164 research outputs found
Improved Signal Detection for Ambient Backscatter Communications
In ambient backscatter communication (AmBC) systems, passive tags connect to
a reader by reflecting an ambient radio frequency (RF) signal. However, the
reader may not know the channel states and RF source parameters and can
experience interference. The traditional energy detector (TED) appears to be an
ideal solution. However, it performs poorly under these conditions. To address
this, we propose two new detectors: (1) A joint correlation-energy detector
(JCED) based on the first-order correlation of the received samples and (2) An
improved energy detector (IED) based on the p-th norm of the received signal
vector. We compare the performance of the IED and TED under generalized noise
modeled using the McLeish distribution and derive a general analytical formula
for the area under the receiver operating characteristic (ROC) curves. Based on
our results, both detectors outperform TED. For example, the probability of
detection with a false alarm rate of 1% for JCED and IED is 14% and 5% higher,
respectively, compared to TED. These gains are even higher using the direct
interference cancellation (DIC) technique, with increases of 16% and 7%,
respectively. Overall, our proposed detectors offer better performance than the
TED, making them useful tools for improving AmBC system performance.Comment: This paper has got Major Revision by IEEE TGC
Enhancing AmBC Systems with Deep Learning for Joint Channel Estimation and Signal Detection
The era of ubiquitous, affordable wireless connectivity has opened doors to
countless practical applications. In this context, ambient backscatter
communication (AmBC) stands out, utilizing passive tags to establish
connections with readers by harnessing reflected ambient radio frequency (RF)
signals. However, conventional data detectors face limitations due to their
inadequate knowledge of channel and RF-source parameters. To address this
challenge, we propose an innovative approach using a deep neural network (DNN)
for channel state estimation (CSI) and signal detection within AmBC systems.
Unlike traditional methods that separate CSI estimation and data detection, our
approach leverages a DNN to implicitly estimate CSI and simultaneously detect
data. The DNN model, trained offline using simulated data derived from channel
statistics, excels in online data recovery, ensuring robust performance in
practical scenarios. Comprehensive evaluations validate the superiority of our
proposed DNN method over traditional detectors, particularly in terms of bit
error rate (BER). In high signal-to-noise ratio (SNR) conditions, our method
exhibits an impressive approximately 20% improvement in BER performance
compared to the maximum likelihood (ML) approach. These results underscore the
effectiveness of our developed approach for AmBC channel estimation and signal
detection. In summary, our method outperforms traditional detectors, bolstering
the reliability and efficiency of AmBC systems, even in challenging channel
conditions.Comment: Accepted for publication in the IEEE Transactions on Communication
Effect of carrier transfer on the PL intensity in self-assembled In (Ga) As/GaAs quantum rings
We present results concerning the carrier transfer between In(Ga)As quantum rings in a stacked multilayer structure, which is characterised by a bimodal size distribution. This transfer of carriers explains the observed temperature behaviour of diode lasers based on that kind of stacked layer structures. The inter-ring carrier transfer can be possible by phonon assisted tunnelling from the ground state of the smallring family towards the big-ring family of the bimodal size distribution. This process is thermally activated in the range 40–80 K.This work was partially supported by Spanish MCyT Nanoself I and II projects TIC2002-04096-C03 and TEC2005-05781-C03-03, the SANDiE Network of excellence (Contract No.
NMP4-CT-2004-500101) and the AECI Spain-Tunisia bilateral research action No. 2/04/R.Peer reviewe
Kinetics of exciton photoluminescence in type-II semiconductor superlattices
The exciton decay rate at a rough interface in type-II semiconductor
superlattices is investigated. It is shown that the possibility of
recombination of indirect excitons at a plane interface essentially affects
kinetics of the exciton photoluminescence at a rough interface. This happens
because of strong correlation between the exciton recombination at the plane
interface and at the roughness. Expressions that relate the parameters of the
luminescence kinetics with statistical characteristics of the rough interface
are obtained. The mean height and length of roughnesses in GaAs/AlAs
superlattices are estimated from the experimental data.Comment: 3 PostScript figure
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