LTE Advanced: 3GPP Solution for IMT-Advanced

10.3 Self-Optimization

10.3.1 Mobility Robustness Optimization

The general task of Mobility Robustness Optimization (MRO) is to guarantee good mobility, that is, proper handovers in connected mode. This is achieved by:

• Minimizing Radio Link Failures (RLF) and call drops; in many cases a connection can be re-established after an RLF before the call drops; or, in worst case, a mobility problem may lead to a call drop. Connection re-establishment is only possible inside LTE, and not possible if another target RAT is involved. Recovery via the core network can help maintaining user service if it can bear temporary degradation of quality.
• Minimizing unnecessary handovers and ping-pongs. Ping-pongs refer to repeated handovers between two cells within a short time. Unnecessary handovers and ping-pongs do not lead to RLF but many of those would lead to inefficient use of network resources and reduction of user throughput so that user perception may be affected as well.

MRO in Release 9 is specified for LTE only (both intra and inter-frequency), while Release 10 addresses some Inter-RAT challenges, such as unnecessary handovers. The full Inter-RAT MRO is a core topic of Release 11. An extensive description, scenarios and related simulations are included in [1].

The MRO idea is to automatically detect and correct errors in mobility configuration that lead to connection failures. This is enabled by failure reporting specified in Release 9 and later extended in Release 10; before Release ...