Adaptive cyclic-shift based multiplexing

• US 10,644,737 B2
• Filed: 04/17/2017
• Issued: 05/05/2020
• Est. Priority Date: 09/30/2016
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Manolakos, Alexandros, Namgoong, June, Yang, Yang, Jiang, Jing
• Primary Examiner(s): Cadeau, Wednel
• Application Number:
  US15/488,881
• Publication Number:
  US 20180097534A1
• Time in Patent Office: 1,114 Days
• Field of Search: 375267
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04B 7/0865 Independent weighting, i.e. weights based on own antenna reception parameters
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/001 the frequencies being arranged in component carriers
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal

Abstract

Aspects of the present disclosure provide techniques for using cyclic-shifts in code division multiplexing to shift transmitted signals (e.g., reference signals, control signals, and/or data) from different antenna ports of the transmitting device. Particularly, for multiple-input multiple-output (MIMO) systems that multiply the capacity of a radio link by using multiple transmit and receive antennas to exploit multipath propagation, aspects of the present disclosure minimize interference at the receiving device by separating the signals from different antenna ports based on the channel impulse response (or delay spread) of each antenna port of the channel. In some examples, the transmitting device may maximize resource utilization by interleaving the reference signals, control signals, and/or data from a plurality of antenna ports while maintaining adequate spacing between each signal.

Claims

1. A method for wireless communications for a base station, comprising:

determining a first delay spread for a first antenna port of a first channel;

assigning a first pilot signal for the first antenna port to a first cyclic shift of a symbol of a subframe based at least in part on the first delay spread;

determining a second delay spread for a second antenna port of a second channel, wherein the first antenna port and the second antenna port are different;

determining a second cyclic shift of the symbol spaced from the first cyclic shift based on a maximum separation of the first channel for the first pilot signal and the second channel for a second pilot signal within the subframe;

assigning the second pilot signal for the second antenna port to the second cyclic shift of the symbol of the subframe based at least in part on one or both of the first delay spread or the second delay spread, wherein the first pilot signal and the second pilot signal are for a same pilot type;

determining remaining available cyclic shifts for the symbol of the subframe; and

multiplexing data on the remaining available cyclic shifts for the symbol, wherein the data is transmitted by one or both of the first antenna port or the second antenna port.

2. The method of claim 1, wherein determining the remaining available cyclic shifts for the symbol of the subframe comprises:

determining a number of cyclic shifts allocated to the first pilot signal and the second pilot signal based on the first delay spread and the second delay spread; and

adjusting a cyclic shift budget of the transmitting device for the symbol of the subframe by subtracting the number of cyclic shifts from the cyclic shift budget.

3. The method of claim 1, wherein multiplexing the data on the remaining available cyclic shifts for the symbol, comprises:

identifying the first antenna port or the second antenna port to transmit the multiplexed data on the symbol, wherein the first antenna port or the second antenna port is identified based on an estimation performed using pilot signals transmitted on a different orthogonal frequency-division multiplexing (OFDM) symbol.

4. The method of claim 1, further comprising:

transmitting the symbol of the subframe to a user equipment (UE).

5. The method of claim 1, wherein assigning the second pilot signal for the second antenna port to the second cyclic shift, comprises:

determining the second delay spread for the second antenna port of the second channel; and

assigning the second set of pilots for the second antenna port to the second cyclic shift based on a determination that the remaining available cyclic shifts would accommodate the second delay spread for the second antenna port and that the transmission of the second set of pilots using the second cyclic shift will not lead to interference to the first antenna port.

6. The method of claim 1, wherein:

the first delay spread identifies a channel impulse response of the first antenna port observed at the UE, and

the second delay spread identifies a channel impulse response of the second antenna port observed at the UE.

7. The method of claim 1, further comprising:

receiving a delay spread feedback from the UE;

determining an updated first delay spread or the second delay spread based on the delay spread feedback; and

adjusting a number of data symbols that can be multiplexed based on the available cyclic shifts after the delay spread adjusting.

8. The method of claim 1, wherein the first antenna port is a demodulation reference signal (DMRS) antenna port and the second antenna port is one of a channel state information-reference signal (CSI-RS), a cell-specific reference signal (CRS) antenna port, or tracking reference signal (TRS).

