共查询到20条相似文献,搜索用时 31 毫秒
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Use of IEEE 802.11 wireless local area networks (WLANs) as an extension to existing wired networks, offering both mobility and portability in a residential or office environment, is growing at an unprecedented rate. One of the critical limitations of current WLANs is the limited energy storage of mobile devices, and the design of energy-efficient protocols for WLANs has therefore become an area of intensive research. An analytical framework to study the energy consumption and energy efficiency of IEEE 802.11a WLANs is proposed. The energy consumption by considering the interactions between IEEE 802.11a PHY and MAC layers is modelled. Simulation results demonstrate that the theoretical model is accurate in predicting the energy efficiency over a wide range of scenarios. In addition, the effects of different PHY and MAC layer parameters on energy efficiency of IEEE 802.11a WLANs are investigated, as are the effects of different parameters on energy efficiency. 相似文献
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The fundamental medium access control mechanism in IEEE 802.11 wireless LANs (WLANs)-distributed coordination function (DCF) only supports the best-effort service and does not support quality-of-service (QoS) differentiation. Enhanced distributed channel access (EDCA) in IEEE 802.11e supports delay differentiation. A new approach, EDCA+ , is proposed to enhance QoS over WLANs. It simultaneously achieves bandwidth, delay and jitter differentiation by distinguishing the minimum contention window, the maximum backoff stage or persistent factor and packet-loss rate differentiation by distinguishing the retry limit. Analytical models are proposed to analyse the performance of EDCA+ in terms of throughput, bandwidth, delay, jitter and packet-loss rate. Extensive simulations are also carried out to evaluate the accuracy of the proposed performance models and to compare the performance of DCF, EDCA and EDCA+. The simulation results show that EDCA+ performs better than DCF and EDCA in ensuring integrated QoS, and that the proposed analytical models are valid. 相似文献
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《IEEE transactions on instrumentation and measurement》2009,58(6):1858-1868
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The IEEE 802.16 system, a promising wireless communication system, has a maximum transmission range of 50 km according to the IEEE 802.16 standard. In reality, the transmission range and coverage probability of an IEEE 802.16 system vary for different wireless scenarios. Evaluating the transmission range and coverage probability of an IEEE 802.16 system prior to implementation is important. Hence, the Stanford University Interim (SUI) channel model in IEEE 802.16 specifications is suitable for evaluating the performance of IEEE 802.16 systems. To generate an effective method for predicting coverage, this study uses the SUI channel model to analyse the coverage probability of an IEEE 802.16 system. Furthermore, this study utilises a smart antenna system (SAS) to enhance IEEE 802.16 system performance. In terms of different antenna heights of the Base Transceiver Station and Customer Premises Equipment, the performance evaluation results show that the cell radius with the SAS is at least 30% more than that without the SAS. 相似文献
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The performance of a new pointer-based medium-access control protocol that was designed to significantly improve the energy efficiency of user terminals in quality-of-service-enabled wireless local area networks was analysed. The new protocol, pointer- controlled slot allocation and resynchronisation protocol (PCSARe), is based on the hybrid coordination function-controlled channel access mode of the IEEE 802.11e standard. PCSARe reduces energy consumption by removing the need for power-saving stations to remain awake for channel listening. Discrete event network simulations were performed to compare the performance of PCSARe with the non-automatic power save delivery (APSD) and scheduled-APSD power- saving modes of IEEE 802.11e. The simulation results show a demonstrable improvement in energy efficiency without significant reduction in performance when using PCSARe. For a wireless network consisting of an access point and eight stations in power-saving mode, the energy saving was up to 39% when using PCSARe instead of IEEE 802.11e non-APSD. The results also show that PCSARe offers significantly reduced uplink access delay over IEEE 802.11e non-APSD, while modestly improving the uplink throughput. Furthermore, although both had the same energy consumption, PCSARe gave a 25% reduction in downlink access delay compared with IEEE 802.11e S-APSD. 相似文献
