WO2025115001A1 - Single layer mimo coverage enhancement using enhanced precoder codebook - Google Patents

Abstract

Various aspects of the present disclosure relate to a user equipment (UE) for wireless communication including at least one memory and at least one processor coupled with the at least one memory and configured to cause the UE to transmit an indication to a network entity indicating UE capability, which includes an enhanced codebook for single-layer uplink multiple input multiple output (MIMO) transmissions, and receive, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook, wherein the enhanced precoder codebook includes a precoder for every combination in which the phase rotation of a first antenna port relative to each of one or more remaining antenna ports of the UE relative to a first antenna port is a multiple of 90 degrees, and the value is associated with a precoder of the enhanced precoder codebook to be used by the UE for uplink transmissions.

Description

Lenovo Docket. No. SMM920230252-WO-PCT 1 SINGLE LAYER MIMO COVERAGE ENHANCEMENT USING ENHANCED PRECODER CODEBOOK CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 63/553,863, filed on February 15, 2024, which is incorporated by reference in its entirety. TECHNICAL FIELD [0002] The present disclosure relates to wireless communications, and more specifically to an enhanced precoder codebook. BACKGROUND [0003] A wireless communications system may include one or multiple network communication devices, such as base stations, which may support wireless communications for one or multiple user communication devices, which may be otherwise known as user equipment (UE), or other suitable terminology. The wireless communications system may support wireless communications with one or multiple user communication devices by utilizing resources of the wireless communication system (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers, or the like). Additionally, the wireless communications system may support wireless communications across various radio access technologies including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g., sixth generation (6G)). SUMMARY [0004] An article “a” before an element is unrestricted and understood to refer to “at least one” of those elements or “one or more” of those elements. The terms “a,” “at least one,” “one or more,” and “at least one of one or more” may be interchangeable. As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of” or “one or more of” or “one or both of”) indicates an Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 2 inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an example step 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. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on. Further, as used herein, including in the claims, a “set” may include one or more elements. [0005] Some implementations of the method and apparatuses described herein may further include a UE for wireless communication including at least one memory and at least one processor coupled with the at least one memory and configured to cause the UE to transmit an indication to a network entity indicating UE capability, which includes an enhanced codebook for single-layer uplink multiple input multiple output (MIMO) transmissions, and receive, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook, wherein the enhanced precoder codebook includes a precoder for every combination in which the phase rotation of a first antenna port relative to each of one or more remaining antenna ports of the UE is a multiple of 90 degrees, and the value is associated with a precoder of the enhanced precoder codebook to be used by the UE for uplink transmissions. [0006] In some implementations of the method and apparatuses described herein, the enhanced precoder codebook comprises a set of 64 length-4 vectors given by: 1 é ^୧୬ ೖ ^ ^{^^} ^ê^ ଶê ೖ _{63, and} ^^^{୧୬^^} ê ë ^^^{^}

in an i-th row of the precoding vector is multiplied by an input to the i-th antenna port. [0007] In some implementations of the method and apparatuses described herein, the UE further comprises four antenna ports, and the set of 64 length-4 vectors represent respective allowed precoding vectors for the four antenna ports. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 3 [0008] In some implementations of the method and apparatuses described herein, the TPMI received from the network entity is a seven-bit indicator. [0009] In some implementations of the method and apparatuses described herein, the 64 length-4 vectors are for coherent uplink transmissions. [0010] In some implementations of the method and apparatuses described herein, the at least one processor is configured to cause the UE to receive an indication from the network entity configuring uplink transmissions from the UE as coherent single layer transmissions, and the TPMI received from the network entity is a six-bit indicator. [0011] In some implementations of the method and apparatuses described herein, the enhanced codebook is configured for range extension of uplink communications. BRIEF DESCRIPTION OF THE DRAWINGS [0012] Figure 1 illustrates an example of a wireless communications system in accordance with aspects of the present disclosure. [0013] Figure 2 illustrates an example of a precoding matrix W for single-layer transmission using two antenna ports. [0014] Figure 3 illustrates an example of a precoding matrix W for single-layer transmission using four antenna ports with transform precoding enabled. [0015] Figure 4 illustrates an example of a set of sequences derived from the precoding matrix W of Figure 3. [0016] Figure 5 illustrates an example of loss due to phase alignment error using a four antenna port codebook with 16 coherent precoders. [0017] Figure 6 illustrates an example of cumulative distribution of beamforming gain relative to the maximum achievable gain in accordance with aspects of the present disclosure. [0018] Figure 7 illustrates an example of MIMO transmissions between a UE and a NE in accordance with aspects of the present disclosure. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 4 [0019] Figure 8 illustrates an example of signals that are exchanged between a UE and an NE in accordance with aspects of the present disclosure. [0020] Figure 9 illustrates an example of a user equipment (UE) 900 in accordance with aspects of the present disclosure. [0021] Figure 10 illustrates an example of a processor 1000 in accordance with aspects of the present disclosure. [0022] Figure 11 illustrates an example of a network equipment (NE) 1100 in accordance with aspects of the present disclosure. [0023] Figure 12 illustrates a flowchart of a method performed by a UE in accordance with aspects of the present disclosure. [0024] Figure 13 illustrates a flowchart of a method performed by a NE in accordance with aspects of the present disclosure. DETAILED DESCRIPTION [0025] Recently, much importance has been placed on uplink coverage enhancement or equivalently, uplink range extension. The reason for this emphasis is to reduce the number of base stations needed for coverage and thereby reduce the associated capital expenditure for network operators. [0026] One way to improve uplink coverage is to use coherent uplink multiple-input and multiple-output (MIMO) with single layer precoders and feedback from a base station. In support of this disclosure, the best, average, and min-max beamforming gains of existing two- and four-port coherent precoders were evaluated with random phase offsets between the antenna ports using a novel technique. Random phase offsets between the antenna ports are considered because there is no phase offset requirement, and also because the phase offset can vary over time. In the results of the evaluation, the relative phase between the two antennas and the relative gain between two antennas can vary by as much as 40 degrees and 4 dB, respectively, in the time interval of 20 msec from the last sounding reference signal (SRS) transmission. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 5 [0027] In coherent uplink MIMO, the relative gain difference between the two antennas is generally unspecified and unknown, but for the purposes of measuring total radiated power (TRP), it can be assumed that both antennas are transmitting at full power. For this reason, minimal variation of the transmit power on the two antennas can also be assumed. [0028] Coherent transmissions may be defined as transmissions for which the maximum difference of relative phase and power errors in a given slot compared to those measured at the last SRS transmitted have a difference of relative phase error of no more than 40 degrees and a difference of relative power error of no more than 4dB over a time period of 20 msec. [0029] The relative phase between the two transmit antennas can be modeled as a uniform random variable in the interval [0, 2^^^. For a UE with two antenna ports, there is only one random phase offset. For a UE with N antenna ports, there are N-1 random phase offsets to be considered. For two antenna ports with a single random phase offset, the precoders indexed 2 through 5 in the precoding matrix W of Figure 2 become the following: ^ _{^ 1} ^, ^{^} _{^ 1} ^, ^{^} 1 ^ 1 ^ _{^^ e} ^{^ఏ൨,} ^ _e^ఏ ^{൨ [Equation 1]}

