Antenna selection for multi-transmitter wireless devices

Abstract

Mechanisms to manage antenna selection for a wireless device are described. The wireless device transmits sounding reference signal (SRS) resources in a set of SRS resources configured by a cellular wireless network, and receives an SRS indicator (SRI) value and / or transmits a pre-decoder matrix indicator (TPMI) value to indicate an antenna for subsequent uplink transmissions of a physical layer channel, such as a physical uplink shared channel (PUSCH), by the wireless device. The wireless device maps an antenna of the wireless device to SRS resources in a set of SRS resources to improve performance of incoherent and coherent uplink (UL) multiple input multiple output (MIMO) transmissions. In some embodiments, the wireless device uses a TPMI group value to indicate a strongest antenna within a group of antennas associated with the SRS resource. In some embodiments, a base station determines whether SRS transmissions and / or PUSCH transmissions are limited by a maximum transmit power level (MTPL), and adjusts parameters for antenna selection accordingly.

Description

Technical Field

[0001] The described embodiments relate to wireless communication, including methods and apparatus for managing antenna selection for a multi-transmitter wireless device. Background Art

[0002] A new generation of cellular radio networks implementing one or more 3rd Generation Partnership Project (3GPP) 5G standards (e.g., 5th Generation (5G) New Radio (NR)) is rapidly evolving and being deployed by network operators globally. The newer cellular radio networks provide a range of packet-based services, where 5G technology provides increased data throughput and lower latency connectivity, which ensures enhanced mobile broadband services for wireless devices. The higher data throughput and lower latency of 5G are expected to introduce a range of new applications and services and improve existing applications and services. A wireless device transmits one or more sounding reference signals (SRS) configured by the cellular radio network to the wireless device in the uplink (UL) direction to measure the UL channel for subsequent UL data transmission and / or control signal transmission. A single-transmitter wireless device or a dual-transmitter wireless device may include multiple (e.g., four) receivers, and the multiple (e.g., four) receivers may process signals received via multiple antennas (in some cases, the signals may be mapped to one or more antenna ports feeding these receivers via a receiver transformation filter matrix). In the case where the number of transmitters is less than the number of receivers, the wireless device may transmit in the UL direction using one or two antenna ports at any given moment (in the simplest case, directly mapped to two different physical antennas). Different antennas (or equivalently, antenna ports) may provide different UL transmission characteristics based on how the wireless device is used (e.g., device physical orientation, antenna blockage, etc.). The performance of UL transmission may vary for different individual antennas and antenna pairs. The wireless device may select the antenna or antenna pair to be used based on an open-loop antenna selection process (e.g., using measured downlink (DL) signal strength and / or signal quality metrics to infer UL channel characteristics) or based on a closed-loop antenna selection process (e.g., using antenna selection provided in a message from the cellular radio network in response to measurements made by the cellular radio network based on the reception of UL SRS transmissions sent by the wireless device). Current mechanisms arbitrarily map the SRS signal to an antenna port (or antenna), which may result in poor performance when different antenna ports (or antennas) within a set of antenna ports (or antennas) have significantly different uplink channel characteristics. There is a need for a mechanism to map the SRS signal to an antenna port (or antenna) to achieve higher performance for both non-coherent UL transmission and coherent UL transmission. Summary of the Invention

[0003] This application relates to wireless communication, including methods and apparatuses for managing antenna selection for a multi-transmitter wireless device. A cellular radio network configures one or more sounding reference signal (SRS) resource sets for the wireless device, each SRS resource set including multiple SRS resources for uplink (UL) transmission, and each SRS resource including multiple SRS ports. Each SRS resource set is designated for a specific purpose, such as a codebook purpose for UL sounding (which can be used for closed-loop antenna selection and / or UL precoder selection) or an antenna switching purpose (which can be used for DL precoder selection). The wireless device measures one or more downlink performance metrics (e.g., signal strength and / or signal quality) through each of multiple antennas (or antenna ports), and maps groups of antennas (or antenna ports) to SRS resources, each SRS resource having multiple SRS ports, where the mapping takes into account the measured downlink performance metrics of the respective antennas (or antenna ports). In some embodiments, each group of antennas (or antenna ports) includes two antennas (or antenna ports), and each SRS resource in the SRS resource set includes two SRS ports. The wireless device can select groups of antennas (or antenna ports) with similar downlink performance or use the ranking of the antennas (or antenna ports) based on the measured downlink performance.

[0004] In a representative embodiment, a two-transmit-chain, four-receive-chain (2T4R) wireless device is configured with an SRS resource set that is designated for codebook use and includes two SRS resources, each SRS resource having two SRS ports, and the two best antennas (or antenna ports) are mapped to the first SRS resource, while the two worst antennas (or antenna ports) are mapped to the second SRS resource. The wireless device uses this mapping to transmit the SRS resources to a base station of the cellular radio network via the antennas (or antenna ports), and the base station of the cellular radio network selects an antenna pair for subsequent UL physical layer channel transmission (e.g., for physical uplink shared channel (PUSCH) transmission) by transmitting a downlink control information (DCI) message that includes an SRS indicator (SRI) value that indicates the SRS resource associated with the selected antenna pair. In some embodiments, the DCI also includes a transmit precoding matrix indicator (TPMI) value that specifies the UL precoder that the wireless device uses in the case of PUSCH transmission. The wireless device can monitor the downlink performance via the antennas (or antenna ports) and update the mapping, for example, periodically, at a predetermined time, on demand, or based on a measurement trigger criterion.

[0005] In another representative embodiment, the 2T4R wireless device is configured with an SRS resource set that is designated for codebook use and includes one SRS resource having two SRS ports, and the two best antennas (or antenna ports) are selected by the wireless device and mapped to the single SRS resource in the SRS resource set. The wireless device sends the SRS resource to the base station, and the base station responds with a TPMI value of a UL precoder designated for the PUSCH transmission. The wireless device can monitor the performance of multiple antennas (or antenna ports) and change which two best (or selected) antennas (or antenna ports) are mapped to the two SRS ports of the single SRS resource in the SRS resource set before UL SRS transmission, so that the base station measures the UL channel via the newly mapped antennas (or antenna ports) for subsequent UL transmission via the newly mapped antennas (or antenna ports).

[0006] When using a specific frequency band, the maximum transmit power level (MTPL) of different antennas (or antenna ports) of the wireless device may vary. When the MTPL difference between different antennas (or antenna ports) within each group of antennas (or antenna ports) that can be used by the wireless device meets the MTPL difference threshold, the wireless device can indicate the strongest antenna (or antenna port) in each group of antennas (or antenna ports) to the base station of the cellular radio network by transmitting a specific TPMI group value to the base station, and map the strongest antenna (or antenna port) in each group of antennas to the same (e.g., first) SRS port of the corresponding SRS resource associated with the group of antennas (or antenna ports). When the MTPL difference between each antenna (or antenna port) in at least one group of antennas (or antenna ports) that the wireless device can use does not meet the MTPL difference threshold, the wireless device does not report a specific TPMI group value to the base station. Due to hardware limitations, in some cases, not all combinations of antennas (or antenna ports) can be grouped together, and thus only certain combinations of antennas (or antenna ports) can be used to form a group of antennas for a specific wireless device.

[0007] In some embodiments, the base station determines whether the MTPL value for SRS resource transmission or PUSCH transmission by the wireless device is restricted. The base station may use the power headroom (PH) value included in the power headroom report (PHR) provided by the wireless device to determine whether the PUSCH transmission is restricted by MTPL. The base station may use the PH value scaled according to the ratio of the bandwidth for the SRS resource transmission to the bandwidth used by the PUSCH transmission to determine whether the SRS resource transmission is restricted by MTPL. When the PUSCH transmission is restricted by MTPL, the base station may adjust the received SRS resource transmission measurement results by an adjustment factor, for example, increasing the received SRS value by 3 dB. When the SRS resource transmission is restricted by MTPL, the base station may adjust the received SRS resource transmission measurement results by another adjustment factor, for example, decreasing the received SRS value by 3 dB. By adjusting the received SRS resource transmission measurement results that can be used to select an antenna (or antenna port), the base station compensates for the MTPL restriction of the SRS resource transmission or the PUSCH transmission and improves the accuracy of antenna selection.

[0008] In some embodiments, a wireless device using coherent UL multiple-input multiple-output (MIMO) transmission calculates the channel capacity of a group of antennas (or antenna ports) that can be used together for the UL MIMO transmission, and selects an antenna group to map to the SRS ports of the SRS resources in an SRS resource set designated for codebook use based on the calculated channel capacity. The wireless device may monitor downlink signal metrics (such as signal strength or signal quality, for example, reference signal received power (RSRP) value or signal-to-noise plus interference (SINR) value), and for each antenna (or antenna port), determine a scaling factor to adjust the channel information estimation. The scaling factor may also include the transmission and reception characteristics of the corresponding antenna (or antenna port), such as the total radiated power (TRP) value and the total isotropic sensitivity (TIS) value. The wireless device determines the cross-correlation channel information matrix of antenna (or antenna port) pairs (or other groups), and uses the cross-channel capacity derived from the cross-correlation channel information matrix (such as based on the eigenvalues of the cross-correlation channel information matrix) to select the best antenna (or antenna port) combination to map to the SRS resources in an SRS resource set designated for codebook use.

[0009] Other aspects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments.

[0010] The present invention content is provided only for the purpose of summarizing some example embodiments, so as to provide a basic understanding of some aspects of the subject matter described herein. Therefore, it should be understood that the above features are only examples and should not be construed as narrowing the scope or essence of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following detailed description, the drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present disclosure will be more readily understood by reference to the following detailed description in conjunction with the accompanying drawings, in which like reference numerals refer to like structural elements.

[0012] Figure 1A A diagram illustrating an example of a sounding reference signal (SRS) resource set for downlink (DL) precoding of a 1T4R wireless device according to some embodiments.

[0013] Figure 1B A diagram illustrating an example of an SRS resource set for uplink (UL) sounding of a 1T4R wireless device according to some embodiments.

[0014] Figure 1C A diagram illustrating an example of an SRS resource set for UL sounding and SRS indicator (SR) antenna selection of a 1T4R wireless device according to some embodiments.

[0015] Figure 1D A diagram illustrating an example of an SRS resource set for DL precoding of a 2T4R wireless device according to some embodiments.

[0016] Figure 1E A diagram illustrating an example of an SRS resource set for antenna selection based on UL sounding and SRS indicator (SRI) of a 2T4R wireless device according to some embodiments.

