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1.
For antenna-array-based multiple-input multiple- output orthogonal-frequency-division-multiplexing (MIMO-OFDM) wireless systems, gain in channel throughput reduced through sufficient feedback of the channel state information (CSI) is significant, particularly when the number of transmit antennas is larger than the number of receive antennas. In this letter, we demonstrate that, in such scenarios, (1) the CSI of each OFDM sub-carrier can be parameterized into a short bit stream by a proposed low-complexity QR decomposition on the corresponding MIMO channel matrix, (2) the overall CSI can be reliably represented by a proposed parameter interpolation on the above bit streams of only a fraction of sub-carriers, and (3) a MIMO-OFDM system with a low-rate CSI feedback parameterized above can provide a channel throughput comparable to the channel capacity. 相似文献
2.
In this paper, a distributed method for coverage optimization of random deployed WMSNs utilizing motility and mobility capabilities of nodes, is proposed. The aims followed by the method are first, maximizing the coverage ratio by minimizing both the covered overlapping areas, and the coverage holes after random deployment, and second, enhancing energy efficiency of the coverage optimization procedure, by minimizing the needed rotations and specially movements, comparing with the previous schemes. To these aims, the most appropriate location and orientation of the nodes are calculated round by round considering all the possible nested compositions of rotation and movement. But, rotating and moving the nodes are performed after terminating the algorithm rounds and achieving the decisive results. So, the proposed method does not impose the overhead of trial and error of rotation or relocation on the network nodes. The performance of the proposed approach has been compared with the previous works for different network configurations; simulation results show that the proposed approach outperforms the previous schemes in terms of both coverage ratio and energy efficiency. 相似文献
3.
The scarcity and large fluctuations of link bandwidth in wireless networks have motivated the development of adaptive multimedia
services in mobile communication networks, where it is possible to increase or decrease the bandwidth of individual ongoing
flows. This paper studies the issues of quality of service (QoS) provisioning in such systems. In particular, call admission
control and bandwidth adaptation are formulated as a constrained Markov decision problem. The rapid growth in the number of
states and the difficulty in estimating state transition probabilities in practical systems make it very difficult to employ
classical methods to find the optimal policy. We present a novel approach that uses a form of discounted reward reinforcement
learning known as Q-learning to solve QoS provisioning for wireless adaptive multimedia. Q-learning does not require the explicit state transition model to solve the Markov decision problem; therefore more general
and realistic assumptions can be applied to the underlying system model for this approach than in previous schemes. Moreover,
the proposed scheme can efficiently handle the large state space and action set of the wireless adaptive multimedia QoS provisioning
problem. Handoff dropping probability and average allocated bandwidth are considered as QoS constraints in our model and can
be guaranteed simultaneously. Simulation results demonstrate the effectiveness of the proposed scheme in adaptive multimedia
mobile communication networks.
This work is based in part on a paper presented at BroadNet's 04, San Jose, CA, Oct. 2004.
Fei Yu received the M.S. degree in Computer Engineering from Beijing University of Posts and Telecommunications, P.R. China, in
1998, and the Ph.D. degree in Electrical Engineering from the University of British Columbia (UBC), Canada, in 2003. From
1998 to 1999, Dr. Yu was a system engineer at China Telecom, P.R. China, working on the planning, design and performance analysis
of national SS7 and GSM networks. From 2002 to 2004, He was a research and development engineer at Ericsson Mobile Platforms,
Sweden, where he worked on dual-mode UMTS/GPRS handsets. He is currently a postdoctoral research fellow at UBC. His research
interests are quality of service, cross-layer design and mobility management in wireless networks.
Vincent W.S. Wong (S'94-M'00) received the B.Sc. (with distinction) degree from the University of Manitoba, Winnipeg, MB, Canada, in 1994,
the M.A.Sc. degree from the University of Waterloo, Waterloo, ON, Canada, in 1996, and the Ph.D. degree from the University
of British Columbia (UBC), Vancouver, BC, Canada, in 2000, all in electrical engineering. From 2000 to 2001, he was a Systems
Engineer at PMC-Sierra, Inc., Burnaby, BC. Since 2002, he has been with the Department of Electrical and Computer Engineering,
UBC, where he is currently an Assistant Professor. His research interests are in wireless communications and networking. Dr.
Wong received the Natural Science and Engineering Research Council (NSERC) postgraduate scholarship and the Fessenden Postgraduate
Scholarship from Communications Research Centre, Industry Canada, during his graduate studies.
Victor C.M. Leung received the B.A.Sc. (Hons.) degree in electrical engineering from the University of British Columbia (U.B.C.) in 1977, and
was awarded the APEBC Gold Medal as the head of the graduating class in the Faculty of Applied Science. He attended graduate
school at U.B.C. on a Natural Sciences and Engineering Research Council Postgraduate Scholarship and obtained the Ph.D. degree
in electrical engineering in 1981.
