Cross-Layer Multi-Rate Routing Strategies in Wireless Multi-Hop Random Access Networks

In this paper, we develop and study combined multi- rate and packet forwarding and routing operations in the context of multi-hop ad hoc wireless networks. Nodes are assumed to employ a software controlled radio that is programmed to use several modulation/coding schemes (MCSs) that operate at different data rates. The underlying MAC scheme is assumed to be based on a random access (pure ALOHA type) protocol. We propose a distributed QoS-aware cross-layer joint routing and rate control algorithm. It is used by nodal stations to jointly select, for each packet that traverses multi-hop routes across the network, the transmit data rate and the neighboring node to which the packet should be routed towards its destination. Each station monitors certain station and network activity states, and uses these data to adapt the selection of its parameter vectors. The mechanism strives to ensure that flow throughput and end- to-end packet delay target levels are met. Once satisfied, the algorithm selects parameters that serve to enhance the transport throughput level, thus occupying limited overall network wide resources. Simulation results demonstrate the significant performance enhancements that are achieved under the use of the proposed scheme. Our analytical models and mechanisms provide important guidelines for the design of such joint channel rate, MAC and routing based operations algorithms.