IEEE Workshop

Exploitation of Higher Frequency Bands in Broadband Aerospace Communications

EHF-AEROCOMM

New Orleans City

November 30, 2008

The exploitation of unexplored higher frequency bands will be a challenge in the future of aerospace communications. In fact, spectrum portions currently employed for satellite networking (L, S, C, Ku, and Ka band) are almost saturated and the push towards the usage of increasingly higher frequency bands has become a crucial issue. Some proposals for the exploitation of V-band (31-60 GHz) and W-band (75-110 GHz) are being issued. In 1983, a preliminary investigation aimed to realize a satellite experiment by means of a 90GHz radiometer has been presented by Heel and Kietzmann of DLR (Germany). In the recent past, experimental activities about the exploitation of W-band have been carried on by Italian Space Agency (DAVID Data Collection Experiment) and are being currently on-going (WAVE missions). WAVE experiment forecasts also the launch of a W-band payload embarked on a stratospheric platform (AeroWAVE mission), considering a very interesting opportunity of extending the use of higher frequency bands also for HAPs and other aeronautic carriers different from satellites.
The exploitation of higher frequency bands for the provision of commercial services presents some clear advantages but also some uncertainties. Millimetre waves domain represents a very large and uncontaminated spectrum region, almost "interference free". Therefore, wide bandwidth portions can be profitably allocated for high-bit-rate transmission. In such a perspective, the "Gigabit connectivity", truly a "must" for future-generation satellite networks targeted to residential broadband services, would become a realistic objective.
Nevertheless, we are not speaking about a desert meadow. Dangerous areas of uncertainty and risk are present that must be carefully investigated in order to avoid technological and market failures. Recent research activities evidenced relevant issues to be solved in the design of the W-band physical layer (phase noise, high Doppler shift, nonlinear distortions, and problems in carrier recovery). Moreover, the strong uncertainty about physical channel characterization may represent another potential "black hole" in the usage of W-band in aerospace connections. Effects of clouds, gases, and atmospheric turbulence on digital satellite transmissions at 90GHz are not still well defined and realistically modelled (very few data are available in open literature). Finally, another open issue concerns with the higher layers of the ISO-OSI diagram. In fact, PHY-layer solutions targeted to provide high data rate transmissions with lower and lower bit-error-rates are currently under investigation. But a question could arise, i.e.: are transport protocols (like satellite-TCP) able to support very high capacities of the order of some Gbit/sec? Could be mitigated in some way the effects of the round-trip-time (very high in geostationary satellite connections) that represent the true bottleneck limiting aerospace connection capacity?
The workshop is a unique event in order to discuss open issues about higher frequency bands in satellite communications and to answer to some of the crucial questions asked before. The expected outcome of the workshop is to make people coming from space industry from scientific and academic world and from national space agencies to cooperate together in a wide and open community, whose task is to explore and exploit unexplored frequency bands with potentialities and drawbacks still to be investigated. A contribution to standardization activities in the field is expected too.