Wireless Communication

Instructor: Jin WangDepartment of Electrical & Electronics EngineeringEmail: wangjinnn99@gmail.com

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Subject Outline

Introduction to Cellular Mobile Communications Radio Propagation : Large Scale Effects

Path loss prediction models Shadowing

Radio Propagation : Small Scale Effects Multi-path models : Rayleigh, Rician Doppler effect, power spectra and signal correlation Coherence time and bandwidth, flat and selective

fading channel Modulation Techniques

Constant envelope and phase modulation QPSK, π /4 QPSK, FSK, GMSK

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Subject Outline

Equalization, Diversity and Coding Techniques Linear and non-linear equalization Selection, equal-gain and maximal ratio combining Interleaving and convolution coding

Multiple Access Techniques FDMA, TDMA, CDMA, SDMA Packet radio and random access

Cellular System Concepts Frequency reuse Channel assignment and control Cellular traffic Cellular coverage System expansion techniques

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Subject Outline

CDMA Cellular Systems Power Control and Interference Multi-user Detection Capacity and Enhancement

More Advanced Topics (if time allows) Orthogonal Frequency Division Mulitplexing (OFDM) Multi-carrier CDMA System

Speech Coding Fundamentals of quantization, PCM, Vocoder Brief Overview of System Standards GSM, IS-95, IMT2000

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References Theodore S. Rappaport, Wireless Communications: Principles &

Practice, Prentice-Hall, 2nd Edition. Jon W Mark, Weihua Zhuang, Wireless Communications and

Networking, Prentice Hall. Simon R. Saunders, Antennas and Propagation for Wireless

Communication Systems, Wiley. William C. Y. Lee, Mobile Communications Engineering, McGraw-

Hill. J. D. Parsons, The mobile radio propagation channel, Wiley, 2nd

Edition. Michel Daoud Yacoub, Foundations of Mobile Radio Engineering,

CRC Press. William C. Jakes, Microwave Mobile Communications, IEEE Press.

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Wireless Communications

Satellite TV Cordless phone Cellular phone Wireless LAN, WIFI Wireless MAN, WIMAX Bluetooth Ultra Wide Band Wireless Laser Microwave GPS Ad hoc/Sensor Networks

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Europe Standards

GSM CT2 Dect

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Japan Standards

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North American Major Standards PCS GSM Coreless FDMA TDMA CDMA Modulation

FM QPSK GMSK BPSK QAM

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Basic concepts

Simplex, half-duplex, and full duplex

Frequency division duplexing, FDD Most of system because of simplicity

Time division duplexing, TDD: indoor system only, because of delay

Different from FDMA and TDMA

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Basic concepts

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Pager System

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Cordless phone Virtually all telephones now sold in the US use the 900 MHz, 2.4 GHz, or

5.8 GHz bands. There is no specific requirement for any particular transmission mode on 900, 2.4, and 5.8, but in practice virtually all 900 MHz phones are inexpensive, bare-bones analog models; digital features such as DSSS and FHSS are generally only available on the higher frequencies.

The recently allocated 1.9 GHz band is used by the popular DECT phone standard from Europe

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Mobile

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Base Station

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Introduction

The target for mobile communications is to provide communications for anyone, from anywhere, at any time.

A demanding task. Technological challenges include: Time–varying, hostile communication channel. Location and tracking complexities due to mobility. Efficient use of scarce resources such as frequency

spectrum ⇒ cellular structure. The amount of interference generated is critical.

Power restrictions due to health issues.

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Introduction

The exponential growth of mobile subscribers worldwide is due to the decreasing service charges and diminishing hardware costs. The continuous development of the enabling technologies is the key.

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Introduction

RF technologies (such as improved frequency stability in electronics)

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Introduction

IC design (size) Battery technology (weight and size) Higher order modulation is made possible due to

the use of more sophisticated advanced digital signal processing techniques.

Speech coding techniques – reduces the required bandwidth per channel.

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Cellular system

Example : Consider a system allocated total bandwidth of 12.5MHz

and each voice channel requires a 10kHz slot. We can only support 12.5MHz/10kHz or 1250 simultaneous conversations.

Supposing the penetration rate in Singapore is 10%, for a population of 3M+, this is equivalent to 300k users. What happen if 1% of the users making call at the same time? Channels need to be in someway reused or shared?

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Cellular system

What can we do? Frequency bands are reused at different

locations. With this, higher user capacity in the same frequency spectrum can be achieved.

Technical challenge: interference issue, location tracking, etc., needs to be overcome.

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Cellular system

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Cellular system

Each cell has a base station (BS), providing the radio interface to the mobile station (MS).

A sophisticated switching technique called a handover enables a call to proceed uninterrupted across cell boundaries.

All the BS’s are connected to a mobile switching center (MSC) which is responsible for connection users to the public switched telephone network (PSTN).

Control channels transmit and receive data messages that carry call initiation and service requests, and are monitored by mobiles when they do not have a call in progress. ~5% of total available channels.

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Cellular system

Communication between the BS and the mobiles is defined by a standard common air interface that specifies 4 different physical channels Forward (Downlink) voice/data channel : BS to MS Reverse (Uplink) voice/data channel : MS to BS Forward (Downlink) control channel : BS to MS Reverse (Uplink) control channel : MS to BS

A MS contains a transceiver, an antenna and control circuitry. A BS consists of several transmitters and receivers.

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1G 2G Distributions

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2G Standard

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2G to 3G evolution

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