[0017] Figure 1F A diagram illustrating another example of an SRS resource set for DL precoding of a 2T4R wireless device according to some embodiments.

[0018] Figure 2A A diagram illustrating an exemplary uplink transmit chain for a wireless device according to some embodiments.

[0019] Figure 2B A diagram illustrating an example of uplink transmit data processing for a wireless device according to some embodiments.

[0020] Figure 2C A diagram illustrating an exemplary UL multiple-input multiple-output (MIMO) precoding matrix with non-coherent antenna port selection according to some embodiments.

[0021] Figure 2D A table illustrating exemplary maximum transmit power level (MTPL) values for respective antenna ports of a wireless device according to some embodiments.

[0022] Figure 3 A table illustrating an example of mapping SRS resources to antenna ports for a 2T4R wireless device according to some embodiments.

[0023] Figure 4 A diagram illustrating an example of device-based antenna mapping and network-based closed-loop antenna pair selection for a 2T4R wireless device according to some embodiments.

[0024] Figure 5A A table illustrating an example of MTPL differences for antenna port pairs of a 2T4R wireless device according to some embodiments.

[0025] Figure 5B and Figure 5C A table illustrating examples of antenna port selection with and without MTPL adjustment for a 2T4R wireless device according to some embodiments.

[0026] Figure 6 A flowchart illustrating an exemplary method for UL transmit antenna selection for a wireless device according to some embodiments.

[0027] Figure 7 A flowchart illustrating another exemplary method for UL transmit antenna selection for a wireless device according to some embodiments.

[0028] Figure 8A A flowchart illustrating yet another exemplary method for UL transmit antenna selection for a wireless device according to some embodiments.

[0029] Figure 8B A flowchart illustrating an exemplary method for a wireless device to calculate the channel capacity of an antenna port group according to some embodiments.

[0030] Figure 9 A flowchart illustrating an additional exemplary method for UL transmit antenna selection for a wireless device according to some embodiments.

[0031] Figure 10 A block diagram showing exemplary elements of a mobile wireless device according to some embodiments. Detailed Description

[0032] Representative applications of the methods and apparatuses according to the present application are described in this section. These examples are provided only to add context and facilitate understanding of the described embodiments. Thus, it will be apparent to those skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well-known processing steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be regarded as restrictive.

[0033] The present application relates to wireless communication, including methods and apparatuses for managing antenna selection for a multi-transmitter wireless device. A cellular radio network configures one or more sounding reference signal (SRS) resource sets for the wireless device, each SRS resource set including one or more SRS resources for uplink (UL) transmission, where each SRS resource may include multiple SRS ports for simultaneous UL transmission via multiple antennas (or more generally antenna ports). The wireless device may be configured with multiple SRS resource sets for different purposes, such as an "antenna switching" use designated for UL channel measurement to select an SRS resource set for a downlink (DL) precoder (assuming reciprocity of time-division duplex communication or compensating for the difference between carriers in different frequency bands for frequency-division duplex communication), or a "codebook" use designated for UL channel sounding for a base station to measure UL channel characteristics and determine an SRS resource set for antennas and UL precoders for subsequent UL transmission. The wireless device may be configured with different SRS resource sets, which include different sets of SRS resources. The wireless device transmits SRS resources to the cellular radio network periodically (when designated as periodic) or triggered by downlink control information (DCI) (when designated as aperiodic) via one or more antenna ports. The SRS ports of the SRS resources may be mapped to physical antennas via spatial filters; however, for simplicity of description herein, it is assumed that each SRS resource is directly mapped to an antenna. The ideas described herein may also be applied to the mapping of SRS resources (or SRS ports) to antenna ports that are also mapped to combinations of physical antennas (e.g., UL beamforming). Each SRS resource set is designated with usage configuration parameters that indicate how the SRS resource set will be used. The SRS resource sets described herein are designated with a codebook use that will be used for UL channel measurement and estimation and subsequently for the transmission of physical layer channels, particularly the physical uplink shared channel (PUSCH).

[0034] The wireless device signals its transmission capabilities regarding antenna switching to the cellular radio network. A wireless device with only one transmit chain and four receive chains (denoted as 1T4R capabilities) can only provide partial sounding (i.e., does not support full sounding of transmitting different SRS resources via all four antennas at once), and thus requires antenna switching to sound all different possible uplink channels via four different antennas (or more generally via four antenna ports corresponding to the respective antennas or antenna combinations of the wireless device). A wireless device with two transmit chains and four receive chains (denoted as 2T4R capabilities) can provide partial sounding via two antennas (or antenna ports) at once, and can provide full sounding by switching between pairs of antennas. A wireless device with four transmit chains and four receive chains (denoted as 4T4R capabilities) can provide full sounding by transmitting different SRS resources via all four antennas at once.

[0035] The wireless device measures one or more downlink performance metrics (e.g., signal strength or signal quality) via each of a plurality of antennas (or antenna ports), and maps groups of antennas (or antenna ports) to sounding reference signal (SRS) resources, each SRS resource having a plurality of SRS ports, where the mapping takes into account the measured downlink performance metrics of the respective antennas (or antenna ports). In some embodiments, each group of antennas (or antenna ports) includes two antennas (or antenna ports), and each SRS resource in the SRS resource set includes two SRS ports. The wireless device may select groups of antennas (or antenna ports) having similar downlink performance or use a ranking of the antennas (or antenna ports) based on the measured downlink performance. In a representative embodiment, a 2T4R wireless device is configured with an SRS resource set that is designated for codebook use and includes two SRS resources, each SRS resource having two SRS ports, and the two best antennas (or antenna ports) are mapped to the first SRS resource and the two worst antennas (or antenna ports) are mapped to the second SRS resource. The wireless device sends the SRS resources to a base station of the cellular radio network via the antennas (or antenna ports) using the mapping, and the base station of the cellular radio network selects an antenna pair for subsequent uplink physical layer channel transmission (e.g., for physical uplink shared channel (PUSCH) transmission) by transmitting a downlink control information (DCI) message that includes an SRS indicator (SRI) value that indicates the SRS resource associated with the selected antenna pair. The wireless device may monitor the DL performance and change the mapping of antennas (or antenna ports) to SRS resources based on the monitored DL performance, e.g., to account for changes in antenna performance individually and relative to each other. In some embodiments, the DCI also includes a transmit precoding matrix indicator (TPMI) value that specifies the UL precoder that the wireless device uses in the case of PUSCH transmission. The wireless device may monitor the downlink performance via the antennas (or antenna ports) and update the mapping, e.g., periodically, at a predetermined time, on demand, or based on a measurement trigger criterion.

[0036] In another representative embodiment, the 2T4R wireless device is configured with an SRS resource set that is designated for codebook use. The SRS resource set includes one SRS resource having two SRS ports, and the two best antennas (or antenna ports) are selected by the wireless device and mapped to the SRS resource. The wireless device sends the SRS resource to the base station, and the base station responds with a TPMI value of the UL precoder designated for the PUSCH transmission. The wireless device can monitor the performance of multiple antennas (or antenna ports) and change which two best (or selected) antennas (or antenna ports) are mapped to the two SRS ports of the SRS resource before UL SRS transmission, so that the base station measures the UL channel via the newly mapped antennas (or antenna ports) for subsequent UL transmission via the newly mapped antennas (or antenna ports).

[0037] In some embodiments, the 2T4R wireless device supports UL MIMO transmission with multiple data layers. Currently, the 3GPP communication standard specifies a single common modulation and coding scheme (MCS) value for the multiple data layers, even though the performance of different antennas may vary. For example, when each data layer is transmitted separately via respective antennas (or antenna ports) and the performance of each antenna is significantly different, the UL performance via the better data layer may be limited by the MCS value selected to accommodate the worse data layer. Large signal performance imbalance has been observed between different antennas in wireless devices operating in cellular radio networks, such as a difference of 20 dB. In addition, Doppler shift and multipath interference may cause different propagation attenuations of different antennas of the wireless device, which also affects performance and results in imbalance between different antennas. Mapping the antennas based on the measured performance and / or known characteristics of the antennas (or antenna ports) can improve UL throughput.

[0038] When using a specific frequency band, the maximum transmit power level (MTPL) of different antennas (or antenna ports) of the wireless device may also vary among the different antennas (or antenna ports). When the MTPL difference between different antennas (or antenna ports) within each set of antennas (e.g., antenna pairs) that can be used by the wireless device for UL transmission satisfies the MTPL difference threshold, the wireless device can indicate the strongest antenna in each set of antennas to the base station of the cellular radio network. For example, a 2T4R wireless device can provide an indication to the base station when the antennas within each available antenna pair have MTPL values that differ by at least the MTPL difference threshold (such as 3 dB). (Due to hardware limitations of the wireless device, not all antenna pairs of the wireless device can be used for MIMO UL transmission.) The wireless device can provide the indication of the strongest antenna in the antenna group by transmitting a specific TPMI group value to the base station and map the strongest antenna in each set of available antennas to the same (e.g., first) SRS port of the corresponding SRS resource associated with the set of antennas. Through the MTPL mapping of antennas to SRS ports performed by the wireless device (which may know the performance limitations of different antennas), and through the indication that a specific SRS resource port of each SRS resource is associated with the strongest transmission (the highest MTPL value within the antenna group), the base station can (at least partially) take into account the difference in MTPL values. When the MTPL difference between the respective antennas (or antenna ports) within at least one set of antennas (or antenna ports) that the wireless device can use does not satisfy the MTPL difference threshold (e.g., less than 3 dB), the wireless device can avoid reporting the specific TPMI group value to the base station. The MTPL values of the respective antennas may vary depending on the different radio frequency (RF) bands used by the wireless device, and thus when using some RF bands, the wireless device can provide the TPMI group value to the base station, while when using other RF bands, the wireless device may not provide the TPMI group value to the base station.

[0039] In some embodiments, the base station determines whether the MTPL value for SRS resource transmission or PUSCH transmission by the wireless device is restricted. The base station may use the power headroom (PH) value included in the power headroom report (PHR) provided by the wireless device to determine whether the PUSCH transmission is restricted by MTPL. The base station may use the PH value scaled according to the ratio of the bandwidth for the SRS resource transmission to the bandwidth used for the PUSCH transmission to determine whether the SRS resource transmission is restricted by MTPL. When the PUSCH transmission is restricted by MTPL, the base station may adjust the received SRS resource transmission measurement results by an adjustment factor, for example, increasing the received SRS value by 3 dB. When the SRS resource transmission is restricted by MTPL, the base station may adjust the received SRS resource transmission measurement results by another adjustment factor, for example, decreasing the received SRS value by 3 dB. By adjusting the received SRS resource transmission measurement results that can be used to select an antenna (or antenna port), the base station (at least partially) compensates for the MTPL restriction.

