Multicast has great potential to be used in many applications. Besides, relay networks play an important role in next generation wireless networks. In this thesis, we study the issues of mobile multicast in relay networks.

First, we propose Cooperative Mobile Multicast Protocol (CMMP). Multicast services normally cannot tolerate high packet delay and high loss rate. However, multicast services
may be disrupted in mobile and wireless networks. Disruption may be caused by different reasons. In this thesis, we consider the disruption resulted from handoffs between base stations. Although many mobile multicast protocols have been proposed, they primarily consider the routing in mobile environment. The protocols usually do not consider how to reduce packet delay and packet loss rate caused by intermittent radio connectivity. In this thesis, we propose a mobile multicast protocol which utilizes cooperative communications for intermittent connected networks. Specifically, multicast packets are cached in helpers, which in turn relay the packets to the mobile hosts disconnected from the network. Therefore, multicast services still can be delivered to the disconnectedmobile hosts. Hence, packet loss rate can be reduced and throughput can be increased significantly. Most of the studies of cooperative communications focus on MAC and physical layers. We demonstrate how cooperative communications can benefit multicast at network layer. Both mathematical model and simulation are developed to analyze the performance of the proposed protocol.

WiMAX is a promising broadband wireless network. In order to improve radio coverage and enhance system throughput in WiMAX networks, Relay Station (RS) has been proposed in IEEE 802.16j. With the high data rate, transmitting higher definition videos can be supported in IEEE 802.16j networks. Normally, videos are layer-encoded to support dif-
ferent requirements. In this paper, we propose an efficient algorithm to allocate resources for layer-encoded videos to maximize user satisfaction in IEEE 802.16j networks. Challenges, such as diversity of channel conditions, multicast transmission, and limited bandwidth, are taken into consideration. We first formulate the problem and prove that it is NP-hard. We then propose a Greedy-based algorithm to solve the problem. Simulation results show that
the proposed algorithm can improve user satisfaction. The results are also close to the optimal solution. On the other hand, the complexity of the proposed algorithm is much less than that of the optimal solution

群撥適合應用於許多網路運用之中。此外，中繼網路在下一代無線網路中也扮演了許多重要的角色。在這篇論文中，我們專注於移動環境下的群撥應用，並結合中繼網路來解決所可能產生的問題。

首先，我們提出了一個合作式的移動群撥協定(CMMP)，群撥服務通常無法忍受高封包延遲率與高封包遺失率。然而，群撥服務可能會因為裝置的移動而臨時中斷。中斷發生的原因有很多種，在我們這篇論文中，我們主要考慮因為基地台間的換手而造成的中斷。雖然目前已經有許多移動群撥協定，但是這些協定主要針對路由協定。這些協定通常沒有考慮如何減少因為連線中斷而造成的封包延遲與封包遺失率。
在這篇論文中，我們提出了一個移動群撥協定並使用合作式的通訊來解決連線中斷的問題。更仔細來說，群撥封包會被暫存於協助者內，接著協助者會將這些封包轉傳給連線中斷的設備。所以，連線中斷的設備仍舊能接受群撥封包。因此，封包遺失率就能降低，且網路的傳輸率也能因此而增加。許多合作式通訊的研究都專注於MAC與PHY層。我們提出了在網路層應用合作式通訊的方法來增進網路效能。此外，我們提出了數學分析與數據模來證明我們提出的通訊協能提昇整體網路效能。

WiMAX是下一代積極開發的網路之一。為了要改善基地台的涵蓋率，以及提昇整體系統的效能，在IEEE 802.16j中引進了中繼站（RS）來達成這個目標。受惠於高傳輸率，高畫質的影音便能夠透過IEEE 802.16j來傳送。一般而言，影音可以透過分層編碼來達到不同的使用者需求。在這篇論文中，我們提出了一個有效率的排程演算法來有效地分配透過分層編碼的影音檔。其中我們也考慮了不同的因素：無線頻道的狀態、群撥傳輸、以及有限的頻寬，這些都會在演算法中考慮。一開始，我們證明這個問題是個NP-Hard的問題。接著，我們提出一個Greedy-based的演算法來解決這個問題。實驗模擬證明我們提出的演算法能夠有效的改善使用者的滿意度。模擬結果也證明我們的演算法能夠接近最佳解。換言之，我們提出的方法能夠以低複雜度來達到原本超高複雜度才能達到的最佳解。

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