Statistical analysis of communications range and reliability in the presence of interference

A statistical method is developed for analysis of interference in land mobile communications systems. Reduction of communication range and degradation of system reliability are calculated. This method can be used for cases in which a desired signal is transmitted by a base station (or mobile unit) and received by a mobile unit (or base station) and is interfered with by a signal transmitted either by a fixed station or a mobile unit. The spatial probability distribution of mobile units is considered. The method is applicable to any frequency band for which path loss statistics are known, and an example of this method is given which calculates reduction in communication range, area, and degradation of communication reliability for different values of splatter protection, and distributions of mobile units.     

A secure and efficient conference scheme for mobile communications

A growing application area in mobile communications is mobile teleconferencing, in which a group of mobile users collaborate in an interactive procedure, such as a board meeting, a task force, a scientific discussion, or even a virtual classroom. Wireless communications transmit conversations via radio, making them more susceptible to eavesdropping and unauthorized access than are conversations carried via wires. Therefore, it is crucial to ensure confidentiality and authenticity in mobile teleconferencing. When deploying secure services in mobile teleconferences, it has to be taken into account that the mobility of users is usually built on portable devices with limited computing capability. A secure conference scheme for mobile communications needs to be executed efficiently on portable devices. We propose a new secure and efficient conference scheme for mobile communications. Based on a modular square root technique, this scheme is secure against eavesdropping, impersonating, and tracking attacks and allows a participant to join or quit a mobile teleconference dynamically. In addition, the scheme is particularly efficient on the mobile user's portable device because the mobile user needs to perform only single modular multiplication plus encryptions and decryptions of a secret key cryptosystem.     

Simulation of mobile fading channels

Many aspects of a mobile radio system are basically determined by the propagation characteristics of the channel. Therefore, an understanding and good knowledge of mobile radio channels is essential for the analysis, design, and operation of wireless systems. It allows the successful development, evaluation, and testing of any current or future communication system, whether it is for cellular mobile telephony, for radio paging, or for mobile satellite systems. This article tries to present a simple and efficient way to simulate mobile channels for development and testing of mobile wireless systems, using some of the commercial circuit-analysis and simulation programs. So, in parallel with an overview of fading-channel propagation mechanisms and aspects, compact simulation models are given that can effectively be used for further analysis and understanding of the operation of mobile fading channels.     

Modeling and performance evaluation of a cellular mobile network

An analytic model of cellular mobile communications networks with instantaneous movement is investigated in this paper. This cellular mobile network is showed to be equivalent to a queueing network and furthermore the equilibrium distribution of this cellular mobile network is proved to have a product form. The explicit expressions for handoff rates of calls from one cell to another, the blocking probability of new calls and handoff calls are then obtained. Actual call connection time (ACCT) of a call in this cellular mobile network is characterized in detail, which is the total time a mobile user engages in communications over the network during a call connection and can be used to design appropriate charging schemes. The average ACCT for both complete call and incomplete call, as well as the probability for a call to be incomplete or complete, are derived. Our numerical results show how the above measures depend on the new call arrival process for some specific reserved channels numbers in each cell. The results presented in this paper are expected to be useful for the cost analysis for updating location and paging in cellular mobile network.     

Ensuring mobile communication transmission quality in the year 2000

The traditional view of mobile telecommunications is to allow a customer to communicate away from his base. However, the vision for the end of the century is to make the mobile communication system the first choice for telecommunications. By the year 2000 there will be a large number of mobile systems operating in Europe, from the current analogue cellular systems to digital GSM cellular systems and potentially the Universal Mobile Telecommunication System (UMTS). The challenge is to ensure that customers, be they fixed or mobile, are provided with acceptable speech quality, no matter what system they are using and what it is interconnecting to. The paper examines the speech transmission parameters which effect the perceived quality and shows how they are apportioned within the mobile systems. It then goes on to show how the transmission quality can be optimised through the transmission plan to ensure that the customer perceives acceptable speech quality     

