Communication Systems doc

Busy hour and grade of service  Busy hour: period of maximum usage demand  Grade of service = blocking probability  B=1% : during busy hour, 1 in 100 calls can be expected to meet b

Communication Systems

Lecturer: M.E P.T.A Quang

Contents

 Chapter 1: Introductory Concepts

 Chapter 2: QoS

 Chapter 3: Transmission and switching

 Chapter 4: Digital networks

 Chapter 5: Signaling

 Chapter 6: PSTN

 Chapter 7: VoIP

 Chapter 8: Mobile communication

 Chapter 9: Satellite communication

 Chapter 10: Fiber-optic communication

Introductory Topics in Telecommunication

 End-users, nodes, and connectivities

 Telephone numbering and routing

 Tandem switches

 Hierarchical structure

 Busy hour and grade of services

 Simplex, half-duplex, and full duplex

 One-way and two-way circuit

 Double seizure

 Supervision signals

 Network topologies

 Variations in traffic flow

End users, nodes, and connectivities

 End-users: inputs to the network / recipients of network

outputs

 Node: a point or junction in a transmission system where lines and trunks meet (switching function)

 Connectivity: links an end-user to a node, and from there

possibly through other nodes to some final end-user

destination

Telephone numbering and routing:

 Every subscriber has an unique number related to physical location

Call 447-8765 Route: look up trunk to 447

Subscriber loop

trunk

Tandem switches in Local Area Connectivity

 Traffic concentrator  reduce the connection  economic expedient

Hierarchical structure

Busy hour and grade of service

 Busy hour: period of maximum usage demand

 Grade of service = blocking probability

 B=1% : during busy hour, 1 in 100 calls can be expected to meet blockage

Simplex, half-duplex, and full duplex

 Simplex: one way operation; no reply channel

 Half-duplex: two-way service Only one direction at a time

 Full duplex: two-way independent transmission (PSTN)

One-way or two-way circuit

 Two-way circuit: any trunk can be selected for operation in either direction

a) two-way b) One-way c) Hybrid scheme

Double seizure

 In bothway groups, it can happen that the exchanges at

both ends of a trunk group seize the same trunk at the same time (double seizure)

 Solutions: it can be arranged that one exchange continues the setup, and the other exchange backs off (tries to seize another trunk for its call) The signaling on bothway

trunks includes provisions to alert the exchanges when a double seizure occurs

Supervision signals

Double seizure

 After A seizes a trunk, it expects to receive a backward change to off-hook (wink signal) However, this change

may also mean that exchange B is sending a seizure signal

 Wink: return on-hook within 100-1000ms If the off-hook duration >1s  double seizure

Network topologies

Mesh

Full-mesh

Star

Multiple-star

Variations in traffic flow:

 Busy hour is different from countries to countries

 Noncoincident busy hour

Quality of service

 How happy the telephone company is keeping the customer

 Customer satisfaction

 GoS

 Can connectivity be achieved?

 Delay before receiving dial tone

 Post dialing delay

 … (refers to material)

Standardization in telecommunications

 ITU (international telecommunication union)

 ISO (international standardization organization)

 IEEE (Institute of Electrical Electronic Engineers)

 ETSI (European Telecommunications Standards Institute)

 EIA (Electronic Industries Alliance)

Telecommunication companies

Mobile Telecommunication Co in VN

Mobile Telecommunication Co in VN