Cognitive radio technology makes efficient use of the valuable radio frequency spectrum in a non-interfering manner to solve the problem of spectrum scarcity. This paper aims to design a scheme for the concurrent use ...Cognitive radio technology makes efficient use of the valuable radio frequency spectrum in a non-interfering manner to solve the problem of spectrum scarcity. This paper aims to design a scheme for the concurrent use of licensed frequencies by Underlay Cognitive Users （UCUs）. We develop a new receiver-initiated Medium Access Control （MAC） protocol to facilitate the selections of alternative reliable carrier frequencies. A circuit is designed to establish reliable carrier selections based on the Received Signal Strength Indicator （RSSI） at the receiving end. Based on both packet-level simulations and various performance parameters, a comparison is carried out among conventional techniques, including the Multiple Access with Collision Avoidance （MACA） and MACA by invitation（MACA-BI） techniques, and our scheme. The simulated results demonstrate that when conventional techniques are used, the system overhead time increases from 0.5 s on the first attempt to 16.5 s on the sixth attempt. In the proposed scheme under the same failure condition, overhead time varies from 0.5 s to 2 s. This improvement is due to the complete elimination of the exponential waiting time that occurs during failed transmissions. An average efficiency of 60% is achieved with our scheme while only 43% and 34% average efficiencies are achieved with the MACA and MACA-BI techniques, respectively. The throughput performance of our scheme on the fourth attempt is 7 Mbps, whereas for the MACA and MACA-BI protocols, it is 1.9 Mbps and 2.2 Mbps respectively.展开更多
Novel enabling technologies from physical layer to Medium Access Control (MAC) layer are proposed to provide energy efficient Radio-over-Fiber (RoF) Distributed Antenna System (DAS) based Wireless Sensor Networks (WSN...Novel enabling technologies from physical layer to Medium Access Control (MAC) layer are proposed to provide energy efficient Radio-over-Fiber (RoF) Distributed Antenna System (DAS) based Wireless Sensor Networks (WSN). The power consumption performance of the network is evaluated in terms of the total network power consumption based on the proposed power consumption models from the physical layer. The results illustrate that for a given power consumption value, the tradeoff among the number of Remote Access Units (RAUs), the number of Multiple-Input Multiple-Output (MIMO) antennas and the number of hops must be taken into account. In order to efficiently reduce the total network power consumption, we also proposed a solution from the MAC layer using a sleep-aware MAC protocol, which can dynamically centralized control MIMO antennas to operate in a sleep mode. The proposed enabling technologies provide basis for selecting suitable RoF DAS based WSN and effectively reduce the power consumption.展开更多
由于认知无线网络(cognitive radio network,简称CRN)固有"二次利用"的特性,使其日益得到重视.而作为CRN核心构成的MAC(medium access control)协议,业已成为当前各研究机构的一个热点.主要对频谱感测技术、信道接入技术等MA...由于认知无线网络(cognitive radio network,简称CRN)固有"二次利用"的特性,使其日益得到重视.而作为CRN核心构成的MAC(medium access control)协议,业已成为当前各研究机构的一个热点.主要对频谱感测技术、信道接入技术等MAC层核心设计问题进行了探讨,并针对认知无线网络MAC的特性及需求进行了分析,然后对设计MAC频谱感知技术、信道接入技术、频谱共享技术等相关研究进展进行了归类总结.最后指出了当前面临的主要研究难点及挑战,并提出了一些方向性建议.展开更多
无线移动Ad H oc 网络由于其无固定基础设施、自我组织、分布管理、动态拓扑、多跳通信等特点成为近年研究的热点。各结点的媒体接入控制( M AC) 层协议规定了结点接入信道进行通信的机制,网络层路由协议规定...无线移动Ad H oc 网络由于其无固定基础设施、自我组织、分布管理、动态拓扑、多跳通信等特点成为近年研究的热点。各结点的媒体接入控制( M AC) 层协议规定了结点接入信道进行通信的机制,网络层路由协议规定了如何搜寻站点和维护高速动态拓扑的网络。介绍了 Ad H oc 网络的基本特性,并分析了现有主要的几种 M AC 协议和路由协议。展开更多
