Per-layer power feedback for enhanced MIMO operation

Abstract

An apparatus configured to process, based on signaling received from a base station, a reporting configuration comprising a per-layer power feedback configuration, measure one or more reference signals (RSs) transmitted by the base station, determine per-layer power feedback for the RSs transmitted by the base station and generate, for transmission to the base station, the per-layer power feedback to the base station.

Description

Per-layer Power Feedback for Enhanced MIMO OperationInventors : Huaning Niu, Chunxuan Ye, Dawei Zhang, Seyed Ali Akbar Fakoorian, Wei Zeng and Weidong YangPriority / Incorporation By Reference

[0001] This application claims priority to U . S . Provisional Application Serial No . 63 / 605 , 283 filed on December 1 , 2023 , entitled "Per-layer Power Feedback for Enhanced MIMO Operation, ” the entirety of which is incorporated by reference herein .Background

[0002] User equipment (UE ) may transmit feedback information to a base station for various purposes including indicating the quality of a channel between the UE and the base station . For example , feedback may include Pre-coding Matrix Indicator ( PMI ) feedback that does not include any power information . Another type of feedback may be Channel Quality Indicator ( CQI ) feedback that is indicated per codeword . However, for a UE with 4 spatial streams , there may be a wide power variation among the streams . This type of feedback may not be helpful to the base station to control communications with the UE .Summary

[0003] Some example embodiments are related to an apparatus comprising processing circuitry configured to process , based on signaling received from a base station, a reporting configuration comprising a per-layer power feedback configuration, measure one or more reference signals (RSs ) transmitted by the base station, determine per-layer power feedback for the RSs transmitted by the base station andgenerate, for transmission to the base station, the per-layer power feedback to the base station.

[0004] Other example embodiments are related to a method for processing, based on signaling received from a base station, a reporting configuration comprising a per-layer power feedback configuration, measuring one or more reference signals (RSs) transmitted by the base station, determining per-layer power feedback for the RSs transmitted by the base station and generating, for transmission to the base station, the per-layer power feedback to the base station.Brief Description of the Drawings

[0005] Fig. 1 shows an example network arrangement according to various example embodiments.

[0006] Fig. 2 shows an example UE according to various example embodiments.

[0007] Fig. 3 shows an example base station according to various example embodiments.

[0008] Fig. 4 shows an example signaling diagram for configuring and reporting power feedback information on a per- layer basis according to various example embodiments.Detailed Description

[0009] The example embodiments may be further understood with reference to the following description and the related appended drawings, wherein like elements are provided with the same reference numerals. The example embodiments relate toconfiguring a UE to perform per-layer power feedback to a base station .

[0010] The example embodiments are described with regard to a user equipment (UE) . However, reference to a UE is merely provided for illustrative purposes. The example embodiments may be utilized with any electronic component that may establish a connection to a network and is configured with the hardware, software, and / or firmware to exchange information and data with the network. Therefore, the UE as described herein is used to represent any electronic component.

[0011] The example embodiments are also described with reference to a 5G New Radio (NR) network. However, the example embodiments may also be implemented in other types of networks, including but not limited to legacy cellular networks (e.g., Long Term Evolution (LTE) ) , future evolutions of the cellular protocol (e.g., 5G advanced, 6G, etc. ) , or any other type of network .

[0012] The example embodiments are described with reference to reporting per-layer power feedback for a UE configured to communicate on four (4) layers. This is only an example as the example embodiments may be used when the UE is reporting power feedback for less than 4 layers (e.g., 2 layers) or more than 4 layers (e.g. , 8 layers) . In some example embodiments, when reporting per-layer feedback for more than 4 layers (e.g. , 8 layers) , the feedback may be split into two separate 4 layer feedback, e.g., layers 1-4 in a first report and layers 5-8 in a second report.

[0013] In the current cellular standards (e.g., 3GPP Technical Specification (TS) 38.214) channel State Information (CSI) feedback is defined as including various information such as a Channel Quality Indicator (CSI) , a Pre-Coding Matrix Indicator (PMI) , CSI-Ref erence Signal (CSI-RS) receiver Indicator (CRI) , Synchronization Signal (SS) / Physical Broadcast Channel (PBCH) Block Resource Indictor (SSBRI) , layer indicator (LI) , rank indicator (RI) , Layerl-Ref erence Signal Received Power (Ll-RSRP) , Layerl-Signal-to-Interf erence Noise Ratio (Ll- SINR) , Capability Index, or time domain channel properties. However, there is no manner of reporting per-layer power information to the network.

[0014] The example embodiments provide manners of configuring a UE to perform per-layer power feedback to a base station. The reporting of the per-layer power information to the base station may allow for an improved pre-coding matrix calculation, for power loading across layers, for rank adaptation, etc. These and other example embodiments are described in greater detail below.

[0015] Fig. 1 shows an example network arrangement 100 according to various example embodiments. The example network arrangement 100 includes a UE 110. The UE 110 may be any type of electronic component that is configured to communicate via a network, e.g. , mobile phones, tablet computers, desktop computers, smartphones, embedded devices, wearables, Internet of Things (loT) devices, etc. An actual network arrangement may include any number of UEs being used by any number of users. Thus, the example of one UE 110 is merely provided for illustrative purposes.

[0016] The UE 110 may be configured to communicate with one or more networks. In the example of the network arrangement 100, the network with which the UE 110 may wirelessly communicate is a 5G NR radio access network (RAN) 120. The UE 110 may also communicate with other types of networks (e.g. , 5G cloud RAN, a next generation RAN (NG-RAN) , a legacy cellular network, etc. ) and the UE 110 may also communicate with networks over a wired connection. With regard to the example embodiments, the UE 110 may establish a connection with the 5G NR RAN 120. Therefore, the UE 110 may have a 5G NR chipset to communicate with the NR RAN 120.

[0017] The 5G NR RAN 120 may be portions of a cellular network that may be deployed by a network carrier (e.g., Verizon, AT&T, T-Mobile, etc. ) . The RAN 120 may include cells or base stations that are configured to send and receive traffic from UEs that are equipped with the appropriate cellular chip set. In this example, the 5G NR RAN 120 includes the gNB 120A and the gNB 120B. However, reference to a gNB is merely provided for illustrative purposes, any appropriate base station or cell may be deployed (e.g., Node Bs, eNodeBs, HeNBs, eNBs, gNBs, gNodeBs, macrocells, microcells, small cells, femtocells, etc. ) .

