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This paper studies the impact of voice traffic on the performance of packet data (PD) transmission in terrestrial trunked radio (TETRA) networks. Particular emphasis is given on the performance of applications characterized by occasionally transmitting small messages between a number of radio terminals and a fixed server while these terminals are also conducting group voice calls. Such applications are constantly increasing in TETRA networks, and so does the need to dimension and configure these networks to meet their reliability, delay, and loss requirements. However, the impact of group voice calls on PD transmission has not been sufficiently studied, and this constitutes the main motivation of our performance analysis. We present simulation results for a variety of practical scenarios, and we discuss how key performance indicators such as PD delay and loss rate are affected by the group call activity of the radio terminals. Our results can help in dimensioning and planning TETRA networks, particularly in determining the number of PD terminals that can be supported in a cell for a given traffic profile and for quality-of-service requirements. Index Terms--Land mobile radio cellular systems, land mobile radio data communication, mobile communication, packet radio.

A reconfigurable space-time coding technique is investigated, for a high-speed downlink packet access multiple-antenna network, which combats the effects of antenna correlation. Reconfigurability is achieved at the link level by introducing a linear precoder in a space-time block coded system. The technique assumes knowledge of the long-term characteristics of the channel, namely the channel correlation matrix at the transmitter. The benefits of the proposed reconfigurable technique as compared to the conventional non-reconfigurable versions are evaluated via system-level simulations. In order to characterize the system-level performance accurately and, at the same time, use a feasible approach in terms of computational complexity, a suitable link-to-system interface has been developed. The average system throughput and the number of satisfied users are the performance metrics of interest. Simulation results demonstrate the performance enhancements achieved by the application of reconfigurable techniques as compared to their conventional counterparts.

In this paper, we introduce a network-based approach for access and interface selection (AIS) in the context of resource management in heterogeneous wireless environments (UMTS, WLAN and DVB-T). We focus on the optimization of resource utilization, while ensuring acceptable quality of service (QoS) provision to the end users. Our objective is to optimally manage the overall system resources and minimize the possibility of QoS handovers (non-mobility handovers). The adopted architecture applies to typical heterogeneous environments and network entities (Access Routers) are enhanced with extra functionalities. We propose an AIS algorithm that exploits the multihoming concept and globally manages network resources at both radio access and IP backbone networks. The algorithm can estimate near-optimal solutions in real time and we also introduce a novel triggering policy. We present simulation results of typical scenarios that demonstrate the advantages of our approach. System performance metrics, derived from the simulations, show minimum degradations in high load and congestion situations. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A variety of hybrid systems combining third-generation mobile communication networks with broadcast systems have been proposed for the delivery of multimedia broadcast multicast services (MBMS) to mobile users. The article discusses one of these alternatives, which involves the use of a geostationary satellite component for MBMS delivery. In particular, it proposes a radio access scheme for the satellite component of the system that features maximum commonalties with the standardized T-UMTS WCDMA- based interface. The ultimate advantage of this approach is more efficient delivery of MBMS as far as the mobile network operator is concerned. The required adaptations at the interface layers are described, and the radio resource management strategy that fulfills the particular requirements of the satellite system is presented. [ABSTRACT FROM AUTHOR]