Performance analysis of type-I and type-II hybrid ARQ protocols using concatenated codes in a DS-CDMA Rayleigh fading channel

To achieve reliable data transmission in a power-controlled, direct-sequence code division multiple access cellular system, we investigate two error-control schemes based on the concatenation of Reed-Solomon and convolutional codes. The first scheme is a type-I hybrid selective repeat ARQ protocol (CC/HARQ) where the error detection capability of the RS outer code is used to trigger retransmission requests. The second scheme is a type-II hybrid selective repeat ARQ protocol where error correction capability is adapted to the varying channel conditions. The performance criteria are the protocol error probability, the throughput and delay efficiencies over a Rayleigh fading DS-CDMA channel with a Gaussian approximation for the multiple access interference. While type-I CC/HARQ yields superior throughput when the number of active users is small, the results show that type-II CC/HARQ provides reliable data transfer to the largest number of users, even in the presence of imperfect power control