How preamble signal is generated in Massive MIMO Hybrid Beamforming

In Massive MIMO Hybrid Beamforming, a preamble signal is sent over all transmitting antenna elements for CSI. It uses the function named helperGenPreamble.m which is designed for 256 carriers. What is the theory behind the choice of Frequency subcarrier tones namely ltfSC. How can we extend it to 1024 carriers?

Answer 1

[Amit Kansal]

The sequence selected in helperGenPreamble.m is based on the Long Training Field (LTF) used in WLAN (802.11) standards. It is basically a set of tones at the subcarriers that are known (pre-designed) at both the transmit and receive ends.

Extensions to other FFT sizes should be straightforward. Just update the ltfSC vector values directly to represent the subcarriers that carry data, which would be hence used for sounding purposes.

hope this helps,

Amit

[Rochelle Thomas]

Could you please explain all the exact changes that need to be done, to extend this to 4096 FFT with an example calculation ?