Performance Improvement of FH CDMA Signals using Rate Compatible Parallel Concatenated Block Codes

Frequency-hopped (FH) CDMA is a digital multiple access system in which individual users selects one of Q frequencies within a wideband channel as carrier frequency. Main drawback of FH CDMA is, it is interference limited. In this paper we analyze the performance of frequency-hopped spread spectrum networks (FHSS) with turbo block codes. After the development of turbo code, using block component codes have received less attention. Block component codes are particularly suited for high rate applications with short block lengths and allow high degree of parallel processing which is desirable for delay sensitive applications. Rate compatible coding is appropriate for communication systems that experience a range of operating SNRs but seek to adhere to a single under laying codec structure. This paper suggests the performance improvement of FH SS signals by using rate compatible parallel-concatenated block codes using BCH (Bose, Chaudhuri, Hocquenghem) codes as component codes and usage of puncturing for making it rate compatible. These codes enjoy more freedom in puncturing pattern selection thus allowing for an almost continuous spectrum of code rates