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Yan Yan Baoxian Zhang Jun Zheng Jian Ma 《Wireless Communications and Mobile Computing》2010,10(7):899-911
In wireless sensor networks (WSNs), a mobile sink can help eliminate the hotspot effect in the vicinity of the sink, which can balance the traffic load in the network and thus improve the network performance. Location‐based routing is an effective routing paradigm for supporting sink mobility in WSNs with mobile sinks (mWSNs). To support efficient location‐based routing, scalable location service must be provided to advertise the location information of mobile sinks in an mWSN. In this paper, we propose a new hierarchical location service for supporting location‐based routing in mWSNs. The proposed location service divides an mWSN into a grid structure and exploits the characteristics of static sensors and mobile sinks in selecting location servers. It can build, maintain, and update the grid‐spaced network structure via a simple hashing function. To reduce the location update cost, a hierarchy structure is built by choosing a subset of location servers in the network to store the location information of mobile sinks. The simulation results show that the proposed location service can significantly reduce the communication overhead caused by sink mobility while maintaining high routing performance, and scales well in terms of network size and sink number. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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研究了一种基于Hermite脉冲的超宽带系统在多径信道下的性能。考虑到定时抖动对Rake相关接收的影响,通过Hermite脉冲的相关函数可以计算Rake捕获的信号能量,进而得到接收机的输出信干比。在假设符号间干扰为高斯噪声下,得出系统在多径信道下的理论误比特性能。结果表明,符号间干扰能量对Rake接收机合并路径数目的变化并不敏感;增加合并路径数目可以提高系统的误比特性能;大的定时抖动范围会造成系统性能下降。 相似文献
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Simone Morosi Tiziano Bianchi Francesco Gei 《Transactions on Emerging Telecommunications Technologies》2013,24(6):545-551
In this letter, we propose frequency domain receivers for an IEEE 802.15.4a short‐range communication network: the uplink case is taken into account, considering a scenario where several devices communicate with a coordinator node. The channel model has been also derived according to the IEEE 802.15.4a recommendations. Results show that the proposed approach can be beneficial in short‐range systems under severe conditions of multipath propagation and interference. An interesting novelty of the proposed approach is that both single‐user and multi‐user FD receivers based on the minimum mean square error criterion can be derived by exploiting the zero padding technique which is intrinsic in the symbol structure of the standard. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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RYOHEI NAKAMURA YUKI OTA NOBUYASU KEYA AKIHIRO KAJIWARA 《Electronics and Communications in Japan》2015,98(5):43-49
Home security sensors are becoming more and more practical today for protection against intruders, and several sensor types, such as infrared, video cameras, and microwave radio are commonly used. Ultra‐wideband impulse‐radio (UWB‐IR) sensors have lately attracted considerable attention because they are expected to measure not only the motion of an intruder but also the distance. This paper presents an indoor intruder detection sensor system using stepped FM based on UWB radio which can detect and track the movement of an intruder. The usefulness of the method is experimentally investigated using our fabricated sensor. The measurements were conducted for various intrusion scenarios inside a typical house. 相似文献
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Simon Rommel Elizaveta P. Grakhova Antonio Jurado‐Navas Albert Kh. Sultanov Juan José Vegas Olmos Idelfonso Tafur Monroy 《International Journal of Communication Systems》2018,31(1)
This paper addresses impulse‐radio ultra‐wideband (IR‐UWB) transmission under the Russian spectral emission mask for unlicensed UWB radio communications. Four pulse shapes are proposed and their bit error rate (BER) performance is both estimated analytically and evaluated experimentally. Well‐known shapes such as the Gaussian, root‐raised cosine, hyperbolic secant, and the frequency B‐spline wavelet are used to form linear combinations of component pulses, shaped to make efficient use of the spectral emission mask. Analytical BER values are derived using a Nakagami‐m model, and good agreement is found with the experimentally obtained BER. The proposed pulse shapes allow IR‐UWB transmission with BERs below the limit for a 7% overhead forward error correction, achieving distances of up to 6.5 m at 1 Gbit/s, 4.5 m at 1.25 Gbit/s, and 1 m at Gbit/s. These results confirm the viability of IR‐UWB transmission under the strict regulations of the Russian spectral emission mask. 相似文献
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Chien‐Ching Chiu Chun‐Liang Liu Shu‐Han Liao 《Wireless Communications and Mobile Computing》2013,13(9):864-873
