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In this paper, we proposed a group node contention algorithm for avoiding continuous collisions in LR-WPAN. The purpose of IEEE 802.15.4 is to achieve low speed, low cost and low power consumption. Recently, as applications of LR-WPAN have been extended, there is a high probability of collision as well. There are two types of collisions in LR-WPAN: i)(More)
For handover in IEEE 802.16e, scanning procedure by mobile station is defined to find the most reliable target base station. However, the conventional scanning schemes cannot guarantee a fast target base station decision because some of the neighbor base stations of the scanning list provided by a serving base station are not actually attachable by the(More)
In wireless sensor networks, the positioning scheme using the received signal strength (RSS) has been widely considered due to its simplicity. Appropriate estimation of path-loss exponent (PLE) between a sensor node and an anchor node plays a key role in reducing position error in this RSS-based positioning. In the conventional researches, a sensor node(More)
Sufficient protection of primary user is a challenging issues in cognitive radio networks. Previous works have considered either the probability of detection higher than a required one given a priori or the interference ratio (probability of collision) below a certain threshold as the constraint for sufficient protection of primary users. However,(More)
Recently, cognitive radio (CR) technology has been spotlighted for the efficient use of limited frequency bands. The most important part of CR technology is to protect the incumbent user communications. Therefore, CR device should periodically sense not only the currently using channel, but also some other channels to prepare candidates. In this paper, we(More)
In cognitive radio networks, secondary users conduct local sensing to use underutilized spectrum bands. However, every secondary user's local sensing usually gives rise to much sensing overhead. Moreover, a globally synchronized quiet period cannot be determined in a decentralized network. In this paper, we propose a zone-based distributed sensing scheme,(More)