# Practical meaning of 'Joint Carrier Frequency Offset and Channel Estimation'

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#### ychang44

##### Newbie level 1
Hi all,

I'm implementing STBC-MIMO and MIMO-OFDM system using SDRs.
Before doing actual coding, I'm working on MATLAB simulation of CFO estimation and recovery and channel estimation.

I'm reading some Dr. Giannakis' papers about joint CFO and channel estimation.
Besides Dr. G, I know that many people have researched joint CFO and channel estimation. However, it's not easy for me to understand the feasibility of this joint estimation.

According to many standard MIMO receiver's structure, the foremost block in the baseband processing is 'symbol clock recovery and carrier recovery'. As I understand, this block should take care clock offset between transmitter and receiver so that the channel should keep steady after this block in the case of flat fading. After this block, the channel estimation can be carried out.

On the otherhand, the joint estimation of CFO and channel estimates both of them simutaneously. But I'm confused the term of 'channel' in the presence of CFO. Many papers use this model;

$\mathbf{y}(t) = e^{(j\omega_0t)}\mathbf{x}(t)\mathbf{H} + v(t)$

In the presence of CFO with above model, people define the channel to be estimated as the channel at t=0. However, in the joint estimation, the channel is usually estimated by using the estimated CFO. Therefore, even if estimated CFO has a very slight error, it makes the whole channel rotate significantly and makes decoding fail.

How can I apply this joint estimation to practical receiver design? Is it really practical technique? Please correct me if I'm wrong.