Cork Institute of Technology
Bachelor of Engineering (Honours) in Electronic Engineering - Award
(EELXE_8_Y4)
Summer 2008
Mobile Communication Systems Engineering
(Time: 2 Hours)
Answer any three questions for full marks
Maximum available marks is 100.
Examiners: Dr. D. Pesch
Prof. W.G. Hurley
Dr. S. Foley
Q1. (a) Calculate the level crossing rate and average fade duration that a mobile
station experiences when the communication parameters are as follows:
• The mobile station experiences an average received power level of
PR = -75dBm (normalised to 1Ω resistance) at a fading threshold of
R = 30µV for Rayleigh fading.
• The carrier frequency of the signal is fc = 2100MHz, the average
mobile user speed is v = 10km/h, and the speed of light is c = 300,000
km/sec.
In what control function and how can the level crossing rate be used to
enhance the operation of a cellular mobile network?
You may find some of the information given in the Appendix below useful for
the required calculations. [10 marks]
(b) List two modulation schemes used in current mobile communication system
standards and list three requirements for modulation schemes used in mobile
radio systems. [10 marks]
(c) A cellular system with two cell sizes is depicted in Figure 1. Calculate the
signal to interference ratio (in dB) that mobile station M, located at the cell
fringe of the centre cell, experiences caused by interfering base stations Ai, i =
1 … 6. Assume that the interfering base stations are located in the centre of
their respective cells, that all cells use omni-directional antennae, constant
transmitter power PTX, and a propagation path loss exponent of γ = 3.5. [13.33 marks]
