CP-EDCA analysis under realistic wireless channel conditions

The foray of wireless sensor networks into time-sensitive applications demands support for emergency services with guaranteed quality of service (QoS) bounds. We introduced CP-EDCA, a channel preemptive enhancement to the IEEE 802.11e EDCA standard, for guaranteed emergency medium access in distributed wireless environments. The performance results for emergency traffic depicted 50% uniform decrease in channel access delays, deterministic delay bounds and insensitivity to routine traffic competition, even under heavy loads. The initial analysis primarily aimed at validating the distributed preemption concept and was performed under ideal channel conditions. In this paper, we analyze the CP-EDCA protocol under realistic wireless channel conditions to quantify the performance of our scheme in real environments with channel impairments. The results suggest that under typical wireless scenarios (10^-2 error rate), the preemptions provide useful performance gains and most importantly the emergency performance is uniform and deterministic, even under increasing routine traffic load. Though the magnitude of improvements is reduced as the channel conditions get bad, the emergency treatment in CP-EDCA scheme still had perceivable improvements relative to the EDCA scheme. We also measure the CP-EDCA trade-off, which is the degradation of routine traffic throughput under normal operating conditions.