在無線環境中，使用廣播方式傳送資料是一種有效率傳輸模式。在此環境下，伺服端連續且不斷的廣播資料，讓使用者擷取自己所需的資料。因此伺服端如何決定廣播頻道上的資料順序，讓使用者的總存取時間達到最小，是個很重要的議題。過去多數的研究只考慮到一筆查詢(query)只有包含一個資料項(單一資料項)，而忽略現實生活中使用者的要求多半會包含兩個以上的資料項(多重資料項)。故本研究針對無線廣播通道環境下，且使用者多重要求資料項時，提出A*演算法找出資料項的廣播排程，以降低使用者接收資料項所需的時間。由實驗結果證明我們所提出的方法較QEM演算法[14]好。 Data Broadcasting is an efficient communication model when clients request data from a server in wireless environment. Data is delivered by a server downstream with a wide bandwidth. All clients keep listening to the broadcast channel and catch the data that interest them. The important issue of designing a proper broadcast schedule is to reduce the clients’ total access time. Most previous researches focused on a query just only include one data item, but not consider multiple data items are included in a query. In this paper, we propose an A* algorithm to the broadcast problem which consider the complex queries where a query include multiple data items. Experiential results show that our method outperforms the QEM algorithm [14] in access time.
