Matthias Holzbock

Stratospheric Optical Inter-Platform Links for High Altitude Platforms

Optical propagation simulations for the case of a laser optical link between two stratospheric High Altitude Platforms have been performed. The simulations, together with communications link budget calculations, show that high data rate communications between such platforms is feasible, at data rates up to several hundred Mbps, and optical transmit-power levels of less than 1W for a 500 km long inter platform path. Such data rates and power levels are close to the capabilities of current technology. The simulations have included use of known parameters of the optical properties of the upper atmosphere, in particular absorption by atmospheric aerosols, and atmospheric turbulence.

Design and validation of QoS aware mobile internet access procedures for heterogeneous networks

In this paper, the requirements for personal environments mobility are addressed from terminal and network perspectives. Practical mobility and Quality of Service (QoS) aware solutions are proposed for a heterogeneous network, comprising of satellite and terrestrial access networks connected to an IP core network. The aim, in adopting a heterogeneous environment, is to provide global, seamless service coverage to a specific area, allowing access to services independently of location. An important assumption is that nomadic user terminals attached to a particular segment should be able to exchange information with any other terminal connected to the network. This is to ensure transparency of device technology. Different communication scenarios are investigated in support of IPv4 and IPv6 operating on user platforms and over access segments. The heterogeneous network necessitates the need to perform handover between access segments to enable coverage extension and seamless connectivity. Handover procedures are analyzed, and an approach is presented that enables various operation and segment specific parameters to be taken into account when deciding upon the need to perform handover and in selecting the optimum access segment. In order to ensure transparency of network technology, the need for end-to-end QoS support is discussed, bearing in mind the deployment of both IntServ and DiffServ enabled routers in the core network. Following this, a new admission control scheme, named Gauge&Gate Reservation with Independent Probing (GRIP), is proposed. The paper concludes with a description of a laboratory testbed, which has been developed in order to verify the presented procedures, together with performance measurements of the handover and the GRIP algorithms.

System design for aeronautical broadband satellite communications

The paper discusses various aspects of aeronautical broadband satellite communications (AirCom). Market issues are addressed, and a range of relevant services is identified and classified. A structured overview of key issues and respective steps for the system design of an AirCom system is given. It is intended to provide a generalized baseline for a systematic AirCom design process and reflect some recent, ongoing and planned R&D activities in the field. This overview focuses on geographic coverage, constellation candidates and crucial terminal antenna issues.

ATM-based multimedia communication via satellite

Within the next years, a large number of new satellite systems for broadband multimedia communications will be developed, mainly for fixed terminals, but to a lesser degree also for portable and mobile terminals. The most important systems will be based on low earth orbit (LEO) satellite constellations with inter satellite links (ISLs), and will be seamlessly integrated into the environment of terrestrial broadband networks. Since most of the terrestrial broadband networks will be based on the Asynchronous Transfer Mode ATM, it is advantageous for the satellite networks to adopt the ATM transmission scheme and implement ATM switches on board the satellites. However, compared to communication in fixed networks, satellite communication is characterised by special constraints (limited bandwidth, propagation delay, transmission errors, dynamic network topology) requiring the development of a new ATM-based communication technology. In the paper, an ISL-based LEO satellite network for multimedia communication will be considered. Several relevant aspects will be discussed, such as the system architecture, the system requirements, and the protocol architecture. Since the users access the satellite network via a radio interface, an error control scheme and a multiple access scheme suitable for multimedia communication must be implemented. The aspects of TDMA- and CDMA-based medium access control are discussed. Further issues are ATM resource management, radio resource management, and ISL routing. Finally, methods for terminal antenna steering are addressed, and the demonstration of aeronautical multimedia communication via the ITALSAT satellite is described.

REVENUES AND PERFORMANCE OF GLOBAL SATELLITE AERONAUTICAL COMMUNICATIONS

In this paper we estimate the revenues that airlines can expect from passenger telephone and Internet services offered on North Atlantic flights, under the assumption of an existing wireless cabin infrastructure, supporting wireless Internet and GSM telephony. According to the expected usage of these services, to the aircrafts’ cabin configurations and to the North Atlantic routes split figures are also presented per aircraft type and for some major airlines serving these routes.

