Closed loop antenna selection for single transmitter wireless devices

Abstract

Mechanisms to manage closed loop antenna selection for a wireless device are described. The wireless device transmits sounding reference signal (SRS) resources configured by a cellular wireless network in a set of SRS resources, and receives an SRS indicator (SRI) value to indicate an antenna for subsequent uplink transmissions of one or more physical layer channels by the wireless device, the one or more physical layer channels include a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a physical random access channel (PRACH). The wireless device supplements the closed-loop antenna selection with an open-loop antenna selection, and uses the open-loop antenna selection for a non-PUSCH channel when the most recent SRI value may be considered outdated. The SRI-based closed loop antenna selection is extended to a frequency division duplex (FDD) band. Transmitting precoding matrix indicator (TPMI) group values is also used to indicate differential transmit power capabilities of respective antennas of the wireless device to the cellular wireless network.

Description

Technical Field

[0001] The described embodiments relate to wireless communications, including methods and apparatus for managing closed loop antenna selection for a single transmitter wireless device. Background Art

[0002] Newer generations (e.g., fifth generation (5G) New Radio (NR)) cellular wireless networks implementing one or more third generation partnership project (3GPP) 5G standards are rapidly evolving and being deployed by network operators around the world. Newer cellular wireless networks offer a range of packet-based services, with 5G technology offering increased data throughput and lower latency connections that promise 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 wireless network to the cellular wireless network in the uplink (UL) direction to measure the UL channel for subsequent UL data and / or control signal transmission. A single transmitter wireless device may include multiple receivers that may process signals received via multiple antennas (which, in some cases, may be mapped to one or more antenna ports feeding the receivers via a receiver transform filter matrix). In the case of only one transmitter, the wireless device may transmit in the uplink direction using only one antenna port (which, in the simplest case, may be mapped to a single antenna) at any given moment. Different antennas (or equivalently, antenna ports) can provide different UL transmission characteristics based on how the wireless device is used (e.g., device physical orientation, antenna blocking, etc.). The performance of the UL transmission can vary for different antennas. The wireless device can select the antenna 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 by feedback from a cellular wireless network in response to the cellular wireless network based on measurements made on the reception of UL SRS transmissions transmitted by the wireless device). The current 5G wireless communication standard provides closed-loop antenna selection based on UL SRS transmissions for time division duplex (TDD) radio frequency (RF) band configurations, and is applied to the physical uplink shared channel (PUSCH) physical layer channel. There is a need for a mechanism to extend closed-loop antenna selection for a single transmitter wireless device to additional RF band configurations, other physical layer channels, with enhanced performance when used with the mechanism. Summary of the invention

[0003] The present application relates to wireless communications, including methods and apparatus for managing closed-loop antenna selection for a single transmitter wireless device. A cellular wireless network configures one or more sounding reference signal (SRS) resource sets to the wireless device, each SRS resource set including one or more SRS resources for uplink (UL) transmissions. The wireless device sends the SRS resources to the cellular wireless network via one or more antennas for uplink (UL) channel measurement to determine UL transmission parameters for subsequent use of the wireless device for certain UL transmissions. The cellular wireless network provides closed-loop feedback via an SRS indicator (SRI) value to indicate the antenna selected by the cellular wireless network for UL transmission by the wireless device. In some embodiments, when operating with a frequency division duplex (FDD) radio frequency (RF) band with the wireless device, the cellular wireless network uses a codebook to configure an SRS resource set with multiple (e.g., two or four) SRS resources. Each SRS resource includes an SRS port corresponding to a single antenna (or antenna port). To allow the wireless device to perform antenna switching, when the SRS resource is to be transmitted in a first orthogonal frequency division multiplexing (OFDM) symbol in the vicinity of a physical layer channel transmission via a first antenna port and in a second OFDM symbol via a second antenna port, the cellular wireless network does not schedule UL transmissions during at least one OFDM symbol interposed between the first OFDM symbol and the second OFDM symbol transmitted via different antenna ports. In some embodiments, the wireless device extends the use of SRI-based feedback from PUSCH to additional physical layer channels, including a physical uplink control channel (PUCCH) and a physical random access channel (PRACH) for UL transmissions via PUCCH and PRACH using the same antenna selected for PUSCH, the UL transmissions occurring within a backoff period of the most recently received SRI from the cellular wireless network. For PUCCH or PRACH transmissions occurring outside of the backoff period, the wireless device selects an antenna port for transmission of the PUCCH or PRACH using an open loop antenna selection process, for example based on measurements of downlink (DL) signals received by the wireless device from the cellular wireless network. The wireless device uses i) DL path loss measurements obtained via closed-loop SRI antenna selection or ii) DL path loss measurements obtained via open-loop antenna selection to adaptively determine the UL transmit power level for each UL physical channel differently. The UL transmit power level for PUSCH is calculated to accommodate higher modulation and coding selection (MCS) values. The UL transmit power level for PRACH is calculated to achieve higher UL performance. The UL transmit power level for PUCCH is calculated to achieve stable performance with lower UL transmit power level and less interference at the cellular wireless network receiver.In some embodiments, based on the wireless device reporting that only one transmission layer is supported in full power mode 2 configuration (UL multiple input multiple output transmission with multiple transmission layers is not supported), the cellular wireless network configures the wireless device with SRS resources having four SRS resources, each SRS resource corresponding to a single antenna port. The wireless device transmits four SRS resources and receives antenna selection from the cellular wireless network via downlink control information (DCI). In some embodiments, the wireless device reports that one transmission layer is supported in full power mode 2 configuration, and additionally reports a transmit precoding matrix indicator (TPMI) group of a two-port version 16 (r16) or a four-port non-coherent r16 configuration. When the wireless device supports closed-loop antenna selection using two SRS resources, the two-port TPMI group is specified, and when the wireless device supports closed-loop antenna selection using four SRS resources, the four-port TPMI group is specified. The specific values ​​of the TPMI group are provided to the cellular wireless network to indicate the relative transmit power capabilities of the respective antennas (or antenna ports) of the wireless device, such as the maximum transmit power level (MTPL) value. When performing UL channel estimation using SRS resources transmitted by individual antennas (or antenna ports), the cellular wireless network can use the reported TPMI group to compensate for MTPL differences between different antennas (or antenna ports) of the wireless device and thereby improve antenna (or antenna port) selection based on a more accurate MTPL value that can be used for transmission via the antenna (or antenna port).

[0004] 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.

[0005] The present disclosure is provided for the purpose of summarizing some example embodiments only, so as to provide a basic understanding of some aspects of the subject matter described herein. Therefore, it should be understood that the above-mentioned 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 through the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present disclosure will be more readily understood through the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements.

[0007] Figure 1A , Figure 1B , Figure 1C and Figure 1D A diagram illustrating an example of closed-loop antenna selection for a wireless device according to some embodiments.

[0008] Figure 1EAn example of open loop antenna selection by a wireless device according to some embodiments is illustrated.

[0009] Figure 1F An example of closed-loop antenna selection by a wireless device according to some embodiments is illustrated.

[0010] Figure 1G An exemplary uplink transmit chain for a wireless device according to some embodiments is illustrated.

[0011] Figure 2A An exemplary 5G New Radio (NR) physical layer frame structure according to some embodiments is illustrated.

[0012] Figure 2B An example of SRS and PUSCH timeslot management for a wireless device operating in an FDD band according to some embodiments is illustrated.

[0013] Figure 3A An example of antenna selection for non-PUSCH channels by a wireless device according to some embodiments is illustrated.

[0014] Figure 3B An example of UL transmit power calculation by a wireless device using channel dependent path loss according to some embodiments is illustrated.

[0015] Figure 4 Table illustrating an example of using a transmit precoding matrix indicator (TPMI) value by a wireless device to report an antenna maximum transmit power level (MTPL) value in accordance with some embodiments.

[0016] Figure 5 An exemplary method for closed-loop uplink (UL) transmit antenna selection for a wireless device communicating with a base station of a cellular wireless network in accordance with some embodiments is illustrated.

[0017] Figure 6 An exemplary method of uplink (UL) transmit antenna selection for a wireless device communicating with a base station of a cellular wireless network according to some embodiments is illustrated.

[0018] Figure 7 Another exemplary method of uplink (UL) transmit antenna selection for a wireless device communicating with a base station of a cellular wireless network in accordance with some embodiments is illustrated.