[0018] Any association procedure may be performed for the UE 110 to connect to the 5G NR RAN 120. For example, as discussed above, the 5G NR RAN 120 may be associated with a particular network carrier where the UE 110 and / or the user thereof has a contract and credential information (e.g. , stored on a SIM card) . Upon detecting the presence of the 5G NR RAN 120, the UE 110 may transmit the corresponding credential information toassociate with the 5G NR RAN 120. More specifically, the UE 110 may associate with a specific cell (e.g., gNB 120A) .

[0019] The network arrangement 100 also includes a cellular core network 130, the Internet 140, an IP Multimedia Subsystem (IMS) 150, and a network services backbone 160. The cellular core network 130 manages the traffic that flows between the cellular network and the Internet 140. The IMS 150 may be generally described as an architecture for delivering multimedia services to the UE 110 using the IP protocol. The IMS 150 may communicate with the cellular core network 130 and the Internet 140 to provide the multimedia services to the UE 110. The network services backbone 160 is in communication either directly or indirectly with the Internet 140 and the cellular core network 130. The network services backbone 160 may be generally described as a set of components (e.g., servers, network storage arrangements, etc.) that implement a suite of services that may be used to extend the functionalities of the UE 110 in communication with the various networks.

[0020] Fig. 2 shows an example UE 110 according to various example embodiments. The UE 110 will be described with regard to the network arrangement 100 of Fig. 1. The UE 110 may represent any electronic device and may include a processor 205, a memory arrangement 210, a display device 215, an input / output (I / O) device 220, a transceiver 225, and other components 230. The other components 230 may include, for example, an audio input device, an audio output device, a battery that provides a limited power supply, a data acquisition device, ports to electrically connect the UE 110 to other electronic devices, sensors to detect conditions of the UE 110, etc.

[0021] The processor 205 may be configured to execute a plurality of engines for the UE 110. For example, the engines may include a power feedback engine 235 for performing operations related to reporting per-layer power feedback to a network. The operations include, but are not limited to, receiving a per-layer power feedback configuration, measuring reference signals to determine the per-layer power, configuring a report comprising the per-layer power feedback and reporting the per-layer power feedback to the network. Each of these example operations will be described in more detail below.

[0022] The above referenced engine being an application (e.g., a program) executed by the processor 205 is only example. The functionality associated with the engines may also be represented as a separate incorporated component of the UE 110 or may be a modular component coupled to the UE 110, e.g. , an integrated circuit with or without firmware. For example, the integrated circuit may include input circuitry to receive signals and processing circuitry to process the signals and other information. The engines may also be embodied as one application or separate applications. In addition, in some UEs, the functionality described for the processor 205 is split among two or more processors such as a baseband processor and an applications processor. The example embodiments may be implemented in any of these or other configurations of a UE .

[0023] The memory arrangement 210 may be a hardware component configured to store data related to operations performed by the UE 110. The display device 215 may be a hardware component configured to show data to a user while the I / O device 220 maybe a hardware component that enables the user to enter inputs. The display device 215 and the I / O device 220 may be separate components or integrated together such as a touchscreen.

[0024] The transceiver 225 may be a hardware component configured to establish a connection with the 5G NR-RAN 120, an LTE-RAN (not pictured) , a legacy RAN (not pictured) , a WLAN (not pictured) , etc. Accordingly, the transceiver 225 may operate on a variety of different frequencies or channels (e.g., set of consecutive frequencies) . The transceiver 225 includes circuitry configured to transmit and / or receive signals (e.g., control signals, data signals) . Such signals may be encoded with information implementing any one of the methods described herein. The processor 205 may be operably coupled to the transceiver 225 and configured to receive from and / or transmit signals to the transceiver 225. The processor 205 may be configured to encode, decode and / or process signals (e.g., signaling from a base station of a network) for implementing any one of the methods described herein.

[0025] Fig. 3 shows an example base station 300 according to various example embodiments. The base station 300 may represent the gNB 120A, the gNB 120B or any other access node through which the UE 110 may establish a connection and manage network operations .

[0026] The base station 300 may include a processor 305, a memory arrangement 310, an input / output (I / O) device 315, a transceiver 320, and other components 325. The other components 325 may include, for example, an audio input device, an audio output device, a battery, a data acquisition device, ports toelectrically connect the base station 300 to other electronic devices and / or power sources, etc.

[0027] The processor 305 may be configured to execute a plurality of engines for the base station 300. For example, the engines may include a power feedback configuration engine 330 for performing operations related to configuring a UE to report per-layer power to the base station 300. The operations include, but are not limited to, configuring the UE 110 to perform per- layer power feedback, triggering the UE 110 to measure one or more reference signals transmitted by the base station 300, receiving the per-layer power feedback from the UE 110 and scheduling the UE 110 based on the per-layer power feedback. Each of these example operations will be described in more detail below.

[0028] The memory 310 may be a hardware component configured to store data related to operations performed by the base station 300. The I / O device 315 may be a hardware component or ports that enable a user to interact with the base station 300. The transceiver 320 may be a hardware component configured to exchange data with the UE 110 and any other UE in the network arrangement 100.

[0029] The transceiver 320 may be a hardware component configured to exchange data with the UE 110 and any other UE in the network arrangement 100. The transceiver 320 may operate on a variety of different frequencies or channels (e.g. , set of consecutive frequencies) . The transceiver 320 includes circuitry configured to transmit and / or receive signals (e.g. , control signals, data signals) . Such signals may be encoded withinformation implementing any one of the methods described herein. The processor 305 may be operably coupled to the transceiver 320 and configured to receive from and / or transmit signals to the transceiver 320. The processor 305 may be configured to encode, decode and / or process signals (e.g., signaling from a UE) for implementing any one of the methods described here.

[0030] Fig. 4 shows an example signaling diagram 400 for configuring and reporting power feedback information on a perlayer basis according to various example embodiments. The signaling diagram is performed between the UE 110 and the base station 300 (e.g., gNB 120A) .

