Impact of Fountain Codes on GPRS channels

The rateless and information additive properties of fountain codes make them attractive for use in broadcast/multicast applications, especially in radio environments where channel characteristics vary with time and bandwidth is expensive. Conventional schemes using a combination of ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction) suffer from serious drawbacks such as feedback implosion at the transmitter, the need to know the channel characteristics apriori so that the FEC scheme is designed to be effective and the fact that a reverse channel is needed to request retransmissions if the FEC fails. This paper considers the assessment of fountain codes over radio channels. The performance of fountain codes, in terms of the associated overheads, over radio channels of the type experienced in GPRS (General Packet Radio Service) is presented. The work is then extended to assessing the performance of Fountain codes in combination with the GPRS channel coding schemes in a radio environment.