Wireless Communications Research Overview

TTT4160-1Mobile

Communications

Professor Geir E. Øien

IET, NTNU

Outline

Course Info and background Course Syllabus Wireless History and Trends Wireless Vision for the Future Technical Challenges Current Wireless Systems Emerging Wireless Systems Spectrum Regulation Standardization

Course Information: People

Lecturer:

Prof. Geir E. Øien, room C349, Elektroblokk C. Tlf: 94315. Mail: [email protected].

Teaching Assistants:

Sébastien de la Kethulle de Ryhove, room C351b, Elektroblokk C. Tlf: 96977. Mail: [email protected].

Changmian Wang, room C351b, Elektroblokk C. Tlf: 93670. Mail: [email protected].

Course Information, cont’d

Prerequisites: TTT4125 Information theory, coding and compression + TTT4130 Digital Communications (or foreign equivalents)

Required Textbook: Wireless Communications, by Prof. Andrea J.

Goldsmith (Cambridge University Press, available at Tapir bookstore)

Class Homepage: http://www.iet.ntnu.no/courses/ttt4160/NB website not yet updated...!

Course Background

This course is partly based on a course which has been developed and taught repeatedly by Professor Andrea Goldsmith (textbook author) at Stanford University in the past decade.

Presentation will be partly based on material from the Stanford course (credits to Prof. Homayoun Hashemi for some of the slides).

Supplements from locally developed course and guest lecturers.

Exercises: One compulsory “midterm” exercise, the rest voluntary Mostly written exercises, but possibly also some in Matlab

later Exercises will be assigned during lectures, and are due next

Monday before 12 am for those who want their answers checked by the T.A.

No exercise assigned today: first on Monday, January 15th. Help from teaching assistant will be given in EL4, Tuesdays

16.15 - 18.00 (first on January 16th). Exercise sessions (except first): Combination of review of last

week’s exercise + help with the current week’s. Exam: Written exam, 09.00 - 13.00, Saturday, June

2nd, 2007 Grading: A - F scale, based on final exam only

Course Information, continued

Tentative Course Syllabus

Overview of Wireless Communications (Ch. 1) 8/1-07 Path Loss and Shadowing (Ch. 2) 15/1-07 Statistical Fading Models (Ch. 3) 22/1-07 Capacity of Wireless Channels (Ch. 4.1 - 4.3.1) 29/1-07 Digital Modulation and its Performance (Ch. 5+6) 5/2-07 + 12/2-07 + 19/2-07 Adaptive Modulation (Ch. 9.1 - 9.4) 12/3-07 Diversity (Ch. 7.1 - 7.3) 19/3-07 Spread Spectrum (Ch. 13) 26/3-07 + 16/4-07 Cellular Systems and Infrastructure-Based Wireless Networks (Ch. 15) 23/4-

07 The GSM System (guest lecture by Dr. Magne Pettersen, Teleplan) 30/4-07NOTE 1: A more detailed syllabus will be handed out towards the end of the

course.NOTE 2: Most of the rest of the book will be covered by the in-depth module

(skall-emne) “Kommunikasjons- og kodingsteori for trådløse kanaler”, fall 2007.

Wireless (Pre-)History

• ”Pre-historic” times: smoke signals, bonfires, lighthouses, torches• 1895: first radio transmission (Marconi, Isle of Wight, 18 mile distance)• 1915: Wireless voice transmission established between San Francisco and New York• 1945: Arthur C. Clarke(sci-fi writer) suggests geostationary satellites• 1946: Public mobile telephony introduced in 25 US cities• 1947: Invention of cellular concept (AT&T)• 1957: First deployed communication satellite (Sputnik, Soviet Union)• 1963: First deployed geostationary satellite (NASA)• 1971: First packet-based radio network (ALOHANET, Univ. of Hawaii)• 1983: First analog cellular system deployed (Chicago)• 1985: Unlicensed frequency bands first authorized for WLAN use• Ca. 1990: First digital cellular systems (”2G”)• 2000 - now: Standardization of 3rd generation mobile communication systems, WLANs, WPANs, sensor network radios,...

