*5.3.2. Simulation results*

68 Wireless Mesh Networks – Efficient Link Scheduling, Channel Assignment and Network Planning Strategies

**5.3. Simulation results based on throughput analysis** 

**Physical Layer Parameter Setting**

TX/RX Antenna Height (meters) 3 Gain of TX/RX Antenna 1 Packet Capture Threshold (SIR) (dB) 10

System Loss Factor 1 **Table 1.** Physical layer node configuration in NS2

**MAC Layer Parameter Setting** Minimum Contention Window 15 Maximum Contention Window 1023 Slot Time (micro seconds) 9 SIFS period (micro seconds) 16 Preamble Length (bits) 96 PLCP Header Length (bits) 24 PLCP Data Rate (Mbps) 6 Basic Rate (Mbps) 6 Data Rate (Mbps) 54

RTS/CTS Threshold (bytes) 10192 (disabled)

**Table 2.** MAC layer node configuration in NS2

Antenna Type Omni Antenna

Packet Reception Threshold (watts) 3.16227e-10 Carrier Sense Threshold (watts) 7.90569e-11

*5.3.1. Simulation parameters* 

each mesh node is set accordingly.

their routing agent.

Grid Topology (GT) is used to evaluate TICA in a densely populated topology. Random Topology (RT) is used to evaluate TICA in an unplanned deployment of randomly and uniformly distributed mesh nodes. Controlled Random Topology (CRT) is used to reflect realworld deployments where mesh routers are uniformly distributed for maximum coverage.

The physical layer and MAC layer settings of the node which are used during the simulation are shown in Tables 1 and 2, respectively. Note that out of the 12 available nonoverlapping 802.11a channels, 11 channels are used for data traffic and channel 12 is used for control. Based on the channel assignment by the gateway node, IEEE 802.11a channels are assigned to the links between the mesh nodes and transmission power for each radio of

As mentioned earlier, the maximum transmission power for all the radios is 27 dBm. In the CCA and SRSC schemes, MRs do not control their power, transmit with the same maximum power (27 dBm), and use AODV (Ad hoc On-Demand Distance Vector) routing protocol as The Average Throughput (AT) in Mega bits per second at the gateway node is calculated using the following formula:

$$AT = \frac{\text{TPR} \times 8 \times 1024}{(\text{TrafficStopTime} - \text{TrafficStartTime}) \times 1 \times 10^6} \tag{7}$$

Note that *TPR* is the Total Packets Received in (7).

#### **a. Random Topology**

Figure 8 shows a graphical comparison of the average throughput of all schemes for ten random topologies. The results in this figure clearly indicate that the proposed algorithm TICA significantly outperforms other schemes for all different random topologies.

#### **b. Controlled Random Topology**

Figure 9 shows a graphical comparison of average throughput of all schemes for ten controlled random topologies. The results in this figure clearly indicate that the proposed algorithm TICA significantly outperforms other schemes for all different controlled random topologies.

The placement of the nodes and hence, the length of links in the MPSPT of a topology affects the interference range and hence, the channel assignment. In random and controlled random topologies, the random placement of nodes results in variation in the length of links in the MPSPT. This results in LICs, which may cause significant interference in the network and degrade the overall throughput.

#### **c. Throughput Comparison for the three topologies**

Figure 10 shows the comparison of average throughput of all schemes for the three topologies (random, controlled random and grid) for a network of 36 nodes.

Note that for random and controlled random topologies in Figure 10, the average throughput is the average over ten different random and controlled random topologies, respectively. Figure 10 shows that as compared to the CCA scheme, the throughput improvement with TICA is 3 times for random topology, 11 times for controlled random topology and 12 times for grid topology. In comparison to the SRSC scheme, the throughput improvement with TICA is 8 times for random topology, 95 times for controlled random topology and 133 times for grid topology.

The results in this figure clearly indicate that the proposed algorithm, TICA, significantly outperforms other schemes for the three topologies.

Channel Assignment Using Topology Control Based on Power Control in Wireless Mesh Networks 71

**Figure 10.** AT of all schemes for the three topologies

topology control based on power control for CA.

**6. Conclusion and future work** 

protocols and complicated routing metrics for route selection.

have not provided any mechanism for recovery after a node failure.

fault tolerance and CA control.

**5.4. Features' comparison of related CA schemes** 

The important features of the related CA schemes are summarized in Table 3. They include channel switching, topology control, power control, knowledge of traffic load, connectivity,

The most significant difference between TICA and existing CA schemes is that TICA uses topology control based on power control to build the topology for CA with the objective of minimizing the interference between the MRs whereas no other CA scheme has used

Another significant difference between TICA and most other existing CA schemes is that TICA performs routing in addition to CA whereas most other CA schemes rely on routing

Unlike TICA and D-HYA, other well-known CA schemes do not possess fault tolerance and

The chapter finally concludes in this section along with some directions for future work.

**Figure 8.** AT for ten random topologies

**Figure 9.** AT for ten controlled random topologies

**Figure 10.** AT of all schemes for the three topologies

**Figure 8.** AT for ten random topologies

**Figure 9.** AT for ten controlled random topologies

#### **5.4. Features' comparison of related CA schemes**

The important features of the related CA schemes are summarized in Table 3. They include channel switching, topology control, power control, knowledge of traffic load, connectivity, fault tolerance and CA control.

The most significant difference between TICA and existing CA schemes is that TICA uses topology control based on power control to build the topology for CA with the objective of minimizing the interference between the MRs whereas no other CA scheme has used topology control based on power control for CA.

Another significant difference between TICA and most other existing CA schemes is that TICA performs routing in addition to CA whereas most other CA schemes rely on routing protocols and complicated routing metrics for route selection.

Unlike TICA and D-HYA, other well-known CA schemes do not possess fault tolerance and have not provided any mechanism for recovery after a node failure.

### **6. Conclusion and future work**

The chapter finally concludes in this section along with some directions for future work.
