Abstract
A peak to average power ratio (PAPR) reduction method is proposed that exploits the precoding or beamforming mode in WiMAX. The method is applicable to any OFDM/A systems that implements beamforming using dedicated pilots which use the same beamforming antenna weights for both pilots and data. Beamforming performance depends on the relative phase shift between antennas, but is unaffected by a phase shift common to all antennas. PAPR, on the other hand, changes with a common phase shift and this paper exploits that property. An effective optimization technique based on sequential quadratic programming is proposed to compute the common phase shift. The proposed technique has several advantages compared with traditional PAPR reduction techniques in that it does not require any side-information and has no effect on power and bit-error-rate while providing better PAPR reduction performance than most other methods.
Highlights
Many recent wide-band digital communication systems use a multi-carrier technology known as orthogonal-frequency-division-multiplexing (OFDM), where the band is divided into many narrow-band channels
To have a better perception of the peak to average power ratio (PAPR) cost function, a 3-D plot is provided in Figure 5, which illustrates the variation of PAPR, or equivalently the maximum amplitude of one OFDM symbol partitioned into two disjoint sub-blocks, versus two phase coefficients
Concluding Remarks We introduced a precoding PAPR reduction technique that is applicable to OFDM/A communication systems using dedicated pilots
Summary
Many recent wide-band digital communication systems use a multi-carrier technology known as orthogonal-frequency-division-multiplexing (OFDM), where the band is divided into many narrow-band channels. The proposed algorithm makes use of the antenna beamforming weights and dedicated pilots at the transmitter [10] It reduces the PAPR by modifying the cluster weights in the WiMAX data structure in a manner similar to the PTS method [7,8]. For the typical case of narrowband weights, a different beamforming weight per cluster is used so that the PAPR reduction method is applied in a joint fashion over the transmitted signal from all antennas. The technique is similar to partial-transmit-sequence (PTS), but without the drawback of requiring side-information which would make it impossible to apply in existing communication standards such as WiMAX These advantages makes it a very attractive technique to reduce PAPR. We propose a realistic optimization algorithm based on the basic configuration of the PTS sub-blocks
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