[0040] In some embodiments, a wireless device using coherent UL multiple-input multiple-output (MIMO) transmission calculates the channel capacity of a group of antennas (or antenna ports) that can be jointly used for the UL MIMO transmission, and selects an antenna group to map to the SRS ports of the SRS resources in an SRS resource set designed for codebook use based on the calculated channel capacity. The wireless device estimates the channel information of each antenna of the wireless device. The wireless device may also monitor downlink signal metrics (such as signal strength or signal quality, for example, reference signal received power (RSRP) value or signal-to-noise plus interference (SINR) value), and for each antenna, determine a scaling factor to adjust the estimated channel information. The scaling factor may include the transmission and reception characteristics of the corresponding antenna, such as the total radiated power (TRP) value and the total isotropic sensitivity (TIS) value of the antenna. The wireless device determines the cross-correlation channel information matrix of antenna pairs (or other groups), and uses the cross-channel capacity derived from the cross-correlation channel information matrix (such as based on the eigenvalues of the cross-correlation channel information matrix) to select an antenna combination to map to the SRS resource.

[0041] These and other embodiments are discussed below with reference to Figures 1A to 10 ; however, those skilled in the art will readily understand that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting.

[0042] Figure 1AFIG. 100 is a block diagram illustrating an exemplary system configured to implement downlink (DL) precoder selection based on an uplink (UL) sounding reference signal (SRS) resource set designated for “antenna switching” for a wireless device 102. The wireless device 102 includes a single transmitter (transmission chain) and multiple receivers (reception chains) communicatively coupled to multiple antennas 104-A, 104-B, 104-C, and 104-D. The single transmitter of the wireless device 102 can transmit an uplink (UL) signal to a gNodeB 112 (base station) of a cellular radio network via individual antennas 104-A / B / C / D, and receive one or more downlink (DL) signals from the gNodeB 112 via one or more of the multiple antennas 104-A / B / C / D. The wireless device 102 can indicate to the gNodeB 112 of the cellular radio network the transmit and receive capabilities of the wireless device 102, such as a single transmit four receive configuration of the wireless device 102 designated as 1T4R. Depending on how the wireless device 102 is being used, based on the orientation of the wireless device 102 and / or based on adjacent (or nearby) objects that block or interfere with radio frequency (RF) signals between the wireless device 102 and the gNodeB 112, transmissions via different antennas 104-A / B / C / D may experience different uplink channel conditions to the gNodeB 112.

[0043] The gNodeB 112 can configure the wireless device 102 with a sounding reference signal (SRS) resource set 106-A that includes four SRS resources SRS-0, SRS-1, SRS-2, and SRS-3. In some embodiments, the gNodeB 112 configures the wireless device 102 with multiple SRS resource sets 106, where each SRS resource set 106 can be used for a different purpose. The SRS resource set 106-A can be designated for measuring UL transmission characteristics by the gNodeB 112 and determining a DL precoder for transmitting signals from the gNodeB 112 to the wireless device 102. Since the single transmitter wireless device 102 can switch between different antennas to transmit different SRS resources in the SRS resource set 106-A to the gNodeB 112, such use of the SRS resource set 106-A can also be referred to as “antenna switching”.

[0044] The SRS resource set 106 can be designated for periodic, semi-persistent, or aperiodic transmission. In some embodiments, the SRS resource set 106 configured for the wireless device 102 is designated as periodic, and the gNodeB 112 expects the wireless device 102 to periodically transmit the SRS resources of the SRS resource set 106 to measure the UL channel. In some embodiments, the SRS resource set 106 configured for the wireless device 102 is designated as aperiodic, and the gNodeB 112 transmits a downlink control information (DCI) message to the wireless device 102 to trigger the transmission of the SRS resources of the SRS resource set 106 at a specified time for UL channel measurement.

[0045] During one or more OFDM symbols of a time slot of the UL orthogonal frequency division multiplexing (OFDM) frame transmitted by the wireless device 102 to the gNodeB 112, four SRS resources SRS-0, SRS-1, SRS-2, and SRS-3 are successively transmitted via respective antennas (or antenna ports) 104-A, 104-B, 104-C, and 104-D. The gNodeB 112 of the cellular radio network measures the received SRS resource signals SRS-0, SRS-1, SRS-2, and SRS-3, and selects a DL precoder for subsequent DL transmission based on the measurement of the received SRS resource signals SRS-0, SRS-1, SRS-2, and SRS-3. The gNodeB 112 provides an indication of the selected DL precoder by transmitting a precoding matrix index (PMI) value to the wireless device 102. The gNodeB 112 then uses the selected DL precoder to transmit a precoded transmission to the wireless device 102.

[0046] Figure 1B FIG. 120 illustrates an example of an SRS resource set 106-B used by the wireless device 102 for UL sounding. The base station (e.g., gNodeB 112) configures the wireless device 102 with an SRS resource set 106-B designated for UL sounding (also referred to as codebook use). In Figure 1BIn the example, the SRS resource set 106-B includes an SRS resource SRS-0, which can be transmitted by the wireless device 102 using one or more OFDM symbols of a time slot through any one of the antennas 104-A, 104-B, 104-C, and 104-D of the wireless device 102. The wireless device 102 can monitor the DL performance received via all antennas 104-A / 104-B / 104-C / 104-D to estimate the UL channel, and select the best antenna for UL transmission to the gNodeB 112 at any given time. The wireless device 102 can map the SRS resource SRS-0 to the identified best antenna, and transmit the SRS resource SRS-0 to the gNodeB 112 to allow the gNodeB 112 to measure the UL channel via the selected antenna. The gNodeB 112 can measure the received SRS resource SRS-0, and estimate the UL channel for subsequent UL transmissions to be received from the wireless device 102. Before transmitting the SRS resource SRS-0 to the gNodeB 112, the wireless device can select different antennas at different times to map to the SRS resource SRS-0. In Figure 1B the example, the wireless device 102 (based on DL measurements and without feedback from the gNodeB 112) performs open-loop antenna selection, and the gNodeB 112 adapts the receiver parameters based on the reception of the SRS resource SRS-0.

[0047] Figure 1CFIG. 130 illustrates an example of an SRS resource set for UL sounding and closed-loop antenna selection based on SRS indicator (SRI) values provided by gNodeB 112 to wireless device 102. The wireless device 102 may indicate to the gNodeB 112 the transmit and receive capabilities of the wireless device 102, such as a single transmit four receive configuration of the wireless device 102 designated as 1T4R. Depending on how the wireless device 102 is being used, based on the orientation of the wireless device 102 and / or based on adjacent (or nearby) objects blocking or interfering with the radio frequency (RF) signal between the wireless device 102 and the gNodeB 112, transmissions via different antennas 104-A / B / C / D may experience different uplink channel conditions to the gNodeB 112. The gNodeB 112 may configure the wireless device 102 with a sounding reference signal (SRS) resource set 106-C, which includes two SRS resources, SRS-0 and SRS-1, each SRS resource having a single SRS port. The SRS resource set 106-C may be designated for use in the case of a particular UL physical layer channel, such as the physical uplink shared channel (PUSCH). The wireless device 102 selects an antenna pair (e.g., 104-A / 104-B) and, during one or more OFDM symbols of a time slot of a UL OFDM frame, sequentially transmits two SRS resources, SRS-0 and SRS-1, to the gNodeB 112 via respective antennas (or antenna ports) 104-A and 104-B. The gNodeB 112 of the cellular radio network measures the received SRS resource signals SRS-0 and SRS-1 and selects an antenna in the antenna pair for the wireless device 102 for subsequent PUSCH transmission based on the measurements of the received SRS resource signals SRS-0 and SRS-1. The gNodeB 112 provides an indication of the selected antenna by transmitting an SRS indicator (SRI) value to the wireless device 102, the SRS indicator (SRI) value specifying the SRS signal corresponding to the selected antenna. For example, for a one-bit value SRI, the SRI value '0' may correspond to SRS-0, while the SRI value '1' may correspond to SRS-1. The wireless device 102 knows through which antenna (or antenna port) 104-A or 104-B different SRS resource signals SRS-0 and SRS-1 are transmitted and can infer the antenna selection from the SRI value. The wireless device 102 then uses the selected antenna 104-A or 104-B to transmit the PUSCH to the gNodeB 112.

[0048] The wireless device 102 may determine to switch to using a different antenna pair (e.g., antennas 104-C / 104-D), such as based on DL performance measured via different antennas 104-A / 104-B / 104-C / 104-D, and determine that the antenna pair 104-C / 104-D can provide better UL performance than the currently used antenna pair 104-A / 104-B. In some embodiments, based on the hardware limitations of the wireless device 102, certain antenna pair combinations may be allowed while other antenna pair combinations are not allowed. The wireless device 102 may successively transmit SRS resources SRS-0 and SRS-1 to the gNodeB 112 via respective antennas (or antenna ports) 104-C and 104-D during one or more OFDM symbols of a time slot of a UL OFDM frame. The gNodeB 112 of the cellular radio network measures the received SRS resource signals SRS-0 and SRS-1 and selects an antenna for the wireless device 102 to be subsequently used for PUSCH transmission based on the measurements of the received SRS resource signals SRS-0 and SRS-1. The gNodeB 112 provides an indication of the selected antenna by transmitting another SRI value to the wireless device 102, the other SRI value specifying the SRS signal corresponding to the selected antenna. The wireless device 102 again knows through which antenna (or antenna port) 104-C or 104-D different SRS resource signals SRS-0 and SRS-1 are transmitted and can infer the antenna selection from the SRI value. The wireless device 102 then uses the selected antenna 104-C or 104-D to transmit a PUSCH to the gNodeB 112.

[0049] Figure 1DFIG. 140 illustrates an example of an SRS resource set 106-D that is designated for “antenna switching” and is used to determine the DL precoder for the 2T4R wireless device 102. A base station of a cellular radio network (e.g., gNodeB 112) configures the wireless device 102 with the SRS resource set 106-D, which includes two SRS resources, SRS-0 and SRS-1, where each SRS resource includes two SRS ports. The wireless device 102 associates SRS-0 with antenna ports A / B and SRS-1 with antenna ports C / D. The wireless device 102 includes two transmit chains and can transmit simultaneously via two antennas (or antenna ports). The wireless device 102 transmits SRS-0 to the gNodeB 112 via antenna ports 104-A and 104-B during one or more OFDM symbols of a time slot of an OFDM frame. The wireless device 102 then transmits SRS-1 to the gNodeB 112 via antenna ports 104-C and 104-D during one or more OFDM symbols of a time slot of the OFDM frame. The gNodeB 112 measures the received versions of the SRS resources SRS-0 and SRS-1 and determines the DL precoder for the DL transmission to the wireless device 102. The gNodeB 112 sends a downlink control information (DCI) message to the wireless device 102, which includes a PMI value to indicate the selected precoder that the gNodeB 112 will use for a subsequent precoded DL transmission to the wireless device 102, e.g., via the physical downlink shared channel (PDSCH). The wireless device 102 can receive and decode the PDSCH knowing the DL precoder used by the gNodeB 112.