[0019] Figure 8 An exemplary method for communicating maximum transmit power level (MTPL) information for multiple antenna ports of a wireless device to a base station of a cellular wireless network in accordance with some embodiments is illustrated.

[0020] Fig. 9 A block diagram illustrating exemplary elements of a mobile wireless device according to some embodiments is illustrated. DETAILED DESCRIPTION

[0021] Representative applications of the methods and apparatus according to the present application are described in this section. These examples are provided only to add context and aid in understanding the described embodiments. Therefore, 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 cases, in order to avoid unnecessarily obscuring the described embodiments, well-known processing steps are not described in detail. Other applications are possible, so that the following examples should not be considered limiting.

[0022] The present application relates to wireless communications, including methods and apparatus for managing closed-loop antenna selection for a single transmitter wireless device. A cellular wireless network configures one or more sounding reference signal (SRS) resource sets to a wireless device, each SRS resource set including one or more SRS resources for uplink (UL) transmissions. A wireless device may be configured with multiple SRS resource sets for different purposes and configured with different properties, such as periodic or aperiodic transmissions. The wireless device transmits SRS resources to the cellular wireless network via one or more antennas periodically (when specified as periodic) or triggered by downlink control information (DCI) (when specified as aperiodic). SRS resources may be used for uplink (UL) channel measurements to determine UL transmission parameters for subsequent use by the wireless device for certain UL transmissions, such as for selecting one or more antennas or precoding matrices to be used. SRS ports may be mapped to physical antennas via spatial filters; however, to simplify the description herein, it is assumed that each SRS resource is directly mapped to an antenna. The ideas described herein can also be applied to the mapping of SRS resources (or SRS ports) to antenna ports, which are also mapped to a combination of physical antennas (e.g., UL beamforming). Each SRS resource set is specified with a usage configuration parameter that indicates how the SRS resource set will be used. The SRS resource sets described herein are specified with a codebook to be used for UL channel measurement and estimation, and subsequently for transmission of physical layer channels, particularly with an extended physical uplink shared channel (PUSCH) used on a physical uplink control channel (PUCCH) and a physical random access channel (PRACH). In the 5G cellular wireless communication standard, SRS resources can be sent within the last six orthogonal frequency division multiplexing (OFDM) symbols of a time slot, or for subsequent revisions that are more flexibly assigned to various OFDM symbols within a time slot.

[0023] The wireless device signals its transmit capability regarding antenna switching to the cellular wireless network. A wireless device with only one transmit chain and four receive chains (denoted as 1T4R capability) can only provide partial sounding (i.e., does not support full sounding of different SRS resources transmitted via all four antennas at once), and therefore requires antenna switching to sound all different possible uplink channels via four different antennas (or more generally via four antenna ports corresponding to the antenna combination of the wireless device). The cellular wireless network may configure the 1T4R wireless device with: i) one SRS resource set with two SRS resources, ii) two SRS resource sets each with two SRS resources, or iii) one SRS resource set with four SRS resources. Each SRS resource includes an SRS port. The wireless device selects the antenna through which the different SRS resources are transmitted (at a time specified by the cellular wireless network), and the cellular wireless network provides closed-loop feedback via an SRS indicator (SRI) value to indicate the antenna selected by the cellular wireless network for UL transmission by the wireless device. Currently, wireless devices with closed-loop SRI-based antenna switching for time division duplex (TDD) configurations are being designed and adopted; however, closed-loop SRI-based antenna switching for frequency division duplex (FDD) configurations is not yet supported. When operating in a TDD configuration, wireless devices communicate in a single common frequency band, where downlink-uplink reciprocity is applicable, while wireless devices operating in an FDD configuration use separate frequency bands that will have different path loss characteristics. Current solutions only allocate one SRS resource for the FDD band (and therefore no selection of SRS resources is available). The new solution described herein configures multiple SRS resources to wireless devices operating in an FDD configuration, and uses SRI values ​​to implement closed-loop antenna selection for the FDD band.

[0024] To extend the use of antenna switching based on closed-loop SRI to the FDD band, in some embodiments, a wireless device configured to operate using the FDD band may receive an SRS resource set configuration from a cellular wireless network, the SRS resource set configuration including multiple (e.g., two or four) SRS resources (rather than just a single SRS resource) with codebook usage designation. Each SRS resource in the SRS resource set includes an SRS port and may correspond to a single antenna (or antenna port). The wireless device may transmit SRS resources corresponding to different antennas (or antenna ports) currently used for a physical uplink channel (e.g., for PUSCH), and needs to switch antennas before transmitting the SRS resources. To allow the wireless device to perform antenna switching, when the SRS resource is to be transmitted in a first OFDM symbol near a physical layer channel transmission (such as a PUSCH transmission) via a first antenna port and in a second OFDM symbol via a second antenna port, the cellular wireless network refrains from scheduling UL transmission during at least one OFDM symbol interposed between the first OFDM symbol (for SRS resource transmission) and the second OFDM symbol (for the physical layer channel) transmitted via different antenna ports. Note that the first OFDM symbol and the second OFDM symbol may appear in the same time slot in either order or in different time slots. For the same time slot case, with PUSCH transmission using antenna port A in time slot N (or other physical layer channel transmission using the same antenna selection as PUSCH, as further described herein) and SRS resources scheduled (or triggered) for transmission using antenna port B in the same time slot N, the cellular wireless network ensures that at least one OFDM symbol separates the PUSCH OFDM symbols using antenna port A from the OFDM symbols with SRS resources using antenna port B. For the sequential time slot case, with SRS resources scheduled (or triggered) for transmission using antenna port B in time slot N and PUSCH transmission using antenna port A in the subsequent time slot N+1 (or other physical layer channel transmission using the same antenna selection as PUSCH), the cellular wireless network again ensures that at least one OFDM symbol separates the SRS resource OFDM symbols from the PUSCH OFDM symbols. At least one intermediate OFDM symbol inserted between the SRS resource OFDM symbol and the PUSCH OFDM symbol allows antenna switching to occur. In some embodiments, the cellular wireless network schedules multiple SRS resources to be sent by the wireless device during one or more OFDM symbols of the same time slot, which allows the wireless device to use multiple SRS resources for efficient UL channel sounding through different antennas and reduces the overhead caused by the inserted OFDM symbols.

[0025] In some embodiments, the wireless device extends the use of SRI-based feedback for closed-loop antenna selection from PUSCH to additional physical layer channels, including a physical uplink control channel (PUCCH) and a physical random access channel (PRACH). The wireless device may use the same antenna selected for PUSCH for UL transmissions via PUCCH and PRACH that occur within a backoff period of the SRI most recently received from the cellular wireless network. Whenever a valid SRI is received from the cellular wireless network, the wireless device may start (or reset) a backoff timer, where the duration of the backoff timer is configurable. When the backoff timer has not expired, the wireless device may use the same antenna selected for PUSCH for PUCCH and PRACH. For PUCCH or PRACH transmissions that occur outside the backoff period (e.g., after the backoff timer expires), the wireless device uses an open-loop antenna selection process to select an antenna port for transmission of PUCCH or PRACH, for example based on measurements of a downlink (DL) signal received by the wireless device from the cellular wireless network. In some cases, the open loop selection antenna for PUCCH and PRACH may be the same as the closed loop selection antenna for PUSCH. In some cases, the open loop selection antenna for PUCCH and PRACH may be different from the closed loop selection antenna for PUSCH.

