在一個高效能多通道無線網路(Multi-channel wireless networks)中, 通道分配(Channel assignment)是一個很重要的研究主題。在先前相關研究通道分配的法則中，大部份的通道分配法則是透過協商(Negotiation)的方式來交換彼此所需要的通道(Channel)。利用協商的方法主要是使用RTS/CTS的封包，內含通道列表(Channel list)，傳送端(Sender)跟接收端(Receiver)會從通道列表中挑選適合的通道，並告知鄰近的結點，最後，傳送端跟接收端會使用先前挑選的通道來倲輸資料。然而，這些方法需要同步性(Synchronization)的機制，因為它們必須在同一個信標間距(Beacon interval)的開始時，去競爭(Contention)並做協商，但同步性機制在無線網路中，是很難以完成的。此外，協商式的通道分配法則會造成端點對端點之間的延遲(End-to-end delay)增加，特別是在多跳(Multi-hop)通訊中，這是因為在多跳傳輸中，每兩個節點之間的連結(Link)必須在協商後才分配通道，在協商的過程中會產生所謂的通道交換延遲(Channel switching delay)，而在愈多級(Hop)的傳輸中，這樣子的延遲會更顯著。我們在本篇論文中，提出了一個以階層式分群(Hierarchical clustering)網路節點(Node)為基本的通道分配方法，且不需要任何同步機制。在我們的通道分配法則中，通道由最高階層的群長(Cluster head of highest level)開始從上往下分配通道，直到所有的成員(Member)都已分配好為止，並利用了通道不會互相干擾的特性，減少了大量的碰撞(Collision)。在模擬結果中，我們展示出我們的通道分配方則比協商式的通道分配法則在整體碰撞(Collision)，端點對端點的延遲(End-to-end delay)及整體產出量(Throughput)有著明顯的改善。

Channel assignment is an important issue in high throughput multi-channel wireless networks. Previous works on channel assignment use a common control channel to negotiate data channels by exchanging RTS/CTS. However, these schemes require time synchronous mechanism for starting to negotiation in each contention window, which is hard to achieve in wireless networks. Moreover, the above negotiation-based scheme may incur the channel switching delay during channel assignment in each hop of a multi-hop communication. In this paper, we propose an asynchronous scheme for channel assignment based on clustering all nodes in a wireless network into a hierarchical clustering architecture. With the hierarchical clustering architecture, our scheme can elect the cluster head of highest level and allocates channels by the cluster head of highest level to all leaves in a level-by-level basis. Simulation results show that the proposed channel assignment scheme outperforms the negotiation-based schemes in terms of packet collision, end-to-end delay, and overall throughput.

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