WO2016026507A1

WO2016026507A1 - Periodical feedback design for three-dimensional multiple-input multiple-output (3d-mimo)

Info

Publication number: WO2016026507A1
Application number: PCT/EP2014/067558
Authority: WO
Inventors: Xiaoyi Wang; Bishwarup Mondal; Weidong Yang
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2014-08-18
Filing date: 2014-08-18
Publication date: 2016-02-25

Abstract

Systems, methods, apparatuses, and computer program products for a periodical feedback design for three-dimensional (3D) multiple-input multiple-output (MIMO) are provided. One method includes configuring a channel state feedback into at least two feedback instances with reduced sizes for transmission over one or more physical feedback channels. The channel state feedback may include a codebook index, indices of channel, or precoder quantization. The method may also include encoding codebook index, indices of channel, or precoder quantization of the channel state feedback, and filling the encoded codebook index, indices of channel, or precoder quantization into the at least two feedback instances of the one or more physical feedback channels.

Description

DESCRIPTION

TITLE

PERIODICAL FEEDBACK DESIGN FOR THREE-DIMENSIONAL MULTIPLE-INPUT

MULTIPLE-OUTPUT (3D-MIMO)

FIELD:

[0001] Embodiments of the invention may generally relate to wireless 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) and/or future 5G radio access technology.

BACKGROUND: [0002] 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 (enhanced UTRAN), no RNC exists and most of the RNC functionalities are contained in the enhanced Node B (eNodeB or eNB).

[0003] Long Term Evolution (LTE) or E-UTRAN refers to improvements of the UMTS through improved efficiency and services, lower costs, and use of new spectrum opportunities. In particular, LTE is a 3GPP standard that provides for uplink peak rates of at least 50 megabits per second (Mbps) and downlink peak rates of at least 100 Mbps. 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).

[0004] 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.

[0005] Certain releases of 3GPP LTE (e.g., LTE Rel-10, LTE Rel-1 1 , LTE Rel-12, LTE Rel-13) are targeted towards international mobile telecommunications advanced (IMT-A) systems, referred to herein for convenience simply as LTE-Advanced (LTE-A).

[0006] LTE-A is 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 keeping the backward compatibility. One the key features of LTE-A is carrier aggregation, which allows for increasing the data rates through aggregation of two or more LTE carriers.

SUMMARY:

[0007] One embodiment is directed to a method including configuring a channel state feedback into at least two feedback instances with reduced sizes for transmission over one or more physical feedback channels. The channel state feedback may include a codebook index, indices of channel, or precoder quantization. The method may further include encoding the codebook index, indices of channel, or precoder quantization of the channel state feedback, and filling the encoded codebook index, indices of channel, or precoder quantization into the at least two feedback instances of the one or more physical feedback channels.

[0008] In one embodiment, a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel. According to an embodiment, the configuring comprises periodicity, offset, and/or the number of feedback instances for the at least two feedback instances.

[0009] In an embodiment, the one or more physical feedback channels comprise a physical uplink control channel (PUCCH). The PUCCH, according to one embodiment, is PUCCH format 2/2a/2b. In certain embodiments, the set comprising the at least two feedback instances are consecutive in time. In an embodiment, the physical feedback channel is a Physical Uplink Shared Channel (PUSCH).

[00010] According to some embodiments, a user equipment may be configured to use a one bit report to indicate transmission of a new codebook or codebook enhancement in a following period. In an embodiment, the method may further include configuring periodical feedback for the new codebook or codebook enhancement. [00011] In one embodiment, the codebook index comprises a first precoding matrix indicator (PMI). According to an embodiment, presence of the new codebook or codebook enhancement may be indicated by an existing precoding type indicator (PTI) and the periodicity is the same as existing codebook. In another embodiment, the new codebook or codebook enhancement has its own periodicity and offset configuration. In certain embodiments, the one bit report is jointly encoded with a precoding type indicator (PTI) to indicate a presence of the new codebook or codebook enhancement in a next period.

[00012] Another embodiment is directed to an apparatus including 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 configure a codebook index, indices of channel, or precoder quantization into a set comprising at least two feedback instances, encode the codebook index, indices of channel, or precoder quantization, and fill the encoded codebook index, indices of channel, or precoder quantization into the set comprising the at least two feedback instances of a physical feedback channel.

