Ensuring Latest-Bound Currency of Read-Only Transactions in Mobile Broadcasting Environments

Boohyung HAN  Sung Kwon CHUNG  Yookun CHO  

IEICE TRANSACTIONS on Information and Systems   Vol.E84-D   No.4   pp.456-464
Publication Date: 2001/04/01
Online ISSN: 
Print ISSN: 0916-8532
Type of Manuscript: PAPER
Category: Databases
mobile broadcast,  read-only transaction,  latest-bound currency,  update consistency,  

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In mobile broadcasting environments, an information server periodically broadcasts a set of data items to a large mobile client population at every broadcast cycle and mobile clients retrieve the data items they need upon arrival at the broadcast channel. In such environments, the cost of data delivery is independent of the number of clients. Many applications such as auctions and stock quotes perform read-only transactions that require the clients to read consistent and current data for accurate result. Previous concurrency control mechanisms designed for such environments ensure that the clients read consistent data, but they cannot ensure latest-bound currency which allows the clients to read the latest or most up-to-date data. In this paper, we propose an efficient concurrency control mechanism that ensures latest-bound currency as well as update consistency, which is appropriate for the mobile broadcasting environments. To ensure latest-bound currency, the server computes control information using "virtual" broadcast cycles. This control information is also used for checking update consistency. Thus, the proposed mechanism allows all data committed in current broadcast cycle to be broadcast. We have performed simulation experiments to measure transaction aborts in order to evaluate the performance of the proposed mechanism. The result confirms that the proposed mechanism produces no stale reads and also shows that the proposed mechanism generates less transaction aborts than previous mechanisms, which implies that we can get higher data currency without increasing data inconsistency.