CN111614594B - Self-adaptive adjusting method for reducing signal peak-to-average ratio - Google Patents

Abstract

The invention discloses a self-adaptive adjusting method for reducing signal peak-to-average power ratio, which belongs to the technical field of communication, wherein a power threshold value P0 is comprehensively set according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like, so that all signal powers are ensured to be in the dynamic linear range of the devices, and the error rate performance of an OFDM system is improved; introducing a self-adaptive idea, setting a PAPR threshold value requirement, and not processing signals smaller than the threshold value; for signals greater than the threshold value, processing parameters V, W are preliminarily given in combination with experience and associated derivation; for different transmission signals, different processing parameters are given, so that system resources are saved, and the time for processing the signals is reduced. Aiming at the signals which still do not meet the power threshold value under the initial given processing parameters, the invention sets the block number V and the adjustment rule of the search space W, and reduces the calculation complexity on the premise of ensuring the PAPR performance.

Description

Self-adaptive adjusting method for reducing signal peak-to-average ratio

Technical Field

The invention relates to the technical field of communication, in particular to a self-adaptive adjusting method for reducing a signal peak-to-average power ratio.

Background

Orthogonal Frequency Division Multiplexing (OFDM) technology is widely used in wired and wireless communication systems by virtue of its characteristics of high transmission rate, strong interference rejection, high spectrum utilization, and easy combination with other multiple access methods. However, a major problem with OFDM technology is the high peak-to-average power ratio (PAPR). The larger PAPR requires that devices such as A/D, D/A, a power amplifier and the like in the system have a large linear range, and OFDM signals with larger peak-to-average ratio easily enter a nonlinear region of the power amplifier, so that nonlinear distortion is generated on the signals, and the performance of the whole system is seriously reduced.

The fifth generation mobile communication technology (5G) is a research hotspot in the field of mobile communication at home and abroad at present, and the performance targets of the 5G are high data rate, delay reduction, energy saving, cost reduction, system capacity improvement and large-scale equipment connection. In order to ensure that OFDM can be well applied to 5G, it is important to improve its performance.

At present, a partial sequence transmission (PTS) method is an effective solution to the problem of relatively high peak average power of an OFDM system. However, as a probabilistic approach, it cannot guarantee that each signal satisfies the power condition. In addition, given processing parameters are fixed for different transmission signals, which wastes certain system resources and is not considered well for the problem of computational complexity.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a self-adaptive adjusting method for reducing the signal peak-to-average ratio, which adaptively adjusts the parameter V, W according to the set power threshold, and reduces the computational complexity as much as possible on the premise of ensuring the PAPR performance of the system.

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

an adaptive adjustment method for reducing the peak-to-average ratio of a signal comprises the following steps:

(1) performing serial-parallel conversion and IFFT processing on the data stream to obtain a time domain signal;

(2) comprehensively setting a power threshold value P according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like_THD；

(3) Calculating the peak-to-average power ratio P of the original signal₀And calculating the power difference a between the power threshold and the power threshold as P₀-P_THD；

31: if the power difference alpha is less than or equal to 0, the original signal meets the power threshold condition, and can be directly transmitted without block processing;

32: if the power difference alpha is larger than 0, entering the step (4);

(4) matching the current signal with a corresponding processing parameter c in combination with the power difference α and the processing capability b of the different PTS parameters V, W, where c is₀Expressed as the number of blocks V, i.e. values

b₀Processing capacity gain brought by adjusting the number V of blocks; c. C₁The value of W is shown as follows,

b₁calculating a power value P of a signal under the condition of an initial parameter for adjusting the processing capacity gain brought by the search space W;

(5) the power value P and the power threshold value P of the signal under the condition of the initial parameter are compared_THDComparing and adjusting parameters;

51: if the signal power value P is less than or equal to P_THDThen the V, W value at this time is saved;

52: if the signal power value P>P_THDAdjusting PTS parameters by combining a calculation complexity comparison function Fc, so that the calculation complexity of the system is reduced as much as possible on the premise that the PAPR performance of the system is ensured by the adjusted parameters;

(6) the resulting signal is combined with the phase factor information and sent to the receiver, which recovers the original signal by the phase factor information.

