Sequences with Low Peak Side Lobe Levels for Constant PAPR VSF OFDMA System

摘要

In multiuser multicarrier systems, constant power schemes are desirable, to reduce the variations in interference power and the requirements on the power amplifier's dynamic range. In this work, variable spreading factor (VSF) orthogonal frequency division multiple access (OFDMA) system is used to support multiple data transmission rates. The effect of using three different spreading sequences, namely, Tent map binary sequences, Zadoff Chu sequences and Orthogonal variable spreading factor codes in VSF OFDMA systems was investigated. Merit factor and peak sidelobe levels (PSL) of sequences were used as metrics for selection of spreading codes and for the study of system performance. It was observed that the use of Tent map and Zadoff Chu sequences with low PSLs resulted in constant peak to average power ratio (PAPR), irrespective of the combinations of data rates used. The use of binary sequences generated from tent map is proposed to reduce PAPR and to maintain constant PAPR. It is an added merit that a large number of chaotic binary sequences with desirable sequence lengths and good correlation property can be generated easily with change in initial conditions.