Enhanced capture effect for slotted ALOHA employing transmission power control corresponding to offered traffic

Abstract

This paper presents a novel slotted ALOHA that has an enhanced capture effect even if heavy traffic is offered. Capture event success probability is improved by controlling the probability of high power transmission permission. This makes it possible to capture the other packets if only one station increases its transmission power. This control method is the key issue of this paper since the capture effect is one of the most promising ways to achieve high throughput without interference (collision) detection/carrier sense. We modified the conventional slotted ALOHA to yield a practical and useful packet transmission scheme. This modified slotted ALOHA has a finite buffer that stores backlog packets. Heavy traffic may cause buffer overflow which implies packet loss. When a station of a wireless LAN or another data terminal intends to send a packet, its transmission power is controlled by the number of stations in an area that covers the same cell shaped by an access point. As a result, only one of the packets can be successfully sent by capturing the other packets. This capture effect is improved significantly by the proposed scheme. This modified and enhanced slotted ALOHA achieves the maximum throughput of 0.74, which is higher than the 0.47 achieved by transmission power control in a previous paper. This is double the throughput of the original slotted ALOHA.