Differential precoder matrix indicators in channel state information feedback according to enhanced e-type ii codebooks

Abstract

Systems and methods for the use of differential precoder matrix indicators (PMIs) in channel state information (CSI) feedback within a framework for Enhanced E-type II (E-type 2) codebooks are disclosed. A differential PMI is made up of one or more PMI parts, each carrying PMI value types of, for example. PMI values of a typical E-type 2 PMI. A differential PMI may ultimately include fewer than all PMI value types of a typical E-type 2 PMI. A user equipment (UE) may construct and send differential PMI to the network by assuming, at least in part, an application of previously sent PMI parts at the base station for PMI reconstruction purposes. Accordingly, the UE is enabled to send fewer than all possible PMI parts in the differential PMI. Mechanisms for providing knowledge of PMI parts within in any particular differential PMI at both the UE and the network are discussed.

Description

DIFFERENTIAL PRECODER MATRIX INDICATORS IN CHANNEL STATEINFORMATION FEEDBACK ACCORDING TO ENHANCED E-TYPE IICODEBOOKSTECHNICAL FIELD

[0001] This application relates generally to wireless communication systems, including wireless communication systems using precoding matrix indicators (PMIs) in channel state information (CSI) feedback / reporting sent from a user equipment (UE) to a base station.BACKGROUND

[0002] Wireless mobile communication technology uses various standards and protocols to transmit data between a base station and a wireless communication device. Wireless communication system standards and protocols can include, for example, 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) (e.g., 4G). 3GPP New Radio (NR) (e.g., 5G), and Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard for Wireless Local Area Networks (WLAN) (commonly known to industry7groups as Wi-Fi®).

[0003] As contemplated by the 3GPP, different wireless communication systems' standards and protocols can use various radio access networks (RANs) for communicating between a base station of the RAN (which may also sometimes be referred to generally as a RAN node, a network node, or simply a node) and a wireless communication device known as a user equipment (UE). 3GPP RANs can include, for example. Global System for Mobile communications (GSM), Enhanced Data Rates for GSM Evolution (EDGE) RAN (GERAN), Universal Terrestrial Radio Access Network (UTRAN), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), and / or Next-Generation Radio Access Network (NG-RAN).

[0004] Each RAN may use one or more radio access technologies (RATs) to perform communication between the base station and the UE. For example, the GERAN implements GSM and / or EDGE RAT, the UTRAN implements Universal Mobile Telecommunication System (UMTS) RAT or other 3GPP RAT, the E-UTRAN implements LTE RAT (sometimes simply referred to as LTE), and NG-RAN implements NR RAT (sometimes referred to herein as 5G RAT, 5G NR RAT, or simply NR). Incertain deployments, the E-UTRAN may also implement NR RAT. In certain deployments, NG-RAN may also implement LTE RAT.

[0005] A base station used by a RAN may correspond to that RAN. One example of an E-UTRAN base station is an Evolved Universal Terrestrial Radio Access Network (E- UTRAN) Node B (also commonly denoted as evolved Node B, enhanced Node B, eNodeB, or eNB). One example of an NG-RAN base station is a next generation Node B (also sometimes referred to as a g Node B or gNB).

[0006] A RAN provides its communication services with external entities through its connection to a core network (CN). For example, E-UTRAN may utilize an Evolved Packet Core (EPC) while NG-RAN may utilize a 5G Core Network (5GC).

[0007] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0008] FIG. 1A illustrates a table providing a breakdown of PMI value types that may be found in various PMI parts of a PMI that uses enhanced type II (E-type 2) encoding and sent from a UE to a base station of a network, according to embodiments herein.

[0009] FIG. IB illustrates a listing of various representations for corresponding PMI value types that may be found in E-type 2 PMI, according to embodiments discussed herein.

[0010] FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D each show respective graphs corresponding to simulation results for various PMI value types of E-type 2 PMIs generated over time at a UE.

[0011] FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D each show respective graphs corresponding to simulation results for various PMI value types of E-type 2 PMIs generated over time at a UE.

[0012] FIG. 4 illustrates a flow diagram for a network controlled use of differential PMI as between a UE and a base station, according to embodiments discussed herein.

[0013] FIG. 5 illustrates a flow diagram for a network controlled use of differential PMI as between a UE and a base station, according to embodiments discussed herein.

[0014] FIG. 6 illustrates a flow diagram for an approach for the use of differential PMI that uses control aspects shared over / spread across both a UE and a base station, according to embodiments discussed herein.

[0015] FIG. 7 illustrates a method of a UE, according to embodiments discussed herein.

[0016] FIG. 8 illustrates a method of a RAN, according to embodiments discussed herein.

[0017] FIG. 9 illustrates an example architecture of a wireless communication system, according to embodiments disclosed herein.

[0018] FIG. 10 illustrates a system for performing signaling between a wireless device and a network device, according to embodiments disclosed herein.

[0019] Various embodiments are described with regard to a 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 appropriate electronic component.

[0020] Embodiments discussed herein relate to cases of wireless communications systems that use channel state information (CSI) feedback / reporting to communicate precoding matrix indicators (PMIs) from a UE to a network. The UE may receive one or more reference signals (e.g., CSI reference signals (CSI-RSs)) from the network and may generate CSI feedback (including a PMI for a recommended precoder) based on its measurements of the received reference signals. This CSI feedback may then be transmitted to the network, and the network can then (e.g., optionally) use the recommended precoder (or a precoder derived from the recommended precoder) in subsequent downlink (DL) communication with the UE.

[0021] It has been recognized, in the context of wireless communication systems that use CSI feedback / reporting to communicate PMIs to a network, that re-using past CSI feedback (e.g., instead of re-sending same / similar PMI information) may reduce PMI- related signaling overhead in the context of some low speed scenarios.

[0022] It has also been recognized that in the context of artificial intelligence (Al) evaluation-based PMI generation, long term short term memory (LTSM) used with atransformer (e.g., such that time aspects are leveraged in addition to frequency and / or spatial domain aspects) may show significant gains over cases that use a transformer only (in which case only frequency and / or spatial domain aspects may be leveraged).

[0023] Further, some definitions for some wireless communications systems (e.g., definitions for 3GPP Release 18 (R18) wireless communication systems) may specify the use of a time / frequency / spatial domain codebook in CSI prediction use cases. These definitions may assume the case of a high speed UE, and may be used in such cases in order to handle CSI aging issues.

[0024] However, such frameworks may lack usabilify / applicabilify for at least some circumstances. For example, such frameworks, whether alone or taken together, do not account for / are not applicable to a case where time domain aspects are desired to be leveraged and where a UE is not moving at high speed (e.g., a low speed UE).

[0025] Accordingly, embodiments herein relate to a framework for reducing CSI transmission overhead that is applicable to a more general class of cases than can be covered using mechanisms previously defined.

[0026] FIG. 1A illustrates a table 100 providing a breakdown of PMI value types 102 that may be found in various PMI parts 118 of a PMI that uses enhanced ty pe II (E-type 2) encoding and sent from a UE to a base station of a network, according to embodiments herein. The PMI may be a PMI of a CSI report that is being sent to the network. Herein, such a PMI that uses E-type 2 encoding may be referred to as an “E- fype 2 PMI.” Also note that, in various instances, value types found in / useable for a PMI as discussed herein be referred to as. for example, “value types of a PMI” or “PMI value types.”

[0027] The E-type 2 encoding used for such a PMI may be understood to include one or more PMI value types 102. These PMI value types 102 may include, as illustrated, a rotation factors for spatial domain (SD) basis value type 104, an SD basis index value type 106, a frequency domain constrained window value type 108, a selected delay taps value type 110, a bitmap of non-zero coefficients value type 112, a location of a strongest coefficient (SCI) for per layer value type 114, and a quantized coefficients value type 116.

[0028] The various value types of a PMI using E-type 2 encoding may be understood to be located in one of multiple parts 118 of the PMI. For example, with reference to the portion of the table 100 corresponding to the parts 118, it may be that the rotation factorsfor SD basis value type 104, the SD basis index value type 106, the frequency domain constrained window value type 108, the selected delay taps value type 110. the bitmap of non-zero coefficients value type 112 and the location of SCI for per layer value type 114 are understood to be sent in a “Part 1” of the PMI, while the quantized coefficients value type 116 are understood to be sent in a “Part 2” of the PMI.

[0029] The table 100 further illustrates information with respect to determining a number of bits 120 that may be used to represent a PMI value of that PMI value type, and a collection of comments 122 corresponding to the PMI value types 102 that may informative or instructive across various embodiments.

[0030] FIG. IB illustrates a listing 124 of various representations for corresponding PMI value types that may be found in E-type 2 PMI, according to embodiments discussed herein.

[0031] The zi,i representation 126 corresponds to the rotation factors for SD basis value type 104 of FIG. 1A and represents rotation factors for a spatial domain basis.

[0032] The zi.2 representation 128 corresponds to the SD basis index value type 106 of FIG. 1A and represents an SD basis indicator.

[0033] The zi,s representation 130 corresponds to the frequency domain constrained window value ty pe 108 of FIG. 1A and represents an Mimtiai indicator.

