570 research outputs found
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
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
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
Non-Linear Digital Self-Interference Cancellation for In-Band Full-Duplex Radios Using Neural Networks
Full-duplex systems require very strong self-interference cancellation in
order to operate correctly and a significant part of the self-interference
signal is due to non-linear effects created by various transceiver impairments.
As such, linear cancellation alone is usually not sufficient and sophisticated
non-linear cancellation algorithms have been proposed in the literature. In
this work, we investigate the use of a neural network as an alternative to the
traditional non-linear cancellation method that is based on polynomial basis
functions. Measurement results from a full-duplex testbed demonstrate that a
small and simple feed-forward neural network canceler works exceptionally well,
as it can match the performance of the polynomial non-linear canceler with
significantly lower computational complexity.Comment: Presented at the IEEE International Workshop on Signal Processing
Advances in Wireless Communications (SPAWC) 201
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
Four-element phased-array beamformers and a self-interference canceling full-duplex transciver in 130-nm SiGe for 5G applications at 26 GHz
This thesis is on the design of radio-frequency (RF) integrated front-end circuits for next generation 5G communication systems. The demand for higher data rates and lower latency in 5G networks can only be met using several new technologies including, but not limited to, mm-waves, massive-MIMO, and full-duplex. Use of mm-waves provides more bandwidth that is necessary for high data rates at the cost of increased attenuation in air. Massive-MIMO arrays are required to compensate for this increased path loss by providing beam steering and array gain. Furthermore, full duplex operation is desirable for improved spectrum efficiency and reduced latency. The difficulty of full duplex operation is the self-interference (SI) between transmit (TX) and receive (RX) paths. Conventional methods to suppress this interference utilize either bulky circulators, isolators, couplers or two separate antennas. These methods are not suitable for fully-integrated full-duplex massive-MIMO arrays. This thesis presents circuit and system level solutions to the issues summarized above, in the form of SiGe integrated circuits for 5G applications at 26 GHz. First, a full-duplex RF front-end architecture is proposed that is scalable to massive-MIMO arrays. It is based on blind, RF self-interference cancellation that is applicable to single/shared antenna front-ends. A high resolution RF vector modulator is developed, which is the key building block that empowers the full-duplex frontend architecture by achieving better than state-of-the-art 10-b monotonic phase control. This vector modulator is combined with linear-in-dB variable gain amplifiers and attenuators to realize a precision self-interference cancellation circuitry. Further, adaptive control of this SI canceler is made possible by including an on-chip low-power IQ downconverter. It correlates copies of transmitted and received signals and provides baseband/dc outputs that can be used to adaptively control the SI canceler. The solution comes at the cost of minimal additional circuitry, yet significantly eases linearity requirements of critical receiver blocks at RF/IF such as mixers and ADCs. Second, to complement the proposed full-duplex front-end architecture and to provide a more complete solution, high-performance beamformer ICs with 5-/6- b phase and 3-/4-b amplitude control capabilities are designed. Single-channel, separate transmitter and receiver beamformers are implemented targeting massive- MIMO mode of operation, and their four-channel versions are developed for phasedarray communication systems. Better than state-of-the-art noise performance is obtained in the RX beamformer channel, with a full-channel noise figure of 3.3 d
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