System implementing closed loop transmit diversity and method thereof

• US 20040001556A1
• Filed: 06/27/2002
• Published: 01/01/2004
• Est. Priority Date: 06/27/2002
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Harrison, Robert Mark, Ahmed, Mansoor, Tonge, Richard, Whinnett, Nick
• Granted Patent: US 7,010,055 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0634 Antenna weights or vector/matrix coefficients
• CPC Class Codes: H04B 7/0656 at the transmitter, e.g. error detection at base station

Abstract

A method of and apparatus for adapting an antenna array for closed loop transmit diversity, the method comprising: receiving an adapting signal corresponding to an antenna array weighting pattern for a time period; demodulating the adapting signal to provide a symbol for the time period; determining a preferred symbol from the symbol for the time period and a previous symbol for a previous time period; and transmitting with an antenna array weighting pattern corresponding to the preferred symbol.

Claims

6. A method of adapting an antenna array for closed loop transmit diversity, the method comprising:

receiving an adapting signal corresponding to an antenna array weighting pattern for a time period;

demodulating said adapting signal to provide a plurality of symbols for said time period;

determining a preferred plurality of symbols from said plurality of symbols for said time period and a previous plurality of symbols for a previous time period; and

transmitting with an antenna array weighting pattern corresponding to said preferred plurality of symbols.

7. The method of claim 6 wherein said receiving said adapting signal includes receiving said adapting signal from a subscriber unit on a control channel.

8. The method of claim 7 wherein said adapting signal on said control channel is composed of one of said plurality of symbols repeated a plurality of times and said plurality of symbols as error control coded.

9. The method of claim 6 wherein said determining said preferred plurality of symbols further includes selecting one of said plurality of symbols for said time period and said previous plurality of symbols for said previous time period.

10. The method of claim 9 wherein said selecting further includes comparing the amplitude of each symbol of said plurality of symbols to a threshold and when said threshold is satisfied for all symbols of said plurality of symbols choosing said plurality of symbols as said preferred plurality of symbols else choosing said previous plurality of symbols as said preferred plurality of symbols.

13. The method of claim 8 wherein said adapting signal on said control channel is composed of one of said plurality of symbols, each repeated a plurality of times and said plurality of symbols as error control coded.

11. A method of adapting an antenna array for closed loop transmit diversity, the method comprising:

receiving an adapting signal corresponding to an antenna array weighting pattern for a time period;

demodulating said adapting signal to provide a plurality of symbols;

determining a confidence metric for each of said plurality of symbols;

forming an ordered set of symbols comprising each of said plurality of symbols having a favorable confidence metric and a last used symbol for each of said plurality of symbols having an unfavorable confidence metric; and

selecting an antenna array weighting pattern corresponding to said ordered set of symbols.

12. The method of claim 11 wherein said receiving said adapting signal includes receiving said adapting signal from a subscriber unit on a control channel.

14. The method of claim 12 wherein said adapting signal is a sequence of Binary Phase Shift Keyed symbols representing feedback bits that form a code word corresponding to said antenna array weighting pattern.

15. The method of claim 11 wherein said determining a confidence metric includes determining a symbol energy for each of said plurality of symbols.

16. The method of claim 15 wherein said each of said plurality of symbols having said favorable confidence metric has a symbol energy that satisfies a threshold and said each of said plurality of symbols having said unfavorable confidence metric has a symbol energy that does not satisfy said threshold.

17. An apparatus for selecting an antenna array weighting pattern for use by a base transmitter using an antenna array in a closed loop transmit diversity system, the apparatus comprising:

a receiver for receiving and demodulating an uplink control channel signal to provide a sequence of symbols and a, respective, sequence of corresponding confidence metrics;

a comparator for comparing each confidence metric of said respective sequence of corresponding confidence metrics to a threshold to determine whether each symbol of said sequence of symbols is reliable;

a register for constructing a code word comprising an ordered set of each of said sequence of symbols that is reliable and a last used symbol for each of said sequence of symbols that is not reliable; and

a decoder for selecting an antenna array weighting pattern corresponding to said code word.

1. A method of adapting an antenna array for closed loop transmit diversity, the method comprising:

receiving an adapting signal corresponding to an antenna array weighting pattern for a time period;

demodulating said adapting signal to provide a symbol for said time period;

determining a preferred symbol from said symbol for said time period and a previous symbol for a previous time period; and

transmitting with an antenna array weighting pattern corresponding to said preferred symbol.

2. The method of claim 1 wherein said receiving said adapting signal includes receiving said adapting signal from a subscriber unit on a control channel.

3. The method of claim 2 wherein said adapting signal on said control channel is composed of one of said symbol repeated a plurality of times and said symbol as error control coded.

4. The method of claim 1 wherein said determining said preferred symbol further includes selecting one of said symbol for said time period and said previous symbol for said previous time period.

5. The method of claim 4 wherein said selecting further includes comparing said symbol amplitude to a threshold and when said threshold is satisfied choosing said symbol as said preferred symbol else choosing said previous symbol as said preferred symbol.

18. The apparatus of claim 17 wherein said receiving said uplink control channel signal includes receiving feedback information from a subscriber unit regarding a forward path emanating from the antenna array.

19. The apparatus of claim 18 wherein said feedback information is composed of one of said sequence of symbols, each repeated a plurality of times and said sequence of symbols as error control coded.

20. The apparatus of claim 18 wherein said feedback information is a sequence of Binary Phase Shift Keyed symbols representing feedback bits that form a code word corresponding to a desired antenna array weighting pattern.

21. The apparatus of claim 17 wherein said sequence of corresponding confidence metrics is a sequence of symbol magnitudes corresponding to said sequence of symbols.

22. The apparatus of claim 21 wherein said symbols are feedback bits and said symbol magnitudes are bit magnitudes

23. The apparatus of claim 17 wherein said register is a latched register with each stage of said register coupled to a switch controlled by said comparator to select said each of said sequence of symbols that is reliable and said last used symbol for said each of said sequence of symbols that is not reliable.

24. The apparatus of claim 17 wherein said code words are Gray coded so that code words with only one symbol change correspond to adjacent antenna array weighting patterns.

26. The apparatus of claim 17 wherein said threshold is selected to balance the effect of errors in the antenna array weighting pattern that is selected due to errors in said sequence of symbols as received versus errors resulting from discarding symbols as received.

20-1. The apparatus of claim 17 operating to update said antenna array weighting pattern according to another code word with a time slot periodicity that is system dependent.