CN113037676A - DSSS-GFDM system PAPR suppression method based on DFT precoding in 5G satellite communication - Google Patents

Abstract

The invention discloses a PAPR suppression method of a DSSS-GFDM system based on DFT precoding in 5G satellite communication, which comprises the steps of carrying out constellation mapping, direct sequence spread spectrum technology and discrete Fourier transform on data streams at a transmitting end, carrying out GFDM modulation and CP addition, and transmitting the data streams to a wireless channel through radio frequency for transmission; and after channel estimation, synchronization, CP deletion and channel equalization are carried out on the received signals at the receiving end in sequence, demodulation, inverse discrete Fourier transform, direct sequence de-spread and constellation de-mapping are carried out. The invention applies Discrete Fourier Transform (DFT) precoding technology in the DSSS-GFDM system to inhibit PAPR, and meanwhile, keeps satisfactory BER performance, so that the DSSS-GFDM system is more suitable for a 5G satellite communication system.

Description

DSSS-GFDM system PAPR suppression method based on DFT precoding in 5G satellite communication

Technical Field

The invention relates to the technical field of communication, in particular to a DSSS-GFDM system PAPR suppression method based on DFT precoding in 5G satellite communication.

Background

In recent years, with the increasing degree of integration of information networks, international standardization organizations such as the International Telecommunications Union (ITU), the third generation partnership project (3GPP), the 5G satellite and terrestrial network (SaT5G) consortium have been working on merging a satellite communication system with a 5G system communication system. The densely deployed 5G ground system can well solve the problem of ultra-large-capacity wireless coverage by a low-cost scheme, but for remote areas and oceans, the ground 5G system lacks an effective low-cost wireless coverage scheme and is difficult to meet the intelligent application requirements of future unmanned systems (such as unmanned ships and the like). However, the satellite communication system has an advantage over the ground 5G communication system in a coverage area, and therefore, it is very important to research the fusion of the 5G and satellite communication systems, and consider the capacity advantage of the ground system and the coverage advantage of the satellite system, and implement mutual communication, mutual supplementation and efficient cooperation between the space network and the ground network.

In a converged 5G and satellite communication system, a user equipment may use both a 5G base station and a satellite to achieve wide information transmission. However, limited Radio Frequency (RF) resources limit the ability to transmit information. In the context of satellite communications, we need to face the problems of limited link budget, high speed mobility of terminals and satellites, low signal-to-noise ratio, non-linear distortion introduced by power amplifiers, etc. Although the cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) waveform currently used by the 5G system can greatly improve spectral efficiency, strict orthogonality between subcarriers in the CP-OFDM system cannot be guaranteed due to large out-of-band leakage (OOB) of the CP-OFDM signal and high sensitivity to Carrier Frequency Offset (CFO) caused by devices and wireless channels, thereby causing degradation of Bit Error Rate (BER) performance. This makes CP-OFDM waveforms a significant challenge in 5G satellite communication systems.

To mitigate the impact of strict orthogonality, a Generalized Frequency Division Multiplexing (GFDM) scheme is proposed that does not require subcarriers to be strictly orthogonal to each other. Furthermore, combining GFDM with Direct Sequence Spread Spectrum (DSSS) techniques, we can mitigate the effect of Carrier Frequency Offset (CFO) on a single symbol thanks to the spreading in the frequency domain. More specifically, the DSSS-GFDM system may transmit multiple sub-symbols in a sub-carrier, modulate each data block and add a CP to each data block instead of each data. Therefore, the DSSS-GFDM transceiver will have lower OOB leakage, lower sensitivity to signal transmission delay and CFO, higher spectrum utilization and more flexible time-frequency resource block configuration. This makes DSSS-GFDM waveforms more suitable when faced with satellite communication scenarios.

However, like other multi-carrier systems, the DSSS-GFDM system also suffers from the common problem of multi-carrier systems, i.e., high peak-to-average power ratio (PAPR) caused by the superposition of multiple carriers.

