分组预约多址协议在DECT系统中的应用

提出了将ＰＲＭＡ协议应用于ＤＥＣＴ,实现ＤＥＣＴ／ＰＲＭＡ系统的方案,分析和仿真表明,ＤＥＣＴ／ＰＲＭＡ系统可以大幅度提高系统的容量,同时也易于实现。     

多址协议中的预约方式

本文简述了卫星信道中几种常用的预控制多址接入协议，并对它们的性能进行了比较，对适用业务类型进行了探讨。     

第三代移动通信系统的一种多址访问协议——分组预约多址协议

论文介绍未来第三代移动通信系统可能采用的多址访问协议－－分组预约多址协议，包括ＰＲＭＡ协议的适用范围，内容及研究状况。     

时分双工环境下的分组预约多址(PRMA/TDD)协议及其性能

在分析标准分组预约多址（PRMA／FDD）协议的基础上,提出了时分双工环境下的分组预约多址（PRMA／TDD）协议,理论分析和计算机仿真均表明,PRMA／TDD与PRMA／FDD的性能相近,可以较大幅度地提高系统的容量。     

基于多信道预约可冲突避免的多址接入协议

本文为多跳分布多无线网络提出了一套灵活而有效的自适应获取冲突避免（AACA）的多址接入协议。在该协议中，各节点竞争公共信道，利用RTS/CTS对话形式来预约各业务信道，成功预约后的分组传输不会受到其他节点的干扰。它使用任意确定数目信道，以异步方式工作，并且使得各节点利用半双工无线电台就可以灵活、简便地实现资源预约。分析和比较结果说明，所提出的多信道预约协议可以有效地解决隐藏终端、暴露终端以及侵入终端的问题。     

一种新的PRMA改进协议——EPRMA

提出了一种新的PRMA改进协议。该改进协议可以同时支持语音和较高速率的数据业务，与MPRMA协议相比提高了系统吞吐量，降低了语音分组丢弃概率，适应移动多媒体业务的接入。     

分组码分多址接入协议研究

本文提出一种用于语音／数据综合业务个人通信网的多址接入协议。该协议基于码分多址技术,分组预约方式,并采用了信道资源动态分配技术。其吞吐量,接入时延,呼损率等性能指标都得到了一定的提高。本文对协议性能进行了分析,并提出了计算机模拟认真的方法。     

无冲突话音/数据综合业务分组预约多址(CF-IPRMA)协议及其性能

本文提出了无冲突话音／数据综合业务的ＰＲＭＡ协议：ＣＦ－ＩＰＲＭＡ协议,并利用马尔可夫链模型法,对ＣＦ－ＩＰＲＭＡ协议中的数据通信性能进行了分析;分析结果表明,该协议在保证话音通信质量的前提下,具有较高的数据业务通过率。     

自适应动态分组预约多址协议

该文提出一种基于自适应传输的动态分组预约多址协议。用来在业务量和信道都时变的环境下，灵活、高效地支持需要各种不同质量需求的无线多媒体通信。在这个方案中根据特点不同将空闲时隙分为“自由”、“长可用”或“短可用”三种，以“自由”时隙数目作为系统实时业务量的判决标准，根据系统实时业务量分别采用不同的多址接入策略，将长数据和短数据安排在语音传输的空隙传输，同时采用了自适应传输体制来进一步提高系统性能。仿真实验表明，通过合理选择系统参数，可以有效地增加系统总容量。     

改进的分组预约多址协议性能分析

分级预约多址（PRMA）协议已被广泛地应用于短距离无线通信系统中,它不仅适用了数据传输,同样也适用于话音传输。但由于PRMA协议的帧长是固定的,竞争的产生使部分时隙被浪费,信道容易不能更好地被提高,而且在重负荷情况下系统会发生不稳定问题。提出了一种改进的分组预约多址协议（IPRMA）。进行了理论分析和计算机仿真,由于采用排队等待方式接入时隙信道,降低了分组时,减少了分组丢弃率,从而提高了系统容量。     

冲突消弱分组预约多址协议及其性能分析

本文讨论了分组预约多址接入（ＰＲＭＡ）协议的缺点,提出了一种突消弱分组预约多址接入（ＣＲ－ＰＲＭＡ）协议,理论分析和计算机仿真均表明ＣＲ－ＰＲＭＡ的性能优于ＰＲＭＡ。     

分组卫星话音／数据综合的混合多址协议性能研究

本文讨论了一种用于分组话音／数据综合的混合多址协议，该协议是固定分配与随机访问的混合，并且赋予话音分组优先传输权，从而保证了无重传话音分组有较小的丢失概率。本文进行了详细的理论分析，并得出了性能比较特性，所得结果认为这是一个兼顾话音／数据综合的较好协议，且具有一定的灵活性。     

Performance of CDMA/PRMA as an Access Technique for Integrated Services in a UMTS High Altitude Platform System

