Opportunistic forwarding in multi-hop OFDMA networks with local CSI

In multi-hop networks, conventional unipath routing approaches force the data transmission to follow a fixed sequence of nodes. In this paper, we widen this path to create a corridor of forwarding nodes. Within this corridor, data can be split and joined at different nodes as the data travels through the corridor towards the destination node. To split data, decode-and-forward OFDMA is used since with OFDMA, one can exploit the benefits of opportunistically allocating different subcarriers to different nodes according to their channel conditions. To avoid interference, each subcarrier is only allocated once per hop. It is assumed that only local channel state information (CSI) for the next hop towards the destination is available at the nodes, i.e. it can not be guaranteed that a certain node is able to forward its received data in the next hop. This leads to additional transmission phases decreasing the overall network throughput. In this paper, different opportunistic forwarding algorithms are presented which differ in the resource allocation strategy and in the amount of cooperation required between the nodes. Simulations show that in multihop networks, corridor-based routing using opportunistic forwarding with a proper resource allocation strategy outperforms conventional unipath routing approaches in terms of achievable throughput, especially in case of a node drop out.