Application and standardization of turbo codes in third-generation high-speed wireless data services

Abstract

This paper addresses the application of turbo codes for third-generation wireless services. It describes the specific characteristics of high-rate data applications in third-generation wide-band code-division multiple-access (CDMA) systems that make turbo codes superior to convolutional codes. In particular, it shows the positive effect of fast power control employed in these systems on the relative performance of turbo codes with respect to convolutional codes. It also shows how turbo and convolutional codes behave differently when the figure of merit is changed to frame error rate from bit error rate for high-speed data services. Furthermore, it describes in detail how and why the standardized turbo code has been selected in the presence of other candidates, which were also based on iterative decoding. Details of turbo interleaving and trellis termination as specified in the standards are explained. Performance of turbo codes under wide-band CDMA operating conditions are presented. The suitability of turbo codes for low-rate data applications is discussed. Finally it is shown that the performance loss as a result of internal decoder parameter quantization is negligible.