基于SPMA协议的混合式信道负载统计方法

战术瞄准网络技术系统作为美军新一代战术数据链系统,在链路层面以"全双工"通信为基础实现了基于优先级概率统计的多址接入协议SPMA(Statistic Priority-based Multiple Access)。战术数据链的链路层协议或称MAC协议描述了节点接入无线信道的规则,采用合适的MAC协议,能够更合理地分配有限的无线带宽资源,是战术数据链的关键技术之一。本文主要对统计优先级多址接入(SPMA)协议的信道占用状态进行研究,从物理层和网络层两方面对信道占用状态进行统计,然后采用预测技术有效的估计实际的信道占用状态,设计了一种准确的混合式信道负载统计方法,有效地降低了信道冲突,保证了数据发送的实时性和高优先级数据较高的成功传输概率。     

一种新的自组织时分多址甚高频数据链隐藏终端分析方法

本文提出一种新的自组织时分多址(S-TDMA)数据链网络性能分析方法——概率周期分析法.一方面提出系统状态熵的概念,将时隙的状态停留时间和稳态概率同时引入分析模型中,给出了一种以时隙的处于成功传送状态的状态真值与系统的状态熵之比作为评价信道吞吐量的新方法;另一方面提出基于同信道干扰(CCI)准则的终端分区模型,分析隐藏终端在不同区域内对终端的影响.最后,提出了一种基于捎带帧技术的解决S-TDMA系统隐藏终端问题的方法.系统仿真的结果表明,该方法行之有效.     

VDL4:一种新型航空VHF数据链

甚高频(VHF)数据链在当今航空通信中具有十分重要的作用。目前航空数据链各异,并各具优势。文中主要论述VDL4,首先介绍了其基本设备结构,说明了协议的层次模型,然后分析了VDL4的时隙选择、网络接入、信道管理等关键技术,最后将它和其余VDL模式数据链进行了比较,从而说明VDL4是一种能满足新航行系统需求、极具竞争力的航空数据链。     

动态时隙控制的双概率随机多址接入ad hoc网络MAC协议分析

提出了一种动态时隙控制的双概率随机多址接入MAC(DSTPMA)协议,用户终端以P1概率侦测空闲信道,以P2概率检测忙信道,并在发送状态调整时隙定位后接入信道发送信息分组.通过对多通道的DSTPMA协议的建模分析,得到了控制协议的系统吞吐量.仿真实验结果表明,理论分析与仿真结果相一致.     

自适应三维概率CSMA控制策略研究

对于无线传感器网络,节点业务负载量是随着时间和环境不断变化的;而且传统的CSMA（Carrier Sense Multi-channel Access）协议对于信道访问机制在自适应方面也存在不足.针对这些特点,本文分析了传统的载波监听多路访问（CSMA）协议的不足,为解决概率型CSMA协议中概率难以选择的问题,提出一种基于自适应机制的自适应三维概率CSMA（ATDP-CSMA）协议,采用平均周期的方法对ATDP-CSMA（Adaptive Three-Dimension Probability-CSMA）协议进行建模分析,得到了系统吞吐率的精确表达式.仿真结果表明,该协议不仅能够较好地适应节点业务负载量的变化,而且在高负载时也能保持一个较稳定的吞吐率.     

多链统一集成接入设计

本文提出一种多数据链接入方法,以进行多信道、组网协议和消息标准的兼容、多数据链综合监控及业务综合分发处理,统一业务处理流程,简化指控系统与数据链接口关系,并通过综合业务复接简化系统引接。     

基于空地数据链的飞机状态监控系统的实现

飞机状态监控系统 (ACMS)通过得到机载设备的各种参数实现对飞机状态的监控。对比其它各种监控方式 ,采用空地数据链方式将机载设备与地面处理系统结合起来 ,实现了对飞机的实时跟踪和在线监控。同时 ,通过对航空公司繁杂机队和报告协议的分析 ,合理设计了地面处理系统 ,为其提供了有效的扩展空间     

6LoWPAN网络能耗性能建模分析

为了改进6LoWPAN网络能耗性能,提出了一种基于超帧睡眠期的信道竞争机制,并对其进行Markov建模.基于本模型,对发送状态概率、信道检测冲突概率等网络参数和节点平均能耗进行了数学分析,并研究了参数λ、minBE和NB对能耗等网络性能的影响.理论分析表明,该模型能够较好的描述和评价6LoWPAN网络MAC协议,新机制降低了网络能耗,也改善了协议的性能.     

