ECE 5930/6930  Wireless Communication

Midterm II 

November 16, 2001

Name ____________________________________

Class:  ECE 5930         ECE 6930

You may use your portfolio, calculator, and a pencil.  No textbooks.

Good luck, and do well!

1. (10 points)  An analog message signal m(t) is shown below.  Assume the carrier is significantly higher frequency than the message signal.

(a) Sketch the AM signal that is transmitted.

(b) Sketch the FM signal that is transmitted.

2. (15 points)

(a) Given a perfect BPSK signal with no noise, sketch the eye diagram if the pulse shape is gaussian.

(b) Sketch the constellation diagram.

(c) Show and/or explain how the CONSTELLATION diagrams will change if

i. The carrier frequency is increased slightly.

ii. White gaussian noise is added to signal.

iii. Strong multipath signal creates echo that is out phase with the signal. 

iv. The signal is poorly synchronized.

v. Power control is poor.

3. (25 points)

(a) Sketch the hardware for a BPSK receiver and explain what each part of the circuit does / how it works.

(b) If you did not already do this in part (a), sketch the hardware for a phase locked loop, and explain how it can be used as a carrier recovery circuit.

(c) Explain how your BPSK system would be adapted for a CDMA Direct Sequence Spread Spectrum (DSSS) receiver.

4. (25 points) How many users can a CDMA IS-95 cell support given:

· Blocking propability = 1%

· Shadow margin = 10 dB

· Path loss exponent = 3.2

· Voice activity factor = 0.6

· Other cell interference factor = 0.6

· Spreading bandwidth = 1.23 mHz

· Data rate = 9.6 kbps

· Cell loading = 0.7

· Power control standard deviation = 4 dB

· Mobile power = 18 dBm.

· Gain of mobile antenna = 1 dB

· Gain of base station antenna = 9 dB

· Fading margin = 5 dB

· Noise figure = 5 dB

· Temperature (Kelvin) = 290

· Boltzman’s constant = 1.380662 x 10^-23

· Frequency reuse factor = 0.4

· Number of users = 20.

5. (25 points) In a CDMA-95 cellular system

· EXPLAIN the following parameters. 

· If the parameter increases, what happens to the system capacity?

Increase this parameter                    What  happens to System Capacity?

      (a)  Chip Rate                                             Decrease          NoChange        Increase

(b) Same Cell Interference              Decrease          NoChange        Increase

(c ) Power Control Standard Deviation       Decrease          NoChange        Increase

(d) Voice Activity Factor                            Decrease          NoChange        Increase

(e) Reverse Link Power                              Decrease          NoChange        Increase

(e) SIR                                                       Decrease          NoChange        Increase

            ECE 5930/6930 Wireless Communication

Midterm II

Name ________________________________

Problem 1  __________ / 10 points

Problem 2 __________ / 15 points

Problem 3 __________ / 25 points

Problem 4 __________ / 25 points

Problem 5 __________ / 25 points

Total         __________ / 100 points

Grades are posted on the website.

Please check your grade using the student id number ON THIS SHEET OF MIDTERM I.

Please email Dr. Furse is grades are missing/incorrectly recorded.  furse@ece.usu.edu

Thank you!

Grading:

Exam grade is based on the best of:

            Average of midterm I, II and Final

            OR Final only.