排序方式: 共有125条查询结果,搜索用时 15 毫秒
81.
82.
This paper gives an overview of 60 GHz indoor wireless channel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error (CPE) and inter-carrier interference (ICI). In this paper, the phase noise suppression (PNS) algorithm in order to reduce the phase noise in OFDM-based 60 GHz WPANs is considered. The PNS algorithm is very simple and easily designed to realize system but it requires more effort to reduce the IC. 相似文献
83.
Path loss plays fundamental roles in system design, spectrum management, and performance evaluation. The traditional path loss model has a slight inconvenience; it depends on the unknown distance. In this letter, we explore the probability distribution function (PDF) of path loss in an indoor office environment by randomizing out the distance variable. It is shown that the resulting PDF is not Gaussian‐like but is skewed to the right, and both the PDF and the moments are related to the size of the office instead of the unknown distance. To be specific, we incorporate the IEEE 802.15.4a channel parameters into our model and tabulate the cumulative distribution function with respect to different room sizes. Through a simple example, we show how our model helps a cognitive spectrum user to infer path loss information of primary users without necessarily knowing their transmitter‐receiver distance. 相似文献
84.
When multiple ZigBee wireless personal area networks (WPANs) are in close proximity to each other, contentions and collisions in transmissions will lead to increased packet delays. However, there is no existing study on how delay performance would be affected in a crowded real‐life environment where each person walking down a busy street would be wearing a ZigBee WPAN. This letter studies the use of ZigBee WPANs in such a real‐life environment for real‐time heart beat monitoring. To be pragmatic, we derived a mobility pattern from the analysis of a real‐life video trace. Then, we estimated the delay performance from the video trace by combining data collected from ZigBee experiments. The results show that the 300 ms packet delay requirement will not be met for only 11% of the time. When failure occurs, it will last for an average duration of 1.4 s. 相似文献
85.
Ana García-Armada Beatriz Bardón Rodríguez Víctor P. Gil Jiménez Matilde Sánchez-Fernández 《Wireless Personal Communications》2007,42(3):367-386
This paper covers the main issues that must be solved in order to design and analyse the performance of Wireless Personal
Area Networks (WPANs) with the aid of simulation tools. We review state-of-the-art channel models to account for small- and
large-scale propagation conditions in waveform- and system-level simulations. When dealing with waveform simulations, we also
look at Montecarlo and importance sampling techniques that allow efficient estimation of error probabilities. Additionally,
discrete channel models are introduced to efficiently link both waveform- and system-level approaches and we point out some
methods to obtain the model parameters that are suitable for the wireless environment. The discussion of these techniques
is complemented with two application examples that show the use of the different simulation levels for system design and performance
study. With the paradigm of Bluetooth piconets we illustrate the usefulness of discrete channel models and we consider the
design of an OFDM-based WPAN system to exemplify simulation from a waveform-level point of view. 相似文献
86.
无线个人区域网络(WPAN)把几米范围内的多个设备通过无线的方式连接在一起,使它们可以相互通信。IEEE 802.15工作组致力于WPAN的网络的物理层和媒体访问层的标准化工作。而802.15.4主要对低速WPAN相关技术进行研究和标准化工作。本文在对802.15工作组介绍的基础上,重点介绍802.15.4工作组研究的相关技术和及其标准化情况。 相似文献
87.
提出了一种新的超宽带通信实现方式,该方式基于MB-OFDM技术,用户数据在时域和频域交织传输,形成了新的MB-TFI(时频交织)-OFDM方式.结合MBOA实际案例,分析了MB-OFDM芯片的商业化和产品化进程及前景展望.研究表明,MB-TFI-OFDM UWB技术以它独特的优势,将会促进MB-OFDM方案的发展,得到越来越多厂商的支持与应用,从而有希望成为WPAN物理层的标准技术. 相似文献
88.
干扰受限环境下蓝芽系统的性能及自适应跳频共存机制 总被引:1,自引:0,他引:1
随着无线局域网(WLAN)的日益普及和无线个人局域网(WPAN)的飞速发展,由于共享同一频段而产生的系统间干扰不可避免。本文着重讨论基于IEEE802.1lb标准的WLAN对基于蓝芽(Bluetooth)的短距离无线通信系统的影响。在利用MATLAB和C 搭建的系统干扰模型的仿真平台上,实现了基于蓝芽物理层的自适应跳频(Adaptive Frequency Hopping-AFH)共存机制(Co—existence Mechanism)。仿真结果显示,通过简单的AFH信道选择模块,可以有效减轻WLAN对蓝芽的干扰影响。 相似文献
89.
Energy-Efficient Operation through Interference Avoidance for Interconnected Bluetooth WPANs 总被引:2,自引:0,他引:2
Petar Popovski Hiroyuki Yomo Liljana Gavrilovska Sergio Guarracino Ramjee Prasad 《Wireless Personal Communications》2005,34(1-2):163-187
A Wireless Personal Area Network (WPAN) provides wireless networking among proximate devices, usually carried by an individual.
Bluetooth is a first instance of the WPAN technology. The basic networking entity in Bluetooth is a piconet. Several piconets
(WPANs) can be interconnected into a scatternet, which can be considered as an extendable multi-hop ad hoc networking structure.
