Patent Description:
The next generation mobile wireless communication system (<NUM>) or new radio (NR), will support a diverse set of use cases and a diverse set of deployment scenarios. The latter includes deployment at both low frequencies (<NUM> of MHz), similar to longer term evolution (LTE) today, and very high frequencies (mm waves in the tens of GHz).

Similar to LTE, NR uses plain Orthogonal Frequency Division Multiplexing (OFDM) with cyclic prefix, also known as CP-OFDM, in the downlink (i.e., from a network node, or gNB, to a wireless device or WD). In the uplink (i.e., from WD to gNB), both CP-OFDM and discrete Fourier transform (DFT)-spread OFDM (DFT-S-OFDM) will be supported.

The basic NR physical resource can thus be seen as a time-frequency grid as illustrated in <FIG>, where each resource element (RE) corresponds to one OFDM subcarrier during one OFDM symbol interval. A component carrier may contain one or multiple bandwidth parts (BWPs), each BWP consists of a group of contiguous physical resource blocks (PRBs) in the frequency domain. PRBs are numbered starting with <NUM> from one end of a BWP. Each PRB consists of <NUM> subcarriers. <FIG> shows an example of a BWP.

Different subcarrier spacing values are supported in NR. The supported subcarrier spacing values (also referred to as different numerologies) in NR are given by Δf=(<NUM>×<NUM>^α) kHz where α is a non-negative integer and where a subcarrier spacing of <NUM> is referred to as the reference numerology.

In the time domain, downlink and uplink transmissions in NR will be organized into equally-sized subframes. Each subframe has a fixed duration of <NUM>. A subframe is further divided into one or multiple slots of equal duration. A <NUM>-symbol slot is shown in <FIG>. Data scheduling in NR can be on a slot basis. The slot duration can be different for different subcarrier spacings.

Downlink transmissions are dynamically scheduled, i.e., in each slot, the gNB transmits downlink control information (DCI) concerning which WD data is to be transmitted to and which PRBs in the current downlink slot the data is transmitted on. This control signaling is typically transmitted in the first one or two OFDM symbols in each slot in NR. The control information is carried on the Physical Downlink Control Channel (PDCCH) and data is carried on the Physical Downlink Shared Channel (PDSCH). A WD first detects and decodes the PDCCH and if a PDCCH is decoded successfully, the WD then decodes the corresponding PDSCH based on the decoded control information in the PDCCH.

Uplink data transmission are also dynamically scheduled using the PDCCH. Similar to downlink, a WD first decodes uplink grants in the PDCCH and then transmits data over the Physical Uplink Shared Channel (PUSCH) based on the decoded control information in the uplink grant such as modulation order, coding rate, uplink resource allocation, and etc..

Multi-antenna techniques can significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a multiple-input multiple-output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO.

A core component in LTE and NR is the support of MIMO antenna deployments and MIMO related techniques. Spatial multiplexing is one of the MIMO techniques used to achieve high data rates in favorable channel conditions. An illustration of the spatial multiplexing operation is provided in <FIG>.

As seen, the information carrying symbol vector s = [s<NUM>, s<NUM>,. , sr]T is multiplied by an NT x r precoder matrix W, which serves to distribute the transmit energy in a subspace of the NT (corresponding to NT antenna ports) dimensional vector space. The precoder matrix is typically selected from a codebook of possible precoder matrices, and typically indicated by means of a precoder matrix indicator (PMI), which specifies a unique precoder matrix in the codebook for a given number of symbol streams. The r symbols in s each correspond to a layer and r is referred to as the transmission rank. In this way, spatial multiplexing is achieved since multiple symbols can be transmitted simultaneously over the same time/frequency resource element (RE). The number of symbols r is typically adapted to suit the current channel properties.

The received signal at a WD with NR receive antennas at a certain RE n is given by <MAT> where yn is a NR × <NUM> received signal vector, Hn a NR × NT channel matrix at the RE, en is a NR × <NUM> noise and interference vector received at the RE by the WD. The precoder W can be a wideband precoder, which is constant over frequency, or frequency selective, i.e. different over frequency.

The precoder matrix is often chosen to match the characteristics of the NRxNT MIMO channel matrix Hn, resulting in so-called channel dependent precoding. This is also commonly referred to as closed-loop precoding and essentially strives for focusing the transmit energy into a subspace which is strong in the sense of conveying much of the transmitted energy to the WD. In addition, the precoder matrix may also be selected to strive for orthogonalizing the channel, meaning that after proper linear equalization at the WD, the inter-layer interference is reduced.

The transmission rank, and thus the number of spatially multiplexed layers, is reflected in the number of columns of the precoder. The transmission rank is also dependent on the Signal to noise plus interference ratio (SINR) observed at the WD. Typically a higher SINR is required for transmissions with higher ranks. For efficient performance, it is important that a transmission rank that matches the channel properties as well as the interference is selected.

CSI-RS are reference signals used for CSI estimations by a WD. The WD estimates individual radio propagation channel between each transmit antenna port at a gNB and a receive antenna at the WD based on the received CSI-RS. Each antenna port carries a CSI-RS signal in certain REs and slots in NR. An example of REs used for carrying CSI-RS signals for eight antenna ports is shown in <FIG>, where one PRB over one slot is shown. The CSI-RS are typically transmitted in the same REs in every PRB within a configured bandwidth. In this example, the CSI-RS resource for the eight ports consists of four RE pairs in one OFDM symbol. Two antenna ports are code division multiplexed (CDM) multiplexed on a pair of adjacent REs using length two orthogonal cover codes (OCC), or CDM2.

Another example of CSI-RS resource for <NUM> ports is shown in <FIG>, where <NUM> REs in two OFDM symbols are allocated. The REs are further divided in four groups, each with <NUM> adjacent REs. Four antenna ports are code division multiplexed (CDM) multiplexed on a group of <NUM> adjacent REs using two by two orthogonal cover codes (OCC), or CDM4.

Table <NUM> below lists all the possible RE patterns for a CSI-RS resource in NR. In Table <NUM> Y and Z respectively indicate the number of adjacent subcarriers and OFDM symbols, respectively, that form a component resource. For example, (Y,Z) = (<NUM>,<NUM>) means that the component resource contains <NUM> REs in two adjacent subcarriers and two adjacent OFDM symbols. A CSI-RS resource can contain one or multiple such component resources. Furthermore, in Table <NUM>, the following notations are used for CDM:.

In case of density <NUM>, a CSI-RS is transmitted in every PRB in the frequency domain and in case of density ½, a CSI-RS is transmitted in every other PRB in the frequency domain, either even or odd numbered PRBs.

