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Wireless Networks
Satellite
Systems
Cellular
Networks
Wireless LANs
Example1:
GSM, 9.6 Kbps,
wide coverage
Example2:
3G, 2 Mbps,
wide coverage
Example1:
802.11b
11 Mbps,
100 Meters
Otherexamples:
802.11g,
HiperLAN2
Wireless WANs
Personal
Area
Networks
Business
LANs
Example1:
Bluetooth
1 Mbps,
10 Meters
Other examples:wireless sensor
networks, UWB
Example1:
Motorola
Iridium
up to 64 Mbps
globally
Example 2:
Deep space
communication
Wireless
Local Loops
(Fixed Wireless)
Wireless MANs
Example1:
LMDS
37 Mbps,
2-4 Km
Example2:
FSO
1.25 Gbps
1-2 KM
Paging
Networks
Example1:
FLEX,
1.2 Kbps
Example2:ReFLEX,
6.4Kbps
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Cellular Networks
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Outline
Fundamentals of cellular network
Brief History of cellular network
GSM
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Copyright: A. Umar
A Cellular Network
Public
Switched
Telephone
Network(PSTN)
And
internet
Mobile
Switching
Center
(MSC)
Base Transceiver Station (BTS)Mobile User
Cell 1
Cell 2
Cordless connection
Wired connection
HLR VLR
HLR = Home Location Register
VLR = Visitor Location Register
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Introduction to cellular networks
Cell covers specific geographical region
BTS(Base transceiver station)
Create cell (similar to Access point)
Mobile station(MS)
Attached to network through BTS
Mobile switching center (MSC)
Connect cell to wide area net
Manages call setups
handles mobility (HLR,VLR)
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History
1G: Basic mobile telephony service analog cellular technology
American Mobile Phone (AMPS) and NMT in Europe
Uses FDMA
2G: service for mass users
Digital cellular technology
D-AMPS: combines FDMA/TDMA
Global System for mobile Communication (GSM ) Combines FDMA/TDMA
Code Division multiple Access(CDMA)
Uses CDMA
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History
2.5G:Mobile Internet/data services together withvoice services
Packet switching technology adding into 2G
Two types :evolved from GSM General Packet Radio Service(GPRS )
Enhanced data rates for global Evolution (EDGE)
EDGE provides a better data rates using enhanced
modulation
CDMA -2000
Evolved from the CDMA
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History
3G: Broad Band internet, multimedia andemerging new applications
Universal Mobile TelecommunicationSystem(UMTS) GSM next step, using CDMA
CDMA-2000 1x EV-DO(Evolution-Data Optimized)
Uses CDMA/TDMA
up to 3Mbps
144 kbps - 384 kbps for high-mobility, highcoverage
2 Mbps for low-mobility and low coverage
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History
4G: LTE ( Long Term Evolution )
More on seminar
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Copyright: A. Umar
1G(
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Cellular concepts
0G Wi d d
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Copyright: A. Umar
0G Wire ess o d days Mobile radio telephones were used for military
communications in early 20th century
Car-based telephones first introduced in mid 1940s Single large transmitter on top of a tall building
Single channel used for sending and receiving
To talk, user pushed a button, enabled transmission and
disabled reception.Became known as push-to-talk . CB-radio, taxis, police cars use this technology
IMTS (Improved Mobile Telephone System)introduced in 1960s
Used two channels (one for sending, one for receiving) No need for push-to-talk
Used 23 channels from 150 MHz to 450 MHz
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First-Generation Cellular
Advanced Mobile Phone Service (AMPS) invented atBell Labs and first installed in 1982
Key ideas:
Exclusively analog
Geographical area divided into cells (typically 10-25km)
Cells are small: Frequency reuse exploited in nearby (not
adjacent) cells
As compared to IMTS, could use 5 to 10 times more users in
same area by using frequency re-use (divide area into cells)
Smaller cells also required less powerful, cheaper, smaller
devices
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Copyright: A. Umar
Cellular Network Organization Cell design (around 5km radius)
Served by base station consisting of transmitter,receiver, and control unit
Base station (BS) antenna is placed in highplaces ( high rise buildings) -
Operators pay per month for BS Different frequencies assigned to each cell
Cells set up such that antennas of all neighbors areequidistant (hexagonal pattern)
In North America, two 25-MHz bands allocated toAMPS
One for transmission from base to mobile unit
One for transmission from mobile unit to base
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possible radio coverage of the cell
(omni-directional)
idealized shape of the cellcell
segmentation of the area into cellscellular network concepts
use of several carrier frequencies
not the same frequency in adjoining cells
cell sizes vary from some 100 m up to 35 km depending on user density,
geography, transceiver power etc.
