METHOD FOR DETERMINING DEMODULATION REFERENCE SIGNAL IN THE UPLINK, UE AND UPLINK SYSTEM

• US 20110002412A1
• Filed: 07/13/2010
• Published: 01/06/2011
• Est. Priority Date: 12/26/2008
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Kayama, Hidetoshi, Zhang, Zhan, HOU, Xiaolin
• Granted Patent: US 8,432,994 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0667 of delayed versions of same signal using space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas
• CPC Class Codes: H04L 27/2607 Cyclic extensions

Abstract

The present invention discloses a method for determining an uplink demodulation reference signal (DMRS), which includes: taking one of multiple transmit antennas in the uplink as a base transmit antenna, taking other transmit antennas as subordinating transmit antennas and setting a DMRS for the base transmit antenna; establishing DMRS subordinating relationships between the base transmit antenna and each of the subordinating transmit antennas; and setting a DMRS for each of the subordinating transmit antennas according to the DMRS of the base transmit antenna and the DMRS subordinating relationship between the base transmit antenna and each of the subordinating transmit antennas. The present invention also provides a user equipment (UE) and an uplink system for providing DMRSs for multiple transmit antennas. The method, UE and system are applicable in both SU-MIMO transmission and MU-MIMO transmission.

Claims

1. A method for determining demodulation reference signal (DMRS) in the uplink, comprising:

taking one of multiple transmit antennas in the uplink as a base transmit antenna, taking other transmit antennas as subordinating transmit antennas and setting a DMRS for the base transmit antenna;

establishing DMRS subordinating relationships between the base transmit antenna and each of the subordinating transmit antennas, and setting a DMRS for each of the subordinating transmit antennas according to the DMRS of the base transmit antenna and the corresponding DMRS subordinating relationship.

2. The method according to claim 1, wherein setting a DMRS for the base transmit antenna comprises:

selecting a base sequence for the DMRS of the base transmit antenna;

obtaining a reference signal of the base transmit antenna by performing a cyclic shift to the base sequence; and

taking the reference signal as the DMRS of the base transmit antenna.

3. The method according to claim 2, wherein setting a DMRS for the base transmit antenna comprises:

calculating the reference signal of the base transmit antenna in accordance with formula r_u,v<sup>(α

)</sup>(n)=e<sup>jα

n</sup> r_u,v(n), 0≦

n>

M_sc^RS;

wherein r_u,v(n) refers to the base sequence, α

refers to a cyclic shift value of the base sequence, and M_sc^RS refers to the length of the base sequence.

4. The method according to claim 3, wherein establishing DMRS subordinating relationships between the base transmit antenna and each of the subordinating transmit antennas comprises:

maximizing the difference between the cyclic shift value of the DMRS of the base transmit antenna and that of each of the subordinating transmit antennas.

5. The method according to claim 3, wherein establishing DMRS subordinating relationships between the base transmit antenna and each of the subordinating transmit antennas comprises:

determining a cyclic shift value for the DMRS of the i_th subordinating transmit antenna in accordance with formula α

_i=2π

n_cs,i/C and formula

6. The method according to claim 5, wherein setting a DMRS for each of the subordinating transmit antennas according to the DMRS of the base transmit antenna and the corresponding DMRS subordinating relationship comprises:

calculating a reference signal for each of the subordinating transmit antennas according to the determined cyclic shift value of the DMRS of each of the subordinating transmit antennas and the base sequence of the DMRS of the base transmit antenna.

7. The method according to claim 3, wherein establishing DMRS subordinating relationships between the base transmit antenna and each of the subordinating transmit antennas comprises:

determining an uplink scheduling component of the cyclic shift value of the DMRS of the i_th subordinating transmit antenna in accordance with formula

8. The method according to claim 7, wherein setting a DMRS for each of the subordinating transmit antennas according to the DMRS of the base transmit antenna and the corresponding DMRS subordinating relationship comprises:

sending, by a base station, an uplink scheduling command to each user equipment (UE) corresponding to each of the subordinating transmit antennas, the uplink scheduling command comprising the uplink scheduling component of the cyclic shift value of the DMRS;

each UE calculating the cyclic shift value of its DMRS according to the uplink scheduling component after receiving the uplink scheduling command, and calculating the reference signal of the corresponding subordinating transmit antenna according to the base sequence of the base transmit antenna and the calculated cyclic shift value.

