小口径TDMA卫星通信地球站应用研究

小口径天线邻星干扰、TDMA帧效率等问题影响了小口径TDMA卫星通信地球站推广应用,其中突发结构设计是提高TDMA帧效率关键,在对DVB-RCS标准进行研究的基础上,分析了几个DVB-RCS商用系统,在分析TDMA突发结构基础上综合考虑帧长、载波速率、时隙数,不同载波速率下适当的突发结构设计是提高MF-TDMA帧效率的方法。针对小口径天线邻星干扰问题,提出扩频的解决方法,经过计算或仿真验证了方法的有效性。     

一种用于水声通信网的TDMA方案

由于海洋中恶劣的传输条件，设计高可靠性、高吞吐量的水下通信网是一项具有很强的挑战性的工作。本文提出了一种适合水下环境中通信网使用的TDMA方案，该方案通过TDMA数据帧的交错布置减少信道的闲置时间，提高网络效率。仿真实验结果表明，该TDMA方案具有较高的网络性能。     

基于LFM信号的TDMA网络精密时间同步方法

针对多作战单元协同作战对时分多址(TDMA)通信网络时间同步精度的新需求,设计了基于线性调频(LFM)脉冲的TDMA网络精密时间同步方法。利用大时间带宽积的LFM脉冲压缩提高了脉冲到达时间的估计精度;通过设计LFM集中交互的TDMA帧结构,减小了脉冲交互时间,降低了节点间相对运动对时间同步精度的影响。最终仿真和实际平台验证显示,该方法能够将TDMA网络的时间同步精度提高到纳秒量级,可以为其他任务载荷提供高精度时统。     

国内卫星通信TDMA系统

本文简要介绍了TDMA的特点、基本组成及TDMA网络的监测与管理。重点对TDMA系统中子帧捕获与同步、调制解调、与地面网络的接口等一些TDMA特有的技术进行了分析。文章力求以适用于国内卫星通信的TDMA系统为基础,进行介绍与分析。     

TDMA战术局域网的性能分析模型

网络性能是衡量战术局域网可用性的重要指标，目前针对TDMA网络的性能分析方法并不能够全面准确地给出网络性能的评价，且具有一定的主观性和局限性。本文建立了一种基于排队论的TDMA战术局域网广谱性能分析模型，并利用该模型对多种TDMA网络进行了分析。从结果可以看出，该模型不仅能对网络性能进行准确的分析，而且能为网络优化提供有力的科学依据。     

协作重传的动态TDMA时隙分配算法

协作通信可以有效地降低衰落信道中数据传输的中断概率,从而提高数据的传输速率。但是在TDMA系统中采用协作通信必然引入额外的带宽开销,为了提高传输速率而采用协作通信,是否能克服因此而产生的不利因素并不明确。在提出的CD-TDMA时隙算法中,在传统TDMA帧的前部增加了一个侦听和动态分配时隙的预约阶段。所有节点在每个数据帧的开始如果没有新产生的数据,则有义务协作转发其他节点在上个时隙帧中发送失败的数据。该算法提高了数据重传的成功概率,提高了整个网络的吞吐量。仿真结果表明,尽管该算法引入了额外的时隙开销,和传统的TDMA接入方式相比,该算法可以有效地提高整个网络的吞吐量。     

改进的紫外光通信网络TDMA邻居发现算法

针对节点数较多的紫外光固定拓扑网络,设计了一种基于时分多址接入(Time Division mMultiple Access,TDMA)技术的紫外光帧结构,结合紫外光大气传输特性提出了一种紫外光定向邻居发现算法.仿真对比了该算法和传统算法的性能,并对该算法不同退避延时下的节点发现效率进行了理论分析和仿真验证.     

TDM/TDMA在点对多点无线局域网中的应用

TDMA方式具有占用频带较窄、无远近效应、易增容、实现简单等优点,在实际中有着广泛的应用。结合实际需求,提出采用TDM/TDMA机制构建了一个有中心的,一点对多点的无线局域网的应用方案。给出了实际的帧结构,详细介绍了数据在多径条件下传输时,上下行帧同步技术和动态时延调整技术,同时针对基于竞争机制的信道分配方法造成分组冲突而降低网络性能的方案,提出采用令牌轮询的方式来动态分配信道。     

TDMA帧结构研究

时分多址(TDMA)卫星通信系统的帧结构设计至关重要,它是TDMA体制卫星通信系统所独有的,而且帧结构设计的优劣直接影响到系统的效率、稳定性、组网能力以及系统能够提供业务服务质量等诸多方面,通过对3个实际TDMA系统帧结构的分析,给出了帧的组成、帧参数的设计考虑。     

