Fronthaul-Constrained Cloud Radio Access Networks: Insights and Challenges

As a promising paradigm for fifth generation (5G) wireless communication systems, cloud radio access networks (C-RANs) have been shown to reduce both capital and operating expenditures, as well as to provide high spectral efficiency (SE) and energy efficiency (EE). The fronthaul in such networks, defined as the transmission link between a baseband unit (BBU) and a remote radio head (RRH), requires high capacity, but is often constrained. This article comprehensively surveys recent advances in fronthaul-constrained C-RANs, including system architectures and key techniques. In particular, key techniques for alleviating the impact of constrained fronthaul on SE/EE and quality of service for users, including compression and quantization, large-scale coordinated processing and clustering, and resource allocation optimization, are discussed. Open issues in terms of software-defined networking, network function virtualization, and partial centralization are also identified.Comment: 5 Figures, accepted by IEEE Wireless Communications. arXiv admin note: text overlap with arXiv:1407.3855 by other author

Cognitive radio DAB MAC protocol performance using a CR specific simulator and software defined radio

Abstract: With the constant advances in wireless technology, radio spectrum has become a very scarce resource. Cognitive Radio (CR) has emerged as a viable way to deal with our inefficient use of the radio spectrum by utilizing unused spectrum holes or white spaces, as they are referred to. Using Software Defined Radio (SDR) we are able to realize CRs and their unique properties. Most of the research that has been done on CR protocols has been based on analytical assessments and simulations using non-CR specific network simulators. In this paper we code and compare two existing CR specific Medium Access Control (MAC) protocols using a CR specific simulator. We then prototype the chosen protocols using the Universal Software Radio Peripheral (USRP). This allows us to see how close the simulated performance results come to those actually achieved in a real prototype

Mobility-aware QoS assurance in software-defined radio access networks: an analytical study

Software-defined networking (SDN) has gained a tremendous attention in the recent years, both in academia and industry. This revolutionary networking paradigm is an attempt to bring the advances in computer science and software engineering into the information and communications technology (ICT) domain. The aim of these efforts is to pave the way for completely programmable networks and control-data plane separation. Recent studies on feasibility and applicability of SDN concepts in cellular networks show very promising results and this trend will most likely continue in near future. In this work, we study the benefits of SDN on the radio resource management (RRM) of future-generation cellular networks. Our considered cellular network architecture is in line with the recently proposed Long-Term Evolution (LTE) Release 12 concepts, such as user/control plane split, heterogeneous networks (HetNets) environment, and network densification through deployment of small cells. In particular, the aim of our RRM scheme is to enable the macro base station (BS) to efficiently allocate radio resources for small cell BSs in order to assure quality-of-service (QoS) of moving users/vehicles during handovers. We develop an approximate, but very time- and space-efficient algorithm for radio resource allocation within a HetNet. Experiments on commodity hardware show algorithm running times in the order of a few seconds, thus making it suitable even in cases of fast moving users/vehicles. We also confirm a good accuracy of our proposed algorithm by means of computer simulations

Advances in compact semiconductor device modelling and circuit macromodelling with the Qucs GPL circuit simulator

Advances in circuit simulation technology suggest a strong movement towards software packages which promote equation based compact semiconductor device model and circuit macromodel development. The Verilog-A subset of the Verilog- AMS hardware description language being a popular choice of hardware description language for model construction. The Qucs circuit simulator is one of the GPL software packages supporting the MOS-AK Verilog-A standardisation initiative. This paper outlines recent advances in Qucs equation based modelling techniques, including (1) Qucs equation defined device/Verilog-A compatibility improvements, (2) non-linear radio frequency equation defined device modelling techniques, (3) modelling non-linear physical processes, and (4) methods for construction Verilog-A models for established and new technologies. The paper also presents a number of examples which illustrate the capabilities of the Qucs model construction tools implemented by the Qucs development team

