Abstract
In this paper, Beam Pattern Scanning (BPS), a transmit diversity technique, is compared with two well known transmit diversity techniques, space-time block coding (STBC) and space-time trellis coding (STTC). In BPS (also called beam pattern oscillation), controlled time varying weight vectors are applied to the antenna array elements mounted at the base station (BS). This creates a small movement in the antenna array pattern directed toward the desired user. In rich scattering environments, this small beam pattern movement creates an artificial fast fading channel. The receiver is designed to exploit time diversity benefits of the fast fading channel. Via the application of simple combining techniques, BPS improves the probability-of-error performance and network capacity with minimal cost and complexity. In this work, to highlight the potential of the BPS, we compare BPS and Space-Time Coding (i.e., STBC and STTC) schemes. The comparisons are in terms of their complexity, system physical dimension, network capacity, probability-of-error performance, and spectrum efficiency. It is shown that BPS leads to higher network capacity and performance with a smaller antenna dimension and complexity with minimal loss in spectrum efficiency. This identifies BPS as a promising scheme for future wireless communications with smart antennas.
Highlights
Transmit diversity schemes use arrays of antennas at the transmitter to create diversity at the receiver
In Space-Time Block Coding (STBC), data is encoded by a channel coder and the encoded data is split into N unique streams, simultaneously transmitted over N antenna array elements
A comparison was preformed between space-time block coding (STBC), STTCQPSK and Beam Pattern Scanning (BPS) transmit diversity techniques in terms of network capacity, BER/FER performance, spectrum efficiency, complexity and antenna dimensions
Summary
Transmit diversity schemes use arrays of antennas at the transmitter to create diversity at the receiver. Antenna elements should be located far enough to achieve space diversity and when antenna arrays at the base station (BS) are used in this fashion, directionality benefits are no longer available [1,2,3] This reduces the network capacity of wireless systems in terms of number of users. BPS has been introduced as a powerful transmit diversity technique capable of enhancing both wireless network capacity and probability-of-error performance with minimal cost [10,11,12,13] In this scheme, antenna elements located at the distance of half a wavelength form an antenna array. BPS technique offers higher quality-of-service and network capacity with a minimal cost of spectrum efficiency This introduces BPS as a powerful scheme for future generation of wireless communications with smart antenna arrays. This generates a high probability-of-error performance at the receiver
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