利用跳频同步的Ad hoc网络时隙同步

本文针对采用跳频数传TDMA接入的Ad hoc网络，提出了一种利用跳频同步来实现TDMA时隙同步的方案。考虑到时隙同步是为了使得各个节点的时隙基准对齐，并不需要保持节点之间具体时间一致，利用跳频同步采用分隔符对跳频帧的定位，对定位进行时延补偿后，可实现时间基准基本对齐。由于同步偏差的存在，通过设置保护带允许时隙的抖动来防止冲突发生。本文给出了具体的同步实现方案，并且与其他的Ad hoc网络时隙同步方案进行了比较。仿真结果表明，该方案占用了较少的传输带宽，提高了效率，并且可以保证一定的同步精度。     

Network Control for Multibeam TDMA and SS/TDMA

This paper concentrates on the control of individual burst transmissions of traffic and reference stations in TDMA and SS/ TDMA networks. In a TDMA system, the principal task of a TDMA terminal is to transmit each burst at the proper time to assure that, at the satellite, the burst resides in its assigned location in the TDMA frame. The composite of assigned positions for all bursts in the TDMA frame, or frames if more than one transponder is involved, is called the burst time plan. The paper discusses a specific concept of control used by a station to acquire and synchronize its burst transmission to assigned time slot(s) in the TDMA frame. The concept is applied to single-beam (global or regional) and muitibeam systems. The method used controls the instant of traffic burst transmission by introducing a time delay at each station which causes the round-trip propagation time between the satellite and all earth stations to be equal for burst position control purposes. This time delay is simple to implement in the TDMA terminal's timing circuitry and does not require the storage of traffic to accomplish it. It is also shown that the control method leads to a simple means for accomplishing synchronous burst time plan changes throughout the network. The functions of the reference stations needed to accomplish the burst time plan control are defined and explained. The discussion extends to SS/TDMA, and explains how the satellite switch state time plan change can be synchronized to the overall network burst time plan change.     

分布式TDMA网络的时隙设计技术

时隙分配是分布式TDMA组网的一个基础性工作,直接影响到Adhoc网络的性能。为支持低延迟数据业务,通常选择TDMA组网技术,但常规的固定时隙TDMA网络对时隙的利用率较低。提出了一种基于跳频的固定时隙分配和动态时隙分配相结合的TDMA时隙资源管理技术,有效地解决了TDMA网络的不同类型用户信息传输时隙分配问题。     

System Capacity and Access Control for Multimedia TDMA/SS Networks

In this paper, we study the system capacity and access control for the TDMA/SS (time division multiple access with spread spectrum) cellular networks supporting multimedia services. In the TDMA/SS system, time is divided into frames and each frame is further divided into slots. Only one user is allowed to transmit in a slot and spread spectrum technique is adopted to combat inter-cell interference. A packet can occupy more than one slot, depending on the user's data rate and quality of service requirement. We derive a necessary and sufficient condition for a group of users to be admissible for the TDMA/SS system and prove that its admission region contains that of the TDMA/CDMA system. In the TDMA/CDMA system, time is also divided into frames and each frame consists of several slots. The difference is that every packet occupies exactly one slot and multiple users can transmit their packets in the same slot. Numerical results show that the admission region of the TDMA/SS system can be significantly larger than that of the TDMA/CDMA system. To further increase bandwidth utilization and guarnatee delay bound requirements, several access control schemes are proposed. Simulation results are obtained for these access control schemes.     

Channel Borrowing Without Locking for Asynchronous Hybrid FDMA/TDMA Cellular Communications

The use of real time channel borrowing in digital cellular asynchronous hybrid FDMA/TDMA systems is considered. These systems, which are exemplified by North American digital cellular (IS-54), are asynchronous in the sense that time slots in different cells are not aligned. CBWL (channel borrowing without locking) techniques can be applied but (without cell-to-cell synchronization) borrowing individual time slots from adjacent cells would violate co-channel interference constraints. Instead, frequency carriers can be borrowed. In IS-54, a carrier supports three TDMA slots. So if only one TDMA slot is needed in the borrowing cell, two TDMA slots are unnecessarily transferred. We devised an appropriate carrier borrowing scheme and an analytical model to determine the traffic performance of TDMA/CBWL. Fast carrier returning is used to increase channel utilization by returning borrowed carriers as soon as possible. An efficient computational method that uses macro-states, decomposition, combinatorial analysis and the convolution algorithm is devised to find blocking probabilities. The results show that in comparison with FCA, the new CBWL scheme can significantly improve system performance of asynchronous TDMA cellular systems that use FDMA/TDMA multiplexing.     