[0031] In 410, the base station 300 provides a radio resource control (RRC) configuration for configuring reporting for the UE 110, e.g., reportConfig in NR networks. In this example, the RRC configuration is extended to include configuration information related to a per-layer power feedback. The configuration information may include whether the power feedback is to be determined for the wideband or for a subband, a method of normalization for reporting the per-layer feedback, a feedback quantization step size, a number of bits to be included per- layer, Uplink Control Information (UCI) mapping and prioritization, etc. Examples of this configuration information related to a per-layer power feedback will be described in greater detail below.

[0032] In 420, the base station 300 triggers the UE 110 to perform the channel measurements, e.g., via Downlink ControlInformation (DCI) . The example of Fig. 4 shows a signalingdiagram 400 for aperiodic feedback triggered by DCI . The example embodiments may also be used for periodic feedback and semi- persistent feedback.

[0033] In 430, the UE 110 may perform the measurements (e.g. , CSI-RS measurements and corresponding calculations (e.g., Preceding Matrix Indicator (PMI) calculations) and the corresponding quantization for the per-layer power feedback. In 440, the UE 110 reports the PMI and the per-layer power information as part of the CSI feedback.

[0034] In 450, the base station 300 may use the per-layer power information for various purposes. For example, the base station 300 may use the per-layer power information for an improved pre-coding matrix calculation, e.g.. Minimum Mean Square Error (MMSE) calculation with an accurate per-layer signal to noise ratio (SNR) . The per-layer power information may also be used by the base station 300 to balance power loading across layers, e.g. , layers with a lower SNR may be allocated more power. In another example, the base station 300 may use the per-layer power information for an improved rank adaptation, e.g., the UE 110 may report rank 4 but the per-layer power information may show a large variation between the 4 layers and the base station 300 may use this information to select rank 2 communications with the UE 110. These are only examples of how the base station 300 may use the per-layer power feedback and other uses may also be possible.

[0035] As stated above, in some example embodiments, the per- layer power feedback may be reported on a wideband basis. The wideband feedback may include an average of the per-layer poweracross the entire wideband, e.g., the average of each layer's power across the entire wideband. Since only a single value may be reported for each layer, the reporting of the per-layer power feedback on a wideband basis may use a limited number of bits, e.g., there is a low signaling overhead associated with such a wideband reporting. There may be various manners of calculating the wideband per-layer power. The following provides two options for calculating the per-layer wideband power but other manners of calculating the per-layer wideband power may also be used with the example embodiments.

[0036] In a first option, the wideband per-layer power may be reported based on a wideband of a selected beam, e.g., the power for the selected beam across the entire wideband. The wideband power calculation may be based on: v'R_{tx} v; where R {tx} is an averaged Transmission (Tx) covariance matrix over all subbands for the selected beam; and v is the wideband precoder based on the selected widebeam.

[0037] The Eigen-value of v'R {tx} v may then be calculated and this may be the wideband per-layer feedback provided to the base station 300.

[0038] In a second option, the wideband per-layer power may be reported based on a subband power for a selected beam, e.g., the power for each subband within the wideband may be determined using a beam selected for the subband. The wideband power calculation for each subband may be based on:v_ { subband } ' R_ { subband } v_ { subband } , where R {subband} is a Tx covariance matrix for the subband for the selected beam; and v {subband} is the subband precoder for the subband for the selected beam.

[0039] Then, for each subband, the Eigen-value of v {subband}'R {subband} v {subband} may be calculated. The average of this Eigen-value over all subbands may then be determined and this may be the wideband per-layer feedback provided to the base station 300.

[0040] As stated above, the per-layer power feedback configuration may also include a method of normalization for reporting the per-layer feedback, a feedback quantization step size, a number of bits to be included per-layer, etc. The following provides some examples of these reporting configurations based on the reporting of per-layer power feedback on a wideband basis.

[0041] In some example embodiments, the per-layer power feedback on a wideband basis may be based on a differential power to the first layer (e.g. , a reference layer) and a uniform quantization per-layer. For example, the actual power (e.g., Eigen-value) of layer 1 may be reported and the reported power of each of layers 2-4 may be based on a differential from the actual power of layer 1. Using differential reporting may reduce the number of bits required to report the per-layer power feedback, e.g., reporting the actual power of each layer may require more bits than reporting some layers using a differential scheme. Some examples of differential powerreporting for wideband per-layer power feedback are provided below .

[0042] In a first option, the reporting of wideband perlayer power feedback may be based on a differential to the first layer (e.g., reference Layer 1) and a same fixed number of bits for each of the lower layers (e.g., Layers 2-4) where each layer may have a different quantization step. To provide an example of this option, it may be considered that the fixed number of bits is 2 (e.g., codepoints 00, 01, 10, 11) for each differential layer to be reported. Normally, the power for each layer will diverge more as the layer is farther away from the selected reference layer, e.g., the layer for which the actual power is reported, which in this example is Layer 1. Thus, it would be expected that the Layer 2 power would diverge from the Layer 1 power less than the Layer 3 power, which would diverge less than the Layer 4 power. While this may not happen all the time, the reporting may be configured to handle this common scenario. However, the configuration does not exclude other possibilities.

[0043] Thus, in this example, because Layer 2 is closer to the reference Layer 1, Layer 2 may be configured with a 2dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. Layer 3 that is farther from Layer 1 may be configured with a 4dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 4dB lower, 01: 8dB lower; 10: 12dB lower; 11: >= 16dB lower. Layer 4 may have an even larger quantization step, e.g., 8dB quantization step resulting in the 2 bit differential codepoints corresponding to:00: 8dB lower, 01: 16dB lower; 10: 24dB lower; 11: >= 32dB lower .

[0044] The fixed number of bits and the quantization steps provided above are only examples and other fixed number of bits (3 bits, 4 bits, etc.) and / or size quantization steps may also be configured (e.g., IdB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different quantization step (e.g., Layer 3 and Layer 4 may have the same quantization step that is different from the Layer 2 quantization step) .

