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Wireless Ad Hoc and Sensor Networks

Wireless Ad Hoc and Sensor Networks

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Optimized Energy <strong>and</strong> Delay-Based Routing 3951310CH 1CH 245811BS61227 913FIGURE 8.24Link cost calculation.CASE II When the CHs have more than one node to relay information,the OEDSR algorithm selection criteria are taken into account. InFigure 8.24, there are two CHs, CH 1 <strong>and</strong> CH 2 . Each CH sends signals toall the other nodes in the network that are in range. Here, CH 1 first sendsout signals to n 1 , n 3 , n 4 , <strong>and</strong> n 5 <strong>and</strong> makes a list on the potential RNs. Thelist is then forwarded to CH 2 . CH 2 checks if it is in range with any of thenodes in the list. Here, n 4 <strong>and</strong> n 5 are selected as potential common RNs.A single node must be selected from both n 4 <strong>and</strong> n 5 , based on the highestlink_cost_ factor. The cost to reach n from CH is given by Equation 8.4. So,based on the OEDSR link_cost_ factor, n 4 is selected as the relay node forthe first hop. Next, n 4 sends signals to all the nodes it is in range of, <strong>and</strong>selects a node as the relay node using the link_cost_ factor. The sameprocedure is carried on until the data is sent to the BS.LEMMA 8.8.1The intermediate nodes on the optimal path are selected as RNs by the previousnodes on the path.PROOF A node is selected as a relay node only if it has the highestlink_cost_ factor <strong>and</strong> is in range with the previous node on the path.Because OEDSR maximizes the link_cost_ factor, intermediate nodes thatsatisfy the metric on the optimal path are automatically selected as RNs.LEMMA 8.8.2A node can correctly compute the optimal path (lower E2E delay, minimum distanceto the BS <strong>and</strong> maximum available energy) for the entire network topology.PROOF When selecting the c<strong>and</strong>idate RNs to the CHs, it is ensured thatthe distance from the c<strong>and</strong>idate relay node to the BS is less than the

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