[0026] In some embodiments, the wireless device adaptively determines the UL transmit power level based on a closed-loop power control mechanism (signaled by a transmit power control (TPC) command from the cellular wireless network) and based on an open-loop power control mechanism implemented at the wireless device using DL measurements. The power of the UL transmission is controlled to ensure comparable reception levels of UL transmissions from different wireless devices at the cellular wireless network. The transmit power level of one wireless device is much higher than the transmit power level of another wireless device, which can cause undesirable interference. The wireless device uses DL path loss measurements of wireless signals received from the cellular wireless network to estimate the amount of attenuation that the UL wireless signal will cause when it is transmitted to the cellular wireless network based on the reciprocity principle. The actual amount of path loss caused will depend on the antenna (or antenna port) selected for the UL transmission. The wireless device can use i) DL path loss measurements obtained via closed-loop SRI selection antennas or ii) DL path loss measurements obtained via open-loop antenna selection to calculate the UL transmit power differently for each UL physical channel. The DL path loss measurements obtained via open-loop antenna selection can be used to calculate the UL transmit power level of the PUSCH. This provides a constant (over the time frame in which the most recent DL path loss measurement via the open loop antenna selection process is valid) DL path loss value that is aligned between the wireless device and the cellular wireless network. In some cases, the UL performance of the PUSCH can adapt to higher modulation and coding selection (MCS) values, such as when the actual UL path loss is less than the measured DL path loss used for the UL transmit power level calculation, because the UL receive power level for the PUSCH obtained at the cellular wireless network can be higher. The UL transmit power level of the PRACH can also be calculated using the DL path loss measurement obtained via the open loop antenna selection, and thus higher performance of the PRACH can be achieved based on the higher UL transmit power level. The UL transmit power level of the PUCCH can be calculated using the corresponding antenna used for PUCCH transmission, that is, the DL path loss measurement obtained via the closed loop SRI selected antenna when the SRI selected antenna is used for PUCCH, and the DL path loss measurement obtained via the open loop antenna when the open loop antenna is used for PUCCH. The DL path loss measurement is selected according to the corresponding antenna for the PUCCH to achieve stable performance with lower UL transmit power level, thereby causing less interference when received at the cellular wireless network because the PUCCH is a shared channel used by other wireless devices as well as the wireless device.

[0027] In some embodiments, based on the wireless device reporting that only one transmission layer is supported in a full power mode 2 configuration (where a single transmitter wireless device does not support UL multiple-input multiple-output transmissions with multiple transmission layers), the cellular wireless network configures the wireless device with SRS resources having four SRS resources, each corresponding to a single antenna (or antenna port). By using the full power mode 2 configuration, the wireless device may be configured with an SRS resource set including four SRS resources (rather than being limited to only two SRS resources as in currently available configurations). The wireless device transmits the four SRS resources via four different antennas (or antenna ports) and receives antenna selection from the cellular wireless network via an SRI value in downlink control information (DCI).

[0028] In some embodiments, the wireless device reports a full power mode 2 configuration that supports one transmit layer, and additionally reports a transmit precoding matrix indicator (TPMI) group value to convey the maximum transmit power level (MTPL) capability of the antenna (or antenna port) of the wireless device to the cellular wireless network. The wireless device may report a two-port version 16 (r16) configuration or a four-port non-coherent r16 configuration for the TPMI group r16 value. When the wireless device supports closed-loop antenna selection using two SRS resources, a two-port TPMI group designation is used, and when the wireless device supports closed-loop antenna selection using four SRS resources, a four-port TPMI group designation is used. The wireless device maps the physical antenna (or antenna port) of the wireless device to the codebook using SRS resources based on the value of the TPMI group. The specific value of the TPMI group is provided to the cellular wireless network to indicate the relative transmit power capabilities of each antenna (or antenna port) of the wireless device, such as the maximum transmit power level (MTPL) value. When the two-port r16 configuration is used, the wireless device maps the antenna (or antenna port) with a higher MTPL value to the reported port index. When using the configured four-port non-coherent r16, the wireless device maps antennas (or antenna ports) to G0, G1, G2, and G3 values ​​to correspond to certain antennas (or antenna ports) with higher MTPL values. The cellular wireless network can read the reported TPMI group value and use the transmit power adjustment (e.g., 3dB) for antennas (or antenna ports) with different MTPL values, for example, some antennas (or antenna ports) support higher maximum transmit power levels, while other antennas support lower maximum transmit power levels. In some cases, the SRS resource is sent as a wideband signal close to (or at) the MTPL level of the corresponding antenna, while the subsequent UL signal (e.g., PUSCH, PUCCH, or PRACH) can be a narrowband signal sent at a lower power level. The cellular wireless network can take into account the transmit power level difference when estimating the signal metric based on the received SRS resource and when selecting the antenna (or antenna port) to be used subsequently for the wireless device based on the estimation performed using the received SRS resource.

[0029] In some embodiments, the cellular wireless network uses a power headroom report (PHR) provided by the wireless device to determine the MTPL value of the antenna (or antenna port). The cellular wireless network may send an SRI to the wireless device when the PHR periodic timer is close to expiration, and the SRI specifies the antenna (or antenna port) used by the wireless device. After the PHR periodic timer expires, the wireless device determines the PHR value and provides it to the cellular wireless network. The PHR received by the cellular wireless network may correspond to the antenna (or antenna port) selected by the SRI. The cellular wireless network may accumulate the PHR value of each of the antennas (or antenna ports) by cycling through different SRI values, and use the PHR value to determine the MTPL value of the corresponding antenna (or antenna port). Using the MTPL values ​​of each antenna (or antenna port), when selecting an antenna (or antenna port) for use by the wireless device (subsequently specified in the SRI transmitted to the wireless device), the cellular wireless network may apply the MTPL difference to the estimated SRS signal metric.

[0030] These and other embodiments are described below with reference to FIGS. Fig. 9 A discussion is made; however, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for illustrative purposes only and should not be construed as limiting.

[0031] Figure 1A and 1BBlock diagrams 100, 110 of exemplary systems configured to implement closed-loop antenna selection for a wireless device 102 are illustrated. The wireless device 102 includes a single transmitter (transmit chain) and multiple receivers (receive 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 uplink (UL) signals to a gNodeB 112 (base station) of a cellular wireless network via a separate antenna 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. In some embodiments, the wireless device 102 can transmit to a gNodeB 112 of a cellular wireless network simultaneously (beamforming) via multiple antennas 104-A / B / C / D. The wireless device 102 may indicate to a gNodeB 112 of a cellular wireless network the transmit and receive capabilities of the wireless device 102, such as a single transmit four receiver configuration of the wireless device 102 designated as 1T4R. Transmissions via different antennas 104-A / B / C / D may experience different uplink channel conditions to the gNodeB 112 based 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. Using an open loop antenna selection process, the wireless device 102 may measure downlink (DL) signals received from the gNodeB 112, estimate the DL path loss of signals transmitted from the gNodeB 112 to the wireless device 102, and select antennas 104-A / B / C / D for UL transmissions based on the DL path loss, assuming reciprocity, such that UL signals transmitted by the wireless device 102 to the gNodeB 112 experience a UL path loss that is comparable to the DL path loss. However, open-loop antenna selection infers UL signal performance without feedback about UL performance from the gNodeB 112. Alternatively, using a closed-loop antenna selection process, the wireless device 102 may use antennas 104-A / B / C / D for UL transmissions based on antenna selections obtained from the gNodeB 112, where the gNodeB 112 measures channel sounding reference signals transmitted by the wireless device 102 through the respective antennas 104-A / B / C / D.

[0032] The gNodeB 112 may configure the wireless device 102 with a sounding reference signal (SRS) resource set 106, which includes two SRS resources, SRS-0 and SRS-1. In some embodiments, the gNodeB 112 configures the wireless device 102 with multiple SRS resource sets 106, where each SRS resource set 106 may be used for a different purpose. The SRS resource set 106 may be designated for use with a specific UL physical layer channel (e.g., a physical uplink shared channel (PUSCH)). Each SRS resource set 106 may also be designated for periodic, semi-persistent, or aperiodic transmission. In some embodiments, the SRS resource set 106 configured to the wireless device 102 is designated as periodic, and the gNodeB 112 expects the wireless device 102 to periodically send the SRS resources of the SRS resource set 106 to measure the UL channel. In some embodiments, the SRS resource set 106 configured to the wireless device 102 is specified 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. The wireless device 102 selects an antenna pair (e.g., 104-A / B) and transmits two SRS resources (SRS-0 and SRS-1) via respective antennas (or antenna ports) 104-A and 104-B, respectively, during one or more orthogonal frequency division multiplexing (OFDM) symbols of a time slot of an UL OFDM frame transmitted to the gNodeB 112. The gNodeB 112 of the cellular wireless network measures the received SRS resource signals SRS-0 and SRS-1, and selects an antenna for the wireless device 102 to subsequently use 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 an SRS indicator (SRI) value to the wireless device 102, which specifies the SRS signal corresponding to the selected antenna. For example, for a one-bit value SRI, an SRI value of "0" may correspond to SRS-0, while an SRI value of "1" may correspond to SRS-0. The wireless device 102 knows through which antenna (or antenna port) 104-A or 104-B the 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 transmits the PUSCH to the gNodeB 112 using the selected antenna 104-A or 104-B.

