WO2021213656A1

WO2021213656A1 - Inter-transmission layer interference tracking for multi-transmission/reception points

Info

Publication number: WO2021213656A1
Application number: PCT/EP2020/061336
Authority: WO
Inventors: Salah Eddine HAJRI; Youngsoo Yuk; Keeth Saliya Jayasinghe LADDU
Original assignee: Nokia Technologies Oy
Priority date: 2020-04-23
Filing date: 2020-04-23
Publication date: 2021-10-28

Abstract

According to certain embodiments, a method and apparatus may include receiving at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include performing at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The method may further include reporting the at least one inter-transmission layer interference measurement.

Description

TITLE: INTER-TRANSMISSION LAYER INTERFERENCE TRACKING FOR MULTI-TRANSMISSION/RECEPTION POINTS

TECHNICAL FIELD:

[0001] Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE), fifth generation (5G) radio access, new radio (NR) access, or other communications systems. For example, certain embodiments may relate to systems and/or methods for dynamic tracking of inter-transmission layer interference.

BACKGROUND:

[0002] Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), LTE Evolved UTRAN (E-UTRAN), LTE- Advanced (LTE-A), MulteFire, LTE-A Pro, 5G radio access technology, and/or NR access technology. 5G wireless systems refer to the next generation (NG) of radio systems and network architecture. A 5G system is mostly built on a 5G NR, but a 5G (or NG) network can also build on the E-UTRA radio. It is estimated that NR provides bitrates on the order of 10-20 Gbit/s or higher, and can support at least service categories such as enhanced mobile broadband (eMBB) and ultra-reliable low-latency-communication (URLLC) as well as massive machine type communication (mMTC). NR is expected to deliver extreme broadband and ultra-robust, low latency connectivity and massive networking to support the Internet of Things (IoT). With IoT and machine-to- machine (M2M) communication becoming more widespread, there will be a growing need for networks that meet the needs of lower power, low data rate, and long battery life. The next generation radio access network (NG-RAN) represents the RAN for 5G, which can provide both NR and LTE (and LTE- Advanced) radio accesses. It is noted that, in 5G, the nodes that can provide radio access functionality to a user equipment (i.e., similar to the Node B, NB, in UTRAN or the evolved NB (eNB) in LTE) may be named next-generation NB (gNB) when built on NR radio, and may be named next-generation eNB (NG-eNB) when built on E-UTRA radio.

SUMMARY:

[0003] In accordance with some embodiments, a method may include receiving at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include performing at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The method may further include reporting the at least one inter transmission layer interference measurement.

[0004] In accordance with certain embodiments, an apparatus may include means for receiving at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The apparatus may further include means for performing at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The apparatus may further include means for reporting the at least one inter-transmission layer interference measurement.

[0005] In accordance with various embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus to at least receive at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least perform at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least report the at least one inter-transmission layer interference measurement.

[0006] In accordance with some embodiments, a non-transitory computer readable medium can be encoded with instructions that may, when executed in hardware, perform a method. The method may include receiving at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include performing at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The method may further include reporting the at least one inter transmission layer interference measurement.

[0007] In accordance with certain embodiments, a computer program product may perform a method. The method may include receiving at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include performing at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The method may further include reporting the at least one inter-transmission layer interference measurement.

[0008] In accordance with various embodiments, an apparatus may include circuitry configured to receive at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter transmission layer interference as at least one reporting parameter. The circuitry may further be configured to perform at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter. The circuitry may further be configured to report the at least one inter-transmission layer interference measurement.

[0009] In accordance with some embodiments, a method may include transmitting at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include receiving at least one inter-transmission layer interference measurement.

[0010] In accordance with certain embodiments, an apparatus may include means for transmitting at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter transmission layer interference as at least one reporting parameter. The apparatus may further include means for receiving at least one inter transmission layer interference measurement.

[0011] In accordance with various embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code can be configured to, with the at least one processor, cause the apparatus to at least transmit at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The at least one memory and the computer program code can be further configured to, with the at least one processor, cause the apparatus to at least receive at least one inter-transmission layer interference measurement. [0012] In accordance with some embodiments, a non-transitory computer readable medium can be encoded with instructions that may, when executed in hardware, perform a method. The method may include transmitting at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include receiving at least one inter-transmission layer interference measurement.

[0013] In accordance with certain embodiments, a computer program product may perform a method. The method may include transmitting at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter-transmission layer interference as at least one reporting parameter. The method may further include receiving at least one inter-transmission layer interference measurement.

[0014] In accordance with various embodiments, an apparatus may include circuitry configured to transmit at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration. At least one configuration may indicate inter transmission layer interference as at least one reporting parameter. The circuitry may further be configured to receive at least one inter-transmission layer interference measurement.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0015] For proper understanding of this disclosure, reference should be made to the accompanying drawings, wherein:

[0016] FIG. 1 illustrates an example of a CSI and inter-transmission layer interference reporting framework according to certain embodiments.

[0017] FIG. 2 illustrates an example of a signaling diagram according to some embodiments.

