LTE Parameter Setting Exercises IDLE Mode Initial Cell Selection 1) Based on the following measurements and thresholds, calculate the Srxlev for each cell and determine which cell will be initially selected by the mobile. Srxlev_A ____________________ Srxlev_B_____________________ Srxlev_C_____________________ 2) Determine from the following, at what Qrxlev_meas,S would intra-freq search and non-intra-freq search begin Qrxlev_meas,S for intra-freq search_________________________ Qrxlev_meas,S for non-intra-freq search______________________

Qrxlevmin; -75dBm Qrxlevmeas_A; -65dBm

Qrxlevmin; -95dBm Qrxlevmeas_B; -75dBm

A

B

C Qrxlevmin; -95dBm Qrxlevmeas_C -100dBm

Sintrasearch = 30

Snonintrasearch = 10

Qrxlevmin = -90dBm

Srxl

ev

Srxlev = Qrxlevmeas,s - Qrxlevmin

3) From the following parameters determine what value Qrxlevmin should be set to, if the intra-frequency search is required to begin at -50dBm Sintrasearch = 20dB Qrxlevmeas = -50 Srxlev = Qrxlevmeas,s Qrxlevmin Qrxlevmin_____________________________________________ 4) Assuming Qhyst = 5 and Qoffset = -3, plot the line of Rs and Rn on the graph below. Rs = Qmeas,s + Qhyst Rn = Qmeas,n + Qoffset Indicate the point on the graph at which cell reselection will take place

What is the actual value of Qmeas,s and Qmeas,n for the serving and neighbor cells when the reselection actually takes place? Qmeas,s________________________________ Qmeas,n________________________________ 5) Discuss the impact on the idle mode mobility of the UE if the Qhyst was set to 10dB-__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________

858075706560555045403530

dBm

6) If no LTE neighbour was available and the Snonintrasearch threshold was set to 10dB what would Qmeas (signal strength) when the UE began searching for an IRAT neighbour? __________________________________________________________________________ __________________________________________________________________________ Random Access Parameters An operator has been testing PRACH performance in the lab and has found that a larger than expected number of preambles are transmitted before a UE gets a response from the eNB. Overall results indicate that on average five preambles are transmitted. You are asked to determine: 1. The average amount of time between the first preamble and the response from the eNB. 2. Some suggested parameter changes that may reduce the number of preamble transmissions; ideally to just one. The current configuration is as follows: preambleInitialReceivedTargetPower is set at 125 dBm powerRampingStep is set at 2 dB ra-responseWindowSize is set at 4 preambleTransMax is set at 20 prach_ConfigIndex is set at 5 UE power class 3 Simulated path loss with attenuators of 125 dB Answers and Workings

Intra-LTE Fast Handovers An operator has installed LTE repeaters on the passenger trains running on a new high speed rail line between two major cities. They are concerned that their current handover parameters may not act fast enough to maintain reliable connections along the route. The operator would like you to review the current parameters and consider adjustments to the standard parameter set prior to the commencement of testing. The current parameter set is as follows: Parameter Value

Parameter Value

s-Measure 95 dBm

eA3

A3-Offset 6 dB

triggerQuantity RSRP reportOnLeave True

reportQuantity Both hysteresis 2 dB

maxReportCells 6 timeToTrigger 640 ms

reportInterval 480 ms

eA5

threshold1-RSRP 104 dBm

reportAmount 8 threshold2-RSRP 98 dBm

hysteresis 2 dB

speedStateParameters Not currently in use timeToTrigger 640 ms Cell are placed along the new rail line approximately every five kilometres. It is expected that on open track the overlap area between cells will be in the order of 1 km, however, in some places, particularly at tunnel entrances it may be as low as 200 m. The normal operating speed for the trains is 500 km/h. Step 1 Calculate how long it will take a train running at normal operating speed to pass through the overlap area between cells. You should do this for both open ground and tunnel entrances.

Answer:

Step 2 Write a brief report indicating whether or not you think changes need to be made to the standard parameter set. Include a brief explanation of each change and consider any other changes that you think might be appropriate outside the set of parameters given here.