Cancelation of LNA distortions in in-band full-duplex systems
Résumé
In‐band full‐duplex (FD) transceiver has been recently proposed to double the channel efficiency. The main challenge of such FD transceiver consists in achieving an efficient self‐interference cancelation. This fact is prevented by receiver imperfections such as the oscillator phase noise, the analog‐to‐digital converter noise, and the nonlinear distortion (NLD) of the low‐noise amplifier (LNA). This paper deals with the mitigation of the NLD of the receiver's LNA by proposing a new FD transceiver architecture. Based on the fact that the NLD coefficients are changing slowly over time, then the period between two successive estimations of the NLD coefficients may be relatively long. Motivated by this fact, a new wire connection is introduced between the transmitting circuit and the receiving one in order to neglect the wireless channel effects when estimating the NLD coefficients. If the estimation of the NLD coefficients is required, then the transmitter stops the wireless transmission and sends a sequence to the receiver via the wire channel. This procedure does not affect the throughput rate since it is repeated every several frames due to the slow time‐variation of the NLD coefficients. The estimated coefficients are used to attenuate the effects of NLD at the receiver's side, where an auxiliary chain is introduced to act as reference to the receiver's ordinary chain. As a proof of the concept, intensive simulations have been done using realistic data parameters. Our numerical results corroborate the efficiency of the proposed architecture, where the NLD of LNA is highly attenuated leading to an efficient self‐interference cancelation.
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