OFDMA_Part12 - 12 by using the slope of the curve of...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 12 by using the slope of the curve of carrier phases for pilots versus the subcarrier index n of the pilots [49]. [50] estimates by using two consecutive OFDM blocks for an AWGN frequency- selective channel. [51] uses training symbols to jointly estimate the timing and frequency offset; this approach simplifies the receiver design. 2.4 Mitigation of Time-Varying Effects Time-varying channel impairments are caused by either a Doppler shift or a frequency offset. As was explained by Dr. Rappaport in class, the effect of a Doppler shift can be understood in terms of the Doppler frequency f d = ( f c *v )/ c , where f c is the carrier frequency, v is the velocity of the mobile node and c is the velocity of light. The impact of the frequency-offset fo can be modeled as a multiplicative factor of e j2 fot . Time-varying effects of the channel cause the OFDM signal to spread in frequency-domain and generate ICI [47]. This ICI in the frequency-domain is analogous to ISI in time-domain; while ICI is caused by time-varying impairments, ISI is caused...
View Full Document

Ask a homework question - tutors are online