Busy Hour Traffic does not affect revenue but governs the Requirements for most resources
– see 10.3.27 Resource requirements.
When there is more than one service in a model (e.g., both residential and business demand), for dimensioning purposes the restrictive assumption is made that all services have the same Busy Hour. This is a conservative assumption as the required network capacity may then be over-estimated.
Nominal bandwidth per connection
For a data service, represents the nominal bandwidth of each connection, which is used as part of the calculation of Busy Hour Traffic – see 10.3.8.3 Distribution. It can be specified directly as a time series or as a reference to the Output of a transformation, as for Penetration (see Penetration).
For a voice service (i.e., when Traffic Calculation is set to Volume Driven) this input is ignored.
Contention ratio
For a data service, this represents the ratio of the theoretical maximum demand to the demand that can be met by the network. For example, a Contention Ratio of 10 means that the network is dimensioned to meet one tenth of the theoretical maximum demand if all users required the service simultaneously. This input is used as part of the calculation of Busy Hour Traffic – see 10.3.8.3 Distribution.
For a voice service (i.e., when Traffic Calculation is set to
Volume Driven) this input is ignored.
Multiple contention ratios
In general, there will be a contention ratio at the first point of aggregation, on the immediate access pipe, where traffic may aggregate across other dwellers of a multi-tenant unit. However, deeper in the core network, there may be a further averaging effect due to multiple nodes coming together, resulting in a higher overall contention ratio (see Figure below). This can be readily modelled through the multiplier of an intermediate Transformation.
Changing contention ratios in a data network
Estimating volumes for metered pricing
For dimensioning purposes, and flat-rate services, it is sufficient to distinguish between nominal and peak bit rates. However, a contention ratio is a measure of contention in the busy hour, rather than an average over the day, so we still need Prop. of Traffic in Busy Hour and Busy Days per Year to calculate:
AT = Connx . BDpYr . UR . NBpC / CR / PropTiBH
Thus we swap ATpC for (NBpC / CR) as a composite measure of busy-hour traffic per connection.
The Rental tariff for a data service is still the price for the connection, but the
Usage
tariff is interpreted in terms of whatever has been chosen as the Annual Traffic Unit, for example per GByte.