Patent Description:
<CIT>, relates to a method and a serving NodeB for adjusting transmit power of a User Equipment (UE) to reduce a relative phase discontinuity (RPD) between a Sounding Reference Signal (SRS) and transmissions on a Physical Uplink Shared Channel (PUSCH).

Certain aspects provide a method for wireless communication by a user equipment (UE). The method generally includes determining a transmit power budget, autonomously allocating the transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission, and transmitting the PUSCH using the transmit chains according to the determined transmit power allocation.

Certain aspects provide a method for wireless communication by a user equipment (UE). The method generally includes determining a transmit power budget, receiving signaling indicating how to allocate the transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission, allocating the transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission, and transmitting the PUSCH using the transmit chains according to the determined transmit power allocation.

Certain aspects provide a method for wireless communication by a network entity. The method generally includes transmitting, to a user equipment (UE), signaling indicating how to allocate a transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission and receiving the PUSCH transmitted from the UE with transmit power allocated across transmit chains based on the signaling.

Certain aspects of the present disclosure also provide various apparatus, means, and computer readable media capable of (or having instructions stored thereon for) performing the operations described above.

Aspects of the present disclosure present disclosure provide apparatus, methods, processing systems, and computer readable mediums for scaling transmission power across transmit chains for physical uplink shared channel (PUSCH) transmissions.

For example, UEs <NUM> may allocate transmit power according to operations described below with reference to <FIG> and <FIG>. BSs <NUM> may perform operations of <FIG> to configure a UE to perform operations shown in <FIG>.

The wireless communication network <NUM> may be a New Radio (NR) or <NUM> network. As illustrated in <FIG>, the wireless network <NUM> may include a number of base stations (BSs) <NUM> and other network entities. A BS may be a station that communicates with user equipments (UEs). Each BS <NUM> may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to a coverage area of a Node B (NB) and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term "cell" and next generation NodeB (gNB), new radio base station (NR BS), <NUM> NB, access point (AP), or transmission reception point (TRP) may be interchangeable. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations or network nodes (not shown) in wireless communication network <NUM> through various types of backhaul interfaces, such as a direct physical connection, a wireless connection, a virtual network, or the like using any suitable transport network.

Some UEs may be considered Internet-of-Things devices, which may be narrowband Internet-of-Things devices.

In some examples, access to the air interface may be scheduled, wherein a. A scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within its service area or cell.

<FIG> illustrates example components of BS <NUM> and UE <NUM> (as depicted in <FIG>), which may be used to implement aspects of the present disclosure. For example, antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM> and/or antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS <NUM> may be used to perform the various techniques and methods described herein.

In NR, a synchronization signal/physical broadcast channel (SS/PBCH) block is transmitted (also referred to as a synchronization signal block (SSB)). The SS/PBCH block includes a PSS, a SSS, and a two symbol PBCH. The SS/PBCH block can be transmitted in a fixed slot location, such as the symbols <NUM>-<NUM> as shown in <FIG>. The PBCH carries some basic system information, such as downlink system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SS/PBCH blocks may be organized into SS bursts to support beam sweeping.

Real-world applications of such sidelink communications may include public safety, proximity services, UE-to-network relaying, vehicle-to-vehicle (V2V) communications, Internet of Everything (IoE) communications, Internet-of-Things communications, mission-critical mesh, and/or various other suitable applications.

Aspects of the present disclosure provide techniques for scaling transmission power across transmit chains for physical uplink shared channel (PUSCH) transmissions.

As used herein, a transmit chain generally refers to a set of components in a signal path to take a baseband signal and generate an RF signal. Example transmit chain components include digital to analog converters (DACs), modulators, power amplifiers (PAs), as well as various filters and switches. Conversely, a receive chain generally refers to a set of components in a signal path to take an RF signal and generate a baseband signal. Example receive chain components include downconverts, demodulators, and analog to digital converters (ADCs), as well as various filters and switches.

