The midterm will include 4 problems (each with multiple parts) on the following topics. Sample questions are given below to help you study. Problems will include both calculation and “explain” parts. You may use your portfolio and calculator, but no textbook. Be sure that you copy the important graphs/tables from your book and put them in your portfolio. The exam is 1 hour long.
Suggested exam-taking strategy: Look through all the questions, and begin with the one you feel most confident. Write down all of the information you need to solve the problem (equation, values of the variables that go into the equation, etc.). Do this for all of the problems. Leave the actual calculations (calculator-punching) until last. Partial credit is given, and more of this partial credit is given for the set-up of the problem than for the calculator-punching. Remember to write down what you are thinking/doing, so that if you make mistakes, I can give you partial credit. NO credit will be given for answers (even if correct) if nothing is given to show how you obtained them. (ie. Don’t just program all the equations in your calculator, and write down the answer without writing down the equation.)
1. Describe how a cellular telephone system works, the major parts (from PSTN to mobile), how a call is made, etc.
2. Understand the major types of systems in use today (with emphasis on GSM and AMPS) What are the aspects that are different/similar between the various systems?
# of channels, # of cells, size of cells
3. Given the available bandwidth and bandwidth of a channel, how many channels are in a given cell, cluster, and system? Understand the different types of channels (voice, control, etc.) and how they are distributed within the system.
4. Given N, find the S/I for cochannel interference, and determine if it meets system specifications. Or, given the required S/I, determine what N needs to be.
5. Determine the minimum radius of a cell for a given S/I.
adjacent channel interference
6. Determine the S/I ratio for a typical system.
trunking and grade of service
7. Calculate traffic intensity for the system, channel, or user.
8. Determine the grade of service given the number of channels and traffic intensity.
cell splitting , cell sectoring
9. Determine how cell splitting or sectoring affects the answers to questions 3-8.
Path Loss / Large Scale Fading
** For the following sections on large and small scale fading, be sure you understand the basis of how the equations/formulas/etc. were derived, what approximations were made, and what the limitations are on when you should/should not use these models. You will not be asked to derive the equations, but should be able to explain what they are based on.
Friiss transmission equation
given distance, antenna gains, received power required, and frequency,
determine the required basestation power. Be sure you understand what
10. Determine the reflected and transmitted field and power levels for given incident angle, frequency, and materials (electrical properties would be given). Be sure you also understand the polarization of the fields.
11. Calculate the field and power received given antenna heights, gains, and frequency.
12. Determine if you are in a peak or shadow fresnel diffraction region.
13. Understand the effect of diffraction and its significance (what does it do in the system).
Rough surface scattering
Global path loss models
Link Budgets (combination of all chapters)
14. Be able to calculate the power received given power transmitted and measured losses within the system. Determine when you should use a given path loss or fading model, and be able to include it in the link budget.
15. Explain the importance of path balance, and be able to determine appropriate base station power to achieve path balance.