[00013] Another embodiment is directed to a computer program, embodied on a computer readable medium. The computer program, when executed by a processor, causes the processor to perform a method including at least configuring a codebook index, indices of channel, or precoder quantization into a set comprising at least two feedback instances. The method may further include encoding the codebook index, indices of channel, or precoder quantization, and filling the encoded codebook index, indices of channel, or precoder quantization into the set comprising the at least two feedback instances of a physical feedback channel.

[00014] Another embodiment is directed to a method including receiving, from a user terminal, at least two feedback instances over one or more physical feedback channels.

The method may also include determining a channel state feedback using the at least two feedback instances. The channel state feedback comprises full channel state information available for a downlink communication to the user terminal.

[00015] In an embodiment, the method may further include configuring a codebook index, indices of channel, or precoder quantization of the channel state feedback into the at least two feedback instances over the one or more physical feedback channels. According to one embodiment, the method may further comprise decoding the codebook index, indices of channel, or precoder quantization of the channel state feedback based on the at least two feedback instances.

[00016] In an embodiment, a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel. According to one embodiment, the configuring comprises at least one of periodicity, offset, or the number of feedback instances for the at least two feedback instances. In one embodiment, the one or more physical feedback channels comprise a physical uplink control channel (PUCCH).

[00017] Another embodiment is directed to an apparatus including 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 receive, from a user terminal, at least two feedback instances over one or more physical feedback channels, and to determine a channel state feedback using the at least two feedback instances. The channel state feedback may comprise full channel state information available for a downlink communication to the user terminal.

[00018] In one embodiment, the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to configure a codebook index, indices of channel, or precoder quantization of the channel state feedback into the at least two feedback instances over the one or more physical feedback channels. According to an embodiment, the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to decode the codebook index, indices of channel, or precoder quantization of the channel state feedback based on the at least two feedback instances.

[00019] In an embodiment, a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel. According to one embodiment, the configuring comprises at least one of periodicity, offset, or the number of feedback instances for the at least two feedback instances. In one embodiment, the one or more physical feedback channels comprise a physical uplink control channel (PUCCH).

BRIEF DESCRIPTION OF THE DRAWINGS:

[00020] For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

[00021] Fig. 1 illustrates an example block diagram, according to an embodiment;

[00022] Fig. 2a illustrates an example for implementing embodiments of the invention into current LTE periodical feedback;

[00023] Fig. 2b illustrates another example for implementing embodiments of the invention into current LTE periodical feedback; [00024] Fig. 2c illustrates another example for implementing embodiments of the invention into current LTE periodical feedback;

[00025] Fig. 3 illustrates a block diagram of an apparatus, according to one embodiment;

[00026] Fig. 4 illustrates a flow diagram of a method, according to one embodiment;

[00027] Fig. 5 illustrates a block diagram of an apparatus, according to another embodiment; and

[00028] Fig. 6 illustrates a flow diagram of a method, according to another embodiment.

DETAILED DESCRIPTION:

[00029] 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 embodiments of systems, methods, apparatuses, and computer program products for a periodical feedback design for three-dimensional (3D) multiple-input multiple-output (MIMO), as represented in the attached figures, is not intended to limit the scope of the invention, but is merely representative of selected embodiments of the invention.

[00030] 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.

[00031] Additionally, if desired, the different functions 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 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. [00032] Certain embodiments may relate to LTE or LTE-A systems, for example, and their further development with 3GPP LTE Rel-13. One embodiment focuses on the design aspects of 3D-MIMO, such as channel state information (CSI) feedback or reporting. A channel state feedback report or instance for a downlink communication may comprise various channel state information available, for example, channel quality indicators (CQI), precoding matrix indicator (PMI) and rank indicator (Rl). For example, a channel state feedback instance, or simply a feedback instance, may comprise a codebook index, indices of channel, or precoder quantization for a corresponding downlink communication.

[00033] Precoding may refer to a technique of beamforming to support multi-layer transmission in multi-antenna wireless communications. Precoding modifies the layer signals before transmission. The precoding choices are defined in a lookup table known as the codebook. The codebook based precoding is an approach adopted by LTE, which fixes a common codebook comprising a set of vectors and matrices at both the transmitter and the receiver. A codebook may be used, for example, to quantize the available options and thus limit the amount of information fed back from the receiver to the transmitter.

