7 research outputs found
A Comparison between Orthogonal and Non-Orthogonal Multiple Access in Cooperative Relaying Power Line Communication Systems
Most, if not all, existing studies on power line communication (PLC) systems as well as industrial PLC standards are based on orthogonal multiple access schemes such as orthogonal frequency-division multiplexing and code-division multiple access. In this paper, we propose non-orthogonal multiple access (NOMA) for decode-and-forward cooperative relaying PLC systems to achieve higher throughput and improve user fairness. To quantitatively characterize the proposed system performance, we also study conventional cooperative relaying (CCR) PLC systems. We evaluate the performance of the two systems in terms of the average capacity. In this respect, accurate analytical expressions for the average capacity are derived and validated with Monte Carlo simulations. The impact of several system parameters such as the branching, impulsive noise probability, cable lengths, the power allocation coefficients and input signal-to-noise ratio are investigated. The results reveal that the performance of the proposed NOMA-PLC scheme is superior compared to that of the CCR-PLC system. It is also shown that NOMA-PLC can be more effective in reducing electromagnetic compatibility associated with PLC and that increasing the network branches can considerably degrade performance. Moreover, optimizing the power allocation coefficients is found to be of utmost importance to maximize the performance of the proposed system
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
Semantic discovery and reuse of business process patterns
Patterns currently play an important role in modern information systems (IS) development and their use has mainly been restricted to the design and implementation phases of the development lifecycle. Given the increasing significance of business modelling in IS development, patterns have the potential of providing a viable solution for promoting reusability of recurrent generalized models in the very early stages of development. As a statement of research-in-progress this paper focuses on business process patterns and proposes an initial methodological framework for the discovery and reuse of business process patterns within the IS development lifecycle. The framework borrows ideas from the domain engineering literature and proposes the use of semantics to drive both the discovery of patterns as well as their reuse
Proceedings of the 8th International Conference on Energy Efficiency in Domestic Appliances and Lighting
At the EEDAL'15 conference 128 papers dealing with energy consumption and energy efficiency improvements for the residential sector have been presented. Papers focused policies and programmes, technologies and consumer behaviour. Special focus was on standards and labels, demand response and smart meters. All the paper s have been peer reviewed by experts in the sector.JRC.F.7-Renewables and Energy Efficienc
Space station systems: A bibliography with indexes (supplement 10)
This bibliography lists 1,422 reports, articles, and other documents introduced into the NASA scientific and technical information system between July 1, 1989 and December 31, 1989. Its purpose is to provide helpful information to researchers, designers and managers engaged in Space Station technology development and mission design. Coverage includes documents that define major systems and subsystems related to structures and dynamic control, electronics and power supplies, propulsion, and payload integration. In addition, orbital construction methods, servicing and support requirements, procedures and operations, and missions for the current and future Space Station are included