9. An apparatus for wireless communications, comprising:

a memory configured to store instructions;

a processor communicatively coupled with the memory, the processor configured to execute the instructions to;

determine a first delay spread for a first antenna port of a first channel;

assign a first pilot signal for the first antenna port to a first cyclic shift of a symbol of a subframe based at least in part on the first delay spread;

determine a second delay spread for a second antenna port of a second channel, wherein the first antenna port and the second antenna port are different;

determine a second cyclic shift of the symbol spaced from the first cyclic shift based on a maximum separation of the first channel for the first pilot signal and the second channel for a second pilot signal within the subframe;

assign the second pilot signal for the second antenna port to the second cyclic shift of the symbol of the subframe based at least in part on one or both of the first delay spread the second delay spread, wherein the first pilot signal and the second pilot signal are for a same pilot type;

determine remaining available cyclic shifts for the symbol of the subframe; and

multiplex data on the remaining available cyclic shifts for the symbol, wherein the data is transmitted by one or both of the first antenna port or the second antenna port.

10. The apparatus of claim 9, wherein the processor is configured to execute the instructions to determine the remaining available cyclic shifts for the symbol of the subframe further include instructions to:

determine a number of cyclic shifts allocated to the first pilot signal and the second pilot signal based on the first delay spread and the second delay spread; and

adjust a cyclic shift budget of the transmitting device for the symbol of the subframe by subtracting the number of cyclic shifts from the cyclic shift budget.

11. The apparatus of claim 9, wherein the processor is configured to execute the instructions to multiplex the data on the remaining available cyclic shifts for the symbol further include instructions to:

identify the first antenna port or the second antenna port to transmit the data on the symbol, wherein the first antenna port or the second antenna port is identified based on an estimation performed using pilot signals transmitted on a different orthogonal frequency-division multiplexing (OFDM) symbol.

12. The apparatus of claim 9, wherein the processor is configured to execute the instructions to:

transmit the symbol of the subframe to a user equipment (UE).

13. The apparatus of claim 9, wherein the instructions to assign the second set of pilots for the second antenna port to the second cyclic shift further include instructions to:

determine a second delay spread for the second antenna port of the second channel; and

assign the second set of pilots for the second antenna port to the second cyclic shift based on a determination that the remaining available cyclic shifts would accommodate the second delay spread for the second antenna port.

14. The apparatus of claim 9, wherein:

the first delay spread identifies a channel impulse response of the first antenna port observed at the UE, and

the second delay spread identifies a channel impulse response of the second antenna port observed at the UE.

15. The apparatus of claim 9, further comprising instructions to:

receive a delay spread feedback from the UE;

determine an updated first delay spread or the second delay spread based on the delay spread feedback; and

adjust a number of data symbols that can be multiplexed based on the available cyclic shifts after the delay spread adjusting.

16. The apparatus of claim 9, wherein the first antenna port is a demodulation reference signal (DMRS) antenna port and the second antenna port is one of a channel state information-reference signal (CSI-RS) or a cell-specific reference signal (CRS) antenna port.

17. A non-transitory computer readable medium for wireless communications, comprising code for:

determining a first delay spread for a first antenna port of a first channel;

assigning a first pilot signal for the first antenna port to a first cyclic shift of a symbol of a subframe based at least in part on the first delay spread;

determining a second delay spread for a second antenna port of a second channel, wherein the first antenna port and the second antenna port are different;

determining a second cyclic shift of the symbol spaced from the first cyclic shift based on a maximum separation of the first channel for the first pilot signal and the second channel for a second pilot signal within the subframe;

assigning the second pilot signal for the second antenna port to the second cyclic shift of the symbol of the subframe based at least in part on one or more of the first delay spread the second delay spread, wherein the first pilot signal and the second pilot signal are for a same pilot type;

determining remaining available cyclic shifts for the symbol of the subframe; and

multiplexing data on the remaining available cyclic shifts for the symbol, wherein the data is transmitted by one or both of the first antenna port or the second antenna port.

18. The non-transitory computer readable medium of claim 17, wherein the code for determining the remaining available cyclic shifts for the symbol of the subframe further includes code for:

determining a number of cyclic shifts allocated to the first pilot signal and the second pilot signal based on the first delay spread and the second delay spread; and

adjusting a cyclic shift budget of the transmitting device for the symbol of the subframe by subtracting the number of cyclic shifts from the cyclic shift budget.

