Uplink ground-based beamforming with multiplex on feeder link and fast adaptive algorithm for weights optimization

The uplink ground-based beamforming (GBBF) with multiplex on feeder link and fast adaptive algorithm for weights optimization is studied in this paper. With the methods of code division multiplex (CDM) and wavelet packet division multiplex (WPDM) against the bottleneck problem on the limited transformation bandwidth and the big number of channels on feeder link, the spectral efficiency for feeder link can be improved obviously. The CDM is applied to separate each channel through orthogonal spreading sequences and improve the spectral efficiency up to multiple times. With orthogonal sub-carriers lapped in frequency domain, the WPDM has a higher spectral efficiency than the frequency division multiplex (FDM). Different from the least mean squares (LMS) algorithm, the constrained stability least mean squares (CS-LMS) algorithm provides a weights optimization recursive formula with adaptive step size updated automatically according to the signal transformation environment. As a result, with the CS-LMS algorithm, a faster convergence rate can be obtained especially under strong interference or time-varying environment, such as some satellite mobile communication scenarios. Simulation experiments shows, the uplink GBBF with multiplex on feeder link and fast adaptive algorithm for weights optimization leads to high spectral efficiency and good convergence performance.