Junyu Lai

On the throughput-energy tradeoff for data transmission between cloud and mobile devices

Mobile cloud computing has recently emerged as a new computing paradigm promising to improve the capabilities of resource-constrained mobile devices. As the data processing and storage are moved from mobile devices to powerful cloud platforms, data transmission has become an important issue affecting user experiences of mobile applications. One of the challenges is how to optimize the tradeoff between system throughput and energy consumption, which are potentially conflicting objectives. Inspired by the feasibility of transmission scheduling for prefetching-friendly or delay-tolerant applications, we mathematically formulate this problem as a stochastic optimization problem, and design an online control algorithm to balance such an energy-performance tradeoff based on the Lyapunov optimization framework. Our algorithm is able to independently and simultaneously make control decisions on admission and transmission to maximize a joint utility of the average application throughput and energy cost, without requiring any statistical information of traffic arrivals and link bandwidth. Rigorous analysis and extensive simulations have demonstrated both the system stability and the utility optimality achieved by our control algorithm.

Decreasing call blocking probability of Broadband TV services by a channel access control scheme

The current trend of network convergence has been best exemplified by the recent emergence of new services such as Broadband TV (BTV) offered by Telcos around the world. A very relevant research topic is to improve the quality of experience (QoE). This paper focuses on decreasing the user call blocking probability (CBP), which is one of the most important BTV QoE metrics. At first, we analyze a currently typical BTV network architecture. And then, a state-vector-based simulation model is proposed to evaluate the CBP (on a single link). After that, we present a class-based distribution model of channel watching probabilities, and based on this distribution model, we elaborate a general TV channel access control (TCAC) scheme in order to reduce the CBP. This scheme is flexible and can be applicable in many different scenarios. Finally, a case study is carried out, and it demonstrates the potential of this TCAC scheme to improve the BTV QoE by decreasing the CBP on a single link.

Unicast versus multicast for live TV delivery in networks with tree topology

Multicasting is an essential technology in applications like IPTV or online multiplayer gaming and has been studied extensively in different networks. In this article, we introduce a new performance criterion, called multicast gain, which can be used for computing multicast efficiency. We analyze multicast transmission for delivery of live TV channels in tree-based networks representing, e.g., multicast trees, and determine the gain of subtrees and links in order to quantify the benefits of multicasting. We also define a threshold in order to identify cases in which unicasting might be preferable. We show that although multicasting can usually outperform multiple unicasting in terms of bandwidth usage, due to the inherent overhead in establishing and maintaining multicast connections, in special cases, using multiple unicast flows can be a better choice.

Availability evaluation of IPTV services in roadside backbone networks with vehicle-to-infrastructure communication

Vehicular Networks represent one of the main topics in the communication systems area. Increased deployment of vehicular networks together with new possibilities for Internet Protocol Television (IPTV) services has spurred the interest in providing mobile IPTV via vehicular networks. Provisioning of IPTV services over vehicular networks can be expected to play a significant role in the next generation of TV systems. Users will choose IPTV based on the Quality of Experience (QoE). Among QoE measures, TV channel availability is one of the most significant. In this paper, we investigate the channel availability in IPTV services with different traffic intensity and a varying number of TV channels offered to find out the acceptable availability of TV channels or the Call Blocking Probability (CBP) in our study. Comprehensive experiments are carried out by means of our own simulation tool, i.e., a Monte Carlo simulator to conduct the evaluations for numerous scenarios taking into account realistic IPTV user behavior.

Modeling the Behavior of IPTV Users with Application to Call Blocking Probability Analysis

Abstract In traditional TV delivery systems, all the channels are pushed toward the subscribers. Therefore, user activities like channel switching have no effect on the provider network. Consequently, TV providers have felt no strong need to analyze and investigate the behavior of their subscribers. In IPTV networks, however, the situation is quite different. Channel switching activity of users imposes extra load on the network and therefore is worth to be investigated and analyzed. In this paper we elaborate the requirements of IPTV user modeling and propose a model taking into account the requirements. The model is implemented using the LoadSpec tool. Our proposed model can produce, in a realistic manner, the workload of switching events of a typical IPTV client during an active session. The application of the proposed model for the IPTV analysis, specifically, for the evaluation of the call blocking probability is shown by two case studies.

Decreasing the Call Blocking Probability of Broadband IPTV Services in Stationary and Peak-hour Scenarios

In the provisioning of broadband Internet Protocol TV (IPTV) services, call blocking probability (CBP) denotes the ratio of failed user requests, which is one of the most important metrics on IPTV quality of experience (QoE). This paper aims to evaluate and further to decrease the end-to-end (E2E) CBP of IPTV services in both stationary and peak-hour scenarios. At first, we analyze a currently typical xDSL based IPTV delivery network architecture and its simplification. Then, a recently developed IPTV user behavior model is briefly presented. Next, a state-vector-based simulation model is proposed to evaluate the E2E CBP in an entire IPTV delivery network with tree topology. The simulation model is then applied to both stationary and peak-hour scenarios, and thereafter, a comparative simulation study demonstrates significant differences between the E2E CBPs evaluated in the two different scenarios. After that, we elaborate an extended TV channel admission control (TCAC) scheme to be applied in an entire IPTV delivery network. Simulation experiments illustrate the potential of our TCAC scheme to enhance the IPTV QoE by relatively decreasing the E2E CBP significantly (up to 25%), in both stationary and peak-hour scenarios.

A Fairness-Based Access Control Scheme to Optimize IPTV Fast Channel Changing

IPTV services are typically featured with a longer channel changing delay compared to the conventional TV systems. The major contributor to this lies in the time spent on intraframe (I-frame) acquisition during channel changing. Currently, most widely adopted fast channel changing (FCC) methods rely on promptly transmitting to the client (conducting the channel changing) a retained I-frame of the targeted channel as a separate unicasting stream. However, this I-frame acceleration mechanism has an inherent scalability problem due to the explosions of channel changing requests during commercial breaks. In this paper, we propose a fairness-based admission control (FAC) scheme for the original I-frame acceleration mechanism to enhance its scalability by decreasing the bandwidth demands. Based on the channel changing history of every client, the FAC scheme can intelligently decide whether or not to conduct the I-frame acceleration for each channel change request. Comprehensive simulation experiments demonstrate the potential of our proposed FAC scheme to effectively optimize the scalability of the I-frame acceleration mechanism, particularly in commercial breaks. Meanwhile, the FAC scheme only slightly increases the average channel changing delay by temporarily disabling FCC (i.e., I-frame acceleration) for the clients who are addicted to frequent channel zapping.

Software-defined cellular networking: a practical path towards 5G

Software-defined networking (SDN) has recently been all the rage. It has already been successfully applied in many practical fields including campus network, wide area network (WAN) and data centre network. As a next step, SDN is expected to be adopted in cellular networks to deal with some most urgent problems faced by carriers, such as ever soaring capacity demands and differentiated quality of service (QoS)/quality of experience (QoE) requirements introduced by emerging services and a large number of exciting applications. This paper first investigates existing proposals and solutions regarding applying SDN in carrier networks from both industry and academia. Then, as the major contribution of this paper, a novel end-to-end (E2E) software-defined cellular network (SDCN) architecture, aiming to the evolution towards 5G, is elaborated with adopting several emerging technologies. The proposed SDCN architecture can provide great flexibility, scalability, agility, and efficiency for carriers to keep profit and sustainability. In addition, some crucial issues for implementing each part of the proposed E2E SDCN architecture, i.e., from radio access network (RAN) to backhaul, and finally to core, are thoroughly discussed, respectively.