hexagonal shape of cells is idealized (cells overlap, shapes depend ongeography)
if a mobile user changes cells handover of the connection to the neighbor cell
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Copyright: A. Umar
E
A
DF
G C
B
E
A
DF
G C
B
E
A
DF
G C
B
Cell Design
Cells grouped into a cluster of seven
Letters indicate frequency use
For each frequency, a buffer of two cells is used before reuse
To add more users, smaller cells (microcells) are used
Frequencies may not need to be different in CDMA (soft handoff)
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How to accommodate many users?
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Approaches to Increase Capacity
Adding/reassigning channels - some channelsare not used for traffic
Frequency borrowing frequencies are takenfrom adjacent cells by congested cells. High traffic cells borrows channel from low traffic
cells
Cell splitting cells in areas of high usage canbe split into smaller cells Decrease the transmission power
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Cellular hierarchy
Femtocell- smallest unit of the hierarchy
Cover only few meters where devices are in thephysical range of the user. e.g. WPANs
Picocells: covers few tens of meters. E.g. WLAN
Microcells :covers hundreds of meters
Macrocells: several kilometer coverage
Megacells: national wide coverage.
E.g Satellites
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Global System for Mobile Communication
(GSM)
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GSM Overview Formerly: Groupe Spciale Mobile (founded 1982)
Now: Global System for Mobile Communication
Pan-European standard (ETSI, EuropeanTelecommunications Standardization Institute)
Goal: was to provide a mobile phone system that allowsusers to roam throughout Europe and provides voiceservices compatible to ISDN and other PSTN systems.
Today many providers all over the world use GSM(219 countries in Asia, Africa, Europe, Australia, America)
more than 5 billion subscribers in more than 800 networks
more than 80% of all digital mobile phones use GSM
Today more people use mobile phone system than thefixed telephones than toilets!
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GSM Technologies
A 2G cellular network (a digital network for voice
communication) Circuit switching for voice (mainly)/data (limited)
transmission rate Connection-oriented service: establish a communication path
(channel) for point-to-point communication
Multiplexing Frequency division multiplexing (FDM) plus Time division
multiplexing (TDM) (adding to Space division multiplexing,
SDM) Uses 124 pair of channels per cell, each channel can support 8
users through TDM (992 users max actually 500 users)
Some channels are used for control signals, etc
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Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de MC -
2011
1 2 3 4 5 6 7 8
higher GSM frame structures
935-960 MHz
124 channels (200 kHz)
downlink
890-915 MHz124 channels (200 kHz)
uplink
time
GSM TDMA frame
GSM time-slot (normal burst)
4.615 ms
546.5 s577 s
tail user data TrainingSguard
space S user data tailguard
space
3 bits 57 bits 26 bits 57 bits1 1 3
GSM - TDMA/FDMA
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GSM Technologies..
Mobility management Two-tier architecture: HLR and VLR
Location area for location update together withpaging for searching
Services
Mainlyfor voice communication
Data communication is very limited (i.e., 9.6kbit/s)
and supporting SMS
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Performance Characteristics of GSMComparing with 1G cellular network
Communication Mobile communication for voice and data services
Total mobility International access, chip-card enables use of access points of different
providers (roaming services)
Worldwide connectivity One number, the network handles localization and interoperability
High capacity Better frequency efficiency (frequency reuses), smaller cells, more customers
per cell
High transmission quality High audio quality and reliability for wireless, uninterrupted phone calls at
higher speeds (e.g., from cars, trains)
Security functions
encryption, authentication via chip-card and PIN
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GSM: Mobile Services
GSM offers
several types of connections voice connections, data connections, short
message service
voice communication services Basic telephony
Emergency number common number throughout Europe (112); mandatory
for all service providers; free of charge; connection withthe highest priority (preemption of other connectionspossible)
Voice mailbox
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GSM: Mobile Services
Non-Voice-services group 3 fax
electronic mail ( Message Handling System,
implemented in the fixed network) Short Message Service (SMS)
alphanumeric data transmission to/from themobile terminal (160 characters) using the
signaling channel, thus allowing simultaneoususe of basic services and SMS(almost ignored inthe beginning now the most successful add-on!)
