23-04-2012, 03:47 PM
LTE Mobility Enhancements Qualcomm
LTE_Mobility_Enhancements.pdf (Size: 383.12 KB / Downloads: 196)
Introduction
The Third Generation Partnership Program (3GPP) has defined Long Term Evolution (LTE) as part of the 3GPP Release 8 specifications. LTE introduces the possibility of complementing High-Speed Packet Access (HSPA) networks with higher peak data rates, greater flexibility for heterogeneous networks and flatter network architecture.
One of the main goals of LTE, or any wireless system for that matter, is to provide fast and seamless handover from one cell (a source cell) to another (a target cell). This is especially true for LTE system because of the distributed nature of the LTE radio access network architecture which consists of just one type of node, the base station, known in LTE as the eNodeB (eNB).
LTE Release 8 Handover Procedures
In Release 8, mobility support for User Equipment (UE) in connected-state comprises of two types of handover procedures: Backward handover Radio Link Failure (RLF) handover (e.g., triggered by RLF, backward handover failure, RLC unrecoverable error, or reconfiguration compliance failure)
RLF Handover
Figure 2 illustrates the RLF handover procedure, also known as the RRC
Connection Reestablishment procedure in the 3GPP Release 8
specifications. RLF handover is UE-based mobility and provides a
recovery mechanism when the backward handover signaling with the
source cell partially fails due to poor radio conditions.
Performance Comparison
In order to demonstrate the performance improvements with forward handover, we show the impact of the current handover procedures and the new forward handover procedure on the system performance of an image download during handover. As shown in Figure 5, the download time during a handover with forward handover improves by ~50% for an average user in a LTE 10 MHz system.