Optical communications and networking solutions for the support of C-RAN in a 5G environment

The widespread availability of mobile devices such as tablets and smartphones has led to fast-increasing mobile data traffic in the last few years [...

Overview on Optical Fronthauling Technologies for Fixed-Mobile Convergence

We present in this Chapter an overviewof optical fronthauling technologies for fixed-mobile convergence in next generation 5G access networks. The Chapter first introduces the general concept of Cloud Radio Access Network, or C-RAN, then it presents the most common proposals for fronthauling, based on Digitized Radioover- Fiber, or D-RoF, according to the CPRI or OBSAI standards. The Chapter then prosecutes by presenting the very recent evolutions of D-RoF toward the "functional split" paradigm, as already available in the latest releases of the CPRI specifications. Finally, some recent research trends towards Analog RoF are presented. The Chapter is intentionally written in a tutorial way, to be used by newcomers in this field. It anyway also reports a vast set of bibliographic references to guide the interested reader toward more detailed technical presentations

Fronthaul network modeling and dimensioning meeting ultra-low latency requirements for 5G

Enabling the transport of fronthaul traffic in next-generation cellular networks [fifth-generation (5G)] following the cloud radio access network (C-RAN) architecture requires a redesign of the fronthaul network featuring high capacity and ultra-low latency. With the aim of leveraging statistical multiplexing gains, infrastructure reuse, and, ultimately, cost reduction, the research community is focusing on Ethernet-based packet-switch networks. To this end, we propose using the high queuing delay percentiles of the G/G/1 queuing model as the key metric in fronthaul network dimensioning. Simulations reveal that Kingman's exponential law of congestion provides accurate estimates on such delays for the particular case of aggregating a number of evolved Common Public Radio Interface fronthaul flows, namely functional splits Iu and IID. We conclude that conventional 10 G, 40 G, and 100 G transponders can cope with multiple legacy 10-20 MHz radio channels with worst-case delay guarantees. Conversely, scaling to 40 and 100 MHz channels will require the introduction of 200G, 400G, and even 1T high-speed transponders.The authors would like to acknowledge the support of the Spanish project TEXEO (grant no. TEC2016-80339-R), and the H2020 EU-funded project BlueSPACE (grant no. 762055)

Simulation of CPRI traffic on Optical Ethernet

Evolution of mobile networks calls for novel ways of reducing delays while improving the network capacity. All application types require a system to utilize the expanding data. In the future, the projection is that quality of service (QoS) will be a key measurement of any network. Delay and jitter present a challenge to achieving the QoS needed. This is due to the loss of packets experienced during transmission and retransmission. Hence, the thesis proposes a Hybrid switching solution to increase the efficiency of transport networks for mobile data. This is done by designing a model that reduces the number of wavelengths needed to transport Common Public Radio interface (CPRI) over Ethernet while sharing the same optical resources for conventional backhaul traffic. CPRI over Ethernet is an ideal method to aid in better exploitation of the resources. The proposed strategy minimizes the loss of packets by making use of the available gaps during the transmission. Implementing such a model requires a Guaranteed Service Traffic (GST) class, which does not allow for packet loss and is treated as high priority traffic. Additionally, GST has a fixed low delay that makes it resilient to any form of network failures. Moreover, CPRI assists in saving costs by exploiting the unused wavelength capacity left by the GST traffic. Backhaul traffic can exploit this unused capacity to make the system compact. The thesis considers two classes of service levels with possible set of services that have QoS. These are CPRI over Ethernet (CPRIoE) and traditional packet-based Backhaul traffic. CPRIoE is considered as the GST traffic while Backhaul is the Best Effort (BE) traffic. Both traffics are transported over the same links, sharing wavelength resources. The results indicate the effectiveness of combining services in managing multiple flows, thus saving resources and optimizing the network

