CogMAC: a cognitive link layer for wireless local area networks
Wireless Networks
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Wireless network is an essential and integral part of the ubiquitous environment. For efficient access control, two different transmission schemes are used: The Basic Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) and Request-To-Send/ Clear-To-Send (RTS/CTS) handshaking. The RTS/CTS handshaking addresses the hidden terminal problem as well as reduces the chance of collision in case of higher node density and traffic. However, in networks with low density, basic scheme would lead to higher throughput due to its less overhead. Efficient switching between these two schemes is imperative to maximize the throughput. We have first investigated to find a meaningful threshold value according to the network situation. The proposed algorithm then dynamically adjusts RTS Threshold according to the packet delivery ratio, which is an indicator of network traffic and shows a significant improvement over existing CSMA/CA and RTS/CTS schemes. Our adaptive scheme performed even better when data rates increases. We verify our proposed scheme with extensive network simulation using ns-2.