[0045] In a second option, the reporting of wideband perlayer power feedback may be based on a differential to the reference layer (e.g., Layer 1) using a same quantization step for each layer and a larger number of bits for lower layers, e.g., Layer 3 has a larger number of bits than Layer 2. To provide an example of this option, it may be considered that a 2dB quantization step is used. The differential reporting for Layer 2 may have 2 bits corresponding to the codepoints for a 2dB quantization step as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. The differential reporting for Layer 3 may have 3 bits corresponding to the codepoints for a 2dB quantization step as follows: 000: 2dB lower; 001: 4dB lower; 010: 6dB lower; 011: 8dB lower; 100: lOdB lower; 101: 12dB lower; 110: 14dB lower; 111: >=16dB lower. The differential reporting for Layer 4 may have 4 bits corresponding to the codepoints for a 2dB quantization step as follows: 0000: 2dB lower; 0001: 4dB lower; 0010: 6dB lower; 0011: 8dB lower; 0100: lOdB lower; 0101: 12dB lower; 0110: 14dB lower; 0111: 16dB lower; 1000: 18dB lower; 1001: 20dB lower; 1010: 22dB lower;1011: 24dB lower; 1100: 26dB lower; 1101: 28dB lower; 1110: 30dB lower; 1111: >=32dB lower.

[0046] The fixed quantization step provided above is only an example and other fixed size quantization steps may also be configured (e.g., ldB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different number of bits (e.g., Layer 3 and Layer 4 may have the same number of bits that is different from the number of bits for Layer 2) .

[0047] In other example embodiments, the per-layer power feedback on a wideband basis may be based on a differential power to the previous layer and a uniform quantization per- layer. For example, the actual power (e.g., Eigen-value) of layer 1 may be reported, the reported power Layer 2 may be based on a differential from the actual power of Layer 1, the reported power of Layer 3 may be based on a differential from the reported power of Layer 2 and the reported power of Layer 4 may be based on a differential from the reported power of Layer 3. Again, using differential reporting may reduce the number of bits required to report the per-layer power feedback.

[0048] To provide an example, a same number of bits per-layer and a same quantization step may be used for each lower layer, e.g., 2 bits with 2dB quantization step. Thus, Layer 2 may be reported relative to layer 1 with a 2dB quantization step using the 2 bit codepoints as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. Layer 3 may be reported relative to Layer 2 with a 2dB quantization step using the 2 bit codepoints as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. Layer 4 may be reported relative toLayer 3 with a 2dB quantization step using the 2 bit codepoints as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower.

[0049] The fixed quantization step provided above is only an example and other fixed size quantization steps may also be configured (e.g., IdB, 1.5dB, 3dB, 5dB, etc. ) . In addition, the fixed number of bits is only an example and other numbers of bits may also be used (e.g., 3 bits, 4 bits, etc. ) .

[0050] As stated above, the per-layer power feedback configuration may also include a UCI mapping and prioritization configuration. The UCI for reporting may have a CSI part 1 and a CSI part 2. The wideband per-layer power feedback may be reported in either CSI part 1 or CSI part 2 as described below.

[0051] Currently, the CSI part 1 includes feedback for RI, wideband CQI, subband CQI, and a total number of non-zero coefficient (NZC) (e.g. , KNZ,TOT) . In some example embodiments, the wideband per-layer power reporting may be added to the CSI part 1. The UCI part 1 is a fixed size. Thus, in these example embodiments, the wideband per-layer power may be a fixed size regardless of the RI . In these examples, for lower ranks, corresponding fields may be padded with zero. To provide an example, it may be considered that 3 bits are used to report the wideband per-layer power for each layer and the wideband per- layer power field has 9 bits. Thus, when RI=2, the wideband per- layer power field may be padded as follows: xxxOOOOOO; when RI=3, the wideband per-layer power field may be padded as follows: xxxyyyOOO; and when RI=4 there may be no padding as follows: xxxyyyzzz.

[0052] Various examples were provided above describing di f ferent numbers of bits that may be used to report the wideband per-layer power and therefore, the above describing a 9 bit wideband per-layer power field and using 3 bits to report wideband per-layer power is only an example . Other values may be used .

[0053] In other example embodiments , the wideband per-layer power reporting may be added to the CSI part 2 . In these example embodiments , the UCI part 1 may include the legacy fields as described above with a total number of wideband power bits field added to indicate the number of bits used for the wideband per- layer power reporting in the CS I part 2 . The total number of wideband power bits depends on the RI . For example, total number of wideband per-layer power bits field may be 3 bits and be used to indicate the following number of bits in the CSI part 2 for the corresponding RI , RI=2 corresponds to 3 bits in the CS I part 2 for the wideband per-layer power reporting, RI=3 corresponds to 6 bits in the CS I part 2 for the wideband per-layer power reporting, and RI=4 corresponds to 9 bits in the CS I part 2 for the wideband per-layer power reporting . Again, various examples were provided above describing dif ferent numbers of bits that may be used to report the wideband per-layer power and therefore , the above describing the number of bits for di f ferent RI s is only an example . Other values may be used .

[0054] The UCI part 2 currently has non-zero coef ficients divided into 3 groups based on priority, e . g . , Priority Group 0 > Group 1 > Group 2a . The wideband per-layer power configuration may also define a priority for the wideband per-layer powerreporting. In one example, the wideband per-layer power may be configured as part of Priority Group 0, which is always transmitted without omission. In other example embodiments, the wideband per-layer power priority may be configured as part of Priority Group 1 or Priority Group 2a.

[0055] In some example embodiments, the per-layer power feedback may be reported on a subband basis. The subband per- layer power may have a larger dynamic range compared to the wideband. The subband per-layer power reporting may use more bits than the wideband per-layer power reporting but may provide a finer granularity when compared to the wideband per-layer power reporting.

[0056] The subband per-layer power may be calculated using the subband PMI as follow: v_ { subband } ' R_ { subband } v_ { subband } , where R_{ subband} is a Tx covariance matrix for the subband; and v {subband} is the subband precoder for the subband.

[0057] The Eigen-value for v {subbandJ'R {subband} v {subband} may be calculated and reported as the subband per- layer power feedback to the base station 300.

[0058] In some example embodiments, the subband configuration for subband per-layer power may be the same as the PMI subband, e.g., the subband size in resource blocks (RBs) is the same as the number of RBs configured for PMI. In other example embodiments, the subband configuration for subband per-layer power may be include multiple PMI subbands, e.g., the PMIsubband may have a first number of RBs and the subband for perlayer power may include more RBs than the PMI subband. In these example embodiments, an average power over the configured subband size may be determined and reported, e.g., the per-layer power for each PMI subband within the per-layer power subband may be determined and averaged.

