464 research outputs found
Artificial-Noise-Aided Physical Layer Phase Challenge-Response Authentication for Practical OFDM Transmission
Recently, we have developed a PHYsical layer Phase Challenge-Response
Authentication Scheme (PHY-PCRAS) for independent multicarrier transmission. In
this paper, we make a further step by proposing a novel artificial-noise-aided
PHY-PCRAS (ANA-PHY-PCRAS) for practical orthogonal frequency division
multiplexing (OFDM) transmission, where the Tikhonov-distributed artificial
noise is introduced to interfere with the phase-modulated key for resisting
potential key-recovery attacks whenever a static channel between two legitimate
users is unfortunately encountered. Then, we address various practical issues
for ANA-PHY-PCRAS with OFDM transmission, including correlation among
subchannels, imperfect carrier and timing recoveries. Among them, we show that
the effect of sampling offset is very significant and a search procedure in the
frequency domain should be incorporated for verification. With practical OFDM
transmission, the number of uncorrelated subchannels is often not sufficient.
Hence, we employ a time-separated approach for allocating enough subchannels
and a modified ANA-PHY-PCRAS is proposed to alleviate the discontinuity of
channel phase at far-separated time slots. Finally, the key equivocation is
derived for the worst case scenario. We conclude that the enhanced security of
ANA-PHY-PCRAS comes from the uncertainty of both the wireless channel and
introduced artificial noise, compared to the traditional challenge-response
authentication scheme implemented at the upper layer.Comment: 33 pages, 13 figures, submitted for possible publicatio
Deep Energy Autoencoder for Noncoherent Multicarrier MU-SIMO Systems
We propose a novel deep energy autoencoder (EA) for noncoherent multicarrier
multiuser single-input multipleoutput (MU-SIMO) systems under fading channels.
In particular, a single-user noncoherent EA-based (NC-EA) system, based on the
multicarrier SIMO framework, is first proposed, where both the transmitter and
receiver are represented by deep neural networks (DNNs), known as the encoder
and decoder of an EA. Unlike existing systems, the decoder of the NC-EA is fed
only with the energy combined from all receive antennas, while its encoder
outputs a real-valued vector whose elements stand for the subcarrier power
levels. Using the NC-EA, we then develop two novel DNN structures for both
uplink and downlink NC-EA multiple access (NC-EAMA) schemes, based on the
multicarrier MUSIMO framework. Note that NC-EAMA allows multiple users to share
the same sub-carriers, thus enables to achieve higher performance gains than
noncoherent orthogonal counterparts. By properly training, the proposed NC-EA
and NC-EAMA can efficiently recover the transmitted data without any channel
state information estimation. Simulation results clearly show the superiority
of our schemes in terms of reliability, flexibility and complexity over
baseline schemes.Comment: Accepted, IEEE TW
Successive-relaying-aided decode-and-forward coherent versus noncoherent cooperative multicarrier space–time shift keying
Abstract—Successive-relaying-aided (SR) cooperative multi-carrier (MC) space–time shift keying (STSK) is proposed for frequency-selective channels. We invoke SR to mitigate the typical 50% throughput loss of conventional half-duplex relaying schemes and MC code-division multiple access (MC-CDMA) to circumvent the dispersive effects of wireless channels and to reduce the SR-induced interference. The distributed relay terminals form two virtual antenna arrays (VAAs), and the source node (SN) successively transmits frequency-domain (FD) spread signals to one of the VAAs, in addition to directly transmitting to the destination node (DN). The constituent relay nodes (RNs) of each VAA activate cyclic-redundancy-checking-based (CRC) selective decode-and-forward (DF) relaying. The DN can jointly detect the signals received via the SN-to-DN and VAA-to-DN links using a low-complexity single-stream-based joint maximum-likelihood (ML) detector. We also propose a differentially encoded cooperative MC-CDMA STSK scheme to facilitate communications over hostile dispersive channels without requiring channel estimation (CE). Dispensing with CE is important since the relays cannot be expected to altruistically estimate the SN-to-RN links for simply supporting the source. Furthermore, we propose soft-decision-aided serially concatenated recursive systematic convolutional (RSC) and unity-rate-coded (URC) cooperative MC STSK and investigate its performance in both coherent and noncoherent scenarios
Coded DS-CDMA Systems with Iterative Channel Estimation and no Pilot Symbols
