CN117336128A - Position demodulation soft decision method of BPM-BPSK receiver - Google Patents
Position demodulation soft decision method of BPM-BPSK receiver Download PDFInfo
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- CN117336128A CN117336128A CN202311318637.0A CN202311318637A CN117336128A CN 117336128 A CN117336128 A CN 117336128A CN 202311318637 A CN202311318637 A CN 202311318637A CN 117336128 A CN117336128 A CN 117336128A
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- 238000013139 quantization Methods 0.000 claims description 4
- 238000004364 calculation method Methods 0.000 claims description 3
- 238000011002 quantification Methods 0.000 claims 1
- 238000004891 communication Methods 0.000 abstract description 9
- 230000005540 biological transmission Effects 0.000 description 6
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/18—Phase-modulated carrier systems, i.e. using phase-shift keying
- H04L27/22—Demodulator circuits; Receiver circuits
- H04L27/227—Demodulator circuits; Receiver circuits using coherent demodulation
- H04L27/2275—Demodulator circuits; Receiver circuits using coherent demodulation wherein the carrier recovery circuit uses the received modulated signals
- H04L27/2278—Demodulator circuits; Receiver circuits using coherent demodulation wherein the carrier recovery circuit uses the received modulated signals using correlation techniques, e.g. for spread spectrum signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/03—Shaping networks in transmitter or receiver, e.g. adaptive shaping networks
- H04L25/03006—Arrangements for removing intersymbol interference
- H04L25/03178—Arrangements involving sequence estimation techniques
- H04L25/03312—Arrangements specific to the provision of output signals
- H04L25/03318—Provision of soft decisions
Abstract
The invention discloses a position demodulation soft decision method of a BPM-BPSK receiver, which belongs to the technical field of time-hopping modulation and demodulation communication and comprises the following steps: step 1, demodulating front and rear sections of a current symbol simultaneously to obtain two demodulation results; step 2, summing the two demodulation results and obtaining a difference; step 3, performing correlation operation on the sum and difference results; step 4, performing soft decision operation by using the correlation operation result, the channel estimation result and the noise estimation result; and 5, quantifying a soft decision operation result. The invention provides a position demodulation soft decision method of a BPM-BPSK receiver, which converts demodulation numerical value information into numerical value representation of position information through sum-difference and correlation operation, thereby carrying out soft decision on the position information and improving demodulation performance.
Description
Technical Field
The invention belongs to the technical field of time-hopping modulation and demodulation communication, and particularly relates to a position demodulation soft decision method of a BPM-BPSK receiver.
Background
Time-hopping communication belongs to a spread spectrum technique, wherein transmitted symbols are uniformly divided into a plurality of slices on a time axis, and the decision of which slice to use to carry a modulation signal is made according to a pseudo-random code and the burst transmission is performed with higher peak power. The BPM-BPSK modulation mode divides each symbol into a front section and a rear section, and the two sections have the same number of slices and slice numbers; each symbol can transmit 2 bits of information, wherein the high order bits carry out BPM modulation to determine which segment the modulated signal is located in, and the pseudo-random code determines which slice is located in the segment; the low order bits are BPSK modulated to determine the polarity of the spreading code in the tile. The technology is widely applied to the current high-precision positioning UWB (Ultra-WideBand) communication system.
The underlying signal form for UWB positioning and communications is a narrow pulse. The currently more widely used UWB communication protocol is the IEEE 802.15.4a/z protocol. In this protocol, after a narrow pulse is modulated using a spreading code, it is BPSK modulated according to the information to be transmitted, and finally the modulated signal is transmitted in a specific segment of the symbol.
At present, the demodulation technology of BPSK is mature, and better performance can be obtained by adopting soft decision. But for demodulation of BPM, hard decisions are typically used. The corresponding slices in the two sections are demodulated according to the slice numbers obtained by the pseudo-random codes, and the section positioned in the corresponding section is judged according to the energy. The hard decision technique has a larger performance gap than the soft decision demodulation technique, which causes inconsistent demodulation performance for the two modulation modes, thereby reducing the overall demodulation performance.
