ELEC 6040 Mobile Radio Communicationssdma/elec6040_2008/Part 1-Introduction.pdf · p. 3 ELEC6040 Mobile Radio Communications, ... Principles & Practice”, 2/e, 2002, ... WCDMA Îuplink/downlink:

ELEC6040 Mobile Radio Communications, Dept. of E.E.E., HKUp. 1

ELEC 6040 Mobile Radio Communications

Lecturers: Dr. S. D. Ma and Dr. Y. Q. Zhou([email protected], [email protected])

Date & Time: Saturday: 9:30am-12:00pm

Place: James Lee Bldg G05

Notes can be obtained from:

https://www.eee.hku.hk/~sdma/elec6040/


Objectives: To gain an understanding of mobile radio communications.

ContentIntroduction to Mobile Radio Communications Systems :• Overview of mobile radio communications• A brief historical review on the development of mobile radio communications;

frequency allocation; and cellular concept• Overview of digital communication systems:• Model of a digital communication system; a brief review of digital modulation,

source coding and channel coding.• Mobile radio propagation characteristics• Error performance over radio links• Multiple access methods• Spread-spectrum multiple-access communications• An introduction to orthogonal frequency division multiplexing


Contents

Mobile Radio Communications Engineering :• Introduction to cellular systems• Basic cellular system; performance criteria; cellular planning• Elements of cellular systems design• concept of frequency reuse; cell coverage; desired C/I from an omni-directional

antenna; handoff mechanism; co-channel interference and power control; channel allocation schemes; cell splitting and traffic consideration.

• Mobile communication standards• 2G and 2.5G systems• 3G and beyond 3G systems• appreciation of GPRS, EDGE, IEEE 802.11a/b wireless LANs and HIPERLAN/2,

Bluetooth, WiMax, LTE, etc.


References

• Theodore S. Rappaport, “Wireless Communications: Principles & Practice”, 2/e, 2002, Prentice Hall.

• John G. Proakis, “Digital Communications”, 4th ed., 2001, McGraw Hill.

• William C. Y. Lee, “Mobile Communications Design Fundamentals”, 1992, John Wiley & Son, Inc.

• IEEE standards• Journal and magazine articles as appropriate


Assessment• Assignments: 30%

• Final Examination: 70%


Lecture Notes

• Part 1. Introduction

• Part 2. Cellular System Engineering

• Part 3. Multiple Access Methods

• Part 4. Communications over Wireless Channels

• Part 5. 2G and 2.5G Systems

• Part 6. 3G Systems

• Part 7. B3G and 4G systems


Part 1. Introduction


• First telephone call – Alexander Bell, March 10, 1876 "Mr. Watson--come here -- I want to see you.”

• 1897: Guglielmo Marconi firstly demonstrated radio's ability to provide continuous contact with ships sailing in the English channel.

• Beginning of 20th century: Short wave radio communications were used in marine secure operation systems.

• 1921: The first car mounted radio telephone

It All Started Like This


Going Further

•1934 – Municipal police radio systems in the US (AM)•1946 – First commercial mobile radio-telephone service by

Bell and AT&T in Saint Louis, USA. Half duplex (FM)

•1968 – AT&T proposed the cellular concept to the FCC•1973 – First handheld cellular phone – Motorola.•1978 – First cellular net Bahrein•1980’s – 1G (1st generation mobile communication systems)

– Employed cellular technique for capacity enhancement– Features: Used analog modulation (FM in majority),

voice service– Examples: E-TACS (UK), NMT (Northern European

countries), AMPS (US), JTACS (Japan)– Well-known names: AT&T, etc.


Historical Review on the Development of Mobile Radio Communications (3)

• 1990’s: 2G (2nd generation mobile communication systems)– Motivation: Increase the capacity, use the frequency spectrum

efficiently– Technical Features: Digital modulation is used. DSP techniques (e.g.,

channel equalization, source coding, channel coding) are also used. Higher capacity than 1G (e.g., USDC versus AMPS: 3 times)

– Service: mainly voice, text message– Political issues: Intense debate on whether CDMA or TDMA was better,

during the first half of 1990’s.– Examples: USDC (some parts of US; TDMA), IS-95 or cdmaOne (some

parts of US, Korea, HK, China, Japan’s KDD, etc.; CDMA), GSM & DCS-1800/PCS (most part of the world; TDMA), GSM-1900 (some parts of US; TDMA), PDC & PHS (Japan’s NTT DoCoMo; TDMA)

