Routing in ad hoc networks - a wireless perspective

Traditionally, the routing problem is addressed at the network layer, an approach that has been extended to the wireless realm. In wireless multihop networks, however, strict layer-base protocol design leads to substantial inefficiencies. This paper addresses the routing problem for large wireless ad hoc networks from a fundamental point of view, not constrained by particular protocol implementations or layered architectures, but taking into account the properties of the wireless channel. First, an analytical channel model is presented that is based on Rayleigh fading. It demonstrates how noise and interference effects can be separated, and how each interfering transmission affects the packet reception probability. Second, the distribution of node distances in networks with uniformly randomly placed nodes is derived. These two ingredients are used to discuss the benefits of different routing strategies. In particular, short-hop and long-hop routing schemes are compared. Further, cooperative strategies such as multipath routing and cooperative diversity are briefly discussed as techniques that are enabled by the broadcast nature of the wireless channel.