Since Bluetooth operates in the unlicensed ISM band, each piconet uses pseudorandom frequency hopping. If collocated piconets
use the same channel simultaneously, the piconets interfere with each other and the transmitted packets are lost in collisions.
This interference is termed self-interference. The piconets that are networked into scatternet exhibit spatial overlapping
and naturally produce multi-piconet self-interference. The collisions cause retransmissions and increase the energy spent
per data portion, which results in energy-inefficient operation. To tackle this problem, in our previous work we have proposed
a self-interference avoidance (SIA) mechanism. However, this basic SIA mechanism is oblivious with respect to the physical
topology and does not account for the mitigation of self-interference due to the propagation effects. Furthermore, the basic
SIA mechanism relies on the assumption that all piconets are using packets of identical and fixed length. In this paper we
will generalize the SIA mechanism to overcome the stated restrictions. We propose the adaptive SIA (A-SIA) algorithm, which adapts the SIA algorithm to the actual interference. The simulation results show that A-SIA largely retains
the energy gain offered by the SIA algorithm, while significantly improving the goodput. We also design an instance of the
SIA mechanism that operates with variable-length packets, referred as generalized SIA (G-SIA) algorithm. Our simulation results show that the G-SIA algorithm offers good performance in terms of goodput and energy efficiency,
but the goodput is degraded if inappropriate segmentation/reassembly policy is used.
Petar Popovski received the Dipl.-Ing. in electrical engineering and M.Sc. in communication engineering from the Faculty of Electrical Engineering,
Sts. Cyril and Methodius University, Skopje, Macedonia, in 1997 and 2000, respectively and a Ph.D. degree from Aalborg University,
Denmark, in 2004. He is currently Assistant Research Professor at the Department of Communication Technology at the Aalborg
University. His research interests are focused on wireless ad hoc networks, wireless sensor networks, and high-speed wireless
multi-carrier communications.
Hiroyuki Yomo received B.S. degree in communication engineering from Department of Communication Engineering, Osaka University, Osaka,
Japan, in 1997, and M.S. and Ph.D. degrees in communication engineering from Department of Electronic, Information, and Energy
Engineering, Graduate School of Engineering, Osaka University, Osaka Japan, in 1999 and 2002, respectively. From April 2002
to March 2004, he was a Post-doctoral Fellow in Department of Communication Technology, Aalborg University, Denmark. From
April 2004 to September 2004, he was working at NEC Corporation, Japan. Since October 2004, he has been an Assistant Research
Professor in Center for TeleInfrastructure (CTIF), Aalborg University, Denmark. His research interests include medium access
protocols, link-layer techniques, routing protocols, and their interactions in wireless networks.
Liljana Gavrilovska received her B.Sc., M.Sc. and Ph.D. from University of Skopje (76), University of Belgrade (85) and University of Skopje
(95) respectively. She joined the Faculty of Electrical Engineering, University of Skopje, Republic of Macedonia, where she
currently holds positions of Professor at the Institute for Telecommunications, chief of Telecommunications Laboratory and
head of CWMC (Center for Wireless and Mobile Communications), working in the area of networking and mobile communications.
During 2001–2002 she joined the Centre for PersonKommunikation, Aalborg University, Denmark, where she was holding a position
as Associate Research Professor and was involved in several EU (ASAP, PACWOMAN, MAGNET) and national/international projects.
She is still working part-time for CTiF, Aalborg University, Denmark. Her major research is concentrated on ad hoc networking,
wireless and personal area networks, cross layer optimizations, future mobile systems, traffic analysis and admission techniques.
She is a senior member of IEEE and serves as a Chair of the Macedonian Communications Chapter.
Ramjee Prasad is a distinguished educator and researcher in the field of wireless information and multimedia communications. During February
1988–May 1999 he has been with the Telecommunications and Traffic-Control Systems Group of Delft University of Technology
(DUT), The Netherlands, where he was actively involved in the area of wireless personal and multimedia communications (WPMC).
He was head of the Transmission Research Section of International research Centre for Telecommunications Transmission and
Radar (IRCTR) and also Founding Program Director of the Centre for Wireless Personal Communications (CWPC). As from June 1999
Ramjee Prasad joined as the Wireless Information Multimedia Communications chair and co-director of Centre for PersonKommunikation
at Aalborg University, Denmark. From January 2004 he is Founding Director of the “Centre for Teleinfrastruktur (CTIF)”. He
has published over 500 technical papers, and authored and co-edited 15 books about Wireless Multimedia Communications (Artech
House). His research interest lies in wireless networks, packet communications, multiple access protocols, adaptive equalisers,
spread-spectrum CDMA systems and multimedia communications. Prof. Prasad is the founding chairperson of the European centre
of Excellence in Telecommunications known as HERMES Partnership. He is the General Chairman of International Wireless Summit
(IWS 2005) to be held in Aalborg, Denmark in September 17–22, 2005. He is a fellow of the IEE, a fellow of IETE, a senior
member of IEEE, a member of NERG, and a member of the Danish Engineering Society (IDA). He is advisor to several multinational
companies. 相似文献
90.
文章介绍了无线局域网和无线个域网所涉及的主要标准的应用场合、技术特点及协议构成,比较了它们存在的差异及各自的特点,并根据市场发展给出了它们可能的发展趋势。 相似文献