FCT- [Engenharia Eletrotécnica - Telecomunicações ][José Figueiredo]
[Descrição do Projecto] [WOWi - Wireless-optical-wireless interfaces for picocellular access networks ] [2010-2013]

WOWi - Wireless-optical-wireless interfaces for picocellular access networks

Título do projecto (em português)

WOWi - Interfaces electro-ópticas para redes de acesso picocelulares
Project title (in english)
WOWi - Wireless-optical-wireless interfaces for picocellular access networks

Projecto financiado pela Fundação para a Ciência e a Tecnologia (FCT)

Sumário / Summary
Instituições / Institutions 
Equipa / Team
Evaluation and rating
Project outputs
Final evaluation 

    

Sumário

As tecnologias actuais de redes sem fios ou de fibras ópticas não são soluções economicamente competitivas para responder à crescente procura de sistemas capazes de assegurar simultaneamente capacidade, cobertura, largura de banda, e mobilidade significativamente superiores às actuais, em espaços como centros de conferências, edifícios universitários, aeroportos, hotéis, centros comerciais, pequenos escritórios e blocos residenciais [1].

As redes Rádio sobre Fibra (RoF, Radio over Fiber) são consideradas as soluções mais promissoras e economicamente viáveis para a implementação de redes de acesso sem fios. Baseiam-se no transporte de sinais de rádio frequência (RF) usando portadoras ópticas desde as estações centrais (CO, Central Offices), até aos pontos de acesso sem fios (AP, Acesss Points) [2]. Esta tecnologia de redes permite aproximar dos utilizadores finais, fixos e móveis,a elevada largura de banda das comunicações ópticas possibilitando a disponibilização de múltiplos serviços [2].

A próxima geração de sistemas de comunicação sem fios, sistemas de quarta geração (4G), usará frequências na gama de 2 GHz e 8 GHz [3,4]. Nesta banda de frequências, taxas de transmissão de dados da ordem de Gb/s apenas serão possíveis se as dimensões da célula de acesso forem reduzidas consideravelmente. Os pontos de acesso com apenas alguns metros de alcance baseados nesta tecnologia são designados pico-células, e permitirão largura de banda elevada e grande mobilidade ao utilizador [2]. Porém, as redes RoF de pico-células só serão economicamente viáveis se forem implementadas com conversores electro-ópticos de muito baixo custo e elevada eficiência.

A solução mais simples consiste no uso de díodos laser (LD, Laser Diode) modulados directamente para obter a função “uplink” e de foto-detectores simples para a função “downlink”. Porém, estas soluções requerem o uso de amplificadores de alta potência [2]. As soluções baseadas em moduladores de electro-absorção e amplificadores ópticos semicondutores que permitam simplificar a conversão eléctrico/óptico, funcionando simultaneamente como detector/modulador [5], são mais indicadas para sistemas na banda milimétrica, tipicamente 60 GHz, devido à complexidade electrónica associada e ao custo quando comparadas com a anterior [6].

Esta proposta propõe uma nova solução de baixo custo para os pontos de acesso sem a necessidade de conversão de frequência e de optoelectrónica e electrónica adicionais, usando circuitos não lineares baseados na integração de osciladores de díodos de efeito túnel ressonante (RTD) com díodos laser (LD) e com foto-detectores (PD), para implementar as funções “uplink” e “downlink”, respectivamente.

O RTD é um nano-dispositivo electrónico com característica corrente-tensão em forma de N, exibindo uma região de resistência diferencial negativa (NDR) que aqui é utilizada para implementar osciladores eléctricos de elevada frequência [7].Os circuitos RTD-LD, obtidos integrando um RTD com um LD, apresentam novas funcionalidades optoelectrónicas como, por exemplo, a capacidade de funcionarem como osciladores optoelectrónicos controlados por tensão [8,9], produzindo uma portadora óptica com uma profundidade de modulação determinada essencialmente pelas características do RTD [10]. Estes osciladores quando perturbados por sinais RF sem fios de muito baixa potência (<-40 dBm) sincronizam e amplificam os sinais eléctricos incidentes, que por sua vez, ao modular o laser, introduzem na portadora óptica uma sub-portadora com as mesmas características do sinal sem fios incidente [11], funcionando como transdutores electro-ópticos (E/O).

