Data Communications Question Paper
Data Communications
Course:Bachelor Of Science In Computer Science
Institution: University Of Nairobi question papers
Exam Year:2016
UNIVERSITY OF NAIROBI
SCHOOL OF COMPUTING AND INFORMATICS
DATA COMMUNICATIONS
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This question is about physical layer transmission system
A transmission system uses a data coding scheme that defines a symbol as a voltage that can have one of sixteen possible values. If the system operates at a transmission rate of 400 symbols per second, determine the data rate measured in:
Baud; [2 marks]
Bits per second. [2 marks]
A transmission system uses a coding scheme that defines a symbol as comprising one of eight possible voltage levels. How many bits of information can be represented by each symbol? [2 marks]
If the coding scheme described in part b) is used to transmit information at the rate of 100 baud, what is the information rate measured in bits/sec? [2 marks]
Show, with the aid of a diagram, how the bit pattern ‘10010111’ would be encoded using Manchester encoding. [2 marks]
Briefly explain how wave division multiplexing (WDM) is able to increase the amount of data that can be transmitted along a single fibre optic cable. [4 marks]
A fibre optic transmission system uses wave division multiplexing with 16 different wavelengths of light. Each of these wavelengths is able to operate at 1Gbps. If it requires 64,000bps to transmit an uncompressed telephone call, determine the maximum number of telephone calls that can be transmitted at the same time using this fibre optic cable. [6 marks]
This question is about multiplexing
Explain why framing and synchronization are important in a TDM system. [4 marks]
In a hierarchical TDM system, at what bit rate does the output of a given level need to operate? (Express the answer in terms of the number and bit rate of inputs.) [2 marks]
Suppose N users compete using a statistical TDM system, and suppose the underlying physical transport can send K bits per second. What is the minimum and maximum data rate that an individual user can experience? [4 Marks]
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