Basics of ADSL Communication Using Simulink

This two-day intensive course covers the foundations of digital communications in the particular setting of Asymmetric Digital Subscriber Line (ADSL) systems and shows how Simulink can be employed to benefit development work in this area. The concerns of this course are almost exclusively confined to Physical Layer issues.

 Both baseband and bandpass digital transmission issues are introduced over the first day of the course, interspersed with various supporting topics. The remainder of the course phases in more ADSL-specific modulation, filtering and noise/interference coverage. The course is focused on signal conditioning matters, and does not furnish any detailed treatment of coding or protocol issues. Throughout, selected application topics highlight the central ideas as well as the ways that appropriate simulation models can be quickly assembled in Simulink. A pictorial approach is taken in the hands-on computer sessions, 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 behavioral 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, with a special thrust into the ADSL application area.

 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 and Communications Blocksets by constructing simple models which are run and examined for sensitivity to subsystem parameter choices. Participants make frequent 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, each participant receives full executable solutions to all in-course exercises and copies of m-files and mdl-files used in the course.

Who Should Attend?

The course is aimed at participants comfortable with the mathematical foundations of communications engineering. Familiarity with the MATLAB environment would be an advantage, but is not required.

Course Content

Day 1:  Introducing ADSL and Simulink

Overview of ADSL objectives, operational constraints and solution approaches. Rate-Reach limitations. Surveying a “bare-bones” ADSL model in Simulink. Displaying vector sizes and sample rates; frame-based signaling advantages in Simulink. Error rates.

Generation of ADSL signals, incorporating voiceband signals. the need for shaping the symbol pulses. Performance degradations arising from Intersymbol Interference (ISI) - at baseband and passband - and background noise. The Nyquist pulse-shaping requirements for evading ISI, featuring raised-cosine Nyquist filters in particular. Generating and interpreting eye diagrams. How root-raised-cosine filters improve the eye.

Multi-Carrier Modulation as a narrowband hedge against broadband channel impairments. Discretizing in both time and frequency; the centrality of the FFT in Discrete Multitone Transmission (DMT). Issues with the FFT in MATLAB and Simulink.  Pushing inside 16-QAM to see detailed modeling techniques and waveforms and how errors are monitored and recorded.

 Gap usage in data rate estimation. Deriving geometric Signal-to-Noise Ratio estimates; using channel gain in loading subchannels to maximize bit rate. Matrix solution of the water-filling optimization analogy; tone-ordered encoding. Dynamic effects in channel filtering models and comparisons to wireless environments.

Day 2:   Deeper ADSL Details

Exercising a fuller ADSL Simulink model; linking to G.922 and other relevant Standards. Scrambling and Forward Errror Correction.  Latency effects.

Measuring signal amplitude distributions; peak-to-average signal levels; clipping effects on DMT signals and their spectra; Conformance to power spectral density transmission masks.

Circular convolution effects with IDFTs, leading to cyclic prefixes in DMT. Imposing noise and fading channel degradations in ADSL; assessing noise/distortion floors.

Impulsive noise; generation of Cook pulses; modeling Near-End and Far-End Crosstalk. AGC modelling and parameterization. De-Interleaving and Descrambling.

Introduction to Stateflow for receiver state machine implementation and protocol modeling.