Cooperation in wireless communication networks is expected to play a key role in addressing performance challenges of future wireless networks. Hence, both academia and industry have issued various proposals to employ cooperation so as to improve the wireless channel reliability, increase the system throughput, or achieve seamless service provision. In the existing proposals, cooperation comes at three different levels, namely among different users, among users and networks, and among different networks. In fact, the current nature of the wireless communication medium constitutes the driving force that motivates the last cooperation level, i.e. cooperation among different networks. Currently, the wireless communication medium is a heterogeneous environment with various wireless access options and overlapped coverage from different networks. Cooperation among these different networks can help to improve the service quality to mobile users and enhance the performance for the networks. In this chapter, we first introduce the concept of cooperation in wireless communication medium, then focus on cooperative networking in heterogeneous wireless access networks and its potential benefits for radio resource management.