The correct answer is:
(a) True
Explanation:
In spectrum management for cognitive radio networks, one of the significant challenges is spectrum decision over heterogeneous spectrum bands that may have different characteristics. These characteristics could include variations in spectrum availability, signal propagation, interference levels, and channel quality across different frequency bands.
When selecting a spectrum band, cognitive radios must make decisions considering these diverse characteristics to ensure efficient utilization of the available spectrum while minimizing interference and maximizing data transmission quality. This challenge is exacerbated by the need for real-time spectrum sensing, decision-making algorithms, and coordination among primary and secondary users.
Thus, spectrum decision in the context of heterogeneous spectrum bands is indeed a challenge, making the statement True.