A Study on LTE Mobility Management and Its Impact on Call Control

• Main Authors: Liou, Ren-Huang, 劉仁煌
• Other Authors: Lin, Yi-Bing
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/91268398685961471001

博士 === 國立交通大學 === 資訊科學與工程研究所 === 102 === 3rd Generation Partnership Project (3GPP) proposed Long Term Evolution (LTE) which evolved from Universal Mobile Telecommunications System (UMTS) to support mobile broadband services. The LTE mobility management tracks the locations of the User Equipments (UEs) so that incoming calls can be delivered to the UEs. After a call is established, if the UE moves around the service area of the LTE network during the call, the call control technique such as enhanced Single Radio Voice Call Continuity (eSRVCC) is responsible to maintain the connectivity of the ongoing call. In this dissertation, we investigate the LTE mobility management and its impact on call control. In the LTE mobility management architecture, the cells (the radio coverages of base stations) are grouped into the Tracking Areas (TAs), and the TAs are further grouped into the TA List (TAL). Mobility management procedures include location update and paging. The location update is executed when the UE leaves the current TAL. When the network attempts to connect to the UE (e.g., when an incoming call arrives), the network executes the paging procedure by sending the paging messages to the cells in the UE's TAL. In the dissertation, we first study the performance of the LTE mobility management. Then we compare the LTE mobility management scheme with two well-known mobility management schemes: the movement-based scheme and the distance-based schemes. Our study shows that under some traffic/mobility patterns, the LTE mobility management scheme outperforms the previously proposed schemes. We also propose a dynamic paging scheme that determines the paging sequence of cells in real time according to the UE movement and call behavior. Our study indicates that the dynamic paging scheme can effectively reduce the paging traffic. For the call control, 3GPP proposed eSRVCC to support the access transfer between LTE and UMTS during a call. If the UE frequently moves back and forth between LTE and UMTS during a call, it may incur large access transfer traffic. To resolve this issue, the number of access transfers should be limited in an eSRVCC call (referred to as the transfer limit) to reduce the transfer traffic. We investigate the performance of eSRVCC with the transfer limit. Our study indicates that an appropriate transfer limit effectively reduces the access transfer traffic with good LTE utilization. We also develop analytic and simulation models to study the impacts of different traffic/mobility patterns. Our study provides guidelines for the telecommunications operators to achieve higher system performance by selecting appropriate parameter values in LTE.