This
two-day intensive course covers the basics of digital communications and shows
how SIMULINK can be employed to benefit development work in this area. Both
baseband and bandpass digital transmission are introduced and selected application
topics highlight the central ideas as well as the ways that appropriate simulation
models can be quickly assembled. A pictorial approach is taken, where there
is only rarely any necessity to resort to traditional programming activity.
Easy-to-use interaction controls facilitate verification of concepts and permit
engineering tradeoffs and even major design departures to be flexibly evaluated.
The course is suitable for newcomers both to the MATLAB programming/ SIMULINK
dynamic block diagram behavioural simulation environment and to the study
of communications systems. Its prime aim is to give an accelerated overview
of SIMULINK's applicability to rapid concept-proving and effective detailed
system design for practicing engineers in industry.
The course style is to present transmitter and receiver
structures as they typically appear in textbook settings and to realize these
with blocks built from the SIMULINK DSP Blockset by constructing simple models
which are run and examined for sensitivity to subsystem parameter choices.
Participants make frequent hands-on use of soft signal analyzers (providing
oscilloscope and spectrum analyzer visualization features) to probe the operation
of models. Throughout, the emphasis is on exercising an exploration environment
closely aligned to the “feel” of laboratory instrumentation situations
which utilize benchtop test equipment.
In addition to comprehensive course notes and copies
of m-files and mdl-files used in the course, each participant receives a copy
of the Addison-Wesley book Digital Communications
by Andy Bateman, which serves as a source of many of the subjects illustrated
in this course
Signal sources
available in Simulink and their underlying discrete-time nature. Depiction
and generation of real and complex-valued discrete-time sequences. Tones,
pulses and tonebursts as the basis of information conveyance.
Spectral
Analysis: Fourier transformation by the FFT, zooming by Chirp-z transformation,
and spot frequency measures by scalar products. Signal energy, power and bandwidth
as ascertained and exhibited in Simulink.
Modification of time-domain characteristics (and attendant
spectra) by both Linear Time-Invariant (LTIV) and non-LTIV system elements.
Use of FIR digital filters in signal shaping, noise combatance and detection of arrival; assessing
rendezvous delays. Simple recursive filters for accumulation and energy determination,
including sliding-window and sum-and-dump realizations. Instantaneous nonlinearities
and time-varying devices for spectral transport and signal detection.
Fundamental transmission capacity limitations arising
from noise and bandwidth restrictions; determining when transmission at baseband
might suffice. Binary data flows and the need for shaping the symbol pulses.
Performance degradations from Intersymbol Interference (ISI) and background
noise. The Nyquist pulse-shaping requirements for evading ISI, featuring raised-cosine
Nyquist filters in particular. Generating and interpreting eye diagrams.
Effects of digital filters on random noise. Deploying
filtering resources at transmitting and receiving ends to meet the combined
ISI and noise threat. Matched filtering and orthogonality; root-raised-cosine
filters and how they improve the eye. Calculating and Simulink-experiencing
bit error rate.
Ways of invoking and balancing usage of MATLAB’s Signal
Processing and Communications Toolboxes and Simulink. Model hierarchy and
subsystem grouping for complexity management. Acceleration of Simulink signal
handling through frame-based processing, with audio demonstrations.
Library navigation
in Simulink. Guidelines for granularity in modelling. Use of Enabled subsystems.
How to mask blocks and build up your own component library.
Channel characteristics and the need for modulation.
On-off keying (OOK) and effects of baseband or bandpass filtering. Noisy reception
and error counting. Comparison of spectral-averaging instrumentation results
and theoretical power spectral curves. An easy modification to obtain binary
phase-shift keying (PSK).
Generation of frequency-shift keying (FSK) modulation.
Spectral spread with and without imposition of phase continuity constraints;
implementation of Sunde’s FSK through an FM modulator. Energy demodulation
of wideband FSK. Complex envelopes and baseband equivalent modelling to avoid
unrealistic RF simulation.
Coherent detection of FSK and effects of bandwidth shrinkage.
Remarkable theoretical aspects of minimum-shift keying (MSK). MSK phase trajectories
in theory and in practice. Confirmation of orthogonal detection of MSK with
matched-filter receivers. Power spectrum containment through baseband signal
shaping. Gaussian minimum-shift keying (GMSK) and an exercise with GSM relevance.
PSK and effects of carrier phase errors in coherent detection.
Data-derived binary PSK carrier recovery; construction and use of a Costas
loop. Extensions to multi-level digital modulation: treatment of quadrature
phase shift keying (QPSK).
Perspectives on modelling beyond the basic physical layer.
On incorporating other tools, such as Stateflow, for combined modulation/coding/protocol
models.