Telemetry Using the IEEE 802 . 11 g Standard , for monitoring target ships

This work consisted in the design, assembly and testing of a low cost system capable of performing telemetry over long distances, using wireless technology. When sinking old decommissioned ships as targets for live fire exercises (a routinely used practice in the Navy), there is the nee d to measure many physical parameters during the impacts. These measurements must be made from a safe distance (between 3 and 8 nautical miles). Due to the situation’s nature, a system capable of sampling and transmitting data over long distances (telemetry) was considered the best solution. This system must be reliable, tough and cheap. It must connect the sensors available aboard the target ship, and then connect these to a monitoring ship located a few miles away. A system based on simple, cheap and available technology was assembled and tested. The tests focused on the following parameters: channel capacity, latency, maximum distance between the analysis point and the sampling point. We implemented a LAN (Local Area Network) using wired connections aboard the target ship , and used a Wi-Fi connection to link this LAN with monitoring ship. We used the 802.11g IEEE standard that specifies the requirements for devices that enable the Transmission/reception (TX/RX) with speeds around 54 Mbps in the 2.4 GHz frequency range. The range of the routers used for the long distance connection was incremented through the use of two amplifiers, two high-gain omnidirectional antennas and low attenuation cables. To measure physical parameters, pressure, acceleration and temperature sensors were used. To make the data collection, a data logger with Ethernet interface was used. For visual observation a camera with Ethernet interface was used. A laptop with suitable software was used aboard the monitoring ship to collect the data. In the target ship, the router was connected to the camera and Ethernet enabled data loggers that were connected to the various sensors. Appropriate software was used to measure the capacity of the channel. It was possible to test the transmission rate during a file transmission, and during the reception of data from the datalogger and camera. The relationship between distance and transmission rate was also tested by moving the antennas.