Question

What is the terminology used to represent the absence of a licensed user in the spectrum?

(a) Grounded hypothesis

(b) Fixed hypothesis

(c) Null hypothesis

(d) Zero hypothesis

This question was addressed to me at a job interview.

Asked question is from Next Generation Wireless Network topic in chapter Next Generation Wireless Network of Cognitive Radio

Answer 1

The correct answer is (c) Null hypothesis

Easy explanation: The following equation represents the basic hypothesis model for transmitter detection,

s(t) = n(t)       [U1]

s(t) = a*i(t) + n(t)   [U2]

where s(t) is the signal available at the xG user, i(t) is the signal transmitted by the primary user, n(t) is the AWGN, and a is the amplitude gain of the channel.

U1 is the null hypothesis which indicates the absence of signals from the licensed users in the spectrum band. U2 is termed alternate hypothesis which indicates the presence of signals from the licensed users in the spectrum band.