隨著無線環境的軟硬體設備的進步，使用者可以不受時間、地點限制，透過無線設備進行資料的查詢。在無線環境下運用廣播技術傳送訊息，是一種有效運用頻寬的方法。因此在本論文中，我們採用廣播的技術。廣播伺服器分成兩部分，廣播模式及經過要求廣播模式，並針對伺服器端提供多個廣播頻道及使用者端配備多個接收器的環境之下，發展即時資料的排程。
在廣播模式部分，經由資料轉換，將多頻道及多接收器的問題轉換成單頻道及單接收器的排程問題。接著，挑選最佳的廣播資料集，利用風車的排程演算法，產生單頻道及單接收器的廣播排程。最後，再將單頻道及單接收器產生出來的廣播排程轉換成多頻道及多接收器的廣播排程。接著，利用上傳頻道，使用者可動態提出資料的查詢。此時，伺服器將使用者的查詢依照不同查詢加入方針所決定的優先順序將其加入優先佇列。接著，伺服器挑選可被滿足的資料查詢並利用分配給經過要求廣播模式的部分頻寬做此資料查詢的廣播。

傳統廣播資料庫技術著重於減少查詢花費的平均存取時間。然而，在此篇論文中，我們致力於滿足更多有時間限制的資料查詢。實驗結果顯示，透過適當的參數調整，此廣播系統可以滿足很高比例有時間限制的資料查詢，且系統排序的負荷可以減到最小。

In the real-time environments, information is disseminated to clients with timing constraint. In this paper, we focus on the problem of data scheduling in multiple broadcast channels environments where the clients equip with multiple receivers. Each request is associated with a deadline. The clients can retrieve data items either from the broadcast channels or make requests to the server and then listen to the broadcast channels. The intention of our work is to serve as many requests as possible.
In our method, the content of the broadcast program is first decided. Afterwards, the periodic broadcast program generation algorithm and the on-demand program generation algorithm are proposed. Simulations are performed to justify the benefit of our approaches. We conclude that our data scheduling algorithms are scalable and the time spent on executing our data scheduling algorithms is low. Moreover, by using our data scheduling algorithms, the percentage of requests that miss their deadlines is also low.

[1]S. Jiang and N. Vaidya, “Scheduling Data Broadcast to Impatient Users”, In International Workshop on Data Engineering for Wireless and Mobile Access, 1999.
[2]P. Xuan, S. Sen, O. Gronzalez, J. Fernandex, and K. Ramaritham, “Broadcast on Demand: Efficient and Timely Dissemination of Data in Mobile Environments”, In Proceedings of the 3rd IEEE Symposium on Real-Time Technology and Application, 1997.
[3]S. Baruah and A. Bestavros, “Pinwheel Scheduling for Fault Tolerant Broadcast Disks in Real-Time Database Systems”, In Proceedings of the 13th International Conference on Data Engineering, pages 543~551, 1997.
[4]K. L. Tan, and J. Cai, “Batch Scheduling for Demand-Driven Servers in Wireless Environments”, In Information Sciences, pages 209~231, 1998.
[5]D. Aksoy, and M. Franklin, “Scheduling for Large-Scale On-Demand Data Broadcasting”, In Proceedings of the 1998 IEEE INFOCOM Conference, 1998.
[6]T. Imielinski, S. Viswanathan, and B. R. Badrinath, “Data On Air: Organization and Access”, In IEEE Transactions on Knowledge and Data Engineering, 353~372, 1997.
[7]S. Acharya, M. Franklin, and S. Zdonik, “Balancing Push and Pull for Data Broadcast”, In Proceedings of the 1997 ACM-SIGMOD International Conference on Management of Data, pages 183~194, 1997.
[8]S. Acharya, R. Alonso, M. Franklin, and S. Zdonik, “Broadcast Disks: Data Management for Asymmetric Communication Environments”, In Proceedings of ACM-SIGMOD International Conference on Management of Data, pages 199~210, 1995.
[9]S. Acharya, R. Alonso and S. Zdonik, “Dissemination-based Data Delivery Using Broadcast Disks”, In IEEE Personal Communications, 1995.
[10]R. Holte, A. Mok, L. Rosier, I. Tulchinsky, and D. Varvel, “The Pinwheel: A Real-Time Scheduling Problem”, In Proceedings of 22nd International Conference on System Science, pages 693~702, 1989.
[11]S. Baruah, and S. Lin, “Improved Scheduling of Generalized Pinwheel Task Systems”, In Proceedings of 4th International Workshop on Real-Time Computer Systems Applications, 1997.
[12]S. Baruah, N. Cohen, G. Plaxton, and D. Varvel, “Proportionate Progress: A Notion of Fairness in Resource Allocation”, In Algorithmica, pages 600~625, 1996.
[13]S. Baruah, Member IEEE, and Shun-Shii Lin, “Pfair Scheduling of Generalized Pinwheel Task Systems”, In IEEE Transactions on Computers, pages 812~816, 1998.
[14]S. C. Lo, and Arbee L. P. Chen, “Optimal Index and Data Allocation in Multiple Broadcast Channels”, In IEEE International Conference on Data Engineering, pages 293~302, 2000.
[15]S. Hameed, and N. H. Vaidya, “Efficient Algorithms for Scheduling Data Broadcast”, In ACM-Baltzer Wireless Networks, pages 183~193, 1999.
[16]K. L. Tan, and B. C. Ooi, “Data Dissemination in Wireless Computing Environments”, Kluwer Academic Publishers, 2000.
[17]J. Fernandex, and K. Ramaritham, “Adaptive Dissemination of Data in Time-Critical Asymmetric Communication Environments”, In EuroMicro Conference on Real-Time Systems, 1997.
[18]N. Shivakumar and S. Venkatasubramanian, "Energy-Efficient Indexing For Information Dissemination In Wireless Systems," In ACM, Journal of Wireless and Nomadic Application, 1996.