Will TCP work in mmWave 5G Cellular Networks?

The vast available spectrum in the millimeter wave (mmWave) bands offers the possibility of multi-Gbps data rates for fifth generation (5G) cellular networks. However, mmWave capacity can be highly intermittent due to the vulnerability of mmWave signals to blockages and delays in directional searching. Such highly variable links present unique challenges for adaptive control mechanisms in transport layer protocols and end-to-end applications. This paper considers the fundamental question of whether TCP - the most widely used transport protocol - will work in mmWave cellular systems. The paper provides a comprehensive simulation study of TCP considering various factors such as the congestion control algorithm, including the recently proposed TCP BBR, edge vs. remote servers, handover and multi- connectivity, TCP packet size and 3GPP-stack parameters. We show that the performance of TCP on mmWave links is highly dependent on different combinations of these parameters, and identify the open challenges in this area.Comment: 7 pages, 4 figures, 2 tables. To be published in the IEEE Communication Magazin

Evaluation of Active Queue Management (AQM) Models in Low Latency Networks

Abstract: Low latency networks require the modification of the actual queuing management in order to avoid large queuing delay. Nowadays, TCP’s congestion control maximizes the throughput of the link providing benefits to large flow packets. However, nodes’ buffers may get fully filled, which would produce large time delays and packet dropping situations, named as bufferbloat problem. For actual time-sensitive applications demand, such as VoIP, online gaming or financial trading, these queueing times cause bad quality of service being directly noticed in user’s utilization. This work studies the different alternatives for active queue management (AQM) in the nodes links, optimizing the latency of the small flow packets and, therefore, providing better quality for low latency networks in congestion scenarios. AQM models are simulated in a dumbbell topology with ns3 software, which shows the diverse latency values (measured in RTT) according to network situations and the algorithm that has been installed. In detail, RED, CoDel, PIE, and FQ_CoDel algorithms are studied, plus the modification of the TCP sender’s congestion control with Alternative Backoff with ECN (ABE) algorithm. The simulations will display the best queueing times for the implementation that mixes FQ_CoDel with ABE, the one which maximizes the throughput reducing the latency of the packets. Thus, the modification of queueing management with FQ_CoDel and the implementation of ABE in the sender will solve the bufferbloat problem offering the required quality for low latency networks.Resumen Las redes de baja latencia requieren la modificación de la actual gestión de las colas con el fin de eludir los extensos tiempos de retardo. Hoy en d´ıa, el control de congestión de TCP maximiza el rendimiento (throughput) del enlace otorgando beneficio a los grandes flujos de datos, sin embargo, los buffers son plenamente cargados generando altos tiempos de retardo y fases de retirada de paquetes, llamada a esta situación el problema de Bufferbloat. Par las aplicaciones contempor´aneas como las llamadas VoIP, los juegos on-line o los intercambios financieros; estos tiempos de cola generan una mala calidad de servicio detectada directamente por los usuarios finales. Este trabajo estudia las diferentes alternativas de la gestión activa de colas (AQM), optimizando la latencia de los peque˜nos flujos y, por lo tanto, brindando una mejor calidad para las redes de baja latencia en situaciones de congestión. Los modelos AQM han sido evaluados en una topolog´ıa ’dumbbell’ mediante el simulador ns3, entregando resultados de latencia (medidos en RTT) de acuerdo con la situación del enlace y el algoritmo instalado en la cola. Concretamente, los algoritmos estudiados han sido RED, CoDel, PIE y FQ_CoDel; adem´as de la modificación del control de congestión TCP del emisor denominada ABE (Alternative Backoff with ECN). Las simulaciones que mejor resultados ofrecen son las que implementan combinación de FQ_CoDel con el algoritmo ABE, maximizando el rendimiento y reduciendo la latencia de los paquetes. Por lo tanto, la modificación con FQ_CoDel en las colas y la de ABE en el emisor ofrecen una solución al problema del Bufferbloat altamente solicitada por las redes de baja latencia

Reducing Internet Latency : A Survey of Techniques and their Merit

Bob Briscoe, Anna Brunstrom, Andreas Petlund, David Hayes, David Ros, Ing-Jyh Tsang, Stein Gjessing, Gorry Fairhurst, Carsten Griwodz, Michael WelzlPeer reviewedPreprin

