CDMA transceiver techniques for wireless communications

• US 20040120274A1
• Filed: 04/25/2003
• Published: 06/24/2004
• Est. Priority Date: 04/25/2002
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Interuniversitair Micro-Electronica Centrum VZW (IMEC International), Katholieke Universiteit Leuven
• Inventors: Leus, Geert, Petre, Frederik
• Granted Patent: US 7,873,021 B2
• Time in Patent Office: Days
• US Class Current: 370/320
• CPC Class Codes: H04B 1/692 Hybrid techniques using combinations of two or more spread spectrum techniques
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/12 Frequency diversity
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/0643 block codes
• CPC Class Codes: H04L 1/0675 characterised by the signaling

Abstract

The present invention is related to a method for multi-user wireless transmission of data signals in a communication system having at least one base station and at least one terminal. It comprises, for a plurality of users, the following steps:

adding robustness to frequency-selective fading to the data to be transmitted.

performing spreading and scrambling of at least a portion of a block of data, obtainable by grouping data symbols by demultiplexing using a serial-to-parallel operation,

combining (summing) spread and scrambled portions of the blocks of at least two users,

adding transmit redundancy to the combined spread and scrambled portions, and

transmitting the combined spread and scrambled portions with transmit redundancy.

Claims

1. A method of communicating data signals among a plurality of users, the method comprising:

spreading and scrambling at least a portion of a block of data obtainable by grouping of data symbols using a serial-to-parallel operation;

combining the spread and scrambled portions of said blocks associated with at least two users;

adding redundant data to said combined spread and scrambled portions; and

transmitting said combined spread and scrambled portions having said redundant data.

2. The method recited in claim 1, wherein said spreading and scrambling comprise using a code sequence obtained by multiplying a user terminal-specific code and a base station specific scrambling code.

3. The method recited in claim 1, further comprising the step of generating a plurality of independent block portions.

4. The method recited in claim 1, further comprising generating a plurality of block portions.

5. The method recited in claim 3, wherein the steps of claim 1 are performed repeatedly to process substantially all of the block portions, thereby generating streams comprising a plurality of combined spread and scrambled block portions.

6. The method recited in claim 5, further comprising encoding each of said streams after the step of combining but before the step of transmitting said spread and scrambled portions.

7. The method recited in claim 5, further comprising encoding said streams in the space-time domain after performing the step of combining and before performing the step of transmitting said spread and scrambled portions, thereby combining information from at least two of said streams.

8. The method recited in claim 7, wherein said step of space-time encoding said streams comprises performing at least one of block space-time encoding and trellis space-time encoding.

9. The method recited in claim 1, further comprising performing inverse subband processing after performing the step of combining and before performing the step of transmitting said spread and scrambled portions.

10. The method recited in claim 1, further comprising performing linear preceding.

11. The method recited in claim 1, comprising the step of applying adaptive loading for each user terminal.

12. The method recited in claim 1, wherein the step of combining spread and scrambled block portions comprises adding a pilot signal to the sum of spread and scrambled block portions.

13. The method recited in claim 1, wherein the step of adding redundant data comprises the addition of at least one of a cyclic prefix, a zero postfix, and a symbol postfix.

14. The method recited in claim 1, wherein a transmit system for wireless communication is configured to perform the steps among the plurality of users.

15. The method recited in claim 1, further comprising performing a processing technique configured to improve integrity of said spread and scrambled portions in the presence of frequency-selective fading.

16. An apparatus for communicating data signals among a plurality of users, the apparatus comprising:

a grouping circuit configured to group data symbols for transmission;

a spreader and scrambling circuit configured to spread and/or scramble said grouped data symbols;

an adder configured to add redundant data to said spread and scrambled grouped data symbols.

17. The apparatus recited in claim 16, further comprising at least one transmit antenna configured to transmit said spread and scrambled grouped data symbols having said redundancy.

18. The apparatus recited in claim 16, further comprising a circuit configured to improve integrity of said grouped data symbols in the presence of frequency-selective fading.

19. The apparatus recited in claim 16, further comprising a space-time encoder.

20. The apparatus recited in claim 16, further comprising one or more circuits configured to perform inverse subband processing on said grouped data symbols.

21. A method for communicating data signals between at least one base station and at least one terminal, the method comprising:

receiving a signal from at least one antenna;

performing subband processing of a version of said received signal;

separating contribution signals associated with a plurality of users, the contribution signals being derivable from said received signal; and

restoring data from each one of the contribution signals, the data having been configured to resist frequency-selective fading.

22. The method recited in claim 21, wherein the step of separating the contributions comprises filtering at a chip rate at least a portion of the subband processed version of said received signal, and then despreading said filtered portion.

