Salman Ghafoor

Imperfect Digital-Fiber-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 modeled imperfect optical-fiber-aided distributed antenna systems (DASs) operating in a multicell multiuser scenario. Given fixed total transmit power, substantial improvement of the cell-edge areas throughput can be achieved without reducing the cell centers throughput. The cell edges throughput supported in the worst-case direction is significantly enhanced by the cooperative linear transmit processing technique advocated. Explicitly, a cell-edge throughput of η = 5 bit/s/Hz may be maintained for an imperfect optical fiber model, regardless of the specific geographic distribution of the users.

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.

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.

Duplex Digitized Transmission of 64-QAM Signals over a Single Fiber Using a Single Pulsed Laser Source

We demonstrate digitized duplex transmission of 64-QAM signals using pulsed optical communications. Bidirectional data transmission is achieved over a single 25 km optical fibre using a single optical pulsed source. The choice of suitable parameters for bandpass sampling technique used for the digitization of the 16 MSamples/s 64-QAM signal are discussed. It is demonstrated that using digitized transmission of RF signals, long distance transmission can be supported at a performance close to that of the back-to-back analogue benchmarker.

The \"Rap\" on ROF: Radio over Fiber Using Radio Access Point for High Data Rate Wireless Personal Area Networks

A wireless personal area network (WPAN) allows the wireless devices in a users personal workspace to be connected to the network. Due to the huge increase in both the number of wireless communication subscribers and the bandwidth required per customer with the proliferation of smart devices, the low-frequency radio spectrum is becoming overcrowded. A natural solution for future WPANs is to migrate to higher radio frequency (RF) carriers [1]. High data-rate WPANs may be implemented based on the Federal Communications Commission (FCC) compliant ultrawideband (UWB) standard [2] or on the IEEE 802.15.3c standard [3]. The UWB signal was defined by the FCC as a signal having a bandwidth larger than 20% of the carrier frequency or a bandwidth of at least 500 MHz in the 3.1-10.6-GHz band; IEEE 802.15.3c relies on a carrier frequency in the 60-GHz license-free industrial, scientific, and medical (ISM) band. The implementation of both the UWB standard and the IEEE 802.15.3c standard faces certain challenges, which may be tackled with the aid of radio over fiber (ROF) techniques that employ optical generation of the wireless signal. ROF networking solutions have been proposed for future high-bandwidth wireless communication systems that rely on the transmission of RF signals between the base station (BS) and remote antennas [1], [4]-[8].

Effect of dispersion slope of highly nonlinear fibre on the performance of Self Phase Modulation based 2R-optical regenerator

In this paper we numerically investigate the effect of dispersion slope of the highly nonlinear fibre on the performance of Self Phase Modulation based 2R-optical regenerators. Our numerical study shows that the dispersion slope has a significant impact on the shape of the transfer function of the regenerator. The dispersion slope can therefore be used together with the dispersion value and the filter offset as an additional parameter to control the performance of the regenerator. It is also shown that a high dispersion slope can be beneficial in increasing the energy yield of the regenerator by a maximum of 23%. Dispersion slope is also helpful in reducing the effect of pulse-to-pulse overlapping

Cost-Efficient Distributed Amplification in a Bidirectional Optical Fiber Link

We propose and demonstrate a novel technique to implement distributed amplification in a bidirectional link. Multiple optical signals are transmitted in a duplex configuration over a single fiber. The multiple channels are generated using only two optical sources on each side of the link. Distributed amplification is achieved using Raman scattering where the data modulated signal in the downlink direction acts as a pump signal as well. To obtain maximum Raman gain and to minimize Rayleigh scattering, the difference between the center frequencies of the downlink and uplink signals is kept at 13 THz. The resulting bit-error-rate plots show low values of receiver sensitivities.

A survey on energy saving in IP-over-WDM networks

In the IP-over-WDM networks, there are the mainly following four reasons for high energy consumption. Firstly, and most importantly, cooling of the IT equipment takes huge chunk from overall energy consumption. Secondly, over provisioning leads to redundant devices at all time. Thirdly, deployed networks are designed without consideration of energy. Lastly, data packet are routed without taking care of energy consumption along the journey. Thus, this work categorizes different approaches into four categories e.g cooling, sleep node, design and traffic grooming,. In each category, we discuss few state-of-the-art research efforts. Hence, this work briefs about energy efficiency for the IP-over-WDM networks.