EC421 WIRELESS COMMUNICATION
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.