WO2019071383A1

WO2019071383A1 - Methods and apparatuses for frequency domain omission of subband channel state information report

Info

Publication number: WO2019071383A1
Application number: PCT/CN2017/105375
Authority: WO
Inventors: Fred VOOK; Xiaomao Mao; Bill HILLERY; Mihai Enescu; Hao Liu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2017-10-09
Filing date: 2017-10-09
Publication date: 2019-04-18
Also published as: CN111201722B; CN111201722A

Abstract

Systems, methods, apparatuses, and computer program products for frequency domain omission of subband channel state information (CSI) reporting are provided. One method includes creating or building a type II CSI report by applying one or more frequency omission rules. The frequency omission rules may be based on at least one of frequency selectivity, CQI and CQI variation, or spatial correlation across subbands.

Description

METHODS AND APPARATUSES FOR FREQUENCY DOMAIN OMISSION OF SUBBAND CHANNEL STATE INFORMATION REPORT

BACKGROUND： Field：

Embodiments of the invention generally relate to wireless or cellular communications networks， such as， but not limited to， the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) ， Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN) ， LTE-Advanced (LTE-A) ， LTE-APro， and/or 5G radio access technology or new radio (NR) access technology. Some embodiments may generally relate， for example， to channel state information (CSI) reporting in such networks.

Description of the Related Art：

Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN) refers to a communications network including base stations， or Node Bs， and for example radio network controllers (RNC) . UTRAN allows for connectivity between the user equipment (UE) and the core network. The RNC provides control functionalities for one or more Node Bs. The RNC and its corresponding Node Bs are called the Radio Network Subsystem (RNS) . In case of E-UTRAN (Evolved-UTRAN) ， the air interface design， protocol architecture and multiple-access principles are new compared to that of UTRAN， and no RNC exists and radio access functionality is provided by an evolved Node B (eNodeB or eNB) or many eNBs. Multiple eNBs are involved for a single UE connection， for example， in case of Coordinated Multipoint Transmission (CoMP) and in dual connectivity (DC) .

Long Term Evolution (LTE) or E-UTRAN improved efficiency and services， offers lower costs， and provides new spectrum opportunities， compared to the earlier generations. In particular， LTE is a 3GPP standard that provides for uplink peak rates of at least， for example， 75 megabits per second (Mbps) per carrier and downlink peak rates of at least， for example， 300 Mbps per carrier. LTE supports scalable carrier bandwidths from 20 MHz down to 1.4 MHz and supports both Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD) . Carrier aggregation or said dual connectivity further allows operating on multiple component carriers at the same time hence multiplying the performance such as data rates per user.

As mentioned above， LTE may also improve spectral efficiency in networks， allowing carriers to provide more data and voice services over a given bandwidth. Therefore， LTE is designed to fulfill the needs for high-speed data and media transport in addition to high capacity voice support. Advantages of LTE include， for example， high throughput， low latency， FDD and TDD support in the same platform， an improved end-user experience， and a simple architecture resulting in low operating costs.

Certain further releases of 3GPP LTE (e.g.， LTE Rel-10， LTE Rel-11) are targeted towards international mobile telecommunications advanced (IMT-A) systems， referred to herein for convenience simply as LTE-Advanced (LTE-A) .

LTE-Ais directed toward extending and optimizing the 3GPP LTE radio access technologies. A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is a more optimized radio system fulfilling the international telecommunication union-radio (ITU-R) requirements for IMT-Advanced while maintaining backward compatibility. One of the key features of LTE-A， introduced in LTE Rel-10， is carrier aggregation， which allows for increasing the data rates through aggregation of two or more LTE carriers. The next releases of3GPP LTE (e.g. LTE Rel-12， LTE Rel-13， LTE Rel-14， LTE Rel-15) are targeted for further improvements of specialized services， shorter latency and meeting requirements approaching the 5G.

5^th generation (5G) or new radio (NR) wireless systems refer to the next generation (NG) of radio systems and network architecture. 5G is also known to appear as the IMT-2020 system. It is estimated that 5G will provide bitrates on the order of 10-20 Gbit/s or higher. 5G will support at least enhanced mobile broadband (eMBB) and ultra-reliable low-latency-communication (URLLC) . 5G is also expected to increase network expandability up to hundreds of thousands of connections. The signal technology of 5G is anticipated for greater coverage as well as spectral and signaling efficiency. 5G 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. In 5G or NR， the Node B or eNB may be referred to as a next generation or 5G Node B (gNB) .

SUMMARY：

One embodiment is directed to a method that may include generating， by a user equipment， a channel state information (CSI) report based on one or more frequency omission rules. The frequency omission rules are based on at least one of frequency selectivity， channel quality indicator (CQI) and CQI variation， or spatial correlation across subbands. The method may then include transmitting the channel state information (CSI) report to a network node.

Another embodiment is directed to an apparatus that may include generating means for generating a channel state information (CSI) report based on one or more frequency omission rules. The frequency omission rules are based on at least one of frequency selectivity， channel quality indicator (CQI) and CQI variation， or spatial correlation across subbands. The apparatus may then include transmitting means for transmitting the channel state information (CSI) report to a network node.

Another embodiment is directed to an apparatus， which may include at least one processor and at least one memory including computer program code. The at least one memory and computer program code are configured， with the at least one processor， to cause the apparatus at least to generate a channel state information (CSI) report based on one or more frequency omission rules. The frequency omission rules are based on at least one of frequency selectivity， channel quality indicator (CQI) and CQI variation， or spatial correlation across subbands. The apparatus may then be controlled to transmit the channel state information (CSI) report to a network node.