一种地空数据链通信系统的无线信道分析方法

基于无线通信信道中电波的传播方式和信道的衰落特性,本文分析得出了在地空数据链通信系统中适用于不同通信区域的无线信道模型;给出了一种针对地空数据链通信系统的链路余量的仿真分析方法。通过该仿真分析方法,可得到地空数据链通信系统在不同通信场景下的链路余量结果,从而为系统的设计提供支撑。     

基于HFC网络上行信道CDMA-预约ALOHA多接入方式吞吐量分析

为了在HFC网络上实现交互式业务,人们对基于HFC网络的介质访问协议进行了广泛的研究.已出现的几种基于HFC的MAC协议基本上都采用了竞争与预约相结合的访问机制.基于CDMA的HFC是新一代的HFC系统.本文提出了一种基于CDMA的双向HFC网络竞争与预约相结合的上行信道多址接入方式.并且为该协议系统建立了四状态Markov链分析模型,对该协议进行了性能分析,并给出了计算机实验结果与分析.     

Analysis of an integrated voice and data transmission system usingpacket reservation multiple access

Packet reservation multiple access (PRMA) is a channel access protocol proposed for the third generation wireless information networks which have attracted considerable attentions recently. By using the equilibrium point analysis (EPA), a PRMA integrated voice and data system has been studied in previous research. However, the error between numerical results of the analysis and those of simulation is relatively large. In this paper, we also study an integrated voice and data system with PRMA. The system performance is evaluated by using a Markov analysis method. First, some analytic models are constructed such that the system transition can be described by a Markov chain. Then, we calculate the entries of the one step state transition matrix using an iterative procedure. Finally, system performance measures, such as throughput and delay, are evaluated. Little error between numerical results of analysis and those of simulation indicates that the method is appropriate to analyze PRMA systems,     

机载甚高频ACARS数据链系统及通信管理单元设计

装备通信管理单元、甚高频电台等机载设备的飞机具备接入飞机通信寻址与报告系统(ACARS)地空数据网络的能力.分析了甚高频ACARS数据链机载系统的结构,探讨了通信管理单元的服务功能和应用功能,基于通信管理单元与甚高频数传电台、机上系统以及驾驶舱之间的接口和协议,设计了实现ACARS协议的通信管理单元的软件结构模型.     

无线双通道网络话音业务信道接入性能分析

无线双通道网络能够有效解决战术环境下码分组网数目过小造成的码分资源浪费问题。混合业务传输环境下,实时话音业务信道接入性能是衡量无线双通道网络性能的关键指标之一。通过使用一种理想的固定时分信道带宽分配方案,在保障话音业务传输实时性的条件下,分别从单跳网络拓扑和多跳网络拓扑结构给出了双通道网络可用信道数目。使用基于优先权的混合业务多服务台离散时间排队模型分析了双通道网络的话音业务平均数目、呼叫阻塞概率、平均网络吞吐量和信道利用率等性能。数值计算结果证明：相比传统网络,双通道网络在混合业务高负载条件下能够容纳更多的话音业务并具有更低的呼叫阻塞概率。     

MC-CDMA在VHF航空信道中的性能研究

文章分析多载波码分多址系统的信号传输模型和甚高频（VHF）航空信道模型，对多载波码分多址（MC-CDMA）系统在航空信道下的误码性能进行了研究和仿真。VHF航空通信信道拥挤，多径现象严重，时延和多普勒频移很大，MC-CDMA结合利用正交频分复用和码分多址技术的优点，能够有效的对抗多径干扰，并提供更大的通信容量，具有良好的应用前景。     

