Spectrum Sensing: Basic Techniques
Spectrum sensing in a cognitive radio is practically challenging, as shown in Table 2.2 [36, 37].
Energy detection is the simplest spectrum sensing technique. It is a blind technique in that no prior information about the signal is required. It simply treats the primary signal as noise and decides on the presence or absence of the primary signal based on the energy of the observed signal. It does not involve complicated signal processing and has low complexity. In practice, energy detection is especially suitable for wideband spectrum sensing. The simultaneous sensing of multiple subbands can be realized by scanning the received wideband signal.
Two stages of sensing are desirable. The first stage uses the simplest energy detection. The second stage uses advanced techniques.
|Very strict sensing requirements||See Table 2.1||To avoid “hidden node” problem|
|Unknown propagation channel and nonsynchronization||Make coherent detection unreliable||To relieve the primary user from the burden|
|Noise/interference uncertainty||Very difficult to estimate their power||Change with time and location|
We follow  and [39–42] ...