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

5

• 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)

6

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

7

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

10

�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)

21

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

23

• 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

24

£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

27

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)

31

•

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