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It is widely believed that IEEE 802.11 standard is aimed mainly for fixed indoor wireless local area networks and is not suited for mobile applications, even though the IEEE 802.11b systems may work in either infrastructure mode or ad hoc mode. The impact of node mobility on ad hoc network performance has already been studied intensively, but these studies mostly do not consider temporal fluctuations of the mobile wireless channel due to the Doppler shift. An investigation of the mobility impact on the performance of IEEE 802.11b ad hoc systems with Rician/Rayleigh fading under different node velocities is presented. A comprehensive and in-depth analysis of the impacts of a multitude of different signal distortions on an IEEE 802.11b system performance is also presented. Specifically, the authors study the bit-error rate performances with respect to node velocities for different modulation schemes. The simulation results show that, owing to its extremely low implementation and deployment cost, the current IEEE 802.11b standard has its potential to be deployed in a mobile ad hoc environment if the line-of-sight path between transmitter and receiver exists. 相似文献
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Cataliotti A. Cosentino V. Nuccio S. 《IEEE transactions on instrumentation and measurement》2008,57(1):85-94
In this paper, the authors present a PC-based instrument for the measurement of electrical-power quantities defined in IEEE Std. 1459. The instrument is based on a time-domain technique for the detection of the fundamental and harmonic components of voltages and currents. The time-domain strategy was originally developed by the authors for three-phase, three-wire systems. In that paper, the strategy had been extended to both three-phase, four-wire and single-phase systems. Simulation tests were carried out to assess the uncertainty contribution of the proposed strategy in the absence of the measurement transducers. Moreover, the accuracy of the PC-based instrument with its transducers was evaluated; the experimental tests were carried out by using a power calibrator. 相似文献
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Direction finding in IEEE802.11 wireless networks 总被引:1,自引:0,他引:1
A novel direction-finding method for stations of IEEE802.11 wireless local area networks is presented in this paper. The method uses a switched beam array for determining the direction of arrival of the incident electromagnetic field in a time efficient way and associates certain medium access control (MAC) layer functions with different radiation patterns of the switched antenna array, in order to determine the proper orientation of directional beams on both entities of a communication link. The application of the proposed method to an IEEE802.11 wireless network is presented and it is depicted how the method improves the network performance without requiring any modifications to the existing MAC protocol. 相似文献
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Experimental Study of Coexistence Issues Between IEEE 802.11b and IEEE 802.15.4 Wireless Networks 总被引:1,自引:0,他引:1
Angrisani L. Bertocco M. Fortin D. Sona A. 《IEEE transactions on instrumentation and measurement》2008,57(8):1514-1523
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The authors propose a new analytical model based on BCMP closed queueing networks in order to evaluate the performance of IEEE 802.11 DCF MAC protocol when all nodes are in the transmission range of each other, that is, a single hop wireless ad hoc network. By the proposed model, some performance metrics such as saturation and non-saturation throughput, distributions of channel access delay and the number of packets in the MAC buffer are derived. An extension of the proposed model is used for the analysis of IEEE 802.11e EDCA and the same performance metrics are evaluated for this protocol. Analytical results on IEEE 802.11e prove that differentiation in service is possible and channel share for each service type may be well assigned by tuning the MAC protocol parameters. Simulation results show consistency with our analytical results. 相似文献
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《IEEE transactions on instrumentation and measurement》2009,58(7):2234-2244
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The authors present an extensive investigation of the performance of the IEEE 802.11 medium access control (MAC) protocol, with respect to throughput and delay. For the protocol analysis, a new model, which describes the protocol's behaviour to a great extent by incorporating and extending the existing models, is proposed. The authors also present a detailed analysis of the end-to-end delay through the study of the MAC delay and the queueing delay. The authors use the Z-transform of backoff duration to obtain the mean value, the variance and the probability distribution of the MAC delay. For the queueing analysis, first the authors consider an M/G/l queue in order to provide a first look at the queueing delay. Second, the authors modify the input process of the queue so that the packet arrival process is described by an ON- OFF model, which expresses the bursty nature of traffic. In the investigations, data rates of 1, 5.5 and 11 Mbps are assumed to highlight the effect of the bit rate on network performance for both Basic and request-to-send/ clear-to-send access mechanisms. The throughput and delay analyses are validated by simulating the distributed coordination function, whereas the models are compared with the existing models based on their results. The accuracy of the analyses was found to be quite satisfactory. 相似文献
