Abstract
Broadband fixed wireless access (BFWA) systems have been recognized as an effective
first kilometer solution for broadband services to residential and business customers. The
large bandwidth available in frequency bands above 20 GHz makes radio systems with
very high capacities possible. Users can be offered bit rates in the order of several
hundred Mbit/s, making (in terms of capacity) such radio links an alternative to optical
fibre in many cases. High capacities BFWA links can be used to serve individual users
directly or function as a backbone for lower capacity systems (both wire line and
wireless) for local distribution of data. In addition, wireless always offers the freedom of
broadband being away from the fixed access point.
At mm-wavelengths the signals are sensitive to time dynamic propagation degradation
caused by precipitation, vegetation and reflections/multipath from e.g. building surfaces.
BFWA need to cope with location and time dependent interference and employ
techniques such as interference cancellation and adaptive modulation and coding to
optimise throughput during varying traffic load conditions. Multiple input multiple output
(MIMO) and space-time coding, as well as adaptive (smart) antennas require knowledge
of the channel dynamics as well.
The objective of this master thesis is to develop a realistic time dynamic channel model
for BFWA operating above 20 GHz utilising adaptive physical layer techniques. The
channel model developed represents the time varying wideband channel impulse response
including degradations due to multipath propagation, rain attenuation and vegetation
fading. The channel model is suitable for simulating mitigation techniques for
interference between base stations as well as adaptive modulation and coding techniques.
The Maseng-Bakken statistical dynamic model of rain attenuation was adapted to model
the rain attenuation. The dynamic vegetation effect was modelled as Nakagami-Rice
distribution with K-factor depending on wind speed. A generic tapped delay line model
was developed, in which the number of taps depend on maximum tap delay.
This thesis is based on work in the project BROADWAN (www.broadwan.org), partly
funded under the Information Society Technologies (IST) priority of the European
Commission Sixth Framework Program.
