The new generation of telemedicine systems enables healthcare service providers to monitor patients not only in the hospital but also when they are at home. In order to efficiently exploit these systems, human information collected from end devices must be sent to the medical center through reliable data transmission. In this paper, we propose an adaptive relay transmission scheme to improve the reliability of data transmission for wireless body area networks. In our proposal, relay nodes that have successfully decoded a packet from the source node are selected as relay nodes in which the best relay with the highest channel gain is selected to forward the failed packet instead of the source node. The scheme addresses both the data collision problem and the inefficient relay selection in relay transmission. Our experimental results show that the proposed scheme provides a better performance than previous works in terms of the packet delivery ratio and end-to-end delay.

A novel cell-level FEC (forward error correction) scheme at SSCS of AAL type 5 for error-free data transmission services in ATM networks is proposed and evaluated. In the proposed cell-level FEC scheme, both the length of user data (e. g. , IP packet) and attached redundant data can be modified based on sender's local decision without any end-to-end parameter re-negotiation procedure. The writing and reading order regarding an interleave matrix for cell-level FEC algorithm are the same, in order to perform pipelining data transmission. The prototype implementation with software processing achieves few Mbps end-to-end throughput. The end-to-end data transmission latency and the amount of retransmission packets due to packet error at the receiver entity are evaluated by computer simulation with correlated cell dropping process. Simulation results show that the benefits of cell-level FEC scheme for the error-free data transmission services, i. e. , by use of cell-level FEC scheme, the amount of retransmitted packets can be reduced, even if the average latency for end-to-end data transmission increases slightly.

This paper discusses and evaluates an effect of cell level FEC (Forward Error Correction) capability on error-free (i.e. reliable) IP multicast service over ATM networks. In the error-free IP multicast service, every receiver is delivered IP packet from the sender synchronously. Without applying the FEC policy, the expected IP packet error/loss probability becomes large, when the number of multicast receivers is large. For example, when the cell error/loss probability of each ATM data-link segment is 10-6 and the number of receivers is 103, the IP packet error/loss probability observed at the sender is about 0.5, which means that about 50% of IP packet sent from the sender will be subject to retransmission. One possible solution would be using the intermediate multicast-TCP entities, that terminate TCP protocol, among the sender and the receivers. However, this approach requires the additional entities within the network and can not provide the ordered message delivery for a multipoint-to-multipoint communication. On the contrary, with applying the FEC policy, the expected IP packet error/loss probability is dramatically reduced. Therefore, an error-free IP multicast service can be provided with a simple architecture, even when the number of multicast receiver is large, e.g. 105. For example, when the cell error/loss probability of each ATM data-link segment is 10-6, the packet error/loss probability observed at the sender is less than 10-2 even for 106 receivers. Finally, even when the cell error/loss probability of ATM data-link segment is large, e.g. 10-3, the IP multicast service without the FEC policy can not apply even for 10 receivers. However, the IP multicast with the FEC policy can apply upto few hundred of receivers.