System and method for demodulating multiple Walsh codes using a chip combiner

• US 6,987,798 B2
• Filed: 05/07/2003
• Issued: 01/17/2006
• Est. Priority Date: 05/07/2002
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Ahn, Seong-Woo, Heo, Seo-Weon
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US10/430,259
• Publication Number:
  US 20030210735A1
• Time in Patent Office: 986 Days
• Field of Search: 375/130, 375/136, 375/137, 375/142, 375/143, 375/145, 375/147, 375/148, 375/140, 375/144, 375/150, 370/342, 370/335, 370/441, 370/332, 370/209, 370/208, 370/210, 370/320
• US Class Current: 375/148
• 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 13/0048 Walsh

Abstract

Disclosed is a system and method for demodulating packet data channels with multiple Walsh codes in a CDMA mobile communication system supporting voice and packet data services. A plurality of fingers process signals received from a transmitter as inputs, perform despreading and channel compensation with spreading codes pre-assigned to the transmitter, and outputting the despread chip signals. A chip combiner combines the chip signals output from the plurality of fingers. A chip buffer stores the combined chip signals until decoding of the packet data control channels is completed and information on the multiple Walsh codes assigned to the packet data channels. Then, a multiple Walsh demodulator generates at least one Walsh symbol performing Walsh decovering of the combined chip signals using information on the multiple Walsh codes. Therefore, the system can efficiently demodulate data transmission channels using the multiple Walsh codes, and thus complexity of the system and demodulation time can be reduced.

Claims

1. A system for demodulating signals received through packet data channels using information on the packet data channels in a wireless packet data communication system, in which the information is received through packet data control channels and the communication system supports code division multiplexing, the system for demodulating signals comprising:

a plurality of fingers for processing signals received from a transmitter as inputs, for performing despreading with pre-assigned spreading codes and outputting the despread chip signals;

a chip combiner for combining the chip signals output from the plurality of fingers; and

a multiple Walsh demodulator for generating Walsh symbols performing Walsh decovering of each of the chip signals combined by the chip combiner using all Walsh codes available to the packet data channels, and when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, selecting and outputting at least one Walsh symbol corresponding to the multiple Walsh codes from among the Walsh symbols.

2. A system for demodulating signals according to claim 1, wherein the multiple walsh demodulator comprises:

a plurality of Walsh generators for generating all Walsh codes available to the packet data channels;

a plurality of Walsh decovers for performing Walsh decovering of each of the chip signals combined by the chip combiner with the Walsh codes generated by the Walsh generators to output Walsh symbols;

a symbol buffer for storing the Walsh symbols output from the plurality of Walsh decovers for a predetermined number of slots until decoding of the packet data control channels is completed; and

a Walsh selector for selecting and outputting, when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, at least one Walsh symbol corresponding to the multiple Walsh codes from among the Walsh symbols stored on the symbol buffer.

3. A system for demodulating signals according to claim 2, wherein the symbol buffer includes a plurality of memory cells for storing each of the Walsh symbols according to each slot for the predetermined number of slots, the Walsh symbols being output from the Walsh decovers.

4. A system for demodulating signals according to claim 1, wherein the fingers each comprise:

a despreader for multiplying signals received from the transmitter by the spreading codes to perform despreading;

a pilot filter for detecting pilot components contained in the despread signals to obtain channel estimation values; and

a channel compensator for multiplying the despread signals by the channel estimation values to perform channel compensation.

5. A system for demodulating signals according to claim 1, further comprising a plurality of first input first output memories (FIFOs) corresponding to the plurality of fingers, wherein the FIFOs store each of the chip signals output from the plurality of fingers and output the stored resultants to the chip combiner, so as to compensate for a delay offset difference between multiple paths caused by the fingers.

