19-11-2012, 04:17 PM
Mobile Communication
Mobile Communication.pdf (Size: 105.31 KB / Downloads: 81)
Wireless propagation of signals
• Faces many complications
• Mobility renders reliable wireless
transmission much more difficult
• Antenna height and size at mobile
terminals generally quite small
Propagation properties
• Obstacles in the vicinity of the antenna a
significant influence on the propagated
signal
• Vary with place and, for a mobile
terminal, with time
Spherical radiation pattern and Line of sight Signal strength
Decreases as the square of the distance
from the transmitter in free space
• Larger distances the radiated power is
distributed over a larger spherical
surface area
Diffraction of signals
Signal bends as a result of diffraction
from the edges of an obstacle of size
equal to or less than the wavelength.
• GSM signal of wavelength 33 cm will
diffract from an object of 33 cm or less.