Balance Threshold Feedback (BTF)

Balance Threshold Feedback (BTF) calculates the available quantity until the next threshold using the gross balance amount.

For data, the available quantity is the product of the rate at which data is used and the price. For example, each of the following scenarios yields the same velocity of consumption of the balance quantity ($0.06/min):
  • Purchased catalog item charges $0.01/MB and download rate is 6MB/min.
  • Purchased catalog item charges $0.02/MB and download rate is 3MB/min.
  • Purchased catalog item charges $0.03/MB and download rate is 2MB/min.
  • Purchased catalog item charges $0.06/MB and download rate is 1MB/min.

BTF uses the reserved amount to detect reservations from other authorizations sharing the balance. BTF considers the proximity to the next threshold, and quota allocation is stepped down when approaching a threshold or credit limit. In general, if 1% of an asset is used and the next threshold is set at 50%, larger quotas are allocated. If 49% of the asset is used and the next threshold is set at 50%, smaller quotas are allocated. A notification is sent as soon as possible after the gross amount reaches a threshold. After a threshold is passed, the proximity to the next threshold is recalculated and quota allocation is reset based on the proximity to the next threshold.

Important: Unlike other meters, BTF is disabled on session meters. Credit limits are supported and enforced for session meters. However, because session meters are used in only one service context of one session, Adaptive Quota Management (AQM) does not reduce the quota size when a session meter is near its credit limit. Also, because threshold notifications do not apply to session meters, AQM does not reduce the quota when nearing a threshold for session meters.

On shared balances, AQM tries to authorize quota across all contexts so that they reach a threshold or credit limit at about the same time. On unshared balances, the quota can drop imder any configured minimums to meet the threshold. AQM grants the target quota if it is less than the scaled distance (D) to the next threshold. Otherwise, AQM grants D if it is greater than the minimum, or if D is less than the minimum, it grants the minimum. On an unshared balance, AQM can grant less than the minimum to hit the unscaled distance to the threshold.

Note: If a charge is zero (for example, when visiting an operator website for balance information), the BTF is not affected because there is no reservation and no thresholds are crossed.
The threshold scale factor attribute defined on the balance template controls the distance before a threshold at which quota drops from default authorization or reauthorization values to the minimum authorization or reauthorization values. The threshold scale factor provides a buffer if additional subscribers request a quota. For example, consider the following:
  • Data consumption velocity: 1MB/minute
  • QVT: 30 seconds (512KB at velocity)
  • Default QVT: 5 minutes (5MB at velocity)
  • Threshold Scale Factor: 2 (50%)

    A factor of 2 implies that usage is two times closer to the threshold than it is. In this case AQM starts to issue smaller quotas twice as early as it normally would, and it issues the quotas more gradually because AQM has more time to slow down.

  • D: distance to the next threshold
In this situation, AQM does the following:
  • If D >= 10MB, grant the default quota and QVT (5MB/5min).
  • If 1MB <= D <= 10MB, the quota grant = 50% of D (between 512KB and 5MB) and the QVT = 1 minute per MB of quota.
  • If the balance is shared and D <= 1MB, grant the minimum quota and QVT (512KB/30 seconds).
  • If the balance is unshared and 512KB < D < 1MB, grant the minimum quota and QVT (512KB/30 seconds).
  • If the balance is unshared and D < 512KB, the quota grant = D and the QVT = 30 seconds.

    In this final situation, the unscaled distance is used to decide to drop under the minimum to exactly hit a threshold on the unshared balance.

When approaching a threshold, a larger scale factor compensates for inaccurate velocity measurements. The result is more frequent reauthorizations with smaller quotas and validity times.

In addition, the threshold scale factor can be set in the adaptive_threshold_scale_factor attribute defined in the service type definition. This attribute can be set in the <service_type> node or the <quantity_info> node. If it is set in the <service_type> node, the attribute value applies to the default context. The value must be greater than or equal to 1.0. The balance template value overrides the service or context type value. If neither value is set, the default value (1.0) is used.
Note: For an unshared balance, if the scale factor = 1 and min and max QVT are the same, AQM can accurately meet the threshold.
Usage continues to be authorized and charged as a sequence of beats, even if a threshold would be reached in the middle of a beat. In this case, the full beat is authorized, and usage of any part of that beat charges for the full beat, resulting in a threshold notification being delivered within one beat of its location.