Mobile agents can benefit from standards efforts on interagentcommunication

On the road to the future success of mobile agents, we believe that interagent communication is an issue that has not been adequately addressed by the mobile agents community. Supplementing mobile agents with the ability to interact with other mobile or static agents, or agentified information sources is a necessity in the vastly heterogeneous arena in which mobile agents are called to compete. Thus, an agent communication language should be interpreted as a tool with the capacity to integrate disparate sources of information. We argue that mobile agents can benefit from current standards efforts on agent communication since the focus of such work is to address heterogeneity by defining a “common language” for communicating agents. We discuss ongoing research on agent-to-agent communication and present current standards efforts relevant to agent communication     

Analysis of a mobile-assisted adaptive location management strategy

Source messages intended for a mobile host can be routed in one of two ways. Either the source knows the direct route to the mobile host, and is informed of all location changes by the mobile host (informed routing), or the source directs messages to a home agent that forwards messages to the mobile host (triangle routing). When the rate at which the mobile host changes location and the rate at which messages are directed to the mobile host are known and fixed, we show that the optimal routing policy is described by a threshold rule that depends on the normalized differential cost of the routing techniques and the ratio of the source messaging to location update rates. Since thiscall to mobility ratio may not be knowna priori or may change slowly with time, we also derive an adaptive policy selection algorithm. The policy is derived from a maximum likelihood estimate of the call to mobility ratio based on observations of message arrivals and location changes. The algorithm is found to work well when there is a clear advantage to either triangle or informed routing. However, when the two routing schemes are relatively close in average cost, the algorithm performance is degraded by repeated policy reversals. For this reason, algorithms which use hysteresis and/or a preset preference (preference threshold) for one routing scheme or another were explored. It was found that neither hysteresis, nor preference threshold techniques alone performed well, but rather a combination of the two resulted in greatly improved performance for a wide range of values of the call to mobility ratio.     

Numbering and addressing in IBCN for mobile communications

Numbering and addressing issues arising in the integrated broadband communication network (IBCN) for the support of the Universal Mobile Telecommunication System (UMTS) and Personal Telecommunication Service (PTS) are discussed. Mobile communications services will allow a user to roam within a network. Thus, there will be a need to identify several types of objects (terminals, network points of attachment, users, customers premises networks or CPN, etc.). The mobility properties of these objects will necessitate dynamic bindings between their addresses and names. The situation is further complicated because the mobility may be embedded. A mobile user may employ a mobile terminal in a mobile CPN. Therefore, in UMTS and PTS there is a need for dynamic binding of various identifiers with location information data. The exclusive use of personal telecommunication numbers (PTNs) as dialing numbers (DNs) is proposed in IBCN for UMTS and PTS. That is, PTNs will be used (during dialing) for making calls to mobile terminals, mobile users, and fixed subscribers. When the personal communication service is not provided, the DN corresponds to the terminal number of the equipment (fixed or mobile) of the called subscriber     

A Random Access Protocol with Multi-Packet Reception for Infrastructure-Less Wireless Autonomic Networks

A random access protocol with multi-packet reception (MPR) capability for infrastructure-less wireless autonomic networks is introduced and analyzed. In these networks mobile nodes may communicate with each other directly without a central entity (base station), where each mobile node either will be in a transmitting mode or in a receiving mode or in an idle mode. The throughput per node and the packet retransmission probability depend exclusively on the MPR capability and the ratio of the transmission probability and the receiving probability of each mobile node. For a given ratio of the transmission probability and the receiving probability of each mobile node, throughput-delay performance increases with the increase of MPR capability. In the proposed infrastructure-less networks, mobile nodes can control the network traffic very precisely by controlling the three parameters. These three parameters are transmission probability, receiving probability and idle mode probability of each mobile node. Since each mobile node can control the network traffic very precisely to obtain the maximum throughput, the network is autonomic, i.e., self-optimizing. The optimum transmission probability of each mobile node to obtain the maximum throughput is evaluated. The throughput utility increases with the increase of MPR capability. On the other hand, the cost per mobile node also increases with the increase of MPR capability. Therefore the MPR capability should be optimized to provide reasonable trade-off between the throughput per node and the cost per mobile node. The results of this study may be used for a system design of an infrastructure-less contention-based multiple access schemes with MPR capability.     

