Variable Rate Superorthogonal Turbo Code with the OVSF Code Tree
When using modern Code Division Multiple Access (CDMA) in mobile communications, the user must be able to vary the transmission rate of users to allocate bandwidth efficiently. In this work, Orthogonal Variable Spreading Factor (OVSF) codes are used with the same principles applied in a low-rate superorthogonal turbo code due to their variable-length properties. The introduced system is the Variable Rate Superorthogonal Turbo Code (VRSTC) where puncturing is not performed on the encoder’s final output but rather before selecting the output to achieve higher rates. Due to bandwidth expansion, the codes outperform an ordinary turbo code in the AWGN channel. Simulations results show decreased performance compared to those obtained with the employment of Walsh-Hadamard codes. However, with OVSF codes, the VRSTC system keeps the orthogonality of codewords whilst producing variable rate codes contrary to Walsh-Hadamard codes where puncturing is usually performed on the final output.
[1] C. Berrou, A. Glavieux, and P. Thitimajshima, "Near shannon limit error-correcting coding and decoding: Turbo-codes,” IEEE International Conference on Communications ICC’93, Geneva, Switzerland 23-26 May 1993, vol. 2, pp. 1064-1070.
[2] B. Sklar, "Turbo code concepts made easy, or how I learned to concatenate and reiterate,” MILCOM 97, vol. 1, pp. 20-26.
[3] G. Ramsawock, "Combined channel coding and modulation using variable rate,” Ph.D. dissertation, University of Mauritius, Mauritius, 2009.
[4] A. Lientz and J. Villasenor, "Very low variable rate convolutional codes for unequal error protection in DS-CDMA systems,” IEEE Transactions on Communications, July 1997, vol. 45, no. 7, pp. 753-755.
[5] K. Pehkonen and P. Komulainen, "A superorthogonal turbo-code for CDMA applications," IEEE 4th International Symposium on Spread Spectrum Techniques and Applications Proceedings, 22-25 Sep 1996, vol. 2, pp. 580-584.
[6] P. Komulainen and K. Pehkonen, "Performance evaluation of superorthogonal turbo codes in AWGN and flat rayleigh fading channels,” IEEE Journal on Selected Areas in Communications, vol. 16, no. 2, 1998, pp. 196-205.
[7] A.J. Viterbi, "Method and apparatus for generating superorthogonal convolutional codes and the decoding thereof,” US005193094A, March 9, 1993.
[8] A.J. Viterbi, CDMA: Principles of Spread Spectrum Communication. Addison-Wesley Publishing Company, ISBN 0-207-63374-4, 1995.
[9] L. Yen and M. Tsou, "An OVSF code assignment scheme utilizing multiple RAKE combiners for W-CDMA,” Computer Communications, vol. 27, no.16, 2004, pp. 1617-1623.
[10] G. Suchitra and M.L. Valarmathi, "BER performance of modified walsh hadamard codes in a DS-CDMA and cognitive underlay system,” European Journal of Scientific Research, vol. 64, no. 4, 2011, pp. 563-578.
[11] M.H. Le and R. Liyana-Pathirana, "Unequal error protection codes for wavelet image transmission over W-CDMA, AWGN and rayleigh fading channels,” 10th International Conference on Telecommunications, ICT 2003, 23 Feb - 1 March 2003, vol. 2, pp. 1140-1146.
[12] P. Robertson, "Illuminating the structure of code and decoder of parallel concatenated recursive systematic (turbo) codes,” IEEE Global Telecommunications Conference, GLOBECOM’94, San Francisco, CA, 28 Nov- 2 Dec 1994, vol. 3, pp. 1298-1303.
[13] R. L. Bahl , J. Cocke , F. Jelinek and J. Raviv, "Optimal decoding of linear codes for minimizing symbol error rate,” IEEE Transactions on Information Theory, vol. 20, no.2, 1974, pp. 284-287.
[14] P. Robertson, E. Villebrun and P. Hoeher, "A comparison of optimal and sub-optimal MAP decoding algorithms operating in the log domain,” Proceedings of the International Conference on Communications, vol. 2, 1997, pp. 1009-1013.
[1] C. Berrou, A. Glavieux, and P. Thitimajshima, "Near shannon limit error-correcting coding and decoding: Turbo-codes,” IEEE International Conference on Communications ICC’93, Geneva, Switzerland 23-26 May 1993, vol. 2, pp. 1064-1070.
