149 research outputs found
Study of the operational SNR while constructing polar codes
Channel coding is commonly based on protecting information to be communicated across an unreliable medium, by adding patterns of redundancy into the transmission path. Also referred to as forward error control coding (FECC), the technique is widely used to enable correcting or at least detecting bit errors in digital communication systems. In this paper we study an original FECC known as polar coding which has proven to meet the typical use cases of the next generation mobile standard. This work is motivated by the suitability of polar codes for the new coming wireless era. Hence, we investigate the performance of polar codes in terms of bit error rate (BER) for several codeword lengths and code rates. We first perform a discrete search to find the best operating signal-to-noise ratio (SNR) at two different code rates, while varying the blocklength. We find in our extensive simulations that the BER becomes more sensitive to operating SNR (OSNR) as long as we increase the blocklength and code rate. Finally, we note that increasing blocklength achieves an SNR gain, while increasing code rate changes the OSNR domain. This trade-off sorted out must be taken into consideration while designing polar codes for high-throughput application
Polar codes based OFDM-PLC systems in the presence of middleton class-A noise
© 2016 IEEE. The performance of power line communication (PLC) systems suffer mainly from non-Gaussian noise, commonly referred to as impulsive noise. To reduce the effect of this noise, various channel coding techniques have been studied in the literature over PLC channels. Unlike existing works, in this paper we investigate the performance and robustness of polar codes over impulsive noise PLC channels for different codeword lengths and noise scenarios in orthogonal frequency division multiplexing (OFDM) systems. In particular, insightful comparisons between hard decision (HD) decoding and soft decision (SD) decoding for the proposed system are made. Furthermore, we investigate the blanking and clipping techniques with polar codes for impulsive noise mitigation. In addition, for the sake of comparison, results for LDPC coding are also presented. The results show that polar codes can considerably improve the performance of PLC systems. It will also be demonstrated that SD decoding offers better performance than HD decoding and that as the codeword length is increased, the performance can be further improved
Polar codes combined with physical layer security on impulsive noise channels
Ph. D. ThesisThe need for secure communications is becoming more and more impor-
tant in modern society as wired and wireless connectivity becomes more
ubiquitous. Currently, security is achieved by using well established
encryption techniques in the upper layers that rely on computational
complexity to ensure security. However, processing power is continu-
ally increasing and well-known encryption schemes are more likely to be
cracked. An alternative approach to achieving secure communication is
to exploit the properties of the communication channel. This is known as
physical layer security and is mathematically proven to be secure. Phys-
ical layer security is an active research area, with a significant amount
of literature covering many different aspects. However, one issue that
does not appear to have been investigated in the literature is the effect
on physical layer security when the noise in the communication channel
is impulsive. Impulsive noise adds large spikes to the transmitted signal
for very short durations that can significantly degrade the signal. The
main source of impulsive noise in wireless communications is electromag-
netic interference generated by machinery. Therefore, this project will
investigate the effect of impulsive noise on physical layer security.
To ensure a high level of performance, advanced error-correcting codes
are needed to correct the multiple errors due to this harsh channel. Turbo
and Low-Density Parity-Check (LDPC) codes are capacity-approaching
codes commonly used in current wireless communication standards, but
their complexity and latency can be quite high and can be a limiting fac-
tor when required very high data rates. An alternative error-correcting
code is the polar code, which can actually achieve the Shannon capacity
on any symmetric binary input discrete memoryless channel (B-DMC).
Furthermore, the complexity of polar codes is low and this makes them
an attractive error-correcting code for high data rate wireless commu-
nications. In this project, polar codes are combined with physical layer
security and the performance and security of the system is evaluated on
impulsive noise channels for the first time.
This project has three contributions:
Polar codes designed for impulsive noise channels using density evo-
lution are combined with physical layer security on a wire-tap chan-
nel experiencing impulsive noise.
The secrecy rate of polar codes is maximised. In the decoding of
polar codes, the frozen bits play an important part. The posi-
tions of the frozen bits has a significant impact on performance and
therefore, the selection of optimal frozen bits is presented to opti-
mise the performance while maintaining secure communications on
impulsive noise wire-tap channels.