[0050] Figure 1EFIG. 150 illustrates an example of an SRS resource set 106-E for UL sounding and SRS indicator (SRI)-based antenna selection for a 2T4R wireless device 102. A gNodeB 112 of a cellular radio network configures the wireless device 102 with an SRS resource set 106-E, which is designated for codebook use and includes two SRS resources, SRS-0 and SRS-1, where each SRS resource includes two SRS ports. The wireless device 102 associates SRS-0 with antenna ports A / B and SRS-1 with antenna ports C / D. The wireless device 102 can determine which antenna ports to pair together based on DL measurements and hardware limitations of the wireless device 102. The wireless device 102 includes two transmit chains and can transmit simultaneously via two antenna ports. The wireless device 102 transmits SRS-0 to the gNodeB 112 via antenna ports 104-A and 104-B during one or more OFDM symbols of a time slot of an OFDM frame. The wireless device 102 then transmits SRS-1 to the gNodeB 112 via antenna ports 104-C and 104-D during one or more OFDM symbols of a time slot of the OFDM frame. The gNodeB 112 measures the received versions of the SRS resources SRS-0 and SRS-1, estimates the UL channel, and selects an antenna pair for the wireless device 102 to use for subsequent UL transmissions (e.g., for PUSCH transmissions). The gNodeB 112 also determines a UL precoder for the wireless device 102 to use for subsequent UL transmissions. The gNodeB 112 transmits a DCI message to the wireless device 102, which includes an SRI value and a transmit PMI (TPMI) value, where the SRI value indicates the SRS resource associated with the antenna pair selected by the gNodeB 112 for the wireless device 102 to use, and the transmit PMI (TPMI) value indicates the UL precoder for the wireless device 102 to use for UL transmissions. The wireless device 102 then uses the antenna pair (indicated by the SRI value) selected by the gNodeB 112 and the UL precoder matrix (indicated by the TPMI value) selected by the gNodeB 112 to transmit the PUSCH. Depending on the number of layers supported by the wireless device 102 for UL MIMO transmissions, the precoding matrix can select one or both antennas in the antenna pair for the wireless device 102 to use when operating in a non-coherent mode.

[0051] Figure 1FFIG. 160 illustrates another example of the SRS resource set 106-F used by the 2T4R wireless device 102 for UL sounding. The gNodeB 112 configures the wireless device 102 with the SRS resource set 106-F, which is designated for codebook use and includes a single SRS resource SRS-0 having two SRS ports. The wireless device 102 can group antenna pairs together based on the hardware capabilities of the wireless device 102 and select an antenna pair for UL transmission based on DL measurements of the signals received via antennas 104-A / 104-B / 104-C / 104-D. In Figure 1F the example, the wireless device 102 pairs antennas 104-A and 104-B together in a first antenna group and pairs antennas 104-C and 104-D together in a second antenna group. The wireless device 102 can select an antenna group (e.g., antenna pair 104-A / 104-B) and transmit the SRS resource SRS-0 to the gNodeB 112 via the selected antenna group. The gNodeB 112 measures the received version of SRS-0, estimates the associated UL channel, and determines a UL precoder for the wireless device 102 to use for subsequent transmissions. Different from Figure 1E the example, the wireless device 102 (instead of the gNodeB 112) selects the antenna group (pair); however, the gNodeB 112 can select antenna 104-A or 104-B or a combination of 104-A and 104-B for the wireless device 102 to use for UL transmission based on the selected UL precoder. The gNodeB 112 transmits a DCI message to the wireless device 102, which includes a TPMI value indicating the selected UL precoder for the wireless device 102 to use subsequently. The wireless device 102 uses the selected precoder to transmit a PUSCH to the gNodeB 112. The wireless device 102 can then determine to switch between using the first antenna pair 104-A / 104-B and the second antenna pair 104-C / 104-D before transmitting the SRS resource SRS-0 to the gNodeB 112. The gNodeB 112 measures the received version of SRS-0 again, estimates the UL channel, determines the UL precoder, and transmits a DCI message with a TPMI value indicating the determined UL precoder for the wireless device 102 to use subsequently when transmitting a PUSCH to the gNodeB 112.

[0052] Figure 2AFIG. 200 illustrates an exemplary uplink transmit chain of wireless device 102. Transmitter 218 may receive a digital data stream 202 of uplink data to be wirelessly communicated to a cellular radio network via one or more antenna ports 214. A digital-to-analog converter (DAC) 204 of transmitter 20 converts the digital data stream 202 into an analog signal, which is modulated by an OFDM modulator 206 of transmitter 218 onto an uplink radio frequency (RF) carrier. The modulated analog signal is amplified by a power amplifier 208 and filtered by a suitable transmit (TX) filter 210 to produce an amplified analog transmit data signal 212, which is wirelessly transmitted via one or more antenna ports 214 over a radio link to the cellular radio network. When multiple antenna ports 214 (or antennas) are used, the UL transmission may be referred to as multiple-input multiple-output (MIMO) transmission and may be used to improve data throughput and / or transmission reliability. The UL transmission output from the antenna ports 214 of wireless device 102 is transmitted at a power level that allows for proper reception by a cell of the cellular radio network. The UL transmission is limited by the radio circuitry of transmitter 218 and the transmission attributes of antenna ports 214. It is required that the UL transmissions from all antenna ports 214 of wireless device 102 meet regulatory requirements, such as specific absorption rate (SAR) limits on human exposure to radio frequency (RF) energy. A maximum transmit power limit (MTPL) may be determined by wireless device 102 for transmission over the radio link used for UL transmission. The MTPL for various transmissions may depend on the RF band used, the radio access technology (RAT) of the transmission, the bandwidth of the transmission, and the physical attributes of the antennas via which the transmission is made. For different transmissions in different RF bands for the same RAT, different antenna ports 214 may have different MTPL values.

[0053] Figure 2B FIG. 220 illustrates uplink transmit data processing for wireless device 102. Codeword data 222 is input to a mapping block 224, which maps the codeword data to different layers for uplink multiple-input multiple-output (MIMO) transmission. The codeword data 222 is an encoded bit stream, which is segmented by the mapping block 224 into individual data layers. Although in Figure 2BOnly two layers are shown, but the same principle of transmit data processing applies to a higher number of layers. The precoder 226 then maps each layer to a different antenna port 228. For non-coherent processing, data from each layer is mapped by the precoder 226 to each antenna port 228, while for coherent processing, data from different layers may be combined by the precoder 226 for output to the antenna port 228. For simplicity, the mapping to OFDM subcarriers and OFDM modulation before transmission by the physical antenna is not shown. The precoder 226 can be represented by matrix operations, where each column of the matrix corresponds to how each layer is mapped to the antenna port 228.

[0054] Figure 2C Figs. 230, 232, 234 show exemplary UL precoding matrices with non-coherent antenna port selection. For single-layer transmission, as shown in Figs. 230, 232, only one layer (layer 0 as shown) of data is scaled and passed by the precoder 226 to the antenna port. A set of precoder matrices for different numbers of transmit layers is defined in the 3GPP cellular radio communication standard. The base station (e.g., gNodeB 112) indicates the selected UL precoder for the wireless device 102 to use by transmitting a TPMI value in a DCI message to the wireless device 102. Different TPMI index values correspond to different precoding matrices. For single-layer transmission, the TPMI index value '0' corresponds to the selection of the first antenna port in the antenna port group, as shown in Fig. 230, while the TPMI index value '1' corresponds to the selection of the second antenna port in the antenna port group. In some embodiments, the wireless device 102 uses an open-loop antenna port group selection process to select an antenna port group (e.g., an antenna pair as exemplified in Figure 2C ), such as based on DL performance monitoring via different antenna ports). In some embodiments, the base station of the cellular radio network (e.g., gNodeB 112) uses a closed-loop antenna port group selection process to select an antenna port group (such as based on UL measurements of the SRS signal), and indicates the selected antenna port group by transmitting an SRS indicator (SRI) value to the wireless device 102 in a DCI message having the TPMI value of the selected precoding matrix. For two-layer transmission, the TPMI index value '0' corresponds to independently mapping each layer to a separate antenna port in the antenna port group, e.g., mapping layer 0 to the first antenna port and mapping layer 1 to the second antenna port. Figure 2C The exemplary UL precoding matrices shown in Figs. correspond to non-coherent transmission, where data from each layer is only transmitted to each antenna port. Coherent transmission would allow combining data from each layer before transmission to the antenna port.

[0055] Figure 2DA table illustrating exemplary maximum transmit power level (MTPL) values for respective antenna ports of a wireless device 102 when operating using different 5G New Radio (NR) radio frequency bands. The physical hardware of the transmit chain including the antenna ports may vary in terms of MTPL capabilities. The MTPL variations between antenna ports may be unknown to a base station of a cellular radio network (e.g., gNodeB 112) that measures UL SRS signals to determine antenna sets and / or antenna ports for subsequent UL transmissions (e.g., PUSCH transmissions transmitted by the wireless device 102 after SRS-based measurements and adaptation by the base station (e.g., gNodeB 112)). The received power level of the measurement of the SRS signal at the base station includes path loss attenuation that reduces the transmit power level of the SRS signal transmitted by the wireless device 102. The base station may estimate the path loss based on the SRS signal; however, the base station is not aware of the different MTPL values of the different antenna ports of the wireless device 102. In some cases, the transmit power level of the SRS signal may be limited based on the MTPL value. For example, when the SRS signal uses a wide bandwidth and the PUSCH transmission uses a narrow bandwidth, the transmit power level of the subsequent PUSCH transmission may not be limited. Thus, the base station may attribute the MTPL limitation of the SRS transmission via an antenna port to the path loss of that antenna port and select a different antenna port for the PUSCH transmission, even when the PUSCH transmission may not be subject to the MTPL limitation when transmitted via the antenna port that is subject to the MTPL limitation for the SRS transmission. Alternatively, the SRS transmission may not be subject to the MTPL limitation while the subsequent PUSCH transmission may be subject to the MTPL limitation, which may also result in errors in the UL signal path loss estimation and antenna port selection at the base station. As further described herein, the base station may estimate whether the SRS transmission and / or the PUSCH transmission is subject to the MTPL limitation and compensate for the MTPL limitation when evaluating UL performance and selecting an antenna set and / or antenna port for the wireless device 102 for PUSCH transmission.

