Abstract-In this paper, we propose a low complexity gradient based approach for enabling the Tone Reservation (TR) technique to reduce the Peak-to-Average Power Ratio (PAPR) of Orthogonal Frequency Division Multiplexing (OFDM) signals. The performance of the proposed algorithm is evaluated for different pilot location in the frequency domain, and also in combination with the Discrete Fourier Transform (DFT) spreading technique proposed in [6]; in order to further reduce the PAPR. Simulation results show that the new technique achieves significant PAPR reductions, which are further enhanced when it is combined with DFT spreading. The simulation results also show that the performance of the technique is dependent on the pilot positions. In addition, further investigation was performed where the reduction tones are constrained, equal to the average power mask for the data tones, by a simple projection rule in the frequency domain both for the TR scheme and for the combined scheme. Simulation results show that the contiguous pilot arrangement provides better PAPR reduction performance in both cases, when the peak-cancellation signal is constrained in the frequency domain.Index Terms-OFDM, PAPR, Tone Reservation, DFT, spreading, DSI( Dummy Sequence Insertion).
I. INTRODUCTIONHE performances of high data rate systems are significantly limited by the multipath interference that occurs in the radio channel environment. As an attractive technique in mitigating the multipath interference, Orthogonal Frequency Division Multiplexing (OFDM) has been widely applied in various high data rate wireless Local Area Networks (LAN) and broadcasting systems [1], [2]. Furthermore, it is also being considered in 3GPP Long Term Evolution (LTE) as an attractive multiple access technique in the downlink [3].Despite its competitive attributes, OFDM signals are characterized by very high Peak-to-Average Power Ratio (PAPR) levels and this can both degrade the link performance and also cause significant out-of-band interference products that make it harder for the operator to comply with stringent spectral masks. The simplest solution to this problem is to operate the high power amplifier in the linear region by allowing a large enough amplifier back-off. However, this approach degrades the power efficiency of the system and often leads to unacceptable cost-efficiency conditions in the overall system [2].Based on this background, reducing the PAPR of OFDM signals is increasingly being considered to be very important in maintaining the cost-effectivess advantages of OFDM in practical systems, especially as new systems are being specified with large number of sub-carriers. Up to date, there have been proposed various PAPR reduction techniques such as Clipping method, Block Coding method, Selective Mapping (SLM) method, Partial Transmit Sequence (PTS) method, and Tone Reservation (TR) method [2]. According to [2], Clipping method does not offer an attractive solution, because it leads to out-of-band distortion. Furthermore, the block coding meth...