The technical scheme of the invention is further improved as follows: in step (1), N modulation symbols X ═ X are used here for better recovery of the time domain signal₀,X₁,...,X_N-1]^TAn oversampling process is employed in which the sampling coefficient L is normally satisfied (L ≧ 4), i.e.

Obtaining time domain signals after IFFT processing

The technical scheme of the invention is further improved as follows: in step (2), for the power threshold value P_THDThe method is comprehensively set according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like, and 80% of the system power tolerance is taken as a system power threshold value.

The technical scheme of the invention is further improved as follows: in step (4), b₀To adjust the throughput gain due to the number of blocks V, which divides the number of subcarriers N, b is defined₀The gain in processing power obtained for each doubling of V, b₀Determining according to the empirical value; b₁To adjust the processing power gain introduced by the search space W, W is only 2, 4, i.e., [1, -1, to reduce the system computational complexity]Or [1, -1, j, -j]，b₁The determination is made based on empirical values.

The technical scheme of the invention is further improved as follows: in step (5) 52, the adjustment rule of the block number V and the phase factor search space W is to perform adaptive adjustment on the block number V and the phase factor search space W in consideration of the computation complexity and PAPR performance; when the interleaving segmentation method is adopted for analysis in a subsequence segmentation mode, the specific method is as follows:

s1: the computational complexity is considered from three aspects:

1) inverse Fourier transform:

2) searching for an optimal phase factor:

C_add＝W^V-1N(V-1)

C_mult＝W^V-1N(V+1)

3) and (3) candidate signal comparison:

C_comp＝W^V-1N-1

then there are:

that is, when the number of subcarriers is given, only the number V of partitions and the search space W, which affect the computational complexity of the system. Therefore, the reasonable adjustment of V and W is of great significance for reducing the complexity of calculation;

note: c_addIndicates the number of additions required, C_multRepresenting the number of multiplications to be performed, C_compIndicates the number of comparisons required, C_totalRepresenting the accumulated operation times;

taking the number of subcarriers N as 64, when V, W takes different values, the computational complexity is as follows:

a. taking V, W as 2, C at this time was obtained_{General assembly}In the order of 1247, the number of,

b. taking V, W as 2, 4, C at this time was obtained_{General assembly}In the form of a gel that is 1887,

c. taking V, W as 2, 6, C at this time was obtained_{General assembly}Is a compound of formula (I) 2527,

d. taking V, W as 4 and 2, C at this time was obtained_{General assembly}In order to achieve the object of 5247,

e. taking V, W as 4, C at this time was obtained_{General assembly}In the order of 37503, is,

f. taking V, W as 4 and 6, C at this time was obtained_{General assembly}125055;

from the above analysis, the computational complexity case a < b < c < d < e < f; to a certain extent, the adjustment of the search space W brings a lower computational complexity than the adjustment of the number of partitions V;

the complexity comparison function F is calculated_CComprises the following steps:

note: f_WTo adjust the computational complexity of W, F_VIn order to adjust the calculation complexity of V, a is the adjustment amount of W, and V is adjusted by 2 times each time;

s2 PAPR Performance:

the larger the number of partitions V and the larger the search space W, the smaller the correlation between subcarriers and the smaller the probability of generating peak power, and the better the corresponding available PAPR performance; on the other hand, increasing the number of partitions V is more effective than increasing the search space W; this is because increasing the number of partitions V can reduce the correlation between subcarriers, increase the number of partitioned subsequences, and increase the probability of generating low peak-to-average ratio signals; the function of increasing the search space W is to increase the searchable space, but only increase the probability of generating low peak-to-average ratio signals;

in summary, the adjustment rule for the block number V and the search space W is formulated as follows:

if the current signal does not meet the set power threshold value condition, the search space W is preferentially adjusted to a certain degree, and F at the moment is calculated_CA value of (d);

if the PAPR performance after W adjustment still can not satisfy the threshold value condition, and F is performed at this time_C<0, continuing to adjust W; if F_C>0, adjusting the block number V and the search space W;

for each signal to be transmitted, the above process is circulated, and V, W is adaptively adjusted; the effect of reducing the calculation complexity of the system as much as possible on the premise of ensuring the PAPR performance is achieved.

