Amplification schemes and multi-channel DBP for unrepeatered transmission

The performance of unrepeatered transmission of a seven Nyquist-spaced 10 GBd PDM-16QAM superchannel using full signal band coherent detection and multi-channel digital back propagation (MC-DBP) to mitigate nonlinear effects is analysed. For the first time in unrepeatered transmission, the performance of two amplification systems is investigated and directly compared in terms of achievable information rates (AIRs): 1) erbium-doped fibre amplifier (EDFA) and 2) second-order bidirectional Raman pumped amplification. The experiment is performed over different span lengths, demonstrating that, for an AIR of 6.8 bit/s/Hz, the Raman system enables an increase of 93 km (36 %) in span length. Further, at these distances, MC-DBP gives an improvement in AIR of 1 bit/s/Hz (to 7.8 bit/s/Hz) for both amplification schemes. The theoretical AIR gains for Raman and MC-DBP are shown to be preserved when considering low-density parity-check codes. Additionally, MC-DBP algorithms for both amplification schemes are compared in terms of performance and computational complexity. It is shown that to achieve the maximum MC-DBP gain, the Raman system requires approximately four times the computational complexity due to the distributed impact of fibre nonlinearity.

First experimental demonstration of nonlinear inverse synthesis transmission over transoceanic distances

We demonstrate for the first time, the transmission performance of 10Gbaud nonlinear inverse synthesis based signal over transoceanic distances, showing a significant improvement in data capacity x distance product (x12) compared with other NFT-based systems.

Optimum wireless power transmission for sensors embedded in concrete

Various nondestructive testing (NDT) technologies for construction and performance monitoring have been studied for decades. Recently, the rapid evolution of wireless sensor network (WSN) technologies has enabled the development of sensors that can be embedded in concrete to monitor the structural health of infrastructure. Such sensors can be buried inside concrete and they can collect and report valuable volumetric data related to the health of a structure during and/or after construction. Wireless embedded sensors monitoring system is also a promising solution for decreasing the high installation and maintenance cost of the conventional wire based monitoring systems. Wireless monitoring sensors need to operate for long time. However, sensor batteries have finite life-time. Therefore, in order to enable long operational life of wireless sensors, novel wireless powering methods, which can charge the sensors’ rechargeable batteries wirelessly, need to be developed. The optimization of RF wireless powering of sensors embedded in concrete is studied here. First, our analytical results focus on calculating the transmission loss and propagation loss of electromagnetic waves penetrating into plain concrete at different humidity conditions for various frequencies. This analysis specifically leads to the identification of an optimum frequency range within 20–80 MHz that is validated through full-wave electromagnetic simulations. Second, the effects of various reinforced bar configurations on the efficiency of wireless powering are investigated. Specifically, effects of the following factors are studied: rebar types, rebar period, rebar radius, depth inside concrete, and offset placement. This analysis leads to the identification of the 902–928 MHz ISM band as the optimum power transmission frequency range for sensors embedded in reinforced concrete, since antennas working in this band are less sensitive to the effects of varying humidity as well as rebar configurations. Finally, optimized rectennas are designed for receiving and/or harvesting power in order to charge the rechargeable batteries of the embedded sensors. Such optimized wireless powering systems exhibit significantly larger efficiencies than the efficiencies of conventional RF wireless powering systems for sensors embedded in plain or reinforced concrete.

Survivability of Deterministic Dynamical Systems

Acknowledgements We acknowledge gratefully the support of BMBF, CoNDyNet, FK. 03SF0472A, of the EIT Climate-KIC project SWIPO and Nora Molkenthin for illustrating our illustration of the concept of survivability using penguins. We thank Martin Rohden for providing us with the UK high-voltage transmission grid topology and Yang Tang for very useful discussions. The publication of this article was funded by the Open Access Fund of the Leibniz Association.

Extended bandwidth for long haul DWDM transmission using ultra-long Raman fiber lasers

We present an ultra-long Raman fibre laser amplified system which, with only a single pump wavelength, provides comparable gain flatness and broader spectral bandwidth than a conventional gain flattened C-band EDFA. A 20x42.7Gb/s experiment shows compatibility with DWDM systems. ©2010 IEEE.