[0033] The wireless device 102 may later switch to using a different antenna pair, such as antennas 104-C / D, using an open loop antenna selection process. The wireless device 102 may transmit SRS resources (SRS-0 and SRS-1) via respective antennas (or antenna ports) 104-C and 104-D, respectively, during one or more OFDM symbols of a time slot of a UL OFDM frame transmitted to the gNodeB 112. The gNodeB 112 of the cellular wireless network measures the received SRS resource signals SRS-0 and SRS-1 and selects an antenna for the wireless device 102 to subsequently use 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 the 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 transmits the PUSCH to the gNodeB 112 using the selected antenna 104-C or 104-D.

[0034] Figure 1C and Figure 1DBlock diagrams 120, 130 illustrate another example of closed-loop antenna selection for a wireless device 102. The gNodeB 112 may configure the wireless device 102 with two sounding reference signal (SRS) resource sets 106-A / B, each of which includes two SRS resources (a first SRS resource set 106-A with SRS-0 and SRS-1 and a second SRS resource set 106-B with SRS-2 and SRS-3). The SRS resource sets 106-A / B may be designated for channel estimation by the gNodeB 112 and for use by the wireless device 102 based on the channel estimation performed by the gNodeB 112. 112 provides antenna selection for subsequent transmission of PUSCH by the wireless device 102. The wireless device 102 may associate a first resource set 106-A with two antennas (or antenna ports) (e.g., 104-A / B) and associate a second resource set 106-B with two other antennas (or antenna ports) (e.g., 104-C / D). The wireless device 102 may select one of the antenna pairs (e.g., 104-A / B) and transmit SRS resources of the SRS resource set 106-A via the selected antenna pair, e.g., SRS-0 via antenna (or antenna port) 104-A and SRS-1 via antenna (or antenna port) 104-B. The gNodeB 112 measures the received SRS resources SRS-0 and SRS-1, determines channel properties of the UL transmission via the antennas (or antenna ports) 104-A / B, and selects an antenna (or antenna port) based on the measured channel properties. The gNodeB 112 transmits a DCI message including an SRI value indicating an SRS resource corresponding to the selected antenna (or antenna port) to the wireless device 102. The wireless device 102 then transmits the PUSCH using the selected antenna.

[0035] The wireless device 102 may later switch to using a different antenna pair, such as antennas 104-C / D, using an open loop antenna selection process. The wireless device 102 may transmit SRS resources SRS-2 and SRS-3 of a second SRS resource set 106-B via respective antennas (or antenna ports) 104-C and 104-D, respectively. The gNodeB 112 measures the received SRS resource signals SRS-2 and SRS-3, and selects an antenna for the wireless device 102 to subsequently use for PUSCH transmission based on the measurements of the received SRS resource signals SRS-2 and SRS-3. The gNodeB 112 provides an indication of the selected antenna by transmitting another DCI message to the wireless device 102 including an SRI value that specifies the SRS signal corresponding to the selected antenna. For example, for a one-bit value SRI, an SRI value of "0" may correspond to SRS-2, while an SRI value of "1" may correspond to SRS-3. The wireless device 102 again knows through which antenna (or antenna port) 104-C or 104-D the different SRS resource signals SRS-2 and SRS-3 are transmitted, and can infer the antenna selection from the SRI value. The wireless device 102 then transmits the PUSCH to the gNodeB 112 using the selected antenna 104-C or 104-D.

[0036] Figure 1E Diagram 140 illustrates an example of open-loop antenna selection by a wireless device 102 without feedback from a cellular wireless network. The wireless device 102 may select an antenna (or antenna port) based on signals received from the cellular wireless network via each of a plurality of antennas (or antenna ports) in a downlink direction (e.g., based on a signal strength metric that may be used to measure a downlink path loss from the cellular wireless network to the wireless device 102 for different downlink channels via each of the antennas), and infer an uplink path loss to the cellular wireless network for transmissions via the same antennas. The wireless device 102 may select an antenna pair (e.g., A / B or C / D) and an antenna from the antenna pair (e.g., A or B when antenna pair A / B is used, or C or D when antenna pair C / D is used) based on the measurements. In some embodiments, the open-loop antenna selection process changes between antenna pairs on the order of seconds (if the measurements indicate that switching would be beneficial). With open loop antenna selection alone, the wireless device 102 does not select the individual antenna to use from the selected antenna pair based on feedback from the cellular wireless network, but instead relies on its own determination. Figure 1EThe example shown in exemplifies that the wireless device 102 selects antenna pair A / B during a first time period, wherein antenna A is selected over antenna B throughout the first time period. Subsequently, the wireless device selects antenna pair C / D during a second time period, wherein antenna C is selected over antenna D throughout the second time period. Signal metrics of the selected antennas are indicated as bold lines. As illustrated, the wireless device 102 will benefit from switching between antenna A and antenna B during the first time period and switching between antenna C and antenna D during the second time period; however, the open-loop antenna selection process used may not provide an opportunity to re-measure and switch antennas within a time period. As shown next, closed-loop antenna selection of individual antennas that complement the open-loop antenna selection of the antenna pair can improve the performance of the wireless device 102.

[0037] Figure 1F Diagram 150 illustrates an example of closed-loop antenna selection by a wireless device 102 with feedback from a cellular wireless network. The wireless device 102 selects an antenna pair based on measurements of signals received from the cellular wireless network via each of a plurality of antennas in a downlink direction (e.g., DL path loss measurements). The wireless device 102 selects an antenna pair, such as A / B or C / D, based on these measurements. The wireless device 102 may also transmit an UL signal (e.g., an SRS resource set 106 (or SRS resources from a plurality of SRS resource sets 106)) to the cellular wireless network via each of the plurality of antennas, and in response receive a DCI message including an SRI that specifies one of the plurality of antennas for a subsequent UL transmission (e.g., for a PUSCH transmission). Figure 1E As in the example of , an open loop antenna selection process changes between antenna pairs on the order of seconds (if measurements indicate that switching would be beneficial). Figure 1F The example illustrates that the wireless device 102 selects antenna pair A / B during a first time period and antenna pair C / D during a second time period. During each time period, the wireless device 102 transmits SRS resources (periodically based on the periodic configuration of the SRS resource set 106, or on-demand in response to a DCI message from the cellular wireless network requesting SRS measurements based on the aperiodic configuration of the SRS resource set 106). The cellular wireless network transmits a DCI message with an SRI value to the wireless device 102 to indicate the selection of the antenna in the antenna pair used (e.g., antenna A or B during the first time period and antenna C or D during the second time period). The combination of open-loop antenna pair selection (or more generally, selection of a group of antennas or antenna ports) based on DL measurements made by the wireless device 102 and closed-loop antenna (or antenna port) selection from an antenna pair (or an antenna group or antenna port) based on UL measurements with feedback to the wireless device 102 provides superior performance as illustrated by the bold signal metric of the selected antenna.

[0038] Figure 1G A diagram 160 of an exemplary uplink transmission chain of a wireless device 102 is illustrated. A transmitter 180 may receive a digital data stream 162 of uplink data to be wirelessly transmitted to a cellular wireless network via one or more antenna ports 174. A digital-to-analog converter (DAC) 164 of the transmitter 180 converts the digital data stream 162 into an analog signal, which is modulated onto an uplink radio frequency (RF) carrier by a modulator 166 of the transmitter 180. The modulated analog signal is amplified by a power amplifier 168 and filtered via a suitable transmit (TX) filter 170, thereby generating an amplified analog transmit data signal 172, which is wirelessly transmitted to the cellular wireless network via one or more antenna ports 174 via a radio link. When multiple antenna ports 174 (or multiple antennas) are used, 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. UL transmission output from the antenna port 174 of the wireless device 102 is transmitted at a power level that allows for proper reception by a cell of the cellular wireless network. UL transmissions are limited by the transmit properties of the radio circuitry of the transmitter 180 and the antenna ports 174. UL transmissions from all antenna ports 174 of the wireless device 102 are required to meet regulatory requirements, such as specific absorption rate (SAR) limits for human exposure to radio frequency (RF) energy. A maximum transmit power limit (MTPL) may be determined by the wireless device 102 for transmissions via the radio link used for UL transmissions.