The technical scheme of the invention is further improved as follows:

due to the adoption of the technical scheme, the invention has the technical progress that:

1. the invention comprehensively sets a power threshold value P according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like₀And all signal power is ensured to be in the dynamic linear range of the device, and the Bit Error Rate (BER) performance of the OFDM system is improved.

2. The invention introduces the self-adapting thought, and does not process the signal which is smaller than the threshold value by setting the PAPR threshold value requirement; for signals greater than the threshold value, processing parameters V, W are preliminarily given in combination with experience and associated derivation; for different transmission signals, different processing parameters are given, so that system resources are saved, and the time for processing the signals is reduced.

3. Aiming at the signals which still do not meet the power threshold value under the initial given processing parameters, the invention sets the block number V and the adjustment rule of the search space W, and reduces the calculation complexity on the premise of ensuring the PAPR performance.

Drawings

FIG. 1 is an overall flow diagram of the method of the present invention;

FIG. 2 is a block diagram of an adaptive partial transmission sequence OFDM system of the present invention;

FIG. 3 is a schematic diagram of the present invention employing an interleaving segmentation method;

FIG. 4 is a graph of the computational complexity results of the present invention when N, V, W takes different values;

FIG. 5 is a flow chart of parameter adjustment according to the present invention.

Detailed Description

The invention relates to a peak-to-average power ratio (PAPR) suppression technology for an Orthogonal Frequency Division Multiplexing (OFDM) technology under an industrial reliable communication scene, an adaptive partial transmission sequence method for reducing the PAPR of OFDM, in particular to an adaptive adjustment method for reducing the PAPR of a signal, which is developed aiming at the problem that the average power ratio of the peak of an OFDM system is higher.

The present invention will be described in further detail with reference to the following examples:

an adaptive adjustment method for reducing the peak-to-average ratio of a signal comprises the following steps:

(1) performing serial-parallel conversion and IFFT processing on the data stream to obtain a time domain signal;

for better recovery of the time domain signal, N modulation symbols X ═ X are used here₀,X₁,...,X_N-1]^TAn oversampling process is employed in which the sampling coefficient L is normally satisfied (L ≧ 4), i.e.

Obtaining time domain signals after IFFT processing

(2) Comprehensively setting a power threshold value P according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like_THD；

For power threshold value P_THDThe operation range of the power amplifier, the A/D, D/A converter and the like is comprehensively set. Generally, 80% of the system power tolerance is taken as a system power threshold;

(3) calculating the peak-to-average power ratio P of the original signal₀And calculating the power difference a between the power threshold and the power threshold as P₀-P_THD；

31: if the power difference alpha is less than or equal to 0, the original signal meets the power threshold condition, and can be directly transmitted without block processing;

32: if the power difference alpha is larger than 0, entering the step (4);

(4) matching the current signal with a corresponding processing parameter c in combination with the power difference α and the processing capability b of the different PTS parameters V, W, where c is₀Expressed as the number of blocks V, i.e. values

b₀Processing capacity gain brought by adjusting the number V of blocks; c. C₁The value of W is shown as follows,

b₁calculating a power value P of a signal under the condition of an initial parameter for adjusting the processing capacity gain brought by the search space W;

b₀to adjust the throughput gain due to the number of blocks V, which divides the number of subcarriers N, b is defined₀The gain in processing power obtained for each doubling of V, b₀Determining according to the empirical value; b₁To adjust the processing power gain introduced by the search space W, W is only 2, 4, i.e., [1, -1, to reduce the system computational complexity]Or [1, -1, j, -j]，b₁The determination is made based on empirical values.

