METHOD AND APPARATUS FOR TRANSMITTING DOWNLINK REFERENCE SIGNAL IN WIRELESS COMMUNICATION SYSTEM THAT SUPPORTS MULTIPLE ANTENNAS

• US 20120134334A1
• Filed: 08/13/2010
• Published: 05/31/2012
• Est. Priority Date: 08/14/2009
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Ko, Hyun Soo, Han, Seung Hee, Chung, Jae Hoon, Ihm, Bin Chul, Lee, Moon Il
• Granted Patent: US 8,717,994 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04L 5/0057 Physical resource allocation for CQI
• CPC Class Codes: H04L 5/0094 Indication of how sub-channels of the path are allocated
• CPC Class Codes: H04W 52/325 Power control of control or pilot channels
• CPC Class Codes: H04W 72/02 Selection of wireless resources by user or terminal
• CPC Class Codes: H04W 72/04 Wireless resource allocation
• CPC Class Codes: H04W 72/542 using measured or perceived quality
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for transmitting a reference signal for a maximum of eight antenna ports includes mapping a portion of common reference signals (CRSs) for a maximum of four antenna ports into a downlink subframe that includes a 1^st slot and a 2^nd slot; mapping channel status information reference signals (CSI-RSs) for the maximum of eight antenna ports into the downlink subframe according to a preset pattern; and transmitting the downlink subframe into which the common reference signal and the channel status information reference signal are mapped, wherein the preset pattern defines the CSI-RSs for the maximum of eight antenna ports to be mapped onto two OFDM symbols of the data region in the downlink subframe, and wherein the portion of the CRSs for the maximum of four antenna ports is limited to the CRSs for a maximum of two antenna ports.

Claims

1. A method for transmitting reference signals for 8 or fewer antenna ports at a base station, the method comprising:

mapping some of common reference signals (CRSs) for four or fewer antenna ports to a downlink subframe including a first slot and a second slot;

mapping channel state information-reference signals (CSI-RSs) for the 8 or fewer antenna ports to the downlink subframe according to a predetermined pattern; and

transmitting the downlink subframe to which the CRSs and the CSI-RSs are mapped,

wherein the predetermined pattern defines the CSI-RSs for the 8 or fewer antenna ports to be mapped to two orthogonal frequency division multiplexing (OFDM) symbols in a data region of the downlink subframe, and

wherein some of the CRSs for the 4 or fewer antenna ports are limited to CRSs for 2 or fewer antenna ports.

2. The method according to claim 1, wherein the downlink subframe has an extended cyclic prefix (CP).

3. The method according to claim 2, wherein the CRSs for the 2 or fewer antenna ports are mapped to first and fourth OFDM symbols of the first slot and first and fourth OFDM symbols of the second slot.

4. The method according to claim 2, wherein the two OFDM symbols defined in the predetermined pattern for the CSI-RSs are fifth and sixth OFDM symbols of the first slot, second and third OFDM symbols of the second slot or fifth and sixth OFDM symbols of the second slot.

5. The method according to claim 1, wherein the predetermined pattern defines the CSI-RSs for the 8 or fewer antenna ports to be mapped to one or more of four subcarrier locations in each of the two OFDM symbols, and

wherein, in the four subcarrier locations defined in the predetermined pattern, the four subcarriers are separated from each other by 2 subcarriers.

6. The method according to claim 5, wherein the four subcarrier locations defined in the predetermined pattern are shifted by 1 subcarrier on a per cell or cell group basis.

7. The method according to claim 5, wherein, if the two OFDM symbols are the first and sixth OFDM symbols of the first slot, the four subcarrier locations are subcarrier indexes 0, 3, 6 and 9 or subcarrier indexes 2, 5, 8 and 11,

wherein, if the two OFDM symbols are the second and third OFDM symbols of the second slot, the four subcarrier locations are subcarrier indexes 0, 3, 6 and 9, subcarrier indexes 1, 4, 7 and 10 or subcarrier indexes 2, 5, 8 and 11, and

wherein, if the two OFDM symbols are the fifth and sixth OFDM symbols of the second slot, the four subcarrier locations are subcarrier indexes 1, 4, 7 and 10 or subcarrier indexes 2, 5, 8 and 11.

8. The method according to claim 1, wherein, if the number of antenna ports of the base station is 2 or 4, the CSI-RSs are mapped to some of the locations defined in the predetermined pattern.

9. The method according to claim 1, wherein the CSI-RSs for the 8 or fewer antenna ports are grouped into a total of four groups such that CSI-RSs for two antenna ports configure one group,

wherein the CSI-RSs for two antennas of each of the four groups are multiplexed at the same subcarrier location of the two OFDM symbols using a code division multiplexing (CDM) scheme, and

wherein the four groups are multiplexed at different subcarrier locations using a frequency division multiplexing (FDM) scheme.

