Required multi-path delay for MIMO spatial multiplexing mode of operation

[thunderdantheman]

Folks,

Researching the various MIMO radio techniques. With regards to spatial multiplexing where discrete data streams are sent via an individual modulator, transmitter and antenna section on the same frequency and bandwidth, what practical path differences or individual channel delays are required so that the receiver can retrieve/reconstruct the independent channel streams?

Am I correct in assuming that a path difference would have to be such that several phase rotations of the carrier would be required between each receiving antenna to ensure the down converted baseband (or low IF) signals are adequately separated in time for the MIMO transforms to work?

Required multi-path delay for MIMO spatial multiplexing mode of operation - Can't edit the title..

 

[kaz1]

I don't quite get it... As far as I know, spatial multiplexing is not based on channel delay or multipath. but the streams are generated to have minimum correlation through changing phase per each stream.
This is done in digital or analogue domain by applying unique phase to each stream. It is used in various areas, not just MIMO for example the lte prach sequences (Zadoff Chu) are sent by mobile handsets that can share the same sequence but each with a different phase (cyclic shift) and send at same time to base station. Same applies to SRS signals. This phase resolution is application dependent.
For lte uplink/downlink it is used to split the signal into layers and send them simultaneously. This is done either in frequency domain data (digital) or in analogue domain and can be further assisted through antenna arrays.

 

[D.A.(Tony)Stewart]

http://etd.lib.metu.edu.tr/upload/12616330/index.pdf