Chinese patent publication No. CN107787573A, 03 and 09, 2018, discloses a method and apparatus for processing signals transmitted with reduced peak-to-average power ratio. The process includes applying (1650) a symbol constellation extension projection to at least one symbol in the constellation, the symbol constellation extension projection having an outward angular region from an original position of the at least one symbol in the constellation, the outward angular region being defined by a value of an angle between a first boundary and a second boundary of the outward angular region, the value of the angle being determined by a selection of the constellation used as part of the transmitted signal and a code rate used to encode the data stream. The technical solution of the patent is also not applicable to multi-carrier systems.

Disclosure of Invention

The invention provides a DSSS-GFDM system PAPR suppression method based on DFT precoding in 5G satellite communication, which solves the problem of high peak-to-average power ratio (PAPR) caused by superposition of multiple carriers.

In order to solve the technical problems, the technical scheme of the invention is as follows:

a DSSS-GFDM system PAPR suppression method based on DFT precoding in 5G satellite communication comprises the following steps:

s1: at a transmitting end, carrying out planet seat mapping pretreatment on binary data bit streams to obtain constellation mapping symbols;

s2: spreading the constellation mapping symbols using a direct sequence spread spectrum technique (DSSS);

s3: performing Discrete Fourier Transform (DFT) on the expanded constellation mapping symbols to obtain DFT pre-coded signals;

s4: performing GFDM modulation on the DFT pre-coded signals, adding a CP (content provider) and transmitting the signals to a wireless channel through radio frequency for transmission;

s5: after receiving the signals processed in steps S1 to S4, the receiving end performs channel estimation, synchronization, CP deletion and channel equalization on the received signals, and then demodulates the signals through a GFDM demodulator;

s6: carrying out Inverse Discrete Fourier Transform (IDFT) on the signal subjected to strip removal by the GFDM demodulator;

s7: performing direct sequence despreading on the signal subjected to Inverse Discrete Fourier Transform (IDFT);

s8: and performing constellation demapping on the despread signal to obtain an estimated value of the binary data bit stream.

Preferably, the binary data bit stream in step S1 is subjected to planet seat mapping preprocessing to obtain a constellation mapping symbol, which specifically includes:

firstly, mapping a binary data bit stream by a planet seat, and then performing serial-parallel conversion on the binary data bit stream to obtain a constellation symbol vector S of M rho multiplied by 1, wherein rho is K/L to represent a spreading factor, L represents the length of an M sequence of the GFDM system, M is the number of subsymbols contained in one data block in the GFDM system, and K is the number of subcarriers contained in one data block in the GFDM system.

Preferably, in step S2, the constellation mapping symbol is spread by using a direct sequence spread spectrum technology DSSS, specifically:

the QPSK symbol vector after DSSS is represented as:

d＝Bs＝[d₀ ^T,d₁ ^T,…,d_K-1 ^T]^T

in the formula (d)_k＝[d_k,0，d_k,1，…，d_k,M-1]^TInput sub-symbol vector representing the k +1 th sub-carrier of dimension M x 1, d_k,mRepresents the m +1 th sub-symbol in the k +1 th sub-carrier, and B is the system spreading matrix.

Preferably, the calculation method of the system spreading matrix B is as follows:

consider a GFDM system in which a data block contains K subcarriers, M subsymbols, with the same index of position in each subcarrier of the original GFDM data blockThe M sequences are subjected to direct sequence spread spectrum, and the whole system adopts M different M sequences; by using

A spreading vector representing each M +1 th subsymbol, where M is 0,1,2, …, M-1, each element in the vector representing a corresponding spreading sequence, resulting in a spreading sequence matrix of dimension ML × M:

a system spreading matrix B of MK multiplied by M rho is constructed through a spreading sequence matrix:

preferably, in step S3, the spread constellation mapping symbol is subjected to discrete fourier transform DFT, so as to obtain a DFT precoded signal:

wherein D is a discrete Fourier transform matrix of MK x MK,

for the DFT-precoded symbol vector,

for the

The l +1 th symbol in (b), whose discrete form can be expressed as:

wherein [ d ] is]_ξDenotes the ξ +1 symbol in d, l ═ 0,1, …, MK-1.