In reciprocity based operation, the uplink channel is estimated based on uplink reference signals such as sounding reference signal (SRS). In a time division duplexing (TDD) system, the same carrier frequency is used for both downlink and uplink. So the estimated uplink channel can be used to derive downlink precoding matrix W. However, since the downlink interference experienced at a WD is typically different from the uplink interference experienced by the gNB, it is difficult to accurately derive CQI (Channel Quality Indicator) based on uplink channel estimation. CQI may be used in LTE and NR to indicate a modulation and coding rate that can be used for data transmission, it may generally be determined by the signal to noise plus interference ratio (SINR) at a receiver and the receiver types.

To improve link adaptation in reciprocity based operation, a non-PMI feedback scheme has been adopted in NR in which the gNB transmits precoded CSI-RS to a WD. An example is shown in <FIG>, where each precoded CSI-RS port corresponds to a MIMO layer and the precoding matrix WNT×r is derived from the uplink, where r is the number of MIMO layers estimated based on the uplink channel. The WD estimates the actual rank and CQI based on the received CSI-RS and the actual interference seen by the WD and feeds back the estimated rank and CQI. For rank and CQI calculation, the WD assumes a single precoder for each rank. The precoder for rank k is a matrix formed by the first k columns of an PxP identity matrix, where P is the number of precoded CSI-RS ports and P=r in the example.

In a <NUM>rd Generation Partnership Project (3GPP) Radio Access Network (RAN) Work Group <NUM> (RAN1) meeting, non-PMI feedback was considered in which a subset of the ports in a CSI-RS resource configured for a WD may be precoded and transmitted to a WD, so the subset of the ports need to be further signaled to the WD for non-PMI feedback. For example, the WD may be configured with a <NUM>-port CSI RS resource and only <NUM> ports may be used for actual precoded CSI-RS transmission. It was considered that the signaling of port indices may be done semi-statically through radio resource control (RRC) signaling. The following was considered for NR:
"For non-PMI feedback, support the following port index indication method:.

It has been considered that in NR a WD can be configured with N'≥<NUM> CSI reporting settings, M'≥<NUM> Resource settings, and one CSI measurement setting, where the CSI measurement setting includes L' ≥<NUM> links. Each of the L' links corresponds to a CSI reporting setting and a resource setting.

At least the following configuration parameters are signaled via RRC at least for CSI acquisition:.

At least following are dynamically selected by Layer <NUM> or Layer <NUM> signaling, if applicable:.

Although it was considered that for non-PMI CSI feedback, port index indication per CSI-RS resource is configured by radio resource control (RRC) to select the CSI-RS port(s) used for RI/CQI calculation per rank, exactly how to configure the port index indication by RRC is an open problem. In addition, for the selected ports, how the precoder is applied to the ports is another open problem.

Document "<NPL>, discloses an evaluation on CSI measurement. The following proposals were made. Proposal <NUM>: For non-PMI codebook, NR supports Alt B: Port index indication is signaled to UE for RI/CQI calculation in non-PMI feedback. Proposal <NUM>: For non-PMI codebook, NR supports dynamic signaling to indicate the port selection for CQI calculation, e.g., RRC + DCI; RRC indicates M configurations of port selection, and DCI indicates which out of M to be used for the UE. Proposal <NUM>: For NZP CSI-RS based interference, NR supports the following alternative: Alt. <NUM>, a single CSI-RS resource for both channel and interference measurement.

Document "<NPL>, discloses a technique pertaining to transparent MU/SU operation. Features required in Release <NUM> to extend the transparent operation of SU and MU beyond Release <NUM>. The features are similar to those agreed in Release <NUM> for dual-stream beamforming. The following proposals were made. UE-RS and control signalling aspects: Limiting the orthogonal multiplexing of users in Release <NUM> to total composite rank of <NUM>; UE-independent and cell-specific sequence initialization for UE-RS: Similar to Release <NUM> consider limiting the possible sequence IDs to two values; Signalling of UE-RS antenna ports and UE-RS pattern in a dynamic fashion in DL control grant; One possible way of such signalling is using <NUM> bits for UE-RS offset and <NUM> bit for UE-RS pattern indication; Considering joint indication of UE-RS antenna ports and rank to reduce signalling overhead. Feedback aspects: Adopting one transmission mode common for SU and MU operation; Additional codebooks should be considered in Rel-<NUM> for the Rel-<NUM> antenna configurations and new antenna configurations: Codebooks with higher granularity for achieving transmit nulling gains, and the configurable/downloadable codebook design for various antenna configurations and propagation conditions should be considered; Common CQI/RI report for different spatial processing techniques (SU-MIMO, MU-MIMO and CoMP) that follows Release <NUM> feedback design, closed loop: CQI/RI report along with CDI, and open loop: CQI/RI based on open loop precoding; employing feedback compression and encoding that scales to different spatial processing techniques: feedback compression in the form of feeding back only the dominant-Eigen vectors of the channel, and feedback encoding based on multiple description coding (MDC) or multi-level coding (MLC) that exploits the time/frequency correlations to reduce feedback overhead can be considered.

Document "<NPL>, discloses a technique pertaining to CSI measurement. The following observations were made. Observation <NUM>: Up to <NUM> bits are required for signaling CBSR with an <NUM>-port CSI-RS resource, dynamic signaling of CBSR is clearly not feasible. Observation <NUM>: Use case for semi-static signaling of CBSR for non-PMI CSI feedback in Alt. A (port selection codebook is used for CQI calculation for non-PMI feedback) is unclear. Observation <NUM>: Up to <NUM> bits are required in Alt. B (Port index indication is signaled to UE for RI/CQI calculation in non-PMI feedback) for full flexible port index indication with an <NUM> ports CSI-RS resource, dynamic signaling is clearly not feasible. Observation <NUM>: The use case of port index indication is unclear. Supporting it would make the CSI framework complicated. Observation <NUM>: For interference measurement with NZP CSI-RS resource, up to <NUM> bits are required for dynamically signaling the ports for channel measurement in Alt. <NUM> (single CSI-RS resource for both channel and interference measurement). Observation <NUM>: For interference measurement with NZP CSI-RS in Alt. <NUM> (separately configured CSI-RS resources for channel and interference measurement), dynamic signaling of NZP CSI-RS resource can be avoided for both channel and interference measurement. Observation <NUM>: ZP CSI-RS should be configured on the same REs available for NZP CSI-RS. Observation <NUM>: A CSI-IM size of <NUM>-<NUM> REs/PRB gives sufficient interference estimation quality. The following proposals were made. Proposal <NUM>: For non-PMI CSI feedback for reciprocity operation, Alt. B with port index indication signaled via RRC is supported and the number of ports selected/indicated can be the same as the number of ports in the CSI-RS resource. Proposal <NUM>: For NZP CSI-RS based MU interference measurement, Alt. <NUM> is supported in which a set of NZP CSI-RS resources is signaled to each UE. A UE is dynamically indicated with the set of NZP CSI-RS resources, the UE selects a NZP CSI-RS resource in the resource set for RI and CQI measurement by assuming the rest of the NZP CSI-RS resource in the resource set are for interference measurement, the UE feedbacks a CRI, RI and CQI, the RI and CQI are calculated by assuming a codebook with a single entry for each rank and the entry for rank K consists of the first K columns of a RxR identity matrix, where R is the number of NZP CSI-RS ports of the NZP CSI-RS resource for channel measurement. Proposal <NUM>: ZP CSI-RS is configured with a bitmap with each bit associated with a 2x1 component REs. Proposal <NUM>: Frequency domain channel and interference measurement restriction configuration is achieved by configuring a CSI reporting band which spans only a subset of subbands in BWP. No additional mechanism is needed. Proposal <NUM>: Time domain measurement restriction for channel or interference is achieved by configuring MR either to measure channel or interference in a single slot (one shot) or an unrestricted number of slots (no restriction).