From 1981 to 1987, Dr. Leung was a Senior Member of Technical Staff at Microtel Pacific Research Ltd. (later renamed MPR Teltech
Ltd.), specializing in the planning, design and analysis of satellite communication systems. He also held a part-time position
as Visiting Assistant Professor at Simon Fraser University in 1986 and 1987. In 1988, he was a Lecturer in the Department
of Electronics at the Chinese University of Hong Kong. He joined the Department of Electrical Engineering at U.B.C. in 1989,
where he is a Professor, Associate Head of Graduate Affairs, holder of the TELUS Mobility Industrial Research Chair in Advanced
Telecommunications Engineering, and a member of the Institute for Computing, Information and Cognitive Systems. His research
interests are in the areas of architectural and protocol design and performance analysis for computer and telecommunication
networks, with applications in satellite, mobile, personal communications and high speed networks.
Dr. Leung is a Fellow of IEEE and a voting member of ACM. He is an editor of the IEEE Transactions on Wireless Communications,
and an associate editor of the IEEE Transactions on Vehicular Technology. He has served on the technical program committees
of numerous conferences, and is serving as the Technical Program Vice-Chair of IEEE WCNC 2005. 相似文献
5.
Wireless Personal Communications - The average throughput of a cognitive radio (CR) system can be increased by performing spectrum handoff, however, it may cause high energy consumption. Therefore,... 相似文献
6.
协同通信融合了分集技术与中继传输技术的优势,可以获得多天线与多跳传输增益,显著改善无线通信系统的性能。首先,阐述协同通信的历史背景、基本概念、操作方式和工作原理、并对有待解决的键技术问题进行了分析。然后,着重说明了协同通信和认知无线电技术的结合,并探讨了协同通信技术可能的应用。 相似文献
7.
In this paper, we propose an approach to support QoS for multimedia applications in ad hoc wireless network. An ad hoc network is a collection of mobile stations forming a temporary network without the aid of any centralized coordinator and is different from cellular networks which require fixed base stations interconnected by a wired backbone. It is useful for some special situations, such as battlefield communications and disaster recovery. The approach we provide uses CSMA/CA medium access protocol and additional reservation and control mechanisms to guarantee quality of service in ad hoc network system. The reason we choose CSMA protocol instead of other MAC protocols is that it is used in most of currently wireless LAN productions. Via QoS routing information and reservation scheme, network resources are dynamically allocated to individual multimedia application connections. 相似文献
8.
To attain high quality of service (QoS) with efficient power consumption with minimum delay through Wireless Local Area Network (WLAN) through mesh network is an important research area. But the existing real-time routing system involves multiple hops with time varying mobility channels for fastest data propagation is greatly degraded with power utilization factor through congestion traffic queue. Required allocation and resource management through desired access points plays vital roles in which multiple hops demands delay rates by interconnected data nodes. In order to achieve high throughput with minimum delay the QoS in real-time data communication have to be concentrated by using Viterbi decoder with convolution codes. By undertaking IEEE 802.11 WLAN physical layers afford multiple transmission rates by engaging various modulations and channel coding schemes, major point arises to pinpoint the desired transmission rate to enhance the performance. Because each node exhibits different dynamic characteristics based on the token rings passed from the server to the end links. In order to validate the real-time traffic with power consumption and average delay communication, an improved Viterbi decoder is designed with convolution codes to determine accurate channel estimation based on learning the utilization ration of the needed to execute the current wireless channel optimization. The proposed methodology can attain accurate channel estimation without additional implementation effort and modifications to the current 802.11 standard. And each node is capable to choose the optimized transmission rate, so that the system performance can be improved with very minimum power with high packet transmission ratio with minimum traffic rate to improve QoS. The proposed scheme also offers an appealing combination of the allocation of transmission rate and the current link condition. Based on the basic relationship between them, the proposed decoding scheme maximizes the throughput with periodic learning of channel variation and system status. 相似文献
9.
本文介绍了多载波直扩码分多址和慢跳频码分多址技术,它的提出使大容量及高速率数据传输的移动通信、个人通信和多媒体通信系统更易实现。 相似文献
11.
对无线多媒体传感器网络(WMSNs)的覆盖增强问题进行了研究.在WMSNs网络中,视频、图像节点的视角范围有限,只能监控周围的部分区域.由于节点数量众多、部署方式受限等原因,网络中往往存在大量的监测重叠与监控盲区,需要对各节点的感知方向进行优化,以提高网络的监控质量.文中基于有向感知模型,提出了一种覆盖增强算法MCE.MCE对各节点的感知方向进行调整,并使用了改进的PSO算法来计算求解.仿真实验表明,MCE算法能够有效地提高网络的覆盖率. 相似文献
12.
