An adaptive pursuit strategy for dynamic spectrum assignment in narrowband PLC

This paper considers an adaptive orthogonal frequency-division multiplexing (OFDM) transmission scheme for narrowband (NB) power line communication (PLC). The NB PLC channel is found to show strong cyclostationary characteristics due to the periodic mains voltage. However, conventional systems do not use these time-varying channel features. An improvement of the performance is achieved by exploiting the cyclic properties of the channel. Therefore, adaptive bit and power loading methods are of great interest for PLC. In this work, we will evaluate a cyclic loading method for an OFDM system in the CENELEC A-band. Our analysis is based on noise measurements at three different locations over an observation time of 23 hours. Our contribution includes an OFDM system model comprising both additive noise and channel attenuation. Furthermore, we present a method for limiting the amplitude and power spectral density to comply with narrowband regulations. In conclusion, our proposed method achieves a lower bit error rate at all locations. The improvement reaches up to a 102 times lower bit error rate compared to non-adaptive carrier allocation at the same data rate.

Although Power Line Communication (PLC) is not a new technology, its use to support data transmission over low voltage (LV) distribution networks is still the focus of ongoing research. This thesis focuses on the channel modelling and performance evaluation of narrowband (NB) PLC system. First, the channel modelling approaches of PLC are studied. Then, the proposed PLC channel modelling method based on the bottom-up approach for LV narrowband PLC in a frequency band between 9 kHz and 490 kHz is presented. This proposed model employs the transmission and scattering matrix methods to calculate the transfer function of a typical LV PLC network which comprises two common cable types (copper cables and aluminium conductor steel reinforced). Unlike the top-down approaches, this model is scalable as the network complexity increases and can better describe the network behaviour as a function of physical parameters.In addition, the noise characteristics and popular noise reduction techniques of PLC are studied. The major impairment to the PLC is the impulsive noise which is mainly generated by the switching transient in the network. Hence, a new technique is proposed to mitigate the impact of impulsive noise on data transmission over power lines. This proposed technique is an optimal Clipping/Blanking nonlinearity technique which is based on the minimum bit error rate (BER) search. Results obtained from the simulation of this technique demonstrate that performance has been enhanced in the NB-PLC system. The performance of the narrowband PLC system is also evaluated in both physical (PHY) and medium access control (MAC) layers. Since Orthogonal Frequency Division Multiplexing (OFDM) is a suitable modulation scheme for hostile environment of the power line, it is used to evaluate the PHY layer performance. As a result of the PHY layer performance analyses, it is found that the BER performance between neighbouring points in the typical LV PLC network is reasonable, but communication beyond one hop have to rely on upper layer protocols. In the MAC layer performance evaluation of the PLC system, the widely known random access MAC protocol that uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) will be utilised. The MAC performance evaluation of the PLC system demonstrates a significant packet loss in LV PLC network even with a light traffic condition due to the noisy channel. Furthermore, the goodput declines abruptly once the individual transmission rate is high enough to block the network. In addition, the simulation results show that the channel errors can be reduced by adjusting the MAC parameters to allow the re-transmissions mechanisms to recoup the lost packets.

In the current work, we formulate a dynamic spectrum assignment (DSA) technique to allocate the experimental licensed 95 GHz Tera-Hertz spectrum to the mobile service providers (MSPs) in India in view of achieving high spectrum usage. For a fixed term of renewal (ToR), the formulated DSA technique compares the number of consumers of an MSP with all the remaining MSPs and then assigns the spectrum accordingly. The DSA then updates the assigned spectrum to an MSP at every ToR in accordance with variation in the amount of consumers compared to the previous ToR. The DSA technique is formulated such that it finds the optimal spectrum amount required by every MSP during each ToR. Also, the mean capacity (MC), spectral efficiency (SE), energy efficiency (EE), and cost efficiency (CE) are derived for each MSP. The aforementioned metrics are used to compare the performance of DSA with the static spectrum assignment (SSA) method, which assigns the spectrum to any MSP without accounting for the actual requirement by the consumer. We conduct extensive simulations considering a specific scenario with four MSPs, and the results demonstrate that the DSA technique is able to meet the demands of the 6G wireless systems as it is able to reuse the available spectrum for every MSP for a fewer number of cells of approximately 38% reduced amount of buildings. Further, the results also demonstrate that, in comparison to the traditional static spectrum assignment (SSA) method, DSA improves the MC and SE by 20% and the EE and CE by 25%.

