Increasing demand for various services and technological development make it possible to provide multi-media services on mobile computing system. Mobile computing system composed of mobile hosts(MHs) and mobile support stations(MSSs) which support communication between MHs and fixed network. Mobile computing system is a sort of distributed system in which processes communicate by message passing. To preserve message order in such distributed systems, causal ordering was proposed. However, causal ordering is not suitable for multi-media services whose data have lifetime. Δ-causal ordering is a communication abstraction designed for distributed applications whose messages have to be delivered preserving causal ordering and have a limited lifetime.
In this thesis, we propose Δ-causal ordering algorithms which provide multicasting as a basic property of multi-media services on mobile computing system. We also propose efficient handoff algorithms supporting that mobile host move in geographical areas(cell). Multicasting property is achieved by updating control information for causal ordering before and after message sending/receiving a message for all destinations. When mobile host move one cell to another, handoff algorithm is executed between old and new MSSs. During handoff, old MSS must send MH's control information to new MSS. Because control information size has much influence on handoff latency and message latency, control information size is reduced by encoding data structures for control information. During handoff, the size is reduced to 50\% by encoding control information. And message latency is reduced to 5\% in the proposed Δ-causal ordering algorithms employing the handoff algorithm.