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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> 329weights of the flows are chosen as 0.1, 0.075, 0.05, <strong>and</strong> 0.025, with 4 flowsselecting each of these weights. Observe that the sum of the weights isequal to one. The figure shows that the ADFS algorithm results in fairallocation of b<strong>and</strong>width even when flows have been assigned differentinitial weights.The fairness index ( FI ) (Bennett 1996) is defined asFI =⎛⎜⎝η *∑∑fT ⎞f⎟φ f ⎠f2⎛ T ⎞f⎜ ⎟⎝ φ f ⎠2(7.83)where T f is the throughput of flow f <strong>and</strong> η is the number of flows.Figure 7.12 displays the FI of networks with different numbers of flows.Note that the fairness indices of ADFS <strong>and</strong> DFS are close to one, whereasthat of IEEE 802.11 is less than one. This confirms that the proposed ADFS<strong>and</strong> DFS render fair allocation of b<strong>and</strong>width, whereas IEEE 802.11 doesnot. Delay variations in the network with 64 nodes are presented in10.980.96ADFSDFS802.110.94Fairness index0.920.90.880.860.840.820.80 10 20 30Number of nodes40 50 60FIGURE 7.12Fairness index comparison.

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