Special issue: Radio-over-fibre for green wireless access networks

Vol. 68, n° 1-2, January-February 2013

Content available on Springerlink

Guest editors
Trevor J. Hall, University of Ottawa, Canada
Frédéric Lucarz, Télécom Bretagne, France
John Mitchell, University College London, UK
Patrice Pajusco, Télécom Bretagne, France


Trevor J. Hall, Frédéric Lucarz, John Michell, Patrice Pajusco

Radio-over-Fibre access for sustainable Digital Cities

Trevor J. Hall1, Ramón Maldonado-Basilio1, Sawsan Abdul-Majid1, Joe Seregelyi1, Ran Li1, Irene Antolín-Pérez1, Hamdam Nikkhah1, Frédéric Lucarz2, Jean-Louis de Bougrenet de La Tocnaye2, Bruno Fracasso2, Patrice Pajusco2, Camilla Kärnfelt2, Daniel Bourreau2, Michel Ney2, Rabiaa Guemri2, Yves Josse2, Hexin Li2
1 University of Ottawa, Canada
2 Télécom Bretagne, France

Abstract Pervasive broadband access will transform cities to the net social, environmental and economic benefit of the e-City dweller as did the introduction of utility and transport network infrastructures. Yet without action, the quantity of greenhouse gas emissions attributable to the increasing energy consumption of access networks will become a serious threat to the environment. This paper introduces the vision of a ‘sustainable Digital City’ and then considers strategies to overcome economic and technical hurdles faced by engineers responsible for developing the information and communications technology (ICT) network infrastructure of a Digital City. In particular, ICT energy consumption, already an issue from an operating cost perspective, is responsible for 3 % of global energy consumption and is growing unsustainably. A grand challenge is to conceive of networks, systems and devices that together can cap wireless network energy consumption whilst accommodating growth in the number of subscribers and the bandwidth of services. This paper provides some first research directions to tackle this grand challenge. A distributed antenna system with radio frequency (RF) transport over an optical fibre (or optical wireless in benign environments) distribution network is identified as best suited to wireless access in cluttered urban environments expected in a Digital City from an energy consumption perspective. This is a similar architecture to Radio-over-Fibre which, for decades, has been synonymous with RF transport over analogue intensity-modulated direct detection optical links. However, it is suggested herein that digital coherent optical transport of RF holds greater promise than the orthodox approach. The composition of the wireless and optical channels is then linear, which eases the digital signal processing tasks and permits robust wireless protocols to be used end-to-end natively which offers gains in terms of capacity and energy efficiency. The arguments are supported by simulation studies of distributed antenna systems and digital coherent Radio-over-Fibre links

Keywords Radio-over-fibre – Green ICT – Digital Cities

Digitized RF-over-fiber as a cost-effective and energy-efficient backhaul option for wireless communications

Yizhuo Yang, Ampalavanapillai Nirmalathas, Christina Lim
The University of Melbourne, Australia

Abstract Digitized RF-over-fiber technique based on bandpass sampling theory is studied as an alternative of analog radio-over-fiber to deliver wireless signals, taking advantage of digital optical link and realizing simpler base station architecture. In this paper, we present an overview of our recent research on digitized radio-over-fiber (RoF) technique, including discussions on the designing issues and possible solutions, proof-of-concept demonstrations and experimental results. Then, we examine the energy efficiency of the digitized RoF technique using a generic base station (BS) power model and compare with conventional BS designs. Based on the estimated energy consumption per square meter, digitized RoF technique has advantage for larger cell size.

Keywords Energy efficiency – Power consumption – RF-over-fiber technique – Wireless communications

Comparisons of system architectures for microwave-photonics transmissions at 60 GHz

B. Cabon, F. Brendel, J. Poëtte
Grenoble INP-MINATEC, France

Abstract We report here on different system architectures for a wireless link operating in the 60 GHz range, which has a high potential for use in short range and highly secure high data rate applications. The millimetre wave around 60 GHz is generated by photonic heterodyning or microwave-photonics using radio-over-fibre concept of transmission. Low error transmission using two techniques at data rates up to 4.2 Gb/s is experimentally demonstrated.