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GSM: Mobile Services.
Supplementary service :May differ between
different service providers, countries and protocol
versions
Caller identification: CallerID forwarding of caller number:callDiverting
automatic call-back
conferencing with up to 7 participants
locking of the mobile terminal (incoming or outgoingcalls)
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Architecture of the GSM System
GSM is a PLMN (Public Land Mobile Network) Main components
MS (mobile station)
BS (base station)
MSC (mobile switching center) LR (location register)
Subsystems
RSS (radio subsystem): covers all radio aspects
NSS (network and switching subsystem): call forwarding, handover,switching
OSS (operation subsystem): management of the network
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Components
Mobile
Station
Base
Transceiver
Station
switching
center
Database
Management
http://localhost/var/www/apps/conversion/tmp/scratch_2/?rm=show_details&modell=1380http://localhost/var/www/apps/conversion/tmp/scratch_2/?rm=show_details&modell=13807/28/2019 Chapter 5-Cellular Networks - Copy
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Prof. Dr.-Ing. Jochen H. Schiller
www.jochenschiller.de MC -
2009
GSM: overview
fixed network
BSC
BSC
MSC MSC
GMSC
OMC, EIR,
AUC
VLR
HLR
NSS
with OSS
RSS
VLR
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Um
Abis
ABSS
radio
subsystem
MS MS
BTS
BSCBTS
BTS
BSCBTS
network and
switching subsystem
MSC
MSC
fixed
partner networks
IWF
ISDN
PSTN
PSPDN
CSPDN
SS7
EIR
HLR
VLR
ISDN
PSTN
GSM: system architecture
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System architecture: radio subsystem
Components MS (Mobile Station) BSS (Base Station Subsystem):
consisting of BTS (Base Transceiver Station):
sender and receiver
BSC(Base Station Controller):
controlling several transceivers
Interfaces Um : radio interface
Abis : standardized, open interfacewith 16 kbit/s user channels
A: standardized, open interface with64 kbit/s user channels
Um
Abis
A
BSS
radio
subsystem
network and switching
subsystem
MS MS
BTS
BSC MSCBTS
BTSBSC
BTS
MSC
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Radio subsystem
The Radio Subsystem (RSS) comprises the cellularmobile network up to the switching centers
Components Base Station Subsystem (BSS):
Base Transceiver Station (BTS):
radio components including sender, receiver, antenna
if directed antennas are used one BTS can cover several cells
Base Station Controller (BSC):
switching between BTSs, controlling BTSs,
mapping of radio channels (Um) onto terrestrial channels (A
interface) BSS = BSC + sum(BTS)
Mobile Stations (MS) MS=ME(mobile Equipment ) + SIM( subscriber identity module)
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Base Transceiver Station and Base
Station Controller
Tasks of a BSS are distributed over BSC and BTS
BTS comprises radio specific functions
BSC is the switching center for radio channels
Functions BTS BSC
Management of radio channels X
Frequency hopping (FH) X X
Management of terrestrial channels X
Mapping of terrestrial onto radio channels X
Channel coding and decoding X
Rate adaptation X
Encryption and decryption X X
Paging X X
Uplink signal measurements X
Traffic measurement X
Authentication X
Location registry, location update X
Handover management X
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Mobile station
Terminal for the use of GSM services
Mobile Equipment (ME)
represents physical terminals, such as a mobile or PDA.
Subscribers identity module (SIM) Stores all user specific data(Static)
i.e Card-type, subscribed service, personal identity
number(PIN) ,PIN unblocking key (PUK), International
mobile subscriber identity(IMSI) ,phone book.
MS=ME + SIM
System architecture: network and
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System architecture: network and
switching subsystem Components
MSC (Mobile Services Switching Center): IWF (Interworking Functions) ISDN (Integrated Services Digital Network) PSTN (Public Switched Telephone Network) PSPDN (Packet Switched Public Data Net.) CSPDN (Circuit Switched Public Data Net.)
