20 research outputs found
Cancellation of Power Amplifier Induced Nonlinear Self-Interference in Full-Duplex Transceivers
Recently, full-duplex (FD) communications with simultaneous transmission and
reception on the same channel has been proposed. The FD receiver, however,
suffers from inevitable self-interference (SI) from the much more powerful
transmit signal. Analogue radio-frequency (RF) and baseband, as well as digital
baseband, cancellation techniques have been proposed for suppressing the SI,
but so far most of the studies have failed to take into account the inherent
nonlinearities of the transmitter and receiver front-ends. To fill this gap,
this article proposes a novel digital nonlinear interference cancellation
technique to mitigate the power amplifier (PA) induced nonlinear SI in a FD
transceiver. The technique is based on modeling the nonlinear SI channel, which
is comprised of the nonlinear PA, the linear multipath SI channel, and the RF
SI canceller, with a parallel Hammerstein nonlinearity. Stemming from the
modeling, and appropriate parameter estimation, the known transmit data is then
processed with the developed nonlinear parallel Hammerstein structure and
suppressed from the receiver path at digital baseband. The results illustrate
that with a given IIP3 figure for the PA, the proposed technique enables higher
transmit power to be used compared to existing linear SI cancellation methods.
Alternatively, for a given maximum transmit power level, a lower-quality PA
(i.e., lower IIP3) can be used.Comment: To appear in proceedings of the 2013 Asilomar Conference on Signals,
Systems & Computer
Modeling and Efficient Cancellation of Nonlinear Self-Interference in MIMO Full-Duplex Transceivers
This paper addresses the modeling and digital cancellation of
self-interference in in-band full-duplex (FD) transceivers with multiple
transmit and receive antennas. The self-interference modeling and the proposed
nonlinear spatio-temporal digital canceller structure takes into account, by
design, the effects of I/Q modulator imbalances and power amplifier (PA)
nonlinearities with memory, in addition to the multipath self-interference
propagation channels and the analog RF cancellation stage. The proposed
solution is the first cancellation technique in the literature which can handle
such a self-interference scenario. It is shown by comprehensive simulations
with realistic RF component parameters and with two different PA models to
clearly outperform the current state-of-the-art digital self-interference
cancellers, and to clearly extend the usable transmit power range.Comment: 7 pages, 5 figures. To be presented in the 2014 International
Workshop on Emerging Technologies for 5G Wireless Cellular Network
Reference Receiver Based Digital Self-Interference Cancellation in MIMO Full-Duplex Transceivers
In this paper we propose and analyze a novel self-interference cancellation
structure for in-band MIMO full-duplex transceivers. The proposed structure
utilizes reference receiver chains to obtain reference signals for digital
self-interference cancellation, which means that all the transmitter-induced
nonidealities will be included in the digital cancellation signal. To the best
of our knowledge, this type of a structure has not been discussed before in the
context of full-duplex transceivers. First, we will analyze the overall
achievable performance of the proposed cancellation scheme, while also
providing some insight into the possible bottlenecks. We also provide a
detailed formulation of the actual cancellation procedure, and perform an
analysis into the effect of the received signal of interest on
self-interference coupling channel estimation. The achieved performance of the
proposed reference receiver based digital cancellation procedure is then
assessed and verified with full waveform simulations. The analysis and waveform
simulation results show that under practical transmitter RF/analog impairment
levels, the proposed reference receiver based cancellation architecture can
provide substantially better self-interference suppression than any existing
solution, despite deploying only low-complexity linear digital processing.Comment: 7 pages, 4 figures. To be presented in the 2014 IEEE Broadband
Wireless Access Worksho
Frequency-Domain Hammerstein Self-Interference Canceller for In-Band Full-Duplex OFDM Systems
In-band full-duplex communications have been spotlighted because they can double the spectral efficiency of the current wireless communication systems. However, it is necessary to mitigate the self-interference (SI). Currently, several time-domain and frequency-domain SI cancellers have been proposed. Timedomain SI cancellers are based on the parallel Hammerstein (PH) model, and they have good flexibility with high computational cost. In contrast, frequency-domain SI cancellers can achieve high cancellation performance with low computational cost but they have less flexibility than time-domain PH based SI cancellers. In this paper, we propose a frequency-domain SI canceller based on the PH model. The proposed scheme estimates the frequency response of the SI channel and regenerates SI signals by the overlap-save method. Therefore, the computational complexity of the proposed scheme is less than time-domain PH based SI canceller. The performance of the proposed scheme is assessed by equivalent baseband signal simulations of a fullduplex transceiver. As a result, the proposed scheme achieves high SI cancellation as the time-domain PH based SI canceller with low computational cost. In addition, the convergence performance of the proposed scheme is faster than the time-domain scheme
Feasibility of In-band Full-Duplex Radio Transceivers with Imperfect RF Components: Analysis and Enhanced Cancellation Algorithms
In this paper we provide an overview regarding the feasibility of in-band
full-duplex transceivers under imperfect RF components. We utilize results and
findings from the recent research on full-duplex communications, while
introducing also transmitter-induced thermal noise into the analysis. This
means that the model of the RF impairments used in this paper is the most
comprehensive thus far. By assuming realistic parameter values for the
different transceiver components, it is shown that IQ imaging and
transmitter-induced nonlinearities are the most significant sources of
distortion in in-band full-duplex transceivers, in addition to linear
self-interference. Motivated by this, we propose a novel augmented nonlinear
digital self-interference canceller that is able to model and hence suppress
all the essential transmitter imperfections jointly. This is also verified and
demonstrated by extensive waveform simulations.Comment: 7 pages, presented in the CROWNCOM 2014 conferenc
Adaptive Nonlinear RF Cancellation for Improved Isolation in Simultaneous Transmit-Receive Systems
This paper proposes an active radio frequency (RF) cancellation solution to
suppress the transmitter (TX) passband leakage signal in radio transceivers
supporting simultaneous transmission and reception. The proposed technique is
based on creating an opposite-phase baseband equivalent replica of the TX
leakage signal in the transceiver digital front-end through adaptive nonlinear
filtering of the known transmit data, to facilitate highly accurate
cancellation under a nonlinear TX power amplifier (PA). The active RF
cancellation is then accomplished by employing an auxiliary transmitter chain,
to generate the actual RF cancellation signal, and combining it with the
received signal at the receiver (RX) low noise amplifier (LNA) input. A
closed-loop parameter learning approach, based on the decorrelation principle,
is also developed to efficiently estimate the coefficients of the nonlinear
cancellation filter in the presence of a nonlinear TX PA with memory, finite
passive isolation, and a nonlinear RX LNA. The performance of the proposed
cancellation technique is evaluated through comprehensive RF measurements
adopting commercial LTE-Advanced transceiver hardware components. The results
show that the proposed technique can provide an additional suppression of up to
54 dB for the TX passband leakage signal at the RX LNA input, even at
considerably high transmit power levels and with wide transmission bandwidths.
Such novel cancellation solution can therefore substantially improve the TX-RX
isolation, hence reducing the requirements on passive isolation and RF
component linearity, as well as increasing the efficiency and flexibility of
the RF spectrum use in the emerging 5G radio networks.Comment: accepted to IEE