Mobile Communication / Antennas & Propagation
In mobile communications the design of the antenna and its interaction within a radio environment is of great importance in both determining what signal power as well as unwanted noise power and interference is received at the mobile terminal as well as at a base station/access point. This is essential information in terms of allowing mobile systems to have appropriate receive power capabilities and maintain minimal error on digital data transmitted. Demand for high data capacity over the wireless air interface is ever increasing, where work carried out at CCSR investigates intelligent techniques with which to increase data throughput over the air interface for several applications.
Recent activity in this area of antennas and propagation includes:
- Intelligent antennas at the mobile, the intelligent quadrifilar helix antenna (IQHA) for use in dual mode land mobile to satellite and terrestrial communications, multiple input multiple output (MIMO).
- MIMO channel modeling and characterisation, in particular with focus upon satellite MIMO channels extending the expertise of satellite communications in the centre.
- Frequency selective surfaces that can isolate or block specific frequencies within an enclosed area that can be applied to interference mitigation and wireless security.
- Ultra wideband (UWB) antennas and propagation, particularly in the area of array processing for time of arrival and body area networks.
- Modeling of diffraction over hilly terrain for digital broadcasting and other fixed link applications.
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More information can be found about antennas and propagation at CCSR by contacting Dr Tim Brown.
Research in MIMO Communications
MIMO is currently used in wireless local area networks (WLANs) as a means to increase data throughput though it is sure to appear in forthcoming terrestrial mobile technologies outdoors. The diagram below demonstrates its principle by creating separate sub-channels or “tubes” over the air interface by applying phased array weights that can steer the direction an antenna radiates its energy. This can also be done in several modes so as to generate different channels of radiation and make tubes in the air space. This then increases the data capacity or throughput.
For MIMO to provide high throughput, it requires many scatterers so that they create many paths from which the array weights can create these “tubes”.
Research at CCSR has interest in both design of antennas for MIMO and also characterisation of radio channels to evaluate their MIMO potential. In particular this has focused on the intelligent quadrifilar helix antenna (IQHA) and the satellite MIMO channel shown below. The IQHA has a great deal of interest as a compact antenna for MIMO compared to larger antennas spatially separated. Further to this CCSR has found results from modelling the satellite MIMO channel using dual polar circular polarised antennas at both ends, which due to the polarisation has provided extra scattering that is otherwise not available in such a link with only a limited number of scatterers on the ground.