– Well-known names: Ericsson, Nokia, Qualcom, A. J. Viterbi


Historical Review on the Development of Mobile Radio Communications (4)

• Late 1990’s: 2.5G– Why 2.5G?

data service: the data rate of 2G is low new standard: a long time replacing 2G systems with 3G systems: huge amount of investment on 2G

Solution: 2.5G, based on the existing 2G systems, increase the data rate

– Standards: GPRS (up to 114kbps; for GSM networks), EDGE (up to 384kbps; for GSM and DCS-1800/1900 networks), IS-95B (IS-95’s data-transmission extension)

– Well-known names: i-mode, WAP (Wireless Application Protocol), Multimedia messaging service (MMS)


Historical Review on the Development of Mobile Radio Communications (5)• 2000’s: 3G (3rd generation mobile communication systems)

– Feature 1: Initially intended to support multimedia communications; currently targeted to support Internet access, mobile TV, games etc

– Feature 2: Employs all sorts of capacity enhancement techniques: turbo codes (invented in 1993), multiuser detection (invented in 1986), transmit diversity (invented in ~1993), fast power control (invented in ~1993), smart antennas (long-known technique).

– Political issues: Initial attempt to unify all mobile radio communications into a single standard; not successful due to disagreements among major players

– Data-transmission rate: from 144kbps (vehicular environments) to 2Mbps (indoor environments)

– Approved standards: WCDMA, cdma2000, TD-SCDMA– Market status: CDMA2000 first commercial service at Seoul in late 2000

and WCDMA in Tokyo in May 2001– Well-known names: NTT DoCoMo, Qualcom, Ericsson, Nokia, 3GPP,

3GPP2


Frequency AllocationStandard Year of

Intro.Multiple Access Frequency Band Modulation Channel

BandwidthNMT-450 1981 FDMA 450-470 MHz FM 25kHz

AMPS 1983 FDMA 824-894 MHz FM 30kHzE-TACS 1985 FDMA 900 MHz FM 25kHz

NMT-900 1986 FDMA 890-960 MHz FM 12.5kHzJTACS 1988 FDMA 860-925 MHz FM 25kHz

NAMPS 1992 FDMA 824-894 MHz FM 10kHz

USDC 1991 TDMA 824-894 MHz π/4-DQPSK 30kHzGSM 1990 TDMA 890-960 MHz GMSK 200kHz

DCS-1800 1993 TDMA 1710-1880 MHz GMSK 200kHzDCS-1900 1994 TDMA 1.85-1.99 GHz GMSK 200kHz

IS-95 1993 CDMA 824-894 MHz; 1.8-2.0GHz QPSK / BPSK 1.25MHzPACS 1994 TDMA / FDMA 1.85-1.99 GHz π/4-DQPSK 300kHzPDC 1993 TDMA 810-1501 MHz π/4-DQPSK 25kHzPHS 1993 TDMA 1895-1907 MHz π/4-DQPSK 300kHz

DECT 1993 TDMA 1880-1900 MHz GFSK 1.728MHz

WCDMA CDMA 1.9-2.1 GHz QPSK / BPSK 5MHzcdma2000 CDMA 1.9-2.1 GHz QPSK / BPSK 5MHz



Source: ITU World Telecommunication/ICT Indicators Database


x

x0

x000

95’ 05’ 15’

1

2

3

.x

Data rate(Mbps)

Year

stage1:• Email,• File transfer,• Web browse,• Voice-over-ip,• etc…

stage2:• On-line game,• Video conference,• Tele-Medicare,• etc…

stage3:• HDTV,• Virtual reality,• etc…

Capacity bottle neck due to• Rare radio resource• Power limitation• Impairments of wireless channel

Date rate requirement increases exponentially due to high desire of better user experience

Big gap needed to be filled. Revolutionary technologies should be explored.

14 Mbps3.5G

2 Mbps3G

Maximum Data Rate

x00

Roadmap

Source: NTT DoCoMo


Targets and Achievable Data Rate in Cellular SystemsD

ata

rate

(bit/

seco

nd)

92 99 00 01

10 M

1 M

100 k

10 k

2 M

14 M

2 to 4 M

Peak data rate

3G & 3.5GAverage data rateMaximum value

in specification

1 k93 94 95 96 97 98 02 03 04 05

384 k

9.6 k

GSM

HSDPA(High-Speed Downlink Packet Access)

2G & 2.5GGPRS171 k

32 k

PHS

W-CDMA

Year

High-rate data services in megabit/second class are possible using HSDPA

EDGE

cdma2000

1X 144k

06 07 08

HSPA+DL:42 MUL:11M


Peak useful data rate (Mb/s)

3G

Mobility

Low

High

1 10 100 1000

New mobile access

New nomadic / Localarea wireless access

Enhanced3G

Enhancement.