In this paper, we describe direct-sequence code-division multiple-access
(DS-CDMA) systems with quadriphase-shift keying in which channel estimation,
coherent demodulation, and decoding are iteratively performed without the use
of any training or pilot symbols. An expectation-maximization
channel-estimation algorithm for the fading amplitude, phase, and the
interference power spectral density (PSD) due to the combined interference and
thermal noise is proposed for DS-CDMA systems with irregular repeat-accumulate
codes. After initial estimates of the fading amplitude, phase, and interference
PSD are obtained from the received symbols, subsequent values of these
parameters are iteratively updated by using the soft feedback from the channel
decoder. The updated estimates are combined with the received symbols and
iteratively passed to the decoder. The elimination of pilot symbols simplifies
the system design and allows either an enhanced information throughput, an
improved bit error rate, or greater spectral efficiency. The interference-PSD
estimation enables DS-CDMA systems to significantly suppress interference.Comment: To appear, IEEE Transactions on Wireless Communication
Successive-relaying-aided decode-and-forward coherent versus noncoherent cooperative multicarrier space–time shift keying
Abstract—Successive-relaying-aided (SR) cooperative multi-carrier (MC) space–time shift keying (STSK) is proposed for frequency-selective channels. We invoke SR to mitigate the typical 50% throughput loss of conventional half-duplex relaying schemes and MC code-division multiple access (MC-CDMA) to circumvent the dispersive effects of wireless channels and to reduce the SR-induced interference. The distributed relay terminals form two virtual antenna arrays (VAAs), and the source node (SN) successively transmits frequency-domain (FD) spread signals to one of the VAAs, in addition to directly transmitting to the destination node (DN). The constituent relay nodes (RNs) of each VAA activate cyclic-redundancy-checking-based (CRC) selective decode-and-forward (DF) relaying. The DN can jointly detect the signals received via the SN-to-DN and VAA-to-DN links using a low-complexity single-stream-based joint maximum-likelihood (ML) detector. We also propose a differentially encoded cooperative MC-CDMA STSK scheme to facilitate communications over hostile dispersive channels without requiring channel estimation (CE). Dispensing with CE is important since the relays cannot be expected to altruistically estimate the SN-to-RN links for simply supporting the source. Furthermore, we propose soft-decision-aided serially concatenated recursive systematic convolutional (RSC) and unity-rate-coded (URC) cooperative MC STSK and investigate its performance in both coherent and noncoherent scenarios
Error Rate Analysis of Amplitude-Coherent Detection over Rician Fading Channels with Receiver Diversity
Amplitude-coherent (AC) detection is an efficient detection technique that
can simplify the receiver design while providing reliable symbol error rate
(SER). Therefore, this work considers AC detector design and SER analysis using
M-ary amplitude shift keying (MASK) modulation over Rician fading channels.
More specifically, we derive the optimum, near-optimum and a suboptimum AC
detectors and compare their SER to the coherent, noncoherent and the heuristic
AC detectors. Moreover, the analytical SER of the heuristic detector is derived
using two different approaches for single and multiple receiving antennas. One
of the derived expressions is expressed in terms of a single integral that can
be evaluated numerically, while the second approach gives a closed-form
analytical expression for the SER, which is also used to derive a simple
formula for the asymptotic SER at high signal-to-noise ratios (SNRs). The
obtained analytical and simulation results show that the SER of the AC and
coherent MASK detectors are comparable, particularly for high values of the
Rician K-factor, and small number of receiving antennas. Moreover, the obtained
results show that the SER of the optimal AC detector is equivalent to that of
the coherent detector. However, the optimal AC detector complexity is
prohibitively high, particularly at high SNRs. In most of the scenarios, the
heuristic AC detector significantly outperforms the optimum noncoherent
detector, except for the binary ASK case at low SNRs. Moreover, the obtained
results show that the heuristic AC detector is immune to phase noise, and thus,
it outperforms the coherent detector in scenarios where system is subject to
considerable phase noise
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