Databases HLR (Home Location Register) VLR (Visitor Location Register) EIR (Equipment Identity Register)
Protocol SS7 (signaling system no. 7)
network
subsystem
MSC
MSC
fixed partner
networks
IWF
ISDN
PSTN
PSPDN
CSPDN
SS7
EIR
HLR
VLR
ISDN
PSTN
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Network and switching subsystem
NSS is the main component of the public mobile network GSM Switching, Hand over , mobility management ( localization ),
Components Mobile Services Switching Center (MSC)
controls all connections via a separated network to/from a mobileterminal within the domain of the MSC - several BSC can belong to a
MSC
Databases (important: scalability, high capacity, low delay)
Home Location Register (HLR)
central master database containing user data, permanent and semi-permanent data of all subscribers assigned to the HLR (one provider
can have several HLRs)
Visitor Location Register (VLR)
local database for a subset of user data, including data about all user
currently in the domain of the VLR
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Mobile Services Switching Center The MSC (mobile services switching center) plays a
central role in GSM
switching functions ( b/n BSC)
Hand over functions for mobility support
management of network resources
interworking functions via Gateway MSC (GMSC)
integration of several databases.
location registration and forwarding of locationinformation
provision of new services (fax, data calls)
support of short message service (SMS)
generation and forwarding ofaccounting and billinginformation
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GSM: elements and interfaces
NSS
MS MS
BTS
BSC
GMSC
IWF
OMC
BTS
BSC
MSC MSC
Abis
Um
EIR
HLR
VLR VLR
A
BSS
PDN
ISDN, PSTN
RSS
radio cell
radio cell
MS
AUCOSS
signaling
O
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Operation subsystem
enables centralized management and maintenance of allGSM subsystems Components
Authentication Center (AUC) Used to protect user identity and data transmission.
authentication parameters and Encryption keys aregenerated and stored May be situated in special protected part of the HLR
Equipment Identity Register (EIR) registers GSM mobile stations devices Black list(stolen or locked ), Gray list( malfunctioning MS) White list (Valid devices)
Operation and Maintenance Center (OMC) control and monitor radio subsystem and the network
subsystem entities via the O interface . Traffic monitoring , status report of the network entities
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Copyright: A. Umar
Databases recap
Mobile Switching Center (MSC) is at core; consists ofseveral databases
Home location register (HLR) database storesinformation about each subscriber that belongs to it
Visitor location register (VLR) database maintainsinformation about subscribers currently physically inthe region
Authentication center database (AuC) used forauthentication activities, holds encryption keys
Equipment identity register database (EIR) keepstrack of the type of equipment that exists at themobile station
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GSM frequency bands
Type Channels Uplink [MHz] Downlink [MHz]
GSM 850 128-251 824-849 869-894
GSM 900
classical
extended
0-124, 955-1023
124 channels
+49 channels
876-915
890-915
880-915
921-960
935-960
925-960
GSM 1800 512-885 1710-1785 1805-1880
GSM 1900 512-810 1850-1910 1930-1990
GSM-R
exclusive
955-1024, 0-124
69 channels
876-915
876-880
921-960
921-925
- Please note: frequency ranges may vary depending on the country!
- Channels at the lower/upper edge of a frequency band are typically not used
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Example coverage of GSM networks (www.gsmworld.com)T-Mobile (GSM-900/1800) Germany O2 (GSM-1800) Germany
AT&T (GSM-850/1900) USA Vodacom (GSM-900) South Africa
(GS 900)
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ETMTN (GSM-900) Ethiopia
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Localization and calling
To always know where a user currently is , GSM
performs periodic location updates even if the MS
is not in use( as long as it is logged on to the GSM
network ). HLR always contains info about the current location
VLR of the MSC informs the HLR about the location
change.
