Insah Bhurtah and P. Clarel Catherine and K. M. Sunjiv Soyjaudah
Variable Rate Superorthogonal Turbo Code with the OVSF Code Tree
258 - 265
2013
7
2
International Journal of Electronics and Communication Engineering
https://publications.waset.org/pdf/9996956
https://publications.waset.org/vol/74
World Academy of Science, Engineering and Technology
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 lowrate superorthogonal turbo code due to their variablelength 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 WalshHadamard codes. However, with OVSF codes, the VRSTC system keeps the orthogonality of codewords whilst producing variable rate codes contrary to WalshHadamard codes where puncturing is usually performed on the final output.
Open Science Index 74, 2013