For uplink data transmissions, according to a conventional PUSCH power scaling approach, a UE is assigned a single transmission (Tx) power budget that is to be split uniformly across all available transmit chains and the assigned RBs.

Unfortunately, there can be scenarios where the UE is unable to transmit at the full power when splitting the Tx power budget uniformly according to the conventional approach. For example, one such scenario is the case where a UE has four Tx chains, and is assigned the precoder [<NUM><NUM><NUM><NUM>]. If the UE is assigned a transmit power budget of P _PUSCH, then the UE is expected to scale transmission power according to a multi-step procedure such as the following <NUM>-step algorithm:.

When the <NUM>-step algorithm is followed as is, for the above example of four TX chains and a precoder [<NUM><NUM><NUM><NUM>], step (a) results in a scaled power of P_PUSCH/<NUM> which, in step (b), is split equally among the two ports that carry non-zero PUSCH. Thus, two ports are assigned P_PUSCH/<NUM> each, resulting is only half the Tx power budget being utilized.

Aspects of the present disclosure provide techniques that may help address this issue by providing new power allocation methods and signaling mechanisms. The techniques may help more efficiently utilize Tx power budget, particularly in UEs with transmit chains that have heterogeneous power amplifiers (PAs) and coherent/noncoherent antennas. As used herein, heterogeneous generally refers to PAs that have different output power ratings.

The following description assumes the following notation:.

According to one proposed solution, a UE may be allowed to autonomously determine its own transmit power allocation. In this context, autonomous means the UE may allocate its Tx power budget as it sees fit, for example, without additional signaling from a base station.

<FIG> illustrates example operations <NUM> for autonomous scaling transmission power of PUSCH transmissions by a user equipment (UE), in accordance with aspects of the present disclosure. For example, operations <NUM> may be performed by a UE <NUM> shown in <FIG> and <FIG>.

Operations <NUM> begin, at <NUM>, by determining a transmit power budget. At <NUM>, the UE autonomously allocates the transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission. At <NUM>, the UE transmits the PUSCH using the transmit chains according to the determined transmit power allocation.

In this case, a UE assigned a target P_PUSCH may be allowed to split this power across multiple Tx chains as it decides, provided it preserves the integrity of any precoder assigned for PUSCH transmission. As used herein, integrity generally refers to the impact of power allocation being equivalent to scaling the precoders by a scalar value. In this case, with a UE allowed to autonomously determine power allocation, steps (a) and (b) of the <NUM>-step algorithm described above may be ignored.

This autonomous approach may provide the UE with maximum flexibility in allocating the transmit power. This approach may be particularly beneficial to UEs with heterogeneous PAs in their transmit chains. As the base station is not likely to know output power ratings of the heterogeneous PAs, the UE is best positioned to determine the right allocation of power among the transmit chains, for example, by factoring in the individual output power rating of the PAs powering each transmit chain.

This autonomous approach may be considered an open loop scheme as it does not require additional signaling from the gNB (e.g., beyond the initial signaling of target P_PUSCH), which is in contrast to other techniques described below.

In other words, in these other techniques, a network entity (e.g., a gNB) may provide signaling to a UE that determines how the UE performs Tx power scaling.

<FIG> illustrates example operations <NUM> that may be performed by a UE for scaling transmission power of PUSCH transmissions based on network signaling, in accordance with aspects of the present disclosure. For example, operations <NUM> may be performed by a UE <NUM> shown in <FIG> and <FIG>.

Operations <NUM> begin, at <NUM>, by determining a transmit power budget. At <NUM>, the UE receives signaling indicating how to allocate the transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission. At <NUM>, the UE allocates the transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission. At <NUM>, the UE transmits the PUSCH using the transmit chains according to the determined transmit power allocation.

<FIG> illustrates example operations <NUM> for wireless communications by a network entity, such as an eNB, in accordance with aspects of the present disclosure. For example, operations <NUM> may be performed by a BS/gNB <NUM> shown in <FIG> and <FIG> to signal a UE to perform transmission power scaling according the operations of <FIG> described above.

