1,904 research outputs found
Resource Allocation for Secure Gaussian Parallel Relay Channels with Finite-Length Coding and Discrete Constellations
We investigate the transmission of a secret message from Alice to Bob in the
presence of an eavesdropper (Eve) and many of decode-and-forward relay nodes.
Each link comprises a set of parallel channels, modeling for example an
orthogonal frequency division multiplexing transmission. We consider the impact
of discrete constellations and finite-length coding, defining an achievable
secrecy rate under a constraint on the equivocation rate at Eve. Then we
propose a power and channel allocation algorithm that maximizes the achievable
secrecy rate by resorting to two coupled Gale-Shapley algorithms for stable
matching problem. We consider the scenarios of both full and partial channel
state information at Alice. In the latter case, we only guarantee an outage
secrecy rate, i.e., the rate of a message that remains secret with a given
probability. Numerical results are provided for Rayleigh fading channels in
terms of average outage secrecy rate, showing that practical schemes achieve a
performance quite close to that of ideal ones
I/Q-Imbalance Self-Interference Coordination
In this paper, we present a novel low-complexity scheme, which improves the
performance of single-antenna multi-carrier communication systems, suffering
from in-phase and quadrature (I/Q)-imbalance (IQI) at the receiver. We refer to
the proposed scheme as I/Q-imbalance self-interference coordination (IQSC).
IQSC does not only mitigate the detrimental effects of IQI, but, through
appropriate signal processing, also coordinates the self-interference terms
produced by IQI in order to achieve second-order frequency diversity. However,
these benefits come at the expense of a reduction in transmission rate. More
specifically, IQSC is a simple transmit diversity scheme that improves the
signal quality at the receiver by elementary signal processing operations
across symmetric (mirror) pairs of subcarriers. Thereby, the proposed
transmission protocol has a similar complexity as Alamouti's space-time block
coding scheme and does not require extra transmit power nor any feedback. To
evaluate the performance of IQSC, we derive closed-form expressions for the
resulting outage probability and symbol error rate. Interestingly, IQSC
outperforms not only existing IQI compensation schemes but also the ideal
system without IQI for the same spectral efficiency and practical target error
rates, while it achieves almost the same performance as ideal (i.e., IQI-free)
equal-rate repetition coding. Our findings reveal that IQSC is a promising
low-complexity technique for significantly increasing the reliability of
low-cost devices that suffer from high levels of IQI.Comment: Published in IEEE Transactions on Wireless Communication
A Survey on MIMO Transmission with Discrete Input Signals: Technical Challenges, Advances, and Future Trends
Multiple antennas have been exploited for spatial multiplexing and diversity
transmission in a wide range of communication applications. However, most of
the advances in the design of high speed wireless multiple-input multiple
output (MIMO) systems are based on information-theoretic principles that
demonstrate how to efficiently transmit signals conforming to Gaussian
distribution. Although the Gaussian signal is capacity-achieving, signals
conforming to discrete constellations are transmitted in practical
communication systems. As a result, this paper is motivated to provide a
comprehensive overview on MIMO transmission design with discrete input signals.
We first summarize the existing fundamental results for MIMO systems with
discrete input signals. Then, focusing on the basic point-to-point MIMO
systems, we examine transmission schemes based on three most important criteria
for communication systems: the mutual information driven designs, the mean
square error driven designs, and the diversity driven designs. Particularly, a
unified framework which designs low complexity transmission schemes applicable
to massive MIMO systems in upcoming 5G wireless networks is provided in the
first time. Moreover, adaptive transmission designs which switch among these
criteria based on the channel conditions to formulate the best transmission
strategy are discussed. Then, we provide a survey of the transmission designs
with discrete input signals for multiuser MIMO scenarios, including MIMO uplink
transmission, MIMO downlink transmission, MIMO interference channel, and MIMO
wiretap channel. Additionally, we discuss the transmission designs with
discrete input signals for other systems using MIMO technology. Finally,
technical challenges which remain unresolved at the time of writing are
summarized and the future trends of transmission designs with discrete input
signals are addressed.Comment: 110 pages, 512 references, submit to Proceedings of the IEE
Optimal Independence-Checking Coding For Secure Uplink Training in Large-Scale MISO-OFDM Systems
Due to the publicly-known deterministic character- istic of pilot tones,
pilot-aware attack, by jamming, nulling and spoofing pilot tones, can
significantly paralyze the uplink channel training in large-scale MISO-OFDM
systems. To solve this, we in this paper develop an independence-checking
coding based (ICCB) uplink training architecture for one-ring scattering
scenarios allowing for uniform linear arrays (ULA) deployment. Here, we not
only insert randomized pilots on subcarriers for channel impulse response (CIR)
estimation, but also diversify and encode subcarrier activation patterns (SAPs)
to convey those pilots simultaneously. The coded SAPs, though interfered by
arbitrary unknown SAPs in wireless environment, are qualified to be reliably
identified and decoded into the original pilots by checking the hidden channel
independence existing in subcarri- ers. Specifically, an independence-checking
coding (ICC) theory is formulated to support the encoding/decoding process in
this architecture. The optimal ICC code is further developed for guaranteeing a
well-imposed estimation of CIR while maximizing the code rate. Based on this
code, the identification error probability (IEP) is characterized to evaluate
the reliability of this architecture. Interestingly, we discover the principle
of IEP reduction by exploiting the array spatial correlation, and prove that
zero-IEP, i.e., perfect reliability, can be guaranteed under
continuously-distributed mean angle of arrival (AoA). Besides this, a novel
closed form of IEP expression is derived in discretely- distributed case.