Wireless History, cont’d

First Mobile Radio Telephone 1924

Pre-Cellular Wireless

One highly-elevated, high-powered antenna in a large service area

Small number of channels (few users)

Analog transmission, inefficient use of spectrum (no frequency reuse)

Very low capacity, power-inefficient

The Cellular Concept

Basic Principles:Frequency Re-useCell Splitting

(First proposed by D.

H. Ring at Bell Laboratories, NJ, USA in 1947.)

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NB: Not ”entirely wireless” since base stations are connected by wired network!

Cellular Systems:Re-use channels to maximize

capacity Geographic regions are divided into cells Frequencies/timeslots/codes reused at spatially separated locations. NB: Co-channel interference (between same-color cells below). Base stations/MTSOs (Mobile Telephone Switching Offices) coordinate handoff and control functions Shrinking cell size increases capacity - but also networking burden..

BASESTATION MTSO

Cellular Phone Networks

BSBS

MTSOPSTN

MTSO

BS

San Francisco

New YorkInternet

PSTN: Public ServiceTelephone Network

The Wireless Revolution

Cellular is the fastest growing sector of communication industry (exponential growth since 1982, with over 2 billion users worldwide today)

Modern-day “generations” of wireless (pre-cellular: 0G): First Generation (1G - ex. NMT, ca. 1982 - ): Analog 25 or 30 KHz

FM, voice only, mostly vehicular communications.

Second Generation (2G - ex. GSM, ca. 1993 - ): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units.

2.5G - 2.75G: Enhancements to 2G network for increased data transmission capabilities (ex. GPRS + EDGE, ca. 2000 - ).

Third Generation (3G - UMTS/IMT-2000, ca. 2002 - ): Wideband TDMA and CDMA, voice and high bit-rate data, portable units

4th Generation (4G/B3G, ca. 2010 - ?): ???... Heterogeneous network of several interacting systems/networks, not one dedicated network; diverse, advanced, adaptive air interfaces, protocols, and resource allocation mechanisms; multitude of services including high-capacity multimedia)

World Telecom Statistics

Crossover happened in May 2002...!



World Cellular Subscribers by Technology

- as of June 20062.41 Billion Cellular Customers Worldwide

GSM/UMTS totals 82.3% of this (GSM dominates)



(PDC: Personal Digital Cellular)

World Cellular Subscriber Distribution as of June

2006



GSM Growth - 1993 to June 2006



Exciting Developments

Internet and laptop use exploding Wireless LANs and PANs growing rapidly Huge cell phone popularity worldwide Emerging systems such as Bluetooth,

UWB, Zigbee, and WiMAX opening new doors

Military and security wireless needs Important interdisciplinary applications Sensor networks

Future Wireless Networks (The

Wireless Vision)

Wireless Internet accessNth generation CellularWireless Ad Hoc NetworksSensor Networks Wireless EntertainmentSmart Homes/SpacesAutomated HighwaysAll this and more…

Ubiquitous Communication Among People and Devices

• Hard Delay Constraints• Hard Energy Constraints

Design Challenges

The wireless channel is a difficult and capacity-limited broadcast communications medium!

Traffic patterns, user locations, and network conditions are constantly changing...

Traffic is nonstationary, both in space and in time

Energy and delay constraints change design principles across all layers of the protocol stack (points towards cross-layer design)

Evolution of Current Systems

Wireless systems today2G + 2.5G Cellular: ~30-70 Kb/s.WLANs: ~10 Mb/s.

Next Generation2.75G + 3G Cellular: ~300 Kb/s.WLANs: ~70 Mb/s.

Technology Enhancements Hardware: Better batteries. Better

circuits/processors. Co-optimization with transmission schemes.

Link: Antennas, modulation, coding, adaptivity, DSP, BW.

Network: Dynamic resource allocation. Mobility support.