Keywords Microwave photonics – Mixers – Up- and down- conversion

90° SOI optical hybrid for Radio-over-fibre links

Sawsan Abdul-Majid1, Imad Hasan1, Qi Zheng1, Ramón Maldonado-Basilio1, Serge Bidnyk2, Trevor J. Hall1
1 University of Ottawa, Canada
2 Enablence Technologies, Ottawa, Canada

Abstract Radio-over-fibre (RoF) technology is receiving large attention due to its ability to provide simple antenna front ends, increased capacity and increased wireless access coverage. Coherently detected RoF systems would enable the information to be carried in both the amplitude and phase or in different states of the polarisation of the optical field. Additionally, the selectivity of coherent receiver is very well suited for access networks. We present a 90° optical hybrid built on a silicon-on-insulator planar light-wave circuit, which can be used as the optical front end of the digital coherent receiver in a digitised RoF link and will lead to reduced receiver footprint and cost. The optical hybrid circuit includes 2 × 2 and 4 × 4 multimode interference (MMI) splitters, in a polarisation diversity configuration. The simulation results at vacuum wavelength 1,550 nm show polarisation independence and phase errors between the ports of less than 0.03°. The properties of the prototyped 4 × 4 MMI were measured over a wide range of wavelengths. The 2 × 2 and 4 × 4 MMI showed nearly equal splitting ratios. Measurements of the relative phase relationship between the ports for Transverse Electric mode polarisation are shown to match the simulation results.

Keywords Optical Hybrid – Silicon-on-insulator – Multimode interference couplers – Radio-over-fibre

Beam steering for wireless optical links based on an optical phased array in silicon

Hamdam Nikkhah1, Karel Van Acoleyen2, Roel Baets2
1 University of Ottawa, Canada
2 Ghent University, Belgium

Abstract The ability to steer optical beams, crucial to the operation of high-speed optical wireless links may be achieved using optical phased array antennas which have significant potential in this application. The beam formed by the phased array antennas is steered by tuning the relative phase difference between the adjacent antenna elements which may be achieved nonmechanically. In this paper, the characteristics and behaviour of two dimensional optical phased arrays with a structure composed of 2 × 2, 4 × 4, and 16 × 16 antenna elements in beam steering are verified. The wavelength beam steering of −0.16°/nm is measured along the θ direction with a required steering range (between main lobes) of 1.97° within a −3 dB envelop of 5° extent in the θ direction and 7° extent in the Φ direction. To achieve two-dimensional beam steering, thermo-optic beam steering can be used in Φ direction. It is found that the thermo-optic phase tuning departs the expected quadratic dependence and is well characterised by a quartic dependence upon heater current or voltage.

Keywords Beam steering – Wireless optical links – Optical-phased array – Si Planar Light Circuit

Experimental evaluation of a R-EAM and noise impact analysis for UWB and Wi-Fi transmission in RoF networks

L. M. Pessoa1,2, J. M. B. Oliveira1,2, D. V. Coelho1,2, J. C. S. Castro1, H. M. Salgado1,2
1 INESC-TEC Porto, Portugal
2 Universidade do Porto, Portugal

Abstract The performance of a reflective electro-absorption modulator transceiver is assessed in terms of both slope efficiency (SE) and responsivity in a radio-over-fiber network. Different biasing schemes are analyzed, specifically zero bias (passive solution), bias for maximum SE, and bias for maximum responsivity. Finally, two case studies on multiband orthogonal frequency division multiplexing ultra-wide band and Wi-Fi are presented, for which the optimum setup parameters are determined.

