Narrow Results

We propose to use Inter Vehicle Communications as part of a distributed system for ubiquitous health monitoring of patients. The biomedical data will be collected by wearable health diagnostic devices, which include various types of sensors. When patients are traveling on highways, we propose to transmit the measured biomedical data towards the corresponding Health Monitoring Centers via an Inter Vehicle Communication Network, which will guarantee the needed reliability, especially in areas where other wireless communications are not available. In particular, it is important that the Inter Vehicle Communication Network provides different priorities to various types of messages, depending on their urgency. We extend, a previously proposed inter vehicle hierarchical routing protocol, with priority scheduling to provide the needed priority services. We study various scheduling techniques and compare their effects on the service.

Safety message transmission is a key issue in wireless networking as it concerns people's lives. The Enhanced Distributed Channel Access (EDCA) mechanism defined in IEEE 802.11e is used in a variety of networks as Medium Access Control (MAC) protocol which concerns the transmission of safety messages. However, due to the random nature of the default parameters of Contention Window (CW) in EDCA, safety messages would be deprived of their chance to access the channel due to low-priority traffic when the two collide. In addition, the priority classification in EDCA is universal and it is not perfectly appropriate for specific applications in some emergency scenarios. To address the above issues, this paper proposes a mechanism called Absolute EDCA (AEDCA). The word “absolute” refers to the guaranteed absolute priority status of safety messages. To ensure fast access and transactions while providing reliable service, the scheme adopts a reclassified priority category. Based on the new priority classification, an AEDCA algorithm to avoid the randomness of backoff's influence on high-priority traffic is proposed. Meanwhile, in order to accommodate and implement the algorithm, a CW parameter adjustment strategy is designed. Simulation results illustrate that the AEDCA scheme can provide more reliable transmission of safety messages and achieve better performance in terms of packet delivery ratio, delay and throughput.