(5) Of signals with initial parametersPower value P and power threshold value P_THDComparing and adjusting parameters;

51: if the signal power value P is less than or equal to P_THDThen the V, W value at this time is saved;

52: if the signal power value P>P_THDAdjusting PTS parameters by combining a calculation complexity comparison function Fc, so that the calculation complexity of the system is reduced as much as possible on the premise that the PAPR performance of the system is ensured by the adjusted parameters;

the adjustment rule of the block number V and the phase factor search space W is to perform self-adaptive adjustment on the block number V and the phase factor search space W by comprehensively considering the calculation complexity and the PAPR performance;

taking the interleaving segmentation method as an example in the subsequence segmentation mode, the specific analysis is as follows:

s1: in terms of computational complexity, consideration is made from three aspects:

1) inverse Fourier transform:

2) searching for an optimal phase factor:

C_add＝W^V-1N(V-1)

C_mult＝W^V-1N(V+1)

3) and (3) candidate signal comparison:

C_comp＝W^V-1N-1

then there are:

that is, when the number of subcarriers is given, only the number V of partitions and the search space W, which affect the computational complexity of the system. Therefore, it is important to reasonably adjust V and W to reduce the complexity of calculation.

Note: c_addIndicates the number of additions required, C_multRepresenting the number of multiplications to be performed, C_compIndicates the number of comparisons required, C_totalIndicating the number of cumulative operations.

Taking the number of subcarriers N as 64, when V, W takes different values, the computational complexity is as follows:

a. taking V, W as 2, C at this time was obtained_{General assembly}In the order of 1247, the number of,

b. taking V, W as 2, 4, C at this time was obtained_{General assembly}In the form of a gel that is 1887,

c. taking V, W as 2, 6, C at this time was obtained_{General assembly}Is a compound of formula (I) 2527,

d. taking V, W as 4 and 2, C at this time was obtained_{General assembly}In order to achieve the object of 5247,

e. taking V, W as 4, C at this time was obtained_{General assembly}In the order of 37503, is,

f. taking V, W as 4 and 6, C at this time was obtained_{General assembly}Is 125055.

From the above analysis, the computational complexity case a < b < c < d < e < f. To a certain extent, the computational complexity of adjusting the search space W is lower than adjusting the number of partitions V.

The complexity comparison function F is calculated_CComprises the following steps:

note: f_WTo adjust the computational complexity of W, F_VTo adjust the computational complexity of V, a is the adjustment amount of W, V is adjusted by 2 times each time.

S2: in terms of PAPR performance:

in terms of PAPR performance, the larger the number of partitions V and the larger the search space W, the smaller the correlation between subcarriers and the smaller the probability of generating peak power, and the better the corresponding available PAPR performance. On the other hand, increasing the number of partitions V is more effective than increasing the search space W. This is because increasing the number of partitions V reduces the correlation between subcarriers, increases the number of partitioned subsequences, and increases the probability of generating a low peak-to-average ratio signal. While increasing the search space W has the effect of increasing the searchable space, simply increasing the probability of producing a low peak-to-average signal.

In summary, the adjustment rule for the block number V and the search space W is formulated as follows: if the current signal does not meet the set power threshold value condition, the search space W is preferentially adjusted to a certain degree, and F at the moment is calculated_CThe value of (c). If the PAPR performance after W adjustment still can not satisfy the threshold value condition, and F is performed at this time_C<0, continuing to adjust W; if F_C>0, adjusting the block number V and the search space W; the above process is looped for each signal to be transmitted, and V, W is adaptively adjusted. The effect of reducing the calculation complexity of the system as much as possible on the premise of ensuring the PAPR performance is achieved.

(6) The resulting signal is combined with the phase factor information and sent to the receiver, which recovers the original signal by the phase factor information.

In particular

As shown in fig. 1, a flow chart of a method for adaptive partial transmission sequence includes the following steps:

(1) performing serial-to-parallel conversion and IFFT processing on the data stream, and in order to ensure that complete information of a signal is recovered at a receiving end, performing 4-time oversampling processing when performing IFFT processing on a modulation signal to obtain a time domain signal;

(2) comprehensively setting a power threshold value P according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like_THDIf the comprehensive power tolerance of each device is 10dB, the power threshold value P is_THD10dB by 80%, i.e. 8 dB;

(3) calculating the peak-to-average power ratio P of the original signal₀And calculating it with a power threshold value P_THDIs equal to P₀-P_THD；

