共查询到20条相似文献，搜索用时 15 毫秒
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N. Celandroni E. Ferro A. Gotta 《International Journal of Communication Systems》2014,27(11):2670-2690
This paper surveys the most popular random access (RA), demand assignment (DA), and hybrids schemes for satellite broadband access networks. In addition, we present some recent research results that we obtained when a reliable transmission control protocol, that is, TCP, is coupled with the most promising RA methods foreseen in the second generation of Digital Video Broadcasting–Return Channel via Satellite standard. In fact, the necessity to support a wider range of IP‐based traffic, as in the case of either Supervisory Control And Data Acquisition systems or Machine‐to‐Machine communications, fosters the introduction of RA schemes for information transport able to cope with large network sizes and low duty cycle bursty traffic with frequent inactivity periods on the return link. As an indication of future research aspects, we also offer, in the Conclusions section, a list of items to be investigated so that the satellite can become an integral part of the Future Internet. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Mehdi Anteur Nathalie Thomas Vincent Deslandes Andr‐Luc Beylot 《International Journal of Satellite Communications and Networking》2019,37(1):56-71
Ultra narrow band (UNB) is a widely used technology for machine‐to‐machine and low‐power wide‐area communications. Its properties, long range with small RF power, make it naturally attractive for satellite communications but also draw new challenges compared with terrestrial systems where this technology is already deployed. Indeed, the main advantage of UNB signals, their small bandwidth, makes them more sensitive to frequency drifts that are particularly present in the case of LEO satellite systems. It also implies the use of a random access method in which the carrier frequency is a parameter unknown by the receiver. In this paper, we propose a general semianalytical model to evaluate the performance of a terrestrial or satellite system using UNB technology, taking into account the multiuser interference and the frequency drift. This model is then used to assess the performance (packet loss ratio and throughput) on the return link medium access control (MAC) of a representative LEO satellite system. With our model, we analyze the effect of frequency drift on the system performance. This paper also proposes to investigate more deeply the multiuser interference modeling in order to estimate accurately the performances of a UNB system in terms of bit error rate (BER). We propose a semianalytical approach to study the interference in presence of arbitrary power imbalance that includes the effect of frequency offset and frequency drift and applicable for any linear modulation and any pulse‐shaping filter. The expression of the multiuser interference is established in the general case. We then propose a methodology to compare this exact model to the Gaussian interference approximation (mainly used through the central limit theorem) in order to assess its accuracy. 相似文献
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Marco Krondorf Martin Goblirsch Riccardo de Gaudenzi Giuseppe Cocco Nikolaos Toptsidis Guray Acar 《International Journal of Satellite Communications and Networking》2020,38(2):177-199
Machine‐to‐machine (M2M) communications being pivotal for internet of things (IoT) networks are characterized by low‐cost, low complexity, and often energy constrained terminals with low traffic duty cycle. Satellite networks provide an attractive low‐cost solution for such application, in particular when the terminals (both fixed and mobile) are distributed over a wide geographical area not well served by terrestrial infrastructure. An ALOHA random access (RA) scheme is a natural candidate for M2M communications since it is well matched to sporadic traffic, and it requires little terminals coordination. However, the classical ALOHA scheme suffers from a low throughput when operated in a load region requiring low probability of packet loss. To overcome this intrinsic ALOHA limitation, in