GUJARAT TECHNOLOGICAL UNIVERSITY B.E. 7 …mytoolbag.in/media/GTUPAPERS/1/2/EC/S7/WC.pdf · ... Wireless Communication ... L T P C Theory Marks Practical Marks Marks ESE (E ... 1

GUJARAT TECHNOLOGICAL UNIVERSITY

BRANCH NAME: Electronics Engineering / Electronics & Communication

Engineering /Electronics & Telecommunication Engineering

SUBJECT NAME: Wireless Communication

SUBJECT CODE: 2171004

B.E. 7th SEMESTER

Type of course:-

The course addresses the fundamentals of wireless communications and provides an overview

of existing and emerging wireless communication Technology and networks. It covers radio

propagation and fading models, fundamentals of cellular communications, multiple access

technologies, and various wireless systems like GSM, CDMA etc., including past and future

generation wireless networks.

Prerequisite: - It is desirable that student is familiar with following domains: Digital and

analog Communication, Signals & Systems, Electromagnetic Theory, Probability & Random

Processes.

Rationale: - The course will provide fundamental about many theoretical & practical concepts that

form the basis for wireless communication systems and Networks. Also the emphasis is given for

creating foundation of cellular concepts which will be useful for understanding the fundamentals

of cellular mobile communication systems design. The students will learn Mobile Radio

Propagation models and various wireless channel effects. Student will understand Multiple Access

techniques. Students will also be exposed to recent emerging trends in wireless communication

like Software Defined Radio as well. The course also covers overview of recent trends like

wireless communication like Wi-Fi, Wi-MAX, bee, UWB Radio and Wireless Adhoc Networks.

Teaching and Examination Scheme:

Teaching Scheme Credits Examination Marks Total

Marks L T P C Theory Marks Practical Marks

ESE

(E)

PA (M) PA (V) PA

(I) PA ALA ESE OEP

4 0 2 6 70 20 10 20 10 20 150

Content:

Sr. No. Content Total

Hrs

% Weightage

1 Introduction to Wireless Communication System:

Evolution of mobile communications, Mobile Radio System

around the world, Types of Wireless communication System,

Comparison of Common wireless system, Trend in Cellular radio

and personal communication. Second generation Cellular

Networks, Third Generation (3G) Wireless Networks , Wireless

Local Loop(WLL),Wireless Local Area network(WLAN),

Bluetooth and Personal Area Networks.

3 10

2 The Cellular Concept- System Design Fundamentals:

Cellular system, Hexagonal geometry cell and concept of

frequency reuse,Channel Assignment Strategies Distance to

frequency reuse ratio,Channel & co-channel interference reduction

factor, S/I ratio consideration and calculation for Minimum Co-

channel and adjacent interference, Handoff Strategies, Umbrella

Cell Concept, Trunking and Grade of Service, Improving Coverage

& Capacity in Cellular System-cell splitting, Cell sectorization,

Repeaters, Micro cell zone concept, Channel antenna system

design considerations.

12 20

3 Mobile Radio Propagation Model, Small Scale Fading and

diversity:

Large scale path loss:-Free Space Propagation loss equation, Path-

loss of NLOS and LOS systems, Reflection, Ray ground reflection

model, Diffraction, Scattering, Link budget design, Max. Distance

Coverage formula, Empirical formula for path loss, Indoor and

outdoor propagation models, Small scale multipath propagation,

Impulse model for multipath channel, Delay spread, Feher’s delay

spread, upper bound Small scale, Multipath Measurement

parameters of multipath channels, Types of small scale Fading,

Rayleigh and rician distribution, Statistical for models multipath

fading channels and diversity techniques in brief.

09 20

4 Multiple Access Techniques:

Introduction, Comparisons of multiple Access Strategies

TDMA,CDMA, FDMA, OFDM , CSMA Protocols.

07 15

5 Wireless Systems:

GSM system architecture, Radio interface, Protocols, Localization

and calling, Handover, Authentication and security in GSM, GSM

speech coding, Concept of spread spectrum, Architecture of IS-95

CDMA system,Air interface, CDMA forward channels, CDMA

reverse channels, Soft handoff, CDMA features, Power control in

CDMA, Performance of CDMA System, RAKE Receiver,

CDMA2000 cellular technology, GPRS system architecture.

