I. Introduction
The ever-growing number of wireless systems and the scarcity for available spectrum necessitates highly efficient spectrum sharing among disparate wireless networks [1]. Many of them are heterogenous in hardware capabilities, wireless technologies, or protocol standards, and are expected to overlap with each other in both frequency and space. This inevitably leads to cross-technology interference (CTI), which can be detrimental to the performance of co-locating networks if it is not properly mitigated [6], [10], [18], [21]. Some examples of existing and future radio devices/networks that create CTI include: IEEE 802.11 (WiFi), 802.15.4 (ZigBee), 802.16 (WiMax), and Bluetooth in the ISM bands, IEEE 802.22 (WRAN) and IEEE 802.11 af (WLAN) in the TV white space, etc. Often, there is no central administration or planning for the coexistence of such networks. To enable spectrum sharing, current approaches mostly follow the interference-avoidance paradigm, where transmissions are separated in frequency, time, or space in order to share bandwidth among different networks, rather than to reduce or eliminate interference.