A connectivity management system for vehicular telemedicine applications in heterogeneous networks.

Wireless access technologies such as UMTS with HSPA extensions, WiMAX, and Flash-OFDM and the convergence towards next generation heterogeneous networks enable the realization of always best connected scenarios. As the resulting heterogeneous networks become easier to access and more reliable to depend on, novel telemedicine services such as vehicular emergency applications emerge. Due to their life-critical characteristics, these applications require connectivity throughout the heterogeneous network. In this study, we propose MIPGATE, our mobile connectivity gateway for vehicular applications in next generation heterogeneous networks. MIPGATE contains modules for the access technologies currently available and a decision mechanism to switch intelligently to the connection offering the most suitable conditions. Link layer triggers and additional context information are used to optimize the handover decision process. MIPGATE is deployed within StrokeNet, a mobile telemedicine project for the remote diagnosis of stroke patients using real-time audio and videoconferencing. The MIPGATE system is validated through measurements on throughput, delay, packet loss, and handover latencies using public wireless network infrastructures with the UMTS technology and a Beyond-3G testbed featuring a Flash-OFDM test network. For the payload packets, mean handover times of 118 ms in case of handovers to UMTS/HSDPA and 23 ms in case of handovers to Flash-OFDM have been achieved in a real-world network setup. The overall packet loss rate is 0.21% and equally distributed over the duration of the measurements. The results show that MIPGATE supports network connectivity under mobility as required by novel vehicular telemedicine applications and demanding real-time services.