Keywords Radio-over-fiber – Electro-absorption modulator – Zero bias – Ultra-wide band

Comparison of theoretical and measured P1dB of a photonic microwave link: influence of some physical parameters of the DFB laser

Anne-Laure Billabert1, Quentin Levesque1,2, Mourad Chtioui2, Catherine Algani1, Christian Rumelhard1, Alexandre Marceaux2, Thomas Merlet2
1 ESYCOM, CNAM, France
2 Thales Air Systems, France

Abstract This paper studies a microwave photonic link built as an IM/DD or intensity modulation–direct detection semiconductor laser system. The radiofrequency gain and 1 dB compression point of the link are both simulated with a modelling approach and compared to measurements. The electrical model of the electro-optic transducer, a distributed feedback laser, is first presented. Taking into account the nonlinearities and noise sources, it is developed on the commercial electrical software Advanced Design System. Owing to this accurate model, the impact of the relaxation oscillation frequency is presented on the system nonlinearity characteristic as for example the input 1 dB compression point. The comparison of simulated results to measured ones confirms the accuracy of this model.

Keywords Photonic microwave link – One decibel compression point – Electrical equivalent circuit

Optimisation of a device for pick-up of low-frequency radio signals and transmission over polymer optical fibres

Ricardo M. Ribeiro1, Andrés P. L. Barbero1, Odair S. Xavier1, Jorge A. M. Souza2, Marbey M. Mosso2
1 Universidade Federal Fluminense, Brasil
2 Pontifica Universidade Catolica do Rio de Janeiro, Brasil

Abstract The development of passive (without RF amplifier) and optimised VHF-detector/optical-modulator circuit module as a device for operation in the 88–108 MHz band will be described in this paper. It uses illumination-type light-emitting diodes (LEDs) emitting at 650 nm as the light source, coupled with poly(methyl methacrylate) polymer optical fibre. Reactive impedance matching is performed between the optoelectronic light source and the antenna by taking into account the some capacitance variation with the frequency of the antenna and of the biased LED, not resolved with the packaging parasitic effects. The relatively simple device presented here and named wireless-over-polymer optical fibre may be useful in many low-frequency radio-over-fibre applications and may contribute to energy savings.

Keywords Radio-over-fibre – Optoelectronics – Polymer optical fibres – Photonic antenna – Conjugate impedance matching – Reactance impedance matching

Open topics

Stochastic analysis of Aloha in vehicular ad hoc networks

Barłomiej Błaszczyszyn1, Paul Mühlethaler2, Yasser Toor2
1 INRIA/ENS, Paris, France
2 INRIA Rocquencourt, France

Abstract The aim of this paper is to study the Aloha medium access (MAC) scheme in 1D, linear networks, which might be an appropriate assumption for vehicular ad hoc networks. We study performance metrics based on the signal over interference plus noise ratio assuming power-law mean path-loss and independent point-to-point fading. We derive closed formulas for the capture probability. We consider the presence or the absence of noise and we study performance with outage or with adaptive coding. We carry out the joint optimization of the density of packet progress (in bit-meters) both in the transmission probability and in the transmission range. We also compare the performance of slotted and non-slotted Aloha. We show that in contrast to planar networks the density of packet progress per unit of length does not increase with the network node density.

Keywords VANETs – Slotted Aloha – Non-slotted Aloha – Medium access control (MAC) – Layer optimization – Throughput

Adaptive allocation of power transmission for high-altitude platforms

R. Goot, T. Trigano, S. Tapuchi, J. Gavan
Shamoon College of Engineering, Israel

Abstract An adaptive power allocation method for signals transmitted from high-altitude platforms is proposed, and justification of its usefulness is provided. The possible structural scheme for the system is given and its performance is investigated. The adaptation algorithm is based on an optimization procedure, which enables the allocation of the available power to a maximal number of users. The proposed algorithm is tested on simulations. It is shown that for Nakagami fading in downlink channels, the adaptive power allocation yields an energetic gain which can attain up to 21 dB.

Keywords Adaptation – Power allocation – High-altitude platforms – Communication quality