Wireless Ad Hoc and Sensor Networks

Optimized Energy and Delay-Based Routing 363E xMPRC sn , , n— Energy level or total available energy of node x .— Cost for MPR selection of node s, to reach the two-hop1 2neighbor n 2 , with one-hop neighbor n 1 as the intermediate node(s ); it is given by−> n 1 −> n 2C C C E=, , , + , + (/ 1 )MPRsn1 n2 sn1 n1 n2 n1(8.1)2where n1 ∈ N() s and n2∈ N (). sCost sd — Energy-delay (cost) of the entire path between a sourceand the destination d , given by:, ssd , = sn , n, n nk−, nk nk,d∑ 1 1 2 1Cost ( C , C ,…, C , C )(8.2)where n 1 , n 2 … n k are intermediate nodes on the path.Optimal-route — Optimal route, between any source–destination pair sand d , is the route with minimum energy-delay cost ( Cost sd , ).8.3.1 Neighbor Sensing and Energy-Delay Metrics CalculationEach node in the network periodically generates HELLO messages andtransmits to all the one-hop neighbors, similar to the OLSR implementationgiven in (Clausen and Jacquet 2003). However, changes are made tothe HELLO message header format to include various fields, like thetransmission time, transmission energy, and the energy level (availableenergy) of the source node, for calculating the energy-delay metrics. Moreover,the HELLO messages also contain information about the list of theone-hop neighbors and the link costs ( C xy , ) between the source node andits neighbors. This information is obtained from the node’s “neighbortable,” which is used to maintain the list of one-hop and two-hop neighbors,and their associated link costs.When a HELLO packet is received by a node, it can calculate the transmissiondelay of the packet as the difference between the transmissiontime stamped in the packet at the source and the received time at thedestination. However, to calculate the exact delay, the clocks of the neighboringnodes have to be synchronized. To achieve this, a mechanism likethe one presented in Mock et al. (2000) can be used to synchronize theclocks of all the nodes with high precision in ad hoc wireless networks.Similarly, the energy used can be calculated as the difference between thetransmission energy stamped in the packet and the received energy. Byusing the energy consumed and delay, an energy-delay product for the