12.07.2015 Views

Wireless Ad Hoc and Sensor Networks

Wireless Ad Hoc and Sensor Networks

Wireless Ad Hoc and Sensor Networks

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Distributed Fair Scheduling in <strong>Wireless</strong> <strong>Ad</strong> <strong>Hoc</strong> <strong>and</strong> <strong>Sensor</strong> <strong>Networks</strong> 353Throughput per weight (Kbps)1009080706050403020100Data transmited from clusters802.11DPC + ADF + Sleep0 1 2 3 4 5 6Source cluster idFIGURE 7.29Throughput over weight ratio with flows.r<strong>and</strong>om variable uniformly distributed in the interval [0.9, 1.1], <strong>and</strong> witha delay error limit of 0.1 sec. The fairness is tested in the presence of fadingchannels.Figure 7.29 shows the throughput over weight ratio achieved for each trafficflow in case of st<strong>and</strong>ard 802.11 <strong>and</strong> with the proposed MAC protocol. Theproposed protocol with ADFS scheduling maintains similar throughput perweight ratio (close) for all clusters whereas 802.11 is not. Hence, the proposedprotocol is fair to all sources. Assigning different initial weights to the flowsat each CH will change the throughputs of the flows.7.7 ConclusionsIn this chapter, a novel adaptive <strong>and</strong> distributed fair scheduling (ADFS)protocol for wireless ad hoc networks is presented. The objective is todevelop a fully distributed fair scheduling algorithm, which meets theoverall QoS. The proposed ADFS protocol uses dynamic adaptation ofthe weights, depending upon the delay experienced, number of packetsin the queue, <strong>and</strong> the previous weight of the packet. The updated weightsare used in making the scheduling decisions <strong>and</strong> also in the calculationof the backoff intervals in the CSMA/CA paradigm.The effectiveness of our proposed ADFS protocol was evaluated usingthe NS simulator. The results show that the proposed protocol can achieve

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