System Information Block Type 7 or with abbreviated version SIB7 contains GERAN frequency group related information and relevant only for cell re-selection from LTE to GSM. The message includes frequency groups with specific re-selection parameters. SIB7 is transmitted from the network to UE through BCCH -> DL-SCH -> PDSCH channels.
Here the list of carried information from the network to UE through SIB7:
t-Reselection GERAN: cell reselection timer for reselection to a GERAN frequency carrier. Value in seconds.
sf-Medium: specifies scaling factor for t-Reselection GERAN for inter-RAT reselection to GERAN in Medium-mobility state. Value oDot25 corresponds to 0.25, oDot5 corresponds to 0.5 etc.
sf-High: specifies scaling factor for t-Reselection GERAN for inter-RAT reselection to GERAN in High-mobility state. Value oDot25 corresponds to 0.25, oDot5 corresponds to 0.5 etc.
Carrier Freqs Info List GERAN: parameters related to a neighboring GERAN frequency group, these parameters are used for Inter-Technology reselection from EUTRAN to GERAN. The parameters might be different set for each frequency group.
Starting ARFCN: specifies first ARFCN in GERAN frequency group.
Band Indicator: specifies GERAN frequency band, either it is GSM1800 or GSM1900.
Explicit List Of ARFCNs: specifies the ARFCN list of the GERAN BCCH.
Cell Reselection Priority: indicates the cell reselection priority of GERAN frequency group. The value 0 indicates the lowest priority.
NCC-Permitted: field encoded as a bit map, where bit N is set to “0” if a BCCH carrier with NCC = N-1 is not permitted for monitoring and set to “1” if a BCCH carrier with NCC = N-1 is permitted for monitoring; N = 1 to 8; bit 1 of the bitmap is the leading bit of the bit string.
q-RxLevMin: required minimum received RSSI level on GERAN frequency carrier for re-selection from LTE to GSM. Actual value in dBm is value * 2 – 115.
Pmax: this parameter is used to limit the allowed UE uplink transmission power on this GERAN carrier frequency.
threshX-High: threshold used when reselecting from lower priority LTE frequency to higher priority GERAN frequency group. Actual value in dB is obtained by multiplying by 2.
threshX-Low: threshold used when reselecting from higher priority LTE frequency to lower priority GERAN frequency group. Actual value in dB is obtained by multiplying by 2.
SIB7 carried information:
Example for SIB7, taken from drive-test tool:
t-ReselectionGERAN : 1
t-ReselectionUTRA-SF
sf-Medium : lDot0
sf-High : oDot75
carrierFreqsInfoList
CarrierFreqsInfoListGERAN :
[0 ] :
carrierFreqs
startingARFCN : 515
bandIndicator : dcs1800
followingARFCNs :
explicitListOfARFCNs
ExplicitListOfARFCNs :
IntegerType = 520
IntegerType = 525
IntegerType = 530
IntegerType = 580
IntegerType = 585
IntegerType = 800
IntegerType = 855
cellReselectionPriority : 1
ncc-Permitted : 11111111
q-RxLevMin : 2
threshX-High : 7
threshX-Low : 8
* Note: there are some parameters which might not be seen in the message list from drive-test tool, so it means this parameter was not configured in the network by the engineers.