QoS Guarantees in Heterogeneous Systems Consisting of IP Core Networks with Satellite Access

This paper aims at investigating the issue of differentiated QoS provision to services over a heterogeneous terrestrial-satellite infrastructure. In particular, the implementation of a dynamic mapping of the main service classes offered by IP IntServ and DiffServ models over satellite bearer services is investigated.Objective of the research is to enable mobile subscribers to access broadband services offered within a fixed IP core network, through satellite links. This has to be performed while still guaranteeing the same Quality of Service (QoS) offered by the IP IntServ and DiffServ models over the terrestrial segment. In such an environment, the considered traffics derive from multimedia applications and are characterised by real-time and non-real-time constraints as well as variable (VBR) and constant (CBR) bit-rate profiles.     

Introducing the Adaptive-QoS Idea into Multi-Tier UMTS Systems: The Lessons Learned

In an integrated terrestrial-satellite system exploiting W-CDMA air interfaces, such as the future UMTS, we conduct an in-depth research on radio resource management techniques for the support of multimedia applications with quality guarantees. The multi-bearer transmission coupled with a multitier coverage has the potentiality of allowing the effective exploitation of the radio resources while guaranteeing an adaptive quality to all end-users. Nevertheless, it still remains to be clearly understood how good they cope with typical features of next-generation multimedia cellular systems, such as soft handoff. This paper tries to contribute to this issue by reporting the lessons learned during a performance assessment study on a simulation platform of a UMTS system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Transport and control issues in multimedia wireless networks

It is not an easy task in the UMTS environment to effectively design the transport and the management of traffic belonging to multimedia teleservices among those defined by ITU Recommendations, due to the hard communication requirements which this kind of application can call for. In this paper the results of an overall research work, dealing with an effective management of multimedia and multi-requirement services in enhanced third-generation mobile radio systems, are presented. The contemporary use of several bearers, one for each traffic component of the service, is proposed as a reference scenario for the transport of multimedia services in future mobile radio environments. The effectiveness of this choice is guaranteed by providing for innovative control techniques, on top of a PRMA-based access protocol, ad-hoc developed to recognise and jointly manage the different parts of a unique multimedia traffic. For this aim, a two-level priority (static and dynamic priorities) mechanism is proposed to be adopted by the higher protocol levels of UMTS for the adptation of call set-up, channel access, handover, and admission control procedures to the nature of multimedia services and for optimising the sharing of radio channel resources and the management of the reservation buffer. Achieved results demonstrate that the priority-based mechanism shows good performance especially during periods in which the system traffic load is high and well reacts to the worsening of multimedia service quality, both in terms of information loss and synchronisation of its different traffic components.     

DVB-H Systems: Quality-Based Active Handoff Assisted by UMTS Return Channels

Digital Video Broadcasting for Handheld terminals (DVB-H) is a new standard developed by DVB Project consortium to enable the delivery of broadcast transmissions to mobile terminals (such as, cellular telephone, PDA, pocket PC, etc.). Being the DVB-H network characterized by a cellular structure, a key issue to avoid the service interruption in these systems is the design of effective handoff procedures. This paper introduces a novel seamless handoff approach for DVB-H networks, which is designed to reduce the user terminal power consumption and to make the handoff algorithm be driven by the quality of the user received signal. This implies the adoption of a method based on the constant monitoring of the Modulation Error Rate (MER), instead of standard RSSI-based procedures. Additional advantages in terms of power saving derive from the use of an Active Handoff procedure that exploits the UMTS return channel as an interaction channel. The proposed scheme has been successfully tested and obtained results make us confident that this can be an interesting research direction to investigate in the view of effective DVB-H handoff protocol design.     

Improving QoS and throughput in single- and multihop WLANs through dynamic traffic prioritization

Nowadays, research efforts are being put into the design of effective mechanisms to provide service quality differentiation in IEEE 802.11-based wireless LANs. In this article we analyze the effects of augmenting the contention-based channel access mechanism of IEEE 802.11e through the assignment of dynamic traffic priorities, that adapt to either the application's quality requirements or the network congestion status. The aim is to show the effectiveness and robustness of the proposed dynamic mechanism in a wireless ad hoc network, in both single-hop and multihop scenarios, under variable traffic and network load conditions.     