Operations <NUM> begin, at <NUM>, by transmitting, to a user equipment (UE), signaling indicating how to allocate a transmit power budget across transmit chains for a physical uplink shared channel (PUSCH) transmission. At <NUM>, the network entity receives the PUSCH transmitted from the UE with transmit power allocated across transmit chains based on the signaling.

In some cases, the Tx power scaling may be provided via a single bit (<NUM>-bit) signaling. For example, a gNB may provide a single bit that indicates whether the UE can skip part of the two-step algorithm described above. For example, the single bit may selectively turn on/off performing step (a) described above, while step (b) may always performed (regardless of the signaled bit value). The single bit may be provided, for example, via a grant that schedules a PUSCH or via some other type of signaling.

By skipping the initial scaling step (a), the entire Tx power budget may be assigned among the ports that transmit non-zero PUSCH.

The effect of this change may be demonstrated by considering the same example presented above, where a UE has four Tx chains, and is assigned the precoder [<NUM>]. In this example, if step (a) is disabled (the UE is allowed to skip this step), then each of two ports that transmit non-zero PUSCH are assigned P_PUSCH/<NUM> power (rather than P_PUSCH/<NUM> as per the conventional algorithm where the initial scaling is performed). Thus, in this example, the entire allocated Tx power budget is used.

Certain UEs may not be able to skip the scaling step even if allowed to, for example, depending on the output power rating of their power amplifiers. To address this case, some UEs may be configured to signal (e.g., an explicitly indication) of whether they can support this <NUM>-bit signaling or not. This indication may be provided, for example, as UE capability information. As an alternative, UEs may be allowed to implicitly ignore this signaling and continue to perform both Step (a) and Step (b).

In some cases, the gNB may provide multi-bit signaling indicating how a UE is to perform transmit power scaling. For example, the gNB may provide multi-bit signaling for the UE to perform transmit power scaling according to a common power boosting. This alternative to the single-bit approach may provide a more fine grained approach to power allocation that can be enabled by adding a third step, a "Step (c)" to the first two steps already described above.

In this Step (c), the UE may be allowed to further alter the power as obtained from steps (a) and (b) via a common power boosting factor α. For example, assuming α is a <NUM>-bit signaling parameter, α may indicate the values shown in <FIG>. Thus, using <NUM>-bits in this example, a gNB can enable boosting the power obtained after step (b) by one of four values (e.g., an additional <NUM>, <NUM>, <NUM>, or <NUM> dB).

Power boosting in this manner may be described, assuming the same example as above, where a UE has <NUM> Tx chains, and is assigned the precoder [<NUM>]. In this example, steps (a) and (b) are followed by step (c) where α is indicated as '<NUM>. ' In this case, using the alpha-power boost table as shown in <FIG>, each port is allowed to boost its power by an additional <NUM> dB, such that the effective power per port is P_PUSCH/<NUM>. Thus, it is easy to see that once again the UE is able to use all available power using this method.

This result may be understood more easily by considering that the signaled α for Step (c) corresponds to a boost of β_dB in dB scale or equivalently β_linear in the linear scale. Thus, the new power assigned to each port is P_c=P_b×β_linear. In the example above, a <NUM> dB corresponds to a 2x gain in the linear scale and, hence, a gain from P_PUSCH/<NUM> to P_PUSCH/<NUM>.

Of course, the signaling of parameter α using <NUM>-bits is an example only. In some cases, more than <NUM>-bits may be used to achieve finer granularity.

In some cases, one or more actions may be taken (at the gNB and/or UE) to ensure that the power boosting in Step (c) does not end up exceeding an originally assigned power of P_PUSCH. For example, such actions may include:.

These fallback mechanisms allow decoupling of the signaling of the precoder and the common power boosting factor. This may help simplify signaling, as a common power boosting factor can be indicated once, and used across several precoders, with K reflecting the number of ports with non-zero PUSCH for each signaled precoder.

