EC421

WIRELESS COMMUNICATION

Syllabus Coverage

Unit I

Introduction to Wireless CommunicationUnit II

Cellular Concepts

Unit III

Mobile Radio PropagationUnit IV

Signal Processing TechniquesUnit V

Wireless Networking

UNIT - I Introduction to Wireless Communication

Evolution of Mobile Radio CommunicationsPaging SystemsCordless Telephone SystemsCellular Telephone Systems

Modern Wireless Communication Systems2G Networks3G NetworksWLL Wireless local LoopLMDS Local Multipoint Distribution SystemsBluetoothPersonal Area Networks

UNIT – II Cellular Concepts

Frequency reuse

Channel assignment strategies

Hand off Strategies

Interference and system capacity

Trunking and Grade of service

Improving Coverage and capacity in Cellular Systems

UNIT – III Mobile Radio Propagation

Large Scale path loss

Free space propagation model

Basic propagation Mechanism

Fading and its typesSmall scale and Multipath fading

Small scale and Multipath Propagation

Impulse response model of Multipath channel

Small scale multipath measurements

Parameters of mobile multipath channel

UNIT – IVSignal Processing Techniques

Modulation techniques for mobile radioEqualization and its Different Types

Linear and Non Linear Equalizers

Diversity TechniquesRake receiverInterleaving

UNIT – V

Wireless Networking Difference between Wireless and Fixed

telephone networks Development of Wireless Networks Fixed network Transmission hierarchy Traffic routing in Wireless networks Wireless data services Signaling techniques Wireless System Standards GSM, CDMA, CT2, PACS

Text Books and References

1. Theodore S. Rappaport, “Wireless communications Principles and Practice”, Pearson Education, Second Edition, 2002.

2. William C.Y.Lee, “Wireless and Cellular Communications”, Tata McGraw Hill Publishers, Third Edition, 2006.

3. Kamilo Feher, “Wireless Digital Communications”, Prentice Hall of India, 2004.

History of Mobile Communication

Martin Cooper

First Mobile Phone

Motorolos DynaTec AMPS Phone

Mobile Phones from 1G to 2G

UNIT - I Introduction to Wireless Communication

Evolution of Mobile Radio CommunicationsPaging SystemsCordless Telephone SystemsCellular Telephone Systems

Modern Wireless Communication Systems2G Networks3G NetworksWLL Wireless local LoopLMDS Local Multipoint Distribution SystemsBluetoothPersonal Area Networks

History of Mobile Cellular

Technology Based:

The analog frequency division multiple access (FDMA) systems are 1G systems.

The digital time division multiple access (TDMA) systems with circuit switching are 2G systems.

The code division multiple access (CDMA) systems with packet/circuit switching are 3G systems

Advanced mobile access technology used with an all Internet protocol (IP) network will be called 4G.

History of Mobile Cellular

With respect to Time period:

The Analog systems are 1G

Digital voice systems are 2GDigital voice/data systems are B2G

Broadband digital systems are 3G Wireless local area network/wireless metropolitan

area network (WLAN/WMAN) are B3G systems

Very-high-speed data-rate systems are 4G systems

Classification of mobile radio transmission system

- Simplex: communication in only one direction

– Half-duplex: same radio channel for both transmission and reception (push-to-talk)

– Full-duplex: simultaneous radio transmission and reception (FDD, TDD)

• Frequency division duplexing uses two radio channel

• Time division duplexing shares a single radio channel in time.

Evolution of Mobile Radio Communications

- 1946 Public Mobile Phone Telephone Service

introduced in 25 major American Cities

- Each System used High Power Transmitter to cover 50 km

- 1940’s Push To Talk used 120 kHz Spectrum (though 3 kHz is sufficient due to filters & ckts)

- By 1960’s FM Spectrum came to 30 kHz- Automatic Channel Trunking (1950’s & 1960’s)- Cellular concept developed by AT &T Bell Labs

• In 1983, FCC allocated 666 duplex Channels (40 MHz of spectrum in the 800 MHz band, each channel having one way bandwidth of 30 kHz) for AMPS system

• In 1989, FCC granted additional 166 Channels (10 MHz) for rapid growth and demand

Example of Mobile Radio Systems

– Garage door openers,

– Remote Controllers

– Pagers

– Cordless phone

– Cellular telephone

– Remote controller

– Hand-held walkie-talkies

– Wireless LAN

• Mobile - any radio terminal that could be moves during operation

• Portable - hand-held and used at walking speed

• Subscriber - mobile or portable user

Pager or Beeper

•A pager (page, beeper, bleep or bleeper) is a simple personal telecommunications device for short messages. •A one-way numeric pager can only receive a message consisting of a few digits, typically a phone number that the user is then expected to call. •Alphanumeric pagers are available, as well as two-way pagers that have the ability to send and receive email, numeric pages, and SMS messages.

