Synchronization Protocol for Real Time Multimedia in Mobile Distributed Systems

Mobile distributed systems (MDS) deal with data transmissions among geographically distributed mobile sources. In this environment, the preservation of temporal dependencies among exchanged real-time multimedia data is mainly affected the asynchronous transmissions, by constant topology changes, unpredictable delays, as well as the lack of global memory and clock. Existing solutions for distributed intermedia synchronization are based on the assumption of a homogeneous end-to-end system, where symmetrical unbounded overhead cannot affect the throughput. This assumption, however, is not feasible for MDS due to the constraints of the wireless medium and the mobility implications. This paper presents a distributed multimedia synchronization protocol oriented to satisfy logical and temporal dependencies in the exchange of real-time data in MDS by using logical mapping, avoiding the use of global references. Two main aspects of the protocol include the computation of the deadline for messages by using only relative time points and by dividing the processing stage to achieve synchronization with an asymmetric principle of design. With the simulations results we demonstrate that our protocol is effective in diminishing the synchronization error. Furthermore, the protocol is efficient as regards processing and storage costs at the mobile hosts, and in the overhead attached per message with a reduced usage of bandwidth across the wired and wireless channels in comparison with the Real-time Transport Protocol.