12 20

6 Recent Trends:

Introduction to Wi-Fi, WiMAX, ZigBee Networks, Software

Defined Radio, UWB Radio, Wireless Adhoc Network and Mobile

Portability, Security issues and challenges in a Wireless network.

09 15

Total 52

Suggested Specification table with Marks (Theory):

Distribution of Theory Marks

R Level U Level A Level N Level E Level C Level

10 15 10 15 10 10

Legends: R: Remembrance; U: Understanding; A: Application, N: Analyze and E: Evaluate

C: Create and above Levels (Revised Bloom’s Taxonomy)

Note: This specification table shall be treated as a general guideline for students and teachers. The

actual distribution of marks in the question paper may vary slightly from above table.

Reference Books:

Text Book:

1 Wireless Communication, Theodore S. Rappaport, Prentice hall

2 Wireless Communications and Networking,Vijay Garg, Elsevier

3 Wireless digital communication, Kamilo Feher, PHI

4 Mobile Communications Engineering, William C. Y. Lee, Mc Graw Hill Publications

5 Mobile and personal Communication system and services by Rajpandya, IEEE press (PHI).

6 Wireless Communications-T.L.Singh-TMH

7 Adhoc Mobile Wireless network, C.K.Toh Pearson.

Course Outcome:

After learning the course the students should be able to:

1 Understand the basics of propagation of radio signals

2 Understand the basic concepts of basic Cellular System and the design requirements

3 Have an understanding of the basic principles behind radio resource management

techniques such as power control, channel allocation and handoffs.

4 Gain insights into various mobile radio propagation models and how the diversity can be

exploited to improve performance

5 Gain knowledge and awareness of the technologies for how to effectively share spectrum

through multiple access techniques i.e. TDMA, CDMA, FDMA etc.

6 Have in-depth understanding of the design consideration and architecture for different

Wireless Systems like GSM, CDMA, GPRS etc

7 Understanding of the emerging trends in Wireless communication like WiFi, WiMAX,

Software Defined Radio (SDR) and related issues and challenges.

List of Experiments:

Experiments and Problems will be based on Concept of GSM, Cellular System Design Concepts,

Wi-Fi, -MAX, Zig bee standard , Multipath propagation Environment and its parameter and loss

measurement, Adhoc N/Ws & Protocols , Software Defined Radio, UWB Radio, GPRS etc.

Following are the examples of Experiments from the various part of syllabus topic. Same or

similar Experiments may be given to the students based on availability of resources in

wireless laboratory of the institute.

Experiments based on MATLAB OR SCILAB

Write a MATLAB/ SCILAB Program/s based on

1 Free space Propagation Model & Frequency Selective Fading Model

2 Ground Reflection (Two-ray) Model

3 Diffraction (Knife-Edge) Model

4 Large-scale Empirical models

5 Small-scale Empirical models

6 Cellular Systems

7 Wireless LANs

Experiments based on GSM (Using Wireless Communication Trainer)

Study the implementation of –GMSK modulation, OQPSK detection.

– Observe phase response of Tx and Rx and Spectrum of Tx and Rx.

– Measure the BER value

– GSM AT Commands

Experiments based on CDMA (Using Wireless Communication Trainer)

Study the performance of DS-CDMA system under multi-path condition for single user

case

– Using RAKE receiver with MRC method and EGC method

– Observation of SNR vs BER curve for two different combining techniques.

Experiments based on OFDM (Using Wireless Communication Trainer)

Study OFDM system synchronization requirement

– Observe the performance of Schmidl-Cox algorithm used for timing acquisition and

fractional freq offset estimation

– Integer Frequency offset estimation

Design based Problems (DP)/Open Ended Problem:-

1. Design of Any Arbitrary Modulation Scheme

–8PSK, QAM (16, 64 etc), EDGE, WCDMA*, WiFi*, WiMAX*

–Compare at base-band, IF and RF

2. Design of Discrete Multi-tone modem, FM Radio Reception.

3. Design/implement the different Channel Coder/Decoder

–Turbo decoder

–LDPC coder / decoder

4. Project based on Reception of local GSM broadcast channel

5. Project based on Frequency Hopping Spread Spectrum (FHSS)

Major Equipment: -

DSO, CRO, Signal Generators, Spectrum Analyzers, GSM, GPRS, GPS, CDMA Trainer Kits,

Mobile Communication & Wireless Communication Trainer Kits etc.

