This report presents a study on the performance of a CSMA based access protocol in a semi mobile backbone network. The networks investigated cover larger areas and include longer links than what is typical for tactical ad hoc networks. The protocols used must therefore be adapted and for CSMA this mainly means that protocol wait times need to be significantly increased. When the wait times increase, data packet length also needs to increase in order for the protocol to perform well. Network simulations are used to determine how different network aspects, traffic models and parameter settings affect the capacity for delivering user traffic. The results suggest a capacity of up to 20-30% of the available bandwidth can be achieved in the evaluated scenarios. However, the capacity is greatly affected by the placement of nodes and the how traffic is distributed in the network.