The Cellular Communication System

workablejeansMobile - Wireless

Nov 21, 2013 (3 years and 11 months ago)

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The Wireless Communication
System

Xihan Lu

Wireless Communication


Cellular phone system


Cordless telephone system


Bluetooth


Infrared communication


Microwave communication


IEEE Wireless LANs (Wi
-
Fi)


Satellite communication

Why

Cellular

?


Three Generations

AMPS

NMT

TACS

HCMTS

GSM

GPRS

WCDMA

CDMA2000

TD SCDMA

2G

3G

1G

1G


Start early 80’s


Analogue technique


AMPT (
Advanced Mobile Phone System
):
North America


NMT
(
Nordic Mobile Telephony
):

North Europe


TACS
(
Total Access Communication Service
):

Europe, China


HCMTS
(
High Capacity Mobile Telephone System
):

Japan

FDMA


Frequency Division Multiple Access


Different carrier frequencies are assigned to
different traffic channels(speech)


One carrier frequency can only carry one
single speech channel at one time

FDMA


Shortage


Voice information only


Unsafe

eavesdropping



Waste of frequency resource

2G


Start early 90’s


Digital technique


GSM :
Global System of Mobilephone



GPRS :
General Packet Radio Service


D
-
AMPS :
Digital AMPS

GSM


TD/FDMA: A mix of FDMA and TDMA


The whole useable spectrum was divided to

many 200k Hz carrier frequencies

FD


Each carrier was divided into 8 timeslots (burst)

TD


Each burst is assigned to a user(a logical traffic
channel)


One carrier frequency can carry up to 8 logical
traffic channels (voice or data) at the same time


The maximum data communication rate is 14.4
kbps

FD / TDMA


Network Structure

BTS,BSC and MSC


BTS & BSC:
Base Transceiver System and

Base Station Controller
. Radio signal

transceiver, a connection between

handset and MSC


MSC:
Mobile services Switching Center
,

switching center of the GSM network,

and connect to other networks

Databases


HLR :
Home Location Register
,
contains static

information of subscribers and location update

data


VLR :
Visitor Location Register
, embedded in MSC

to avoid delay, contains current location

information of handsets


AUC :
Authentication Center
, stores secret keys

for authentication and encryption of the

radio channel



EIR :
Equipment Identity Register
, contains a list

of all valid mobile equipment in the network,

by its International Mobile Equipment Identity

(IMEI)

GPRS



Upgrade of existed GSM network


Improves the data communication ability

GPRS


Network nodes


GGSN:
Gateway GSM Support Node
,


Protocol transferring, data encapsulation, a
connection to external networks


SGSN:
Service GSM Support Node
,


Communicate with HLR and mobile
handsets, authorization and admission
control, charging, mobility management

Data communications


In GSM, one user occupies one traffic channel to
exchange voice/data information


In GPRS, up to 8 traffic channels(a whole carrier)
can be dynamically combined together for one
data communication application


The theoretically maximum data transmission rate:
14.4k bps * 8 = 115.2k bps

Advantages of GPRS


Higher data rate


Seamless connection to internet


Packet switching rather than circuit switch,
bandwidth is only used when the data is
actually used, even though it is always
connected


A primary step to 3G

shortage


Not fast enough for the multimedia service


The data rate falls when the network is busy


Upgrade of handset

3G


3G
-
Standards


Three CDMA standards approved by ITU:


Direct Spread CDMA(WCDMA) : Europe,
Japan


Multi
-
Carrier CDMA(CDMA 2000) : North
America


TD
-
Synchronous CDMA(CDMA TDD) :
Europe, China

3G
-
CDMA


Code Division Multi Address


Spread spectrum technology


Each single traffic channel occupies the
whole spectrum, but distinguished by a
unique digital code


Walsh code: an orthogonal 64 bit pattern,
unique in the network

CDMA


Features


Better voice quality


Up to 2 Mbps data communication rate


Increase battery life


Soft hand
-
off


Excellent data safety


More effective spectrum usage than 2G

Conclusion


Conclusion


1G

2G

3G

Voice Quality

OK

OK

Good

Data
communication

N/A

~115K

~2M

Spectrum usage

X

5~6X

10~20X

Communication
safety

Weak

OK

Good

References


www.gsmworld.com/technology/gprs/index.html


www.3gsmamericas.com/pdfs/EOF_Cannes_2003/Nortel_David_Smit
h.pdf


http://www.fcc.gov/Bureaus/Wireless/Reports/fcc98091.pdf


www.rogers.com


http://www.itu.int/ITU
-
D/ict/publications/wtdr_99/material/glossary.html


www.itu.int/home/imt.html


http://www.boeschatt.at/Mobil/mobilfunk_html.php?gsm_netzarchitekt
ur.php


http://www.pt.com/products/gsmintro.html