Question 1 (a) Radio wave propagation does not necessarily require a line of sight between the transmitter and receiver antennas. Describe the various mechanisms that enable radio communication in the...

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Question 1 (a) Radio wave propagation does not necessarily require a line of sight between the transmitter and receiver antennas. Describe the various mechanisms that enable radio communication in the absence of a line of sight. Your answer should consider communication both locally and across continents and describe in general terms how these mechanisms depend on frequency or wavelength. You may use diagrams where appropriate. (250 words). A square wave is described by the following Fourier series: By means of a suitable diagram, show the frequency-domain representation (amplitude only) of the square wave for the first four components. Label the frequency axis in Hz or kHz and state the amplitude of each component. (8 marks) (c) This part of the question is about Shannon’s equation. There is reference material on this topic at the end of this paper. (i) What assumptions did Shannon make about noise in deriving his equation? (ii) A channel has a signal-to-noise ratio of 30:1 and a bandwidth of 6 MHz. What is the maximum channel capacity in Mbit s-1? (iii) In order to increase the channel capacity you calculated in (c)(ii), which of the following options would be effective, and which would not? Which would have the greatest effect? (200 words) • Increasing the number of bits per symbol in the modulation scheme • Increasing the signal power to bring the S/N ratio up to 200:1 • Using error-correcting coding • Doubling the bandwidth (10 marks) PART 2 Question 2 (a) A (6,1) Repetition code is used for channel coding purposes. Determine the following: (i) What is the Hamming Distance of this code? (ii) State the error detecting and correcting capability of this code. (iii) Expressed as a percentage, what is the redundancy R of this code? (iv) Explain with reasons, whether this code is a perfect code. (5 marks) (b) Both Turbo Codes and Low-Density Parity Codes employ soft-decision decoding in preference to hard-decision decoding. What is the difference between these two decoding methods, and by means of a simple sketch or diagram, explain in your own words, the benefit of using soft-decision decoding in the error correcting process? (7 marks) (c) Table Q10 displays the respective probabilities pi of a data source comprising six different symbols, A to F. The entropy H of this code = 2.15 bits per symbol. Determine the following: (i) How many bits are required if a fixed-length binary code is used to represent these symbols? (1 mark) (ii) Generate the corresponding Huffman coding tree and determine the respective code words for each of the six symbols. (11 marks) (iii) What is the average Huffman code word length? (2 marks) (iv) What is the efficiency of the Huffman code? (2 marks) (v) By calculating the corresponding efficiency of the fixed-length code in part i., comment upon how this compares with the Huffman code efficiency in part iv. (2 marks) Question 3 (a) 4G and 5G mobile communications use the same method for sharing the radio spectrum between multiple simultaneous users. Explain this multiple access method and compare how it is used in 4G and 5G. (200 words) (7 marks) (b) Figure 1 shows a 4G LTE resource block, like the one shown in the Block 3 module materials. Explain what an LTE resource block is, including what the y-axis and x-axis in this diagram represent. (100 words) (c) If the minimum number of resource blocks that can be allocated to a user in the frequency domain is 6, and the shortest duration of allocation is 1ms, what is the minimum resource allocation to a single user in terms of resource blocks? If all subcarriers are modulated using 64-QAM what is the theoretical data rate for a user with the minimum resource allocation? (8 marks) Question 11 8 TM355 June 2021 (d) Figure 1 and the calculations in Part (c) assume a standard cyclic prefix. Explain why an extended cyclic prefix is sometimes used, what changes this makes to the resource block illustrated previously, and how this affects the data rate calculated in part (c). (50 words) (6 marks) (e) OFDM is widely used in current communication systems. As well as 4G LTE, OFDM is used in Wi-Fi. Discuss the key differences in how these two systems use OFDM subchannels, particularly with respect to providing multiple access. (150 words) (5 marks)
Answered Same DayJun 14, 2021

Answer To: Question 1 (a) Radio wave propagation does not necessarily require a line of sight between the...

Swapnil answered on Jun 14 2021
132 Votes
Question 1
(a) Radio wave propagation doesn’t require a line of sight between the transmitter and receiver antennas. Radio propagation can basically give the behaviour of travelling waves for one level to another level. In this the communication happe
ns while using the radio and the television broadcasting and the cell phones so basically it can have called as the two-way transmission radios. The radio waves are basically used for the carrying the information from transmitter to receiver where it can help to the sight line by the transmitter and receiver antennas.
Various mechanisms that can enable the radio communication are following.
In the radio waves the propagation in space can give the different mechanisms these are basically includes like reflection, transmission, diffraction and the scattering etc.
When the radio wave basically encounters the changing the size in medium and the propagation of new medium that can reflected via electromagnetic waves. So this medium also called as the reflection of wave.
The line of site can have used for the radio communication that can basically describe the link and its channel that cannot give the visual effect of line of sight in between the transmitting antenna and the receiving antenna.
In the line of sight, the waves are travelling in the direct path from source to receiver where it may be diffracted and refracted to the various atmosphere and the obstructions with the material and the obstacles.
In the transmission mechanism the different ways for electromagnetic waves are transmitted from the wavelength and this frequency can be used for the radiation and its particular use.
The diffraction can be used to refer the wave encounters an obstacle or the opening. SO it is defined on the waves bending that can give the obstacle and an aperture into the region of geometrical shadow of the obstacle. The frequency and number of cycles of the wavelength are gives the radio waves and the type of electromagnetic radiation with the wavelengths in the electromagnetic spectrum of the radio waves.
B) The frequency domain representation of the square ware ha the zero rise time and it is not a real waveform so the approximate value gives the real world value. So the insight can be gained by looking to the spectrum and an ideal square wave for the real waveforms can gives the 50% of the duty cycle. So the peak voltage can be 1v.
So in the idea square wave frequency that can be give the 1GHz. So the frequency values can be multiple of...
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