Tutorial Set 7
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| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering | ___________________________________________________________________________________ | TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 | Tutorial Set 7 Use the following questions to explore the subject areas involved, exploring your understanding on the topics rather than to simply stop at answering the questions. 1) State the basic propagation mechanisms that impact propagation in mobile communication, outlining how they arise. 2) What is meant by Free Space Propagation? How does this compare with Multipath propagation? 3) Define Rayleigh and Rician Fading. How do the amplitude and phase variations of the received signal envelopes compare? 4) Which propagation models are utilized by the operators in Tanzania? 5) Explain the cause of Frequency Selective Fading. How would you characterise this in the time domain and what is its effect on digital transmission? 6) Define the term coherence bandwidth and explain its significance. 7) How does the phase of a ray vary as a mobile receiver moves? How can this be used to derive an expression for the maximum Doppler frequency? 8) What factors influence the maximum Doppler frequency experienced by a radio system? 9) What is the significance of the coherence distance and how does it relate to the coherence bandwidth? 10) Describe the significance of the Rayleigh and Rician PDF and CDF statistics. 11) How can the Level Crossing Rate and Average Fade Duration statistics be used to help predict the performance of a cellular radio system? 12) What do you understand by the term “Irreducible Error”? In a typical mobile radio channel, what mechanisms result in such error floors? 13) What are the definitions of normalised Doppler and normalised Delay Spread? Why are these normalised values useful? 14) What value of normalised Delay Spread is often assumed as the maximum tolerable for non- equalised systems? 15) In a cellular system, what do you understand by the terms Reuse Distance and Cluster Size? How is this linked to Co-channel Interference? 16) How does a system’s C/I protection ratio effect the networks capacity? 17) The term D/R often denotes the co-channel reuse ratio. Prove that this value squared is equal to 3N, where N is the cluster size. 18) Derive an expression relating the cluster size N to the S/I ratio. List any assumptions made.
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TE 412
Transcript of Tutorial Set 7
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
___________________________________________________________________________________
| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 |
Tutorial Set 7
Use the following questions to explore the subject areas involved, exploring your understanding on the
topics rather than to simply stop at answering the questions.
1) State the basic propagation mechanisms that impact propagation in mobile communication,
outlining how they arise.
2) What is meant by Free Space Propagation? How does this compare with Multipath propagation?
3) Define Rayleigh and Rician Fading. How do the amplitude and phase variations of the received
signal envelopes compare?
4) Which propagation models are utilized by the operators in Tanzania?
5) Explain the cause of Frequency Selective Fading. How would you characterise this in the time
domain and what is its effect on digital transmission?
6) Define the term coherence bandwidth and explain its significance.
7) How does the phase of a ray vary as a mobile receiver moves? How can this be used to derive an
expression for the maximum Doppler frequency?
8) What factors influence the maximum Doppler frequency experienced by a radio system?
9) What is the significance of the coherence distance and how does it relate to the coherence
bandwidth?
10) Describe the significance of the Rayleigh and Rician PDF and CDF statistics.
11) How can the Level Crossing Rate and Average Fade Duration statistics be used to help predict the
performance of a cellular radio system?
12) What do you understand by the term “Irreducible Error”? In a typical mobile radio channel, what
mechanisms result in such error floors?
13) What are the definitions of normalised Doppler and normalised Delay Spread? Why are these
normalised values useful?
14) What value of normalised Delay Spread is often assumed as the maximum tolerable for non-
equalised systems?
15) In a cellular system, what do you understand by the terms Reuse Distance and Cluster Size? How is
this linked to Co-channel Interference?
16) How does a system’s C/I protection ratio effect the networks capacity?
17) The term D/R often denotes the co-channel reuse ratio. Prove that this value squared is equal to
3N, where N is the cluster size.
18) Derive an expression relating the cluster size N to the S/I ratio. List any assumptions made.
| University of Dar es Salaam | Department of Electronics and Telecommunications Engineering |
___________________________________________________________________________________
| TE 412 Introduction to Wireless Communications | Christine Mwase | 10/03/2014 |
19) What are the disadvantages of cellular systems with small cells?
20) What is Handover and why is it required in a cellular system? Assuming a single user moving
between cells, describe the mechanism for a simple 4 frequency reuse pattern.
21) What advantages are presented by the umbrella cell approach?
22) What are the various channel allocation techniques used in cellular communication?
23) What is an Erlang?
24) Write down an equation for the capacity of a cellular system in Erlangs/MHz/km2.
25) What would you suggest for increasing the capacity of a cellular radio network?
26) What would you suggest for increasing the coverage of a cellular radio network?
27) What are microcells and why do they offer high potential capacities?
28) What are picocells and femtocells?
29) State the international, regional and national organizations that ultimately influence spectrum
management in Tanzania.
30) Distinguish allocation, allotment and assignment as used in spectrum management.
31) Provide reasons for the choice of the 900 MHz band for mobiles.
32) How is it that multiple operators make use of the same band?
33) Describe technical efficiency and economic efficiency as considered by regulators when managing
radio spectrum.
34) What is refarming and when does TCRA apply it?
35) What is spectrum congestion? What causes it and what can be done to avoid it? What can be done
once spectrum is congested?
36) Distinguish between 1G, 2G, 3G and 4G networks. Detail the network architecture, speeds,
frequency band, bandwidth and access technologies.
37) Provide examples of 1G, 2G and 3G systems used in Tanzania.
38) What are the benefits of paging systems?
39) State the multiple access technologies used in mobile communication, outlining their differences.
40) Describe the near-far effect and the power control mechanism used in CDMA.
41) State the duplexing techniques used in mobile communication, outlining their differences.
42) Describe the architecture of a GSM system.
43) What frequencies are used on the forward and reverse links in GSM?