BRIEF DESCRIPTION OF THE DRAWINGS：

For proper understanding of the invention， reference should be made to the accompanying drawings， wherein：

Fig. 1 illustrates a system level diagram according to an embodiment；

Fig. 2a illustrates a block diagram of an apparatus， according to one embodiment；

Fig. 2b illustrates a block diagram of an apparatus， according to another embodiment；

Fig. 3a illustrates an example flow diagram of a method， according to an embodiment； and

Fig. 3b illustrates an example flow diagram of a method， according to another embodiment.

DETAILED DESCRIPTION：

It will be readily understood that the components of the invention， 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 the embodiments of systems， methods， apparatuses， and computer program products for frequency domain omission of subband channel state information (CSI) report， as represented in the attached figures and described below， is not intended to limit the scope of the invention but is representative of selected embodiments of the invention.

The features， structures， or characteristics of the invention described throughout this specification may be combined in any suitable manner in one or more 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 the embodiment may be included in at least one embodiment of the present invention. 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 embodiments.

Additionally， if desired， the different functions or steps 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 steps may be optional or may be combined. As such， the following description should be considered as merely illustrative of the principles， teachings and embodiments of this invention， and not in limitation thereof.

Fig. 1 illustrates an example of a system level diagram of an embodiment of a communication system including a wireless communication system. The wireless communication system may be configured to provide evolved UMTS terrestrial radio access network ( ″E-UTRAN″ ) universal mobile telecommunications services， LTE services， and/or 5G/NR services， for example. The system may include one or more servers or gateways 110. The servers 110 may include， for example， a mobile management entity/system architecture evolution gateway (MME/SAE GW) that may provide control functionality for a base station 120. Other examples of servers 110 may include， but are not limited to， a streaming server， data server， policy server， etc.

Base stations 120 may be eNBs， gNBs， WLAN access points， or any combination thereof. The base stations 120 can communicate with servers 110 via communication links. The various communication links may be fiber， microwave， or other high-frequency metallic communication paths such as coaxial links， or combinations thereof. The base stations 120 may host functions such as radio resource management. For instance， the base stations 120 may perform functions such as internet protocol ( ″IP″ ) header compression and encryption of user data streams， ciphering of user data streams， radio bearer control， radio admission control， connection mobility control， dynamic allocation of communication resources to user equipment in both the uplink and the downlink， selection of a mobility management entity at the user equipment attachment， routing of user plane data towards the user plane entity， scheduling and transmission of paging messages (originated from the mobility management entity) ， scheduling and transmission of broadcast information (originated from the mobility management entity or operations and maintenance) ， and measurement and reporting configuration for mobility and scheduling.

The base stations 120 maycommunicate with wireless communication devices such as UE 130. While only a single UE is illustrated in Fig. 1， it should be understood that such systems may include multiple UEs. Communication links coupling the base stations 120 to the user equipment 130 can be air links employing a wireless communication signal such as， for example， an orthogonal frequency division multiplex (OFDM) signal. While the user equipment 130 may be part of a primary communication system， the user equipment 130 and other devices such as machines (not shown) may be a part of a secondary communication system to participate in， without limitation， device-to-device and machine-to-machine communications or other communications. It is noted that Fig. 1 is just one example illustrating a possible system configuration， and other configurations are possible according to certain embodiments.

As mentioned above， certain embodiments may relate to methods for channel state information reporting. CSI generally refers to the known properties of a communication link. For example， CSI may include channel quality information (e.g.， channel quality indicator (CQI) ) ， precoding matrix indicator (PMI) ， precoding type indicator (PTI) ， and/or rank indicator (RI) . This information helps describe how a signal propagates from the transmitter to the receiver. CSI makes it possible to adapt transmissions to current channel conditions， in order to achieve reliable communication with high data rates in， for example， multiple input multiple output (MIMO) systems. CSI may be estimated at the receiver and usually quantized and fed back to the transmitter. The time and frequency resources that may be used by the UE to report CSI are usually controlled by the eNB or gNB.

It has been agreed in 3GPP that a CSI reporting omission rule (s) is to be decided. For a partial CSI report omission rule， one of the following rules may need to be selected and specified： (a) omitted subbands are determined based on a decimation ratio and/or a priority pattern used to order subband CSI， and/or (b) omitted subbands are determined based on the measured subband CQI.

In the 3GPP NR MIMO discussion， it was agreed that a type II CSI codebook is to be supported. A CSI report with a type II CSI codebook may include reporting of selected beams and the combining coefficients of the beams. The combining coefficients may include amplitudes (powers) and phases for each beam which may each be selected using wideband or subband channel statistics and may be specific to each antenna polarization and data layer (rank) . Generally， a codebook is understood to include a look-up table of cross coupling factors used for precoding， and is shared by the UE and base station (e.g.， eNB or gNB) . However， one problem with respect to the type II CSI codebook is that the CSI report payload for a subband report may be very large. It may involve transmitting hundreds of bits to feed back the report for a complete set of subbands for a UE. Another problem is that the feedback payload depends on the value of the RI and the values of the wideband amplitudes determined by the UE for the beams the UE selects from the type II codebook. For example， a UE may select 4 beams as configured by the base station (e.g.， gNB or eNB) but report some of the beams as zero-power beams； in this case， the subband combining coefficients corresponding to the zero-power beams will not be reported. As the CSI report payload highly depends on the channel condition of the UE and the channel estimation algorithm used by the UE， the base station (e.g.， gNB or eNB) may not be able to precisely predict the payload size. The base station can create a resource allocation (RA) for the maximum possible payload， but such an allocation will waste resources. If the RA from the base station is too small to accommodate the entire payload， rules must be in place to determine what part of the report is omitted.

