Question 1

A. The digital data representing two ASCII characters ‘Hi’ (8-bit each) is to be transmitted as a binary signal. Draw the signal waveforms if data is encoded according to following schemes. Also state the encoding rules for each scheme (i.e. how bits are converted to signals)

1. RZ
2. NRZ-L
3. NRZ-I
4. Manchester (look it up online)

(2 marks × 4)

B. Now suppose that the same data is to be transmitted as an analog signal. Draw the signal waveforms if the following modulation methods are used. Once again, also state the modulation rules for each method.

1. ASK
2. FSK
3. 16-QAM

(2 + 2 + 4 marks)

Question 2

Comment on the correctness of these statements. Provide justifications to support your argument. No credit will be awarded for simply stating true or false.

1. A spread spectrum signal appears as noise to narrow band receiver.
2. Packet switching is ideal for voice communications.
3. A bandpass filter is used to convert an input signal to a higher desired frequency.
4. Time division multiple access eliminates the problem of crosstalk.
5. A telephone conversation is an example of simplex transmission.
6. It is always beneficial to have a high gain antenna.

(4 marks × 6)

Question 3

A point to point, line of sight communication link operates at a frequency of 3 GHz. Assume the transmitter and receiver antenna gains are 10 dB each. Before the transmitting antenna, a 5 dB power amplifier is also installed. Receiver can correctly decode the signal as long as it is above the noise level of -70 dBm.

1. If the distance between transmitter and receiver is 2 km, calculate the minimum source power required so that receiver can easily detect the signal.
   Provide the answer in watts or milliwatts. Show all workings
2. If source signal power is 500 W, how far the transmitter and receiver can be (at most)?

You will need to use the free space path lossformula.

(5 + 5 marks)

Question 4

Do a research on Bluetooth Low Energy (BLE) and write a short essay on it. You should briefly cover its technical specifications, hardware requirements and applications.

Limit your essay to 500-700 words.

(28 marks)

To demonstrate academic integrity, cite all of your information sources. Use APA-7 referencing style.