[0059] In the example of subband per-layer power feedback, differential reporting may also be used in a similar manner as described above with reference to the wideband per-layer power feedback. For example, the reference layer (e.g., Layer 1) power per subband may be reported, while the remaining layers (e.g., Layers 2-4) feedback may be reported as a differential based on the reference layer. As will be described in greater detail below, the power feedback may also represent a frequency domain selectivity. There may be various manners in which the differential subband per-layer power feedback may be reported. The following provides several examples of providing the differential feedback.

[0060] In some example embodiments, the differential power may be reported based on a Layer 1 wideband average power. In these example embodiments, the average power for the wideband of Layer 1 may be determined, e.g., the average of all the Layer 1 subbands across the wideband. Then, each of the Layer 1-4 subbands may be reported as a differential to this Layer 1 wideband power. Since the differential is reported with respect to an average of the reference layer, the feedback for the individual subbands may have (+ / -) values. Some of the below examples provided examples of (+ / -) values.

[0061] In one option for reporting the differential subband per-layer power feedback with respect to the average of the reference layer wideband, a fixed same number of bits may be used per layer and different layers may have different quantization steps. For example, it may be considered that the fixed number of bits is 2. Layer 1 may have a IdB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: IdB lower; 01:>=2dB lower; 10: IdB higher; 11: >=2dB higher. Layer 2 may have a 2dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. Layer 3 may have a 4dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 4dB lower, 01: 8dB lower; 10: 12dB lower; 11: >= 16dB lower. Layer 4 may have an 8dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 8dB lower, 01: 16dB lower; 10: 24dB lower; 11: >= 32dB lower.

[0062] The fixed number of bits and the quantization steps provided above are only examples and other fixed number of bits (3 bits, 4 bits, etc.) and / or size quantization steps may also be configured (e.g., IdB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different quantization step (e.g., Layer 3 and Layer 4 may have the same quantization step that is different from the Layer 2 quantization step) .

[0063] In a second option, the reporting of the subband perlayer power feedback may be based on a differential to the average power of the reference layer (e.g., Layer 1) using a same quantization step for each layer and a larger number of bits for lower layers, e.g., Layer 3 has a larger number of bitsthan Layer 2. To provide an example of this option, it may be considered that a 2dB quantization step is used. The differential reporting for Layer 1 may have 1 bit corresponding to the codepoints for a 2dB quantization step as follows: 0: 2dB lower; 1: 2dB higher. The differential reporting for Layer 2 may have 2 bits corresponding to the codepoints for a 2dB quantization step as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. The differential reporting for Layer 3 may have 3 bits corresponding to the codepoints for a 2dB quantization step as follows: 000: 2dB lower; 001: 4dB lower; 010: 6dB lower; Oil: 8dB lower; 100: lOdB lower; 101: 12dB lower; 110: 14dB lower; 111: >=16dB lower. The differential reporting for Layer 4 may have 4 bits corresponding to the codepoints for a 2dB quantization step as follows: 0000: 2dB lower; 0001: 4dB lower; 0010: 6dB lower; 0011: 8dB lower; 0100: lOdB lower; 0101: 12dB lower; 0110: 14dB lower; 0111: 16dB lower; 1000: 18dB lower; 1001: 20dB lower; 1010: 22dB lower; 1011: 24dB lower; 1100: 26dB lower; 1101: 28dB lower; 1110: 30dB lower; 1111: >=32dB lower.

[0064] The fixed quantization step provided above is only an example and other fixed size quantization steps may also be configured (e.g., IdB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different number of bits (e.g., Layer 3 and Layer 4 may have the same number of bits that is different from the number of bits for Layer 2) .

[0065] In other example embodiments, the differential power reporting for the subbands may be reported based on a differential from the reference layer subband having a highest power, e.g., the Layer 1 subband that has the highest power. Inthese example embodiments, the reporting may include an index that indicates the subband with the highest power. The number of bits used for reporting this differential may be log2 (nchoosek ( #subbands , 1) . In addition, in these example embodiments, because the differential power is calculated and reported based on the reference layer (e.g., Layer 1) subband with the highest power value, all other subbands in Layer 1 and the other layers will have lower values. Thus, the differential values may only include negative values.

[0066] In one option, the differential subband per-layer power feedback based on the Layer 1 subband with the highest power may be reported using a fixed same number of bits per layer and different layers may have different quantization steps. For example, it may be considered that the fixed number of bits is 2. Layer 1 may have a IdB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: IdB lower; 01:2dB lower; 10: 3dB lower; 11: >=4dB lower. Layer 2 may have a 2dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. Layer 3 may have a 4dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 4dB lower, 01: 8dB lower; 10: 12dB lower; 11: >= 16dB lower. Layer 4 may have an 8dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 8dB lower, 01: 16dB lower; 10: 24dB lower; 11: >= 32dB lower .

[0067] The fixed number of bits and the quantization steps provided above are only examples and other fixed number of bits (3 bits, 4 bits, etc.) and / or size quantization steps may alsobe configured (e.g., IdB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different quantization step (e.g., Layer 3 and Layer 4 may have the same quantization step that is different from the Layer 2 quantization step) .

[0068] In a second option, the differential subband per-layer power feedback based on the Layer 1 subband with the highest power may be reported using a same quantization step for each layer and a larger number of bits for lower layers, e.g., Layer 3 has a larger number of bits than Layer 2. To provide an example of this option, it may be considered that a 2dB quantization step is used. The differential reporting for Layer 1 may have 1 bit corresponding to the codepoints for a 2dB quantization step as follows: 0: 2dB lower; 1: >=4dB lower. The differential reporting for Layer 2 may have 2 bits corresponding to the codepoints for a 2dB quantization step as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. The differential reporting for Layer 3 may have 3 bits corresponding to the codepoints for a 2dB quantization step as follows: 000: 2dB lower; 001: 4dB lower; 010: 6dB lower; 011: 8dB lower; 100: lOdB lower; 101: 12dB lower; 110: 14dB lower; 111: >=16dB lower. The differential reporting for Layer 4 may have 4 bits corresponding to the codepoints for a 2dB quantization step as follows: 0000: 2dB lower; 0001: 4dB lower; 0010: 6dB lower;0011: 8dB lower; 0100: lOdB lower; 0101: 12dB lower; 0110: 14dB lower; 0111: 16dB lower; 1000: 18dB lower; 1001: 20dB lower; 1010: 22dB lower; 1011: 24dB lower; 1100: 26dB lower; 1101: 28dB lower; 1110: 30dB lower; 1111: >=32dB lower.

