Optimum delivery of telemedicine over low bandwidth links

Telemedicine is frequently used to support the delivery of medicine to remote regions, but it can often be the case that these areas are poorly served by communications. The AIDMAN project investigates the delivery of telemedicine in remote regions of Greece using satellite. However the high cost of such links can severely limit the bandwidth available to applications. In addition the satellite link is a clear channel and may be configured to emulate any protocol. This presents a problem of determining which protocol may best support the applications. We have modelled the three types of link protocol, circuit switched (ISDN), packet switched (TCP/IP) and cell switched (ATM) to determine how their characteristics affect the performance when bandwidth is severely restricted. We further investigate how performance may be optimised when the link is used to carry mixed traffic of real-time videoconference and image transfer. Our simulation shows that TCP/IP can support telemedicine applications reasonably well, so long as the number of simultaneous image transfers are restricted. Furthermore, IPv6, which supports prioritisation of traffic, can overcome this restriction. Use of TCP/IP has a further advantage, in that it permits integration of wider networks, is cheap, widely available and supports virtually all telemedicine applications. Real-time measurements using the virtual consultation workstations developed for the AIDMAN project on a low bandwidth link implemented on routers connected using ISDN to simulate a link with 128 kbps confirms the findings of the simulation