The document defines several metrics for measuring Quality of Service (QoS) in telecommunications networks: - Call Completion Rate measures successfully completed calls as a percentage of total attempted calls. - Answer Seizure Ratio measures successful calls as a percentage of total outgoing calls. - Call Setup Success Rate measures unblocked call attempts as a percentage of total call attempts. - Several other metrics are defined for call drops, post-dialing delay, handover success, bit error rates, traffic channel congestion, SMS/MMS delivery failures, customer satisfaction, and problem resolution times.

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QoS Metrics
The following are the metrics and their definitions for measuring Quality of Service (QoS).
• Call Completion Rate
The ratio of successfully completed calls to the total number of attempted calls (ITU-T E600/2.13).
That is, the ratio of the number of completed call attempts to the total number of call attempts, at a
given point of a network.
Note: This ratio is typically expressed as either a percentage or a decimal fraction. It is the
number of calls of specific duration successfully completed; measured per 100 calls.
Note: A complete call is a call that is released by normal call clearing (i.e., Released
Message “RL_M” and Released Complete Message “RLC_M” has been successfully
exchanged in the signaling flow), be it during a ringing phase or conversation phase
by either the caller or called party.
• Answer Seizure Ratio (ASR)
The ratio of the number of successful calls over the total number of outgoing calls from a carrier’s
network (i.e. On a route or a Destination Point Code (DPC) basis, and during a specified time interval,
the ratio of the number of seizures that result in an answer signal to the total number of seizures:
ITU-T E600/2.14).
Note: ASR is line seizures that are answered by person or device divided by total number
of seizures.
Note: Seizure is achieved after a successful “Call setup”. It means seizing a trunk circuit for
conversation or other network services. In GSM network, it refers to seizing a Traffic
Channel (TCH) after a successful “Call setup”.
Note: A successful call is a call that is answered by a called party or machine (e.g., fax
machine, answering machine, e.t.c.).
• Call Setup Success Rate
Number of the unblocked call attempts divided by the total number of call attempts.
Or (1 - Blocking Probability) x 100%
Note: A call setup is an exchange of signaling information in the call process that leads to
Traffic Channel (TCH) seizure.
• Call Drop Rate
The Call Drop Rate is the number of dropped calls divided by the total number of call attempts.
Or (1 - Call Completion Ratio) x 100%
Note: A dropped call is a call that is prematurely terminated before being released normally
by either the caller or called party (i.e., the call is dropped before the exchange of
Released Message “RL_M” and Released Complete Message “RLC_M” in the
signaling flow).
• Post Dialing Delay
In GSM network, is the average time between pressing send button (after pressing correct digits) and
getting a ring back tone. This is also called “Call Setup Time” or time to connect a call.
• Handover Success Rate
This is the ratio of the number of successfully completed handovers to the total number of initiated
handovers. This ratio can be expresses as a percentage.
• Bit Error Rate (BER) Per Link
The link Bit Error Rate (BER) refers to the average bit error rate on the MSC-PSTN link, Inter MSC link,
A-Interface and Abis-Inteface. This parameter should not deteriorate above 10 -9.

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• The End-to-End Bit Error Rate
This refers to the average end-to-end bit error rate. This parameter should not deteriorate above 10 -
6
.
• Busy Hour Traffic Channel Congestion (%)
This is the percentage congestion of the TCH measured at the busy hour and is given by:
Busy Hour TCH Traffic (Erlang) – Average TCH Traffic (Erlang)
× 100
Busy Hour TCH Traffic (Erlang)
• % of Failures for Credit Balance Inquiry
This is the ratio of the number of failures of credit balance inquiry to the total number of credit
balance inquiry expressed as a percentage at some instant on the network. This parameter is for a
prepaid subscriber.
Number of failures for credit balance inquiry
× 100
Total number of credit balance enquiry
• Minimum Data Rate
This is the minimum TCH encoding rate for data (Half-Rate channel, 4.8kbps: GSM Specification
06.20).
• Minimum Speech Rate
This is the minimum TCH encoding rate for speech (Half-Rate channel, 6.5kbps: GSM Specification
06.20).
• % of SMS-MMS Delivery Failures
This is the ratio of SMS/MMS to the recipients undelivered to the total number of SMS/MMS received
at the Service Center within specified period of 10 days.
Number of SMS/MMS to recipients undelivered
× 100
Total Number of SMS/MMS received at Service Center
• % of SMS/MMS Incorrect Feedback
This is the ratio of the number of SMS/MMS transmitted in which the sender received wrong feedback
to the total number of SMS/MMS received at the Service Center at some instant on the network.
Number of SMS/MMS in which the senders received wrong feedback
× 100
Total Number of SMS/MMS received at Service Center
• % of SMS/MMS Multiple Billing
This is the ratio of the number of SMS/MMS messages in which more than one charges are applied per
message to the total number of SMS/MMS received at the Service Center at some instant on the
network.
Number of SMS/MMS in which more than one charges are applied
× 100
Total Number of SMS/MMS received at Service Center
• Number of Customers Satisfaction Index
This is the percentage of the number of customers satisfied with the services of an operator in
randomly distributed samples of customers.
• Speed of Problem Resolution
a. % cleared same day
This is the percentage of the number of problems resolved on the day they were received.
Number resolved problems in day one × 100

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Total number of problems received on that day
b. % in two days
This is the percentage of the number of problems resolved within the second day they were
received.
Number resolved problems in day one and two
× 100
Total number of problems received on day one
c. % cleared in three days and above
This is the percentage of the number of problems resolved within three days and above to the day
they were received.
Number resolved problems in day 1, 2, 3 and above
× 100
Total number of problems received on day one
• Billing Integrity
a. % of total bills overcharged
This parameter is the percentage of the number of Post-Paid accounts that are overcharged within
a particular month.
b. % of incorrect credit balance
This parameter is the percentage of number of Pre-Paid accounts that suffer incorrect credit
balance within a particular month.
c. % of failures for Credit Balance Inquiry
This is the ratio of the number of failures of credit balance inquiry to the total number of credit
balance inquiry expressed as a percentage at some instant on the network. This parameter is for
prepaid subscribers.
• Customer Care Accessibility
a. 100% Call Completion Rate
This means that all calls to the center must be answered by a customer care personnel or a
machine to put a customer on hold for sometime (the line must never be busy at any time).
Alternatively, all calls to the center must go through.
b. Minutes a customer spends on the queue
This is the average time in minutes a customer is expected to spend on customer care center
queue.
• Customer Interface Points
a. Number of Interface points
This is an office where a customer can go to lodge complaints. This is in addition to customer care
centers.
b. Minutes a customer spends on the queue
This is the average time in minutes a customer is expected to spend on customer interface point
queue before being attended to by a staff.
• Recharge Cards
a. % of Recharge Cards Loading Errors
This is the ratio of the number of times Recharge Card loading failed to the total number of loading
attempts at some instant on the network expressed as a percentage.
Number resolved problems in day one
× 100
Total number of problems received on that day
b. % of Recharge Cards loading incorrect feedback
This is the ratio of the number of times an incorrect feedback is received during Calling Card /
voucher loading to the total number of loading attempts expressed as a percentage.

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Number of incorrect feedback received during voucher loading
× 100
Total Number of loading attempts