[0034] The zi,6,z representation 132 corresponds to the selected delay taps value type 110 of FIG. 1A and represents a frequency domain basis indicator for a layer I.

[0035] The zi,7,z representation 134 corresponds to the bitmap of non-zero coefficients value type 112 of FIG. 1A and represents the bitmap for a layer I.

[0036] The zi.8,z representation 136 corresponds to the location of SCI for per layer value type 114 of FIG. 1A and represents an SCI for a layer I.

[0037] The Z2,3.z representation 138 corresponds to the quantized coefficients value type 116 of FIG. 1A and represents reference amplitudes for a layer / .

[0038] The Z2,4.z representation 140 corresponds to the quantized coefficients value type 116 of FIG. 1A and represents a matrix of differential amplitude values for a layer I.

[0039] The ,5,i representation 142 corresponds to the quantized coefficients value type 116 of FIG. 1A and represents a matrix of phase values for a layer I.

[0040] FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D each show respective graphs 200, 202, 204, and 206 corresponding to simulation results for various PMI value types of E-type 2PMIs generated over time at a UE. In the case of FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 2D, the UE is configured to use four wideband beams (e.g., corresponding to a 3GPP configuration 5 for Z = 4, non-zero coefficient (NZC), selection first, quality second). The simulation results of these figures were taken over a period of 200 milliseconds (ms) and assume a receipt of a CSI-RS every 5 ms. Note that each of FIG. 2A, FIG. 2B, FIG. 2C. and FIG. 2D correspond to various / different UE behaviors that occurred during the same 200 ms period.

[0041] The graph 200 of FIG. 2A provides simulation results for the UE behavior over the period with respect to selected wide beam indexes over time. Note that these results correspond to the SD basis index value type 106 of FIG. 1A and the zi,2 representation 128 of FIG. IB.

[0042] The graph 202 of FIG. 2B provides simulation results for the UE behavior over the period with respect to a selected over sampling index (e.g., oH and oV) over time. Note that these results correspond to the rotation factors for SD basis value type 104 of FIG. 1A and the ii,i representation 126 of FIG. IB. As shown, the graph 202 divides its results as between the horizontal polarization (oH) and the vertical polarization (oV).

[0043] The graph 204 of FIG. 2C provides simulation results for the UE behavior over the period with respect to a strongest beam index over time. Note that these results correspond to the location of SCI for per layer value type 114 of FIG. 1A and the zi,s,z representation 136 of FIG. IB. As shown, the graph 204 divides its results as between two different layers.

[0044] The graph 206 of FIG. 2D provides simulation results for the UE behavior over the period with respect to a delay tap index used by the UE over time. As can be seen, the graph 206 includes a first graph corresponding to a first layer and a second graph corresponding to a second layer. Note that these results correspond to the selected delay taps value type 110 of FIG. 1A, and the zi.6,z representation 132 of FIG. IB.

[0045] As can be seen with reference to the graphs 200, 202, 204, and 206, it may be that different PMI value types of an E-type 2 PMI may change with different rates / different frequencies. For example, the rate of change to the UE's selected wide beam indexes over time as represented in the graph 200 is relatively lower than the rate of change to the delay tap index(es) used at the UE over time as represented in the graph 206.

[0046] FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D each show respective graphs 300, 302, 304, and 306 corresponding to simulation results for various PMI value ty pes of E-type 2 PMIs generated over time at a UE. In the case of FIG. 3 A, FIG. 3B, FIG. 3C, and FIG. 3D, the UE is configured to use two wideband beams (e.g., corresponding to a 3GPP configuration 1 for £ = 2, non-zero coefficient (NZC), selection first, quality second). The simulation results of these figures were taken over a period of 200 ms and assume a receipt of a CSI-RS every 5 ms. Note that each of FIG. 3A, FIG. 3B, FIG. 3C, and FIG. 3D correspond to various / different UE behaviors that occurred during the same 200 ms period.

[0047] The graph 300 of FIG. 3A provides simulation results for the UE behavior over the period with respect to selected wide beam indexes over time. Note that these results correspond to the SD basis index value type 106 of FIG. 1A and the ii,2 representation 128 of FIG. IB.[004S] The graph 302 of FIG. 3B provides simulation results for the UE behavior over the period with respect to a selected over sampling index (e.g., oH and oV) over time. Note that these results correspond to the rotation factors for SD basis value ty pe 104 of FIG. 1A and the ii,i representation 126 of FIG. IB. As shown, the graph 302 divides its results as between the horizontal polarization (oH) and the vertical polarization (oV).

[0049] The graph 304 of FIG. 3C provides simulation results for the UE behavior over the period with respect to a strongest beam index over time. Note that these results correspond to the location of SCI for per layer value type 114 of FIG. 1A and the ,s.i representation 136 of FIG. IB. As shown, the graph 304 divides its results as between two different layers.

[0050] The graph 306 of FIG. 3D provides simulation results for the UE behavior over the period with respect to a delay tap index used by the UE over time. As can be seen, the graph 306 includes a first graph corresponding to a first layer and a second graph corresponding to a second layer. Note that these results correspond to the selected delay taps value type 110 of FIG. 1A, and the zi,6, / representation 132 of FIG. IB.

[0051] The graphs 300, 302, 304, and 306 provide still further evidence that different PMI value types of an E-type 2 PMI may change with different rates / different frequencies. For example, the rate of change to the UE's selected wide beam indexes over time as represented in the graph 300 is relatively lower than the rate of change to the delay tap index(es) used at the UE over time as represented in the graph 306.

[0052] It has been determined that differences / general patterns in substantive periodicity across different PMI value types (e.g., in average / general periodicity at which these PMI value types change, as determined based on data such as that found in FIG.2A through FIG. 3D as discussed herein) may be leveraged such that a different feedback periodicity and / or time for different PMI value types or components corresponding to, for example, an E-type 2 PMI may be used. Embodiments are contemplated where some (but not all) of the PMI value types of a typical E-type 2 PMI (e.g., as found in FIG. I A) at any one instance of a CSI report may be transmitted, while other (un-transmitted) PMI value types may re-use a previously sent / received PMI value for that PMI value type at the UE and / or the network, as will be described. This means that an overhead (e.g., signaling overhead) used for CSI reporting may be reduced as compared to a case where, for example, every CSI feedback / report includes every PMI value type.

[0053] Generally, the use of a PMI scheme that can configure a PMI to (optionally) contain fewer than all PMI value types of. for example, a typical E-type 2 PMI may be understood generally as a use of '‘differential PMI.” Accordingly, '‘differential PMI” may be understood to be a type of PMI in a CSI report that has been particularly configured to contain particular PMI value types (and not necessarily all possible PMI value types) of a typical E-type 2 PMI.

[0054] PMI value types as sent in a differential PMI may correspond to “PMI parts” that are found in the differential PMI. Note that as used herein, a “PMI part” of a differential PMI may not necessarily follow / correspond to the “Part 1 / Part 2” breakdown for PMI value types as was previously discussed above with respect to a typical E-type 2 PMI (see discussion above in relation to FIG. 1A). Instead, it will be understood that a “PMI part” of a differential PMI may include any one or more PMI value types for the differential PMI (e.g.. any one or more of the PMI value types 102 of the typical E-type 2 PMI that are present in the differential PMI) as these are determined / configured for that PMI part (as will be discussed). In some cases, a PMI part for differential PMI may use one or more PMI value types as found from only a single one of “Part 1” or “Part 2” of the framework for a typical E-type 2 PMI, but such cases should be understood to be given only by way of example and not by way of requirement. PMI parts including information other than value types found in, for example, typical E-type 2 PMI are also contemplated for use in at least some embodiments described herein.

[0055] In some cases discussed herein, the network may determine one or more configurations for the use of a differential PMI in CSI feedback. Additionally and / or alternatively, a UE may determine one or more configurations for the use of a differential PMI in CSI feedback.

[0056] When using differential PMI, particular design feedback schemes may be based on expected rates of variation for applicable PMI value types. It may be that available PMI value types are understood generally as falling within various feedback categories based on how frequently they change (e.g., as informed by simulation results such as those described herein in relation to FIG. 2A through FIG. 3D). In one such example, a first set of PMI value types that update with a relatively lower frequency may be considered long-term feedback PMI value types. Examples of long-term feedback PMI value types may include, in some embodiments, an SD basis index value type (e.g., as in the SD basis index value type 106 of FIG. 1A), a rotation factors for SD basis value type (e.g.. as in the rotation factors for SD basis value type 104 of FIG. 1A). and / or a rank indicator (RI) and location of SCI for per layer value type (e.g., as in the location of SCI for per layer value type 114).

[0057] Further, a second set of PMI value types that update with a relatively moderate frequency may be considered medium-term PMI value ty pes. Examples of medium-term feedback PMI value types may include, in some embodiments, an M path selection PMI value type (e.g., a bitmap of non-zero coefficients value type such as the bitmap of nonzero coefficients value type 112 of FIG. 1A).

