Slotted ALOHA mobile network with vertical array antenna diversity

In mobile radio networks, receiver capture is known to enhance the performance of the slotted ALOHA random access protocol substantially. The efficiency of narrowband slotted ALOHA radio networks can be further enhanced by using sector antennas. The paper investigates the effect of partially overlapping, realistic antenna patterns which gives highly correlated received power levels at different receiver branches. The author proposes a method for computing the joint throughput from two base station antennas. The a posteriori information provided by the event of one message capturing one antenna is used to find conditional probabilities of capturing the other antennas. Any overlap in the antenna patterns decreases the throughput, but transmissions from the overlap area face a larger probability of capture than signals from directions in which only one antenna has significant gain