31: if the power difference alpha is less than or equal to 0, the original signal meets the power threshold condition, and can be directly transmitted without block processing;

32: if the power difference alpha is greater than 0, entering a step 4;

(4) the corresponding processing parameter c is matched for the current signal in combination with the power difference value alpha and the processing capability b of the different PTS parameter V, W. Wherein c is₀Expressed as the value of the number of blocks V, i.e.

b₀Processing capacity gain brought by adjusting the number V of blocks; c. C₁The value of W is shown as follows,

b₁to adjust the processing power gain introduced by the search space W. And calculating the power value P of the signal under the condition of the initial parameter. According to experience, b is taken here₀Is 1.5 dB; considering the computational complexity problem, the search space W is limited to 2, 4, i.e., W ═ 1, -1]Or W ═ 1, -1; j, -j]And take b₁Is 1.0 dB. Then, according to the initial parameter c₀、c₁And performing block division and phase factor search processing on the subsequences, wherein the subsequence division mode adopts an interleaving division mode, as shown in fig. 3.

(5) The power value P and the power threshold value P of the signal under the condition of the initial parameter are compared_THDComparing and adjusting parameters;

51: if the signal power value P is less than or equal to P_THDThen the V, W value at this time is saved;

52: if the signal power value P>P_THDAnd adjusting PTS parameters by combining with a calculation complexity comparison function Fc, so that the calculation complexity of the system is reduced as much as possible on the premise that the PAPR performance of the system is ensured by the adjusted parameters. Wherein Fc is obtained by balancing computational complexity and PAPR performance, the computational complexity of different processing parameters is shown in fig. 4, and the parameter adjustment rule is shown in fig. 5;

(6) the processed signal and the phase factor combination are transmitted to a receiver, and the receiver recovers the original signal by using the phase factor information.

In summary, the present invention sets the adjustment rule of the block number V and the search space W for the signal that still does not satisfy the power threshold under the initially given processing parameter, and reduces the computational complexity on the premise of ensuring the PAPR performance.

Claims (5)

1. A self-adaptive adjusting method for reducing signal peak-to-average power ratio is characterized in that: the method comprises the following steps:

(1) performing serial-parallel conversion and IFFT processing on the data stream to obtain a time domain signal;

(2) comprehensively setting a power threshold value P according to the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like_THD；

(3) Calculating the peak-to-average power ratio P of the original signal₀And calculating the power difference a between the power threshold and the power threshold as P₀-P_THD；

31: if the power difference alpha is less than or equal to 0, the original signal meets the power threshold condition, and can be directly transmitted without block processing;

32: if the power difference alpha is larger than 0, entering the step (4);

(4) matching the current signal with a corresponding processing parameter c in combination with the power difference α and the processing capability b of the different PTS parameters V, W, where c is₀Expressed as the number of blocks V, i.e. values

b₀Processing capacity gain brought by adjusting the number V of blocks; c. C₁The value of W is shown as follows,

b₁calculating a power value P of a signal under the condition of an initial parameter for adjusting the processing capacity gain brought by the search space W;

(5) the power value P and the power threshold value P of the signal under the condition of the initial parameter are compared_THDComparing and adjusting parameters;

51: if the signal power value P is less than or equal to P_THDThen the V, W value at this time is saved;

52: if the signal power value P>P_THDAdjusting PTS parameters by combining a calculation complexity comparison function Fc, so that the calculation complexity of the system is reduced as much as possible on the premise that the PAPR performance of the system is ensured by the adjusted parameters; computational complexity comparison function F_CComprises the following steps:

note: f_WTo adjust the computational complexity of W, F_VTo adjust the computational complexity of V, a is the adjustment amount of W,

v is adjusted by 2 times each time;

(6) the resulting signal is combined with the phase factor information and sent to the receiver, which recovers the original signal by the phase factor information.

2. The adaptive adjustment method for reducing the peak-to-average ratio of a signal as claimed in claim 1, wherein: in step (1), N modulation symbols X ═ X are used here for better recovery of the time domain signal₀，X₁，...，X_N-1]^TAn oversampling process is employed in which the sampling coefficient L is normally satisfied (L ≧ 4), i.e.