In the preceding discussion, it may be important that the power P_c assigned to a port with non-zero PUSCH transmission does not exceed the maximum output power rating of the power amplifier on that antenna port. To avoid such a scenario, the UE may signal/report its (RF) capability to the eNB. This signaling may indicate, for example, a maximum common power boost supported by the UE.

In some cases, as an extension to signaling a multi-bit power boost parameter as described above, the power boosting factor can be specified on a per-port basis (i.e., α<NUM>, α<NUM>,. , αN assuming N ports). This approach may allow even greater flexibility in how each port is assigned a transmit power.

This per-port method may be described by assuming an example where P_b is the power assigned per port after steps (a) and (b) and the signaled αi for Step (c) corresponds to a boost of β_(i,dB) in dB scale or equivalently β_(i,linear). In the linear scale, then, the new power assigned to the ith port according to this approach is: <MAT> In some cases, the bit-width of each αi may be different.

If the ports with non-zero PUSCH are known apriori, then it suffices to only signal values of αi for the ports with non-zero PUSCH (although additional signaling may be required if/when the precoder changes). Alternatively, the per-port power boosting values (corresponding to different precoding) can be signaled once for all the antenna ports and used across several transmission even when precoding changes.

Similar to the single value case above, steps may be taken in the "per-port" case to ensure that the power boosting in Step (c) does not exceed the original assigned power of P _PUSCH. In other words, these steps may be taken to ensure that:
<MAT>
For example, such actions may include:.

These fallback mechanisms effectively allow decoupling the signaling of the precoder and the per-port power boosting factors. Per-port power boosting factors can be indicated once, and used across several precoders, with K reflecting the number of ports with non-zero PUSCH for each signaled precoder. In the preceding discussion, it may be important that the power P_c,i assigned to a port with non-zero PUSCH transmission does not exceed the maximum output power rating of the power amplifier on that antenna port. To avoid such a scenario, the UE may signal/report RF capability to eNB on the maximum per-port power boost supported by the UE.

Aspects of the present disclosure also provide various additional features that may be considered enhancements for cases where a UE is allowed to determine power allocation for a PUSCH transmission. The enhancements may be applicable, for example, to any power allocation scheme where a UE is provided with some level of autonomy or when the UE implementation is not known to gNB.

In some such cases, a value indicated (by a UE) in a power headroom report (PHR) accompanying the PUSCH transmission may be dependent on a transmit precoding matrix indicator (TPMI) used for the PUSCH transmission. In general, each TPMI may have a different PHR value, for example, due to different characteristics in the power amplifiers used in the different transmit chains associated with the different TPMIs.

Because of this, when a UE is allowed to determine power allocation autonomously, the actual transmit power used by the UE can be TPMI-dependent. In other words, a PHR based on a slot with a PUSCH transmission may also be dependent on the exact TPMI used in that slot. This may be illustrated by considering an example of a UE with <NUM> antenna ports:.

Assuming the UE is asked to a transmit at <NUM> dBm power then, for a TPMI corresponding to the precoder [<NUM>, <NUM>], which selects the first port, the PHR should indicate a headroom of <NUM> dB (<NUM> dBm - <NUM> dBm). On the other hand, if the TPMI corresponds to the precoder [<NUM><NUM>], selecting the second port, the PHR should indicate a headroom of <NUM> dB (<NUM> dBm - <NUM> dBm).

For this reason, the PHR that accompanies the PUSCH transmission should indicate the appropriate value for the TPMI used in that slot. In some cases, it may not be necessary to explicitly tag (or signal) the exact TPMI, as the gNB may already know the TPMI used, so it can track this on its end.

Given the PHR signaled in this example is for a particular TPMI, it may be important that the UE keep its implementation/configuration consistent over a certain period of time. For example, it may be desirable that the UE avoid dynamically switching the port to Tx-chain mapping too frequently (every slot).

