Mesh network will become an additional access technology instead of being a renewed technology in the next generation networks which are called Fourth Generation. The most important advantage of wireless mesh networks is their capability of working without an infrastructure. In recent years, there have been many studies about wireless mesh networks especially for multi-channel multi-radio structures for their routing and channel assignment methods. Basically, multi-channel structures present higher data capacity. In this paper, multi-channel multi-radio wireless mesh networks and several channel assignment schemes are explained. A recently studied architecture Directional Mesh (DMesh), that supports directional antenna-based multi-channel structure, is particularly analyzed based on the channel assignment procedure. This architecture is improved with proposing a new channel assignment scheme. Several results of the experimental analysis that compares both architectures and proves the outperforming of the proposed method are also presented.