Ad hoc wireless LAN是一相當方便的區域網路，不過，由於其具有網路會隨著網路上的工作站移動而造成topology的變化，因此，對於每個工作站而言，要能夠了解當時網路的情況就必須要靠著彼此交換訊號，而通常這些訊息都是利用廣播 (broadcast)的方式傳送。也就因為如此，MAC layer能夠有效率的將這些廣播有效並且盡快的傳送出去就顯得非常重要。在我們這篇論文中，我們提出一新的廣播方法，CBP (Contention-base Broadcast Protocol)。CBP的做法主要和一般的TDMA-based的方法一樣，必需要能夠精確的達到時間的同步，而同步的方法可以利用GPS或是切割小channel的方法達到。不同於大部份的TDMA-based的做法，CBP取得data slot的方式是採用競爭的方式，而不用預留的方法。並且利用將控制slot切割成更小的mini slot以減少控制訊號碰撞的可能來增加throughputs。在CBP中也區別了unicast和broadcast的傳送，以盡量增加網路的使用率。最後，我們經由模擬比較CBP和其他不同的做法，以確定CBP的throughputs的確較佳。

Ad hoc wireless networks are quite convenient local area networks. Because ad hoc wireless networks have a property what its topology is changed as hosts move. In order to efficiently and quickly broadcasting data, it is very important to have efficacious protocols in MAC (Medium Access Control) layer. In this paper, we propose a new broadcast protocol, Contention-based Broadcast Protocol (CBP). CBP is a TDMA-based protocol. There are three characteristics which make CBP an efficient protocol. They are (1) CBP utilize a backoff algorithm and some mini slot in contention request phase to avoid collisions. Most protocols do not implement a backoff algorithm. (2) A host only reserves a data slot each time instead of many slots in most TDMA-based protocol. It has the advantage of reducing the influence of host mobility because the time between a data slot is reserved and the time the data slot is utilized has greatly decreased, and (3) CBP differentiates unicast data and broadcast data and allows a host to reuse by channel for a unicast if it is impossible for a broadcast.

Chapter 1 Introduction ………………………………………………………………..1
Chapter 2 Background & Related Works ……………………………………………..4
2.1 IEEE 802.11 Ad hoc wireless networks ……………………………………..4
2.2 TDMA-based protocols ……………………………………………………...7
Chapter 3 Contention-based Broadcast Protocol …………………………………….17
3.1 Assumptions ………………………………………………………………..17
3.2 Idea and point of view ………………………………………………….......18
3.3 CBP …………………………………………………………………………19
3.3.1 Contention Request Phase …………………………………………..20
3.3.2 Feedback Phase ……………………………………………………..23
3.3.3 Data slot and after sending data …………………………………….29
3.3.4 Control signal’s overhead …………………………………………...31
3.4 The advantages of CBP …………………………………………………….31
Chapter 4 Simulations and simulation results ……….………………………………33
4.1 Comparisons for three schemes …………………………………………….33
4.2 Simulation Environment ……………………………………………………34
4.3 Simulation results …………………………………………………………..35
Chapter 5 Conclusion and Future Works …………………………………………….43
Reference …………………………………………………………………………….45

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