. 5 through 8.

At1515, the UE may identify a set of allocated resource blocks and a number of the allocated resource blocks for at least a first transmission using the π/2 BPSK modulation scheme. The operations of1515may be performed according to the methods described herein. In some examples, aspects of the operations of1515may be performed by a resource allocation component as described with reference toFIGS. 5 through 8.

At1520, the UE may determine a bit sequence length for the reference signal corresponding to the number of allocated resource blocks. The operations of1520may be performed according to the methods described herein. In some examples, aspects of the operations of1520may be performed by a reference signal component as described with reference toFIGS. 5 through 8.

At1525, the UE may generate the reference signal based on a bit sequence having the bit sequence length. The operations of1525may be performed according to the methods described herein. In some examples, aspects of the operations of1525may be performed by a reference signal component as described with reference toFIGS. 5 through 8.

At1530, the UE may transmit the reference signal within communications that use the π/2 BPSK modulation scheme. The operations of1530may be performed according to the methods described herein. In some examples, aspects of the operations of1530may be performed by a π/2 BPSK modulation component as described with reference toFIGS. 5 through 8.

At1605, the base station may establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE. The operations of1605may be performed according to the methods described herein. In some examples, aspects of the operations of1605may be performed by a connection establishment component as described with reference toFIGS. 9 through 12.

At1610, the base station may transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme. The operations of1610may be performed according to the methods described herein. In some examples, aspects of the operations of1610may be performed by a reference signal component as described with reference toFIGS. 9 through 12.

At1615, the base station may receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence. The operations of1615may be performed according to the methods described herein. In some examples, aspects of the operations of1615may be performed by a reference signal component as described with reference toFIGS. 9 through 12.

At1620, the base station may demodulate the transmission based on the reference signal. The operations of1620may be performed according to the methods described herein. In some examples, aspects of the operations of1620may be performed by a π/2 BPSK modulation component as described with reference toFIGS. 9 through 12.

At1705, the base station may establish a connection with at least a first UE that uses a π/2 BPSK modulation scheme for at least a portion of wireless communications with the first UE. The operations of1705may be performed according to the methods described herein. In some examples, aspects of the operations of1705may be performed by a connection establishment component as described with reference toFIGS. 9 through 12.

At1710, the base station may receive, from the first UE, a capability indication that indicates supported types of reference signals at the UE, where an indication of the type of reference signal sequence is transmitted to the first UE responsive to the capability indication. The operations of1710may be performed according to the methods described herein. In some examples, aspects of the operations of1710may be performed by a capability indication component as described with reference toFIGS. 9 through 12.

At1715, the base station may transmit an indication of a type of reference signal sequence to be included within transmissions of at least the first UE that use the π/2 BPSK modulation scheme. The operations of1715may be performed according to the methods described herein. In some examples, aspects of the operations of1715may be performed by a reference signal component as described with reference toFIGS. 9 through 12.

At1720, the base station may receive a transmission from at least the first UE that uses the π/2 BPSK modulation scheme and that includes a reference signal based on the indication of the type of reference signal sequence. The operations of1720may be performed according to the methods described herein. In some examples, aspects of the operations of1720may be performed by a reference signal component as described with reference toFIGS. 9 through 12.

At1725, the base station may demodulate the transmission based on the reference signal. The operations of1725may be performed according to the methods described herein. In some examples, aspects of the operations of1725may be performed by a π/2 BPSK modulation component as described with reference toFIGS. 9 through 12.