Sequential decoding of tailbiting convolutional codes for hybrid ARQ on wireless channels

Sequential decoding of long constraint length convolutional codes is proposed for hybrid automatic repeat request packet data transmission on a Rayleigh fading channel. In this scheme computational complexity (the timeout condition) is applied for error detection. In order to improve the throughput, tailbiting codes are used. Furthermore, a method for estimating the initial state of the encoder is described, and for most packet lengths the tailbiting scheme with initial state/tail estimation yields significantly improved throughput compared to the case with a known tail. A throughput of 0.90 at a signal to noise ratio per coded bit of 15 dB shows this coding scheme to be competitive for wireless packet data services. Although interleaving must be performed over one packet only, high throughput is maintained also for correlated fading.