List of Open Source Software/learning website:-

Students may use SCILAB, MATLAB, NETSIM, NS2 and NPTL Videos, MIT open course

website,Virtual Labs (Source:http://vlab .co.in).

ACTIVE LEARNING ASSIGNMENTS: Preparation of power-point slides, which include

videos, animations, pictures, graphics for better understanding theory and practical work – The

faculty will allocate chapters/ parts of chapters to groups of students so that the entire syllabus to

be covered. The power-point slides should be put up on the web-site of the College/ Institute,

along with the names of the students of the group, the name of the faculty, Department and College

on the first slide. The best three works should be submitted to GTU.

1

Seat No.: ________ Enrolment No.___________

GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII (NEW) - EXAMINATION – SUMMER 2017

Subject Code: 2171004 Date: 04/05/2017 Subject Name: Wireless Communication Time: 02.30 PM to 05.00 PM Total Marks: 70 Instructions:

1. Attempt all questions. 2. Make suitable assumptions wherever necessary. 3. Figures to the right indicate full marks.

Q.1 (a) Define following terns: (1) Forward Channel (2) Reverse Channel (3) Control

Channel (4) Paging System (5) Hand-off (6) Base Station (7) Full Duplex

Systems

07

(b) What is interference? Explain the difference between co-channel interference

and adjacent channel interference. Derive equation for signal to interference

ratio.

07

Q.2 (a) A unit gain antenna with a maximum dimension of 1 m produces 50 W power

at 900 MHz. Find (i) the transmit power in dBm and dB, (ii) the received

Power at a free space distance of 5 m and 100 m using free space distance

formula.

07

(b) (i) Why hexagonal cell shape is preferred in cellular architecture?

(ii) Explain the concept of umbrella cell.

03

04

OR

(b) Explain different channel assignment strategies in detail. 07

Q.3 (a) Explain the concept of cell splitting with require figure. 07

(b) Explain Free space propagation model with necessary equations. 07

OR

Q.3 (a) Describe empirical formula for path loss in mobile networks. 07

(b) What is diffraction? Briefly explain knife-edge diffraction model with figure. 07

Q.4 (a) Describe Time Division Multiple Access (TDMA) in detail. Write the equation

for efficiency of TDMA and number of channels in TDMA system.

07

(b) Explain the following term with reference to CDMA

(i) Power Control

(ii) Soft hand-off

(iii) Frequency hopping

07

OR

Q.4 (a) Write a short note on OFDM. 07

(b) Describe a Rake receiver in CDMA. 07

Q.5 (a) With the help of a neat sketch, describe GPRS architecture. 07

(b) Write a short note on UWB radio. 07

OR

Q.5 (a) With neat diagram explain wireless Ad-Hoc network. 07

(b) Write a short note on software defined radio. 07

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII(NEW) • EXAMINATION – WINTER 2016

Subject Code:2171004 Date:23/11/2016

Subject Name:Wireless Communication

Time: 10.30 AM to 1.00 PM Total Marks: 70 Instructions:

1. Attempt all questions.

2. Make suitable assumptions wherever necessary.

3. Figures to the right indicate full marks.

Q.1 (a) Define the following terms regarding wireless communication:

(1) Page

(2) Full duplex channel

(3) Simplex systems

(4) Mobile Switching Center

(5) Control channel

(6) Base station

(7) Forward channel

7

(b) What is ZigBee ? Explain in details ZigBee networks. 7

Q.2 (a) If 20 MHz of total spectrum is allocated for a duplex wireless cellular system and

each simplex channel has 25 KHz RF bandwidth, find:

(i)The number of duplex channels

(ii) The total number of channels per cell site ,if N=4 cell reuse is used.

