Handoff Parameters
Overview (Back to top)
This page gives a detailed description of handoff-related parameters in LTE. We first give an summary of parameters, then explain each parameter in three categories (basic cell information, idle-state handoff, and active-state handoff ) in details.
Summary of handoff parameters (LTE) (Back to top)
| Parameter used in MMMap | Parameter name used in this document | Description | Message type |
|---|---|---|---|
| Category I: basic cell information | |||
| MCC | MCC | Mobile Country Code | Serving cell info |
| MNC | MNC | Mobile Network Code | Serving cell info |
| TAC | TAC | Tracking Area Code | Serving cell info |
| Cell Identity | Cell Identity | Cell Identity | Serving cell info |
| Cell ID | cellID | physical cellid | Serving cell info |
| downlinkBW | downlinkBandwidth | downlink bandwidth | Serving cell info |
| downlinkFreq | downlinkFrequency | downlink frequency | Serving cell info |
| uplinkBW | uplinkBandwidth | uplink bandwidth | Serving cell info |
| uplinkFreq | uplinkFrequency | uplink frequency | Serving cell info |
| Category II: idle-state handoff | |||
| Serving cell information | |||
| cellReselectionPriority | cellReselectionPriority | priority for cell reselection | SIB3 |
| q_RxLevMin | Qrvlevmin for serving cell | minimum required RX level in the cell (RSRP, dBm) | SIB1 |
| Q_RxLevMinOffset | Q_RxLevMinOffset | offset for signal strength | SIB1 |
| p_Max | PEMAX for serving cell | maximum TX power level an UE may use when transmitting on the uplink in the cell (dBm) | SIB1 |
| s_IntraSearch | SIntraSearchP | intra frequency search signal strength | SIB3-intraFreq |
| s_NonIntraSearch | SnonIntraSearchP | non intra frequency search signal strength | SIB3-ServingFreqInfo |
| q_Hyst | QHyst | signal strength hysterist | SIB3-InfoCommon |
| threshServingLow | ThreshServing, LowP | serving cell’s threshold to do cell selection | SIB3-ServingFreqInfo |
| Intra-frequency target cell handoff parameters | |||
| q_RxLevMin | Qrvlevmin for intra-freq cell | minimum required RX level in the cell (RSRP, dBm) | SIB3 |
| Q_RxLevMinOffset | Q_RxLevMinOffset for intra-freq cell | for intra-freq cell | SIB3 |
| t_ReselectionEUTRA | TreselectionRAT for intra-freq | time interval for intra frequency selection | SIB3-intraFreq |
| Key: physCellId | cellID | physical cell id | SIB4 |
| q_OffsetCell | Qoffsettemp | offset for signal strength | SIB4 |
| Inter-frequency target cell handoff parameters | |||
| Key: dl_CarrierFreq | downlinkFrequency | downlink carrier frequency | SIB5 |
| q_RxLevMin | Qrvlevmin for inter-freq target cell | minimum required RX level in the cell (RSRP, dBm) | SIB5 |
| p_Max | PEMAX for inter-freq tartget cell | maximum TX power level an UE may use when transmitting on the uplink in the cell (dBm) | SIB5 |
| t_ReselectionEUTRA | TreselectionRAT for inter-freq | time interval for inter frequency selection | SIB5 |
| threshX_High | ThreshX, HighP for inter-freq | adjacent cell’s threshold for inter freq cell selection to higher priority cell | SIB5 |
| threshX_Low | ThreshX, LowP for inter-freq | adjacent cell’s threshold for inter freq cell selection to lower priority cell | SIB5 |
| q_OffsetFreq | Qoffsettemp | offset frequency | SIB5 |
| Key: dl_CarrierFreq | downlinkFrequency | downlink carrier frequency | SIB5 |
| Key: physCellId | cellID | physical cell id | SIB5NeighCell |
| q_OffsetCell | Qoffset | offset for cell | SIB5NeighCell |
| Inter-rat target cell handoff paramters | |||
| Key: dl_CarrierFreq | downlinkFrequency | carrier frequency | SIB6 |
| cellReselectionPriority | cellReselectionPriority | priority for cell reselection | SIB6 |
| q_RxLevMin | Qrvlevmin for inter-RAT target cell | minimum required RX level in the cell (RSRP, dBm) | SIB6 |
| q_QualMin | Qqualmin for inter-RAT target cell | minimum required quality level in the cell (RSRQ, dB) | CarrierFreqUTRA_FDD_element |
| p_MaxUTRA | PEMAX for inter-RAT target cell | maximum TX power level an UE may use when transmitting on the uplink in the cell (dBm) | SIB6, CarrierFreqUTRA_FDD_element |
| threshX_High | ThreshX, HighP for inter-RAT | adjacent cell’s threshold for inter rat cell selection to higher priority cell | SIB6, CarrierFreqUTRA_FDD_element |
| threshX_Low | ThreshX, LowP for inter-RAT | adjacent cell’s threshold for inter rat cell selection to lower priority cell | SIB6, CarrierFreqUTRA_FDD_element |
