Communications network

Details Communications network Communications network

1998-03-05

2001-12-11

Kuntz, Curtis (Department: 2743)

Telephonic communications

With usage measurement

Call traffic recording or monitoring

C379S112040

Reexamination Certificate

active

06330313

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communications network, and in particular to a method and apparatus for preventing overloads in such a network.
2. Related Art
Some of the most demanding traffic patterns on a telecommunications network relate to the operation of telemarketing call answering centres. For example, the number of a call answering centre might be displayed as part of a nationally broadcast advertisement for a product. This may result in many thousands of calls being made to the number in a short period of time following the advertisement. Such call levels have the potential to overload the network at a number of points, including intermediate DMSU's (digital main switching units) and the destination exchange.
In networks which employ an IN (intelligent network) architecture, it has previously been proposed to equip IN platforms with a call gapping mechanism. This enables the platform to transmit an instruction to a service switching point (SSP) to reduce the rate of inbound calls to the IN platform from the SSP. However, although this mechanism is effective to prevent overloading at the IN platform, it does not in itself provide adequate protection for a destination exchange which is downstream from the platform. The IN platform has a call handling capacity which is typically several times greater than the capacity of an individual exchange. Therefore, long before the call gapping mechanism is invoked to protect the IN platform, the platform may be passing calls to a destination exchange at a rate which is sufficient to bring a risk of software failure at the destination exchange. Even if the destination exchange withstands a sudden peak in traffic and passes the calls on to the answering centre, if the capacity of the answering centre is exceeded then many of the calls will not be completed but will result in a BUSY signal being returned to the caller. Ineffectives , as such calls are known, earn no revenue for the network operator, nor for the answering centre, but add to the network traffic and so have to be supported by the network infrastructure.
In order to prevent overloading of the destination exchange, and to reduce the number of ineffectives, the present applicant has previously proposed mechanisms for controlling call rates on the outward leg from a network platform to a destination exchange. International Patent Application no. PCT/GB 94/02512 discloses and claims an approach in which call levels are monitored and controlled to maintain a predetermined and relatively low level of BUSY signals from the call answering centre. This has helped to ensure that the resources of the answering centre are used effectively while protecting the local exchange from overload. However while it reduces to an extent the number of ineffectives on the network, a significant number remain. Furthermore, since a predetermined number of excess calls are admitted for each answering centre, the total number of ineffectives rises when call answering is distributed over several centres.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a method of operating a communications network including steps of:
a) maintaining, for a selected destination number which has the capacity to receive a multiplicity of calls, a count of the number of calls currently in progress;
b) automatically updating the said count when calls are admitted to the selected destination number and when calls are terminated;
c) storing a value for the maximum capacity of the selected destination number;
d) when a new call is made to the destination number comparing the count of the number of calls in progress and the said value for the maximum capacity and rejecting the new call when admitting the call would cause the maximum capacity to be exceeded.
The term “selected destination number” as used herein encompasses both a single number , e.g. 0800 400 496, or a selected group of numbers or a range of numbers, e.g. 0800 400 *** where *** may be any three digits.
The present invention adopts a new approach to controlling call levels to a destination number, such as the number of an answering centre. Instead of relying solely upon the generation of a certain rate of BUSY signals, the capacity, that is the maximum number of simultaneous calls, and the current state of the destination number are modelled within the network, for example at an answering centre server located at an IN platform. Then, as soon as it is ascertained that the full capacity of the answering centre is in use, any further calls are released or redirected rather than being passed to the local exchange. This ensures good use of the capacity of the answering centre while reducing the number of ineffectives to negligible levels.
Preferably the method further comprises:
e) subsequently amending, in dependence upon the response of the network to an admitted call, the value for the maximum capacity which was stored in step (c).
The present inventor has found that the efficiency of the call control process is enhanced significantly by allowing the value for the capacity to be amended based upon feedback from the network. This allows the process to adapt automatically to changes in capacity, and removes the need for the value of the capacity to be determined with complete accuracy at the outset.
Preferably step (c) includes:
estimating the maximum capacity of the destination number and storing the estimated value. Preferably the step of estimating the capacity includes:
for a period of time, monitoring the number of calls N
C
to the number which are completed, and recording the time T
C
taken to complete each of the calls; and
calculating an estimate for the capacity from the mean holding time for calls to the number, where the mean holding time is derived from the values of N
C
and T
C
which are recorded during the said period of time.
This preferred feature of the invention minimises the amount of data and signalling which is required in order to support the modelling of the answering centre or other destination number. Instead of storing data on the capacity of every answering centre, and having to update manually that data every time the capacity of a centre changes, the model may go through a training process in which an initial estimate of answering centre capacity is calculated. During the training process, either all offered calls are admitted to the answering centre, or at least a significant excess of calls are admitted above the answering centre's answering rate capability. On completion of the training process, in a preferred implementation, the system enters a tracking mode in which an offered call is admitted only if its admission will not cause the current calls-in-progress total to exceed the current estimate of answering centre capacity. In addition, in tracking mode, the invention may adapt its current estimate of answering centre capacity in response to signalling from the network which conveys information about the status of the destination. This tracking process may, for example, rely upon detecting when the destination number responds with a BUSY signal. When this occurs, then the estimated value may be decremented. Conversely, if a new call is admitted when the estimated capacity has already been reached, and if the new call is connected rather than a BUSY signal being returned, then the estimated value for the capacity may be incremented.
Preferably, steps (a) to (d) are initiated only when congestion is detected at the destination number. Preferably steps (a) to (d) are carried out at a single server which serves a plurality of the said selected destination numbers, and in which resources for carrying out steps (a) to (d) are allocated on the server to a respective destination number when congestion is detected at the said destination number.
The efficiency of the monitoring process is further maximised by allocating resources to monitoring a particular number dynamically and automatically, as and when a number beco

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