Toward Reliable Broadcast/Unicast in Wireless Mobile Ad Hoc Networks

Abstract

A mobile ad-hoc network (MANET) is a dynamic, self-organizing network that is composed of numerous mobile devices scattered in a particular area. Each device is equipped with a wireless transceiver for physical-layer communication. In MANET, data traffic should traverse intermediate nodes between the source and the destination due to the limited communication range of devices. In this dissertation, we develop routing schemes for reliable and scalable broadcast/unicast communication service in MANETs.

First, we develop efficient broadcast protocol, named ST-BCAST, that exploits collision resilient tone-signals and employs receiver triggered forwarding decision / cancellation mechanism. It reliably disseminates a packet over MANET without any topological information. We verify the reliability and efficiency of ST-BCAST through logical analysis and NS-3 based simulations.

Second, we investigate two well-known classes of routing mechanisms for unicast service in MANET: hop-by-hop routing and gradient routing. We evaluate their performance under realistic MANET environments with unreliable links and node mobility. Based on the understanding of their behaviors, we propose a practical gradient forwarding architecture (E-GRAD) that includes on-demand cost update and SNR-based cost calculation. We demonstrate that the performance of E-GRAD is closed to that of the ideal routing scheme with global information.

Last, we consider wireless multi-hop access networks with a single gateway, e.g., sensor networks and smart-phone based disaster recovery networks, and design novel gradient routing schemes for uplink/downlink unicast services. In our proposed scheme, every node can efficiently calculate the routing cost to the gateway by relaying a tone signal across subcarriers, where a cost value (e.g., hop count to the gateway) is pre-assigned to each subcarrier. The cost calculation is initiated by the gateway and is computed as the signal propagates to the network boundary. For uplink gradient routing, the cost can be used directly, and for downlink gradient routing, the cost is used in conjunction with uplink transmission history. We verify through NS-3 simulations that our proposed single-gateway routing scheme provides reliable uplink and downlink traffic, and substantially reduces the routing overhead by successfully exploiting OFDM signals.