Improved selective repeat ARQ schemes for data communication

Many of the communication protocols require an error free transmission of data which cannot be guaranteed by using only a forward error correction technique. For packet switched communications, quite a number of ARQ (automatic repeat request) protocols have been designed which are able to cope with stringent memory requirements, but they either lack safety at high block error rates, or they require a large bandwidth due to low throughput. We introduce two simple and effective strategies (called Stutter-XOR or SXOR and XOR selective repeat or XOR-SR strategies) to increase throughput of existing protocols. In contrast to existing hybrid schemes (combinations of ARQ and forward error correction), the SXOR strategy does not only correct bit errors occurring on radio channels, but also handles block losses caused by buffer overflow in gateways, routers and receivers with limited buffer capacity. This is achieved by sending additional blocks, so called XOR blocks, which are created by combining other blocks using the XOR (modulo-2-addition) operation. We developed several variants of this strategy. Two of them are evaluated by means of simulation. For point-to-multipoint communication the new XOR selective repeat strategy can improve the throughput of existing systems remarkably. The idea of the XOR selective repeat strategy is to physically combine several blocks negatively acknowledged by different receivers by XORing them to minimize the number of retransmissions and hence to increase throughput