Reduced Dispersion Duplex DQPSK Radio-Over-Fiber Communications Using Single-Laser-Based Multiple Side-Bands

Multiple side-bands are generated from a single laser diode with the aid of optical carrier suppression, which facilitates the transmission of reduced-rate parallel streams mapped to the side-bands. As a benefit, all the signal processing tasks including demultiplexing of a high data rate signal into multiple low data rate signals can be performed at the central unit. The technique can also be useful in reducing the effect of dispersion in case of high frequency Radio Over Fiber (ROF) communications by transmitting a single high data rate signal as multiple low data rate signals using the side-bands generated. We demonstrate the duplex transmission of a bit-rate of 768 Mbit/s over a 50 km fiber using three side-bands in each direction. The three side-band aided system has a BER performance which is close to that of the idealized benchmarker operating in a back-to-back mode

Sub-Carrier-Multiplexed Duplex 64-QAM Radio-Over-Fiber Transmission for Distributed Antennas

We demonstrate the feasibility of Radio Over Fiber (ROF) transmission of 4 Sub-Carrier Multiplexed (SCM) 64- QAM data streams to a pair of low-complexity Radio Access Units (RAUs), which form part of a virtual MIMO architecture under the control of a Central Unit (CU). The ROF signal is transmitted over low frequency RF carriers and heterodyne detection is used at the RAUs. The 4 coherent optical carriers used for data transmission as well as for heterodyning at the RAUs are generated using a single laser rather than several inevitably non-coherent lasers. Our proposed system transmits duplex data of 480 Mbit/s and 240 Mbit/s in the downlink and uplink directions, respectively at mm-wave frequencies of 25 GHz or 50 GHz

Radio over fiber systems

The three main types of Radio Over Fiber (ROF)communication systems, namely analogue ROF, baseband ROF and digitized ROF are investigated. Optical fibers are increasingly replacing copper wires. In long-haul, high-bit-rate communication systems optical fiber has already become the dominant mode of transmission due to its enormous bandwidth and low loss. ROF facilitate the seamless integration of optical and wireless communication systems. Since the RF spectrum is limited, wireless systems rely on re-using the frequencies at different geographic locations, but the ever-increasing tele-traffic demands require ever-reduced cell-sizes. This enables wireless systems to provide high data rates for a reduced number of users by assigning each of them a larger fraction of the total bandwidth. Furthermore, higher frequencies, expanding to the microwave and mmwavelength bands are capable of supporting increased data rates. Since high-frequency signals travel shorter distances due to their higher path-loss, the cell sizes have to be further reduced. This reduction in cell size implies that more Radio Access Units (RAUs) are required for the increased number of cells, which are located close to each other. Conceiving these RAUs relying on complex signal processing is costly. Therefore, it is desirable to have simple RAUs that are connected to a central unit where all the signal processing tasks are carried out. In this scenario, ROF plays an important role in connecting these RAUs to the central unit. The major factors that makes ROF suitable is its transparency to the type of RF signal being transported, the large available bandwidth of fiber and its low attenuation. The first type of ROF communication investigated is baseband ROF (BROF), where electronic baseband data is directly transmitted over the fiber after Electronic-to-Optical (EO) conversion. Baseband optical communications generally transmit optical pulses that have a Gaussian timedomain profile associated with the most compact spectrum for transmitting baseband digital data. Optical pulsed laser sources are capable of generating narrow Gaussian pulses that may be used for high-rate systems relying on ON-OFF keying. All-optical regeneration of signals is investigated, where the signals transmitted over large distances may be regenerated at regular intervals. The second type of ROF communication is analogue ROF (AROF), where the analogue RF signal is transmitted over the fiber using an optical carrier. Finally, digitized ROF (DROF) communication is discussed, which digitizes the RF signal at the transmitter and after transmitting it over the fiber, it converts the digital signal back to analogue at the receiver. The thesis is concluded with the comparative study of the pros and cons of BROF, AROF and DROF techniques

Imperfect Digital Fibre Optic Link Based Cooperative Distributed Antennas with Fractional Frequency Reuse in Multicell Multiuser Networks

The achievable throughput of the entire cellular area is investigated, when employing fractional frequency reuse techniques in conjunction with realistically modelled imperfect optical fibre aided distributed antenna systems (DAS) operating in a multicell multiuser scenario. Given a fixed total transmit power, a substantial improvement of the cell-edge area's throughput can be achieved without reducing the cell-centre's throughput. The cell-edge's throughput supported in the worst-case direction is significantly enhanced by the cooperative linear transmit processing technique advocated. Explicitly, a cell-edge throughput of $\eta=5$ bits/s/Hz may be maintained for an imperfect optical fibre model, regardless of the specific geographic distribution of the users

Baseband Radio over Fiber Aided Millimeter-Wave Distributed Antenna for Optical/Wireless Integration

