Low PAPR Preamble for IEEE802.16a OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a key enabling technology for future wireless communications systems. OFDM makes equalization simple and effective. However, accurate channel estimates are necessary at the receiver for the optimum operation of OFDM systems. Channel estimation usually employs some form of training signal, also known as the preamble, in the front of the packet. It is desirable to have a preamble signal with the lowest peak-to-average power ratio (PAPR) so that the estimation signal to noise ratio (SNR) can be maximized. In this work, we address the problem of designing very low peak-to-average power ratio (PAPR) preamble for orthogonal frequency division multiplexing (OFDM) systems. The initial preamble is designed using generalized chirp like (GCL) sequences. In order to obtain the lowest PAPR, the preamble is optimized using constrained nonlinear optimization technique. Results show that the proposed preamble has a PAPR of just 0.871 dB that translates into a gain of 2.129 dB when compared to the prescribed preamble of IEEE 802.16a standard that has a PAPR of 3 dB.