the last decade, a lot of effort has been devoted to the investigation of evolutions of the ALOHA scheme reducing the probability of destructive packet collisions thus making it more attractive for satellite IoT. In such context, the Contention Resolution Diversity ALOHA (CRDSA) scheme and the Asynchronous Contention Resolution Diversity ALOHA (ACRDA) have emerged as promising solutions thanks to their high spectral efficiency achievable with low packet loss probability. The results reported in literature are however assuming ideal demodulator performance. This paper investigates the design and optimization of RA burst demodulator algorithms for single‐frequency and multifrequency CRDSA and ACRDA. It evaluates the performance of such algorithms in a number of system scenarios of practical interest and studies the impact of relevant system parameters on several performance metrics. 相似文献
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《Digital Communications & Networks》2019,5(2):63-68
The Constrained Application Protocol (CoAP) is a mechanism that enables the efficient transmission of information in the context of Wireless Sensor Networks (WSNs) characteristic of the Internet of Things (IoT). CoAP is specifically intended to work well with low complexity sensors that have limited access to computational resources. And because it lacks the overhead of other more sophisticated transport protocols, it is suitable for high packet loss wireless networks. Relying on the User Datagram Protocol (UDP), CoAP introduces, among other things, confirmable and non-confirmable message types, depending on the nature of the source data. This paper presents a novel analytical model that can relate the application to network packet loss and be used to estimate the effect of lossy wireless channels in CoAP scenarios. Moreover, the model is ultimately validated by an experimental framework in which theoretical and experimental results are compared. 相似文献
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为了实现卫星通信系统低延迟高可靠接入,研究了两步随机接入技术中的信道设计及接收端检测算法.针对卫星场景提出了一种两步随机接入信道设计方案,对两步随机接入信道中数据部分的信道结构以及前导和数据之间的映射方式进行了设计.针对传统最小均方串行干扰消除(Minimum Mean Squared Error-Successive Interference Cancellation,MMSE-SIC)算法中存在误差传播问题导致解码性能降低的问题,提出了一种多判决排序串行干扰消除(Multi-decision Ordered Successive Interference Cancellation,MD-OSIC)算法,以提升多用户发起接入时数据部分检测的可靠性.仿真结果验证了所设计信道及检测算法在典型卫星通信场景下应用的可行性. 相似文献
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Rung‐Shiang Cheng Chung‐Ming Huang Guan‐Shiun Cheng 《Wireless Communications and Mobile Computing》2016,16(16):2477-2494
The Long Term Evolution‐advanced cellular network is designed for human‐to‐human communication. When a large number of machine‐to‐machine (M2M) devices are trying to access the network simultaneously, it leads to a low random access (RA) successful rate and high congestion problem, which may cause the waste of radio resources, packet loss, latency, extra power consumption, and the worst, M2M service error. There is an urge to propose an efficient method for M2M communication on the LTE‐A network to resolve the congestion problem. In this paper, we propose a congestion reduction mechanism, which can analyze and model the RA procedure on the Long Term Evolution‐advanced network, to find out the collapse point in the RA procedure and then design a scheme named device‐to‐device cooperative relay scheme to relieve the congestion problem. Meanwhile, this work also adds a relay access barring algorithm to improve performance and an RA resource separation mechanism for human‐to‐human communication. The proposed method can effectively reduce the network congestion problem. Simulation results show that the network throughput and the congestion can be significantly improved using the proposed mechanism. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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为了实现低轨卫星通信系统高效率低时延的用户接入,提出了适用于低轨卫星系统的两步随机接入方案,对随机接入信道的数据发送、信道结构、前导码设计以及映射关系进行了设计,并进行了现场可编程门阵列（Field Programmable Gate Array,FPGA)实现。针对传统MAX-LOG-MPA算法FPGA处理时延长的问题,提出了一种节点并行迭代更新的FPGA接收机设计来降低处理时延。仿真结果验证了所设计的信道结构以及FPGA实现的可行性,相比传统接入方式可接入的用户数量更多,同时采用并行节点迭代更新的接收机将迭代处理时延降低为1/6。 相似文献