(b) Explain the concept of Cell Splitting and Cell Sectoring. 7

OR

(b) (i) Explain the concept of Umbrella cell.

(ii) Explain the concept of Frequency Reuse. 7

Q.3 (a) What is fading? List and explain various types of small scale fading. 7

(b) With necessary equations explain Free space propagation model in detail. 7

OR

(a) Prove that for a hexagonal symmetry,the co-channel reuse ratio is given by

Q=(3N)1/2. Where, N=i2+ij+j2. 7

(b) Enumerate various radio propagation model and explain any two of them. 7

Q.4 (a) Explain the following diversity techniques briefly:

1. Space diversity techniques

2. Frequency diversity techniques

7

(b) Describe: Time Division Multiple Access (TDMA) in detail. Write the equation

for efficiency of TDMA and The number of channels in TDMA system. 7

OR

(a) Write short note on Code Division Multiple Access (CDMA). 7

(b) Describe evolution of 1G, 2G and 3G mobile phone systems. 7

Q.5 (a) Describe in details GSM architecture with necessary block diagram and its various

blocks. 7

(b) Describe RAKE receiver in CDMA. 7

2

OR

(a) What is meant by Hand off and explain different Hand off strategies How handoff

operation is performed while mobile moves into a different cell while a

conversation is in progress.Discuss the cases for proper and improper handoff

situations.

7

(b) Explain in brief: (i) Wi - Fi (ii) Wi Max (iii) UWB. 7

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII (OLD) - EXAMINATION – SUMMER 2017

Subject Code: 171004 Date: 06/05/2017 Subject Name: Wireless Communication Time: 02:30 PM to 05:00 PM Total Marks: 70 Instructions:


Q.1 (a) Explain in details the 3G W-CDMA (UMTS) and 3G cdma2000. 07

(b) Explain HLR and VLR functions 07

Q.2 (a) List all the propagation models? How they are different to one another? 07

(b) Explain power control in CDMA technology. 07

OR

(b) Explain GPRS architecture 07

Q.3 (a) Explain any one technique of small-scale multipath measurements 07

(b) Give names of all logical channels of GSM and write function of each 07

OR

Q.3 (a) Draw the frame structure of GSM and write the timing parameters 07

(b) Describe international roaming 07

Q.4 (a) Write short note on Zigbee technology 07

(b) Describe Architecture of IS-95 CDMA system 07 OR

Q.4 (a) Give comparison of Indoor and outdoor propagation models 07

(b) What is hand off? Describe types of hand off and its importance 07

Q.5 (a) Explain how coverage and capacity of GSM system can be improved? 07

(b) Write note on RAKE receiver 07

OR

Q.5 (a) What are diversity techniques to help in improving SNR? Explain in brief 07

(b) Explain coherence time and coherence bandwidth 07

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII EXAMINATION – SUMMER 2016

Subject Code:171004 Date:18/05/2016 Subject Name:Wireless Communication Time:02:30 PM to 05:00 PM Total Marks: 70 Instructions:


Q.1 (a) What is ZigBee ? Explain in details ZigBee networks. 07

(b) Compare Wi Fi and Wi Max technologies. 07

Q.2 (a) Describe evolution of 1G, 2G and 3G mobile phone systems 07

(b) Explain the antenna design systems for mobile networks 07

OR

(b) With respect to mobile networks, explain co channel and adjacent channel

interference 07

Q.3 (a) Describe in details GSM architecture with necessary block diagram and its

various blocks 07

(b) Explain GSM network’s hexagonal cellular concept and frequency reuse concept 07

OR

Q.3 (a) Enumerate various radio propagation model and explain any two of them 07

(b) Describe empirical formula for path loss in mobile networks 07

Q.4 (a) What is fading? List and explain various types of small scale fading. 07

(b) Describe various GSM logical and physical channels 07 OR

Q.4 (a) Write a short note on mobile portability 07

(b) What is hand over in GSM? Give comparison of hard hand over and soft hand

over 07

Q.5 (a) Describe RAKE receiver in CDMA 07

(b) Write a short note on software defined radio 07

OR

Q.5 (a) What is the difference between 2G, 2.5G and 3G? Describe GPRS architecture. 07

