Study on Effect of Cyclic Prefix Extension and Windowing in Cable Modem System

This paper provides the effect of cyclic prefix (CP) extension and windowing defined in DOCSIS 3.1. When using windowing, a larger roll-off period (RP) leads to sharper spectrum edge in frequency domain. However, from the perspective of synchronization or multipath fading immunity, the selection of low RP can offer better performance. Therefore, the optimum length of value for RP is needed to take into account the given channel, bandwidth and QAM modulation. In this paper, we present the frequency spectrum characteristics and compare the synchronization performance of orthogonal frequency division multiplexing (OFDM) symbol according to the different length of RP.