在這篇論文中，我們主要探討在Zigbee網路使用群播的應用。在無線感測網路裡，群播是一個很有效率的一對多傳送資料的方法，而許多群播的方法也被廣泛的討論在不同的網路環境下。然而，Zigbee網路是一個具有低速率、低消耗功率特徵的感測網路，許多的群播機制並不適合在這一類的網路中使用，例如：ODMRP需要source不斷的發出Join Request以及Receiver需要廣播回傳Join Reply的封包來維持forwarding group的狀態；MAODV維持一個Multicast樹狀的結構來傳遞封包，而當這個樹狀的路徑斷掉了，需要花費相當的overhead來做維護的動作。另外，Group leader也要不斷的發送Group Hello來維持Multicast樹的完整。而這些的缺點都使得群播的機制在Zigbee網路中的效能大打折扣。
在這裡我們利用Zigbee網路的特性，如網路一開始對所有節點形成的邏輯樹狀架構，提出一個傳送節點選擇的演算法，使其在不建立Multicast路由路徑下，省下建立路由路徑所花的成本，並利用Multi-destination與stateless的觀念，達到傳送封包的目的。

In this thesis, we focus on the multicast in Zigbee network. The multicast is a useful operation that facilitates group communication in WSN (wireless sensor network). Many kinds of methods for multicasting are discussed in different kinds of network environments. The Zigbee network, however, is characterized as low data rate and low cost. Many of the multicast methods are not suitable for this kind of sensor network. For example, in the ODMRP the source need periodically send Join Request and receivers need rebroadcast Join Table back to the source to maintain the forwarding group state; in the MAODV need to maintain a multicast tree to use to forward packet. If the tree link is broken, then it takes much more effort to rebuild the multicast tree. On the other side, group leader also need to periodically broadcast the group hello message to hold the network entirely. All these disadvantages will reduce the multicast performance in Zigbee network.

Here, we use the characteristic of Zigbee network, like the logical tree structure when network build up and propose the forwarding group selection algorithm on it. This algorithm will reduce the overhead of routing information to build in multicast. We also use the multi-destination and stateless idea to reach the goal of multicast transmission.

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