Investigation and comparison of the effect of peak-to-average-power ratio (PAPR) reduction techniques on an OFDM-based system and a MC-CDMA-based system.

摘要

This thesis investigates the issue of high peak-to-average-power ratio (PAPR) inherent with Orthogonal Frequency Division Multiplexing (OFDM). The main aim was to reduce the PAPR in OFDM based schemes using two techniques: Clipping-Filtering and Peak Windowing.; The reduction techniques were also demonstrated on another scheme, Multi Carrier CDMA (MC-CDMA). Here, the input data was spread using a spreading code and then transmitted over an OFDM skeleton. This study was performed using computer simulations in Matlab.; A comparison of the two reduction schemes was investigated to determine the effects of each on the Bit Error Rate (BER) and the power spectrum. A comparison of OFDM and MC-CDMA was also examined to determine the advantages and disadvantages of one over the other.; It was found that Clipping-Filtering is a reliable scheme for peak power reduction. Such a scheme adds little additional complexity to the system. Moreover, as compared to peak windowing, Clipping-Filtering does not severely degrade the BER. Also, with the inclusion of the filter, the out of band radiation is greatly reduced.; It was also found that MC-CDMA is a superior technology and is a very robust scheme. It handles the reduction techniques extremely well without significantly affecting the BER rates. Using this scheme it was possible to achieve a low BER in spite of the inclusion of reduction schemes. OFDM could not achieve the same under the influence of clipping or windowing.