Simon Hoff

Impacts of mobility on telecommunication and data communication networks

The article gives an overview of architectures and service aspects of existing networks and of those under development, with a special focus on mobility support. The authors discuss relations and differences of concepts being rooted in data communications and telecommunications, respectively, while paying special attention to the future role of the ISO/OSI reference model. They have subdivided the discussion based on different network classes with different degrees of mobility support; starting with fixed networks and finishing with networks enabling unlimited mobility of users and terminals. Finally, they describe the impact of unlimited terminal mobility on next generation communication networks. >

Computer-aided design and evaluation of mobile radio local area networks in RTI/IVHS environments

An approach to designing and evaluating protocols for a class of mobile radio networks is presented. Characteristics of these mobile radio LANs are described, derived from the background of road transport informatics/intelligent vehicle highway system (RTI/IVHS) applications. Performance measures defined as suitable for the requirements of multipoint intervehicle communication are based on the concept of the zone of relevance, an area around a vehicle where communication to relevant neighbors is required. The simulation environment MONET3 has been designed to evaluate these measures. Protocol design in MONET3 requires an exact model of propagation characteristics and a realistic model of road traffic. A measurement-based 60-GHz channel model developed for intervehicle communication is presented. MONET3 is interconnected to a dedicated traffic simulator, the Autobahn Simulator, originally designed for traffic engineering in RTI systems. A case study using the simulator is presented as an example. >

Simulative evaluation of a decentralized packet synchronization algorithm for short range mobile radio networks

Hoff et al. (Proc. IEEE Vehic. Techn. Conf., 1991) presented the transmit majority synchronization (TMS) algorithm for decentralized mobile radio networks. A first scenario was analyzed, and early simulation results were given. Detailed simulation results of TMS are presented with a comparison to a simple reference protocol called last received synchronization (LRS). A different performance measure, the synchronization time of two unsynchronized groups, is evaluated for different group sizes and vehicle speeds. TMS shows a good performance in any case. Looking at realistic group sizes and group ranges TMS needs fewer than three frames to synchronize the two groups completely. LRS is a trivial algorithm, which does not need any overhead. Nevertheless, the performance is worse than that of TMS. The synchronization time of LRS is 2 to 6 times larger than with TMS.<<ETX>>

Protocols for mobile short range communication based on transponders

A difficult task in road traffic is to increase safety. A possible solution for this is direct vehicle-to-vehicle communication, with transmission of a cars position, speed, and the drivers intention. Microwave transponder techniques have been proposed for such a system. The authors propose medium-access control protocols well suited for use with transponder techniques. Simulation results are very encouraging and indicate that global synchronization is not absolutely necessary to achieve high-performance channel access.<<ETX>>

Anonymous mobility management for third generation mobile networks

With the increasing use of mobile and nomadic communication devices requirements for security and privacy are rising as well. Following brief surveys of existing approaches to mobility management, general security considerations for UMTS and confidential storing of location information we introduce the ideas and concepts behind the new ‘anonymous subscriber’ method for UMTS, largely based on extended MIX networks. Finally, an application of this method conveniently employing the X.500 directory service infrastructure is described in some detail.

Integration of DECT and OSI to support mobile computing applications

DECT is the European standard for digital cordless telecommunication. Currently, most DECT systems have been established as standard PABX islands only. However, emerging application areas for DECT networks include data communication oriented mobile computing, making OSI conformance a major issue. This paper presents an approach towards the integration of mobile and fixed OSI-based networks using DECT as an example. Problems to be addressed include the registration, tracking and localization of mobile users roaming across cooperating DECT islands, in order to provide network-wide reachability and service access. We propose the ITU-T X.500 directory service as the natural solution to this problem. Using X.500 enables mapping of a DECT international portable users identity onto the users current location. After briefly introducing the DECT and the X.500 standard, different schemes for location management using X.500 are discussed. Once the X.500 directory system is established, it can be accessed and utilized by telecommunication services and mobile applications. Examples include wireless access to an overall X.400 service as well as trading services for X.9tr based mobile distributed computing applications.

Light-weight application layer architecture for short-range communication networks

This paper focuses on the application layer architecture for dedicated short range communication (DRSC) networks. The current state-of-the-art in the development of layer 7 structures and related objects Is presented. Exemplary methods of DSRC management are explained.<<ETX>>

Architectures for wireless ATM access

This paper presents a study on possible architecture design concepts for integrating wireless networks with ATM technology. We discuss four different solutions for wireless ATM access, starting with transparent cell-relaying over the air interface, thereafter focussing on ATM- and AAL-based interworking concepts, and finally discussing proxy approaches. Our analyses show that the performance benefits of higher layer interworking justify their comparatively high technical expenses.

Simulation and formal specification of protocols for mobile radio networks-an integrated approach

Formal description tools allow a very detailed specification and microscopic analysis of a communication system in a mobile radio network. Additionally the performance of protocols in a mobile radio environment has to be evaluated on a larger scale where several protocol instances communicate in parallel via the radio channel. The paper presents an integrated simulation approach combining the benefits of a detailed standardised protocol specification with the performance evaluation in larger environments. A prototype implementation and a case study show the feasibility of the integrated approach.<<ETX>>

Directory Services: Basis for Mobile Computing with DECT

DECT is the European standard for digital cordless telecommunication. Currently, most DECT systems have been established as standard PABX islands only. However, emerging application areas for DECT networks include data communication oriented mobile computing, making OS1 conformance a major issue. This paper presents an approach towards the integration of mobile and fixed OSI-based networks using DECT as an examplie. Problems to be addressed include the registration, tracking and localization of mobile users roaming across Cooperating DECT islands, in order to provide network-wide reachability and service access. We propose the ITU-T X.500 directory service as the natural solution to this problem. Using X.500 enables mapping of a DECT international portable users identity onto the user’s current location. After briefly introducing the X.500 and the DECT standard, different schemes for location management using X.500 are discussed. Once the X.500 directory system is established, it can be accessed and utilized by telecommunication services and mobile applications. Examples include wireless access to an overall X.400 service as well as trading services for X.9tr based mobile distributed computing applications.