precoders, the radiated power may be averaged over the distribution of the phase ^^. Alternatively, the performance of the precoders can be evaluated for the worst-case phase ^^. Neither of these approaches can be implemented via measurement as there is no way to measure or control the phase between the antennas in a radiated test. However, the average and worst-case performance of the precoders over the phase ^^ can be evaluated analytically using the per-antenna power measurements. [0031] Below, the best performance, ^^_{୫ୟ^,୫ୟ^}, is for the best precoder for the best phase offset. The min-max performance, ^^_{୫୧୬,୫ୟ^}, is the best precoder for the worst-case phase offset. The average performance, ^^_{ୟ^^,୫ୟ^}, is for the best precoder for each phase offset, averaged over all possible phase offsets. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 6 [0032] For two-port precoders, there are only four precoders in the precoding matrix of Figure 2 (indices 2-5), and so the results can be analytically derived using the following expressions: 1 ଶగ ^_ఏ ଶ _^ఏ ଶ ଶ ^^ ൌ _{^ max ^ห ^^ ^ ^^e ห , ^ఏ ୟ^^,୫ୟ^} 2^^ _{^ ^ ^ ଶ ห^^^^ െ ^^^ଶe ห , ห^^^^ ^ ^^ ^^^ଶe ห , ห^^^^} ^

^_ఏ ଶ _^ఏ ଶ _^ ଶ ^_{^ ൌ max max ^ห ^^ ^ ^^e ห ఏ ୫ୟ^,୫ୟ^ ఏ ^ ^ ^ ଶ , ห^^^^ െ ^^^ଶe ห , ห^^^^ ^ ^^ ^^^ଶe ห , ห^^^^}

B_{est: ^^୫ୟ^,୫ୟ^ ൌ 4 ^^ Average: ^^} ^ସ _√ ^ଶ ୟ_{^^,୫ୟ^ ൌ 2 ^^ ^ ^^ ൌ 3.8 ^^ (0.2 dB loss) Minmax:}

^ _{ଶ 2 ^^^^^ଶ ൌ 3.4 ^^ (0.7 dB loss)} [0034] As can be seen by

of ^^_{୫୧୬,୫ୟ^} with ^^_{୫ୟ^,୫ୟ^}, the relative phase offset between antenna ports has little impact on the achievable beamforming gain. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 7 [0035] The situation for four antenna ports is substantially different. For four antenna ports, there are a total of 16 fully coherent precoders for single layer transmission for the precoding matrix in Figure 3 (indices 12-27). For four antenna ports, three random phases (θ1, θ2, θ3) are used to represent the random phase offsets between any two precoders. With random phase offsets, the precoders with indices 12-15 in Figure 3 become: 1 1 1 ^^ఏ 1 ^^ఏ ^ e^{^ఏభ} ^ e ^భ ^ e^{^ఏభ} ^ e ^భ

16-27 in the precoding matrix of Figure 3 can be represented in a similar fashion. By averaging over the presumed random phase offsets between the antenna ports, the average performance of the best precoder is given by: ^^_{ୟ^^,୫ୟ^} ൌ ^ ଶగ ଶగ ଶగ ^_ଶగ^ ^య _^ ^ _^ ^ _^ ^ ^ଶ _m ஸ^_a ஸ_x ଶ^ _{^ห^^^,^^^^^ ^ ^^ ^ఏ ^,ଶ^^^ଶe భ ^ ^^ ^ఏ ^,ଷ^^^ଷe మ ^ 2]}

shown in Figure 4. [0037] The minimum of the maximum power over the set of precoders is given by: ^_{ఏ ^ఏ ^} ଶ ^_{^୫୧୬,୫ୟ^ ൌ min} max _{^ห^^^,^^^^^ ^ ^^^,ଶ^^^ଶe భ ^ ^^^,ଷ^^^ଷe మ ^ ^^^,ସ^^^e ఏయห}^ ,

and the maximum of the maximum power over the set of precoders is given by: ୫_{ୟ^,୫ୟ^ ,ఏin} max _{^ห^^^,^^^^^ ^ ^^^,ଶ^^^ଶe^ఏ ^ ^^ ^ఏ} ଶ ^_{^ ൌ m భ ^,ଷ^^^ଷe మ ^ ^^ ^ఏ ^,ସ మ ^^^e యห}^ . [Equation 4]

[0038] The expressions in Equations 2 to 4 can be evaluated numerically. In the special c_{ase in which ^^ ൌ ^^ ൌ ^^ ൌ ^^ ൌ ^^, the resulting loss values are ^^ ൌ 12.7 ^^ଶ ^ ଶ ଷ ସ ୟ^^,୫ୟ^ , (1 dB loss) and ^^୫୧୬,୫ୟ^ ൌ 8 ^^ଶ (3 dB loss).} Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 8 [0039] For the case of four antenna ports, the average beamforming gain of the best precoder over phase is 1 dB less than that of the best precoder with the best-case phase. More significantly, the beamforming gain of the best precoder with the worst-case phase is 3 dB worse than that of the best precoder with the best-case phase. The cumulative distribution of the beamforming gain relative to the maximum achievable gain is shown in Figure 5. [0040] In embodiments of the present disclosure, a UE is configured with an enhanced coherent single-layer MIMO precoder which includes all precoders for which the phase rotation of each antenna port relative to the first antenna port is a multiple of 90 degrees. The enhanced precoder may comprise a set 64 length-4 vectors given by the following equation, in which the complex value in the i-th row of the precoding vector is multiplied by the input to the i-th antenna port: 1 é ^୧ ^ ù ^^ ^{୬^^} _^^ ^{^}

[0041] When a UE is configured with an enhanced precoder according to an embodiment of the present disclosure, the power of uplink single-layer MIMO transmissions from the UE have substantially higher power at a receiver. Accordingly, embodiments may be used to extend the range UE transmissions, effectively increasing cell coverage in a wireless network. The increased range can be applied to facilitate uplink transmissions in low coverage areas, and to reduce the need to install additional base stations to provide adequate coverage for a geographic area. [0042] Aspects of the present disclosure are described in the context of a wireless communications system. [0043] Figure 1 illustrates an example of a wireless communications system 100 in accordance with aspects of the present disclosure. The wireless communications system 100 may include one or more NE 102, one or more UE 104, and a core network (CN) 106. The wireless communications system 100 may support various radio access technologies. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 9 In some implementations, the wireless communications system 100 may be a 4G network, such as an LTE network or an LTE-Advanced (LTE-A) network. In some other implementations, the wireless communications system 100 may be a NR network, such as a 5G network, a 5G-Advanced (5G-A) network, or a 5G ultrawideband (5G-UWB) network. In other implementations, the wireless communications system 100 may be a combination of a 4G network and a 5G network, or other suitable radio access technology including Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20. The wireless communications system 100 may support radio access technologies beyond 5G, for example, 6G. Additionally, the wireless communications system 100 may support technologies, such as time division multiple access (TDMA), frequency division multiple access (FDMA), or code division multiple access (CDMA), etc. [0044] The one or more NE 102 may be dispersed throughout a geographic region to form the wireless communications system 100. One or more of the NE 102 described herein may be or include or may be referred to as a network node, a base station, a network element, a network function, a network entity, a radio access network (RAN), a NodeB, an eNodeB (eNB), a next-generation NodeB (gNB), or other suitable terminology. An NE 102 and a UE 104 may communicate via a communication link, which may be a wireless or wired connection. For example, an NE 102 and a UE 104 may perform wireless communication (e.g., receive signaling, transmit signaling) over a Uu interface. [0045] An NE 102 may provide a geographic coverage area for which the NE 102 may support services for one or more UEs 104 within the geographic coverage area. For example, an NE 102 and a UE 104 may support wireless communication of signals related to services (e.g., voice, video, packet data, messaging, broadcast, etc.) according to one or multiple radio access technologies. In some implementations, an NE 102 may be moveable, for example, a satellite associated with a non-terrestrial network (NTN). In some implementations, different geographic coverage areas 112 associated with the same or different radio access technologies may overlap, but the different geographic coverage areas may be associated with different NE 102. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 10 [0046] The one or more UE 104 may be dispersed throughout a geographic region of the wireless communications system 100. A UE 104 may include or may be referred to as a remote unit, a mobile device, a wireless device, a remote device, a subscriber device, a transmitter device, a receiver device, or some other suitable terminology. In some implementations, the UE 104 may be referred to as a unit, a station, a terminal, or a client, among other examples. Additionally, or alternatively, the UE 104 may be referred to as an Internet-of-Things (IoT) device, an Internet-of-Everything (IoE) device, or machine-type communication (MTC) device, among other examples. [0047] A UE 104 may be able to support wireless communication directly with other UEs 104 over a communication link. For example, a UE 104 may support wireless communication directly with another UE 104 over a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular-V2X deployments, the communication link 114 may be referred to as a sidelink. For example, a UE 104 may support wireless communication directly with another UE 104 over a PC5 interface. [0048] An NE 102 may support communications with the CN 106, or with another NE 102, or both. For example, an NE 102 may interface with other NE 102 or the CN 106 through one or more backhaul links (e.g., S1, N2, N2, or network interface). In some implementations, the NE 102 may communicate with each other directly. In some other implementations, the NE 102 may communicate with each other or indirectly (e.g., via the CN 106. In some implementations, one or more NE 102 may include subcomponents, such as an access network entity, which may be an example of an access node controller (ANC). An ANC may communicate with the one or more UEs 104 through one or more other access network transmission entities, which may be referred to as a radio heads, smart radio heads, or transmission-reception points (TRPs). [0049] The CN 106 may support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. The CN 106 may be an evolved packet core (EPC), or a 5G core (5GC), which may include a control plane entity that manages access and mobility (e.g., a mobility management entity (MME), an access and mobility management functions (AMF)) and a user plane entity that routes packets or Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 11 interconnects to external networks (e.g., a serving gateway (S-GW), a Packet Data Network (PDN) gateway (P-GW), or a user plane function (UPF)). In some implementations, the control plane entity may manage non-access stratum (NAS) functions, such as mobility, authentication, and bearer management (e.g., data bearers, signal bearers, etc.) for the one or more UEs 104 served by the one or more NE 102 associated with the CN 106. [0050] The CN 106 may communicate with a packet data network over one or more backhaul links (e.g., via an S1, N2, N2, or another network interface). The packet data network may include an application server. In some implementations, one or more UEs 104 may communicate with the application server. A UE 104 may establish a session (e.g., a protocol data unit (PDU) session, or the like) with the CN 106 via an NE 102. The CN 106 may route traffic (e.g., control information, data, and the like) between the UE 104 and the application server using the established session (e.g., the established PDU session). The PDU session may be an example of a logical connection between the UE 104 and the CN 106 (e.g., one or more network functions of the CN 106). [0051] In the wireless communications system 100, the NEs 102 and the UEs 104 may use resources of the wireless communications system 100 (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, carriers)) to perform various operations (e.g., wireless communications). In some implementations, the NEs 102 and the UEs 104 may support different resource structures. For example, the NEs 102 and the UEs 104 may support different frame structures. In some implementations, such as in 4G, the NEs 102 and the UEs 104 may support a single frame structure. In some other implementations, such as in 5G and among other suitable radio access technologies, the NEs 102 and the UEs 104 may support various frame structures (i.e., multiple frame structures). The NEs 102 and the UEs 104 may support various frame structures based on one or more numerologies. [0052] One or more numerologies may be supported in the wireless communications system 100, and a numerology may include a subcarrier spacing and a cyclic prefix. A first numerology (e.g., ^^=0) may be associated with a first subcarrier spacing (e.g., 15 kHz) and a normal cyclic prefix. In some implementations, the first numerology (e.g., ^^=0) associated with the first subcarrier spacing (e.g., 15 kHz) may utilize one slot per subframe. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 12 A second numerology (e.g., ^^=1) may be associated with a second subcarrier spacing (e.g., 30 kHz) and a normal cyclic prefix. A third numerology (e.g., ^^=2) may be associated with a third subcarrier spacing (e.g., 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. A fourth numerology (e.g., ^^=3) may be associated with a fourth subcarrier spacing (e.g., 120 kHz) and a normal cyclic prefix. A fifth numerology (e.g., ^^=4) may be associated with a fifth subcarrier spacing (e.g., 240 kHz) and a normal cyclic prefix. [0053] A time interval of a resource (e.g., a communication resource) may be organized according to frames (also referred to as radio frames). Each frame may have a duration, for example, a 10 millisecond (ms) duration. In some implementations, each frame may include multiple subframes. For example, each frame may include 10 subframes, and each subframe may have a duration, for example, a 1 ms duration. In some implementations, each frame may have the same duration. In some implementations, each subframe of a frame may have the same duration. [0054] Additionally or alternatively, a time interval of a resource (e.g., a communication resource) may be organized according to slots. For example, a subframe may include a number (e.g., quantity) of slots. The number of slots in each subframe may also depend on the one or more numerologies supported in the wireless communications system 100. For instance, the first, second, third, fourth, and fifth numerologies (i.e., ^^=0, ^^=1, ^^=2, ^^=3, ^^=4) associated with respective subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz may utilize a single slot per subframe, two slots per subframe, four slots per subframe, eight slots per subframe, and 16 slots per subframe, respectively.^ Each slot may include a number (e.g., quantity) of symbols (e.g., OFDM symbols). In some implementations, the number (e.g., quantity) of slots for a subframe may depend on a numerology. For a normal cyclic prefix, a slot may include 14 symbols. For an extended cyclic prefix (e.g., applicable for 60 kHz subcarrier spacing), a slot may include 12 symbols. The relationship between the number of symbols per slot, the number of slots per subframe, and the number of slots per frame for a normal cyclic prefix and an extended cyclic prefix may depend on a numerology. It should be understood that reference to a first numerology (e.g., ^^=0) associated with a first subcarrier spacing (e.g., 15 kHz) may be used interchangeably between subframes and slots. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 13 [0055] In the wireless communications system 100, an electromagnetic (EM) spectrum may be split, based on frequency or wavelength, into various classes, frequency bands, frequency channels, etc. By way of example, the wireless communications system 100 may support one or multiple operating frequency bands, such as frequency range designations FR1 (410 MHz – 7.125 GHz), FR2 (24.25 GHz – 52.6 GHz), FR3 (7.125 GHz – 24.25 GHz), FR4 (52.6 GHz – 114.25 GHz), FR4a or FR4-1 (52.6 GHz – 71 GHz), and FR5 (114.25 GHz – 300 GHz). In some implementations, the NEs 102 and the UEs 104 may perform wireless communications over one or more of the operating frequency bands. In some implementations, FR1 may be used by the NEs 102 and the UEs 104, among other equipment or devices for cellular communications traffic (e.g., control information, data). In some implementations, FR2 may be used by the NEs 102 and the UEs 104, among other equipment or devices for short-range, high data rate capabilities. [0056] FR1 may be associated with one or multiple numerologies (e.g., at least three numerologies). For example, FR1 may be associated with a first numerology (e.g., ^^=0), which includes 15 kHz subcarrier spacing; a second numerology (e.g., ^^=1), which includes 30 kHz subcarrier spacing; and a third numerology (e.g., ^^=2), which includes 60 kHz subcarrier spacing. FR2 may be associated with one or multiple numerologies (e.g., at least 2 numerologies). For example, FR2 may be associated with a third numerology (e.g., ^^=2), which includes 60 kHz subcarrier spacing; and a fourth numerology (e.g., ^^=3), which includes 120 kHz subcarrier spacing. [0057] Figure 7 illustrates an example of MIMO transmissions between a UE 102 and a NE 104, and Figure 8 illustrates an example of signals that are exchanged between the UE and the NE in accordance with aspects of the present disclosure. In the example of Figure 7, a UE 102 implements a precoder for RF signals transmitted from four transmit antennas P1- P4. A UE 102 that implements an enhanced precoder codebook of an embodiment of the present disclosure may have two transmit antennas, four transmit antennas, or more than four transmit antennas. The RF signals are transmitted to a NE 104, which receives the signals at one or more receive antenna from antennas P1-N. [0058] The precoded transmissions 814 from a UE may be single-layer or rank one transmissions in which one symbol is sent per resource element (RE). In an embodiment, Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 14 the UE is configured for beamforming, and the same information is transmitted by multiple antennas of the UE. The transmitted beams interact with one another to cause constructive or destructive interference. When beams are aligned in an optimum orientation, the beams constructively interfere with one another at the receiver. The boosted signal effectively increases the transmission range of the UE, which also increases the effective size of a cell (e.g., when a cell area is defined by a 3dB drop in signal strength). [0059] The UE is not aware of the phase of transmitted RF signals due to physical characteristics of the circuitry. Accordingly, the UE applies precoding to the antennas at 812 based on feedback from reference signals 806 transmitted to a receiver. The precoding values are generally applied with respect to a reference antenna. For example, the reference antenna may have a static phase orientation, and precoding is applied to the remaining antennas to cause the highest signal power at the receiver. [0060] A disadvantage of conventional codebook designs for four antenna ports is that, depending on the relative phases of the signals received at a base station and the random phase offsets between the antenna ports, there may not be any precoder which can effectively align the phases at the receiver. [0061] In an embodiment of the present disclosure, precoders of the form: 1 1 ^ _{^^^൨ , ^^: 0 ^ ^^ ^ 3} are included in the set of

