Soft combining hybrid ARQ techniques application to 3G wireless packet networks

This paper deals with the application of hybrid automatic repeat request (H-ARQ) techniques to reliable data communications in wireless 3G networks, whose typical applications have to match accurate quality of service (QoS) requirements. A common approach to guarantee such services enhances the H-ARQ features by exploiting turbo codes error correction capabilities. This paper, following the previous approach, investigates the further benefits achievable by developing a strategy that establishes a connection between packet retransmissions and decoding results. Two kinds of these techniques, belonging to soft recombining schemes, are proposed and applied, respectively, to consecutive received packet replicas, or to decoding algorithm outputs, in both cases, without remarkable hardware complexity increase. By means of analytical derivations and simulations, focused on a typical universal mobile telecommunication system (UMTS) environment, a noticeable bit error rate (BER) and, then, frame error rate (FER) improvements have been shown. For the proposed schemes, whenever communications suffer from low signal to noise ratio (SNR) values, significant link throughput increase is also pointed out. As a consequence, these techniques can assure a lower packet delivery delay, besides avoiding transmitted power wasting, if compared with protocols commonly used in wired networks.