共查询到19条相似文献,搜索用时 140 毫秒
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蜂窝网络中移动性管理的目的是根据用户的位置查找、识别和跟踪用户,以向他们提供蜂窝服务。GSM和UMTS网络的主要功能是为其用户提供高质量的蜂窝服务。这意味着如果用户在靠近移动终端或在丘陵地区使用他们的设备,则这些设备都必须被GSM蜂窝网络覆盖。通信的稳定性、可靠性都是蜂窝网络中移动性管理的最终目标。文章讨论了5G超密集小蜂窝网络两种类型的移动性技术、位置管理和切换。 相似文献
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在3G蜂窝网络中,归属位置寄存器(HLR)、网关位置寄存器(GLR)、访问位置寄存器(VLR)组成三级数据库结构。当漫游移动用户在GLR中的位置信息错误或过时时,对该用户的入呼将失败。由于三层结构设计中,GLR与HLR的通信一般涉及国际长途信令,使得GLR的故障恢复设计非常重要。为尽可能减少对长途资源的占有,对GLR故障恢复提出了一种新的算法并对其性能作了相应的分析。 相似文献
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由于终端及个人的移动性,我们需要随时跟踪用户的位置。位置管理是移动通信领域中一类非常重要的问题,属于移动性管理的范畴。就位置管理而言,网络的目标是为了准备到移动用户的路由。为此,网络必须记住每个用户在什么地方注册,当前在什么地方活动。因此,一个简单的解决方法是在数据库中存储每个用户标识符,他是否注册的指示,以及在哪儿可以找到他的信息。在实际应用中,位置管理主要包括两个部分。第一部分是位置更新,即移动终端向网络报告其当前位置信息,由网络进行更新。第二部分是位置查询,即当需呼叫某个用户时,由网络提供其位置信息。 相似文献
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位置管理或移动性管理是移动计算研究领域的一个具有挑战性的问题.我国及其他国家目前正在使用的个人通信网络如GSM、IS-41中,用两层数据库HLR/VLR支持位置管理.在这些网络中,每当移动台从一个位置区LA(Location area)移动到另一个位置区,其基本的位置管理策略(简称"基本策略")不管是否必要均立即进行位置更新操作,因而造成系统资源的极大浪费,降低了系统的性能.本文给出一种带门槛的环形搜索策略(简称"门槛环形策略")——将位置区分成环,设定一个门槛(整数),当移动台越过的位置区的环数没有达到门槛时,系统不进行位置更新操作,以减少位置管理的费用.在假定移动台的呼入是一个泊松过程,移动台在各个位置区的逗留时间是符合一般概率分布的随机变量的条件下,推导出在两次呼入之间移动台处于各位置区环的概率及移动台所越过的位置区环数公式,给出了"门槛环形策略"的位置管理费用小于"基本策略"的条件. 相似文献
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《Digital Communications & Networks》2019,5(2):111-120
The Very High Frequency band (VHF) currently used for aeronautical communications is becoming congested, and future Air-to-Ground (A/G) communication will require much greater use of data communications. For meeting future capacity requirements in aeronautical communications, we propose two new approaches one of which is a cognitive radio based A/G communication network that provides dynamic spectrum access to airplanes to overcome the spectrum scarcity problem in the VHF band. Another approach involves use of a new spectrum in the Ultra-High Frequency band (UHF) to create a new A/G link. In this paper, we propose and investigate the possibilities for developing a spectrum sensing approach to detect idle band in the VHF spectrum and analyze the possible interference between future L-band Digital Aeronautical Communication System (L-DACS) and legacy aeronautical systems. 相似文献
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A new technique for designing three-dimensional cellular systems for VHF air/ground communications is proposed to solve the problem of frequency congestion for air traffic control (ATC) and flight services. In VHF air/ground communication systems, a radio line of sight (RLOS) between the aircraft and ground station must exist. The frequency reuse distance is reduced by using the radio horizon to block cochannel interferences. In the proposed system, cells of different sizes to cover different altitude ranges are separated by different reuse distances. With nine groups of channels, the altitude range from 740 ft to 45000 ft can be covered without interference. The proposed system utilizes the spectrum efficiently by covering a certain airspace according to a well-organized plan with the minimum number of frequency channels and cell sites. Thus, it has more frequency reuse than the current systems 相似文献
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Bala Rajagopalan 《Mobile Networks and Applications》1996,1(3):273-285
There is an emerging interest in integrating mobile wireless communication with Broadband ISDN based on the ATM technology. Many issues arise when such integration is attempted. This paper addresses the problem of mobility management, i.e., that of tracking the current ATM addresses of mobile terminals and sustaining active ATM connections as mobiles move. The paper presents some architectural options for integrating wireless access to ATM networks and highlights an architecture based oninterworking devices to provide transparent mobility support in existing ATM networks. Location management and handoff solutions for this architecture are then presented. Also, how procedures for multiprotocol transport over ATM networks may be adopted to perform location management is described.A version of this paper appeared in the proceedings of ACM Mobicom '95. 相似文献
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The Global System for Mobile Communications (GSM) is widely recognized as the modern digital mobile network architecture. Increasing market demands point toward the relevancy of securityrelated issues in communications. The security requirements of mobile communications for the mobile users include: (1) the authentication of the mobile user and Visitor Location Register/Home Location Register; (2) the data confidentiality between mobile station and Visitor Location Register, and the data confidentiality between Visitor Location Register and Visitor Location Register/Home Location Register (VLR/HLR); (3) the location privacy of mobile user. However, GSM does not provide enough security functions to meet these requirements. We propose three improved methods to enhance the security, to reduce the storage space, to eliminate the sensitive information stored in VLR, and consequently to improve the performance of the system. Proposed methods include an improved authentication protocol for the mobile station, a data confidentiality protocol, and a location privacy protocol. The merit of the proposed methods is to improve but not to alter the existing architecture of the system. Furthermore, this study also performs computational and capacity analyses to evaluate the original GSM system and proposed approaches on a comparative basis. 相似文献
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