This course gives a very practical approach to channel modeling and simulation as well as wideband modulation parameterization and simulation. Beginning with channel parameters description, the student model in Matlab a multipath channel. This channel is then sounded in order to analytically extract the parameters it has been created with. After that, the basics of spread spectrum and multicarreier modulations are introduced. From previous channel acquired knowledge, the student is trained in modulation adjustment to channel parameters and joint simulation, also in Matlab.
Titular Professors
Professors
- Signal processing. - Digital communications.
The main objectives of C4HC are as follows:
- To develop advanced skills in channel parameterization and simulation.
- To extract channel parameters by sounding techniques.
- To develop advanced skills in wideband modulations and coding parameterization and simulation.
- To be able to design a proper wideband modulation and coding scheme in order to cope with channel impairments.
- To acquire sufficient coding skills to demonstrate previous objectives.
1. Modeling of transmission channels
1.1. Introduction
1.2. Mobile radio channel
1.3. Channel degradation factors
2. Channel estimation
3. Optimal equalization in Gaussian channels
4. Equalization based on filters
5. Cases
5.1. Satellite communications
5.2. Vehicular communications
5.3. Underwater communications
5.4. Ionospheric communications
5.5. Power line communications
The subject has a weekly operation with 1 teaching session of 3 hours a week. The first six sessions are dedicated to the theoretical presentation of the contents, while the other six are dedicated to practically implementing a case where the concepts learned in the theory are deepened.
Theoretical part
During the six theoretical sessions, the theoretical foundations of propagation in multi-path environments and the sounding and equalization techniques used in this type of channel are explained. The explanation is done with the help of the transparencies and the collection of problems of the subject.
The explanation of this theory is combined with the realization of an exercise of continuous evaluation consisting of the study and comprehension of a scientific article.
Finally, all this is complemented by exercises with Matlab so that students know the basic functions that they will have to use during the realization of the practical case.
Case study
For the case study, each group of three students receives a different scientific article. These articles deal with different multi-path channels (ionospheric channel, NVIS, PLC, underwater acoustic communications, ...).
Each group of students works independently of the others and follows their own pace. In addition to advancing with the simulations, the groups take advantage of the class sessions to resolve any doubts that may have arisen in their work at home.
The first part of the case study consists of the analysis of the corresponding article to extract the parameters of its channel. With this information, students have to implement this channel with Matlab and then extract the parameters.
Once they have implemented the channel model, they must use it to transmit information. The ultimate goal is to achieve the maximum possible transmission speed by keeping a bit error rate below a certain threshold. Usually groups start by evaluating channel behavior with simple modulations such as BPSK. With this type of modulation they achieve low performance. Most groups are able to evaluate the channel with more complex modulations such as OFDM or DSSS. With this they usually achieve much better performance. Finally, students propose channel codes, interleaving, and so on. which they believe are most suitable for their channel.
To pass the subject, the theoretical part and the practical part must be passed separately. In this case, the final evaluation of the subject is the arithmetic mean of the evaluation of each of the two parts.
The following will be assessed:
- Ability to model and analyse transmission channels, adequately identifying degradation factors and relating them to the theoretical concepts of the subject.
- Mastery of estimation and equalization techniques, assessing the correct application and interpretation of optimal methods based on filters in Gaussian scenarios.
- Rigor in the simulation case study, evaluating the implementation of the channel model, the coherence of the analysis and the ability to optimize and justify the goodput obtained.
- Clarity and quality in technical communication, including the formal presentation of the work, the argumentation of the results and the appropriate use of simulation and analysis tools.
Course slides.
[1] Smith, C., `3g wireless networks´, McGraw Hill, 2002.
[2] Hanzo, L., `OFDM and MC-CDMA for broadband multi-user communications, WLAN & broadcast´, Wiley, 2003.
[3] Bahai et al., `Multi-carrier digital communications. Theory and applications of OFDM´, Springer, 2011.
[4] Wong V. et al. `Key Technologies for 5G Wireless Systems´, Cambridge University Press, 2017.