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CCM 4300 Lecture 16Computer Networks, Wireless and Mobile
Communication Systems
1
3G, 4G, Satellite and Bluetooth Communications
Dr S Rahman
Session Content� Recap of last session
� Lesson Objectives
� Roadmap to Cellular services
� Evolution to 3G standard
� Introduction to 4G systems
2
� Introduction to 4G systems
� Satellite Systems – LEO, MEO, GEO, Handover
� Bluetooth – PAN, Protocols, Architecture, Security
� Summary
Recap of Last Session
� What are cellular services and GSM
� GSM and it’s detailed architecture
� Why GSM is the backbone of Mobile Services
� GSM Security, Handover
3
� Move from GSM to GPRS
� UMTS standards
Lecture objectivesAt the completion of this lecture you should be able to:
� Understand the roadmap towards 4G mobile services/systems
� Use of satellite systems in mobile communications
� Various satellite systems – LEO, MEO, GEO and their handover operation
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� Various satellite systems – LEO, MEO, GEO and their handover operation
� Bluetooth and its architectural details
IMT-2000
• ITU’s approach to 3G wireless
• “Umbrella” activity from ITU:
• mainly European interest, though international in theory
• Intended to provide:
• coordination between different 2.5/3G systems
• harmonisation of services to allow use efficient of
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• harmonisation of services to allow use efficient of
Spectrum
• http://www.umts-forum.org/imt2000.html
IMT: international Mobile Communications
Simplified Roadmap – one to another
GSM
only
(+SMS)
EDGE
UMTS
2G2.5G
3G (IMT-2000)
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GSM GSM + GPRS
GSM
only
(+SMS)
UMTS
IS-136
TDMA
D-AMPS
GSM
PDC
GPRS
IMT-DS
EDGE
AMPSNMT
IMT-SC
IS-136HS
UWC-136
CT0/1
CT2IMT-FT
DECT
TD
MA
FD
MA
Development of mobile telecommunication systems
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1G 2G 3G2.5G
IS-95
cdmaOne
IMT-DS
UTRA FDD / W-CDMA
IMT-TC
UTRA TDD / TD-CDMA
cdma2000 1X
1X EV-DV
(3X)
IMT-TC
TD-SCDMACD
MA
IMT-MC
cdma2000 1X EV-DO
GLOBAL EVOLUTION TO 3G MULTIRADIO NETWORKS
GSM
TDMA
UMTS Multiradio Network
WCDMA(Wideband Code Division Multiple Access)Internet, multimedia, video and other capacity-demanding applications.
GSM/GPRS/EDGEGSM/GPRS
cdma2000 1xEV-DV
cdma2000 1xEV-DO
cdmaOne cdma2000 1x
3G Phase 1 Evolved 3G Networks
2G
First Steps to 3G
Internet, multimedia, video and other capacity-demanding applications.
PDC
?
Performance characteristics of GSM (wrt. analog sys.)
Communication
�mobile, wireless communication; support for voice and data services
Total mobility
�international access, chip-card enables use of access points of different providers
Worldwide connectivity
�one number, the network handles localization
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�one number, the network handles localization
High capacity
�better frequency efficiency, 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
�access control, authentication via chip-card and PIN
Disadvantages of GSMThere is no perfect system!!
�no end-to-end encryption of user data (was developed in Surrey)
�no full ISDN bandwidth of 64 kbit/s to the user, no transparent B-channel
�reduced concentration while driving
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�reduced concentration while driving
�electromagnetic radiation
�abuse of private data possible
�roaming profiles accessible
�high complexity of the system
�Incompatibilities within the GSM standards
•http://www.gsmworld.com/
• http://www.umts-forum.org/
• http://www.uwcc.org/
Universal Wireless Communications Consortium
• http://www.3gpp.org/
GSM and 3G – more information can be found at ...
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• http://www.3gpp.org/
Third Generation Partnership Project
• Not covered in these notes, however, …
http://www.wapforum.org/
Wireless Application Protocol Forum
4G Systems
• 4G refers to the next generation of wireless
technology that promises higher data rates and
expanded multimedia services.
