An understanding of the basic principals of network design, will allow a telecommunications manager to optimize available resources. Equipped with an understanding of queuing theory and the ability to use traffic tables are an asset in gathering data to answer many telecommunication questions. Calculating traffic formulas, with the use of traffic tables or computer applications (such as like the ACD Analyzer), the manager can reach a balance between costs and service.

Listed below are the four basic principals that govern network design:
1.      Large groups of servers are more efficient than smaller groups - this is commonly called occupancy
2.      For a given amount of traffic load, the greater the number of servers, the less likely it is that callers will have to wait
3.      The rate at which calls arrive is seldom uniform - there is a wide variation in the number of calls
4.      Alternate routes to the destination increase the robustness of a network - traffic can overflow to an alternate route

In order to administer a telecommunications system, the following are needed:

Grade of service – the percentage of calls that encounter some form of blockage
·        If too high – many circuits will carry little or no traffic
·        If too low – many circuits will be busy and productivity will decrease
·        Most circuits are designed for grade of service between 1 and 5 percent blockage
·        A way of increasing the load on a group of circuits is through alternate routing

Traffic load – expressed as the amount of traffic presented to a trunk group in its busiest hour
·        Measured in minutes, hours, hundreds of call seconds (CCS) or erlangs.
·        Expressed as the relationship between the calling rate and length of an average call

Busy hour – the average amount of traffic that flows during the 10 highest days of the year

Offered verses carried load -
·        The difference between the two lies in the time required for call setup and handling incomplete and blocked calls
·        Long distance call statements must be adjusted to convert billed minutes into usage minutes

Quantity of trunks – can be calculated from traffic tables when the load and grade of service are known

Using Erlang C tables – used when callers wait in queue
·        Limitations of Erlang C – it does not provide information about the service received by callers are not within the objective service level range and it assumes that calls arrive randomly
·        Utilization – the percentage of time agents are activity handling calls either in talking or in wrap-up mode

Calculating voice mail port requirements – calculate using Erlang B tables

Using an ACD Analyzer for traffic calculations – this computer application simplifies the process
·        Two modes
·        Trunking using the Erlang B formula
·        Queuing using the Erlang C formula

Busy Signals

Busy signals may send the wrong message to your callers. The alternative is typically waiting in a queue.
·        Busy signals can be returned in two ways
·        Reduce the number of trunks, allowing the carrier to provide the busy signal
·        Provide the busy signal from the ACD
·        Busy signals can tell you if a caller returns if the call center gathers automatic number identification with each call

Sources of Traffic Usage Information

The following are sources of traffic usage data and methods used to interpret and adjust traffic usage:
·        Switching system data – readings can be obtained in raw form or a GUI-based program
·        Usage-sensitive bills – local and toll billing statements
·        LEC traffic or busy study – LECs can perform a busy study
·        Call accounting system – reasonably accurate usage information

Case Study: Using Traffic Theory to Optimize Local Trunks

In a case study involving the review of bills from a LEC and an IXC, it is evident that the PBX has trunking problems.
·        There are not enough two-way central office trunks
·        Several assumptions are made in order to correct the problems
·        When rearranging trunks, telecommunications managers must review assumptions carefully

Summary

In summary, the use of traffic tables and computer applications are an asset to the telecommunications manager. He/she must make many assumptions and the data is often inaccurate. By frequently monitoring the data and making trunk adjustments, the data will be more accurate.