1 Gbps

100 Mbps

Extracted from ITU-R.1645

Targets for Systems Beyond 3G

Systems beyond 3G


3.5G and LTE• Ongoing: Beyond 3G (B3G)

– Existing 3G: uplink/downlink: 200/500kbps, much lower than expected– Improving existing 3G systems to support data rates up to 10Mbps

Mid-term evolution:WCDMA uplink/downlink: HSUPA/HSDPA, up to 5.76/14Mbpscdma2000 cdma2000 1xEV-DO Rel. 0 Rev A Rev B

– Commercial service:2003: Verizon Wireless, CDMA2000 1xEV-DO, the United States 2003: KDDI, CDMA2000 1xEV-DO, JapanMay 2006: SK Telecom, the world first HSDPA service, KoreaAug. 2006: NTT DoCoMo, HSDPA, JapanSept. 2006: Smartone, HSDPA (3.6 Mbps), Hong Kong

– 3GPP LTE (long term evolution): using 4G technologies (MIMO, OFDMA, etc.) on 3G systemsobject: uplink/downlink: 170/320Mbps standards in progress...


4G Mobile Communications (1)

• Research ongoing: 4G– 4G: replacing existing 3G systems– Objectives: a fully IP-based integrated system; being capable of providing

between 100 Mbit/s and 1 Gbit/s speeds both indoors and outdoors, with premium quality and high security.

– Feature 1: totally new broadband frequency spectrum is needed, 100M– Feature 2: A mixture of different communication systems, including:

broadcasting systems, cellular networks, wireless LANs (WLANs), wireless personal-area networks (WPANs), and fixed networks. Inter-system handover required. Billing among different operators more difficult.

– Feature 3: IP-based; packetized communications.– Expected enabling technologies: MIMO, OFDM, space-time coding,

smart antennas, software radio– Well-known names: NTT DoCoMo, Samsung, Nokia, Sony-Ericsson,

Philips, Northern European countries


Cellular system Isolated-cell environment

local area coveragelow mobilitywide coverage

full mobility

4G wireless network

4G: target data rate

3G: currentdata rate

14Mbps 100Mbps1Gbps

• Research target of 4G4G Mobile Communications (2)


• Asymmetric data traffic

Downlink:heavy traffic high data rate

Uplink:light traffic, low data rate

Broad bandwidth: 100MHz

Relatively narrowbandwidth: 40MHz

Typical service: watching HD movie in real time

sending orders

video streams



Cellular system

Local area environment

Same air interface

All IP-based core network

• Broadband wireless access

To reduce network cost



HK Economic Journal June 21 2006

In 2007, NTT DoCoMo announced it achieved a maximum packet transmission rate of approximately 5Gbpsin the downlink using 100MHz frequency bandwidth to a mobile station moving at 10km/h, the world's first 5Gbps packet transmission in 4G Field Experiment .


1G~4G

WiMax, 802.16e

IEEE 802.15

Wireless Networks


Wireless LAN (1)

•WLAN– utilizes spread-spectrum/OFDM technology based on radio waves to enable communication between devices in a limited area– gives users the mobility to move around within a broad coverage area and still be connected to the network

•Different WLAN Standards– various version of IEEE 802.11

by vendors joined IEEE– HIPERLAN

5GHz standardby researchers in ETSI (European Telecommunications Standards Institute)no strong vendor influence


IEEE 802.11 / IEEE 802.11b

Current market status • 802.11b dominated the market Approved & standardized

• 1997 (IEEE 802.11) • early 2000 (IEEE 802.11b)

Major market players • Intersil, Agere, etc. Rates • 1Mbps, 2Mbps (IEEE 802.11)

• 5.5Mbps, 11Mbps (IEEE 802.11b) Carrier frequency • 2.4GHz (unlicensed ISM band) [NA for infrared]

Transmission techniques

• Direct-sequence spread spectrum (802.11 & 802.11b) • Frequency-hopped spread spectrum (802.11) • Infrared (802.11)