In this paper, the channel characteristics of ultra‐wideband systems with single co‐channel interference are investigated. A ray‐tracing technique is developed to calculate channel frequency responses in an indoor environment, of which the frequency dependence for the dielectric constant and the conductivity are carefully considered. By using the frequency responses, the channel capacities with single co‐channel interference are calculated. The outage probability of the channel capacities are also calculated for analyzing the channel statistical property. Furthermore, some useful channel statistical parameters are also investigated for different material partitions. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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Yanzhe Che Qinming He Xiaoyan Hong Kevin Chiew 《International Journal of Communication Systems》2015,28(1):167-186
While enjoying various LBS (location‐based services), users also face the threats of location privacy disclosure. This is because even if the communications between users and LBS providers can be encrypted and anonymized, the sensitive information inside LBS queries may disclose the exact location or even the identity of a user. The existing research on location privacy preservation in mobile peer‐to‐peer (P2P) networks assumed that users trust each other and directly share location information with each other. Nonetheless, this assumption is not practical for most of the mobile P2P scenarios, for example, an adversary can pretend to be a normal user and collect the locations of other users. Aiming at this issue, this paper presents x‐region as a solution to preserve the location privacy in a mobile P2P environment where no trust relationships are assumed amongst mobile users. The main idea is to allow users to share a blurred region known as x‐region instead of their exact locations so that one cannot distinguish any user from others inside the region. We propose a theoretical metric for measuring the anonymity property of x‐region, together with three algorithms for generating an x‐region, namely, benchmark algorithm, weighted expanding algorithm, and aggressive weighted expanding algorithm. These algorithms achieve the anonymity and QoS requirements with different strategies. Our experiments verify the performance of the algorithms against three key metrics. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Sung‐Yoon Jung 《International Journal of Communication Systems》2014,27(12):4443-4448
We propose a new preamble that can reduce the performance degradation because of the diminishing of operational complexity in coarse timing acquisition. The reduced‐complexity acquisition algorithm uses a received preamble that has been shortened by summing its elements group‐by‐group. Therefore, the performance deteriorates because it loses the impulsive autocorrelation property of the preamble after summation and correlation. In this paper, we design a preamble sequence with a sliding correlator output function that shows a distinct peak at zero delay and symmetry even after summation based on a flipping and doubly spreading concept. By comparing with other preamble sequences, we prove that the proposed preamble shows better timing acquisition performance in ultra‐wideband channel environment.Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Eirini Karapistoli Ioannis Gragopoulos Ioannis Tsetsinas Fotini‐Niovi Pavlidou 《Wireless Communications and Mobile Computing》2012,12(11):956-968
This paper presents a distributed medium access control (MAC) protocol for low data rate ultra‐wideband (UWB) wireless sensor networks (WSNs), named LA‐MAC. Current MAC proposal is closely coupled to the IEEE 802.15.4a physical layer and it is based on its Impulse‐Radio (IR) paradigm. LA‐MAC protocol amplifies its admission control mechanism with location‐awareness, by exploiting the ranging capability of the UWB signals. The above property leads to accurate interference predictions and blocking assessments that each node in the network can perform locally, limiting at the same time the actions needed to be performed towards the admission phase. LA‐MAC is evaluated through extensive simulations, showing a significant improvement in many critical parameters, such as throughput, admission ratio, energy consumption, and delay, under different traffic load conditions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Zhiquan Bai Fang Zhao Changhui Wang Cheng‐Xiang Wang 《International Journal of Communication Systems》2014,27(12):4430-4442
