4.1 Computing Throughput Bound of OR
The first fundamental issue to address is the maximum end-to-end throughput when OR is used. Any traffic load higher than the throughput capacity is not supported and even causes performance to deteriorate as a result of excessive medium contention. The knowledge of throughput capacity can be used to reject any excessive traffic in the admission control for real-time services. It can also be used to evaluate the performance of different OR variants. Furthermore, the derivation of throughput of OR may suggest novel and efficient candidate selection and prioritization schemes.
In this section we present our methodology to compute the throughput bound between two end nodes in a given network with a given OR strategy (i.e., given each node's forwarding candidate set, node relay priority, and transmission/broadcast rate at each node). We first introduce two concepts, transmitter based conflict graph and concurrent transmission set, which are used to represent the constraints imposed by the interference among wireless transmissions in a multihop wireless network. We then present methods for computing bounds on the optimal throughput that a network can support when OR is used.
4.1.1 Transmission Interference and Conflict
Wireless interference is a key issue affecting throughput. Existing wireless interference models generally fall into two categories: protocol model and physical model (Gupta and Kumar 2000). Under the protocol model, a transmission ...