To reduce overhead or to fit the CSI report into the allocated resources in case the base station (e.g.， gNB or eNB) does not allocate enough resources， a CSI report on some subbands can be dropped. Dropping a CSI report for some subbands causes performance degradation， and rules are required to select the subbands for which subband CSI will be omitted. These rules are required to solve the problems discussed above and control the system design complexity while minimizing the decrease in performance.

Frequency parameterization can reduce the subband CSI report overhead by exploring the frequency domain correlation across subbands. The assumption of this approach is that the type II CSI report combining coefficients， both amplitude and phase， are continuous functions over the entire bandwidth. If CSI on selected subbands is reported， combining coefficients on omitted subbands can be retrieved by proper curve fitting and high order interpolation. This approach may be able to reduce overhead sufficiently while maintaining system performance， but with high complexity. In addition， sophisticated signalling needs to be designed to support this approach to feed back， for example， the curve fitting coefficients， the interpolation order， and so on.

The best-M subband CSI report in legacy LTE is another approach that can reduce overhead. According to this approach， a UE reports only the M out of K subbands (K＞M) which preserve the highest M reported CQI values. Because a subband with a high CQI value should contribute more to the system performance， the best-M subband CSI report makes the best use of the available payload. A problem with applying the legacy best-M subband CQI report to the NR type II CSI case is that a high CQI value in a current reporting time instance does not guarantee that a certain subband will make the best contribution to the system performance； the variation of CQI on a subband over time also needs to be considered. The type II CSI codebook is targeted at high precision CSI acquisition and multi-user transmission； to take advantage of type II CSI feedback， stable channel conditions at the UE are preferred. Fast channel variation for a high speed UE or a dispersive transmission scenario with fast moving reflectors will break the usefulness of type II CSI feedback， and for these cases feedback latency will decrease the precision of the CSI.

Certain embodiments provide frequency omission rules for type II CSI feedback， for example， in order to reduce report overhead and to fit the CSI report into the available payload in case the allocated resources are not sufficient for a complete subband type II CSI report.

According to an embodiment， a first rule may be based on frequency selectivity (Rule #1) . According to this frequency selectivity rule， a UE may calculate the correlation bandwidth in the frequency domain. If the correlation bandwidth is larger than the subband size， the UE may select one subband within the correlation bandwidth to report. If the correlation bandwidth is less than or equal to the subband size， the UE may report on the subband. If the resulting subband report size does not fit into the RA signaled by the network (i.e.， gNB) ， subband decimation is applied so that the report size fits into the resources signaled by the network. In one example embodiment， subband decimation by the order of 2 may be applied until the report size fits the resources signaled by the network. However， embodiments are not limited to performing decimation by the order of 2， and other integers may be selected as a best integer decimation factor according to certain embodiments.

In another embodiment， a second rule may be based on CQI and CQI variation (Rule #2) . According to this CQI/CQI variation rule， a UE may calculate the reporting coefficients for subbands and report just those subbands with the best reporting coefficients. In this embodiment， the reporting coefficient may be a weighted combining of the CQI value and CQI variation of a subband. The best M subbands may be selected with M determined from the RA signaled by the network (e.g.， gNB) .

According to another embodiment， a third rule may be based on spatial correlation across subbands (Rule #3) . According to this spatial correlation across subbands rule， phase coefficient correlation for every adjacent subband pair may be calculated and compared to a correlation threshold. If the correlation is greater than the threshold， then just one subband within the subband pair will be reported. If the correlation is less than or equal to the threshold， both subbands within the subband pair will be reported. According to this embodiment， the threshold may be adjusted and the rule may be run until the resulting subband report fits into the resources (i.e.， RA) signaled by the network (e.g.， gNB) . In one example embodiment， the threshold may be bisectionally adjusted. It is noted that this is just one example for a factor of adjustment， and other examples are possible according to other embodiments.

It is noted that， in certain embodiments， the three rules (i.e.， Rule #1， Rule #2， and Rule #3) discussed above may be mixed and/or used in any combination.

Fig. 2a illustrates an example of an apparatus 10 according to an embodiment. In an embodiment， apparatus 10 may be a node， host， or server in a communications network or serving such a network. For example， apparatus 10 may be a base station， a Node B， an evolved Node B (eNB) ， 5G Node B or access point， next generation Node B (NG-NB or gNB) ， WLAN access point， mobility management entity (MME) ， or subscription server associated with a radio access network， such as a GSM network， LTE network， 5G or NR.

It should be understood that apparatus 10 may be comprised of an edge cloud server as a distributed computing system where the server and the radio node may be stand-alone apparatuses communicating with each other via a radio path or via a wired connection， or they may be located in a same entity communicating via a wired connection. It should be noted that one of ordinary skill in the art would understand that apparatus 10 may include components or features not shown in Fig. 2a.