6. A system for demodulating signals received through packet data channels using information on the packet data channels in a wireless packet data communication system, in which the information is received through packet data control channels and the communication system supports code division multiplexing, the system for demodulating signals comprising:

a plurality of fingers for processing signals received from a transmitter as inputs and for performing despreading with pre-assigned spreading codes and outputting the despread chip signals;

a chip combiner for combining the chip signals output from the plurality of fingers;

a multiple walsh demodulator for generating Walsh symbols for performing Walsh decovering of each of the chip signals combined by the chip combiner using all Walsh codes available to the packet data channels, and when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, selecting and outputting at least one Walsh symbol corresponding to the multiple Walsh codes from among the Walsh symbols; and

a demapping section for demapping at least one Walsh symbol output from the multiple Walsh demodulator according to a modulation mode of the packet data channels obtained by completing decoding of the packet data control channels.

7. A system for demodulating signals according to claim 6, wherein the multiple Walsh demodulator comprises:

a plurality of Walsh generators for generating all Walsh codes available to the packet data channels;

a plurality of Walsh decovers for performing Walsh decovering of each of the chip signals combined by the chip combiner with the Walsh codes generated by the Walsh generators to output Walsh symbols;

a plurality of reference symbol energy calculators for processing the Walsh symbols output from the plurality of Walsh decovers as inputs to calculate each of reference symbol energy values;

a symbol buffer for storing both the Walsh symbols output from the plurality of Walsh decovers for a predetermined number of slots and the reference symbol energy values output from the plurality of reference symbol energy calculators, until decoding of the packet data control channels is completed; and

a Walsh selector for selecting, when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, at least one Walsh symbol corresponding to the multiple Walsh codes from among the stored Walsh symbols and at least one reference symbol energy value corresponding to the multiple Walsh codes from among the reference symbol energy values and for outputting the selected resultants to the demapping section.

8. A system for demodulating signals according to claim 7, wherein the plurality of reference symbol energy calculators calculate reference symbol energy values for the Walsh symbols output from the plurality of Walsh decovers per each slot.

9. A system for demodulating signals according to claim 7, wherein the symbol buffer comprises:

a plurality of memory cells for storing each of the Walsh symbols according to each slot for the predetermined number of slots, the Walsh symbols being output from the Walsh decovers; and

a plurality of reference symbol energy buffers for storing each of the reference symbol energy values according to each slot for the predetermined number of slots, the reference symbol energy values being output from the plurality of reference symbol energy calculators.

10. A system for demodulating signals according to claim 6, wherein the fingers each comprise:

a despreader for multiplying signals received from the transmitter by the spreading codes to perform despreading;

a pilot filter for detecting pilot components contained in the despread signals to obtain channel estimation values; and

a channel compensator for multiplying the despread signals by the channel estimation values to perform channel compensation.

11. A system for demodulating signals according to claim 6, further comprising a plurality of first input first output memories (FIFOs) corresponding to the plurality of fingers, wherein the FIFOs stores each of the chip signals output from the plurality of fingers and outputs the stored resultants to the chip combiner, so as to compensate for a delay offset difference between multiple paths caused by the fingers.

12. A system for demodulating signals according to claim 6, wherein the demapping section comprises:

a reference level calculator for processing at least one reference symbol energy value and a carrier to interference ratio (CIR) of the combined chip signals as inputs and for calculating a reference level of at least one Walsh symbol; and

a symbol demapper for demapping the Walsh symbols output from the multiple Walsh demodulator to output coded symbols using the reference level of at least one Walsh symbol if necessary according to the modulation mode of the packet data channels.

13. A system for demodulating signals received through packet data channels using information on the packet data channels in a wireless packet data communication system, in which the information is received through packet data control channels and the communication system supports code division multiplexing, the system for demodulating signals comprising:

a plurality of fingers for processing signals received from a transmitter as inputs and for performing despreading with pre-assigned spreading codes and outputting the despread chip signals;

a chip combiner for combining the chip signals output from the plurality of fingers;

a chip buffer for storing the chip signals combined by the chip combiner; and

a multiple Walsh demodulator for outputting, when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, at least one Walsh symbol performing Walsh decovering of the chip signals stored on the chip buffer using information on the multiple Walsh codes.

