Extended superconformal algebras on AdS3

We study a supersymmetric extension of the Virasoro algebra on the boundary of the anti-de Sitter space-time AdS3. Using the free field realization of the currents, we show that the world-sheet affine Lie superalgebras osp(1|2)(1), sl(1|2)(1) and sl(2|2)(1) provide the boundary N=1,2 and 4 extended superconformal algebras, respectively.