Software Defined Applications in Cellular and Optical Networks

abstract: Small wireless cells have the potential to overcome bottlenecks in wireless access through the sharing of spectrum resources. A novel access backhaul network architecture based on a Smart Gateway (Sm-GW) between the small cell base stations, e.g., LTE eNBs, and the conventional backhaul gateways, e.g., LTE Servicing/Packet Gateways (S/P-GWs) has been introduced to address the bottleneck. The Sm-GW flexibly schedules uplink transmissions for the eNBs. Based on software defined networking (SDN) a management mechanism that allows multiple operator to flexibly inter-operate via multiple Sm-GWs with a multitude of small cells has been proposed. This dissertation also comprehensively survey the studies that examine the SDN paradigm in optical networks. Along with the PHY functional split improvements, the performance of Distributed Converged Cable Access Platform (DCCAP) in the cable architectures especially for the Remote-PHY and Remote-MACPHY nodes has been evaluated. In the PHY functional split, in addition to the re-use of infrastructure with a common FFT module for multiple technologies, a novel cross functional split interaction to cache the repetitive QAM symbols across time at the remote node to reduce the transmission rate requirement of the fronthaul link has been proposed.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

DSP-enabled Reconfigurable Optical Network Devices and Architectures for Cloud Access Networks

To meet the ever-increasing bandwidth requirements, the rapid growth in highly dynamic traffic patterns, and the increasing complexity in network operation, whilst providing high power consumption efficiency and cost-effectiveness, the approach of combining traditional optical access networks, metropolitan area networks and 4-th generation (4G)/5-th generation (5G) mobile front-haul/back-haul networks into unified cloud access networks (CANs) is one of the most preferred “future-proof” technical strategies. The aim of this dissertation research is to extensively explore, both numerically and experimentally, the technical feasibility of utilising digital signal processing (DSP) to achieve key fundamental elements of CANs from device level to network architecture level including: i) software reconfigurable optical transceivers, ii) DSP-enabled reconfigurable optical add/drop multiplexers (ROADMs), iii) network operation characteristics-transparent digital filter multiple access (DFMA) techniques, and iv) DFMA-based passive optical network (PON) with DSP-enabled software reconfigurability. As reconfigurable optical transceivers constitute fundamental building blocks of the CAN’s physical layer, digital orthogonal filtering-based novel software reconfigurable transceivers are proposed and experimentally and numerically explored, for the first time. By making use of Hilbert-pair-based 32-tap digital orthogonal filters implemented in field programmable gate arrays (FPGAs), a 2GS/s@8-bit digital-to-analogue converter (DAC)/analogue-to-digital converter (ADC), and an electro-absorption modulated laser (EML) intensity modulator (IM), world-first reconfigurable real-time transceivers are successfully experimentally demonstrated in a 25km IMDD SSMF system. The transceiver dynamically multiplexes two orthogonal frequency division multiplexed (OFDM) channels with a total capacity of 3.44Gb/s. Experimental results also indicate that the transceiver performance is fully transparent to various subcarrier modulation formats of up to 64-QAM, and that the maximum achievable transceiver performance is mainly limited by the cross-talk effect between two spectrally-overlapped orthogonal channels, which can, however, be minimised by adaptive modulation of the OFDM signals. For further transceiver optimisations, the impacts of major transceiver design parameters including digital filter tap number and subcarrier modulation format on the transmission performance are also numerically explored. II Reconfigurable optical add/drop multiplexers (ROADMs) are also vital networking devices for application in CANs as they play a critical role in offering fast and flexible network reconfiguration. A new optical-electrical-optical (O-E-O) conversion-free, software-switched flexible ROADM is extensively explored, which is capable of providing dynamic add/drop operations at wavelength, sub-wavelength and orthogonal sub-band levels in software defined networks incorporating the reconfigurable transceivers. Firstly, the basic add and drop operations of the proposed ROADMs are theoretically explored and the ROADM designs are optimised. To crucially validate the practical feasibility of the ROADMs, ROADMs are experimentally demonstrated, for the first time. Experimental results show that the add and drop operation performances are independent of the sub-band signal spectral location and add/drop power penalties are <2dB. In addition, the ROADMs are also robust against a differential optical power dynamic range of >2dB and a drop RF signal power range of 7.1dB. In addition to exploring key optical networking devices for CANs, the first ever DFMA PON experimental demonstrations are also conducted, by using two real-time, reconfigurable, OOFDM-modulated optical network units (ONUs) operating on spectrally overlapped multi-Gb/s orthogonal channels, and an offline optical line terminal (OLT). For multipoint-to-point upstream signal transmission over 26km SSMF in an IMDD DFMA PON, experiments show that each ONU achieves a similar upstream BER performance, excellent robustness to inter-ONU sample timing offset (STO) and a large ONU launch power variation range. Given the importance of IMDD DFMA-PON channel frequency response roll-off, both theoretical and experimental explorations are undertaken to investigate the impact of channel frequency response roll-off on the upstream transmission of the DFMA PON system Such work provides valuable insights into channel roll-off-induced performance dependencies to facilitate cost-effective practical network/transceiver/component designs