Obtaining time domain signals after IFFT processing

3. The adaptive adjustment method for reducing the peak-to-average ratio of a signal as claimed in claim 1, wherein: in step (2), for the power threshold value P_THDThe system power tolerance is obtained according to the comprehensive setting of the working ranges of devices such as a power amplifier, an A/D, D/A converter and the like80% is the system power threshold.

4. The adaptive adjustment method for reducing the peak-to-average ratio of a signal as claimed in claim 1, wherein: in step (4), b₀To adjust the throughput gain due to the number of blocks V, which divides the number of subcarriers N, b is defined₀The gain in processing power obtained for each doubling of V, b₀Determining according to the empirical value; b₁To adjust the processing power gain introduced by the search space W, W is only 2, 4, i.e., [1, -1, to reduce the system computational complexity]Or [1, -1, j, -j]，b₁The determination is made based on empirical values.

5. The adaptive adjustment method for reducing the peak-to-average ratio of a signal as claimed in claim 1, wherein: in step (5) 52, the adjustment rule of the block number V and the phase factor search space W is to perform adaptive adjustment on the block number V and the phase factor search space W in consideration of the computation complexity and PAPR performance; when the interleaving segmentation method is adopted for analysis in a subsequence segmentation mode, the specific method is as follows:

s1: the computational complexity is considered from three aspects:

1) inverse Fourier transform:

2) searching for an optimal phase factor:

C_add＝W^V-1N(V-1)

C_mult＝W^V-1N(V+1)

3) and (3) candidate signal comparison:

C_comp＝W^V-1N-1

then there are:

namely, only the block number V and the search space W which influence the calculation complexity of the system are given; therefore, the reasonable adjustment of V and W is of great significance for reducing the complexity of calculation;

note: c_addIndicates the number of additions required, C_multRepresenting the number of multiplications to be performed, C_compIndicates the number of comparisons required, C_totalRepresenting the accumulated operation times;

taking the number of subcarriers N as 64, when V, W takes different values, the computational complexity is as follows:

a. taking V, W as 2, C at this time was obtained_totalIn the order of 1247, the number of,

b. taking V, W as 2, 4, C at this time was obtained_totalIn the form of a gel that is 1887,

c. taking V, W as 2, 6, C at this time was obtained_totalIs a compound of formula (I) 2527,

d. taking V, W as 4 and 2, C at this time was obtained_totalIn order to achieve the object of 5247,

e. taking V, W as 4, C at this time was obtained_totalIn the order of 37503, is,

f. taking V, W as 4 and 6, C at this time was obtained_total125055;

from the above analysis, the computational complexity case a < b < c < d < e < f; to a certain extent, the adjustment of the search space W brings a lower computational complexity than the adjustment of the number of partitions V;

the complexity comparison function F is calculated_CComprises the following steps:

note: f_WTo adjust the computational complexity of W, F_VTo adjust the computational complexity of V, a is the adjustment amount of W,

v is adjusted by 2 times each time;

s2: in terms of PAPR performance:

in terms of PAPR performance, the larger the number of partitions V and the larger the search space W, the smaller the correlation between subcarriers and the smaller the probability of generating peak power, the better the corresponding available PAPR performance; on the other hand, increasing the number of partitions V is more effective than increasing the search space W; this is because increasing the number of partitions V can reduce the correlation between subcarriers, increase the number of partitioned subsequences, and increase the probability of generating low peak-to-average ratio signals; the function of increasing the search space W is to increase the searchable space, but only increase the probability of generating low peak-to-average ratio signals;

in summary, the adjustment rule for the block number V and the search space W is formulated as follows:

if the current signal does not meet the set power threshold value condition, the search space W is preferentially adjusted to a certain degree, and F at the moment is calculated_CA value of (d);

if the PAPR performance after W adjustment still can not satisfy the threshold value condition, and F is performed at this time_C<0, continuing to adjust W; if F_C>0, adjusting the block number V and the search space W;

for each signal to be transmitted, the above process is circulated, and V, W is adaptively adjusted; the effect of reducing the calculation complexity of the system as much as possible on the premise of ensuring the PAPR performance is achieved.

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