A Multi-Dimensional and Multi-Domain Communication Method for Intelligent Transportation Scenarios

Abstract

The present invention belongs to the field of wireless communication technologies, and particularly relates to a multi-dimensional multi-domain communication method for intelligent transportation scenarios. Specifically, in the present invention, the subcarriers of an OFDM symbol are divided into two groups. One group of subcarriers adopts an amplitude-phase modulation scheme based on the maximum distance separable (MDS) code to improve the reliability of the system, and the other group of subcarriers adopts a selective mapping scheme that does not require side information transmission to achieve a reduction in the peak-to-average power ratio (PAPR), thereby improving the energy efficiency of the power amplifier (PA). The positions of the subcarriers with reduced PAPR are further used as dimensions for information transmission to improve the spectral efficiency and transmission rate of the system. To further balance the system bit error rate performance and PAPR, the power dimensions of different functional subcarriers are further designed. The present invention can significantly improve the energy efficiency of the PA while maintaining the reliability of the system, and thus is more suitable for future intelligent transportation scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to a multi-dimensional multi-domain communication method for intelligent transportation scenarios. Background Art

[0002] With the completion of the deployment of the 5th Generation Mobile Communication Technology (5G) in multiple countries, the current research focus in the industry has shifted to the next generation of mobile communication, namely 6G. The scenarios faced by 6G communication will be more extensive, including integrated communication and sensing scenarios, unmanned aerial vehicle communication scenarios, and intelligent transportation scenarios, etc. Among them, the intelligent transportation scenario will face faster-changing channels, which not only requires the system to have higher reliability but also poses more stringent requirements on the energy efficiency of the Power Amplifier (PA).

[0003] Based on the lower implementation complexity, efficient spectrum reuse, and the ability to combat multipath fading, the OFDM waveform and its variants are still considered to be hot waveforms for achieving reliable communication in intelligent transportation scenarios. In addition, applying the Index Modulation (IM) scheme to the OFDM waveform (OFDM-IM) is beneficial to further improve the bit error rate performance and spectrum efficiency of the waveform. In 2022, F. Yarkin and J. Coon proposed an OFDM waveform based on the Maximum Distance Separable Code (MDS) and proved that this waveform has better bit error rate performance than the OFDM-IM waveform and the traditional OFDM waveform. Therefore, considering the requirements of future intelligent transportation scenarios for system reliability, the MDS-OFDM waveform is a potential candidate method.

[0004] However, although the MDS-OFDM waveform shows outstanding advantages in terms of reliability, it also faces the problem of high Peak to Average Power Ratio (PAPR). High PAPR means that a higher-power PA needs to be used, which will reduce the energy efficiency of the PA and violate the high requirements of the intelligent transportation scenario for the energy efficiency of the PA. Therefore, considering the dual requirements of the intelligent transportation scenario for system reliability and the energy efficiency of the PA, it is necessary to design an improved MDS-OFDM waveform to further balance its bit error rate and PAPR performance.

[0005] Traditional PAPR reduction methods include peak clipping, partial subcarrier reservation, and selective mapping. However, peak clipping technology will change the amplitude of some subcarriers, thus seriously affecting the reliability of the MDS-OFDM waveform that uses the subcarrier amplitude to carry information. In addition, the partial subcarrier reservation technology will reduce the spectral efficiency of the system, and the selective mapping technology requires using channel side information to transmit additional information. Considering that the MDS-OFDM waveform already uses some subcarriers to carry parity information for error detection, the PAPR reduction technology that will further reduce the spectral efficiency and transmission rate is no longer applicable to the MDS-OFDM waveform. At present, the research on the MDS-OFDM waveform mainly focuses on the system design and the analysis of the bit error rate performance, and the joint optimization of its PAPR performance and reliability in the intelligent transportation scenario has received very limited attention. Summary of the Invention

[0006] The purpose of the present invention is to propose an improved multi-dimensional multi-domain MDS-OFDM waveform to balance the bit error rate performance and PAPR of the waveform for the high PAPR problem existing in the MDS-OFDM waveform, making it more suitable for future intelligent transportation scenarios, which is called the MDS-OFDM-IM waveform.

[0007] The technical solution of the present invention is: a multi-dimensional multi-domain OFDM waveform for intelligent transportation scenarios. The subcarriers of this waveform have two selectable functions. Most of the subcarriers adopt an encoding and modulation scheme based on MDS codes to achieve error detection, and the remaining subcarriers adopt a selective mapping method without side information to achieve PAPR reduction. To improve the spectral efficiency, the idea of IM is further introduced into the subcarrier position dimension of this multi-domain waveform, and the positions of the PAPR reduction subcarriers are used to carry additional information. At the same time, the subcarriers with different functions are redesigned in the power dimension to balance the bit error rate performance and PAPR of this waveform. As Figure 1 shown, the proposed multi-dimensional multi-domain OFDM waveform first uses some input bits to select subcarriers at specific positions as PAPR reduction subcarriers, and then uses the remaining bits to perform amplitude and phase modulation based on MDS codes on the unselected subcarriers. Subsequently, different phases are assigned to the PAPR reduction subcarriers to generate a group of alternative symbols with different PAPRs. In addition, to balance the bit error rate and PAPR performance of the waveform, further design of the waveform is performed in the power dimension based on a search method. Finally, the symbol with the lowest PAPR is selected from all the symbols after power allocation and OFDM operation is performed on it to generate this multi-domain multi-dimensional OFDM waveform.