• 4G network as one that operates on Internet
technology, combines it with other applications and
technologies such as WiFi and WiMAX, and runs at
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technologies such as WiFi and WiMAX, and runs at
speeds ranging from 100 Mbps (in cell-phone
networks) to 1 Gbps (in local WiFi networks).Totally packet-based:
• IPv6
• Higher data rates:
• up to 100Mb/s
• Better security
• Totally digital
Key 4G technologies:
• Orthogonal Frequency Division Multiplexing
(OFDM)
• Software Defined Radio (SDR)
• Multiple-input multiple-output ( MIMO )
Basics – Satellite Systems
� elliptical or circular orbits
� complete rotation time depends on distance satellite-earth
� inclination: angle between orbit and equator
� elevation: angle between satellite and horizon
� LOS (Line of Sight) to the satellite necessary for connection
� high elevation needed, less absorption due to e.g.
buildings
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buildings
� Uplink: connection base station - satellite
� Downlink: connection satellite - base station
� typically separated frequencies for uplink and downlink
– transponder used for sending/receiving and shifting of
frequencies
– transparent transponder: only shift of frequencies
– regenerative transponder: additionally signal regeneration
�Traditionally
weather satellites
radio and TV broadcast satellites
military satellites
satellites for navigation and localization (e.g., GPS)
�Telecommunication
Applications – Satellite Systems
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global telephone connections
backbone for global networks
connections for communication in remote places or
underdeveloped areas
global mobile communication
� satellite systems to extend cellular phone systems (e.g.,
GSM or AMPS)
Satellite systems
•LEO and MEO:
• satellite constellations
• no terrestrial network
support
• “total” area coverage
• Very expensive:
•Service providers finding
it hard to break into the market
• Safety concerns:
• MS power output
• Voice only systems
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• Very expensive:
• to construct and maintain
to use
• Complex:
• hand-off between satellites
• routing
• Voice only systems
• Voice and data systems
• Broadband systems
• Will they succeed?
Inter Satellite Link (ISL)
Mobile User Link (MUL) Gateway Link
(GWL)
small cells (spotbeams)
GWL
MUL
Classical satellite systems
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base stationor gateway
footprint
User data
PSTNISDN GSM
PSTN: Public Switched Telephone Network
Four different types of satellite orbits can be identified
depending on the shape and diameter of the orbit:
�GEO: geostationary orbit, ca. 36000 km above earth
surface
�LEO (Low Earth Orbit): ca. 500 - 1500 km
Orbits I
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�LEO (Low Earth Orbit): ca. 500 - 1500 km
�MEO (Medium Earth Orbit) or ICO (Intermediate
Circular Orbit): ca. 6000 - 20000 km
�HEO (Highly Elliptical Orbit) elliptical orbits
Orbit 35,786 km distance to earth surface, orbit in equatorial plane
(inclination 0°)
� complete rotation exactly one day, satellite is synchronous to earth rotation
�fix antenna positions, no adjusting necessary
�satellites typically have a large footprint (up to 34% of earth surface!),
Geostationary satellites
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�satellites typically have a large footprint (up to 34% of earth surface!), therefore difficult to reuse frequencies
�bad elevations in areas with latitude above 60° due to fixed position above the equator
�high transmit power needed
�high latency due to long distance (ca. 275 ms)
� not useful for global coverage for small mobile phones and data transmission, typically used for radio and TV transmission
Orbit ca. 500 - 1500 km above earth surface
�visibility of a satellite ca. 10 - 40 minutes
�global radio coverage possible
�latency comparable with terrestrial long distance connections, ca. 5 - 10 ms
�smaller footprints, better frequency reuse
�but now handover necessary from one satellite to another
LEO systems
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�but now handover necessary from one satellite to another
�many satellites necessary for global coverage
�more complex systems due to moving satellites
Examples:
Iridium (start 1998, 66 satellites)
�Bankruptcy in 2000, deal with US DoD (free use, saving from “deorbiting”)
Globalstar (start 1999, 48 satellites)
�Not many customers (2001: 44000), low stand-by times for mobiles
Orbit ca. 5000 - 12000 km above earth surface comparison with LEO systems:
�slower moving satellites
�less satellites needed
�simpler system design
�for many connections no hand-over needed
MEO systems
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�higher latency, ca. 70 - 80 ms
�higher sending power needed
�special antennas for small footprints needed
Example:
ICO (Intermediate Circular Orbit, Inmarsat) start ca. 2000
�Bankruptcy, planned joint ventures with Teledesic, Ellipso – cancelled again, start planned for 2003
• One solution: inter satellite links (ISL)
• reduced number of gateways needed
• forward connections or data packets within the satellite network
as long as possible
• only one uplink and one downlink per direction needed for the
connection of two mobile phones
Routing (Passing Information Between satellites)
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connection of two mobile phones
• Problems:
• more complex focusing of antennas between satellites
• high system complexity due to moving routers
• higher fuel consumption thus shorter lifetime
• Iridium and Teledesic planned with ISL (Inter Sattelite Link)
• Other systems use gateways and additionally terrestrial networks
• Mechanisms similar to GSM
• Gateways maintain registers with user data
– HLR (Home Location Register): static user data
– VLR (Visitor Location Register): (last known) location of the mobile
station
– SUMR (Satellite User Mapping Register):
• satellite assigned to a mobile station
Localisation of Mobile Stations
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• satellite assigned to a mobile station
• positions of all satellites
• Registration of mobile stations
– Localisation of the mobile station via the satellite’s position
– requesting user data from HLR
– updating VLR and SUMR
• Calling a mobile station
– localization using HLR/VLR similar to GSM
– connection setup using the appropriate satellite
• Several additional situations for handover in satellite systems compared to cellular terrestrial mobile phone networks caused by the movement of the satellites
– Intra satellite handover
• handover from one spot beam to another
Spot beams are used so that only earth stations in a particular intended reception area can properly receive the satellite signal.