| Category III: active-state handoff | |||
| A1(hyst) | Hys | hysteresis | RRC measurement report |
| A1(thresh) | Thresh | threshold | RRC measurement report |
| A2(hyst) | Hys | hysteresis | RRC measurement report |
| A2(thresh) | Thresh | threshold | RRC measurement report |
| A3(hyst) | Hys | hysteresis | RRC measurement report |
| A3(offset) | Off | offset | RRC measurement report |
| A4(hyst) | Hys | hysteresis | RRC measurement report |
| A4(thresh) | Thresh | threshold | RRC measurement report |
| A5(hyst) | Hys | hysteresis | RRC measurement report |
| A5(thresh1) | Thresh1 | threshold1 | RRC measurement report |
| A5(thresh2) | Thresh2 | threshold2 | RRC measurement report |
| A6(hyst) | Hys | hysteresis | RRC measurement report |
| A6(offset) | Off | offset | RRC measurement report |
| B1(hyst) | Hys | hysteresis | RRC measurement report |
| B1(thresh) | Thresh | threshold | RRC measurement report |
| B2(hyst) | Hys | hysteresis | RRC measurement report |
| B2(thresh1) | Thresh1 | threshold1 | RRC measurement report |
| B2(thresh2) | Thresh2 | threshold2 | RRC measurement report |
Detailed descriptions of handoff parameters (LTE) (back to top)
Basic cell information(back to top)
MCC（Mobile Country Code), MCC（Mobile Network Code), TAC(Tracking Area Code), Cell Identity, and CellID, all are related to cell identity information, which can be used to identify one base station (cell). Other parameters like downlinkFrequency, downlinkBandwidth, uplinkFrequency, and uplinkBandwidth, correspond to the cell's downlink and uplink frequency and bandwidth.
Idle-state handoff (back to top)
Calculation of Srxlev and Squal
- Srxlev = Qrxlevmeas - (Qrxlevmin + Qrxlevminoffset) – Pcompensation
- Squal = Qqualmeas - (Qqualmin + Qqualminoffset)
where
- Srxlev: Cell selection RX level value (RSRP, dBm)
- Squal : Cell selection quality value (RSRQ, dB)
- Qrxlevmeas : Measured cell RX level value (RSRP, dBm)
- Qqualmeas: Measured cell quality value (RSRQ, dB)
- Qrxlevmin: Minimum required RX level in the cell (RSRP, dBm)
- Qqualmin: Minimum required quality level in the cell (RSRQ, dB)
- Qrxlevminoffset: Offset to the signaled Qrxlevmin taken into account in the Srxlev evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN
- Qqualminoffset: Offset to the signaled Qqualmin taken into account in the Squal evaluation as a result of a periodic search for a higher priority PLMN while camped normally in a VPLMN
- Pcompensation: max(PEMAX - PPowerClass, 0) (dBm);
- PEMAX: Maximum TX power level an UE may use when transmitting on the uplink in the cell (dBm);
- PPowerClass: Maximum RF output power of the UE (dBm) according to the UE power class;
Measurement rules for cell-reselection (back to top)
- Intra-frequency
- If the serving cell fulfils Srxlev > SIntraSearchP and Squal > SIntraSearchQ, the UE may choose not to perform intra-frequency measurements.
- Otherwise, the UE shall perform intra-frequency measurements.
- Inter-frequency
- If Srxlev > SnonIntraSearchP and Squal > SnonIntraSearchQ then the UE shall search for inter-frequency layers of higher priority at least every Thigher_priority_search.
- If Srxlev ≤ SnonIntraSearchP or Squal ≤ SnonIntraSearchQ then the UE shall search for and measure inter-frequency layers of higher, equal or lower priority in preparation for possible reselection.
- Inter-RAT
- If Srxlev > SnonIntraSearchP and Squal > SnonIntraSearchQ then the UE shall search for inter-RAT layers of higher priority at least every Thigher_priority_search.
- If Srxlev ≤ SnonInterSearchP or Squal ≤ SnonInterSearchQ then the UE shall search for and measure inter-RAT layers of higher, lower priority in preparation for possible reselection.
Cell selection criterion (back to top)
The cell selection criterion S is fulfilled when: Srxlev > 0 and Squal > 0
Cell reselection criteria (back to top)
Inter-frequency and inter-RAT cell reselection(back to top)
- To higher priority:
cell reselection to a cell on a higher priority E-UTRAN frequency or inter-RAT frequency than the serving frequency shall be performed if:
- A cell of a higher priority RAT/ frequency fulfils Srxlev > ThreshX, HighP during a time interval TreselectionRAT; and
- More than 1 second has elapsed since the UE camped on the current serving cell.
