S-72.227 Digital Communication Systems
Study Guide 7: Equalization in (wideband) TDMA

Topics

• Three basic equalization methods
• Linear equalization (LE)
• Decision feedback equalization (DFE)
• Maximum likelihood sequence estimation using Viterbi algorithm (MLSE-VA)
• Example of channel estimation circuit

• What is meant by equalization in a TDMA system?
• List three kinds of linear equalization algorithms (Answer: zero-forcing, LMS, and RLS algorithm)
• What is the basic idea in zero-forcing equalization? (Hint: use frequency domain for demonstration)
• Define the basic structure of an LMS equalizer (needed: FIR filter, decision circuit, and LMS functional block)
• Define the basic structure of a DFE equalizer.
• Explain implementation details of feed-forward filter (FFF) and feedback filter (FBF), including coefficient calculation.
• Define the basic structure of a channel estimation circuit.
• What is meant by training sequence and decision directed operation?
• Can these two concepts (training sequence and decision directed operation) also be used in case of LMS equalizer?
• Define the basic structure of a Maximum likelihood sequence estimation circuit using Viterbi algorithm (MLSE-VA).
• Explain the meaning of sequence estimation state, state trellis, and state transition.

Lecture notes; John G. Proakis: Digital communications (selected parts of Chapter 10 and 11, 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.