MIMO single Stream and dual stream

[Mdaf]

Hello,
Could anyone please explain the differnce between single stream & dual stream modes in MIMO, the only difference I can find is described below and still unclear:

In case of single stream, the same block of data is transmitted
by the BTS using two Tx antennas with a different antenna pre-coding for each of them.
In case of dual stream, two different blocks of data are transmitted from both antennas
at the same time using the orthogonal antenna pre-coding for the two blocks. In case of
dual stream, the HSDPA peak data rate is doubled as a result of the operation of two
parallel data streams.

Also what does it mean "using the orthogonal antenna pre-coding "?
Many thanks

[rsv12]

Hi,
In other words: single stream - the same symbol is transmitted in parallel by each antenna, let say in our case we have only two antennas. Receiver can get the same symbol twice. So,if for somehow it did not receive/decode the symbol from antenna 1 it still can receive/decode its from antenna 2.
Dual stream - first symbol is transmitted by antenna 1 and in parallel second symbol is transmitted by antenna 2. At one time receiver
can receive two symbols. So, compare to one symbol case peak rate is doubled.
About pre-coding you can go http://en.wikipedia.org/wiki/Precoding

[dimooon11]

It is a very good question since I have a picture for it:29962

[Mdaf]

So what is the differenc between single stream MIMO and TX diversity?

[Bilal]

Hi Mdaf,

I think that they are same. See: http://www2.rohde-schwarz.com/file_17063/1MA186_0e.pdf

regards, B.

[rajaganesh]

yeah single stream mimo and tx diversity is same. up to some extent beamforming is also same as single stream. single stream - improve channel condition. dual stream - improve data rate. if channel condition is good we can go for dual stream. if user is cell edge and cqi is bad we can go for single stream beamforming or transmit diversity. precoding is used to differentiate which antenna tx's which stream. if same block of data is sent through diff antenna's, @ receiver we can combine those signals and get single stream of data and there by improve BLER.

[firstmaxim]

Let us consider a 2 x 2 MIMO example: Single stream transmission is triggered when UE reports a Rank Indicator , RI =1. This is same as TX diversity, where both antennas transmit the same code block to the UE. However, if UE reports RI = 2, both antennas transmit a different code block to the UE. This will enhance throughput, but is used only during good channel conditions. There is another feedback called PMI (precoding matrix identifier) sent by UE which helps the transmit side to orthogonalize the two different streams.

[Mdaf]

Let us consider a 2 x 2 MIMO example: Single stream transmission is triggered when UE reports a Rank Indicator , RI =1. This is same as TX diversity, where both antennas transmit the same code block to the UE. However, if UE reports RI = 2, both antennas transmit a different code block to the UE. This will enhance throughput, but is used only during good channel conditions. There is another feedback called PMI (precoding matrix identifier) sent by UE which helps the transmit side to orthogonalize the two different streams.

Many thanks, fro my knowledge using MIMO in a cell will effect non MIMO UEs due to the fact of enabling S-CPICH so would the TX diversity do the same?