Dropped Call Rates and their Evaluation

In telecommunications, the dropped-call rate (DCR) is the fraction of the telephone calls which, due to technical reasons, were cut off before the speaking parties had finished their conversational tone and before one of them had hung up (dropped calls). This fraction is usually measured as a percentage of all calls.

Dropped Call Rates and their Evaluation

What are the reasons for call drop?

Dropped calls occur when a phone call is terminated unexpectedly as a result of technical reasons, including poor network signal. Call drops happen because of inadequate coverage, quality of signal, including interference, network congestion and network failures. It happens when there is low or no signal.

Customers moving from a coverage area to a non-coverage one also experience call drops. Call drops frequently take place in trains.

Call drops happen mostly due to high inflow or outflow of calls from a single mobile tower. If a mobile tower is over-utilized, calls tend to drop.

The problem becomes more acute if mobile towers are overloaded with calls. Some calls are then dropped to accommodate the others.

In many practical cases this definition needs to be further expanded with a number of detailed specifications describing which calls exactly are counted as dropped, at what stage of the call setup procedure a call is counted as connected, etc. In modern telecommunication systems, such as cellular (mobile) networks, the call setup procedure may be very complex and the point at which a call is considered successfully connected may be defined in a number of ways, thus influencing the way the dropped call rate is calculated.

The dropped call rate in conventional (so-called land-line) networks is extremely low and is significantly less than 0.01%. In mobile communication systems using radio channels the dropped call rate is higher and may range for commercial networks between 0.1% and a few percent. The main reasons for dropped calls in mobile networks are lack of radio coverage (either in the downlink or the uplink),radio interference between different subscribers, imperfections in the functioning of the network (such as failed handover or cell-resellection attempts), overload of the different elements of the network (such as cells), etc.

The dropped call rate is one of the key performance indicators (KPI) used by the network operators to assess the performance of their networks. It is assumed to have direct influence on the customer satisfaction with the service provided by the network and its operator. The dropped call rate is usually included, together with other technical parameters of the network, in a key performance indicator known as call retainability.

The operators of telecommunication networks aim at reducing the call dropped rate as much as practical and affordable. In mobile networks this is achieved by improving radio coverage, expanding the capacity of the network and optimizing the performance of its elements, all of which may require considerable effort and significant investments on the part of the network operator.

Process for evaluating expressions

An algebraic expression is a process for evaluating expressions. Replacing variables with numerals and following a standard order of operations is used for the process. The vendor evaluation and rating process is very important in selection of vendors. It is important that you have detailed knowledge about your priorities and requirements as this would be the basis on which you will have to evaluate your vendors. Following are the key steps:

System Requirement analysis: Against which you will compare each vendor.

Prioritized Requirements: Highlighting requirements upon which rating or scoring is done.

Ongoing evaluation is required because in life circumstances change. These changes usually result in effects on existing processes. The ongoing evaluation of these effects allow you to take proactive steps to insure that your processes remain relevant and effective.

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