Preferably, the GFDM modulation in step S4 includes three processes of upsampling, loop filtering and upconversion.

Preferably, the GFDM modulated signal can be expressed as:

wherein

A GFDM symbol vector representing mkx 1, a representing a GFDM modulation matrix, in particular in the form of a ═ g_0,0…g_0,M-1g_1,0…g_1,M-1…g_k-1,M-1]Each column of the GFDM modulation matrix A represents a cyclic filter vector of MK 1 dimensions, and g_k,mIs g_0,0The cyclic time-frequency shift version of (a), the cyclic filter corresponding to each sub-symbol can be represented as:

the discrete form GFDM symbol can be expressed as:

wherein n is 0,1, …, MK-1,

represents

The m +1 th sub-symbol in the (k + 1) th sub-carrier.

Preferably, the channel estimation, synchronization and CP deletion performed by the receiving end on the received signal in step S5 are represented as:

y＝Hx+ω

where y denotes a received symbol vector, H denotes a channel matrix, and ω denotes additive white gaussian noise.

Preferably, in step S5, zero-forcing equalization is used for channel equalization, and GFDM matching receiver is used for GFDM demodulation.

Preferably, in steps S6 and S7, symbol vectors before QPSK demodulation are obtained through IDFT and direct sequence spread spectrum despreading processes

Expressed as:

in the formula, A^H、D^H、B^HRespectively representing the corresponding GFDM demodulation, IDFT, direct sequence despreading matrices.

Compared with the prior art, the technical scheme of the invention has the beneficial effects that:

the invention provides that a discrete Fourier transform DFT precoding technology is applied in a DSSS-GFDM system to inhibit PAPR, DFT can scatter data symbols bearing information into all sub-symbols, thus reducing the probability of overlapping of different sub-carriers with the same phase and obtaining peak power, effectively inhibiting the peak-to-average ratio under the condition of unchanged average power of signals, and simultaneously keeping satisfactory BER performance, so that the DSSS-GFDM system is more suitable for a 5G satellite communication system.

Drawings

FIG. 1 is a schematic flow chart of the method of the present invention.

Fig. 2 is a block diagram of a transceiver in an embodiment using the present invention.

Fig. 3 is a diagram illustrating the correspondence relationship of direct sequence spread spectrum in the embodiment.

Fig. 4 is a graph illustrating PAPR performance of the proposed scheme of the present invention compared with conventional GFDM scheme, CP-OFDM scheme and DSSS-GFDM scheme.

Figure 5 is a graph showing BER performance of the proposed scheme compared to conventional GFDM and CP-OFDM schemes and DSSS-GFDM schemes on AWGN channel.

Fig. 6 is a graph showing BER performance of the proposed scheme of the present invention compared to conventional GFDM and CP-OFDM schemes and DSSS-GFDM schemes, without considering Carrier Frequency Offset (CFO) in satellite channels.

Fig. 7 is a graph showing BER performance of the proposed scheme of the present invention compared to conventional GFDM and CP-OFDM schemes and DSSS-GFDM schemes when Carrier Frequency Offset (CFO) is considered in a satellite channel.

FIG. 8 is a diagram showing the BER performance comparison between the proposed scheme of the present invention and the conventional GFDM scheme and the CP-OFDM scheme and the DSSS-GFDM scheme under different CFO normalized frequency offset coefficients λ.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent;

for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;

it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

Example 1

The embodiment provides a PAPR suppression method for a DSSS-GFDM system based on DFT precoding in 5G satellite communication, as shown in fig. 1 to 2, comprising the following steps:

s1: at a transmitting end, carrying out planet seat mapping pretreatment on binary data bit streams to obtain constellation mapping symbols;

s2: spreading the constellation mapping symbols using a direct sequence spread spectrum technique (DSSS);

s3: performing Discrete Fourier Transform (DFT) on the expanded constellation mapping symbols to obtain DFT pre-coded signals;