[0018] FIG. 3 illustrates an example of a flow diagram of a method performed by a user equipment according to various embodiments.

[0019] FIG. 4 illustrates an example of a flow diagram of a method performed by a network entity according to certain embodiments.

[0020] FIG. 5 illustrates an example of various network devices according to some embodiments.

[0021] FIG. 6 illustrates an example of a 5G network and system architecture according to various embodiments.

DETAILED DESCRIPTION:

[0022] It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for dynamic fracking of inter-transmission layer interference is not intended to limit the scope of certain embodiments, but is instead representative of selected example embodiments.

[0023] In Third Generation Partnership Project (3GPP) release (Rel)-16, design for multi-transmission/reception point (TRP) for enhanced mobile broadband (eMBB) was partially based on two design choices for non coherent joint transmission. The first design choice includes single physical downlink control channel (PDCCH)-based multi-TRP transmission, where a single PDCCH may schedule a single physical downlink shared channel (PDSCH), and different layers are transmitted from separate TRPs. In the second design choice of a multiple PDCCH-based multi-TRP transmission, PDCCHs from different TRPs may schedule respective PDSCHs.

[0024] 3 GPP Rel-17 is expected to continue developing NR multiple input multiple output (MIMO) enhancements. For example, work item (WI) “Further enhancements on MIMO for NR” (RP- 193133) addresses improvements for multi-TRP support in RANI, including channel state information (CSI) reporting and interference hypotheses aspects. In particular, Rel-17 seeks to identify and specify features to improve reliability and robustness for channels other than PDSCH, such as PDCCH, physical uplink control channel (PUSCH), and physical uplink control channel (PUCCH), using multi-TRP and/or multi-panel, with Rel-16 reliability features as the baseline.

[0025] Rel-17 also seeks to identify and specify quasi co location (QCL)/transmission configuration indicator (TCI)-related enhancements to enable inter-cell multi-TRP operations, assuming multi-downlink control information (DCI) based multi-PDSCH reception. In addition, this WI may specify beam-management-related enhancements for simultaneous multi- TRP transmission with multi-panel reception, if necessary. The WI may also provide enhancements to support high speed train high-speed train (HST)- system frame number (SFN) deployment scenarios. For example, support may include identifying and specifying solutions on QCL assumptions for a demodulation reference signal (DMRS), such as multiple QCL assumptions for the same DMRS ports and/or targeting downlink (DL)-only transmissions. This could also include identifying benefits over Rel-16 HST enhancements, and specifying QCL/QCL-like relations, such as applicable types and their associated requirements, between DL and uplink (UL) signal by reusing the unified transmission configuration indicator (TCI) framework.

[0026] Furthermore, the WI may include enhancements to CSI measurements and reporting. For example, Rel-17 may evaluate and specify CSI reporting for DL multi-TRP and/or multi-panel transmission to enable more dynamic channel/interference hypotheses for non-coherent joint transmission (NCJT), targeting both frequency range 1 (FR1) and FR2. The WI may also evaluate and specify Type II port selection codebook enhancements based on Rel- 15/16 Type II port selection, where information related to angles and delays can be estimated at the network entity based on sounding reference signal (SRS) by utilizing DL/UL reciprocity of angle and delay. The remaining DL CSI may be reported by the user equipment (UE), mainly targeting frequency division duplex (FDD) FR1 to improve the trade-offs among UE complexity, performance, and reporting overhead.

[0027] Multi-TRP communication can provide a multitude of benefits, such as improved reliability thanks to increased spatial diversity. Depending on which multi-TRP transmission scheme used (i.e., coherent joint transmission scheme (CJT), non-coherent joint transmission (NCJT), DPS, coordinated scheduling/coordinated beamforming (CS/CB), dynamic power muting (DPM), etc.), the superior macro-diversity inherent to multi-TRP scenarios may be exploited at the network side differently. However, the performance of a multi-TRP transmission scheme depends on the accuracy of beamforming and link adaptation.

[0028] In order to provide a minimal level of performance, the availability of accurate CSI at the TRPs/NEs is critical and can be provided by NR codebooks like Rel-15 and Rel-16 type II. Inmulti-TRP scenarios, aUE may transmit several CSI reports to the cooperating TRPs/network entities, such as joint or independent PMIs, and jointly or independently computed channel quality indicator (CQI), for the different cooperating TRPs/NEs.

[0029] Independent CSI reporting in these scenarios provides enough flexibility to dynamically control the uplink control information (UCI) payload. As an example, this could enable independently triggered PMI reports for each of the TRPs. Additionally, independent CSI reporting for each TRP also has the advantage of being an extension of the Rel-15 and Rel-16 CSI reporting frameworks. The Rel-16 type II codebook supports up to four spatial layers, which the Rel-15 type II codebook did not provide due to the non-negligible overhead that high rank and accurate PMI reporting requires. Providing support for up to four spatial layers in the framework of joint transmission for multi- TRP, whether coherent or non-coherent, provides numerous advantages. For example, diversity gain may be increased for non-coherent joint transmission, and combining gain may be increased for coherent joint transmission.

