Điện tử viễn thông c1 4 điện thoại số và truy nhập số khotailieu

TRƯỜNG ĐẠI HỌC ĐIỆN LỰC
KHOA ĐIỆN TỬ - VIỄN THÔNG

TỔNG ĐÀI &
KỸ THUẬT CHUYỂN MẠCH

Chương 1: Lý thuyết tổng quan và cơ sơ
IV. Điện thoại số và truy nhập số trong mạng VT

Giảng viên: Phan Thị Thanh Ngọc
1

EPU - 2012


Nội dung
•
•
•
•

2

ISDN
DECT
GSM
TETRA

J.Tiberghien - VUB

The Telephone
Analog
/ Digital
Network
ABX
ABX
ABX

ABX
ABX

ABX

PABX

PABX
ABX

3

J.Tiberghien - VUB


ISDN
Đặc tính chính
• Communication channels :
– B = 64 kb/s data channel
– D = 16 or 64 kb/s signaling channel

• Data rates :

– Basic Access : 144 kb/s = 2B+D(16)
– Primary Rate Access : 2048 kb/s = 30 B + D(64)

• Standard services
– # simultaneous communications = # B channels
– Calling line identification
4

J.Tiberghien - VUB


The Telephone Network
ISDN Basic Access
A/D converter
in phone

Digital
switch

S bus
144Kb/s twisted pair, average length 2.5 Km
modem
2 * 64 Kb/s + 16 Kb/s
5

144Kb/s
modem
J.Tiberghien - VUB

ISD
N

Sbus

NT2

6

T

NT1

Terminal
Adapter

Analog

Terminal
Adapter

V24

Terminal
Adapter

Fax Gr 3

U

J.Tiberghien - VUB


Belgacom
TWIN
S bus
available for extensions
192 Kb/s
Up to 8 terminals
Terminal
Adapter
Terminal
Adapter

7

Network
Terminator

U
interface

NT12ab
J.Tiberghien - VUB


The Telephone
Calling Line
Identification Protocol
Network

ABX
ABX
ABX

ABX
ABX

ABX

PABX

PABX
ABX

8

J.Tiberghien - VUB


The Telephone
Cordless
Telephones
Network
ABX
ABX
ABX

ABX
ABX

ABX

PABX

PABX
ABX

9

J.Tiberghien - VUB


Digital Cellular Radio
Systems
Name
Freq.(MHz)

CT2

DECT

GSM

864-868

1880-1890

890-915
935-960

10

# can.rad.

40

10

124

P.max.(W)

0.01

0.25

8

r.max.(Km)

0.2

0.15

30

datarate (Kb/s)

32

32

13
J.Tiberghien - VUB


Wireless Local
Loop
Radio is sometimes cheaper
than digging the streets !

11

J.Tiberghien - VUB


Wireless Local
Loop
Planes or balloons could be cheaper
than building towers !

12

J.Tiberghien - VUB


The Telephone
Network
gsm
ABX

ABX
ABX

ABX
ABX

ABX

PABX

PABX
ABX

13

J.Tiberghien - VUB


Radio Communications
• The main limitation = transmission capacity
– Bandwidth limited by
» Physical availability
» Political & commercial availability
– Signal / noise limited by
» Electromagnetic noise sources
» Other radio transmitters
» Multi-path propagation
14

J.Tiberghien - VUB

Reuse of Frequencies
Pr/sa = Pt/r2
r
transmitter

15

J.Tiberghien - VUB


Cellular
Radio

16

J.Tiberghien - VUB


Cellular
k = number available
frequencies per cell
Radio

S = Area of a cell = Π *r2
n = Number of simultaneous calls per km2
pt = Power of transmitter
P0/Sa= Minimal field strenght at receiver input
n =k/S

pt = p0/Sa * r2

17

With smaller cells,
- more antenna sites are needed ...
- more simultaneous calls are possible
- transmitted power can be reduced

J.Tiberghien - VUB


Flanders

Cellular
Radio

Ardennes

in practice

18

J.Tiberghien - VUB


Cellular Radio

19

J.Tiberghien - VUB


GSM System Architecture
BSS

R
A
D
I
O

NSS

16Kb/s

GSTN
TRAU

64Kb/s

MSC
ISDN

BSC

VLR
SS7

BTS

HLR

NSS

MS

20

BSS : Base Station Sub-system
BSC : Base Station Controller
BTS : Base Transceiver Station
TRAU : Transcoder / Rate Adapter Unit

NSS : Network and Switching Sub-system
MSC: Mobile service Switching Center
HLR : Home Location Register
VLR : Visitors Location Register
J.Tiberghien - VUB


GSM
• MS : Mobileacronyms
Station
– ME : Mobile Equipment
– SIM : Subscriber Identity Module

• BSS : Base Station Sub-system
– BSC : Base Station Controller
– BTS : Base Transceiver Station

– TRAU : Transcoder / Rate Adapter Unit

• NSS : Network and Switching Sub-system
– MSC: Mobile service Switching Center
– HLR : Home Location Register
– VLR : Visitors Location Register
21

J.Tiberghien - VUB


Mobilit
• Location Management : 3 y
options
– Ubiquitous paging :

» call made in all cells.
» No need to know where MS is
» Waste of radio capacity
– Systematic location updating

» call made in the single cell where MS is
» Overload of NSS
– Location Area

» call made in a group of adjacent cells
» location information transmitted only when
leaving the area.
22

J.Tiberghien - VUB


GSM Radio
Transmission
• Two transmission
modes
– Idle Mode - via a "common channel"

» MS lists to paging messages
» Monitors radio environment to select base
station
» Sends and receives short messages
– Dedicated Mode - via a "Traffic Channel"

23

» A TCH (13 kb/s full duplex) is assigned to a
specific call for voice/data transmission
» A "Slow Associated Control Channel" is used
for radio measurements
» For "Fast associated signaling" (needed for
handover), capacity is stolen from the TCH

J.Tiberghien - VUB


GSM security
MS

VLR

....
i:K i
....

HLR

Ki
imsi

rand
sres
data & signalling
enciphered by Kc
24

vlr,imsi

sres = A3(Ki,rand)
rand,sres, Kc
Kc = A8(Ki,rand)

J.Tiberghien - VUB


GSM Voice Transmission
Layers

Analog

13 Kb/s
64 Kb/s

25

J.Tiberghien - VUB