Robust H.264/AVC video transmission using data partitioning and unequal loss protection

In this work, we present an adaptive unequal loss protection (ULP) scheme for H264/AVC video transmission over lossy networks. This scheme combines erasure coding, H.264/AVC error resilience techniques and importance measures in video coding. The unequal importance of the video packets is identified in the group of pictures (GOP) and the H.264/AVC data partitioning levels. The presented method can adaptively assign unequal amount of forward error correction (FEC) parity across the video packets according to the network conditions, such as the available network bandwidth, packet loss rate and average packet burst loss length. A near optimal algorithm is developed to deal with the FEC assignment for optimization. The simulation results show that our scheme can effectively utilize network resources such as bandwidth, while improving the quality of the video transmission. In addition, the proposed ULP strategy ensures graceful degradation of the received video quality as the packet loss rate increases. © 2010 IEEE.

Capacity estimates for optical transmission based on the nonlinear Fourier transform

What is the maximum rate at which information can be transmitted error-free in fibre-optic communication systems? For linear channels, this was established in classic works of Nyquist and Shannon. However, despite the immense practical importance of fibre-optic communications providing for >99% of global data traffic, the channel capacity of optical links remains unknown due to the complexity introduced by fibre nonlinearity. Recently, there has been a flurry of studies examining an expected cap that nonlinearity puts on the information-carrying capacity of fibre-optic systems. Mastering the nonlinear channels requires paradigm shift from current modulation, coding and transmission techniques originally developed for linear communication systems. Here we demonstrate that using the integrability of the master model and the nonlinear Fourier transform, the lower bound on the capacity per symbol can be estimated as 10.7 bits per symbol with 500 GHz bandwidth over 2,000 km.

Exploring a new transmission window for telecommunications in the 2 μm waveband

In this paper, we will demonstrate the possibility of opening a new telecommunications transmission window around the 2 μm wavelength, in order to exploit the potential low loss of hollow-core photonic bandgap fibers, with the benefits of significantly lower non-linearity and latency. We will show recent efforts developing a dense wavelength division multiplexing testbed at this waveband, with 100 GHz spacing wavelength channels and 105 Gbit/s total capacity achieved.

Optimal generation scheduling of interconnected wind-coal intensive power systems

Large scale wind power generation complicated with restrictions on the tie line plans may lead to significant wind power curtailment and deep cycling of coal units during the valley load periods. This study proposes a dispatch strategy for interconnected wind-coal intensive power systems (WCISs). Wind power curtailment and cycling of coal units are included in the economic dispatch analysis of regional systems. Based on the day-ahead dispatch results, a tie line power plan adjustment strategy is implemented in the event of wind power curtailment or deep cycling occurring in the economic dispatch model, with the objective of reducing such effects. The dispatch strategy is designed based on the distinctive operation characteristics of interconnected WCISs, and dispatch results for regional systems in China show that the proposed strategy is feasible and can improve the overall system operation performance.

Rate Maximization of Decode-and-Forward Relaying Systems with RF Energy Harvesting

We consider a three-node decode-and-forward (DF) half-duplex relaying system, where the source first harvests RF energy from the relay, and then uses this energy to transmit information to the destination via the relay. We assume that the information transfer and wireless power transfer phases alternate over time in the same frequency band, and their time fraction (TF) may change or be fixed from one transmission epoch (fading state) to the next. For this system, we maximize the achievable average data rate. Thereby, we propose two schemes: (1) jointly optimal power and TF allocation, and (2) optimal power allocation with fixed TF. Due to the small amounts of harvested power at the source, the two schemes achieve similar information rates, but yield significant performance gains compared to a benchmark system with fixed power and fixed TF allocation.

