On Selfish Distributed Access Selection Algorithms in IEEE 802.11 Networks

An important question for future wireless networks is whether the prioritization between different accesses should be controlled by the networks or terminals. Herein we evaluate the performance of distributed access-selection algorithms where terminals are responsible for both AP selection and the necessary measurements. In particular, we focus on determining whether selfish distributed algorithms can perform as well as centralized ones (for comparison we include max-sum, max-min, proportional fair and minimum delay allocations). The study is conducted by time-dynamic simulations in a IEEE 802.11a network and as performance measures we use file transfer delay and supportable load at a maximum tolerable delay. Our results show that selfish algorithms can offer similar performance, both in terms of throughput and fairness, as the centralized schemes as long as they account for both path- loss and access point load. This is an important result and it suggests that terminal-controlled algorithms are just as efficient as centralized schemes, which besides extensive measurements also require that AP exchange information, for improving the efficiency in WLAN networks. Compared with a minimum path- loss selection criteria, which is standard in the IEEE 802.11 family today, our distributed load-aware algorithm increases the maximum supportable load with more than 200 percent even after accounting for measurement time and estimation errors. With fast reselection during ongoing sessions the gains can be further increased with, typically, 20 percent.