[00034] Multi-antenna/MIMO techniques such as closed loop precoding in elevation domain have received a lot of attention in the 3GPP for many years. A key design aspect in all closed loop MIMO related features is the channel state information (CSI) feedback (e.g., consisting of one or more of channel quality indicators (CQI), precoding matrix indicator (PMI) and rank indicator (Rl)) provided by the user equipment (UE) that helps the eNodeB (eNB) in selecting the transmission parameters so that the sector/UE throughput is maximized. From that point of view, feedback is a key in the design of any close loop MIMO scheme. Considering 3D-MIMO relies on a large number of antenna elements (e.g., typically more than 8 antenna ports are needed) to improve the total performance, accurate CSI is especially important. Performance enhancement may be achieved with more bits of CSI feedback.

[00035] Current periodical feedback systems are designed to use physical uplink control channel (PUCCH) format 2/2a/2b to carry RI/PMI/CQI. The payload size of PUCCH format 2/2a/2b is 1 1 bits maximum. It would be difficult to enlarge the payload size since it would entail a new PUCCH channel design requiring a heavy standardization effort. In view of this issue, embodiments enable the use of current PUCCH format 2/2a/2b to carry larger payload size. In particular, certain embodiments support larger feedback bits (e.g., ~20bits) without changing the PUCCH format 2/2a/2b.

[00036] In order to reuse the existing PUCCH format, embodiments are able to encode one channel state feedback or report into two or more channel feedback instances with reduced sizes over one or multiple physical feedback channels such as PUCCHs. For example, one large PMI report may be encoded into two or more PMI feedback instances with reduced sizes over one or multiple physical feedback channels, such as PUCCHs. Fig. 1 illustrates an example block diagram depicting one embodiment of the invention. In the example embodiment of Fig. 1 , W3 denotes the enhancement parts of CSI reports. For example, W3 may be a new codebook potentially for quantizing the elevation dimension of the channel or additional bits to enhance current W1 or W2 to support 3D-MIMO. The current W1 and W2 refers to the first PMI and the second PMI structure as defined in 3GPP 36.213 (LTE Rel-10 onwards).

[00037] Assuming as an example that W3 will be encoded into 2 PUCCH reports, then 40 coded bits can be carried by PUCCH format-2, denoted as W3-1 and W3-2 in Fig. 1 . Then, in an embodiment, a (A,40) encoding scheme can be applied. It should be noted, however, that other encoding schemes are also possible. In order to guarantee a similar reception quality as the current PUCCH format-2, a maximum of 22 information bits can be supported for W3, according to one embodiment.

[00038] Just as other PMI feedback, the eNB can configure periodical PUCCH feedback for W3, and the UE may report W3-1 and W-2 in consecutive PUCCH instances. The periodicity and offset of W3 report are configurable in the same way as W1 or W2 feedback. Fig. 1 illustrates an example of configured W3 report co-existing with W1 and W2 report. In this example, W3 has a higher priority than W1/W2 such that, when collision happens, W3 wins.

[00039] Also, to further enhance efficiency, certain embodiments may provide for a one bit report, namely 3D PTI, from the UE to indicate the presence of W3 feedback for a certain period of time. For example, when 3D_PTI=0, then UE will not report W3 until another 3D_PTI=1 is received. In some embodiments, 3D PTI may be jointly encoded with RI/PTI with a configurable periodicity and offset too, or 3D PTI could be implicitly indicated by existing precoding type indicator (PTI) and the periodicity of H' may be reused.

[00040] Therefore, according to an embodiment, a single CSI feedback or reporting may be split or mapped into multiple different CSI feedback instances with reduced sizes over one or more separate PUCCHs. For example, a codebook index of a large-size CSI feedback report is encoded and filled into two or more feedback instances with reduced sizes over one or multiple PUCCHs. In an embodiment, the codebook index of the large- size CSI feedback report may be a first PMI as defined in 3GPP 36.213. If codebook is not used in the large-size CSI feedback report, then indices of channel or precoder quantization (depending on the feedback method) in the large-size CSI feedback report may be encoded and filled into feedback instances with reduced sizes over one or multiple physical feedback channels, such as PUCCHs. In an embodiment, the UE can use one bit report to indicate the transmission of W3 in the following period.

