Documentation

The WiMesh system comprises of a two-tier, architecture. The first tier comprises of portable, powerful, battery-powered, multi-radio multi-channel wireless mesh nodes which will be equipped with antennas to create the backbone wireless mesh infrastructure. IEEE 802.11 based wireless mesh networks have become quite popular during the recent years. Often built from cheap, off-the-shelf equipment, mesh networks can be quickly deployed and provide extended wireless coverage as well as increased capacity through spatial reuse. Free from any infrastructure requirements, mesh nodes can be added as required thereby offering excellent flexibility and providing wireless access to a large number of users spread over geographical regions. Mesh networks are infrastructure-free, self-healing and self-configuring, which makes them an attractive alternative to traditional communication networks. These features of the mesh are very desirable in the WiMesh system, which requires a rapidly deployable, auto-configuring and self-healing backbone. The second tier of WiMesh comprises of Wi-Fi equipped mobile handheld phones carried by rescue workers. The mobile sets will automatically connect with the nearest mesh node through Wi-Fi and will eventually enable the workers to communicate and coordinate with other team members.

WiMesh Server

The WiMesh server is one of the most important part of the WiMesh system as it handles communication among clients as well as the overall system including the mesh backhaul network. The Server hosts the opensource OpenSIPs server and the Application Server. The application server is based on the Asynchronous Event-Driven Network Application Framework. For multi-threading an innovative approach called Staged Event-Driven Architecture (SEDA) is used which is very efficient. The server handles registration & authentication of users, the relaying of audio calls in both broadcast mode and unicast mode,  and several other features:

§  Multimedia exchange (image, video, data files, SMS) with a client or group of clients

§  Audio (unicast and broadcast modes)

§  Ability to view the geographical position of a specific user or group of users

§  Overall monitoring and control of the system

WiMesh Mesh Backhaul

The WiMesh backhaul comprises of 802.11n equipped multi-radio multi-channel mesh nodes comprising of Ubiquiti Nanostation and PicoStation Nodes. The nodes are equipped with solar panels and batteries. Each mesh node has several wireless devices tuned to different channel. One AP per-node and a dedicated wireless channel is used for the mesh backhaul, while the other devices are used for mesh Access networking to provide connectivity to user nodes. The APs have been re-programmed with open-source OpenWRT embedded Linux. The mesh backhaul uses the Expected Link Performance (ELP) metric for routing which has been integrated into the Optimized Link-State Routing (OLSR) Protocol. 

WiMesh Client

The WiMesh client comprises of an Android application that has been designed to be installed on Android mobile phones. It uses the opensource Sipdroid application for VoIP calling, but adds several additional features:

§  Sharing of multimedia content (image, video, data, SMS) between clients, in both one-to-one and one-to-many modes

§  Making audio calls in unicast, and broadcast mode

§  Ability to receive from and send live video stream to other client(s)/control station

§  Ability to view the geographical position of a specific user or group of users