Performance of a Multi-Interface based Wireless Mesh Backbone to support VoIP Service Delivery

In this paper we evaluate the performance of a wireless IEEE 802.11-based node multi-hop mesh backbone for the provision of VoIP services, in the cases when nodes are provided with just a single NIC and when they are equipped with more than one NIC and different codecs are used. In particular, we show that the hard delay and packet loss constraints demanded by real time services constrain the size of the wireless backhaul to a few nodes when single-NIC nodes are used. Furthermore, this constraint depends on the link rate. This limitation is due to overlapping carrier sensing ranges that generate additional delay due to contention, which results in a strong degradation of the overall quality of the conversation. For the scenarios tested, the utilization of multi-NIC nodes overcomes these problems by allowing keeping the delay and losses within acceptable values while permitting larger wireless backhauls in terms of number of nodes. In this way, the MAC 802.11 policy keeps on playing a prevalent role in the very actual trend to build `all-wireless' architectures in spite of the limitations experienced in the single-NIC case