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1.
时隙ALOHA DS/CDMA系统与多载波时隙ALOHA系统吞吐性能的比较研究 总被引:1,自引:0,他引:1
该文对同样带宽下时隙 ALOHA DS/CDMA系统和多载波时隙 ALOHA系统的吞吐量进行了理论计算、比较和仿真。结果表明,在总负载较大时,采用高纠错能力的时隙 ALOHA DS/CDMA系统可以在吞吐量上有更好的性能。但若网络负载过重,时隙ALOHA DS/CDMA系统的吞吐性能较多载波时隙ALOHA的系统下降快;码字总数受限会带来码字选择的冲突,从而降低系统的吞吐性能。 相似文献
2.
Harry H. Tan Santiago V. Hung 《International Journal of Satellite Communications and Networking》1992,10(1):31-41
The ALOHA protocol has been proposed for accessing reservation channels in demand-assigned channel access protocols for land mobile satellite communications networks. This paper provides a rigorous performance analysis of both the slotted ALOHA protocol and two-packet replication ALOHA protocol taking into account the effects of the fading multipath communications environment. Throughput, delay and stability of these two protocols are determined using a Gilbert channel error model with memory. Comparison of slotted ALOHA and two-packet replication ALOHA shows that a smaller average delay can be achieved by replication. Moreover average throughput is improved in some cases. However replication reduces stability. 相似文献
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F. L. Lo T. S. Ng T. I. Yuk 《International Journal of Wireless Information Networks》1996,3(4):195-202
ALOHA is a simple and efficient way of allowing many machines with bursty data streams to communicate with a central computer. For cases where machines are equally likely to transmit to one another, CDMA ALOHA, which allows for full connectivity, may be a better multiple access protocol than slotted ALOHA through a central machine. This paper first describes a model for a fully connected, full duplex, and slotted CDMA ALOHA network where the receiver-based code access protocol is used. The stations can send data to, and receive data from, different stations simultaneously. The model is analyzed using discrete-time Markov chain, and some numerical results are presented. For a system with a large number of users where Markov analysis is impractical, equilibrium point analysis is used to predict the stability of the system and determine the throughput as well as the delay performance of the system when it is stable. It is shown that a CDMA slotted ALOHA network has a much better performance compared to simple slotted ALOHA networks. 相似文献
4.
本文对具有多重码的预约Slotted ALOHA协议进行了性能分析。它是基于帧的协议且在一个时隙内有多重码可用来传输分组信息。文中利用离散时间,离散状态和Markov链来分析一个小区上行链路的话音分组吞吐量和数据分组延时性能,并提出了两种改进碰撞解决的方法,得到了较好的系统特性。 相似文献
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本文讨论了卫星分组话音/数据综合的扩频时隙ALOHA的性能,并认为该协议较适合于卫星分组话音/数据综合的通信网中,给出了在扩频多址干扰为改进型高斯分布和某一时隙用户数有限的前提下,系统吞吐量的近似解析表达式和平均时延表达式,这比通常的标准高斯分布和无限用户的假设更精确,模拟说明结果性能是优越的。 相似文献
6.
