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Data Communication and Net-Centric Computing (COSC1111)
Answer questions (10 marks in total)
Q1 (5 marks)
Figure 1 shows a multiplexer in a synchronous Time Division Multiplexing (TDM) system. The bits arrive at the multiplexer is from sources A, B, then C. One frame will take 4 bits from each source until all the bits from source A, B and C are transmitted completely.
The binary from Source A is shown in the figure, while Source B is the binary converted from your student ID based-on mod 2 operation. The Source C is a voice signal.
1. Give an example to show the details for adapting the voice signal of Source C into the multiplexer. (2 marks)
2. Based on above example, give the output stream of first two frames. (1 mark)
3. What kind of error may occur for the multiplexer collects input at Source C, and how this error affects the performance at receiver end? (1 mark)
4. Further to discuss how the above-mentioned error differs from the error at data link layer from system level. (1 mark)
Figure 1 Synchronised TDM Multiplexing.
Q2 (5 marks)
There is an example in week 5 lecture notes regarding Transmission time: T = L/R, where L is the length of the frame, R is the transmission rate. The transmission time of this packet T = 0.12 ms, while it takes 20 ms for a packet being transmitted from Melbourne to Cairns.
1. What conclusion you can draw in comparison of the transmission delay and propagation delay? Give your justification for your conclusion. (1 mark)
2. Following figure show Frame 0 and ACK1 in stop-and-wait error control. Give detailed information in relates to the calculation of t1 and t2 . (2 marks)
3. If ACK 2 is lost, draw a figure to show the processing at both the sending-end and the receiving-end. (2 marks)
Figure 2 Stop-and-wait error control.