Henrik Andersson and Mikael Landing

Licentiate Thesis, Signals and Systems, Uppsala University, February 1998. 

Background:

The digital mobile telecommunications industry has grown beyond all expectations. In order to cope with the explosive increase in the number of users, methods to increase the spectral efficiency, i.e. the number of users per MHz and square kilometer, are required. This can be achieved by improved algorithms for coding and modulation, improved equalizers and by other means.

Considerable research is also done on how to utilize the spatial dimension. An obvious approach is of course to decrease the cell size. This is however associated with great costs. The spatial dimension can also be exploited by means of adaptive antennas. The most common approach is then to place the "smart" antenna at the base station site.

Abstract:

An adaptive antenna for the receiver base station part of the DCS1800 system has been designed, built and evaluated. The antenna works as a testbed to gather experience of adaptive antennas techniques for base stations and to draw conclusions on the usability of base station adaptive antennas in mobile telephone systems. Primarily the system should reduce C/I-problems, i.e. increase the traffic capacity by suppresssion of interfering signals.

In this thesis the architecture, the different building blocks, simulations and measurements for the adaptive system are presented. Measurements show that a C/I improvement compared to an omnidirectional antenna of upt o 35 dB is achieved.

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