One of the first things to get affected during natural disasters and accidents is the communication network. In a country where over a billion use mobile phones, providing mobile connectivity during a disaster, at least for emergency usage, is a priority.
In this context, an IIT Madras team is developing a low-cost communication system that can enable rescue workers to communicate with a locally established centre and, through this centre, to the National Disaster Management Agency (NDMA) in Delhi.
The plan is also to enable citizens within the reach of this system to communicate essential messages, such as “I am safe” or basic information – name, age, gender, etc, of persons discovered. The whole system is compatible with basic model mobile phones, as most users in India do not own smart phones. The system, named DISANET, allows basic services such as voice, text and video communications to be exchanged within this network of rescue workers, Master Operation Centre and the NDMA.
The design has four subsystems — WiFi, a satellite link, single-carrier GSM and LTE (Long Term Evolution) which is a standard for high-speed wireless communication for mobile phones and data terminals. The compact system can be easily transported in trucks to the site of the Master Operation Centre within a few hours of the disaster. The wireless system should provide coverage over an area of approximately 1,000 square kilometres.
At present, people who are involved in rescue operations, such as police personnel, use walkie/talkie handsets (VHF/UHF). “VHF/UHF handsets are expensive, costing anywhere up to a couple of lakhs of rupees. So the police are very selective of who gets to use them… Much of the police force depends on GSM for its communication needs, and they are subject to all the disruptions that affect GSM network,” says Devendra Jalihal of the Electrical Engineering department of IIT, who along with David Koilpillai, also from the same department, is developing this system.
Rescue workers with GSM handsets, WiFi cameras and WiFi nodes can spread out over an area of 12-25 square kilometre to form the primary deployment area. These workers supply communication between the affected area and the Master Operation Centre (MOC). The MOC has pico- or micro-sized LTE-Base Stations which are mounted at a height of 15 to 20 metres.
This is achieved by a tethered-balloon that is inflated and hoisted at the MOC. But this system is being improved – instead of balloons, drones are being tested. “We tested a variant of this during Mahamaham [festival] at Kumbakonam in February, this year, for Tamil Nadu Police. Police personnel with smart phones could initiate and receive calls using WiFi channels. We are proposing this kind of system whenever there is a large gathering, as the GSM network experiences ‘congestion’ and the police need another line of communication,” says Dr Jalihal. The architecture, which mainly supports usage by rescue workers, can be extended to allow citizen victims to send short SMSs communication.
Also, the rescue team can directly communicate with citizens about the arrangements using FM broadcast, which citizens receive on their mobiles. This enables the flow of authenticated information from the authorities to the citizens and prevents rumour-mongering during times of disaster.
“We are now trying to build a GSM network with low cost hardware and open source software and hope to test it in the next couple of months,” says Dr Jalihal.