Single Radio Voice Call Continuity (SRVCC)

A VoLTE voice service continuity solution, mainly in order to solve problem of how to ensure that the voice call continuity when a single radio UE moves between the LTE / Pre-LTE network and 2G/3G CS network, i.e. to ensure a single RF UE smooth switching between IMS VoIP voice control and CS domain voice.

The simplest use model can be illustrated as in < Case 1 > of the following figure showing the SRVCC between LTE and UMTS (The detailed mechanism would vary depending on what kind of legacy technology is involved). A little bit complicated use-model can be illustrated as in < Case 2 >. In < Case 2 >, user is doing VoIP while he is using another packet transaction (e.g, email, browsing etc). In this case, the radio bearer on WCDMA side should be a multiple Radio Bearer (CS + PS). There may be many different type of use model as well.

Vo Lte

Vo Lte

Intra RAT HO events in LTE

Below is the List and How Intra RAT HO events in LTE.

• Event A1 : Serving becomes better than threshold
• Event A2 : Serving becomes worse than threshold
• Event A3 : Neighbor becomes offset better than serving
• Event A4 : Neighbor becomes better than threshold
• Event A5 : Serving becomes worse than threshold1 and neighbor becomes better than threshold2

Event A1 (Serving becomes better than threshold)

Ms − Hys > Thresh (Entering condition)
Ms + Hys < Thresh (Leaving condition)

Event A2 (Serving becomes worse than threshold)

Ms + Hys < Thresh (Entering condition)
Ms − Hys > Thresh Leaving condition

Event A3 (Neighbor becomes offset better than serving)

Mn +Ofn +Ocn − Hys > Ms +Ofs +Ocs +Off (Entering condition)
Mn +Ofn +Ocn + Hys < Ms +Ofs +Ocs +Off (Leaving condition)

Event A4 (Neighbor becomes better than threshold)

Mn +Ofn +Ocn− Hys > Thresh (Entering condition)
Mn +Ofn +Ocn + Hys < Thresh (Leaving condition)

Event A5 (Serving becomes worse than threshold1 and neighbor becomes better than threshold2)

Ms + Hys < Thresh1 AND Mn +Ofn +Ocn − Hys > Thresh2 (Entering condition)
Ms − Hys > Thresh1 OR Mn +Ofn +Ocn + Hys < Thresh2 (Leaving condition)

Ms (dBm, dB) is the measurement result of the serving cell, not taking into account any cell individual offset.

Hys (dB) is the hysteresis parameter for this event (i.e. hysteresis as defined within the VarMeasurementConfiguration for this event)

Thresh (dBm, dB) is the threshold parameter for this event (i.e. a1/a2/a4-Threshold as defined within the VarMeasurementConfiguration for this event)

Mn (dBm, dB) is the measurement result of the neighboring cell.

Ofn is the frequency specific offset of the frequency of the neighbor cell (equals Ofs for intra-frequency measurements and is included in MeasObjectEUTRA corresponding to the inter frequency as offsetFreq for inter-frequency measurements)

Ocn is the cell specific offset of the neighbor cell. If not configured zero offset shall be applied (included in MeasObjectEUTRA of the serving frequency as parameter cellIndividualOffset for intra-f measurements and included in MeasObjectEUTRA corresponding to the inter frequency as parameter cellIndividualOffset for interfrequency measurements).

Ofs (dB) is the frequency specific offset of the serving frequency (i.e. offsetFreq within the MeasObjectEUTRA corresponding to the serving frequency)

Ocs (dB) is the cell specific offset of the serving cell (included in MeasObjectEUTRA of the serving frequency as parameter cellIndividualOffset)

Off (dB) is the offset parameter for this event (i.e. a3-Offset as defined within the VarMeasurementConfiguration for this event)

Thresh1 is the threshold parameter for this event (i.e. a5-Threshold1 as defined within the VarMeasurementConfiguration for this event)

Thresh2 is the threshold parameter for this event (i.e. a5-Threshold2 as defined within the VarMeasurementConfiguration for this event)