High Altitude Platforms (HAPs) have gained a great interest in recent years. HAP systems will be global in nature but national in service provision. They will deliver IMT-2000 mobile and fixed wireless access using the proposed IMT-2000 terrestrial component radio transmission technologies and protocols. Under the above consideration, in this paper the performance of a MAC protocol based on the combination of the well-known Packet Reservation Multiple Access (PRMA) scheme with Code Division Multiple Access (CDMA) technologies in a Frequency Division Duplex (FDD) mode is studied, for a HAP operating at the 2 GHz frequency band at an altitude of 22 km. The impact of acknowledgement delay has been examined through computer simulations, along with the selection of suitable channel access functions (CAFs) to control the access of mobile users. Moreover the protocol performance is investigated in a cellular HAP environment and compared to that of a ground-based system. Finally, different traffic scenarios have been considered in order to investigate the access delay for non-real time traffic and the packet dropping performance for real time traffic.Nikolaos Batsios received his diploma degree in electrical & computer engineering (Telecommunication Division) from Aristotle University of Thessaloniki (Greece) in 2000. At the end of his studies, his diploma thesis was awarded from ERICSSON Hellas. He was also one of the six finalists of the IEEE Region 8 Student Paper Contest. He has worked as a Research Engineer in Space Engineering S.p.A. (Rome, Italy) and he was involved in ATB, ROBMOD and VIRTUOUS projects. Currently he is working in Intracom S.A. as Telecom Engineer. His research interests are in the field of satellite and terrestrial communication systems including physical layer design, medium access control layer architectures and protocols.Fotini-Niovi Pavlidou received the PhD degree in electrical engineering from the Aristotle University of Thessaloniki, Greece, in 1988 and the diploma in mechanical-electrical engineering in 1979 from the same institution. She is currently an associate professor at the Department of Electrical and Computer Engineering at the Aristotle University engaged in teaching for the under- and post-graduate program in the areas of mobile communications and telecommunications networks. Her research interests are in the field of mobile and personal communications, satellite and HAP communications, multiple access systems, routing and traffic flow in networks and QoS studies for multimedia applications over the Internet. She is involved in many national and international projects in these areas and she has chaired the European COST262 Action on Spread Spectrum Techniques. She has served as a member of the TPC of many IEEE/IEE conferences. She is a permanent reviewer for many international journals. She has published about 80 papers in refereed journals and conferences. She is a senior member of IEEE, currently chairing the joint IEEE VTS & AESS Chapter in Greece.     

Rapid Access Protocols for Discontinuous Transmission in DS-CDMA Systems

In this paper, three reverse link access protocols (AP) enabling discontinuous transmission (DTX) in DS-CDMA personal communication systems are introduced and discussed. The first protocol is synchronous (SDTX-AP), and it uses a so-called synchronous reservation channel to accommodate access requests in a time slotted frame structure. The second uses an asynchronous approach (ADTX-AP) with a spread slotted ALOHA protocol for access requests; access request messages consist of a synchronizing preamble and a user identifier appendix. The third one employs a synchronous structure of overlapping slots, offset in time by a minimum interval (mini-slot) necessary to enable resolution of overlapping access probes sent by different mobile users (MSDTX-AP). Instead of using different spreading codes for different mobile transmitters, all transmitters are assigned the same spreading code to send their access request messages on the access reservation channel. Analysis considers the mean access delay and throughput of the protocols in a multipath fading channel. Numerical results indicate that at high values of offered traffic of access requests mean access delays of ADTX-AP and SDTX-AP are comparable. The mean access delay for the MSDTX-AP depends on the number of minislots or users within each frame, but its throughput is much higher than that of either SDTX-AP or ADTX-AP.     

CDMA随机多址接入技术研究

CDMA作为一种多址接入技术在无线网络中已广为应用,在多码CDMA和单码CDMA研究的基础上,构造了多码CDMA和单码CDMA在无线分组数据网络中的随机多址接入模型,并且分析了两种系统的吞吐率特性和归一化时延特性。结果证明单码CDMA和多码CDMA具有相同的多址接入性能。     

一种基于服务质量(QoS)的分组预约多址协议

本文从用户角度和实际通信情况考虑,提出了一种基于服务质量的分组预约多址协议（ＥＴ－ＰＲＭＡ）。该方法利用用户信息之间的相关性,适当地调整分组预约多址（ＰＲＭＡ）协议中的话音用户再次竞争信道的概率,提高ＰＲＭＡ系统中话音终端获取信道的速度,从而达到提高话音业务性能,从计算机仿真的结果看,该方法对提高ＰＲＭＡ系统中话音业务的性能确有帮助。     

移动Ad Hoc网络中一种分布式QoS保证的多址接入协议

基于随机竞争和冲突解决的思想,本文为多跳移动Ad Hoc网络提出了一种分布式服务质量(QoS)保证的多址接入(QMA)协议.该协议中,节点在发送业务分组前利用预报突发进行竞争接入,节点根据业务分组时延情况和最早失效优先原则确定预报突发的长度,所发预报突发能持续到最后的节点优先获得接入.同时,具有实时业务的节点可以按照其优先级在更早的竞争微时隙中开始发送预报突发,而有非实时业务的节点只能在前面竞争微时隙空闲的情况下,才能在后面的微时隙开始发送预报突发,因此发送实时业务的节点可以比发送非实时业务的节点更优先接入信道,从而在移动Ad Hoc网络中实现了对多媒体业务的QoS保证.最后利用OPNET仿真评估了QMA协议的多址性能,并与IEEE 802.11e协议的性能做了比较,结果表明QMA协议可以提供较高的吞吐量和较低的实时业务时延.     

直扩卫星通信系统中多用户检测算法比较

实际在CDMA系统中,多址干扰(MAI)是主要的干扰来源,多用户检测技术完全可以抑制这种多址干扰。论文分析了几种典型的多用户检测技术,并在高斯信道环境下对解相关检测器、最小均方误差检测器和传统检测器进行了仿真和性能比较。