A Vocabulary for Growth: Topic Modeling of Content Popularity Evolution

In this paper, we present a novel method to predict the long-term popularity of user-generated content (UGC). At first, the method clusters the dynamics of UGC popularity into a vocabulary of growth in popularity (sequence) by using a mixture model. Eventually, the method assigns to each sequence a topic model to describe the dynamics of the sequence in a compact way. We then use this topic model to identify similar patterns of growth in popularity of newly observed UGC. The proposed method has two key features: First, it considers the historical dynamics of the UGC popularity, and second it provides long-term popularity prediction. Results on the real dataset of UGC show that the proposed method is flexible, and able to accurately forecast the complete growth in popularity of a given UGC

Robust optimisation of green wireless LANs under rate uncertainty and user mobility

We present a robust optimisation approach to energy savings in wireless local area networks, that incorporates both link capacity fluctuations and user mobility under Bertsimas and Sim's robust optimization paradigm. Preliminary computational results are discussed

An Experimental Cross-Layer Approach to Improve the Vertical Handover Procedure in Heterogeneous Wireless Networks

Users of next generation wireless devices will be likely to move across a heterogeneous network environment. This will give them the possibility to always exploit the best connection to the global Internet. In order to keep a seamless connection, the handover between different access technologies, also known as vertical handover, must be as smooth as possible. The current evolution of network architectures toward an all-IP core favours the use of the Mobile IPv6 protocol to handle such handovers. However, this protocol still presents several drawbacks, mainly related to the assumption of static devices and wired connections. Hence we have designed and implemented a software module that exploits information from the lower layers (e.g. physical) to extend the capabilities of Mobile IPv6 to wireless environments. We have then evaluated both the plain Mobile IPv6 and our proposed implementation over an experimental testbed. The outcome of the assessment proves the effectiveness of our solution and reveals the possibility to perform a seamless vertical handover in heterogeneous wireless networks

A branch-and-Benders-cut method for nonlinear power design in green wireless local area networks

We consider a problem arising in the design of green wireless local area networks. Decisions on powering-on a set of access points (APs), via the assignment of one power level (PL) to each opened AP, and decisions on the assignment of the user terminals (UTs) to the opened APs, have to be taken simultaneously. The PL assigned to an AP affects, in a nonlinear way, the capacity of the connections between the AP and the UTs that are assigned to it. The objective is to minimize the overall power consumption of the APs, which has two components: location/capacity dimensioning costs of the APs; assignment costs that depend on the total demands assigned to the APs. We develop a branch-and-Benders-cut (BBC) method where, in a non-standard fashion, the master problem includes the variables of the Benders subproblem, but relaxes their integrality. The BBC method has been tested on a large set of instances, and compared to a Benders decomposition algorithm on a subset of instances without assignment costs, where the two approaches can be compared. The computational results show the superiority of BBC in terms of solution quality, scalability and robustness

Modeling RACH Arrivals and Collisions for Human-Type Communication

This letter proposes an analytical model to evaluate the collision probability on the Random-Access CHannel (RACH) in Long-Term Evolution systems as a function of the number of user equipment, the number of available preambles, and the Inter-arrival times of the RACH Requests (IRRs) of the average user. The model for the IRR of the average user is obtained from real traffic data captured at the eNodeB of a mobile operator, and is derived by emulating the radio resource control (RRC) state machine for different RRCs Inactivity timer (RRCIT) settings. The results of this letter suggest that when RRCIT is set to a few seconds, a mixture model is more accurate than the Poisson hypothesis both in modeling the IRR and in estimating the RACH performance

Antennas and photovoltaic panels: Toward a green Internet of Things

The perspective of a wide use of green power motivates the scientific community to study the possibility of fabricating integrated stand-alone devices. In particular, solar energy is one of the most promising renewable powers, and it is widely used in autonomous wireless communication systems. Specifically, integration of sensors and antennas in a solar panel represents a challenge for future technology. In this paper, the feasibility of a single integrated autonomous device equipped with WiFi capability is analyzed, discussing its potentiality in the framework of the Internet of Things

Experimental Analysis of ViLTE Service

Long-term evolution (LTE) is a broadband wireless cellular system currently available in about 200 countries. From the mobile network operator point of view, one of the most appealing characteristics of LTE is the possibility of providing the users with mobile broadband services like voice over LTE and video over LTE (ViLTE), with strict quality of service (QoS) guarantees. The success of such services, which usually require a subscription fee, is obviously tightly bound to the users' quality of experience (QoE), that must be significantly better than the quality perceived in case of free services. This paper attempts to evaluate the perceived quality of the ViLTE service. In more detail, we present the results of an experimental test–bed realised at one of the most popular italian MNO, aimed at evaluating the impact of several network layer QoS parameters on the QoE of the ViLTE service

CAC algorithm for per-VC queueing systems loaded by fractal traffic

ATM technology is expected to support a broad variety of services and applications, satisfying a wide range of user quality needs and network performance objectives. In this scenario a per-Virtual Connection (per-VC) queueing is needed to guarantee different Quality of Service (QoS) requirements and to provide adequate congestion avoidance techniques (such as Early Packet Discard) to single traffic flows. In the paper we present a Call Admission Control (CAC) scheme with per-VC management of network resources. Starting from the widely accepted long memory properties of broadband traffics, fractional Brownian motion (fBm) is used as a parsimonious traffic model. The proposed CAC scheme employs the knowledge of the exact asymptotic queue length distribution to efficiently allocate network resources (buffer and output link capacity) to the contending sources. We analyze the multiplexing gain considering an appropriate distribution of the bandwidth among different sources, highlighting its advantages over the Rate Envelope Multiplexing scheme, suggested by ITU-T

A survey on multi-constrained optimal path computation: Exact and approximate algorithms

The paper presents a survey on the techniques to solve the multi-constrained optimal path (MCOP) problem Computing the MCOP is a task shared by many research areas from transportation systems to telecommunication networks In the latter the MCOP is often related to the issue of Quality of Service (QoS) routing which consists in finding a route between a couple of nodes that meets a series of QoS requirements such as bounded delay pack et loss and other parameters The MCOP problem has been faced by several authors and a plethora of solving methods is now available In the present work we draw the state of the art of exact and approximate MCOP computation algorithms with particular attention to the networking area We describe and analyse the most representative methods and for each of them we derive the worst case computational complexity In addition we provide the reader with a uniform notation and with the detailed pseudo-code of various algorithms so that the paper can indeed serve as a workable starting point for further studies on the MCOP problem (C) 2010 Elsevier B V All rights reserve

Experimental and simulation study of a WiMAX system in the sea port scenario

The paper presents a measurement campaign carried out on a 2.5 GHz Mobile WiMAX test-bed in a sea port scenario, aimed at evaluating the system performance. The analysis of acquired data suggested the definition of a 2-ray pathloss model, which is able to fit the actual behavior of the observed marine channel. In order to evaluate the effects of the proposed pathloss model on system performance the paper presents a simulation study carried out by means of OPNET simulator. In particular, the simulation study is aimed at comparing the throughput at IP level obtained using different pathloss models implemented in OPNET, with that obtained when the proposed 2-ray model is considered. Further, the throughput at IP level obtained by simulation is compared with the one measured in the actual test-bed. This comparison points out that the WiMAX OPNET model is able to reproduce in most cases the system performance observed during the measurement campaign, when the proposed 2-ray pathloss model is used. However, the simulator is not able to predict the behavior of actual system in all situations. Indeed, in the areas where the pathloss presents peaks, the breakdown of system performance, mainly caused by synchronization problems, is not predicted by the simulator