Spatially divided channel scheme using sectored antennas for CSMA/CA “directional CSMA/CA”

One of the most spotlighted medium access control (MAC) scheme is carrier sense multiple access with collision avoidance (CSMA/CA). This scheme, adopted by the IEEE 802.11 standard, avoids packet collision by virtual carrier sensing considered for the “hidden terminal” problem, gathering physical channel sensing. Therefore, it attains higher throughput than the other MAC scheme such as slotted ALOHA (S-ALOHA), but in increasing the number of terminals and traffic in a contention scheme, serious transmission delay occurs because of avoiding packet collision. In order to solve the above problem, we propose dividing the channel by the directivity of the sector antennas specially. It is named “directional CSMA/CA”. This proposal makes channel usage efficient since many terminals can transmit their packets simultaneously. From computer simulation, it is confirmed that this scheme attains a high throughput and decreases the transmission delay, and it constructs a system with high efficiency. Moreover, at the same time, sectorization limits the paths of arriving packets, and the propagation characteristics such as delay spread are improved