[0039] Figure 2A A diagram 200 of an exemplary 5G NR physical layer time domain frame structure with slot and symbol usage is illustrated. NR transmissions are grouped into frames that span 10 ms each and are divided into equally sized subframes of 1 ms each. A subframe is divided into one, two, four, eight, or sixteen slots, each depending on the length of an OFDM symbol within the slot, where the length of an OFDM symbol depends on the subcarrier spacing used for OFDM transmission. Each slot includes 14 symbols. SRS resources are sent in the uplink direction in one, two, or four adjacent OFDM symbols within the last six OFDM symbols of a single slot. In some extensions of the 5G NR wireless communication standard, SRS resources may be sent in any of the OFDM symbols of a single slot. In the frequency domain (not shown), SRS resources are sent on every two or every four subcarriers of an OFDM symbol used to allow frequency multiplexing of SRSs from different wireless devices 102.

[0040] The wireless device 102 signals its transmit capabilities to the cellular wireless network regarding antenna switching. A wireless device with only one transmit chain and four receive chains (denoted as 1T4R capability) can only provide partial sounding (i.e., does not support full sounding of different SRS resources transmitted via all four antennas at once), and therefore requires antenna switching to sound all different possible uplink channels via four different antennas (or more generally via four antenna ports corresponding to the antenna combination of the wireless device). The cellular wireless network may configure the 1T4R wireless device 102 with: i) one SRS resource set 106 (e.g., 1T4R) with two SRS resources; Figure 1A / B), ii) two SRS resource sets 106 each having two SRS resources (as shown in Figure 1B / C as shown), or iii) one SRS resource set with four SRS resources (not shown). Each SRS resource includes one SRS port. The wireless device 102 selects the antenna through which different SRS resources are transmitted (at a time specified by the cellular wireless network), and the cellular wireless network provides closed-loop feedback via an SRS indicator (SRI) value to indicate the antenna selected by the cellular wireless network for UL transmission by the wireless device 102. Currently, cellular wireless communication standards allow closed-loop SRI-based antenna switching for time division duplex (TDD) configurations, but do not allow closed-loop SRI-based antenna switching for frequency division duplex (FDD) configurations because the cellular wireless network only allocates one SRS resource for the FDD band.

[0041] Figure 2BA diagram 250 illustrating an example of SRS and PUSCH time slot management for a wireless device 102 operating in an FDD band is illustrated. In order to extend the use of antenna switching based on closed-loop SRI to the FDD band, in some embodiments, a wireless device 102 configured to operate using the FDD band may receive an SRS resource set configuration from a cellular wireless network, the SRS resource set 106 configuration including multiple (e.g., two or four) SRS resources (rather than just a single SRS resource) with codebook usage designation. Each SRS resource in the SRS resource set 106 includes an SRS port and may correspond to a single antenna (or antenna port). The wireless device 102 may transmit the SRS resource via an antenna (or antenna port) different from the antenna (or antenna port) currently being used for physical uplink channel (e.g., PUSCH) transmission. The wireless device 102 may switch antennas before transmitting the SRS resource via different antennas (or antenna ports). To allow the wireless device 102 to perform antenna switching, when an SRS resource is to be transmitted via a first antenna port in a first OFDM symbol near a physical layer channel transmission (such as a PUSCH transmission) and via a second antenna port in a second OFDM symbol, the cellular wireless network refrains from scheduling UL transmission during at least one OFDM symbol interposed between the first OFDM symbol (for SRS resource transmission) and the second OFDM symbol (for the physical layer channel) transmitted via different antenna ports.

[0042] The first OFDM symbol and the second OFDM symbol used for SRS resource transmission and PUSCH transmission, respectively, may occur in any order and in the same time slot or in different time slots. For the case where different antennas are used in the same time slot ( Figure 2B), PUSCH transmission (or other physical layer channel transmission using the same antenna selection as PUSCH as further described herein) uses antenna port A during OFDM symbol 11 in time slot N, and SRS resources are periodically scheduled (or triggered based on a DCI message) for transmission in OFDM symbol 13 using antenna port B in the same time slot N. The cellular wireless network ensures that at least one OFDM symbol (e.g., OFDM symbol 12) separates the PUSCH OFDM symbol (OFDM symbol 11) using antenna port A from the OFDM symbol with SRS resources (OFDM symbol 13) using antenna port B. For the case of consecutive time slots, in the case where the SRS resources are scheduled (or triggered) for transmission using antenna port B in time slot N (e.g., in OFDM symbol 13) and PUSCH (or other physical layer channel transmission using the same antenna selection as PUSCH) using antenna port A in the subsequent time slot N+1 (e.g., in OFDM symbol 1), the cellular wireless network again ensures that at least one OFDM symbol (in this example, OFDM symbol 0 of time slot N+1) separates the SRS resource OFDM symbol (OFDM symbol 13) from the PUSCH OFDM symbol (OFDM symbol 1). Inserting at least one intermediate OFDM symbol between the SRS resource OFDM symbol and the PUSCH OFDM symbol allows antenna switching to occur during the blocked (no scheduled transmission) OFDM symbols. In some embodiments, the cellular wireless network schedules multiple SRS resources to be transmitted by the wireless device during one or more OFDM symbols of the same time slot, which allows the wireless device to use multiple SRS resources for effective UL channel sounding through different antennas and reduces the overhead caused by blocking transmission on certain OFDM symbols.

[0043] Figure 3AA diagram 300 illustrates an example of antenna selection for physical layer channels other than PUSCH (i.e., for non-PUSCH channels). The wireless device 102 extends the use of SRI-based feedback to provide closed-loop antenna selection for PUSCH to additional UL physical layer channels, such as a physical uplink control channel (PUCCH) and a physical random access channel (PRACH). The wireless device 102 starts (or resets) a backoff timer after receiving an SRI value from a cellular wireless network that indicates an antenna (or antenna port) to use for PUSCH based on a measurement of an SRS resource previously sent by the wireless device 102 to the cellular wireless network. The backoff timer may delineate a backoff period during which the most recently received SRI value may be considered by the wireless device 102 to be valid for UL transmissions on one or more non-PUSCH UL physical channels. The wireless device 102 may transmit PUSCH based on the closed-loop antenna selection indicated by the most recently received SRI value, regardless of the state of the backoff timer. When the backoff timer has not expired, i.e., during the backoff period when the most recent SRI value may be considered valid for non-PUSCH UL physical channel transmission, the wireless device 102 may use the same closed-loop antenna selection indicated by the most recently received SRI value for PUSCH to transmit one or more non-PUSCH UL physical layer channels. For non-PUSCH transmissions that occur after the backoff timer expires (and before a new SRI value is received that resets the backoff timer) (i.e., during a period when the SRI value may be considered invalid for non-PUSCH transmissions), the wireless device 102 selects an antenna port for transmission of PUCCH or PRACH using an open-loop antenna selection process, for example, based on measurements of downlink (DL) signals received by the wireless device 102 from the cellular wireless network. In some cases, the open-loop selected antennas for PUCCH and PRACH may be the same as the closed-loop selected antennas for PUSCH. In some cases, the open-loop selected antennas for PUCCH and PRACH may be different from the closed-loop selected antennas for PUSCH.

