On the Performance of Hybrid Wireless/Wired Mesh Networks

Wireless mesh networks (WMNs) transparently extend the coverage of a portal via mesh points (MPs) which relay data over multiple hops to the associated stations. While this concept lowers costly wire installations, capacity is reduced by the multiple transmissions. Therefore, multiple portals are needed to limit the route length, resulting in a wireless network supported by a wired backbone. In this paper, we analyze how the variation of the average ratio of MPs per portal effects the network performance. To do so, a realistic system model is defined which incorporates the typical characteristics of a wireless link based on IEEE 802.11a. Then, we use an analytical framework which allows to compute the capacity in an arbitrary network topology under the conditions of the system model. The comparison of the average system capacity with different ratios shows that the performance gain diminishes with increasing number of portals: While the step from one to two portals doubles the capacity, there is only a small difference between 1 and 0.5 MPs per portal. Furthermore, a simple cost model provides insights to the economical feasibility of WMNs: in the case that an MP costs about 10% of a portal, the optimal ratio is found to be around 5 MPs per portal.