10. A method of, at a user equipment, estimating a channel using channel state information-reference signals (CSI-RSs) for 8 or fewer antenna ports from a base station, the method comprising:

receiving a downlink subframe including a first slot and a second slot, to which some of common reference signals (CRSs) for four or fewer antenna ports are mapped and to which channel state information-reference signals (CSI-RSs) for the 8 or fewer antenna ports are mapped according to a predetermined pattern; and

estimating the channel using the CSI-RSs,

wherein the predetermined pattern defines the CSI-RSs for the 8 or fewer antenna ports to be mapped to two orthogonal frequency division multiplexing (OFDM) symbols in a data region of the downlink subframe, and

wherein some of the CRSs for the 4 or fewer antenna ports are limited to CRSs for 2 or fewer antenna ports.

11. The method according to claim 10, wherein the downlink subframe has an extended cyclic prefix (CP).

12. The method according to claim 11, wherein the CRSs for the 2 or fewer antenna ports are mapped to first and fourth OFDM symbols of the first slot and first and fourth OFDM symbols of the second slot.

13. The method according to claim 11, wherein the two OFDM symbols defined in the predetermined pattern for the CSI-RSs are fifth and sixth OFDM symbols of the first slot, second and third OFDM symbols of the second slot or fifth and sixth OFDM symbols of the second slot.

14. The method according to claim 10, wherein the predetermined pattern defines the CSI-RSs for the 8 or fewer antenna ports to be mapped to one or more of four subcarrier locations in each of the two OFDM symbols, and

wherein, in the four subcarrier locations defined in the predetermined pattern, the four subcarriers are separated from each other by 2 subcarriers.

15. The method according to claim 14, wherein the four subcarrier locations defined in the predetermined pattern are shifted by 1 subcarrier on a per cell or cell group basis.

16. The method according to claim 14, wherein, if the two OFDM symbols are the first and sixth OFDM symbols of the first slot, the four subcarrier locations are subcarrier indexes 0, 3, 6 and 9 or subcarrier indexes 2, 5, 8 and 11,

wherein, if the two OFDM symbols are the second and third OFDM symbols of the second slot, the four subcarrier locations are subcarrier indexes 0, 3, 6 and 9, subcarrier indexes 1, 4, 7 and 10 or subcarrier indexes 2, 5, 8 and 11, and

wherein, if the two OFDM symbols are the fifth and sixth OFDM symbols of the second slot, the four subcarrier locations are subcarrier indexes 1, 4, 7 and 10 or subcarrier indexes 2, 5, 8 and 11.

17. The method according to claim 10, wherein, if the number of antenna ports of the base station is 2 or 4, the CSI-RSs are mapped to some of the locations defined in the predetermined pattern.

18. The method according to claim 10, wherein the CSI-RSs for the 8 or fewer antenna ports are grouped into a total of four groups such that CSI-RSs for two antenna ports configure one group,

wherein the CSI-RSs for two antennas of each of the four groups are multiplexed at the same subcarrier location of the two OFDM symbols using a code division multiplexing (CDM) scheme, and

wherein the four groups are multiplexed at different subcarrier locations using a frequency division multiplexing (FDM) scheme.

19. A base station for transmitting reference signals (RSs) for 8 or fewer antenna ports, comprising:

a reception module configured to receive an uplink signal from a user equipment;

a transmission module configured to transmit a downlink signal to the user equipment; and

a processor configured to control the base station including the reception module and the transmission module,

wherein the processor maps some of common reference signals (CRSs) for four or fewer antenna ports to a downlink subframe including a first slot and a second slot, maps channel state information-reference signals (CSI-RSs) for the 8 or fewer antenna ports to the downlink subframe according to a predetermined pattern, and controls transmission of the downlink subframe to which the CRSs and the CSI-RSs are mapped,

wherein the predetermined pattern defines the CSI-RSs for the 8 or fewer antenna ports to be mapped to two orthogonal frequency division multiplexing (OFDM) symbols in a data region of the downlink subframe, and

wherein some of the CRSs for the 4 or fewer antenna ports are limited to CRSs for 2 or fewer antenna ports.

20. A user equipment for estimating a channel using channel state information-reference signals (CSI-RSs) for 8 or fewer antenna ports from a base station, comprising:

a reception module configured to receive a downlink signal from the base station;

a transmission module configured to transmit an uplink signal to the base station; and

a processor configured to control the user equipment including the reception module and the transmission module,

wherein the processor receives a downlink subframe including a first slot and a second slot, to which some of common reference signals (CRSs) for four or fewer antenna ports are mapped and to which channel state information-reference signals (CSI-RSs) for the 8 or fewer antenna ports are mapped according to a predetermined pattern, and controls estimation of the channel using the CSI-RSs,

wherein the predetermined pattern defines the CSI-RSs for the 8 or fewer antenna ports to be mapped to two orthogonal frequency division multiplexing (OFDM) symbols in a data region of the downlink subframe, and

wherein some of the CRSs for the 4 or fewer antenna ports are limited to CRSs for 2 or fewer antenna ports.