Investigations into a Slotted ALOHA protocol for a MIMO system operating under Rician channel conditions

This paper investigates a Slotted ALOHA protocol for a multi-user wireless system operating under partial Line of Sight (LOS) conditions in which both the base station and mobile users are equipped with multiple element antennas. The investigations focus on how physical layer parameters such as spatial correlation, mutual coupling and Rician factor K affect the system capacity. Probability model for a Slotted ALOHA under the condition of a Rician channel model to form two-layer (Physical-Medium Access Control) expressions is considered. The model includes spatial correlation and mutual coupling in array antennas. The obtained results show that spatial correlation has a negative effect on the system performance while mutual coupling can improve capacity under the small spacing of array antenna elements. It is also shown that active LOS nodes in the network can have an adverse impact on the system capacity. Controlling probability of transmission of LOS nodes is presented as a possible solution to the problem.