1 TELECOMMUNICATION NUMBERING ETI2506 Monday, February 15, 2016

2 OBJECTIVE OF NUMBERING 1. Objective of Numbering Plan is to uniquely identify a subscriber who is connected to a telecommunications Network. 2. Initially numbering was restricted to single local exchanges with each exchange identified by its name. 3. With introduction of multi-exchange areas common numbering plans started evolving. 4. Introduction of Subscriber trunk dialling (STD) for inter city/town dialling led to the introduction of National Numbering. 5. Later, the development of International Subscriber Dialling led to the development of International Numbering Plans. NUMERING AT LOCAL EXCHANGES …. 999 STD NUMBERING … INTERNATIONAL NUMBERING …

3 INTERNATIONAL NUMBERING PLAN International Numbering Plan has been defined by ITU in recommendations E160- E163. Country Code National Number 1-3 Digits 9-11 Digits 12 Digits Maximum

4 WORLD NUMBERING ZONES Europe North America Central & South America Africa Old USSR Australia South-East AsiaME & India

5 WORLD TELEPHONE NUMBERING PLAN

6 NATIONAL NUMBERING PLANS Area/Trunk Code Exchange CodeLine Number Area/Trunk Code identifies a particular numbering area or multi- exchange area, e.g. 20 for Nairobi or 56 for Kakamega (Telkom). Exchange Code identifies a specific exchange within a numbering area, e.g. 21 and 22 for Nairobi Central-Telkom.

7 GENERAL CATEGORIES OF NUMBER SCHEMES Number Schemes can be Open, Semi-Open or Closed. 1. Open Number Scheme (also known as non-uniform numbering scheme) permits a wide degree of variations in the number of digits used to identify a subscriber within a country. 2. Semi-Open allows the number length to differ by 1-2 digits. 3. Closed numbering plan or uniform numbering plan has a fixed number of digits. Used in USA, Canada, France and recently in Kenya. Examples: 1.Large city with longer number, Small town with short numbers, Examples: 1.Big operator with long numbers, Small operator with short numbers, Examples: 1.Safaricom: Airtel:

8 NUMBERING PLAN IN KENYA

9 SHORT CODES

10 SHORT CODES

11 NAIROBI AREA

12 NAIROBI (CONTINUED)

13 KAKAMEGA REGION

14 EXAMPLE: TO BE CARRIED OUT IN CLASS Consider a 11-digit international number with 2-digit country code, 2-digit area code and a 7-digit subscriber number. Prefixes '0' and '00' are used for identifying national and international numbers respectively. A few special services like fire, ambulance and police are given short subscriber numbers in the range The network is designed for remote maintenance and the maintenance exchanges are identified by the number range Determine the number space available for subscribers and the fraction of the space lost.

15 SOLUTION 1. Maximum possible number space 10 2 x 10 2 x 10 7 = Due to prefixes, area codes and subscriber numbers cannot start with zero. Due to special services, the subscriber numbers cannot start with a 1. Due to maintenance, the number range starting with 9 is not available for subscribers. Hence, we have the total available number space as: 10 2 x 90 x 7 x 10 6 = 63 x 10 9 Fraction of Lost Space is

16 CHARGING PLAN ETI 2506 Monday, February 15, 2016

17 WHY WE NEED A CHARGING PLAN? 1. Providing a telecommunication service. calls for investment in capital items as well as meeting operational expenses. a) The capital cost includes that of line plant, switching systems, buildings and land. b) Operating costs include staff salaries, maintenance costs, water and electricity charges and miscellaneous expenses. 2. A telecommunication administration receives its income from its subscribers. 3. A charging plan provides a means for recovering both the capital costs and the operating costs from subscribers.

18 CALCULATING THE COSTS 1. The cost of shared resources like the switching and transmission equipment is amortized among a large number of subscribers over a period of time. 2. The cost of dedicated resources like the telephone instrument and the subscriber line (for wired connections) must be recovered from individual customers. 3. The operating costs must be worked out depending on the quantum of resources used in providing a service and the duration for which these resources are used.

19 CHARGES LEVIED ON A SUBSCRIBER A telecommunication service can levy three categories of charges to a subscriber, i.e 1. An initial charge for providing a network connection; 2. A rental or leasing charge; 3. Charges for individual calls made.

20 CHARGES TO INDIVIDUAL CALLS The following charges are levied to individual calls: 1. Operating costs for telephone exchanges and transmission networks. 2. Government policy charges e.g. policy on subsidy of local calls by trunk/international calls, taxes or USO. 3. Regulator controlled charges, e.g. CAK’s guidelines on interconnection.

21 CHARGING METHODS FOR INDIVIDUAL CALLS 1. Duration Independent Charging Local calls in the fixed Networks are usually charged on a duration independent-basis. The subscriber meter is incremented once at the start of a local call. 2. Duration Dependent Charging Periodic pulse train of pulses from a common pulse generator operate the subscribers meter; Modern exchanges store date, time and duration in seconds for the purpose of charging; Mobile operators usually use duration dependent charges, i.e per second or per minute.

22 DISTANCE-RELATED CHARGING 1.Distance related charges are used more commonly in fixed telecommunication systems and rarely in mobile. 2.They are more realistic because they provide for transmission costs.

23 TARIFF VARIATION 1. Traffic in a telecommunication network varies throughout the day. 2. However telephone exchange capacity is based on the estimated capacity at the busy hour. 3. As a result, a large part of the capacity remains idle during off-peak hours. 4. Most operators lower tariffs to encourage subscribers to call at off-peak hours

24 EXAMPLE OF TARIFF VARIATION SCHEME

25 EXAMPLE A telephone administration provides leased lines at the rate of Kshs. 600 per km for a minimum rental period of 3 months. MMU, a point-to-point traffic user, has offices located 600 km apart and is confronted with the choice of using STD or leased lines. At what traffic volume per day, would he start saving money by using a leased line? Assume 20 working days per month and a rate of Kshs. 1 per unit recorded by the meter. Assume that Subscriber Trunk Dialing (STD) calls are charged at Kshs. 20 per minute.

26 SOLUTION 1. Cost of renting the leased line is 600 x 600 = Kshs. 360, Cost of STD calls per hour is 60 X 20 = Kshs Let the break-even point occur when the STD line is used for x hours in three months. Then we have 1200x = 360,000, or x = 300 hours in 3 months = 100 Hours in a Month = 5 hours per day

27 Common Channel Signaling ETI2506 Monday, 15 February 2016

28 TELECOMMUNICATION NETWORK SIGNALING 1. Exchange Hierarchy Classification Subscriber loop signaling Intra-exchange or register signaling Inter-exchange or inter-register signaling. 2. Channel-Level Classification In Channel Signaling Common Channel Signaling

29 SIGNALING TECHNIQUES

30 COMMON CHANNEL SIGNALLING SignalingT erminal Modem

31 CCS SIGNALLING FRAME FORMAT Header Signalling Information Circuit Label Error Check

32 COMPARISON OF IN-CHANNEL AND COMMON-CHANNEL IN-CHANNELCOMMON-CHANNEL Trunks are held up during signalling Trunks are not required for signaling Interference between Voice and Control Signals may occur No interference since the voice and control channels are separate Separate signaling equipment is required in each trunk hence expensive Only one set of signaling equipment is required for a large group of trunk circuits hence economical Can be misused by customers since it is easy to mimic voice signaling Control channel is in-accessible to users Signalling is relatively slow Signalling is much faster Speech circuit continuity is assured when signaling is received State of speech circuit not automatically assured It is difficult to change or add signals There is flexibility to add or change signals