[0044] Figure 3BTable 350 illustrates an example of UL transmit power calculations performed by the wireless device 102 using channel dependent path loss. The wireless device 102 may determine a UL transmit power level for communicating via the UL physical channel via an antenna (or antenna port) based on the particular UL physical channel being transmitted, e.g., different UL physical channels transmitted via the same physical antenna (or antenna port) may be transmitted at different UL transmit power levels. The PUSCH UL physical layer channel is transmitted using resources for the PUSCH allocated to the wireless device 102 by the cellular wireless network, and the PUSCH UL physical layer channel is not shared with other wireless devices 102 connected to the same cell of the cellular wireless network. The power level of the UL physical layer channel received at the cellular wireless network may be calculated based on a fixed value P0, a closed-loop transmit power control (TPC) value set by the cellular wireless network, and an open-loop transmit power control determined by the wireless device 102 using a measured downlink path loss, wherein the wireless device 102 determines the UL transmit power level at least in part to compensate for an expected uplink path loss (assuming reciprocity in the uplink and downlink directions, the measured downlink path loss provides an indication of the expected uplink path loss). The actual amount of path loss incurred will depend on the antenna (or antenna port) selected for the UL transmission. The wireless device 102 may calculate the UL transmit power differently for each UL physical channel using i) DL path loss measurements obtained via closed-loop SRI selection of antennas or ii) DL path loss measurements obtained via open-loop antenna selection. PUSCH is transmitted via closed-loop selection of antennas; however, the wireless device 102 may use DL path loss measurements obtained via open-loop antenna selection for UL transmit power level calculations. When transmitting within a valid SRI period, PUCCH and PRACH are transmitted using antennas selected by closed-loop SRI, or when transmitting outside a valid SRI period, PUCCH and PRACH are transmitted using antennas selected by open-loop, which may be the same or different from the antennas selected by closed-loop SRI. The UL transmit power level of PUSCH can be calculated using DL path loss measurements obtained via open-loop antenna selection. This provides a constant (on the time frame in which the most recent DL path loss measurement via the open-loop antenna selection process is valid) DL path loss value aligned between the wireless device and the cellular wireless network. In some cases, the UL performance of PUSCH can adapt to higher modulation and coding selection (MCS) values, such as when the actual UL path loss is less than the measured DL path loss used for UL transmit power level calculation, because the UL receive power level for PUSCH obtained at the cellular wireless network can be higher. The UL transmit power level of PRACH can also be calculated using DL path loss measurements obtained via open-loop antenna selection, and thus higher performance of PRACH can be achieved based on higher UL transmit power levels.The UL transmit power level of the PUCCH may be calculated using the corresponding antenna used for PUCCH transmission, i.e., DL path loss measurements obtained via closed loop SRI selected antennas when the SRI selected antennas are used for PUCCH, and DL path loss measurements obtained via open loop antennas when the open loop antennas are used for PUCCH. The DL path loss measurements are selected based on the corresponding antennas used for PUCCH to achieve stable performance with lower UL transmit power levels, thereby causing less interference when received at a cellular wireless network, because the PUCCH is a shared channel used by other wireless devices as well as the wireless device 102.

[0045] Figure 4 Table 400 illustrates an example of reporting an antenna maximum transmit power level (MTPL) value by a wireless device 102 to a cellular wireless network using a transmit precoding matrix indicator (TPMI) value. In some embodiments, the wireless device 102 reports a full power mode 2 configuration that supports only one transmit layer (UL MIMO with multiple transmit layers is not supported). The full power mode 2 configuration was introduced in Release 16 of the 5G NR wireless communication standard. Although the use of the full power mode 2 configuration is intended for UL MIMO, in some cases, the wireless device 102 may limit transmission to using only a single layer even when using the full power mode 2 configuration. The full power mode 2 configuration advantageously allows the cellular wireless network to configure the wireless device 102 with an SRS resource set 106 having four SRS resources, each of which may be used with a different antenna (or antenna port) of the wireless device 102. In some embodiments, the wireless device 102 sends four SRS resources via four different antennas (or antenna ports), and receives antenna selection from a cellular wireless network via SRI information (e.g., a first bit value of SRI and a second bit value of SRI) in a downlink control information (DCI) message to select one of the four different antennas (or antenna ports) for subsequent PUSCH transmission.

[0046] The wireless device 102 may also report a full power mode 2 configuration with a TPMI group value to the cellular wireless network to indicate the maximum transmit power level (MTPL) capability of the antenna (or antenna port) of the wireless device 102. For certain antennas (or antenna ports), the TPMI group value may indicate a higher MTPL capability. The wireless device 102 may transmit a two-port version 16 (r16) TPMI group value (e.g., two bits specifying "01" or "10") or a four-port non-coherent r16 TPMI group value (e.g., "g0", "g1", "g2", or "g3" value) to the cellular wireless network in the capability report. When the wireless device 102 supports closed-loop antenna selection using two SRS resources, the wireless device 102 uses the two-port TPMI group designation. When the wireless device 102 supports closed-loop antenna selection using four SRS resources, the wireless device 102 uses the four-port TPMI group designation.

[0047] The wireless device 102 maps the physical antenna (or antenna port) of the wireless device 102 to the codebook using SRS resources based on the value reported for the TPMI group. The specific value of the TPMI group is provided to the cellular wireless network to indicate the relative MTPL capabilities of each antenna (or antenna port) of the wireless device. When using the two-port r16 configuration, the wireless device maps the antenna (or antenna port) with a higher MTPL value to the reported port index. When using the four-port non-coherent r16 configuration, the wireless device 102 maps the antenna (or antenna port) to G0, G1, G2 and G3 values ​​to correspond to certain antennas (or antenna ports) with higher MTPL values. The cellular wireless network can read the TPMI group value reported by the wireless device 102 and apply the transmit power adjustment (e.g., 3dB) to antennas (or antenna ports) with different MTPL values, for example, some antennas (or antenna ports) can support higher maximum transmit power levels, while other antennas can support lower maximum transmit power levels. In some cases, the wireless device 102 may transmit the SRS resources as wideband signals at or near the MTPL level of the corresponding antenna (or antenna port) through which the SRS resources are transmitted. The wireless device 102 may transmit subsequent UL physical layer channel transmissions (e.g., PUSCH, PUCCH, or PRACH transmissions) as narrowband signals at a lower transmit power level. The cellular wireless network may take into account the transmit power level difference when estimating signal metrics from the received SRS resources and when selecting an antenna (or antenna port) for the wireless device 102 to subsequently use.

[0048] In some embodiments, the cellular wireless network uses a power headroom report (PHR) provided by the wireless device 102 to determine the MTPL value of the antenna (or antenna port). The cellular wireless network may send a DCI message including an SRI value to the wireless device, which specifies the antenna (or antenna port) used by the wireless device. The DCI message may be transmitted close to the expiration of the periodic PHR timer. After the periodic PHR timer expires, the wireless device 102 determines the PHR value and provides it to the cellular wireless network. The PHR received by the cellular wireless network may correspond to the antenna (or antenna port) selected by the most recently received SRI value. The cellular wireless network may accumulate the PHR value of each of the antennas (or antenna ports) by cycling through different SRI values ​​to specify different antennas (or antenna ports), and use the PHR value to determine the MTPL value of the corresponding antenna (or antenna port). Using the MTPL values ​​of the respective antennas (or antenna ports), when selecting an antenna (or antenna port) for use by the wireless device 102 (subsequently specified in the SRI transmitted to the wireless device 102), the cellular wireless network may apply the MTPL difference to the estimated SRS signal metric.

[0049] Figure 5 A flow chart 500 is illustrated of an exemplary method for closed-loop uplink (UL) transmit antenna selection for a wireless device 102 communicating with a base station (e.g., a gNodeB 112) of a cellular wireless network. At 502, the base station configures the wireless device 102 with a sounding reference signal (SRS) resource set 106 having a plurality of SRS resources. At 504, the base station schedules at least one unused orthogonal frequency division multiplexing (OFDM) symbol between a first OFDM symbol carrying a physical layer channel transmission from the wireless device 102 using a first antenna port and a second OFDM symbol carrying an SRS resource from a plurality of SRS resources of the SRS resource set 106, wherein the SRS resource 106 uses a second antenna port different from the first antenna port. At 506, the base station receives a transmission based on at least two of the plurality of SRS resources from the wireless device 102. At 508, the base station selects an antenna port for the wireless device 102 based on the received transmission. At 510, the base station transmits an SRS indicator (SRI) to the wireless device 102, which specifies the antenna port that the wireless device 102 uses to transmit a physical layer channel to the base station. Figure 5 In the method, the wireless device 102 is configured to communicate with a base station of a cellular wireless network using a frequency domain duplex (FDD) configuration.

[0050] In some embodiments, the first OFDM symbol and the second OFDM symbol appear in the same time slot of the UL frame. In some embodiments, the first OFDM symbol and the second OFDM symbol appear in different consecutive time slots of the UL frame. In some embodiments, the base station configures the wireless device 102 to send multiple SRS resources in the second OFDM symbol. In some embodiments, the wireless device 102 is configured not to transmit UL transmission to the base station of the cellular wireless network during at least one unused OFDM symbol. In some embodiments, the SRS resource set 106 includes two or four SRS resources, each SRS resource is associated with a different antenna port of the wireless device 102. In some embodiments, the wireless device 102 is configured for codebook-based physical layer uplink shared channel (PUSCH) transmission. In some embodiments, the physical layer channel transmission includes physical layer uplink shared channel (PUSCH) transmission.