14. A system for demodulating signals according to claim 13, wherein the chip buffer stores the chip signals combined by the chip combiner for a predetermined number of slots until decoding of the packet data control channels is completed.

15. A system for demodulating signals according to claim 13, wherein the multiple Walsh demodulator comprises:

a plurality of Walsh generators for generating at least one Walsh code corresponding to the multiple Walsh codes assigned to the packet data channels; and

a plurality of Walsh decovers for outputting at least one Walsh symbol performing Walsh decovering of each of the chip signals stored on the chip buffer with at least one Walsh code generated by the Walsh generators.

16. A system for demodulating signals according to claim 13, further comprising a plurality of first input first output memories (FIFOs) corresponding to the plurality of fingers, wherein the FIFOs stores each of the chip signals output from the plurality of fingers and outputs the stored resultants to the chip combiner, so as to compensate for a delay offset difference between multiple paths caused by the fingers.

17. A system for demodulating signals received through packet data channels using information on the packet data channels in a wireless packet data communication system, in which the information is received through packet data control channels and the communication system supports code division multiplexing, the system for demodulating signals comprising:

a plurality of fingers for processing signals received from a transmitter as inputs and for performing despreading with pre-assigned spreading codes and outputting the despread chip signals;

a chip combiner for combining the chip signals output from the plurality of fingers;

a chip buffer for storing the combined chip signals;

a multiple Walsh demodulator for outputting, when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, at least one Walsh symbol performing Walsh decovering of the chip signals stored on the chip buffer using information on the multiple Walsh codes; and

a demapping section for demapping at least one Walsh symbol output from the multiple Walsh demodulator according to a modulation mode of the packet data channels obtained by completing decoding of the packet data control channels.

18. A system for demodulating signals according to claim 17, wherein the chip buffer stores the chip signals combined by the chip combiner for a predetermined number of slots until decoding of the packet data control channels is completed.

19. A system for demodulating signals according to claim 17, wherein the multiple Walsh demodulator comprises:

a plurality of Walsh generators for generating at least one Walsh code corresponding to the multiple Walsh codes assigned to the packet data channels; and

a plurality of Walsh decovers for performing Walsh decovering of each of the chip signals stored on the chip buffer with at least one Walsh code generated by the Walsh generators to output at least one Walsh symbol.

20. A system for demodulating signals according to claim 19, further comprising a symbol buffer for storing at least one Walsh symbol until measurement of a carrier to interference ratio (CIR) of the chip signals combined by the chip combiner is completed, if necessary according to the modulation mode of the packet data channels.

21. A system for demodulating signals according to claim 17, wherein the demapping section comprises:

a reference level calculator for calculating a reference level of at least one Walsh symbol using a carrier to interference ratio (CIR) of the combined chip signals if necessary according to the modulation mode of the packet data channels;

a 16QAM symbol demapper for demapping at least one Walsh symbol according to 16QAM to output coded symbols using the reference level of at least one Walsh symbol; and

a QPSK/8PSK symbol demapper for demapping at least one Walsh symbol according to any one of QPSK and 8PSK to output coded symbols.

22. A system for demodulating signals according to claim 17, wherein the fingers each comprise:

a despreader for multiplying signals received from the transmitter by the spreading codes to perform despreading;

a pilot filter for detecting pilot components contained in the despread signals to obtain channel estimation values; and

a channel compensator for multiplying the despread signals by the channel estimation values to perform channel compensation.

23. A system for demodulating signals according to claim 17, further comprising a plurality of first input first output memories (FIFOs) corresponding to the plurality of fingers, wherein the FIFOs stores each of the chip signals output from the plurality of fingers and outputs the stored resultants to the chip combiner, so as to compensate for a delay offset difference between multiple paths caused by the fingers.