s4: performing GFDM modulation on the DFT pre-coded signals, adding a CP (content provider) and transmitting the signals to a wireless channel through radio frequency for transmission;

s5: after receiving the signals processed in steps S1 to S4, the receiving end performs channel estimation, synchronization, CP deletion and channel equalization on the received signals, and then demodulates the signals through a GFDM demodulator;

s6: carrying out Inverse Discrete Fourier Transform (IDFT) on the signal subjected to strip removal by the GFDM demodulator;

s7: performing direct sequence despreading on the signal subjected to Inverse Discrete Fourier Transform (IDFT);

s8: and performing constellation demapping on the despread signal to obtain an estimated value of the binary data bit stream.

In step S1, the binary data bit stream is subjected to planet seat mapping preprocessing to obtain constellation mapping symbols, which specifically include:

firstly, mapping a binary data bit stream by a planet seat, and then performing serial-parallel conversion on the binary data bit stream to obtain a constellation symbol vector S of M rho multiplied by 1, wherein rho is K/L to represent a spreading factor, L represents the length of an M sequence of the GFDM system, M is the number of subsymbols contained in one data block in the GFDM system, and K is the number of subcarriers contained in one data block in the GFDM system.

In step S2, the spreading the constellation mapping symbol by using a direct sequence spread spectrum technology DSSS specifically includes: as shown in fig. 3, the QPSK symbol vector after DSSS is represented as:

d＝Bs＝[d₀ ^T，d₁ ^T，…，d_K-1 ^T]^T

in the formula (d)_k＝[d_k,0，d_k，1，…，d_k，M-1]^TInput sub-symbol vector representing the k +1 th sub-carrier of dimension M x 1, d_k,mRepresents the m +1 th sub-symbol in the k +1 th sub-carrier, and B is the system spreading matrix.

The calculation method of the system spreading matrix B is as follows:

considering a GFDM system with a data block comprising K subcarriers and M subsymbols, performing direct sequence spread spectrum on the subsymbols with the same position index in each subcarrier of an original GFDM data block by adopting the same M sequence, wherein the whole system adopts M different M sequences; by using

A spreading vector representing each M +1 th subsymbol, where M is 0,1,2, …, M-1, each element in the vector representing a corresponding spreading sequence, resulting in a spreading sequence matrix of dimension ML × M:

a system spreading matrix B of MK multiplied by M rho is constructed through a spreading sequence matrix:

in step S3, discrete fourier transform DFT is performed on the spread constellation mapping symbols to obtain DFT precoded signals:

wherein D is a discrete Fourier transform matrix of MK x MK,

for the DFT-precoded symbol vector,

for the

The l +1 th symbol in (b), whose discrete form can be expressed as:

wherein [ d ] is]_ξDenotes the ξ +1 symbol in d, l ═ 0,1, …, MK-1.

The GFDM modulation in step S4 includes three processes of upsampling, loop filtering, and upconversion.

The GFDM modulated signal can be expressed as:

wherein

A GFDM symbol vector representing mkx 1, a representing a GFDM modulation matrix, in particular in the form of a ═ g_0,0…g_0,M-1g_1,0…g_1,M-1…g_K-1,M-1]Each column of the GFDM modulation matrix A represents a cyclic filter vector of MK 1 dimensions, and g_k,mIs g_0,0The cyclic time-frequency shift version of (a), the cyclic filter corresponding to each sub-symbol can be represented as:

the discrete form GFDM symbol can be expressed as:

wherein n is 0,1, …, MK-1,

represents

The m +1 th sub-symbol in the (k + 1) th sub-carrier.

In step S5, the receiving end performs channel estimation, synchronization, and CP deletion on the received signal, which is represented as:

y＝Hx+ω

wherein y represents a received symbol vector, H represents a channel matrix, and ω represents additive white Gaussian noise, and satisfies

In step S5, zero-forcing equalization is used for channel equalization, and GFDM demodulation is performed by using a GFDM matching receiver.

