Streaming video from Beaglebone over Xbee module
You cannot do this due to distance and of course the UART protocol(single-ended) is not made for video streaming.You will need a LVDS(Low Voltage Differential Signal) for this.The distance of 4 Km is to big for a single wireless transmitter.You will need to use an available network which could be your relay.What resolution does the camera have ?