**4. Short range channel modelling**

Utilising the full capacity of the underwater acoustic channel is extremely important as the channel exhibits such challenging and limited resources as has been discussed. For short range data transmission operations there are a number of benefits that can be gained over current longer range underwater acoustic transmission. These will now be explored further in terms of data communication protocol design and development. In particular, finding the optimum signal frequency and bandwidth at different ranges and under various channel conditions will be evaluated on the basis of using the best Signal-to-Noise ratio (SNR) possible at the hydrophone. Investigation into channel capacity and BER for various possible modulation schemes will also be analysed to set up the background to the challenges for MAC and routing protocol design.
