An adaptive type-II hybrid ARQ/FEC protocol suitable for GSM

To combat errors in data transmission in mobile radio systems, forward error correction (FEC) and automatic repeat request (ARQ) schemes are combined to hybrid type-I ARQ protocols without using disturbed packets. In poor radio conditions type-I ARQ schemes produce a low throughput with a high delay jitter. Due to these unforeseeable channel delays type-I ARQ protocols are critical for use in cases where timing conditions have to be fulfilled as in speech and e.g. FAX-T30 transmission. Type-II hybrid ARQ (HARQ) protocols combine disturbed and retransmitted packets using FEC methods and limit the mean transmission delay by increasing the throughput. A type-II hybrid ARQ with punctured convolutional codes suitable for GSM data traffic and performance was compared to the recommended radio link protocol (type-I). A new type-II hybrid ARQ protocol is proposed which makes use of the state information given by the equalization process to estimate the amount and best location of the redundancy to be retransmitted