*2.2.1. Fixed channel assignment schemes*

Fixed assignment schemes assign channels to radios either permanently, or for intervals that are long with respect to the radio switching time. Such schemes can be further subdivided into two types.

#### **a. Common Channel Assignment (CCA)**

In CCA scheme [13], the radios of each node are all assigned the same set of channels. For example, if each node has two radios, then the same two channels are used at every node. The main benefit is that the connectivity of the network is the same as that of a single channel approach, while the use of multiple channels increases network throughput. However, it does not take into account the effect of interference on the channel assignment in a WMN.

#### **b. Varying Channel Assignment (VCA)**

In the VCA class of schemes, the radios of different nodes are assigned different sets of channels. However, the assignment of channels may lead to network partitions and/or topology changes, which may increase the length of routes between mesh nodes. Therefore, in such a scheme, channel assignment needs to be carried out carefully. The VCA approach is discussed in more detail by presenting algorithms that belong to this category.

i. Centralized Hyacinth (C-HYA)

C-HYA, a centralized channel assignment algorithm for multi-radio multi-channel WMNs, was proposed in [11]. Assuming that the offered traffic load is known, this algorithm assigns channels ensuring network connectivity and satisfying the bandwidth limitations of each link.

ii. Mesh-based Traffic and interference-aware Channel-assignment (MesTiC)

MesTiC, a fixed algorithm for centralized CA, was proposed in [14], and visits nodes once in the decreasing order of their rank. The rank of each node is computed on the basis of its link-traffic characteristics, topological properties and number of radios on a node.
