Cork Institute of Technology
Bachelor of Engineering (Honours) in Electronic Engineering - Award
(NFQ Level 8)
Summer 2006
Mobile Communication Systems Engineering
(Time: 2 Hours)
Answer any three questions for full marks
Maximum available marks is 100.
Examiners: Dr. D. Pesch
Prof. G. Hurley
Dr. S. Foley
Q1. (a) Calculate the average fade duration a mobile station experiences when the
communication parameters are as follows:
• The mobile station experiences an average received power level of
PR = -60dBm (normalised to 1Ω resistance) at a fading threshold of
R = 50µV for Rayleigh fading.
• The carrier frequency of the signal is fc = 900MHz, the average mobile
user speed is v = 60km/h, and the speed of light is c = 300,000 km/sec.
What mechanisms are available to the radio interface designer to combat this
type of fading?
You may find some of the information given in the Appendix below useful for
the required calculations. [9 marks]
(b) List three requirements for modulation schemes for use in mobile
communication systems. Which are the typical modulation schemes used in
commercial systems and briefly state as to how they fulfil the listed
requirements [9 marks]
(c) For the cellular system shown in Figure 1, show a detailed calculation of the
value of the worst case signal to interference ratio in uplink and downlink
based on a cluster size K = 7. Consider in your calculation a worst case
interferers constellation with all interferers excited, assume omni-directional
antennae, constant transmitter power PTX, and a propagation path loss
exponent of
γ
= 3.5. [15.33 marks]
