A Comparative Study on Improving Quality of Service in Networks Carrying Multi-Service Level Data over Resource-Limited Multi-Hop Wireless Networks

摘要

Multi-hop Wireless Networks (MWNs) based on Single-Radio Single-Channel (SRSC) networks will likely attract more deployments if the required Quality of Service (QoS) can be provided. Carrier sense multiple access with collision avoidance (CSMA/CA) in MWNs faces an increase in packet loss and contention with an increase in the number of hops to reach the destination. This results in an increase in collisions and a wastage of bandwidth. The Distributed Coordination Function (DCF) treats all data the same, while the Enhanced Distributed Channel Access (EDCA) method was mainly designed for delay-sensitive applications to provide multi-service differentiation. EDCA is known to provide unfairness, where higher-priority data can starve low-priority data under high loads. We have shown that Schedule-Before-Contention (SBC) packet scheduling strategies can address the limitation of EDCA, but it is still unclear which SBC strategy provides the best performance in distributed networks. Good scheduling mechanisms can reduce packet loss to the maximum, as well as avoid unnecessary delay. In this paper, we assert that the queue selection mechanism plays a critical role in the achievable Quality of Service (QoS). A comparative analysis of four SBC mechanisms is carried out and it is found that the transmission of lower-priority data helps lower packet loss, as this uses larger contention window ranges for back-off.