Performance in a Multihop Chain Network

IEEE 802.11 is known to encounter significant performance problems in a multihop network [34]. For example, if all nodes are on the same channel, the RTS/CTS mechanism allows at most one hop in an $A-\>B-\>C-\>D$ chain to be active at any given time. SSCH reduces the throughput drop due to this behavior by allowing nodes to communicate on different channels. To examine this, we evaluate both SSCH and IEEE 802.11a in a multihop chain network.

Figure 15: Multihop Chain Network: Variation in throughput as chain length increases.

We vary the number of nodes, which are all in communication range, from 2 to 18. We initiate a single flow that encounters every node in the network. Although more than 4 nodes transmitting within interference range of each other would be unlikely to arise from multihop routing of a single flow, it could easily arise in a more general distributed application. Figure 15 shows the maximum throughput as the number of nodes in the chain is varied. We see that there is not much difference between SSCH and IEEE 802.11a for flows with few hops. As the number of hops increases, SSCH performs much better than IEEE 802.11a since it distributes the communication on each hop across all the available channels.