CHAPTER 5

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1. You can experiment with various parameters for serial communication using the Hyper Terminal program on Windows. You need to connect two PCs using an RS232 cable. Figure C.4 shows the screenshot to set the serial communication parameters.

   
   Figure C.4: Screenshot to set the serial communication parameters.

   To get this screen, you need do the following:

   • Click on Start

   • Go to Programs

   • Go to Accessories

   • Go to Hyper Terminal

   • Double click on HYPERTERM.EXE

   • Enter a name for New Connection "xxxx" and Click OK

   • You will get a screen with the title Connect To. Select COM1 or COM2 from the Connect Using listbox and click OK.

2. "Parity can detect errors only if there are odd number of errors". To prove this statement, consider the bit stream 1010101. If we add an even parity bit, the bit stream would be 10101010. If there is one error, the bit stream may become 11101010. Now the number of ones is 5, but the parity bit is 0. Hence, you can detect that there is an error. If there are two errors, the corrupted bit stream is 11111010. However, in this case, the calculated parity bit is 0, the received parity bit is also 0, and the even number of errors cannot be detected.

3. If the information bits are 1101101, the even parity bit is 1, and the odd parity bit is 0.

4. If the information bits are 110110110, when Rate 1/3 FEC is used for error correction, the transmitted bit stream will be
   111111000111111000111111000
   Suppose the received bit stream is
   101011100011110001110110100
   There is one bit error for every three bits. Even then at the receiver, the correct bit stream can be obtained. However, suppose the first three bits received are 001, then the receiver will decode it as 0 though the actual information bit is 1.

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