# RDSP: Rapidly Deployable Wireless Ad Hoc System for Post-Disaster Management
## 3 System Architecture of the RDSP Scheme  
This section presents the architecture of the RDSP scheme, which aims to reduce the average waiting times for transmitting victim's information towards the server by utilizing the following key features:  
* Client Device: The client devices are the end point communication devices held by rescue team members and victims. The client device is a WiFi-enabled device that manages to transmit the victim's location information to the server device using relay devices. The client devices are used to establish the communication between rescue teams and server and to send feedback about the emergency situation. * Relay Device: Relay devices are randomly deployed at a distance of 90 m from each other to transmit the victim's location information generated by the client device towards the server and then send back acknowledgment information to the client device. Relay devices dynamically connect with each other in a manner to establish the shortest path towards the server. * Server Device: The server device continuously listens for the arrival of incoming messages sent by the client device via relay devices in order to alert the rescue teams. Moreover, it sends the control and operational messages and is also responsible for receiving the feedback from rescue teams. Figure 1 illustrates a deployment scenario of the RDSP system after disaster. When disaster occurs, the rescue team members will deploy the RDSP system as follows: A server device is installed in the incident area that will receive updates from rescue teams and victims. Additionally, rescue team members will move forward towards disaster areas while deploying relay devices at equal distances of about 90 m until any victim is sighted. Then, the client device that is carried by the rescue team members is used to send the victim's position information to the server. The distance of 90 m between relays is managed by incorporating GPS modules in relays. After the server module is installed in an incident area, we start deploying the relays as follows: First of all, the first relay wirelessly connects with the server module. Afterwards, while carrying the relay and moving away from the server module, the relay continuously calculates its distance from the server using the GPS module that provides location coordinates of the relay module, whereas the location coordinates of the server are fixed and known to the relay module. If the calculated distance is 90 m, a green LED (installed on relay module) lights up, indicating to drop the first relay module at that particular position. Similarly, a second relay is chosen which connects with the first relay and the distance between the first relay and the second relay is again calculated by the second relay and it is dropped when the green LED on the second relay lights up. Following this procedure, all the relay devices manage to maintain a distance of 90 m between each other. The 90 m distance was selected because the relay device uses WiFi technology that has a transmission range of 90 m. However, the transmission range can be increased by using other advanced technologies, which is highly application dependent. It is indicated in Figure 1 that both the client device and relay device communicate wirelessly with the server device via WiFi. The server device manages all the request messages received and sends back an acknowledgment to the client device to ensure the reception of the request message. Figure 2 presents a flow chart of the server device. After the initialization, the server waits for the arrival of request messages. If a message arrives, the server sends back an acknowledgment message to the client device via relay devices and generates an alarm message to alert the rescue teams. Figure 1: Deployment scenario of the RDSP scheme. Algorithm 1 presents the operation of the microcontroller in the server device. The input to the server device is a request message \(R_{msg}\), whereas the output is an acknowledgment message and an alarm message.