Transcript Lecture 3

Cellular Networks
Lecture 6
Paul Flynn
Cellular Telephony Architecture
Radio tower
PSTN
Telephone
Network
Mobile Switching
Center
Very Basic Cellular/PCS
Architecture
Public Switched
Telephone Network
Mobility
Database
Base Station
Controller
Mobile
Switching
Center
(MSC)
Radio Network
Base Station
(BS)
Mobile Station
Duplex Communication - FDD
• FDD: Frequency Division Duplex
Mobile
Terminal
M
Forward Channel
Reverse Channel
Base Station
B
Forward Channel and Reverse Channel use different frequency
bands
Access Methods
Frequency
Frequency
FDMA
Time
Time
Frequency
TDMA
CDMA
Time
Clusters
• A cluster is a group of cells
– No channels are reused within a cluster
A seven Cell Cluster
Example - Frequency Spectrum
Allocation in U.S. Cellular Radio
Service Forward Channel
Reverse Channel
991 992
…
1023
1
…
2
799
824-849 MHz
991 992
…
1023
1
2
…
799
869-894 MHz
Channel Number
Reverse Channel 1 <=N <= 799
991 <= N <= 1023
Center Frequency (MHz)
0.030N + 825.0
0.030(N-1023) + 825.0
Forward Channel 1 <=N <= 799
0.030N + 870.0
991 <= N <= 1023
0.030(N-1023) + 870.0
(Channels 800-990 are unused)
Channel bandwidth is 45 MHz
Frequency Reuse
• Only a small number of radio channel
frequencies were available for mobile
systems
– Therefore engineers had to find a way to reuse
radio channels to carry more than one
conversation at a time
– The solution the industry adopted was called
frequency reuse. Implemented by restructuring the
mobile telephone system architecture into the
cellular concept
Frequency Reuse
• The concept of frequency reuse is based on
assigning to each cell a group of radio channels
used within a small geographic area
– Cells are assigned a group of channels that is
completely different from neighbouring cells
– The coverage area of cells is called the footprint and
is limited by a boundary so that the same group of
channels can be used in cells that are far enough
apart
Frequency Reuse
• Cells with the
same number
have the same
set of
frequencies
Frequency Reuse
Frequency Reuse using 7
frequencies allocations
f2
f7
f3
f7
f1
f6
f4
f6
f5
f2
f2
f7
f3
f7
f3
f1
f1
f6
f4
f6
f4
f5
f5
f2
f3
f1
f4
f5
f2
f7
f3
f1
f6
f4
f5
Each cell is generally 4 to 8 miles in diameter with a lower limit
around 2 miles.
Cell Splitting
• Allows urban centres to be split into as many
areas as necessary for acceptable service levels
in heavy-traffic regions, while larger, less
expensive cells can be used to cover remote
rural regions
Cellular Concept with Sectors
frequency re-use
base station
Hand-off
• The final obstacle
in the development
of the cellular
network involved
the problem
created when a
mobile subscriber
moved from one
cell to another
during a call
GSM infrastructure
MSC, BSC, BTS, VLR, HLR, GSGN, GSSN
Compared to a fixed network
Transit exchang
Gateway MSC
Local switches
MSC
BSC
Subscriber stage
Fixed phone
MS
What’s new?
•
•
•
•
•
•
Radio access network
Encryption
Voice coding
Locate a mobile station
Identify and authenticate
Handle mobility during a call
A bird eye’s view
Access Network
BTS
MSC
GMSC
databases
BSC
BSC
BSC
MS
BTS
BTS
”Typical” Mobile operator
• One to ten MSC per 1 M subscribers
• Ten to one hundred BSC per MSC
• Thousands of BTS per 1 M subscribers
Base Transceiver Station
• Controls the radio link
– encryption
– error control
– signal strength
• 1 - 6 duplex carriers, for
example:
– two layers
– 120o sectors
– (6+8)*3 = 42 voice calls
• Cost ~ 100 – 200 k$
Base Station Controller
• communication with the mobile
terminal
–
–
–
–
local hand-over
voice codecs
carrier allocation
paging to terminals
• talks to the MSC
• serves up to 40 BTSs
• could be co-located with MSC
Mobile Switching Centre
• Mobility management
– identifies and authenticates
– locates
– switches between BSCs
– Handover to other MSCs
• 64 kbps regular voice channels
Radio Access network
A carrier is divided into logical channels
control channels CCH
traffic channels TCH
The first carrier holds 2 controll channels and
6 traffic channels. Additional carriers holds only
traffic channels.