Buffer De-bloating in Wireless Access Networks

PhDExcessive buffering brings a new challenge into the networks which is known as Bufferbloat, which is harmful to delay sensitive applications. Wireless access networks consist of Wi-Fi and cellular networks. In the thesis, the performance of CoDel and RED are investigated in Wi-Fi networks with different types of traffic. Results show that CoDel and RED work well in Wi-Fi networks, due to the similarity of protocol structures of Wi-Fi and wired networks. It is difficult for RED to tune parameters in cellular networks because of the time-varying channel. CoDel needs modifications as it drops the first packet of queue and the head packet in cellular networks will be segmented. The major contribution of this thesis is that three new AQM algorithms tailored to cellular networks are proposed to alleviate large queuing delays. A channel quality aware AQM is proposed using the CQI. The proposed algorithm is tested with a single cell topology and simulation results show that the proposed algorithm reduces the average queuing delay for each user by 40% on average with TCP traffic compared to CoDel. A QoE aware AQM is proposed for VoIP traffic. Drops and delay are monitored and turned into QoE by mathematical models. The proposed algorithm is tested in NS3 and compared with CoDel, and it enhances the QoE of VoIP traffic and the average endto- end delay is reduced by more than 200 ms when multiple users with different CQI compete for the wireless channel. A random back-off AQM is proposed to alleviate the queuing delay created by video in cellular networks. The proposed algorithm monitors the play-out buffer and postpones the request of the next packet. The proposed algorithm is tested in various scenarios and it outperforms CoDel by 18% in controlling the average end-to-end delay when users have different channel conditions

Evaluation of Active Queue Management (AQM) Models in Low Latency Networks

Abstract: Low latency networks require the modification of the actual queuing management in order to avoid large queuing delay. Nowadays, TCP’s congestion control maximizes the throughput of the link providing benefits to large flow packets. However, nodes’ buffers may get fully filled, which would produce large time delays and packet dropping situations, named as bufferbloat problem. For actual time-sensitive applications demand, such as VoIP, online gaming or financial trading, these queueing times cause bad quality of service being directly noticed in user’s utilization. This work studies the different alternatives for active queue management (AQM) in the nodes links, optimizing the latency of the small flow packets and, therefore, providing better quality for low latency networks in congestion scenarios. AQM models are simulated in a dumbbell topology with ns3 software, which shows the diverse latency values (measured in RTT) according to network situations and the algorithm that has been installed. In detail, RED, CoDel, PIE, and FQ_CoDel algorithms are studied, plus the modification of the TCP sender’s congestion control with Alternative Backoff with ECN (ABE) algorithm. The simulations will display the best queueing times for the implementation that mixes FQ_CoDel with ABE, the one which maximizes the throughput reducing the latency of the packets. Thus, the modification of queueing management with FQ_CoDel and the implementation of ABE in the sender will solve the bufferbloat problem offering the required quality for low latency networks.Resumen Las redes de baja latencia requieren la modificación de la actual gestión de las colas con el fin de eludir los extensos tiempos de retardo. Hoy en d´ıa, el control de congestión de TCP maximiza el rendimiento (throughput) del enlace otorgando beneficio a los grandes flujos de datos, sin embargo, los buffers son plenamente cargados generando altos tiempos de retardo y fases de retirada de paquetes, llamada a esta situación el problema de Bufferbloat. Par las aplicaciones contempor´aneas como las llamadas VoIP, los juegos on-line o los intercambios financieros; estos tiempos de cola generan una mala calidad de servicio detectada directamente por los usuarios finales. Este trabajo estudia las diferentes alternativas de la gestión activa de colas (AQM), optimizando la latencia de los peque˜nos flujos y, por lo tanto, brindando una mejor calidad para las redes de baja latencia en situaciones de congestión. Los modelos AQM han sido evaluados en una topolog´ıa ’dumbbell’ mediante el simulador ns3, entregando resultados de latencia (medidos en RTT) de acuerdo con la situación del enlace y el algoritmo instalado en la cola. Concretamente, los algoritmos estudiados han sido RED, CoDel, PIE y FQ_CoDel; adem´as de la modificación del control de congestión TCP del emisor denominada ABE (Alternative Backoff with ECN). Las simulaciones que mejor resultados ofrecen son las que implementan combinación de FQ_CoDel con el algoritmo ABE, maximizando el rendimiento y reduciendo la latencia de los paquetes. Por lo tanto, la modificación con FQ_CoDel en las colas y la de ABE en el emisor ofrecen una solución al problema del Bufferbloat altamente solicitada por las redes de baja latencia

