Wideband multiple access telecommunication method and apparatus

• US 20030095529A1
• Filed: 04/26/2002
• Published: 05/22/2003
• Est. Priority Date: 04/26/2001
• Status: Active Grant

• Current Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International), Katholieke Universiteit Leuven, Keysight Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc., Interuniversitair Micro-Electronica Centrum VZW (IMEC International), Katholieke Universiteit Leuven
• Inventors: Leus, Geert, Moonen, Marc, Petre, Frederik
• Granted Patent: US 7,158,558 B2
• Time in Patent Office: Days
• US Class Current: 370/342
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers

Abstract

The present invention is related to a system and method for wideband multiple access telecommunication. In the method, a block is transmitted from a basestation to a terminal. The block comprises a plurality of chip symbols scrambled with a base station specific scrambling code, the plurality of chip symbols comprising a plurality of spread user specific data symbols which are user specific data symbols spread by using user specific spreading codes and at least one pilot symbol. In the terminal, at least two independent signals that comprise at least a channel distorted version of the transmitted block are generated. The two independent signals are combined with a combiner filter with filter coefficients which are determined by using the pilot symbol, thus a combined filtered signal is obtained. The combined filtered signal is despread and descrambled with a composite code of the basestation specific scrambling code and one of the user specific codes.

Claims

1. In a wireless communication system having at least one basestation and at least one terminal, a method of wideband multiple access communication, comprising:

transmitting a block from a basestation to a terminal, the block comprising a plurality of chip symbols scrambled with a base station specific scrambling code, the plurality of chip symbols comprising a plurality of spread user specific data symbols which are user specific data symbols spread by using user specific spreading codes and at least one pilot symbol; and

performing in the terminal;

generating a plurality of independent signals having at least a channel distorted version of the transmitted block;

combining the plurality of independent signals with a combiner filter with filter coefficients which are determined by using the pilot symbol, thus obtaining a combined filtered signal; and

despreading and descrambling the combined filtered signal with a composite code of the base-station specific scrambling code and one of the user specific spreading codes.

2. The method of claim 1, wherein the combining comprises filtering the plurality of independent signals with a filter having filter coefficients which are determined by using the pilot symbol to obtain filtered signals, and combining the filtered signals to obtain the combined filtered signal.

3. The method of claim 1, wherein the filter coefficients are determined without channel estimation.

4. The method of claim 1, wherein the filter coefficients are determined such that one version of the combined filtered signal is as close as possible to a version of the pilot symbol.

5. The method of claim 4, wherein, in the transmitted block, the pilot symbol is spread by a pilot code.

6. The method of claim 5, wherein the version of the combined filtered signal is the combined filtered signal after despreading with a composite code of the basestation specific scrambling code and the pilot code, and wherein the version of the pilot symbol is the pilot symbol.

7. The method of claim 5, wherein the version of the combined filtered signal is the combined filtered signal, after projecting on the orthogonal complement on the subspace spanned by the composite codes of the base station specific scrambling code and the user specific codes, and

wherein the version of the pilot symbol is the pilot symbol spread with a composite code of the base station specific scrambling code and the pilot code.

8. The method of claim 4, wherein the transmitted block comprises a plurality of pilot symbols, each being spread by a user specific code.

9. The method of claim 8, wherein the version of the combined filtered signal is the combined filtered signal after despreading with a composite code of the basestation specific scrambling code and a user specific code, and wherein the version of the pilot symbol is the pilot symbol.

10. The method of claim 8, wherein the version of the combined filtered signal is the pilot portion of the combined filter signal, and wherein the version of the pilot symbol is the sum of the spread pilot symbols within the transmitted block.

11. The method of claim 10, wherein further the filter coefficients are determined such that the data portion of the combined filter signal after projecting on the orthogonal complement on the space spanned by the composite codes of the base station specific scrambling code and the user specific codes is as close as possible to the zero space.

12. The method of claim 1, wherein at least J base stations are transmitting the block to the terminal having at least an integer number M greater than or equal to J+1/(St*Sp) physical antennas, where St is a temporal oversampling factor and Sp is a polarization diversity.

13. The method of claim 1, wherein the terminal constructs at least M=J+1 independent signals, and performs space-time combining J times, each of the combined filtered signals being a multi-user interference suppressed version of the signal transmitted from one of the basestations;

and

wherein the despreading is performed J times, to obtain J intermediate soft estimates of a user specific data symbol.

14. The method of claim 13, further comprising:

performing linear combining of the J despread combined signals so as to obtain a final soft estimate of a user specific data symbol; and

determining a hard estimate for the user specific data symbol from the final soft estimate.

15. In a wireless communication system having at least one basestation and at least one terminal, a method of wideband multiple access communication, comprising:

transmitting a block from a basestation to a terminal, the block comprising a plurality of chip symbols scrambled with a base station specific scrambling code, the plurality of chip symbols comprising a plurality of spread user specific data symbols, which are user specific data symbols spread by using user specific spreading codes and at least one pilot symbol;

transmitting projection information, enabling projecting of a signal on the orthogonal complement of the space spanned by the composite codes of the basestation specific scrambling code and the user specific codes; and

performing in the terminal;

generating at least two independent signals comprising at least a channel distorted version of the transmitted block;

combining with a combiner filter with filter coefficients determined by using the projection information being determined on the signals, thus obtaining a combined filtered signal; and

despreading and descrambling the combined filtered signal with a composite code of the basestation specific scrambling code and one of the user specific codes.