9. The method according to claim 1, further comprising:

the base station receiving the DMRSs sent by the multiple transmit antennas, performing Fast Fourier Transform to the received DMRSs and converting them from time domain to frequency domain, and multiplying the frequency-domain DMRSs by the complex conjugation of the DMRS of the base transmit antenna previously stored or calculated in the base station;

the base station performing Inverse Fast Fourier Transform to the DMRSs multiplied by the complex conjugation and converting them from the frequency domain to the time domain, and setting multiple channel impulse response regions for the DMRSs in the time domain;

the base station distinguishing multiple channel impulse responses corresponding to different transmit antennas within the channel impulse response regions according to the cyclic shift value of the DMRS of each of the transmit antennas, extracting the distinguished channel impulse responses respectively, and performing Fast Fourier Transform to the extracted channel impulse response corresponding to each transmit antenna and converting it from the time domain to the frequency domain.

10. The method according to claim 9, further comprising:

performing a frequency-domain windowing operation before performing the Inverse Fast Fourier Transform;

performing a frequency-domain dewindowing operation after performing the Fast Fourier Transform to the extracted channel impulse response corresponding to each transmit antenna.

11. The method according to claim 9, wherein setting a channel impulse response region for the DMRSs in the time domain comprises:

taking

12. The method according to claim 9, wherein setting a channel impulse response region of the DMRSs in the time domain comprises:

taking

13. A user equipment (UE), wherein the UE has multiple transmit antennas and a multiplier is set for each transmit antenna;

the UE further comprises;

a base sequence selection module and a demodulation reference signal (DMRS) subordination module;

the base sequence selection module is adapted to determine a base sequence for DMRSs of the multiple transmit antennas;

the DMRS subordination module is adapted to take one of the multiple transmit antennas as a base transmit antenna and take other transmit antennas as subordinating transmit antennas, establish subordinating relationships between a cyclic shift value of the DMRS of the base transmit antenna and that of each of the subordinating transmit antennas; and

determine the cyclic shift value of the DMRS of each subordinating transmit antenna according to the cyclic shift value of the DMRS of the base transmit antenna;

the multiplier set for each transmit antenna is adapted to multiply the cyclic shift value of the corresponding transmit antenna and the base sequence to obtain the DMRS of the corresponding transmit antenna.

14. The UE according to claim 13, wherein the DMRS subordination module is adapted to calculate the cyclic shift value of the DMRS of the i_th subordinating transmit antenna according to formula α

_i=2π

n_cs,i/C and formula

15. An uplink communication system, comprising:

a base station and multiple user equipments (UE), each of the UEs having one transmit antenna;

the base station is adapted to take one of the multiple transmit antennas of the multiple UEs as a base transmit antenna, take other transmit antennas as subordinating transmit antennas, and inform each UE of an uplink scheduling component of the cyclic shift value of corresponding demodulation reference signal (DMRS) through an uplink scheduling command, wherein DMRS subordinating relationships are established between the uplink scheduling component of the base transmit antenna and that of each of the subordinating transmit antennas;

each UE is adapted to calculate the DMRS according to the uplink scheduling component of the cyclic shift value informed by the base station and a base sequence of the DMRS of the base transmit antenna.

16. The system according to claim 15, wherein the base station is adapted to determine the uplink scheduling component of the cyclic shift value of the DMRS of the i_th transmit antenna according to formula

17. A method for determining demodulation reference signal (DMRS) in the uplink, comprising:

taking one of multiple first data streams as a base data stream, taking other first data streams as subordinating data streams and setting a DMRS for the base data stream;

establishing DMRS subordinating relationships between the base data stream and each of the subordinating data streams, and setting a DMRS for each of the subordinating data streams according to the DMRS of the base data stream and the corresponding DMRS subordinating relationship; and

precoding each first data stream together with the DMRS set for the first data stream to form one or more second data streams, each of the second data streams being sent out from one transmit antenna in the uplink.

18. The method according to claim 17, wherein setting a DMRS for the base data stream comprises:

calculating the reference signal of the base data stream in accordance with formula r_u,v<sup>(α

)</sup>(n)=e<sup>jα

n</sup> r_u,v(n), 0≦

n<

M_sc^RS;

wherein r_u,v(n) refers to a base sequence, α

refers to a cyclic shift value of the base sequence, and M_sc^RS refers to the length of the base sequence.

19. The method according to claim 17, wherein establishing DMRS subordinating relationships between the base data stream and each of the subordinating data streams comprises:

determining a cyclic shift value for the DMRS of the i_th subordinating data stream in accordance with formula α

_i=2π

n_cs,i/C and formula

20. The method according to claim 17, wherein establishing DMRS subordinating relationships between the base data stream and each of the subordinating data streams comprises:

determining an uplink scheduling component of the cyclic shift value of the DMRS of the i_th subordinating data stream in accordance with formula