Paging SystemsConventional paging system send brief messages to a subscriber• Modern paging system: news headline, stock quotations, faxes, etc.• Simultaneously broadcast paging message from each base station(simulcasting)•Large transmission power to cover wide area.

Cordless telephone systems are full duplex communication systems.

• First generation cordless phone

– in-home use

– communication to dedicated base unit

– few tens of meters

• Second generation cordless phone

– outdoor

– combine with paging system

– few hundred meters per station

Cordless Systems

• Provide connection to the PSTN for any user location within the radio range of the system.

• Characteristic

– Large number of users

– Large Geographic area

– Limited frequency spectrum

– Reuse of the radio frequency by the concept of “cell’’.

• Basic cellular system:

mobile stations,

base stations,

Base station Controller

mobile switching center.

Cellular Systems

Illustration of Cellular System

Call from PSTN to Mobile Phone

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Call from Mobile Phone to PSTN

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More about Cellular SystemThere are two basic cellular systems;

–Circuit-switched system and–Packet-switched system.

Circuit Switched System - each traffic channel is dedicated to a user until its cell is terminated.

We can further distinguish circuit-switched systems into two: – Analog system and– Digital system

Analog System

A basic analog cellular system1–3 consists of three subsystems: • a mobile unit, • a cell site,• and a mobile telephone switching office (MTSO) ,

1. Mobile units. A mobile telephone unit

control unit,

transceiver and

antenna system.

2. Cell site. The cell site provides interface between the MTSO and the mobile units.

Control unit,

Radio cabinets,

antennas,

a power plant, and

data terminals

3. MTSO. The switching office, the central coordinating element for all cell sites,

The cellular processor and

Cellular switch.

4. Connections. The radio and high-speed data links connect the three subsystems.

B. Digital Systems

A basic digital system consists of four elements:

mobile station (MS),

base transceiver station (BTS),

base station controller (BSC), and

switching subsystems (SS),

MS: It consists of two parts, mobile equipment (ME) and subscriber identify module

(SIM). SIM contains all subscriber-specific data stored on the MS side.

BTS: Besides having the same function as the analog BTS, it has the Transcoder/Rate

Adapter Unit(TRAU), which carries out coding and decoding as well as rate adaptation

in case data rate varies.

BSC: A new element in digital systems that performs the Radio Resource (RR) management for the cells under its control. BSC also handles handovers, power management time and frequency synchronization, and frequency reallocation among BTSs.

Switching Subsystems:

a. MSC: The main function of MSC is to coordinate the setup of calls between MS and PSTN users.

b. VLR (Visitor Location Register): A database of all mobiles roaming in the MSC’s area of control.

c. HLR(Home Location Register):Acentralized database of all subscribers registered in a Public Land Mobile Network (PLMN).

d. AUC (Authentication Center): Provides HLR with authentication parameters and ciphering keys that are used for security purposes.

e. EIR (Equipment Identity Register): A database for storing all registered mobile equipment numbers.

f. IWF (Inter Working Function): Provides the subscriber with data services that can acess data rate and protocol conversion facilities and interfaces with public and private data networks.

g. EC (Echo Canceller): Used on the PSTN side of the MSC for all voice circuits.

h. XC (Transcoder): Usually installs in each BTS. But for the cost reason, it can be installed in BSC or MSC.

i. OMC(Operational and Maintenance Center): This function resided in analog MSC but became a separated entity in digital systems.

A cellular packet-switched system

There are six elements: MS, Node B, RNC, SGSN, GGSN, and GF

MS: Provides the voice and packet data services. It is also called UE (User Equipment).

Node B: The name for base station in GSM.

RNC (Radio Network Controller): Controls the radio resources of the Node Bs that are connected to it. Its function is similar to BSC.

PCU (Packet Control Unit) converts the data stream into packet format.

SGSN (Service GPRS Support Node): Analogous to MSC/VLR in the circuit-switched system. This includes mobility management, security, and access control functions. It interfaces to HLR.

GGSN (Gateway GPRS Support Node): The point of interface with external packet data networks such as the Internet.

CGF (Changing Gateway Function): Mainly for billing.

RNS (Radio Network Subsystem): It consists of RNC and Node B. UTRAN consists of two or more RNS.