Common data path rake receiver for a CDMA demodulator circuit

• US 20030210733A1
• Filed: 05/07/2002
• Published: 11/13/2003
• Est. Priority Date: 05/07/2002
• Status: Active Grant

• Current Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Original Assignee: STMicroelectronics Incorporated (STMicroelectronics NV)
• Inventors: Cervini, Stefano
• Granted Patent: US 7,103,091 B2
• Time in Patent Office: Days
• US Class Current: 375/147
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2201/70707 Efficiency-related aspects

Abstract

An architecture for a rake receiver of a CMDA demodulator utilizes a common data path for signal processing. This common data path is shared by all channels (either physical channels or propagation paths within physical channels) to avoid redundant calculations, reduce circuit space and reduce power consumption. The sharing of the common data path for demodulation is made on a time divided manner, with each channel being given sequential access to the data path to perform all or part of a given demodulation function (for example, de-scrambling, de-spreading, de-rotating, and de-skewing accumulation).

Claims

1. A demodulator for demodulating a spread spectrum signal transmitted over a physical channel and received with multiple instances corresponding to plural propagation paths, comprising:

a demodulating data path operable to perform spread spectrum demodulating operations; and

a control system operable to manage time-shared access to the demodulating data path for performing spread spectrum demodulating operations on each of the instances of the spread spectrum signal in a time divided manner.

2. The demodulator of claim 1 wherein the demodulating data path includes a de-scrambling and de-spreading function, and the control system further operates to manage time-shared access to the de-scrambling and de-spreading function of the demodulating data path for performing de-scrambling and de-spreading operations on each of the instances of the spread spectrum signal in the time divided manner.

3. The demodulator of claim 2 wherein the demodulating data path further includes a de-rotating function, and the control system further operates to manage time-shared access to the de-rotating function of the demodulating data path for performing de-rotating operations on symbols within each of the instances of the spread spectrum signal in the time divided manner.

4. The demodulator of claim 3 wherein the demodulating data path further includes a symbol accumulating function, and the control system further operates to manage time-shared access to the symbol accumulating function for performing accumulating operations on de-rotated symbols from each of the instances of the spread spectrum signal in the time divided manner to generate an accumulated symbol from across all propagation paths for the physical channel.

5. The demodulator as in claim 1 wherein the demodulator is fabricated as an integrated circuit.

6. A demodulator for demodulating spread spectrum signals transmitted over a plurality of channels, comprising:

a demodulating data path operable to perform spread spectrum demodulating operations; and

a control system operable to manage time-shared access to the demodulating data path for performing spread spectrum demodulating operations on each of the spread spectrum signals in a time divided manner.

7. The demodulator of claim 6 wherein the spread spectrum demodulating operations performed by the demodulating data path comprise de-scrambling and de-spreading, and the control system further operates to manage time-shared access to the demodulating data path for de-scrambling and de-spreading each of the spread spectrum signals in the time divided manner.

8. The demodulator of claim 7 wherein the spread spectrum demodulating operations performed by the demodulating data path further comprise de-rotating, and the control system further operates to manage time-shared access to the demodulating data path for de-rotating symbols within each of the spread spectrum signals in the time divided manner.

9. The demodulator of claim 8 wherein the spread spectrum demodulating operations performed by the demodulating data path further comprise accumulating de-rotated symbols from multiple propagation paths for each spread spectrum signal, and the control system further operates to manage time-shared access to the demodulating data path for accumulating the de-rotated symbols from the propagation paths within each of the spread spectrum signals in the time divided manner to generate an accumulated symbol from across all propagation paths for each of the spread spectrum signals.

10. The demodulator as in claim 6 wherein the demodulator is fabricated as an integrated circuit.

11. The demodulator as in claim 6 wherein the plurality of channels are a plurality of physical channels.

12. The demodulator as in claim 6 wherein the plurality of channels are a plurality of propagation paths within each one of a plurality of physical channels.

13. A method for demodulating a spread spectrum signal transmitted over a physical channel and received with multiple instances corresponding to plural propagation paths, comprising the steps of:

performing spread spectrum demodulating operations on the received spread spectrum signal along a single demodulating data path; and

managing time-shared access to the demodulating data path for performing spread spectrum demodulating operations on each of the instances of the spread spectrum signal in a time divided manner.