A fair cooperative content-sharing service

Wireless cooperative content sharing, based on the synergistic use of cellular and short-range technologies, has recently gained much interest from academic and industrial communities. Besides energy saving and information transfer delay reduction, this paradigm can enable a significant reduction in cellular bandwidth usage, which also means monetary saving for users. In fact, such a cooperation is usually opposed by network and service providers, because it strongly reduces their potential profits. This paper deals with the provider perspective, too. In particular, a “mediated cooperative behavior” is proposed and analyzed within a scenario of short-range wireless file-sharing. The basic idea is that providers offer the possibility to users of cooperatively downloading contents, and increase their own profits because more users are attracted by such a service. Indeed, by participating in the devised service, users both avoid a (possibly expensive) stand-alone download of the desired product, and benefit of a special group-discount. The costs (and download tasks) distribution among users is based on a cooperative game theoretic model. Indeed, suitable solution concepts are applied to provide a fair solution, acceptable by all users, and hence to overcome the limitation of traditional optimization approaches to costs (and tasks) distribution.     

Traffic management techniques to face the effects of intrinsicdelays in geostationary satellite networks

A new scheme for the management of real-time traffic over high-latency broadband satellite networks is described. Early studies on this topic have been reported by Iera, Molinaro and Marano (see IEEE J. Select Areas Commun.,, vol.18, p.2393-2403, 2000), with reference to an integrated terrestrial-satellite platform. In this paper, further enhancement is introduced into the traffic management scheme with a view to both the reduction of intrinsic impairments caused by the adverse operational environment and the achievement of better performance levels and QoS guarantees. A real-time traffic handling strategy, including distributed connection admission control (CAC) and traffic resource management (TRM) schemes, is harmonized with an in-band signaling technique for burst-based bandwidth request and with an effective policy for the allocation of radio resources. Furthermore, the impact of traffic reshaping at the satellite terminal on the CAC-TRM technique is tested. Added features reduce the adverse effects of the long propagation delay across the satellite link and show outstanding effectiveness in improving CAC-TRM performance and network resource efficiency, while matching service quality requirements. The main reason for the improved performance of the overall management scheme is the adaptability to different traffic profiles conveyed over satellite links     

Providing Throughput Guarantees in 802.11e WLAN Through a Dynamic Priority Assignment Mechanism

Supporting real-time and interactive traffic in addition to traditional data traffic with a best-effort nature represents a constantly rising need in any kind of telecommunications environment. The IEEE 802.11 based WLAN (Wireless Local Area Network) environment does not represent an exception. This is why at different protocol layers, and primarily at the MAC layer, many efforts are being put by both the research community and the standardization bodies to design effective mechanisms for user QoS (Quality of Service) differentiation. Although early results are coming into sight, such as, for example, the IEEE 802.11e standard release, still a thorough research activity is required. Aim of the present paper is to contribute to the cited research issue by proposing an improvement to the “static” traffic prioritisation mechanism foreseen by the IEEE 802.11e MAC (Medium Access Control) protocol. This latter shows a twofold drawback. First, there is no certainty that QoS requirements relevant to a given application are always fulfilled by the “statically” associated priority. Second, resource requests of the applications are not adapted to the (usually highly) variable traffic conditions of a distributed WLAN environment. The algorithm we propose is specifically tailored to “dynamically” assign 802.11e MAC priorities, depending on both application QoS requirements and observed network congestion conditions. It is carefully designed, implemented into a system simulation tool, and its highly effective behaviour assessed under variable traffic and system conditions. Antonio Iera graduated in Computer Engineering at the University of Calabria, Italy, in 1991 and received a Master Diploma in Information Technology from CEFRIEL/Politecnico di Milano, Italy, in 1992 and a Ph.D. degree from the University of Calabria, Italy, in 1996. From 1994 to 1995 he has been at the Mobile Network Division Research Center, Siemens AG Muenchen, Germany to participate to the CEC Project “RACE II 2084 ATDMA (Advanced TDMA Mobile Access)” under a “Commission of European Communities Fellowship Contract in RACE Mobility Action”. He has been with the University of Reggio Calabria, Italy, from 1997 to 2000 as Assistant Professor, and from 2001 to 2005 as Associate Professor. Currently, he is Full Professor of Telecommunications at the same University. In 1995 and in 1996 he has been the recipient of an IEEE Paper Award for the papers presented at the IEEE International Conference on Universal Personal Communications ICUPC'95, and an IEICE/IEEE Outstanding Paper Award for the paper presented at the IEEE ATM Workshop'99, respectively. He served as member of Technical Program Committees of several International Conferences, and in 2003 he has been co-Guest Editor for the special issue “QoS in Next-generation Wireless Multimedia Communications Systems” in the IEEE Wireless Communications Magazine. His research interests include QoS control and resource management in Personal Communications Systems and Enhanced Wireless and Satellite Systems. Giuseppe Ruggeri received the degree in electronics engineering from the University of Catania, Italy, in 1998. He received the Ph.D. degree in electronics, computer science and telecommunications engineering with a dissertation on “Advanced Methods to Improve the QoS in VoIP Systems Based on VBR Speech Coders”. His interests include the field of adaptive-rate voice transmission for IP Telephony applications, and support of Quality of Service in heterogeneous wireless networks and WLAN-3G interconnection-integration . He is currently Assistant Professor in the Department of Computer Science, Mathematics, Electronic and transportation systems (DIMET) at the University “Mediterranea” of Reggio Calabria. His mail address is ruggeri@ing.unirc.it. Domenico Tripodi received M.S. degree (cum laude) in electronic engeneering from the University ‘Mediterranea' of Reggio Calabria, Italy in 2003. He won a post-degree scholarship from CNIT in 2004, and he is currently at CNIT Research Unit of Reggio Calabria. His reasearch interest are in the area of QoS provisioning in Mobile Ad-Hoc Networks.     

