George L. Lyberopoulos

Evaluation of location area planning scenarios in future mobile telecommunication systems

In third generation mobile telecommunication systems, signalling requirements due to location updating and paging are expected to be remarkable, mainly because of the huge number of mobile subscribers. Location area planning is characterised by the trade-off between the number of location updates and the amount of paging signalling that the network has to deal with. Location area planning should be based on criteria which guarantee that signalling load will be kept under tolerable levels. Various approaches for location area planning in a city environment—the worst case environment—are discussed in this paper. The simplest approach is the use of heuristic algorithms for approximating the optimum location area configuration. Then more complex scenarios which are based on geographical criteria (population distribution, highway topology, etc.) are investigated. Finally, user mobility characteristics are taken into account in the most complex scenarios. All scenarios are applied over a simulation model representing a city area, providing us with a very clear view of their performance characteristics.

Traffic model for third generation cellular mobile telecommunication systems

Traffic analysis for third generation mobile telecommunication systems should take into account a variety of services (e.g., voice, data, video) and “environments” (private, public outdoor, public indoor) as well as the user mobility behavior. The analytical traffic model presented in this paper incorporates all the above mentioned features. The model utilizes a set of simplifying assumptions regarding the distribution of certain random time intervals (e.g., call duration and “cell residence time”) and the handover arrival process. The core of the model focuses on the estimation of the cell border crossing rate and the time it takes a busy mobile user to leave a cell area. This allows for the estimation of the handover rate and the call duration within a cell, which in turn, utilizing an iterative method, allows for the calculation of the offered traffic load per cell. The major advantages of the model are: (a) the simple closed form solutions, (b) its independence from the applied radio resource management scheme, and (c) its accuracy. The latter is validated via a simulation tool, which accommodates different cell-layout scenarios over a geographical area, representing a ‘typical’ city center, modeled as a Manhattan grid.

Core network planning, optimization and forecasting in GSM/GPRS networks

Despite the wide theoretical and technical knowledge about the capabilities of Global System for Mobile communications (GSM) elements, there is no specific methodology for designing from scratch either the network sub-system (NSS) or the base station subsystem (BSS) parts or optimizing and expanding the existing NSS/BSS architecture, by forecasting future requirements in terms of network elements/resources. Thus, for an evolving network operator who wishes to have a network running at lower cost, offering a competitive quality of service (QoS) to its subscribers, a planning, optimization and forecasting tool (POFTool) is of pivotal importance. This paper aims at identifying the main features of a proper POFTool that efficiently supports dimensioning and optimization studies for a combined GSM/General Packet Radio System (GPRS) network and proposes an evaluation methodology which enables prioritization of alternative core network configurations according to operator-driven criteria.

Radio resource management schemes for combined GSM/GPRS mobile systems

Data services like Web browsing, e-mail and file transfer are becoming more and more popular in cellular systems. In contemporary systems like Global System for Mobile communications (GSM), data transfer has been circuit-switched, that is, physical resources are allocated to a user for the entire call/session duration. However, this is inefficient in case of bursty traffic, where bursts are separated by long intervals of inactivity. This has been the main reason for the introduction of General Packet Radio Service (GPRS), which on the one hand acts as a mobile access network to the Internet, while on the other hand it enables the operator to offer a wide variety of value-added services [Wireless Access Protocol (WAP) over GPRS, e/m-banking, e/m-commerce, push services, etc.] efficiently. However, in contemporary commercial implementations of GPRS the radio resource allocation algorithm does not take into account the Quality of Service (QoS)-related service characteristics—although such information is exchanged between the terminal and the network—and consequently all service requests are treated the same way (‘best effort’). In this paper, we propose and evaluate via a simulation platform various Radio Resource Management (RRM) schemes capable of differentiating the handling of ‘service requests’ (in uplink and downlink), taking into account the GPRS-related QoS parameters (precedence, reliability, delay, mean and peak throughput). The evaluation is performed for a range of voice (circuit-switched) traffic loads, number of Transmit Receive eXchange (TRXs), offered data (packet-switched) services characteristics, number of dedicated Packet Data Channels (PDCHs), and so on, taking into account the respective QoS requirements for both service types (circuit- and packet-switched). Copyright

Overview of the CCITT X.500 recommendations series

Abstract An overview of the salient features of the Directory Systems defined in the CCITT X.500 Recommendations series is given. We touch upon the models and concepts of the Directory, and overview the services and capabilities which they provide along with the underlying mechanisms through which these services can be obtained or propagated. A brief description of the various aspects concerning the operation and maintenance of the Directory Systems is also provided. The arising requirements for Directory services within the forthcoming mobile and broadband communication networks are presented. Taking into account the structure, the services and the capabilities which the X.500 Directory System can provide for, its possible use to future telecommunication networks is investigated.