19. The non-transitory computer readable medium of claim 17, wherein the code for multiplexing the data on the remaining available cyclic shifts for the symbol further includes code for:

identifying the first antenna port or the second antenna port to transmit the data on the symbol, wherein the first antenna port or the second antenna port is identified based on an estimation performed using pilot signals transmitted on a different orthogonal frequency-division multiplexing (OFDM) symbol.

20. The non-transitory computer readable medium of claim 17, further comprising code for:

transmitting the symbol of the subframe to a user equipment (UE).

21. The non-transitory computer readable medium of claim 17, wherein the code for assigning the second set of pilots for the second antenna port to the second cyclic shift further includes code for:

determining a second delay spread for the second antenna port of the second channel; and

assigning the second set of pilots for the second antenna port to the second cyclic shift based on a determination that the remaining available cyclic shifts would accommodate the second delay spread for the second antenna port.

22. The non-transitory computer readable medium of claim 17, wherein:

the first delay spread identifies a channel impulse response of the first antenna port observed at the UE, and

the second delay spread identifies a channel impulse response of the second antenna port observed at the UE.

23. The non-transitory computer readable medium of claim 17, further comprising code for:

receiving a delay spread feedback from the UE;

determining an updated first delay spread or the second delay spread based on the delay spread feedback; and

adjusting a number of data symbols that can be multiplexed based on the available cyclic shifts after the delay spread adjusting.

24. The non-transitory computer readable medium of claim 17, wherein the first antenna port is a demodulation reference signal (DMRS) antenna port and the second antenna port is one of a channel state information-reference signal (CSI-RS) or a cell-specific reference signal (CRS) antenna port.

25. An apparatus for wireless communications, comprising:

means for determining a first delay spread for a first antenna port of a first channel;

means for assigning a first pilot signal for the first antenna port to a first cyclic shift of a symbol of a subframe based at least in part on the first delay spread;

means for determining a second delay spread for a second antenna port of a second channel, wherein the first antenna port and the second antenna port are different;

means for determining a second cyclic shift of the symbol spaced from the first cyclic shift based on a maximum separation of the first channel for the first pilot signal and the second channel for a second pilot signal within the subframe;

means for assigning the second pilot signal for the second antenna port to the second cyclic shift of the symbol of the subframe based at least in part on one or more of the first delay spread the second delay spread, wherein the first pilot signal and the second pilot signal are for a same pilot type;

means for determining remaining available cyclic shifts for the symbol of the subframe; and

means for multiplexing data on the remaining available cyclic shifts for the symbol, wherein the data is transmitted by one or both of the first antenna port or the second antenna port.

26. The apparatus of claim 25, wherein the means for determining the remaining available cyclic shifts for the symbol of the subframe further comprises:

means for determining a number of cyclic shifts allocated to the first pilot signal and the second pilot signal based on the first delay spread and the second delay spread; and

means for adjusting a cyclic shift budget of the transmitting device for the symbol of the subframe by subtracting the number of cyclic shifts from the cyclic shift budget.

27. The apparatus of claim 25, wherein the means for multiplexing the data on the remaining available cyclic shifts for the symbol further comprises:

means for identifying the first antenna port or the second antenna port to transmit the data on the symbol, wherein the first antenna port or the second antenna port is identified based on an estimation performed using pilot signals transmitted on a different orthogonal frequency-division multiplexing (OFDM) symbol.

28. The apparatus of claim 25, further comprising:

means for transmitting the symbol of the subframe to a user equipment (UE).

29. The apparatus of claim 25, wherein the means for assigning the second set of pilots for the second antenna port to the second cyclic shift further includes:

means for determining a second delay spread for the second antenna port of the second channel; and

means for assigning the second set of pilots for the second antenna port to the second cyclic shift based on a determination that the remaining available cyclic shifts would accommodate the second delay spread for the second antenna port.

30. The apparatus of claim 25, further comprising:

means for receiving a delay spread feedback from the UE;

means for determining an updated first delay spread or the second delay spread based on the delay spread feedback; and

means for adjusting a number of data symbols that can be multiplexed based on the available cyclic shifts after the delay spread adjusting.