According to the present disclosure, methods, computer-readable media, a network node and a wireless device according to the independent claims are provided. Developments are set forth in the dependent claims.

Some embodiments advantageously provide port index signaling for non-precoder matrix indicator (PMI) channel state information (CSI) feedback.

Some RRC signaling methods for port index indication are proposed, which may include, for example:.

In some embodiments, for precoder determination, N selected ports may be arranged in ascending order according to port indices, a precoding matrix for rank k consisting of the first k columns for an NxN identity matrix, with the first element of each column of the identity matrix associated with the first port having the smallest port index and the last element of each column of the identity matrix associated with the last port having the largest port index.

According to one aspect, a network node configured to communicate with a wireless device, WD, is provided. The network node includes processing circuitry configured to generate at least one port indication in one of a rank-nested and a non-rank-nested manner; and a radio interface configured to signal the at least one port indication in the one of the rank-nested and the non-rank-nested manner.

In some embodiments of this aspect, the at least one port indication includes at least one port index indication. In some embodiments of this aspect, the radio interface is configured to signal the at least one port indication by being further configured to signal the at least one port indication in a channel state information, CSI, report setting configuration. In some embodiments of this aspect, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments of this aspect, in the rank-nested manner, the at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments of this aspect, in the non-rank-nested manner, the at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments of this aspect, the at least one port indication for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments of this aspect, the at least one port indication is signalled to the wireless device. In some embodiments of this aspect, the at least one port indication includes at least one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments of this aspect, the radio interface is configured to receive, from the wireless device, a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

According to another aspect, a method for a network node is provided. The method includes generating at least one port indication in one of a rank-nested and a non-rank-nested manner; and signalling the at least one port indication in the one of the rank-nested and the non-rank-nested manner.

In some embodiments of this aspect, the at least one port indication includes at least one port index indication. In some embodiments of this aspect, the signalling the at least one port indication further comprises signalling the at least one port indication in a channel state information, CSI, report setting configuration. In some embodiments of this aspect, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments of this aspect, in the rank-nested manner, the at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments of this aspect, in the non-rank-nested manner, the at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments of this aspect, the at least one port indication for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments of this aspect, the signalling the at least one port indication further comprises signalling the at least one port indication to the wireless device. In some embodiments of this aspect, the at least one port indication includes at least one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments of this aspect, the method further includes receiving, from the wireless device, a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

According to yet another aspect, a wireless device, WD, configured to communicate with a network node is provided. The WD includes a radio interface configured to receive at least one port indication from a network node, the at least one port indication being received in one of a rank-nested and a non-rank-nested manner; and processing circuitry configured to generate channel state information, CSI, feedback based on the at least one port indication.

In some embodiments of this aspect, the at least one port indication includes at least one port index indication. In some embodiments of this aspect, the at least one port indication is included in a channel state information, CSI, report setting configuration. In some embodiments of this aspect, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments of this aspect, in the rank-nested manner, the received at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments of this aspect, in the non-rank-nested manner, the received at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments of this aspect, the at least one port indication includes a plurality of portion indications and one of the plurality of port indications for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments of this aspect, the at least one port indication includes a plurality of portion indications and each one of the plurality of port indications includes one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments of this aspect, the generated CSI-RS feedback comprises a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

According to another aspect, a method for a wireless device, WD, is provided. The method includes receiving at least one port indication from a network node, the at least one port indication being received in one of a rank-nested and a non-rank-nested manner; and generating channel state information, CSI, feedback based on the at least one port indication.

In some embodiments of this aspect, the at least one port indication includes at least one port index indication. In some embodiments of this aspect, the receiving the at least one port indication further comprises receiving the at least one port indication in a channel state information, CSI, report setting configuration. In some embodiments of this aspect, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments of this aspect, in the rank-nested manner, the received at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments of this aspect, in the non-rank-nested manner, the received at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments of this aspect, the at least one port indication includes a plurality of portion indications and one of the plurality of port indications for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments of this aspect, the at least one port indication includes a plurality of portion indications and each one of the plurality of port indications includes one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments of this aspect, the generating the CSI-RS feedback comprises generating a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

Before describing in detail exemplary embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to port index signaling for non-precoder matrix indicator (PMI) channel state information (CSI) feedback. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

In some embodiments described herein, the term "coupled," "connected," and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and/or a wireless connections.

The term "network node" used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell/multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term "radio node" used herein may be used to also denote a wireless device (WD) such as a wireless device (WD) or a radio network node.

Also in some embodiments the generic term "radio network node" is used. It can be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).

Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE, may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system.

Embodiments provide methods, wireless devices and network nodes for port index signaling for non-precoder matrix indicator (PMI) channel state information (CSI) feedback. The signaling includes a bitmap based approach in which each bit is associated with a different port in the CSI-RS resource of a WD. A port is selected by selecting its associated bit. Alternatively, the signaling includes a starting port index and a number of ports. Alternatively, the port index may be restricted to be in the same CDM group. Thus, embodiments provide alternatives for configuring the port index by RRC.

