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Final Transmitted Sequence - Spread Spectrum Communication - Exam, Exams of Communication

Unity Degree College - Lucknow Communication

Main points of this exam paper are: Final Transmitted Sequence, Transmitter, Receiver Block Diagram, Advantages, Frequency Hop, Spread Spectrum, Transmission Bandwidth Process, Fast Hop, Frequency Hop Spread, Spectrum

Typology: Exams

2012/2013

Uploaded on 04/15/2013

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Cork Institute of Technology

Bachelor of Engineering (Honours) in Electronic Engineering- Award

(NFQ Level 8)

Summer 2007

Spread Spectrum Communications

(Time: 2 Hours)

Examiner: Dr R.A. Guinee

Answer 3 questions Prof. G. Hurley

Dr. S. Foley

Q1. (a) Draw the transmitter and receiver block diagram for a Frequency Hop spread spectrum

system and explain its operation. Discuss the advantages and disadvantages of this form

of spread spectrum communication. Determine the transmission bandwidth process

gain for a fast hop system in terms of the FH_SS parameters.

(14 %)

(b) A Frequency Hop spread spectrum system employs a fast hop with

k = 10 hops per message bit

M = 1024 frequencies

Message bit rate =2.5 kBPS

Final RF multiplication =10

Determine (i) the RF signal bandwidth, (ii) Processing gain in dB, pN Code generator

clock rate and (iv) the frequency separation in kHz.

(12 %)

(c) Explain the parallel method of receiver code search used in a frequency hopping

acquisition scheme and its advantages.

(7.33 %)

[33.33 %]

Discover Exams of Communication Unity Degree College - Lucknow

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Cork Institute of Technology

Bachelor of Engineering (Honours) in Electronic Engineering- Award

(NFQ Level 8)

Summer 2007

Spread Spectrum Communications

(Time: 2 Hours)

Examiner: Dr R.A. Guinee

Answer 3 questions Prof. G. Hurley

Dr. S. Foley

Q1. (a) Draw the transmitter and receiver block diagram for a Frequency Hop spread spectrum

system and explain its operation. Discuss the advantages and disadvantages of this form

of spread spectrum communication. Determine the transmission bandwidth process

gain for a fast hop system in terms of the FH_SS parameters.

(b) A Frequency Hop spread spectrum system employs a fast hop with

k = 10 hops per message bit

M = 1024 frequencies

Message bit rate =2.5 kBPS

Final RF multiplication =

Determine (i) the RF signal bandwidth, (ii) Processing gain in dB, pN Code generator

clock rate and (iv) the frequency separation in kHz.

(c) Explain the parallel method of receiver code search used in a frequency hopping

acquisition scheme and its advantages.

Q2. (a) A pseudonoise (pN) code generator produces a 63-bit sequence at a clock rate of

20MHz. What is the equation and graphical form of the autocorrelation function (ACF)

of the sequence assuming that the pulses have values ±2 volt. Comment on the shape of

the ACF and the line density of the PSD in terms of the pN sequence length and clock

rate (10 %)

(b) The data sequence x(t), given by 100110001, is fed to the DS/BPSK spread spectrum

transmitter in Fig Q2-(a) at a rate of 75 BPS with the leftmost bit first.

Data Signal x(t)

pN Code g(t)

Carrier 2 P cos ω 0 t

BPSK o/p

s ( t )= 2 Px ( t ) g ( t )cos ω 0 t

BPSK

Modulator

Fig. Q2_(a)

Fig. Q2_(b)

g(t) 1 0 1 0

The pN code generator in Fig Q2-(b) emits the PRBS stream g(t) at a rate of 225 chips

per sec from an initial seed 1010.

(i) Sketch the final transmitted sequence x(t)g(t).

(ii) What is the bandwidth of the transmitted signal?

(iii) What is the processing gain?