As noted above, in some cases, a gNB may provide one or more bits of signaling to indicate whether a UE is to allocate power in a manner different from a conventional approach (e.g., what is currently specified in a standard). In some cases, however, a UE may not be allowed to deviate from what is specified (e.g., a UE may not be able to skip a power scaling step). Therefore, it may be desirable for a UE to indicate support for this feature (e.g., during call setup) as noted above.

Further, in some cases, whether a UE supports this particular feature (or similar features) may depend on one or more band combinations supported by the UE for carrier aggregation (CA).

For example, if there are three component carriers (cc1, cc2 and cc3), the UE may support combinations cc1+cc3 and cc2+cc3. Thus, in addition to indicating support for these band combinations in general, the UE may also indicate, for each supported band combination, whether a change to the power allocation rule is supported or not.

In some cases, the UE may provide a pair of bits the values of which indicate whether or not the UE supports a new power allocation rule for each of the band combinations supported. For example, assuming the bit combinations from the example above, if the UE supports a new rule for the cc1+cc3 combination, but not for the cc2+cc3 combination, then the UE may signal the following pairs: [Cc1+cc3, b=<NUM>] and [cc2+cc3, b=<NUM>], where bit b is used to indicate support for the new power allocation rule.

As discussed above, antennas may have different antenna coherence. In certain systems, antennas may be classified as coherent, non-coherent, or partially-coherent. Two antenna ports are said to be coherent, for example, if their relative phase remains constant between the time of sounding reference signal (SRS) transmission and a subsequent physical uplink shared channel (PUSCH) transmission using the same ports. PUSCH precoding may be impacted by the antenna coherence. Coherent antennas can act in unison (e.g., their relative phases stay constant) and precoding can span across all antennas. Non-coherent antennas act independently of each other and precoding across antennas is not maintained. Partially-coherent antennas may include a subset of antennas that are coherent, but might not be coherent across these subsets, and precoding spans only across the coherent sets of antennas.

In certain systems with different antenna coherence, PUSCH transmissions may be limited to (e.g., restricted to) coherent sets of antennas. In this case, the precoder codebook may be limited to the coherent antennas. Thus, some antennas (e.g., the antennas that are not coherent) are not used for transmitting PUSCH. Without use of these antennas, PUSCH transmission may not be at full power.

As discussed above, in some examples, transmission at full power may be possible if a power allocation rule, e.g., following the conventional <NUM>-step algorithm for the UE to scale transmission power, is modified.

In some cases, a UE may support full uplink transmission power with full rates on each transmit (TX) chain. For example, such a UE may have a power class (e.g., referred to as PC3) having <NUM> dBm and <NUM> dBm PAs (e.g., for a UE with two TX chains). This may be referred to as a UE capability <NUM> or a "cap1" UE.

In some cases, a UE may support full uplink transmission power with no TX chains assumed to deliver full rate power (e.g., none having a full PA). For example, the UE can have a power class (e.g., PC3) having <NUM> dBm and <NUM> dBm PAs (e.g., for a UE with two TX chains). This may be referred to as a UE capability <NUM> or a "cap2" UE.

In some cases, a UE may support full uplink transmission power with a subset of TX chains with full rated PAs. For example, the UE can have a power class (e.g., PC3) having <NUM> dBm and <NUM> dBm PAs (e.g., for a UE with two TX chains). This may be referred to as a UE capability <NUM> or a "cap3" UE.

In some cases, a single bit (b) may be used to indicate whether the UE supports full power. For example, the UE can indicate a power scaling factor (e.g., set a bit equal to <NUM>) to indicate that the step (a) of the <NUM>-step scaling algorithm can be skipped, or the UE can set a power scaling factor (e.g., to zero), or select a number of non-zero power and/or number of total ports in a SRS resource, to indicate that the step (a) of the <NUM>-step scaling algorithm is not skipped (e.g., a conventional power scaling algorithm is followed/adhered to).