[0051] Figure 6 A flowchart 600 is illustrated of an exemplary method for uplink (UL) transmit antenna selection for a wireless device 102 communicating with a base station (e.g., gNodeB 112) of a cellular wireless network. At 602, the wireless device 102 determines whether a backoff timer has expired after receiving a most recently received sounding reference signal (SRS) indicator (SRI) value in a downlink control information (DCI) message from a base station of the cellular wireless network. At 604, when a physical layer channel transmission occurs within a backoff period after receiving the most recently received SRI value, the wireless device 102 transmits a physical layer channel transmission other than a physical layer uplink shared channel (PUSCH) transmission to the base station using a first antenna port specified by the SRI value for the PUSCH transmission. At 606, when the physical layer channel transmission occurs outside of the backoff period, the wireless device 102 transmits the physical layer channel transmission to the base station using a second antenna port selected by the wireless device 102 based on an open loop antenna selection process. For Figure 6 In the method, the back-off timer of the wireless device 102 expires at the end of the back-off period after receiving the most recently received SRI value.

[0052] In some embodiments, the wireless device 102 initiates or resets the backoff timer in response to receiving the SRI value from the base station. In some embodiments, the physical layer channel transmission includes a physical uplink control channel (PUCCH) transmission, and the wireless device 102 calculates the UL transmit power of the PUCCH transmission based on a path loss estimate determined by the wireless device 102 for the corresponding antenna port used for the PUCCH transmission. In some embodiments, the physical layer channel transmission includes a physical random access channel (PRACH) transmission, and the wireless device 102 calculates the UL transmit power of the PRACH transmission based on a path loss estimate determined by the wireless device 102 for the second antenna port, regardless of whether the first antenna port or the second antenna port is used for the PRACH transmission. In some embodiments, the wireless device 102 uses the UL transmit power calculated based on the path loss estimate determined by the wireless device 102 for the second antenna port based on an open-loop antenna selection process to send the PUSCH transmission to the base station via the first antenna port specified by the SRI value for the PUSCH transmission. In some embodiments, the wireless device 102 selects the second antenna port based on a signal strength measurement of a downlink (DL) signal received from the base station.

[0053] Figure 7 A flowchart 700 is illustrated of another exemplary method for uplink (UL) transmit antenna selection for a wireless device 102 communicating with a base station (e.g., a gNodeB 112) of a cellular wireless network. At 702, the wireless device 102 transmits a capability report to the base station indicating that the wireless device 102 supports single-layer transmissions in a full power Mode 2 configuration. At 704, the wireless device 102 receives a Sounding Reference Signal (SRS) resource set from the base station including four SRS resources, each SRS resource including a single SRS port. At 706, the wireless device 102 transmits the four SRS resources to the base station, each SRS resource being transmitted via a different antenna port of the wireless device 102. At 708, the wireless device 102 receives a downlink control information (DCI) message from the base station including an indication of an antenna port selected by the base station for a physical uplink shared channel (PUSCH) transmission by the wireless device 102. At 710, the wireless device 102 transmits at least one PUSCH transmission to the base station via the selected antenna port. For Figure 7 The wireless device 102 is configured for codebook-based PUSCH transmission. In some embodiments, the DCI message includes two SRS indicator (SRI) bits to specify the selected antenna port.

[0054] Figure 8A flowchart 800 is illustrated of an exemplary method for communicating maximum transmit power level (MTPL) information for multiple antenna ports of a wireless device 102 to a base station (e.g., a gNodeB 112) of a cellular wireless network. At 802, the wireless device 102 transmits a capability report to the base station indicating that the wireless device 102 supports single-layer transmission in a full power mode 2 configuration, wherein the capability report also includes a transmit precoding matrix indicator (TPMI) group value. At 804, the wireless device 102 receives a sounding reference signal (SRS) resource set including multiple SRS resources from the base station based on the reported TPMI group value. At 806, the wireless device 102 maps the SRS resources in the SRS resource set to the antenna ports of the wireless device 102 based on the reported TPMI group value.

[0055] In some embodiments: i) the reported TPMI group value indicates that the wireless device 102 supports closed-loop antenna selection using two SRS resources, ii) the SRS resource set includes two SRS resources, and iii) the wireless device 102 maps at least one antenna port of the wireless device 102 with a higher MTPL value to the reported TPMI group value. In some embodiments: i) the reported TPMI group value indicates that the wireless device 102 supports closed-loop antenna selection using four SRS resources with non-coherent transmission, ii) the SRS resource set includes four SRS resources, and iii) the wireless device 102 maps at least one antenna port of the wireless device 102 with a higher MTPL value to the reported TPMI group value.

[0056] Representative exemplary devices

[0057] Fig. 9 An exemplary computing device 900 that can be used to implement various components and techniques described herein according to some embodiments is illustrated in a block diagram format. In particular, a detailed view of the exemplary computing device 900 illustrates various components that can be included in a wireless device (e.g., wireless device 102). Fig. 9As shown, the computing device 900 may include one or more processors 902 representing a microprocessor or controller for controlling the overall operation of the computing device 900. In some embodiments, the computing device 900 may also include a user input device 908 that allows a user of the computing device 900 to interact with the computing device 900. For example, in some embodiments, the user input device 908 may take a variety of forms, such as buttons, keypads, dials, touch screens, audio input interfaces, visual / image capture input interfaces, input in the form of sensor data, etc. In some embodiments, the computing device 900 may include a display 910 (screen display) that can be controlled by the processor 902 to display information (e.g., information related to incoming, outgoing, or active communication sessions) to the user. The data bus 916 can facilitate data transfer between at least the storage device 940, the processor 902, and the controller 913. The controller 913 can be used to interact with and control different equipment through the equipment control bus 914. The computing device 900 may also include a network / bus interface 911 coupled to the data link 912. In the case of a wireless connection, the network / bus interface 911 may include wireless circuitry, such as a wireless transceiver and / or a baseband processor. The computing device 900 may also include a secure element 924. The secure element 924 may include an eUICC.

[0058] The computing device 900 also includes a storage device 940, which may include a single storage device or multiple storage devices (e.g., a hard drive), and includes a storage management module that manages one or more partitions within the storage device 940. In some embodiments, the storage device 940 may include flash memory, semiconductor (solid-state) memory, etc. The computing device 900 may also include a random access memory (RAM) 920 and a read-only memory (ROM) 922. The ROM 922 may store programs, utilities, or processes to be executed in a non-volatile manner. The RAM 920 may provide volatile data storage and store instructions related to the operation of the computing device 900.

[0059] Wireless Terminology

[0060] 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 common consumer electronic devices that may be capable of performing the processes associated with various embodiments of the present disclosure. According to various specific implementations, any of these consumer electronic devices may relate to: a cellular phone or smart phone, a tablet computer, a laptop computer, a notebook computer, a personal computer, a netbook computer, a media player device, an e-book device, Devices, wearable computing devices, and any other type of electronic computing device with wireless communication capabilities, which wireless communication capabilities may include communication via one or more wireless communication protocols, such as protocols used to communicate on the following networks: wireless wide area networks (WWAN), wireless metropolitan area networks (WMAN), wireless local area networks (WLAN), wireless personal area networks (WPAN), near field communication (NFC), cellular wireless networks, fourth generation (4G) LTE, advanced LTE (LTE-A) 5G, and / or 5G advanced or other currently or future developed advanced cellular wireless networks.

[0061] 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, which may also be referred to as stations, client wireless devices, or client wireless communication devices, interconnected to an access point (AP) (e.g., as part of a WLAN), and / or interconnected with 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, the WLAN technology may include a Wi-Fi (or more generally, a WLAN) wireless communication subsystem or radio component, which may implement the 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.

