Hybrid wideband multipath self-interference cancellation with an LMS pre-adaptive filter for in-band full-duplex OFDM signal transmission

Abstract

A wideband multipath self-interference cancellation (SIC) system employing both dual-drive Mach–Zehnder modulator-based analog SIC and least mean square (LMS) algorithm-based pre-adaptive filter digital SIC is proposed and demonstrated for the cancellation of multipath self-interference (SI) and facilitation of in-band full-duplex (IBFD) orthogonal frequency-division multiplexing (OFDM) signal transmission. The multipath effect is an unavoidable challenge in SIC due to the dynamic and unpredictable properties in each path, as well as the need for separate matching components for compensating for each path. In this Letter, an LMS algorithm-based adaptive filter is used as a pre-equalizer to adapt and generate the matching signal to the closest approximate of the multipath SI signal. The adaptation is based on the minimization of the error signal generated from the matching signal and multipath SI signal in the LMS algorithm. With the introduction of the LMS adaptive filter to the analog SIC, an additional 9 dB cancellation improvement is obtained, resulting in a total of 32 dB cancellation depth over a cancellation bandwidth of 2.7 GHz at a center frequency of 1.65 GHz. To the best of our knowledge, the achieved performance is by far the widest cancellation bandwidth in a multipath SIC system, which is essential in a large bandwidth and high data rate transmission system. With the help of the proposed LMS adaptive filter digital SIC assisted analog SIC located at the remote node, power-efficient IBFD transmission of an OFDM signal through a 25 km fiber is experimentally demonstrated with a 6 dB bit error rate and 8% error vector magnitude improvements.

A Microwave Photonic 2 × 2 IBFD–MIMO Communication System with Narrowband Self-Interference Cancellation

“…The cancellation depth within the 200 MHz bandwidth range can reach 40 dB. Apart from the analog SIC method based on the dual-driver Mach-Zehnder modulator (DDMZM) [24], an adaptive filter employing the least mean squares (LMS) algorithm is constructed as a pre-equalizer to dynamically adapt and generate a signal closely resembling the multipath SI signal.…”

Scalable Photonic-Assisted Multipath Self-Interference Cancellation Based on Optical Frequency Comb

“…However, this element relies on a coupling lens system, and its structure will grow more complex as the number of inputs increases [24]. Furthermore, to simplify multipath systems, several digitally assisted multi-path SIC methods have been proposed based on a least square (LS) algorithm [25], recursive least square (RLS) algorithm [26,27], and least mean square (LMS) algorithm [28] etc. These methods require an additional transmitter system for digitally generating the reference signals.…”

Signal enhancement in wireless sensor networks based on adaptive filters

“…Maurya A. K. and other researchers have made a detailed study on the improved LMS adaptive filter algorithm, mainly by modifying the error equation in the traditional LMS to improve the model. Compared with the traditional LMS adaptive noise elimination model, the experimental improved model has higher signal-tonoise ratio and superior performance [16].…”