Doing the project on ldpc codes

[sdmcet]

hi,i m doing project on ldpc my statement is as follows:
tx = bpskMod + sqrt(N0/2)*randn(size(bpskMod));

where bpskmod=2*c-1 and N0=1
what is mean by randn(size(bpskMod)) here
please help me
thank u