Which among the following an expression for spectrum capacity in OFDM based xG networks?α refers to a set of unused spectrum units, G(f) is the channel power gain at frequency f, S0 is the signal power per unit frequency and N_0is the noise power per unit frequency.

• A. C=∫α\(\frac{1}{2}\)log2(1+\(\frac{G(f)S_0}{N_0})\)
• B. C=∫α\(\frac{1}{2}\)log2(1+\(\frac{S_0}{N_0})\)
• C. C=∫αB log2(1+\(\frac{G(f)S_0}{N_0})\)
• D. C=∫αB log2(1+\(\frac{G(f)N_0}{S_0})\)