Description: Roll off period maximizes channel capacity by sharpening the edges of the spectrum of the OFDM signal. For windowing purposes another segment at the start of the IDFT output is appended to the end of the IDFT output - the roll-off postfix (RP). There are five possible values for the (RP), and the choice depends on the bandwidth of the channel and the number of exclusion bands within the channel. A larger RP provides sharper edges in the spectrum of the OFDM signal; however, there is a time vs. frequency trade-off. Larger RP values reduce the efficiency of transmission in the time domain, but because the spectral edges are sharper, more useful subcarriers appear in the frequency domain. There is an optimum value for the RP that maximizes capacity for a given bandwidth and/or exclusion band scenario.