• mobile station still in the footprint of the satellite, but in another cell
Handover in Satellite Systems
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• mobile station still in the footprint of the satellite, but in another cell
– Inter satellite handover
• handover from one satellite to another satellite
• mobile station leaves the footprint of one satellite
– Gateway handover
• Handover from one gateway to another
• mobile station still in the footprint of a satellite, but gateway leaves the footprint
– Inter system handover (VERTICAL?)
• Handover from the satellite network to a terrestrial cellular network
• mobile station can reach a terrestrial network again which might be cheaper, has a lower latency etc.
Bluetooth: “Personal Area” wireless connectivity
•Universal radio interface for ad-hoc wireless connectivity
•Interconnecting computer and peripherals, handheld
devices, PDAs, cell phones – replacement of IrDA
•Embedded in other devices, goal: £5/device (2002:
£50/USB bluetooth), (Mini Bluetooth Network adapter
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£50/USB bluetooth), (Mini Bluetooth Network adapter
USB £6)
•Short range (10m), low power consumption, license-free
2.45 GHz ISM
•Voice and data transmission, approx. 1 Mbit/s gross data
rate
•Bluetooth 2.0 Enhanced Data Rate (EDR) 2.1 Mbit/s
Inter-device connections
Scenario 1:
• PDA, mobile phone, laptop
• PDA ⇔ mobile phone: 1 cable
• PDA ⇔ laptop: another (different) cable
• mobile phone ⇔ laptop: yet another (different) cable
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• mobile phone ⇔ laptop: yet another (different) cable
Scenario 2:
• desktop computer, PDA, laptop all need to use printer
• again, more cables, hard to configure
• standard wireless inter-device
communication?
Bluetooth: The Rational
• Standard, convenient device inter-connectivity
• Mobile phones, headsets, PDAs, laptops:
• coffee machines, utility meters, hi-fi equipment, etc.
• Simple, low-cost, radio-based system:
• simple, “wire-replacement” system, re-use existing
standards
26
standards
• aiming for cost of ~£5 to build into a device
• uses ISM radio band (2.4000-2.4835GHz)
• http://www.bluetooth.com/
• Named after a Viking called Harald Bluetooth
Bluetooth: Characteristics• 2.4 GHz ISM band, 79 (23) RF channels, 1 MHz carrier spacing
– Channel 0: 2402 MHz … channel 78: 2480 MHz
– G-FSK modulation, 1-100 mW transmit power
• FHSS and TDD
– Frequency hopping with 1600 hops/s
– Hopping sequence in a pseudo random fashion, determined by a master
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master
– Time division duplex for send/receive separation
• Voice link – SCO (Synchronous Connection Oriented)
– FEC (forward error correction), no retransmission, 64 kbit/s duplex, point-to-point, circuit switched
• Data link – ACL (Asynchronous Connectionless)
– Asynchronous, fast acknowledge, point-to-multipoint, up to 433.9 kbit/s symmetric or 723.2/57.6 kbit/s asymmetric, packet switched
• Topology - Overlapping piconets (stars) forming a scatternet
Bluetooth Architecture: An overview•Two link types:
• synchronous, connection oriented (SCO)
• asynchronous, connection-less (ACL)
• Bi-directional link (symmetric and asymmetric data rates)
• Can use existing protocols, e.g. IP
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• Can use existing protocols, e.g. IP
• Several profiles defined:
• e.g. dial-up networking, headset, fax, LAN access
• Products now becoming available in all almost all new
mobile phones and some laptops
Bluetooth: Basic Components
Four basic components to architecture:
1. RF component: for receiving and transmitting