[00041] Figs. 2a-2c illustrate examples for implementing embodiments of the invention into current LTE periodical feedback. Fig. 2a illustrates a first option in which the presence of W3 is implicitly indicated by existing PTI, and the periodicity is the same as existing H' (H=JK+1 ~> 10, J=3, K=3, MRI=2, H'=4).

[00042] Fig. 2b illustrates a second option in which W3 has its own periodicity and offset configuration, for example such that H=JK+1 -> 10, J=3, K=3, MRI=2, H'=4, H"=20 (where H" is the new configuration for the periodicity of W3).

[00043] Fig. 2c illustrates a third option in which W3 has its own periodicity and offset configuration, and 3D PTI is jointly encoded with PTI to indicate the presence of W3 in the next period, for example such that H=JK+1 -> 10, J=3, K=3, MRI=2, H'=4, H"=20 (where H" is the new configuration for the periodicity of W3).

[00044] Fig. 3 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, such as a base station or eNB in LTE. 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. 3.

[00045] As illustrated in Fig. 3, apparatus 10 includes a processor 22 for processing information and executing instructions or operations. Processor 22 may be any type of general or specific purpose processor. While a single processor 22 is shown in Fig. 3, multiple processors may be utilized according to other embodiments. In fact, processor 22 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.

[00046] Apparatus 10 may further include or be coupled to a memory 14 (internal or external), which may be coupled to processor 22, for storing information and instructions that may be executed by processor 22. 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, 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 22, enable the apparatus 10 to perform tasks as described herein.

[00047] Apparatus 10 may also include or be coupled to one or more antennas 25 for transmitting and receiving signals and/or data to and from apparatus 10. Apparatus 10 may further include or be coupled to a transceiver 28 configured to transmit and receive information. 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 10. In other embodiments, transceiver 28 may be capable of transmitting and receiving signals or data directly.

[00048] Processor 22 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.

[00049] In an embodiment, memory 14 may store 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 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.

[00050] In one embodiment, apparatus 10 may be a network node such as, for example, a UE. In this embodiment, apparatus 10 may be controlled by memory 14 and processor 22 to configure a (large size) CSI feedback reporting, comprising a codebook index, indices of channel, or precoder quantization, for example, into a set comprising at least two feedback instances with reduced sizes over one or multiple physical feedback channels such as PUCCHs. Apparatus 10 may be further controlled by memory 14 and processor 22 to encode the codebook index, indices of channel, or precoder quantization of the large-size CSI feedback, and fill the encoded codebook index, indices of channel, or precoder quantization into the set comprising the at least two feedback instances with reduced sizes of one or more physical feedback channels. In an embodiment, the physical feedback channel is a PUCCH. According to one embodiment, the PUCCHs are of PUCCH format 2/2a/2b.

[00051] In another embodiment, apparatus 10 may be a network node, such as a base station, eNB. In this embodiment, apparatus 10 may be controlled by memory 14 and processor 22 to configure a (large size) CSI feedback reporting, comprising a codebook index, indices of channel, or precoder quantization, for example, into a set comprising at least two feedback instances with reduced sizes over one or multiple physical feedback channels such as PUCCHs. Apparatus 10 may be further controlled by memory 14 and processor 22 to receive the encoded codebook index, indices of channel, or precoder quantization from the set comprising the at least two feedback instances with reduced sizes of one or more physical feedback channels. In an embodiment, the physical feedback channel is a PUCCH. According to one embodiment, the PUCCHs are of PUCCH format 2/2a/2b.

[00052] In an embodiment, the codebook index comprises a first precoding matrix indicator (PMI). Then, a one bit report may be used to indicate transmission of a new codebook or codebook enhancement in a following period. According to an embodiment, apparatus 10 may be controlled by memory 14 and processor 22 to configure periodical feedback for the new codebook or codebook enhancement. In one embodiment, up to 22 information bits may be supported for the new codebook or the codebook enhancement.

[00053] In one embodiment, the presence of the new codebook or codebook enhancement may be implicitly indicated by an existing precoding type indicator (PTI) and the periodicity is the same as an existing codebook. In another embodiment, the new codebook or the codebook enhancement has its own periodicity and offset configuration. According to one embodiment, the one bit report may be jointly encoded with a precoding type indicator (PTI) to indicate the presence of the new codebook or the codebook enhancement in a next period.

[00054] Fig. 4 illustrates an example of a flow diagram of a method, according to an embodiment. In one embodiment, the method may be performed by a mobile device or UE, for instance.

[00055] As illustrated in Fig. 4, the method may include, at 400, configure a CSI feedback or reporting, comprising a codebook index, indices of channel, or precoder quantization, for example, into a set comprising at least two feedback instances with reduced sizes.

[00056] The method may also include, at 410, encoding or mapping the codebook index, indices of channel, or precoder quantization of the large-size CSI report into feedback instances with reduced sizes for transmission over one or more different physical feedback channels such as PUCCHs. According to an embodiment, the reduced-size feedback instances may be consecutive in time over one physical feedback channel. According to another embodiment, the reduced-size feedback instances may be concurrent in time over two or more different physical feedback channels.

[00057] The method may further include, at 420, filling the encoded codebook index, indices of channel, or precoder quantization into the set comprising the at least two feedback instances of one or more physical feedback channels.

[00058] Fig. 5 illustrates a block diagram of an apparatus 500, according to an embodiment. The apparatus 500 may include a splitting unit 505, encoding unit 510, and transceiver unit 515. In an embodiment, the splitting unit 505 is configured to split a single CSI feedback or reporting over a physical feedback channel such as PUCCH into two or more CSI feedback instances with reduced sizes over one or multiple physical feedback channels such as PUCCHs. The encoding unit 510 may be configured to encode a codebook index, indices of channel, or precoder quantization of the initial single CSI feedback, and to fill the encoded codebook index, indices of channel, or precoder quantization into two or more CSI feedback instances over the one or multiple physical uplink control channels such as PUCCHs. In an embodiment, a one bit report may be used to indicate transmission of a new codebook or codebook enhancement in a following period. According to an embodiment, apparatus 500 may configure periodical feedback for the new codebook or codebook enhancement. In one embodiment, up to 22 information bits may be supported for the new codebook or the codebook enhancement.

[00059] Fig. 6 illustrates an example of a flow diagram of a method, according to another embodiment. In one embodiment, the method may be performed by a base station or eNB, for example. The method may include, at 600, receiving, from a user terminal, at least two feedback instances over one or more physical feedback channels. The method may then include, at 610, determining a channel state feedback using the at least two feedback instances. The channel state feedback may comprise full channel state information available for a downlink communication to the user terminal.

[00060] In some embodiments, the functionality of any of the methods described herein, such as those illustrated in Figs. 4 and 6 discussed above, may be implemented by software and/or computer program code stored in memory or other computer readable or tangible media, and executed by a processor. In other embodiments, the functionality may be performed by hardware, 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.

[00061] 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

WE CLAIM:

1 . A method, comprising: configuring a channel state feedback into at least two feedback instances with reduced sizes for transmission over one or more physical feedback channels.

2. The method according to claim 1 , wherein the channel state feedback comprises a codebook index, indices of channel, or precoder quantization.

3. The method according to claim 1 , further comprising: encoding codebook index, indices of channel, or precoder quantization of the channel state feedback; and filling the encoded codebook index, indices of channel, or precoder quantization into the at least two feedback instances of the one or more physical feedback channels.

4. The method according to claim 1 , wherein a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel.

5. The method according to claim 1 , wherein the configuring comprises at least one of periodicity, offset, or the number of feedback instances for the at least two feedback instances.

6. The method according to any one of claims 1 -5, wherein the one or more physical feedback channels comprise a physical uplink control channel (PUCCH).

7. The method according to any one of claims 1 -6, wherein the at least two feedback instances are consecutive in time.

8. The method according to claim 1 , wherein user equipment is configured to use a one bit report to indicate transmission of a new codebook or codebook enhancement in a following period.

9. The method according to claim 8, further comprising configuring periodical feedback for the new codebook or codebook enhancement.

10. The method according to claim 6, wherein the physical uplink control channel (PUCCH) is of physical uplink control channel (PUCCH) format 2/2a/2b.

1 1 . The method according to claim 1 , wherein the codebook index comprises a first precoding matrix indicator (PMI).

12. The method according to claim 8, wherein a presence of the new codebook or codebook enhancement is indicated by an existing precoding type indicator (PTI) and periodicity is same as existing codebook.

13. The method according to claim 8, wherein the new codebook or codebook enhancement has its own periodicity and offset configuration.

