This paper presents an analysis for optimal design
of switched beamforming applied to a linear array for wireless
communication systems. The beam switching scheme provides
coverage of a given sector in azimuth and controls the sidelobe
level simultaneously. The analysis was developed considering
arrays composed of Quasi-Yagi elements. The model assumes a
user moving in the azimuthal direction under a constant velocity
and with an estimation of the signal-to-noise ratio (SNR) at the
mobile user (MU). The radio base station applies the beam that
yields the best performance during transmission. The decision is
based on the feedback information received from the MU. The
goal of the analysis is to determine the best trade-off between the
array size and number of feedback bits necessary to maximize the
SNR at the receiver. The results show that a compromise between
the number of beam-pointing directions and the array size should
be taken into consideration for a wireless communication system
design.

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Linear Array Design with Switched Beams for Wireless Communications Systems

This study devises a simple mathematical model that predicts the number of beams that maximizes system capacity for different WCDMA network configurations. The ideal number of beams to be synthesized within a cell by an antenna array (AA) with a fixed number of elements at the base station (BS) is primarily influenced by the average antenna gain and the relative power allocated to the secondary common pilot channel (S-CPICH) transmitted on each directional beam. It is shown that for a fixed maximum Node-B transmit power the overall system capacity gain in the downlink (DL) provided by switched beam forming (SBF) decreases with the cell size, that is, as more power is needed by the pilot channels to assure coverage. Predictions from our model are compared with simulation results obtained from a detailed dynamic system level simulator in order to be validated. A remarkably good match is observed.

M.A. Ingale

Papers

Impact of the Pilot Signal per Beam on the Ideal Number of Beams and Capacity Gain of Switched Beam Forming for WCDMA