Effective Transport Capacity in Ad Hoc Wireless Networks
5.1 Introduction
Ad hoc wireless networks represent a new and exciting communication paradigm which could have multiple applications in future wireless communication systems. In particular, over the last few years routing issues in ad hoc wireless networks, such as routing in the presence of node mobility [4,5,9,42,117] or energy consumption-aware routing [35,[37][38][39]46,118,119], have been studied extensively. While routing is fundamental in ad hoc wireless networks, the approach taken by most recent studies is such that physical layer limitations are not considered. This approach is meaningful in networks where links are basically error-free (such as the Internet), but it could be misleading in wireless networks, where the reliability of radio links might be very limited.
Fundamental performance limits of such a communication paradigm need to be studied. The concept of transport capacity has been introduced in order to quantify the maximum achievable bandwidth-distance product which can be supported by the network. In [16], the authors compute the transport capacity of stationary wireless networks, considering two possible models where inter-node interference (INI) is not taken into account: these are defined as a protocol model (in this case, a transmission between two nodes is error-free, provided that their distance is suitably lower than the distance from the destination node to any of the other nodes in the network) and a physical model (in this case, error-free transmission between two neighboring nodes is guaranteed if the signal-to-noise ratio, SNR, at the receiving node is above a specific threshold). Moreover, in [16] the authors distinguish between arbitrary networks -where the locations of nodes, destinations of sources and traffic demands are all arbitrary -and random networks -where the nodes and their destinations are randomly chosen. From the results in [16], it is possible to conclude that using a physical model without interference, an upper bound on the transport capacity for a stationary wireless network with free-space path loss is (R b โ AN ), where R b is the channel data-rate of a node,