Wireless Sensor Network (WSN) consist of large number of battery operated sensing and computing devices deployed randomly for monitoring applications. With the advent of new technologies WSNs are providing a new class of information to human beings. In most cases the networks were stationary but as a evolutionary step the WSNs have to consider mobility. This new class of sensor networks is Mobile Wireless Sensor Networks. Eg moving robots, surveillance aircrafts. Nodes share a single channel for communication. To share communication channel, establishment of a MAC protocol is required in the sensor nodes. The objective of the MAC protocol is to regulate access of the shared wireless medium, so that the performance requirements of the underlying application are satisfied. Energy efficiency and Mobility are big challenges for Medium Access Control protocol design to give a reliable communication. Paper describes a Mobility aware MAC protocol, implemented using OMNeT++ network simulator. OMNeT++ is open source discrete event simulator. Mixim is 'mixed simulator', developed for wireless and mobile simulations in OMNeT++.