The Role of HAPs in Supporting Multimedia Broadcast and Multicast Services in Terrestrial-Satellite Integrated Systems

New-generation telecommunications systems are expected to meet the rising user exigencies of mobility and ubiquitous access to multimedia services. As a consequence, 3GPP consortium has introduced the Multimedia Broadcast and Multicast Service (MBMS) concept into 3G/beyond-3G networks. Supporting MBMS in next generation hybrid wireless platforms becomes a challenging issue due to high traffic load deriving from both signaling message exchange and data transmission between multicast sources (BM-SC) and end users. Therefore, in this context, key research issues are surely: effective exploitation of the limited radio spectrums available, coordination of users accessing radio resources, as well as provisioning of desired QoS guarantees. Given the high mobility profiles typical of UMTS users, it clearly appears that the cited target performance can only be achieved through networking solutions based on an overlapped terrestrial-HAP-satellite coverage. An inter-working scenario where HAPs operate in synergy with the UMTS terrestrial and satellite segments seems to be the most promising solution to provide mobile users with MBMS services. Our work, dealing with architectural design options, takes into account many metrics relevant to aspects, such as: frequency allocation, costs in terms of resource utilization, signaling traffic load, number and location of customers, reliability, possible retransmission paths, user mobility, and QoS.Giuseppe Araniti received a degree in Electronic Engineering from the University of Reggio Calabria, Italy, in 2000. He received the Ph.D. in Electronic Engineering from the same University, in March 2004. He is currently a junior researcher at the D.I.M.E.T., of the University of Reggio Calabria, Italy. His major area of research is the traffic and resource management in third and fourth generation mobile radio systems.Antonio Iera graduated in Computer Engineering at the University of Calabria, Italy, in 1991 and received a Master Diploma in Information Technology from CEFRIEL, Italy, in 1992 and a Ph.D. degree from the University of Calabria, Italy, in 1996.Since 1997 he has been with the University of Reggio Calabria, Italy, first as an Assistant Professor and then as an Associate Professor. Currently, he is Professor at the same University. His research interests include Personal Communications Systems, Enhanced Wireless and Satellite Systems.Antonella Molinaro received a degree in Computer Engineering from the University of Calabria, Italy, in 1991, a Master degree in Information Technology from CEFRIEL, Italy, in 1992, and a Ph.D. degree from the University of Calabria, Italy, in 1996. Since 1998 she has been an Assistent Professor first at the University of Messina and then at the University of Calabria. She is currently an Associate Professor at the University Mediterranea of Reggio Calabria, Italy. Her interests include mobile radio systems and inter-working wireless-wired networks.