[0058] Finally, a third set of PMI value types that update with a relatively higher frequency may be considered short-term feedback PMI value types. Examples of shortterm feedback value types may include, in some embodiments, a bitmap of non-zero coefficients value ty pe (e.g., as in the bitmap of non-zero coefficients value type 112 discussed herein) and / or quantized coefficients value type (e.g., as in the quantized coefficients value type 116 discussed herein).

[0059] Accordingly, with respect to such embodiments, it may be that a first PMI part for differential PMI maps to the first set of PMI value types (that update at the UE side with relatively lower frequency), and thus may be used at a relatively lower frequency for constructing differential PMI.

[0060] Further, a second PMI part for differential PMI maps to the second set of PMI value types (that update at the UE side with the relatively moderate frequency), and thus may be used at a relatively moderate frequency for constructing differential PMI.

[0061] Finally, a third PMI part for differential PMI maps to the third set of PMI value types (that update at the UE side with the relatively higher frequency), and may be used at a relatively higher frequency for constructing differential PMI.

[0062] Note that in some embodiments, “Part 1” components of a typical E-type 2 PMI are further separated into multiple (e.g., alternative) parts (e.g., as in the example embodiment just discussed) for purposes of differential PMI construction. Further, as also shown by this example, it may be that one or more “Part 1” components and one or more “Part 2” components of a ty pical E-type 2 PMI may be mixed together when formulating (e.g., alternative) parts that will be used for the construction of differential PMI as described.

[0063] It is expressly noted that the present example (involving the use of three PMI parts for differential PMI) is given by way of example and not by way of limitation. Fewer or more than three PMI parts may be used with respect to differential PMI construction in other embodiments. Further, an arrangement / assignment of PMI value types into the PMI parts (of whatever number) can also be varied from the example provided here. Finally, note that arranging PMI value types into various PMI parts based either in whole or in part on an analysis of how frequently those PMI value types are expected to change at the UE side is given by way of example and not by limitation (the use of such a criteria is not strictly required).Embodiments of Network-Controlled Differential PMI Use

[0064] In some embodiments, a network (e.g., a base station of the network) controls a UE's use of differential PMI in CSI feedback.

[0065] In some such embodiments, it may be that the arrangement of PMI value types as found in PMI parts used in the construction of the differential PMI may be configured by the network. In other cases, the PMI value ty pes used in parts then used in the construction of the differential PMI are hardcoded (e.g., per a specification for the wireless communication system).

[0066] In one example using network-configured PMI parts, the network may configure the UE with: a first PMI part that includes a spatial basis selection PMI value type, asampling index PMI value type, and a RI and strongest beam index value type; a second PMI part that includes an M path selection PMI value type; and a third PMI part that includes a bitmap of non-zero coefficients PMI value type.

[0067] It may be that a further fourth PMI part that includes a quantized coefficients value type is also understood. This fourth PMI part may be referred to in embodiments herein as a “coefficient PMI part.” In the present example, this coefficient PMI part is intended to be sent in every differential PMI. The use of this coefficient PMI part may (also) be configured to the UE by the network, or it may simply be pre-configured at the UE.

[0068] FIG. 4 illustrates a flow diagram 400 for a network controlled use of differential PMI as between a UE 402 and a base station 404, according to embodiments discussed herein. As illustrated, the UE 402 and the base station 404 may (optionally) first exchange capability information 406. Capability information 406 sent by the UE 402 may inform the base station 404 that the UE 402 is capable of using differential PMI. Further, capability information 406 sent by the base station 404 may inform the UE 402 that the base station 404 is capable of using differential PMI.

[0069] The base station 404 then sends configuration information 408 (e.g., radio resource control (RRC) configuration information) to the UE 402. This configuration information 408 may indicate information such as the number of PMI parts and / or the PMI value types that are present in each of the PMI parts. In alternative cases, this information is preconfigured per a definition for the wireless communication system of the UE 402 and the base station 404.

[0070] In some embodiments, with respect to an upcoming transmission of a differential PMI, the UE 402 calculates 412 a (e.g., full) PMI representing all possible PMI parts of the differential PMI. To accomplish this, the UE 402 measures reference signals (e.g., CSI-RSs). These measurements are used to calculate PMI values for at least the PMI value ty pes of the PMI parts that are to be included in the differential PMI.

[0071] Note that in cases of dependency of a first PMI value ty pe for a first PMI part that is to be included in the differential PMI on a second PMI value type of a second PMI part that is not included in the upcoming differential PMI, a PMI value for the first PMI value type may be determined by applying, as relevant, a PMI value of the second PMI value type as was found in a prior PMI part that was transmitted to the base station 404. This corresponds to the anticipated use, at the base station, of that prior PMI part withthe forthcoming differential PMI to generate or re-construct the full PMI as presently understood at the UE 402.

[0072] It is contemplated that, in some cases, the base station 404 may configure the UE 402 to construct and send differential PMI in CSI feedback on a periodic basis (e.g., corresponding to the transmission by the network of periodic or semi-persistent CSI- RSs). In such cases, the configuration information 408 may include periodicity(s) for / corresponding to the use of the configured part(s) at the UE 402 in constructing a differential PMI. The differential PMIs so constructed and then sent by the UE 402 maybe sent without PMI parts for which a periodicity corresponding to that part has not passed at the UE 402 since the last time that part was used in a prior PMI (e.g.. a prior full PMI or a prior differential PMI).

[0073] In alternative cases, the base station 404 may configure the UE 402 to construct and send differential PMI in CSI feedback on an aperiodic / triggered / on demand basis (e g., corresponding to the transmission by the network of an aperiodic CSI-RSs). Such embodiments may use a trigger 410, (e.g., a downlink control information (DCI) or medium access control control element (MAC CE) trigger) as illustrated in FIG. 4. The trigger 410 may inform the UE 402 of the upcoming reference signal(s) (e.g.. CSI-RS(s)) to measure for purposes of generating the differential PMI.

[0074] Further, the trigger 410 may include an indication of which PMI part(s) to use for the construction of the differential PMI at the UE 402. With respect to an example where each of a first PMI part, a second PMI part, a third PMI part, and a coefficient PMI part are (e.g., optionally) used for differential PMI, it may be that at various instances a trigger 410 triggers a use of zero or more of the first PMI part, the second PMI part, and the third PMI part.

[0075] In a first case of this example, where none of the first PMI part, the second PMI part, or the third PMI part are triggered in the trigger 410, the UE 402 calculates 412 the full PMI by reusing previously sent PMI values (e.g.. in prior full PMI(s) / prior differential PMI(s)) for each of the first PMI part, the second PMI part, and the third PMI part and by calculating a quantized coefficient value for the coefficient PMI part. The PMI value(s) for the coefficient PMI part (e.g., the quantized coefficient PMI value for the coefficient PMI part) may be calculated using results of CSI-RS measurement and / or any previously determined PMI values corresponding to each for the first PMIpart, the second PMI part, and / or the third PMI part, as necessary. The UE 402 then constructs and sends a differential PMI 414 having only the coefficient PMI part.

[0076] Upon decoding this differential PMI, the base station 404 constructs 416 the full PMI using the quantized coefficient values from the coefficient PMI part and previously received PMI values (e.g., by referring to the same prior full PMI(s) / prior differential PMI(s) that were referred to by the UE) for each of the PMI value types corresponding to the first PMI part, the second PMI part, and the third PMI part. The base station 404 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0077] In a second case of this example, where the trigger 410 triggers the third PMI part (but not the first PMI part or the second PMI part), the UE 402 calculates 412 a full PMI by reusing previously sent PMI values (e.g., in prior full PMI(s) / prior differential PMI(s)) for each of the first PMI part and the second PMI part, and by calculating a value for each PMI value t pe found in the third PMI part and a quantized coefficient value for the coefficient PMI part. The PMI values for the third PMI part and the coefficient PMI part may be calculated using results of CSI-RS measurement, results of PMI values corresponding to any other PMI parts currently being determined based at least in part on the CSI-RS measurement, and / or any previously determined PMI values of each for the first PMI part and the second PMI part, as necessary. The UE 402 then constructs and sends a differential PMI 414 having only the third PMI part and the coefficient PMI part.

[0078] Upon decoding this differential PMI, the base station 404 constructs 416 the full PMI using the quantized coefficient values from the coefficient PMI part, the PMI values from the third PMI part, and previously received PMI values (e.g., by referring to the same prior full PMI(s) / prior differential PMI(s) that were also referred to by the UE) for each of the PMI value types corresponding to the first PMI part and the second PMI part. The base station 404 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0079] In a third case of this example, where the trigger 410 triggers the second PMI part and the third PMI part (but not the first PMI part), the UE 402 calculates 412 a full PMI by reusing previously sent PMI values (e.g., in prior full PMI(s) / prior differential PMI(s)) for the first PMI part, and by calculating a value for each PMI value type found in each of the second PMI part, the third PMI part, and a quantized coefficient value for the coefficient PMI part. The PMI values for the second PMI part, the third PMI part,and the coefficient PMI part may be calculated using results of CSI-RS measurement, results of PMI values corresponding to any other PMI parts currently being determined based at least in part on the CSI-RS measurement, and / or any previously determined PMI values the for the first PMI part, as necessary. The UE 402 then constructs and sends a differential PMI 414 having only the third PMI part and the coefficient PMI part.

