8.6 Performance Evaluation

In this section, we evaluate the performance of MGOR by simulation, and compare the performance of MGOR with multirate geographic routing (MGR), single-rate geographic routing (GR), and single-rate opportunistic routing. Our MGOR degenerates into MGR, when we choose only one forwarding candidate and further degenerates into GR, when we also fix the transmission rate. For all the OR protocols, candidates closer to the destination are assigned higher relay priorities. The performance metrics we evaluate include: throughput, delay and hop count. In order to get insight into our rate and candidate selection algorithm, for MGOR, we show the number of packets transmitted at each rate in the whole network and the average number of forwarding candidates used at each node on each data rate.

8.6.1 Simulation Setup

We implement the multirate link quality measurement mechanism and MGOR protocol with compressed slotted ACK in GlomoSim. The FindMOEOT algorithm proposed in Section 8.4 is used to select transmission rate and forwarding candidates for MGOR. This algorithm is also used to select forwarding candidates for single-rate GOR by fixing the transmission rate. According to the analysis in Section 8.4 and considering the candidate coordination overhead, the maximum allowable forwarding candidate number (rmax) is set as 3. Other than the candidate coordination scheme, our OR protocol follows the same CSMA/CA medium access mechanism as that in 802.11b. The simulated ...

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