A distributed collision-free time slot and channel assignment algorithm for OFDM/TDMA wireless relay networks

In wireless multi-hop networks employing OFDM/TDMA, a collision-free time slot assignment is equal to finding a matching set in the network routing graph if an exclusive node (single hop) interference model is assumed. In order to maximize throughput, one must compute the maximum weighted matching set of the routing graph. Since the exclusive node interference model does not take into account interference caused by hidden terminals, two-hop interfering links should be scheduled on different channels during a same time slot. For this purpose, we introduce a distributed scheduling algorithm that assigns both time slots and channels to wireless transmission links in a conflict free manner. The suggested algorithm is a greedy solution which finds the local maximum weight of the links. Furthermore, the proposed algorithm can incorporate the effects of changes in topology and routing. We present simulation results for networks where all nodes use a single-radio antenna, the MAC layer protocol is synchronized OFDM, and each channel uses TDMA. Comparisons are made using the proposed algorithm and the three-way handshaking algorithm suggested in the 2004 WiMAX standard.