[0062] In addition, it should be understood that the UE described herein may be configured as a multi-mode wireless communication device that is also capable of communicating via different third generation (3G) and / or second generation (2G) RATs. In these cases, the multi-mode user equipment (UE) may be configured to prefer attaching to an LTE network that provides a faster data rate throughput over other 3G legacy networks that provide a lower data rate throughput. For example, in some specific implementations, the multi-mode UE may be configured to fall back to a 3G legacy network, such as an evolved high speed packet access (HSPA+) network, or a code division multiple access (CDMA) 2000 evolution-data only (EV-DO) network when 5G, LTE, and LTE-A networks are otherwise unavailable.

[0063] It is understood that the use of personally identifiable information should be subject to privacy policies and practices that are generally recognized to meet or exceed industry or government requirements for maintaining user privacy. Specifically, personally identifiable information data should be managed and processed to minimize the risk of unintentional or unauthorized access or use, and the nature of the authorized use should be clearly stated to users.

[0064] The various aspects, embodiments, specific implementations or features of the described embodiments may be used individually or in any combination. Various 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-transient computer-readable medium. A non-transient computer-readable medium is any data storage device that can store data, which can then be read by a computer system. Examples of non-transient computer-readable media include read-only memory, random access memory, CD-ROM, HDD, DVD, magnetic tape, and optical data storage devices. Non-transient computer-readable media may also be distributed on network-coupled computer systems so that the computer-readable code is stored and executed in a distributed manner.

[0065] For the purpose of explanation, the foregoing description uses specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to those skilled in the art that specific details are not required in order to practice the described embodiments. Therefore, the foregoing description of specific embodiments is presented for the purpose of illustration and description. The foregoing description is not intended to be exhaustive or to limit the described embodiments to the precise form disclosed. It will be apparent to those of ordinary skill in the art that, in view of the above teachings, many modifications and variations are possible.

Claims

1. A method for closed-loop uplink (UL) transmit antenna selection for a wireless device communicating with a base station of a cellular wireless network, the method comprising: By the base station: configuring the wireless device with a sounding reference signal (SRS) resource set having a plurality of SRS resources; scheduling at least one unused orthogonal frequency division multiplexing (OFDM) symbol between a first OFDM symbol carrying a physical layer channel transmission from the wireless device using a first antenna port and a second OFDM symbol carrying an SRS resource from the plurality of SRS resources from the set of SRS resources, wherein the SRS resource uses a second antenna port different from the first antenna port; receiving, from the wireless device, a transmission based on at least two of the plurality of SRS resources; selecting an antenna port of the wireless device based on the received transmission; as well as transmitting an SRS indicator (SRI) to the wireless device, the SRS indicator (SRI) specifying the antenna port used by the wireless device to send a physical layer channel to the base station, Wherein the wireless device is configured to communicate with the base station of the cellular wireless network using a frequency domain duplex (FDD) configuration.

2. The method of claim 1, wherein the first OFDM symbol and the second OFDM symbol occur in the same time slot of a UL frame.

3. The method according to claim 1, wherein: The first OFDM symbol and the second OFDM symbol appear in different consecutive time slots of a UL frame.

4. The method according to claim 1, further comprising: By the base station: The wireless device is configured to transmit the plurality of SRS resources in the second OFDM symbol. 5 . The method of claim 1 , wherein the wireless device is configured to not transmit an UL transmission to the base station of the cellular wireless network during the at least one unused OFDM symbol. 6 . The method of claim 1 , wherein the SRS resource set comprises two or four SRS resources, each SRS resource being associated with a different antenna port of the wireless device.

7. The method of claim 1, wherein the wireless device is configured for codebook-based physical layer uplink shared channel (PUSCH) transmission.

8. The method of claim 1, wherein the physical layer channel transmission comprises a physical layer uplink shared channel (PUSCH) transmission.

9. A method for uplink (UL) transmit antenna selection for a wireless device communicating with a base station of a cellular wireless network, the method comprising: By the wireless device: determining whether a backoff timer has expired after receiving a most recently received sounding reference signal (SRS) indicator (SRI) value in a downlink control information (DCI) message from the base station; When the physical layer channel transmission occurs within a backoff period after receiving the most recently received SRI value, sending a physical layer channel transmission other than a PUSCH transmission to the base station using a first antenna port specified by the SRI value for a physical layer uplink shared channel (PUSCH) transmission; as well as When the physical layer channel transmission occurs outside the backoff period, transmitting the physical layer channel transmission to the base station using a second antenna port selected by the wireless device based on an open loop antenna selection process, Wherein the back-off timer expires at the end of the back-off period after receiving the most recently received SRI value.

10. The method according to claim 9, further comprising: By the wireless device: The back-off timer is initiated or reset in response to receiving an SRI value from the base station.

11. The method according to claim 9, wherein: The physical layer channel transmission includes a physical uplink control channel (PUCCH) transmission; and The wireless device calculates a UL transmit power for the PUCCH transmission based on a path loss estimate determined by the wireless device for a corresponding antenna port used for the PUCCH transmission.

12. The method according to claim 9, wherein: The physical layer channel transmission includes a physical random access channel (PRACH) transmission; and The wireless device calculates a UL transmit power for the PRACH transmission based on a path loss estimate determined by the wireless device for the second antenna port, regardless of whether the first antenna port or the second antenna port is used for the PRACH transmission.

13. The method according to claim 9, further comprising: By the wireless device: A PUSCH transmission is sent to the base station via a first antenna port designated for PUSCH transmission by the SRI value using a UL transmit power calculated based on a path loss estimate determined by the wireless device for the second antenna port based on the open loop antenna selection process.

14. The method of claim 9, wherein the wireless device selects the second antenna port based on a signal strength measurement of a downlink (DL) signal received from the base station.

15. A method for uplink (UL) transmit antenna selection for a wireless device communicating with a base station of a cellular wireless network, the method comprising: By the wireless device: transmitting to the base station a capability report indicating that the wireless device supports single layer transmission in a full power mode 2 configuration; receiving, from the base station, a sounding reference signal (SRS) resource set including four SRS resources, each SRS resource including a single SRS port; Sending the four SRS resources to the base station, each SRS resource being sent via a different antenna port of the wireless device; receiving a downlink control information (DCI) message from the base station, the downlink control information (DCI) message including an indication of an antenna port selected by the base station for a physical uplink shared channel (PUSCH) transmission by the wireless device; and sending at least one PUSCH transmission to the base station via the selected antenna port, The wireless device is configured for codebook-based PUSCH transmission.

16. The method of claim 15, wherein the DCI message includes two SRS indicator (SRI) bits to specify the selected antenna port.

17. A method for communicating maximum transmit power level (MTPL) information of a plurality of antenna ports of a wireless device to a base station of a cellular wireless network, the method comprising: By the wireless device: transmitting to the base station a capability report indicating that the wireless device supports single layer transmission in a full power mode 2 configuration, wherein the capability report further includes a transmit precoding matrix indicator (TPMI) group value; receiving, from the base station, a sounding reference signal (SRS) resource set including a plurality of SRS resources based on the TPMI group value; as well as SRS resources of the SRS resource set are mapped to antenna ports of the wireless device based on the TPMI group value.

18. The method of claim 17, wherein: The TPMI group value indicates that the wireless device supports closed loop antenna selection using two SRS resources; The SRS resource set includes the two SRS resources; and The wireless device maps at least one antenna port of the wireless device having a higher MTPL value to the TPMI group value.

19. The method of claim 17, wherein: The TPMI group value indicates that the wireless device supports closed loop antenna selection using four SRS resources with non-coherent transmission; The SRS resource set includes the four SRS resources; and The wireless device maps at least one antenna port of the wireless device having a higher MTPL value to the TPMI group value.

20. A wireless device comprising at least one processor communicatively coupled to wireless circuitry comprising one or more antennas and to a memory storing instructions that, when executed by the at least one processor, configure the wireless device to perform the method of any one of claims 9 to 19.

21. An apparatus for operating in a wireless device, the apparatus comprising at least one processor communicatively coupled to a memory storing instructions that, when executed by the at least one processor, configure the wireless device to perform the method of any one of claims 9 to 19.

22. A base station, comprising wireless circuitry configured to communicate with one or more wireless devices; and at least one processor communicatively coupled to the wireless circuitry and to a memory storing instructions that, when executed by the at least one processor, configure the base station to perform a method according to any one of claims 1 to 8.

23. An apparatus for operation in a base station, the apparatus comprising at least one processor, the at least one processor being 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 1 to 8.

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