In steps S6 and S7, symbol vectors before QPSK demodulation are obtained through Inverse Discrete Fourier Transform (IDFT) and direct sequence spread spectrum despreading processes

Expressed as:

in the formula, A^H、D^H、B^HRespectively representing the corresponding GFDM demodulation, IDFT, direct sequence despreading matrices.

PAPR analysis and BER performance discussion under Additive White Gaussian Noise (AWGN) channel are performed on the transmitted signal.

Performing PAPR analysis on the signal after S4, specifically as follows:

by definition, the peak-to-average ratio, PAPR, can be expressed as the ratio of the peak power of a signal to the average power of the signal:

without loss of generality, assuming that the data symbols are independently and identically distributed, E { | x [ n ] can be calculated by the following equation]|²}：

The PAPR characteristic is usually characterized by Complementary Cumulative Distribution Function (CCDF), which means that the PAPR value is larger than a certain preset value_ζI.e.:

CCDF(PAPR_ζ)＝Pr(PAPR>PAPR_ζ)

in a specific implementation process, simulation parameters are set as follows: the constellation mapping mode is QPSK, the number of subcarriers K is 112, the number of subsymbols M is 5, the type of prototype filter is RRC, the roll-off coefficient is 0.5, the spreading code length L is 7, channel estimation and synchronization are assumed to be ideal, and the wireless channel is set as an Additive White Gaussian Noise (AWGN) channel.

Comparing the PAPR and BER performance of the DFT-DSSS-GFDM scheme proposed by the present invention with the conventional GFDM scheme, CP-OFDM scheme and DSSS-GFDM scheme, as shown in fig. 4, the PAPR of the DSSS-GFDM scheme is much higher than that of the CP-OFDM scheme and conventional GFDM (cov.gfdm) scheme because the direct sequence spreading increases the number of subcarriers of the GFDM system, increasing the probability of subcarrier overlap. And the DSSS-GFDM system adopting DFT precoding can better restrain PAPR. Specifically, the PAPR of the proposed scheme is about 7.5dB lower than that of the DSSS-GFDM scheme, 4dB lower than that of the conventional GFDM scheme, and 3dB lower than that of the CP-OFDM scheme.

According to fig. 5, the BER performance of the DFT-DSSS-GFDM scheme proposed by the present invention is superior to that of the conventional GFDM scheme and the CP-OFDM scheme and the DSSS-GFDM scheme in the BER performance over AWGN channel. It is also worth noting that the proposed DFT-DSSS-GFDM scheme can achieve a slightly better BER performance than the DSSS-GFDM scheme by virtue of the orthogonality of the DFT matrix when Eb/N0 is relatively high.

The comparison shows that the method of the invention can keep reliable BER performance while inhibiting PAPR well, and solves the problem of compromise between PAPR inhibition and BER performance reduction.

On the basis of the above, the BER performance of the method of the present invention under the satellite channel is further discussed.

The simulation parameters of the wireless channel in the above embodiment are changed to satellite channel, and a satellite channel model C in ITU-R M.1225 is adopted, wherein the maximum Doppler frequency shift in the model is 32.2kHz, the multipath time delay is [0,60,100,130,250] ns, and the normalized power is [ -12.1, -17, -18.3, -19.1, -22.1] dB.

In a specific implementation, when Carrier Frequency Offset (CFO) is not considered in the satellite channel, the DFT-DSSS-GFDM and DSSS-GFDM schemes achieve better BER performance than the conventional GFDM and CP-OFDM schemes, as shown in fig. 6, due to the use of spread spectrum techniques. However, in multipath propagation, the orthogonality of the DFT matrix cannot be guaranteed, so that the reliability performance of the DFT-DSSS-GFDM system is slightly worse than that of the DSSS-GFDM system.

By combining the PAPR analysis in embodiment 1, it is further shown that the method of the present invention can better suppress the PAPR while maintaining the reliable BER performance in the scenario of 5G satellite communication, thereby solving the tradeoff problem of PAPR suppression and BER performance degradation.

