Saturday, June 6, 2009

Traffic Congestion

Md. Habibur Rahman
Director, BTTB

What is Traffic :
Any type of load imposed on a system which is supposed to be carried by the system is defined as the traffic. For example, Road traffic, Railway traffic, Telephone traffic etc. In an office number of files given to a clerk for disposal is also a kind of traffic. In telecommunication, voice, data and images in the form of electrical signal which is to be transferred from one telecom equipment to another telecom equipment through telecom network is defined as telecom traffic.

Traffic Congestion in telecommunication network:
It is defined as "The condition of a network where the immediate establishment of a new connection is impossible owing to the unavailability of network element". It may happen momentarily for an unusually high traffic. Accumulation of traffic in any portion of network is the traffic congestion.
Behavior of Telephone Subscriber:
Only a small portion of subscribers will be using their telephones at any time, even during busiest hour. The probability of a subscriber to make a call is completely uncertain. But the system is made always ready for a response to the subscriber.

The nature of telephone traffic:
It is so uncertain that some times a huge number of calls are accumulated. Either calls are lost or held in que and some times there is no call so that a portion of network remains idle.
Tele-Traffic Engineering And Traffic Congestion:
The object of Tele-traffic Engineering is to formulate a set of procedure for the design and day to
day management of a telecom system that will result in the most economic provision of telecom
switching equipment and trunk circuits subject to providing a satisfactory service at an
acceptable cost to the users of the system Traffic congestion is a big problem to engineer for
designing equipment it is I to provide sufficient equipment to permit the subscribers
simultaneously to be on calls but practically it is not require

Telecommunication Administration & Traffic Congestion:
Telephone network are so designed that the limit to the simultaneous calls they can ha is the telecom administration who decides w limit be. As the demand of the subscribe unpredictable, traffic calculation for de; equipment made on the basis of assumption theme of the administration is to give uninterrupted service to the subscriber though an unusually high traffic may be generated by the subscribe a very short time, it is not economic to design a network which will overcome a very high for a very short time. Dimensioning of equipment is made on the basis of average traffic on bus and not on the basis of peak traffic.

Measurement of Traffic:
I. Generally the traffic carried by the cc control equipment like Processor, Memory Registers etc. are measured by considering occupancy of the equipment.
Line circuit, Trunk circuit, DTI and peripheral equipment are scanned periodically and from the Busy/Idle status counted from scanned result the traffic carried by the equipment is calculated.
Traffic Congestion are of two types:
1. Time congestion The ratio of time for congestion exists to the total time cons; for measurement. It is an estimate of the ability that an external observer will fin system in a state of congestion.
Call Congestion The ratio of number of call attempts which can not be matured immediately to the total number of call attempts.

Causes of traffic congestion
The congestion occurs for various reasons depending on switch facilities, Exchange equipment and transmission link. Traffic congestion mainly occurs due to inadequate capacity of equipment and improper network management. Causes of Congestion may be classified as follow
I. Congestion due to faulty equipment.
2. Congestion due to generation of high traffic.
3. Congestion due to improper configuration of network.

Congestion due to faulty equipment:
Faulty equipment refuse to carry traffic. The load is transferred to working equipment. When a switching system failed to process a call, the subscriber try again and again. As a result traffic increases and congestion occurs. Moreover, a faulty equipment faces congestion more than that of a good one. Failure of a transmission equipment may cause congestion to the switching equipment as the traffic stored in the memory of the stored program controlled switching system is increased.

Congestion due to generation of high traffic:
A sudden increase in the originating and terminationg call can cause traffic congestion. The traffic may be increased in a particular area due to
1. Natural disaster (Flood, Cyclone, Earth-quake, Fire-hazards, Accident etc.)
2. Unusual manmade situation (Accidental explosion, Mass agitation, Strike, Political gathering, Failure of Electric Supply system.).
3. Seasonal factor (Eid, Puja, X-Mas day, Summer, Winter & other Vacations)
4. Other activities (Recreational Programs in Radio and Television Broadcasting system, Death of a renowned person, Distance Education & Healthcare etc.)
Congestion due to improper configuration of Networks:
Sometimes it appears congestion in a portion of network while there exist idle equipment in
another portion of network. Particularly in transmission links, one link may be in congestion while another link remains idle. In this case overflow traffic from one link may be transmitted through alternate link via transit to another node. Due to failure of one link, the traffic may be re-routed to another link and causes congestion to that link.
Traffic Congestion Relieving Procedure:
1. Detect the occurrence of traffic congestion.
2. Analyze and find the location, portion of equipment which is under congestion and cause of congestion.
3. Each portion of network where there is no congestion should be informed the occurrence of congestion. So that preventive measure may be taken.
4. Determine the command and restriction grade to be used for automatic traffic control according to the status of congestion.
5. Start restriction at the originating and transit offices, so that congestion in one station can not influence other station.
6. Start restriction at the terminating offices if other restriction proves insufficient.
7. Release restriction as congestion subsides.
Traffic Control
With the increase in the occupancy of the equipment, traffic is restricted so that congestion can not cause the failure of equipment. In this case either the traffic loss is allowed or a mechanism of delaying the traffic is introduced.
Effect of Traffic congestion on Revenue:
Due to traffic congestion a large volume of traffic is lost or delayed. The equipment may be failed to work. Subscribers become unhappy as they are not getting the service. Less revenue will be earned.

Traffic Congestion is a problem appeared at random. It is also increasing day by day in every sphere of life. Our objective is to overcome the problem efficiently, effectively and economically. Congestion may be minimized through expert planning, proper dimensioning and efficient management of network.

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