Modeling Time Aware Shaping in an Ethernet Fronthaul

An Opnet model of a time-aware shaper (TAS) based on the IEEE 802.1Qbv standard is presented. The TAS model is assumed to be the scheduling entity in an Ethernet-based fronthaul network, comprising of Ethernet switches. The fronthaul transports different traffic flow types as envisioned in next generation Radio Access Networks (RANs), including those for a timing protocol (based on the precision time protocol) and those from the implementation of different RAN functional subdivisions. The performance of the TAS is compared to that of a strict priority regime and is quantified through the frame delay variation of the high priority traffic when this contends with lower priority traffic. The results show that with the TAS implementation, contention effects can be overcome and frame delay variation (frame jitter) can be removed. Timing instability in the significant events of the scheduler is considered and a solution to overcome this issue is proposed

Scheduling in an Ethernet Fronthaul Network

This paper investigates and compares the performance of different scheduling techniques in an Ethernet fronthaul network in the presence of both time-sensitive/high priority and background traffic streams. A switched Ethernet architecture is used as the fronthaul section of a cloud radio access network (C-RAN) and a comparison of two scheduling schemes, strict priority scheduling and time-aware shaping, is carried out. The different streams are logically separated using virtual local area network identifiers and contend for the use of trunk links formed between aggregator/switch nodes. The scheduling schemes are applied in the access and trunk ports in the fronthaul, and need to handle the queue management and prioritization of the different streams. In such cases, contention induced latency variation has to be characterized, especially when the fronthaul transports precision time protocol traffic, as it directly leads to errors in timestamping. OPNET models for strict priority and time-aware schedulers have been built and employed, and simulation results are used to compare the performance of the two scheduling schemes

Lossless Ethernet and its applications

Ethernet network is the most widely used transport network in access and data-center networks. Ethernet-based networks provide several advantages such as i) low-cost equipment, ii) sharing existing infrastructure, as well as iii) the ease in the Operations, Administration and Maintenance (OAM). However, Ethernet network is a best-effort network which raises significant issues regarding packet loss and throughput. In this research, we investigate the possibility of achieving lossless Ethernet while keeping network switches unchanged. We present three lossless Ethernet applications namely i) switch fabric for routers, ii) lossless data center fabric, and iii) zero-jitter fronthaul network for Common Public Radio Interface (CPRI) over Ethernet for 5th Generation Mobile Networks (5G) network. Switch fabric in routers requires stringent characteristics in term of packet loss, fairness, no head-of-line blocking and low latency. We propose a novel concept to control and prevent congestion in switch fabrics to achieve scalable, flexible, and more cost-efficient router fabric while using commodity Ethernet switches. On the other hand, data center applications require strict characteristics regarding packet loss, fairness, head-of-line blocking, latency, and low processing overhead. Therefore, we present a congestion control for data center networks. Our proposal is designed to achieve minimum queue length and latency while guaranteeing fairness between flows of different rates, packet sizes and Round-trip Times (RTTs). Besides, Using Ethernet as a transport network for fronthaul in 5G networks draws significant attention of both academia and industry due to i) the low cost of equipment, ii) sharing existing infrastructure, as well as iii) the ease of operations, administration and maintenance (OAM). Therefore, we introduce a distributed scheduling algorithm to support CPRI traffic over Ethernet. The results obtained through testbed implementations and simulations show that Lossless Ethernet is feasible and could achieve minimum queue length, latency, and jitter while preventing Head Of Line (HOL) blocking

Enhancing LTE with Cloud-RAN and Load-Controlled Parasitic Antenna Arrays

Cloud radio access network systems, consisting of remote radio heads densely distributed in a coverage area and connected by optical fibers to a cloud infrastructure with large computational capabilities, have the potential to meet the ambitious objectives of next generation mobile networks. Actual implementations of C-RANs tackle fundamental technical and economic challenges. In this article, we present an end-to-end solution for practically implementable C-RANs by providing innovative solutions to key issues such as the design of cost-effective hardware and power-effective signals for RRHs, efficient design and distribution of data and control traffic for coordinated communications, and conception of a flexible and elastic architecture supporting dynamic allocation of both the densely distributed RRHs and the centralized processing resources in the cloud to create virtual base stations. More specifically, we propose a novel antenna array architecture called load-controlled parasitic antenna array (LCPAA) where multiple antennas are fed by a single RF chain. Energy- and spectral-efficient modulation as well as signaling schemes that are easy to implement are also provided. Additionally, the design presented for the fronthaul enables flexibility and elasticity in resource allocation to support BS virtualization. A layered design of information control for the proposed end-to-end solution is presented. The feasibility and effectiveness of such an LCPAA-enabled C-RAN system setup has been validated through an over-the-air demonstration