System design, capacity dimensioning and revenue estimation for aeronautical communications via satellite

The paper discusses various system aspects of commercial aeronautical broadband satellite communications (AirCom). An integrated global system design approach is presented, and key R&D issues along this path are discussed. Some focus is laid on geographic satellite coverage and constellation alternatives. A capacity dimensioning method for global aeronautical communications is developed, using a global flight database, and numerical results from computer simulations are presented. Finally, we estimate the revenues that airlines can expect from passenger telephone and Internet services offered on North Atlantic flights, under the assumption of an existing wireless cabin infrastructure, supporting wireless Internet and GSM telephony.

IP Based User Mobility in Heterogeneous Wireless Satellite-Terrestrial Networks

Thinking of future mobile communication from a user acceptance point of view, people are getting more and more used to personalised equipment accommodated for their own special needs. On the other hand a number of different access network (segment) solutions are currently used on local platforms, which increases the need of a transparent interworking between the access networks. In order to extend access areas not only beyond segment coverage, but also to collectively mobile networks like passengers in an aircraft, new network concepts are necessary. Especially such collectively mobile networks are likely to cross coverage areas. Practical user mobility solutions are proposed for a heterogeneous network, comprising of satellite and terrestrial access networks connected to an IP core network. Different communication scenarios are investigated in support of IPv4 and IPv6 operating on user platforms and over access segments. The paper concludes with a description of a laboratory testbed, which has been assembeld in order to verify the presented procedures, together with performance measurements of the handover algorithms during an in field vehicular trial.

Advances of aeronautical communications in the EU framework

This paper reports on the advancement in the research and development of aeronautical satellite communications within the EU framework. Starting from key aspects such as spectrum regulatory and marketing issues which affect the development of aeronautical communication systems, discussion on the motivation behind the two EU projects, ABATE and WirelessCabin and their interconnection then follows. ABATE concentrated on the development of an aeronautical communications system for flight routes in the European and Northern Atlantic regions. The enabling technology considered in ABATE is discussed. Major achievements and results obtained in the project are reported in this paper. These include the development of a powerful software tool based on a logical design methodology for aeronautical satellite communication systems as well as the characterization of the aeronautical channel through a series of channel measurement campaign and a demonstration of in-flight multimedia satellite communication. The evolvement from ABATE to WirelessCabin is then highlighted. The main objective and current development of WirelessCabin since the start of the project are presented. In particular, issues on electromagnetic compatibility between different electronic equipments on board the aircraft cabin are discussed. Networking aspects for mobility, QoS and VPN support are studied. Specifically, different scenarios for the location management and address assignment schemes for mobility and VPN support are discussed in detail.

Combined PAT algorithms for mobile multimedia satellite services

Next generation satellite services will offer high capacity links for multimedia applications. Mobile receivers for these future applications will use high gain antennas with a beamwidth of 5 degrees and smaller. These antennas require a precise pointing, acquisition and tracking (PAT) process to steer the antenna exactly towards the satellite direction. The channel characteristics at high frequencies, like fading and shadowing, seriously affect the steering algorithms. In the framework of SECOMS (Satellite EHF Communications for Mobile Multimedia Services) and ABATE (ACTS Broadband Aeronautical Terminal Experiment, both European ACTS projects) several field trials and service demonstrations have been performed for future wideband multimedia satellite services at higher frequency bands (20/30 GHz and 40/50 GHz). These experiments were performed using high gain antennas with various beamwidth in different scenarios and environments. This paper gives an overview of these experiments and describes the used antenna PAT algorithms. The measured propagation data allows the implementation of the effects of the land mobile satellite (LMS) channel in a detailed antenna pointing simulator.

EHF-band channel characterisation for mobile multimedia satellite systems

A measurement campaign is presented for high data rate satellite services at EHF-band using a land mobile terminal in a vehicle. A high-gain antenna with a beamwidth of 25/spl deg/ is used for reception. The antenna is controlled by a GPS-based steering processor. Dual narrowband as well as wideband measurements have been performed simultaneously using independent antennas and receiver equipment. The results of the measurements are presented. The data have been fitted to the Lutz (1991) model and the channel parameter are given.