Network slicing architecture for SDM and analog-radio-over-fiber-based 5G fronthaul networks

\u3cp\u3eThe blueSPACE project focuses on the study of innovative technologies to overcome the limitations of current fronthaul networks. The key technology proposed is space-division multiplexing, which makes it possible to increase the capacity available in conventional single-mode fibers, effectively encompassing this capacity to the forecasted bandwidth demands imposed by 5G mobile communications. In this paper, we present the innovative optical fronthaul infrastructure proposed in the project and the tailored extensions to the European Telecommunications Standards Institute network function virtualization management and orchestration architecture for this enhanced infrastructure together with practical implementation considerations.\u3c/p\u3

Data transport over optical fibre for ska using advanced modulation flexible spectrum technology

Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA.We optimise the flexible spectrum for real-time dynamic channel wavelength assignment, to ensure optimum network performance. We needed to identify and develop novel hardware and dynamic algorithms for these networks to function optimally to perform critical tasks. Such tasks include wavelength assignment, signal routing, network restoration and network protection. The antennas of the Square Kilometre Array (SKA) network connect to the correlator and data processor in a simple point-to-point fixed configuration. The connection of the astronomer users to the data processor, however, requires a more complex network architecture. This is because the network has users scattered around South Africa, Africa and the whole world. This calls for upgrade of the classical fixed wavelength spectrum grids, to flexible spectrum grid that has improved capacity, reliable, simple and cost-effectiveness through sharing of network infrastructure. The exponential growth of data traffic in current optical communication networks requires higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilisation and resolve wavelength contention associated with the flexible spectrum. Flexible Spectrum Dense Wavelength Division Multiplexed (DWDM) optical fibre networks are next-generation technology for handling extremely high data rates of the kind produced by MeerKAT and SKA. Each DWDM channel is capable of 10 Gbps transmission rate, which is sliceable into finer flexible grid 12.5 GHz granularity to offer the network elastic spectrum and channel spacing capable of signal routing and wavelength switching for the scalability of aggregate bandwidth. The variable-sized portions of the flexible spectrum assignment to end users at different speeds depend on bandwidth demand, allowing efficient utilisation of the spectrum resources. The entire bandwidth of dynamic optical connections must be contiguously allocated. However, there is an introduction of spectrum fragmentation due to spectrum contiguity related to the optical channels having different width. Thus large traffic demands are likely to experience blocking regardless of available bandwidth. To minimise the congestion and cost-effectively obtain high performance, the optical network must be reconfigurable, achievable by adding wavelength as an extra degree of freedom for effectiveness. This can introduce colourless, directionless and contentionless reconfigurability to route individual wavelengths from fibre to fibre across multiple nodes to avoid wavelength blocking/collisions, increasing the flexibility and capacity of a network. For these networks to function optimally, novel hardware and dynamic algorithms identification and development is a critical task. Such tasks include wavelength assignment, signal routing, network restoration and network protection. In this work, we for the first time to our knowledge proposed a spectrum defragmentation technique through reallocation of the central frequency of the optical transmitter, to increase the probability of finding a sufficient continuous spectrum. This is to improve network resource utilisation, capacity and resolve wavelength contention associated with a flexible spectrum in optical communication networks. The following chapter provides details on a flexible spectrum in optical fibre networks utilising DWDM, optimising transmitter-receivers, advanced modulation formats, coherent detection, reconfigurable optical add and drop multiplexer (ROADM) technology to implement hardware and middleware platforms which address growing bandwidth demands for scalability, flexibility and cost-efficiency. A major attribute is tunable lasers, an essential component for future flexible spectrum with application to wavelength switching, routing, wavelength conversion and ROADM for the multi-node optical network through spectrum flexibility and cost-effective sharing of fibre links, transmitters and receivers. Spectrum slicing into fine granular sub-carriers and assigning several frequency slots to accommodate diverse traffic demands is a viable approach. This work experimentally presents a spectral efficient technique for bandwidth variability, wavelength allocation, routing, defragmentation and wavelength selective switches in the nodes of a network, capable of removing the fixed grid spacing using low cost, high bandwidth, power-efficient and wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) transmitter directly modulated with 10 Gbps data. This to ensure that majority of the spectrum utilisation at finer channel spacing, wastage of the spectrum resource as caused by the wavelength continuity constraint reduction and it improves bandwidth utilisation. The technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency