CA2620101A1 - Quadriphase spreading codes in code division multiple access communications - Google Patents
Quadriphase spreading codes in code division multiple access communicationsInfo
- Publication number
- CA2620101A1 CA2620101A1 CA002620101A CA2620101A CA2620101A1 CA 2620101 A1 CA2620101 A1 CA 2620101A1 CA 002620101 A CA002620101 A CA 002620101A CA 2620101 A CA2620101 A CA 2620101A CA 2620101 A1 CA2620101 A1 CA 2620101A1
- Authority
- CA
- Canada
- Prior art keywords
- code
- codes
- cdma
- family
- original
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/10—Code generation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0022—PN, e.g. Kronecker
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
Optimal code sequences are generated for use in spreading and de-spreading functions in a code division multiple access (CDMA) communications system. In particular, a family of quadriphase spreading codes is employed that provides a maximal number of spreading codes to achieve a high capacity in the CDMA
communications system while at the same time having a minimal peak cross-correlation between any two spreading codes within that family to ensure cross-correlation interference is kept at or below acceptable levels. That optimal quadriphase spreading code family is the S(2) family of four phase code sequences of length L = 2m-1 where m is an integer greater than or equal to 5. The size of the S(2) family of quaternary spreading codes is (L
+ 2)(L + 1)2, and the maximum cross-correlation is 1 + 4.sqroot.(L +1). The spreading codes are preferably allocated to base stations using specific code subsets of the S(2) family having the same cross-correlation properties of the S(O) and/or S(1) family of codes.
Spreading codes are advantageously extended by one or more code symbols as necessary or otherwise desirable. For example, to support variable transmission rate services, it is desirable to employ spreading codes whose length may be expressed as an integer multiple of each spreading factor in the mobile communications system. Since individual spreading codes have a length of 2m-1, one code symbol is added to the generated spreading code.
communications system while at the same time having a minimal peak cross-correlation between any two spreading codes within that family to ensure cross-correlation interference is kept at or below acceptable levels. That optimal quadriphase spreading code family is the S(2) family of four phase code sequences of length L = 2m-1 where m is an integer greater than or equal to 5. The size of the S(2) family of quaternary spreading codes is (L
+ 2)(L + 1)2, and the maximum cross-correlation is 1 + 4.sqroot.(L +1). The spreading codes are preferably allocated to base stations using specific code subsets of the S(2) family having the same cross-correlation properties of the S(O) and/or S(1) family of codes.
Spreading codes are advantageously extended by one or more code symbols as necessary or otherwise desirable. For example, to support variable transmission rate services, it is desirable to employ spreading codes whose length may be expressed as an integer multiple of each spreading factor in the mobile communications system. Since individual spreading codes have a length of 2m-1, one code symbol is added to the generated spreading code.
Claims (35)
1. In a code division multiple access (CDMA) mobile communications system in which a plurality of mobile radio stations communicate with one or more radio base stations located in corresponding geographic areas over a radio channel, each radio channel corresponding to one of a set of spreading codes, one or more of the radio stations comprising:
a code generator configured to provide quadriphase spreading codes determined from an S(2) set of quaternary spreading codes having a maximal number of quaternary spreading codes with a minimal cross-correlation and to extend a length of the S(2) quaternary spreading codes to support multi-rate communications in the CDMA mobile communications system;
a spreader configured to spread an information signal to be transmit by the radio station using one of the quadriphase spreading codes allocated to the radio station to provide a spread signal; and a modulator configured to modulate the spread signal onto a radio carrier.
a code generator configured to provide quadriphase spreading codes determined from an S(2) set of quaternary spreading codes having a maximal number of quaternary spreading codes with a minimal cross-correlation and to extend a length of the S(2) quaternary spreading codes to support multi-rate communications in the CDMA mobile communications system;
a spreader configured to spread an information signal to be transmit by the radio station using one of the quadriphase spreading codes allocated to the radio station to provide a spread signal; and a modulator configured to modulate the spread signal onto a radio carrier.