5G fronthaul-latency and jitter studies of CPRI over ethernet

Common Public Radio Interface (CPRI) is a successful industry cooperation defining the publicly available specification for the key internal interface of radio base stations between the radio equipment control (REC) and the radio equipment (RE) in the fronthaul of mobile networks. However, CPRI is expensive to deploy, consumes large bandwidth, and currently is statically configured. On the other hand, an Ethernet-based mobile fronthaul will be cost-efficient and more easily reconfigurable. Encapsulating CPRI over Ethernet (CoE) is an attractive solution, but stringent CPRI requirements such as delay and jitter are major challenges that need to be met to make CoE a reality. This study investigates whether CoE can meet delay and jitter requirements by performing FPGA-based Verilog experiments and simulations. Verilog experiments show that CoE encapsulation with fixed Ethernet frame size requires about tens of microseconds. Numerical experiments show that the proposed scheduling policy of CoE flows on Ethernet can reduce jitter when redundant Ethernet capacity is provided. The reduction in jitter can be as large as 1 μs, hence making Ethernet-based mobile fronthaul a credible technology

Transmission of 5G signals in multicore fibers impaired by inter-core crosstalk

A capacidade de dados exigida pelo surgimento do 5G levou a mudanças na arquitetura das redes sem fios passando a incluir fibras multinúcleo (MCFs, acrónimo anglo-saxónico de multicore fibers) no fronthaul. No entanto, a transmissão de sinais nas MCFs é degradada pela interferência entre núcleos (ICXT, acrónimo anglo-saxónico de intercore crosstalk). Neste trabalho, o impacto da ICXT sobre o desempenho na transmissão de sinais CPRI (acrónimo anglo-saxónico de Common Public Radio Interface) numa rede de acesso 5G com detecção direta, suportada por MCFs homogéneas com um acoplamento reduzido entre núcleos, é estudado através de simulação numérica. A taxa de erros de bit (BER, acrónimo anglo-saxónico de bit error rate), a análise de padrões de olho, a penalidade de potência e a indisponibilidade são utilizadas como métricas para avaliar o impacto da ICXT no desempenho do sistema, considerando dois modelos para a polariza- ção dos sinais. Os resultados numéricos são obtidos através da combinação de simulação de Monte Carlo com um método semi-analítico para avaliar a BER. Para uma penalidade de potência de 1 dB, para sinais CPRI com FEC (acrónimo anglo-saxónico de forward-error correction), devido ao aumento do walkoff da MCF de 1 ps/km para 50 ps/km, a tolerância dos sinais CPRI relativamente à ICXT aumenta 1.4 dB. No entanto, para níveis de interferência que levam a uma penalidade de potência de 1 dB, o sistema está praticamente indisponível. Para alcançar uma probabilidade de indisponibilidade de 10-5 usando sinais com FEC, são necessários níveis de interferência muito mais reduzidos, abaixo de -27:8 dB e -24:8 dB, para sinais de polarização única e dupla, respectivamente. Este trabalho demonstra que é essencial estudar a indisponibilidade em vez da penalidade de potência de 1 dB para garantir a qualidade do serviço em sistemas de comunicação óptica com detecção direta suportados por MCFs homogéneas com um acoplamento reduzido entre núcleos onde a ICXT domina a degradação do desempenho.The data capacity demanded by the emergence of 5G lead to changes in the wireless network architecture with proposals including multicore fibers (MCFs) in the fronthaul. However, the transmission of signals in MCFs is impaired by intercore crosstalk (ICXT). In this work, the impact of ICXT on the transmission performance of Common Public Radio Interface (CPRI) signals in a 5G network fronthaul supported by homogeneous weakly-coupled MCFs with direct detection is studied by numerical simulation. Bit error rate (BER), eye-patterns analysis, power penalty and outage probability are used as metrics to assess the ICXT impact on the system performance, considering two models for the signals polarizations. The results are obtained by combining Monte Carlo simulation and a semi-analytical method to assess numerically the BER. For 1 dB power penalty, with forward error correction (FEC) CPRI signals, due to the increase of the MCF walkoff from 1 ps/km to 50 ps/km, an improvement of the tolerance of CPRI signals to ICXT of 1.4 dB is observed. However, for crosstalk levels that lead to 1 dB power penalty, the system is unavailable with very high outage probability. To reach a reasonable outage probability of 10−5 for FEC signals, much lower crosstalk levels, below -27:8 dB, and -24:8 dB, for single and dual polarization signals, respectively, are required. Hence, this work shows that it is essential to study the outage probability instead of the 1 dB power penalty to guarantee quality of service in direct-detection optical communication systems supported by weakly-coupled homogeneous MCFs and impaired by ICXT