transmission. With this set, it is possible to align the phase of the second antenna, as observed at the receiver, within 45 degrees of the phase of the first antenna. [0062] In order to align the phases of second, third, and fourth antennas, as observed at the receiver, within 45 degrees the phase of the first antenna, an embodiment may use 64 precoders. In some embodiments, the set can be expressed as: 1 [_{Equation 5]}

Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 15 where int^^^^ denotes the largest integer less than or equal to ^^ and j denotes the square-root of -1 (√െ1) and is a complex number used to rotate the phase as known in the art. In such an embodiment, the 64 precoders may each represent a combination of phases at 90 degree intervals for three antenna ports relative to a first antenna port. [0063] Alternatively, the set of precoders may be expressed as: 1 ^^^{^} ^ _{^ ^ 6]} [0064]

the set _{of precoders in Equation 5 and Equation 6. In the special case in which ^^^ ൌ ^^ଶ ൌ ^^ଷ ൌ ^^ ൌ ^^, the loss values are ^^ ൌ 14.6 ^^ଶ, (0.4 dB los ଶ ସ ୟ^^,୫ୟ^ s) and ^^୫୧୬,୫ୟ^ ൌ 13.2 ^^ . (0.8} dB loss). [0065] For the case of four antenna ports with the set of precoders in Equations (5) and (6), the average beamforming gain of the best precoder over phase is 0.4 dB less than that of the best precoder with the best-case phase. Significantly, the beamforming gain of the best precoder with the worst-case phase in such an embodiment is only 0.8 dB worse than that of the best precoder with the best-case phase. An example of cumulative distribution of beamforming gain relative to the maximum achievable gain of an embodiment of the present disclosure is shown in Figure 6. [0066] Accordingly, for an enhanced precoder codebook according to an embodiment, loss due to the worst-case phase alignment error is reduced from 3 dB to 0.8 dB, and the average loss is reduced from 1 dB to 0.4 dB. For cases in which coverage and range are important, the benefits of implementing an enhanced precoder codebook for 4 antenna ports at a UE are substantial. [0067] To accommodate the additional phase configurations, and enhanced precoder codebook may include at least 75 precoders, in contrast to the 28 precoders shown in Figure 3. In some embodiments, a value of an enhanced precoder codebook may be indicated using seven bits to represent all values in the codebook. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 16 [0068] The number of bits used to indicate a value of the codebook may be reduced by limiting the precoder selection to fully coherent single-layer precoders in the codebook which can be represented by a six bit indication. Accordingly, in some embodiments, an indication 804 is transmitted to a UE to limit the precoders available for selection to fully coherent single-layer precoders, thereby reducing the signaling overhead for indicating values of the enhanced precoder. [0069] An enhanced precoder codebook can be used to extend the range of uplink communications. In some embodiments, a UE may include a legacy codebook as well as an enhanced precoder codebook, and the enhanced precoder codebook is used for communications in which enhanced range is desired. For example, a network may determine that coverage of a UE is limited, and configure range extension including use of the enhanced precoder codebook and single-layer transmissions at the UE. Accordingly, it is possible for a network to control implementing the enhanced precoder codebook selectively to extend the range of uplink communications. [0070] Figure 9 illustrates an example of a UE 900 in accordance with aspects of the present disclosure. The UE 900 may include a processor 902, a memory 904, a controller 906, and a transceiver 908. The processor 902, the memory 904, the controller 906, or the transceiver 908, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. These components may be coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces. [0071] The processor 902, the memory 904, the controller 906, or the transceiver 908, or various combinations or components thereof may be implemented in hardware (e.g., circuitry). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or other programmable logic device, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. [0072] The processor 902 may include an intelligent hardware device (e.g., a general- purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination thereof). In some implementations, the processor 902 may be configured to operate the memory 904. In Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 17 some other implementations, the memory 904 may be integrated into the processor 902. The processor 902 may be configured to execute computer-readable instructions stored in the memory 904 to cause the UE 900 to perform various functions of the present disclosure. [0073] The memory 904 may include volatile or non-volatile memory. The memory 904 may store computer-readable, computer-executable code including instructions when executed by the processor 902 cause the UE 900 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such the memory 904 or another type of memory. Computer-readable media includes both non- transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. [0074] In some implementations, the processor 902 and the memory 904 coupled with the processor 902 may be configured to cause the UE 900 to perform one or more of the functions described herein (e.g., executing, by the processor 902, instructions stored in the memory 904). For example, the processor 902 may support wireless communication at the UE 900 in accordance with examples as disclosed herein. The UE 900 may be configured to support a means for transmitting an indication to a network entity indicating that the UE capability includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions and receiving, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook [0075] The controller 906 may manage input and output signals for the UE 900. The controller 906 may also manage peripherals not integrated into the UE 900. In some implementations, the controller 906 may utilize an operating system such as iOS®, ANDROID®, WINDOWS®, or other operating systems. In some implementations, the controller 906 may be implemented as part of the processor 902. [0076] In some implementations, the UE 900 may include at least one transceiver 908. In some other implementations, the UE 900 may have more than one transceiver 908. The transceiver 908 may represent a wireless transceiver. The transceiver 908 may include one or more receiver chains 910, one or more transmitter chains 912, or a combination thereof. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 18 [0077] A receiver chain 910 may be configured to receive signals (e.g., control information, data, packets) over a wireless medium. For example, the receiver chain 910 may include one or more antennas for receiving the signal over the air or wireless medium. The receiver chain 910 may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. The receiver chain 910 may include at least one demodulator configured to demodulate the receive signal and obtain the transmitted data by reversing the modulation technique applied during transmission of the signal. The receiver chain 910 may include at least one decoder for decoding the processing the demodulated signal to receive the transmitted data. [0078] A transmitter chain 912 may be configured to generate and transmit signals (e.g., control information, data, packets). The transmitter chain 912 may include at least one modulator for modulating data onto a carrier signal, preparing the signal for transmission over a wireless medium. The at least one modulator may be configured to support one or more techniques such as amplitude modulation (AM), frequency modulation (FM), or digital modulation schemes like phase-shift keying (PSK) or quadrature amplitude modulation (QAM). The transmitter chain 912 may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over the wireless medium. The transmitter chain 912 may also include one or more antennas for transmitting the amplified signal into the air or wireless medium. [0079] Figure 10 illustrates an example of a processor 1000 in accordance with aspects of the present disclosure. The processor 1000 may be an example of a processor configured to perform various operations in accordance with examples as described herein. The processor 1000 may include a controller 1002 configured to perform various operations in accordance with examples as described herein. The processor 1000 may optionally include at least one memory 1004, which may be, for example, an L1/L2/L3 cache. Additionally, or alternatively, the processor 1000 may optionally include one or more arithmetic-logic units (ALUs) 1006. One or more of these components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces (e.g., buses). Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 19 [0080] The processor 1000 may be a processor chipset and include a protocol stack (e.g., a software stack) executed by the processor chipset to perform various operations (e.g., receiving, obtaining, retrieving, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) in accordance with examples as described herein. The processor chipset may include one or more cores, one or more caches (e.g., memory local to or included in the processor chipset (e.g., the processor 1000) or other memory (e.g., random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), static RAM (SRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, phase change memory (PCM), and others). [0081] The controller 1002 may be configured to manage and coordinate various operations (e.g., signaling, receiving, obtaining, retrieving, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) of the processor 1000 to cause the processor 1000 to support various operations in accordance with examples as described herein. For example, the controller 1002 may operate as a control unit of the processor 1000, generating control signals that manage the operation of various components of the processor 1000. These control signals include enabling or disabling functional units, selecting data paths, initiating memory access, and coordinating timing of operations. [0082] The controller 1002 may be configured to fetch (e.g., obtain, retrieve, receive) instructions from the memory 1004 and determine subsequent instruction(s) to be executed to cause the processor 1000 to support various operations in accordance with examples as described herein. The controller 1002 may be configured to track memory address of instructions associated with the memory 1004. The controller 1002 may be configured to decode instructions to determine the operation to be performed and the operands involved. For example, the controller 1002 may be configured to interpret the instruction and determine control signals to be output to other components of the processor 1000 to cause the processor 1000 to support various operations in accordance with examples as described herein. Additionally, or alternatively, the controller 1002 may be configured to manage flow of data within the processor 1000. The controller 1002 may be configured to control Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 20 transfer of data between registers, arithmetic logic units (ALUs), and other functional units of the processor 1000. [0083] The memory 1004 may include one or more caches (e.g., memory local to or included in the processor 1000 or other memory, such RAM, ROM, DRAM, SDRAM, SRAM, MRAM, flash memory, etc. In some implementations, the memory 1004 may reside within or on a processor chipset (e.g., local to the processor 1000). In some other implementations, the memory 1004 may reside external to the processor chipset (e.g., remote to the processor 1000). [0084] The memory 1004 may store computer-readable, computer-executable code including instructions that, when executed by the processor 1000, cause the processor 1000 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such as system memory or another type of memory. The controller 1002 and/or the processor 1000 may be configured to execute computer-readable instructions stored in the memory 1004 to cause the processor 1000 to perform various functions. For example, the processor 1000 and/or the controller 1002 may be coupled with or to the memory 1004, the processor 1000, the controller 1002, and the memory 1004 may be configured to perform various functions described herein. In some examples, the processor 1000 may include multiple processors and the memory 1004 may include multiple memories. One or more of the multiple processors may be coupled with one or more of the multiple memories, which may, individually or collectively, be configured to perform various functions herein. [0085] The one or more ALUs 1006 may be configured to support various operations in accordance with examples as described herein. In some implementations, the one or more ALUs 1006 may reside within or on a processor chipset (e.g., the processor 1000). In some other implementations, the one or more ALUs 1006 may reside external to the processor chipset (e.g., the processor 1000). One or more ALUs 1006 may perform one or more computations such as addition, subtraction, multiplication, and division on data. For example, one or more ALUs 1006 may receive input operands and an operation code, which determines an operation to be executed. One or more ALUs 1006 be configured with a variety of logical and arithmetic circuits, including adders, subtractors, shifters, and logic Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 21 gates, to process and manipulate the data according to the operation. Additionally, or alternatively, the one or more ALUs 1006 may support logical operations such as AND, OR, exclusive-OR (XOR), not-OR (NOR), and not-AND (NAND), enabling the one or more ALUs 1006 to handle conditional operations, comparisons, and bitwise operations. [0086] The processor 1000 may support wireless communication in accordance with examples as disclosed herein. The processor 1000 may be configured to or operable to support a means for transmitting an indication to a network entity indicating that the UE capability includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions and receiving, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook. [0087] Figure 11 illustrates an example of a NE 1100 in accordance with aspects of the present disclosure. The NE 1100 may include a processor 1102, a memory 1104, a controller 1106, and a transceiver 1108. The processor 1102, the memory 1104, the controller 1106, or the transceiver 1108, or various combinations thereof or various components thereof may be examples of means for performing various aspects of the present disclosure as described herein. These components may be coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more interfaces. [0088] The processor 1102, the memory 1104, the controller 1106, or the transceiver 1108, or various combinations or components thereof may be implemented in hardware (e.g., circuitry). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or other programmable logic device, or any combination thereof configured as or otherwise supporting a means for performing the functions described in the present disclosure. [0089] The processor 1102 may include an intelligent hardware device (e.g., a general- purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination thereof). In some implementations, the processor 1102 may be configured to operate the memory 1104. In some other implementations, the memory 1104 may be integrated into the processor 1102. The processor 1102 may be configured to execute computer-readable instructions Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 22 stored in the memory 1104 to cause the NE 1100 to perform various functions of the present disclosure. [0090] The memory 1104 may include volatile or non-volatile memory. The memory 1104 may store computer-readable, computer-executable code including instructions when executed by the processor 1102 cause the NE 1100 to perform various functions described herein. The code may be stored in a non-transitory computer-readable medium such the memory 1104 or another type of memory. Computer-readable media includes both non- transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that may be accessed by a general-purpose or special-purpose computer. [0091] In some implementations, the processor 1102 and the memory 1104 coupled with the processor 1102 may be configured to cause the NE 1100 to perform one or more of the functions described herein (e.g., executing, by the processor 1102, instructions stored in the memory 1104). For example, the processor 1102 may support wireless communication at the NE 1100 in accordance with examples as disclosed herein. The NE 1100 may be configured to support a means for receiving an indication from a UE indicating that the UE capability includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions, and transmitting, to the UE, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook. [0092] The controller 1106 may manage input and output signals for the NE 1100. The controller 1106 may also manage peripherals not integrated into the NE 1100. In some implementations, the controller 1106 may utilize an operating system such as iOS®, ANDROID®, WINDOWS®, or other operating systems. In some implementations, the controller 1106 may be implemented as part of the processor 1102. [0093] In some implementations, the NE 1100 may include at least one transceiver 1108. In some other implementations, the NE 1100 may have more than one transceiver 1108. The transceiver 1108 may represent a wireless transceiver. The transceiver 1108 may include one or more receiver chains 1110, one or more transmitter chains 1112, or a combination thereof. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 23 [0094] A receiver chain 1110 may be configured to receive signals (e.g., control information, data, packets) over a wireless medium. For example, the receiver chain 1110 may include one or more antennas for receiving the signal over the air or wireless medium. The receiver chain 1110 may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. The receiver chain 1110 may include at least one demodulator configured to demodulate the received signal and obtain the transmitted data by reversing the modulation technique applied during transmission of the signal. The receiver chain 1110 may include at least one decoder for decoding the demodulated signal to receive the transmitted data. [0095] A transmitter chain 1112 may be configured to generate and transmit signals (e.g., control information, data, packets). The transmitter chain 1112 may include at least one modulator for modulating data onto a carrier signal, preparing the signal for transmission over a wireless medium. The at least one modulator may be configured to support one or more techniques such as amplitude modulation (AM), frequency modulation (FM), or digital modulation schemes like phase-shift keying (PSK) or quadrature amplitude modulation (QAM). The transmitter chain 1112 may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over the wireless medium. The transmitter chain 1112 may also include one or more antennas for transmitting the amplified signal into the air or wireless medium. [0096] Figure 8 illustrates an example of operations of a UE and NE in accordance with aspects of the present disclosure. The operations of Figure 8 are illustrated as a signal diagram showing signals exchanged between the UE and NE and certain operations performed by those entities. [0097] Figure 12 illustrates a flowchart of a method in accordance with aspects of the present disclosure. The operations of the method may be implemented by a UE as described herein. In some implementations, the UE may execute a set of instructions to control the function elements of the UE to perform the described functions. [0098] At 1202, the method may include transmitting an indication 802 to a NE that the UE capability includes an enhanced codebook. The operations of 1202 may be performed Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 24 in accordance with examples as described herein. In some implementations, aspects of the operations of 1202 may be performed by a UE as described with reference to Figure 9. [0099] In an embodiment, the UE informs the NE that the UE capability includes an enhanced codebook with a precoder for every combination in which the phase rotation of each antenna port of the UE relative to a first antenna port is a multiple of 90 degrees. The precoder may comprise a set of 64 length-4 vectors given by: 1 é ^{୧୬^^} ೖ^ù ^ ^^ భల 6_{3, and} In which

