Paolo Chini

Dynamic resource allocation based on a TCP‐MAC cross‐layer approach for DVB‐RCS satellite networks

Satellite communication networks can provide multimedia broadband services to fixed and mobile users in several scenarios where terrestrial networks are not present or where they need to be complemented. Moreover, satellite links can be useful to bypass crowded terrestrial networks, thus helping in reducing congestion. In such a scenario, characterized by a high propagation delay and a radio channel affected by losses, standard bandwidth allocation schemes prove to be inefficient when Transmission Control Protocol (TCP) is running. Hence, we propose a novel resource allocation scheme based on the cross-layer interaction between TCP and Medium Access Control (MAC) layers. The interest is here in achieving an efficient transfer of files by means of the FTP application protocol. Our scheme permits to avoid network congestion, to reduce the average file transfer time and to achieve a fair sharing of resources among competing flows. The allocation technique has been applied to an Interactive Satellite Network (ISN) based on the DVB-RCS standard with a group of fixed satellite terminals, which communicate with a Netivork Control Center (NCC) through a geostationary bent-pipe satellite, according to a classical star topology. Results are obtained through a network simulator. Copyright (c) 2006 John Wiley & Sons, Ltd.

Dynamic Resource Allocation based on a TCP-MAC Cross-Layer Approach for Interactive Satellite Networks

DVB-RCS is an open standard for interactive broadband satellite services. According to the standard, interactive terminals communicate with the network control center through the return channel adopting MF-TDMA. In this scenario, classical bandwidth allocation schemes do not take into account TCP evolution, leading to sub-optimal performance when TCP-based traffic share the return link. A cross-layer approach, based on exchange of information between not-adjacent layers, can help to improve efficiency. This paper presents an innovative allocation algorithm based on a cross-layer interaction between TCP and MAC layers. Such an algorithm aims to synchronize the requests of resources with the TCP transmission window trend. The obtained results show that our scheme permits both to reduce the delay, to increase the utilization of air interface resource and to achieve a fair share of resources among competing flows

Cross-layer management of radio resources in an interactive DVB-RCS-based satellite network—(invited paper)

Recently, the request for multimedia broadband services via satellite has been rapidly increasing. We envisage a group of terminals that have to transmit (uplink) to a Network Control Center (NCC) via a geostationary bent-pipe satellite; the NCC is interconnected to the Internet through a router. Terminals employ the DVB-RCS standard to communicate with the NCC. Due to both the intrinsic propagation delay and the presence of a lossy radio channel, the Transport Control Protocol (TCP) is particularly inefficient in the satellite scenario. Therefore, we propose a novel cross-layer mechanism where resources are allocated by the Medium Access Control (MAC) layer at the NCC depending on the TCP behavior at remote terminals. Moreover, the MAC layer can also intervene on the TPC data injection rate to avoid system congestion. Simulation results show that: (i) our scheme prevents the occurrence of TCP timeouts (due to the satellite network congestion), thus improving the utilization of radio resources; (ii) it reduces the mean file transfer time for ftp applications with respect to a classical allocation scheme. This paper has been carried out within AT contract No. 507052) belonging to the 6-th framework of the European Commission. Index Terms:Satellite Networks, DVB-RCS, TCP.

A mobile satellite systems frame work for network centric applications

Commercial Satellite Communications (SATCOM) provide a range of services to network centric military applications. In addition to fixed satellite systems, a wide range of mobile satellite systems are suitable to support mobile services to emergency applications and communications on the move. The unique capabilities such as robustness, wide area coverage and broadcast/multicast capabilities make SATCOM a preferred choice for worldwide war fighter communication services. In this paper we survey current mobile satellite networks and services, encompassing recent standardization efforts and currently available and planned systems characteristics. An efficiency comparison is also presented to emphasize the impact of different design parameters in selecting a GEO or LEO based system architecture.

Resource Management in Hybrid DVB-RCS and WiFi Networks

Satellite networks are an attractive solution to provide broadband communication services anytime, anywhere with quality of service support. The aim of this paper is to study the integration of GEO satellite networks, DVB-RCS- based, with WiFi networks. This is particularly important in emergency scenarios where reliable satellite networks could be integrated with WiFi systems for local mobility support. In this paper, a combined-dynamic resource management scheme, CRA & A/VBDC, is investigated for the satellite segment to support VoIP and FTP elephant connections. A corresponding QoS differentiation is considered in the WiFi segment, based on the IEEE 802.11e standard; in particular, a suitable traffic class mapping is proposed for an efficient interconnection of the DVB- RCS segment with the WiFi one. The obtained results prove the efficiency achieved by the proposed dynamic approach as the number of terminals increases, the good performance obtained with Scalable TCP and the importance of the proposed traffic mapping in the WiFi segment.

QoS Support in Hybrid WiFi and DVB-S Networks

The aim of this paper is to investigate QoS in a hybrid satellite-WiFi network and to study mapping issues in the interconnection of these two segments. We have considered both a DVB-RCS-based satellite network and a wireless system based on IEEE 802.11e. Both TCP-based and UDP-based traffic flows are considered. In the satellite network, a dynamic bandwidth allocation scheme is used that is managed by a network control center: differentiated QoS support is guaranteed by the use of separate queues at the Gateway for distinct traffic classes. An ns-2-based simulator has been implemented to study the hybrid scenario. We have been able to show the impact of both different traffic mapping solutions in the interconnection of the network segment and different channel condition on the TCP performance.

QoS in hybrid WiFi and DVB-RCS networks

Nowadays there is an increasing need of broadband communications anytime, anywhere for users requiring multimedia services with quality of service support. This paper deals with the integration of GEO satellite networks and terrestrial wireless networks. Our interest is for a DVB-RCS GEO system integrated with a WiFi terrestrial segment based on the IEEE 802.11b and e standards. Such a scenario is particularly relevant for the provision of multimedia interactive services in emergency areas. In this paper, we focus on a satellite DAMA strategy with related MAC buffer sizing, on the support of FTP and VoIP traffic flows, and on the traffic mapping with the WiFi segment. An ns-2-based simulation tool has been developed that permits to achieve a fine understanding on TCP-MAC interactions in terms of frame and buffer sizes. Finally, referring to the Skyplex DVB-RCS payload on board of HotBird 6 GEO satellite, simulation results have permitted to show the good utilization of resources with the considered DAMA strategy for FTP traffic flows.

A Comparison Framework for MSSs

Satellite networks can provide the possibility to access communication services on wide areas of the earth; this characteristic coupled with the support of user mobility allows satellite networks having unique features well suited for different scenarios, like: land mobile, aeronautical, maritime, transports, rescue and disaster relief. Mobile satellite networks, however, entail crucial technological challenges, such as: link budget, antenna technologies for both the satellite and the mobile terminal, and efficient utilization of the radio spectrum. This paper investigates these aspects and provides an analytical framework that can be used to evaluate the characteristics of satellite networks in the design phase as well as for their operational phase. In particular, quantitative comparisons are presented here for different systems in terms of supported user density, bandwidth efficiency, and mobility aspects.