ece 442 c ommunication s ystem d esign l ecture 1. m odulation husheng li dept. of eecs the...
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ECE 442 COMMUNICATION SYSTEM DESIGNLECTURE 1. MODULATIONHusheng Li
Dept. of EECS
The University of Tennessee
COURSE INFORMATION
Lecturer: Husheng Li Time: 12:40pm --- 1:55pm Location: MK404 Office time: 3pm --- 4pm, everyday Office: MK644 Course website http://web.eecs.utk.edu/~husheng/ECE442_2012.htm
TEXTBOOK
A. B. Carlson and P. B. Crilly, Communication Systems, 5th edition, McGraw Hill, 2010
REFERENCE BOOK (1)
J.Proakis and M. Salehi, Digital Communications, 5th Edition, McGraw Hill, 2008
REFERENCE BOOK (2)
A. Goldsmith, Wireless Communications, Cambridge, 2005
REFERENCE BOOK (3)
D. Tse and P. Viswanath, Fundamentals of Wireless Communication, Cambridge, 2005
LOGISTICS
Grading: midterm/final tests (50%), homework (4 problems each week, 25%), projects (totally 3, 25%)
Projects: Project 1: Use Matlab Simulink to simulate the
performance of a communication system (deadline: midterm)
Project 2: Use Matlab to implement the coding and decoding algorithms of convoulutional codes. Evaluate the performance (deadline: April 15th).
Project 3: A report about 4G systems (deadline: Final exam)
COVERAGE
DIGITAL MODULATION / DEMODULATION
Modulation means loading digital information bits into the continuous waveforms at the transmitter. Demodulation is the inverse procedure.
When a sinusoidal signal is used for radio emission, the information can be carried at the three elements: amplitude (amplitude-shift keying: ASK), frequency (frequency-shift keying: FSK) and phase (phase-shift keying: PSK).
)sin()( wtAtx
ILLUSTRATION
BANDPASS SIGNAL
Any modulated bandpass signal can be writtend in the following quadratic-carrier form:
The equivalent lowpass spectrum is defined as
)sin()()cos()()( twtxtwtxAtx cqcic
)()()( fGfGfG qilp
AMPLITUDE MODULATION
An M-ary ASK signal can be written as
A special case is called OOK.
k
Dk kDtpatx )()(
SPECTRUM EFFICIENCY The spectrum efficiency is given by
HzbpsM /log2
QAM
Quadrature-carrier AM (QAM) achieves twice the spectrum efficiency of binary ASK
Signal Constellation
PHASE MODULATION
An M-ary PSK signal is expressed in general by
which can be decomposed into the quadrature form.
k
Dkccc kDtptwAtx )()cos()(
QPSK 8-PSK
FREQUENCY MODULATION
In FSK, the frequency is given by
kdck afff
SPECTRUM OF FSK
The i and q elements of Sunde’s FSK are mutually independent.
Sunde’s FSK has very little spillover.
M-ARY ORTHOGONAL FSK AND CPFSK
For the M-ary orthogonal FSK, the M keyed frequencies are spaced by
In CPFSK, the information signal is
the RF signal is then given by
2/2/12 rDfd
0
)()(k
Dk kDtpatx
t
dccc dxwtwAtx0
cos)(
COHERENT BINARY SYSTEMS
A coherent bandpass system employs information about the carrier frequency and phase at the receiver to detect the message.
A noncoherent system does not need synchronization with the carrier phase, thus causing performance degradation compared with coherent bandpass system.
BANDPASS BINARY RECEIVER
The filter for optimum binary detection should be matched to the difference between the two signaling waveforms.
TWO ALTERNATIVE APPROACHES
Parallel matched
filter
Correlation detector
HOW TO ANALYZE THE BIT ERROR RATE?
When the two possible outputs are z1 and z0, the bit error rate is given by
2
|| 01 zzQPe