2. Link control: for processing information to/from
RF component
29
RF component
3. Link management: manages transmission process
(media access)
4. Supporting applications: uses other three
components through a well-defined interface
Bluetooth: Link Types
SCO (synchronous, connection oriented)
• Packet-based
• Mainly for voice
• Up to 3 simultaneous
channels supported
ACL (asynchronous, connection-less )
• For data
• Asymmetric:
• 721Kb/s (either direction)
30
channels supported
(64Kb/s each)
• Can be used in parallel
with an ACL channel
• 721Kb/s (either direction)
+ 57.6Kb/s reverse
direction
• Symmetric:
• 432.6Kb/s
Basic CommunicationCharacteristics
• Antenna power of 0dBm
(1mW):
• ~10m range
• Optionally, 20dBm
(100mW):100m range
Radio
• 2.402-2.480GHz:
• minor change in ES, FR, JP
• FH-SS:
• 79 channels
• (23 channels, ES, FR, JP)
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•
1Mb/s max:
• 721Kb/s available
to user after protocol
overhead
• (23 channels, ES, FR, JP)
• 1MHz spacing
• Hop rate – 1600 hops/s:
• 625ms timeslot
• TDM slots
• Possible interference:
• 2.4GHz band used by
IEEE802.11 wireless LANs
Basic Communication•Master-slave relationship
• master initiates
communication using
PAGE or INQUIRY
message
• odd timeslots for
•TDM timeslots are numbered:
• use clock from master
• 227 slots
• Transmission in packets
• Packet normally uses one
timeslot:
32
• odd timeslots for
master
• even timeslots for
slave(s)
• Master-slave set-up:
• 255 slaves, 8-bit
address
• 7 active slaves, 3-bit
addresses
timeslot:
• one packet per freq. hop
• can use up to 5 timeslots
• Master-slave sync:
• use of clocks, slaves
sync with master
Basic Communication
•Piconet (single pico-cell):
• single master
• up to 255 slaves
• only 7 active slaves at any
time
• At power on:
•Every device has a unique 48-bit
address.
•Instead, friendly Bluetooth names
are used, which can be set by the
user.
•If address of another device
known:
M
S
SP
P
33
• At power on:
• in standby (sniff mode)
• listen every 1.28s
• check one of 32 hop
frequencies for other
devices
known:
• send PAGE message
• If address not known:
• send INQUIRY message
• SDP is used to discover
device capabilities
P
SB S
SB
SDP- service discovery protocol
M=MasterS=SlaveP=ParkedSB=Standby
Basic Communication … continues…
General packet format
• Header:
• AM_ADDR (3)
• type (4)
• flow control (1)
• ARQN (1)
Access code:
• provides receiver sync
• Payload:
• indicates length and number
of timeslots that will be
used
34
• ARQN (1)
• SEQN (1)
• HEC (8)
used
• contains CRC
• if FEC used used, 5 parity
bits added after each 10
bits, including CRC bits
• padding may be required
for FEC usage
access code header payload
72bits 54bits 0-2745 bits
access code packet header payload
68(72) 54 0-2745
AM_ADDR active member address
ARQN automatic repeat request number
HEC head error correction
SEQN sequence number
Forming a piconet• All devices in a piconet hop together
– Master gives slaves its clock and device ID• Hopping pattern: determined by device ID (48 bit,
unique worldwide)• Phase in hopping pattern determined by clock
• Addressing– Active Member Address (AMA, 3 bit)
35
SB
SB
SB
SB
SB
SB
SB
SB
SB
M
S
P
SB
S
S
P
P
SB
�
�
�
�
�
�
�
�
�
�
�
�
�
– Active Member Address (AMA, 3 bit)– Parked Member Address (PMA, 8 bit)
SB StandBy
Error Correction
3 options:
• 1/3 rate FEC
• 2/3 rate FEC
• CRC + ARQ
• Packet header:
•Corrects all 1-bit errors in
10 bits and detects all 2-bit
errors
•may need 0-9 bits of
padding
36
• Packet header:
• always uses 1/3 rate FEC
• Data:
• 2/3 rate FEC
• (15,10) shortened
Hamming code
padding
• CRC + ARQ:
• (not always used)
• ACK or NAK for each pkt
• Un-numbered scheme, i.e.