- To lower priority:
cell reselection to a cell on a lower priority E-UTRAN frequency or inter-RAT frequency than the serving frequency shall be performed if:
- The serving cell fulfils Srxlev < ThreshServing, LowP and a cell of a lower priority RAT/ frequency fulfils Srxlev > ThreshX, LowP during a time interval TreselectionRAT; and
- More than 1 second has elapsed since the UE camped on the current serving cell.
Intra-frequency and equal-priority inter-frequency cell reselection(back to top)
The cell-ranking criterion Rs for serving cell and Rn for neighbouring cells is defined by:
- Rs = Qmeas,s + QHyst – Qoffsettemp
- Rn = Qmeas,n - Qoffset – Qoffsettemp
- Qoffset
- For intra-frequency: Equals to Qoffsets,n, if Qoffsets,n is valid, otherwise this equals to zero; or
- For inter-frequency: Equals to Qoffsets,n plus Qoffset frequency, if Qoffsets,n is valid, otherwise this equals to Qoffsetfrequency;
The UE shall reselect the new cell, only if the following conditions are met:
- The new cell is better ranked than the serving cell during a time interval TreselectionRAT; and
- More than 1 second has elapsed since the UE camped on the current serving cell.
Active-state handoff (back to top)
Measurement reporting events (back to top)
The UE reports measurement information in accordance with the measurement configuration as provided by E-UTRAN. E-UTRAN provides the measurement configuration applicable for a UE in RRC_CONNECTED by means of dedicated signaling, i.e. using the RRCConnectionReconfiguration message.
Event A1(back to top)
Serving cell measurement(Ms) becomes better than threshold(Thresh) with a hysterisis(Hys).
A1 Entering condition:
- A1-1: Ms – Hys > Thresh
A1 Leaving condition:
- A1-2: Ms + Hys < Thresh
Event A2(back to top)
Serving Measurement(Ms) becomes worse than threshold(Thresh) with a hysterisis(Hys)
A2 Entering condition:
- A2-1 Ms + Hys < Thresh
A2 Leaving condition:
- A2-2 Ms – Hys > Thresh
Event A3(back to top)
Neighbour mesurement(Mn) becomes offset(off) better than PCell measurement with hysterisis(Hys),offsetfreqency(Ofp,Ofn),offsetcell(Ocn,Ocp)
A3 Entering condition:
- A3-1: Mn + Ofn + Ocn – Hys > Mp + Ofp + Ocp + Off
A3 Leaving condition
- A3-2: Mn + Ofn + Ocn + Hys < Mp + Ofp + Ocp + Off
Event A4(back to top)
Neighbour measurement(Mn) becomes better than threshold(Thresh) with hysterisis(Hys),offsetfreqency(Ofn),offsetcell(Ocn):
A4 Entering condition:
- A4-1: Mn + Ofn + Ocn – Hys > Thresh
A4 Leaving condition:
- A4-2: Mn + Ofn + Ocn + Hys < Thresh
Event A5(back to top)
PCell measument(Mp) becomes worse than Threshold1 with hysterisis(Hys),offsetfreqency(Ofp,Ofn),offsetcell(Ocn,Ocp) and neighbour becomes better than Threshold2 with hysterisis(Hys),offsetfreqency(Ofn),offsetcell(Ocn)
A5 Entering condition
- A5-1: Mp + Hys < Thresh1
- A5-2: Mn + Ofn + Ocn – Hys > Thresh2
A5 Leaving condition 1
- A5-3: Mp – Hys > Thresh1
- A5-4: Mn + Ofn + Ocn + Hys < Thresh2
Event A6 (back to top)
Neighbour measurment(Mn) becomes offset(off) better than Scell with offsetcell(Ocn),hysterisis(Hys)
A6 Entering condition:
- A6-1: Mn + Ocn – Hys > Ms + Ocs + Off
A6 Leaving condition
- A6-2: Mn + Ocn + Hys < Ms + Ocs + Off
Event B1(back to top)
Inter RAT neighbour measurement(Mn) becomes better than threshold(Thresh) with offsetfrequency(Ofn),hysterisis(Hys)
B1 Entering condition:
- B1-1: Mn + Ofn – Hys > Thresh
B1 Leaving condition:
- B1-2: Mn + Ofn + Hys < Thresh
Event B2 (back to top)
PCell measurement(Mp) becomes worse than threshold1(Thresh1) with hysterisis(Hys) and inter RAT neighbour becomes better than threshold2(Thresh2) with offsetfrequency(ofn),hysterisis(Hys)
B2 Entering conditions:
- B2-1: Mp + Hys < Thresh1,
- B2-2: Mn + Ofn – Hys > Thresh2
B2 Leaving conditions:
- B2-3: Mp – Hys > Thresh1,
- B2-4: Mn + Ofn + Hys < Thresh2.
Reference
3GPP standards: http://www.3gpp.org/specifications.