Mobile Computing in Military Ambulatory Care

Although satellite and cellular communication advances have enabled users of mobile computers the ability to access information regardless of location, it introduces new problems for transaction management in distributed database systems. Traditional transaction mechanisms and criteria have to be adjusted to accommodate the limitations of a mobile computing environment. Data replication is an example of a technique that is used in traditional database systems to increase the availability and the fault-tolerance of the data, but at the same time adds the overhead of maintaining replica consistency across multiple sites of the network. Data replication is a useful tool in mobile computing due to the fact that a mobile host may be disconnected from the network for long periods of time. The data replication allows the mobile host to use a local data copy while it is disconnected from the network. Mobile hosts that have the capability to store copies of data items increase the diiculty of maintaining replica consistency, because of the mobile host's volatile storage. Also, the mobile host must be assured that the local copies that it is using are valid, and any changes made locally to a copy are reeected in the rest of the system. In this paper, we introduce a mobile replica management algorithm. A mobile transaction manager (MTM) coordinates the transactions initiated by mobile hosts, which query and update replicated databases stored at both mobile and static hosts in a battleeeld environment. This battleeeld environment is based upon the U.S. telemedicine (Prime Time III) support in Bosnia. The MTM is responsible for the synchronization of the replicated data items in the network. 1: Introduction Recent advances in various types of wireless communications (cellular and satellite) have granted users of portable computers the ability to communicate with pre-existing distributed database systems. Users of palm-top computers are able to maintain their network connection while traveling from one area to another. Compared to the wired connections of traditional database systems, the wireless connections of a mobile network are limited in bandwidth and are susceptible to frequent disconnections. A mobile network consists of a pre-existing static network that communicates with the mobile hosts via a wireless connection. Within the mobile network there are two hosts, mobile and xed hosts. A host that can move while retaining its network connection is a mobile host 7]. The specialized xed host that communicates with the static network and has a wireless …