3G: ITU-developed, UMTS/IMT-2000

Satellite

MacrocellMicrocell

UrbanIn-Building

Picocell

Global

Suburban

Basic TerminalPDA Terminal

Audio/Visual Terminal

Future Generations

Rate

Mobility

2G

3G

4G802.11b WLAN

2G Cellular

Other Tradeoffs: Rate vs. Coverage Rate vs. Delay Rate vs. Cost Rate vs. Energy

Still: Fundamental Design Breakthroughs Needed

Current Wireless Systems

Cellular Systems Wireless LANs (802.11a/b/g, Wi-Fi) Satellite Systems Paging Systems Bluetooth Ultrawideband radios (UWB) Zigbee/802.15.4 radios WiMAX (802.16)

Wireless Local Area Networks (WLANs)

WLANs connect “local” computers (~100 m range)

Breaks data into packets Channel access is shared (random

access) Backbone Internet provides best-effort

servicePoor performance in some app’s

(e.g. video)

01011011

InternetAccessPoint

0101 1011

Wireless LAN Standards (Wi-Fi)

802.11b (Current Generation)Standard for 2.4GHz ISM band (bw 80 MHz)Frequency hopped spread spectrum1.6-10 Mbps, 500 ft range

802.11a (Emerging Generation)Standard for 5GHz NII band (bw 300 MHz)OFDM with time division20-70 Mbps, variable rangeSimilar to HiperLAN in Europe

802.11g (New Standard)Standard in both 2.4 GHz and 5 GHz bandsOFDM (multicarrier modulation)Speeds up to 54 Mbps

In futureall WLAN cards will have all 3 standards...

Satellite Systems

Cover very large areas Different orbit heights

GEOs (39000 Km) via MEOs to LEOs (2000 Km)Trade-off between coverage, rate, and power budget!

Optimized for one-way transmission:Radio (e.g. DAB) and movie (SatTV) broadcasting

Most two-way systems struggling or bankrupt...(Too) expensive alternative to terrestrial systems(But: a few ambitious systems on the horizon)

Paging Systems (Personsøk)

Broad coverage for (very) short messaging

Message broadcast from all base stations

Simple terminalsOptimized for 1-way transmissionAnswer-back is hardOvertaken by cellular

8C32810.61-Cimini-7/98

Bluetooth

“Cable replacement” RF technology (low cost)

Short range (10 m, extendable to 100 m) 2.4 GHz ISM band (crowded!) 1 Data (700 Kbps) + 3 voice channels

Widely supported by telecommunications, PC, and consumer electronics companies

Few applications beyond cable replacement!

UltraWideband Radio (UWB)

Impulse radio: sends pulses of tens of picoseconds (10-

12) to nanoseconds (10-9) - duty cycle of only a fraction of a percent

Uses a lot of bandwidth (order of GHz)

Low probability of detection by others + beneficial interference properties: low transmit power (density) spread over wide bandwidth

This also results in short range. But : Excellent positioning (ranging) capability +

potential of high data rates

Multipath highly resolvable: both good and bad Can use e.g. OFDM or equalization to get around multipath

problem.

Why is UWB interesting?

Unique Location and Positioning properties1 cm accuracy possible

Low Power CMOS transmitters100 times lower than Bluetooth for same range/data

rate

Very high data rates possible (although low spectral efficiency) - 500 Mbps at ~10 feet range under current regulations

7.5 Ghz of “free spectrum” in the U.S.FCC (Federal Communications Commission) recently legalized

UWB for commercial use in the USSpectrum allocation overlays existing users, but allowed power

level is very low, to minimize interference

“Moore’s Law Radio”Data rate scales with the shorter pulse widths made possible with

ever faster CMOS circuits

IEEE 802.15.4/ZigBee radios

Low-Rate WPAN (Wireless Personal Area Network) - for communications < 30 meters.

Data rates of 20, 40, 250 kbps Star topology or peer-to-peer operation, up to 255

devices/nodes per network Support for low-latency devices CSMA-CA (carrier sense multiple access with collision

avoidance) channel access Very low power consumption: targets sensor networks

(battery-driven nodes, lifetime maximization) Frequency of operation in ISM bands

WiMAX: Worldwide Interoperability for Microwave

Access Standards-based (PHY layer: IEEE 802.16 Wireless MAN family/ETSI

HiperMAN) technology, enabling delivery of ”last mile” (outdoor) wireless broadband access, as an alternative to cable and DSL (MAN = Metropolitan Area Network). Several bands possible.

OFDM-based adaptive modulation, 256 subchannels. TDM(A)-based. Antenna diversity/MIMO capability. Advanced coding + HARQ.

Fixed, nomadic, portable, and mobile wireless broadband connectivity without the need for direct line-of-sight (LOS) to base station.

In a typical cell radius deployment of 3 to 10 kms, expected to deliver capacities of up to 40 Mbps per channel, for fixed and portable access.