[0030] However, increasing the number of spatial layers may impede inter- transmission layer interference, especially when the transmission antenna ports are not co-located, such as in the framework of multi-TRP. The development of Rel-16 type II codebook considered the challenges of inter-transmission layer interference with respect to rank extension. Indeed, a poor representation of a high rank PMI may cause an increase in inter-transmission layer interference due to a loss of orthogonality between transmission layers. Furthermore, since the relative speed of UE movement with respect to each of the coordinating TRPs is different, the channels change at different rates. As a result, when the UE moves, the feedback PMIs begin deviating from the actual channels realization at different rates, resulting in increasing interference between the streams transmitted from different TRPs. This would impede the performance of both multi-TRP transmission designs, including single and multiple PDCCH. [0031] Certain embodiments described herein may have various benefits and/or advantages to overcome the disadvantages described above. For example, certain embodiments may report frameworks that would help the UE and network avoid excessive inter-transmission layer interference in multi-TRP. By leveraging a novel feedback quantity, the UE may help the network select improved timings for triggering full CSI feedback, including PMI.

[0032] Furthermore, in some embodiments, the network entity may track the impact of radio environment evolution and UE mobility on inter-transmission layer interference for multi-TRP joint transmission. The UE may also be enabled to assist the network in selecting the opportune time to trigger PMI reporting based on experienced inter-transmission layer interference power/strength. This could include reducing the frequency of PMI feedback triggering which results in lower feedback overhead and better overall uplink resources management and/or complexity at the UE side as PMI computations are performed when required by the radio channel conditions.

[0033] Some embodiments of the inter-transmission layer interference reporting may be used to optimize link adaptation (MCS, outer-loop link adaptation) based on channel conditions variations. Due to its low computational complexity and payload, inter-transmission layer interference reporting may provide a convenient method to cope with highly dynamic channels, especially for multi-TRP scenarios. Finally, some embodiments do not require additional trigger states as inter-transmission layer interference reporting whether aperiodic can be jointly triggered with CSI reporting (conventional CSI reporting quantities). Thus, certain embodiments are directed to improvements in computer-related technology.

[0034] Certain embodiments described herein may also improve inter transmission layer interference for multi-TRP joint transmission. In particular, some embodiments may enable dynamic tracking of inter-transmission layer interference for multi-TRP using a novel feedback quantity, allowing a network entity to pinpoint an optimal time to trigger PMI feedback, select suitable codebook configurations (if needed), and optimize link adaptation based on radio environment variations. Various embodiments may be applicable for single and multiple PDCCH multi-TRP, addressing the loss of orthogonality between spatial layers whether the same or different codewords are transmitted by the different TRPs.

[0035] Some techniques described below may provide an efficient feedback framework, especially in terms of payload management on uplink channels, and assist the network entity select an appropriate timing to trigger a CSI feedback, based on the interference between the spatial layers received from different TRP. This may include reporting inter-transmission layer interference measured power/strength over PUSCH or PUCCH in aperiodically, periodically, or semi- persistently schedules. The reported inter-transmission layer interference could be measured according to, for example, a configured CSI-RS and/or on downlink DMRS.

[0036] In contrast to the 5G NR CSI reporting framework discussed above, the techniques reviewed below may enable the UE to assist the network in selecting an opportune time to trigger PMI reporting based on experienced interference power/strength. In addition, providing more flexibility in managing uplink resources as PMI feedback and computations may be triggered when necessary. In addition, the network may be enabled to select appropriate CSI reporting configurations, PMI codebook configuration based on the radio environment, for example, Rel-16 type II, maximum rank, number spatial of beams L, number of frequency domain components M, total number of non-zero coefficients, and number of PMI sub-bands. As a result, there may be a trade-off between PMI accuracy and overhead over uplink channels. The network entity may also modify the codebook configuration to increase accuracy if interference is above a threshold, or decrease feedback overhead if permitted by radio conditions. Finally, link adaptations may be optimized based on reported inter-transmission layer interference, such as MCS and outer-loop link adaptation.

[0037] In another aspect, inter-transmission layer interference reporting configuration may be included in CSI reporting configuration or set independently in RRC. In order to minimize the impact of certain embodiments on the downlink control information formats, triggering aperiodic inter transmission layer interference reporting may be performed using the CSI request field of uplink grant DCI, such as format 0 1 in 5G NR. In such an example, trigger states for aperiodic CSI reporting may be associated with inter transmission layer interference reporting configuration or with CSI reporting configurations that include inter-transmission layer interference related information elements. Inter-transmission layer interference reporting may also be performed according to a lower or higher periodicity than PMI reporting, and/or in the same or separate time instances based on the configuration, as illustrated in FIG. 1.

[0038] FIG. 2 illustrates an example of a system according to certain embodiments. A system may include one or more of at least one UE, such as UE 250, and at least one NE, such as NE 260 and NE 270. UE 250 may be similar to UE 510 in FIG. 5, and NE 260 and NE 270 may be similar to NE 520 in FIG. 5.