[0056] Figure 3Tables 300, 310, and 320 illustrate examples of mapping SRS resources in an SRS resource set designated for codebook use to the antenna ports of a 2T4R wireless device 102. Prior art methods for antenna port mapping can arbitrarily assign different antenna ports to different SRS resources; however, this arbitrary assignment may result in poor performance. Instead, the wireless device 102 can measure the downlink performance metrics of each antenna port of the wireless device 102, such as signal strength (such as the reference signal received power (RSRP) value) and / or signal quality (such as the signal-to-interference-plus-noise (SINR) value). The wireless device 102 can consider the respective antenna port characteristics known to the wireless device 102, such as the MTPL limits transmitted with different bandwidths when using different RF bands, the total isotropic sensitivity (TIS) value of the receive chain of the antenna port, and the total radiated power (TRP) value of the transmit chain of the antenna port. The wireless device 102 can map a set of antenna ports to different SRS resources to achieve balanced and / or optimal performance for transmission and / or reception via individual antenna ports and / or combinations of antenna ports. For the 2T4R wireless device 102 with two UL transmit chains, the wireless device 102 can group the four antenna ports into antenna port groups, each antenna port group having two antenna ports, where each antenna port group can have comparable signal performance metrics. For example, the wireless device 102 can use the performance metrics to rank the individual antenna ports and then map these antenna ports to SRS resources as shown in Tables 300, 310, or 320. For Table 300, the wireless device 102 groups the two best antenna ports together as the first antenna port group and maps the first antenna port group to the first SRS resource in the SRS resource set, such as mapping to SRS-0. The wireless device 102 also groups the next two best (or, in the case of only having four antenna ports, the two worst) antenna ports together as the second antenna port group and maps the second antenna port group to the second SRS resource in the SRS resource set, such as mapping to SRS-1. Alternatively, as shown in Table 310, the wireless device 102 can map the first antenna port group to the second SRS resource in the SRS resource set, such as mapping to SRS-1, and map the second antenna port group to the first SRS resource in the SRS resource set, such as mapping to SRS-0. As described for Figure 1E what is described, the wireless device 102 can transmit SRS resources via each antenna group respectively, and the base station can select an antenna group and a precoding matrix for the wireless device to subsequently use for UL physical layer channel transmission, such as for PUSCH transmission. The base station can use the SRI value to indicate the selected antenna group, and the SRI value indicates the SRS resource associated with the selected antenna group. The base station can also indicate a specific non-phase precoding matrix by indicating a specific TPMI value to select individual antennas within the selected antenna group.

[0057] In an alternative configuration, the wireless device 102 groups the two best antennas into an antenna group and maps the antenna group to a single SRS resource SRS-0 in an SRS resource set configured for the wireless device 102 and designated for codebook use, where the SRS resource set includes only SRS-0, as shown in Table 320. The wireless device 102 transmits the SRS resource SRS-0 to the base station via the antenna group, and the base station determines a UL transmission precoder for the wireless device 102 and indicates the determined UL transmission precoder by transmitting a TPMI value to the wireless device 102 in a DCI message. This alternative arrangement summarized in Table 320 corresponds to Figure 1F the UL sounding scheme illustrated in. The wireless device 102 may change the antenna grouping and mapping based on DL performance metric monitoring. The base station may not be aware of the change in the antenna grouping and / or the mapping of the antenna group to the SRS resource by the wireless device 102, although there is still a change in UL performance and a selection of a precoder for the two-port SRS resource transmitted via the antenna group.

[0058] Figure 4 FIG. 400 illustrates an example of device-based antenna grouping and mapping and network-based closed-loop antenna group (pair) selection for a 2T4R wireless device 102. The wireless device 102 monitors the DL performance metrics of four antenna ports, pairs these antenna ports together into antenna port pairs, and maps these antenna port pairs to SRS resources in an SRS resource set configured for the wireless device 102 and designated for codebook use. As Figure 4As shown, initially antenna ports A and B are grouped together, mapped to SRS-0, and have a higher performance metric than antenna ports C and D, which are also grouped together and mapped to SRS-1. Wireless device 102 transmits SRS resources SRS-0 and SRS-1 in the SRS resource set to the base station via the assigned (mapped) antenna port pairs A / B and C / D, respectively. The base station measures the received SRS resources and selects an antenna port pair A / B or C / D for UL transmission. The base station uses the SRI value in the DCI message (e.g., SRI = '0' for selecting the antenna port pair A / B associated with SRS-0) to indicate the selected antenna port pair to wireless device 102. Wireless device 102 then transmits a UL physical layer channel transmission, such as a PUSCH transmission, via the selected antenna port pair A / B. Wireless device 102 can continue to use the selected antenna port pair A / B and change which antenna port pair to use based on subsequent SRI received from the base station. Wireless device 102 can continue to monitor the downlink performance via multiple antenna ports and change the grouping of antenna ports into antenna port pairs and the mapping of antenna port pairs to SRS resources. The time interval between successive changes in antenna port grouping and mapping can be significantly longer than the time interval between successive SRS transmissions and SRI responses. As Figure 4 As shown, wireless device 102 re-groups the antenna ports into new antenna port pairs based on the measured DL performance metric, where antenna ports A and D are grouped together and mapped to SRS-0, while antenna ports B and C are grouped together and mapped to SRS-1. Wireless device 102 transmits SRS resources SRS-0 and SRS-1 in the SRS resource set to the base station via the assigned (mapped) antenna port pairs A / D and B / C, respectively. The base station measures the received SRS resources and selects an antenna port pair A / D or B / C for UL transmission. The base station uses the SRI value in the DCI message (e.g., SRI = '0' for selecting the antenna port pair A / D associated with SRS-0) to indicate the selected antenna port pair to wireless device 102. Wireless device 102 then transmits a UL physical layer channel transmission, such as a PUSCH transmission, via the selected antenna port pair A / D.

[0059] In some cases, e.g., due to hardware limitations of wireless device 102, only certain antenna port groupings are available for UL MIMO transmission. When different antenna ports are grouped together (e.g., paired) as an antenna port group for mapping to SRS resources, wireless device 102 can be restricted to using only specific antenna port groupings. As discussed herein, different antenna ports can have different MTPL values for full (or wide) bandwidth transmission, examples of which are summarized in Figure 2D Table 240 of Figure 5Ais shown again. Grouping antenna ports together into antenna port groups may result in antenna ports having different MTPL values within the same antenna port group. Figure 5A Tables 500, 510, 520 illustrate examples of MTPL differences of antenna port pairs of the 2T4R wireless device 102 when transmitted in different 5G NR radio frequency bands, where the antenna ports of the wireless device 102 have the MTPL values shown in Table 240. For the 2T4R wireless device 102, exemplary allowed antenna port groupings include antenna port pairs A / B, C / D, A / D, and B / C, while exemplary disallowed antenna port groupings (e.g., due to hardware limitations of the 2T4R wireless device 102) include antenna port pairs A / C and B / D. The MTPL differences of different antenna port pairs may vary based on the 5G NR frequency band used for UL transmission. For the n41 band (which is a time division duplex (TDD) band at 2.5 GHz), all combinations of antenna port pairings have an MTPL difference of less than 3 dB, as shown in Table 500. For the n78 and n79 bands (which are TDD bands at 3.5 GHz and 4.7 GHz, respectively), all combinations of antenna port pairs have an MTPL difference of at least 3 dB, as shown in Table 510. Table 520 summarizes the MTPL differences of disallowed antenna pair combinations that the wireless device 102 cannot use.

[0060] A base station that measures the performance of an antenna port group may not know the MTPL difference between the antenna ports within each antenna port group. To overcome this limitation, in some embodiments, the wireless device 102 maps the strongest antenna port within each antenna port group to a specific SRS port within the SRS resource, such as to the SRS resource with the lowest index value (alternatively, the highest index value). The wireless device 102 may signal the mapping of the strongest antenna port to the base station by reporting a specific TPMI group value. In some embodiments, the wireless device 102 reports full power mode 2 capability to the base station and provides the two-port TPMI group value '01' to indicate that the strongest antenna port in each antenna port group is mapped to the first SRS port (e.g., SRS-0) of the SRS resource associated with that antenna port group. Alternatively, the wireless device 102 may report full power mode 2 capability to the base station and provide the TPMI group value '10' to indicate that the strongest antenna port in each antenna port group is mapped to the second SRS port (e.g., SRS-1) of the SRS resource associated with that antenna port group. When the MTPL difference between the antenna ports in all antenna port groups (pairs) meets the MTPL difference threshold (e.g., at least 3 dB), the wireless device 102 may selectively transmit the two-port TPMI group value, and when the MTPL difference between the antenna ports in all antenna port groups (pairs) does not meet the MTPL difference threshold (e.g., at least one antenna port pair has an MTPL difference of less than 3 dB), the wireless device 102 may avoid transmitting the two-port TPMI group value. For the n41 band shown in Table 500, the wireless device 102 does not report the two-port TPMI group value because the MTPL difference between the antenna ports in the antenna port group does not meet the MTPL difference threshold (e.g., 3 dB). For the n78 and n79 bands shown in Table 510, the wireless device 102 does report the two-port TPMI group value because the MPTL differences between the antenna ports in the antenna groups all meet the MTPL difference threshold (e.g., 3 dB). The base station may identify the reported full power mode 2 capability and the reported TPMI group value to know that the indicated antenna port (at a specific location within the antenna port group) has higher performance (e.g., a higher MTPL value), and may consider this difference in MPTL values between the antenna ports when determining antenna port group selection and / or when determining antenna port selection within an antenna port group.