23. The method recited in claim 21, wherein the step of separating the contributions comprises despreading at least a portion of the subband processed version of said received signal, and then filtering said despread portion.

24. The method recited in claim 21, wherein the step of receiving a signal comprises receiving the signal from a plurality of antennas, and generating data streams, and wherein the step of subband processing is performed on each of said data streams, and producing a subband processed version of said received signal.

25. The method recited in claim 21, further comprising performing the step of space-time decoding on each of the streams.

26. The method recited in claim 25, wherein the step of space-time decoding comprises performing at least one of block decoding and trellis decoding.

27. The method recited in claim 22, further comprising performing the step of inverse subband processing on at least one filtered, subband processed version of the received signal.

28. The method recited in claim 22, wherein the step of filtering comprises processing said portion with a filter characterized by filter coefficients that are determinable in a semi-blind or in a training-based technique.

29. The method recited in claim 22, wherein the step of filtering comprises processing said portion with a filter characterized by filter coefficients that are determinable without the necessity to perform channel estimation.

33. The method recited in claim 21, further comprising removing transmit redundancy resulting from adding redundant data.

34. The method recited in claim 21, wherein the step of restoring data comprises performing the step of linear de-precoding.

35. The method recited in claim 21, wherein a receiver is configured to perform all said steps among a plurality of users in a wireless communication system.

30. The method recited in 22, wherein the step of filtering comprises processing said portion with a filter characterized by filter coefficients that are determined while maintaining one version of the filtered signal as close as possible to a version of the pilot symbol.

31. The method recited in claim 30, wherein the version of the filtered signal comprises the filtered signal after despreading with a composite code associated with the base station-specific scrambling code and the pilot code, and wherein the version of the pilot symbol comprises the pilot symbol as formulated in a per tone ordering.

32. The method recited in claim 30, wherein the version of the filtered signal comprises the filtered signal after projecting on an orthogonal complement on a subspace spanned by a plurality of composite codes associated with the base station-specific scrambling code and user-specific codes, and wherein the version of the pilot symbol comprises the pilot symbol spread with a composite code associated with the base station-specific scrambling code and the pilot code as put in per tone ordering.

36. An apparatus for communicating data signals among a plurality of users, the apparatus comprising:

a plurality of circuits configured to perform subband processing on received signals;

a despreader circuit configured to determine an estimate of a plurality of subband processed symbols received for at least one user terminal from the received signals.

37. The apparatus recited in claim 36, further comprising a plurality of antennas receiving signals.

38. The apparatus recited in claim 36, wherein said circuitry adapted for determining an estimate of symbols comprises a plurality of circuits for inverse subband processing.

39. The apparatus recited in claim 36, wherein said despreader circuit comprises a plurality of filters configured to filter at least a portion of a subband processed version of said received signals.

40. The apparatus recited in claim 36, wherein said despreader circuit comprises a plurality of filters configured to filter at a chip rate at least a portion of a subband processed version of said received signals.

41. The apparatus recited in claim 36, further comprising a space-time decoder configured to decode at least a portion of said received signals.

42. A method of communicating data signals among a plurality of users, the method comprising:

transforming data symbols associated with the plurality of users into respective user sequences;

performing linear precoding on each user sequence;

converting each user sequence into data blocks;

spreading each user data block with a user-specific composite code sequence derived from the multiplication of an orthogonal spreading code specific to said user and a base station-specific scrambling code;

adding the spread block sequences of all users; and

performing an inverse transform on the added block sequences into the time domain.

43. A method of communicating data signals among a plurality of users, the method comprising:

converting data symbols associated with the plurality of users into respective user data blocks;

linearly preceding said data blocks;

placing said preceded data blocks onto a plurality of carrier signals;

demultiplexing said precoded data blocks into a plurality of sequences;

spreading each demultiplexed sequence with a user code sequence, which is derivable from the multiplication of a respective user-specific orthogonal spreading code by a base station-specific scrambling code;

adding all spread sequences to a pilot block sequence to produce a sum sequence; and

performing a space-time encoding on the sum sequence.

44. A method of communicating data signals among a plurality of users, the method comprising:

demultiplexing data symbol sequence into several data streams;

converting said data streams into respective symbol blocks;

spreading said symbol blocks with a user composite code sequence, which is derivable from the multiplication of a user-specific orthogonal spreading code by a base station-specific scrambling code;

adding a pilot block sequence to each spread sequence to produce an output chip block;

padding each of the output chip block with a zero postfix; and

performing a parallel-to-serial conversion on the padded block.