[0039] At 201, NE 260 may transmit to UE 250 at least one RRC configuration, which may include at least one trigger state list and at least one associated CSI reporting configuration. In some embodiments, if inter-transmission layer interference is configured to be measured on CSI-RS resources, at least one procedure, such as port selection, may be used. For example, UE 250 may be configured with at least one CSI-RS resource set, which may include a plurality of CSI-RS ports from multiple network entities such as NE 260 and NE 270. A combined port selection codebook may be configured to indicate the ports over which high inter-transmission layer interference was detected. Thus, UE 250 may transmit at least one indication of the selected port/ports and associated frequency selective or wideband power/gains, if configured to NE 260. In contrast to type II port- selection codebook, UE 250 would not be required to transmit the whole PMI. The indicated ports may correspond to the layers experiencing high inter-transmission layer interference, along with their associated wideband or per sub-band coefficients, and may correspond to the interference power/strength.

[0040] In various embodiments, inter-transmission layer interference may be computed according to specific spatial-domain support of each of the transmission layers. In Rel-15 and Rel-16 type II codebook, the spatial domain compression matrix, denoted by Wi, may be common for all layers in a given PMI. However, if Wi selection is permitted to be independent for different layers, UE 250 may select different spatial beams per layer. Consequently, inter transmission layer interference may be measured by the correlation/distance between independently selected spatial supports, per layer, quantize and feedback an inter-PMI or inter-transmission layer spatial distance. In one example, chordal distance may be used.

[0041] In certain embodiments, inter-transmission layer interference may be computed as the power leakage between layers computed by UE 250. In this case, PDSCH DMRS may be used to measure inter-transmission layer interference for each scheduled downlink transmission. In various other embodiments, inter-transmission layer measurement may include the impact of UE-side wideband or frequency- selective beamforming. UE 250 would not provide NE 260 with any indication of the beamformer being used by UE 250; instead, this information may be included in the reported inter-transmission layer interference, implicitly. Consequently, leakage between transmission layers may be computed after the application of the reception filter.

[0042] At 203, NE 260 may transmit to UE 250 one or more of at least one low layer trigger for aperiodic CSI reporting and at least one low layer trigger for semi-persistent inter-transmission interference reporting.

[0043] At 205, NE 270 may transmit to UE 250 at least one CSI-RS, and similarly at 207, NE 260 may also transmit to UE 250 at least one CSI-RS. At 209, UE 250 may perform at least one CSI measurement according to the at least one RRC configuration received in step 201. At 211, UE 250 may transmit to NE 260 at least one CSI report over PUSCH and/or PUCCH. At 213, NE 270 may transmit to UE 250 at least one CSI-RS, and similarly at 215, NE 260 may also transmit to UE 250 at least one CSI-RS.

[0044] At 217, UE 250 may perform at least one inter-transmission layer interference measurement. As an example, as the impact of inter-transmission layer interference increases for high rank PMI, channel aging may worsen. This may be further worsened in multi-TRP settings based on relative directions and velocities of UE 250 differing with respect to NE 260 and NE 270. As a result, the rate of channel aging and radio environment variation may differ among NE 260 and NE 270, allowing NE 260 to track such interference. Although the conventional CSI reporting framework may permit it using frequent PMI feedback, PMI calculation and feedback may place significant strain on UE 250 and associated uplink resources. Indeed, based on inter-transmission layer interference, NE 260 and NE 270 may coordinate to trigger PMI feedback when needed to change selected trigger state and, consequently, selected PMI configuration in order to reduce the overhead when the interference conditions allow it, or to increase accuracy, when uplink resources are sufficient to fit higher payloads.

[0045] At 219, UE 250 may transmit to NE 260 at least one inter-transmission layer interference report over PUSCH and/or PUCCH. At 221, NE 270 may transmit to UE 250 at least one CSI-RS, and similarly at 223, NE 260 may also transmit to UE 250 at least one CSI-RS. At 225, UE 250 may perform at least one inter-transmission layer interference measurement. At 227, UE 250 may transmit to NE 260 at least one inter-transmission layer interference report over PUSCH and/or PUCCH.

[0046] At 229, NE 260 and NE 270 may coordinate CSI trigger state selection. At 231, NE 260 may transmit to UE 250 at least one low layer trigger (deactivation) configured for cross layer interference reporting. At 233, NE 260 and NE 270 may coordinate CSI reporting triggering. At 235, NE 260 and NE 270 may coordinate updating MCS and outer-loop link adaptation adjustments. [0047] At 237, NE 260 may transmit to UE 250 at least one low layer trigger configured for aperiodic CSI reporting. Then at 239, NE 270 may transmit to UE 250 at least one CSI-RS, and similarly at 241, NE 260 may also transmit to UE 250 at least one CSI-RS. At 243, UE 250 may perform at least one CSI measurement. At 245, UE 250 may transmit to NE 260 at least one CSI report over PUSCH/PUCCH.