移动代理技术在Ad Hoc无线网络中的应用研究

Ad Hoc无线网络是一组具有路由和转发功能的移动节点组成的一个多跳的临时性自治系统,是一种无中心的无线网络。现有的主动路由协议或者按需路由协议都不能很好地满足Ad Hoc网络的需要。介绍了Ad Hoc无线移动网络和移动代理技术。在分析了现有的2种路由协议后,提出了在按需路由协议中加入移动代理技术来增强Ad Hoc无线网络的性能。在这些结果的基础上,提出了移动代理通信协议。     

Prediction-Based Object Tracking in Visual Sensor Networks

This paper is to investigate the mobile object tracking in visual sensor networks. When visual sensors equipped with cameras are randomly deployed in a monitoring environment, many sensors are involved in covering the same mobile object. In a visual sensor network, images of the object may be captured by different sensors in different orientations simultaneously, and the captured images are then sent back to a base station or server. However, achieving full coverage for a set of selected characteristic points of an object invariably involves a great deal of redundant image data consuming the transmission energy for a visual sensor network. A novel approach is proposed to overcome this problem. The minimal number of sensors required for set coverage can be determined by predicting the direction and speed of the mobile object. Such sets are capable of covering the maximal number of characteristic points of view related to the mobile object at one time. The simulation results show that this approach reduces transmission cost while preserving the maximal coverage range of mobile objects.     

Home agent placement and IP address management for integrating WLANs with cellular networks

Seamless roaming between cellular networks (3G or upcoming 4G) and wireless local area networks can be provided using Mobile IP. However, GPRS/UMTS and 802.11-based WLAN networks have no native support for mobile IP. Mobile IP requires the deployment of home agents and a protocol between the mobile nodes, home agent, and corresponding nodes. We address the home agent placement and home address assignment issues for supporting mobile IP for heterogeneous roaming. Placement techniques for mobile IP home agents are presented including dynamic HA assignment in either WLAN or cellular network domains using the diameter mobile IP application. Next, we present several IPv4 home address assignment schemes for mobile nodes visiting in the WLAN domain such as NAT/NAPT traversal, reverse tunneling, and mobile VPNs. It is shown that HA placement and address management are orthogonal, and any combination is possible. Various architectures for both issues are evaluated against the optimal solutions     

Mobile communications

The principal problem faced by networks with mobile users is how to ensure that the service provider functions keep pace with the continually changing network state resulting from user mobility, without consuming large amounts of network resources in the process. Regardless of whether the users are mobile or stationary, all telecommunications networks must perform basic service provider functions such as controlling access to services, locating users, routing traffic, and accounting and billing for service use. However, in the presence of mobile users, all of these functions must be performed much more often and much more rapidly. Developing low-overhead high-performance service provider solutions has been and will continue to be a key area of research in mobile communications. This special issue on mobile communications comprises five articles, each of which covers a different aspect of mobile communications     

MIMO与MISO雷达定位精度分析

 在某些应用中需要使小型机动接收平台(飞机或舰船)对目标进行定位,该文利用基站阵列辅助小型机动平台定位目标,可构成多输入多输出(MIMO)和多输入单输出(MISO)两种工作模式。文中建立了几何模型,并分别在这两种模式下推导了目标相对定位精度的几何稀释(GDOP)的计算公式,分析了两种模式下影响GDOP的各种因素。仿真结果证明,MIMO模式下,目标的相对定位精度与目标方位角和小型机动平台位置均无关;阵列天线数目较大或小型机动平台离目标较远时,MIMO模式的定位精度高于MISO模式;当阵列天线数目较小且小型机动平台离目标较近时,MISO模式的定位精度高于MIMO模式。     

On the performance of error control coding with diversity formobile channels

Upper bounds on the bit error probability are applied to evaluate the error performance of coded systems over non-interleaved and partially interleaved Rician fading mobile channels. The correlation between successive received symbols is exploited to bound the error performance. The bound allows useful evaluation of coding gains on realistic communication systems without going into lengthy computer simulations. By further defining the maximum energy degradation factors, compact upper bounds are expressed in a similar way as on the fully interleaved or memoryless channels. The maximum energy degradation factors are computed for a wide variety of mobile channel conditions. These factors give an interesting evaluation of the fading conditions and may be used to design coded communication systems on mobile channels. Furthermore, independent space or frequency diversity may be taken into account in these bounds and it is shown that the energy degradation due to correlation is independent of this added independent diversity     

