This document provides the Network Architecture Model (NAM) for the Ultra Mobile BroadbandTM (UMBTM)1 system. The NAM supports the requirements in [1] and the Phase II requirements in [2]. The UMB system provides an additional Access Network (AN) to the overall architecture document in the AllIP NAM [3]. Except as documented in this document, all reference points and network entities in [3] are hereby incorporated by reference. Note: If not explained in this document, then refer to AllIP NAM [3]. 1 Ultra Mobile BroadbandTM and (UMBTM) are trade and service marks owned by the CDMA Development Group (CDG).