| As the increasing pace of global deployment and commercial usage of LTE (Long Term Evolution) network, the alternative process of 2G (2nd Generation) and 3G (3th Generation) networks by 4G (4th Generation) has also been accelerated gradually. The number of new subscribers and mobile data traffic volume in LTE continues to grow, puts forward higher requirements on the network capacity. At the same time, the development of technologies as well as needs in daily life promote further popularity and penetration of smartphones, and various APPs (Applications) based on them has extended into every area of daily life, changing the way of users interacting with the Internet and the way of communication between themselves. The emerging popular mobile APPs such as instant messaging and social networks has different operation mechanism and data structure from most of traditional mobile internet applications, like web browsing and file transfer, by using keep-alive messages in background to maintain the always-on connection with internet, leading the increase of proportion of small data packets and short connection behavior. Such characteristics of data traffic are quite different from earlier versions of LTE network, which were well designed for traditional applications, therefore, causing several problems. On the one hand, it causes significant increase of corresponding extra signaling traffic from the network perspective, as well as the power consumption from the user perspective, in the end reducing the network capacity and user experience without dealing these problems well enough.This work was mainly supported by the cooperative research project about LTE network evolution strategy with LG U+, one of the biggest operators in South Korea, during the internship in Nokia. Based on a real LTE network scenario operated by LG U+, this paper studies the impact of signaling overhead and user device power saving mechanism on LTE from network perspective and user perspective, respectively. Since LG U+is running one of the most developed LTE network in the world, the research of the paper can provide reference for operators when planning LTE network evolution to improve user experience. The main work in the paper is as follows:1) Considering the current and future development of mobile data traffic in LTE network, a traffic generation framework including an application level traffic growth forecast has been constructed from the network planning perspective, with detailed analysis of the generation mechanism and traffic model of keep-alive message which is suitable for the network evolution scenario. Comprehensive traffic models and parameters of other traditional mobile internet applications as well as VoLTE (Voice over LTE) application have been considered in the framework. The foundation of the forecast in the framework, which is merged into traffic models of each application, is mainly based on the realistic situation of data traffic usage in LG U+LTE network. The framework proposed here is mainly the basis of the work in the paper.2) A reference network as the study scenario has been constructed based on a selected real LTE network from LG U+. The actual data information collected from the selected real network has been analyzed including traffic volume from downlink, LTE subscribers, active user number, and RRC (Radio Resource Control) connection call attempts. Using such measurements, the traffic generation framework has been compared to verify, showing the validation of the proposed framework for the analyzed network, and paving the way for the following work.3) From the network perspective, the signaling overhead has been evaluated by using RRC stat transition related signaling as the object. Using the resource consumption in physical channels mapping from the signaling as the metrics, channel resource overhead as well as scheduling resource consumption caused by data traffic, especially by keep-alive messages and VoLTE application, has been evaluated from control plane and user plane, respectively. The effect of RRC inactivity timer has also been discussed. Considering the increase of traffic volume combining with subscribers in the cell, the capacity of control plane has been evaluated. By using the system level simulation, the impact of signaling and VoLTE usage on LTE network upgrade strategy has been evaluated for LG U+.4) From the user perspective, LTE user equipment power consumption problem brought by emerging APPs has been analyzed. Based on the summary of DRX (Discontinuous Reception) mechanism research work, a new DRX long cycle switching scheme, which is suitable for delay-tolerant type application and attractable in practice implementation, has been studied, with an example of air interface scheme combining with the 3GPP (3rd Generation Partnership Project) user assistance mechanism.
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