<p>Structured LDPC codes have been
constructed using balanced incomplete block (BIB) designs, resolvable BIB
designs, mutually orthogonal Latin rectangles, partial geometries, group
divisible designs, resolvable group divisible designs and finite geometries.
Here we have constructed LDPC codes from <i>α
</i>–<b> </b>resolvable BIB and Group divisible
designs. The sub–matrices of incidence matrix of such block design are used as
a parity – check matrix of the code which satisfy row – column constraint. Here
the girth of the proposed code is at least six and the corresponding LDPC code
(or Tanner graph) is free of 4– cycles. </p>
LDPC Codes Based on α – Resolvable BIB and Group Divisible Designs