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邝楚文;周永丰;黄燕 《电子技术与软件工程》2022,(13):57-60
本文针对畜禽养殖场往往地处偏僻,落后的设备及异地养殖存在管理难点的问题,采用中移M6315模组,分析LwM2M协议、MQTT协议的发布订阅机制,以轻量级TCP协议进行网络传输,通过网络报文的上传与下发达到智慧养殖的目的。研究实现畜禽养殖的即时性数据采集、实时性指令等应用,分析M6315模组应用物联网MQTT协议、TCP透传的场景,分别以M5311模组的LwM2M协议、M6315模组的MQTT协议和TCP透传实时下发控制指令,实现畜禽养殖自动饲养机、通电水阀等功能。 相似文献
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机器通讯(M2M)是物联网的研究热点。国内外各标准组织已经启动M2M的相关研究。目前属于第三代合作伙伴计划(3GPP,3rd Generation Partnership Project)类型移动网络占有绝对优势地位。3GPP在R8阶段就开始了相关研究,现在已经进展到了R12阶段。描述了3GPP的M2M研究发展动态和最新进展,对比了3GPP机器通讯标准MTC的更新架构,介绍了最新的MTC框架和相关协议栈,分析了架构更新的原因,对下一步发展方向进行了展望。 相似文献
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针对卫星通信系统的特点,研究了结合CDMA和随机接入协议的扩频随机接入方式。在卫星通信的传播时延较长和短数据通信为主的情况下,这种接入技术能根据分组数据等业务的不同需求,实现满足多优先级业务的接入。理论分析和仿真结果表明,这种接入技术可以提高系统的综合性能。 相似文献
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结合3GPP协议的性能要求，根据理论分析和计算机仿真，提出了WCDMA随机接入信道前缀码捕获的一种实现方法。 相似文献
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Erich Lutz 《International Journal of Satellite Communications and Networking》1992,10(5):275-281
This paper considers a satellite network with data messages being transmitted by land mobile users according to slotted Aloha multiple access. The mobile communication links suffering from multipath fading and signal shadowing are modelled as Gilbert-Elliott channels. FEC block coding is used to correct transmission errors. The maximum achievable information throughput and the mean packet delay are derived from a combined analysis of the multiple access and FEC/ARQ protocol. The results show that the additional overhead necessary for FEC is outweighed by the benefit in throughput and delay. Finally, the capture effect and its consequences are discussed. 相似文献
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Axel Bttcher Christoph Meier-Hedde 《International Journal of Satellite Communications and Networking》1993,11(5):271-277
Slotted Aloha can be an attractive multiple access scheme for mobile radio applications, mainly for mobile satellite services. This is especially so when capture-effects occur, i.e. when one out of several colliding data packets can capture the common receiver. Mostly this is due to varying signal levels of the transmitters. It is well-known that a slotted Aloha channel can become unstable. It performs acceptably only if a good retransmission control policy is applied. In this paper, static and dynamic stabilization methods for slotted Aloha in transmission channels with capture and erasure are compared. They are analysed by analytical methods as well as by simulation. It turns out that a dynamic control procedure is more flexible and outperforms a static retransmission policy also in mobile radio channels. 相似文献
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Kai Yu Pingzhi Fan Li Hao Xianfu Lei 《Wireless Communications and Mobile Computing》2012,12(6):503-515
In this paper, large code division multiple access (CDMA) random access systems employing the decorrelator and minimum mean square error (MMSE) detectors are investigated over Rayleigh fading channels under the assumption that both the number of users and the spreading gain tend to infinity, but their ratio converges to a constant. The signal to interference ratio (SIR) is shown to converge almost surely to a constant and the bit‐error rate (BER) is expressed as a function of the traffic load, transmission probability, channel coefficient, and distribution of transmission power. Furthermore, the throughput, the spectrum efficiency, and the stability region are analyzed and simulated. For dominating systems, it is shown that the MMSE detector achieves much higher throughput and spectral efficiency than decorrelator detector. Besides, it is also disclosed that, when the signal to noise ratio (SNR) is larger than an optimum value, the spectrum efficiency increases as the ratio of bit energy to noise power spectrum density (Eb/N0) increases; however, when SNR is smaller than the optimum value, the spectrum efficiency decreases as Eb/N0 increases. For ordinary stable systems, it is demonstrated that their stability region gets narrower as the traffic load increases. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献