i-th row of the precoding vector is multiplied by an input to the i-th antenna port. The UE may inform the NE of this capability using MAC layer signaling, e.g., by transmitting a radio resource control (RRC) message. In some embodiments, the UE may transmit the indication to the NE at 1202 in response to a query from the NE, but in other embodiments the UE simply may signal this capability without being prompted by the NE. [0100] At 1204, the method may include receiving an indication 804 from the NE that MIMO uplink transmissions to the NE are limited to single layer transmissions. The operations of 1204 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1204 may be performed by a UE as described with reference to Figure 9. [0101] In some embodiments, the number of bits used to indicate a value in an enhanced codebook is seven bits considering all entries in the enhanced codebook. However, when the entries are limited to entries for coherent single-layer transmissions, the number of entries is lower, and can be encoded using a six-bit indication. Accordingly, when a UE receives an indication 804 from the NE at 1204 that associated uplink MIMO transmissions are to be coherent single layer transmissions, the number of bits used to indicate an enhanced codebook value can be reduced. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 25 [0102] At 1206, the method may include transmitting reference signals 806 to the NE. The operations of 1206 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1206 may be performed by a UE as described with reference to Figure 9. [0103] The reference signals 806 transmitted to the NE may be sounding reference signals (SRS). The UE may transmit an SRS from each active antenna port that will be used for subsequent MIMO uplink transmissions. In some embodiments, the reference signals may be transmitted on different frequency resources at the same time to avoid interference between the signals, e.g., by using different subcarriers. In another embodiment, the signals are interlaced with one another. The specific mode of reference signal transmission may be configured by a base station by RRC messages (e.g., RRCSetup, RRCReconfiguration) as known in the art. [0104] At 1208, the method may include receiving a transmit precoding matrix indicator (TPMI) 810 from the network entity. The operations of 1208 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1208 may be performed by a UE as described with reference to Figure 9. [0105] The TPMI received at 1208 may indicate a value in the enhanced codebook. As noted above, in various embodiments the TPMI may be a six or seven bit indication that corresponds to a specific value in the enhanced precoder codebook. [0106] At 1210, the method may include applying a precoding vector associated with the TPMI value 810 received from the NE. The operations of 1210 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1210 may be performed by a UE as described with reference to Figure 9. In particular, the UE may apply precoding vectors from the enhanced precoding codebook to the four antenna ports P1-P4 of Figure 7. An example of applying precoding associated with the TPMI value is shown as element 812 of Figure 8. [0107] At 1212, the method may include transmitting uplink MIMO signals 814 using the precoding vectors associated with the precoding index of the enhanced precoding codebook indicated by the TPMI received from the NE. The operations of 1212 may be Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 26 performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1212 may be performed by a UE as described with reference to Figure 9. The MIMO transmissions 814 may be four port single-layer transmissions with substantially extended range by using precoder values in the enhanced precoder codebook. [0108] It should be noted that the method described herein describes a possible implementation, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. [0109] Figure 13 illustrates a flowchart of a method in accordance with aspects of the present disclosure. The operations of the method may be implemented by a NE as described herein. In some implementations, the NE may execute a set of instructions to control the function elements of the NE to perform the described functions. [0110] At 1302, the method may include receiving an indication 802 from a UE indicating that the UE capability includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions. The operations of 1302 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1302 may be performed by a NE as described with reference to Figure 10. [0111] In an embodiment, the UE informs the NE that the UE capability includes an enhanced codebook with a precoder for every combination in which the phase rotation of each antenna port of the UE relative to a first antenna port is a multiple of 90 degrees. The precoder may comprise a set of 64 length-4 vectors given by: 1 é ೖ 6_{3, and}

