Apparatus and method for reference symbol transmission in an OFDM system

• US 9,077,415 B2
• Filed: 11/16/2012
• Issued: 07/07/2015
• Est. Priority Date: 12/19/2011
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Josiam, Kaushik, Abu-Surra, Shadi, Li, Ying, Rajagopal, Sridhar, Pi, Zhouyue
• Primary Examiner(s): Tran, Khanh C
• Application Number:
  US13/678,795
• Publication Number:
  US 20130156120A1
• Time in Patent Office: 963 Days
• Field of Search: 375/260, 375/267, 375/285, 375/295, 375/299, 375/316, 375/340, 375346-349, 455/562.1, 455/63.4, 455/575.7, 455/132, 455134-135
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0224 using sounding signals
• 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

Abstract

A base station is capable of communicating with a plurality of subscriber stations using a beamforming scheme that varies beams over different time instances. The base station includes a plurality of antenna arrays configured to transmit N spatial beams and carry a reference symbols corresponding to specific spatial beams. The base station also includes N_RF number of radio frequency (RF) processing chains coupled to respective ones of the plurality of antenna arrays, wherein N>>N_RF. The subscriber station includes M_RF processing receive paths configured to receive M number of beams from the base station.

Claims

1. For use in a wireless communications network, a base station capable of communicating with a plurality of subscriber stations using a beamforming scheme, the base station comprising:

a plurality of antenna arrays configured to transmit N spatial beams; and

N_RF number of radio frequency (RF) processing chains coupled to respective ones of the plurality of antenna arrays, wherein N>

>

N_RF, wherein a first of the RF processing chains is configured to carry a reference symbol corresponding to a specific spatial beam.

2. The base station as set forth in claim 1, wherein the N_RF RF processing chains are configured to transmit different spatial beams in at least N/N_RF time instances.

3. The base station as set forth in claim 1, wherein the N_RF RF processing chains are configured to transmit the different spatial beams in the at least N/N_RF time instances in different directions.

4. For use in a wireless communications network, a base station capable of communicating with a plurality of subscriber stations using a beamforming scheme, the base station comprising:

a plurality of antenna arrays configured to transmit N spatial beams; and

N_RF number of radio frequency (RF) processing chains coupled to respective ones of the plurality of antenna arrays, wherein N>

>

N_RF, wherein at least one RF processing chain is configured to reduce a duration of an Orthogonal Frequency Division Multiplexing (OFDM) symbol that carries a reference symbol such that the duration of the OFDM symbol that carries a reference symbol is shorter than a duration of a symbol for data transmission, wherein the symbol that carries the reference symbol includes fewer subcarriers as compared to the symbol for data transmission.

5. The base station as set forth in claim 4, wherein a cyclic prefix for the symbol that carries the reference symbol is the same as the symbol for data transmission.

6. The base station as set forth in claim 4, wherein a plurality of the symbol that carries the reference symbol are configured to fit within a duration of the symbol for data transmission.

7. The base station as set forth in claim 4, wherein each of a plurality of the symbols that carries the reference symbol carries reference symbols corresponding to N spatial beams with at least N_RF spatial beams per symbol.

8. The base station as set forth in claim 4, wherein reducing the duration of the OFDM symbol comprises increasing a sampling frequency.

9. For use in a wireless communications network, a method for beamforming, the method comprising:

transmitting N spatial beams by N_RF number of radio frequency (RF) processing chains, wherein N>

>

N_RF, and wherein transmitting comprises carrying a reference symbol corresponding to a specific spatial beam.

10. The method as set forth in claim 9, wherein transmitting comprises, transmitting, by each of the N_RF RF processing chains, different spatial beams in at least N/N_RF time instances.

11. The method as set forth in claim 10, wherein transmitting the different spatial beams at least N/N_RF time instances comprises transmitting in different directions.

12. For use in a wireless communications network, a method for beamforming, the method comprising:

transmitting N spatial beams by N_RF number of radio frequency (RF) processing chains, wherein N>

>

N_RF; and

reducing a duration of a symbol that carries a reference symbol such that the duration of a symbol that carries a reference symbol is shorter than a duration of a symbol for data transmission, wherein the symbol that carries the reference symbol includes fewer subcarriers as compared to the symbol for data transmission.

13. The method as set forth in claim 12, wherein a cyclic prefix for the symbol that carries the reference symbol is the same as the symbol for data transmission.

14. The method as set forth in claim 12, wherein a plurality of the symbol that carries the reference symbol are configured to fit within a duration of the symbol for data transmission.

15. The method as set forth in claim 12, wherein each of a plurality of the symbols that carries the reference symbol carries reference symbols corresponding to N spatial beams with at least N_RF spatial beams per symbol.

16. The method as set forth in claim 12, wherein reducing the duration of the symbol comprises increasing a sampling frequency.

17. For use in a wireless communications network, a subscriber station capable of communicating with at least one base station using a beamforming scheme, the subscriber station comprising:

a plurality of antenna arrays configured to receive M spatial beams; and

M_RF number of radio frequency (RF) processing chains coupled to respective ones of the plurality of antenna arrays, wherein M>

>

M_RF, wherein a first of the RF processing chains is configured to receive a reference symbol corresponding to a specific spatial beam.

18. The subscriber station as set forth in claim 17, wherein M_RF RF processing chains are configured to receive different spatial beams in at least each of M/M_RF time instances.

19. The subscriber station as set forth in claim 18, wherein the M_RF RF processing chains are configured to use the reference symbols received on the different spatial beams to estimate a wireless channel between the subscriber station and the at least one base station.

20. The subscriber station as set forth in claim 18, wherein the different spatial beams in at least each of M/M_RF time instances are transmitted by the at least one base station in different directions.

21. The subscriber station as set forth in claim 17, wherein at least one symbol comprises a shortened symbol that carries a reference symbol is received, the shortened symbol having a duration that is shorter than a duration of a symbol for data transmission.

22. The subscriber station as set forth in claim 21, wherein the shortened symbol includes fewer subcarriers as compared to the symbol for data transmission.

23. The subscriber station as set forth in claim 21, wherein a cyclic prefix for the shortened symbol is the same as the symbol for data transmission.

24. The subscriber station as set forth in claim 21, wherein a plurality of the shortened symbol are configured to fit within a duration of the symbol for data transmission.

25. The subscriber station as set forth in claim 21, wherein each of a plurality of the symbols that carries the reference symbol carries a reference symbol corresponding to N spatial beams with N_RF spatial beams per symbol.