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Localization
To locate the MS several numbers are needed. Mobile subscriber international ISDN number (MSISDN)
Phone number E.g. +251917111213
country code (CC) (+251) Ethiopia
National Destination code(NDC). ( 917 ) Jimma
Subscriber number(SN)..(111213) individual
International mobile subscriber identity (IMSI)
Used by the network provider
Mobile country code (MCC) Mobile network code (MNC)-code of network provider
Mobile subscriber identification number (MSIN)
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Localization
Temporary mobile subscriber identity (TMSI) To hide the IMSI by BSC
By the VLR
Mobile station roaming number (MSRN)
Temporary address to hide the identity and location of asubscriber by MSC Visitor country code (VCC)
Visitor national destination code(VNDC)
International mobile Equipment identity (IMEI) Unique code to each mobile equipment
device specific theft protection
Stored in EIR( Equipment identity register )
Dial *#06#
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Mobile Terminated Call(MTC)
PSTNcalling
stationGMSC
HLR VLR
BSSBSSBSS
MSC
MS
1 2
3
45
6
7
8 9
10
11 12
1316
10 10
11 11 11
14 15
17
1: calling a GSM subscriber 2: forwarding call to GMSC
3: signal call setup to HLR
4, 5: request MSRN from VLR
6: forward responsible
MSC to GMSC
7: forward call to
current MSC
8, 9: get current status of MS
10, 11: paging of MS
12, 13: MS answers
14, 15: security checks
16, 17: set up connection
Mobile Originated Call(MOC)
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Prof. Dr.-Ing. Jochen H. Schiller www.jochenschiller.de MC - 2009
Mobile Originated Call(MOC)
1, 2: connection request
3, 4: security check
5-8: check resources (free circuit)
9-10: set up call
PSTNGMSC
VLR
BSS
MSC
MS1
2
6 5
3 4
9
10
7 8
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MTC/MOCBTSMS
paging request
channel request
immediate assignment
paging response
authentication request
authentication response
ciphering commandciphering complete
setup
call confirmed
assignment command
assignment complete
alerting
connect
connect acknowledge
data/speech exchange
BTSMS
channel request
immediate assignment
service request
authentication request
authentication response
ciphering commandciphering complete
setup
call confirmed
assignment command
assignment complete
alerting
connect
connect acknowledge
data/speech exchange
MTC MOC
GSM R i
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GSM Roaming
The ability for a cellular customer to automaticallymake and receive voice calls, send and receive data, oraccess other services when travelling outside thegeographical coverage area of the home network, by
means of using a visited network. Roaming Agreements between network operators
required .
National Roaming(visited network in the same country as
the home network) International Roaming( visited network is outside the
home country)
H R i W k
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How Roaming Works
Subscribe for the roaming service roaming agreement is needed b/n operators .
Phone support the radio frequency
e.g. 850, 900, 1800 and 1900 MHz
Switch on your phone in the foreign network.
Note that when roaming you have to pay both
for calls that you make and receive.
GSM d t k i f
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GSM coverage and network info
ETHIOPIA
Network Information Operator: Ethiopian Telecommunications
Corporation Also known as: ETMTN Currently : Ethiotelecom
Technology: GSM
Frequency: 900
Launch Date: APR 1999
Services Short Message Service
Source :www.mobileworldlive .com
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Roaming Partners: ETMTN A Afghanistan, Albania, Algeria, Angola, Argentina, Armenia, Australia, Austria,
Azerbaijan, B Bahrain, Bangladesh, Belarus, Belgium, Benin, Bosnia Herzegovina,Botswana, Brazil, Bulgaria, Burkina Faso, Burundi,C Cameroon, Canada, Chad, China,Comoros, Congo, Cote D Ivoire, Croatia, Cyprus, Czech Republic, D Denmark, DjibouitE Egypt, Equatorial Guinea, Estonia, F Finland, France, G Gabon, Gambia, Georgia,Germany, Ghana, Greece, Guinea, Guinea Bissau, H Hong Kong, Hungary, I Iceland
India, Indonesia, Iran, Iraq, Ireland, Israel, Italy, J Jamaica, Japan, Jordan,K Kazakhstan, Kenya, Korea, Kuwait, L Latvia, Lebanon, Lesotho, Liberia, Libya,Liechtenstein, Lithuania, Luxembourg, M Madagascar, Malawi, Malaysia, Mali ,MaltaMauritius, Mexico, Mongolia, Morocco, Mozambique, N Namibia, Netherlands,Niger, Nigeria, Norway, O Oman, P Pakistan, Panama, Papua New Guinea,Philippines, Poland, Portugal, Puerto Rico, Q Qatar, R Romania, Russia, Rwanda,S Saudi Arabia, Senegal, Serbia, Seychelles, Sierra Leone, Singapore, Slovakia,Slovenia, South Africa, Spain, Sri Lanka, Sudan, Swaziland, Sweden, Switzerland,
Syria,T Tanzania, Thailand, Togo, Trinidad and Tobago, Tunisia, Turkey, Turkmenistan,U Uganda, Ukraine, United Arab Emirates, United Kingdom, United States, Uruguay,Uzbekistan, Y Yemen, Z Zambia, Zimbabwe.