[0048] FIG. 3 illustrates an example of a method performed by a UE, such as UE 510 illustrated in FIG. 5, according to certain embodiments. At 301, the UE may receive from a first NE, such as NE 520 in FIG. 5, at least one RRC configuration, which may include at least one trigger state list and at least one associated CSI reporting configuration. In some embodiments, if inter transmission layer interference is configured to be measured on CSI-RS resources, at least one procedure, such as port selection, may be used. For example, the UE may be configured with at least one CSI-RS recourse set, which may include a plurality of CSI-RS ports from multiple network entities such as the first NE and a second NE, which may also be similar to NE 520 in FIG. 5. A combined port selection codebook may be configured to indicate the ports over which high inter-transmission layer interference was detected. Thus, the UE may transmit at least one indication of the selected port/ports and associated frequency selective or wideband power/gains, if configured, to the first NE. In contrast to type II port- selection codebook, the UE would not be required to transmit the whole PMI. The indicated ports may correspond to the layers experiencing high inter-transmission layer interference, along with their associated wideband or per sub-band coefficients, and may correspond to the interference power/strength.

[0049] In some embodiments, inter-transmission layer interference may be computed according to specific spatial-domain support of each of the transmission layers. In Rel-15 and Rel-16 type II codebook, the spatial domain compression matrix, denoted by Wi, may be common for all layers in a given PMI. However, if Wi selection is permitted to be independent for different layers, the UE may select different spatial beams per layer. Consequently, inter transmission layer interference may be measured by the correlation/distance between independently selected spatial supports, per layer, quantize and feedback an inter-PMI or inter-transmission layer spatial distance. In one example, chordal distance may be used.

[0050] In certain embodiments, inter-transmission layer interference may be computed as the power leakage between layers computed by the UE. In this case, PDSCH DMRS may be used to measure inter-transmission layer interference for each scheduled downlink transmission. In various other embodiments, inter-transmission layer measurement may include the impact of UE-side wideband or frequency-selective beamforming. The UE would not provide the first NE with any indication of the beamformer being used by the UE; instead, this information may be included in the reported inter-transmission layer interference, implicitly. Consequently, leakage between transmission layers may be computed after the application of the reception filter.

[0051] At 303, the UE may receive from the first NE one or more of at least one low layer trigger for aperiodic CSI reporting and at least one at least one low layer trigger for semi-persistent inter-transmission interference reporting. At 305, the UE may receive from the first NE at least one CSI-RS, and similarly at 307, the UE may also receive from the second NE at least one CSI-RS. At 309, the UE may perform at least one CSI measurement according to the at least one RRC configuration received in step 301. At 311, the UE may transmit to the first NE at least one CSI report over PUSCH and/or PUCCH. At 313, the UE may receive from the first NE at least one CSI-RS, and similarly at 315, the UE may receive from the second NE at least one CSI-RS.

[0052] At 317, the UE may perform at least one inter-transmission layer interference measurement. As an example, as the impact of inter-transmission layer interference increases for high rank PMI, channel aging may worsen. This may be further worsened in multi-TRP settings based on relative directions and velocities of the UE differing with respect to the first NE and the second NE. As a result, the rate of channel aging and radio environment variation may differ among the coordinating the first NE and the second NE, allowing the first NE to track such interference. Although the conventional CSI reporting framework may permit it using frequent PMI feedback, PMI calculation and feedback may place significant strain on the UE and associated uplink resources. Indeed, based on inter-transmission layer interference, the first NE and the second NE may coordinate to trigger PMI feedback when needed to change selected trigger state and, consequently, selected PMI configuration in order to reduce the overhead when the interference conditions allow it, or to increase accuracy, when uplink resources are sufficient to fit higher payloads.

[0053] At 319, the UE may transmit to the first NE at least one inter transmission layer interference report over PUSCH and/or PUCCH. At 321, the UE may receive from the first NE at least one CSI-RS, and similarly at 323, the UE may receive from the second NE at least one CSI-RS. At 325, the UE may perform at least one inter-transmission layer interference measurement. At 327, the UE may transmit to the first NE at least one inter-transmission layer interference report over PUSCH and/or PUCCH.

[0054] At 329, the UE may receive from the first NE at least one low layer trigger (deactivation) configured for cross layer interference reporting. At 331, the UE may receive from the first NE at least one low layer trigger configured for aperiodic CSI reporting. At 333, the UE may receive from the first NE at least one CSI-RS, and similarly at 335, the UE may also receive from the second NE at least one CSI-RS. At 337, the UE may perform at least one CSI measurement. At 339, the UE may transmit to the first NE at least one CSI report over PUSCH/PUCCH.

