# What exactly is precoding and what does it do?

1. ## What exactly is precoding and what does it do?

What is precoding? Can anyone explain me or give me a link to provide a fundamental knowledge on precoding please.
Thank you.

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2. ## what is precoder

I have checked the wikipedia "http://en.wikipedia.org/wiki/Precoding", it says that it is related to Beamforming & MIMO. does everyone think so?

3. ## channel precoder

Precoding is a technique which exploits transmit diversity by weighting information stream, i.e. the transmitter send the coded information to the receiver in order to the pre-knowledge of the channel. The receiver is a simple detector, such as matched filter, and does not have to know the channel side information. This technique will reduce the corrupted effect of communication channel.

For example you are sending information, s
and it will pass through the channel, h
and Gaussian noise, n

The receiver will have to know the information about h and n. It will supress the effect of n by increasing SNR but what about h? It need information about the channel, h and this will increase the complexity. The receiver, mobile units, have to be simple for many reasons like cost, size of mobile unit. So, the transmitter, base station, will do the hard work and predicts the channel.

Let call the predicted channel, h_est
and for a system with precoder the information will be coded, s/h_est
and the received signal will be, r=(h/h_est)s+n

if your prediction is perfect, h_est=h, and r=s+n, and it turns out to be the detection problem in Gaussian channels which is simple.

4. ## need of precoding

So why do they call it "coding"? what you explain sounds much like "equalization at the transmitter".

5. ## precoding fundamental

It is a preprocessing technique that performs transmit diversity and it is similar to equalization but the main difference is you have to optimize precoder with a decoder. Channel equalization aims to minimize channel errors, but precoder aims to minimize the error in the receiver output.

6. ## precoder wikipedia

usually transmitter does not know about channel, if there is a feedback than transmitter will get a information about the channel by adaptive filter.

The adaptive coading at the transimitter will be done in this way. This is called precoading of the signal at the transmitter

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7. ## common precoder

By using pilot-assisted techniques, transmitter will have ability to predict the channel without feedback. It is called forward error control, and precoding is a technique of forward error control.

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8. ## precoding book

Originally Posted by ks1267
What is precoding? Can anyone explain me or give me a link to provide a fundamental knowledge on precoding please.
Thank you.
I have some works about precoding over MIMO channels. If you need tell me.

1 members found this post helpful.

9. ## common precoder

Originally Posted by ks1267
What is precoding? Can anyone explain me or give me a link to provide a fundamental knowledge on precoding please.
Thank you.
I have some works about precoding over MIMO channels. If you need tell me.

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