(b) Compare CDMA forward and reverse channel. 07

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII EXAMINATION – WINTER 2015

Subject Code: 171004 Date:16/12/2015

Subject Name: wireless communication

Time: 10:30am to 1:00pm Total Marks: 70 Instructions:




Q.1 (a) Define the following terms regarding wireless communication:

(1) Control channel

(2) Half duplex channel

(3) Base station

(4) Mobile Switching Center

(5) Simplex systems

(6) Full duplex systems

(7) Reverse channel

07

(b) (1) With figure explain the concept of frequency reuse in detail.

(2) With figure explain hand off scenario at cell boundary

07

Q.2 (a)

(b)

If a signal to interference ratio of 15 dB is required for satisfactory forward

channel performance of a cellular system, what is the frequency reuse factor

and cluster size that should be used for maximum capacity if the path loss

exponent is (1) n=4 (2) n=3 ?

Assume that there are six co channel cells in the first tier and all of them are at

the same distance from the mobile. Use suitable approximations.

Explain the concept of Cell splitting in detail with figure.

07

07

OR

(b) Explain the concept of sectoring in detail with figure. 07

Q.3 (a) With necessary equations explain Free space propagation model in detail. 07

(b) If a transmitter produces 50 W of power express the transmit power in units of

(1) dBm and (2) dBW.

If 50 watt is applied to a unity gain antenna with a 900 MHz carrier frequency

.Find the received power in dBm at a free space distance of 100 m from the

antenna. What is Pr (10 km)? Assume unity gain for the receiver antenna.

07

OR

Q.3 (a) Assume a receiver located 10 km from a 50 W transmitter .The carrier

frequency is 900MHz.Free space propagation is assumed.Gt=1 and Gr=2. Find:

(1) The power at the receiver.

(2) The magnitude of E field at the receiver antenna.

(3) The rms voltage applied to the receiver input assuming that the receiver

antenna has a purely real impedance of 50 Ω and is matched to the

receiver.

07

(b) With figure explain Knife-edge diffraction model in detail. Write the

Equation for diffraction gain.

07

Q.4 (a) Describe the factors influencing small scale fading. 07

(b) Consider a transmitter which radiates a sinusoidal carrier frequency of 07

2

1850Mhz.For a vehicle moving 60 mph ,compute the received carrier

frequency if the mobile is moving:

(1) Directly toward the transmitter.

(2) Directly away from the transmitter.

(3) In a direction which is perpendicular to the direction of arrival

Of transmitted signal. OR

Q.4 (a) Describe briefly the types of small scale fading ( based on multipath time delay

spread)

07

(b) Describe: Time Division Multiple Access (TDMA) in detail. Write the equation

for efficiency of TDMA and The number of channels in TDMA system.

07

Q.5 (a) (1) If GSM uses a frame structure where each frame consists of 8 time slots

and each time slot contains 156.25 bits and data is transmitted at 270.833 kbps

in the channel find:

(i) The time duration of a bit.

(ii) The time duration of a slot.

(iii) The time duration of a frame.

(iv) How long must a user occupying a single time slot wait between two

successive transmissions.

(2) If a normal GSM time slot consists of 6 trailing bits, 8.25 guard bits, 26

training bits and two traffic bursts of 58 bits of data. Find the frame efficiency.

07

(b) Draw GSM system architecture and explain it in detail. 07

OR

Q.5 (a) Write short note on Code Division Multiple Access (CDMA). 07

(b) Write short note on Frequency Division Multiple Access (FDMA).

Describe non linear effects in FDMA.Also write equation for number

of channels that can be simultaneously supported in a FDMA system.

07

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII • EXAMINATION – SUMMER 2015

Subject Code: 171004 Date:04/05/2015 Subject Name: Wireless Communication Time: 02.30pm-05.00pm Total Marks: 70 Instructions:


Q.1 (a) How co-channel interference and system capacity are related?