When considering CFO under the satellite channel, the signal received by the receiving end after passing through the satellite channel after removing CP can be expressed as:

y_CFO＝QHx+ω

where the matrix Q represents the carrier frequency offset matrix:

where N is MK and λ is the normalized frequency offset.

In a specific implementation, it is assumed that the normalized frequency offset λ of the CFO is set to 0.15.

As shown in fig. 7, the BER performance of the method and the comparison scheme of the present invention is degraded when information is transmitted in a satellite channel with CFOs because the presence of CFOs will increase inter-carrier interference (ICI). In addition, regardless of whether the adopted satellite channel has CFO, the BER performance of the method is better than that of the traditional GFDM scheme and the CP-OFDM scheme, and the better BER performance similar to that of the DSSS-GFDM scheme is kept.

In combination with the analysis of the PAPR in the above embodiment, this also further shows that the method of the present invention can better suppress the PAPR while maintaining the reliable BER performance in the scenario of 5G satellite communication, thereby solving the tradeoff problem between PAPR suppression and BER performance degradation.

The DFT-DSSS-GFDM scheme of the present invention also maintains similar and more reliable BER performance when considering different degrees of CFO in satellite channels as compared to the DSSS-GFDM scheme.

In a specific implementation, different CFO normalized frequency offset coefficients λ are set to 0, 0.05, 0.1, and 0.15.

According to fig. 8, as λ increases, the BER performance of both the DFT-DSSS-GFDM scheme and the DSSS-GFDM scheme of the present invention decreases accordingly. Furthermore, due to the orthogonality of the DFT precoding, the BER performance of the proposed DFT-DSSS-GFDM scheme is increasingly closer to that of the DSSS-GFDM scheme for different λ, while at the same time the scheme of the present invention has a lower PAPR, as shown in fig. 4. In summary, the DFT-DSSS-GFDM scheme of the invention is superior to the DSSS-GFDM scheme.

In combination with the analysis of the PAPR in the above embodiment, this again shows that the method of the present invention can better suppress the PAPR while maintaining the reliable BER performance in the scenario of 5G satellite communication, and solves the tradeoff problem of PAPR suppression and BER performance degradation.

The same or similar reference numerals correspond to the same or similar parts;

the terms describing positional relationships in the drawings are for illustrative purposes only and are not to be construed as limiting the patent;

it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (10)

1. A DSSS-GFDM system PAPR suppression method based on DFT precoding in 5G satellite communication is characterized by comprising the following steps:

s1: at a transmitting end, carrying out planet seat mapping pretreatment on binary data bit streams to obtain constellation mapping symbols;

s2: spreading the constellation mapping symbols using a direct sequence spread spectrum technique (DSSS);

s3: performing Discrete Fourier Transform (DFT) on the expanded constellation mapping symbols to obtain DFT pre-coded signals;

s4: performing GFDM modulation on the DFT pre-coded signals, adding a CP (content provider) and transmitting the signals to a wireless channel through radio frequency for transmission;

s5: after receiving the signals processed in steps S1 to S4, the receiving end performs channel estimation, synchronization, CP deletion and channel equalization on the received signals, and then demodulates the signals through a GFDM demodulator;

s6: carrying out Inverse Discrete Fourier Transform (IDFT) on the signal subjected to strip removal by the GFDM demodulator;

s7: performing direct sequence despreading on the signal subjected to Inverse Discrete Fourier Transform (IDFT);

s8: and performing constellation demapping on the despread signal to obtain an estimated value of the binary data bit stream.

2. The PAPR suppression method for DFT-precoding based DSSS-GFDM system in 5G satellite communication according to claim 1, wherein the binary data bit stream is preprocessed by planet seat mapping in step S1 to obtain constellation mapping symbols, specifically:

firstly, mapping a binary data bit stream by a planet seat, and then performing serial-parallel conversion on the binary data bit stream to obtain a constellation symbol vector S of M rho multiplied by 1, wherein rho is K/L to represent a spreading factor, L represents the length of an M sequence of the GFDM system, M is the number of subsymbols contained in one data block in the GFDM system, and K is the number of subcarriers contained in one data block in the GFDM system.