Optimal puncturing patterns are investigated to obtain polar codes
with arbitrary block lengths and can be applied to different modu-
lation schemes, such as binary phase shift keying (BPSK) and M-
ary Quadrature Amplitude Modulation (QAM), that can be rate
compatible with practical communication systems. The punctured
polar codes are combined with physical layer security, allowing the
construction of a variety of different code rates while maintaining
good performance and security on impulsive noise wire-tap chan-
nels.
The results from this work have demonstrated that polar codes are ro-
bust to the effects of impulsive noise channel and can achieve secure
communications. The work also addresses the issue of security on im-
pulsive noise channels and has provided important insight into scenarios
where the main channel between authorised users has varying levels of
impulsiveness compared with the eavesdropper's channel. One of the
most interesting results from this thesis is the observation that polar
codes combined with physical layer security can achieve good perfor-
mance and security even when the main channel is more impulsive than
the eavesdropper's channel, which was unexpected. Therefore, this thesis
concludes that the low-complexity polar codes are an excellent candidate
for the error-correcting codes when combined with physical layer security
in more harsh impulsive wireless communication channels
Short-Packet Downlink Transmission with Non-Orthogonal Multiple Access
This work introduces downlink non-orthogonal multiple access (NOMA) into
short-packet communications. NOMA has great potential to improve fairness and
spectral efficiency with respect to orthogonal multiple access (OMA) for
low-latency downlink transmission, thus making it attractive for the emerging
Internet of Things. We consider a two-user downlink NOMA system with finite
blocklength constraints, in which the transmission rates and power allocation
are optimized. To this end, we investigate the trade-off among the transmission
rate, decoding error probability, and the transmission latency measured in
blocklength. Then, a one-dimensional search algorithm is proposed to resolve
the challenges mainly due to the achievable rate affected by the finite
blocklength and the unguaranteed successive interference cancellation. We also
analyze the performance of OMA as a benchmark to fully demonstrate the benefit
of NOMA. Our simulation results show that NOMA significantly outperforms OMA in
terms of achieving a higher effective throughput subject to the same finite
blocklength constraint, or incurring a lower latency to achieve the same
effective throughput target. Interestingly, we further find that with the
finite blocklength, the advantage of NOMA relative to OMA is more prominent
when the effective throughput targets at the two users become more comparable.Comment: 15 pages, 9 figures. This is a longer version of a paper to appear in
IEEE Transactions on Wireless Communications. Citation Information: X. Sun,
S. Yan, N. Yang, Z. Ding, C. Shen, and Z. Zhong, "Short-Packet Downlink
Transmission with Non-Orthogonal Multiple Access," IEEE Trans. Wireless
Commun., accepted to appear [Online]
https://ieeexplore.ieee.org/document/8345745
Fifty Years of Noise Modeling and Mitigation in Power-Line Communications.
Building on the ubiquity of electric power infrastructure, power line communications (PLC) has been successfully used in diverse application scenarios, including the smart grid and in-home broadband communications systems as well as industrial and home automation. However, the power line channel exhibits deleterious properties, one of which is its hostile noise environment. This article aims for providing a review of noise modeling and mitigation techniques in PLC. Specifically, a comprehensive review of representative noise models developed over the past fifty years is presented, including both the empirical models based on measurement campaigns and simplified mathematical models. Following this, we provide an extensive survey of the suite of noise mitigation schemes, categorizing them into mitigation at the transmitter as well as parametric and non-parametric techniques employed at the receiver. Furthermore, since the accuracy of channel estimation in PLC is affected by noise, we review the literature of joint noise mitigation and channel estimation solutions. Finally, a number of directions are outlined for future research on both noise modeling and mitigation in PLC
Coded-OFDM for PLC systems in non-Gaussian noise channels
PhD ThesisNowadays, power line communication (PLC) is a technology that uses the power
line grid for communication purposes along with transmitting electrical energy, for
providing broadband services to homes and offices such as high-speed data, audio,
video and multimedia applications. The advantages of this technology are to eliminate
the need for new wiring and AC outlet plugs by using an existing infrastructure,
ease of installation and reduction of the network deployment cost. However,
the power line grid is originally designed for the transmission of the electric power
at low frequencies; i.e. 50/60 Hz. Therefore, the PLC channel appears as a harsh
medium for low-power high-frequency communication signals. The development
of PLC systems for providing high-speed communication needs precise knowledge
of the channel characteristics such as the attenuation, non-Gaussian noise and selective
fading. Non-Gaussian noise in PLC channels can classify into Nakagami-m
background interference (BI) noise and asynchronous impulsive noise (IN) modelled
by a Bernoulli-Gaussian mixture (BGM) model or Middleton class A (MCA)
model. Besides the effects of the multipath PLC channel, asynchronous impulsive
noise is the main reason causing performance degradation in PLC channels.
