Unfortunately we dont have any clear answer to this question either.So detailed detection implementation is up to UE maker and eNodeB maker, but we can think of several guidelines.So the individual RLF detection mechanism may vary chipset-to-chipset.
If all of them are overload, more physical resources need to be reserved for RACH. The configuration of the random access procedure has a critical impact on end-user experience and overall network performance. A poorly configured Random Access CHannel (RACH) may increase access setup time and accesses failures, impacting both call setup and handover performance. With optimal random access parameter setting, maximum end-user experience can be obtained. This is achieved by reaching the desired balance in the radio resource allocation between random accesses and services while at the same time avoiding creating excessive interference. In LTE, RACH (Random Access Channel) is an uplink unsynchronized channel, used for initial access or uplink synchronization. The triggers for Random Access procedure include: Connection setup Radio Link Failure Downlink data transmission in uplink unsynchronized state Uplink data transmission in uplink unsynchronized state Handover So the Random Access procedure performance influences the call setup delay, handover delay, data resuming delay, call setup success rate and handover success rate. Besides, physical resources for RACH are reserved for its special use. So the configuration for RACH influences the capacity of the whole network. An optimized RACH configuration enables end-user benefits and network performance gains through: Reduced connection time Higher throughput Better cell coverage. By automating the optimization of RACH, maximum performance is achieved with no operator intervention or effort. The network will dynamically adapt to network changes and end-user behavior to always deliver best possible performance and resource utilization. Necessity for RACH optimization The performance of Random Access performance is evaluated by its delay and success rate. The performance depends on following factors: Population under the cell coverage; Call arrival rate; Incoming handover rate; Whether the cell is at the edge of a tracking area; Traffic pattern, as it affects the DRX (Discontinuous Reception) and uplink synchronization states, and hence the need to use RACH. These factors are affected by network configurations, such as antenna tilt, transmission power and handover threshold, and also by the load of network. If network configurations or load is changed, the performance of Random Access procedure may change greatly, which influences the performance of other procedures, such as call setup, data resuming and handover. Possible RACH optimization algorithm The configurations of RACH include: RACH physical resources RACH preamble allocation for different sets (dedicated, random-low and randomhigh) RACH persistence level and backoff control RACH transmission power control Measurements are done in eNB, recording random access delay, random access success rate and random access load. The random access load can be indicated by the number of received preambles in a cell in a time interval. It is measured per preamble range (dedicated, random-low and random-high), and averaged over the PRACHs configured in a cell. Thresholds are set separately for random access delay and success rate. If either of the thresholds is reached, RACH optimization is triggered. First, Random access load is analyzed to check if the random access is overload in any of the three preamble ranges. If one of them is overload, RACH preambles are reallocated among these three preamble ranges.
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