[2] B. Sklar, "Turbo code concepts made easy, or how I learned to concatenate and reiterate,” MILCOM 97, vol. 1, pp. 20-26.
[3] G. Ramsawock, "Combined channel coding and modulation using variable rate,” Ph.D. dissertation, University of Mauritius, Mauritius, 2009.
[4] A. Lientz and J. Villasenor, "Very low variable rate convolutional codes for unequal error protection in DS-CDMA systems,” IEEE Transactions on Communications, July 1997, vol. 45, no. 7, pp. 753-755.
[5] K. Pehkonen and P. Komulainen, "A superorthogonal turbo-code for CDMA applications," IEEE 4th International Symposium on Spread Spectrum Techniques and Applications Proceedings, 22-25 Sep 1996, vol. 2, pp. 580-584.
[6] P. Komulainen and K. Pehkonen, "Performance evaluation of superorthogonal turbo codes in AWGN and flat rayleigh fading channels,” IEEE Journal on Selected Areas in Communications, vol. 16, no. 2, 1998, pp. 196-205.
[7] A.J. Viterbi, "Method and apparatus for generating superorthogonal convolutional codes and the decoding thereof,” US005193094A, March 9, 1993.
[8] A.J. Viterbi, CDMA: Principles of Spread Spectrum Communication. Addison-Wesley Publishing Company, ISBN 0-207-63374-4, 1995.
[9] L. Yen and M. Tsou, "An OVSF code assignment scheme utilizing multiple RAKE combiners for W-CDMA,” Computer Communications, vol. 27, no.16, 2004, pp. 1617-1623.
[10] G. Suchitra and M.L. Valarmathi, "BER performance of modified walsh hadamard codes in a DS-CDMA and cognitive underlay system,” European Journal of Scientific Research, vol. 64, no. 4, 2011, pp. 563-578.
[11] M.H. Le and R. Liyana-Pathirana, "Unequal error protection codes for wavelet image transmission over W-CDMA, AWGN and rayleigh fading channels,” 10th International Conference on Telecommunications, ICT 2003, 23 Feb - 1 March 2003, vol. 2, pp. 1140-1146.
[12] P. Robertson, "Illuminating the structure of code and decoder of parallel concatenated recursive systematic (turbo) codes,” IEEE Global Telecommunications Conference, GLOBECOM’94, San Francisco, CA, 28 Nov- 2 Dec 1994, vol. 3, pp. 1298-1303.
[13] R. L. Bahl , J. Cocke , F. Jelinek and J. Raviv, "Optimal decoding of linear codes for minimizing symbol error rate,” IEEE Transactions on Information Theory, vol. 20, no.2, 1974, pp. 284-287.
[14] P. Robertson, E. Villebrun and P. Hoeher, "A comparison of optimal and sub-optimal MAP decoding algorithms operating in the log domain,” Proceedings of the International Conference on Communications, vol. 2, 1997, pp. 1009-1013.
@article{"International Journal of Electrical, Electronic and Communication Sciences:66003", author = "Insah Bhurtah and P. Clarel Catherine and K. M. Sunjiv Soyjaudah", title = "Variable Rate Superorthogonal Turbo Code with the OVSF Code Tree", abstract = "When using modern Code Division Multiple Access (CDMA) in mobile communications, the user must be able to vary the transmission rate of users to allocate bandwidth efficiently. In this work, Orthogonal Variable Spreading Factor (OVSF) codes are used with the same principles applied in a low-rate superorthogonal turbo code due to their variable-length properties. The introduced system is the Variable Rate Superorthogonal Turbo Code (VRSTC) where puncturing is not performed on the encoder’s final output but rather before selecting the output to achieve higher rates. Due to bandwidth expansion, the codes outperform an ordinary turbo code in the AWGN channel. Simulations results show decreased performance compared to those obtained with the employment of Walsh-Hadamard codes. However, with OVSF codes, the VRSTC system keeps the orthogonality of codewords whilst producing variable rate codes contrary to Walsh-Hadamard codes where puncturing is usually performed on the final output.
", keywords = "CDMA, MAP Decoding, OVSF, Superorthogonal Turbo Code. ", volume = "7", number = "2", pages = "264-8", }
