Methods for selecting precoding vectors for multi-point MIMO (multiple-input-multiple-output) communications and related wireless termainals and radio network nodes

Patent metadata

Field	Value
Publication number	US-9300369-B2
Application number	US-201514717719-A
Country	US
Kind code	B2
Filing date	May 20, 2015
Priority date	Jan 27, 2012
Publication date	Mar 29, 2016
Grant date	Mar 29, 2016

Abstract

A wireless terminal may receive multiple-input-multiple-output (MIMO) downlink communications from a wireless communication network including a plurality of base station sector antenna arrays using a codebook of precoding vectors. MIMO downlink communications may be received from the wireless communication. When receiving the MIMO downlink communications as multi-point MIMO downlink communications from first and second base station sector antenna arrays of the plurality of base station sector antenna arrays, a precoding vector may be selected for the multi-point MIMO downlink communications from only a subset of the precoding vectors of the codebook.

First claim

What is claimed is:

1. A method of operating a wireless terminal in a wireless communication network providing multiple-input-multiple-output (MIMO) downlink communications from a plurality of base station sector antenna arrays using a codebook of precoding vectors, the method comprising:
during multi-point MIMO downlink communications with first and second base station sector antenna arrays, estimating first channel characteristics for a first downlink channel from the first base station sector antenna array to the wireless terminal and second channel characteristics for a second downlink channel from the second base station sector antenna array to the wireless terminal;
during the multi-point MIMO downlink communications with the first and second base station sector antenna arrays, selecting first and second precoding vectors for the multi-point MIMO downlink communications from a subset of the precoding vectors of the codebook, wherein the first precoding vector is selected based on estimating the first channel characteristics for the first downlink channel, wherein the second precoding vector is selected based on estimating the second channel characteristics for the second downlink channel, and wherein selection of the first and second precoding vectors is restricted to the subset of the precoding vectors of the codebook during the multi-point MIMO downlink communications; and
transmitting respective first and second identifications of the respective first and second precoding vectors selected for the multi-point MIMO downlink communications.

2. The method of Claim 1 further comprising:
during single-point MIMO downlink communications with the first base station sector antenna array, estimating channel characteristics for the first downlink channel between the wireless terminal and the first base station sector antenna array; and
during the single-point MEMO downlink communications with the first base station sector antenna array, selecting a third precoding vector fbr the single-point MEMO downlink communications based on estimating the channel characteristics for the first downlink channel during the single-point MEMO downlink communications, wherein the third precoding vector is selected from any of the precoding vectors of the codebook.

3. The method of claim 1 wherein the codebook includes rank 1 precoding vectors supporting one layer of MEMO downlink data transmission from a base station sector antenna array and rank 2 precoding vectors supporting two layers of downlink data transmission from a base station sector antenna array, wherein the subset of the precoding vectors includes the rank 1 precoding vectors and excludes the rank 2 precoding vectors, and wherein selection of the first and second precoding vectors is restricted to the rank 1 precoding vectors during the multi-point MIMO downlink communications with the first and second base station sector antenna arrays.

4. The method of Claim 1 further comprising:
during the multi-point MIMO downlink communications with the first and second base station sector antenna arrays, computing Signal-to-Noise-Ratios, SNRs, for the subset of the precoding vectors for the first downlink channel between the wireless terminal and the first base station sector antenna array and for the subset of the precoding vectors for the second downlink channel between the wireless terminal and the second base station sector antenna array without computing SNRs for precoding vectors of the codebook outside the subset;
wherein selecting the first and second precoding vectors comprises selecting the first and second precoding vectors based on the SNRs computed for the subset of the precoding vectors.

5. A method of operating a node in a wireless communication network providing multiple-input-multiple-output (MIMO) downlink communications from a plurality of base station sector antenna arrays using a codebook of precoding vectors, the method comprising:
during multi-point MIMO downlink communications from first and second base station sector antenna arrays of the plurality of base station sector antenna arrays to a wireless terminal, selecting a precoding vector for the multi-point MIMO downlink communications from a subset of the precoding vectors of the codebook, wherein selecting comprises selecting the precoding vector at the node in the wireless communication network providing MIMO downlink communication, and wherein selection of the precoding vector is restricted to the subset of the precoding vectors of the codebook during the multipoint MIMO downlink communications.

6. The method of claim 5 further comprising:
during single-point MIMO downlink communications from only one base station sector antenna array to the wireless terminal, selecting at the node in the wireless communication network a precoding vector for the single-point MIMO downlink communications from any of the precoding vectors of the codebook.

7. The method of claim 5 wherein the codebook includes rank 1 precoding vectors supporting one layer of MEMO downlink data transmission from a base station sector antenna array to the wireless terminal and rank 2 precoding vectors supporting two layers of downlink data transmission from a base station sector antenna array to the wireless terminal, wherein the subset of the precoding vectors includes the rank 1 precoding vectors and excludes the rank 2 precoding vectors, and wherein selection of the precoding vector is restricted to the rank 1 precoding vectors during the multi-point MIMO downlink communications.

8. The method of claim 5 wherein selecting the precoding vector for the multi-point MIMO downlink communications comprises selecting a first precoding vector for a downlink channel between the wireless terminal and the first base station sector antenna array and selecting a second precoding vector for a downlink channel between the wireless terminal and the second base station sector antenna array, wherein selection of the first precoding vector is restricted to the subset of the precoding vectors of the codebook during the multi-point MIMO downlink communications, and wherein selection of the second precoding vector is restricted to the subset of the precoding vectors of the codebook during the multi-point MIMO downlink communications.

9. The method of claim 5 further comprising:
after selecting the precoding vector, transmitting downlink communications from the node to the wireless terminal during the multi-point MIMO downlink communications using the precoding vector selected from the subset for the downlink communications.

10. The method of claim 5 further comprising:
receiving channel quality information from the wireless terminal wherein the channel quality information includes an identification of a recommended rank 2 precoding vector of the codebook of precoding vectors;
wherein selecting the precoding vector for the multi-point MIMO downlink communications comprises forcing selection of the precoding vector for the multi-point downlink communications from the subset of the precoding vectors to override the recommended rank 2 precoding vector.

11. The method of claim 5 wherein the node comprises a base station of the wireless communication network.

12. A method of operating a node in a wireless communication network providing multiple-input-multiple-output (MIMO) downlink communications from a plurality of base station sector antenna arrays using a codebook of precoding vectors, the method comprising:
transmitting MIMO downlink communications from the wireless communication network to a wireless terminal;
receiving channel quality information from the wireless terminal wherein the chan

Assignees

• Ericsson Telefon Ab L M
• Ericsson Telefon Ab L M

Inventors

• Nammi Sairamesh
• Miao Qingyu
• Von Wrycza Peter

Classifications

• H04B7/0486

  taking channel rank into account · CPC title

• H04B7/0639

  Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection · CPC title

• H04B7/046 Primary

  taking physical layer constraints into account · CPC title

• H04B7/0495 Primary

  using overlapping sectors in the same base station to implement MIMO for antennas · CPC title

• H04B7/024 Primary

  Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems · CPC title