Disclosure of Invention
The invention aims to provide a position demodulation soft decision method of a BPM-BPSK receiver, which solves the problems of poor technical performance of position demodulation hard decision and reduced overall demodulation performance in the prior art.
In order to achieve the above object, the present invention provides a soft decision method for position demodulation of a BPM-BPSK receiver, comprising the steps of:
step 1, demodulating front and rear sections of a currently received symbol simultaneously to obtain two demodulation results;
step 2, summing the two demodulation results and obtaining a difference;
step 3, performing correlation operation on the sum and difference results;
step 4, performing soft decision operation by using the correlation operation result, the channel estimation result and the noise estimation result;
and 5, quantifying the soft decision operation result.
Preferably, the procedure for obtaining two demodulation results in step 1 is as follows: obtaining the number of the section where the modulation signal of the current symbol is located according to the pseudo-random sequence agreed at the two ends of the receiving and transmitting, and taking out the two signals corresponding to the number of the section in the front and rear sections of the currently received symbol according to the front and rear sections divided by the BPM modulation mode, carrying out demodulation or despreading processing corresponding to the modulation of the transmitting end to obtain two demodulation results, and marking as D l And D r ，D l And D r And respectively corresponding to the demodulation results of the front section and the rear section.
Preferably, the specific formula for summing and differencing the two demodulation results in step 2 is as follows:
D s ＝D l +D r
D d ＝D l -D r
wherein D is l And D r Demodulation results corresponding to the front section and the rear section respectively, D s Representing the sum of the front-section and back-section demodulation results, D d Representing the difference between the front-stage and back-stage demodulation results.
Preferably, the specific expression of the correlation operation in step 3 is as follows:
wherein abs () is an absolute value operation, D cor Representing the result of the correlation operation, D s Representing the sum of the front-section and back-section demodulation results, D d Representing the difference between the front-stage and back-stage demodulation results.
Preferably, in step 4, the calculation formula for performing the soft decision operation using the correlation operation result, the channel estimation result, and the noise estimation result is as follows:
D 0 ＝(D cor -(+chan_est)) 2
D 1 ＝(D cor -(-chan_est)) 2
the modulation scheme of BPM is assumed to be: if the corresponding code bit is 0, burst is positioned at the front section; if the corresponding code bit is 1, burst is located in the latter stage, where D cor Representing the result of the correlation operation, D dem Represents the quantized result of reliability in positive and negative distinction under the current noise condition, D 0 Indicating D with current reception after reaching the current receiving end through the channel under the condition of assuming that the coding bit is 0 cor Proximity of (3); d (D) 1 Shows the D with the current receiving end after the current receiving end is reached through the channel under the condition of assuming the coding bit is 1 cor And +chan_est and-chan_est each represent a theoretical value of the demodulation result.
Preferably, the specific process of quantizing the soft decision operation result in step 5 is as follows: setting the quantization bit width to N, D dem Is rounded and +2 (N-1) Post-limiting to [0:2 ] N -1]In the range, as a soft decision output of demodulation, wherein a closer to 0 indicates a greater probability that the demodulation result is 0; the closer to 2 N -1 indicates a greater probability of demodulation result being 1.
Therefore, the invention adopts the position demodulation soft decision method of the BPM-BPSK receiver, and the demodulation numerical value information is converted into the numerical value representation of the position information by processing the demodulation results of the corresponding slices in the two sections, so that the soft decision can be carried out, and the demodulation performance of the receiver is improved.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
Fig. 1 is a general flow chart of a method for soft decision for position demodulation of a BPM-BPSK receiver according to the invention;
fig. 2 is a symbol structure diagram of the UWB communication system of the present invention.
