Is it possible to do some measurements with a different cyclic prefix?

[ref110]

Hi,

in our measurements we want simulate a LTE network with different cyclic prefixs.

Is this supported by the Communications System Design Suite or the LTE Framework?

How can we realize such measurements?

Regards

Markus

[joergho]

Hi Markus,

Could you give a bit more details on what you are planning to do? Do you already have a transmitter and only need a receiver or do you need both? Do you need LTE-compliant channel coding or are you fine with uncoded signals? Do you need it to work in real-time (e.g. where the algorithms should be implemented on the FPGA) or are you fine with a non-real-time system (e.g. where the calculations could also be done on the host)?

Depending on your requirements you could either use LabVIEW Communications to write a custom solution or benefit from the already existing LTE Application Framework. The framework would be preferrable if you need need a real-time soultion and if you need channel coding following the LTE standard.

The LTE Application Framework implements a transmitter and receiver for the LTE physical layer (downlink). It implements only normal cyclic prefix by default, but you could easily change it to support extended cyclic prefix. It includes channel estimation based on cell-specific reference symbols (CRS) or alternatively UE-specific reference symbols (UERS) and automatically compensates for clock and frequency offset.

What kind of measurements do you anticipate?

Kind regards,
Jörg

[ref110]

We need only a receiver. It is the same project as the embms threat.

We got a real LTE tesbed and we want to measure with this. But as I see so far, it is at the moment impossible

[joergho]

Hi,

similar to the other MBSFN aspects, the extended cyclic prefix does not work "out of the box", i.e. with the readily provided FPGA code and bitfile. However, the idea of the LTE Application Framework is that you have full access to the source code (Host *and* FPGA) and can easily do all modifications which deviate from the readily implemented features. This means that you can implement missing features yourself. If they are not completely new but just deviation from the existing features, this should be fairly easy to do.

Changing the cyclic prefix length mainly affects timing aspects (CP length=512 instead of 160/144, 6 subframes per slot instead of 7), so when you change a couple of numeric constants (7->6, 160/144->512), you are almost done (next steps: adopt resource mapping, channel decoder parameter calculations, also easy to do).

In case of 7,5 kHz carrier spacing (CP length=1024, 3 subframes per slot), you also have to reconfigure the FFT (FFT size: 4096 instead of 2048).

So as you can see, although it is not supported "out of the box", the LTE Application Framework offers you everything you need to implement it in a short time.

Regards,

Joerg