14. The method according to claim 8, wherein the one bit report is jointly encoded with a precoding type indicator (PTI) to indicate a presence of the new codebook or codebook enhancement in a next period.

15. An apparatus, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured, with the at least one processor, to cause the apparatus at least to configure a channel state feedback into at least two feedback instances with reduced sizes for transmission over one or more physical feedback channels.

16. The apparatus according to claim 15, wherein the channel state feedback comprises a codebook index, indices of channel, or precoder quantization.

17. The apparatus according to claim 15, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to: encode codebook index, indices of channel, or precoder quantization of the channel state feedback; and fill the encoded codebook index, indices of channel, or precoder quantization into the at least two feedback instances of the one or more physical feedback channels.

18. The apparatus according to claim 15, wherein a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel.

19. The apparatus according to claim 15, wherein the configuring comprises at least one of periodicity, offset, or the number of feedback instances for the at least two feedback instances.

20. The apparatus according to any one of claims 15-19, wherein the one or more physical feedback channels comprise a physical uplink control channel (PUCCH).

21 . The apparatus according to any one of claims 15-20, wherein the at least two feedback instances are consecutive in time.

22. The apparatus according to claim 15, wherein user equipment is configured to use a one bit report to indicate transmission of a new codebook or codebook enhancement in a following period.

23. The apparatus according to claim 22, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to configure periodical feedback for the new codebook or codebook enhancement.

24. The apparatus according to claim 20, wherein the physical uplink control channel is of physical uplink control channel (PUCCH) format 2/2a/2b.

25. The apparatus according to claim 15, wherein the codebook index comprises a first precoding matrix indicator (PMI).

26. The apparatus according to claim 22, wherein a presence of the new codebook or codebook enhancement is implicitly indicated by an existing precoding type indicator (PTI) and periodicity is same as existing codebook.

27. The apparatus according to claim 22, wherein the new codebook or codebook enhancement has its own periodicity and offset configuration.

28. The apparatus according to claim 22, wherein the one bit report is jointly encoded with a precoding type indicator (PTI) to indicate a presence of the new codebook or codebook enhancement in a next period.

29. A computer program, embodied on a computer readable medium, the computer program, when executed by a processor, causes the processor to perform a method according to any one of claims 1 -14.

30. A method, comprising: receiving from a user terminal, at least two feedback instances over one or more physical feedback channels; and determining a channel state feedback using the at least two feedback instances, wherein the channel state feedback comprises full channel state information available for a downlink communication to the user terminal.

31 . The method according to claim 30, further comprising configuring a codebook index, indices of channel, or precoder quantization of the channel state feedback into the at least two feedback instances over the one or more physical feedback channels.

32. The method according to claim 31 , further comprising decoding the codebook index, indices of channel, or precoder quantization of the channel state feedback based on the at least two feedback instances.

33. The method according to claim 30, wherein a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel.

34. The method according to claim 30, wherein the configuring comprises at least one of periodicity, offset, or the number of feedback instances for the at least two feedback instances.

35. The method according to any one of claims 30-34, wherein the one or more physical feedback channels comprise a physical uplink control channel (PUCCH).

36. An apparatus, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured, with the at least one processor, to cause the apparatus at least to receive, from a user terminal, at least two feedback instances over one or more physical feedback channels; and determine a channel state feedback using the at least two feedback instances, wherein the channel state feedback comprises full channel state information available for a downlink communication to the user terminal.

37. The apparatus according to claim 36, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to configure a codebook index, indices of channel, or precoder quantization of the channel state feedback into the at least two feedback instances over the one or more physical feedback channels.

38. The apparatus according to claim 37, wherein the at least one memory and the computer program code are further configured, with the at least one processor, to cause the apparatus at least to decode the codebook index, indices of channel, or precoder quantization of the channel state feedback based on the at least two feedback instances.

39. The apparatus according to claim 36, wherein a feedback instance comprises physical resources within a subframe corresponding to one physical feedback channel.

40. The apparatus according to claim 36, wherein the configuring comprises at least one of periodicity, offset, or the number of feedback instances for the at least two feedback instances.

41 . The apparatus according to any one of claims 36-41 , wherein the one or more physical feedback channels comprise a physical uplink control channel (PUCCH).

42. A computer program, embodied on a computer readable medium, the computer program, when executed by a processor, causes the processor to perform a method according to any one of claims 30-35.