A Baseband Radio Over Fiber (BROF) architecture is proposed, where upto four Radio Frequency (RF) carriers can be generated, while using the heterodyne photo-detection of only two optical signals. This proposed BROF architecture has a star-like structure and it is composed of six Radio Access Units (RAUs), where data is transmitted from the Central Unit (CU) to the Base Station (BS) and from the BS to the RAU over a distance of 20 Km and 0.3 Km, respectively, at a rate of 768 Mbps. The performance of the system supporting four carrier frequencies drops by at most 1dB, at a BER of 10-9, compared to conventional heterodyne photo-detection

A Full-Duplex Diversity-Assisted Hybrid Analogue/Digitized Radio Over Fibre for Optical/Wireless Integration

A duplex Radio Over Fibre (ROF) ring architecture is proposed taking into account the constraints imposed by the cost of fibre laying and of the optical/electronic components, as well as the spectral efficiency and the duplex link performance. It has been shown that relying on Analogue ROF (AROF) and state-of-the-art Digitized ROF (DROF) architectures for downlink and uplink transmission, respectively, attains a high-integrity duplex performance. A sophisticated amalgam of Optical Carrier Suppression (OCS), Code Division Multiplexing (CDM), optical frequency multiplexing, Optical Carrier Reuse (OCR) and distributed antennas is conceived

Lack of Academic-Industrial Liaison in Pakistan – A Quantitative Study

The primary focus of this work is to explore the causes and key limitations in Pakistan's current academic-industrial liaison. This work is aimed at highlighting the different forms and benefits and the conditions for the university-business partnership. The study has a quantitative structure and a chosen philosophy of positivism and deductive methodology, and the novel knowledge is obtained through a 5-point Likert Scale questionnaire. Pakistani organizations should help universities to use the views on education programs, learning achievements, practical training, internships and vocational training for businesses contributing to schools. The scientists at the school should also address other issues of the economy and business sector and provide the answers as a guide in the cycle for companies.Keywords: Pakistan; Academic-industry liaison; university-business; Positivism philosophyDOI: 10.7176/EJBM/12-2-09Publication date: January 31st 202

Modeling Off-line Routing and Spectrum Allocation Problem in Elastic Optical Network

The swift escalation in internet traffic due to diverse bandwidth starving applications and innovative concepts of modern technologies such as Elastic Optical Networks (EONs) and Software-defined networking (SDN) demands a dynamic and flexible optical network architecture both at the control and data plane. Characteristically, the flexibility in EONs is achieved by the emerging SDN-enabled sliceable bandwidth variable transponders (SBVTs) that support multiple optical carriers' simultaneous generation. These generated multiple optical carriers can operate different lightpaths using slice-ability or combined into a single high-rate super-channel. In this perspective, one of the major issues in EON is Routing and Spectrum Allocation (RSA). Typically, in EON, RSA is a spectrum management and Nondeterministic Polynomial-time hardness (NP-hard) problem in which network resources mainly bank on the applied ordering strategy. This article proposed a novel heuristic algorithm, Minimum Hops with Least Slot Spectrum (MHLS), to accommodate maximum traffic requests with better spectrum utilization. The proposed algorithm aims to minimize block requests, block traffic, and the total number of spectrum slots used in the network. The MHLS exploits Dijkstra-shortest-path and SDN-enabled SBVTs for RSA problem. The performance evaluation of MHLS is accomplished on the entire USA network

Routing and Spectrum Allocation Heuristic for Sliced Elastic Optical Network System

We proposed a heuristic algorithm, Minimum Hops with Least Slots spectrum (MHLS), to solve the Routing and spectrum assignment problem in elastic optical networks. The proposed MHLS is implemented in conjunction with the transponder supporting slice-ability

Quantum Long Short-Term Memory (QLSTM) vs Classical LSTM in Time Series Forecasting: A Comparative Study in Solar Power Forecasting

Accurately forecasting solar power generation is crucial in the global progression towards sustainable energy systems. In this study, we conduct a meticulous comparison between Quantum Long Short-Term Memory (QLSTM) and classical Long Short-Term Memory (LSTM) models for solar power production forecasting. Our controlled experiments reveal promising advantages of QLSTMs, including accelerated training convergence and substantially reduced test loss within the initial epoch compared to classical LSTMs. These empirical findings demonstrate QLSTM's potential to swiftly assimilate complex time series relationships, enabled by quantum phenomena like superposition. However, realizing QLSTM's full capabilities necessitates further research into model validation across diverse conditions, systematic hyperparameter optimization, hardware noise resilience, and applications to correlated renewable forecasting problems. With continued progress, quantum machine learning can offer a paradigm shift in renewable energy time series prediction. This pioneering work provides initial evidence substantiating quantum advantages over classical LSTM, while acknowledging present limitations. Through rigorous benchmarking grounded in real-world data, our study elucidates a promising trajectory for quantum learning in renewable forecasting. Additional research and development can further actualize this potential to achieve unprecedented accuracy and reliability in predicting solar power generation worldwide.Comment: 17 pages, 8 figure