Returning to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in <FIG> a schematic diagram of a communication system, according to an embodiment, including a communication system <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a radio access network, and a core network <NUM>. The access network <NUM> comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes <NUM>), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas <NUM>). Each network node 16a, 16b, 16c is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first wireless device (WD) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16c. A second WD 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16a. While a plurality of WDs 22a, 22b (collectively referred to as wireless devices <NUM>) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole WD <NUM> is in the coverage area or where a sole WD <NUM> is connecting to the corresponding network node <NUM>. Note that although only two WDs <NUM> and three network nodes <NUM> are shown for convenience, the communication system may include many more WDs <NUM> and network nodes <NUM>.

The OTT connection may be transparent in the sense that the participating communication devices through which the OTT connection passes are unaware of routing of uplink and downlink communications.

A network node <NUM> is configured to include a port indication generator <NUM>, which is configured to generate at least one port indication in one of a rank nested and a non-rank nested manner; and signal the at least one port indication in the one of the rank nested and the non-rank nested manner. In an alternative embodiment, the network node <NUM> is configured to include the port indication generator <NUM>, which may be configured to receive signalling indicating at least one desired port for channel state information, CSI feedback, the at least one desired port associated with a rank; and generate at least one port indication based at least in part on the received signaling.

A wireless device <NUM> is configured to include a CSI feedback generator <NUM>, which is configured to receive at least one port indication from a network node, the at least one port indication being signalled in one of a rank nested and a non-rank nested manner; and generate channel state information, CSI, feedback based on the at least one port indication. In an alternative embodiment, the wireless device <NUM> includes a CSI feedback generator <NUM>, which is configured to determine a signal-to-interference-plus-noise ratio, SINR, of at least one hypothesized serving port; and signal an indication of at least one desired port for channel state information, CSI feedback based at least in part on the determined SINR, the at least one desired port associated with a rank calculation.

In particular, in addition to a traditional processor and memory, the processing circuitry <NUM> may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions.

Thus, the host computer <NUM> may further comprise software (SW) <NUM>, which is stored in, for example, memory <NUM> at the host computer <NUM>, or stored in external memory (e.g., database) accessible by the host computer <NUM>. The host application <NUM> may be operable to provide a service to a remote user, such as a WD <NUM> connecting via an OTT connection <NUM> terminating at the WD <NUM> and the host computer <NUM>. In one embodiment, the host computer <NUM> may be configured for providing control and functionality to a service provider and may be operated by the service provider or on behalf of the service provider. The processing circuitry <NUM> of the host computer <NUM> may be configured to enable the service provider to observe functionality of and process data from the network node <NUM> and/or the wireless device <NUM>.

The communication system <NUM> further includes a network node <NUM> provided in a telecommunication system <NUM> and comprising hardware <NUM> enabling it to communicate with the host computer <NUM> and with the WD <NUM>. The connection <NUM> may be direct or it may pass through a core network <NUM> of the telecommunication system <NUM> and/or through one or more intermediate networks <NUM> outside the telecommunication system <NUM>.

In particular, in addition to a traditional processor and memory, the processing circuitry <NUM> may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions.

Thus, the network node <NUM> further has software <NUM> stored internally in, for example, memory <NUM> or stored in external memory (e.g., database) accessible by the network node <NUM> via an external connection. The processing circuitry <NUM> may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by network node <NUM>. Processor <NUM> corresponds to one or more processors <NUM> for performing network node <NUM> functions described herein. The memory <NUM> is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software <NUM> may include instructions that, when executed by the processor <NUM> and/or processing circuitry <NUM>, causes the processor <NUM> and/or processing circuitry <NUM> to perform the processes described herein with respect to network node <NUM>. For example, processing circuitry <NUM> of the network node <NUM> may include a port indication generator <NUM> to generate a port index indication. The port indication generator <NUM> may be configured to generate at least one port indication in one of a rank nested and a non-rank nested manner. The radio interface <NUM> may be configured to signal the at least one port indication in the one of the rank nested and the non-rank nested manner.

In some embodiments, the at least one port indication includes at least one port index indication. In some embodiments, the radio interface <NUM> is configured to signal the at least one port indication by being further configured to signal the at least one port indication in a channel state information, CSI, report setting configuration. In some embodiments, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments, in the rank-nested manner, the at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments, in the non-rank-nested manner, the at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments, the at least one port indication for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments, the at least one port indication is signalled to the wireless device. In some embodiments, the at least one port indication includes at least one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments, the radio interface <NUM> is configured to receive, from the wireless device, a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

In an alternative embodiment, the network node <NUM> may include a port indication generator <NUM>, which is configured to, such as via radio interface <NUM>, receive signalling indicating at least one desired port for channel state information, CSI feedback, the at least one desired port associated with a rank; and generate, such as via processing circuitry <NUM>, at least one port indication based at least in part on the received signaling.

In some embodiments, the at least one port indication includes at least one port index indication. In some embodiments, the signalling indicating the at least one desired port corresponds to a table. In some embodiments, the signalling indicating the at least one desired port is in the CSI feedback.

In particular, in addition to a traditional processor and memory, the processing circuitry <NUM> may comprise integrated circuitry for processing and/or control, e.g., one or more processors and/or processor cores and/or FPGAs (Field Programmable Gate Array) and/or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions.

Thus, the WD <NUM> further comprises software <NUM>, which is stored in, for example, memory <NUM> at the WD <NUM>, or stored in external memory (e.g., database) accessible by the WD <NUM>.

Processing circuitry <NUM> may be configured to control any of the methods and/or processes described herein and/or to cause such methods, and/or processes to be performed, e.g., by WD <NUM>. Processor <NUM> corresponds to one or more processors <NUM> for performing WD <NUM> functions described herein. The WD <NUM> includes memory <NUM> that is configured to store data, programmatic software code and/or other information described herein. In some embodiments, the software <NUM> and/or the client application <NUM> may include instructions that, when executed by the processor <NUM> and/or processing circuitry <NUM>, causes the processor <NUM> and/or processing circuitry <NUM> to perform the processes described herein with respect to WD <NUM>. For example, the processing circuitry <NUM> of the wireless device <NUM> may be configured to implement a CSI feedback generator <NUM> to generate CSI feedback based on ports indicated by the port index indication. The CSI feedback generator <NUM> may be configured to receive, such as via radio interface <NUM>, at least one port indication from a network node <NUM>, the at least one port indication being received in one of a rank nested and a non-rank nested manner. The CSI feedback generator <NUM> may be configured to generate channel state information, CSI, feedback based on the at least one port indication.

