Digital communication system having improved pilot encoding

• US 20040120304A1
• Filed: 12/19/2002
• Published: 06/24/2004
• Est. Priority Date: 12/19/2002
• Status: Active Grant

• Current Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kloos, Michael N., Palac, Michael S., Thind, Yashpal
• Granted Patent: US 6,909,761 B2
• Time in Patent Office: Days
• US Class Current: 370/347
• CPC Class Codes: H04B 7/2643 using time-division multiple access [TDMA] H04B7/2615, H04B7/2618 take precedence
• CPC Class Codes: H04L 2027/0095 in a preamble or similar structure

Abstract

A time division multiple access communication system is provided having multiple sub-channels according to known quadrature amplitude modulation techniques. Each sub-channel has a pre-determined time duration and is divided by a pre-determined number of symbol position time divisions. The symbol positions carry color codes and ACP codes in addition to sync, pilot and data symbols. Pilot symbols in the second half of the slot are replaced with dual purpose color code and ACP symbols. The dual purpose symbols are either modulated with a lower order modulation than data symbols or are repeated values of dedicated symbols located earlier in the same slot, or both. Slot throughput is attained with a minimal bit error rate penalty.

Claims

1. A digital time division multiple access communication system comprising:

a time slot comprising four quadrature amplitude modulation sub-channels of pre-selected time duration;

a plurality of sync, pilot and data symbols in respective sync, pilot and data symbol positions of each sub-channel, with the pilot symbols arranged in a pre-selected pilot symbol format;

said data symbols modulated according to a pre-selected order of modulation; and

a plurality of dual purpose symbols in respective pilot symbol positions of said pilot symbol format and modulated with an order of modulation less than that of said data symbols.

2. A system of claim 1 wherein said dual purpose symbol comprises a color code symbol and a modulated pilot symbol.

3. The system of claim 1 wherein said dual purpose symbol comprises an ACP symbol and a modulated pilot symbol.

4. The system of claim 1 wherein said four quadrature amplitude modulation sub-channels comprise two inner channels disposed between outer channels and said dual purpose symbols are located in pilot symbol positions in said middle channels.

5. The system of claim 4 wherein the pilot symbols of the inner sub-channels are timewise staggered with respect to pilot symbols of the outer sub-channels.

6. The system according to claim 4 wherein said pilot symbol format comprises a spaced array of pilot symbols in said outer sub-channels, timewise staggered with respect to a spaced array of pilot symbols in said inner sub-channels.

7. A digital time division multiple access communication system comprising:

a time slot comprising four quadrature amplitude modulation sub-channels of pre-selected time duration;

a plurality of color code, ACP, sync, pilot and data symbols in respective color code, ACP, sync, pilot and data symbol positions of each sub-channel, with the pilot symbols arranged in a pre-selected pilot symbol format; and

a plurality of dual purpose symbols in respective pilot symbol positions of said pilot symbol format and comprising copies of at least one of said color code symbols and said ACP symbols.

8. A system of claim 7 wherein said dual purpose symbol comprises a color code symbol and a modulated pilot symbol.

9. The system of claim 7 wherein said dual purpose symbol comprises an ACP symbol and a modulated pilot symbol.

10. The system of claim 7 wherein said four quadrature amplitude modulation sub-channels comprise two inner channels disposed between outer channels and said dual purpose symbols are located in pilot symbol positions in said middle channels.

11. The system of claim 10 wherein the pilot symbols of the inner sub-channels are timewise staggered with respect to pilot symbols of the outer sub-channels.

12. The system according to claim 10 wherein said pilot symbol format comprises a spaced array of pilot symbols in said outer sub-channels, timewise staggered with respect to a spaced array of pilot symbols in said inner sub-channels.

13. A digital time division multiple access communication system comprising:

a time slot comprising four quadrature amplitude modulation sub-channels of pre-selected time duration;

a plurality of sync, pilot and data symbols in respective sync, pilot and data symbol positions of each sub-channel, with the pilot symbols arranged in a pre-selected pilot symbol format;

said data symbols modulated according to a pre-selected order of modulation; and

a plurality of dual purpose symbols comprising copies of at least one of said color code symbols and said ACP symbols, located in respective pilot symbol positions of said pilot symbol format and modulated with an order of modulation less than that of said data symbols.

14. A system of claim 13 wherein at least one of said dual purpose symbol comprises a color code symbol and a modulated pilot symbol.

15. The system of claim 13 wherein at least one of said dual purpose symbol comprises an ACP symbol and a modulated pilot symbol.

16. The system of claim 13 wherein said four quadrature amplitude modulation sub-channels comprise two inner channels disposed between outer channels and said dual purpose symbols are located in pilot symbol positions in said middle channels.

17. The system of claim 16 wherein the pilot symbols of the inner sub-channels are timewise staggered with respect to pilot symbols of the outer sub-channels.

18. The system according to claim 16 wherein said pilot symbol format comprises a spaced array of pilot symbols in said outer sub-channels, timewise staggered with respect to a spaced array of pilot symbols in said inner sub-channels.

