**4. Topology control and channel assignment algorithms**

In this section, the network architecture of the proposed model is presented. The section presents the proposed topology control and channel assignment algorithms for MRMC WMNs, and details on the working of different phases of the proposed algorithms are discussed. The procedure of fault recovery with the proposed CAA is also presented in this section.

#### **4.1. Network architecture**

In our proposed model, each mesh router is equipped with five radios which operate on IEEE 802.11a channels (5 GHz band). One of these radios is used for control purpose while other radios are used for data traffic.

The control radios of all mesh nodes operate on the same non-overlapping IEEE 802.11a channel. Out of the 12 available non-overlapping 802.11a channels, channel 12 is used as the common control channel. Each mesh router is equipped with 4 data radios in order to utilize the remaining 11 non-overlapping channels available in IEEE 802.11a frequency band. Each MR communicates with its transmission range (TR) neighbors using these data radios for data transmission. So, each MR can have a maximum of 4 TR neighbors with whom it can communicate for data transmission which implies that the Maximum Node Degree (MND) per node is four. The MND of 4 is selected in order to fully utilize the 11 available non-overlapping 802.11a frequency channels. Results have shown that with 12 available non-overlapping channels, the network throughput increases until a MND of four but saturates after that [11].

## **4.2. Topology control algorithm**

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

nodes [12].

channels.

the number of radios it has.

link to reach the gateway.

**4.1. Network architecture** 

other radios are used for data traffic.

scarce radio spectrum. So, the key issue in a MRMC WMN architecture is the channel assignment problem, which involves assigning a channel to each radio of a MR in a way that minimizes interference on any given channel and guarantees connectivity between the mesh

Given the connectivity graph, the main challenge for CAA is to assign a channel to each radio in a way that minimizes interference between MRs and ensures connectivity between them. In order to achieve these goals, the CAA should satisfy the following requirements.

1. In order to communicate, a pair of nodes within transmission range of each other needs

2. Links in direct interference range of each other should be assigned non-overlapping

3. The number of distinct channels that can be assigned to a mesh router is bounded by

5. Since the traffic in a WMN is directed to and from the gateway, the traffic flows aggregate at routers close to the gateway. Therefore, priority in channel assignment should be given to links starting from the gateway based on the number of nodes that use a

At first glance, the problem of assigning channels to links in a mesh network appears to be a graph-coloring problem. However, standard graph-coloring algorithms cannot satisfy all of its constraints, and it is NP-hard to find an optimal channel assignment to maximize the overall network throughput [11]. Also, the channel assignment problem for mesh networks

In this section, the network architecture of the proposed model is presented. The section presents the proposed topology control and channel assignment algorithms for MRMC WMNs, and details on the working of different phases of the proposed algorithms are discussed. The

In our proposed model, each mesh router is equipped with five radios which operate on IEEE 802.11a channels (5 GHz band). One of these radios is used for control purpose while

The control radios of all mesh nodes operate on the same non-overlapping IEEE 802.11a channel. Out of the 12 available non-overlapping 802.11a channels, channel 12 is used as the common control channel. Each mesh router is equipped with 4 data radios in order to utilize the remaining 11 non-overlapping channels available in IEEE 802.11a frequency band. Each MR communicates with its transmission range (TR) neighbors using these data radios for data transmission. So, each MR can have a maximum of 4 TR neighbors with whom it can

procedure of fault recovery with the proposed CAA is also presented in this section.

to have a common channel assigned to their end-point radios.

4. The total number of non-overlapping channels is fixed.

is similar to the list coloring problem, which is NP-complete [21].

**4. Topology control and channel assignment algorithms** 

The proposed Topology Control Algorithm (TCA) controls the network topology by selecting the nearest neighbors for each node in the network. The objective of the proposed TCA is to build a connectivity graph with a small node degree to mitigate the co-channel interference and enhance spatial channel reuse as well as preserve network connectivity with the use of minimal power, as less transmit power translates to less interference.