As illustrated in Fig. 2a， apparatus 10 may include a processor 12 for processing information and executing instructions or operations. Processor 12 may be any type of general or specific purpose processor. In fact， processor 12 may include one or more of general-purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) ， field-programmable gate arrays (FPGAs) ， application-specific integrated circuits (ASICs) ， and processors based on a multi-core processor architecture， as examples. While a single processor 12 is shown in Fig. 2a， multiple processors may be utilized according to other embodiments. For example， it should be understood that， in certain embodiments， apparatus 10 may include two or more processors that may form a multiprocessor system (i.e.， in this case processor 12 represents a multiprocessor) that may support multiprocessing. In certain embodiments， the multiprocessor system may be tightly coupled or loosely coupled (e.g.， to form a computer cluster) .

Processor 12 may perform functions associated with the operation of apparatus 10 which may include， for example， precoding of antenna gain/phase parameters， encoding and decoding of individual bits forming a communication message， formatting of information， and overall control of the apparatus 10， including processes related to management of communication resources.

Apparatus 10 may further include or be coupled to a memory 14 (internal or external) ， which may be coupled to processor 12， for storing information and instructions that may be executed by processor 12. Memory 14 may be one or more memories and of any type suitable to the local application environment， and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device， a magnetic memory device and system， an optical memory device and system， fixed memory， and removable memory. For example， memory 14 can be comprised of any combination of random access memory (RAM) ， read only memory (ROM) ， static storage such as a magnetic or optical disk， hard disk drive (HDD) ， or any other type of non-transitory machine or computer readable media. The instructions stored in memory 14 may include program instructions or computer program code that， when executed by processor 12， enable the apparatus 10 to perform tasks as described herein.

In an embodiment， apparatus 10 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium， such as an optical disc， USB drive， flash drive， or any other storage medium. For example， the external computer readable storage medium may store a computer program or software for execution by processor 12 and/or apparatus 10.

In some embodiments， apparatus 10 may also include or be coupled to one or more antennas 15 for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 may further include or be coupled to a transceiver 18 configured to transmit and receive information. The transceiver 18 may include， for example， a plurality of radio interfaces that may be coupled to the antenna (s) 15. The radio interfaces may correspond to a plurality of radio access technologies including one or more of GSM， NB-IoT， LTE， 5G， WLAN， Bluetooth， BT-LE， NFC， radio frequency identifier (RFID) ， ultrawideband (UWB) ， MulteFire， and the like. The radio interface may include components， such as filters， converters (for example， digital-to-analog converters and the like) ， mappers， a Fast Fourier Transform (FFT) module， and the like， to generate symbols for a transmission via one or more downlinks and to receive symbols (for example， via an uplink) . As such， transceiver 18 may be configured to modulate information on to a carrier waveform for transmission by the antenna (s) 15 and demodulate information received via the antenna (s) 15 for further processing by other elements of apparatus 10. In other embodiments， transceiver 18 may be capable of transmitting and receiving signals or data directly.

In an embodiment， memory 14 may store software modules that provide functionality when executed by processor 12. The modules may include， for example， an operating system that provides operating system functionality for apparatus 10. The memory may also store one or more functional modules， such as an application or program， to provide additional functionality for apparatus 10. The components of apparatus 10 may be implemented in hardware， or as any suitable combination of hardware and software.

In certain embodiments， apparatus 10 may be a network node or RAN node， such as a base station， access point， Node B， eNB， gNB， WLAN access point， or the like. According to certain embodiments， apparatus 10 may be controlled by memory 14 and processor 12 to perform the functions associated with any of the embodiments described herein.

In one embodiment， apparatus 10 may be controlled by memory 14 and processor 12 to provide or allocate resources for CSI reporting to one or more UEs. For example， in an embodiment， apparatus 10 may be controlled by memory 14 and processor 12 to allocate the resources for CSI reporting by creating a RA for the payload and signaling the RA to the UE (s) . According to an embodiment， apparatus 10 may then be controlled by memory 14 and processor 12 to receive a CSI report from one or more UEs on the allocated resources. The CSI report may be a type II CSI report. In certain embodiments， the CSI report may be generated or built by the UE (s) according to one or more frequency omission rules. For example， the frequency omission rule (s) may be based on frequency selectivity， CQI and CQI variation， spatial correlation across subbands， or any combination thereof.

Fig. 2b illustrates an example of an apparatus 20 according to another embodiment. In an embodiment， apparatus 20 may be a node or element in a communications network or associated with such a network， such as a UE， mobile equipment (ME) ， mobile station， mobile device， stationary device， Iot device， or other device. As described herein， UE may alternatively be referred to as， for example， a mobile station， mobile equipment， mobile unit， mobile device， user device， subscriber station， wireless terminal， tablet， smart phone， IoT device or NB-IoT device， or the like. As one example， apparatus 20 may be implemented in， for instance， a wireless handheld device， a wireless plug-in accessory， or the like.

In some example embodiments， apparatus 20 may include one or more processors， one or more computer-readable storage medium (for example， memory， storage， and the like) ， one or more radio access components (for example， a modem， a transceiver， and the like) ， and/or a user interface. In some embodiments， apparatus 20 may be configured to operate using one or more radio access technologies， such as GSM， LTE， LTE-A， NR， 5G， WLAN， WiFi， NB-IoT， Bluetooth， NFC， MulteFire， and any other radio access technologies. It should be noted that one of ordinary skill in the art would understand that apparatus 20 may include components or features not shown in Fig. 2b.

As illustrated in Fig. 2b， apparatus 20 may include or be coupled to a processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general or specific purpose processor. In fact， processor 22 may include one or more of general-purpose computers， special purpose computers， microprocessors， digital signal processors (DSPs) ，field-programmable gatearrays (FPGAs) ， application-specific integrated circuits (ASICs) ， and processors based on a multi-core processor architecture， as examples. While a single processor 22 is shown in Fig. 2b， multiple processors may be utilized according to other embodiments. For example， it should be understood that， in certain embodiments， apparatus 20 may include two or more processors that may form a multiprocessor system (i.e.， in this case processor 22 represents a multiprocessor) that may support multiprocessing. In certain embodiments， the multiprocessor system may be tightly coupled or loosely coupled (e.g.， to form a computer cluster) .

Processor 22 may perform functions associated with the operation of apparatus 20 including， without limitation， precoding of antenna gain/phase parameters， encoding and decoding of individual bits forminga communication message， formatting of information， and overall control of the apparatus 20， including processes related to management of communication resources.

Apparatus 20 may further include or be coupled to a memory 24 (internal or external) ， which may be coupled to processor 22， for storing information and instructions that may be executed by processor 22. Memory 24 may be one or more memories and of any type suitable to the local application environment， and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device， a magnetic memory device and system， an optical memory device and system， fixed memory， and removable memory. For example， memory 24 can be comprised of any combination of random access memory (RAM) ， read only memory (ROM) ， static storage such as a magnetic or optical disk， or any other type of non-transitory machine or computer readable media. The instructions stored in memory 24 may include program instructions or computer program code that， when executed by processor 22， enable the apparatus 20 to perform tasks as described herein.

In an embodiment， apparatus 20 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium， such as an optical disc， USB drive， flash drive， or any other storage medium. For example， the external computer readable storage medium may store a computer program or software for execution by processor 22 and/or apparatus 20.

In some embodiments， apparatus 20 may also include or be coupled to one or more antennas 25 for receiving a downlink signal and for transmitting via an uplink from apparatus 20. Apparatus 20 may further include a transceiver 28 configured to transmit and receive information. The transceiver 28 may also include a radio interface (e.g.， a modem) coupled to the antenna 25. The radio interface may correspond to a plurality of radio access tectmologies including one or more of GSM， LTE， LTE-A， 5G， NR， WLAN， NB-IoT， Bluetooth， BT-LE， NFC， RFID， UWB， and the like. The radio interface may include other components， such as filters， converters (for example， digital-to-analog converters and the like) ， symbol demappers， signal shaping components， an Inverse Fast Fourier Transform (IFFT) module， and the like， to process symbols， such as OFDMA symbols， carried by a downlink or an uplink.

For instance， transceiver 28 may be configured to modulate information on to a carrier waveform for transmission by the antenna (s) 25 and demodulate information received via the antenna (s) 25 for further processing by other elements of apparatus 20. In other embodiments， transceiver 28 may be capable of transmitting and receiving signals or data directly. Apparatus 20 may further include a user interface， such as a graphical user interface or touchscreen.

In an embodiment， memory 24 stores software modules that provide functionality when executed by processor 22. The modules may include， for example， an operating system that provides operating system functionality for apparatus 20. The memory may also store one or more functional modules， such as an application or program， to provide additional functionality for apparatus 20. The components of apparatus 20 may be implemented in hardware， or as any suitable combination of hardware and software.

According to one embodiment， apparatus 20 may be a UE， mobile device， mobile station， ME， Iot device and/or NB-IoT device， for example. According to certain embodiments， apparatus 20 may be controlled by memory 24 and processor 22 to perform the functions associated with embodiments described herein. For example， in some embodiments， apparatus 20 may be configured to perform one or more of the processes depicted in any of the flow charts or signaling diagrams described herein.

According to one embodiment， apparatus 20 may be controlled by memory 24 and processor 22 to generate or build a CSI report based on one or more frequency omission rules. For example， the frequency omission rule (s) may be based on frequency selectivity， CQI and CQI variation， spatial correlation across subbands， or any combination thereof. In an embodiment， the CSI report may be a type II CSI report. In an embodiment， apparatus 20 may be controlled by memory 24 and processor 22 to transmit or send the CSI report to a network node (e.g.， eNB or gNB) on resources allocated by the network node.

In an embodiment， when the frequency omission rule (s) is based on frequency selectivity， apparatus 20 may be further controlled by memory 24 and processor 22 to calculate correlation bandwidth， ω， in the frequency domain. If the correlation bandwidth is higher than the subband size (i.e.， ω ＞ N， where Nis a subband size for a configured bandwidth) ， apparatus 20 may be controlled by memory 24 and processor 22 to select one subband within the correlation bandwidth to include in the CSI report. For example， according to one embodiment， if the correlation bandwidth is greater than the subband size (ω ＞ N) ， for every group of

(or

) subbands， apparatus 20 may be controlled to select one subband from each group to include in the CSI report. For example， in one embodiment， apparatus 20 may be controlled to report the first subband in each group. In an embodiment， when the correlation bandwidth is less than or equal to the subband size (ω ≤ N) ， apparatus 20 may be controlled to report on all of the subbands. According to certain embodiments， if the resulting subband CSI report size does not fit into the resources allocated by the network node (e.g.， eNB or gNB) ， apparatus 20 may be controlled by memory 24 and processor 22 to iteratively apply further decimation until the resulting report size fits into the allocated resources.