3. The PAPR suppression method for DFT-precoding based DSSS-GFDM system in 5G satellite communication according to claim 2, wherein step S2 uses DSSS spread spectrum technique to spread the constellation mapping symbols, specifically:

the QPSK symbol vector after DSSS is represented as:

d＝Bs＝[d₀ ^T,d₁ ^T,…,d_K-1 ^T]^T

in the formula (d)_k＝[d_k,0,d_k,1,…,d_k,M-1]^TInput sub-symbol vector representing the (k + 1) th sub-carrier of dimension x 1, d_k,mRepresents the m +1 th sub-symbol in the k +1 th sub-carrier, and B is the system spreading matrix.

4. The PAPR suppression method for DSSS-GFDM system based on DFT precoding in 5G satellite communication according to claim 3, wherein the calculation method of the system spreading matrix B is as follows:

considering a GFDM system with a data block comprising K subcarriers and M subsymbols, performing direct sequence spread spectrum on the subsymbols with the same position index in each subcarrier of an original GFDM data block by adopting the same M sequence, wherein the whole system adopts M different M sequences; by using

A spreading vector representing each M +1 th subsymbol, where M is 0,1,2, …, M-1, each element in the vector representing a corresponding spreading sequence, resulting in a spreading sequence matrix of dimension ML × M:

a system spreading matrix B of MK multiplied by M rho is constructed through a spreading sequence matrix:

5. the PAPR suppression method for DSSS-GFDM system based on DFT precoding in 5G satellite communication according to claim 4, wherein in step S3, Discrete Fourier Transform (DFT) is performed on the spread constellation mapping symbols to obtain DFT precoded signals:

where D is the discrete Fourier transform matrix of MK x MK, D% is the symbol vector after DFT precoding,

for the

The l +1 th symbol in (b), whose discrete form can be expressed as:

wherein [ d ] is]_ξThe ξ +1 symbol in this representation, l ═ 0,1, …, MK-1.

6. The PAPR suppression method for DSSS-GFDM based on DFT precoding in 5G satellite communication according to claim 5, wherein the GFDM modulation in step S4 comprises three processes of up-sampling, cyclic filtering and up-conversion.

7. The PAPR suppression method for DSSS-GFDM based on DFT precoding in 5G satellite communication according to claim 6, wherein the GFDM modulated signal is expressed as:

wherein

A GFDM symbol vector representing mkx 1, a representing a GFDM modulation matrix, in particular in the form of a ═ g_0,0…g_0,M-1g_1,0…g_1,M-1…g_K-1,M-1]Each column of the GFDM modulation matrix A represents a cyclic filter vector of MK 1 dimensions, and g_k,mIs g_0,0The cyclic time-frequency shift version of (a), the cyclic filter corresponding to each sub-symbol can be represented as:

the discrete form GFDM symbol can be expressed as:

wherein n is 0,1, …, MK-1,

represents

The m +1 th sub-symbol in the (k + 1) th sub-carrier.

8. The PAPR suppression method for DFT-precoding based DSSS-GFDM system in 5G satellite communication according to claim 7, wherein the step S5 for the receiving end to perform channel estimation, synchronization and CP removal on the received signal is represented as:

y＝Hx+ω

where y denotes a received symbol vector, H denotes a channel matrix, and ω denotes additive white gaussian noise.

9. The PAPR suppression method for DFT-based precoded DSSS-GFDM system in 5G satellite communication as claimed in claim 8, wherein in step S5 channel equalization is performed using zero-forcing equalization and GFDM demodulation is performed using GFDM matched receiver.

10. The PAPR suppression method for DSSS-GFDM system based on DFT precoding in 5G satellite communication according to claim 9, wherein the PAPR suppression method is characterized in thatIn steps S6 and S7, symbol vectors before QPSK demodulation are obtained through IDFT and direct sequence spread spectrum despreading processes

Expressed as:

in the formula, A^H、D^H、B^HRespectively representing the corresponding GFDM demodulation, IDFT, direct sequence despreading matrices.

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