19. A method of digital time division multiple access communication comprising the steps of:

providing a time slot comprising four quadrature amplitude modulation sub-channels of pre-selected time duration;

providing a plurality of sync, pilot and data symbols in respective sync, pilot and data symbol positions in said time slot, with the pilot symbols arranged in a pre-selected pilot symbol format;

modulating said data symbols with a pre-selected order of modulation;

providing a derived pilot symbol, modulating said derived pilot symbol with an order of modulation less than that of said data symbols to produce a dual purpose symbol comprising one of said dual purpose color code symbol and said dual purpose ACP symbol and placing said dual purpose symbol in a pre-selected pilot symbol position of said pilot symbol format.

20. The method of claim 19 wherein said step of placing said dual purpose symbol in a pre-selected pilot symbol position of said pilot symbol format comprises placing said dual purpose symbol in a pre-selected pilot symbol position in an inner sub-channel of said pilot symbol format.

21. The method of claim 19 further comprising the step of demodulating said one of said dual purpose color code symbol and said dual purpose ACP symbol to produce a derived pilot symbol.

22. The method of claim 21 further comprising the step of performing pilot interpolation on said one of said dual purpose color code symbol and said dual purpose ACP symbol to produce said derived pilot symbol.

23. The method of claim 22 wherein:

said one of said dual purpose color code symbol and said dual purpose ACP symbol comprises a derived pilot symbol; and

said method further comprising the steps of providing a second derived pilot symbol;

modulating said second derived pilot symbol with an order of modulation less than that of said data symbols to produce a dual purpose ACP symbol;

placing said dual purpose ACP symbol in a pre-selected pilot symbol position of said pilot symbol format;

demodulating said dual purpose color code symbol to produce a derived pilot symbol and performing pilot interpolation on said dual purpose ACP symbol with said derived pilot symbol to produce a decoded ACP symbol which comprises another derived pilot symbol.

24. The method of claim 23 further comprising the step of performing pilot interpolation with said derived pilot symbols and said pilot symbols to perform pilot interpolation on said data symbols.

25. A method of digital time division multiple access communication system comprising the steps of:

providing a time slot comprising four quadrature amplitude modulation sub-channels of pre-selected time duration;

providing a plurality of color code, sync, pilot and data symbols in respective color code, sync, pilot and data symbol positions in said time slot, with the pilot symbols arranged in a pre-selected pilot symbol format; and

copying at least one of said color code symbols and said ACP symbols to provide a dual purpose symbol and placing said dual purpose symbol in a pre-selected pilot symbol position of said pilot symbol format.

26. The method of claim 25 further comprising the step of demodulating said dual purpose color code symbol to produce a derived pilot symbol.

27. The method of claim 26 further comprising the step of performing pilot interpolation on said dual purpose symbol to produce said derived pilot symbol.

28. The method of claim 25 wherein:

said dual purpose symbol comprises a dual purpose color code symbol; and

said method of digital time division multiple access communication further comprising the steps of providing a dual purpose ACP symbol;

placing said dual purpose ACP symbol in a pre-selected pilot symbol position of said pilot symbol format;

demodulating said dual purpose color code symbol to produce a trial value and performing pilot interpolation on said trial value, demodulating said copied symbol and performing pilot interpolation on said copied symbol to produce a second trial value, max ratio combining said first and said second trial values to produce said derived pilot symbol at said color code position.

29. The method of claim 28 wherein the step of performing pilot interpolation on said trial value includes performing pilot interpolation with substantially all of said pilot symbols in said time slot.

30. The method of claim 27 further comprising the step of performing pilot interpolation with said derived pilot symbol and said pilot symbols to perform pilot interpolation on said data symbols.

31. A method of digital time division multiple access communication system comprising the steps of:

providing a time slot comprising four quadrature amplitude modulation sub-channels of pre-selected time duration;

providing a plurality of color code, sync, pilot and data symbols in respective color code, sync, pilot and data symbol positions in said time slot, with the pilot symbols arranged in a pre-selected pilot symbol format;

modulating said data symbols with a pre-selected order of modulation; and

copying at least one of said color code symbols and said ACP symbols to produce a derived pilot symbol, modulating said derived pilot symbol with an order of modulation less than that of said data symbols to produce a dual purpose symbol and placing said dual purpose symbol in a pre-selected pilot symbol position of said pilot symbol format.

32. The method of claim 31 further comprising the step of demodulating said dual purpose symbol to produce a derived pilot symbol.

33. The method of claim 32 further comprising the step of performing pilot interpolation on said dual purpose symbol.

34. The method of claim 31 wherein said dual purpose symbol comprises a dual purpose color code symbol;

and said method further comprising the steps of copying an ACP symbol located at an earlier symbol position to produce a second derived pilot symbol, modulating said second derived pilot symbol with an order of modulation less than that of said data symbols to produce a dual purpose ACP symbol;

placing said dual purpose ACP symbol in a pre-selected pilot symbol position of said pilot symbol format;

demodulating said copied symbol to produce a first trial value and performing pilot interpolation on said copied symbol to produce a second trial value, max ratio combining said first and said second trial values to produce said derived pilot symbol at said color code position.

35. The method of claim 34 wherein the step of performing pilot interpolation on said copied symbol includes performing pilot interpolation with substantially all of said pilot symbols in said time slot.

36. The method of claim 31 further comprising the step of performing pilot interpolation with said derived pilot symbol and said pilot symbols to perform pilot interpolation on said data symbols.