Impact of probability of transmission on slotted ALOHA for wireless networks employing MIMO spatial multiplexing

Multiple-input-multiple-output (MIMO) spatial multiplexing techniques can significantly increase data transmission rate of a communication system in a rich scattering environment at no cost to the allocated frequency spectrum. However, to fully exploit the physical layer gain, upper layer protocols need to be adjusted appropriately. This paper investigates the significance of transmission control from the media access control (MAC) layer point of view by comparing the performance of the slotted ALOHA with spatial multiplexing (SM) in two scenarios; one with and the other one without the controlled probability of transmissions. It is also shown that the maximum average throughput (frames/slot) does not translate into the highest success rate. The analysis provides a useful insight into the cross-layer design that takes into account MIMO spatial multiplexing.