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Analysis and modelling of YouTube traffic

YouTube currently accounts for a significant percentage of the Internets global traffic. Hence, understanding the characteristics of the YouTube traffic generation pattern can provide a significant advantage in predicting user video quality and in enhancing network design. In this paper, we present a characterisation of the traffic generated by YouTube when accessed from a regular PC. On the basis of this characterisation, a YouTube server traffic generation model is proposed, which, for example, can be easily implemented in simulation tools. The derived characterisation and model are based on experimental evaluations of traffic generated by the application layer of YouTube servers. A YouTube server commences the download with an initial burst and later throttles down the generation rate. If the available bandwidth is reduced (e.g. in the presence of network congestion), the server behaves as if the data excess that cannot be transmitted because of the reduced bandwidth were accumulated at a servers buffer, which is later drained if the bandwidth availability is recovered. As we will show, the video clip encoding rate plays a relevant role in determining the traffic generation rate, and therefore, a cumulative density function for the most viewed video clips will be presented. The proposed traffic generation model was implemented in a YouTube emulation server, and the generated synthetic traffic traces were compared with downloads from the original YouTube server. The results show that the relative error between downloads from the emulation server and the original server does not exceed 6% for the 90% of the considered videos. Copyright

Performance of the M-LWDF scheduling algorithm for streaming services in HSDPA

The present paper analyzes the paradigm of providing streaming services over HSDPA. The provision of QoS to streaming users imposes two major challenges on the HSDPA technology, namely, satisfying the guaranteed bit rate and delay jitter constraints. Focusing on the latter QoS requirement, the operation of the packet scheduling functionality completely determines the node B queuing streaming packets prior to their transmission through the radio interface, and therefore the scheduler plays a key role in the satisfaction of the delay jitter constraint.

QoE oriented cross-layer design of a resource allocation algorithm in beyond 3G systems

The provision of high speed access to Internet and IP-based services is one of the main goals of beyond 3G (B3G) wireless systems. These systems will benefit from cross-layer protocol designs that will introduce interactions between different layers to obtain performance gains. The majority of the research in the field of cross-layer in B3G systems aims at improving quality of service (QoS) system centric metrics such as spectral efficiency, service latency, delay variation (jitter), etc. However, minor attention has been paid to the satisfaction of the subjective quality requirements from human users. With the goal of incorporating the subjective human perception into the cross-layer design of B3G systems, this work carries out an experimental survey of the sensitivity of the user subjective quality to the service response time for the Web browsing application. From the experimental results, a mapping from service response time and user data rate (provided by the wireless link) to mean opinion score (MOS) is derived. The presented results will show that the Web page size plays an important role in the mapping function. The derived mapping function is incorporated into a radio resource allocation algorithm for orthogonal frequency division multiple access (OFDMA) systems. This incorporation is carried out maximizing the aggregate utility over all the users in the cell. Its performance has been compared to that of the multicarrier proportional fair (MPF) under heavy load conditions with a 3G LTE simulator. The results have shown that the proposed methodology can provide an interesting enhancement of the user experienced quality compared to the MPF algorithm.

Interaction of transmit diversity and proportional fair scheduling

In evolving 3G systems, the proportional fair packet scheduling algorithm promises an attractive trade-off between average cell capacity and user fairness by exploiting multi-user selection diversity in time-shared channels. However, in these systems the option of antenna transmit diversity already exist, whose performance benefit is dependent on the considered scheduling strategy. This study focuses on the interaction between proportional fair packet scheduling and open or closed-loop transmit diversity techniques. The basic interaction is studied by using an analytical model. Additionally, Monte Carlo simulations are conducted to study the effect of scheduling delays. In the low mobility Rayleigh fading case, the potential average cell capacity gain with proportional fair scheduling, compared to a simple round robin in time approach, is on the order of 60% for single-antenna transmission. It reduces, however, to around 35% when dual antenna transmit diversity is additionally deployed. Comparing the performance of the different transmit diversity schemes to single-antenna transmission, conditioned on proportional fair scheduling, it is found that the closed-loop schemes provide a benefit over a wide range of terminal speeds, whereas open-loop space-time block coding exhibits limited performance and in some cases even a loss.

Characteristics of mobile youtube traffic

In this work we present the characterization of the mobile network traffic generated by one of the most relevant social networking applications: YouTube. Understanding its characteristics is of major importance to evaluate its impact on mobile networks and optimize network or application design. For this purpose, we have performed a set of experiments capturing traffic from Apple iOS and Android terminals connected to 3G mobile networks. Our results show that the video formats are 3GP formats, which use lower encoding rates than in other networks. As in accesses from other networks, YouTube servers transfer the video clip with an initial burst and a throttling phase, but they apply different parameters for clients located in mobile networks. Additionally, the mobile terminal can strongly influence the download. Our results with high-end Android terminals show that the client implements a dual-threshold buffer policy that interrupts and resumes the download depending on its buffer occupancy. Our results with iOS terminals show that the video clip download is not interrupted by the client, and a large amount of data may be accumulated at the player buffer. In mid-range Android terminals the TCP receive window may additionally throttle the download if the player buffer is filled up.

Traffic Models Impact on OFDMA Scheduling Design

This article studies the impact on the design of scheduling algorithms for Orthogonal Frequency Division Multiple Access (OFDMA) systems of two traffic models described in the evaluation methodology proposals from standardization bodies: the full buffer and the finite buffer traffic models. The analysis concentrates on utility-based scheduling with an α-fair utility function for Non-Real Time (NRT) services. The results show that a gradient scheduling algorithm is able to maximize the aggregate utility over all the users when the less realistic full buffer model is adopted; but not when the finite buffer model is applied. The results also show that with the full buffer model a gradient scheduler exhibits a trade-off between average user throughput and the user throughput at 5% outage, but it does not when the more realistic finite buffer is used. Therefore, it is concluded that designs of scheduling algorithms for NRT services for OFDMA systems carried out under the full buffer model assumption may fail to provide the desired performance benefits in realistic scenarios. Based on the results presented, a recommendation on scheduling design is provided.

Network Slicing for 5G with SDN/NFV: Concepts, Architectures, and Challenges

The fifth generation of mobile communications is anticipated to open up innovation opportunities for new industries such as vertical markets. However, these verticals originate myriad use cases with diverging requirements that future 5G networks have to efficiently support. Network slicing may be a natural solution to simultaneously accommodate, over a common network infrastructure, the wide range of services that vertical- specific use cases will demand. In this article, we present the network slicing concept, with a particular focus on its application to 5G systems. We start by summarizing the key aspects that enable the realization of so-called network slices. Then we give a brief overview on the SDN architecture proposed by the ONF and show that it provides tools to support slicing. We argue that although such architecture paves the way for network slicing implementation, it lacks some essential capabilities that can be supplied by NFV. Hence, we analyze a proposal from ETSI to incorporate the capabilities of SDN into the NFV architecture. Additionally, we present an example scenario that combines SDN and NFV technologies to address the realization of network slices. Finally, we summarize the open research issues with the purpose of motivating new advances in this field.

A QoE-Aware Scheduler for HTTP Progressive Video in OFDMA Systems

HTTP progressive video downloading is becoming increasingly relevant in wireless and mobile networks. Therefore, improving the quality of experience (QoE) for this service is important for customer satisfaction. In this letter we propose a QoE-aware scheduling solution for the HTTP progressive video downloading in OFDMA systems. Whereas most scheduling strategies consider QoS metrics such as delay, jitter or throughput, our proposal takes into account a metric that directly affects the end-users experience. In particular, we propose to use an estimation of the amount of video data stored in the player buffer as the main criterion for resource assignment. The ultimate goal of using this criterion is the avoidance of playback interruptions. In particular, we have evaluated this scheduler in an LTE network simulator for the YouTube service, which is the most visited HTTP video streaming site. Our results show a significant improvement compared to the Multicarrier Proportional Fair scheduler, e.g. the number of videos with pauses decrease from 16.1% to 0% for 12 Mbps of cell offered load.

Performance of packet scheduling methods with different degree of fairness in HSDPA

The present paper focuses on assessing the performance of the packet scheduler in HSDPA. The investigation has especially concentrated on assessing different scheduling methods with different degrees of fairness for non-delay-sensitive elastic traffic. The fairness ultimately determines the QoS perceived by the users. The results show that very unfair scheduling methods provide the highest HSDPA cell throughput for best effort NRT traffic, although, under heavy load situations, the unfairness of these policies causes the starvation of users under poor average radio propagation conditions. Under minimum user throughput guarantees, the proportional fair algorithm provides the highest cell capacity of all tested algorithms. With this scheduler, the provision of user throughput guarantees of CA, 128 and 384 kbit/s (for at least 95% of the users) incurs on a cell throughput reduction respectively of around 10, 30 and 80% relative to the maximum cell throughput for best effort traffic (i.e. no user throughput guarantees at all).

Video Tester — A multiple-metric framework for video quality assessment over IP networks

This paper presents an extensible and reusable framework which addresses the problem of video quality assessment over IP networks. The proposed tool (referred to as Video-Tester) supports raw uncompressed video encoding and decoding. It also includes different video over IP transmission methods (i.e.: RTP over UDP unicast and multicast, as well as RTP over TCP). In addition, it is furnished with a rich set of offline analysis capabilities. Video-Tester analysis includes QoS and bitstream parameters estimation (i.e.: bandwidth, packet inter-arrival time, jitter and loss rate, as well as GOP size and I-frame loss rate). Our design facilitates the integration of virtually any existing video quality metric thanks to the adopted Python-based modular approach. Video-Tester currently provides PSNR, SSIM, ITU-T G.1070 video quality metric, DIV and PSNR-based MOS estimations. In order to promote its use and extension, Video-Tester is open and publicly available.