Wednesday, 2 May 2012

LTE 'Antenna Ports' and their Physical mapping

People who work with LTE Physical layer and maybe higher layers would be aware of this term called 'Antenna Ports'. I have always wondered how these antenna ports are mapped to physical antennas.

The following is from R&S whitepaper:

The 3GPP TS 36.211 LTE standard defines antenna ports for the downlink. An antenna port is generally used as a generic term for signal transmission under identical channel conditions. For each LTE operating mode in the downlink direction for which an independent channel is assumed (e.g. SISO vs. MIMO), a separate logical antenna port is defined. LTE symbols that are transmitted via identical antenna ports are subject to the same channel conditions. In order to determine the characteristic channel for an antenna port, a UE must carry out a separate channel estimation for each antenna port. Separate reference signals (pilot signals) that are suitable for estimating the respective channel are defined in the LTE standard for each antenna port. 

Here is my table that I have adapted from the whitepaper and expanded. 




The way in which these logical antenna ports are assigned to the physical transmit antennas of a base station is up to the base station, and can vary between base stations of the same type (because of different operating conditions) and also between base stations from different manufacturers. The base station does not explicitly notify the UE of the mapping that has been carried out, rather the UE must take this into account automatically during demodulation (FIG 2).


If there is another way to show this physical mappings, please feel free to let me know.

The R&S Whitepaper is available here if interested.

5 comments:

Mark said...

Thanks for the info: Very Helpful

Emi Sam said...

This is not for the novice. Mapping of logical antenna ports to physical ones needs a good technological base. Thanks for the informative content.

Md. Aliullah said...

Hi,

Looks like the whitepaper link is broken.
I found the new link http://www.rohde-schwarz.co.uk/file/NEWS_204_english_LTE_Option_K84.pdf

Zahid Ghadialy said...

Thanks for letting us know, I have fixed the link.

Gabriela said...

Thank you very much!