ch1 gsm – global system for mobile communication
DESCRIPTION
ÂTRANSCRIPT
GSM – GLOBAL SYSTEM FOR
MOBILE COMMUNICATIONS
BY: ENG. Waleed Elsafoury
Copyright © 2013 Waleed Elsafoury
HISTORY OF COMMUNICATION
- CONTENT- communication systems overview- Introduction to Cellular Fundamentals- Network Architecture- GSM Air Interface- Digital Mobile Elements- GSM Network Protocols- Understanding GPRS & EDGE
HISTORY OF COMMUNICATION
• Communication systems
HISTORY OF COMMUNICATION
Voice Communications
HISTORY OF COMMUNICATION
Basic Communications System Elements
● Source
● Destination
● Transmission Medium
Source DestinationTransmission Medium
HISTORY OF COMMUNICATION
Transmission Medium
Wired Wireless
• Transmission Medium
HISTORY OF COMMUNICATION
Long Distance Communications
Telecommunication is the process of long distance communications.
Early telecommunications involved smoke, flags, drums, and other such methods
to relay messages and information.
HISTORY OF COMMUNICATION
TelegraphThe first wire line communications was the telegraph. Invented in the mid 19thcentury, it opened a new era in long-distance telecommunication.
HISTORY OF COMMUNICATION
TelephoneWhen we talk over the telephone, our voice is converted to a electronic signal bythe microphone in the handset. This signal is then transmitted over telephone wires.
HISTORY OF COMMUNICATION
Telephone Networks Early Switching DevicesSwitches are devices that cause a connection between two transmitting/receiving devices.Modern Switching DevicesToday many different types of automated switches are used which make it possible for fast placement of calls.
HISTORY OF COMMUNICATION
Wired VS Wireless• Losses• Mobility• Security• Bandwidth• Cost
Cellular FUNDEMENTALS
Transition from analog to digital
• Capacity
• Cost
• Quality
• Security
Cellular FUNDEMENTALS
1 0 0 0 1 1 00 1 0 0 1 0 10 0 1 0 0 1 10 0 0 1 1 1 1
G =
1 1 0 1 1 0 01 0 1 1 0 1 00 1 1 1 0 0 1
H =
C = D G = ( 1 0 1 1 : 0 0 1 (
D = ( 1 0 1 1 )
THIS IS SENT OVER THE CHANNEL
CHECK AT THE RECIVER
S = C H T = ( 0 0 0 )
S = C H T = ( 1 0 1 ) =
IF WE RECIVER ERROR AT BIT No. 5 C = ( 1 0 0 1 : 0 0 1 )
5
Some techniques used in wireless communication:
FDM
TDM
FDMA
TDMA
Cellular FUNDEMENTALS
FDM
Cellular FUNDEMENTALS
TDM
Cellular FUNDEMENTALS
Freq
uenc
y FDMA
FDMA is the division of each bandwidth (RX,TX) into many frequency bands (channels)
Cellular FUNDEMENTALS
TDMA It allows several users to share the same radio frequency (RF)by dividing it into different timeslots
Time
Freq
uenc
yCellular FUNDEMENTALS
TDMA/FDMA
Cellular FUNDEMENTALS
Time
Freq
uenc
y
Cellular FUNDEMENTALS• Types of telephones
Fixed (PSTN) telephones
Cordless Telephones
Mobile Telephones
Handset The base
Modes OF Transmission in wireless
Simplex communication system Example:
Television , radio
TX RXCommunication is possible in one direction only
Cellular FUNDEMENTALS
Half – Duplex communication system Example :
Police radio
TX+RX TX +RX Two-way communication on the same channel.
At any given time a user can only transmit or receive
Cellular FUNDEMENTALS
Full – Duplex communication system Example :
GSM mobile radio
TX+RX TX +RX
• simultaneous two-way communication• Two simultaneous but separate channels are
provided for communication to and from the terminals
Cellular FUNDEMENTALS
Simple growth was the single transmitting/receiving station
- heavy, bulky and expensive- no switching between regions- low quality- limited capacity- rapid market saturation- power hungry transceiver - power level was not safe
MS
High transmitted power Up link
Down link
Cellular FUNDEMENTALS
Cellular FUNDEMENTALS
First generation cellular system- Introduction of analog cellular systems in the late 1970s and 1980s- analog system- incompatible systems- limited to voice service- no encryption- FM modulation- FDMA transmission technology- suffer from capacity saturation
Cellular FUNDEMENTALS
NMT 900
TACS
JTACS/NTACS
820 830 840 850 860 870 880 890 900 910 920 930 940 950
MCS
AMPS/NAMPS
960
820 830 840 850 860 870 880 890 900 910 920 930 940 950 960
Uplink Downlink
824 849 869 894
Uplink Downlink
905 935
885
Downlink
925
Uplink
Uplink
915 935
Downlink
Downlink
885 925
Uplink
MHz
1G Frequency Bands
Cellular FUNDEMENTALS
Systems of first generation
SystemYear of
Introduction RegionAccess Mode/Modulation
