Compelexity L1 minimization

hi dear,
I have compute complexity L1 minimization. Please help me.
min norm(||x||_1)
subject to : norm(||AS-n||_2) < e ;
X is 2(M-1)*1 Dimension
A is 2(M-1)*Ns Dimension
S is Ns * 1 Dimension
n is 2(M-1)*1 Dimension