[0080] Upon decoding this differential PMI, the base station 404 constructs 416 the full PMI using the quantized coefficient values from the coefficient PMI part, the PMI values from the second PMI part and the third PMI part, and previously received PMI values (e.g., from the same prior full PMI(s) / prior differential PMI(s) that were also referred to by the UE) for each the PMI value t pes corresponding to the first PMI part. The base station 404 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0081] In a fourth case of this example, where the trigger 410 triggers the first PMI part, the second PMI part, and the third PMI part, the UE 402 calculates 412 a value for each PMI value type found in each of the first PMI part, the second PMI part, and the third PMI part, and a quantized coefficient value for the coefficient PMI part based on CSI measurement. The UE 402 then constructs and sends a differential PMI 414 having the first PMI part, the second PMI part, the third PMI part, and the coefficient PMI part. It is contemplated that there are cases where the first PMI part, the second PMI part, the third PMI part, and the coefficient PMI parts accordingly together represent current / up dated values corresponding to all possible PMI value types of a full PMI.

[0082] Upon decoding this differential PMI, the base station 404 constructs 416 the full PMI using the quantized coefficient value from the coefficient PMI part and the PMI values from the first PMI part, the second PMI part, and the third PMI part. It may be that in this case no use of previously received PMI values is necessary. The base station 404 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.Embodiments of UL-Conirolled Differential PMI Use

[0083] In some embodiments, the UE controls its own use of differential PMI in CSI feedback.

[0084] In some such embodiments, it may be that the PMI value types used in PMI parts then used in the construction of the differential PMI may be configured by thenetwork. In other cases, the PMI value types used in PMI parts then used in the construction of the differential PMI are hardcoded (e.g., per a specification for the wireless communication system).

[0085] In one example using network-configured parts, the network may configure the UE with: a first PMI part that includes a spatial basis selection PMI value type, a sampling index PMI value type, and a RI and strongest beam index PMI value type; a second part that includes an M path selection PMI value type; and a third part that includes a bitmap of non-zero coefficients PMI value type.

[0086] It may be that a further coefficient PMI part (that includes a quantized coefficients value type) is also understood. In the present example, this coefficient PMI part is intended to be sent in every differential PMI. In such cases, this coefficient PMI part may (also) be configured to the UE by the network, or it may simply be preconfigured at the UE.

[0087] FIG. 5 illustrates a flow diagram 500 for a network controlled use of differential PMI as between a UE 502 and a base station 504, according to embodiments discussed herein. As illustrated, the UE 502 and the base station 504 may (optionally) first exchange capability information 506. Capability information 506 sent by the UE 502 may inform the base station 504 that the UE 502 is capable of using differential PMI. Further, capability information 506 sent by the base station 504 may inform the UE 502 that the base station 504 is capable of using differential PMI.

[0088] The base station 504 then sends configuration information 508 (e.g., RRC configuration information) to the UE 502. This configuration information 508 may indicate information such as the number of PMI parts and / or the PMI value types that are present in the PMI parts. In alternative cases, this information is preconfigured per a definition for the wireless communication system of the UE 502 and the base station 504.

[0089] In some embodiments, with respect to an upcoming transmission of a differential PMI, the UE 502 calculates 512 a (e.g., full) PMI representing all possible PMI parts of the differential PMI (other than, e.g., UCI / Part 0 PMI, to be described). To accomplish this, the UE 502 measures reference signals (e.g., CSI-RSs). These measurements are used to calculate PMI values for PMI value types present in at least the PMI parts that are to be included in the differential PMI.

[0090] Note that in cases of dependency of a first PMI value type for a first PMI part that is to be included in the differential PMI on a second PMI value type of a second PMI part that is not included in the upcoming differential PMI, a PMI value for the first PMI value type may be determined by applying, as relevant, a PMI value of the second PMI value type as was found in a prior PMI part that was transmitted to the base station 504. This corresponds to the anticipated use of that prior PMI part with the forthcoming differential PMI to generate or re-construct, at the base station, the full PMI as presently- understood at the UE 502.

[0091] It is contemplated that, in some cases, the base station 504 may configure the UE 502 to construct and send differential PMI in CSI feedback on a periodic basis (e.g.. corresponding to the transmission by the network of periodic or semi-persistent CSI- RSs). In such cases, the configuration information 508 may include periodicity(s) for / corresponding to the use of the configured PMI part(s) at the UE 402 in constructing differential PMI. The differential PMIs then constructed and sent by the UE 502 may be sent without PMI parts for which a periodicity corresponding to that part has not passed at the UE 502 since the last time that PMI part was used in a prior PMI (e.g., a prior full PMI or a prior differential PMI).

[0092] In alternative cases, the base station 504 may configure the UE 502 to construct and send differential PMI in CSI feedback on an aperiodic / triggered / on demand basis (e.g., corresponding to the transmission by the network of aperiodic CSI-RSs). Such embodiments may use a trigger 510 (e.g., a DCI or MAC CE trigger), as illustrated in FIG. 5. The trigger 510 may inform the UE 502 of the upcoming reference signal(s) (e.g., CSI-RS(s)) to measure for purposes of generating the differential PMI.

[0093] However, as opposed to the case described above in relation to of FIG. 4, in the embodiment of FIG. 5 the trigger does not include any indication of which PMI part(s) to use for the construction of the differential PMI at the UE 502. Rather, the UE 502 makes an independent determination of which PMI parts to include in differential PMI (e.g., per a particular UE implementation).

[0094] With respect to an example where each a first PMI part, a second PMI part, a third PMI part, and a coefficient PMI part are used at the UE 502, it may be that at various instances the UE determines to optionally use zero or more of the first PMI part, the second PMI part, and the third PMI part.

[0095] In a first case of this example, where the UE 502 determines not to send any of the first PMI part, the second PMI part, or the third PMI part, the UE 502 calculates 512 the full PMI by reusing previously sent PMI values (e.g., in prior full PMI(s) / prior differential PMI(s)) for each of the first PMI part, the second PMI part, and the third PMI part and by calculating a quantized coefficient value for the coefficient PMI part. The PMI value(s) for the coefficient PMI part (e.g.. the quantized coefficient PMI value for the coefficient PMI part) may be calculated using results of CSI-RS measurement and / or any previously determined PMI values of each of the first PMI part and the second PMI part, as necessary. The UE 502 then constructs and sends a differential PMI 514 having only the coefficient PMI part. As illustrated, the differential PMI 514 may be sent with uplink control information (UCI) that indicates that none of the first PMI part, the second PMI part, or the third PMI part is included in the differential PMI 514

[0096] Upon receiving this differential PMI 514, the base station 504, based on the information regarding contents of the differential PMI 514 in the UCI, decodes it into the coefficient PMI part. Then, the base station 504 constructs 516 the full PMI using the quantized coefficient values from the coefficient PMI part and previously received PMI values (e.g., by referring to the same the prior full PMI(s) / prior differential PMI(s) that were also referred to by the UE) for each of the PMI value t pes corresponding to the first PMI part, the second PMI part, and the third PMI part. The base station 504 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0097] In a second case of this example, where the UE 502 determines to send the third PMI part (but not the first PMI part or the second PMI part), the UE 502 calculates 512 a full PMI by reusing previously sent PMI values (e.g., in prior PMI(s) / prior differential PMI(s)) for each of the first PMI part and the second PMI part, and by calculating a value for each PMI value type found in the third PMI part and a quantized coefficient value for the coefficient PMI part. The PMI values for the third PMI part and the coefficient PMI part may be calculated using results of CSI-RS measurement, results of PMI values corresponding to any other PMI parts currently being determined based at least in part on the CSI-RS measurement, and / or any previously determined PMI values of each of the first PMI part and the second PMI part, as necessary. The UE 502 then constructs and sends a differential PMI 514 having only the third PMI part and the coefficient PMI part. As illustrated, the differential PMI 514 may be sent with UCI that indicates that the third PMI part is included in the differential PMI 514.

[0098] Upon receiving this differential PMI, the base station 504, based on the information regarding contents of the differential PMI 514 in the UCI, decodes it into the third PMI part and the coefficient PMI part. Then, the base station 504 constructs 516 the full PMI using the quantized coefficient values from the coefficient PMI part, the PMI values from the third PMI part, and previously received PMI values (e.g., by referring to the same prior full PMI(s) / prior differential PMI(s) that were also referred to by the UE) for each of the PMI value types corresponding to the first PMI part and the second PMI part. The base station 504 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0099] In a third case of this example, where the UE 502 determines to send the second PMI part and the third PMI part (but not the first PMI part), the UE 502 calculates 512 a full PMI by reusing previously sent PMI values (e.g., in prior PMI(s) / prior differential PMI(s)) for the first PMI part, and by calculating a value for each PMI value ty pe found in each of the second PMI part, the third PMI part, and a quantized coefficient value for the coefficient PMI part. The PMI values for the second PMI part, the third PMI part, and the coefficient PMI part may be calculated using results of CSI-RS measurement, results of PMI values corresponding to any other PMI parts currently being determined based at least in part on the CSI-RS measurement, and / or any previously determined PMI values from the first PMI part, as necessary. The UE 502 then constructs and sends a differential PMI 514 having only the second PMI part, the third PMI part, and the coefficient PMI part. As illustrated, the differential PMI 514 may be sent with UCI that indicates that the second PMI part and the third PMI part are included in the differential PMI 514.