Le contrôle de congestion dans les applications Pair-à-Pair : le cas de LEDBAT

In the last years, Internet delays are considerably growing, causing a performance deterioration of interactive applications. This phenomenon is getting worse with the increasing popularity of bandwidth-intensive applications, as video streaming, remote backup and P2P systems. The cause of these delays has been identified with the excess buffering inside the network, called “bufferbloat”. Research efforts in this direction head toward active queue management techniques and end-to-end congestion control. In this context, we investigated LEDBAT, a low-priority delay-based transport protocol introduced by BitTorrent. This protocol is designed to transfer large amount of data without affecting the delay experienced by other applications or users. First we analysed transport-level performance of LEDBAT using experimental measurement, simulation and analytical model. Specifically, we evaluated LEDBAT as is, comparing its performance to standard TCP or to other low priority protocols. We then identified a later-comer advantage and we proposed fLEDBAT, which re-introduces intra-protocol fairness maintaining the original LEDBAT objectives. Finally we studied the impact of the LEDBAT protocol on BitTorrent performance. Through simulations and real network experiments, we analysed how BitTorrent impacts on the buffer occupancy of the access node. BitTorrent performance was evaluated in terms of completion time, the main metric to assess the user quality of experience. Results showed that LEDBAT decreases the completion time with respect to standard TCP and significantly reduces the buffer occupancy, that translates in lower delays experienced by competing interactive applications.Durant ces dernières années, les délais de transmission sur Internet ont augmenté de manière considérable, causant une détérioration de performances des applications interactives. La cause de ces augmentations de délais est l’excès de mémoire tampon à l’intérieur du réseau, appelé "bufferbloat". Les efforts de recherche dans cette direction vont vers des techniques de gestion des files d’attente actives et des techniques de contrôle de congestion de bout-à-bout. Dans ce contexte, nous avons examiné LEDBAT, un protocole introduit par BitTorrent qui se base sur le délai au niveau transport, et conçu pour transférer grandes quantités de données sans affecter les délais expérimentés par d’autres applications ou utilisateurs. Nous avons analysé la performance de niveau de transport de LEDBAT avec de mesures expérimentales, de simulations et de modèles analytiques, en comparant ses performances au standard TCP ou à d’autre protocoles de failbe priorité. Nous avons ensuite identifié un problème d’iniquité, et nous avons proposé fLEDBAT, qui ré-introduit l’équité intra-protocole. Dans un deuxième temps, nous avons étudié l’impact du protocole LEDBAT sur la performance de BitTorrent. Par des simulations et des expérimentations sur réseaux réelles, nous avons analysé les effets de LEDBAT sur le remplissage des tampons des noeuds d’accès. Les performances de BitTorrent ont été évaluées en termes de temps d’exécution, qui reflète la qualité de l’expérience utilisateur. Dans les deux cas, les résultats ont montré que LEDBAT diminue le temps de traitement par rapport à TCP et réduit de manière significative l’utilisation de tampons, ce qui se traduit par une baisse des délais

Intelligence in 5G networks

Over the past decade, Artificial Intelligence (AI) has become an important part of our daily lives; however, its application to communication networks has been partial and unsystematic, with uncoordinated efforts that often conflict with each other. Providing a framework to integrate the existing studies and to actually build an intelligent network is a top research priority. In fact, one of the objectives of 5G is to manage all communications under a single overarching paradigm, and the staggering complexity of this task is beyond the scope of human-designed algorithms and control systems. This thesis presents an overview of all the necessary components to integrate intelligence in this complex environment, with a user-centric perspective: network optimization should always have the end goal of improving the experience of the user. Each step is described with the aid of one or more case studies, involving various network functions and elements. Starting from perception and prediction of the surrounding environment, the first core requirements of an intelligent system, this work gradually builds its way up to showing examples of fully autonomous network agents which learn from experience without any human intervention or pre-defined behavior, discussing the possible application of each aspect of intelligence in future networks

Performance and Power Characterization of Cellular Networks and Mobile Application Optimizations.

Smartphones with cellular data access have become increasingly popular with the wide variety of mobile applications. However, the performance and power footprint of these mobile applications are not well-understood, and due to the unawareness of the cellular specific characteristics, many of these applications are causing inefficient radio resource and device energy usage. In this dissertation, we aim at providing a suite of systematic methodology and tools to better understand the performance and power characteristics of cellular networks (3G and the new LTE 4G networks) and the mobile applications relying upon, and to optimize the mobile application design based on this understanding. We have built the MobiPerf tool to understand the characteristics of cellular networks. With this knowledge, we make detailed analysis on smartphone application performance via controlled experiments and via a large-scale data set from one major U.S. cellular carrier. To understand the power footprint of mobile applications, we have derived comprehensive power models for different network types and characterize radio energy usage of various smartphone applications via both controlled experiments and 7-month-long traces collected from 20 real users. Specifically, we characterize the radio and energy impact of the network traffic generated when the phone screen is off and propose the screen-aware traffic optimization. In addition to shedding light to the mobile application design throughout our characterization analysis, we further design and implement a real optimization system RadioProphet, which uses historical traffic features to make predictions and intelligently deallocate radio resource for improved radio and energy efficiency.PhDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99905/1/hjx_1.pd