A cooperative Bayesian and lower bound estimation in dynamic framed slotted ALOHA algorithm for RFID systems 下载免费PDF全文
Mustapha Benssalah Mustapha Djeddou Brahim Dahou Karim Drouiche Abdelmadjid Maali 《International Journal of Communication Systems》2018,31(13)
A novel estimation scheme that combines Bayesian and lower bound estimating radio frequency identification tag population size is proposed. The developed methodology is based on the fusion between the Bayesian and lower bound estimating techniques. It turns out that the fusion rule is built up thanks to an existing linear relationship between the cited techniques. Simulation results show that the developed technique significantly improves the accuracy of the estimating tag quantity and presents less estimation error. Also, the resulting advanced dynamic framed slotted ALOHA protocol considerably improves the performance and efficiency of the radio frequency identification anti‐collision compared with the most recent protocols using others estimating methods. 相似文献
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针对采用时隙ALOHA算法的无线Ad Hoc网络,考虑数据包到达的动态性与数据包传输的随机性,以最大化吞吐量为目标,同时满足数据队列稳定性,构建了关于接纳控制与竞争接入的随机优化问题。由于在时隙ALOHA算法中数据包传输的最优概率取决于无线Ad Hoc网络中数据队列非空的活跃节点数,提出了一种基于活跃节点数预测的时隙ALOHA算法。该算法要求无线Ad Hoc网络中的所有发送节点实时地侦听通信信道的忙闲状态,计算基于信道状态的活跃节点数条件期望,从而动态地预测无线Ad Hoc网络在不同时刻的活跃节点数,达到网络节点依据局部网络状态信息自适应地优化数据包传输概率的目的。仿真结果表明,所提算法能够有效估计无线Ad Hoc网络在每个时隙的活跃节点数,从而显著提升网络吞吐量并且降低数据包的平均排队时延。 相似文献
9.
Orthogonal frequency division multiple access (OFDMA) systems provide multiple channels that can be accessed via random access schemes. In this paper a channel-aware multichannel random access, based on local channel state information (CSI), was investigated and a multichannel slotted ALOHA scheme was proposed accordingly. Also an analytical investigation of total system throughput and the queue state evolution of generic node in the network were present by assuming the channel has been modeled by means of a two state Markov chain. Through the theoretical model and simulation results, we confi rm that the proposed algorithm has the advantage of high throughput and low access delay. 相似文献
10.
Zhao Liang 《International Journal of Communication Systems》2000,13(4):353-364
Since the 1970s random multiple access techniques have made big progress and found a wide application in modern communication systems. In this paper we review the evolution of ALOHA random multiple access techniques: from pure ALOHA to Spread ALOHA. We introduce the principle of Spread ALOHA, investigate the relationship between spread‐spectrum CDMA and Spread ALOHA, and discuss the prospective applications of Spread ALOHA. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
11.
RFID(RadioFrequencyIdentification)—射频识别技术是一种利用射频信号自动识别目标对象并获取相关信息的技术,现在已经涉及到人们日常生活的各个方面,被称为21世纪最有前途的技术之一。但是,它在应用中存在碰撞问题,使数据读取不正确。论文对最简单的反碰撞算法ALOHA算法进行了研究,在识别时间和重发次数之间作一下折衷,确定如何选择退避时间。 相似文献
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Mohammad Muntaseer Mahfuz Md. Farhad Hossain Rashed Hossain Bhuiyan Naiemul Haq Mohammed Nazrul Islam 《Wireless Communications and Mobile Computing》2005,5(3):355-363
The combined effect of capture ratio and number of transmission on the performance of a slotted ALOHA based wireless access network is analyzed. The network quality parameters are evaluated to investigate the effect of lowering the capture ratio and increasing the number of transmission. It is found that the slotted ALOHA based access network shows its stable operation in low capture environment even if the retransmission cut‐off is increased. As a result the success rate of accessing the core network is improved. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
13.