[0100] Upon receiving this differential PMI, the base station 504, based on the information regarding contents of the differential PMI 514 in the UCI, decodes it into the second PMI part, the third PMI part, and the coefficient PMI part. Then, the base station 504 constructs 516 the full PMI using the quantized coefficient values from the coefficient PMI part, the PMI values from the second PMI part and the third PMI part, and previously received PMI values (e.g., by referring to the same prior full PMI(s) / prior differential PMI(s) that were also referred to by the UE) for each of the PMI value types corresponding to the first PMI part. The base station 504 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0101] In a fourth case of this example, where the UE 502 determines to send the first PMI part, the second PMI part, and the third PMI part, the UE 502 calculates 512 a value for each PMI value type found in each of the first PMI part, the second PMI part, and the third PMI part, and a quantized coefficient PMI value for the coefficient PMI part based on the CSI measurement. The UE 502 then constructs and sends a differential PMI 514 having the first PMI part, the second PMI part, the third PMI part, and the coefficient PMI part. It is contemplated that there are cases where the first PMI part, the second PMI part, the third PMI part, and the coefficient PMI parts accordingly together represent current / up dated values corresponding to all possible PMI value ty pes of a full PMI. As illustrated, the differential PMI 514 may be sent with UCI that indicates to the base station 504 that each of the first PMI part, the second PMI part, and the third PMI part are included in the differential PMI 514. As illustrated, the differential PMI 514 may be sent with UCI that indicates that the first PMI part, the second PMI part, and the third PMI part are included in the differential PMI 514.

[0102] Upon receiving this differential PMI, the base station 504, based on the information regarding contents of the differential PMI 514 in the UCI, decodes it into the first PMI part, the second PMI part, the third PMI part, and the coefficient PMI part. Then, the base station 504 constructs 516 the full PMI using the quantized coefficient value from the coefficient PMI part and the PMI values from the first PMI part, the second PMI part, and the third PMI part. It may be that in this case no use of previously received PMI values is necessary . The base station 504 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0103] Details / embodiments of information in a UCI that may be used in cases of UE- controlled differential PMI use are now discussed. Corresponding to the present example. UCI may identify the ones of the first PMI part, the second PMI part, and the third PMI part that are present in a differential PMI using three bits. For example, it may be that a bitmap of ‘000’ corresponds to the case where the UE 502 sends only the coefficient PMI part and none of the first PMI part, the second PMI part, and the third PMI part in the differential PMI 514. A bitmap of ‘001’ may correspond to the case where the UE 502 sends the coefficient PMI part and the third PMI part, but not the first PMI part or the second PMI part, in the differential PMI 514. A bitmap of ‘011 ’ may correspond to the case where the UE 502 sends the coefficient PMI part, the third PMI part, and the second PMI part, but not the first PMI part, in the differential PMI 514.Finally, a bitmap of ‘ 111 ’ may correspond to the case where the UE 502 sends each of the coefficient PMI part, the third PMI part, the second PMI part, and the first PMI part in the differential PMI 514.

[0104] Note that in some such cases of UE-controlled differential PMI, the bitmap containing this UCI may be understood to be a "‘Part 0” PMI part of the differential PMI.

[0105] It is contemplated that in some arrangements, a bitmap may be sized to correspond to the total number of possible states for PMI parts included in differential PMI that may need to be signaled. For instance, in the present example, there are four possible states that can be signaled in UCI: accordingly, alternative bitmap / signaling arrangements where two (rather than three) bits are used in UCI to cover representations for these four possible states.

[0106] It is noted that the states discussed in relation to the present example assume / rely upon the fact that a coefficient PMI part that is dedicated to the quantized coefficients value type and / or a Part 0 PMI part including a bitmap indicating (other) PMI parts included in a differential PMI is / are always sent in differential PMI (and thus no signaling in UCI is provided with respect to these PMI parts).

[0107] It has further been recognized that the use of a combined-control approach for the use of differential PMI, where control aspects with respect to the use of differential PMI are spread across each of the UE and the network, may engender still better CSI overhead reductions and / or more relevant reconstructed full PMI at the network.

[0108] For example, with respect to network-controlled approaches for using differential PMI (at least in aperiodic / triggered contexts), an appropriate timing for differential PMI (e.g.. the particular timing of periodicities corresponding to various PMI parts used by the UE for measuring for / determining PMI values for the one or more PMI parts of a differential PMI) is not known to the network (as such information is not tightly corresponded between the UE and the network). Accordingly, the network may at least sometimes fail to trigger the sending of particular PMI parts at efficient / relevant times for those PMI parts.

[0109] Further, UE-controlled approaches for differential PMI use (e.g., in aperiodic / triggered contexts) may be complicated by the fact that uplink (UE) physical uplink shared channel (PUSCH) transmissions may not rely on / use acknowledgement(ACK) / negative acknowledgement (NACK) signaling. Accordingly, at the stage of determining whether or not to include a PMI part in differential PMI, the UE may not actually be sure whether a previous UCI corresponding to a previous differential PMI was correctly decoded by the network. Thus, the UE cannot be fully confident that the network actually properly received PMI parts as sent in prior full PMI / prior differential PMI (and thus cannot be fully confident that the PMI values thereof are available at the network for purposes of constructing a full PMI in view of the present differential PMI). It may be that to account for this, in some embodiments, the UE bases its PMI part inclusion / exclusion decision making based (further) on the status of an UL hybrid automatic repeat request (HARQ) retransmission timer. For example, the UE may determine to include a particular PMI part in a present differential PMI once a HARQ retransmission timer corresponding to a prior full PMI / prior differential PMI that also used that particular PMI part is no longer running (meaning, e.g., that prior full PMI / prior differential PMI was at some point received at the network). This procedure, however, may introduce an overall delay to the transmission of the present differential PMI.

[0110] FIG. 6 illustrates a flow diagram 600 for an approach for the use of differential PMI that uses control aspects shared over / spread across both a UE 602 and a base station 604, according to embodiments discussed herein. The approach of FIG. 6 may. in at least some ways, be more efficient than a purely UE-controlled or purely network-controlled approach for using differential PMI (at least with respect to aperiodic / triggered differential PMI use contexts). For example, the combined approach illustrated in FIG. 6 leverages the fact that the base station 604 is aware of which previously transmitted PMI part(s) were received correctly, and the further recognition that the UE 602 is best positioned to accurately / immediately become aware of circumstances where a use of updated version of one or more PMI parts is warranted / relevant.[OH l] As illustrated, the UE 602 and the base station 604 may (optionally) first exchange capability information 606. Capability information 606 sent by the UE 602 may inform the base station 604 that the UE 602 is capable of using differential PMI. Further, capability information 606 sent by the base station 604 may inform the UE 602 that the base station 604 is capable of using differential PMI.

[0112] The base station 604 then sends configuration information 608 (e.g., RRC configuration information) to the UE 602. This configuration information 608 mayindicate information such as the number of PMI parts and / or the PMI value ty pes that are present in each of the parts. In alternative cases, this information is preconfigured per a definition for the wireless communication system of the UE 602 and the base station 604.

[0113] The base station 604 may configure the UE 602 to construct and send differential PMI in CSI feedback on an aperiodic / triggered / on demand basis (e.g., corresponding to the transmission by the network of aperiodic CSI-RSs). Such embodiments may use a trigger such as, for example, the first trigger 610 (e.g., a DCI or MAC CE trigger), as illustrated in FIG. 6. The first trigger 610 may inform the UE 602 of the upcoming reference signal(s) (e.g., CSI-RS(s)) to measure for purposes of generating differential PMI. Further, the first trigger 610 may include an indication of which PMI part(s) to use for the construction of the differential PMI at the UE 602.

[0114] The UE then calculates 612 a PMI that is updated corresponding to the instruction in the first trigger 610 and generates a corresponding first differential PMI 614 that includes at least the PMI parts indicated in the first trigger 610. In such cases, the UE 602 generates new PMI values for the indicated PMI parts based on present CSI- RS measurements, current PMI values currently being calculated for other PMI parts to be used in the first differential PMI 614, and / or (potentially) further based on a reuse of previously determined PMI values of other PMI parts that are not to be included in the first differential PMI 614, consistent with disclosure herein.

[0115] The UE then sends the first differential PMI 614 to the base station 604. As illustrated, the first differential PMI 614 may be sent with UCI (e.g., which in some cases may be considered a ‘‘Part 0"’ PMI part of the first differential PMI 614, as is discussed elsewhere herein) that indicates to the base station 604 zero or more (e.g., non- Part-0) PMI parts corresponding to PMI values that are expected to be updated at the UE 602 / that the UE 602 wants to recalculate and provide to the base station 604 corresponding to the next CSI feedback / report. This information may be determined by the UE 602 and sent to the base station 604 in response to, for example, a change in channel conditions between the UE 602 and the base station 604 as identified by the UE 602, and to which the UE 602 wants to proactively respond. This UCI may accordingly be understood to indicate, to the base station 604, that the change to the channel has occurred.

