S-72.227 Digital Communication Systems
Study Guide 8: Diversity techniques for flat fading channels

Topics

• BER vs. S/N in a flat fading channel
• Different kinds of diversity techniques
• Selection diversity
• Maximum ratio combining (MRC)

• Derive the BER vs. S/N relationship for 2-PSK in case of a flat fading channel.
• List the corresponding BER vs. S/N relationships for DPSK and 2-FSK.
• How does the BER vs. S/N curve behave when S/N becomes very large?
• What kind of diversity methods are available in case of a flat fading channel?
• What is the difference between selection diversity, EGC (equal gain combining) and MRC (maximum ratio combining)?
• How does the BER vs. S/N relationship change when the diversity order increases?
• Derive the performance of selection diversity.
• Derive the performance of MRC.
• What is the relation between MRC and matched filtering?

Lecture notes; John G. Proakis: Digital communications (selected parts of Chapter 14, 3rd Edition)
 

DAG Instructions

This guide is intended for Discussion Agent Group (DAG) members, but it can be used also by other students. DAG members should get themselves familiar with the lecture material and Study Guide well before the lecture and make clear for themselves the themes they would like to generate discussion. If it appears that there remain unsolved questions after the session they will be discussed in next sessions. It is important to note that the time reserved for discussion is maximum of 45 min. only.

Group's tasks

• Group should select session Chair. The role of the session chair is to give the floor for audience and to guide discussion generally.
• Group should select a secretary whose task is to write down all the questions and answers popping out at the session. The minutes should be submitted to the course instructor within two days and it will appear at the course homepage.
• Lecture themes (from lecture transparencies and study guides) must be divided to group members such that each member shall carry about the same workload. Also chair and secretary must participate on drafting the questions.

Each group member should

• Make a list of interesting questions/issues she/he knows the answer. Purpose of these questions is to clarify/underline important topics of the lecture (from one's personal view)
• Make a list of topics/themes/details that are not understood
• Propose answers to the suggested questions (as listed above)
• Ask the suggested questions from the audience during the session.