What is precoding and its advantages?

1. what is precoding ? and their benifits....

2. In what way precoding matrix differ from normal matrix and their special structure...

pls i need this info...

precoding question

Precoding assigns each subcarrier a different number of bits.

That is a very effective method much better than redundant encoding. The problem is that only the receiver nows which number is best.

Todays protocols have to much overhead to fed this receive side information back to the transmitter.

Re: precoding....

Thank u very much......


1. wheather channel state information(CSI) information require or not? if require means how to detect it...

2. How Precoding assigns each subcarrier a different number of bits?

3. In what way precoding matrix differ from normal matrix(i.e N*N) and what are the special structure of this matrix...

Re: precoding....

Sorry I messed up "precoding" with "channel coding"

Precoding if the beamforming based on subcarrier individual complex channel state information of a MIMO transmission.

Channel coding is the subcarrier individual bit coding.


Yes, both need information to send back to the transmit side.

Re: precoding....

According to ur reply, whether Precoding is only used for MIMO or SISO also...
Iam still not clear about precoding, my question is that actually what precoding doing at the transmitter side...

1. Why precoding requires knowledge of the channel state information (CSI) at the transmitter.

2. what is the importance of CSI and Wht are their parameters?

3. In what way precoding matrix differ from normal matrix and their special structure...

pls help....

Re: precoding....

Hi,

Precoding is a technique that exploits channel information at Transmitier. CSI (Channel State Information) is mandatory because precoding matrix is a function of the mimo channel.
To obtain CSI, in TDD systems it is possible to exploit the concept of reciprocity. In FDD systems, a feedback control channel is used to provide channel information to the base station.

About matrix structure...

Y= HFS+V eq (1)

where F is an Mt x M precoding matrix, S is an Mt x T space-time block codeword, and V is an Mr x T noise matrix. The precoder parameter M is chosen so that M<=Mt.

The precoder is chosen using a function "f" that maps an Mr x Mt channel realization to an Mt x M precoding matrix F= f(H).

The equation 1 covers a large range of closed-loop MIMO techniques, including beamforming (that convert a MIMO channel into an equivalent SISO channel), precoded spatial multiplexing, precoded orthogonal space-time block codes and antenna selection techniques -where M out of Mt antennas are selected for transmission (in that case F consists of M different columns of the MxMt identity matrix).

so.. the structure depends on the technique that is used.

Added after 12 minutes:


.......

"my question is that actually what precoding doing at the transmitter side... "

Precoding helps to customize the transmitted waveforms to provide higher link capacity and throughput. Using CSI at transmitter improve system capacity by sharing spatial channel with multiple users simultaneously , simplify multi-users receivers through interference avoidance, and provide a general means to exploit spatial diversity.

Re: precoding....

Thank u very much Yonel....

iam using linear precoding matrix before IFFT Modulation... also my system is SISO not MIMO..

my question are

1. if i use linear precoding matrix in SISO OFDM system, what represents rows and columns in precoding matrix...

( say for example , if i use MIMO system the matrix structure shows rows and colums are no of transmiting and receiving antennas...)

2. why it is called precoding? is there any specific reason for this name..

3. how precoding matrix helps to increase spectral compactness ? pls justify