[0116] Upon receiving the first differential PMI 614, the base station 604 constructs 616 a full PMI using the PMI part(s) that were included in the first differential PMI 614 and previously-received PMI values (e.g., from prior PMI(s) / prior differential PMI(s)) for each of the PMI value types corresponding to any PMI parts that were not included in the first differential PMI 614. The base station 604 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0117] Continuing the procedure, the base station 604 may proceed to send the UE 602 a second trigger 618. The second trigger 618 may inform the UE 602 of the upcoming reference signal(s) (e.g., CSI-RS(s)) to measure for purposes of generating differential PMI. Further, the second trigger 618 may include an indication of which PMI part(s) to use for the construction of the differential PMI at the UE 602. These PMI parts may have been selected at the base station 604 (e.g., at least in part) based on the UCI received with the first differential PMI 614 that indicates one or more PMI parts having PMI values that have become relevant from the perspective of the UE 602 (e.g., corresponding to the changed channel condition previously identified at the UE 602).

[0118] The UE then calculates 620 one or more PMI parts that are to be updated corresponding to the instruction in the second trigger 618 and generates a corresponding second differential PMI 622 that includes at least the indicated PMI parts (e.g., according to the manners discussed herein).

[0119] The UE then sends the second differential PMI 622 to the base station 604. Similarly to the first differential PMI 614, as illustrated, the second differential PMI 622 may be sent with UCI that indicates to the base station 604 zero or more (e.g., non-part- 0) PMI parts corresponding to PMI values that are expected to be updated at the UE 602 / that the UE 602 wants to recalculate and provide to the base station 604 corresponding to a still next CSI feedback / report.

[0120] Upon receiving the second trigger 618, the base station 604 constructs 624 a full PMI using the PMI part(s) that were included in the second differential PMI 622 and previously-received PMI values (e.g., from prior PMI(s) / prior differential PMI(s), such as, for example, the first differential PMI 614) for each of the PMI value types corresponding to any PMI parts that were not included in the second differential PMI 622. The base station 604 may then proceed to use this full PMI for DL transmission precoding and / or other purposes.

[0121] FIG. 7 illustrates a method 700 of a UE, according to embodiments discussed herein. The method 700 includes calculating 702 a PMI based on one or more reference signals received from a network. The method 700 further includes selecting 704 one or more selected PMI parts of the PMI to include in a differential PMI. The method 700 further includes generating 706 the differential PMI using the one or more selected PMI parts and a coefficient PMI part of the PMI, the coefficient PMI part comprising quantized coefficients associated with delay taps of the PMI. The method 700 further includes sending 708 the differential PMI to the network.

[0122] In some embodiments, the method 700 further includes receiving, from the network, configuration information defining first one or more PMI value types for use in a first PMI part of the one or more selected PMI parts. In some such embodiments, the configuration information further defines second one or more PMI value types for use in a second PMI part of the one or more selected PMI parts.

[0123] In some embodiments, the method 700 further includes receiving, from the network, configuration information comprising a first periodicity for using a first PMI part of the one or more selected PMI parts; and the selecting the one or more selected PMI parts comprises identifying the first PMI part for inclusion in the one or more selected PMI parts based on a determination that no prior PMI sent to the network within the first periodicity for the first PMI part included first one or more PMI value types for the first PMI part. In some such embodiments, the configuration information further comprises a second periodicity for using a second PMI part of the one or more selected PMI parts; and the selecting the one or more selected PMI parts comprises identifying the second PMI part for inclusion in the one or more selected PMI parts based on a determination that no prior PMI sent to the network within the second periodicity for the second PMI part included the second one or more PMI value types for the second PMI part.

[0124] In some embodiments, the method 700 further comprises, receiving, from the network, a trigger for the differential PMI; and the selecting the one or more selected PMI parts comprises identifying a first PMI part for inclusion in the one or more selected PMI parts based on a determination that the trigger identifies the first PMI part. In some such embodiments, the selecting the one or more selected PMI parts comprises identify ing a second PMI part for inclusion in the one or more selected PMI parts based on a determination that the trigger identifies the second PMI part. In some suchembodiments, the method 700 further includes: detecting a change to a channel between the UE and the network; and sending, to the network, an indication that the change to the channel has occurred, wherein the trigger is received from the network in response to the indication of the change to the channel.

[0125] In some embodiments, the method 700 further includes sending, to the network, UCI identifying the selected PMI parts that are included in the differential PMI.

[0126] In some embodiments of the method 700, the selecting the one or more selected PMI parts comprises identifying whether an UL HARQ retransmission timer corresponding to a prior PMI that was transmitted to the network is running.

[0127] In some embodiments, the method 700 further includes sending, to the network, capability information indicating that the UE is capable of sending the differential PMI.

[0128] In some embodiments of the method 700, the one or more selected PMI parts are selected from a set of PMI parts comprising: a first PMI part associated with long-term feedback, the first PMI part including first one or more PMI value types; a second PMI part associated with medium-term feedback, the second PMI part including second one or more PMI value types; and a third PMI part associated with short-term feedback, the third PMI part including third one or more PMI value ty pes.

[0129] FIG. 8 illustrates a method 800 of a RAN, according to embodiments discussed herein. The method 800 includes receiving 802, from a UE, a differential PMI comprising one or more selected PMI parts of a PMI and a coefficient PMI part of the PMI, the coefficient PMI part comprising quantized coefficients associated with delay taps of the PMI. The method 800 further includes constructing 804 the PMI based on the differential PMI and one or more prior PMI parts previously received at the network. The method 800 further includes precoding 806 a DL transmission for the UE using the PMI.

[0130] In some embodiments, the method 800 further includes sending, to the UE, configuration information defining first one or more PMI value ty pes for a first PMI part of the one or more selected PMI parts. In some such embodiments, the configuration information further defines second one or more PMI value ty pes for a second PMI part of the one or more selected PMI parts.

[0131] In some embodiments, the method 800 further includes sending, to the UE, configuration information comprising a first periodicity for using a first PMI part of the one or more selected PMI parts. In some such embodiments, the configurationinformation further comprises a second periodicity for using a second PMI part of the one or more selected PMI parts.

[0132] In some embodiments, the method 800 further includes sending, to the UE, a trigger for the differential PMI, wherein the trigger identifies a first PMI part for inclusion in the one or more selected PMI parts. In some such embodiments, the trigger identifies a second PMI part for inclusion in the one or more selected PMI parts. In some such embodiments, the method 700 further includes receiving, from the UE, an indication that a change to a channel between the UE and the network has occurred, wherein the trigger is sent to the UE in response to the indication of the change to the channel.

[0133] In some embodiments of the method 800, receiving, from the UE, UCI identifying the selected PMI parts that are included in the differential PMI.

[0134] In some embodiments, the method 800 further includes receiving, from the UE, capability information indicating that the UE is capable of sending the differential PMI.

[0135] In some embodiments of the method 800, the one or more selected PMI parts comprises one or more of: a first PMI part associated with long-term feedback, the first PMI part including first one or more PMI value types; a second PMI part associated with medium-term feedback, the second PMI part including second one or more PMI value types; and a third PMI part associated with short-term feedback, the third PMI part including third one or more PMI value types.

[0136] FIG. 9 illustrates an example architecture of a wireless communication system 900, according to embodiments disclosed herein. The following description is provided for an example wireless communication system 900 that operates in conjunction with the LTE system standards and / or 5G or NR system standards, as provided by 3GPP technical specifications.

[0137] As shown by FIG. 9, the wireless communication system 900 includes UE 902 and UE 904 (although any number of UEs may be used). In this example, the UE 902 and the UE 904 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks), but may also comprise any mobile or non-mobile computing device configured for wireless communication.

[0138] The UE 902 and UE 904 may be configured to communicatively couple with a RAN 906. In embodiments, the RAN 906 may be NG-RAN, E-UTRAN, etc. The UE 902 and UE 904 utilize connections (or channels) (shown as connection 908 and connection910, respectively) with the RAN 906, each of which comprises a physical communications interface. The RAN 906 can include one or more base stations (such as base station 912 and base station 914) that enable the connection 908 and connection 910.

[0139] In this example, the connection 908 and connection 910 are air interfaces to enable such communicative coupling, and may be consistent with RAT(s) used by the RAN 906, such as, for example, an LTE and / or NR.

[0140] In some embodiments, the UE 902 and UE 904 may also directly exchange communication data via a sidelink interface 916. The UE 904 is shown to be configured to access an access point (shown as AP 918) via connection 920. By way of example, the connection 920 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein the AP 918 may comprise a Wi-Fi® router. In this example, the AP 918 may be connected to another network (for example, the Internet) without going through a CN 924.

