Diversity - 3 [Under LTE]
Macro diversity
In transmit (antenna) diversity, transmitter employ multiple antennas separated by certain distance (or direction). Similarly, multiple transmitters can be made to transmit same signals (provided receiver is able to receive multiple transmitters). This is still space diversity; earlier method can be called Micro (space) diversity and the latter can be called Macro (space) diversity.
The advantage of macro diversity is that it improves coverage greatly. But since it use resources of multiple transmitters, it is not similarly efficient and at the same time, create more inter-cell interference.
Macro diversity can be used in both uplink and downlink direction.
It can be seen that macro diversity require additional resources at network side for communication to share signals to be sent to or received.
More specific example of macro diversity is soft handover wherein (for temporary period) mobile terminal use resources from two cells in uplink and/or downlink.
Conclusion
It can be seen that there is lot of overlap between diversity techniques and it is difficult to categorise them. In fact, number of diversity scenarios are at play in field. In my opinion, for simplicity, diversity techniques can be considered as combinations of three basic diversity presentations: time, space and frequency (as shown below).
References: UMTS by Sanchez and Thioune, WCDMA for UMTS by Holma and Toskala, 3G Evolution: HSPA and LTE by Dahlman, Parkvall, Sköld, and Beming, and WiMAX handbook by Ahson and Ilyas.
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