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Lab Course Communications Technology / Praktikum Nachrichtentechnik

Description

Lecturer: Prof. J. Lindner, Prof. W. Minker, Dr. W. Teich
Supervisors:Members of the Institute
Program of Studies:Master Elektrotechnik, Communications Technology, Informationssystemtechnik
Hours:0/0/4/0 (5 ECTS)
Contents:The aim of the laboratory course is to consolidate and complement the subjects covered in the lectures "Communcations Engineering I" and "Communcations Engineering II". Therefore it is recommended to take the laboratory course accompanying to the lecture "Communications Engineering II". In the experiments measurements on signals, transmission channels, and simulated transmission systems are carried out. The equipment consists of PCs, special hardware, workstations, and measurement hardware like oscilloscopes etc. Detailed material (lab handouts) is provided for each experiment. The laboratory course consists of the following nine experiments, eight of which have to be carried out successfully in order to pass the laboratory course:
Semester:Winter (ENGC7007) / Summer (ENGC6004)
Requirements:Communications Engineering I / Nachrichtentechnik I
Language: Englisch / German
Exam:Certificate
Time and Place:Friday, 8:00-12:00, 43.1.102
Additional Information:

Topics

1. Measurements on Stochastic Signals. This experiment is connected with the foundations treated in the lecture "Signals and Systems", respectively in the beginning or the lecture "Communications Engineering I". It is intended to repeat some basic knowledge in the field of stochastic signals by using noise and speech signals. Probability and probability density functions, power density spectra, and quantities derived from that are measured.

2. Modelling and Simulation of Transmission Media. Measurements with a Channel Simulator Here the topic "time-varying transmission channels" is considered. Time-variant channel impulse responses and transfer functions are measured and analysed. The real-time baseband channel is realised with transputer boards plugged into a PC.

3. Digital Transmission with Linear Modulation Methods, Part 1. Transmission in Baseband With the examples NRZ, AMI, Manchester, and bipolar transmission with "raised cosine" the most important details of a digital transmission are treated: transmission models, correlation receiver, spectral power density of transmitted signals, eye pattern, and bit error rates. Measurements are made with oscilloscopes and a PC.

4. Digital Transmission with Linear Modulation Methods, Part 2. Transmission over Bandpass Channels The core of this trial is a modem, designed for data transmission over stochastic time-varying multipath channels. It uses 2,4,8, or 16PSK as modulation and has an adaptive decision feedback equalizer (DFE). Signal space scatter plots are measured and discussed, also error rates and time-variant channel impulse responses of the actual channel, which are measured internally by the modem algorithms. A special channel simulator is used. The consequences of switching-off the DFE are also evaluated.

5. Application of Orthogonal Signals in Communications. The principle of orthogonality plays a central role in communications. This trial looks at the most important methods which are based on it: Transmission with orthogonal waveforms and multiplexing (TDM, FDM, CDM). In addition to basic measurements, the consequences of non-orthogonality are demonstrated and analysed.

6. Spread Spectrum Method. Because of their inherent advantages compared with more conventional methods, methods based on spread spectrum are discussed as candidates for mobile communications. This trial deals with the two most important of those methods (Direct Sequence and Frequency Hopping). Power density spectra of PN sequences are measured and discussed and also the resistance of these methods against narrow and broadband interference.

7. Channel Coding and Modelling of Data Channels. This topic is treated by considering simple Hamming codes and Reed Solomon (RS) codes, which have become more and more important in practical applications. For discrete channels (BSC) and a channel which is disturbed by bursts, error probabilities are measured and the influence of coding parameters is discussed.

8. Source Coding for Automatic Speech Recognition. With the example of automatic speech recognition, several methods of feature extraction, i. e. source coding of speech signals are examined. At first, the discrete Fourier transform and speech signal preprocessing are discussed, then the performance of speech recognition systems (using different source coding methods) are compared with the help of self-recorded speech signals.

9. Transmission over real HF channels. Synchronization aspects Real data transmission is carried out on HF frequencies between remotely controlled transmitter/receiver stations in Ulm and Lancaster, UK. The effect of frame synchronization, carrier synchronization, and symbol synchronization becomes immediately clear from viewing the received picture of a transmitted black/white image. Also the properties of HF propagation are considered.