TCOM 370

Exam 2 Information

Exam 2 will be given on Wednesday March 17, 1999

The exam rooms and times are as follows:

6:00 - 7:30 in Room 315, Towne Building

7:00 - 8:30 in Moore 216

Please come to either one of these two sections, according to your convenience.

You are allowed one information page, and you may also use the one from the last exam.

Material Covered for Exam 2:

You are responsible for all the material covered in class since your first exam.

You should study the Notes that have been handed out, and any notes you have from classroom lectures. You should also study the appropriate sections in your text book.

- Voice Digitization. Sampling and Quantization.
- Synchronization and Line Coding
- Error Control Coding

Time Division Multiplexing in the PSTN

Study **Notes 6.** Know the sampling theorem, understand the quantization process. Understand how bit-rate depends on quality of the digital representation.

Understand the basic idea of time-division multiplexing and how it is applied in the early stages of multiplexing of voice channels.

Relevant **textbook** material is on pages 69 through 73

Study **Notes 7**. Study the following:

Asynchronous (start/stop) transmission with free-running clocks.

Synchronous transmission, and the two ideas used in implementing it (clock extraction, local clock synchronization with received timing information). The use of appropriate line coding to achieve these. In particular, know all the line coding* *schemes treated in Notes 7.

Also understand the basic ideas for achieving frame synchronization for asynchronous character transmission and for synchronous transmission.

Relevant **textbook** material is on pages 101 through 125. Use the Notes as the main guide and read the text for additional details and discussion.

Review homework problems you have done and previous exam questions on this topic.

The textbook is not very detailed on this, **your main focus should be on** **Notes 8 and 9.**

Study Notes 8 on *linear block codes* and Huffman codes. Some explanations and details were given in class, such as the relationship between d_{min} and the error correction, and error detection, capability of a code.

Now how to compute error probabilities in simple situations involving coding.

Study Notes 9 on Cyclic Codes and CRC coding. You should know the definition of linear cyclic block codes and its implications. You should know how a systematic polynomial error detection code is constructed using long division, and how long division is also used at the receiver to check for errors.

You should know the basic error detection capabilities of CRC codes.

Notes 9b contains some additional information, it is *mostly optional*. One important fact that it contains is that a generator polynomial for a cyclic code must divide X^{N}+1 without a remainder.

You need not worry about details of practical shift-register implementations of the coder/decoder.

The main part of the textbook to focus on is **section 3.4.3,** excluding implementation details at the end.

Study the homework problems/solutions, and previous exam problems.

J GOOD LUCK ! J