[0069] The fixed quantization step provided above is only an example and other fixed size quantization steps may also beconfigured (e.g., IdB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different number of bits (e.g., Layer 3 and Layer 4 may have the same number of bits that is different from the number of bits for Layer 2) .

[0070] In still further example embodiments, the differential power reporting for the subbands may be reported based on a differential to a corresponding reference layer (e.g., Layer 1) subband. For example, it may be considered that 5 subbands per layer are reported. Thus, the actual power for Layer 1 subbands 1-5 may be reported. For the remaining layers (e.g., Layers 2- 4) , the differential power may be reported. For example, the Layer 2, subband 3 reporting will be the differential from the Layer 1, subband 3 power, the Layer 4, subband 2 reporting will be the differential from the Layer 1, subband 2 power, etc.

[0071] In a first option, the differential subband per-layer power feedback based on the corresponding Layer 1 subband may be reported using a same fixed number of bits for each of the lower layers (e.g., Layers 2-4) where each layer may have a different quantization step. For example, Layer 2 may be configured with a 2dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. Layer 3 may be configured with a 4dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 4dB lower, 01: 8dB lower; 10: 12dB lower; 11: >= 16dB lower. Layer 4 may be configured with an 8dB quantization step resulting in the 2 bit differential codepoints corresponding to: 00: 8dB lower, 01: 16dB lower; 10: 24dB lower; 11: >= 32dB lower.

[0072] The fixed number of bits and the quantization steps provided above are only examples and other fixed number of bits (3 bits, 4 bits, etc.) and / or size quantization steps may also be configured (e.g., IdB, 1.5dB, 3dB, 5dB, etc.) . In addition, each layer is not required to have a different quantization step (e.g., Layer 3 and Layer 4 may have the same quantization step that is different from the Layer 2 quantization step) .

[0073] In a second option, differential subband per-layer power feedback based on the corresponding Layer 1 subband may be reported using a same quantization step for each layer and a larger number of bits for lower layers, e.g., Layer 3 has a larger number of bits than Layer 2. To provide an example of this option, it may be considered that a 2dB quantization step is used. The differential reporting for Layer 2 may have 2 bits corresponding to the codepoints for a 2dB quantization step as follows: 00: 2dB lower; 01: 4dB lower; 10: 6dB lower; 11: >=8dB lower. The differential reporting for Layer 3 may have 3 bits corresponding to the codepoints for a 2dB quantization step as follows: 000: 2dB lower; 001: 4dB lower; 010: 6dB lower; Oil: 8dB lower; 100: lOdB lower; 101: 12dB lower; 110: 14dB lower; 111: >=16dB lower. The differential reporting for Layer 4 may have 4 bits corresponding to the codepoints for a 2dB quantization step as follows: 0000: 2dB lower; 0001: 4dB lower; 0010: 6dB lower; 0011: 8dB lower; 0100: lOdB lower; 0101: 12dB lower; 0110: 14dB lower; 0111: 16dB lower; 1000: 18dB lower; 1001: 20dB lower; 1010: 22dB lower; 1011: 24dB lower; 1100: 26dB lower; 1101: 28dB lower; 1110: 30dB lower; 1111: >=32dB lower.

[0074] The fixed quantization step provided above is only an example and other fixed size quantization steps may also beconfigured (e.g., IdB, 1.5dB, 3dB, 5dB, etc. ) . In addition, each layer is not required to have a different number of bits (e.g. , Layer 3 and Layer 4 may have the same number of bits that is different from the number of bits for Layer 2) .

[0075] In the above examples of reporting the subband perlayer power, the differential was reported based on differentials across layers, e.g., differential with respect to a reference layer such as average wideband reference power, highest reference layer subband power, corresponding reference layer subband, etc.

[0076] In some example embodiments, the differential may be reported across subbands. For example, for each layer, a subband with the maximum power may be considered the reference subband and the power for the remaining subbands of the layer may be reported as a differential to the reference subband of the layer. In these example embodiments, the UE 110 may indicate the subband index of the subband with the maximum power for each layer, calculate the power difference between the subband with the maximum power and each of the remaining subbands in the layer and then report, for each layer, the differential power level with respect to the subband with the maximum power.

[0077] In some example embodiments, the configuration for the per-layer power feedback may include an indication that the feedback is to be reported with a domain transformation. For example, instead of quantizing the power in the frequency domain, a domain transformation to the delay domain may be performed. In this example, the per-layer power feedback may then comprise one or more dominant delay taps per layer. Forexample, the largest delay tap per layer may be determined to be the reference delay tap. Any delay taps in the layer that are lower than a threshold may be discarded and the remaining delay taps may be normalized to the largest, quantized (e.g., using a differential as described above) and reported as the per-layer feedback .

[0078] The subband per-layer power feedback may be reported using the CSI part 2. In these examples, the UCI part 1 may be modified to include a total number of subband power bits field. For example, the total number of subband power bits field may be 3 bits and be used to indicate the following number of bits in the CSI part 2 for the corresponding RI, RI=2 corresponds to 3 bits in the CSI part 2 for the subband per-layer power reporting, RI=3 corresponds to 6 bits in the CSI part 2 for the subband per-layer power reporting, and RI=4 corresponds to 9 bits in the CSI part 2 for the subband per-layer power reporting. Again, various examples were provided above describing different numbers of bits that may be used to report the subband per-layer power and therefore, the above describing the number of bits for different RIs is only an example. Other values may be used.

[0079] The UCI part 2 currently has non-zero coefficients divided into 3 groups based on priority, e.g., Priority Group 0 > Group 1 > Group 2a. The subband per-layer power configuration may also define a priority for the subband per-layer power reporting. In one example, the subband per-layer power may be configured as part of Priority Group 0, which is always transmitted without omission. In other example embodiments, thesubband per-layer power priority may be configured as part of Priority Group 1 or Priority Group 2a.

