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In a wireless sensor network, sensor nodes are deployed in an ad hoc fashion and they deliver data packets using multihop transmission. However, transmission failures occur frequently in the multihop transmission over wireless media. Thus, a loss recovery mechanism is required to provide end-to-end reliability. In addition, because the sensor nodes are very(More)
— In wireless sensor networks, clustering schemes have been adopted as an efficient solution to prolong the network lifetime. In these schemes, the performance of energy-efficient data transmission is affected the cluster ratio (CR). This paper analyzes the optimal CR from the perspective of network energy efficiency, and its impact on the network lifetime.(More)
Coexistence problem occurs when a single WBAN(Wireless Body Area Network) locates in multiple WBANs environment. In that case, WBANs are suffered from serious channel interferences which may degrade the performance of each WBAN due to failure of data transmission. Because WBAN handles physical signal or emergency data affecting human life, WBAN requires the(More)
WBAN(Wireless Body Area Network) which has received a lot of attention for developing medical and entertainment services is standardized by IEEE 802.15 Task Group 6(TG6). WBAN should be guaranteed low data latency because medical data must be timely and correctly transferred. Since the standard considers only a single-channel, it has problems such as(More)
Applying cognitive radio technologies to wireless sensor networks (WSNs) explores new possibilities for network architectures. The cognitive radio technology enables opportunistic access of unlicensed sensor nodes to licensed bands without influencing primary users (PUs). Spectrum sensing is a key technology to identify the presence of PUs. Benefit from the(More)
In Cognitive Radio Sensor Networks (CRSNs), the cognitive radio technology enables sensor nodes to occupy licensed bands in a opportunistic manner and provides advantages in terms of spectrum utilization and system throughput. This paper proposes a routing scheme based on semi-supervised learning, which jointly considers energy efficiency,(More)
Cooperative communications are adopted as a promising solution to achieve high data rate over large areas in the future 4G wireless system, and the relay station (RS) is the key concept in cooperative communications. However, most existing works in this area focus only on optimal RS selections. In addition, there are only few works consider another crucial(More)
Medical data often consists of a large number of disease markers. For medical data analysis, some disease markers are not helpful and sometimes even have negative effects. Therefore, applying feature selection is necessary as it can remove those unimportant disease markers. Among many feature selection methods, rough set based feature selection (RSFS) has(More)