16. The method of claim 15, wherein the user specific codes have length N and the projection information is determined by using the active user signals.

17. The method of claim 15, wherein the user specific codes have length N and the projection information is determined by using a predetermined fixed set of maximum allowable active user signals.

18. A receiver system for wireless communication, comprising:

a receiver configured to receive a block comprising a plurality of chip symbols which are data symbols spread by using scrambling and spreading codes and at least one pilot symbol;

at least one combining filter circuit configured to receive at least two independent signals derived from the received block and output a multi-user interference suppressed signal; and

at least one despreading circuit configured to despread the multi-user interference suppressed signal with one of the scrambling and spreading codes.

19. The system of claim 18, farther comprising a circuit configured to determine coefficients of the combining filter circuit by using the pilot symbol, and wherein the combining filter circuit outputs the multi-user interference suppressed signal based on the coefficients.

20. A receiver system for wireless communication, comprising:

a receiver configured to receive a block comprising a plurality of chip symbols which are data symbols spread by using scrambling and spreading codes, and projection information, enabling projecting of a signal on the orthogonal complement of the space spanned by scrambling and spreading codes;

at least one combining filter circuit configured to input at least two independent signals derived from the received block and output a multi-user interference suppressed signal; and

at least one despreading circuit configured to despread the multi-user interference suppressed signal with one of the scrambling and spreading codes.

21. The system of claim 20, further comprising a circuit configured to determine the coefficients of the combining filter circuit'"'"'s by using the projection information, and wherein the combining filter circuit outputs the multi-user interference suppressed signal based on the coefficients.

22. A receiver system for wireless communication, comprising:

J combining filter circuits, each of the combining filter circuits receiving a plurality of independent signals and outputing a multi-user interference suppressed signal

a circuit configured to determine the coefficients of the combining filters circuit;

a plurality of despreading circuits configured to despread the J multi-user interference suppressed signals; and

a combining circuit configured to combine the J multi-user interference suppressed signals.

23. In a wireless communication system having at least one basestation and at least one terminal, a method of wideband multiple access communication, comprising:

receiving a block comprising a plurality of chip symbols scrambled with a base station specific scrambling code, the plurality of chip symbols comprising a plurality of spread user specific data symbols which are user specific data symbols spread by using user specific spreading codes and at least one pilot symbol;

generating at least two independent signals based on the received block; and

combining the at least two independent signals with a combiner filter having filter coefficients which are determined by using the pilot symbol, thus obtaining a combined filtered signal.

24. The method of claim 23, further comprising despreading and descrambling the combined filtered signal with a composite code of the basestation specific scrambling code and one of the user specific spreading codes.

25. A receiver system for wireless communication, comprising:

means for receiving a block comprising a plurality of chip symbols scrambled with a base station specific scrambling code, the plurality of chip symbols comprising a plurality of spread user specific data symbols which are user specific data symbols spread by using user specific spreading codes and at least one pilot symbol;

means for generating at least two independent signals based on the received block; and

means for combining the at least two independent signals with a combiner filter having filter coefficients which are determined by using the pilot symbol, thus obtaining a combined filtered signal.

26. The method of claim 25, further comprising means for despreading and descrambling the combined filtered signal with a composite code of the basestation specific scrambling code and one of the user specific spreading codes.

27. A method of retrieving a desired user data symbol sequence from a received signal, the method comprising:

receiving a channel modified version of a transmitted signal comprising a plurality of user data symbol sequences, each being encoded with a user specific known code;

determining an equalization filter directly and in a deterministic way from the received signal; and

applying the equalization filter on the received signal to thereby retrieve the transmitted signal.

28. The method recited in claim 27, further comprising retrieving the desired user data symbol sequence by correlating the retrieved transmitted signal with the desired user specific known code.

29. The method recited in claim 27, wherein the determining the equalization filter does not rely on estimation of the channel characteristics.

30. The method recited in claim 27, wherein the determining the equalization filter does not rely on signal statistics.

31. The method recited in claim 27, wherein the transmitted signal further comprises a known pilot symbol sequence, being encoded with a pilot specific known code.

32. The method recited in claim 31, wherein the determining the equalization filter exploits the known pilot symbol sequence and the pilot specific known code.

33. The method recited in claim 32, wherein the determining the equalization filter further exploits substantially all user specific known codes.

34. The method recited in claim 27, wherein the transmitted signal further comprises user specific known pilot symbol sequences, each being encoded with the user specific known code.

35. The method recited in claim 34, wherein the determining the equalization filter exploits the desired user specific known pilot symbol sequence and the desired user specific known code.

36. The method recited in claim 35, wherein the determining the equalization filter further exploits substantially all the user specific known pilot symbol sequences and substantially all the user specific known codes.

37. The method recited in claim 29, wherein the received signal comprises each of the plurality of channel modified version being substantially different.

38. A system for retrieving a desired user data symbol sequence from a received signal, comprising:

means for receiving a channel modified version of a transmitted signal comprising a plurality of user data symbol sequences, each being encoded with a user specific known code;

means for determining an equalization filter directly and in a deterministic way from the received signal; and

means for applying the equalization filter on the received signal to thereby retrieve the transmitted signal.