[0141] In embodiments, the UE 902 and UE 904 can be configured to communicate using orthogonal frequency division multiplexing (OFDM) communication signals with each other or with the base station 912 and / or the base station 914 over a multicarrier communication channel in accordance with various communication techniques, such as, but not limited to, an orthogonal frequency division multiple access (OFDMA) communication technique (e.g., for downlink communications) or a single carrier frequency division multiple access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications), although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality7of orthogonal subcarriers.

[0142] In some embodiments, all or parts of the base station 912 or base station 914 may be implemented as one or more software entities running on server computers as part of a virtual network. In addition, or in other embodiments, the base station 912 or base station 914 may be configured to communicate with one another via interface 922. In embodiments where the wireless communication system 900 is an LTE system (e.g., when the CN 924 is an EPC), the interface 922 may be an X2 interface. The X2 interface may be defined between two or more base stations (e.g., two or more eNBs and the like) that connect to an EPC. and / or between two eNBs connecting to the EPC. In embodiments where the wireless communication system 900 is an NR system (e.g., whenCN 924 is a 5GC), the interface 922 may be an Xn interface. The Xn interface is defined between two or more base stations (e.g.. two or more gNBs and the like) that connect to 5GC, between a base station 912 (e.g., a gNB) connecting to 5GC and an eNB, and / or between two eNBs connecting to 5GC (e.g., CN 924).

[0143] The RAN 906 is shown to be communicatively coupled to the CN 924. The CN 924 may comprise one or more network elements 926, which are configured to offer various data and telecommunications services to customers / subscribers (e.g., users of UE 902 and UE 904) who are connected to the CN 924 via the RAN 906. The components of the CN 924 may be implemented in one physical device or separate physical devices including components to read and execute instructions from a machine-readable or computer-readable medium (e g., a non-transitory machine-readable storage medium).

[0144] In embodiments, the CN 924 may be an EPC, and the RAN 906 may be connected with the CN 924 via an S I interface 928. In embodiments, the S I interface 928 may be split into two parts, an SI user plane (Sl-U) interface, which carries traffic data between the base station 912 or base station 914 and a serving gateway (S-GW), and the SI -MME interface, which is a signaling interface between the base station 912 or base station 914 and mobility management entities (MMEs).

[0145] In embodiments, the CN 924 may be a 5GC, and the RAN 906 may be connected with the CN 924 via an NG interface 928. In embodiments, the NG interface 928 may be split into two parts, an NG user plane (NG-U) interface, which carries traffic data between the base station 912 or base station 914 and a user plane function (UPF), and the SI control plane (NG-C) interface, which is a signaling interface between the base station 912 or base station 914 and access and mobility management functions (AMFs).

[0146] Generally, an application server 930 may be an element offering applications that use internet protocol (IP) bearer resources with the CN 924 (e.g., packet switched data services). The application server 930 can also be configured to support one or more communication services (e.g., VoIP sessions, group communication sessions, etc.) for the UE 902 and UE 904 via the CN 924. The application server 930 may communicate with the CN 924 through an IP communications interface 932.

[0147] FIG. 10 illustrates a system 1000 for performing signaling 1034 between a wireless device 1002 and a network device 1018, according to embodiments disclosed herein. The system 1000 may be a portion of a wireless communications system asherein described. The wireless device 1002 may be, for example, a UE of a wireless communication system. The network device 1018 may be, for example, a base station (e.g., an eNB or a gNB) of a wireless communication system.

[0148] The wireless device 1002 may include one or more processor(s) 1004. The processor(s) 1004 may execute instructions such that various operations of the wireless device 1002 are performed, as described herein. The processor(s) 1004 may include one or more baseband processors implemented using, for example, a central processing unit (CPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein.

[0149] The wireless device 1002 may include a memory’ 1006. The memory 1006 may be a non-transitory computer-readable storage medium that stores instructions 1008 (which may include, for example, the instructions being executed by the processor(s) 1004). The instructions 1008 may also be referred to as program code or a computer program. The memory' 1006 may also store data used by, and results computed by, the processor(s) 1004.

[0150] The wireless device 1002 may include one or more transceiver(s) 1010 that may include radio frequency (RF) transmitter circuitry and / or receiver circuitry that use the antenna(s) 1012 of the wireless device 1002 to facilitate signaling (e.g.. the signaling 1034) to and / or from the wireless device 1002 with other devices (e.g., the network device 1018) according to corresponding RATs.

[0151] The wireless device 1002 may include one or more antenna(s) 1012 (e.g., one, two, four, or more). For embodiments with multiple antenna(s) 1012, the wireless device 1002 may leverage the spatial diversity of such multiple antenna(s) 1012 to send and / or receive multiple different data streams on the same time and frequency resources. This behavior may be referred to as. for example, multiple input multiple output (MIMO) behavior (referring to the multiple antennas used at each of a transmitting device and a receiving device that enable this aspect). MIMO transmissions by the wireless device 1002 may be accomplished according to precoding (or digital beamforming) that is applied at the wireless device 1002 that multiplexes the data streams across the antenna(s) 1012 according to known or assumed channel characteristics such that each data stream is received with an appropriate signal strength relative to other streams andat a desired location in the spatial domain (e.g., the location of a receiver associated with that data stream). Certain embodiments may use single user MIMO (SU-MIMO) methods (where the data streams are all directed to a single receiver) and / or multi user MIMO (MU-MIMO) methods (where individual data streams may be directed to individual (different) receivers in different locations in the spatial domain).

[0152] In certain embodiments having multiple antennas, the wireless device 1002 may implement analog beamforming techniques, whereby phases of the signals sent by the antenna(s) 1012 are relatively adjusted such that the (joint) transmission of the antenna(s) 1012 can be directed (this is sometimes referred to as beam steering).

[0153] The wireless device 1002 may include one or more interface(s) 1014. The interface(s) 1014 may be used to provide input to or output from the wireless device 1002. For example, a wireless device 1002 that is a UE may include interface(s) 1014 such as microphones, speakers, a touchscreen, buttons, and the like in order to allow for input and / or output to the UE by a user of the UE. Other interfaces of such a UE may be made up of transmitters, receivers, and other circuitry' (e.g., other than the transceiver(s) 1010 / antenna(s) 1012 already described) that allow for communication between the UE and other devices and may operate according to known protocols (e.g., Wi-Fi®, Bluetooth®, and the like).

[0154] The wireless device 1002 may include a differential PMI module 1016. The differential PMI module 1016 may be implemented via hardware, software, or combinations thereof. For example, the differential PMI module 1016 may be implemented as a processor, circuit, and / or instructions 1008 stored in the memory' 1006 and executed by the processor(s) 1004. In some examples, the differential PMI module 1016 may be integrated within the processor(s) 1004 and / or the transceiver(s) 1010. For example, the differential PMI module 1016 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry ) within the processor(s) 1004 or the transceiver(s) 1010.

[0155] The differential PMI module 1016 may be used for various aspects of the present disclosure, for example, aspects of FIG. 4 through FIG. 8. The differential PMI module 1016 is configured to cause the wireless device 1002 to, for example, generate and send differential PMI, receive and apply configuration information related todifferential PMI from the network, and / or generate and send UCI corresponding to differential PMI, according to the manners discussed herein.

[0156] The network device 1018 may include one or more processor(s) 1020. The processor(s) 1020 may execute instructions such that various operations of the network device 1018 are performed, as described herein. The processor(s) 1020 may include one or more baseband processors implemented using, for example, a CPU, a DSP, an ASIC, a controller, an FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein.

[0157] The network device 1018 may include a memory 1022. The memory 1022 may be a non-transitory computer-readable storage medium that stores instructions 1024 (which may include, for example, the instructions being executed by the processor(s) 1020). The instructions 1024 may also be referred to as program code or a computer program. The memory 1022 may also store data used by. and results computed by. the processor(s) 1020.

[0158] The network device 1018 may include one or more transceiver(s) 1026 that may include RF transmitter circuitry and / or receiver circuitry that use the antenna(s) 1028 of the network device 1018 to facilitate signaling (e.g., the signaling 1034) to and / or from the network device 1018 with other devices (e.g., the wireless device 1002) according to corresponding RATs.

[0159] The network device 1018 may include one or more antenna(s) 1028 (e.g., one, two, four, or more). In embodiments having multiple antenna(s) 1028, the network device 1018 may perform MIMO, digital beamforming, analog beamforming, beam steering, etc., as has been described.

[0160] The network device 1018 may include one or more interface(s) 1030. The interface(s) 1030 may be used to provide input to or output from the network device 1018. For example, a network device 1018 that is a base station may include interface(s) 1030 made up of transmitters, receivers, and other circuitry (e.g., other than the transceiver(s) 1026 / antenna(s) 1028 already described) that enables the base station to communicate with other equipment in a core network, and / or that enables the base station to communicate with external networks, computers, databases, and the like for purposes of operations, administration, and maintenance of the base station or other equipment operably connected thereto.

[0161] The network device 1018 may include a differential PMI module 1032. The differential PMI module 1032 may be implemented via hardware, software, or combinations thereof. For example, the differential PMI module 1032 may be implemented as a processor, circuit, and / or instructions 1024 stored in the memory 1022 and executed by the processor(s) 1020. In some examples, the differential PMI module 1032 may be integrated within the processor(s) 1020 and / or the transceiver(s) 1026. For example, the differential PMI module 1032 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the processor(s) 1020 or the transceiver(s) 1026.

