Mattias Wennström (Frenne)

PhD Thesis, Uppsala University, ISBN 91-506-1619-6 Oct. 2002.

Dissertation in Signal Processing publicly examined on October 11, 2002 at 10.15 a.m.
Faculty Opponent: Prof. Michael A Jensen, Brigham Young University, Provo, Utah, USA.

Paper copies of the thesis can be obtained from Ylva Johansson, Signals and Systems Group, Uppsala University, Box 528, SE-75120 Uppsala, Sweden.

Outline:

The thesis deals with multiple antenna systems in wireless communications. The channel is assumed to be frequency flat and different transmission strategies are derived and compared. See an introduction to multiple antenna communication here.

Also an adaptive antenna testbed has been developed and measurement results are presented. For an overview of the testbed project, see this link

Abstract:

This thesis is concerned with the use of multiple antenna elements in wireless communication over frequency non-selective radio channels. Both measurement results and theoretical analysis are presented. New transmit strategies are derived and compared to existing transmit strategies, such as beamforming and space time block coding (STBC). It is found that the best transmission algorithm is largely dependent on the channel characteristics, such as the number of transmit and receive antennas and the existence of a line of sight component.

Rayleigh fading multiple input multiple output (MIMO) channels are studied using an eigenvalue analysis and exact expressions for the bit error rates and outage capacities for beamforming and STBC is found. In general are MIMO fading channels correlated and there exists a mutual coupling between antenna elements. These findings are supported by indoor MIMO measurements. It is found that the mutual coupling can, in some scenarios, increase the outage capacity.

An adaptive antenna testbed is used to obtain measurement results for the single input multiple output (SIMO) channel. The results are analyzed and design guidelines are obtained for how a beamformer implemented in hardware shall be constructed.

The effects of nonlinear transmit amplifiers in array antennas are also analyzed, and it is shown that an array reduces the effective intermodulation distortion (IMD) transmitted by the array antenna by a spatial filtering of the IMD. A novel frequency allocation algorithm is proposed that reduces IMD even further.

The use of a low cost antenna with switchable directional properties, the switched parasitic antenna, is studied in a MIMO context and compared to array techniques. It is found that it has comparable performance, at a fraction of the cost for an array antenna.

Keywords:

antenna array, calibration, mutual coupling, MIMO system, flat fading, nonlinear amplifier, switched parasitic antenna, analog beamformer, adaptive antenna testbed.

Related publications:

M.Wennström, T.Öberg and A.Rydberg
Effects of Nonlinear Distortion on Switched Multibeam FDMA Systems IEEE Transactions on Antennas and Propagation, vol.50, to appear
Abstract In Pdf (253K)

M.Wennström, T.Öberg and A.Rydberg
Effects of finite weight resolution and calibration errors on the performance of adaptive array antennas.
IEEE Transactions on Aerospace and Electronic Systems, vol.37, no.2, April 2001, pp.549--562
Abstract In Pdf (1590K)

M.Wennström, T.Öberg, J.Strandell, A. Rydberg and E.Lindskog.
Auto-Calibrating Adaptive Array for Mobile Telecommunications.
IEEE Transactions on Aerospace and Electronic Systems, vol.36, no.2, April 2000 .
Abstract; Paper in Postscript : compressed(gz) (94K) , uncompressed (953K). In Pdf (532K).

M.Wennström, T.Öberg and A.Rydberg
Analysis of Intermodulation Distortion on Log-Normal Shadowed WLAN Channels.
IEE Electronic Letters,Vol.36, No.9, pp.833-834
Abstract; Paper in Postscript : compressed(gz) (53K) , uncompressed (129K). In Pdf (121K).

M.Wennström. M.Helin, A.Rydberg and T. Öberg
On the Optimality and Performance of Transmit and Receive Space Diversity in MIMO Channels.
IEE Technical Seminar on MIMO Communication Systems: From Concept to Implementation.
London, December 12, 2001. Abstract ; Paper  in Pdf (232K)