O circuito RTD-PD complementar, obtido integrando um RTD com uma região foto-condutora, é capaz de sincronizar com a sub-portadora de um sinal óptico incidente [11]. Esta funcionalidade é utilizada para a transferência da sub-portadora óptica do domínio óptico para o domínio eléctrico, que é também amplificada pelo RTD [11]. O RTD-PD funciona como transdutor optico-eléctrico (O/E). A amplificação eléctrica intrínseca associada aos osciladores RTD e a simplicidade destes circuitos torna possíveis implementações de pontos de acesso de baixo custo e mais fiáveis. Este conceito foi objecto de um pedido de patente no Reino Unido, submetido recentemente pela Universidade de Glasgow, em pareceria com a Universidades do Algarve [12].

O “know-how” do IR em dispositivos e circuitos optoelectrónicos baseados em RTDs, e as competências dos restantes membros da equipa na área de modelação, sistemas RoF, sistemas de comunicação óptica e redes WDM, garantem a capacidade de realização dos objectivos da proposta: demonstrar funções de “uplink” e de “downlink” de baixo custo e reduzida complexidade para futuros pontos de acesso das redes RoF, baseadas em circuitos osciladores RTD-LD e RTD-PD não-lineares, respectivamente. Actualmente, dois membros da equipa estão envolvidos em paralelo no projecto PTDC/EEA-TEL/71678/2006 com o objectivo de demonstrar uma rede RoF reconfigurável que opera na banda de frequências milimétricas.

 

Summary

Current wireless or optical technologies alone can not provide economically competitive solutions for the growing demand for communication networks capable of simultaneously ensuring higher capacity, coverage, bandwidth, and mobility in environments such as conference venues, university buildings, airports, hotels, shopping centers, and in the end to small offices and homes. Optical-wireless access solutions based on the integration of radio signals into optical carrier at a central office (CO) that are then transmitted by optical fiber to the wireless access point (AP), known as radio-over-fiber (RoF) networks, are being considered the most promising solution because they can bring the optical network bandwidths closer to the fixed and to the mobile users and at same time allowing the deliver of multiple services.

The next generation wireless-communication systems will use air frequencies in the range of 2-8 GHz. With these frequencies Gb/s data rates are possible only if cell size is reduced considerably. The so-called pico-cellular optical-wireless access with few meters range cells are being considered as a highly promising route for delivering high bandwidth and mobility access for in-building applications.

Due to the moderate frequencies and the fiber transmission lengths involved (few km at maximum), the most cost-effective access point (AP) interface transponder solution is to use direct laser diode modulation for uplink and direct photo-detection for downlink. These solutions require the use of high power amplifiers and other RF processing electronics. Solutions employing electro-absorption modulators and semiconductor optical amplifiers can simplify electrical/optical conversion because these devices can perform detector/modulator functions simultaneously. However, they need complex optoelectronics and electronics for signals processing, which increase cost, complexity and power consumption.


Recognizing that a major challenge towards economically viable pico-cellular RoF networks is to implement low cost cell transponders with high efficient electrical and optical functionalities, we propose to investigate electrical optical (E/O) uplink and optical-electrical (O/E) downlink transponder functions using non-linear circuits based on the integration of resonant tunneling diode (RTD) oscillators with laser diodes (LD) and photo-detectors (PDs), respectively. The main advantages of these circuits are their intrinsic RF signals amplification and circuit simplicity, which makes them low-cost and more reliable.