[0080] In the above example embodiments, it was described that the UE 110 may be configured to report per-layer power feedback to the base station 300. This configuration was described, for example, as being sent from the base station 300 to the UE 110 in operation 410 of Fig. 4. This per-layer power feedback configuration was described as including various parameters related to measuring, calculating and reporting the per-layer power feedback. In some example embodiments, one or more of these example parameters related to measuring, calculating and reporting the per-layer power feedback may be hard coded into standards (e.g., 3GPP Technical Specifications) . For example, it was described in several example embodiments that the reporting of differential per-layer power included a fixed number of bits per layer and different quantization steps for different layers . Thus, in some example embodiments, instead of these parameters being signaled from the base station 300 to the UE 110, these parameters may be hard coded into the standards. This may apply to none of the parameters, some of the parameters or all of the parameters described herein.Examples

[0081] In a first example, a method, comprising, processing based on signaling received from a base station, a reporting configuration comprising a per-layer power feedback configuration, measuring one or more reference signals (RSs) transmitted by the base station, determining per-layer power feedback for the RSs transmitted by the base station andgenerating, for transmission to the base station, the per-layer power feedback to the base station.

[0082] In a second example, the method of the first example, wherein the per-layer power feedback configuration indicates the per-layer power feedback is to be reported for a wideband.

[0083] In a third example, the method of the second example, wherein the wideband comprises a wideband per-layer power for a selected beam.

[0084] In a fourth example, the method of the second example, wherein the wideband comprises a per-layer power for a plurality of subbands, wherein the per-layer power of each of the plurality of subbands is for a selected beam.

[0085] In a fifth example, the method of the second example, wherein the per-layer power feedback comprises a differential power feedback with respect to a reference layer and a uniform quantization per layer.

[0086] In a sixth example, the method of the fifth example, wherein the differential power feedback is reported using a same number of bits per layer, wherein the differential power feedback for a first layer is reported based on a first quantization step and the differential power feedback for a second layer is reported based on a second quantization step, wherein the first quantization step and the second quantization step have a different value.

[0087] In a seventh example, the method of the fifth example, wherein the differential power feedback is reported using a same quantization step for each layer, wherein the differential power feedback for a first layer is reported using a first number of bits and the differential power feedback for a second layer is reported using a second number of bits, wherein the first number of bits is different from the second number of bits.

[0088] In an eighth example, the method of the second example, wherein the per-layer power feedback comprises a differential power feedback with respect to a previously reported layer and a uniform quantization per layer, wherein the differential power feedback is reported using a same number of bits and a same quantization step per layer.

[0089] In a ninth example, the method of the second example, wherein the per-layer power feedback is reported in a Channel State Information (CSI) part 1.

[0090] In a tenth example, the method of the second example, wherein the per-layer power feedback is reported in a Channel State Information (CSI) part 2, wherein a CSI part 1 corresponding to the CSI part 2 comprises a field indicating a total number of bits used in the CSI part 2 to report the per- layer power feedback.

[0091] In an eleventh example, the method of the tenth example, wherein the per-layer power feedback configuration comprises a priority for reporting the per-layer power feedback using the CSI part 2.

[0092] In a twelfth example, the method of the first example, wherein the per-layer power feedback configuration indicates the per-layer power feedback is to be reported per subband, wherein a size of each subband is based on a size of a configured Precoding Matrix Indicator (PMI) subband.

[0093] In a thirteenth example, the method of the twelfth example, wherein the size of each subband is the same as the size of the configured PMI subband.

[0094] In a fourteenth example, the method of the twelfth example, wherein the size of each subband is a multiple of the size of the configured PMI subband.

[0095] In a fifteenth example, the method of the twelfth example, wherein the per-layer power feedback comprises a differential power feedback with respect to an average power for all subbands of a reference layer.

[0096] In a sixteenth example, the method of the fifteenth example, wherein the differential power feedback is reported using a same number of bits per layer, wherein the differential power feedback for a first layer is reported based on a first quantization step and the differential power feedback for a second layer is reported based on a second quantization step, wherein the first quantization step and the second quantization step have a different value.

[0097] In a seventeenth example, the method of the fifteenth example, wherein the differential power feedback is reported using a same quantization step for each layer, wherein thedifferential power feedback for a first layer is reported using a first number of bits and the differential power feedback for a second layer is reported using a second number of bits, wherein the first number of bits is different from the second number of bits .

[0098] In an eighteenth example, the method of the twelfth example, wherein the per-layer power feedback comprises a differential power feedback with respect to a subband of a reference layer having a highest power.

[0099] In a nineteenth example, the method of the eighteenth example, wherein the differential power feedback is reported using a same number of bits per layer, wherein the differential power feedback for a first layer is reported based on a first quantization step and the differential power feedback for a second layer is reported based on a second quantization step, wherein the first quantization step and the second quantization step have a different value.

[0100] In a twentieth example, the method of the eighteenth example, wherein the differential power feedback is reported using a same quantization step for each layer, wherein the differential power feedback for a first layer is reported using a first number of bits and the differential power feedback for a second layer is reported using a second number of bits, wherein the first number of bits is different from the second number of bits .

[0101] In a twenty first example, the method of the twelfth example, wherein the per-layer power feedback comprises adifferential power feedback with respect to a corresponding subband of a reference layer.

[0102] In a twenty second example, the method of the twenty first example, wherein the differential power feedback is reported using a same number of bits per layer, wherein the differential power feedback for a first layer is reported based on a first quantization step and the differential power feedback for a second layer is reported based on a second quantization step, wherein the first quantization step and the second quantization step have a different value.

[0103] In a twenty third example, the method of the twenty first example, wherein the differential power feedback is reported using a same quantization step for each layer, wherein the differential power feedback for a first layer is reported using a first number of bits and the differential power feedback for a second layer is reported using a second number of bits, wherein the first number of bits is different from the second number of bits.

[0104] In a twenty fourth example, the method of the twelfth example, wherein the per-layer power feedback comprises a differential power feedback for each subband of a layer with respect to a subband of the layer having a highest power.

[0105] In a twenty fifth example, the method of the twelfth example, wherein the per-layer power feedback configuration comprises an indication to perform a domain transformation from a frequency domain to a delay domain, wherein the per-layerpower feedback comprises per-layer power feedback in the delay domain .

[0106] In a twenty sixth example, the method of the twenty fifth example, wherein the per-layer power feedback in the delay domain comprises delay taps for one or more subbands in each layer, wherein the one or more delay taps comprise a largest delay tap in each layer and any additional delay taps that satisfy a threshold, wherein the additional delay taps are reported based on a differential from the largest delay tap.

