Operating Systems and Computer Networks / Datenverarbeitung 2 / Data Processing 2

Transcription

1 Computer Networks / Datenverarbeitung 2 / Data Processing 2 Exercise 7: Network Transmission & Code Efficiency Faculty of

2 Question 7.1 Code Efficiency Block Length S S S Y Y O N N H 5 characters S T X E S C 2 bytes E T B C B C E O X C C T S S Y Y N N Payload Total Block Length B L = SOH + 5 bytes + STX + Payload + ETX+ BCC + BCC+ EOT = =161bytes = 161 Faculty of

3 Question 7.1 Code Efficiency No. of ESC sequences in payload = = 5 bytes Pure Payload = B L header information ESC sequences in payload = 145 bytes Code Efficiencyi Faculty of

4 Question 7.2 Optimal Block Length For erroneous transmission: net tare preamble payload trailer gross Payload transfer rate Optimal block length Faculty of

5 Question 7.2 Optimal Block Length Faculty of

6 Question 7.3 Code Efficiency STM STX ETX CRC CRC ETM 64 byte audio data (fixed length) Faculty of

7 Question 7.4 Protocol information vs. data Adding an ESC ESC ETX Adding exception sequence STT and ETT STT ETX ETT Doubling the character ETX ETX Exclude ETX from payload Possible because audio data a is transmitted Faculty of

8 Question 7.5 Probability of ETX in payload 1 Byte = 8 bits Possible distinct t number of codewords d = 256 The probability that this Byte is ETX Probability that ETX is in the payload Faculty of

9 Question 7.6 Code Efficiency a. Additional ESC Sequence b. Additional exception Sequence c. Additional ETX d. Exclude ETX from payload Faculty of

10 Question 7.7 Sampling rate, bit width Voice signal bandwidth Accuracy Sampling rate No. of discrete values To represent 200 discrete values Faculty of

11 Question 7.8 No. of phone calls Effective Bandwidth No of phone calls Faculty of

12 Question 7.9 Sender & Receiver reaction Receiver: Discards non-correctable frames Sends NACK or sends nothing at all Sender: Retransmits frame after receiving NACK Faculty of

13 Question 7.10 No. of Phone calls Error rate No. of transmitted frame per second Effective Bandwidth Faculty of

14 Question 7.10 No. of Phone calls No. of phone calls transmitted Faculty of