This Annex provides an example to demonstrate the handling of Apply Charging GPRS and Apply Charging Report GPRS.

In Figure A.1, data volumes transferred for the active PDP context are listed on the left-hand side of diagram. The following is a description of the example:

1. Apply Charging GPRS threshold set to 2000, no tariff switch timer set.
2. After 2000 units of data have been transferred, an Apply Charging Report GPRS is sent to the gsmSCF.
3. The gsmSCF sends another Apply Charging GPRS with a 2000 unit threshold.
4. After 2000 units of data have been transferred, an Apply Charging Report GPRS is sent to the gsmSCF.
5. Another threshold (2000) is set by the gsmSCF in Apply Charging GPRS, and a tariff switch timer is set.
6. After 2000 units have been transferred, Apply Charging Report GPRS is sent to the gsmSCF, as a tariff switch timer has expired since the last Apply Charging GPRS, values for volumeTariffSwitchInterval and Volume transferred since the tariff switch are sent. The gsmSCF stores the value volumeTariffSwitchInterval.
7. The gsmSCF sends another Apply Charging GPRS with a 2000 unit threshold.
8. After 2000 units of data have been transferred, an Apply Charging Report GPRS is sent to the gsmSCF.
9. Apply Charging GPRS sets a tariff switch timer, which does not expire before the next Apply Charging Report GPRS.
10. A change in QoS is reported so Apply Charging Report GPRS is returned to the gsmSCF containing VolumeIfNoTariffSwitch as no tariff switch has occurred since the last Apply Charging Report GPRS. The gsmSCF should store this value if the volume of data transferred at each QoS level is to be calculated. The Tsw sent in the previous Apply Charging GPRS is stopped. In this example the tariff switch timer (Tsw) does not expire before this QoS change. If Tsw had expired the Apply Charging Report GPRS would report the volumeTariffSwitchInterval in the normal way.
11. An Apply Charging GPRS is sent giving a new threshold. This threshold is service logic dependent and does not rely on any previous value sent. In the example it is 'previous threshold - volume transferred since last threshold was set'.
12. The VolumeSinceLastTariffSwitch is reported in the Apply Charging Report GPRS. Note: this includes data transferred before and after the QoS change.
13. Note that a tariff switch timer is set and expires.
14. A final Apply Charging Report GPRS is returned containing the data volume transferred since the last tariff switch, and also the total volume transferred at the previous tariff.

The calculations made by the gsmSCF in this example are:

1. Total Data Volume Transferred in this example: Total of all volumeTariffSwitchInterval received + final volumeSinceLastTariff switch is (5500 + 5000) + 1500 = 12000 units of data
2. Data Volume transferred for each tariff: (periods separated by Tsw in Figure A.1)
   • 1st Tariff: taken from Apply Charging Report GPRS (signal f)) volumeTariffSwitchInterval = 5500 units of data
   • 2nd Tariff: taken from Apply Charging Report GPRS (signal n)) volumeTariffSwitchInterval = 5000 units of data
   • 3rd Tariff: taken from VolumeSinceLastTariffSwitch (signal n)) volumeTariffSwitchInterval = 1500 units of data
3. Data Volume Transferred at each QoS level (One QoS Change Occurs in Figure A.1)
   • 1st QoS level (up to signal 10): All volumeTariffSwitchIntervals + final VolumeSinceLastTariffSwitch at QoS change is 5500 + 3200 = 8700 units of data.
   • 2nd QoS level (from signal 10 onwards): (Value of first VolumeTariffSwitchInterval received after QoS change - VolumeNoTariffSwitch Received directly after QoS change ) + Volume transferred since this tariff switch is (5000-3200) + 1500 = 3300 units of data.