Supporting service differentiation in wireless packet networks using distributed control

This paper investigates differentiated services in wireless packet networks using a fully distributed approach that supports service differentiation, radio monitoring, and admission control. While our proposal is generally ap plicable to distributed wireless access schemes, we design, implement, and evaluate our framework within the context of existing wireless technology. Service differentiation is based on the IEEE 802.11 Distributed Coordinatio n Function (DCF) originally designed to support best-effort data services. We analyze the delay experienced by a mobile host implementing the IEEE 802 .11 DCF and derive a closed-form formula. We then extend the DCF to provide service differentiation for delay-sensitive and best-effort traffic based on the results from the analysis. Two distributed estimation algorithms are proposed. These algorithms are evaluated using simulation, analysis, and e xperimentation. A Virtual MAC (VMAC) algorithm passively monitors the radio channel and estimates locally achievable service levels. The VMAC estimate s key MAC level statistics related to service quality such as delay, delay variation, packet collision, and packet loss. We show the efficiency of the VMAC algorithm through simulation and consider significantly overlapping c ells and highly bursty traffic mixes. In addition, we implement and evaluat e the VMAC in an experimental differentiated services wireless testbed. A V irtual Source (VS) algorithm utilizes the VMAC to estimate application-leve l service quality. The VS allows application parameters to be tuned in resp onse to dynamic channel conditions based on "virtual delay curves." We demo nstrate through simulation that when these distributed virtual algorithms a re applied to the admission control of the radio channel then a globally st able state can be maintained without the need for complex centralized radio resource management.