The RTD is a nano-electronic device with a N shaped current-voltage characteristic exhibiting a negative differential resistance (NDR) region that can be used to implement high frequency electrical oscillators. When integrated with optoelectronic devices, such as LDs, can lead to novel optoelectronic functionalities such as optoelectronic voltage controlled oscillators (OVCO). This RTD-LD free-running oscillator when perturbed by radio-frequency broadcasted signals can synchronize and amplify very low power (<-40 dBm) incoming wireless signals, with the laser modulation depth being mainly determined by the NDR extension and not by wireless signal level. The oscillator locking range allows also a dynamic use of the frequency spectra available. This novel OVCO concept works as a wireless-to-optical interface converting a received low power wireless signal into an optical signal sub-carrier.

A complementary circuit is obtained integrating a RTD oscillator with a photoconductive region, the RTD-PD oscillator, that when directly illuminated by a modulated optical signal locks to the optical signal subcarrier. The optical injection locking capacity is used to O/E conversion to implement optical-to-wireless interfaces where the electrical output power is determined by the NDR region extension.

The objective of our proposal is to demonstrate simple and low-cost downlink and uplink transponder functions using RTD-LD and RTD-PD oscillators, based on locking to wireless and to optical injected signals, respectively. This proposal foresees a low-cost AP solution with no need of format and frequency conversion or complex optoelectronic and electronic circuitry, such as high power amplifiers. A UK patent application of this concept was filled last November.


The PI know-how on RTD based optoelectronic circuits, and other team members’ wide range of skills that includes knowledge of RoF systems, optical communication systems, and WDM networks, makes the team well qualified to accomplish the main goals of the proposal: implement access point E/O and O/E transponders uplink and downlink using RTD-LD and RTD-PD oscillators. Two member of the team are also involved with the project PTDC/EEA-TEL/71678/2006 aiming the demonstration of a reconfigurable RoF network operating at millimeter-wave frequencies.

  
   


Instituições Participantes / Participating Institutions
Centro de Electrónica Optoelectrónica e Telecomunicações (CEOT/UAlg)
Instituto de Engenharia de Sistemas e Computadores do Porto (INESC Porto/FE/UP)

Unidade de Investigação Adicional / Additional Research Unit
Department of Electronics and Electrical Engineering, University of Glasgow, UK
Instituto de Microelectrónica de Sevilla, IMSE-CNM, Universidad de Sevilla, Spain

Instituição de Acolhimento / Host Institution
Universidade do Algarve (UAlg)
   
 
Equipa de investigação / Research team
José Figueiredo (CEOT/UALG) - Inv. Responsável / Principal Investigator
Bruno Romeira (CEOT/UALG)
Horacio Cantu (CEOT/UALG)
Ricardo Luz (MSc student
Lígia Luís (MSc student

Henrique Salgado (INESC Porto/FE/UP)
João Oliveira  (INESC Porto/FE/UP)
Luis Pessoa  (INESC Porto/FE/UP)
Ricardo Avó  (CEOT/UALG)
    
   


Evaluation and Rating

Evaluation: Overall, the proposal is well written and detailed. The challenges that need to be addressed are clear and there is a definite research plan and roadmap in terms of what needs to be achieved and how the challenges will be addressed. If successful, the technologies developed can have a positive impact on the scientific and engineering communities.


Overall rating: 90 

 


Project outputs  
- Wireless interrogation of an optically modulated resonant tunnelling diode oscillator, Cantu, H. I.; Romeira, B.; Kelly, A. E.; Ironside, C. N.; Figueiredo, J. M. L., Microwave and Optical Technology Letters, Vol. 55 (8), 1728-1730, 2013. (PDF

- Modulation Accuracy of Binary Phase-Shift Keying Signal Broadcast after Injection Locking of a Resonant Tunnelling Diode Microwave Oscillator, Cantu, H. I.; Romeira, B.; Kelly, A. E.; Ironside, C. N.; Figueiredo, J. M. L., Microwave and Optical Technology Letters, Vol. 55 (4), 705-711, 2013. (PDF)  

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An Optical to Wireless Data Link using Radio Frequency Backscatter,  H. I. Cantú, C. N. Ironside, A. E. Kelly, B. Romeira, and J. M. L. Figueiredo, IEEE Microwave and Wireless Components Letters, Vol. 23 (2), 102-104, 2013. (PDF) JCR® impact factor1.7 DOI   

