Mobility offers clear benefits to the end users: low delay services such as voice or real time video connections can be maintained while moving even in high speed trains. Mobility is beneficial also for nomadic services, such as laptop connectivity, since it allows a reliable connection to be maintained in the areas between two cells where the best serving cell is changing. This also implies a simple setup of the broadband connection without any location related configurations. Mobility typically has its price in the network complexity: the network algorithms and the network management get complex. The target of the LTE radio network is to provide seamless mobility while simultaneously keeping network management simple.
The mobility procedures can be divided into idle mode and connected mode for the attached UE (see Figure 7.1). Idle mode mobility is based on UE autonomous cell reselections according to the parameters provided by the network, thus this is quite similar to the one in WCDMA/HSPA today. The connected mode mobility in LTE, on the other hand, is quite different in LTE than in WCDMA/HSPA radio networks. The UE transition between idle and RRC connected mode is controlled by the network according to the UE activity and mobility. The algorithms for RRC connection management are described in Chapter 8.
This chapter explains ...