[0107] In a twenty seventh example, the method of the twelfth example, wherein the per-layer power feedback is reported in a Channel State Information (CSI) part 2, wherein a CSI part 1 corresponding to the CSI part 2 comprises a field indicating a total number of bits used in the CSI part 2 to report the per- layer power feedback.

[0108] In a twenty eighth example, the method of the twenty seventh example, wherein the per-layer power feedback configuration comprises a priority for reporting the per-layer power feedback using the CSI part 2.

[0109] In a twenty ninth example, a processor configured to perform any of the methods of the first through twenty eight examples .

[0110] In a thirtieth example, a user equipment (UE) configured to perform any of the methods of the first through twenty eight examples.

[0111] Tho se skilled in the art will understand that the above-described example embodiments may be implemented in any suitable software or hardware configuration or combination thereof . An example hardware platform for implementing the example embodiments may include , for example, an Intel x86 based platform with compatible operating system, a Windows OS , a Mac platform and MAC OS , a mobile device having an operating system such as iOS , Android, etc . The example embodiments of the above described method may be embodied as a program containing lines of code stored on a non-transitory computer readable storage medium that , when compiled, may be executed on a processor or microprocessor .

[0112] Although this application described various embodiments each having different features in various combinations , those skilled in the art will understand that any of the features of one embodiment may be combined with the features of the other embodiments in any manner not speci fically disclaimed or which is not functionally or logically inconsistent with the operation of the device or the stated functions of the disclosed embodiments .

[0113] It is well understood that the use of personally identi fiable information should follow privacy policies and practices that are generally recogni zed as meeting or exceeding industry or governmental requirements for maintaining the privacy of users . In particular, personally identifiable information data should be managed and handled so as to minimi ze risks of unintentional or unauthori zed access or use , and the nature of authori zed use should be clearly indicated to users .

[0114] It will be apparent to those skilled in the art that various modi fications may be made in the present disclosure , without departing from the spirit or the scope of the disclosure . Thus , it is intended that the present disclosure cover modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalent .

Claims

What is claimed:

1. An apparatus comprising processing circuitry configured to: process, based on signaling received from a base station, a reporting configuration comprising a per-layer power feedback configuration; measure one or more reference signals (RSs) transmitted by the base station; determine per-layer power feedback for the RSs transmitted by the base station; and generate, for transmission to the base station, the per- layer power feedback to the base station.

2. The apparatus of claim 1, wherein the per-layer power feedback configuration indicates the per-layer power feedback is to be reported for a wideband.

3. The apparatus of claim 2, wherein the wideband comprises (i) a wideband per-layer power for a selected beam or (ii) a per-layer power for a plurality of subbands, wherein the per- layer power of each of the plurality of subbands is for a selected beam.

4. The apparatus of claim 2, wherein the per-layer power feedback comprises a differential power feedback with respect to a reference layer and a uniform quantization per layer.

5. The apparatus of claim 4, wherein the differential power feedback is reported using a same number of bits per layer, wherein the differential power feedback for a first layer is reported based on a first quantization step and the differential power feedback for a second layer is reported based on a secondquantization step, wherein the first quantization step and the second quantization step have a different value.

6. The apparatus of claim 4, wherein the differential power feedback is reported using a same quantization step for each layer, wherein the differential power feedback for a first layer is reported using a first number of bits and the differential power feedback for a second layer is reported using a second number of bits, wherein the first number of bits is different from the second number of bits.

7. The apparatus of claim 2, wherein the per-layer power feedback comprises a differential power feedback with respect to a previously reported layer and a uniform quantization per layer, wherein the differential power feedback is reported using a same number of bits and a same quantization step per layer.

8. The apparatus of claim 2, wherein the per-layer power feedback is reported in (i) a Channel State Information (CSI) part 1 or (ii) a CSI part 2, wherein a CSI part 1 corresponding to the CSI part 2 comprises a field indicating a total number of bits used in the CSI part 2 to report the per-layer power feedback .

9. The apparatus of claim 1, wherein the per-layer power feedback configuration indicates the per-layer power feedback is to be reported per subband, wherein a size of each subband is based on a size of a configured Pre-coding Matrix Indicator (PMI) subband.

10. The apparatus of claim 9, wherein the size of each subband is (i) a same as a size of the configured PMI subband or (ii) a multiple of the size of the configured PMI subband.

11. The apparatus of claim 9, wherein the per-layer power feedback comprises a differential power feedback with respect to an average power for all subbands of a reference layer.

12. The apparatus of claim 11, wherein the differential power feedback is reported using a same number of bits per layer, wherein the differential power feedback for a first layer is reported based on a first quantization step and the differential power feedback for a second layer is reported based on a second quantization step, wherein the first quantization step and the second quantization step have a different value.

13. The apparatus of claim 11, wherein the differential power feedback is reported using a same quantization step for each layer, wherein the differential power feedback for a first layer is reported using a first number of bits and the differential power feedback for a second layer is reported using a second number of bits, wherein the first number of bits is different from the second number of bits.

14. The apparatus of claim 9, wherein the per-layer power feedback comprises a differential power feedback with respect to a subband of a reference layer having a highest power.

15. The apparatus of claim 9, wherein the per-layer power feedback comprises a differential power feedback with respect to a corresponding subband of a reference layer.16 . The apparatus of claim 9 , wherein the per-layer power feedback comprises a di f ferential power feedback for each subband of a layer with respect to a subband of the layer having a highest power .17 . The apparatus of claim 9 , wherein the per-layer power feedback configuration comprises an indication to perform a domain trans formation from a frequency domain to a delay domain, wherein the per-layer power feedback comprises per-layer power feedback in the delay domain .18 . The apparatus of claim 17 , wherein the per-layer power feedback in the delay domain comprises delay taps for one or more subbands in each layer, wherein the one or more delay taps comprise a largest delay tap in each layer and any additional delay taps that satisfy a threshold, wherein the additional delay taps are reported based on a di fferential from the largest delay tap .19 . The apparatus of claim 9 , wherein the per-layer power feedback is reported in a Channel State Information ( CSI ) part 2 , wherein a CSI part 1 corresponding to the CS I part 2 comprises a field indicating a total number of bits used in the CS I part 2 to report the per-layer power feedback .20 . The apparatus of claim 19 , wherein the per-layer power feedback configuration comprises a priority for reporting the per-layer power feedback using the CS I part 2 .

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