Binary/non-binary low-density parity check B/NB-(LDPC) codes and turbo codes
(TC) with soft iterative decoders have been proposed for Orthogonal Frequency
Division Multiplexing (OFDM) system to improve the bit error rate (BER) performance
degradation by exploiting frequency diversity. The performances are investigated
utilizing high-order quadrature amplitude modulation (QAM) in the presence
of non-Gaussian noise over multipath broadband power-line communication (BBPLC)
channels. OFDM usually spreads the effect of IN over multiple sub-carriers
after discrete Fourier transform (DFT) operation at the receiver, hence, it requires
only a simple single-tap zero forcing (ZF) equalizer at the receiver.
The thesis focuses on improving the performance of iterative decoders by deriving
the effective, complex-valued, ratio distributions of the noise samples at the zeroforcing
(ZF) equalizer output considering the frequency-selective multipath PLCs,
background interference noise and impulsive noise, and utilizing the outcome for
computing the apriori log likelihood ratios (LLRs) required for soft decoding algorithms.
On the other hand, Physical-Layer Network Coding (PLNC) is introduced to help
the PLC system to extend the range of operation for exchanging information between
two users (devices) using an intermediate relay (hub) node in two-time slots
in the presence of non-Gaussian noise over multipath PLC channels. A novel detection
scheme is proposed to transform the transmit signal constellation based on
the frequency-domain channel coefficients to optimize detection at the relay node
with newly derived noise PDF at the relay and end nodes. Additionally, conditions
for optimum detection utilizing a high-order constellation are derived. The closedform
expressions of the BER and average BER upper-bound (AUB) are derived for
a point-to-point system, and for a PLNC system at the end node to relay, relay to
end node and at the end-to-end nodes. Moreover, the convergence behaviour of
iterative decoders is evaluated using EXtrinsic Information Transfer (EXIT) chart
analysis and upper bound analyses. Furthermore, an optimization of the threshold
determination for clipping and blanking impulsive noise mitigation methods are
derived. The proposed systems are compared in performance using simulation in
MATLAB and analytical methods.Ministry of
Higher Education in Ira
Emulation of Narrowband Powerline Data Transmission Channels and Evaluation of PLC Systems
This work proposes advanced emulation of the physical layer behavior of NB-PLC channels and the application of a channel emulator for the evaluation of NB-PLC systems. In addition, test procedures and reference channels are proposed to improve efficiency and accuracy in the system evaluation and classification. This work shows that the channel emulator-based solution opens new ways toward flexible, reliable and technology-independent performance assessment of PLC modems
Communications protocols for wireless sensor networks in perturbed environment
This thesis is mainly in the Smart Grid (SG) domain. SGs improve the safety of electrical networks and allow a more adapted use of electricity storage, available in a limited way. SGs also increase overall energy efficiency by reducing peak consumption. The use of this technology is the most appropriate solution because it allows more efficient energy management. In this context, manufacturers such as Hydro-Quebec deploy sensor networks in the nerve centers to control major equipment. To reduce deployment costs and cabling complexity, the option of a wireless sensor network seems the most obvious solution. However, deploying a sensor network requires in-depth knowledge of the environment. High voltages substations are strategic points in the power grid and generate impulse noise that can degrade the performance of wireless communications. The works in this thesis are focused on the development of high performance communication protocols for the profoundly disturbed environments. For this purpose, we have proposed an approach based on the concatenation of rank metric and convolutional coding with orthogonal frequency division multiplexing. This technique is very efficient in reducing the bursty nature of impulsive noise while having a quite low level of complexity. Another solution based on a multi-antenna system is also designed. We have proposed a cooperative closed-loop coded MIMO system based on rank metric code and max−dmin precoder. The second technique is also an optimal solution for both improving the reliability of the system and energy saving in wireless sensor networks
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