Compare and contrast transmit and receive diversity. Describe how each diversity type lead to an improvement in system performance. Solution Diversity refers to a technique for improving the transmission of a signal, by receiving and processing multiple versions of the same transmitted signal. The multiple versions can be the result of signals following different propagation paths, being transmitted at different times or frequencies. In Transmit diversity, Spatial diversity is introduced into the signal by transmitting through multiple antennas. The antennas are spaced far enough so that the signals emanating from them can be assumed to undergo independent fading. In addition to diversity gain, antenna gain can also be incorporated through channel state feedback. TD can improve the receiver performance in the presence of flat fading. It reduces impact of fading by offering mutliple copies of the digitally modulated waveform at the receiver, where the chance that all copies are simultaneously in a fade is very small. In receiver diversity, the use of diversity at receiver needs combining the outputs of statistically independent fading channels, in accordance with a criterion that leads to improved receiver performance. Several techniques have been studied for diversity combining. Some of these techniques are selection combining, maximal ratio, equal gain and square law combining. When using diversity transmission and reception, the amount of received signal improvement depends on the independence of the fading characteristics of the signal as well as circuit outages and failures..

1. Compare and contrast transmit and receive diversity. Describe how each diversity type lead to an
improvement in system performance.
Solution
Diversity refers to a technique for improving the transmission of a signal, by receiving and
processing multiple versions of the same transmitted signal. The multiple versions can be the
result of signals following different propagation paths, being transmitted at different times or
frequencies. In Transmit diversity, Spatial diversity is introduced into the signal by transmitting
through multiple antennas. The antennas are spaced far enough so that the signals emanating
from them can be assumed to undergo independent fading. In addition to diversity gain, antenna
gain can also be incorporated through channel state feedback. TD can improve the receiver
performance in the presence of flat fading. It reduces impact of fading by offering mutliple
copies of the digitally modulated waveform at the receiver, where the chance that all copies are
simultaneously in a fade is very small. In receiver diversity, the use of diversity at receiver
needs combining the outputs of statistically independent fading channels, in accordance with a
criterion that leads to improved receiver performance. Several techniques have been studied for
diversity combining. Some of these techniques are selection combining, maximal ratio, equal
gain and square law combining. When using diversity transmission and reception, the amount of
received signal improvement depends on the independence of the fading characteristics of the
signal as well as circuit outages and failures.