2. The radio station of claim 1, further comprising:
a demodulator configured to demodulate a received CDMA signal from the radio carrier; and a de-spreader configured to de-spread the received CDMA signal using the one quadriphase spreading code to provide a received information signal.
a demodulator configured to demodulate a received CDMA signal from the radio carrier; and a de-spreader configured to de-spread the received CDMA signal using the one quadriphase spreading code to provide a received information signal.
3. The radio station of claim 1 or 2, wherein information signals to be transmit are allocated into a real data stream and an imaginary data stream, the radio station further comprising:
a real channel spreader configured to spread the real data stream using a real channelization code;
an imaginary channel spreader configured to spread the imaginary data stream using an imaginary channelization code; and a combiner configured to combine outputs from the real and imaginary channel spreaders to generate a complex signal;
wherein the spreader is configured to spread the complex signal using the one quadriphase spreading code allocated to the mobile radio.
a real channel spreader configured to spread the real data stream using a real channelization code;
an imaginary channel spreader configured to spread the imaginary data stream using an imaginary channelization code; and a combiner configured to combine outputs from the real and imaginary channel spreaders to generate a complex signal;
wherein the spreader is configured to spread the complex signal using the one quadriphase spreading code allocated to the mobile radio.
4. The radio station of claim 3, wherein the modulator is a quadrature phase shift keying (QPSK) modulator and wherein the complex signal is split into real and imaginary components which are then input to real and imaginary inputs of the QPSK
modulator.
modulator.
5. The radio station of claim 4, wherein the code generator is configured to map the quaternary spreading code to a quadriphase spreading code.
6. The radio of any one of claims 1 to 5, wherein the code generator is configured to extend the length of the S(2) quaternary spreading codes periodically.
7. The radio station of any one of claims 1 to 6, wherein the S(2) quaternary spreading codes are extended by one quaternary symbol so that the S(2) quaternary spreading code length is a multiple of each of multiple spreading factors used in the CDMA mobile communications system.
8. In a code division multiple access (CDMA) communications system in which a plurality of communications devices communicate using allocated communications channels, each channel corresponding to one of a set of CDMA spreading codes, a method comprising:
generating a family of original codes, each original code having a predetermined length;
and extending the length of original codes from the family of spreading codes by a code symbol to generate a family of CDMA spreading codes by detecting the end of one of the original codes, and adding the code symbol to the end of one of the original codes.
generating a family of original codes, each original code having a predetermined length;
and extending the length of original codes from the family of spreading codes by a code symbol to generate a family of CDMA spreading codes by detecting the end of one of the original codes, and adding the code symbol to the end of one of the original codes.
9. The method of claim 8, wherein the code symbol is the same for all of the original codes in the family.
10. The method of claim 8 or 9, wherein the code symbol is the same as a first code symbol in the one original code.
11. The method of any one of claims 8 to 10, wherein the family of original codes are quadriphase codes, and the code symbol used to extend the original code has four possible values.
12. In a code division multiple access (CDMA) communications system in which a plurality of communications devices communicate using allocated communications channels, each channel corresponding to one of a set of CDMA spreading codes, a method comprising:
generating a family of original codes, each original code having a predetermined length;
and extending the length of original codes from the family of spreading codes by a code symbol to generate a family of CDMA spreading codes by detecting the end of one of the original codes, and adding the code symbol to the end of one of the original codes;
wherein the family of original codes has a length of L=2m-1, where m is an integer, and a single code symbol is added to the end of the original code periodically.
generating a family of original codes, each original code having a predetermined length;
and extending the length of original codes from the family of spreading codes by a code symbol to generate a family of CDMA spreading codes by detecting the end of one of the original codes, and adding the code symbol to the end of one of the original codes;
wherein the family of original codes has a length of L=2m-1, where m is an integer, and a single code symbol is added to the end of the original code periodically.
