On Performance of Analog Least Mean Square Loop for Self-Interference Cancellation in In-Band Full-Duplex OFDM Systems

Abstract

On performance of analog least mean square loop for self-interference cancellation in in-band fullduplex OFDM systems," in 85th IEEE Vehicular Technology Conference (VTC2017-Spring), 2017, pp. 1-5.On performance of analog least mean square loop for self-interference cancellation in in-band full-duplex OFDM systems AbstractThis paper evaluates the performance of an analog least mean square (ALMS) loop employed to cancel selfinterference in in-band full-duplex (IBFD) orthogonal frequency division multiplexing (OFDM) systems. Cyclostationary analysis is applied to investigate the behavior of the ALMS filter. It is revealed that the performance of the ALMS filter for OFDM systems primarily depends on windowing function rather than pulse shaping as in single carrier systems. It is also noticed that the ALMS loop in OFDM systems provides a much higher level of sel-interference (SI) suppression because OFDM signals lead to reduced the error of the interference channel modelling with the adaptive filter. Simulations are then conducted to verify the theoretical findings. Abstract-This paper evaluates the performance of an analog least mean square (ALMS) loop employed to cancel selfinterference in in-band full-duplex (IBFD) orthogonal frequency division multiplexing (OFDM) systems. Cyclostationary analysis is applied to investigate the behavior of the ALMS filter. It is revealed that the performance of the ALMS filter for OFDM systems primarily depends on windowing function rather than pulse shaping as in single carrier systems. It is also noticed that the ALMS loop in OFDM systems provides a much higher level of sel-interference (SI) suppression because OFDM signals lead to reduced the error of the interference channel modelling with the adaptive filter. Simulations are then conducted to verify the theoretical findings.

Analog Least Mean Square Loop for Self-Interference Cancellation: A Practical Perspective

“…The level of cancellation is also measured with different roll-off factors of the pulse shaping filter to confirm the analyses shown in [22]. Finally, the prototype is evaluated with a 20 MHz-bandwidth orthogonal frequency-division multiplexing (OFDM) signal to confirm that the ALMS loop works well in both single carrier and multicarrier signaling systems as mentioned in [21,22,24].…”

“…Denoting u l (t) = h l − w l (t)e j2π f c lT d as the difference between the channel coefficient and the weighting coefficient in the l-th tap of the ALMS loop, we can see that the power of u l (t) indicates the performance of the ALMS loop. By evaluating u l (t) in different scenarios, the behaviors of the ALMS loop have been investigated and published in [12,19,[21][22][23][24].…”

“…The promising application of the ALMS loop in IBFD MIMO systems has been presented in [20] with a beam-based analog SI cancellation structure. The behaviors of this adaptive filter are comprehensively investigated in [12,19,[21][22][23][24]. It has been shown that the performance of the ALMS loop depends on the transmitted signal properties and the structure of the loop.…”

Beam-Based Analog Self-Interference Cancellation in Full-Duplex MIMO Systems

“…Instead, a simple Resistor-Capacitor (RC) low-pass filter (LPF) is utilized to synthesize the weighting coefficients for each tap. The behaviors of the ALMS loop in different FD single antenna systems have been presented in [13], [31]- [35]. A prototype of the ALMS loop has been demonstrated in [36].…”

“…It means that the ALMS loop in the FD single antenna system is a special case of this beam-based cancellation structure. Hence, the properties of the ALMS loop presented in [13], [31], [32], [34], [35], such as the interference suppression lower bound and convergence speed, are also applicable in this case.…”