Communications system and method for multi-carrier orthogonal coding

• US 6,680,928 B1
• Filed: 06/28/1999
• Issued: 01/20/2004
• Est. Priority Date: 07/22/1997
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Dent, Paul W.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Le, Danh C
• Application Number:
  US09/340,907
• Time in Patent Office: 1,667 Days
• Field of Search: 455/63, 370/208, 370/209, 370/328, 370/329, 370/335, 370/342, 370/330, 370/343
• US Class Current: 370/342
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04J 11/0023 Interference mitigation or co-ordination direct sequence spread spectrum [DSSS] systems H04B1/7097; frequency hopping H04B1/713; allocation criteria for ingress interference avoidance H04L5/0062; frequency allocation criteria for requirements on out-of-channel emissions H04L5/0066; arrangements for removing intersymbol interference or baseband equalisers H04L25/03006; peak power aspects in multicarrier modulation H04L27/2614; power management H04W52/00; traffic scheduling H04W72/54, H04W72/541
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 1/004 by using forward error control H04L1/0618 takes precedence; coding, decoding or code conversion, for error detection or correction H03M13/00
• CPC Class Codes: H04L 1/08 by repeating transmission, e.g. Verdan system H04L1/1858 and H04L1/189 take precedence
• CPC Class Codes: H04L 5/026 using code division

Abstract

In CDMA systems, a message to be transmitted is redundantly coded for transmission using a combination of error-correction coding and a spread-spectrum access code. The coded message is modulated to a first radio frequency channel, or band, and also to at least one other frequency channel, which may be either an adjacent or a non-adjacent channel. Other messages for transmission are generated likewise and the signals for transmission on the first channel are summed using a set of weighting factors, with the weighted sum transmitted on the first channel. The same signals are summed for transmission on the at least one other frequency channel, but using weighting factors that have a progressive relative phase rotation compared to their Values on the first channel. The sequence of weighting factors used for one signal across the different frequency channels is preferably orthogonal to the sequence of weighting factors used for a different signal.

Claims

1. A signal converter for use in a Code Division Multiple Access (CDMA) communications system utilizing multiple frequency channels for transmission, said signal converter comprising:

a plurality of weighting multipliers each receiving a different one of a plurality of information signals for transmission in each of a plurality of frequency channels, each of said plurality of weighting multipliers multiplying its received information signal by a different sequence of frequency-channel-associated weights and developing a plurality of weighted information signals that are across-channel coded;

a plurality of combiners each associated with a different one of the plurality of frequency channels, each of said plurality of combiners receiving a select weighted information signal from each of the plurality of weighting multipliers corresponding to different information signals and combining said select weighted information signals for transmission in the same one of said plurality of frequency channels to develop a plurality of combined weighted information signals; and

a spread-spectrum coder receiving one of either (a) the plurality of information signals, or (b) the plurality of combined weighted information signals, and encoding the received signals using respective spread-spectrum access codes to develop one of either (a) a plurality of spread-spectrum information signals, or (b) a plurality of spread-spectrum combined weighted information signals, wherein the plurality of spread-spectrum information signals comprises the plurality of information signals received by the plurality of weighting multipliers when the spread-spectrum coder receives the plurality of information signals.

2. The signal converter of claim 1, wherein said spread-spectrum coder uses a first spread-spectrum access code to encode a subgroup of said plurality of information signals in one of said plurality of frequency channels, with each information signal within said subgroup weighted by the plurality of weighting multipliers with a frequency-channel-associated weight orthogonal to the frequency-channel-associated weights used by other information signals in said subgroup.

3. The signal converter of claim 2, wherein said first and second sets of orthogonal sequences of frequency-channel-associated weights comprise Fourier sequences.

4. The signal converter of claim 1, wherein said spread-spectrum coder uses a first set of respective spread-spectrum access codes which are mutually orthogonal to encode a first subgroup of said plurality of information signals in one of said plurality of frequency channels.