Full-Duplex Spectrum Sharing in Cooperative Single Carrier Systems

We propose cyclic prefix single carrier full-duplex transmission in amplify-and-forward cooperative spectrum sharing networks to achieve multipath diversity and full-duplex spectral efficiency. Integrating full-duplex transmission into cooperative spectrum sharing systems results in two intrinsic problems: 1) the residual loop interference occurs between the transmit and the receive antennas at the secondary relays and 2) the primary users simultaneously suffer interference from the secondary source (SS) and the secondary relays (SRs). Thus, examining the effects of residual loop interference under peak interference power constraint at the primary users and maximum transmit power constraints at the SS and the SRs is a particularly challenging problem in frequency selective fading channels. To do so, we derive and quantitatively compare the lower bounds on the outage probability and the corresponding asymptotic outage probability for max–min relay selection, partial relay selection, and maximum interference relay selection policies in frequency selective fading channels. To facilitate comparison, we provide the corresponding analysis for half-duplex. Our results show two complementary regions, named as the signal-to-noise ratio (SNR) dominant region and the residual loop interference dominant region, where the multipath diversity and spatial diversity can be achievable only in the SNR dominant region, however the diversity gain collapses to zero in the residual loop interference dominant region.

Secure Transmission in Cooperative Relaying Networks with Multiple Antennas

We investigate the secrecy performance of dualhop amplify-and-forward (AF) multi-antenna relaying systems over Rayleigh fading channels, by taking into account the direct link between the source and destination. In order to exploit the available direct link and the multiple antennas for secrecy improvement, different linear processing schemes at the relay and different diversity combining techniques at the destination are proposed, namely, 1) Zero-forcing/Maximal ratio combining (ZF/MRC), 2) ZF/Selection combining (ZF/SC), 3) Maximal ratio transmission/MRC (MRT/MRC) and 4) MRT/Selection combining (MRT/SC). For all these schemes, we present new closed-form approximations for the secrecy outage probability. Moreover, we investigate a benchmark scheme, i.e., cooperative jamming/ZF (CJ/ZF), where the secrecy outage probability is obtained in exact closed-form. In addition, we present asymptotic secrecy outage expressions for all the proposed schemes in the high signal-to-noise ratio (SNR) regime, in order to characterize key design parameters, such as secrecy diversity order and secrecy array gain. The outcomes of this paper can be summarized as follows: a) MRT/MRC and MRT/SC achieve a full diversity order of M + 1, ZF/MRC and ZF/SC achieve a diversity order of M, while CJ/ZF only achieves unit diversity order, where M is the number of antennas at the relay. b) ZF/MRC (ZF/SC) outperforms the corresponding MRT/MRC (MRT/SC) in the low SNR regime, while becomes inferior to the corresponding MRT/MRC (MRT/SC) in the high SNR. c) All of the proposed schemes tend to outperform the CJ/ZF with moderate number of antennas, and linear processing schemes with MRC attain better performance than those with SC.

A novel methodology for analysis of large scale interconnected power and gas systems

The European Union continues to exert a large influence on the direction of member states energy policy. The 2020 targets for renewable energy integration have had significant impact on the operation of current power systems, forcing a rapid change from fossil fuel dominated systems to those with high levels of renewable power. Additionally, the overarching aim of an internal energy market throughout Europe has and will continue to place importance on multi-jurisdictional co-operation regarding energy supply. Combining these renewable energy and multi-jurisdictional supply goals results in a complicated multi-vector energy system, where the understanding of interactions between fossil fuels, renewable energy, interconnection and economic power system operation is increasingly important. This paper provides a novel and systematic methodology to fully understand the changing dynamics of interconnected energy systems from a gas and power perspective. A fully realistic unit commitment and economic dispatch model of the 2030 power systems in Great Britain and Ireland, combined with a representative gas transmission energy flow model is developed. The importance of multi-jurisdictional integrated energy system operation in one of the most strategically important renewable energy regions is demonstrated.

OFDM-based schemes for next generation wireless systems

The purpose of this study is to investigate two candidate waveforms for next generation wireless systems, filtered Orthogonal Frequency Division Multiplexing (f-OFDM) and Unified Filtered Multi-Carrier (UFMC). The evaluation is done based on the power spectral density analysis of the signal and performance measurements in synchronous and asynchronous transmission. In f-OFDM we implement a soft truncated filter with length 1/3 of OFDM symbol. In UFMC we use the Dolph-Chebyshev filter, limited to the length of zero padding (ZP). The simulation results demonstrates that both waveforms have a better spectral behaviour compared with conventional OFDM. However, the induced inter-symbol interference (ISI) caused by the filter in f-OFDM, and the inter-carrier interference (ICI) induced in UFMC due to cyclic prefix (CP) reduction , should be kept under control. In addition, in a synchronous transmission case with ideal parameters, f-OFDM and UFMC appear to have similar performance with OFDM. When carrier frequency offset (CFO) is imposed in the transmission, UFMC outperforms OFDM and f-OFDM.

