# Precoding algorithm for OFDM

I working on an implementation of a linear precoding algorithm for MIMO OFDM system and I have an issue with symbol estimation part. Let me briefly explain what I am doing:

• H- channel matrix Nr x Nt x N ( received and transmitted antenna, subcarrier)
• x- input data (F x Nt x N) ( streams x Tx antenna x subcarrier)

I have started with a calculation linear precoding matrix -V: 1) I have computed SVD for each subcarrier Hn (Nr x Nt)

2) "x" has been split into streams and each vector Nt x 1 has benn used for " V *x_vector".

I have made the same calculation for each stream and get a precoded input data "D (Fx Nt x N) "

Then I use "D" in the standard OFDM block diagram(IFFT, add CP, channel, FFT, remove CP) and get a received data "R (Fx Nr x N)"

Now to estimate the input data, I have split into streams, then vectors Nr x 1 and take a product U [svd(Hn)] with Nr x 1 and after a result has been ./diag(S) I have exected to get better performance of the system with precoding, but SER I have got bigger than without precoded algorithm.

Could anyone suggest where I have mistaken?