[0008] The present invention includes the following steps:

[0009] S1. For an OFDM symbol with N cThe sub - carriers are evenly divided into F groups in sequence, and then the sub - carriers in each group are evenly divided into M sub - blocks in sequence, with each sub - block having N sub - carriers;

[0010] S2. Select one sub - block from each group as the PAPR reduction sub - block according to the index bits. The length of the index bits that each group can carry is Taking the f - th group as an example (f ∈ {1, 2, …, F}), let the input bits be The calculation formula for the position of the selected sub - block is as follows in Formula 1:

[0011]

[0012] where L f represents the position of the selected PAPR reduction sub - block in the f - th group;

[0013] S3. Perform MDS encoding on the G = F(M - 1) unselected sub - blocks. Each sub - block can carry information bits, where A and P are the orders of amplitude modulation and phase modulation respectively. Taking the g - th sub - block as an example (g ∈ {1, 2, …, G}), the MDS encoding process is as follows:

[0014] First, divide the l 2 input bits into two groups. The first group consists of the first information bits, and the second group consists of the remaining ; Then, convert each bit in into a decimal number between 1 and A to obtain the MDS codeword for amplitude modulation of the first N - 1 sub - carriers; Similarly, convert each bit in into a decimal number between 1 and P to obtain the MDS codeword for phase modulation of the first N - 1 sub - carriers. The conversion method is the same as Formula 1; The last sub - carrier carries the parity information, and its MDS codeword is determined by the first N - 1 MDS codewords. The calculation formula is as follows in Formula 2:

[0015]

[0016] where and respectively represent the MDS codewords for amplitude modulation and phase modulation on the n - th sub - carrier in the g - th sub - block, and mod is the modulo operation;

[0017] S4. According to the MDS codewords of each sub - block, perform amplitude and phase modulation on the sub - carriers in each sub - block respectively. Taking the g - th group of sub - carriers as an example, the calculation formulas for amplitude and phase are as follows in Formulas 3 and 4:

[0018]

[0019]

[0020] where a n (g) and p n (g) represent the amplitude and phase of the nth subcarrier in the gth sub-block respectively; the calculation formula of the modulation symbol is as follows in Formula 5:

[0021]

[0022] S5. Generate W equally spaced phases [θ 1 , θ 2 , …, θ W , and select different phase shifts to be assigned to the PAPR reduction sub-blocks, then combine all sub-blocks according to the positions of the PAPR reduction sub-blocks to obtain multiple candidate symbols. Specifically, for each candidate symbol, the positions of the F PAPR reduction sub-blocks are selected by Formula 1, and the symbols at these positions are selected from the following set:

[0023]

[0024] The symbols at the remaining G positions are the MDS modulation symbols generated in S4;

[0025] S6. Perform power allocation on all candidate symbols, and the power allocation criterion is obtained through a search-based method. Specifically, set a threshold to represent the maximum tolerable bit error rate loss, then increase the amplitude of the PAPR reduction subcarriers from 0 in equal steps, calculate the bit error rate and PAPR of the system in each iteration, and finally select the amplitude that minimizes the PAPR of the system among the amplitudes that meet the bit error rate requirements. The corresponding power is the power of the PAPR reduction subcarriers, and the power of the MDS modulation subcarriers is calculated by the power normalization criterion. The calculation formula is as follows in Formula 7:

[0026]

[0027] where β p and β m are the powers of the PAPR reduction subcarriers and the MDS coded modulation subcarriers respectively;

[0028] S7. Perform OFDM modulation on all candidate symbols after power allocation, including oversampling, Inverse Fast Fourier Transform (IFFT), and adding a Cyclic Prefix (CP) operation;

[0029] S8. Calculate the PAPR of all alternative symbols after OFDM modulation, and select the alternative symbol with the lowest PAPR as the final transmitted symbol.

[0030] The beneficial effects of the present invention are that the present invention can significantly improve the PA energy efficiency while maintaining the system reliability, and thus is more suitable for future intelligent transportation scenarios. Description of the Drawings

[0031] Figure 1 It is a schematic diagram of multi-domain multi-dimensional OFDM waveform generation in the present invention;

[0032] Figure 2 It is a schematic diagram of PAPR comparison between the present invention and traditional OFDM waveform, OFDM-IM waveform, and MDS-OFDM waveform;

[0033] Figure 3 It is a schematic diagram of bit error rate comparison between the present invention and traditional OFDM waveform, OFDM-IM waveform, and MDS-OFDM waveform; Detailed Embodiment

[0034] The following combines the drawings and simulation examples to prove the effectiveness and practicability of the present invention:

[0035] The simulation parameters are set as follows: When simulating, a time-varying single-path Rayleigh channel is adopted. The number of subcarriers is set to 128, with a total of 16 groups, each group having 4 sub-blocks, and each sub-block having 2 subcarriers. The amplitude modulation and phase modulation orders are both 2, and 128 bits can be transmitted each time. The power of the PAPR reduction subcarriers is set to 1.96, and the average power of the MDS modulation subcarriers is set to 0.68. The oversampling factor in OFDM modulation is set to 4.

