WLAN Nodes Research Articles

Study on the Signal Transmission Characteristics of 2.4GHz Wireless Network in Dorms

In accordance with the deployment requirements of WLAN node in college student dorms and its features of application environment, this paper studies the relevance among factors like radio-frequency signal transmission characteristics, communication distance, AP height and transmission path, etc., with a case study of AP radio frequency 2.4GHz. Experiments show that the attenuation of wireless network signal in student dorms conforms to Keenan-Motley model. When AP is fixed, the signal strength received by laptop generally reduces with the increase of communication distance, yet just opposite with packet loss rate. When deploying AP, 1.25-1.75 height is ideal, and one-side coverage of 3 dorm rooms optimal. Based on the above researches, a relational model of AP height, communication distance and received signal strength is established. In it, model parameter and AP height display a cubic polynomial relationship, and attenuation coefficient and AP height show a quadratic polynomial relationship. Experiment results demonstrate that this model can satisfactorily predict the received signal strength of different AP heights and communication distances, providing technical support for wireless network deployment in student dorms.

USN 환경에서 실시간 상황인식 QoS 보장을 위한 범용 미들웨어 설계

유비쿼터스 컴퓨팅 시대가 도래하면서 USN(Ubiqutious Sensor Network) 관련 핵심기술 개발에 대한 관심이 급증하고 있다. 특히, ZigBee, Bluetooth, WLAN, CDMA 등과 같이 다양한 종류의 무선통신 기술과, Nano 계열, Mote계열, NeurFon계열 등과 같은 여러 종류의 센서노드들에 대한 연구가 세계 각 대학과 연구소를 중심으로 진행되고 있다. 이러한 연구 중 본 논문에서는 USN 응용 시스템과 센서노드 하드웨어의 중간 부분에 위치하여, 수많은 센서 데이터들을 수집 및 처리하고 USN 응용서비스의 실시간 상황인식 QoS를 보장할 수 있게 조력하는 USN 미들웨어를 설계하고 그 성능을 시뮬레이션을 통해 증명 한다. Recently, many researchers interested in core technology related to USN(Ubiqutious Sensor Network) with emerging Ubiqutious computing era. Especially, researched about various wireless telecommunication technologies such as ZigBee, Bluetooth, WLAN, CDMA, and various sensor nodes such as nano, Mote, and NeurFon are progressed in universities and research institutes of the world. In this paper, an advanced algorithm is proposed by analyzing problems of circumstance recognition and conventional real-time QoS of USN middleware technology. Finally, the performance of the proposed USN middleware is demonstrated through simulation.

GUIDE-gradient: A Guiding Algorithm for Mobile Nodes in WLAN and Ad-hoc Networks

Whereas there is a lot of work related to finding the location of users in WLAN and ad-hoc networks, guiding users in these networks remains mostly an unexplored area of research. In this paper we present the concept of node-to-node guidance and introduce a method that can be used to implement it. This method relies on the computation of a local gradient in the neighborhood of the moving node. We named this protocol GUIDE-gradient, which is a GPS-free and infrastructure-free node-to-node guiding system. In this paper we also discuss how the guiding algorithm can be generalized to node-to-node guidance in multihop ad-hoc networks.