6.3.3 OFDM systems 3.The block diagram of a OFDM system One of the major challenges of ODFM systems is to maintain the synchronization among subcarriers. Another major problem with all multicarrier systems is the high peak- average-ratio (PAR)in their transmission signals.Large signals peaks occur when many signals of sub-channels add constructively in phase.Such large peaks may saturate the PA at TX and result in heavily distorted signals. UESTC-Digital transmission thro BL AWGN channels Prof李晓峰 12