SummarySeveral techniques for a state‐of‐the‐art advanced metering infrastructure (AMI) within the smart grid are being extensively studied and evaluated around the world. Advanced metering infrastructure provides an enhanced and efficient energy management infrastructure that can facilitate the latest demands of electric utilities, consumers, and smart grid. In the past few years, standardization process for the implementation of AMI using narrowband power line communications (NB‐PLC) transceivers has been completed by ITU‐T and IEEE. This paper is focused on the utilization of CENELEC band of NB‐PLC for deployment aspects. The power transformer model of 200 and 75 kVA transformers for 9 to 90 kHz frequency range that lies in CENELEC‐A band of NB‐PLC is also proposed. The proposed model is more simple than previously presented models in the literature and has the capability to evaluate the transformers working not only under normal condition but also under resonance condition for frequency of interest. Moreover, the efficient procedure for field measurements that provides a generalized NB‐PLC channel model for low voltage access network to deploy AMI within Lahore, Pakistan, is presented. A Simulink model is developed to validate the results. The analysis of measured and simulated results illustrates a close agreement of channel transfer functions. This research work proposes an improved and more accurate NB‐PLC channel model especially for South Asian countries.

Elastic optical networks are seen as a promising solution to improve spectrum utilization efficiency by utilizing flex-grid optical orthogonal frequency division multiplexing technology and facilitating flexible bandwidth allocation to services with heterogeneous demands. With dramatic growth of Internet traffic and imminent fiber capacity exhaustion, multiple fibers per link are required to accommodate increasing demands. In this paper, we investigate path selection and spectrum management for heterogeneous bandwidth requests by taking the network topology and expected traffic pattern into account. A novel and efficient solution for path selection and spectrum assignment that optimizes the state of the network after assignment is proposed. We first develop integer linear programming formulations to calculate path selection probabilities offline. Then, we propose a spectrum partition scheme that provides a particular spectrum range for each request size. A next-state-aware spectrum assignment algorithm with resource sharing among partitions is then introduced. We use the demand blocking ratio for dynamically arriving requests as the performance indicator. Simulation results indicate the effectiveness of our proposed schemes for routing and spectrum assignment, as they perform 1 to 2 orders of magnitude better than several baseline schemes.

The growing interest in backscatter communications as a low-powered solution in various fields necessitates pushing the envelope of current backscatter systems in multiple frontiers, among which is spectral efficiency. The increase in spectral efficiency can drive real-time applications such as augmented reality. In most of backscatter-system applications such as radio-frequency identification, backscatter modulation is implemented using binary schemes realized with square pulses, which are not spectral efficient. To address the spectral efficiency concern, this article reviews—with a scope limited to prototyped systems—some of the existing works in the literature that pertain to increasing the spectral efficiency of backscatter systems. The prototyped systems can be grouped—based on the implementation technique used—into three groups: High-order modulation, single-sideband modulation, and pulse shaping. Based on the current trends and studied literature, the article concludes with discussions on some future directions and open-ended research problems such as optimal pulse shaping, the use of artificial intelligence, multi-carrier modulation, and agile modulation; which are all aim for overcoming the spectral-efficiency limit of contemporary backscatter systems.

The indoor narrowband power line communication (NB-PLC) suffers from noise impairments, which emanate from several end-user electrical devices connected across the PLC channel. These noise impairments result into burst errors, which consequently lead to data corruption. Therefore, in order to implement robust communication techniques that will thrive on the noisy PLC channel, a full knowledge and modeling of the noise that exists on the NB-PLC channel is inevitable. This paper thus reports a First-order Markov modeling of NB-PLC channel noise, based on experimental measurements. For the modeling, BPSK, DBPSK, QPSK and DQPSK modulation schemes were implemented using Universal Software Radio Peripheral (USRP). The resulting channel models are useful for improving the robustness of the above modulation schemes as well as designing forward error correction techniques for mitigating the effect of noise impairments. The results are also useful in optimizing NB-PLC system design, thereby, enhancing the accuracy and improving the overall PLC system performance.