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Delayed Feedback Dynamics of Liénard-type Resonant Tunneling-Photo-Detector Optoelectronic Oscillators, B. Romeira, Julien Javaloyes, José Figueiredo, Charles N. Ironside, Horacio  Cantu, A.  Kelly; IEEE JOURNAL OF QUANTUM ELECTRONICS, VOL. 49, NO. 1, pp. 31-42,  2013. (PDF) DOI  JCR® impact factor: 1.879  

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Resonant Tunneling Diode Optoelectronic Circuits Applications in Radio-Over-Fiber Networks;  Cantu, H. I.; Romeira, B.; Kelly, A. E.; Ironside, C. N.; Figueiredo, J. M. L. Microwave Theory and Techniques, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 60, NO. 9, pp. 2903-2912, 2012.  (PDF) http://dx.doi.org/10.1109/TMTT.2012.2206606  JCR® impact factor: 1.853 


- Conversion of Phase Modulated Signals from Optical Network to Wireless Domain using Resonant Tunneling Diode Optoelectronic Integrated Circuits, Horacio Cantu; Bruno Romeira; Krishna Seunarine; Anthony Kelly; Charles Ironside; Jose Figueiredo; to be presented at The Optical Fiber Communication Conference 2012 (OFC/NFOEC 2012). (PDF)  

- Nonlinear dynamics of a Liénard delayed-feedback optoelectronic oscillator, B. Romeira, J. M. L. Figueiredo, C. N. Ironside, K. Seunarine, and J. Javaloyes, Joint conference Third International Workshop on Nonlinear Dynamics and Synchronization (INDS'11) and Sixteenth International Symposium on Theoretical Electrical Engineering (ISTET'11), Session: Nonlinear Dynamics, chaos and Synchronization - 2, Klagenfurt, Austria, July 25-27, 2011. (
PDF

- Clock Recovery of an Injection-Locked Resonant Tunneling Diode Microwave-Photonics Oscillator, B. Romeira, L. M. Pessoa, H. M. Salgado, S. Silva, J. M. L. Figueiredo, 13th International Conference on Transparent Optical Networks (ICTON 11), paper We.C5.6, Stockholm, Sweden, June 26-30, 2011. (
PDF)

- A Liénard optoelectronic oscillator with time-delayed feedback, B. Romeira, K. Seunarine, C. N. Ironside, J. Javaloyes, A. E. Kelly, J. M. L. Figueiredo, The European Conference on Lasers and Electro-Optics (CLEO) and the European Quantum Electronics Conference (EQEC) Conference Digest, OSA Technical Digest (CD) (Optical Society of America, 2011), paper CI3.2, Munich, Germany, May 22-26, 2011. (
PDF)

- Review of optoelectronic oscillators based on modelocked lasers and resonant tunneling diode optoelectronics, C. N. Ironside, M. Haji, L. Hou, J. Akbar, A. E. Kelly, K. Seunarine, B. Romeira, J. M. L. Figueiredo, International Conference on Applications of Optics and Photonics (AOP11), Proc. SPIE 8001, 80011T, Braga, Portugal, May 3-7, 2011. (
PDF)

- Optoelectronic Oscillator Topologies based on Resonant Tunneling Diode Fiber Optic Links, B. Romeira, J. M. L Figueiredo, K. Seunarine, C. N. IronsideInternational Conference on Applications of Optics and Photonics (AOP11), Proc. SPIE 8001, 80011T, Braga, Portugal, May 3-7, 2011. (
PDF)

- A Self-Synchronized Optoelectronic Oscillator based on an RTD Photo-Detector and a Laser Diode, B. Romeira, K. Seunarine, C. N. Ironside, A. E. Kelly, J. M. L. Figueiredo, Photon. Technol. Lett., 23 (16), pp. 1148-1150, 2011. (
PDF)

