排序方式: 共有56条查询结果,搜索用时 15 毫秒
21.
Giuseppe Araniti Antonio Iera Antonella Molinaro 《Wireless Personal Communications》2005,32(3-4):195-213
New-generation telecommunications systems are expected to meet the rising user exigencies of mobility and ubiquitous access to multimedia services. As a consequence, 3GPP consortium has introduced the Multimedia Broadcast and Multicast Service (MBMS) concept into 3G/beyond-3G networks. Supporting MBMS in next generation hybrid wireless platforms becomes a challenging issue due to high traffic load deriving from both signaling message exchange and data transmission between multicast sources (BM-SC) and end users. Therefore, in this context, key research issues are surely: effective exploitation of the limited radio spectrums available, coordination of users accessing radio resources, as well as provisioning of desired QoS guarantees. Given the high mobility profiles typical of UMTS users, it clearly appears that the cited target performance can only be achieved through networking solutions based on an overlapped terrestrial-HAP-satellite coverage. An inter-working scenario where HAPs operate in synergy with the UMTS terrestrial and satellite segments seems to be the most promising solution to provide mobile users with MBMS services. Our work, dealing with architectural design options, takes into account many metrics relevant to aspects, such as: frequency allocation, costs in terms of resource utilization, signaling traffic load, number and location of customers, reliability, possible retransmission paths, user mobility, and QoS.Giuseppe Araniti received a degree in Electronic Engineering from the University of Reggio Calabria, Italy, in 2000. He received the Ph.D. in Electronic Engineering from the same University, in March 2004. He is currently a junior researcher at the D.I.M.E.T., of the University of Reggio Calabria, Italy. His major area of research is the traffic and resource management in third and fourth generation mobile radio systems.Antonio Iera graduated in Computer Engineering at the University of Calabria, Italy, in 1991 and received a Master Diploma in Information Technology from CEFRIEL, Italy, in 1992 and a Ph.D. degree from the University of Calabria, Italy, in 1996.Since 1997 he has been with the University of Reggio Calabria, Italy, first as an Assistant Professor and then as an Associate Professor. Currently, he is Professor at the same University. His research interests include Personal Communications Systems, Enhanced Wireless and Satellite Systems.Antonella Molinaro received a degree in Computer Engineering from the University of Calabria, Italy, in 1991, a Master degree in Information Technology from CEFRIEL, Italy, in 1992, and a Ph.D. degree from the University of Calabria, Italy, in 1996. Since 1998 she has been an Assistent Professor first at the University of Messina and then at the University of Calabria. She is currently an Associate Professor at the University Mediterranea of Reggio Calabria, Italy. Her interests include mobile radio systems and inter-working wireless-wired networks. 相似文献
22.
手机电视技术的相关研究 总被引:1,自引:0,他引:1
结合目前国内外手机电视技术及业务发展情况,对国内可采用的主要手机电视技术进行了阐述及分析,根据技术发展情况及政策条件提出了一些手机电视发展的相关建议. 相似文献
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A slightly sooting premixed ethylbenzene flame with an equivalence ratio of 1.90 was investigated at low pressure (4.0 kPa) using molecular-beam mass spectrometry (MBMS) and tunable synchrotron vacuum ultraviolet (VUV) photoionization. Basing on the ionization threshold measurements of photoionization efficiency (PIE) spectra, combustion intermediates up to C19H12 were identified, including a number of radicals and isomeric species. Mole fraction profiles of observed flame species were evaluated from the measurements of burner scan at the photon energies near ionization thresholds. Besides, the flame temperature profile was measured by a Pt/Pt-13%Rh thermocouple. From the intermediate identification and mole fraction measurements, the degradation of ethylbenzene, as well as the formation of some interested polycyclic aromatic hydrocarbons (PAHs), was discussed in detail. It is suggested that the formation of most typical PAHs observed in this work can be related to the H-abstraction/C2H2-addition (HACA) mechanism. Furthermore, the high concentration levels of intermediates in this flame is ascribed to the weak C-C bonds in the sidechain of ethylbenzene, which provides a potential explanation of the high sooting tendencies of ethylbenzene and other monocyclic aromatic fuels with complex sidechain structure. This study is anticipated to be constructive for combustion investigations of aromatic fuels, and the discussion is hoped to be helpful for further modeling studies concerning PAHs formation in combustion process. 相似文献
24.
Antonios Alexiou Christos Bouras Vasileios Kokkinos Evangelos Rekkas 《Wireless Communications and Mobile Computing》2009,9(9):1159-1172
Along with the widespread deployment of the Third Generation (3G) cellular networks, the fast‐improving capabilities of the mobile devices, content, and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). To this direction, the Third Generation Partnership Project (3GPP) is currently standardizing the Multimedia Broadcast/Multicast Service (MBMS) framework of UMTS. In this paper, we present an overview of the MBMS multicast mode of UMTS. We analytically present the multicast mode of the MBMS and analyze its performance in terms of packet delivery cost under various network topologies, cell types, and multicast users' distributions. Furthermore, for the evaluation of the scheme, we consider different transport channels for the transmission of the multicast data over the UMTS Terrestrial Radio‐Access Network (UTRAN) interfaces. Finally, we propose a scheme for the efficient radio bearer selection that minimizes total packet delivery cost. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
25.
Armando Soares João C. Silva Nuno Souto Filipe Leitão Américo Correia 《Wireless Personal Communications》2007,42(2):225-246
MIMO systems promise high performance gains over conventional single antenna systems. To accomplish high data rates over wireless
links the use of multiple transmit and receive antennas is an alternative that does not require any extra bandwidth. It has
the potential to address the unprecedented demand for wireless services, particularly for the Multimedia Broadcast Multicast
Service (MBMS). This service supports downlink streaming and download-and-play type services to large groups of users. From
the radio perspective, MBMS includes point-to-point (PtP) and point-to-multipoint (PtM) modes. New proposed MBMS related enhancements
in the physical layer specifications and their effects on resource requirements are presented in this paper, such as the use
of High Speed Downlink Packet Access (HSDPA) to broadcast/multicast video streaming using the Deficit Round Robin (DRR) scheduler
algorithm as a way to maintain an acceptable QoS for all the users. Other improvements, based on the use of MIMO including
macro-diversity, are independent of the mode used and are dependent on deployment scenarios, but can yield substantial reduction
in resource demand. 相似文献
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介绍了多媒体广播组播服务(MBMS)和IP多媒体系统(IMS)的融合方案,分析了该方案的系统架构设计和关键步骤的信令流程.最后,在该方案基础上提出了应用实例,并对该方案的应用前景进行了展望. 相似文献
29.
MBMS移动多媒体广播/组播业务,基于广播业务的一对多的特性,为了保证数据传输过程的保密性,流媒体传输过程的安全问题已受到普遍关注.一个具有安全保护功能的RTP协议即SRTP协议系统的实现不仅有利于对抗网络安全攻击,而且能够为用户提供隐私、加密和认证保护.SRTP协议通过对RTP数据分组中的有效载荷部分进行加密,从而实现RTP数据分组的机密保护.实验结果表明在MBMS中应用SRTP协议有效的保证了MBMS业务的机密性. 相似文献
30.
张保峰 《电信工程技术与标准化》2008,21(2):18-22
手机电视是在手机上收看电视节目的业务。本文阐述了手机电视业务的实现方式、标准、发展、运营模式及存在的问题等方面,提出了相关的建议,并对其前景进行了展望。 相似文献