Evaluation of mobile handset recovery from radio link failure in a multi-RATS environment

Radio link failure (RLF) is a common phenomenon in all radio access technologies like GSM or UMTS or wireless-LAN etc., when the radio channel signal strength is weak to continue with the application. RLF is a local event detected by mobile handset (or user equipment-UE) immediately and network nodes come to know later. It is also difficult to recover for the UE due to low signal. Hence, RLF has to be dealt locally by the UE. In case of RLF, 3GPP specification indicates to release of dedicated data and signaling resources which leads to discontinuation of the application. In order to avoid discontinuation of application one of the solution proposed to use other available RAT (radio access technology) from multi-RATs in the UE. A few literatures present the possibility of single-RAT or multi-RATs RLF recovery [2-11]. However, to the best of authorspsila knowledge, none of these publications present any performance evaluation for selecting an available RAT from multi-RATs environment after a RLF. In this paper, the authors have investigated the impact of three key parameters namely, RSSI (received signal strength identifier), QoS (quality of service), connection re-establishment time for RLF recovery across all available RATs. The analytical studies show that, two times increase in radio resources along with three times increase in number of mobile handsets experiencing RLF, the probability of success of RLF recovery increases significantly. Furthermore, one of the studies reveals that, when mean utilization of resources in the cells increases by 50% and the number of mobile handsets suffering from RLF increase by two times, the probability of success of RLF recovery decreases by 15%.