[0061] In some embodiments, the base station estimates whether SRS transmission or PUSCH transmission is limited by MTPL for each antenna port in an antenna port group (pair), and compensates for the MTPL limitation (of SRS transmission or PUSCH transmission) when determining antenna port selection. Figure 5BTables 530 and 540 illustrate examples of antenna port selection with and without adjustment based on MTPL constraints for a first representative example (Case A), in which the SRS transmission of wireless device 102 is subject to MTPL constraints, while the PUSCH transmission of wireless device 102 is not subject to MTPL constraints. In Table 530, the base station does not adjust antenna selection for MTPL constraints. Wireless device 102 is configured with an SRS resource set that includes SRS resources having two SRS ports 0 and 1 mapped to respective antenna ports A and B. The transmission of the SRS resource by wireless device 102 via antenna port A is limited to 28 dBm, and the transmission of the SRS resource via antenna port B is limited to 25 dBm. In the example of Table 530, the actual path loss attenuation for transmissions via antenna ports A and B are 100 dB and 99 dB, respectively, resulting in a received SRS resource measurement of -72 dBm for antenna port A and a received SRS resource measurement of -74 dBm for antenna port B. In the example of Table 530, the base station does not recognize the MTPL constraints affecting the received SRS resource measurement and may determine that antenna port A (associated with SRS port 0) has better performance and select antenna port A for subsequent PUSCH transmission. However, when transmitting PUSCH, wireless device 102 is not subject to the MTPL constraints of these antenna ports, as the PUSCH transmission power level via each antenna port is only 15 dBm, resulting in a received PUSCH power level of -85 dBm for antenna port A and a received PUSCH power level of -84 dBm for antenna port B. In this case, the UL performance of the PUSCH via antenna port B is better than that of antenna port A, and the base station may make an incorrect decision for PUSCH transmission based on using the SRS measurement results without compensating for the MTPL difference between the antenna ports. In Table 540, the base station does not consider MTPL constraints when selecting antenna ports. The base station determines that the SRS of SRS port 0 (corresponding to antenna port A) is subject to MTPL constraints and downward adjusts the received SRS power level of SRS port 0 by subtracting an adjustment factor (e.g., 3 dB) from the measured received SRS power level. By this adjustment, the base station can select and indicate SRS port 1 corresponding to antenna port B, which can provide a higher level of performance for subsequent PUSCH transmission compared to antenna port A. By this adjustment, the base station makes a correct decision for PUSCH transmission by considering the MTPL difference between the antenna ports.

[0062] Figure 5CTables 550 and 560 illustrate examples of antenna port selection with and without adjustment based on MTPL constraints for a second representative example (Case B), in which the SRS transmission of wireless device 102 is not subject to MTPL constraints, while the PUSCH transmission of wireless device 102 is subject to MTPL constraints. In Table 550, when determining antenna selection, the base station does not consider MTPL constraints. Wireless device 102 is configured with an SRS resource set that includes SRS resources having two SRS ports 0 and 1 mapped to respective antenna ports A and B. Wireless device 102 transmits the SRS resource at 15 dBm via antenna port A and at 15 dBm via antenna port B. The SRS transmission in Case B may use a narrower bandwidth (and thus less total power) than the SRS transmission in Case A. In the example of Table 550, the actual path loss attenuation for transmissions via antenna ports A and B are 100 dB and 99 dB, respectively, resulting in a measured SRS resource at the receiving side of antenna port A of -85 dBm and a measured SRS resource at the receiving side of antenna port B of -84 dBm. In the example of Table 550, the base station does not recognize that subsequent PUSCH transmissions will have MTPL constraints and may determine that antenna port B (associated with SRS port 1) has better performance and select antenna port B for subsequent PUSCH transmissions. However, when transmitting PUSCH, wireless device 102 is subject to the MTPL of the antenna port, since the PUSCH transmission power level via antenna port A is limited to 28 dBm and the PUSCH transmission power level via antenna port B is limited to 25 dBm, resulting in a received PUSCH power level of -72 dBm for antenna port A and a received PUSCH power level of -74 dBm for antenna port B. In this case, the UL performance of the PUSCH via antenna port A is better than that of antenna port B, and the base station may make an incorrect decision for PUSCH transmission based on using the previously received SRS measurement results without compensating for the MTPL difference of the antenna port for subsequent PUSCH transmissions. In Table 560, the base station does not consider MTPL constraints when selecting antenna ports. The base station determines that the PUSCH of SRS port 0 (corresponding to antenna port A) is subject to MTPL constraints and upward adjusts the received SRS power level of SRS port 0 by adding an adjustment factor (e.g., 3 dB) to the measured received SRS power level. By this adjustment, the base station can select and indicate SRS port 0 corresponding to antenna port A, which can provide a higher level of performance for subsequent PUSCH transmissions compared to antenna port B. By this adjustment, the base station makes a correct decision for PUSCH transmission by considering the MTPL difference of the antenna port.

[0063] The base station can determine whether the PUSCH transmission of the wireless device 102 is limited by MTPL based on the power headroom report (PHR) provided by the wireless device 102. The base station can also use the power headroom (PH) value included in the PHR and the knowledge of the bandwidths for PUSCH transmission and SRS transmission respectively to determine whether the SRS transmission of the wireless device 102 is limited by MTPL. The PHR can provide the PH value of the PUSCH, and the wireless device 102 can scale the PH value of the PUSCH based on the ratio of the bandwidth for PUSCH transmission to the bandwidth for SRS transmission to derive the corresponding PH value of the SRS.

[0064] In some embodiments, the wireless device 102 supports coherent UL MIMO transmission. In this case, grouping antenna ports together based on the performance of each antenna port (as in the case of non - coherent UL MIMO) may not provide an optimal solution. Instead, the wireless device 102 can determine the optimal antenna port combination based on the performance metrics of each antenna port and the channel correlation between the UL channels of different antenna ports in the antenna port combination. The wireless device can determine the allowable antenna port groupings. For example, for a 2T4R wireless device 102, the allowable antenna port groups can include antenna port combinations of {A,B}, {C,D}, {A,D}, and {B,C}. The wireless device 102 can then select an antenna port group to map to the first codebook SRS resource based on the estimated channel capacity of each of these antenna port combinations. The wireless device 102 can monitor the downlink performance metrics of each antenna port, such as the signal strength (e.g., reference signal received power (RSRP) value) and the signal quality (e.g., signal - to - interference - plus - noise (SINR) value). The wireless device 102 can also measure (or obtain from the base station) the estimated channel information value of each antenna port. The estimated channel information value of antenna port 'x' can be represented as H port_x . The wireless device 102 can determine the scaling factor for each antenna port based on a linear combination of the SINR value SINR port_x of the antenna port, the MTPL value MTPL port_x of the antenna port, the TIS value TIS port_x of the antenna port, and the TRP value TRP port_x of the antenna port. The scaling factor is represented as Scaling port_x .

[0065] Scaling port_x = linear(SINR port_x + MTPL port_x + TIS port_x - TRP port_x )

[0066] The wireless device 102 may apply the scaling factor of each antenna port to the channel information estimate of the corresponding antenna port to derive a scaled channel information estimate for each antenna port.

[0067]

[0068] The wireless device 102 may derive the cross-correlation channel information matrix R between two antenna ports x and y as follows <x,y> , where ( ) H denotes the Hermitian transform.

[0069]

[0070]

[0071] The wireless device 102 may determine the mutual information channel capacity of the antenna port combination of antenna ports x and y based on the eigenvalues of the cross-correlation channel information matrix R <x,y> . The wireless device 102 may select the best antenna port combination (e.g., the best antenna port pair) having the highest mutual information channel capacity, and map two SRS ports of the first codebook SRS resource to the selected best antenna port combination (pair).

[0072] Figure 6 FIG. 600 is a flow chart showing an exemplary method for UL transmit antenna selection for the wireless device 102. At 602, the wireless device 102 monitors one or more downlink signal performance metrics of each of the plurality of antenna ports of the wireless device 102. At 604, the wireless device 102 groups each of the plurality of antenna ports into antenna port groups based on the one or more downlink signal performance metrics. At 606, the wireless device 102 maps the antenna port groups to SRS resources in a sounding reference signal (SRS) resource set, where each SRS resource includes a plurality of SRS ports. At 608, the wireless device 102 transmits the plurality of SRS resources to a base station of a cellular radio network via the corresponding antenna port groups. At 610, the wireless device 102 receives a downlink control information (DCI) message from the base station, the downlink control information (DCI) message including an SRS indicator (SRI) value that selects a particular antenna port group. At 612, the wireless device 102 transmits a PUSCH transmission to the base station via the selected antenna port group.

[0073] In some embodiments, the wireless device 102 groups each of the plurality of antenna ports together into antenna port groups based on the grouped antenna ports having comparable downlink signal performance metrics. In some embodiments, the wireless device maps the antenna port groups to the SRS resources by at least the following operations: i) mapping a first antenna port group having the highest value downlink signal performance metric to a first SRS resource; and ii) mapping a second antenna port group having the second highest value downlink signal performance metric to a second SRS resource. In some embodiments, the first SRS resource corresponds to an SRS resource identifier value of 0. In some embodiments, the first SRS resource corresponds to an SRS resource identifier value of 1. In some embodiments, the method for UL transmission selection performed by the wireless device 102 further includes the wireless device 102: i) continuing to monitor the one or more downlink signal performance metrics of each of the plurality of antenna ports; ii) re-grouping each of the plurality of antenna ports into new antenna port groups based on one or more updated downlink signal performance metrics; iii) re-mapping the new antenna port groups to the plurality of SRS resources; and iv) transmitting the plurality of SRS resources to the base station via the respective re-mapped antenna port groups. In some embodiments, re-grouping the plurality of antenna ports includes: pairing at least one antenna port with an antenna port different from the antenna port previously paired in the antenna port group. In some embodiments, the one or more downlink signal performance metrics of each antenna port include one or more of the following: reference signal received power (RSRP), reference signal received quality (RSRQ), or signal-to-interference plus noise (SINR) of the respective antenna port. In some embodiments, the DCI message further includes a transmit precoding matrix indicator (TPMI) value that indicates the precoder to be used by the wireless device 102 when transmitting the PUSCH to the wireless network. In some embodiments, the wireless device 102 is configured for non-coherent uplink multiple-input multiple-output (MIMO) rank 1 transmission, and the TPMI value selects a single antenna port in the antenna port group selected for the PUSCH transmission.

[0074] Figure 7Flowchart 700 illustrates another exemplary method for UL transmission antenna selection for wireless device 102. At 702, wireless device 102 groups each of the multiple antenna ports of wireless device 102 into antenna port groups based on the transmission hardware capabilities of wireless device 102. At 704, wireless device 102 maps the antenna port group to multiple SRS resources in an SRS resource set based on the difference in the maximum transmission power level (MTPL) values of the antenna ports within each antenna port group, where each SRS resource includes multiple SRS ports. At 706, wireless device 102 determines that the MPTL difference of the antenna ports within each antenna port group satisfies the MTPL difference threshold. At 708, the wireless device transmits a capability report to the base station, the capability report indicating that wireless device 102 supports a full power mode 2 configuration with a transmission precoding matrix indicator (TPMI) group value that indicates the antenna port with the highest MTPL value in each antenna port group.