5. The signal converter of claim 4, wherein the spread-spectrum coder uses a second set of mutually orthogonal spread-spectrum access codes, which second set is not orthogonal to the first set, to encode a second subgroup of said plurality of information signals in said one of said plurality of frequency channels.

6. The signal converter of claim 5, wherein respective weighting multipliers weight the first subgroup of orthogonally spread-spectrum encoded information signals using a first set of frequency-channel-associated weights, and respective weighting multipliers weight the second subgroup of orthogonally spread-spectrum encoded information signals using a second set of frequency-channel-associated weights, the first set of weights used for the first subgroup being orthogonal to the second set of weights used for said second subgroup.

7. The signal converter of claim 5, wherein the first and second sets of mutually orthogonal spread-spectrum access codes are chip-interleaved to reduce the loss of orthogonality resulting from multi-path propagation during transmission.

8. The signal converter of claim 5, wherein the first and second sets of mutually orthogonal spread-spectrum access codes comprise Fourier sequences.

9. The signal converter of claim 5, wherein the first and second sets of mutually orthogonal spread-spectrum access codes comprise Walsh codes.

10. The signal converter of claim 5, wherein the first and second sets of mutually orthogonal spread-spectrum access codes comprise Walsh codes modified by the addition of common access codes.

11. The signal converter of claim 10, wherein said common access codes comprise Bent sequences.

12. The signal converter of claim 2, wherein said first and second sets of orthogonal sequences of frequency-channel-associated weights comprise Walsh codes.

13. The signal converter of claim 1, wherein each of said frequency-channel-associated weights in the first and second sets incorporates a power level setting for each of said plurality of information signals.

14. The signal converter of claim 13, wherein the plurality of weighting multipliers keep the relative power level ratio of one information signal to another equal in each of said plurality of frequency channels.

15. The signal converter of claim 13, wherein the power level setting for a particular information signal in each of said plurality of frequency channels is controlled by feeding back, to the plurality of weighting multipliers, signal strength measurements made by a receiver of the CDMA communications system receiving the particular information signal in each of said plurality of frequency channels.

16. The signal converter of claim 15, wherein the plurality of weighting multipliers reduce the power level setting for said particular information signal in a first one of said plurality of frequency channels compared to the power level setting for said particular information signal in a second one of said frequency channels if the signal strength measurements made by the receiver indicate a lower received signal strength for said particular information signal in the first frequency channel as compared to the second frequency channel.

17. The signal converter of claim 1, wherein said plurality of frequency channels are non-contiguous.

18. The signal converter of claim 1, wherein said signal converter is included as a component of a cellular telephone base station.

19. The signal converter of claim 18, wherein one of said plurality of information signals is a call-alerting signal.

20. The signal converter of claim 18, wherein one of said plurality of information signals is a pilot signal including known information symbols.

21. The signal converter of claim 1, wherein said plurality of information signals include pilot symbols.

22. A transmitter for use in a Code Division Multiple Access (CDMA) communications system utilizing multiple frequency channels for transmission, said transmitter comprising:

a signal converter comprising;

a plurality of weighting multipliers each receiving a different one of a plurality of information signals for transmission in each of a plurality of frequency channels, each of said plurality of weighting multipliers multiplying its received information signal by a different sequence of frequency-channel-associated weights and developing a plurality of weighted information signals that are across-channel coded;

a plurality of combiners each associated with a different one of the plurality of frequency channels, each of said plurality of combiners receiving a select weighted information signal from each of the plurality of weighting multipliers corresponding to different information signals and combining said select weighted information signals for transmission in the same one of said plurality of frequency channels to develop a plurality of combined weighted information signals; and

a spread-spectrum coder receiving one of either (a) the plurality of information signals, or (b) the plurality of combined weighted information signals, and encoding the received signals using respective spread-spectrum access codes to develop one of either (a) a plurality of spread-spectrum information signals, or (b) a plurality spread-spectrum combined weighted information signals, wherein the plurality of spread-spectrum information signals comprises the plurality of information signals received by the plurality of weighting multipliers when the spread-spectrum coder receives the plurality of information signals;

a modulator receiving one of either (a) the plurality of combined weighted information signals, or (b) the plurality spread-spectrum combined weighted information signals, and modulating the received signals with respective channel frequencies to develop a plurality of modulated information signals; and

at least one antenna receiving the plurality of modulated information signals and transmitting the plurality of modulated information signals across the CDMA communications system in each of the plurality of frequency channels.