(iv) If the received signal delay T d is a single chip with respect to the receiver PRBS

g(t) sketch the resultant despread sequence. (14 %)

Correlator

pN Code g ( t − T ˆ d )

A *^2 P ⋅ x ˆ( t − T ˆ d )

r ( t )= A 2 Px ( t − Td ) g ( t − Td )cos[ω 0 ( t − Td )+ φ ]

BPSK Data Demodulator

Fig. Q2_(c)

Filter

Final Transmitted Sequence - Spread Spectrum Communication - Exam, Exams of Communication

Related documents

Partial preview of the text

Download Final Transmitted Sequence - Spread Spectrum Communication - Exam and more Exams Communication in PDF only on Docsity!

Cork Institute of Technology

Bachelor of Engineering (Honours) in Electronic Engineering- Award

(NFQ Level 8)

Summer 2007

Spread Spectrum Communications

(Time: 2 Hours)

Examiner: Dr R.A. Guinee

Answer 3 questions Prof. G. Hurley

Dr. S. Foley

Q1. (a) Draw the transmitter and receiver block diagram for a Frequency Hop spread spectrum

system and explain its operation. Discuss the advantages and disadvantages of this form

of spread spectrum communication. Determine the transmission bandwidth process

gain for a fast hop system in terms of the FH_SS parameters.

(b) A Frequency Hop spread spectrum system employs a fast hop with

k = 10 hops per message bit

M = 1024 frequencies

Message bit rate =2.5 kBPS

Final RF multiplication =

Determine (i) the RF signal bandwidth, (ii) Processing gain in dB, pN Code generator

clock rate and (iv) the frequency separation in kHz.

(c) Explain the parallel method of receiver code search used in a frequency hopping

acquisition scheme and its advantages.

Q2. (a) A pseudonoise (pN) code generator produces a 63-bit sequence at a clock rate of

20MHz. What is the equation and graphical form of the autocorrelation function (ACF)

of the sequence assuming that the pulses have values ±2 volt. Comment on the shape of

the ACF and the line density of the PSD in terms of the pN sequence length and clock

rate (10 %)

(b) The data sequence x(t), given by 100110001, is fed to the DS/BPSK spread spectrum

transmitter in Fig Q2-(a) at a rate of 75 BPS with the leftmost bit first.

s ( t )= 2 Px ( t ) g ( t )cos ω 0 t

BPSK

The pN code generator in Fig Q2-(b) emits the PRBS stream g(t) at a rate of 225 chips

per sec from an initial seed 1010.

(i) Sketch the final transmitted sequence x(t)g(t).

(ii) What is the bandwidth of the transmitted signal?

(iii) What is the processing gain?

(iv) If the received signal delay T d is a single chip with respect to the receiver PRBS

g(t) sketch the resultant despread sequence. (14 %)

Correlator

r ( t )= A 2 Px ( t − Td ) g ( t − Td )cos[ω 0 ( t − Td )+ φ ]

(c) Describe the demodulation process illustrated in Fig.Q2_(c) and discuss in detail the

action of the correlator in the synchronization process. (9.33 %)

Q4. (a) Describe briefly the operation of a Bluetooth Wireless Personnel Area Network

(WPAN) as envisaged in the Bluetooth Baseband Specification in terms of (i)

transmission power constraints, (ii) system timing and available hop frequencies, and

(iii) Master-Slave link types with payload capacities. (9 %)

(b) Discuss Bluetooth Wireless packet structure according to the standard packet format

shown in Fig Q4-(b0) under the following headings:

(i) Access Code - format shown in Fig Q4-(b1)

(ii) Packet Header - format shown in Fig Q4-(b2) (15.33 %)

ACCESS CODE HEADER PAYLOAD

LSB 72 54 0 - 2745 MSB

Fig Q4-(b0) Bluetooth Standard Packet Format

PREAMBLE SYNC WORD TRAILER

LSB 4 64 4 MSB

Fig Q4-(b1) Bluetooth Access Code Format

AM_ADDR TYPE HEADER ERROR CHECK

LSB 3 4 8 MSB

Fig Q4-(b2) Bluetooth Header Format

FLOW

ARQN

SEQN

(c) Discuss the operation, usage and payload rates of the following physical link types

associated with Bluetooth master – slave dialogue

(i) Asynchronous Connection-Less link

(ii) Synchronous Connection Oriented channel (9 %)

Explain the purpose of error control in the packet header field in each case.