In some cases, a cap1 UE may be configured to always skip the step (a) (e.g., set the bit to <NUM>) and a cap2 UE may be configured to always adhere to the step (a) (e.g., set the bit to <NUM>). In an illustrative example, b=<NUM> may indicate that the UE supports full power with power scaling factor equal to <NUM> (always); b=<NUM> may indicate that the UE supports full power with power scaling factor equals to # nonzero ports/# total ports in a SRS resource. In some examples (e.g., for cap3 UEs), the UE may signal a single bit (b) per transmit precoding matrix indicator (TPMI), or per TPMI group, to indicate whether the UE supports full power for that TPMI/TPMI group.

In some examples, certain TPMIs may categorized based on their use for certain TPMIs. For example, certain TPMIs may be categorized as TPMIs that can only be used by coherent UEs, TPMIs that can only be used by coherent and partially-coherent UEs, or TPMIs that may only be used by coherent, partially-coherent, and non-coherent UEs. Thus, a broad codebook may be configured for coherent UEs, and subsets of this coherent codebook may be used for non-coherent and partially coherent UEs.

In some examples, a UE may indicate a list of up to K TPMIs for which step (a) of the <NUM>-step scaling algorithm is skipped. For these TPMIs, the UE skips the first step of the power scaling rule and only follows the second step. The list of TPMIs, for which step (a) can be skipped, may be selected from the coherent codebook set (e.g., may not be limited to codebook subsets that are allowed for non-coherent or partially-coherent UEs).

In an illustrative example, a cap2 non-coherent PC3 UE with four 17dBm PAs can list a single TPMI [<NUM><NUM><NUM><NUM>] (from the coherent codebook set). While the TPMI [<NUM><NUM><NUM><NUM>] may not normally be allowed for the non-coherent UE, this indication can implicitly indicate to the gNB that UE can support full power on the TPMI. For example, the UE may support full power on the TPMI via a cyclic diversity delay (CDD) implementation. The CCD may add an additional (cyclic) delay to one precoded port, and not to another port. The different delays for different ports may add further incoherency. In this example, the power scaling rule steps may not actually be skipped (e.g., because all antenna ports are used, it is not impacted by the step (a) rule), but the availability of a CDD solution may be indicated to the gNB. In another illustrative example, a cap3 non-coherent PC3 UE with two 17dBm PAs and two <NUM> dBm PAs can list TPMIs [<NUM><NUM><NUM><NUM>] and [<NUM><NUM><NUM><NUM>] to the gNB.

Generally, where there are operations illustrated in figures, those operations may have corresponding counterpart means-plus-function components. For example, various operations shown in <FIG>, <FIG> and <FIG> may be performed by various processors shown in <FIG>. More particularly, operations <NUM> and <NUM> of <FIG> and <FIG> may be performed by one or more of processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM>, while operations <NUM> of <FIG> may be performed by processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS <NUM> shown in <FIG>.

For example, instructions for performing the operations described herein and illustrated in <FIG>, <FIG>, and/or <NUM>.

Claim 1:
A method (<NUM>) of wireless communications by a user equipment, UE (<NUM>), comprising:
determining (<NUM>) a transmit power budget;
receiving (<NUM>) signaling indicating how to allocate the transmit power budget across transmit chains for a physical uplink shared channel, PUSCH, transmission;
allocating (<NUM>) the transmit power budget across transmit chains that have a PUSCH transmission, wherein the transmit power budget is allocated across transmit chains by a multi-step procedure comprising:
(a) scaling the transmission power budget by the ratio of a number of antenna ports with a non-zero PUSCH transmission to a number of configured antenna ports, and
(b) splitting the resulting scaled power equally across the antenna ports on which non-zero PUSCH is to be transmitted;
wherein the signaling indicates whether or not the UE can skip at least one step of the multi-step procedure for allocating the transmit power budget across transmit chains; and
transmitting (<NUM>) the PUSCH using the transmit chains according to the determined transmit power allocation.