Neveu-Schwarz 5-brane and little string duality in the pp-wave limit

We study NSR strings in the Nappi-Witten background, which is the Penrose limit of a certain Neveu-Schwarz (NS) 5-brane supergravity solution. We solve the theory in the light-cone gauge, obtaining the spectrum, which is space-time supersymmetric. In light of the little string theory NS5-brane duality, this spectrum should be in correspondence with the states of little string theory in the appropriate limit. A semi-classical analysis verifies that the relationship between energy and angular momentum, after a field redefinition, matches the known result for a flat background.