Abstract: An improved SLM scheme is proposed to address the drawbacks of high computational complexity and reduced transmission efficiency caused by transmitting sideband information in SLM methods. The improvement scheme selects and maps data packets at the sending end, and obtains a random phase shift sequence at the receiving end by analyzing the power changes of the received data. The improvement scheme can reduce computational complexity without the need for transmitting sideband information, avoiding the loss of transmission efficiency.

Orthogonal Frequency Division Multiplexing (OFDM) technology has been widely used in recent years due to its high spectral efficiency and ability to effectively combat multipath interference. However, OFDM has the problem of high peak to average power ratio (PAPR). Due to the limited linear range of the power amplifier, signals with high PAPR will produce nonlinear distortion when passing through the power amplifier. To reduce this nonlinear distortion, it is necessary to expand the linear range of the power amplifier, which in turn leads to a decrease in power transmission efficiency and an increase in cost [1].

At present, the methods for reducing the PAPR of OFDM systems can be divided into three categories: amplitude limiting, encoding, and probability [2]. The methods proposed in references [3] to [5] belong to the limiting class, encoding class, and probability class, respectively. The Selective Mapping (SLM) method can effectively reduce the PAPR of OFDM systems, but it has high computational complexity and requires additional bandwidth to transmit sideband information, thereby reducing transmission efficiency. At present, the improvement work on SLM mainly focuses on the above two shortcomings of SLM methods. For example, the improvement schemes proposed in references [6] and [7] can reduce computational complexity, while the improvement schemes proposed in references [8] and [9] can eliminate the need for transmitting sideband information. However, there is no improvement scheme that can simultaneously solve these two shortcomings. This article analyzes the principle of SLM and combines the schemes proposed in references [7] and [9] to propose a new SLM scheme, which not only reduces computational complexity but also does not require the transmission of sideband information.

 

In order to provide multiple OFDM signals for selection, the REL551 1MRK002480-AE method requires M IFFT calculators, which greatly improves the computational complexity. At the receiving end, in order to receive signals correctly, it is necessary to know the information of the random phase shift sequence. Therefore, it is necessary to transmit the random phase shift sequence as sideband information, which will occupy additional bandwidth and reduce transmission efficiency.

2 Improved SLM solutions

Aiming at the drawbacks of high computational complexity and reduced transmission efficiency caused by transmitting sideband information in SLM method, an improved SLM scheme is proposed. The improvement scheme selects and maps data packets at the sending end, thereby reducing computational complexity. It uses the amplitude changes of the sent data to represent random phase shift information, eliminating the need for transmitting sideband information and improving transmission efficiency.

 

2.2 Processing of Random Phase Shift Sequences

In traditional SLM methods, the amplitude of the random phase shift sequence is always 1. Here, amplitude is used to label the random phase shift sequence, achieving the goal of eliminating the need for transmitting sideband information. The specific method is as follows:

 

REL551 1MRK002480-AE uses the same algorithm to generate the same random phase shift table for both the sender and receiver. After the random phase shift sequence is identified, other parts are consistent with traditional SLM methods.

Due to the fact that the amplitude of the element pdl in the random phase shift sequence may be 1 or C, the amplitude of the output data obtained by multiplying the frequency domain sampled data Xn with the element pdl in the random phase shift sequence will be greater than or equal to the amplitude of Xn. Therefore, the average power of the signal will increase, which may affect the PAPR performance of the OFDM system.

Next, analyze how the receiving end extracts a random phase shift sequence from the received data. Assuming that the sending symbol received by the receiving end is x（ μ）， Channel estimation can accurately eliminate the interference of channel fading, and Y can be obtained through FFT variation（ μ）。