- DC Characterization of Tunnel Diodes Under Stable Non-Oscillatory Circuit Conditions, L. Wang,  J. M. L. Figueiredo, C. N. Ironside, E. Wasige, IEEE Transactions on Electron Devices, 58 (2), pp. 343-347, 2011. (
PDF

- Applications of laser diode sources with integrated resonant tunnelling diode technology, C. N. Ironside, B. Romeira, K. Seunarine, , A. E. Kelly, T. J Slight, and J. M. L. Figueiredo,
Photonex2010 – Industry Programme, C6: Novel Sources and detectors, Telford, UK, 3-4 November 2010. (PDF)

- Optical Control of a Resonant Tunneling Diode Microwave-Photonic Oscillator, B. Romeira, J. M. L. Figueiredo, C. N. Ironside, A. E. Kelly, T. J. Slight, IEEE Photonics Technology Letters, vol. 22, no. 21, pp. 1610-1612, 2010. (
PDF)

- An Optoelectronic Oscillator based on a Resonant Tunneling Diode Photo-Detector Integrated Chip, B. Romeira, K. Seunarine, C. N. Ironside, A. E. Kelly, T. J Slight, J. M. L. Figueiredo,
The 23rd Annual Meeting of the IEEE Photonics Society, paper MD4, Denver, Colorado, USA, 7-11 November, 2010. (PDF

- Microwave-Photonic Oscillators for Radio-over-Fibre Access Networks, J. M. L. Figueiredo, B. Romeira, T. J. Slight, C. N. Ironside,
VIII Symposium On Enabling Optical Networks and Sensors (SEON 10), FEUP, Porto, Portugal, 2010. (PDF)

- Microwave Photonic Oscillators for Femtocellular Access Networks, B. Romeira, T. J. Slight, A. E. Kelly, C. N. Ironside, J. M L Figueiredo,
15th European Conference on Networks and Optical Communications (NOC 2010), Components and modulation strategies, Faro-Algarve, Portugal, 8-10 Junho 2010. (PDF)

- Interfaces and Method For Wireless-Optical and Optical-Wireless Conversion, J. M. L. Figueiredo, B. Romeira, C. N. Ironside, T. J. Slight, 2010, Patent Application GB2465184-A; Patent Application WO2010052481-A1 (publication date 14-05-2010). (PDF)  
  
- Telecommunications interfacing systems and methods, Patent Application No GB0820432.3 (publication date 12-05-2010). (PDF)

 
- Optical injection locking of a resonant tunneling diode - optical waveguide photo-detector, Bruno Romeira, José Figueiredo, C. N. Ironside, A. E. Kelly, T. J. Slight,
15th European Conference on Integrated Optics (ECIO 2010), Cambridge, April 7-9, 2010. (PDF

  


Final evaluation 

"Os objectivos científicos previstos foram plenamente atingidos. Os resultados evidenciam grande qualidade científica, nomeadamente ao nível das publicações em revistas internacionais com referee. O projecto contribuiu para a formação de jovens investigadores e para a projecção internacional da equipa envolvida."
 
"The context of the project was related to the development of novel low-cost cell transponders with efficient electrical and optical functionalities for radio access points over fiber. To that end the project targeted the investigation of electro-optical upling and optical-electrical downlink functions using nonlinear circuits based on integrating resonant tunneling diode (RTD) oscillators together with laser diodes (LD) and photo-detectors (PD). The goal was therefore the demonstration of working simple, low-cost, RTD transponders for up- and downlink communication. A patent was previously issued in the UK to protect intellectual property and the project intended on demonstrating the possibilities and viability of this technology.
 
From the data provided by the team members, the proposed indicators were met and even exceeded, with the exception of the patent which is said to be under consideration, a reasonable situation given the results obtained.
 
Overall, both the scientific as well as the financial execution of the
project have be be considered very good."
 

Departamento de Física & CEOT-UALG, Faculdade de Ciências e Tecnologia, Universidade do Algarve, Campus de Gambelas, 8005-139 FARO, Portugal. E-mail: jlongras@ualg.pt, URL: http://w3.ualg.pt/~jlongras/