Open-Loop Beamforming for Frequency-Division Duplex Mobile Wireless Access

Abstract

An open-loop eigenbeamformer is designed for frequencydivision duplex (FDD) mobile wireless access. In this approach, the base station transmitter does not need any channel feedback nor does the mobile receiver need knowledge of the channel or the transmit beamforming weights. The transmit beamforming weights in the downlink are generated based on the estimate of the uplink spatial covariance matrix. The base station assigns multiple beamforming weights for transmission in the signal subspace, and the mobile combines signals from multiple dimensions to preserve the received signal strength against fast channel fading. Simulation results show that, when the distance between the uplink and downlink signal subspaces is negligible, the open-loop beamformer can improve the performance of FDD systems without spatial covariance matrix transformation from uplink to downlink frequency.

Improving Isolation in Monostatic Simultaneous Transmit and Receive Systems Using a Quasi-Symmetrical Self-Interference Cancellation Architecture

“…Current communication systems have operated in a mutually exclusive manner, requiring either two frequency bands to operate simultaneously (i.e., Frequency Division Duplexing, FDD) or two time slots to operate on the same band (i.e., Time Division Duplexing, TDD) [1], [2]. In contrast full duplex (FD) systems presents an efficient use of time-frequency resources by enabling simultaneous transmission (Tx) and reception (Rx) in the same frequency band.…”

“…Nevertheless, several research indicate that multiple cancellation stages must be implemented in the analog and digital domains to target SI and achieve the desired isolation levels [10], [11], [12] for both monostatic and bistatic FD designs. In fact, across the STAR literature, most works, [13], [14], have recognized the following as the main stages for SIC: (1) the antenna stage, which involves making space or design modifications to the physical antenna to reduce the coupling between the transmit and receive antennas; (2) the RF stage, which involves implementing RF SIC circuits; and (3) the digital stage, which involves the use of probabilistic channel models.…”