[0075] In some embodiments, wireless device 102 maps the antenna port to the multiple SRS resources by at least the following operations: In each antenna port group, map the antenna port with the highest MTPL value to the SRS resource in the corresponding SRS resource set with the lowest identifier value. In some embodiments, wireless device 102 supports a 2T4R configuration and reports the TPMI group value '01' or '10' for the two-port configuration to the base station of the cellular radio network according to which antenna ports have the highest MTPL value. In some embodiments, the wireless device supports a 4T4R configuration and reports the TPMI group value 'G0', 'G1', 'G2', or 'G3' for the four-port configuration to the base station of the cellular radio network according to which antenna ports have the highest MTPL value. In some embodiments, the method for UL transmission antenna selection further includes wireless device 102: i) transmitting the multiple SRS resources to the base station via the corresponding antenna ports; ii) receiving a downlink control information (DCI) message from the base station, the downlink control information (DCI) message including an SRS indicator (SRI) value that selects an antenna port group; and iii) transmitting a physical uplink shared channel (PUSCH) transmission to the base station via the selected antenna port group.

[0076] Figure 8AFlowchart 800 illustrates another exemplary method for UL transmission antenna selection for wireless device 102. At 802, wireless device 102 groups each of the plurality of antenna ports of wireless device 102 into antenna port groups based on the transmission hardware capabilities of wireless device 102, with each antenna port group having a plurality of antenna ports. At 804, wireless device 102 calculates the channel capacity of each antenna port group. At 806, wireless device 102 maps one or more antenna port groups to SRS resources in a sounding reference signal (SRS) resource set received from the base station based on the channel capacity, where each SRS resource in the SRS resource set includes a plurality of SRS ports. At 808, wireless device 102 transmits the plurality of SRS resources to the base station via the respective antenna port groups. At 810, wireless device 102 receives from the base station a DCI message including an SRI value for the selected antenna port group. At 812, wireless device 102 transmits a PUSCH transmission to the base station via the selected antenna port group.

[0077] Figure 8B Flowchart 820 shows a method for calculating the channel capacity of an antenna port group of wireless device 102. At 822, for each of the plurality of antenna ports of wireless device 102, wireless device 102 determines a downlink signal performance metric and a channel information estimate value. At 824, for each antenna port, wireless device 102 determines a scaling factor based on: i) the corresponding downlink signal performance metric; ii) the maximum transmit power level (MTPL) value of the antenna port; iii) the total isotropic sensitivity (TIS) value of the antenna port; and iv) the total radiated power (TRP) value of the antenna port. At 826, for each antenna port, wireless device 102 determines a scaled channel information estimate value by multiplying the corresponding channel information estimate value by the corresponding scaling factor. At 828, wireless device 102 calculates a cross-correlation channel information matrix for one or more antenna port groups formed by wireless device 102 grouping antenna ports together (such as based on allowable antenna port combinations). At 830, wireless device 102 calculates the channel capacity of the antenna port group based on the eigenvalues of the cross-correlation channel information matrix of the corresponding antenna port group. In some embodiments, the number of antenna port groups exceeds the number of SRS resources in the SRS resource set, and wireless device 102 maps the one or more antenna port groups to the SRS resources by at least: associating antenna port groups with SRS resources starting from the highest channel capacity antenna port group; and continuing in descending order of the calculated channel capacity of the antenna port groups.

[0078] Figure 9Flowchart 900 illustrates a method for UL transmit antenna selection of wireless device 102 performed by a base station (e.g., gNodeB 112) of a cellular radio network. At 902, the base station configures wireless device 102 with a set of SRS resources having a plurality of SRS resources, each SRS resource including a plurality of SRS ports. At 904, the base station determines, based on a power headroom report (PHR) from wireless device 102, that the MTPL value for SRS transmission via an antenna port in an antenna port group of wireless device 102 or for PUSCH transmission via the antenna port is restricted, where the antenna port group is associated with an SRS resource among the plurality of SRS resources in the set of SRS resources. At 906, the base station determines an adjusted received power level of the SRS port of the SRS resource corresponding to the antenna port for which the MTPL value is restricted. At 908, the base station selects a specific antenna port in the antenna port group of wireless device 102 based on the adjusted received power level of the SRS port. At 910, the base station transmits a TPMI value to wireless device 102, the TPMI value indicating that wireless device 102 selects the specific antenna port in the antenna port group for subsequent PUSCH transmission to the base station.

[0079] In some embodiments, the base station determines the adjusted received power level of the SRS port of the SRS resource by at least the following operations: when PUSCH transmission via the antenna port is restricted by MTPL and SRS transmission via the antenna port is not restricted by MTPL, increasing the received power level of the SRS port by an adjustment value. In some embodiments, the base station determines that the MTPL value for PUSCH transmission via the antenna port is restricted based on a power headroom value included in the PHR received from wireless device 102. In some embodiments, the base station determines the adjusted received power level of the SRS port of the SRS resource by at least the following operations: when SRS transmission via the antenna port is restricted by MTPL and PUSCH transmission via the antenna port is not restricted by MTPL, decreasing the received power level of the SRS port by an adjustment value. In some embodiments, the base station determines that the MTPL value for SRS transmission via the antenna port is restricted by at least the following operations: i) calculating a ratio of a first transmission bandwidth for PUSCH transmission to a second transmission bandwidth for SRS transmission; ii) applying the ratio to a reported power headroom value included in the PHR received from the wireless device to derive a scaled power headroom value; and iii) determining, based on the scaled power headroom value, whether the MTPL for SRS transmission is restricted.

[0080] Representative exemplary apparatus

[0081] Figure 10 An exemplary computing device 1000 that can be used to implement the various components and techniques described herein is illustrated in block diagram format. Specifically, a detailed view of the exemplary computing device 1000 illustrates the various components that may be included in a wireless device (e.g., wireless device 102). As Figure 10 shown, the computing device 100 may include one or more processors 1002 representing a microprocessor or controller for controlling the overall operation of the computing device 1000. In some embodiments, the computing device 1000 may also include a user input device 1008 that allows a user of the computing device 1000 to interact with the computing device 1000. For example, in some embodiments, the user input device 1008 may take various forms, such as buttons, keypads, dials, touchscreens, audio input interfaces, visual / image capture input interfaces, input in the form of sensor data, etc. In some embodiments, the computing device 1000 may include a display 1010 (screen display) that can be controlled by the processor 1002 to display information to the user (e.g., information related to incoming, outgoing, or active communication sessions). A data bus 1016 may facilitate data transfer between at least the storage device 1040, the processor 1002, and the controller 1013. The controller 1013 may be used to interact with and control different equipment via an equipment control bus 1014. The computing device 1000 may also include a network / bus interface 1011 coupled to a data link 1012. In the case of a wireless connection, the network / bus interface 1011 may include wireless circuitry, such as a wireless transceiver and / or a baseband processor. The computing device 1000 may also include a security element 1024. The security element 1024 may include an eUICC.

[0082] The computing device 1000 also includes a storage device 1040, which may include a single storage device or multiple storage devices (e.g., hard disk drives), and includes a storage management module that manages one or more partitions within the storage device 1040. In some embodiments, the storage device 1040 may include flash memory, semiconductor (solid-state) memory, etc. The computing device 1000 may also include a random access memory (RAM) 1020 and a read-only memory (ROM) 1022. The ROM 1022 may store programs, utilities, or processes that will be executed in a non-volatile manner. The RAM 1020 may provide volatile data storage and store instructions related to the operation of the computing device 1000.

[0083] Wireless terminology

[0084] According to various embodiments described herein, the terms "wireless communication device", "wireless device", "mobile device", "mobile station", and "user equipment (UE)" may be used interchangeably herein to describe one or more general consumer electronic devices that may be capable of performing processes associated with various embodiments of the present disclosure. According to various specific implementations, any one of these consumer electronic devices may relate to: a cellular phone or smartphone, a tablet computer, a laptop computer, a notebook computer, a personal computer, a netbook computer, a media player device, an e-book device, a device, a wearable computing device, and any other type of electronic computing device having wireless communication capabilities, which wireless communication capabilities may include communication via one or more wireless communication protocols, such as protocols for communicating on the following networks: wireless wide area network (WWAN), wireless metropolitan area network (WMAN), wireless local area network (WLAN), wireless personal area network (WPAN), near field communication (NFC), cellular wireless network, fourth generation (4G) LTE, advanced LTE (LTE-A) 5G, and / or 5G advanced or other currently or future-developed advanced cellular wireless networks.

[0085] In some embodiments, the wireless communication device may also operate as part of a wireless communication system, which may include a group of client devices, also referred to as stations, client wireless devices, or client wireless communication devices, that are interconnected to an access point (AP) (e.g., as part of a WLAN), and / or interconnected to each other (e.g., as part of a WPAN and / or "ad hoc" wireless network). In some embodiments, the client device may be any wireless communication device capable of communicating via WLAN technology (e.g., according to a wireless local area network communication protocol). In some embodiments, WLAN technology may include a Wi-Fi (or more generally, WLAN) wireless communication subsystem or radio component, which Wi-Fi radio component may implement Institute of Electrical and Electronics Engineers (IEEE) 802.11 technology, such as one or more of the following: IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE 802.11n; IEEE 802.11-2012; IEEE 802.11ac; or other currently or future-developed IEEE 802.11 technology.

[0086] In addition, it should be understood that the UEs described herein may be configured as multimode wireless communication devices that are also capable of communicating via different third-generation (3G) and / or second-generation (2G) RATs. In these cases, the multimode user equipment (UE) may be configured to preferentially attach to an LTE network that provides a faster data rate throughput compared to other 3G legacy networks that provide a lower data rate throughput. For example, in some specific implementations, the multimode UE may be configured to fallback to a 3G legacy network, such as an evolved high-speed packet access (HSPA+) network, or a code division multiple access (CDMA) 2000 evolved-data only (EV-DO) network, when 5G, LTE, and LTE-A networks are otherwise unavailable.

[0087] It is well known that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of inadvertent or unauthorized access or use, and the nature of the authorized use should be clearly explained to the user.

