Mobile to Satellite Communications
A key player in CCSR’s work is in mobile to satellite communications from which several UK and EU grants have been received in this area. This page gives some of the key highlights from recent projects in this area with appropriate contacts included.
The satellite communications team have been fully involved in a FP6 EU project called ANASTASIA, which started in April 2005 and runs for 4 years. The project, coordinated by Thales Avionics in France, combines expertise from 29 partners from large industrials, SMEs, universities and research centres from 12 countries.
Inputs to the project are:
As an example of a research result produced by CCSR within the FP6 MOWGLY is the accurate characterization of the 2nd order statistics (Doppler spectrum) of the multipath fading process, by making precise assumptions regarding wave propagation in the 3 spatial dimensions and the types of antennas used in this type of system (directional tracking antennas).
Based on statistical modelling of the arriving waves, new equations that describe the Doppler spectrum of the multipath fading process were derived, and were shown to have a significant impact on the link performances; relative to previously considered but inaccurate models. The coloured curves in the figure below illustrate examples of the derived autocorrelation function (of the multipath fading process), for different antenna azimuth and elevation angles; assuming antenna beam-width of 2 degrees, and vehicular speed of 300km/h. The black curve shows the autocorrelation function predicted by the classical Jakes model.
The channel correlation times predicted by the two different models differ by 3 orders of magnitude, and this makes a pronounced difference on the link-performances, as it is illustrated in the figure below. It is observed that that the produced channel model predicts additional link performance degradations of 2.5dB relative to an AWGN channel. This is because of the increased fade correlation time leading to complete bursts/frames being attenuated by deep-fading events. With the classical Jakes model, on the other hand, the channel decoder benefits from time-diversity within on FEC block.
These results, which appear in the December 2007 issue of IET communications, have been adopted by the DVB-RCS technical group in the specification of a ‘mobile-RCS’ standard, which is presently under development.
ANASTASIA – EU Project
- The foreseen increase of air traffic will require improvement to operational capacity and safety of the air transport system.
- New communications and navigation systems will be required for future more fuel efficient operations (4DT management).
- More efficient use of scarce and expensive spectrum is required.
- To propose new Communications, Navigation and Surveillance systems and architectures to fit with these new needs, based on satcom and satnav technologies.
- SP1:- Project Coordination (Thales Avionics-France)
- SP2:- Aircraft Needs & Requirements (Airbus-France)
- SP3:- Navigation Space Based Technologies (Thales Avionics-France)
- SP4:- Communication Space Based Technologies (Thales Avionics-UK)
- SP5:- Operational Characterisation & Evaluation (DLR-Germany)
- SP6:- Dissemination (Dassault Aviation-France)
Mobile to Satellite and Broadcasting Channels
CCSR is collaborating with major European satellites and avionics industrial actors (e.g. Thales-Alenia Space, Inmarsat, Thales Avionics), through European research programs and industrial contracts, for carrying out research into next generation mobile communications and broadcasting satellite systems. One such system specifies the adaptation of fixed satellite broadcasting and interactive standards (DVB-S2/RCS), that operate at very high frequency bands (Ku/Ka), for supporting broadband services onboard commercial vehicular platforms, such as aircrafts, vessels and trains. CCSR, through its involvement in the FP6 MOWGLY project has analyzed and proposed solutions to several challenges related to the design of such system:- Adaptation of the DVB-S2/RCS standards for mobility management.
- Accurate channel modeling of the multipath fading process.
- Regulatory constraints coming to effect due to the requirement of small dish antennas
- Fading effects, especially in the railroad environment where the LOS is regularly obstructed by physical structures.
People
The satellite communications team contains some 10 researchers, comprising academics, research fellows, visiting research fellows, and research students:
