Hard decision packet combining methods for industrial wireless relay networks

We consider wireless relay networks for use in industrial applications with strict requirements on both reliable and timely communications. In most cases commercially available transceivers must be used, which implies that only hard decision detector outputs are available. Since relay networks typically use retransmissions of erroneous packets, packet combining methods have the potential to increase the information reliability without excessive delay. We evaluate three different hard decision packet combining methods for different placement of the source, the relay node and the destination. Packet combining can in general be improved with knowledge of the current channel state information, which, however, is often not available. In this paper we find a packet combining method which does not use channel state information but which delivers similar performance as the scheme that has knowledge of the channel state.