[0088] Aspects, embodiments, specific implementations, or features of the described embodiments may be used individually or in any combination. Aspects of the described embodiments may be implemented by software, hardware, or a combination of hardware and software. The described embodiments may also be implemented as computer-readable code on a non-transitory computer-readable medium. A non-transitory computer-readable medium is any data storage device that can store data that can later be read by a computer system. Examples of non-transitory computer-readable media include read-only memory, random access memory, CD-ROM, HDD, DVD, magnetic tape, and optical data storage devices. The non-transitory computer-readable media may also be distributed over network-coupled computer systems such that the computer-readable code is stored and executed in a distributed fashion.

[0089] For purposes of explanation, the foregoing description uses specific names to provide a thorough understanding of the described embodiments. However, it will be apparent to those skilled in the art that no specific details are required in order to practice the described embodiments. Accordingly, the foregoing description of specific embodiments is presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the described embodiments to the precise form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art in light of the above teachings.

Claims

1. A method for uplink (UL) transmit antenna selection of a wireless device for communicating with a base station of a cellular radio network, the method comprises: by the wireless device: monitoring one or more downlink signal performance metrics of each of a plurality of antenna ports; grouping each of the plurality of antenna ports into antenna port groups based on the one or more downlink signal performance metrics; mapping the antenna port groups to a plurality of sounding reference signal (SRS) resources in a SRS resource set, each SRS resource comprising a plurality of SRS ports; transmitting the plurality of SRS resources to the base station via corresponding antenna port groups; receiving a downlink control information (DCI) message from the base station, the downlink control information (DCI) message comprising a sounding reference signal indicator (SRI) value that selects an antenna port group; and transmitting a physical uplink shared channel (PUSCH) transmission to the base station via the selected antenna port group.

2. The method according to claim 1, wherein: each of the plurality of antenna ports is grouped together into the antenna port groups based on having comparable downlink signal performance metrics.

3. The method according to claim 1, wherein: mapping the antenna port groups to the plurality of SRS resources comprises: mapping a first antenna port group having the highest value downlink signal performance metric to a first SRS resource; and mapping a second antenna port group having the second highest value downlink signal performance metric to a second SRS resource.

4. The method according to claim 3, wherein the first SRS resource corresponds to a SRS resource identifier value of 0.

5. The method according to claim 3, wherein the first SRS resource corresponds to a SRS resource identifier value of 1.

6. The method according to claim 1, the method further comprises: continuing to monitor the one or more downlink signal performance metrics of each of the plurality of antenna ports; re-grouping each of the plurality of antenna ports into new antenna port groups based on one or more updated downlink signal performance metrics; re-mapping the new antenna port groups to the plurality of SRS resources; and transmitting the plurality of SRS resources to the base station via corresponding re-mapped antenna port groups.

7. The method according to claim 1, wherein re-grouping the plurality of antenna ports comprises: pairing at least one antenna port with an antenna port different from a previously paired antenna port.

8. The method according to claim 1, wherein the one or more downlink signal performance metrics of each antenna port comprise one or more of the following: reference signal received power (RSRP), reference signal received quality (RSRQ), or signal to interference plus noise (SINR) of the corresponding antenna port.

9. The method according to claim 1, wherein the DCI message further includes a transmit precoding matrix indicator (TPMI) value, and the transmit precoding matrix indicator (TPMI) value indicates the precoder to be used by the wireless device when transmitting the PUSCH to the cellular radio network.

10. The method according to claim 9, wherein: the wireless device is configured for non-coherent uplink multiple-input multiple-output (MIMO) rank-1 transmission; and the TPMI value selects a single antenna port from the antenna port group selected for the PUSCH transmission.

11. A method for uplink (UL) transmit antenna selection of a wireless device for communicating with a base station of a cellular radio network, the method comprises: by the wireless device: grouping each of the multiple antenna ports of the wireless device into antenna port groups based on the transmit hardware capabilities of the wireless device; mapping the antenna port groups to multiple sounding reference signal (SRS) resources in a SRS resource set based on the maximum transmit power level (MTPL) difference between the antenna ports within each antenna port group, each SRS resource including multiple SRS ports; determining that the MTPL difference of the antenna ports in each antenna port group satisfies an MTPL difference threshold; and transmitting a capability report to the base station, the capability report indicating that the wireless device supports a full power mode 2 configuration with a transmit precoding matrix indicator (TPMI) group value, the transmit precoding matrix indicator (TPMI) group value indicating the antenna port with the highest MTPL value in each antenna port group.

12. The method according to claim 11, wherein mapping the antenna ports to the multiple SRS resources comprises: in each antenna port group, mapping the antenna port with the highest MTPL value to the SRS resource with the lowest identifier value in the corresponding SRS resource set.

13. The method according to claim 12, wherein: the wireless device supports a 2T4R configuration and reports to the base station of the cellular radio network a TPMI group value '01' or '10' for a two-port configuration according to which antenna ports have the highest MTPL value.

14. The method according to claim 12, wherein: the wireless device supports a 4T4R configuration and reports to the base station of the cellular radio network a TPMI group value 'G0', 'G1', 'G2' or 'G3' for a four-port configuration according to which antenna ports have the highest MTPL value.

15. The method according to claim 11, the method further comprises: by the wireless device: transmitting the multiple SRS resources to the base station via corresponding antenna ports; receiving a downlink control information (DCI) message from the base station, the downlink control information (DCI) message including a sounding reference signal indicator (SRI) value, the sounding reference signal indicator (SRI) value selecting an antenna port group; and Transmit a Physical Uplink Shared Channel (PUSCH) via a selected antenna port group to the base station.

16. A method for uplink (UL) transmit antenna selection of a wireless device for communicating with a base station of a cellular radio network, the method comprising: by the wireless device: Based on the transmit hardware capabilities of the wireless device, group each of the plurality of antenna ports of the wireless device into antenna port groups, each antenna port group having a plurality of antenna ports; Calculate the channel capacity of each antenna port group; and Based on the channel capacity, map one or more antenna port groups to SRS resources in a sounding reference signal (SRS) resource set received from the base station, each SRS resource in the SRS resource set including a plurality of SRS ports; Transmit the plurality of SRS resources to the base station via the corresponding antenna port group; Receive a Downlink Control Information (DCI) message from the base station, the Downlink Control Information (DCI) message including an SRS indicator (SRI) value that selects an antenna port group; and Transmit a Physical Uplink Shared Channel (PUSCH) to the base station via the selected antenna port group.

17. The method according to claim 16, wherein calculating the channel capacity of the antenna port group comprises: For each of the plurality of antenna ports, determine a downlink signal performance metric and a channel information estimate value; For each antenna port, determine a scaling factor based on: the corresponding downlink signal performance metric; the maximum transmit power level (MTPL) value of the antenna port; the total isotropic sensitivity (TIS) value of the antenna port; and the total radiated power (TRP) value of the antenna port; For each antenna port, determine a scaled channel information estimate value by multiplying the corresponding channel information estimate value by the corresponding scaling factor; Calculate the cross-correlation channel information matrix of the antenna port group; and Based on the eigenvalues of the cross-correlation channel information matrix of the antenna port group, calculate the channel capacity of the antenna group.

18. The method according to claim 16, wherein: the number of antenna port groups exceeds the number of SRS resources in the SRS resource set; and mapping the one or more antenna port groups to the SRS resources includes: associating antenna port groups with SRS resources starting from the highest channel capacity antenna port group and continuing in descending order of the calculated channel capacity of the antenna port groups.

19. A method for uplink (UL) transmit antenna selection of a wireless device for communicating with a base station of a cellular radio network, the method comprising: by the base station: Configure the wireless device with an SRS resource set having a plurality of sounding reference signal (SRS) resources, each SRS resource including a plurality of SRS ports; Based on a power headroom report (PHR) received from the wireless device, it is determined that the maximum transmit power level (MTPL) value for sounding reference signal (SRS) transmission via an antenna port in an antenna port group of the wireless device or the MTPL value for physical uplink shared channel (PUSCH) transmission via the antenna port is restricted, where the antenna port group is associated with an SRS resource among the plurality of SRS resources; measure the received power level for transmission of the plurality of SRS ports of the SRS resource received from the wireless device; determine an adjusted received power level of the SRS port of the SRS resource corresponding to the antenna port whose MTPL value is restricted; select a specific antenna port in the antenna port group of the wireless device based on the adjusted received power level of the SRS port; and transmit a transmit precoding matrix indicator (TPMI) value to the wireless device, the transmit precoding matrix indicator (TPMI) value indicating that the wireless device selects the specific antenna port in the antenna port group for subsequent transmission of the PUSCH to the base station.

20. The method according to claim 19, wherein determining the adjusted received power level of the SRS port of the SRS resource comprises: when the PUSCH transmission via the antenna port is restricted by the MTPL and the SRS transmission via the antenna port is not restricted by the MTPL, increase the received power level of the SRS port by an adjustment value.

21. The method according to claim 20, wherein determining that the MTPL value for PUSCH transmission via the antenna port is restricted is based on a power headroom value included in the PHR received from the wireless device.

22. The method according to claim 19, wherein determining the adjusted received power level of the SRS port of the SRS resource comprises: when the SRS transmission via the antenna port is restricted by the MTPL and the PUSCH transmission via the antenna port is not restricted by the MTPL, decrease the received power level of the SRS port by an adjustment value.

23. The method according to claim 22, wherein determining that the MTPL value for SRS transmission via the antenna port is restricted comprises: calculate a ratio of a first transmission bandwidth for PUSCH transmission to a second transmission bandwidth for SRS transmission; and apply the ratio to a reported power headroom value included in the PHR received from the wireless device to derive a scaled power headroom value; and based on the scaled power headroom value, determine whether the MTPL for SRS transmission is restricted.

24. A wireless device, the wireless device including at least one processor, the at least one processor communicatively coupled to a wireless circuit including one or more antennas and coupled to a memory storing instructions, the instructions when executed by the at least one processor configuring the wireless device to perform the method according to any one of claims 1 to 18.

25. An apparatus for operating in a wireless device, the apparatus including at least one processor, the at least one processor communicatively coupled to a memory storing instructions, the instructions when executed by the at least one processor configuring the wireless device to perform the method according to any one of claims 1 to 18.

26. A base station, the base station comprising: a wireless circuit configured to communicate with one or more wireless devices; and at least one processor, the at least one processor communicatively coupled to the wireless circuit and coupled to a memory storing instructions, the instructions when executed by the at least one processor configuring the base station to perform the method according to any one of claims 19 to 23.

27. An apparatus for operating in a base station, the apparatus including at least one processor, the at least one processor communicatively coupled to a memory storing instructions, the instructions when executed by the at least one processor configuring the base station to perform the method according to any one of claims 19 to 23.

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