Gianni Pasolini

SHINE: Simulation platform for Heterogeneous Interworking Networks

The interworking of different radio access technologies aimed at providing always the best service to mobile users is the future of wireless communications. Many researchers are already investigating appropriate architectural solutions, coexistence problems, common radio resource management algorithms and other topics concerning this issue. In this paper we illustrate a simulation platform developed in our research group to investigate the performance and to test new management strategies of such interworking networks. Our purpose, however, is not to show the details of our tool, that would be useless for the reader; we aim, on the contrary, at providing those researchers who are facing the realization of a similar simulation tool with the main general criteria to develop a flexible and efficient simulation platform.

WLAN call admission control strategies for voice traffic over integrated 3G/WLAN networks

Heterogeneous networks integration and interwork- ing, with particular reference to third generation (3G) cellular networks and wireless local area networks (WLANs), is a challenging issue for the early future wireless communications world. In our researches we consider the opportunity to convert those circuit switched voice flows that would be blocked by UMTS for resource saturation into voice over IP streams to be served through the WLAN connection. In order to increase voice users satisfaction when WLAN available resources are critically falling off, in this paper we investigate, by means of a simulation approach, different WLAN call admission control strategies within the context of 3G-WLAN integrated networks. I. INTRODUCTION Heterogeneous networks integration and interworking, with particular reference to third generation (3G) cellular networks and wireless local area networks (WLANs), is a challenging issue for the early future wireless communications world. Provided that the WLAN hot spot is within the 3G network coverage and that the final user is equipped with a dual mode terminal, integrating the two technologies, thus increasing the pool of available resources, would considerably increase both users satisfaction and networks utilization efficiency. In the last few years several projects were dedicated to the issue of 3G/WLAN interworking networks (e.g., (1)) and many papers appeared, investigating specific aspects mainly related to architectural/signalling issues (e.g., (2)) and vertical handover (e.g., (3)). Besides the data users exchange between UMTS and WLAN, in this paper we focused our attention on the possi- bility to serve by means of the WLAN technology those voice calls that within the hot spot region cannot be served by the 3G network (and would therefore be blocked) in case of saturation of its radio resources. Obviously a format conversion from circuit-switched (CS) voice flows into packet-switched (PS) Voice over IP (VoIP) flows (and vice versa) is needed in order to allow the radio network switching (see (4) for details on the network architecture). The benefits of 3G/WLAN interworking are here inves- tigated with reference to the Chinese TD-SCDMA UMTS This work was carried out in the framework of VICOM Project funded by MIUR. technology (5) and to the upcoming IEEE802.11e (6) WLAN technology. In this paper, in particular, the users satisfaction level provided in a realistic scenario by the integrated network is assessed by means of a dedicated simulation platform. Three simple but effective call admission control (CAC) strategies for the WLAN are implemented in our simulation platform in order to prevent WLAN overloads. Their performance have been derived and compared. The paper is outlined as follows. In section II the WLAN CAC strategies are described, in section III the scenario under investigation is introduced; in section IV and in section V the simulations settings and the related numerical results are reported and finally, in section VI the final conclusions are drawn.

DVB-S Gap Fillers for Railway Tunnels

Broadband connectivity to passengers of high speed trains by means of a satellite link requires the realization of gap fillers (GFs) to extend the service coverage inside railway tunnels. In this paper we investigate the performance of GFs based on the digital video broadcasting-satellite (DVB-S) technology in a reference railway tunnel whose propagation characteristics have been derived by means of the ray tracing technique. The channel impulse response has been investigated in order to derive DVB-S performance in terms of bit error rate at different train position along the tunnel. Then, the statistical properties of the received power inside the tunnel has been assessed, showing a log-normal distribution with a strong correlation in time. Finally, based on the statistical behavior of the fading, an analytical expression of the system outage is provided and the transmitted power required to guarantee a given coverage has been derived.

PHY Level Modelling for Network Simulations: Strategies, Approximations and Costs

In this paper several strategies are presented aimed at reducing the burden of physical level simulations within the context of network simulations, and their characteristics are discussed, both in terms of time efficiency and accuracy. The simulation of an IEEE802.11a network is also presented as a case study in order to highlight the peculiarities of each strategy and the impact on accuracy of correlation in both the time and frequency domains

Selection Diversity for Bluetooth in the Presence of IEEE802.11G Interference

In this work we propose an analytical framework aiming at studying the coexistence issue between Bluetooth (BT) and IEEE802.11g in fading channels. With the goal to improve the BT performance in the presence of interference, we consider a non coherent selection diversity (SD) scheme at the receiver side. In fact, due to its simplicity, the SD scheme is fully compliant with the low-cost requirement of BT equipped devices. Through the analysis, we derive the BT performance in terms of packet error probability averaged over Ricean fading when IEEE802.11g acts as interferer, taking into account all physical and medium access control (MAC) aspects. Results show the performance improvement and the reduction of the minimum coexistence distance due to the adoption of the simple SD receiving scheme

Exploiting diversity for coverage extension of Bluetooth-based mobile services

This paper investigates the impact of diversity reception techniques on the performance of Bluetooth (BT) packet transmission in wireless channels with fast fading and shadowing to improve the coverage extension. We firstly derive a tight parametric exponential approximation for the instantaneous bit error probability (BEP) in additive white Gaussian noise with parameters dependent on GFSK modulation format according to the BT standard. Then, from this expression, we derive the mean block error probability (BLEP) for DH packets transmission in Rayleigh fading channel by adopting different diversity reception techniques, such as selection diversity (SD) and maximal ratio combining (MRC). In particular, the joint impact of the diversity order, the combining techniques and the block length on the BLEP, is shown. For both MRC and SD schemes, we also obtain a tight and invertible bound on the BLEP, that enables us to analytically evaluate the quality of service expressed in terms of outage probability in channel affected by fading and shadowing and, as a consequence, the impact of multiple antennas on the system coverage.

TCP Performance of MC-CDMA Systems with Partial Equalization in Correlated Fading Channels

This paper addresses the performance evaluation of multi-carrier code division multiple access systems both at physical and TCP levels. A partial equalization technique improving the performance at physical layer in the presence of interference is investigated and its impact on the performance at upper layer is studied. The results are obtained through an integrated simulation platform carefully reproducing all main aspects affecting the quality of service perceived by the final user. Works of this nature enable a deep investigation of the real gain perceived by the user provided by proper signal processing techniques at the physical level.

Analytical evaluation of throughput for a bluetooth piconet with MAC level link adaptation

In this paper a MAC level Link Adaptation (LA) strategy to be implemented in a Bluetooth piconet is investigated: the performance level that can be achieved in terms of throughput is derived and the comparison with the case of no LA is performed.Suitable definitions of the performance figures related to throughput are given and, starting from the knowledge of the physical level performance obtained via simulation, their analytical evaluation is performed in both the cases of LA and no LA.All aspects related to the propagation characteristics of the environment, the modulation/demodulation and coding/decoding techniques, and the multiple access strategy are taken into account in an integrated way; moreover a reference scenario analytically characterized along with a realistic scenario have been considered for the performance level assessment.The analytical results have been compared with simulation outcomes which confirm the validity of the approach adopted.