Abstract:
The frequency division multiplexing (OFDM) has been used in wireless local area network, digital
audio broadcasting and in 4G mobile communication. The techniques present a high data
transmission, efficient use of bandwidth and also reduce inter symbol interference. Besides the
bandwidth efficiency and high data transmission of the OFDM, a high peak to average power ratio
(PAPR) is a major impairment to the scheme; large peaks due to sinus waves in inverse fast
fourrier transformer (IFFT), limited word length which lead to saturation, frequency errors, carrier
phase noise and timing error among others reduces the power efficiency at the transmitter side and
lead to an inefficiency of the OFDM scheme. In order to respond to the problem of high PAPR two
techniques are proposed; the peak windowing and the clipping techniques. Peak windowing
consist of multiplying the envelop of OFDM signal with a window function; when the amplitude
of the envelop of the OFDM signal exceeds a threshold, a window function is applied to the
envelop of the OFDM signal to eliminate the peak amplitude; three window techniques were
considered in the reduction of PAPR; the Hamming, Hanning and Kaiser . Another technique we
considered in this research work is the clipping techniques where we limit the maximum of
transmit signal to a specified level and evaluate the performance of the BER.
As results, when comparing the effect of clipping technique in OFDM, the result indicated that
clipped signal has less peak average power ratio compare to the unclipped signal. The effect of
clipping ratio in the ODFM system was also been investigated and found that when less value of
threshold clipping level improve the PAPR but affect the BER. The complementary cumulative
distribution function and bit error rate were used to measure the reduction of PAPR in OFDM
using the two proposed techniques; Peak windowing and clipping.
