Teletraffic engineeringTeletraffic engineers use their knowledge (2).pptx

Teletraffic engineers use their knowledge of statistics including queuing theory, the nature of traffic, their practical models, their measurements and simulations to make predictions and to plan telecommunication networks such as a telephone network or the Internet. These tools and knowledge help provide reliable service at lower cost.

1. Telecom Traffic Engineering Md.Sharif Uddin Shajib Master of Engineering ( M.Engg ) in Telecommunication Roll:06

2. Traffic Theory   Teletraffic engineers use their knowledge of statistics including queuing theory, the nature of traffic, their practical models, their measurements and simulations to make predictions and to plan telecommunication networks such as a telephone network or the Internet. These tools and knowledge help provide reliable service at lower cost. Covers specific types of random processes in telecommunications – Average connection duration – Average number of users – Busy time – Service time – Call arrival 2

3. Traffic Engineering Required in telecommunications network planning to ensure that network costs are minimized without compromising the quality of service ( QoS ) delivered to the user of the network. – It is based on probability theory and can be used to analyze mobile radio networks as well as other telecommunications networks. Mobile radio networks have traffic issues that do not arise in the fixed line PSTN. A mobile handset, moving in a cell, receives a signal with varying strength. This signal strength is subject to: – slow fading, – fast fading – interference from other signals, 3

4. Traffic Engineering Traffic engineering balances the following factors based on given amount of traffic • Grade of Service (GOS) • Resources (e.g. trunk channels) Two types of systems implemented to provide voice communications – Blocking • Voice or data is blocked (by a busy signal) if network resource ( e.g trunk channel) is not available. • GOS = Blocking probability – Delay System • Voice or data is queued until network resource is available • GOS = Queuing Probability and average time in queue 4

5. Traffic Engineering Holding Time - the length of time that a resource is being held ( e.g the duration of a phone call) Traffic volume - for an interval is the sum of all the traffic holding times for that interval Traffic intensity = traffic volume / time interval which is a measure of demand 5

6. Traffic Engineering Erlangs - describe traffic intensity in terms of the number of hours of resource time required per hour of elapsed time CCS( Centum Call Seconds) - measures the exact same traffic intensity as the Erlangs but expresses it as the number of 100 second holding times required per hour. Traffic registers sample stations every 100 seconds per hour to check for busies. Since there are 36 sets of hundred seconds in an hour 36 CCS = 1 Erlangs 6

7. Traffic Measurement Unites Erlangs : Traffic intensity (named after of a Danish mathematician) is the average number of calls simultaneously in progress over a certain time. It is a dimensionless unit. – Erlang • one hour of continuous use of one channel = 1 Erlang • 1 Erlang = 1 hour (60 minutes) of traffic – In data communications, an 1 E = 64 kbps of data – In telephone, 1 Erlang = 60 mins = 1 x 3600 call seconds % of Occupancy 7

8. Call Holding Time Call holding time is the length of time during which a traffic source engages a traffic path or channel. 1 – 3 minutes typical, >10 minutes infrequent for voice. H = average holding time, 3 minutes. Negative exponential

9. Busy Hour Busy hour is that continuous 60 minutes time span of the day during which the highest usage occurs.

10. Offered, Carried and Blocked Traffic Offered traffic is the traffic intensity that would occur if all traffic submitted to a group of circuits could be processed. Carried traffic is the traffic intensity actually handled by the group. Blocked traffic is that portion of traffic that cannot be processed by the group of circuits (I.e. offered traffic minus carried traffic). Blocked traffic may be rejected, retried or offered to another group of circuits (overflow).

11. Traffic Intensity - contd. In a trunks system of C channels and equally Distributed traffic among the channels, the traffic intensity per channel is: A C = UA/C Erlangs /channels The traffic volume is a measure of the total work done by a resource or facility, normally over 24 hours V T = A * T Erlangs -Hours 11

12. Grade of Service ( GoS ) A measure of the performance of a telephone system GOS is a measure of the ability of a user to access a trunked system during the busiest hour Also an indication of the user not being able to secure a channel during the busiest hour Telephone networks are designed with specified GOS, usually for the busiest hour. If a subscriber is able to make a call during the busiest hour, he will be able to make a call at any other time