TECHNICAL FIELD

The present disclosure relates to a pre-5th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4th-Generation (4G) communication system such as Long-Term Evolution (LTE). More particularly, the present disclosure is directed to hybrid CSI acquisition for generating multi-user precoders for multi-user multi-input multi-output (MU-MIMO) antennas.

BACKGROUND

To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.

The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.

In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.

Downlink (DL) massive MIMO (mMIMO) systems have mainly been implemented for time division duplex (TDD) bands, in which uplink (UL) & DL channel reciprocity holds. Exploiting channel reciprocity, DL channel state information (CSI) on the full DL band can be acquired at the base station (BS) using UL sounding reference signals (SRS) channel estimates. Relying on this full bandwidth DL CSI, frequency-selective multi-user MIMO (MU-MIMO) precoding can be performed. This frequency-selective precoding important to demonstrate the MU-MIMO performance gain over single-user MIMO (SU-MIMO). For frequency division duplex (FDD) bands, channel reciprocity does not hold in general. The channels in the UL BW are not the same as those in DL BW.

SUMMARY

Embodiments of the present disclosure include a base station, a method, and a computer-readable medium for generating multi-user precoders.

One embodiment is directed to a base station that includes a transceiver configured to receive one or more sounding reference signals (SRSs) from a set of user equipments (UEs), and a processor operably connected to the transceiver, which is configured to select, for one or more UEs in the set of UEs, one or more codewords from an uplink codebook based on a correlation between the one or more codewords and the one or more SRSs; determine, using a composite downlink codebook, downlink codewords for the selected uplink codewords, respectively, the composite downlink codebook mapping uplink codewords to downlink codewords based on steering angles derived from the uplink codewords; and transmit a set of pre-coded channel state information reference signals (CSI-RSs) to the one or more UEs. The pre-coded CSI-RSs are pre-coded based on the determined downlink codewords. The processor is also configured to identify a downlink channel matrix based on CSI feedback from the one or more UEs and the pre-coded CSI-RSs.

In another embodiment, a method for generating multi-user precoders is disclosed. The method includes receiving one or more sounding reference signals (SRSs) from a set of user equipments (UEs); selecting, for one or more UEs in the set of UEs, one or more codewords from an uplink codebook based on a correlation between the one or more codewords and the one or more SRSs; determining, using a composite downlink codebook, downlink codewords for the selected uplink codewords, respectively, the composite downlink codebook mapping uplink codewords to downlink codewords based on steering angles derived from the uplink codewords; and transmitting a set of pre-coded channel state information reference signals (CSI-RSs) to the one or more UEs. The pre-coded CSI-RSs are pre-coded based on the determined downlink codewords. The method also includes identifying a downlink channel matrix based on CSI feedback from the one or more UEs and the pre-coded CSI-RSs.

In yet another embodiment a non-transitory, computer-readable medium is disclosed. The non-transitory, computer-readable medium stores instructions that, when executed by a processor of a base station, cause the base station to receive one or more sounding reference signals (SRSs) from a set of user equipments (UEs); select, for one or more UEs in the set of UEs, one or more codewords from an uplink codebook based on a correlation between the one or more codewords and the one or more SRSs; determine, using a composite downlink codebook, downlink codewords for the selected uplink codewords, respectively, the composite downlink codebook mapping uplink codewords to downlink codewords based on steering angles derived from the uplink codewords; and transmit a set of pre-coded channel state information reference signals (CSI-RSs) to the one or more UEs. The pre-coded CSI-RSs are pre-coded based on the determined downlink codewords. The non-transitory, computer-readable medium also stores instructions that, when executed by a processor of a base station, cause the base station to identify a downlink channel matrix based on CSI feedback from the one or more UEs and the pre-coded CSI-RSs.

Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The term “couple” and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms “transmit,” “receive,” and “communicate,” as well as derivatives thereof, encompass both direct and indirect communication. The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation. The term “or” is inclusive, meaning and/or. The phrase “associated with,” as well as derivatives thereof, means to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” means any device, system or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of: A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C. Likewise, the term “set” means one or more. Accordingly, a set of items can be a single item or a collection of two or more items.

Moreover, various functions described below can be implemented or supported by one or more computer programs, each of which is formed from computer readable program code and embodied in a computer readable medium. The terms “application” and “program” refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in a suitable computer readable program code. The phrase “computer readable program code” includes any type of computer code, including source code, object code, and executable code. The phrase “computer readable medium” includes any type of medium capable of being accessed by a computer, such as read only memory (ROM), random access memory (RAM), a hard disk drive, a compact disc (CD), a digital video disc (DVD), or any other type of memory. A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transport transitory electrical or other signals. A non-transitory computer readable medium includes media where data can be permanently stored and media where data can be stored and later overwritten, such as a rewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many if not most instances, such definitions apply to prior as well as future uses of such defined words and phrases.