MCS-L2 1988 (1979) Japan FDMA/PMNMT 450 1981 Scandinavia FDMA/FMNMT 900 1986 Scandinavia FDMA/FMAMPS 1983 North America FDMA/FMNAMPS 1991 North America FDMA/FMTACS 1985 United Kingdom FDMA/FMETACS 1988 United Kingdom FDMA/FMJTACS 1989 Japan FDMA/FMNTACS 1991 Japan FDMA/FMC450 1985 Germany FDMA/FMRadioCom 1985 France FDMA/FM
Cellular FUNDEMENTALS
Second Generation cellular system- Introduction of digital cellular systems (90’s) - development of unified international standard for mobile communications- pan-national roaming- digital encryption- enhanced range of services (data + voice)- low power consumption- light weight, compact and pocket size terminals- TDMA transmission technology- huge capacity
Cellular FUNDEMENTALS
- WORLDWIDE GSM NETWORKS IN SERVICE
Countries with GSM serviceCountries without GSM service
Cellular FUNDEMENTALS
Third generation cellular system
- Multimedia services
- W-CDMA transmission technology
- Large BW
- Higher Bit Rate
- More Services
Cellular FUNDEMENTALS
FUNDAMENTAL OF CELLULAR SYSTEM
Cluster size=7
FUNDAMENTAL OF CELLULAR SYSTEM
• Cell shape
FUNDAMENTAL OF CELLULAR SYSTEM
Area Map
Elevations
Traffic Distribution
Simulation
Design parameters Effect
Drive Test(Optimization )
Drive Test readings
FUNDAMENTAL OF CELLULAR SYSTEM
cell sectorization
FUNDAMENTAL OF CELLULAR SYSTEM
cell sectorization
Sector 1
Sector 2
Sector 3
FUNDAMENTAL OF CELLULAR SYSTEM
F1
F1
F1
F1
F1 F1
F1
FUNDAMENTAL OF CELLULAR SYSTEM
cell sectorization Sector 1
Sector 2Sector 3
Sector 4
Sector 5Sector 6
FUNDAMENTAL OF CELLULAR SYSTEM
cell sectorization
FUNDAMENTAL OF CELLULAR SYSTEM
adaptive power control - as cellular mobile moves power seen at Bs changed - so we use adaptive power control to maintain it
P1P2
FUNDAMENTAL OF CELLULAR SYSTEM
FUNDAMENTAL OF CELLULAR SYSTEM
cell types- macrocell- microcell- picocell
Very small cells
Macrocell BS
BS
BS
Microcell
Microcell
FUNDAMENTAL OF CELLULAR SYSTEM
FUNDAMENTAL OF CELLULAR SYSTEM
Pico Cell
FUNDAMENTAL OF CELLULAR SYSTEM
Satellite
Global Suburban& rural
Urban
Pico-Cell
Micro-Cell Macro-Cell
In-building
Pico-Cell
FUNDAMENTAL OF CELLULAR SYSTEM
cell splitting - as traffic load increases in a cell - to increase channels designer tend to split cell into smaller cells - R decrease Dc decrease so more capacity
FUNDAMENTAL OF CELLULAR SYSTEM channel allocation techniques
- Fixed channel assignment technique (less Ts)
- dynamic channel assignment technique (largest Ts)
- hybrid channel assignment technique (Improved)
1,4,7
2,5,8
3,6,9
1-9 7,8,9
1,4
2,5
3,6
Fixed Dynamic Hybrid
FUNDAMENTAL OF CELLULAR SYSTEM
channel characteristics - Multipath fading
FUNDAMENTAL OF CELLULAR SYSTEM
- It gives a Rayleigh fading distribution- Rayleigh fading is frequency selective
FUNDAMENTAL OF CELLULAR SYSTEM
• To overcome multipath fading we use :- Microscopic diversity and combining techniques
- Frequency hopping
- Error correction
- Interleaving technique
- adaptive power control
FUNDAMENTAL OF CELLULAR SYSTEM
- Microscopic diversity techniques : 1-Time diversity technique
2-Frequency diversity technique
FUNDAMENTAL OF CELLULAR SYSTEM
3-Space diversity technique
FUNDAMENTAL OF CELLULAR SYSTEM
-Space diversity technique
FUNDAMENTAL OF CELLULAR SYSTEM
- Combining techniques :
1-Selective technique
2-Maximal ratio technique 3-Equal gain technique
Receiver
comparator
FUNDAMENTAL OF CELLULAR SYSTEM
- Shadow fading -The Solution of this problem by using Macroscopic Diversity By selecting a BS which is not shadowed when others are.
FUNDAMENTAL OF CELLULAR SYSTEM- Doppler shift - +ve if the mobile moves toward the BS
- -ve if the mobile moves away from the BS- The Doppler frequency shift should be compensated so that
a correct frequency synchronization is achieved .
FUNDAMENTAL OF CELLULAR SYSTEM
- Co-channel interference
Dc
FUNDAMENTAL OF CELLULAR SYSTEM
- Adjacent channel interference
Frequency
Signal level (dB)
Filter
Required ch.
Adjacent channel interference
FUNDAMENTAL OF CELLULAR SYSTEM
- Channel management
1,8,15
2,9,16
5,12,19
6,13,20
7,14,21
4,11,18
3,10,17
Frequency (MHz)
Amplitude
FUNDAMENTAL OF CELLULAR SYSTEM
- Delay Spread (Time dispersion)
- Due to multipath fading
- To overcome this we use delay equalizer
1 2 3 4 65
1 2 3 4 65
Path 1
Path 2
FUNDAMENTAL OF CELLULAR SYSTEM
- Distance between MS and BS
- This makes Time alignment Problem
- To overcome this system should respond to this delay
T1 T2 T3
AB
A
B
FUNDAMENTAL OF CELLULAR SYSTEM
- Path lossPr α Pt
Rβ
β = 3 ~ 4
Signal level (dB)
Distance
FUNDAMENTAL OF CELLULAR SYSTEM
- Combined signal loss
Path loss
Rayleigh fading
Shadowing
Signal level (dB)
Log d