In another embodiment， when the frequency omission rule is based on CQI and CQI variation， apparatus 20 may be controlled by memory 24 and processor 22 to calculate the reporting coefficients for subbands and select those subbands with high reporting coefficients to include in the CSI report. The reporting coefficient is a weighted combining of the CQI value and CQI variation of a subband. In an embodiment， apparatus 20 may select the subbands with high reporting coefficients by selecting the best M subbands with M determined from the resources (RA) signaled by the network node. For example， in one embodiment， apparatus 20 may be controlled to calculate the reporting coefficients for subbands according to the following formulas： w_i，l ＝ α*CQI_i， l+β*ΔCQI_i， l

where， w_i， l is the reporting coefficient for subband l at time instance i， α and β are the combining weights for CQI and CQI variance， α ＝ 1-β. In an embodiment， apparatus 20 may then be controlled by memory 24 and processor 22 to order the subbands by decreasing order of the reporting coefficients. Apparatus 20 may be further controlled by memory 24 and processor 22 to report the first M subbands with higher reporting coefficients， where M is determined by RA signaled by the network node.

In another embodiment， when the frequency omission rule is based on spatial correlation across subbands， apparatus 20 may be controlled by memory 24 and processor 22 to calculate phase coefficient correlation for every two adjacent subbands， l andl+1. Apparatus 20 may then be controlled by memory 24 and processor 22 to compare the calculated phase coefficient correlation to a correlation threshold. When the correlation is greater than the correlation threshold， then only one subband within the subband pair will be included in the CSI report. For example， if the correlation is greater than threshold x，

apparatus 20 may be controlled to report the first subband within the subband pair. Here， c′_{r， l， i} and c″_{r， l， i} represent the phase coefficients， the total number of phase coefficients for a subband is N. In one embodiment， when the correlation is less than the correlation threshold， apparatus 20 may be controlled by memory 24 and processor 22 to report on both of the subbands. According to an embodiment， if the resulting subband CSI report size does not fit in the allocated RA， apparatus 20 may be controlled by memory 24 and processor 22 to adjust the correlation threshold， and again perform the calculation of the phase coefficient correlation and the comparison of the calculated phase coefficient correlation to the adjusted correlation threshold. In an example embodiment， the range of phase coefficient correlation may be [0， 1] .

Fig. 3a illustrates an example flow diagram of a method， according to one example embodiment. The method may be performed by a network node， such as a base station， eNB， gNB， or access node， for example. The method of Fig. 3a may include， at 300， providing or allocating resources for CSI reporting to one or more UEs. According to an embodiment， the method may also include， at 310， receiving a CSI report from one or more UEs. The CSI report may be a type II CSI report. In certain embodiments， the CSI report is generated or built， by the UE (s) ， by applying one or more frequency omission rules. For example， in certain embodiments， the frequency omission rule (s) may be based on frequency selectivity， CQI and CQI variation， spatial correlation across subbands， or any combination thereof.

Fig. 3b illustrates an example flow diagram of a method， according to one example embodiment. The method of Fig. 3b may be performed by a UE or mobile station， for example. In an embodiment， the method may include， at 350， generating or building a CSI report by applying one or more frequency omission rules. For example， in certain embodiments， the frequency omission rule (s) may be based on frequency selectivity， CQI and CQI variation， spatial correlation across subbands， or any combination thereof. In an embodiment， the CSI report may be a type II CSI report. In an embodiment， the method may also include， at 360， transmitting or sending the CSI report to a network node (e.g.， eNB or gNB) on resources allocated by the network node.

In an embodiment， when the frequency omission rule (s) is based on frequency selectivity， the generating or building 350 may include calculating correlation bandwidth， ω， in frequency domain. If the correlation bandwidth is greater than the subband size (i.e.， ω ＞ N， where N is a subband size for a configured bandwidth) ， the generating or building 350 may further include selecting one subband within the correlation bandwidth to include in the CSI report. For example， according to one embodiment， if the correlation bandwidth is greater than the subband size (ω ＞ N) ， for every group of

(or

) subbands， the generating or building 350 may include selecting one subband from each group to include in the CSI report. For example， in one embodiment， the generating or building 350 may include selecting the first subband in each group and the transmitting 360 may include reporting the selected first subband in each group. In an embodiment， when the correlation bandwidth is less than or equal to the subband size (ω ≤ N) ， the transmitting 360 may include reporting on the subbands. According to certain embodiments， if the resulting subband CSI report size does not fit into the resource allocated by the network node (e.g.， eNB or gNB) ， the method may further include iteratively applying further decimation until the resulting report size fits into the allocated resources.

In another embodiment， when the frequency omission rule is based on CQI and CQI variation， the generating or building 350 may include calculating the reporting coefficients for subbands and selecting those subbands with high reporting coefficients to include in the CSI report. The reporting coefficient may be a weighted combining of the CQI value and CQI variation of a subband. In an embodiment， the generating or building 350 may further include selecting the subbands with high reporting coefficients by selecting the best M subbands with M determined from the resources (RA) signaled by the network node. For example， in one embodiment， the calculating may include calculating the reporting coefficients for subbands according to the following formulas：

w_i， l ＝ α*CQI_i， l+β*ΔCQI_i， l

where， w_i， l is the reporting coefficient for subband l at time instance i， α and β are the combining weights for CQI and CQI variance， α ＝ 1-β. In an embodiment， the method may further include ordering the subbands by decreasing order of the reporting coefficients. The transmitting 360 may then include reporting the first M subbands with the largest reporting coefficients， where M is determined by RA signaled by the network node.