24. A method for demodulating signals received through packet data channels using information on the packet data channels in a packet data channel receiver of a wireless packet data communication system, in which the information is received through packet data control channels and the communication system supports code division multiplexing, the method for demodulating signals comprising the steps of:

a) processing signals received from a transmitter as inputs, performing despreading with pre-assigned spreading codes, and outputting the despread chip signals;

b) combining the chip signals; and

c) generating Walsh symbols performing Walsh decovering of each of the combined chip signals using all Walsh codes available to the packet data channels, and when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, selecting and outputting at least one Walsh symbol corresponding to the multiple Walsh codes from among the Walsh symbols.

25. A method for demodulating signals according to claim 24, wherein the step c) comprises the sub-steps of:

generating all Walsh codes available to the packet data channels;

performing Walsh decovering of each of the combined chip signals with the generated Walsh codes to output Walsh symbols;

storing the Walsh symbols generated through decovering for a predetermined number of slots until decoding of the packet data control channels is completed; and

when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, selecting and outputting at least one Walsh symbol corresponding to the multiple Walsh codes from among the stored Walsh symbols.

26. A method for demodulating signals according to claim 24, wherein the step a)comprises the sub-steps of:

multiplying signals received from the transmitter by the spreading codes to perform despreading;

detecting pilot components contained in the despread signals to obtain channel estimation values; and

multiplying the despread signals by the channel estimation values to perform channel compensation.

27. A method for demodulating signals according to claim 24, further comprising the step of:

d) demapping at least one Walsh symbol according to a modulation mode of the packet data channels obtained by completing decoding of the packet data control channels.

28. A method for demodulating signals according to claim 27, further comprising the steps of:

e) processing the at least one Walsh symbol as inputs to calculate each of reference symbol energy values, storing the reference symbol energy values until decoding of the packet data control channels is completed, and when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, selecting and outputting at least one reference symbol energy value corresponding to the multiple Walsh codes from among the reference symbol energy values.

29. A method for demodulating signals according to claim 27, wherein the step d) performs demapping of at least one Walsh symbol with a reference level obtained using a carrier to interference ratio (CIR) of the combined chip signals and at least one Walsh symbol, if necessary according to the modulation mode of the packet data channels.

30. A method for demodulating signals received through packet data channels using information on the packet data channels in a packet data channel receiver of a wireless packet data communication system, in which the information is received through packet data control channels and the communication system supports code division multiplexing, the method for demodulating signals comprising the steps of:

a) processing signals received from a transmitter as inputs, performing despreading with pre-assigned spreading codes, and outputting the despread chip signals;

b) combining the chip signals;

c) storing the combined chip signals; and

d) when decoding of the packet data control channels is completed and information on multiple Walsh codes assigned to the packet data channels is obtained, outputting at least one Walsh symbol performing Walsh decovering of the stored chip signals using information on the multiple Walsh codes.

31. A method for demodulating signals according to claim 30, wherein the step c) stores the combined chip signals for a predetermined number of slots until decoding of the packet data control channels is completed.

32. A method for demodulating signals according to claim 30, wherein the step d) comprises the sub-steps of:

generating at least one Walsh code corresponding to the multiple Walsh codes assigned to the packet data channels; and

performing Walsh decovering of each of the stored chip signals with at least one Walsh code to output at least one Walsh symbol.

33. A method for demodulating signals according to claim 30, further comprising the step of:

e) demapping at least one Walsh symbol according to a modulation mode of the packet data channels obtained by completing decoding of the packet data control channels.

34. A method for demodulating signals according to claim 33, wherein the step e) performs demapping of at least one Walsh symbol with a reference level obtained using a carrier to interference ratio (CIR) of the combined chip signals and at least one Walsh symbol, if necessary according to the modulation mode of the packet data channels.