Narrowband power line communications (NB-PLC) systems operating in the frequency range 3-500 kHz were developed and used in the past few decades for telecommunications, metering, control, and automation. Recently, OFDM-based NB-PLC solutions known as G3 and PRIME came to the market after a long monopoly of single-carrier technologies, offering higher bit rates, robustness, and flexibility, which are vital for smart grid applications. However, it was realized that an international standard is important to ensure worldwide interoperable products and avoid market fragmentation. In the beginning of 2010, the IEEE Standards Association and ITU-T started standardization of NBPLC technologies based on OFDM, launching the P1901.2 and G.hnem projects, respectively. This article gives a technical overview of the ITU-T G.hnem standard, which defines a unified NB-PLC OFDM-based technology targeting multiple smart grid applications: smart metering, distributed automation, in-home energy management, generic home automation, car charging, and others, using IPv6 as the main networking protocol. ITU-T Recommendations G.9955 (G.hnem physical layer) and G.9956 (G.hnem data link layer) were consented for approval in February 2011; their final approval is expected in December 2011.

A seamless, sustainable and reliable communication infrastructure is crucial to realise smart grid operations and functionalities. The communications infrastructure in smart grid is not only required to be pervasive, scalable, and secure but also expected to be resilient and guarantee a required Quality of Service (QoS) to an end node. Narrow band power line communications (NBPLC) is believed to be a natural and cost effective choice for smart grid communication because it uses the existing infrastructures of the power grid that is much more extensive and pervasive than any other wired or wireless alternatives. This also eliminates the need for additional wire installation and external subscription for data transfer. However, because most smart grid applications have critical timing requirements, the frequency and time varying characteristics of the power line channel together with its background noise, limited band width and harmonic interference results in unacceptable packet loss during service transmission. Communication solution with Reliable, timely delivery which supports a given QoS for smart grid applications with critical timing requirements will although challenging is highly desirable. This paper investigates the resilience and performance of time critical smart grid application data over power line channels; specifically DLC (Distribution Line Carrier). It was shown that employing RoHC compression scheme on smart grid application IP packets can maximise bandwidth usage and enhance low delay and latency on both uplinks and downlink in a DLC channel.

Advanced Metering Infrastructure (AMI) is the foundation of the Smart Grid system. One of the most important parts of AMI is smart meter communication. Power Line Communication (PLC) technology utilizes the existing power line network for communication media between smart meters and Data Collector Units (DCU). One of the biggest challenges of communication using PLC is the noise level due to residential loads. In this study, laboratory test set up to measure noise caused by PV rooftop and residential loads are observed. Each PLC frequency band was measured and observed to determine the suitable frequency for PLC communication which was the low noise level. Some experiments in the field were conducted to determine the performance of the PLC. Laboratory test measurement result shows the FCC band (150-490 kHz) was outside the range of PV rooftop and residential load noise. On the other hand, the Cenelec A (35-90 kHz) frequency range was in the range of noise signal. Therefore, NB-PLC G3 using FCC frequency band was proposed to achieve robust data communication and lower noise level. G3 PLC FCC band was tested in the real field residential area, the experimental results showed 97.62% successful rate within one-week data collection.