In order to alleviate multiple access interference and multipath interference of ultra‐wideband (UWB) system, we propose the orthogonal complementary code (OCC)‐based direct‐sequence UWB system and offset‐stacking (OS)‐UWB system. OCC has perfect partial autocorrelation and cross‐correlation characteristics. With the application of OCC in UWB system, we can obtain better performance in multiple access interference and multipath interference. The proposed OS‐UWB structure can also achieve variable data rate transmission because of its innovative OS spreading technique. Theoretical analysis and simulation results show that the proposed UWB system can achieve excellent performance and outperform the unitary code‐based direct‐sequence UWB system. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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针对无线传感器网络(WSN)中多径路由的可靠性和能量效率问题,提出了一种基于代理和位置感知的多径路由发现方案(LABMR).事件节点根据位置信息,动态寻找其到Sink节点之间的特殊中间节点,来构建多径路由.利用移动代理来收集多径路由的局部拓扑结构信息,Sink节点根据代理收集的路由参数来计算路径权值,以此选择最优不相交路径.同时,对于信息的重要性差异,Sink节点选择单条或多条路径来传输数据,在保证传输可靠性的同时减少能耗.与现有的基于代理的多径路由(ABMR)方法相比,LABMP在数据包投递率、能量消耗、额外开销和延迟方面具有更好的性能. 相似文献
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如何利用现有的数字CATV系统开展各种增值业务已成为一个重要课题.首先简要介绍了数字CATV和超宽带技术,然后给出了两种超宽带技术在现有数字CATV系统中的应用方案,利用这些方案可以有效地开展各项增值业务. 相似文献
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目前全国各地正在积极推广数字有线电视,其中如何开展各种增值业务成为一个重要课题。文章首先简要介绍了数字有线电视和超宽带技术,然后给出了两种超宽带技术在现有数字有线电视系统中的应用方案,利用这些方案可以有效地开展各项增值业务。 相似文献
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Wei‐dong Wang Jun‐an Yang Chun Zhang 《International Journal of Communication Systems》2015,28(3):472-482
Due to the low power spectral density and complicated transfer propagation of ultra‐wideband (UWB) signal, it is important to estimate UWB channel accurately. But it is difficult to sample UWB signals directly due to their wider band width. However, compressed sensing (CS) theory provides a feasible way through lower sampling speed. Common CS‐UWB channel estimation methods adopt convex optimization, non‐sparse or non‐restricted form. In order to strengthen the restriction on sparsity of the reconstructed channel vector, a non‐convex optimization method is proposed in this paper to estimate UWB channel. Proposed method sets the objective function as a non‐convex optimization model using lp–norm. This model is combined as a convex function to approximate the objective function and reconstruct the UWB channel vector iteratively. Because lp–norm is closer to l0–norm than l1 and l2–norm, its restriction on sparsity of objective vector is stricter. The simulation results show that this method can enhance reconstruction performance compared with existing CS‐UWB channel estimation methods. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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As mobility became the norm rather than the exception, location‐based services are playing more of a key role in assisting mobile users. In this paper, we address the challenges of providing location‐based services to users in areas of sudden population increases, such as stadiums and traffic jams. A sudden increase in the number of mobile users leads to an increasing demand for the already scarce wireless bandwidth, thus causing dramatical throughput degradation and an increase in connectivity failures. We propose a hybrid model within which a peer‐to‐peer mode is deployed to assist the cellular‐based network whenever a sudden increase in population density is sensed by the base station. Location‐based data is migrated to selected elite nodes, thus allowing other peer nodes to get their information locally. This approach is proven, through experimental results, to decrease the query response time and number of query failures. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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The ultra‐wideband (UWB) signal radiation process in an antenna is different from that of a narrowband signal. In this paper, we study the degradation of the desired signal component according to the antenna structure and location of a receiver in a bipolar time‐hopping UWB system. And we propose a receiver structure with an adaptive template waveform generator to compensate for the degradation caused by a realistic TX‐RX antenna system. 相似文献
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Existing methods to process continuous range queries are not scalable. In particular, as the number of continuous range queries on a large number of moving objects becomes larger, their performance degrades significantly. We propose a novel query indexing method called the projected attribute bit (PAB)‐based query index. We project a two‐dimensional continuous range query on each axis to get two one‐dimensional bit lists. Since the queries are transformed to bit lists and query evaluation is performed by bit operations, the storage cost of indexing and query evaluation time are reduced significantly. Through various experiments, we show that our method outperforms the containment‐encoded squares‐based indexing method, which is one of the most recently proposed methods. 相似文献