Source of external interference

• BluetoothTM devices • Microwave ovens

European counterpart • HIPERLAN/1 (no commercial products!) IEEE 802.11g • Up to 54 Mbps adopt 802.11a technique in 802.11b


IEEE 802.11a

Current market status • products incorporate into PCs; awaiting market acceptance Approved & standardized

• end of 1999

Major market players • Atheros, Intersil, etc. Rates • 6Mbps – 54Mbps

Carrier frequency • 5.2GHz (unlicensed band called UNII) Transmission

techniques • OFDM (orthogonal frequency division multiplexing)

Source of external interference

• other IEEE 802.11a access points or mobile stations • no other known interference up to now

European counterpart • HIPERLAN/2 (standard published) Japanese counterpart • MMAC (published)


Summary of IEEE 802.11a/b WLANs and HIPERLAN/2

Source: J. De Vriendt, P. Lainé, C. Lerouge and X. Xu, “Mobile network evolution: a revolution on the move,” IEEE Communications Magazine, pp. 104-111, Apr. 2002.

HIPERLAN/2 is better than IEEE 802.11a in QoS support and security.


Wireless LAN (2)

•IEEE 802.11a - 6~54 Mbps, in unlicensed 5-GHz radio band

•IEEE 802.11b - older, up to 11 Mbps, in 2.4 GHZ radio band

•IEEE 802.11d – to add support for "additional regulatory domains". This support includes the addition of a country information element to beacons, probe requests, and probe responses.

•IEEE 802.11e - QoS (quality of service) issue in LANs

•IEEE 802.11g - to increase the speed of 802.11b - 54 Mbps in 2.4 GHz band

•IEEE 802.11x - security and other class of service specifications.

•IEEE 802.11n - for very high-speed WLANs (200-500 Mbps) over short distances.


•IEEE 802.16 (2001) - point to multi-point broadband wireless transmission

in the 10-66 GHz band, using single carrier physical standard

•IEEE 802.16a - for 2 ~ 11 GHz, adding OFDM/OFDMA

•IEEE 802.16d (IEEE 802.16-2004) –fixed WiMax (supersedes the earlier amendments)

•IEEE 802.16e - mobile WiMax, OFDM and MIMO techniques, full mobility support

WiMax is very different from WiFi

WiMax: over many kilometers, stronger encryption, less interference

WiFi: short range (10's of meters), WEP/WPA encryption, suffer from interference

WiMax


• Bluetooth– an industrial specification for wireless personal area networks (PANs).– provides a way to connect and exchange information between devices such

as mobile phones, laptops, PCs, printers, digital cameras and video gameconsoles via a secure, globally unlicensed short-range radio frequency

– proposed by Ericssonnamed after Harald Bluetooth, a king of Denmark and Norway in 10thcentury, known for his unification of previously warring tribesBluetooth: intended to unify different technologies like computers andmobile phones.

– technical information:2.4G ISM band, low power consumption, short range (<100m) low-cost transceiver, data rate (<1Mbps)


• Typical Applications– Wireless control of and communication between a cell phone and a hand

free headset– Wireless control of a games console

Nintendo's Wii and Sony's PlayStation 3– Wireless communications with PC input and output devices

mouse, keyboard and printer

a Bluetooth mobile phone headset Apple wireless keyboard and mouse


Other Wireless Network: WSN (1)• WSN (Wireless Sensor Network)

– A wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations

– Standards: ZigBee, WirelessHART, ISA100, etc.,all based on IEEE 802.15)


Other Wireless Network: WSN (2)

• WSN (Wireless Sensor Network)– originally motivated by military applications such as battlefield surveillance

– civilian applications: environment and habitat monitoring, healthcareapplications, home automation, and traffic control

the size of a sensor environment and habitat monitoring


Mobile Phone

PDA

LaptopVehicle Handset

Computer Accessories

Home Appliance

Wireless Access Network

Future Wireless World


Important Technologies

• Important technologies for the flourish of mobile communications

– Cellular concepts:

the ability to provide mobile radio communications to an entire population

detailed illustration in Part 2

– Digital communications:

digital techniques such as source coding, channel coding, digital modulation...

capacity improvement over analog systems: USDC three times AMPS


Overview of Cellular Concepts (1)

• Early-day mobile radio communications:– Objective: achieve a large

coverage by using a single, high powered transmitter

– Macro-cell system: one central base station served all mobiles

– Advantage: large coverage: a thousand square miles

– Disadvantages:small number of supported users (capacity)impossible to reuse frequencyhigh transmit power


Overview of Cellular Concepts (2)

• Cellular Mobile Systems: Introduced by AT&T during 1960’s.• Made use of signal attenuation after traveling a certain distance; so that

the same carrier frequency can be reused after a certain distance.• Capacity is greatly increased.


