Point 2 Point Comm.

1. UNIT-2
Point-to-Point Communication:
Detection in a Rayleigh Fading Channel
Time Diversity
Antenna Diversity .
Frequency Diversity
Impact of Channel Uncertainty

2. Diversity

6. • Similarly Transmit Diversity, if there are
multiple Transmit antenna.
• And it is also possible multiple transmit as
well as receive antenna than both Transmit
as well as receive diversity.
• Similarly we can send the signal at different
time slot it is called as Temporal diversity

7. • Similarly, signal is send at different carrier a
frequency called frequency diversity.
• Transmit the signal between different user
called multi user diversity.
• Hence Diversity play a major role to combat
fading and decrease the bit error rate and
improves the performance.

33. Receive Diversity
• In a flat fading channel with 1 transmit
antenna and L receive antenna, , the channel
model is as follows:
• where the noise and independent
across the antennas.

34. • We would like to detect
• If the antennas are spaced sufficiently far
apart, then we can assume that the gains
are are independent Rayleigh, and we get a
diversity gain of L.

35. • With receive diversity, there are actually
two types of gain as we increase L.
• for the error probability of BPSK
conditioned on the channel gains:

36. • We can break up the total received SNR
conditioned on the channel gains into a product of
two terms:
• The first term corresponds to a power gain (also called
array gain): by having multiple receive antennas and
coherent combining at the receiver, the effective total
received signal power increases linearly with L:The second
term reflects the diversity gain: