Light-trains: An Integrated Optical-Wireless Solution for High Bandwidth Applications in High-Speed Metro-Trains

Moving trains represent a voluminous mass of users moving at high velocities that require bandwidth (on demand). Existing solutions typically based on wireless technology alone cannot scale efficiently to provide for bandwidth to such fastmoving voluminous users. A new approach is proposed that facilitates dynamic provisioning, good scalability and efficient use of available bandwidth. The proposed approach called lighttrains seamlessly integrates optical and wireless networking techniques to provide an ideal broadband Internet access solution to users in moving trains. We identify the set of requirements that a solution would require – such as fast handoff, low-cost of deployment, mature technology and ability to provide dynamic bandwidth provisioning (and hence low experienced delay). The requirements mentioned influence our choices of technologies for different domains in the network: (1) For access to end-users that reside within the train we use an efficient wireless last-inch solution like WiFi in the Point Coordination Function (PCF) mode. (2) For providing access between the wired backbone network and the train we use a modified WiMax system that gives good throughput and efficient channel utilization capacity in a point-to-point configuration. (3) Finally, to be able to provision bandwidth between the core network and the WiMax base-stations we propose the use of light-trail technology at the optical layer. The light-trail technology allows for dynamic provisioning of bandwidth at the optical layer through a unique node architecture and out-of-band control protocol. It turns out that the light-trail control protocol is useful for assisting fast hand-offs. The hand-off time being drastically reduced enables efficient utilization of the wireless channel even at very high speeds. A protocol that enable end-toend provisioning across the three domains of technology aka light-trails, WiMax and WiFi is also proposed. The proposed protocol is a cornerstone mechanism for providing inter-domain (technology) connectivity in a pragmatic way. Different aspects of the protocol are considered, amongst which delay and efficiency are computed. The protocol and system requirements juxtaposed are simulated extensively. Results pertaining to utilization, delay, efficiency and network wide performance are all showcased. Viability of the model in being able to provide bandwidth to moving users is shown.