CENG 5931 GNU Radio Instructor:Dr.Collins Presented by Geetha Paturi ( )

Contents

 Data communication system (requirements)  Robust to error  Sufficient data rates  Network capacity constraints  Achieve balance between these requirements to overcome conflicting system operating parameters.

 Bit error rate(BER)  Band width efficiency

 Representation of Signals  Euclidean Distance between Signals  Decision Rule  Power Efficiency  M-ary Phase Shift Keying  M-ary Quadrature Amplitude Modulation

 From a signal constellation plot we can see how an error may occur in the transmission whenever the actually received signal vector is incorrectly shifted to another signal constellation point by noise contribution.  Euclidean Distance and vector representation between two signals is defined as

Nearest neighbor rule waveform representation

Constellation map of 16 QAM

Single input/Single output MCM transmitter Single input/Single output MCM receiver

ADVANTAGES Transmission agility High data rate Immunity to non-flat fading response. “divide-and-conquer” channel distortion Adaptive bit loading DISADVANTAGES Sensitive to narrowband noise Sensitive to amplitude clipping Sensitive to timing jitter, delay

 To improve quality of received signal equalizers are employed.  Design decisions of equalizer depend on a number of factors such as type of distortion and implementation complexity. Distortion reduction  To mitigate effects of distortion introduced by the channel there are two techniques. Channel coding-Adding redundancy Channel equalization-effects of channel are inverted at receiver

 When transmissions are sent across a dispersive channel it is possible for the output of that channel intercepted by the receiver to be distorted via temporal spreading resulting in overlapping of individual symbol pulses.

To channel SOURCE IMPULSE MODULATION H(f)Pulse shaping filter

 Mathematical tools necessary for enabling advanced features  Various modulation schemes can be used for transmission under different constraints and expectations  Bit Error Rate is primarily used to define performance  Digital communication theory at the core of cognitive radio operations

1.“Cognitive radio communications and networks principles and practice” By A.M.Wyglinski,M.nekovee,Y.T.Hou(Elevier,December 2009) 2. Sklar, B.;, "Defining, designing, and evaluating digital communication systems," Communications Magazine, IEEE, vol.31, no.11, pp , Nov 1993 doi: / Kolumban, G.; Kennedy, M.P.; Chua, L.O.;, "The role of synchronization in digital communications using chaos. I. Fundamentals of digital communications," Circuits and Systems I: Fundamental Theory and Applications, IEEE Transactions on, vol.44, no.10, pp , Oct 1997 doi: /