Mr. Thilak de Silva. BSc. Eng., MSc, CEng, FIE(SL), FIET(UK), CITP(UK), MBCS(UK), MIEEE (USA) M.Sc. in IT - Year 1 Semester II

Expenditure Beget Tender Document / Bidding Document Request for proposal – RFP Stakeholders of Procurement Process Contents of Tender Document Calling for Tender Document Contract Document M.Sc. in IT - Year 1 Semester II

At the end of this session you will understand about the entire Procurement Process of an organization and about related artifacts such as Tender document, Request for Proposals, Contract document etc. M.Sc. in IT - Year 1 Semester II

PSTN – Voice Mobile - Public networks 1G – Voice 2G-Voice,data 3G-Data Data – Private Networks M.Sc. in IT - Year 1 Semester II

CPE – Customer Premises Equipment This located in between customer premises and Service provider premises. Terminal Equipment is connected to this. This is the interface between user equipment and network Operates at layer 1 (Physical layer) of ISO/OSI model. M.Sc. in IT - Year 1 Semester II

CPE is connected to the core network via a Access Node/Access Gateway. Many users connects to it. M.Sc. in IT - Year 1 Semester II

Switching Circuit switching Packet Switching Aggregation Combining many users Multiplexing is a kind of aggregation M.Sc. in IT - Year 1 Semester II

Involve in Voice communications IS a Real Time connection Requires a dedicated connection. Circuit switching has two variations Space switching Time switching M.Sc. in IT - Year 1 Semester II

For PSNT network Access gateway is the telephone exchange. M.Sc. in IT - Year 1 Semester II

TE is the telephone. Converts the voice signal in to an analog signal M.Sc. in IT - Year 1 Semester II

This signal can be input to the telephone exchange directly as it is. There for in PSTN we do not need to have a CPE. Telephone is not a passive device. The required power is fed by the telephone exchange. M.Sc. in IT - Year 1 Semester II

This is a fixed wired connection and it is costly. M.Sc. in IT - Year 1 Semester II

Here we have logical dedicated connections between exchanges. Generally TDM is used. A single time slot is allocated for each user. This time slot is dedicated until the connection is over. This dedication is temporal and allocated in need only. This is known as switching. M.Sc. in IT - Year 1 Semester II

Switching Establish the Link Exchange Information between endpoints Monitor until conversation is over. Keep track of Accounting information. User authentication is not done here. The exchange assumes that the copper loop is connected to the legitimate user M.Sc. in IT - Year 1 Semester II

Different types of facilities are provided by the exchange. Eg: Call conferencing, call forwarding All customers will not get all the services. Exchange will check what are the authorizes servicers for a particular user before giving any services. This is known as Authorization and is done in the exchange. M.Sc. in IT - Year 1 Semester II

The basic information like customer details, customer telephone number, authorized services etc. are stored in a separate database by the exchange. Accounting information are kept I the hard disk. Analog to Digital conversion is done in the telephone exchange and vice versa. M.Sc. in IT - Year 1 Semester II

Monitor whether a user needs a service. (off hook) Then exchange should inform that it is ready to provide the service. (Dial tone) The requirement to make available the service is to find a free register or memory for the user. This is needed to store the dialed numbers. M.Sc. in IT - Year 1 Semester II

The user will dial the number. It is a signal. The exchange will analyze the number and find out the destination. The exchange finds a free time slot between two exchanges and allocate it to user. The exchange will send the destination number to the other exchange. M.Sc. in IT - Year 1 Semester II

If the destination user is not busy the ringing tone is sent to the user and ring back tone is sent to the originating exchange. The destination user off hook the telephone. The destination exchange send information to the originating exchange. (connection established). This indication is called the answer signal. M.Sc. in IT - Year 1 Semester II

Then the originating exchange starts billing. Once the connection is over, either side will off hook the telephone and that exchange will send a signal to the other exchange indicating that the call is over. The originating exchange records the start time and the end time of the call. M.Sc. in IT - Year 1 Semester II

The originating exchange will keep A number (originating number), B number (destination number),start time and end time as a record for each call. This is known as CDR – Call Data Record. M.Sc. in IT - Year 1 Semester II

IN PSTN signaling plays an important role. There are two main types of signals. Addressing signals Supervisory Signals IN addition to switching exchange is responsible in handling some signaling functions too. M.Sc. in IT - Year 1 Semester II