文摘Cognitive radio technology makes efficient use of the valuable radio frequency spectrum in a non-interfering manner to solve the problem of spectrum scarcity. This paper aims to design a scheme for the concurrent use of licensed frequencies by Underlay Cognitive Users （UCUs）. We develop a new receiver-initiated Medium Access Control （MAC） protocol to facilitate the selections of alternative reliable carrier frequencies. A circuit is designed to establish reliable carrier selections based on the Received Signal Strength Indicator （RSSI） at the receiving end. Based on both packet-level simulations and various performance parameters, a comparison is carried out among conventional techniques, including the Multiple Access with Collision Avoidance （MACA） and MACA by invitation（MACA-BI） techniques, and our scheme. The simulated results demonstrate that when conventional techniques are used, the system overhead time increases from 0.5 s on the first attempt to 16.5 s on the sixth attempt. In the proposed scheme under the same failure condition, overhead time varies from 0.5 s to 2 s. This improvement is due to the complete elimination of the exponential waiting time that occurs during failed transmissions. An average efficiency of 60% is achieved with our scheme while only 43% and 34% average efficiencies are achieved with the MACA and MACA-BI techniques, respectively. The throughput performance of our scheme on the fourth attempt is 7 Mbps, whereas for the MACA and MACA-BI protocols, it is 1.9 Mbps and 2.2 Mbps respectively.
基金supported in part by National Key Basic Research Program of China (973 Program) under Grant No.2012CB315705National Hi-Tech Research and Development Program of China under Grant No.2011AA010306+2 种基金National Natural Science Foundation of China under Grant No.60932004, 61001121, 61107058 and 61120106001Beijing Excellent Doctoral Thesis Project under Grant No.YB20101001301the Cooperation Project between Province and Ministries under Grant No.2010B090400112
文摘Novel enabling technologies from physical layer to Medium Access Control (MAC) layer are proposed to provide energy efficient Radio-over-Fiber (RoF) Distributed Antenna System (DAS) based Wireless Sensor Networks (WSN). The power consumption performance of the network is evaluated in terms of the total network power consumption based on the proposed power consumption models from the physical layer. The results illustrate that for a given power consumption value, the tradeoff among the number of Remote Access Units (RAUs), the number of Multiple-Input Multiple-Output (MIMO) antennas and the number of hops must be taken into account. In order to efficiently reduce the total network power consumption, we also proposed a solution from the MAC layer using a sleep-aware MAC protocol, which can dynamically centralized control MIMO antennas to operate in a sleep mode. The proposed enabling technologies provide basis for selecting suitable RoF DAS based WSN and effectively reduce the power consumption.
文摘由于认知无线网络(cognitive radio network,简称CRN)固有"二次利用"的特性,使其日益得到重视.而作为CRN核心构成的MAC(medium access control)协议,业已成为当前各研究机构的一个热点.主要对频谱感测技术、信道接入技术等MAC层核心设计问题进行了探讨,并针对认知无线网络MAC的特性及需求进行了分析,然后对设计MAC频谱感知技术、信道接入技术、频谱共享技术等相关研究进展进行了归类总结.最后指出了当前面临的主要研究难点及挑战,并提出了一些方向性建议.
基金Supported by the National High-Tech Research and Development Plan of China under Grant No.2005AA121570(国家高技术研究发展计划(863))the National Basic Research Program of China under Grant No.2003CB314802(国家重点基础研究发展计划(973))
文摘无线移动Ad H oc 网络由于其无固定基础设施、自我组织、分布管理、动态拓扑、多跳通信等特点成为近年研究的热点。各结点的媒体接入控制( M AC) 层协议规定了结点接入信道进行通信的机制,网络层路由协议规定了如何搜寻站点和维护高速动态拓扑的网络。介绍了 Ad H oc 网络的基本特性,并分析了现有主要的几种 M AC 协议和路由协议。