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As the demand for broadband multimedia wireless is increasing, improving the quality of service (QoS) of the widely deployed IEEE 802.11 wireless LAN has become crucial. In order to attain the QoS required by a wide range of applications, the IEEE 802.11 working group has denned a new standard - the IEEE 802.lie. However, very limited work has been performed to address the QoS transmission problem of real-time video over IEEE 802.11e. A novel measurement-based dynamic transmission opportunity (MBDTXOP) scheme is proposed, which adaptively allocates resources to a variable bit rate (VBR) video on the basis of the estimation of future traffic demand to support efficient QoS transmission of VBR video. The novelty of the proposed scheme, when compared with existing methods, lies in estimating the required network resources by exploiting the characteristics of digital video; this capability enables the MBDTXOP scheme to substantially increase network utilisation while preserving the required QoS for the transmission of VBR video. Simulations comparing the proposed scheme with other mechanisms clearly demonstrate the outstanding performance of the former. 相似文献
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Researches and development efforts in wireless networking and systems are progressing at an incredible rate. Among them, measurement and analysis of performance achieved at network layer and perceived by end users is an important task. In particular, recent advances concerning IEEE 802.11b-based networks seem to be focused on the measurement of key parameters at different protocol levels in a cross-layered fashion, because of their inherent vulnerability to in-channel interference. By adopting a cross-layer approach on a real network set-up operating in a suitable experimental testbed, packet loss against signal-to-interference ratio in IEEE 802.11b-based networks is hereinafter assessed. Results of several measurements aimed at establishing the sensitivity of IEEE 802.11b carrier sensing mechanisms to continuous interfering signals and evaluating the effects of triggered interference on packet transmission. 相似文献
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《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(7):1300-1300
The Administrative Committee of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society takes great pleasure in announcing the selection of the Outstanding Paper published in its 2007 Transactions, vol. 54. The award was presented during ceremonies at the 2008 IEEE International Ultrasonics Symposium in Beijing, China, on November 3rd, 2008. The award winner is Clark T.-C. Nguyen for his paper "MEMS Technology for Timing and Frequency Control." This paper appeared in the February 2007 issue, no. 2, on pages 251-270. Award Committee members selected this paper among all others that appeared in vol. 54 of the IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control. 相似文献
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《Radar, Sonar & Navigation, IET》2009,3(4):287-289
This special issue is based on a selection of the innovative ideas and trends presently growing in the international radar community, as expressed by the contributions presented at the 2008 IEEE Radar Conference (http:// www.radarcon2008.org). This conference is one of a series of radar conferences promoted by the IEEE Aerospace and Electronics Systems Society, and has always been held in the United States. For the first time in 2008, the conference was held in Rome Italy, which largely stimulated the participation of European scientists and the conference achieved an extraordinary attendance. 相似文献
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Mosleh M. Abualhaj Abdelrahman H. Hussein Manjur Kolhar Mwaffaq Abu AlHija 《计算机、材料和连续体(英文)》2021,66(2):1283-1300
The IEEE 802.11n standard has provided prominent features that greatly contribute to ubiquitous wireless networks. Over the last ten years, voice over IP (VoIP) has become widespread around the globe owing to its low-cost or even free call rate. The combination of these technologies (VoIP and wireless) has become desirable and inevitable for organizations. However, VoIP faces a bandwidth utilization issue when working with 802.11 wireless networks. The bandwidth utilization is inefficient on the grounds that (i) 80 bytes of 802.11/RTP/UDP/IP header is appended to 10–730 bytes of VoIP payload and (ii) 765 µs waiting intervals follow each 802.11 VoIP frame. Without considering the quality requirements of a VoIP call, be including frame aggregation in the IEEE 802.11n standard has been suggested as a solution for the bandwidth utilization issue. Consequently, several aggregation methods have been proposed to handle the quality requirements of VoIP calls when carried over an IEEE 802.11n wireless network. In this survey, we analyze the existing aggregation methods of VoIP over the A-MSDU IEEE 802.11n wireless standard. The survey provides researchers with a detailed analysis of the bandwidth utilization issue concerning the A-MSDU 802.11n standard, discussion of the main approaches of frame aggregation methods and existing aggregation methods, elaboration of the impact of frame aggregation methods on network performance and VoIP call quality, and suggestion of new areas to be investigated in conjunction with frame aggregation. The survey contributes by offering guidelines to design an appropriate, reliable, and robust aggregation method of VoIP over 802.11n standard. 相似文献