23. A method of developing wide-channel Code Division Multiple Access (CDMA) information signals for transmission in multiple frequency channels, said method comprising the steps of:

multiplying each of a plurality of information signals for transmission in each of a plurality of frequency channels by a different sequence of frequency-channel-associated weights to develop a plurality of weighted information signals that are across-channel coded;

combining select weighted information signals corresponding to different information signals for transmission in the same one of said plurality of frequency channels to develop a plurality of combined weighted information signals; and

encoding one of either (a) the plurality of information signals, or (b) the plurality of combined weighted information signals, using respective spread-spectrum access codes to develop one of either (a) a plurality of spread-spectrum information signals, or (b) a plurality of spread-spectrum combined weighted information signals, wherein the plurality of spread-spectrum information signals comprises the plurality of information signals multiplied at said multiplying step when the plurality of information signals are encoded at said encoding step.

24. The method of claim 23, wherein a first subgroup of said plurality of information signals in one of said plurality of frequency channels is encoded using a first set of respective spread-spectrum access codes which are mutually orthogonal.

25. The method of claim 24, wherein a second subgroup of said plurality of information signals in said one of said plurality of frequency channels is encoded using a second set of mutually orthogonal spread-spectrum access codes, which second set is not orthogonal to the first set of codes used by said first subgroup.

26. The method of claim 25, wherein the first subgroup of orthogonally spread-spectrum encoded information signals is weighted using a first set of frequency-channel-associated weights, and the second subgroup of orthogonally spread-spectrum encoded information signals is weighted using a second set of frequency-channel-associated weights, the first set of weights being orthogonal to the second set of weights.

27. The method of claim 25, further comprising the step of chip-inter-leaved the first and second sets of mutually orthogonal spread-spectrum access codes to reduce the loss of orthogonality resulting from multi-path propagation during transmission.

28. The method of claim 25, wherein the first and second sets of mutually orthogonal spread-spectrum access codes comprise Fourier sequences.

29. The method of claim 25, wherein the first and second sets of mutually orthogonal spread-spectrum access codes comprise Walsh codes.

30. The method of claim 25, wherein the first and second sets of mutually orthogonal spread-spectrum access codes comprise Walsh codes modified by the addition of common access codes.

31. The method of claim 30, wherein said common access codes comprise Bent sequences.

32. The method of claim 23, wherein a subgroup of said plurality of information signals in one of said plurality of frequency channels is encoded using a first spread-spectrum access code, and wherein each information signal within said subgroup is weighted with a frequency-channel-associated weight orthogonal to the frequency-channel-associated weights used by other information signals in said subgroup.

33. The method of claim 32, wherein said first and second sets of orthogonal sequences of frequency-channel-associated weights comprise Walsh codes.

34. The method of claim 32, wherein said first and second sets of orthogonal sequences of frequency-channel-associated weights comprise Fourier sequences.

35. The method of claim 32, wherein each of said frequency-channel-associated weights in the first and second sets incorporates a power level setting for each of said plurality of information signals.

36. The method of claim 35, wherein the relative power level ratio of one information signal to another is substantially equal in each of said plurality of frequency channels.

37. The method of claim 23, further comprising the steps of:

modulating one of either (a) the plurality of combined weighted information signals, or (b) the plurality spread-spectrum combined weighted information signals, with respective channel frequencies to develop a plurality of modulated information signals; and

transmitting the plurality of modulated information signals across the CDMA communications system in each of the plurality of frequency channels.