14. The method of claim 13 wherein the step of performing comprises the step of de-scrambling and de-spreading, and the step of managing comprises the step of time-shared allocating each of the instances of the spread spectrum signal to the single demodulation data path in the time divided manner for performance of the de-scrambling and de-spreading step.

15. The method of claim 14 wherein the step of performing further comprises the step of de-rotating, and the step of managing further comprises the step of time-shared allocating each of the instances of the spread spectrum signal to the single demodulation data path in the time divided manner for performance of the de-rotating step.

16. The method of claim 15 wherein the step of performing further comprises the step of accumulating de-rotated symbols from all propagation paths for the physical channel, and the step of managing further comprises the step of time-shared allocating each of the instances of the spread spectrum signal to the single demodulation data path in the time divided manner for performance of the accumulating step to generate an accumulated symbol from across all propagation paths for the physical channel.

17. A method demodulating spread spectrum signals transmitted over a plurality of channels, comprising:

performing spread spectrum demodulating operations on the received spread spectrum signals along a single demodulating data path; and

managing time-shared access to the demodulating data path for performing spread spectrum demodulating operations on each of the spread spectrum signals in a time divided manner.

18. The method of claim 17 wherein the step of performing comprises the step of de-scrambling and de-spreading, and the step of managing comprises the step of selectively granting each of spread spectrum signals access to the single demodulation data path in the time divided manner for performance of the de-scrambling and de-spreading step on the spread spectrum signals in the time divided manner.

19. The method of claim 18 wherein the step of performing further comprises the step of de-rotating, and the step of managing comprises the step of selectively granting each of spread spectrum signals access to the single demodulation data path in the time divided manner for performance of the de-rotating step on the spread spectrum signals in the time divided manner.

20. The method of claim 19 wherein the step of performing further comprises the step of accumulating de-rotated symbols from multiple propagation paths for each spread spectrum signal, and the step of managing comprises the step of selectively granting each of spread spectrum signals access to the single demodulation data path in the time divided manner for performance of the accumulating step on the spread spectrum signals in the time divided manner to generate an accumulated symbol from across all propagation paths for each of the spread spectrum signals.

21. The method as in claim 17 wherein the plurality of channels are a plurality of physical channels.

22. The method as in claim 17 wherein the plurality of channels are a plurality of propagation paths within each one of a plurality of physical channels.

23. A demodulator for spread spectrum signals, comprising:

a shared access data path, comprising;

a symbol integration stage operable to perform de-scrambling and de-spreading operations on the spread spectrum signals to produce recovered symbols; and

a symbol combining stage operable to perform de-rotation on the recovered symbols and to accumulate de-rotated symbols and produce a output symbol; and

a control circuit selectively granting each spread spectrum signal time divided access to the shared access data path for the purpose of utilizing an appropriate one of the symbol integration stage and the symbol combining stage to operate on the spread spectrum signals.

24. The demodulator of claim 23 wherein the control circuit grants a first time divided access to the symbol integration stage with respect to a certain spread spectrum signal to de-scramble and de-spread that certain spread spectrum signal and recover a first symbol, and wherein the control circuit grants a second time divided access to the symbol combining stage to de-rotate that first symbol of the certain spread spectrum signal.

25. The demodulator of claim 24 wherein the control circuit grants a third time divided access to the symbol combining stage to accumulate that first symbol with other symbols to produce the output symbol for that certain spread spectrum signal.

26. The demodulator of claim 25 wherein each of the first, second and third time divided accesses with respect to the certain spread spectrum signal are interposed with other control circuit granted time divided accesses to the shared access data path for the handling of spread spectrum signals other than the certain spread spectrum signal.

27. The demodulator of claim 26 wherein the other spread spectrum signals comprise signals on other propagation paths for a same physical channel.

28. The demodulator of claim 23 wherein the spread spectrum signals comprise signals from plural physical channels.

29. The demodulator of claim 23 wherein the spread spectrum signals comprise signals from plural propagation paths of a single physical channel.