[0055] FIG. 4 illustrates an example of a method performed by a first NE, such as NE 520 illustrated in FIG. 5, according to certain embodiments. At 401, the first NE may transmit to a UE, such as UE 510 in FIG. 5, at least one RRC configuration, which may include at least one trigger state list and at least one associated CSI reporting configuration. In some embodiments, if inter transmission layer interference is configured to be measured on CSI-RS resources, at least one procedure, such as port selection, may be used. For example, the UE may be configured with at least one CSI-RS recourse set, which may include a plurality of CSI-RS ports from multiple network entities such as the first NE and a second NE, which may also be similar to NE 520 in FIG. 5. A combined port selection codebook may be configured to indicate the ports over which high inter-transmission layer interference was detected. Thus, the NE may receive at least one indication of the selected port/ports and associated frequency selective or wideband power/gains, if configured, from the UE. In contrast to type II port- selection codebook, the UE would not be required to transmit the whole PMI. The indicated ports may correspond to the layers experiencing high inter-transmission layer interference, along with their associated wideband or per sub-band coefficients, and may correspond to the interference power/strength.

[0056] In various embodiments, inter-transmission layer interference may be computed according to specific spatial-domain support of each of the transmission layers. In Rel-15 and Rel-16 type II codebook, the spatial domain compression matrix, denoted by Wi, may be common for all layers in a given PMI. However, if Wi selection is permitted to be independent for different layers, the UE may select different spatial beams per layer. Consequently, inter transmission layer interference may be measured by the correlation/distance between independently selected spatial supports, per layer, quantize and feedback an inter-PMI or inter-transmission layer spatial distance. In one example, chordal distance may be used.

[0057] In certain embodiments, inter-transmission layer interference may be computed as the power leakage between layers computed by the UE. In this case, PDSCH DMRS may be used to measure inter-transmission layer interference for each scheduled downlink transmission. In various other embodiments, inter-transmission layer measurement may include the impact of UE-side wideband or frequency-selective beamforming. The UE would not provide the first NE with any indication of the beamformer being used by the UE; instead, this information may be included in the reported inter-transmission layer interference, implicitly. Consequently, leakage between transmission layers may be computed after the application of the reception filter.

[0058] At 403, the first NE may transmit to the UE one or more of at least one low layer trigger for aperiodic CSI reporting and at least one low layer trigger for semi-persistent inter-transmission interference reporting. At 405, the first NE may transmit to the UE at least one CSI-RS. At 407, the first NE may receive from the UE at least one CSI report over PUSCH and/or PUCCH. At 409, the first NE may transmit to the UE at least one CSI-RS.

[0059] At 411, the first NE may receive from the UE at least one inter transmission layer interference report over PUSCH and/or PUCCH. At 413, the first NE may transmit to the UE at least one CSI-RS. At 415, the first NE may receive from the UE at least one inter-transmission layer interference report over PUSCH and/or PUCCH.

[0060] At 417, the first NE and the second NE may coordinate CSI trigger state selection. At 419, the first NE may transmit to the UE at least one low layer trigger (deactivation) configured for cross layer interference reporting. At 421, the first NE and the second NE may coordinate CSI reporting triggering. At 423, the first NE and the second NE may coordinate updating MCS and outer-loop link adaptation adjustments.

[0061] At 425, the first NE may transmit to the UE at least one low layer trigger configured for aperiodic CSI reporting. At 427, the first NE may transmit to the UE at least one CSI-RS. At 429, the first NE may receive from the UE at least one CSI report over PUSCH/PUCCH.

[0062] FIG. 5 illustrates an example of a system according to certain embodiments. In one embodiment, a system may include multiple devices, such as, for example, user equipment 510 and/or network entity 520.

[0063] User equipment 510 may include one or more of a mobile device, such as a mobile phone, smart phone, personal digital assistant (PDA), tablet, or portable media player, digital camera, pocket video camera, video game console, navigation unit, such as a global positioning system (GPS) device, desktop or laptop computer, single-location device, such as a sensor or smart meter, or any combination thereof.

[0064] Network entity 520 may be one or more of a base station, such as an evolved node B (eNB) or 5G or New Radio node B (gNB), a serving gateway, a server, and/or any other access node or combination thereof. Network entity 520 may also be similar to user equipment 510. Furthermore, user equipment 510 and/or network entity 520 may be one or more of a citizens broadband radio service device (CBSD).

[0065] One or more of these devices may include at least one processor, respectively indicated as 511 and 521. Processors 511 and 521 may be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device. The processors may be implemented as a single controller, or a plurality of controllers or processors.

[0066] At least one memory may be provided in one or more of devices indicated at 512 and 522. The memory may be fixed or removable. The memory may include computer program instructions or computer code contained therein. Memories 512 and 522 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory and which may be processed by the processors may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. Memory may be removable or non-removable.

[0067] Processors 511 and 521 and memories 512 and 522 or a subset thereof, may be configured to provide means corresponding to the various blocks of FIGS. 2-4. Although not shown, the devices may also include positioning hardware, such as GPS or micro electrical mechanical system (MEMS) hardware, which may be used to determine a location of the device. Other sensors are also permitted and may be included to determine location, elevation, orientation, and so forth, such as barometers, compasses, and the like.

[0068] As shown in FIG. 5, transceivers 513 and 523 may be provided, and one or more devices may also include at least one antenna, respectively illustrated as 514 and 524. The device may have many antennas, such as an array of antennas configured for multiple input multiple output (MIMO) communications, or multiple antennas for multiple radio access technologies. Other configurations of these devices, for example, may be provided. Transceivers 513 and 523 may be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception.

