T. Frantti (Finland)
open-loop control, WLAN, packet switching.
Transmission power control is an effective way to save en ergy in wireless devices on wireless local area networks (WLANs). In WLANs nodes can transmit only when a communication channel is unoccupied. The transmission bursts intervals for nodes vary mainly according to the type of media access control and the number of nodes compet ing or reserving the channel time. Due to varying burst intervals, there is not a continuous transmission channel between the node and the access point. Therefore, deliv ery of real-time feedback information from the access point to the transmitting node for, e.g., closed loop power con trol, is meaningless. In WLANs the nodes around the ac cess point transmit with a high value fixed power in order to guarantee as error-free transmission as possible. How ever, this approach is quite energy inefficient and causes unnecessary interference to adjacent access points and as sociated nodes. This paper considers energy-efficient Dis tributed Coordination Function (DCF) operation of IEEE 802.11 WLANs via an open-loop power control algorithm based on the fuzzy set theory. The main idea is to minimize transmission power of the nodes, while keeping the trans mission errors at an acceptable level. The functionality of the proposed solution is evaluated via simulations.
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