13. In a code division multiple access (CDMA) communications system in which a plurality of communications devices communicate using allocated communications channels, each channel corresponding to:
generating a family of original codes, each original code having a predetermined length;
and extending the length of original codes from the family of spreading codes by a code symbol to generate a family of CDMA spreading codes by detecting the end of one of the original codes, and adding the code symbol to the end of one of the original codes;
wherein the family of original codes are an S(2) family of codes and the code symbol is selected to minimize cross-correlation between CDMA spreading codes.
generating a family of original codes, each original code having a predetermined length;
and extending the length of original codes from the family of spreading codes by a code symbol to generate a family of CDMA spreading codes by detecting the end of one of the original codes, and adding the code symbol to the end of one of the original codes;
wherein the family of original codes are an S(2) family of codes and the code symbol is selected to minimize cross-correlation between CDMA spreading codes.
14. A CDMA code generator providing CDMA spreading codes, the generator comprising:
one or more feedback shift registers having m stages, where m is an integer, where an output of a last stage is fed back to an input of a first stage, the output of the one or more feedback shift registers corresponding to one of a family of codes; and electronic circuitry for adding an additional code symbol to the one code to provide an extended code corresponding to one of the CDMA spreading codes.
one or more feedback shift registers having m stages, where m is an integer, where an output of a last stage is fed back to an input of a first stage, the output of the one or more feedback shift registers corresponding to one of a family of codes; and electronic circuitry for adding an additional code symbol to the one code to provide an extended code corresponding to one of the CDMA spreading codes.
15. The CDMA code generator of claim 14, further comprising:
a comparator for detecting an end of the one code and signaling the electronic circuitry to add to the additional code symbol to the end of the one code.
a comparator for detecting an end of the one code and signaling the electronic circuitry to add to the additional code symbol to the end of the one code.
16. The CDMA code generator of claim 14 or 15, further comprising:
a counter for generating a counter output at the end of an extended code period which causes the shift registers to be set respective initial states.
a counter for generating a counter output at the end of an extended code period which causes the shift registers to be set respective initial states.
17. The CDMA code generator of any one of claims 14 to 16, wherein the added code symbol is the same for all of the codes in the family.
18. The CDMA code generator of any one of claims 14 to 17, wherein the added code symbol is the same as the first code symbol in the one original code.
19. The CDMA code generator of claim 16, wherein the family of original codes has a length L=2m-1, where m is a positive integer, and a single code symbol added to the end of one of the original codes is selected to reduce cross-correlation between the CDMA spreading codes.
20. The CDMA code generator of any one of claims 14 to 19, wherein the family of codes correspond to a family of quaternary sequences of length L=2m-1, where m is an integer greater than or equal to 5, having code elements from an alphabet {0, 1, 2, 3}, generated by summing modulo-4 three component sequences including a first component quaternary sequence a, a second component binary sequence b, and a third component binary sequence c, wherein the one or more feedback shift registers includes first, second, and third feedback shift registers that generate the first, second, and third component quaternary sequences, respectively, with the output of the second and third shift registers being multiplied by 2 before the first, second, and third component quaternary sequences are modulo-4 summed.
21. The CDMA code generator of claim 20, wherein the code generator is configured to map the extended quaternary sequence to complex quadriphase CDMA spreading codes.
22. The method of any one of claims 8 to 10, wherein the length of the original codes are extended without having to increase the number of the original codes from the family.
23. In a code division multiple access (CDMA) communications system in which a plurality of communications devices communicate using allocated communications channels, each channel corresponding to one of a set of CDMA spreading codes, a method comprising:
generating a family of original S(2) quaternary spreading codes, each original code having a predetermined length; and extending the length of original codes from the family of original S(2) quaternary spreading codes by a code symbol to generate a family of CDMA spreading codes without having to increase the number of the original codes from the family.
generating a family of original S(2) quaternary spreading codes, each original code having a predetermined length; and extending the length of original codes from the family of original S(2) quaternary spreading codes by a code symbol to generate a family of CDMA spreading codes without having to increase the number of the original codes from the family.
24. The method of claim 23, wherein the extending further comprises:
detecting the end of one of the original codes; and adding the code symbol to the end of one of the original codes.
detecting the end of one of the original codes; and adding the code symbol to the end of one of the original codes.