07

(b) If 20 MHz of total spectrum is allocated for a duplex wireless cellular system and each simplex channel has 25 kHz RF bandwidth, find:

(i) The number of duplex channels (ii) The total number of channels per cell site ,if N=4 cell reuse is used

07

Q.2 (a) If a transmitter produces 50 W of power, express the transmit power in units of (i) dBm and (ii) dBW. If 50 W is applied to a unity gain antenna with a 900 MHz carrier frequency, find the received power in dBm at a free space distance of 100 m from the antenna. What is Pr(10 km)? Assume unity gain for the receiver antenna.

07

(b) Define and explain mean excess delay, rms delay spread and excess delay spread. 07

OR (b) Explain coherence time and coherence bandwidth. 07

Q.3 (a) Which are various multiple access schemes used in wireless communications? 07 (b) Explain any one technique of small-scale multipath measurements.

07

OR Q.3 (a) Briefly explain GSM logical channels.

07

(b) With the help of timing parameters, explain frame structure for GSM. 07

Q.4 (a) How does GSM radio subsystem work?

07

(b) Give differences between HLR and VLR functions. 07

OR Q.4 (a) Which are commonly used wireless propagation models? How do they differ? 07

(b) How do diversity techniques help in improving SNR? 07

Q.5 (a) Discuss the concept of spread spectrum. 07 (b) Explain how power control is achieved in CDMA. 07

OR

2

Q.5 (a) With the help of a neat sketch, describe GPRS architecture. 07 (b) Compare Wi-Fi and Wi-MAX system parameters . 07

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII • EXAMINATION – WINTER • 2014

Subject Code: 171004 Date: 27-11-2014

Subject Name: Wireless Communication

Time: 10:30 am - 01:00 pm Total Marks: 70 Instructions:




Q.1 (a) Assume a 1 Amp-Hour battery is used on a cellular phone. Also assume that this

phone draws 35 mA in the idle mode and 250 mA during call. How long the

phone will work if the phone is not switched off and has one call of 3-minute

every day? Repeat the calculation if there is one call of 3 minute every hour. Also

calculate the maximum possible talk time available with this cellular phone.

07

(b) A cellular system has 32 cells; each cell has 1.6 km radius and the system reuse

factor of 7. The system is to support 336 traffic channels in total. Determine the

total geographical area covered, the number of traffic channels per cell and total

number of simultaneous calls supported by this system.

07

Q.2 (a) In a two-ray ground reflection model, assume that phase difference must be kept

below 6.261 radians for phase cancellation reasons. Assuming a receiver height

of 2 m, and given a requirement that angel of incidence must be less than 5º,

what are the minimum allowable values for the Transmitter-Receiver separation

distance and the height of the transmitter antenna? Take the carrier frequency as

900 MHz.

07

(b) For a regular hexagonal geometry show that co-channel reuse ratio is Q= (3N)1/2,

where N= i2+ij+j2.

07

OR

(b) Compare HSCSD, GPRS & EDGE in terms of their channel bandwidth (in

KHZ), duplexing technique (FDD or TDD), maximum raw data rate supported

and name of carrier modulation used.

07

Q.3 (a) What is a Fresnel Zone?

A general design rule for microwave links is to have 55% clearance of the first

Fresnel zone. For a 1 km link at 2.5 GHz, what is the maximum first Fresnel zone

radius? What clearance is required for this system?

07

(b) Calculate the worst case carrier to interference ratio for a mobile receiver located

at the boundary of its serving cell if it is under the influence of interfering signals

from two nearest co-channels cells in a cellular system. Assume 3-sectors per cell

and a reuse pattern of 4.

07

OR

Q.3 (a) For an identical received power at the boundaries of original larger cell with

radius R0 and the new split cell with half the radius of the original cell, show that

transmitter power of any of the new split cell must be 12 dB less than the original

large cell.

07

2

(b) Suppose that a mobile station is moving along a straight smooth surface between

base stations BS1 and BS2. The distance between BS1 and BS2 is 2000 m.

Assume that the received power in dBm at a Base station is given by Pr=P0-

10*n*log (d/d0), where d is the distance between mobile station and base station

in meters. P0 is the power at distance d0 from the mobile. Assume that P0=0 dBm

and d0=1 m. Let n denote path loss exponent which is 2.9. Given that the

minimum usable level of signal is -88dBm and the mobile is currently connected

to BS1, determine the hand-off margin if hand-off time is 4.5 second and the

mobile speed is 100 km/hr.

