Internet Protocol based (IP-based) cellular networks, including cellular networks based on the fourth-generation (4G) Long Term Evolution (LTE) standard and on the Worldwide Interoperability for Microwave Access (WiMAX) standard, provide significantly higher data rates than previous generations of cellular networks. However, the spectrum allocated to cellular networks remains scarce, thus limiting the ability of fourth-generation and future-generation cellular networks to accommodate the growing demand for mobile data driven by mobile devices, including smartphones and the like. Therefore, improved techniques to utilize the limited cellular spectrum and to make use of non-cellular spectrum are desirable both in fourth-generation as well as future-generation cellular networks.