[0162] The differential PMI module 1032 may be used for various aspects of the present disclosure, for example, aspects of FIG. 4 through FIG. 8. The differential PMI module 1032 may be configured to cause the network device 1018 to receive and use differential PMI, generate and send configuration information related to differential PMI from the network, and / or receive and use UCI corresponding to differential PMI, according to the manners discussed herein.

[0163] Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of the method 700. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 1002 that is a UE, as described herein).

[0164] Embodiments contemplated herein include one or more non -transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of the method 700. This non-transitory computer-readable media may be. for example, a memory of a UE (such as a memory 1006 of a wireless device 1002 that is a UE, as described herein).

[0165] Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of the method 700. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 1002 that is a UE, as described herein).

[0166] Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors toperform one or more elements of the method 700. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 1002 that is a UE. as described herein).

[0167] Embodiments contemplated herein include a signal as described in or related to one or more elements of the method 700.

[0168] Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processor is to cause the processor to carry' out one or more elements of the method 700. The processor may be a processor of a UE (such as a processor(s) 1004 of a wireless device 1002 that is a UE, as described herein). These instructions may be, for example, located in the processor and / or on a memory of the UE (such as a memory 1006 of a wireless device 1002 that is a UE, as described herein).

[0169] Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of the method 800. This apparatus may be, for example, an apparatus of a base station (such as a network device 1018 that is a base station, as described herein).

[0170] Embodiments contemplated herein include one or more non -transitory7computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of the method 800. This non-transitory computer-readable media may be, for example, a memory' of a base station (such as a memory 1022 of a network device 1018 that is a base station, as described herein).

[0171] Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of the method 800. This apparatus may be, for example, an apparatus of a base station (such as a network device 1018 that is a base station, as described herein).

[0172] Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of the method 800. This apparatus may be. for example, an apparatus of a base station (such as a network device 1018 that is a base station, as described herein).

[0173] Embodiments contemplated herein include a signal as described in or related to one or more elements of the method 800.

[0174] Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processing element is to cause the processing element to carry out one or more elements of the method 800. The processor may be a processor of a base station (such as a processor(s) 1020 of a network device 1018 that is a base station, as described herein). These instructions may be, for example, located in the processor and / or on a memory’ of the base station (such as a memory 1022 of a network device 1018 that is a base station, as described herein).

[0175] For one or more embodiments, at least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, and / or methods as set forth herein. For example, a baseband processor as described herein in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth herein. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth herein.

[0176] Any of the above described embodiments may be combined with any other embodiment (or combination of embodiments), unless explicitly stated otherwise. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments.

[0177] Embodiments and implementations of the systems and methods described herein may include various operations, which may be embodied in machine-executable instructions to be executed by a computer system. A computer system may include one or more general-purpose or special-purpose computers (or other electronic devices). The computer system may include hardware components that include specific logic for performing the operations or may include a combination of hardware, software, and / or firmware.

[0178] It should be recognized that the systems described herein include descriptions of specific embodiments. These embodiments can be combined into single systems. partially combined into other systems, split into multiple systems or divided or combinedin other ways. In addition, it is contemplated that parameters, attributes, aspects, etc. of one embodiment can be used in another embodiment. The parameters, attributes, aspects, etc. are merely described in one or more embodiments for clarity, and it is recognized that the parameters, attributes, aspects, etc. can be combined with or substituted for parameters, attributes, aspects, etc. of another embodiment unless specifically disclaimed herein.

[0179] It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized 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 minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users.

[0180] Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered illustrative and not restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims

CLAIMS1. A method of a user equipment (UE), comprising: calculating a precoder matrix indicator (PMI) based on one or more reference signals received from a network; selecting one or more selected PMI parts of the PMI to include in a differential PMI; generating the differential PMI using the one or more selected PMI parts and a coefficient PMI part of the PMI, the coefficient PMI part comprising quantized coefficients associated with delay taps of the PMI; and sending the differential PMI to the network.

2. The method of claim 1, further comprising receiving, from the network, configuration information defining first one or more PMI value types for use in a first PMI part of the one or more selected PMI parts.

3. The method of claim 2, wherein the configuration information further defines second one or more PMI value types for use in a second PMI part of the one or more selected PMI parts.

4. The method of claim 1, further comprising receiving, from the network, configuration information comprising a first periodicity for using a first PMI part of the one or more selected PMI parts; wherein the selecting the one or more selected PMI parts comprises identifying the first PMI part for inclusion in the one or more selected PMI parts based on a determination that no prior PMI sent to the network within the first periodicity for the first PMI part included first one or more PMI value ty pes for the first PMI part.

5. The method of claim 4, wherein: the configuration information further comprises a second periodicity for using a second PMI part of the one or more selected PMI parts; and the selecting the one or more selected PMI parts comprises identifying the second PMI part for inclusion in the one or more selected PMI parts based on a determination that no prior PMI sent to the network within the second periodicity for the second PMI part included the second one or more PMI value types for the second PMI part.

6. The method of claim 1, further comprising receiving, from the network, a trigger for the differential PMI; and wherein the selecting the one or more selected PMI parts comprises identifying a first PMI part for inclusion in the one or more selected PMI parts based on a determination that the trigger identifies the first PMI part.

7. The method of claim 6, wherein the selecting the one or more selected PMI parts comprises identify ing a second PMI part for inclusion in the one or more selected PMI parts based on a determination that the trigger identifies the second PMI part.

8. The method of claim 6, further comprising: detecting a change to a channel between the UE and the network; and sending, to the network, an indication that the change to the channel has occurred, wherein the trigger is received from the network in response to the indication of the change to the channel.

9. The method of claim 1, further comprising sending, to the network, uplink control information (UCI) identifying the selected PMI parts that are included in the differential PMI.

10. The method of claim 1, wherein the selecting the one or more selected PMI parts comprises identifying whether an uplink (UL) hybrid automatic repeat request (HARQ) retransmission timer corresponding to a prior PMI that was transmitted to the network is running.

11. The method of claim 1, further comprising sending, to the network, capability information indicating that the UE is capable of sending the differential PMI.

12. The method of claim 1, wherein the one or more selected PMI parts are selected from a set of PMI parts comprising: a first PMI part associated with long-term feedback, the first PMI part including first one or more PMI value types; a second PMI part associated with medium-term feedback, the second PMI part including second one or more PMI value types; and a third PMI part associated with short-term feedback, the third PMI part including third one or more PMI value types.

13. A method of a radio access network (RAN), comprising: receiving, from a user equipment (UE), a differential precoder matrix indicator (PMI) comprising one or more selected PMI parts of a PMI and a coefficient PMI part of the PMI, the coefficient PMI part comprising quantized coefficients associated with delay taps of the PMI; constructing the PMI based on the differential PMI and one or more prior PMI parts previously received at the network; and precoding a downlink (DL) transmission for the UE using the PMI.

14. The method of claim 13, further comprising sending, to the UE, configuration information defining first one or more PMI value t pes for a first PMI part of the one or more selected PMI parts.

15. The method of claim 14, wherein the configuration information further defines second one or more PMI value types for a second PMI part of the one or more selected PMI parts.

16. The method of claim 13, further comprising sending, to the UE, configuration information comprising a first periodicity for using a first PMI part of the one or more selected PMI parts.

17. The method of claim 16, wherein the configuration information further comprises a second periodicity for using a second PMI part of the one or more selected PMI parts.

18. The method of claim 13, further comprising sending, to the UE, a trigger for the differential PMI, wherein the trigger identifies a first PMI part for inclusion in the one or more selected PMI parts.

19. The method of claim 18, wherein the trigger identifies a second PMI part for inclusion in the one or more selected PMI parts.

20. The method of claim 18, further comprising receiving, from the UE, an indication that a change to a channel between the UE and the network has occurred; wherein the trigger is sent to the UE in response to the indication of the change to the channel.

21. The method of claim 13, further comprising receiving, from the UE, uplink control information (UCI) identifying the selected PMI parts that are included in the differential PMI.

22. The method of claim 13, further comprising receiving, from the UE, capability information indicating that the UE is capable of sending the differential PMI.

23. The method of claim 13, wherein the one or more selected PMI parts comprises one or more of: a first PMI part associated with long-term feedback, the first PMI part including first one or more PMI value types; a second PMI part associated with medium-term feedback, the second PMI part including second one or more PMI value types; and a third PMI part associated with short-term feedback, the third PMI part including third one or more PMI value types.

24. An apparatus comprising means to perform the method of any of claim 1 to claim 23.

25. A computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform the method of any of claim 1 to claim 23.

26. An apparatus comprising logic, modules, or circuitry to perform the method of any of claim 1 to claim 23.

27. A baseband processor for a user equipment (UE) that is configured to cause the UE to perform one or more elements of any one of claim 1 to claim 12.

28. A baseband processor for a radio access network (RAN) that is configured to cause the RAN to perform one or more elements of any one of claim 13 to claim 23.

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