A simple gradient sign algorithm for transmit antenna weight adaptation with feedback

• Published in: IEEE transactions on signal processing Vol. 51; no. 5; pp. 1156 - 1171
• Main Authors: Banister, B.C., Zeidler, J.R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-05-2003; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Adaptation; Adaptive arrays; Algorithm design and analysis; Algorithms; Antenna feeds; Applied sciences; Baseband; Bit error rate; Channels; Detection, estimation, filtering, equalization, prediction; Exact sciences and technology; Fading; Feedback; Information, signal and communications theory; Mathematical analysis; Performance analysis; Receivers; Receiving antennas; Signal and communications theory; Signal, noise; Studies; Telecommunications and information theory; Transmitting antennas; Vectors (mathematics); Fading channels; Performance evaluation; Array signal processing; Bit error rate; Adaptive beamforming; Algorithm; Adaptive method; Beam forming; Simulation; Transmitting antenna; transmit beamforming; Antenna array; Gradient method; stochastic gradient algorithms
• ISSN: 1053-587X; 1941-0476
• DOI: 10.1109/TSP.2002.808104

In this paper, a simple algorithm for adaptation of the complex baseband weights of a transmit antenna array using feedback from the receiver is proposed and analyzed. The system utilizes stochastic gradient adaptation to maximize the power delivered to the receiver for a constrained transmission power, which provides both fading diversity and beam steering gain. Dual perturbed transmission weight vectors are time multiplexed onto the pilot signal, and the receiver generates feedback selecting the perturbed weight vector which delivers greater power. This feedback is used to provide weight adaptation at the transmitter, and this adaptation is shown to be an update by a coarse estimate of the gradient of the delivered power. The performance of the algorithm is analyzed in terms of convergence and tracking of an AR1 fading channel, with simulations confirming the analysis. Bit error rate (BER) simulations in a dynamic fading channel show that the algorithm outperforms previously proposed vector selection feedback, and in slower fading, the algorithm substantially outperforms diversity space time coding.