Control Channels
• Broadcast
– Frequency correction: to synchronize (FCCH)
– Broadcast control: this is me, these are my neighbours (BCCH)
• Common control
– Paging: to notify a mobile station (PCH)
– Random access: for the mobile to request service (RACH)
– Access grant: reply with assigned dedicated control channel (AGCH)
• Dedicated control
–
–
–
–
Standalone dedicated control: used during call set-up, SMS etc (SDCCH)
Slow associated control: power, time etc (SACCH)
Fast associated control: handover etc, uses the TCH (FACCH)
Cell broadcast: cell broadcast
Traffic Channels
• Duplex
• Error control
– Forward Error Correction (FEC)
– retransmission (ARQ)
• Full rate (TCH/F)
– 13 Kbps speech
– 9,6 or 14,4 Kpbs data
• Half rate (TCH/H)
– 6,5 Kbps speech
– 7,2 or 4,8 Kbps data
Logical channels
Hyperframe: 2048 superframes
3h28m
Superframe: 26 or 51 multiframes
CCH
6.12 s
CCH
Multiframe: 26 or 51 TDMA frames
CCH
TCH
8 time-slot TDMA frame
4.143 ms
One TDMA frame
148 b 0.577 ms
tail
Normal burst
3
tail
training
57 b
26 b
user data
57 b
user data
stealing flags
Frequency correction burst
Synchronization burst
Dummy burst
Access burst
3
guard 8.25
Keeping track of a mobile
station
Location area
VLR
visiting location register
Location area
update the VLR with new
location area
Moving to a new MSC
VLR
which LA which MSC ?
Location area
Location area
update the VLR with new
location area and new MSC
but also….
HLR
home location register
VLR
update the home location register!
Home Location Register
PSTN
incomming call
where is the mobile?
GMSC
HLR
MSC
VLR
How do we reach him?
Mobile station numbers
PSTN
mobile subscriber ISDN number
(MSISDN) i.e. the phone number
GMSC
HLR
Mobile Station Roaming
Number (MSRN).
MSC
VLR
International Mobile
Subscriber Identity
Temporary Mobile
Subscriber Identity
GPRS
Internet
Gateway GPRS Support Node
GGSN
Access Network
Packet Control Unit
BTS
BSC
UDP/TCP tunnel
Serving GPRS Support Node
SGSN
MS
BTS
BTS
Looking to PCS from different
Angles
PSTN
(Telephone Network)
Internet
Wireless Access
Mobile Users
-Cell phone users
-Cordless phone users
Telecom People View
Mobile Users
-Laptop users
-Pocket PC users
-Mobile IP, DHCP enabled
computers
Data Networking People View
Telecom and Data Networking
Telecom Interest
- Voice Transmission
- Frequency Reuse
- Handoff
Management
-Location Tracking
-Roaming
-QoS
-GSM, CDMA,
Cordless Phones,
-GPRS, EDGE
Data Networking Interest
-Radio Propagation
-Link Characteristics
-Error Models
-Wireless Medium
Access (MAC)
- Error Control
-Data Transmission
-Mobile IP (integrating
mobile hosts to
internet)
-Ad-hoc Networks
-TCP over Wireless
-Service Discovery
Major Mobile Radio Standards Europe
Standard
Type
Year
Intro
Multiple
Access
Frequency
Band
(MHz)
Modulation
Channe
l
BW
(KHz)
ETACS
Cellular
1985
FDMA
900
FM
25
NMT-900
Cellular
1986
FDMA
890-960
FM
12.5
GSM
Cellular/PCS
1990
TDMA
890-960
GMSK
200KHz
C-450
Cellular
1985
FDMA
450-465
FM
20-10
ERMES
Paging
1993
FDMA4
Several
4-FSK
25
CT2
Cordless
1989
FDMA
864-868
GFSK
100
DECT
Cordless
1993
TDMA
1880-1900
GFSK
1728
1993
TDMA
1710-1880
GMSK
200
DCS-1800 Cordless/PC
S
Example - Frequency Spectrum
Allocation in U.S. Cellular Radio
Service Forward Channel
Reverse Channel
991 992
…
1023
1
…
2
799
824-849 MHz
991 992
…
1023
1
2
…
799
869-894 MHz
Channel Number
Reverse Channel 1 <=N <= 799
991 <= N <= 1023
Center Frequency (MHz)
0.030N + 825.0
0.030(N-1023) + 825.0
Forward Channel 1 <=N <= 799
0.030N + 870.0
991 <= N <= 1023
0.030(N-1023) + 870.0
(Channels 800-990 are unused)
Channel bandwidth is 45 MHz
2G Technologies
cdmaOne (IS-95)
GSM, DCS-1900
IS-54/IS-136
PDC
Uplink Frequencies
(MHz)
824-849 (Cellular)
1850-1910 (US PCS)
890-915 MHz (Eurpe)
1850-1910 (US PCS)
800 MHz, 1500 Mhz
(Japan)
1850-1910 (US PCS)
Downlink Frequencies
869-894 MHz (US
Cellular)
1930-1990 MHz (US
PCS)
935-960 (Europa)
1930-1990 (US PCS)
869-894 MHz (Cellular)
1930-1990 (US PCS)
800 MHz, 1500 MHz
(Japan)
Deplexing
FDD
FDD
FDD
Multiple Access
CDMA
TDMA
TDMA
Modulation
BPSK with Quadrature
Spreading
GMSK with BT=0.3
p/4 DQPSK
Carrier Seperation
1.25 MHz
200 KHz
30 KHz (IS-136)
(25 KHz PDC)
Channel Data Rate
1.2288 Mchips/sec
270.833 Kbps
48.6 Kbps (IS-136)
42 Kbps (PDC)
Voice Channels per
carrier
64
8
3
Speech Coding
CELP at 13Kbps
EVRC at 8Kbps
RPE-LTP at 13 Kbps
VSELP at 7.95 Kbps
GSM Speech Signal Processing
GSM and CDMA Coverage Map
Worldwide
Evolution
1G TECHNOLOGY
1G refers to the first generation of wireless telephone
technology, mobile telecommunications which was first
introduced in 1980s and completed in early 1990s.
It's Speed was upto 2.4kbps.
It allows the voice calls in 1 country.
1G network use Analog Signal.
AMPS was first launched in USA in 1G mobile
systems.
DRAWBACKS OF 1G
Poor Voice Quality
Poor Battery Life
Large Phone Size
No Security
Limited Capacity
Poor Handoff Reliability
1G Wireless System
2G TECHNOLOGY
 2G technology refers to the 2nd generation which is
based on GSM.
 It was launched in Finland in the year 1991.
 2G network use digital signals.
 It’s data speed was upto 64kbps.
Features Includes:
 It enables services such as text messages,
picture messages and MMS (multi media message).
 It provides better quality and capacity .
DRAWBACKS OF 2G
 2G requires strong digital signals
to help mobile phones work. If there
is no network coverage in any specific
area , digital signals would weak.
 These systems are unable to
handle complex data such as Videos.
2G Wireless System
3G TECHNOLOGY
3G technology refer to third generation which was
introduced in year 2000s.
Data Transmission speed increased from
144kbps- 2Mbps.
Typically called Smart Phones and
features increased its bandwidth
and data transfer rates to accommodate
web-based applications and audio
and video files.
FEATURES OF 3G TECHNOLOGY
 Providing Faster Communication
 Send/Receive Large Email Messages
 High Speed Web / More Security
Video Conferencing / 3D Gaming
 TV Streaming/ Mobile TV/ Phone Calls
 Large Capacities and Broadband Capabilities
 11 sec – 1.5 min. time to download a 3 min Mp3 song.
DRAWBACKS OF 3G TECHNOLOGY
 Expensive fees for 3G Licenses Services
 It was challenge to build the infrastructure
for 3G
 High Bandwidth Requirement
 Expensive 3G Phones.
 Large Cell Phones
4G TECHNOLOGY (Anytime ,Anywhere)
4G TECHNOLOGY (Anytime ,Anywhere)
4G technology refer to or short name of fourth Generation
which was started from late 2000s.
Capable of providing 100Mbps – 1Gbps speed.
One of the basic term used to describe 4G is MAGIC.
MAGIC:
Mobile Multimedia
Anytime Anywhere
Global Mobility Support
Integrated Wireless Solution
Customized Personal Services
Also known as Mobile Broadband Everywhere.
Countries Have 4-G
Except for the Scandinavian Countries (Northern Europe that includes
Denmark and two of the nations of Scandinavian , Norway and
Sweden. ), a few countries have started the 4G commercially.
In the US, Sprint Nextel and Others Germany , Spain, China , Japan
and England are also using the 4G services and mobiles .
WIRLESS MODELS OF 3G & 4G
 3G WIRELESS SYSTEM
 4G WIRELESS SYSTEM
5G TECHNOLOGY
5G technology refer to short name of fifth Generation
which was started from late 2010s.
Complete wireless communication
with almost no limitations.
It is highly supportable to WWWW
(Wireless World Wide Web).
BENEFITS OF 5G TECHNOLOGY
High Speed, High Capacity
5G technology providing large broadcasting of data in Gbps .
Multi - Media Newspapers, watch T.V programs with the
clarity
as to that of an HD Quality.
Faster data transmission that of the
previous generations.
Large Phone Memory, Dialing Speed,
clarity in Audio/Video.
Support interactive multimedia , voice,
streaming video, Internet and other
5G is More Effective and More Attractive.
EVOLUTION OF 1G TO 5G TECHNOLOGY
WIRELESS APPLICATIONS
Wireless applications are those
which we use free space as the
transmission medium & do not
involve cabling like fibre or
copper cables.
WIRELESS SERVICES
Wireless solution for:
Business and Industry
Schools , Colleges
Doctors , Pilots
Police and Vehicles etc.
CONCLUSION
 All totally the best way to help all users is to use 5G as the
next wireless system and in totally it is safety and secure for
public, this the need that demands the solution.
 Today’s wired society is going wireless and if it has problem,
5G is answer.
 5G technology is going to give tough competition to
Computers and Laptops.
 It will be available in the market 2020 at affordable cost with
more reliability than previous mobiles.