Transmit Diversity In 4G Wireless Communications
4G Communications
MIMO can be used to exploit Diversity and increase the robustness of data transmission. Each transmit antenna transmits essentially the same Stream of data, so the receiver gets replicas of the same signal.
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1- Frequency shift transmit diversity:
In the frequency shift transmit diversity scheme, a given modulation
symbol is transmitted on a single antenna in a given subcarrier. Let yp (k) represent the signal transmitted from the pth Antenna on the kth subcarrier.
2- Time shift transmit diversity:
The time shift transmit diversity (TSTD) scheme is similar to the FSTD scheme with the difference that switching now happens in time.
Note:
The power spectral density per antenna on the transmitted subcarriers
in case of FSTD is 6 dB higher than in the uniform PSD case, With TSTD, only a single antenna can transmit at a given time. Therefore, the TSTD scheme results in 6 dB power loss compared to the reference case .In order to overcome the power loss problem of TSTD, the switching in time can be performed across virtual antenna created by precoding rather than by the physical antennas. The resulting scheme is referred to as precoding vector switching
(PVS).
3- Cyclic delay diversity (CDD):
A delay introduced multi-antenna signals. Reduce the impact of possible
unwanted signal cancellation that can occur if the same signal is transmitted from multiple antennas.
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Transmit Diversity In 4G wireless Communication channel,wireless Communication channel,
Transmit Diversity In 4G wireless Communications channel,wireless Communications channel,
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