In some embodiments, the at least one port indication includes at least one port index indication. In some embodiments, the at least one port indication is included in a channel state information, CSI, report setting configuration. In some embodiments, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments, In some embodiments, in the rank-nested manner, the received at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments, in the non-rank-nested manner, the received at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments, the at least one port indication includes a plurality of portion indications and one of the plurality of port indications for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments, the at least one port indication includes a plurality of portion indications and each one of the plurality of port indications includes one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments, the generated CSI feedback comprises a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

In an alternative embodiment, the WD <NUM> includes a CSI feedback generator <NUM> configured to determine a signal-to-interference-plus-noise ratio, SINR, of at least one hypothesized serving port; and configured to signal, such as a radio interface <NUM>, an indication of at least one desired port for channel state information, CSI feedback based at least in part on the determined SINR, the at least one desired port associated with a rank calculation.

In some embodiments, the at least one port indication includes at least one port index indication. In some embodiments, the indication of the at least one desired port corresponds to a table. In some embodiments, the indication of at least one desired port is in the CSI feedback.

In certain embodiments, measurements may involve proprietary WD <NUM> signaling facilitating the host computer's <NUM> measurements of throughput, propagation times, latency and the like.

<FIG> is a block diagram of an alternative host computer <NUM>, which may be implemented at least in part by software modules containing software executable by a processor to perform the functions described herein. The host computer <NUM> include a communication interface module <NUM> configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system <NUM>. The memory module <NUM> is configured to store data, programmatic software code and/or other information described herein.

<FIG> is a block diagram of an alternative network node <NUM>, which may be implemented at least in part by software modules containing software executable by a processor to perform the functions described herein. The network node <NUM> includes a radio interface module <NUM> configured for setting up and maintaining at least a wireless connection <NUM> with a WD <NUM> located in a coverage area <NUM> served by the network node <NUM>. The network node <NUM> also includes a communication interface module <NUM> configured for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system <NUM>. The communication interface module <NUM> may also be configured to facilitate a connection <NUM> to the host computer <NUM>. The memory module <NUM> that is configured to store data, programmatic software code and/or other information described herein. The port indication generation module <NUM> is configured to generate a port index indication.

<FIG> is a block diagram of an alternative wireless device <NUM>, which may be implemented at least in part by software modules containing software executable by a processor to perform the functions described herein. The WD <NUM> includes a radio interface module <NUM> configured to set up and maintain a wireless connection <NUM> with a network node <NUM> serving a coverage area <NUM> in which the WD <NUM> is currently located. The memory module <NUM> is configured to store data, programmatic software code and/or other information described herein. The CSI feedback generator module <NUM> is configured to generate CSI-RS feedback based on ports indicated by the port index indication.

<FIG> is a flowchart illustrating an exemplary method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG>. In a first step of the method, the host computer <NUM> provides user data (block S100). In an optional substep of the first step, the host computer <NUM> provides the user data by executing a host application, such as, for example, the host application <NUM> (block S102). In a second step, the host computer <NUM> initiates a transmission carrying the user data to the WD <NUM> (block S104). In an optional third step, the network node <NUM> transmits to the WD <NUM> the user data which was carried in the transmission that the host computer <NUM> initiated, in accordance with the teachings of the embodiments described throughout this disclosure (block S106). In an optional fourth step, the WD <NUM> executes a client application, such as, for example, the client application <NUM>, associated with the host application <NUM> executed by the host computer <NUM> (block S108).

<FIG> is a flowchart illustrating an exemplary method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG>. In a first step of the method, the host computer <NUM> provides user data (block S110). In an optional substep (not shown) the host computer <NUM> provides the user data by executing a host application, such as, for example, the host application <NUM>. In a second step, the host computer <NUM> initiates a transmission carrying the user data to the WD <NUM> (block S112). In an optional third step, the WD <NUM> receives the user data carried in the transmission (block S114).

<FIG> is a flowchart illustrating an exemplary method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG> and <FIG>. In an optional first step of the method, the WD <NUM> receives input data provided by the host computer <NUM> (block S116). Additionally or alternatively, in an optional second step, the WD <NUM> provides user data (block S120). In an optional substep of the second step, the WD provides the user data by executing a client application, such as, for example, client application <NUM> (block S118). In a further optional substep of the first step, the WD <NUM> executes the client application <NUM>, which provides the user data in reaction to the received input data provided by the host computer <NUM> (block S122). In providing the user data, the executed client application <NUM> may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the WD <NUM> may initiate, in an optional third substep, transmission of the user data to the host computer <NUM> (block S124). In a fourth step of the method, the host computer <NUM> receives the user data transmitted from the WD <NUM>, in accordance with the teachings of the embodiments described throughout this disclosure (block S126).

<FIG> is a flowchart illustrating an exemplary method implemented in a communication system, such as, for example, the communication system of <FIG>, in accordance with one embodiment. The communication system may include a host computer <NUM>, a network node <NUM> and a WD <NUM>, which may be those described with reference to <FIG> and <FIG>. In an optional first step of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the network node <NUM> receives user data from the WD <NUM> (block S128). In an optional second step, the network node <NUM> initiates transmission of the received user data to the host computer <NUM> (block S130). In a third step, the host computer <NUM> receives the user data carried in the transmission initiated by the network node <NUM> (block S132).

<FIG> is a flowchart of an exemplary process in a network node <NUM> for generating and signaling a port index indication according to some embodiments of the present disclosure. One or more blocks and/or functions and/or methods performed by the network node <NUM> may be performed by one or more elements of network node <NUM> such as by port indication generator <NUM> in processing circuitry <NUM>, processor <NUM>, radio interface <NUM>, etc. According to the example method, which includes generating (block S134) at least one port indication in one of a rank nested and a non-rank nested manner; and signalling (block S136) the at least one port indication in the one of the rank nested and the non-rank nested manner.

In some embodiments, the at least one port indication includes at least one port index indication. In some embodiments, the signalling the at least one port indication further comprises signalling, such as via radio interface <NUM>, the at least one port indication in a channel state information, CSI, report setting configuration. In some embodiments, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments, in the rank-nested manner, the at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments, in the non-rank-nested manner, the at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments, the at least one port indication for rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments, the signalling the at least one port indication further comprises signalling, such as via radio interface <NUM>, the at least one port indication to the wireless device. In some embodiments, the at least one port indication includes at least one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments, the method further includes receiving, from the wireless device <NUM>, a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

Alternatively, or in addition, the process includes generating, via the port indication generator <NUM>, a port index indication. The process also includes signaling, via the radio interface <NUM>, the port index indication to a wireless device. The signaling may be one of the following: a bitmap in which each bit is associated with one port in a channel state information-reference signal, CSI-RS, resource and a port is selected based on a value of the bit associated with the port, signaling a starting port index and number of ports in which only adjacent ports in a CSI-RS resource are selected, and restricting port indices to be in a same code division multiplex, CDM, group.

<FIG> is a flowchart of an exemplary process in a wireless device <NUM> for receiving and processing a port index indication according to some embodiments of the present disclosure. One or more blocks and/or functions and/or methods performed by WD <NUM> may be performed by one or more elements of WD <NUM> such as by CSI feedback generator <NUM> in processing circuitry <NUM>, processor <NUM>, radio interface <NUM>, etc., which example method includes receiving (block S138), such as via radio interface <NUM>, at least one port indication from a network node <NUM>, the at least one port indication being received in one of a rank nested and a non-rank nested manner. The process includes generating (block S140), such as via the CSI feedback generator <NUM>, channel state information, CSI, feedback based on the at least one port indication.

In some embodiments, the at least one port indication includes at least one port index indication. In some embodiments, the receiving the at least one port indication further comprises receiving, such as via radio interface <NUM>, the at least one port indication in a channel state information, CSI, report setting configuration. In some embodiments, the at least one port indication indicates which ports in at least one channel state information reference signal, CSI-RS, resource to use for measuring channel quality for a rank assumption for a non-precoder matrix indicator, non-PMI, CSI feedback, the non-PMI CSI feedback being a CSI feedback without a precoder matrix indicator. In some embodiments, in the rank-nested manner, the received at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k (k=<NUM>,<NUM>,. ,<NUM>) port indices in the list indicates one or more ports for a rank k CSI measurement. In some embodiments, in the non-rank-nested manner, the received at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank. In some embodiments, the at least one port indication includes a plurality of portion indications and one of the plurality of port indications rank k (k=<NUM>,<NUM>,. ,<NUM>) includes k port indices for a rank k CSI measurement. In some embodiments, the at least one port indication includes a plurality of portion indications and each one of the plurality of port indications includes one port index indication, the at least one port index indication indicating port indices in at least one channel state information reference signal, CSI-RS, resource. In some embodiments, the generating the CSI feedback comprises generating, such as via the processing circuitry <NUM>, a non-precoder matrix indicator, non-PMI, channel state information, CSI, feedback, the non-PMI CSI feedback including a rank indicator, RI, and at least one channel quality indicator, CQI.

Alternatively, or in addition, the process includes receiving, via the radio interface <NUM>, a port index indication from a network node <NUM>. The signaling may be one of the following: a bitmap in which each bit is associated with one port in a channel state information-reference signal, CSI-RS, resource and a port is selected based on a value of the bit associated with the port, signaling a starting port index and number of ports in which only adjacent ports in a CSI-RS resource are selected, and restricting port indices to be in a same code division multiplex, CDM, group. The process also includes generating, via the CSI feedback generator <NUM>, CSI-RS feedback based on ports indicated by the port index indication.

<FIG> is a flowchart of an yet another exemplary process in a network node <NUM> for generating a port index indication based on signaling received from a wireless device according to some embodiments of the present disclosure. One or more blocks and/or functions and/or methods performed by the network node <NUM> may be performed by one or more elements of network node <NUM> such as by port indication generator <NUM> in processing circuitry <NUM>, processor <NUM>, radio interface <NUM>, etc. according to yet another example method, which includes receiving (block S142), such as via radio interface <NUM>, signalling indicating at least one desired port for channel state information, CSI, the at least one desired port associated with a rank; and generating (block S <NUM>), such as via port indication generator <NUM>, at least one port indication based at least in part on the received signaling.

Alternatively, or in addition, the process includes receiving, via the radio interface <NUM>, signaling from a WD <NUM>, the signaling indicating M desired ports for CSI-RS feedback. The process also includes generating, via the port indication generator <NUM>, a port index indication based on the received signaling.

<FIG> is a flowchart of yet another exemplary process in a wireless device <NUM> for signaling an indication of desired ports according to some embodiments of the present disclosure. One or more blocks and/or functions and/or methods performed by WD <NUM> may be performed by one or more elements of WD <NUM> such as by CSI feedback generator <NUM> in processing circuitry <NUM>, processor <NUM>, radio interface <NUM>, etc., which example method includes determining (block S146), such as via CSI feedback generator <NUM>, a signal-to-interference-plus-noise ratio, SINR, of at least one hypothesized serving port; and signalling (block S <NUM>), such as via radio interface <NUM>, an indication of at least one desired port for channel state information, CSI feedback based at least in part on the determined SINR, the at least one desired port associated with a rank calculation.

In some embodiments, the indication of the at least one desired port corresponds to a table. In some embodiments, the indication of at least one desired port is in the CSI feedback.

Alternatively, or in addition, the process includes determining, via the processing circuitry <NUM>, an SINR of different hypothesized serving ports. The process also includes signaling, via the radio interface <NUM>, to a network node <NUM> an indication of M desired ports for CSI-RS feedback based on the determined SINR.

Having generally described example embodiments for a method that can be used to select any port combinations in a CSI-RS resource for the flexible allocation ports in a CSI-RS resource, the following provides more detailed explanations, examples and embodiments.

For a CSI-RS resource of P ports with port index pi, (i=<NUM>,<NUM>,. ,P-<NUM>), a WD <NUM> with M receive antennas ports can be configured to perform non-PMI CSI feedback based on the CSI-RS resource. More generally, M can be the maximum number of layers the WD <NUM> is able to report, or alternatively the number of layers the WD <NUM> is capable of receiving rather than the number of receive antennas ports. In some embodiments, general steps may include one or more of the following:
Step <NUM>: The WD <NUM> is signaled with one or more CSI-RS resources or resource sets and a port index indication is also signaled to the WD <NUM> for each CSI-RS resource or resource set. Alternatively, the port index indication is included in a CSI report setting configuration and signaled to the WD <NUM>. The port index indication provides information on which ports in the CSI-RS resource should be used for rank and CQI calculation for non-PMI CSI feedback. The signaling may be RRC signaling.

Step <NUM>: The network node <NUM> sends a request to the WD <NUM> for non-PMI CSI feedback based on a CSI-RS resource and an associated port index indication.

Step <NUM>: The WD <NUM> measures CSI over the selected ports in the CSI-RS resource according to the port index indication. For the given selected ports, the WD <NUM> may assume a precoder or precoding matrix for each rank and CSI estimation. The network node <NUM> should know the precoder per rank used by the WD <NUM>. For this purpose, an implicit rule may be defined.

Step <NUM>: The WD <NUM> reports to the network node <NUM> a rank indicator (RI) and one or two CQIs depending on the value of the RI. For example, if RI <=<NUM>, one CQI is reported and if RI><NUM>, <NUM> CQIs are reported.