动态ALOHA法在解决RFID反碰撞问题中的应用 总被引:35,自引:0,他引:35
通过分析在射频识别技术(RFID)中碰撞发生的概率和阅读器对应答器的读时间之间的数学模型,发现只要正确调整阅读器对应答器读时间的期限就可大大减小碰撞发生的概率。遂提出动态ALOHA方法作为RFID中反碰撞问题的一种简易实现。这种反碰撞方法可以在实时性不高的场合得到应用。 相似文献
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Nesreen Alsbou Sylvain Prigent Hazem H. Refai 《Wireless Communications and Mobile Computing》2015,15(4):716-725
With the exception of required time synchronization, the Reservation‐ALOHA (R‐ALOHA) protocol is simple to implement and suitable for medium access control in ad hoc wireless networks. In this paper, we propose an innovative protocol, referred to as Reservation ALOHA with priority (PR‐ALOHA) that provides differentiated services on the basis of traffic priority. To date, the carrier sense multiple access/collision avoidance (CSMA/CA) protocol has been widely used for this purpose by employing an interframe spacing (IFS) for priority service, that is, nodes ready for packet transmissions are required to wait for an IFS amount of time, where a shorter IFS is used to gain faster access to the radio channel. However, sensing and collision avoidance mechanisms make CSMA/CA unsuitable for delay‐sensitive applications, that is, congested scenarios with high traffic. In contrast, the proposed PR‐ALOHA protocol may be considered a good candidate for such applications. In this paper, the performance of the PR‐ALOHA protocol is investigated analytically and by simulation. Its comparison with regular R‐ALOHA is also carried out. Modeling and simulation results of PR‐ALOHA show that PR‐ALOHA improves the performance of high‐priority traffic with limited effect on normal network traffic. Thus, PR‐ALOHA may be useful in vehicular communications, where traffic may be separated into emergency messages having high priority and multimedia messages having low priority. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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改进的基于ALOHA的RFID防碰撞算法 总被引:2,自引:0,他引:2
为了解决RFID系统中电子标签识别效率不高的问题,对基于ALOHA的随机性防碰撞算法进行了详细分析,提出了一种新的ALOHA防碰撞算法.在该算法中,针对标签估计,采用动态调整的方式自动改变标签估计式中的系数,使得标签估计个数随着已识别的标签数动态变化,从而估计下一帧待识别标签数;而对于帧长调整,根据估计的标签数,通过帧长与标签数分组的关系确定.通过MATLAB进行仿真,结果表明,该算法能明显提高系统的吞吐率和稳定性. 相似文献
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Harald Øverby 《Photonic Network Communications》2007,13(2):183-194
Optical packet switching (OPS) has emerged as a promising architecture for the future all-optical network scenario. In order
to have a successful deployment of OPS networks, several networking issues must be resolved, e.g., how to resolve contentions
and how to provide Quality-of-Service (QoS) differentiation. Such networking studies often rely on teletraffic analysis in
order to quantify the performance of the OPS network. In this paper, we introduce new and review existing traffic models for
slotted buffer-less OPS networks. In particular, we present a novel asymmetric traffic model, suitable for studying the effects
of non-uniform traffic. Optical packet switches with and without wavelength conversion are studied. Numerical evaluations
and a comparison study of the presented traffic models are reported. The main contributions of this paper are to advance the
field of establishing a theoretical framework for slotted OPS networks and to act as a tutorial for teletraffic engineering
in such networks.
http://www.item.ntnu.no/~haraldov. 相似文献
19.
This paper addresses the problem of maximizing the capacity of multichannel slotted ALOHA networks subject to a user-specified deadline and a permissible probability of exceeding it. A previous paper proposed to transmit a non-decreasing number of copies of a message in successive rounds until success or deadline. This yielded a low probability of failure due to the large maximum number of copies per message, with only minimal pollution due to the small mean number of copies. In this paper, we examine another way of implementing variable resource expenditure in different rounds: the channels are partitioned into groups, one for each round, and the channels used in later rounds are operated with lower offered loads, i.e., at different working points. The delay-constrained capacity with these Single-Copy Multiple-Working-Point (SC-MWP) policies is shown to be substantially higher than that with conventional ALOHA, but lower than with the optimal Multicopy Single-Working-Point (MC-SWP) scheme. Combining the two to form an MC-MWP scheme only slightly improves capacity over MC-SWP. The SC-MWP approach can be more attractive when using a single transmitter per station because, unlike with multiple copies, transmission time is not prolonged. Therefore, multiple-working-point policies become more attractive when propagation delay is lower (e.g., low orbit satellites). 相似文献