[0069] The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as user equipment to perform any of the processes described below (see, for example, FIGS. 1-4). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, certain embodiments may be performed entirely in hardware.

[0070] In certain embodiments, an apparatus may include circuitry configured to perform any of the processes or functions illustrated in FIGS. 1-4. For example, circuitry may be hardware-only circuit implementations, such as analog and/or digital circuitry. In another example, circuitry may be a combination of hardware circuits and software, such as a combination of analog and/or digital hardware circuit(s) with software or firmware, and/or any portions of hardware processor(s) with software (including digital signal processor(s)), software, and at least one memory that work together to cause an apparatus to perform various processes or functions. In yet another example, circuitry may be hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that include software, such as firmware for operation. Software in circuitry may not be present when it is not needed for the operation of the hardware.

[0071] FIG. 6 illustrates an example of a 5G network and system architecture according to certain embodiments. Shown are multiple network functions that may be implemented as software operating as part of a network device or dedicated hardware, as a network device itself or dedicated hardware, or as a virtual function operating as a network device or dedicated hardware. The NE and UE illustrated in FIG. 5 may be similar to UE 510 and NE 520, respectively. The UPF may provide services such as intra-RAT and inter-RAT mobility, routing and forwarding of data packets, inspection of packets, user plane QoS processing, buffering of downlink packets, and/or triggering of downlink data notifications. The AF may primarily interface with the core network to facilitate application usage of traffic routing and interact with the policy framework. [0072] The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases “certain embodiments,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, appearances of the phrases “in certain embodiments,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments.

[0073] Additionally, if desired, the different functions or procedures discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions or procedures may be optional or may be combined. As such, the following description should be considered as illustrative of the principles and teachings of certain example embodiments, and not in limitation thereof.

[0074] One having ordinary skill in the art will readily understand that the example embodiments as discussed above may be practiced with procedures in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although some embodiments have been described based upon these example embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of example embodiments.

[0075] Partial Glossary [0076] 3 GPP Third Generation Partnership Project [0077] 5G Fifth Generation [0078] 5GC Fifth Generation Core [0079] 5GS Fifth Generation System [0080] 5QI Fifth Generation Quality of Service Indicator [0081] ASIC Application Specific Integrated Circuit [0082] BS Base Station [0083] CBSD Citizens Broadband Radio Service Device [0084] CCCH Common Control Channel [0085] CE Control Element [0086] CJT Coherent Joint Transmission [0087] CPU Central Processing Unit [0088] CQI Channel Quality Indicator [0089] CRI CSI-RS Resource Indicator [0090] CS/CB Coordinated Scheduling/Coordinated Beamforming [0091] CSI Channel State Information [0092] CSI-RS Channel State Information-Reference Signal [0093] DCCH Dedicated Control Channel [0094] DMRS Demodulation Reference Signal [0095] DCI Downlink Control Information [0096] DL Downlink [0097] DMRS Demodulation Reference Signal [0098] DPM Dynamic Power Muting [0099] DPS Dynamic Point Selection [0100] eMBB Enhanced Mobile Broadband [0101] eNB Evolved Node B [0102] EPS Evolved Packet System [0103] E-UTRAN Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network [0104] FDD Frequency Division Duplex [0105] FR Frequency Range [0106] gNB Next Generation Node B [0107] GPS Global Positioning System [0108] HARQ Hybrid Automatic Repeat Request [0109] HARQ PID Hybrid Automatic Repeat Request Process Identifier [0110] HDD Hard Disk Drive [0111] HST High-Speed Train [0112] IoT Internet of Things [0113] JT Joint Transmission [0114] LTE Long-Term Evolution [0115] M2M Machine-to-Machine [0116] MAC Medium Access Control [0117] MAC CE Medium Access Control Control Element [0118] MCS Modulation and Coding Scheme [0119] MEMS Micro Electrical Mechanical System [0120] MIMO Multiple Input Multiple Output [0121] MME Mobility Management Entity [0122] mMTC Massive Machine Type Communication [0123] NAS Non-Access Stratum [0124] NCJT Non-Coherent Joint Transmission [0125] NE Network Entity [0126] NG Next Generation [0127] NG-RAN Next Generation Radio Access Network [0128] NR New Radio [0129] NR-U New Radio Unlicensed [0130] PDA Personal Digital Assistance [0131] PDCCH Physical Downlink Control Channel [0132] PDSCH Physical Downlink Shared Channel [0133] PMI Precoding Matrix Indicator [0134] PUCCH Physical Uplink Control Channel [0135] PUSCH Physical Uplink Shared Channel [0136] QCL Quasi Co-location [0137] QoS Quality of Service [0138] RAM Random Access Memory [0139] RAN Radio Access Network [0140] RRC Radio Resource Control [0141] SDU Service Data Unit [0142] SFN System Frame Number [0143] SR Scheduling Report [0144] TCI Transmission Configuration Indicator [0145] TR Technical Report [0146] TRP Transmission/Reception Point [0147] TS Technical Specification [0148] Tx Transmission [0149] UCI Uplink Control Information [0150] UE User Equipment [0151] UL Uplink [0152] UMTS Universal Mobile Telecommunications System [0153] URLLC Ultra-Reliable and Low-Latency Communication [0154] UTRAN Universal Mobile Telecommunications System

Terrestrial Radio Access Network

[0155] WI Work Item

[0156] WLAN Wireless Local Area Network

Claims

WE CLAIM:

1. A method for inter-transmission layer interference measurement and reporting for multi-TRP transmission, comprising: receiving, by a user equipment, at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration, wherein at least one configuration indicates inter-transmission layer interference as at least one reporting parameter; performing, by the user equipment, at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter; and reporting, by the user equipment, the at least one inter-transmission layer interference measurement.

2. The method of claim 1, wherein at least one trigger state is associated with at least one CSI reporting configuration comprising at least one information element related to one or more of inter-transmission layer interference power/strength measurements and reporting or at least one specific configuration of inter-transmission layer interference power/strength measurements and reporting.

3. The method of any preceding claim, wherein the at least one CSI reporting configuration defines inter-transmission layer interference reporting as periodic, aperiodic, or semi-persistent.

4. The method of any preceding claim, wherein the at least one inter transmission layer interference measurement is performed on at least one CSI-RS or at least one downlink DMRS with at least one reference signal port per transmission layer.

5. The method of any preceding claim, wherein the at least one inter transmission layer interference measurement is performed according to at least one configured inter-transmission layer interference measurement resource.

6. The method of any preceding claim, wherein the at least one CSI-RS or at least one downlink DMRS is precoded based on at least one last reported PMI.

7. The method of any preceding claim, wherein the at least one inter transmission layer interference reporting is performed in the same or different time instances as PMI, CQI, RI, RSRP, or CRI/SSBRI reporting.

8. The method of any preceding claim, wherein the inter-transmission layer interference reporting is based on at least one downlink DMRS when multi- TRP PDSCH transmission is scheduled and the UE receives at least one uplink scheduling DCI triggering CSI reporting with at least one configuration that indicates inter-transmission layer interference as reporting quantity and does not include associated CSI-RS resources.

9. A method for inter-transmission layer interference measurement and reporting for multi-TRP transmission, comprising: transmitting, by a network entity, at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration, wherein at least one configuration indicates inter-transmission layer interference as at least one reporting parameter; and receiving, by the network entity, at least one inter-transmission layer interference measurement.

10. The method of claim 9, wherein at least one trigger state is associated with at least one CSI reporting configuration comprising at least one information element related to one or more of inter-transmission layer interference power/strength measurements and reporting or at least one specific configuration of inter-transmission layer interference power/strength measurements and reporting.

11. The method of any preceding claim, wherein the at least one CSI reporting configuration defines inter-transmission layer interference reporting as periodic, aperiodic, or semi-persistent.

12. The method of any preceding claim, wherein the at least one inter transmission layer interference measurement is performed on at least one CSI-RS or at least one downlink DMRS with at least one reference signal port per transmission layer.

13. The method of any preceding claim, wherein the at least one inter transmission layer interference measurement is performed according to at least one configured inter-transmission layer interference measurement resource.

14. The method of any preceding claim, wherein the at least one CSI-RS or at least one downlink DMRS is precoded based on at least one last reported PMI.

15. The method of any preceding claim, wherein the at least one inter transmission layer interference reporting is performed in the same or different time instances as PMI, CQI, RI, RSRP, or CRI/SSBRI reporting.

16. The method of any preceding claim, wherein the inter-transmission layer interference reporting is based on at least one downlink DMRS when multi- TRP PDSCH transmission is scheduled and the UE receives at least one uplink scheduling DCI triggering CSI reporting with at least one configuration that indicates inter-transmission layer interference as reporting quantity and does not include associated CSI-RS resources.

17. An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration, wherein at least one configuration indicates inter-transmission layer interference as at least one reporting parameter; perform at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter; and report the at least one inter-transmission layer interference measurement.

18. An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: transmit at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration, wherein at least one configuration indicates inter-transmission layer interference as at least one reporting parameter; and receive at least one inter-transmission layer interference measurement.

19. An apparatus, comprising: means for receiving at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration, wherein at least one configuration indicates inter-transmission layer interference as at least one reporting parameter; means for performing at least one inter-transmission layer interference measurement on at least one downlink reference signal based on at least one received CSI reporting configuration indicating inter-transmission layer interference as at least one reporting parameter; and means for reporting the at least one inter-transmission layer interference measurement.

20. An apparatus, comprising: means for transmitting at least one trigger state list comprising at least one trigger state associated with at least one channel state information (CSI) reporting configuration, wherein at least one configuration indicates inter-transmission layer interference as at least one reporting parameter; and means for receiving at least one inter-transmission layer interference measurement.