Hello,

My name is Maria Christopoulou and I’m a physics student in National and

Kapodistrian University of Athens in Greece.

My final year project is simulating an OFDM communications system, which

is

a relevant subject to the current LDPC codes project.

I have done some research and realized that the project should tackle

the

following aspects:

- Code construction, based on desirable properties, such as the size,

rate

and weight.

There are many algorithms to construct the code, depending on whether

we

want a pseudorandom or structured construction.

It’s a question of mine about the appropriate code construction method

to

apply for a real-time application.

Also, would a visual representation of a Tanner graph be required ?

- Optimization

The performance of the code could be increased by changing the code’s

parameters, such as the minimum distance and the girth.

I guess we should define the appropriate technique for this.

- Encoding: The goal is to map the messages into the codewords.

I have found two methods for this:

a) We get the codeword by applying the equation c=u*G, where c is the

codeword, u is the message and G is the Generator Matrix of the above

code.

The Generator Matrix is found by performing Gauss-Jordan Elimination on

the above constructed matrix of the code, denoted H.

b) The above constructed matrix of the code H is transformed into lower

triangular form H_new, using the appropriate maths.

The codewords must satisfy the parity check equation c*H_new=0, from

which

we get the parity bits of the codeword.

I have read that a structured code can be used for (a), while for an

arbitrary matrix, (b) is more suitable.

So the approach depends on the type of the construction, which has to be

defined.

- Decoding can be either hard or soft decision.

The hard decision can be implemented with a bit-flipping decoding.

The soft decision can be implemented with Sum-product decoding.

Matlab has a dedicated LDPC block decoder, that includes both methods,

so I

guess we have to define the methods in the project.

Apart from the above questions of mine, please let me know the way you

think we have to process the project, so that to submit my relevant

proposal.

Best Regards,

Maria Christopoulou