In this paper we study the internetworking of WWANs and WLANs for next generation wireless packet data networks motivated by the capacity and coverage tradeoffs of the two networks. We compare different types of network architectures and propose a one-hop WWAN and multi-hop WLAN architecture to provide users with guaranteed service and smooth hand-offs. We then show through simulations that the proposed architecture coupled with a fine-grained packet scheduling algorithm achieves higher performance. Finally we identify several open research issues associated with the proposed architecture.