25. The method of claim 23 or 24, wherein the code symbol is the same for all of the original codes in the family.
26. The method of any one of claims 23 to 25, wherein the code symbol is the same as the first code symbol in the one original code.
27. The method of any one of claims 23 to 26, wherein the code symbol is added to the end of one of the original codes periodically.
28. The method of any one of claims 23 to 27, wherein the family of original codes are quadriphase codes, and the code symbol used to extend the original code has four possible values.
29. The method of any one of claims 23 to 28, wherein the code symbol is selected to minimize cross-correlation between CDMA spreading codes.
30. A CDMA code generator providing CDMA spreading codes, the generator comprising:
one or more feedback shift registers having m stages, where m is an integer, where an output of a last stage is fed back to an input of a first stage, the output of the one or more feedback shift registers corresponding to one of a family of S(2) quaternary spreading codes of length L=2m-1; and electronic circuitry for adding an additional code symbol to the one S(2) quaternary spreading code to provide an extended S(2) quaternary spreading code corresponding to one of the CDMA spreading codes.
one or more feedback shift registers having m stages, where m is an integer, where an output of a last stage is fed back to an input of a first stage, the output of the one or more feedback shift registers corresponding to one of a family of S(2) quaternary spreading codes of length L=2m-1; and electronic circuitry for adding an additional code symbol to the one S(2) quaternary spreading code to provide an extended S(2) quaternary spreading code corresponding to one of the CDMA spreading codes.
31. The CDMA code generator of claim 30, further comprising:
a comparator for detecting an end of the one S(2) quaternary spreading code and signaling the electronic circuitry to add to the additional code symbol to the end of the one S(2) quaternary spreading code.
a comparator for detecting an end of the one S(2) quaternary spreading code and signaling the electronic circuitry to add to the additional code symbol to the end of the one S(2) quaternary spreading code.
32. The CDMA code generator of claim 30 or 31, further comprising:
a counter for generating a counter output at the end of an extended code period which causes the shift registers to be set respective initial states.
a counter for generating a counter output at the end of an extended code period which causes the shift registers to be set respective initial states.
33. The CDMA code generator of any one of claims 30 to 32, wherein the added code symbol is the same for all of the codes in the family.
34. The CDMA code generator of any one of claims 30 to 33, wherein the added code symbol is the same as the first code symbol in the one original code.
35 35. The CDMA code generator of any one of claims 30 to 34, wherein a value of the additional code symbol is selected to reduce cross-correlation between the CDMA
spreading codes.
spreading codes.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/097,916 US6393047B1 (en) | 1998-06-16 | 1998-06-16 | Quadriphase spreading codes in code division multiple access communications |
| US09/097,916 | 1998-06-16 | ||
| CA002335018A CA2335018C (en) | 1998-06-16 | 1999-06-11 | Quadriphase spreading codes in code division multiple access communications |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002335018A Division CA2335018C (en) | 1998-06-16 | 1999-06-11 | Quadriphase spreading codes in code division multiple access communications |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2620101A1 true CA2620101A1 (en) | 1999-12-23 |
| CA2620101C CA2620101C (en) | 2012-08-07 |
Family
ID=39315345
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2619679A Expired - Lifetime CA2619679C (en) | 1998-06-16 | 1999-06-11 | Quadriphase spreading codes in code division multiple access communications |
| CA2620101A Expired - Lifetime CA2620101C (en) | 1998-06-16 | 1999-06-11 | Quadriphase spreading codes in code division multiple access communications |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2619679A Expired - Lifetime CA2619679C (en) | 1998-06-16 | 1999-06-11 | Quadriphase spreading codes in code division multiple access communications |
Country Status (1)
| Country | Link |
|---|---|
| CA (2) | CA2619679C (en) |
-
1999
- 1999-06-11 CA CA2619679A patent/CA2619679C/en not_active Expired - Lifetime
- 1999-06-11 CA CA2620101A patent/CA2620101C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2619679C (en) | 2010-03-23 |
| CA2620101C (en) | 2012-08-07 |
| CA2619679A1 (en) | 1999-12-23 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20190611 |