为了提高簇内通信的能耗均衡性,提出了一种能量有效的分簇无线传感器网络簇内空分通信方案——近簇头节点采用单跳传输,远簇头节点多跳传输,给出了空分通信方案的工程实现。仿真结果验证了空分混合通信方案在能量有效性和能耗均衡分配方面的优势。 相似文献
13.
为了检测不同天线的时延和频偏,提高多输入多输出正交频分复用(MIMO-OFDM)系统同步算法性能,给出了一种有效的MIMO-OFDM系统定时和频率同步算法。该算法构造了一种新颖的基于恒包络零自相关码(CAZAC)的良好正交特性的训练序列结构,利用该训练序列结构可以有效地完成各发射天线的迟延和载波频偏估计。仿真结果表明,所给方法具有高的定时估计精度和低的计算复杂度,适用于各发射天线信号到达时延不同情况的MIMO-OFDM系统,具有很好的实用价值。 相似文献
14.
Network selection in a heterogeneous wireless environment is a major challenge to ensue seamless mobility across different radio air interfaces. To provide the desired quality of service for a given application in a multimedia environment, different parameters, including delay, bandwidth, packet loss and cost per byte, play an important role in network selection. In this paper, we present a novel algorithm for optimal network selection. A heterogeneous environment consisting of four networks, UMTS, WLAN, GPRS and WiMAX has been considered. We propose a network selection algorithm in which weight estimation for the representative set of the network attributes is computed using entropy and technique for order preference by similarity to ideal solution approach. The numerical results show that the proposed model can be effectively implemented to select the desired network in a heterogeneous environment employing triple-play services. 相似文献
15.
1 Motivation Nowadays , the QoS provided by the wideband IPnetwork starts at an edge-router and ends at anotheredge-router .Therefore ,the trunk QoSisfinished,suchas RSVP[1]and DiffServ[2].In order to complete theend-to-end QoS,the mechanism of entrance QoS (thebandwidth controller) is introduced. As Fig.1 shows ,if the bandwidth controller circledby the dashed frame is not used,the Ethernet is con-nected with the router directly through 100 Mbit/sbandwidth. Then this router is connect… 相似文献
16.
In this paper, we propose a cross layer congestion optimization scheme for allocating the resources of wireless sensor networks to achieve maximization of network performance. The congestion control, routing selection, link capacity allocation, and power consumption are all taken account to yield an optimal scheme based on the Lagrangian optimization. The Lagrangian multiplier is adopted to adjust power consumption, congestion rate, routing selection and link capacity allocation, so that the network performance can be satisfied between the trade-off of efficiency and fairness of resource allocation. The proposed algorithm can significantly achieve the maximization of network performance in relieving the network congestion with less power consumption. Excellent simulation results are obtained to demonstrate our innovative idea, and show the efficiency of our proposed algorithm. 相似文献
17.
本文介绍了多载波直扩码分多址技术,它的提出使大容量及高速率数据传输的移动、个人和多媒体通信系统更易实现。 相似文献
18.
介绍了多载波直扩码分多址技术。它的提出使大容量及高速率数据传输的移动、个人和多媒体通信系统更易实现。 相似文献
19.
Third generation wireless communication systems will support multimedia, and W-CDMA will be the common air interface technology. Due to the interference limited nature of CDMA, power is the main resource of the network, and power control is a means of resource management. In this article, we introduce Dynamic Resource Scheduling (DRS) as a framework which employs power control for QoS provisioning of multimedia traffic in W-CDMA. In DRS, we propose the application of optimal power assignment to the W-CDMA architecture, and we also suggest several implementation strategies. A simulation model of the Japanese W-CDMA standard (ARIB) has been developed for performance evaluation. The DRS framework is shown to accommodate different service classes efficiently by optimal resource management. Quantitative advantages are proven in terms of gains in capacity, throughput, power saving and QoS stability. 相似文献
20.
A large portion of silicon area and the energy consumed by the Viterbi decoder (VD) is dedicated to the survivor memory and the access operations associated with it. In this work, an efficient pre-traceback architecture for the survivor-path memory unit (SMU) of high constraint length VD targeting wireless communication applications is proposed. Compared to the conventional traceback approach which is based on three kinds of memory access operations: decision bits write, traceback read, and decode read, the proposed architecture exploits the inherent parallelism between the decision bit write and decode traceback operation by introducing pre-traceback operation. Consequently, the proposed pre-traceback approach reduces the survivor memory read operations by 50%. As a result of the reduction of the memory access operations, compared to the conventional 2-pointer traceback algorithm, the size of the survivor memory as well as the decoding latency is reduced by as much as 25%. Implementation results show that the pre-traceback architecture achieves up to 11.9% energy efficiency and 21.3% area saving compared to the conventional traceback architecture for typical wireless applications. 相似文献
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