Simulation results finally verify the effectiveness of the proposed
architecture.Comment: accepted in IEEE International Conference on Communications 201
Comparison of DCO-OFDM and M-PAM for LED-Based Communication Systems
Light-emitting diode (LED)-based communications, such as visible light
communications (VLC) and infrared (IR) communications, are candidate techniques
to provide short-range and high-speed data transmission. In this paper, M-ary
pulse amplitude modulation (M-PAM), used as a high bandwidth efficiency scheme,
is compared with an optimized DC-biased optical orthogonal frequency division
multiplexing (DCO-OFDM) scheme. Considering the bandwidth limit and constrained
peak transmitted power characteristics of LEDs, a bit loading algorithm with an
optimized modulation index is used for the DCO-OFDM. To reduce the inter-symbol
interference caused by LEDs, a waveform design algorithm with a minimum mean
squared error (MMSE) equalizer is applied to the M-PAM system. From numerical
results, M-PAM with the optimized signal processing can provide a substantially
higher data rate than the optimally designed DCO-OFDM for the same performance
Achieve Sustainable Ultra-Dense Heterogeneous Networks for 5G
Due to the exponentially increased demands of mobile data traffic, e.g., a
1000-fold increase in traffic demand from 4G to 5G, network densification is
considered as a key mechanism in the evolution of cellular networks, and
ultra-dense heterogeneous network (UDHN) is a promising technique to meet the
requirements of explosive data traffic in 5G networks. In the UDHN, base
station is brought closer and closer to users through densely deploying small
cells, which would result in extremely high spectral efficiency and energy
efficiency. In this article, we first present a potential network architecture
for the UDHN, and then propose a generalized orthogonal/non-orthogonal random
access scheme to improve the network efficiency while reducing the signaling
overhead. Simulation results demonstrate the effectiveness of the proposed
scheme. Finally, we present some of the key challenges of the UDHN
Physical Layer Security of Generalised Pre-coded Spatial Modulation with Antenna Scrambling
We now advocate a novel physical layer security solution that is unique to
our previously proposed GPSM scheme with the aid of the proposed antenna
scrambling. The novelty and contribution of our paper lies in three aspects: 1/
principle: we introduce a `security key' generated at Alice that is unknown to
both Bob and Eve, where the design goal is that the publicly unknown security
key only imposes barrier for Eve. 2/ approach: we achieve it by conveying
useful information only through the activation of RA indices, which is in turn
concealed by the unknown security key in terms of the randomly scrambled
symbols used in place of the conventional modulated symbols in GPSM scheme. 3/
design: we consider both Circular Antenna Scrambling (CAS) and Gaussian Antenna
Scrambling (GAS) in detail and the resultant security capacity of both designs
are quantified and compared
Sparse Signal Processing Concepts for Efficient 5G System Design
As it becomes increasingly apparent that 4G will not be able to meet the
emerging demands of future mobile communication systems, the question what
could make up a 5G system, what are the crucial challenges and what are the key
drivers is part of intensive, ongoing discussions. Partly due to the advent of
compressive sensing, methods that can optimally exploit sparsity in signals
have received tremendous attention in recent years. In this paper we will
describe a variety of scenarios in which signal sparsity arises naturally in 5G
wireless systems. Signal sparsity and the associated rich collection of tools
and algorithms will thus be a viable source for innovation in 5G wireless
system design. We will discribe applications of this sparse signal processing
paradigm in MIMO random access, cloud radio access networks, compressive
channel-source network coding, and embedded security. We will also emphasize
important open problem that may arise in 5G system design, for which sparsity
will potentially play a key role in their solution.Comment: 18 pages, 5 figures, accepted for publication in IEEE Acces
Iterative Detection for Orthogonal Precoding in Doubly Selective Channels
Ultra-reliable wireless communication links require the utilization of all
diversity sources of a wireless communication channel. Hadani et al. propose a
two dimensional discrete symplectic Fourier transform (DSFT) as orthogonal
pre-coder for a time-frequency modulation scheme. In this paper we explore
\emph{general} orthogonal precoding (OP) and its performance in time- and
frequency-selective channels. We show that iterative parallel interference
cancellation (PIC) and iterative channel estimation methods can be used for the
detection of OP. A scalar signal model for OP transmission is obtained by PIC.
Based on this signal model, we can prove that all constant modulus sequences,
e.g. the DSFT basis functions or Walsh-Hadamard sequences, lead to the same
performance for OP. We validate our receiver structure by numerical link level
simulations of a vehicle-to-vehicle communication link with a relative velocity
of . We demonstrate that OP achieves a gain of about
if compared to orthogonal frequency division multiplexing at a
bit error rate of . Our performance results for coded OP are the best
results for a fully documented receiver architecture, published so far.Comment: 7 pages, 5 figures, submitted to IEEE International Symposium on
Personal, Indoor and Mobile Radio Communications (PIMRC
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