Terminologies Used in Cellular Systems (1)

• Base Station (Access Point, Node B in WCDMA)– A fixed station in a mobile radio system used for radio communication

with mobile stations• Mobile Station

– A station in the cellular radio service intended for use while in motion at unspecified locations

• Mobile Switching Center (MSC)– Switching center which coordinated the routing of calls in a large service

area. In a cellular radio system, the MSC connects the cellular base stations and the mobiles to the PSTN (Public switched telephone network)

• Roaming– A MS which operates in a service area other than that from which

service has been subscribed


•Dual Band–allowed to use different frequency bands, e.g., GSM900 and GSM1800

•Dual Mode–allowed to use different air interfaces, e.g., WCDMA and GSM

•Forward Channel–downlink channel, BS→MS

•Reversed Channel–uplink channel, MS→BS

•Control Channel–radio channels used for transmission of call setup, call request, call initiation, or control purposes




•Traffic Channel–radio channels used for transmission of user voice or data

•Full Duplex–Transmitter (TX) and Receiver (RX) are allowed simultaneously, e.g., GSM, WCDMA

•Half Duplex–TX or RX is allowed at any given time, e.g., police radio

•Simplex–only one-way transmission, e.g., paging


Overview of Digital Communication Systems

• Analog Communication System1G is an analog radio communication system with FM modulation


Digital Communication System

SourceEncoding

ChannelEncoding Modulation

PhysicalChannel

InformationSource

SourceDecoding

ChannelDecoding DemodulationInformation

Sink

Dig

ital

Dom

ain

Ana

log

Wav

efor

m

Transmitter

Receiver


Elements of Digital Communication Systems (1)

• Information source:– voice signals for 1G and 2G systems– voice and/or video signals for 3G and post-3G systems– Internet data for 2.5G, 3G and post-3G systems

• Source coding:– To remove redundancy in source signals before transmission.– Transmission efficiency is improved.– Also known as data compression.– Examples: code excited linear prediction (CELP), MPEG.



• Channel coding:– To add redundancy in the digital signal so that the signal can be

recovered even in the presence of noise and interference.– Transmission reliability is improved.– Examples: repetition code, Reed-Solomon code, BCH code,

convolutional code.

• Modulation and Demodulation:– Modulation (demodulation) maps (retrieves) the digital information into

(from) an analog waveform appropriate for transmission over the channel.

– Generally involve translating (recovering) the baseband digital information to (from) a bandpass analog signal at a carrier frequency that is very high compared to the baseband frequency.

– Examples: BPSK, QPSK, π/4-DQPSK, GMSK, OFDM



• Communication channels:– The physical medium used to send

the signal from the transmitter to the receiver.

– Essential feature: the transmitted signal is corrupted in a random manner

– Examples:o Wireline channelso Fiber-optic channelso Wireless electromagnetic

channelso Underwater acoustic channelso Storage channel


A Simple Example of Source Coding (Remark: Not very relevant to Mobile Communications)

Original Picture (2M TIF file) Highly compressed picture (177k JPEG file)


Example of Channel Coding: Convolutional Code used for IS95 Forward Links

+

+

Coded symbols

Coded symbols

Data

Forward link; rate = 1/2;constraint length = 9


Example of Channel Coding: Convolutional Code used for IS95 Reverse Links

+

+

Coded symbols

Coded symbols

Data

Reverse link; rate = 1/3;constraint length = 9

+Coded symbols


Example of Channel Coding: Coding Gains of the ConvolutionalCode used for IS95Good for voice communications

Good for video transmission

Source: CDMA Systems Engineering Handbook, pp. 914-915.


Examples of Digital Modulations

Popular for mobile communications (IS-95, WCDMA)

Documents

ELEC 6040 Mobile Radio Communicationssdma/elec6040_2008/Part 1-Introduction.pdf · p. 3 ELEC6040 Mobile Radio Communications, ... Principles & Practice”, 2/e, 2002, ... WCDMA Îuplink/downlink: