Tuesday, January 24, 2012


We begin by presenting our metrics results in a comparative way, to show that they can give a good insight into the model performance. In Figure 1 we show the four previously defined performance metrics for the scenario with low population density and flat terrain and with low traffic requirements. We can see that the percentage of connected users Image from book increases with the the number of sites. There are additional connected users with relay topology and even more with mesh topology. We can also see that the increase in the number of sites reduces the number of users per base station, i.e., reduces efficiency. The percentage of frame occupancy shows that as the number of sites increases, every base station has a lower number of users connected to it and this causes a lower frame occupancy. With many base stations, the frame occupancy is really low. We can see that a mesh solution has a higher occupancy up to four active sites. This is because it increases the number of connected users but consumes more resources because of multihop links.

Figure 1: Results comparison for low density—flat scenario and low traffic requirements.
The equivalent transmission profile clearly shows that a PMP topology has a higher spectrum efficiency than a mesh or relay solution. This is because multihop topologies require more capacity due to multiple hops. In PMP topology this parameter remains almost constant, which means that the addition of new base stations allows the inclusion of more users but does not improve link quality. We analyze that this is caused by the reduction of the transmission power of some base stations due to interference restrictions. The increase of link efficiency with the number of sites for mesh and relay topologies, means that users reduce the number of hops to reach the nearest base station. The similarity between mesh and relay topology means that with many active sites, there are paths with at most two hops for some users. As the number of sites is higher, there is a low use of multihop links.
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