in which th row of the precoding vector is multiplied by an input to the i-th antenna port. The UE may inform the NE of this capability using MAC layer signaling, and the specific MAC signal is not particularly limited. In some embodiments, Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 27 the NE receives the indication from the UE at 1202 in response to a query from the NE, but in other embodiments the UE may signal this capability without being prompted by the NE. [0112] At 1304, the method may include transmitting an indication 804 to the UE that MIMO uplink transmissions are limited to single layer transmissions. The operations of 1304 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1304 may be performed by a NE as described with reference to Figure 10. [0113] In some embodiments, the number of bits used to indicate a value in an enhanced codebook is seven bits considering all entries in the enhanced codebook. However, when the entries are limited to entries for coherent single-layer transmissions, the number of entries is lower, and can be encoded using a six-bit indication. Accordingly, when a NE provides an indication to a UE at 1304 that associated uplink MIMO transmissions are to be coherent single layer transmissions, the number of bits used to indicate an enhanced codebook value can be reduced. [0114] At 1306, the method may include receiving reference signals 806 from the UE. The operations of 1306 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1306 may be performed by a NE as described with reference to Figure 10. [0115] The reference signals 806 received by the NE may be sounding reference signals (SRS). The NE may receive an SRS from each active antenna port of the UE that will be used for subsequent MIMO uplink transmissions. In some embodiments, the reference signals may be transmitted on different frequency resources at the same time to avoid interference between the signals, e.g., by using different subcarriers. In another embodiment, the signals are interlaced with one another. The specific mode of reference signal transmission may be configured by a base station by RRC messages (e.g., RRCSetup, RRCReconfiguration) as known in the art. [0116] At 1308, the method may include measuring the reference signals received from the UE at 1306. The operations of 1308 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1308 may be Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 28 performed by a NE as described with reference to Figure 10. An example of measuring the reference signals is shown as element 808 of Figure 8. [0117] Upon receiving the reference signals from the UE, the NE measures and analyzes the received signals. The NE may estimate channel state information (CSI) by comparing a received SRS with a known reference signal. The NE may evaluate various parameters, such as the path loss, propagation delay (phase delay), and received signal strength, to understand the current radio environment and channel conditions between the NE and the UE. [0118] In an embodiment, the NE measures the phase of at least one reference signal from each antenna port of the UE, determines an optimum combination of phase offsets to be applied to the respective antenna ports, and identifies a value of the enhanced precoder codebook that most closely matches the optimum combination of phase offsets. The optimum combination of phase offsets may be a combination of phase offsets that maximizes the signal strength of transmissions from the associated antenna ports of the UE. [0119] At 1310, the method may include transmitting a transmit precoding matrix indicator (TPMI) 810 from the network entity. The operations of 1310 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1310 may be performed by a NE as described with reference to Figure 10. [0120] The TPMI 810 transmitted at 1310 may indicate a value in the enhanced codebook. As noted above, in various embodiments the TPMI may be a six or seven bit indication that corresponds to a specific antenna configuration of the enhanced precoder codebook. [0121] At 1312, the method may include receiving uplink MIMO signals 814 using the precoding vectors associated with the precoding value of the enhanced precoding codebook indicated by the TPMI from the UE. The operations of 1312 may be performed in accordance with examples as described herein. In some implementations, aspects of the operations of 1312 may be performed by a NE as described with reference to Figure 10. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 29 [0122] It should be noted that the method described herein describes A possible implementation, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. [0123] The description herein is provided to enable a person having ordinary skill in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to a person having ordinary skill in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein. Attorney Docket No.793MS0138PC