[0036] From Figure 2 It can be seen that the PAPR of the present invention is significantly lower than that of traditional OFDM waveform, OFDM-IM waveform, and MDS-OFDM waveform, which proves the effectiveness of the present invention in reducing PAPR, and thus has better PAPR energy efficiency. Therefore, the excellent PAP energy efficiency of the present invention makes it more suitable for future intelligent transportation scenarios.

[0037] From Figure 3 It can be seen that the bit error rate performance of the present invention is significantly better than that of traditional OFDM waveform and OFDM-IM waveform, which proves that the present invention can significantly improve the system reliability. In addition, compared with the traditional high-PAPR MDS-OFDM waveform, the loss of bit error rate performance of the present invention is very small, which proves that the present invention can reduce the system PAPR while ensuring reliability, achieving a trade-off between the system reliability and the PA energy efficiency, and is a feasible and effective solution for future intelligent transportation scenarios.

Claims

1. A multi - dimensional multi - domain communication method for intelligent transportation scenarios, characterized in that, it includes the following steps: S1. Divide the N subcarriers of an OFDM symbol into F groups in sequence, and then divide the subcarriers of each group into M sub-blocks in sequence, where each sub-block has N subcarriers; c ​ S2. Select one sub-block from each group as the PAPR reduction sub-block according to the index bits, and the length of the index bits that each group can carry is Taking the f-th group as an example (f ∈ {1, 2, …, F}), let the input bits be The calculation formula for the position of the selected sub-block is as follows, Formula 1: where L f represents the position of the f-th selected PAPR reduction sub-block; S3. Perform MDS coding on the G = F(M - 1) unselected sub - blocks. Each sub - block can carry information bits, where A and P are the orders of amplitude modulation and phase modulation respectively. Taking the g - th sub - block as an example (g ∈ {1, 2, …, G}), the MDS coding process is as follows: First, divide the l 2 input bits into two groups. The first group consists of the first information bits, and the second group consists of the remaining ; then, for each in bit, convert it into a decimal number between 1 and A to obtain the MDS codewords for amplitude modulation of the first N - 1 subcarriers; similarly, for each in bit, convert it into a decimal number between 1 and P to obtain the MDS codewords for phase modulation of the first N - 1 subcarriers, and the conversion method is the same as formula 1; the last subcarrier carries the parity information, and its MDS codeword is determined by the first N - 1 MDS codewords, and the calculation formula is as follows: formula 2 wherein and respectively represent the MDS codewords for amplitude modulation and phase modulation on the n-th subcarrier in the g-th sub-block, and mod represents the modulo operation; S4. According to the MDS codewords of each sub - block, perform amplitude and phase modulation on the sub - carriers in each sub - block respectively. Taking the g - th group of sub - carriers as an example, the calculation formulas for amplitude and phase are as follows in Formula 3 and Formula 4: where a n (g) and p n (g) represent the amplitude and phase of the nth sub - carrier in the gth sub - block respectively; the calculation formula of the modulation symbol is as follows in Formula 5: S5. Generate W equally spaced phases [θ 1 , θ 2 , …, θ W , and select different phase shifts to be assigned to the PAPR reduction sub-blocks from them. Then, combine all sub-blocks according to the positions of the PAPR reduction sub-blocks to obtain multiple candidate symbols. Specifically, for each candidate symbol, the positions of the F PAPR reduction sub-blocks are selected by Equation 1, and the symbols at these positions are selected from the following set: The symbols at the remaining G positions are the MDS modulation symbols generated in S4; S6. Perform power allocation on all candidate symbols. The power allocation criterion is obtained through a search - based method. Specifically, set a threshold representing the maximum acceptable bit - error rate loss, and then increase the amplitude of the PAPR - reduced sub - carriers from 0 with equal step lengths. Calculate the bit - error rate and PAPR of the system in each iteration. Finally, select the amplitude that minimizes the PAPR of the system among the amplitudes that meet the bit - error rate requirements. The corresponding power is the power of the PAPR - reduced sub - carriers, and the power of the MDS - modulated sub - carriers is calculated by the power normalization criterion. The calculation formula is as follows in Formula 7: where β p and β m are the powers of the PAPR reduction subcarrier and the MDS coded modulation subcarrier, respectively; S7. Perform OFDM modulation on all candidate symbols after power allocation, including oversampling, inverse Fourier transform, and adding a cyclic prefix operation; S8. Calculate the PAPR of all candidate symbols after OFDM modulation, and select the candidate symbol with the lowest PAPR as the final transmission symbol.

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