07

Q.4 (a) Match the following terms with its most appropriate function/use

Term Function/use

VLR Stolen phone numbers

HLR Network and country codes

EIR Current location of the subscriber

MSC Verification of the SIM

IMSI Identity of an user

SIM Temporary storage

AuC Handover

07

(b) Explain the following term with reference to CDMA

1. Power Control

2. Soft hand-off

3. Frequency hopping

07

OR

Q.4 (a) Give complete classification of small scale fading and summarize the conditions

for each type of small scale fading.

07

(b) Explain the following diversity techniques briefly:

1. Space diversity techniques

2. Frequency diversity techniques

07

Q.5 (a) Explain the salient features of ZigBee networks. 07

(b) In an omnidirectional CDMA cellular system Eb/No required is 20 dB. If 100

users, each with a baseband data rate of 13 kbps are to be accommodated,

determine the minimum channel bit rate of spread spectrum chip sequence

assuming voice activity factor of 0.4.

07

OR

Q.5 (a) Explain in details about architecture of UWB radio and its applications. 07

(b) Determine frame efficiency of a TDMA frame structure used in GSM system.

07

*************

1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII • EXAMINATION – SUMMER • 2014



Time: 02:30 pm - 05:00 pm Total Marks: 70 Instructions:




Q.1 (a) Derive an expression for a ground reflection model assuming distance between

transmitter and receiver antenna is very large compare to heights of the

antennas.

09

(b) The received power at a distance of 100 km is 5 nw for a communication link.

Determine the received power at a distance 200 km for the same link. Assume

free space propagation mechanism.

05

Q.2 (a) For the Knife-edge geometry of FIG.1 show that ʋ=α(2 d1 d2/(λ(d1+d2)))

1/2 ,

approximately. Assume d1,d2>>h

07

(b) If a baseband binary message with a bit rate of 100 kbps is modulated by an RF

carrier using BPSK , answer the following:

a. Find the range of values required for the rms delay spread of the channel

such that the received signal is a flat-fading signal

b. If the carrier frequency is 5.8 GHz, what is the coherence time of the

channel, assuming a vehicle speed of 30 miles/hr

c. For your answer in part b, is the channel “fast” or “slow” fading?

07

OR

(b) Approximately how large can the rms delay spread be in order for a binary

modulated signal with a bit rate of 25 kbps to operate without an equalizer?

What about an 8-PSK system with a bit rate of 75 kbps?

07

Q.3 (a) Draw the architecture of GSM system and explain each block in brief. 07

(b) Suppose that a mobile station is moving along a straight smooth surface

between base stations BS1 and BS2. The distance between BS1 and BS2 is

2000 m. Assume that the received power in dBm at Base station is given by

Pr=P0- 10*n*log (d/d0), where d is the distance between mobile station and

base station in meters. P0 is the power at distance d0 from the mobile. Assume

that P0=0 dBm and d0=1 m. Let n denote path loss exponent which is 2.9.

Given that the minimum usable level of signal is -88dBm and the mobile is

currently connected to BS1, determine the hand-off margin if hand-off time is

4.5 second and the mobile speed is 100 km/hr.

07

OR

Q.3 (a) For a seven cell reuse pattern and hexagonal cell geometry show that 120

sectoring improves signal to interference ratio by about 5 dB.

07

(b) Explain HSCSD for 2.5 GSM. 07

Q.4 (a) Explain in details about various channel assignment strategies. 07

(b) Describe the concept of Doppler effect with relevant mathematical expressions. 07

OR

2

Q.4 (a) Consider two different cellular systems that share the following characteristics.

The frequency bands are 825-845 MHz for uplink and 870-890 MHz for the

downlink. A duplex circuit consists of one 30 kHz channel in each direction.