Load-Balanced Location Management for Cellular Mobile Systems Using Quorums and Dynamic Hashing

This paper presents a new distributed location management strategy for cellular mobile systems. Its salient features are fast location update and query, load balancing among location servers, and scalability. The strategy employs dynamic hashing techniques and quorums to manage location update and query operations. The proposed strategy does not require a home location register (HLR) to be associated with each mobile node. Location updates and queries for a mobile node are multicast to subsets of location servers, which change with time depending on the location of mobile node/querying node and load on the servers. Simulation experiments demonstrate that such dynamism prevents situations of heavy load on some location servers when mobile nodes are not uniformly distributed in space, or when some mobile nodes have their location updated or queried more often than others. Also, queries return the latest location information of a mobile node with a very high probability. The proposed scheme requires at most one unicast and two rounds of message multicasting for location update and query operations. All multicast messages have a small payload and are restricted to the high bandwidth wired part of the mobile network resulting in low communication overhead. Moreover, if a quorum of location servers gets overloaded, part of its load can be transferred to another lightly loaded quorum using dynamic hashing techniques.     

Selective Mobile Communication in Socially Sensitive Environments

In certain environments, the use of mobile phones must be curtailed for the sake of security or out of respect for others. We present a novel method for selectively controlling mobile phone services in such areas using a base station controller and a sequence of detection steps to identify when the mobile device is within the coverage area. A prototype for the method has been developed using commercial off-the-shelf and custom designed hardware and software subsystems. Key components in the prototype system are two directional antennas located at the entry to the controlled area with one antenna facing outwards and the other inwards. By using the proposed detection method, the base station controller is able to detect when a mobile station enters or leaves the controlled area. Experiments using a variety of detection sequences by the two directional antennas and associated white- and blacklists of allowable and disallowed devices, respectively, confirm that the prototype system is able to effectively control the use of mobile devices within the coverage area.     

利用中继提高小区高数据速率覆盖的研究

利用中继将传统蜂窝网络中基站到移动台的直接链路拆分成两跳或多跳,能够有效地克服路径损耗和阴影衰落的影响,从而提高小区高数据速率覆盖范围。对比分析在蜂窝网络中引入固定中继和移动中继2种形式,可以得出当小区中的用户随机分布并且用户数较多时,采用移动中继较为合适;在用户数较少或者用户服从均匀分布时,则应采用固定中继。     

Mobility management for VoIP in 3G systems: evaluation of low-latency handoff schemes

The introduction of IP-based real-time services in next-generation mobile systems requires coupling mobility with quality of service. The mobility of the node can disrupt or even intermittently disconnect an ongoing real-time session. The duration of such an interruption is called disruption time or handover latency, and can heavily affect user satisfaction. Therefore, this delay needs to be minimized to provide good quality of VoIP services. In this article, we focus on network-layer mobility and mobile IP since it is a natural candidate for providing such mobility. We evaluate different low-latency schemes based on mobile IP and compare their performances in terms of disruption time for VoIP services. Low-latency handoffs are performed by anticipating and/or postponing the mobile IP registration process. With these methods, disruption time is reduced to 200 ms in most considered cases.     

Building a signaling protocol architecture for future mobile networks

Third-generation mobile systems are emerging. These systems will support a unified user access to a variety of services, including the existing mobile and fixed network (PSTN, N-ISDN) services, the enhanced multimedia and multiparty services envisaged for broadband networks, and personal communication services as well. The role of signaling is predominant in building a flexible, efficient, and evolving system. The aim of this paper is to provide a framework for developing a signaling protocol architecture for future mobile networks. The study especially focuses on the universal mobile telecommunication system (UMTS). Within this framework various design and operational requirements imposed on UMTS can be satisfied. A method to deal with the functional complexity of UMTS is provided. Mobile networks are viewed as integral parts of the broadband infrastructure and are built upon the IN principles.