Rede sensível ao tempo: um estudo do mapeamento sistemático

The time sensitive network (TSN) is a technology that aims to provide a whole new level of determinism. It is made up of a set of standards, which are still being developed by the IEEE 802.1 working group. Its goal is to provide a network with extremely small packet loss in addition to calculable latencies and jitter. Because it is fairly recent, there is a certain di culty nding relevant materials for conducting research or developing it. Based on this problem this problem, the objective of this work is to perform a survey, gathering the important information about this new technology. The TSN is a set of several mechanisms. Each of them belongs to the 802.1 standard group. The work done here, talks about eight of the main mechanisms. In this way, a reader who has some level of information about networks, is able to understand the most relevant mechanisms and therefore can understand how the time sensitive network works, and its full potential.A rede sensível ao tempo (TSN) é uma tecnologia que visa fornecer um nível de determinismo totalmente novo. Ela é formada por um conjunto de padrões, os quais ainda estão sendo desenvolvidos pelo grupo de trabalho IEEE 802.1. Eles visam fornecer uma rede com perda de pacotes extremamente pequena alem de latências calculáveis e jitter limitado. Por ser razoavelmente recente, ha uma certa dificuldade de encontrar materiais relevantes para a realização uma pesquisa ou para o desenvolvimento da mesma. Visando essa problemática, o objetivo deste trabalho é realizar um mapeamento sistemático reunindo as informações importantes sobre esta nova tecnologia. A TSN é um conjunto de vários mecanismos. Cada um deles pertence a um padrão do grupo 802.1. O trabalho realizado aqui, fala sobre oito dos principais mecanismos. Deste modo o leitor, que possua algum nível de informação sobre redes, é capaz de compreender os mecanismos mais relevantes e por conseguinte entender como a rede sensível ao tempo funciona e todo o seu potencial

Ethernet Fronthaul and Time-Sensitive Networking for 5G and Beyond Mobile Networks

Ethernet has been proposed to be used as the transport technology in the future fronthaul network. For this purpose, a model of switched Ethernet architecture is developed and presented in order to characterise the performance of an Ethernet mobile fronthaul network. The effects of traditional queuing regimes, including Strict Priority (SP) and Weighted Round Robin (WRR), on the delay and delay variation of LTE streams under the presence of background Ethernet traffic are investigated using frame inter-arrival delay statistics. The results show the effect of different background traffic rates and frame sizes on the mean and Standard Deviation (STD) of the LTE traffic frame inter-arrival delay and the importance of selecting the most suitable queuing regime based on the priority level and time sensitivity of the different traffic types. While SP can be used with traffic types that require low delay and Frame Delay variation (FDV), this queuing regime does not guarantee that the time sensitive traffic will not encounter an increase in delay and FDV as a result of contention due to the lack of pre-emptive mechanisms. Thus, the need for a queuing regime that can overcome the limitations of traditional queuing regimes is shown. To this extent, Time Sensitive Networking (TSN) for an Ethernet fronthaul network is modelled. Different modelling approaches for a Time Aware Shaper (TAS) based on the IEEE 802.1Qbv standard in Opnet/Riverbed are presented. The TAS model is assumed to be the scheduling entity in an Ethernet-based fronthaul network model, located in both the Ethernet switches and traffic sources. The TAS with/without queuing at the end stations has been presented as well. The performance of the TAS is compared to that of SP and WRR and is quantified through the FDV of the high priority traffic when this contends with lower priority traffic. The results show that with the TAS, contentioninduced FDV can be minimized or even completely removed. Furthermore, variations in the processing times of networking equipment, due to the envisaged softwarization of the next generation mobile network, which can lead to time variation in the generation instances of traffic in the Ethernet fronthaul network (both in the end-nodes and in switches/aggregators), have been considered in the TAS design. The need for a Global Scheduler (GS) and Software Defined Networking (SDN) with TAS is also discussed. An Upper Physical layer functional Split (UPS), specifically a pre-resource mapper split, for an evolved Ethernet fronthaul network is modelled. Using this model and by incorporating additional traffic sources, an investigation of the frame delay and FDV limitations in this evolved fronthaul is carried out. The results show that contention in Ethernet switch output ports causes an increase in the delay and FDV beyond proposed specifications for the UPS and other time sensitive traffic, such as legacy Common Public Radio Interface (CPRI)-type traffic. While TAS can significantly reduce or even remove FDV for UPS traffic and CPRI-type traffic, it is shown that TAS design aspects have to carefully consider the different transmission characteristics, especially the transmission pattern, of the contending traffic flows. For this reason, different traffic allocations within TAS window sections are proposed. Furthermore, it is demonstrated that increased link rates will be important in enabling longer fronthaul fibre spans (more than ten Kilometres fibre spans with ten Gigabit Ethernet links). The results also show that using multiple hops (Ethernet switches/aggregators) in the network can result in a reduction in the amount of UPS traffic that can be received within the delay and FDV specifications. As a result, careful considerations of the fibre span length and the number of hops in the fronthaul network should be made

Massive MIMO Pilot Scheduling over Cloud RAN

Cloud-RAN (C-RAN) is a promising paradigm for the next generation radio access network infrastructure, which offers centralized and coordinated base-band signal processing. On the other hand, this requires extremely low latency fronthaul links to achieve real-time centralized signal processing. In this paper, we investigate massive MIMO pilot scheduling in a C- RAN infrastructure. Three commonly used scheduling policies are investigated with simulations in order to provide insight on how the scheduling performance is affected by the latency incurred by the C-RAN infrastructure