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Hand over
Hand off is used to provide continuity ofservices while a mobile unit moves from one
cell to another.
hand off is necessary due to the limited powerof the MS and BTS
Reason for hand over
> Low signal strength ( out of cell range ) > Load balancing (too high in one cell)
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Hand over
Hand off parameters (measurements)
word error indicator( WEI)
Demodulation error
Received signal strength indicator (RSSI)
Quality indicator (QI)
Quality with respect to interference
The handoff algorithm will be based on thevalue of this parameters .(threshold value )
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Types of handover
In general there are 3 types of handovers forcellular network. Mobile controlled hand over (MCHO)
Mobile unit measures the parameters and make handover
decision by itself . Network controlled hand over (NCHO)
Base station measures the parameters and makes thehandover decision.
Mobile Assisted hand over (MCHO) Mobile unit measures the parameters and sends the values
to the network.
Then the base station(BS) makes the hand over decision.
Used by GSM.
4 types of GSM handover
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4 types of GSM handover
MSC MSC
BSC BSCBSC
BTS BTS BTSBTS
MS MS MS MS
1
2 3 4
1. Intracell HO
2. Intercell /Intra-BSC HO
3. Inter-BSC/Intra-MSC HO
4. Inter-MSC HO
Handover decision
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Handover decision
receive level
BTSold
receive level
BTSnew
MS MS
HO_MARGIN
BTSold BTSnew
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Hand off decisions algorithms
Using Relative signal strength
Switch to BTS with better signal
Using Relative signal strength and threshold
Switch to BTS with better signal plus threshold
Common hand of problems
False handoff(multipath propagation )
Ping pond effect
Handover procedure
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Handover procedure
HO access
BTSold BSCnew
measurement
result
BSCold
Link establishment
MSCMS
measurement
report
HO decision
HO required
BTSnew
HO request
resource allocation
ch. activation
ch. activation ackHO request ackHO commandHO commandHO command
HO completeHO completeclear commandclear command
clear complete clear complete
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63
GSM Evolution review
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Evolution of cellular communication
Services
From voice communication to voice and data
communication
Technologies
From circuit switching to packet switching
High speed circuit switched data
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High-speed circuit-switched data
(HSCSD)
is an enhancement to the original data
transmission mechanism of the GSM system,
four times faster than GSM, up to 38.4 kbit/s.
circuit-switched mode.
Higher speeds are achieved as a result of
superior coding methods, and the ability to
use multiple time slots to increase data
throughput.
High Speed Circuit Switched Data
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High Speed Circuit Switched Data
(HSCSD)
General Packet Radio Service
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General Packet Radio Service
(GPRS)
2.5G is a packet oriented mobile data service.
usage charging is based on volume of data.
Use packet switching method.
provides data rates of56-114 kbps GPRS extends the GSM Packet circuit switched data
capabilities and makes the following services possible: "Always on" internet access
Multimedia messaging service (MMS) Push to talk over cellular (PoC/PTT)
Instant messaging (IM)
Global Packet Radio Service
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Global Packet Radio Service
(GPRS)
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Evolution ofGSM
EDGE (Enhanced Data rate for GSM Evolution) 2.5 G , also known as Enhanced GPRS (EGPRS)
new modulation scheme, GMSK(Gaussian minimum-shift keying) &8PSK ( 8 phase shift keying)
384 kbps is the maximum data rate
designed for service providers that may or may not migrate to UMTS
UMTS (Universal Mobile Telecommunications Systems)
3G
144kbps for vehicular access
384 kbps for wide-area coverage (pedestrian) 2 Mbps for local coverage (stationary)
WCDMA (wideband CDMA)
Adopted by Europe and Japan
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Evolution of CDMA
CDMA2000 1X 2.5G
use CDMA channel access, to send voice, data, andsignaling data between mobile phones and cell sites.
up to 153 kbps
CDMA2000 1xEV-DO (Evolution-Data Optimized)
3G
broadband Internet access
Uses CDMA/TDMA
up to 3Mbps