MARTE based design flow for Partially Reconfigurable Systems-on-Chips

International audienceSystems-on-Chip (SoCs) are considered an integral solution for designing embedded systems, for targeting complex intensive parallel computation applications. As advances in SoC technology permit integration of increasing number of hardware resources on a single chip, the targeted application domains such as software-defined radio are become increasingly sophisticated. The fallout of this complexity is that the system design, particularly software design, does not evolve at the same pace as that of hardware leading to a significant productivity gap. Adaptivity and reconfigurability are also critical issues for SoCs which must be able to cope with end user environment and requirements

Software-defined radio using LabVIEW and the PC sound card: A teaching platform for digital communications

Different modulation techniques and protocols require a standard communications laboratory for engineering courses to be equipped with a broad set of equipment, tools and accessories. However, the high costs involved in a hardware-based laboratory can become prohibitively expensive for many institutions. Software simulations alone can replicate most real-world applications with much lower costs. Nevertheless, they do not replace the real-world feeling provided by hardware-based systems, which can produce and receive physical signals to and from the exterior media. Advances in computer technology are allowing software-defined radio (SDR) concepts to be applied in many areas of communications. In this type of system, the baseband processing is performed completely in software while an analog RF front end hardware can be used for RF processing. The use of a software-defined radio platform in a digital communications laboratory can offer the benefits of software simulations coupled with the enthusiasm presented by hardware-based systems. A low-cost software-defined radio teaching platform implemented in LabVIEW using the personal computer sound card was developed for a digital communications laboratory along with a set of exercises to help students assimilate the concepts involved in communications theory and system implementation. This system allows for the generation, reception, processing, and analysis of signals in a 4 QAM (quadrature amplitude modulation) transceiver using the personal computer sound card to transmit and receive modulated signals. This teaching platform provides the means necessary to explore the theoretical concepts of digital communication systems in a laboratory environment. National Instruments\u27 LabVIEW graphical programming environment allows a more intuitive way of coding, which helps students to spend more time learning the relevant theory concepts and less time coding the applications. Being a flexible and modular system, modifications can be made for optimization and use with different and/or more complex techniques

A software-defined architecture for next-generation cellular networks

In the recent years, mobile cellular networks are undergoing fundamental changes and many established concepts are being revisited. New emerging paradigms, such as Software-Defined Networking (SDN), Mobile Cloud Computing (MCC), Network Function Virtualization (NFV), Internet of Things (IoT),and Mobile Social Networking (MSN), bring challenges in the design of cellular networks architectures. Current Long-Term Evolution (LTE) networks are not able to accommodate these new trends in a scalable and efficient way. In this paper, first we discuss the limitations of the current LTE architecture. Second, driven by the new communication needs and by the advances in aforementioned areas, we propose a new architecture for next generation cellular networks. Some of its characteristics include support for distributed content routing, Heterogeneous Networks(HetNets) and multiple Radio Access Technologies (RATs). Finally, we present simulation results which show that significant backhaul traffic savings can be achieved by implementing caching and routing functions at the network edge

UWB FastlyTunable 0.550 GHz RF Transmitter based on Integrated Photonics

Currently, due to the 6G revolution, applications ranging from communication to sensing are experiencing an increasing and urgent need of software-defined ultra-wideband (UWB) and tunable radio frequency (RF) apparatuses with low size, weight, and power consumption (SWaP). Unfortunately, the coexistence of ultra-wideband and software-defined operation, tunability and low SWaP represents a big issue in the current RF technologies. Recently, photonic techniques have been demonstrated to support achieving the desired features when applied in RF UWB transmitters, introducing extremely wide operation and instantaneous bandwidth, tunable filtering, tunable photonics-based microwave mixing with very high port-to-port isolation, and intrinsic immunity to electromagnetic interferences. Moreover, the recent advances in photonics integration also allow to obtain very compact devices. In this article, to the best of our knowledge, the first example of a complete tunable software-defined RF transmitter with low footprint (i.e. on photonic chip) is presented exceeding the state-of-the-art for the extremely large tunability range of 0.5-50 GHz without any parallelization of narrower-band components and with fast tuning (< 200 s). This first implementation represents a breakthrough in microwave photonics