Step <NUM>: The network node <NUM> can schedule and transmit data to the WD <NUM> with the reported rank RI and CQI(s) and with the precoding matrix used by the WD <NUM> in deriving the RI and CQI(s) over the selected ports. Let the selected N ports be denoted by {ps<NUM>,ps<NUM>,. ,ps(N-<NUM>)} where s<NUM> < s<NUM> < ··· < sN-<NUM> and si ∈ (<NUM>,<NUM>,. , P - <NUM>), i ∈ (<NUM>,<NUM>,. , N - <NUM>). If the reported RI=k, the precoding matrix used by the network node <NUM> is then <MAT>, where <MAT> is a length-N column-vector with its l-th element set to <NUM> for l = m (l ∈ (<NUM>,<NUM>,. , N - <NUM>)), and <NUM> otherwise. The l-th element of <MAT> is associated with port psl. For rank k transmission, ports {ps<NUM>, ps<NUM>,. , psk-<NUM>} are used.

Some example embodiments for this disclosure are discussed below.

Embodiment 1A: A bitmap-based RRC configuration for port index indication is used in the implementation of step <NUM>. In this embodiment, a bitmap is used to indicate N ∈ (<NUM>,<NUM>, min(<NUM>, P)) ports in the CSI-RS resource to be used for non-PMI CSI feedback. The bit map is given by <MAT>.

Each bit in the bit map is associated with a port in the CSI-RS resource. For example, ai (i = <NUM>,<NUM>,<NUM>,. , P - <NUM>) is associated with port pi. Port pi is selected if ai = <NUM> and is not selected if ai = <NUM>. When indicating N ports in the CSI-RS resource to be selected for non-PMI CSI feedback, there will be N bits in the bitmap that are set to <NUM>. Let p̃<NUM>, p̃<NUM>,. , p̃N-<NUM> be the N selected ports.

In this embodiment, rank-nested property is assumed by the network node and the WD so that port p̃<NUM> is assumed for rank-<NUM> hypothesis, ports p̃<NUM>, p̃<NUM> are assumed for rank-<NUM> hypothesis, and so forth. That is, for a rank-R hypothesis, the WD <NUM> assumes that ports p̃<NUM>, p̃<NUM>,. , p̃R-<NUM> shall be used for deriving CSI. Similarly, when rank R is reported by the WD to the network node, ports p̃<NUM>, p̃<NUM>,. , p̃R-<NUM> will be used by the network node to send data to the WD. By utilizing the rank-nested property, RRC signaling overhead can be saved as only a single bitmap indicating the ports to be used for the maximum rank needs to be signaled, while the ports to be used for lower ranks may be implicitly derived.

Since the maximum number of layers the WD <NUM> can receive is M, if M<=<NUM> <=P, then at most M ports correspond to desired layers, while N-M ports correspond to interference. Similarly, when the hypothesized rank R is less than M, N-R layers are interference. It is desirable in this case to identify which layers are desired and which are interference. In one embodiment, the first R ports p̃<NUM>, p̃<NUM>,. , p̃R-<NUM> are desired layers, while the remaining N-R ports p̃R, p̃R+<NUM>,. , p̃N are interference. In some embodiments the remaining N-R ports p̃R, p̃R+<NUM>,. , p̃N are identified as being comprised within an interference measurement resource.

If the CSI resource containing the N ports is shared by multiple WDs <NUM>, it may be desirable to allow different WDs <NUM> to have different desired and interfering ports, since the ports cannot always be reordered in the CSI resource without affecting all WDs <NUM>. Therefore, in an embodiment, a second bitmap of length N is indicated that identifies the M desired ports carrying desired layers out of the N selected ports.

There are M non-zero bits out of the N bits in the bitmap, and the first non-zero bit in the bitmap corresponds to the first desired layer, while the second non-zero bit corresponds to the desired layer, and so on.

Since the WD <NUM> is generally able to determine the signal to interference plus noise ratio (SINR) of different hypothesized serving ports better than the gNB, it may be desirable for the WD <NUM> to determine which of the N ports should correspond to the M desired ports. In one such embodiment, the WD <NUM> is configured with N ports using the bitmap {a<NUM>, a<NUM>,. , aP-<NUM>} and the WD <NUM> later feeds back the bitmap {a'<NUM>, a'<NUM>,. , a'N-<NUM>} to indicate to the gNB which layers should be used for the desired layers. In an alternative embodiment, the WD <NUM> indicates the M desired ports via a table containing all combinations of M out of N ports. In this alternative embodiment, the WD <NUM> feeds back an index to an entry in the table where each entry corresponds to one combination of M out of N ports. In other embodiments, the M desired ports are selected consecutively from N ports, where a starting index <NUM> ≤ I < N indicates the first of the M antenna ports, and the M antenna ports may 'wrap around' in the list of N selected antenna ports. This may be expressed as further selecting the antenna ports p̃I, p̃(I+<NUM>)%N,. , p̃(I+M-<NUM>)%N from the list of N antenna ports, where x%y denotes the remainder of x divided by y.

In some embodiments, this indication of M desired ports out of the N port subset of the CSI-RS resource is carried by a CSI-RS resource indicator ('CRI') field in CSI feedback.

Embodiment 1B: Independent bitmap based RRC configuration for port indication: In another embodiment implementing Step <NUM>, the rank-nested property is not utilized and separate bitmaps are used to indicate the port subset selection for each rank hypothesis. For instance, a first bitmap <MAT> is used to indicate which port the WD <NUM> shall use for CQI calculation for rank-<NUM> hypothesis (containing one non-zero bit) and a second bitmap <MAT> is used to indicate which two ports are used for CQI calculation for rank-<NUM> hypothesis (containing two non-zero bits), and so forth. In this embodiment, multiple bitmaps, one for each rank, are signaled to the WD <NUM>. This approach allows more flexibility in what precoding can be applied by the gNB. One motivation for introducing such a flexibility is that the precoders for different rank hypotheses may not be rank-nested, especially if some form of null-forming is applied. This is actually the case for minimum mean square error (MMSE), zero forcing (ZF) and minimum signal to linkage and interference ratio (SLNR) precoders. That is, the precoder for rank-<NUM> transmission is not equal to the first column of the precoder for rank-<NUM> transmission. Hence the corresponding CSI-RS ports cannot be shared between rank hypotheses.

Embodiment 2A: port index indication includes a starting port index in the CSI-RS resource and a number of ports. In this embodiment, the port index indication comprises.

The selected ports are {ps, ps+<NUM>,. , p(s+N-<NUM>)mod(P)}, i.e., N consecutive ports starting from ps.

