LTE Reselection points and IRAT thresholds

changes

Description of the Change:

• Some configurable parameters include suffixes used to specify a subset of cells to which the parameter recommendation applies. The distinction is known as the “Cell Designation” and in LTE exists as follows:

• 1) interRAT_10 – 10MHz cells where neither intraLTE nor interLTE are options. Those cells are not able to maintain good performance (retainability & throughput) without performing IRAT handover

• More information regarding LTE cell designations and the algorithm used to determine them can be found here. “Cell Designation” concept will be applied on parameters involved in the LTE/UMTS reselection process and IRAT mobility. Here is the list of LTE cells and their collocated UMTS cells with their initial cell designations

• The cell selection and reselection process allows the UE to look for a suitable cell and to camp on it in the idle mode. The cell selection criterion (the S criterion) is based on the measured Reference Signal Received Power (RSRP) level in the serving cell, normalized with respect to the minimum required receive signal level in the cell and certain compensations. A cell fulfills the cell selection criterion when

• Srxlev > 0, Srxlev = Qrxlevmeas – (qRxLevMin+ Qrxlevminoffset) – Pcompensation

• where Qrxlevmeas is measured RSRP in the cell (dBm), qRxLevMin is the parameter defining minimum required RSRP level (dBm), Qrxlevminoffset is the parameter defining an offset to qRxLevMin and Pcompensation = max (pMaxServingCell – PpowerClass, 0), where pMaxServingCell the maximum UE power in the cell while Ppowerclass is the maximum UE power capability

• The cell reselection procedure (the R criterion) is performed by the UE to make sure it always camps on the best cell regardless of the frequency and technology. The LTE IRAT cell reselection is the process where IRAT neighboring cells that fulfill the S criterion are considered for the reselection. It consists of three phases

• (UMTS carriers) when the following condition for serving LTE cell is met:

• Srxlev <= sNonIntraSearch • where sNonIntraSearch is the parameter defining threshold for measurements of

inter-RAT frequencies of lower priority than the serving cell.

• 2) The UE measurement - the UE measures the RSRP of the serving LTE cell at least every DRX Cycle, while the UE will measure IRAT cells with a minimum periodicity of 1-4 DRX cycle depending on DRX cycle length

• 3) The LTE IRAT cell reselection triggering - the cells with lower Absolute Priority (UMTS) than the serving cell must meet the S-criterion to be subject for cell reselection. In addition, the cell reselection to a lower priority IRAT cell occurs when:

• Srxlev > threshXLow for lower priority IRAT cell and

• Srxlev < threshServingLow for a duration of tReselectionUtra for serving LTE cell • where threshXLow is the parameter defining the threshold used by the UE when

reselecting towards a lower priority IRAT frequency from the current serving frequency and threshServingLow defines the signal threshold below which the serving cell must be in order to allow cell reselection to a lower priority IRAT cell

• The Inter-RAT LTE mobility corresponds to UE transition between technologies during active connections. The IRAT mobility is initiated by eventA2 trigger indicating that serving cell becomes worse than absolute threshold. The expression used by the UE to evaluate entry to eventA2 is shown in the following expression:

• Ms + hysteresisA2Prim < a2ThresholdRsrpPrim

• where Ms is measured RSRP value of the serving cell, hysteresisA2Prim is the parameter defining the hysteresis value for the primary eventA2 measurement and a2ThresholdRsrpPrim defines the primary RSRP threshold value for eventA2.

The default border parameters

Parameters settings:

Based on the results from the testing markets, the will have following impact on network performance: • Significant reduction in % IRAT • Degradation in Retainability up to 0.08%. • Overall reduction in Accessibility by ~0.1%. • Up to ~3.5% degradation in the DL cell level throughput.

Implementation sites

eNBId SiteName_TD Label Cluster PAC_Cluster eUtranCellName eUtranCellF

DD PCI PCI=Blank_TD Lat Lon Azimuth_Geo Azimuth_Mag Height MechanicalAnten-Tilt ElectricalAntennaTilt RETStatus

DF0351L2100 DF0351 NOXCALCO Mex31 2 DF0351L001 90351001 348 348 19.213878 -98.984514 87 80 39 0 0 OK

DF0351L2100 DF0351 NOXCALCO Mex31 2 DF0351L002 90351002 349 349 19.213878 -98.984514 205 198 39 1 0 OK

DF0351L2100 DF0351 NOXCALCO Mex31 2 DF0351L003 90351003 350 350 19.213878 -98.984514 297 290 39 0 0 OK

DF0621L2100 DF0621 MIXQUIC Mex31 DF0621L001 90621001 351 351 19.225314 -98.956197 102 95 28 3 0 OK

DF0621L2100 DF0621 MIXQUIC Mex31 DF0621L002 90621002 352 352 19.225314 -98.956197 187 180 28 4 0 OK

DF0621L2100 DF0621 MIXQUIC Mex31 DF0621L003 90621003 353 353 19.225314 -98.956197 297 290 28 0 30 OK

MX5132L2100 MX5132 SAN JUAN Y SAN PEDRO TEZOMPA Mex31 2 MX5132L001 155132001 354 354 19.205768 -98.960464 37 30 40 0 30 OK

MX5132L2100 MX5132 SAN JUAN Y SAN PEDRO TEZOMPA Mex31 2 MX5132L002 155132002 355 355 19.205768 -98.960464 127 120 40 0 0 OK

MX5132L2100 MX5132 SAN JUAN Y SAN PEDRO TEZOMPA Mex31 2 MX5132L003 155132003 356 356 19.205768 -98.960464 287 280 40 0 20 OK

KPI MX5132L2100

E-RAB Drop rate

KPI DF0621L2100

E-RAB Drop rate

KPI DF0351L2100

E-RAB Drop rate

Implementation sites Cluster 5 sites