Robust sensing strategy for dynamic spectrum access in the 2.4 GHz ISM band

This paper proposes a robust spectrum sensing strategy to identify white-spaces in the unlicensed 2.4GHz ISM band where radio transmission technologies coexist. Implicitly, collocated networks have different levels of spectrum access priority due to their design parameters (e.g., transmission power, modulation and coding), such that a WLAN tends to achieve a higher access priority compared to a coexisting WPAN. Instead of using a predetermined radio channel in the ISM band, a device can perform dynamic spectrum access using a frequency agile radio to take advantage of spectrum holes that are found between transmissions of collocated networks, thus improving its opportunities to access the ISM band for interference-free transmissions. This paper proposes the dual spectrum sensing strategy for capturing spectrum holes that are wide enough to accommodate the transmissions of a device. Our method makes no assumption about the technologies (e.g., modulation schemes or power spectral density) of detected radio transmissions, and properly handles power variations in the form of gradually changing power values as well as sharp rise/fall edges in the detection of occupied parts of the spectrum. Field test results show that ample white-spaces exist to enable frequency-agile IEEE 802.15.4-based devices to access the ISM band opportunistically.