**5.1. Simulation environment**

For the performance evaluation via throughput analysis, NS2 (version 2.30) [26] simulation tool is used. However, MATLAB [27] is used to generate the power controlled topology, the MPSPT graph, the link ranking of the MPSPT and the channel assignment for the links of the MPSPT.

Multi-interface wireless mesh nodes are created in NS2 by modifying the built-in IEEE 802.11 node model in NS2, using the procedure given in [28]. Based on the channel assignment by the gateway, the radio interfaces are configured for each node and the transmission power for each radio of each mesh node is set accordingly. All the mesh nodes at the periphery of the network send traffic to the gateway. Each of these nodes generates an 8 Mbps Constant Bit Rate (CBR) traffic stream consisting of 1024 byte packets, and sends data to the gateway node at the same time. They do not stop transmitting until the end of the simulation. So, this is a scenario in which multiple flows within the mesh network interfere with each other.

All radios are IEEE 802.11a radios and support 12 channels. The first 11 non-overlapping channels are used by the data radios, whereas the 12th channel is used by the control radio on each node. If the distance between the nodes is less than the cross-over distance, free space propagation model is used; if the distance between the nodes is greater than the crossover distance, two-ray propagation model is used. As per [4], the minimum receiver sensitivity (*RxThresh*) is set to -65 dBm ( -10 3.16227 10 Watts) in order to achieve a maximum data rate of 54 Mbps supported by IEEE 802.11a.

In order to achieve a strongly connected topology, the maximum transmission power for all the radios is set to 27 dBm. The maximum power transmission range is 164 meters and the maximum power interference range is 328 meters. RTS/CTS is disabled. Note that in the CCA and SRSC schemes, the mesh nodes do not control their power, transmit with the same maximum power (27 dBm) and use AODV (Ad hoc On-Demand Distance Vector) [29] routing protocol as their routing agent.