Mobile network deployments are expected to provide up to 15 Mbps of capacity within a typical cell radius deployment of up to 3 kms.

WiMAX technology already has been incorporated in some notebook computers and PDAs. Potentially important part of 4G?

Data rate

10 kbits/sec

100 kbits/sec1 Mbit/sec

10 Mbit/sec

100 Mbit/sec

0 GHz 2 GHz1GHz 3 GHz 5 GHz4 GHz 6 GHz

802.11a

UWBZigBee

Bluetooth

ZigBee

802.11b

802.11g

3G

UWB

Frequencies occupied

Range

1 m

10 m

100 m

1 km

10 km


802.11a

UWB

ZigBee BluetoothZigBee

802.11b,g

3G

UWB

Power Dissipation

1 mW

10 mW

100 mW

1 W

10 W


802.11a

UWB

UWBZigBee

Bluetooth

ZigBee

802.11bg3G

Emerging Systems

Ad hoc wireless networks

Sensor networks

Distributed control networks

Ad-Hoc Networks

Peer-to-peer communications. No backbone infrastructure (no base stations). I.e. “Truly wireless”! Routing can be multihop. Topology is dynamic in time; networks self-organize. No centralized cooordination. Fully connected, even with different link SINRs

(signal-to-interference plus noise ratios)

Design Issues Ad-hoc networks provide a flexible network

infrastructure for many emerging applications.

The capacity of such networks is however yet generally unknown (hot research topic).

Transmission, access, and routing strategies for ad-hoc networks are generally also still ad-hoc...

Cross-layer design critical and very challenging.

Energy constraints impose interesting design tradeoffs for communication and networking (nodes typically battery-driven).

Sensor NetworksEnergy is the driving

constraint

Nodes typically powered by nonrechargeable batteries.Data (sensor measurements) flow to one centralized

location (sink node, data fusion center).Low per-node rates - but up to 100,000 nodes.Sensor data highly correlated in time and space.Nodes can cooperate in transmission, reception,

compression, and signal processing.

Energy-Constrained Nodes

Each node can only send a finite number of bits.Transmit energy minimized by maximizing bit timeCircuit energy consumption increases with bit time Introduces a delay versus energy tradeoff for each bit!

Short-range networks must consider transmit, circuit, and processing energy - jointly.Most sophisticated transmission techniques not

necessarily most energy-efficient! Sleep modes save energy - but complicate networking.

Changes everything about the network design:Bit allocation must be optimized across all protocols.Delay vs. throughput vs. node/network lifetime

tradeoffs.Optimization of node cooperation.

Spectrum Regulation Spectrum is a limited natural resource used by many.

The worldwide radio spectrum is controlled by ITU-R

(International Telecommunications Union) In Europe, by ETSI (European Telecommunications

Standardization Institute). In the US, by FCC (Federal Communications Commission;

commercial) and OSM (Office of Spectral Management; defense).

In Norway, by Post- og teletilsynet (PT).

Spectrum can be auctioned, paid fixed price for, or “given

away” (unlicensed bands).

Some spectrum typically set aside for universal use.Regulation, although necessary, can also stunt innovation, cause economic

disasters, and delay system rollout... (cf. UMTS spectrum auctions in Europe)

Standards Interacting systems require standardization (compatibility,

interoperability)

Typically: Companies want their own systems adopted as standard! Alternatively: try for “de-facto” standards

Worldwide standards determined by ITU-T (International Telecommunications Union)

In Europe, by ETSI (European Telecommunications Standardization Institute)

In the US by TIA (Telecommunications Industry Association) IEEE standards often adopted (also worldwide) Process fraught with inefficiencies and interest conflicts...

Standards for current systems are summarized in Appendix D in the textbook.

Main Points The wireless vision for the future encompasses many

exciting systems and applications

Technical challenges transcend across all layers of the system design.

Cross-layer design is emerging as a key theme in wireless.

Existing and emerging systems provide excellent quality for certain applications, but poor interoperability.

Standards and spectral allocation heavily impact the evolution of wireless technology.

This course will however focus on basic technology issues related to and relevant for current and upcoming wireless systems.

Wireless Communications Research Overview

Technology

Transcript of Wireless Communications Research Overview