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The growth of music streaming market is expected to be boosted by the rising use of smart devices and the streaming platforms in the forecast period. Music recommendation systems for groups have been intensively studied as the application scenario becomes more dynamic, where different kinds of group formulations lead to different levels of similarity in music tastes. This paper proposes a music recommendation framework to generate a Top-N list in high-similar, high-dissimilar, and regular groups. Additionally, we investigate the performance of the recommendation system in a wide range of aspects, including precision, ranking quality, and novelty. Based on the listening frequency of each user and for each track, implicit feedback is also derived from the track popularity. To prevent popularity bias, we combine track popularity and group popularity into latent factor models to improve the performance of the recommendation algorithm. As a result of our evaluation, we found that the proposed methods provided excellent recommendations regarding accuracy, diversity, and novelty. [ABSTRACT FROM AUTHOR]

Universal mobile-telecommunication system supports IP multimedia services through the IP multimedia corenetwork subsystem OMS). This paper proposes a prepaid application server (PAS) to handle both the prepaid calls and messaging services in the IMS. When both voice and messaging are simultaneously offered, a potential problem is that the delivery of a message during a call may result in force-termination of that call due to credit depletion. To address this issue, we describe a strategy to determine if a prepaid message can be sent out during a call session. We propose an analytic model to investigate the performance of this strategy. This paper provides guidelines to select appropriate input parameters for the PAS. Index Terms--Billing, diameter protocol, IP multimedia corenetwork subsystem (IMS), session initiation protocol (SIP), VoIP.

With the proliferation of mobile devices in recent years, the volume of global mobile data traffic has grown exponentially. As a result, effective approaches for mobile data offloading are urgently required. In the past few years, two main Wi-Fi offloading techniques, namely, opportunistic offloading and delayed offloading, have been widely discussed. A promising L4-approach known as multipath transmission control protocol has recently been standardized, which allows a single transport connection to use multiple paths simultaneously over multiple interfaces, which then calls for a new Wi-Fi offloading model that considers discontinuous Wi-Fi connection periods. This paper presents an analytical model for multipath Wi-Fi offloading in deriving the aggregate offloading time via an alternative path for the use of multipath offloading. Then, the respective offloading volume and ratio are computed. Our theoretical results are supported by extensive simulations. We show how this model further assists the cellular operators to make better decision in resource allocation. Compared with opportunistic offloading, multipath offloading results in a significantly improved performance in the support for a guaranteed minimum bit rate. [ABSTRACT FROM AUTHOR]

The performance of single-segment short messaging service (SMS) (i.e., the message sizes are smaller than 140 octets) has been intensively investigated. On the other hand, multisegment messages (with sizes larger than 140 octets) are seldom evaluated in the literature. This paper proposes analytical models to study two transmission policies for multisegment short messages. We show how to improve the performance of multisegment short message delivery by selecting appropriate transmission parameters: the retransmission interval and the maximum number of transmissions. The proposed models are validated by measured data collected from the largest telecom operator in Taiwan over a period of six months. We provide useful guidelines to configure parameters for SMS transmission policy. Numerical examples showed that the performance can be improved by over 20% in terms of successful delivery ratio. [ABSTRACT FROM AUTHOR]

In Vehicular Ad Hoc Networks (VANETs), there are generally very few communicating vehicles along a routing path in areas with low traffic density. Existing schemes based on the Store-Carry-Forward (SCF) technique utilize a moving vehicle to bridge the communication gap between two disconnected vehicles on the opposite lane. This letter investigates network performance over multiple communication gaps in SCF-based vehicular routing. To investigate the influence of the transmission range on the end-to-end delivery delay, we develop an analytical model to quantify the performance in terms of the Laplace transform of the end-to-end delay via SCF-based vehicular routing. Extensive simulation results are presented to validate the proposed model. [ABSTRACT FROM PUBLISHER]

The Third-Generation Partnership Project (3GPP) has recently standardized the policy and charging control (PCC) system to provide dynamic policy enforcement for network resource allocation combined with real-time charging. The upward trend in smartphone use and the subsequent explosion of data traffic on third-generation (3G) networks have pressed carriers to offload the data traffic from the cellular domain. One key challenge is to elaborate on PCC functionality and mobility management for offloading sessions. This paper proposes an enhanced Wi-Fi offloading model to bring mobile Internet Protocol (IP) integration to a core network with PCC. Specifically, we develop a comprehensive analytical model to quantify the performance of data offloading concerning the amount of 3G resources saved by offloading and the deadline assurance for measuring the quality of user experience with PCC support. Numerical results demonstrate that deadline assurance can be satisfied while saving a significant amount of 3G resources in many situations. [ABSTRACT FROM AUTHOR]

Recent advances in wireless technology provide interesting and effective solutions for vehicular applications. Due to the high deployment cost, implementing roadside units (RSUs) with low cost while maintaining high data throughput has become an important topic. This letter develops a selfishness detection mechanism for file sharing that addresses fairly use vehicle-to-vehicle communications. In locations where an RSU is not immediately available or cannot be directly used, the selfish behavior of not sharing with neighbors or not downloading from an RSU is difficult to detect. This letter proposes a novel selfishness detection mechanism, SDM, to force vehicles to stabilize at a socially optimal operating point incurring maximum total utility. The SDM along with our proposed hybrid self-history mechanism outperforms previous shared history mechanisms, even though the majority of users are selfish. [ABSTRACT FROM PUBLISHER]

In a Vehicular Ad Hoc Network (VANET), the wireless Collision Avoidance (CA) system issues warnings to drivers before they reach a potentially dangerous zone on the road. This paper proposes an analytical model for evaluating the performance of emergency messaging via wireless CA systems. First, we utilize the dichotomized headway model, the braking model, and Greenberg's logarithmic model to generate vehicular mobility traces for analysis. Second, we derive the probability of a rear-end collision between two vehicles that travel in the same direction when a sudden event occurs. Third, we quantify the probability of vehicles failing to receive the emergency message. Numerical results from the model show that the number of car crashes per accident is much higher when a wireless CA system is not used. We also find it interesting that the number of car crashes is not directly proportional to the vehicle density when the vehicular mobility traces follow the speed-density relationship offered by Greenberg's logarithmic model. By integrating flow theory into VANET analysis, our model provides useful insights for future intelligent transportation. [ABSTRACT FROM PUBLISHER]

The Evolved Packet System (EPS) is standardized to support a common IP-based core network with heterogeneous radio accesses in the latest 3GPP release. In the EPS, the Policy and Charging Control (PCC) framework provides dynamic policy control combined with real-time charging management. Long core network signaling for PCC degrades session continuity performance during handover. In this paper, we investigate the handover for an EPS session. Based on the results, we propose a proactive scheme along with a user mobility tracking model to improve session continuity. More specifically, our proposed scheme attempts to reduce PCC reauthorization signaling delay during the handover procedure. Then, we formulate a Markov process to model the user mobility pattern and to derive the session continuity probability. Numerical results show that our scheme can significantly keep the session continuity at a user acceptable level even when the mobility pattern is high. We also provide guidelines for operators to set up the network configuration parameters according to various traffic conditions. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]