The systems are distinguished by the reuse factor, which are 4 and 19

respectively. For these systems, (i) Find the number of simultaneous

communications that can be supported by a single cell in each system. (ii)

Suppose that in each systems the cluster of cells (4,19) is duplicated 16 times,

find the number of simultaneous communications that can be supported by each

system. (iii)Suppose the average user makes 6 calls per 24 hours and mean call

duration is 6 minutes, estimate the total number of users that can be supported

by each system.

08

(b) Compare GSM, IS-136 and IS-95 standards in terms of modulation schemes,

multiple access schemes, frequencies used, physical channel bandwidth, number

of users/ physical channel and typical power radiated by mobile stations using

these standards. Give your answer in tabulated form.

06

Q.5 (a) Differentiate adhoc wireless networks from cellular networks. 07

(b) List advantages and disadvantages of CDMA compared to GSM. 07

OR

Q.5 (a) Draw the architecture of GPRS system and explain in brief about each block. 07

(b) What is software defined radio? List key features of software defined radio.

Also, mention its applications.

07

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1


GUJARAT TECHNOLOGICAL UNIVERSITY BE - SEMESTER–VII • EXAMINATION – WINTER 2013



Time: 10:30 TO 01:00 Total Marks: 70 Instructions:




Q.1 (a) Explain the following terms with respect to wireless networks:

(i) Frequency Reuse (ii) Co-channel interference (iii) handoff (iv)

Umbrella cell approach v) Dwell time vi) Cell dragging

06

(b) Explain (i) Concept of frequency reuse (ii) 2G and 3G wireless networks. 06

( c) Why is hexagonal cell shape preferred over square or triangular cell shape

to represent the cellular architecture

02

.

Q.2 (a) Calculate the total available channels for a cellular system having a total

bandwidth of 60MHz which uses two 50 kHz simplex channels to provide

full duplex voice and control channels. Assume that the system has nine

cell reuse pattern and 1 MHz of the total BW is allocated for control

channels, determine an equitable distribution of control channels. Also

calculate the number of the control channels and voice channels/cell.

Assume the area of the cell is 9 Sq Km and the area of the entire system is

3630 Sq Km. If the cluster size is reduced to 4, what is the system capacity.

Comment on this.

07

(b) Prove that for a hexagonal symmetry,the co-channel reuse ratio is given by

Q=√(3N).

07

OR

(b) Illustrate the principle of cell splitting in a cellular system. Prove that the

transmit power of the microcell must be reduced by 12 dB in order to fill in

the original coverage area with microcells, while maintaining the S/I

requirement for the path loss exponent n=4.

07

Q.3 (a) Discuss the fixed channel allocation, Channel borrowing and dynamic

channel allocation techniques in cellular systems.

07

(b) Explain the three basic propagation mechanisms which

impact the propagation of signal in a mobile environment.

07

OR

Q.3 (a) Compare the S/I ratio for a mobile radio for the following cases of cellular

system with frequency reuse factor of 7 for (i) Omni directional antenna (ii)

1200 Directional antennas.

07

(b) Explain free space propagation of radio signal.Establish the relation for the

received power in free space. Define path loss in free space.Calculate the

received power at a distance of 3 KM from the transmitter if the path loss

exponent α is 4.Assume that the transmitting power of 4 W at 1800MHz.,a

shadow effect of 10.5 dB,and the path loss at a reference distance (do=100

m) of -32dB.What is the allowable path loss? .

07

2

Q.4 (a) Draw the block diagram of the reference architecture of GSM and explain

the function of each subsystem

07

(b) Explain (i ) The effects of multipath fading

(ii) Doppler spectrum

(iii) Multipath delay spread

07

OR

Q.4 (a) With the aid of block diagrams, explain in detail the IS-95 CDMA forward

and reverse channels and compare the two

07

(b) What is meant by Hand off and explain different Hand off strategies How

handoff operation is performed while mobile moves into a different cell

while a conversation is in progress.Discuss the cases for proper and

improper handoff situations.

07

Q.5 (a) Describe GPRS system architecture. 07

(b) Comparison of TDMA and CDMA multiple Access Techniques in detail. 07

OR

Q.5 (a) Discuss the need and features of Ad hoc wireless network 05

(b) List the security issues of wireless networks. 03

(c) Write a brief note on OFDM. 06

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