On cooperative coding for narrow band PLC networks

Power lines (PLC), mainly dedicated and optimized for delivering electricity, are, nowadays, used to transfer data. Its low cost and wide coverage makes it one of the pivotal technologies in building up smart grid. The actual role of PLC technology is controversial while some preconize that PLC systems are very good candidates for some applications others discard it and look at wireless as a more elaborated alternative. It is obvious that Smart Grid will include multiple types of communications technologies ranging from optics to wireless and wireline. Among wireline solutions, PLC appears to be the only technology that has deployment cost comparable to wireless as power installation and line are already existent. Narrowband PLCs are a key point in smart grid that is elaborated to support several applications such as Automatic Meter Reading (AMR), Advanced Metering Infrastructure (AMI), demand side management, in-home energy management and Vehicle-to-grid communications A critical stage in designing an efficient PLC system remains in getting sufficient knowledge about channel behavior characteristics such as attenuation, access impedance, multiple noise scenarios and synchronization. That's why; characterizing power line network has been the interest of several research works aiming to compromise between robustness of powerline communication and higher data rate. This interest in narrowband PLC systems to find the adequate one is inciting to deeply focus on channel characterization and modeling methods. It represents a first step to simulate channel behavior then propose a stand-alone hardware for emulation. Authors are investigating the building blocks of a narrowband PLC channel emulator that helps designers to evaluate and verify their systems design. It allows a reproduction of real conditions for any narrowband PLC equipment (single carrier or multicarrier) by providing three major functionalities: noise scenarios, signal attenuation and zero crossing reference mainly used for single carriers systems. For this purpose, authors deploy a bottom up approach to identify a real channel transfer function (TF) based on a prior knowledge of used power cables characteristics and connected loads. A simulator is, then, defined based on Matlab that generates a given TF according to defined parameters. The AC mains zero crossing variation is also studied. In field exhaustive measurements of this reference have shown a perpetual fluctuation presented as a jitter error. It is the reflection of variant AC mains characteristics (frequency, amplitude) which could be related to non-linearity of connected loads at network and used detection circuit in PLC systems. Authors propose a ZC variation model according to system environment (home/ lab, rural). This model will be embedded on channel emulator to reproduce ZC reference variation. Regarding noise, few models are found in literature, specific to narrowband PLCs. An implementation of some models is done and tested on a DSP platform which will include the two previous elements: TF and ZC variation.

To meet the goal of ten-fold increase in spectral efficiency, multiuser multiple-input-multiple-output (MU-MIMO) techniques capable of achieving high spatial multiplexing gains are expected to be an essential component of fifth-generation (5G) radio access systems. This increase in multiplexing gain, made possible by equipping base stations with a large number of antennas, entails a proportional increase in channel state information (CSI) acquisition overhead. This article addresses the problem of reducing this CSI overhead by optimizing the amount of time-frequency resources allocated for channel training purposes while not affecting the quality of the associated channel estimate. First we show that in MU-MIMO, adapting pilot symbol density in the time-frequency grid should be performed both on a per resource block (RB) basis and on the basis of groups of users sharing similar channel conditions. Next, we propose a practical scheme that can perform grouping based per-RB pilot pattern adaptation. Finally, we evaluate using both analytical and numerical results the gain in spectral efficiency that can be achieved using this scheme as compared to conventional MU-MIMO systems that use fixed pilot patterns.

Envelope elimination and restoration (EER) based transmitters have attracted attention recently for two reasons: 1) The desire for increased spectral efficiency has mandated modulation standards that have large peak-to-average ratios (PAR). The increase in spectral efficiency is traded off against a decrease in average power-added-efficiency (PAE) when a linear power amplifier is used; however, when EER is used, it is decoupled somewhat from spectral efficiency. 2) Through the use of fast on-chip signal processing, the natural advantage of scaled CMOS is exploited by enabling switching power amplifier classes (e.g., class-E). This letter examines limitations associated with voltage supply switching glitches in class-G power amplifiers.

The achievement of the boundary values of spectral efficiency is associated with the development of methods for generating and receiving signals with a compact spectrum. The reason is a constant increase in the capacity of existing communication channels caused by an increase in the volume of transmitted information. Moreover, the allocated frequency bandwidths have natural limitations, and they are almost all reached. The effective way to approach the boundary values of spectral efficiency is the application of spectrally efficient signals, such as FTN (Faster-Than-Nyquist) signals. This article proposes to synthesize optimal FTN signals that are more compact in the spectrum than RRC (root raised cosine) pulses-based signals. The criterion of maximum energy concentration in the occupied frequency bandwidth and the constraint on the cross-correlation coefficient are used to solve the optimization problem. The contribution of this work is the optimization of FTN signal shape. The obtained optimal FTN signals provide a 24% increase in spectral efficiency compared to the RRC pulses-based signals. At the same time, the energy loss stays almost unchanged. To the best of authors’ knowledge, this is the first case when the frequency bandwidth reduction is achieved at practically no energy loss. The simulation modeling in channels with additive white Gaussian noise and fading channels is done with regard to the FTN-SC-FDE (Faster-Than-Nyquist - Single Carrier system with Frequency Domain Equalization) structure. The optimal FTN signals presented in this work can be used to increase the spectral efficiency of satellite broadcasting systems, such as DVB-S2/S2X.