卫星网络管理系统控制信道设计

设计了一套用于卫星网络管理系统的控制信道。采用TDM/TDMA专用控制信道和复接控制信道互为备份的方式保证信息传输的畅通,2种信道都可保证卫星网管所有功能的完成。主用TDM/TDMA专用控制信道,一旦专用信道中断,采用复接控制信道。复接控制信道与业务复接在一起利用业务信道传输网管信息。TDM/TDMA专用控制信道由链路适配器和突发卫星调制解调器组成,重点描述其设计方案。     

Message Delays in FDMA and TDMA Communication Channels

Message delays under a Time Division Multiple Access (TDMA) scheme and the corresponding Frequency Division Multiple Access (FDMA) scheme are studied and compared. Under a TDMA scheme, a network station is assigned a number of slots for each time frame. Under the corresponding FDMA scheme, this station is allocated a separate frequency band for which the ratio between its width and the channel bandwidth is equal to the corresponding time portion allocated by the TDMA scheme. The distribution of the message delay difference under the corresponding TDMA and FDMA schemes, for any message arrival stream, any service ordering discipline and at any time, is derived. This distribution is shown to be equal to that of a simple random variable associated with the message arrival stream. Message delays under a TDMA scheme are shown to be always lower than those under the corresponding FDMA scheme, but the difference value is lower than the time frame duration. Station-buffer queue sizes under both schemes are shown to be essentially the same.     

Throughput analysis for interference limited TDMA and TDMA/CDMA wireless ad hoc networks

The node throughput, which is defined as the total rate received at each node, is evaluated for the interference limited TDMA and TDMA/CDMA wireless ad hoc networks. In the TDMA wireless ad hoc network, there is only one transmission link connected to each node in the same time slot, whereas in the TDMA/CDMA wireless ad hoc network there are multiple transmission links connected to each node in the same time slot. We first derive the node throughput for these two wireless ad hoc networks and then make a comparison of the node throughput between them. The theoretical results and simulation results both reveal that the TDMA wireless ad hoc network outperforms the TDMA/CDMA wireless ad hoc network in the node throughput. Copyright © 2008 John Wiley & Sons, Ltd.     

3D-IC中基于时分复用的TSV蜂窝容错设计

三维芯片(3D-IC)通过硅通孔(TSV)技术来实现电路的垂直互连,延续了摩尔定律,但在制造、绑定等过程中,TSV容易引入各类缺陷。添加冗余TSV是解决该问题的有效方法之一,但TSV面积开销大、制造成本高。提出一种基于时分复用(TDMA)的TSV蜂窝结构容错设计方案,它基于时间对信号TSV进行复用。实验结果表明,与一维链式TDMA结构相比,蜂窝TDMA结构提高了30%的故障覆盖率,并且故障覆盖率随着蜂窝阵列的扩展持续提升。在64TSV阵列中,与一维TDMA结构相比,蜂窝拓扑结构的面积开销降低了10.4%。     

Delay and throughput characteristics of TH, CDMA, TDMA, and hybridnetworks for multipath faded data transmission channels

The new concepts of adaptive time hopping and variable frame code division (CDMA) multiple access are introduced. By a unified analysis, the probabilities of bit and packet errors in multipath fading environment for five time division (TDMA), code division, and time hopping (TH) related multiaccess networks are obtained; namely, TDMA, CDMA, CDMA/TDMA, Adaptive CDMA/TH, and variable frame CDMA/TDMA networks. The delay and useful throughputs of the five systems are also evaluated for data and voice traffic. All systems compared have the same channel power and bandwidth and support the same traffic. Though implementation issues are not covered, CDMA systems are put at a disadvantage (compared to cellular-type FDMA networks, for example) by ignoring such inherent advantages as voice silence utilizations and automatic frequency reuse. Nontheless, two CDMA systems outperform TDMA systems at low and medium input traffics     

Study of various TDMA schemes for wireless networks in the presenceof deadlines and overhead

The objective of this paper is to determine the minimum system dropping rate (or, equivalently, dropping probability) induced by time division multiple access (TDMA) schemes supporting time-constrained applications with common maximum cell delay tolerance. Expressions are derived for the induced system dropping rate for various TDMA schemes with different overhead and the maximum number of users than can be admitted in the network without violating the maximum dropping rate constraint is determined. The system dropping rate achieved by suboptimal TDMA schemes is compared against the optimal (although ideal) TDMA scheme performance. The performance limiting factors associated with the suboptimal schemes are identified, and the magnitude of their (negative) impact is evaluated. Based on this information it is possible to point to performance improving modifications which should be pursued to the extent permitted by technological constraints. Finally, based on this derivations a network designer may choose the best TDMA scheme-among realizable variations of those considered here-to use in a particular situation