Understanding Performance for Two 802.11 Competing Flows

It is well known that 802.11 suffers from both inefficiency andunfairness in the face of competition and interference. This paperprovides a detailed analysis of the impact of topology and traffic typeon network performance when two flows compete with each other forairspace. We consider both TCP and UDP flows and a comprehensive set ofnode topologies. We vary these topologies to consider all combinationsof the following four node-to-node interactions: (1) nodes unable toread or sense each other, (2) nodes able to sense each other but notable to read each other's packets and nodes able to communicate with (3)weak and with (4) strong signal. We evaluate all possible cases throughsimulation and show that the cases can be reduced to 9 UDP and 10 TCP802.11g models with similar efficiency/fairness characteristics. We alsovalidate our simulation results with extensive experiments conducted ina laboratory testbed. These more detailed models improve on previouswork such as hidden-exposed-terminal categorization and are thus bettersuited as a basis for adaptive techniques to improve performance in802.11 multi-hop WLAN or Mesh Networks.