Claims

Lenovo Docket. No. SMM920230252-WO-PCT 30 CLAIMS What is claimed is: 1. A user equipment (UE) for wireless communication, comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the UE to: transmit an indication to a network entity indicating UE capability, which includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions; and receive, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook, wherein the enhanced precoder codebook includes a precoder for every combination in which the phase rotation of a first antenna port of the UE relative to each of one or more remaining antenna ports is a multiple of 90 degrees, and the value is associated with a precoder of the enhanced precoder codebook to be used by the UE for uplink transmissions. 2. The UE of claim 1, wherein the enhanced precoder codebook comprises a set of 64 length-4 vectors given by: 1 é ^^^^ ù 6_{3, and}

in an i-th row of the precoding vector is multiplied by an input to the i-th antenna port. 3. The UE of claim 2, wherein the UE further comprises four antenna ports, and the set of 64 length-4 vectors represent respective allowed precoding vectors for the four antenna ports. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 31 4. The UE of claim 2, wherein the TPMI received from the network entity is a seven-bit indicator. 5. The UE of claim 2, wherein the 64 length-4 vectors are for coherent uplink transmissions. 6. The UE of claim 1, wherein the at least one processor is configured to cause the UE to: receive an indication from the network entity configuring uplink transmissions from the UE as coherent single layer transmissions, wherein the TPMI received from the network entity is a six-bit indicator. 7. The UE of claim 1, wherein the enhanced precoder codebook is configured for range extension of uplink communications. 8. A processor for a user equipment (UE) for wireless communication with a network entity, the processor comprising: at least one controller coupled with at least one memory and configured to cause the processor to: transmit an indication to the network entity indicating UE capability, which includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions; and receive, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook, wherein the enhanced precoder codebook includes a precoder for every combination in which the phase rotation of a first antenna port relative to each of one or more remaining antenna ports of the UE is a multiple of 90 degrees, and the value is associated with a precoder of the enhanced precoder codebook to be used by the UE for uplink transmissions. Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 32 9. The processor of claim 8, wherein the enhanced precoder codebook comprises a set of 64 length-4 vectors given by: 1 é ^^^^ ù ^ ^int( ₁₆) 1ê^^^ ú 6_{3, and} in an i-th row of the precoding vector is multiplied by

an input 10. The processor of claim 9, wherein the UE further comprises four antenna ports, and the set of 64 length-4 vectors represent respective allowed precoding vectors for the four antenna ports. 11. The processor of claim 9, wherein the TPMI received from the network entity is a seven-bit indicator. 12. The processor of claim 9, wherein the 64 length-4 vectors are for coherent uplink transmissions. 13. The processor of claim 8, wherein the at least one controller is configured to cause the processor to: receive an indication from the network entity configuring uplink transmissions from the UE as coherent single layer transmissions, wherein the TPMI received from the network entity is a six-bit indicator. 14. The processor of claim 8, wherein the enhanced precoder codebook is configured for range extension of uplink communications. 15. A method performed by a user equipment (UE), the method comprising: Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 33 transmitting an indication to a network entity indicating UE capability, which includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions; and receiving, from the network entity, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook, wherein the enhanced precoder codebook includes a precoder for every combination in which the phase rotation of a first antenna port relative to each of one or more remaining antenna ports of the UE is a multiple of 90 degrees, and the value is associated with a precoder of the enhanced precoder codebook to be used by the UE for uplink transmissions. 16. The method of claim 15, wherein the enhance precoder codebook comprises a set of 64 length-4 vectors given by: 1 é ^^^^ ù ^^^^^int( 6_{3, and}

in an i-th row of the precoding vector is multiplied by an input to the i-th antenna port. 17. The method of claim 16, wherein the UE further comprises four antenna ports, and the set of 64 length-4 vectors represent respective allowed precoding vectors for the four antenna ports. 18. A base station for wireless communication, comprising: at least one memory; and at least one processor coupled with the at least one memory and configured to cause the base station to: receive an indication from a user equipment (UE) indicating UE capability, which includes an enhanced precoder codebook for single-layer uplink multiple input multiple output (MIMO) transmissions; and Attorney Docket No.793MS0138PC Lenovo Docket. No. SMM920230252-WO-PCT 34 transmit, to the UE, a transmit precoding matrix indicator (TPMI) indicating a value of the enhanced precoder codebook, wherein the enhanced precoder codebook includes a precoder for every combination in which the phase rotation of a first antenna port relative to each of one or more remaining antenna ports of the UE is a multiple of 90 degrees, and the value is associated with a precoder of the enhanced precoder codebook to be used by the UE for uplink transmissions. 19. The base station of claim 18, wherein the enhanced precoder codebook comprises a set of 64 length-4 vectors given by: 1 é ^int( ^^^^)ù 1ê ^^^^ ₁₆ 2ê ^int( _{63, and} ê ^^^^ ₄ ë ^^^^^{^^^^}

in an i-th row of the precoding vector is multiplied by an input to the i-th antenna port. 20. The base station of claim 18, wherein the at least one processor is configured to cause the base station to: transmit an indication to the UE configuring uplink transmissions from the UE as single layer transmissions, wherein the TPMI transmitted to the UE is a six-bit indicator. Attorney Docket No.793MS0138PC