**1.4. Organization**

The rest of the chapter is organized as follows. The related work on topology control and CAAs is presented in Section 2. Section 3 discusses the medium access issues encountered by IEEE 802.11 [4] single-radio single-channel nodes. The channel assignment problem is presented in this section with respect to multi-radio multi-channel wireless mesh network. Section 4 presents the network architecture for the proposed model and the proposed topology control algorithm and CAA, along with the details of their respective phases. The FRM of the proposed CAA is also presented in this section. Section 5 provides a performance evaluation of the proposed CAA. The network topologies used for performance evaluation are discussed.

The results of simulations for performance evaluation of the proposed CAA based on throughput analysis of a 36-node mesh network are presented in this section. Section 6 presents the conclusions, along with some directions for future work.

Channel Assignment Using Topology Control Based on Power Control in Wireless Mesh Networks 51

In addition, the assumption of fixed power levels is so ingrained into the design of many protocols in the OSI stack that changing the power levels results in their

Changing power levels can create uni-directional links, which can happen when a node

Medium access control protocols in IEEE 802.11 implicitly rely on bi-directionality as-

This is the basic type of TC, as all the nodes are assumed to use the same transmitting range. So, the topology control problem reduces to determining the minimum value of transmission range that ensures network connectivity. This minimum transmission range is

In this type of TC, nodes are allowed to choose different transmitting ranges, provided they do not exceed the maximum range. Depending on the type of information that is used to compute the topology, non-homogeneous topology control is further classified into three

In such schemes, exact node positions are known. If this information is used by a centralized authority to compute a set of transmitting range assignments which optimizes a certain measure such as the energy cost, this is the case of the Range Assignment Problem and its variants. The Local Minimum Spanning Tree (LMST) algorithm [5] and the Enhanced Local Minimum Shortest-Path Tree (ELMST) algorithm [6] are examples of location-based

In such schemes, it is assumed that nodes do not know their position, but they can estimate

In such schemes, nodes are assumed to know only the ID of the neighbors, and are able to

**b. Effect of TC on the Performance of the MAC and Routing Protocols** 

*i*'s power level is high enough for a node *j* to hear it, but not vice versa. Bi-directionality of links is implicitly assumed in many routing protocols.

malfunctioning.

sumption of links.

**a. Homogeneous** 

**b. Non-homogeneous** 

i. Location-based schemes

topology control schemes.

ii. Direction-based schemes

iii. Neighbor-based schemes

the relative direction of each of their neighbors.

order them according to some criterion such as link quality.

categories.

*2.1.3. Taxonomy of topology control schemes* 

These schemes are mainly divided into two types [10].

also called the Critical Transmitting Range (CTR).