In another embodiment， when the frequency omission rule is based on spatial correlation across subbands， the generating or building 350 may include calculating phase coefficient correlation for every two adjacent subbands， l and l+1， and comparing the calculated phase coefficient correlation to a correlation threshold. When the correlation is greater than the correlation threshold， then the transmitting 360 may include reporting only one subband within the subband pair in the CSI report. For example， if the correlation is greater than threshold x，

the CSI report may include the first subband within the subband pair. Here， c′_{r， l， i} and c″_{r， l， i} represent the phase coefficients， the total number of phase coefficients for a subband is N. In one embodiment， when the correlation is less than the correlation threshold， the CSI report may include both of the subbands. According to an embodiment， if the resulting subband CSI report size does not fit in the allocated RA， the method may include adjusting the correlation threshold， and again performing the calculation of the phase coefficient correlation and the comparison of the calculated phase coefficient correlation to the adjusted correlation threshold， until the resulting CSI report size fits in the allocated resources. In an example embodiment， the range of phase coefficient correlation may be [0， 1] .

Therefore， embodiments of the invention provide several technical improvements and/or advantages. For example， as a result of certain embodiments， overhead can be reduced and payload size can be decreased. As such， embodiments of the invention can improve performance and throughput of network nodes including， for example， base stations/eNBs/gNBs and UEs. Accordingly， the use of embodiments of the invention result in improved functioning of communications networks and their nodes.

In some embodiments， the functionality of any of the methods， processes， signaling diagrams， or flow charts described herein may be implemented by software and/or computer program code or portions of code stored in memory or other computer readable or tangible media， and executed by a processor.

In some embodiments， an apparatus may be included or be associated with at least one software application， module， unit or entity configured as arithmetic operation (s) ， or as a program or portions of it (including an added or updated software routine) ， executed by at least one operation processor. Programs， also called program products or computer programs， including software routines， applets and macros， may be stored in any apparatus-readable data storage medium and include program instructions to perform particular tasks.

A computer program product may comprise one or more computer-executable components which， when the program is run， are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it. Modifications and configurations required for implementing functionality of an embodiment may be performed as routine (s) ， which may be implemented as added or updated software routine (s) . Software routine (s) may be downloaded into the apparatus.

Software or a computer program code or portions of it may be in a source code form， object code form， or in some intermediate form， and it may be stored in some sort of carrier， distribution medium， or computer readable medium， which may be any entity or device capable of carrying the program. Such carriers include a record medium， computer memory， read-only memory， photoelectrical and/or electrical carrier signal， telecommunications signal， and software distribution package， for example. Depending on the processing power needed， the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers. The computer readable medium or computer readable storage medium may be a non-transitory medium.

In other embodiments， the functionality may be performed by hardware or circuitry included in an apparatus (e.g.， apparatus 10 or apparatus 20) ， for example through the use of an application specific integrated circuit (ASIC) ， a programmable gate array (PGA) ， a field programmable gate array (FPGA) ， or any other combination of hardware and software. In yet another embodiment， the functionality may be implemented as a signal， a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network.

According to an embodiment， an apparatus， such as a node， device， or a corresponding component， may be configured as circuitry， a computer or a microprocessor， such as single-chip computer element， or as a chipset， including at least a memory for providing storage capacity used for arithmetic operation and an operation processor for executing the arithmetic operation.

One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with steps in a different order， and/or with hardware elements in configurations which are different than those which are disclosed. Therefore， although the invention has been described based upon these preferred 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 the invention. In order to determine the metes and bounds of the invention， therefore， reference should be made to the appended claims.

Claims

A method， comprising：

generating， by a user equipment， a channel state information (CSI) report based on one or more frequency omission rules， wherein the frequency omission rules are based on at least one of frequency selectivity， channel quality indicator (CQI) and CQI variation， or spatial correlation across subbands； and

transmitting the channel state information (CSI) report to a network node.
The method according to claim 1， wherein the channel state information (CSI) report comprises a type II channel state information (CSI) report.
The method according to claims 1 or 2， wherein， when the frequency omission rule is based on frequency selectivity， the method further comprises：

calculating correlation bandwidth in the frequency domain；

when the correlation bandwidth is greater than the subband size， selecting one subband from within the correlation bandwidth to include in the channel state information (CSI) report； and

when the correlation bandwidth is less than or equal to the subband size， selecting the subbands to include in the channel state information (CSI) report.
The method according to claim 3， wherein the selecting of said one subband from within the correlation bandwidth when the correlation bandwidth is greater than the subband size comprises， for every for every group of
subbands， selecting one subband from each group to include in the channel state information (CSI) report， where ω is the correlation bandwidth and N is the subband size for a configured bandwidth.
The method according to claims 3 or 4， wherein， when the channel state information (CSI) report does not fit into resources allocated by the network node， iteratively applying further decimation until the resulting channel state information (CSI) report fits into the resources.
The method according to claims 1 or 2， wherein， when the frequency omission rule is based on channel quality indicator (CQI) and CQI variation， the method further comprises：