Modulateurs intégrés sur silicium pour la transmission de signaux à modulation d'amplitude multi-niveau

Au cours des dernières années, la photonique intégrée sur silicium a progressé rapidement. Les modulateurs issus de cette technologie présentent des caractéristiques potentiellement intéressantes pour les systèmes de communication à courte portée. En effet, il est prévu que ces modulateurs pourront être opérés à des vitesses de transmission élevées, tout en limitant le coût de fabrication et la consommation de puissance. Parallèlement, la modulation d’amplitude multi-niveau (PAM) est prometteuse pour ce type de systèmes. Ainsi, ce travail porte sur le développement de modulateurs de silicium pour la transmission de signaux PAM. Dans le premier chapitre, les concepts théoriques nécessaires à la conception de modulateurs de silicium sont présentés. Les modulateurs Mach-Zehnder et les modulateurs à base de réseau de Bragg sont principalement abordés. De plus, les effets électro-optiques dans le silicium, la modulation PAM, les différents types d’électrodes intégrées et la compensation des distorsions par traitement du signal sont détaillés.Dans le deuxième chapitre, un modulateur Mach-Zehnder aux électrodes segmentées est présenté. La segmentation des électrodes permet la génération de signaux optiques PAM à partir de séquences binaires. Cette approche permet d’éliminer l’utilisation de convertisseur numérique-analogique en intégrant cette fonction dans le domaine optique, ce qui vise à réduire le coût du système de communication. Ce chapitre contient la description détaillée du modulateur, les résultats de caractérisation optique et de la caractérisation électrique, ainsi que les tests systèmes. De plus, les tests systèmes incluent l’utilisation de pré-compensation ou de post-compensation du signal sous la forme d’égalisation de la réponse en fréquence pour les formats de modulation PAM-4 et PAM-8 à différents taux binaires. Une vitesse de transmission de 30 Gb/s est démontrée dans les deux cas et ce malgré une limitation importante de la réponse en fréquence suite à l’ajout d’un assemblage des circuits radiofréquences (largeur de bande 3 dB de 8 GHz). Il s’agit de la première démonstration de modulation PAM-8 à l’aide d’un modulateur Mach-Zehnder aux électrodes segmentées. Finalement, les conclusions tirées de ce travail ont mené à la conception d’un deuxième modulateur Mach-Zehnder aux électrodes segmentées présentement en phase de test, dont les performances montrent un très grand potentiel. Dans le troisième chapitre, un modulateur à réseau de Bragg à deux sauts de phase est présenté. L’utilisation de réseaux de Bragg est une approche encore peu développée pour la modulation. En effet, la réponse spectrale de ces structures peut être contrôlée précisément, une caractéristique intéressante pour la conception de modulateurs. Dans ces travaux, nous proposons l’ajout de deux sauts de phase à un réseau de Bragg uniforme pour obtenir un pic de transmission dans la bande de réflexion de celui-ci. Ainsi, il est possible d’altérer l’amplitude du pic de transmission à l’aide d’une jonction pn. Comme pour le deuxième chapitre, ce chapitre inclut la description détaillée du modulateur, les résultats des caractérisations optique et électrique, ainsi que les tests systèmes. De plus, la caractérisation de jonctions pn à l’aide du modulateur à réseau de Bragg est expliquée. Des vitesses de transmission PAM-4 de 60 Gb/s et OOK de 55 Gb/s sont démontrées après la compensation des distorsions des signaux. À notre connaissance, il s’agit du modulateur à réseau de Bragg le plus rapide à ce jour. De plus, pour la première fois, les performances d’un tel modulateur s’approchent de celles des modulateurs de silicium les plus rapides utilisant des microrésonateurs en anneau ou des interféromètres Mach-Zehnder.