stop-wait scheme
ARQ: automatic repeat request: If the sender does not receive an acknowledgment before the timeout, it usually
re-transmits the frame
Power Saving Modes
•Different power modes:
• conserve battery life
• Active mode:
• normal operation
• Sniff mode:
Hold mode:
• less power than sniff mode
• clock remains sync’d
• e.g. inactive slave, retains
8-bit piconet address
37
• Sniff mode:
• less power than active mode
• listen to network
• e.g. standby
8-bit piconet address
• Park mode:
• less power than hold mode
• no contact with master
• does not retain piconet addr
Interface Support
• Can emulate different interface protocols, e.g.:
• USB (universal serial bus)
• RS232
• PC card (for laptops)
• Uses a serial cable emulation protocol:
38
• Uses a serial cable emulation protocol:
• allows use of PPP etc. (point-to-point protocol)
• Allows use of telephony protocols:
• TCS binary (telephony control protocol)
• Hayes AT commands
Bluetooth Protocol Stack
TCS BIN SDPIP
TCP/UDP
BNEP
RFCOMM (serial line interface)
AT modem
commands
PPPAudio
39
AT: attention sequenceTCS BIN: telephony control protocol specification – binaryBNEP: Bluetooth network encapsulation protocol
Bluetooth Radio
Baseband
Link Manager Protocol
Logical Link Control and Adaptation Protocol (L2CAP)
SDP: service discovery protocolRFCOMM: radio frequency comm.
Protocol Architecture
•Bluetooth radio:
• transmit and receive
• Baseband:
• physical RF control
• LMP(Link Manager Protocol):
• link setup
L2CAP(logical link control and
adaptation):
• SCO and ACL link types
• segmentation and
reassembly (max SDU size
is 64Kbytes)
40
• link setup
• authentication
• power mode control
• connection states in piconet
(master or slave)
is 64Kbytes)
• SDP(Service Discovery):
• selects usage model or
profile
• exchange of device
capability information
• RFCOMM(Radio Freq.
Communications:
• serial line “emulation”
Protocol ArchitectureAddressing
• 48-bit IEEE address
(similar to Ethernet
address) BD_ADDR
• Within a piconet:
Transmission control
• Freq. hopping sequence:
• derived from BD_ADDR of
master
• Access codes used for
41
• Within a piconet:
• one master
• many slaves
• members of piconet
• 8-bit piconet PM_ADDR
• 3-bit AM_ADDR
• Access codes used for
signalling:
• derived from BD_ADDR
• access codes used as part
of the every packet
• allows sync of receiver
clock
BD-ADDR - Bluetooth device address
Example usage methods
SDP
Modern emulator or driver
RFCOMM
AT modem
commandsPPP
SDP
Modern emulator or driver
PPP
IP
42
• LAN access:
• dial-up server emulation
• e.g. wireless access point
for multiple users
•Dial-up networking:
• serial line emulation
• e.g. wireless modem for
access
(L2CAP)
(L2CAP)
RFCOMM
Security
•Easy wireless connectivity
for roaming devices
• Bluetooth security modes
1, 2, 3
• Mode 1: insecure
• Mode 2: service-
•Authentication:
• challenge-response
• device authentication
• Link-level encryption:
• Bluetooth specific algorithms
• Key generation mechanism:
43
• Mode 2: service-
level security (not
required at link set-
up)
• Mode 3: link-level
security (required at
link set-up)
• Key generation mechanism:
• private user key (128bits)
used to generate session
encryption key (8-128bits)
• Random number generation
E
E2
link key (128 bit)
Authentication key generation
(possibly permanent storage)
Encryption key generation
PIN (1-16 byte)
User input (initialization)
Pairing
Authentication
E
E2
link key (128 bit)
PIN (1-16 byte)
Security … continues
44
E3
encryption key (128 bit)
payload key
Keystream generator
Data Data
Cipher data
Encryption key generation
(temporary storage)
Encryption
Ciphering
E3
encryption key (128 bit)
payload key
Keystream generator
NetworkingPiconet:
• a single Bluetooth cell
• multiple cells could overlap
• devices in overlap of cells
can form an ad hoc
scatternet• Scatternet – a single
device:
• is in multiple piconets
• has more than one master
• still maturing – may be
used in IEEE802.15 WPANspiconet
45
used in IEEE802.15 WPANs
M=MasterS=SlaveP=ParkedSB=Standby
M
S
P
SB
S
S
P
P
SB
M
S
S
P
SB
Piconets
(each with a
capacity of
< 1 Mbit/s)Scatternet
M
S
P
SB
S
S
P
P
SB
piconet
Piconet 1 Piconet 2
Summary
•Inter-device communication:
• many standards
• many different cables
• Bluetooth provides:
• common wireless connectivity (not really mobility)
46
• common wireless connectivity (not really mobility)
• cheap
• potentially, standard connectivity for any device,
including consumer electronics
• primitive networking - scatternet