Performance Analysis of an Enhanced PRMA-HS Protocol for LEO Satellite Communication

The packet reservation multiple access with hindering state （PRMA-HS） is a protocol suitable for LEO satellite mobile communication. Although working well with light system payload （amount of user terminals）, the protocol imposes high channel congestion on system with heavy payload, thus degrades the system＇s quality of service. To controlling the channel congestion, a scheme of enhanced PRMA-HS protocol is proposed, which aims to reduce the collision of voice packets by adopting a mechanism of access control. Through theoretic analysis, the system＇s mathematic model is presented and the packet drop probability of the scheme is deduced. To testify the performance of the scheme, a simulation is performed and the results support our analysis.     

Analysis of a hybrid multiple access protocol with free access ofnew arrivals during conflict resolution

A hybrid multiple access protocol (HYMAP) was proposed by M. Rios and N.D. Georganas (1985), combining the best features of CSMA/CD and of a conflict-free protocol. Control is transferred from one protocol to the other according to state information sensed on the channel. The performance of HYMAP was evaluated by computer simulation. An exact analysis of this hybrid protocol is presented. Since HYMAP permits free access of new arrivals during collision resolution, the mean length of the conflict-free period is determined by solving a large system of linear equations. The basic mean performance measures (throughput, delay) can then be easily computed and compared to the performance of CSMA/CD     

Performance analysis of IEEE 802.11e contention-based channel access

The new standard IEEE 802.11e is specified to support quality-of-service in wireless local area networks. A comprehensive study of the performance of enhanced distributed channel access (EDCA), the fundamental medium access control mechanism in IEEE 802.11e, is reported in this paper. We present our development of an analytical model, in which most new features of the EDCA such as virtual collision, different arbitration interframe space (AIFS), and different contention window are taken into account. Based on the model, we analyze the throughput performance of differentiated service traffic and propose a recursive method capable of calculating the mean access delay. Service differentiation functionality and effectiveness of the EDCA are investigated through extensive numerical and simulation results. The model and the analysis provide an in-depth understanding and insights into the protocol and the effects of different parameters on the performance.     

Satellite forward VDES channel modeling and impact on higher-layer performance

VHF data exchange system (VDES) is an emerging maritime communications standard that is meant to provide ship-to-shore, shore-to-ship, and ship-to-ship information services. VDES also includes a satellite component to extend the service coverage also to the high sea. Ships can receive important information via VDES and access this service via satellite when they are far from the shore. This paper uses data taken during a measurement campaign to develop an ON-OFF model for the VDE-SAT downlink channel taking the multipath effects caused by sea reflections into account. This model has been used to evaluate the impact of packet-level forward error correction (FEC) schemes (i.e., ideal codes, RaptorQ codes, and 2-Dimension Reed-Solomon codes) to further protect transmissions from deep fading events and to evaluate the impact at the transport level considering the possibility to adopt the transmission control protocol (TCP) for a file map delivery service.     

Improving CSMA/CA network performance under hidden collision

Dynamic spectrum access policy allows a secondary user (SU) to access a primary user (PU) channel when it is idle. However, the idle state may result from the PU's silent activities, which can be wrongly perceived as an opportunity for the SU to access the channel and lead to “hidden collision” when it effectively tries to access the channel under this condition. At best of our knowledge, this issue has yet to be addressed in the literature. In this paper, we will first define a three‐state model that describes hidden collision conditions, then propose a probabilistic model in which a transient state is added to force the SU to wait a certain period of time before accessing the channel, thereby translating into better protection for the PU. Based on this model and using Carrier Sense Multiple Access/Collision Avoidance protocol, we will evaluate the PU's and SU's throughput and delay with and without transient state as well as the gain in using our approach. Our computation results show a substantial improvement of the PU's throughput from 19.6 to 61.1%.