calculating a reporting coefficient for subbands， wherein the reporting coefficient is a weighted combination of the CQI value and CQI variation of a subband； and

selecting the subbands with higher reporting coefficients for including in the channel state information (CSI) report.
The method according to claim 6， wherein the calculating comprises calculating the reporting coefficients for subbands according to the following formulas：

w_i， l＝α*CQI_i， l+β*ΔCQI_i， l

where w_i， l is the reporting coefficient for subband l at time instance i， and α and β are the combining weights for CQI and CQI variance， α ＝ 1 -β.
The method according to claim 7， wherein the selecting further comprises ordering the subbands by decreasing order of the reporting coefficients， and wherein the transmitting comprises reporting the first M subbands with the higher reporting coefficients， where M is determined by the resources allocated by the network node.
The method according to claims 1 or 2， wherein， when the frequency omission rule is based on spatial correlation across subbands， the method further comprises：

calculating a phase coefficient correlation for every adjacent subband pair；

comparing the phase coefficient correlation to a correlation threshold；

when the phase coefficient correlation is greater than the correlation threshold， including one subband from the subband pair in the channel state information (CSI) report； and

when the phase coefficient correlation is less than or equal to the correlation threshold， including both subbands from the subband pair in the channel state information (CSI) report.
The method according to claim 9， wherein， when a resulting subband channel state information (CSI) report size does not fit in resources allocated by the network node， the method further comprises：

adjusting the correlation threshold， and again performing the calculating of the phase coefficient correlation and the comparing of the calculated phase coefficient correlation to the adjusted correlation threshold.
An apparatus， comprising：

generating means for generating a channel state information (CSI) report based on one or more frequency omission rules， wherein the frequency omission rules are based on at least one of frequency selectivity， channel quality indicator (CQI) and CQI variation， or spatial correlation across subbands； and

transmitting means for transmitting the channel state information (CSI) report to a network node.
The apparatus according to claim 11， wherein the channel state information (CSI) report comprises a type II channel state information (CSI) report.
The apparatus according to claims 11 or 12， wherein， when the frequency omission rule is based on frequency selectivity， the method further comprises：

calculating means for calculating a correlation bandwidth in the frequency domain；

when the correlation bandwidth is greater than the subband size， selecting means for selecting one subband from within the correlation bandwidth to include in the channel state information (CSI) report； and

when the correlation bandwidth is less than or equal to the subband size， selecting means for selecting the subbands to include in the channel state information (CSI) report.
The apparatus according to claim 13， wherein the selecting means for selecting one subband from within the correlation bandwidth when the correlation bandwidth is greater than the subband size comprises， for every for every group of
subbands， means for selecting one subband from each group to include in the channel state information (CSI) report， where ω is the correlation bandwidth and N is the subband size for a configured bandwidth.
The apparatus according to claims 13 or 14， wherein， when the channel state information (CSI) report does not fit into resources allocated by the network node， applying means for iteratively applying further decimation until the resulting channel state information (CSI) report fits into the resources.
The apparatus according to claims 11 or 12， wherein， when the frequency omission rule is based on channel quality indicator (CQI) and CQI variation， the apparatus further comprises：

calculating means for calculating reporting coefficient for subbands， wherein the reporting coefficient is a weighted combination of the CQI value and CQI variation of a subband； and

selecting means for selecting the subbands with higher reporting coefficients for including in the channel state information (CSI) report.
The apparatus according to claim 16， wherein the calculating means comprises means for calculating the reporting coefficients for subbands according to the following formulas：

w_i， l＝α*CQI_i， l+β*ΔCQI_i， l

where w_i， l is the reporting coefficient for subband l at time instance i， and α and β are the combining weights for CQI and CQI variance， α ＝ 1 -β.
The apparatus according to claim 17， wherein the selecting means further comprises means for ordering the subbands by decreasing order of the reporting coefficients， and wherein the transmitting means comprises means for reporting the first M subbands with the higher reporting coefficients， where M is determined by the resources allocated by the network node.
The apparatus according to claims 11 or 12， wherein， when the frequency omission rule is based on spatial correlation across subbands， the apparatus further comprises：

calculating means for calculating phase coefficient correlation for every adjacent subband pair；

comparing means for comparing the phase coefficient correlation to a correlation threshold；

when the phase coefficient correlation is greater than the correlation threshold， including means for including one subband from the subband pair in the channel state information (CSI) report； and

when the phase coefficient correlation is less than or equal to the correlation threshold， including means for including both subbands from the subband pair in the channel state information (CSI) report.
The apparatus according to claim 19， wherein， when a resulting subband channel state information (CSI) report size does not fit in resources allocated by the network node， the apparatus further comprises：

adjusting means for adjusting the correlation threshold， and means for again performing the calculating of the phase coefficient correlation and the comparing of the calculated phase coefficient correlation to the adjusted correlation threshold.
An apparatus， comprising：

at least one processor； and

at least one memory including computer program code，

wherein the at least one memory and computer program code are configured， with the at least one processor， to cause the apparatus at least to

generate a channel state information (CSI) report based on one or more frequency omission rules， wherein the frequency omission rules are based on at least one of frequency selectivity， channel quality indicator (CQI) and CQI variation， or spatial correlation across subbands； and

transmit the channel state information (CSI) report to a network node.
A computer program， embodied on a non-transitory computer readable medium， the computer program configured to control a processor to perform a method according to any one of claims 1-10.