Note that N may not be explicitly indicated in the port index indication signaling, but may be implicitly derived by the WD <NUM> elsewhere, such as from a reported WD <NUM> capability and/or determined from another RRC parameter. Again, in this embodiment, rank-nested property is assumed by the network node and the WD such that port p̃<NUM> is assumed for rank-<NUM> hypothesis, ports p̃<NUM>, p̃<NUM> are assumed for rank-<NUM> hypothesis, and so forth.

Embodiment 2B: Port index indication for non-rank nested precoding includes starting port index in the CSI-RS resource and a number of ports. By using independent bitmaps for each rank as was done in Embodiment 1A, full flexibility in supporting both rank-nest and non-rank-nested precoding is achieved, as well as a mix thereof. That is, some ports may be shared across rank hypotheses while others are not. In this embodiment, multiple port index indications, one for each rank, are signaled to the WD. If only completely non-overlapping port allocations across ranks needs to be supported, such flexibility may not be needed. Thus, in an embodiment, a starting port index ps, s ∈ (<NUM>,<NUM>,. , P - <NUM>) and a maximum rank R is indicated. According to a predefined rule, the port used for CQI calculation for rank-<NUM> hypothesis is ps, the ports used for rank-<NUM> hypothesis is ps + <NUM>, ps + <NUM>, the ports used for rank-<NUM> hypothesis is ps + <NUM>, ps + <NUM>, ps + <NUM>, and so forth, so that ports for the different rank hypotheses are allocated subsequently in a non-overlapping fashion.

Embodiment 3A: port index restriction within same CDM group(s): In NR, Code Division Multiplexing (CDM) is used to multiplex a group of CSI-RS ports. For example, ports {<NUM>,<NUM>,<NUM>,<NUM>} in a CSI-RS resource may be grouped together to share <NUM> resource elements (REs), i.e. each CSI-RS signal is transmitted in the same <NUM> REs, and different length-<NUM> orthogonal codes (OCCs) are applied to CSI-RS signals from the <NUM> ports so that the signals from <NUM> ports can still be separated at the WD <NUM>. The benefit is that due to CDM processing gain, better signal to noise ratio (SNR) for each of the CSI-RS signal can be achieved at the WD <NUM>. In the example shown in <FIG>, a CSI-RS resource for <NUM> ports with CDM <NUM> is illustrated. It can be seen that the ports in the CSI-RS resource are grouped into <NUM> groups. If ports in different CDM groups are selected, for example, ports {<NUM>, <NUM>, <NUM>,<NUM>} are selected, then the WD <NUM> needs to process signals received on all <NUM> REs in order to obtain signals for the selected ports {<NUM>, <NUM>, <NUM>,<NUM>}.

By restricting port selection such that the ports in the same CDM group(s) are selected, the WD <NUM> needs to process received signals only in the same CDM group. For example, if ports {<NUM>,<NUM>,<NUM>,<NUM>} are selected, the WD <NUM> needs only to process signals received on <NUM> REs of CD4 group <NUM> in <FIG>. This can be done by restricting the value of s based on the value of N in embodiment <NUM>. For example, for N = <NUM>, s = <NUM>, <MAT>, i.e. s is restricted to even numbers. For N ∈ (<NUM>,<NUM>), s = <NUM>, <MAT> and for N ∈ (<NUM>,<NUM>,<NUM>,<NUM>), s = <NUM>k ( <MAT>). For embodiment <NUM>, the seleted ports can be restricted to {as, as+<NUM>,. , as+N-<NUM>}.

Embodiment 3B: port index restriction within same OFDM symbol: In another embodiment, port selection is restricted to be within the same OFDM symbol. By restricting the port selection to be within the same OFDM symbol, the WD <NUM> can process the signals from the N selected ports within one OFDM symbol and start CQI calculation right away. If the N selected ports are spread between multiple OFDM symbols, then the WD <NUM> has to wait until the multiple OFDM symbols are received before starting CQI calculation. Hence, this embodiment has the advantage that the WD <NUM> can calculate CQI faster compared to the case where the N selected ports are spread between multiple OFDM symbols. Note that one way of achieving this embodiment is by configuring P ports to be within one OFDM symbol which is possible when the CSI-RS resource contains P=<NUM>,<NUM>, <NUM>, or <NUM> ports (see Table <NUM>).

Embodiment 4A: precoder determination for selected ports: In this embodiment, let the selected N ports be denoted by {ps<NUM>, ps<NUM>,. , ps(N-<NUM>)} where s<NUM> < s<NUM> < ··· < sN-<NUM> and si ∈ (<NUM>,<NUM>,. , P - <NUM>), i ∈ (<NUM>,<NUM>,. , N - <NUM>). In this embodiment, for rank k ∈(<NUM>,<NUM>,. , N), the WD <NUM> should assume a precoding matrix of Wk = <MAT> over the N ports for calculating CQI, where <MAT> is a length-N column-vector with its l-th element set to <NUM> for l = m (l ∈ (<NUM>,<NUM>,. , N - <NUM>)), and <NUM> otherwise. The l-th element of <MAT> is associated with port psl. So with port index indication with a single bitmap as discussed in Embodiment 1A, for rank <NUM> transmission, port ps<NUM> is used and generally for rank k transmission, ports {ps<NUM>, ps<NUM>,. , psk-<NUM>} are used.

Embodiment <NUM>: Port index indication for multiple CSI-RS resources: When more than one CSI-RS resources are configured for a WD <NUM> for non-PMI feedback purposes, a separate port index indication can be configured for each CSI-RS resource. The CSI-RS resource can be dynamically indicated to the WD <NUM>. Thus, some methods described herein may be used to select any port combinations for a given CSI-RS resource, and some methods described herein allow for simpler WD <NUM> implementation.

Accordingly, all embodiments can be combined in any way and/or combination within the scope of the appended claims.

Claim 1:
A method for a network node (<NUM>), the method comprising:
generating (S134) at least one port indication in one of a rank-nested and a non-rank-nested manner; and
signalling (S136) the at least one port indication in the one of the rank-nested and the non-rank-nested manner,
wherein in the rank-nested manner, the at least one port indication includes a list of port indices in which a first port index in the list indicates a port for a rank <NUM> channel state information, CSI, measurement, first two port indices in the list indicates ports for a rank <NUM> CSI measurement, one or more first k, k=<NUM>,<NUM>,...,<NUM>, port indices in the list indicates one or more ports for a rank k CSI measurement, and
wherein in the non-rank-nested manner, the at least one port indication includes a plurality of port indications, each one of the plurality of port indications for each associated rank.