Detailed Description
The following detailed description of the embodiments of the invention, provided in the accompanying drawings, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Referring to fig. 1, a soft decision method for position demodulation of a BPM-BPSK receiver includes the following steps:
step 1, demodulating front and rear sections of a currently received symbol simultaneously to obtain two demodulation results, wherein the specific process is as follows: obtaining the number of the section where the modulation signal of the current symbol is located according to the pseudo-random sequence agreed at the two ends of the receiving and transmitting, and taking out the two signals corresponding to the number of the section in the front and rear sections of the currently received symbol according to the front and rear sections divided by the BPM modulation mode, carrying out demodulation or despreading processing corresponding to the modulation of the transmitting end to obtain two demodulation results, and marking as D l And D r ，D l And D r The demodulation results of the front section and the rear section are respectively corresponding, the BPSK modulated signals of the transmitting end are plus 1 and minus 1, and the theoretical values of the demodulation results are +chan_est and-chan_est after the processing such as amplifying and filtering of a channel and a receiver in the transmission process;
and 2, summing two demodulation results and solving a difference, wherein the specific formula is as follows:
D s ＝D l +D r
D d ＝D l -D r
wherein D is l And D r Demodulation results corresponding to the front section and the rear section respectively, D s Representing the sum of the front-section and back-section demodulation results, D d Representing the difference between the demodulation results of the front section and the rear section, since burst is only located in one section of the front section and the rear section, there must be a demodulation result with a theoretical value of 0, and if it is located in the front section, the sum and difference result have the same theoretical sign; if the result is positioned at the rear stage, the sum and difference result have opposite signs in theory;
and step 3, performing correlation operation on the sum and difference results, wherein the specific expression is as follows:
wherein abs () is an absolute value operation, D cor Representing the result of the correlation operation, D s Representing the sum of the front-section and back-section demodulation results, D d Representing the difference between the front and back demodulation results, the above formula shows a correlation calculation with a sequence length of 1, according to which if burst is in the front, D cor Is chan_est; if burst is in the posterior segment, D cor Is-chan_est; d (D) cor The closer to 0, description D s And D d The larger the amplitude difference, i.e. D l And D r The larger the influence of noise is, the smaller the result reliability is; d (D) cor The larger the amplitude of (D), description D s And D d The smaller the amplitude difference, i.e. D l And D r The smaller the influence of noise is, the higher the result reliability is;
and 4, performing soft decision operation by using the correlation operation result, the channel estimation result and the noise estimation result, wherein the distribution of the correlation result of the Gaussian distribution sequence with the length of 1 is close to Gaussian distribution, so that the Gaussian distribution sequence can be approximately considered to be accordant with the Gaussian distribution in engineering. Accordingly, the value of the reliability can be calculated according to the soft decision method as follows:
D 0 ＝(D cor -(+chan_est)) 2
D 1 ＝(D cor -(-chan_est)) 2
the modulation scheme of BPM is assumed here to be: if the corresponding code bit is 0, burst is positioned at the front section; if the corresponding code bit is 1, burst is located in the latter stage, where D cor Representing the result of the correlation operation, D dem Representing the quantization result in positive and negative confidence under the current noise condition, if the value is negative, the larger the absolute value is, indicating that the code bit isThe greater the probability of 0; if the value is positive, a larger absolute value indicates a greater probability of 1 for the code bit, D 0 Indicating D with current reception after reaching the current receiving end through the channel under the condition of assuming that the coding bit is 0 cor Proximity of (3); d (D) 1 Shows the D with the current receiving end after the current receiving end is reached through the channel under the condition of assuming the coding bit is 1 cor In the above-described embodiments, +chan_est and-chan_est each represent a theoretical value of the demodulation result;
step 5, quantizing the soft decision operation result, D due to the limitation of probability distribution and noise size dem The absolute value of (2) exceeds a certain value, so that the influence on the final demodulation performance after the values are ignored is very small, and the specific process of quantifying the soft decision operation result is as follows: setting the quantization bit width to N, D dem Is rounded and +2 (N-1) Post-limiting to [0:2 ] N -1]In the range, as a soft decision output of demodulation, wherein a closer to 0 indicates a greater probability that the demodulation result is 0; the closer to 2 N -1 indicates a greater probability of demodulation result being 1.
Fig. 2 is a symbol structure diagram of a UWB communication system, where a symbol is equally divided into front and rear sections, each section has a length of t_bpm, each t_bpm is divided into front and rear sections, which are respectively an information transmission area and a protection interval, and the information transmission area is evenly divided into a plurality of slices with equal time lengths for time hopping information transmission. In the communication transmission process, each UWB symbol transmits 2-bit information, namely position information and polarity information. The polarity bit of the information to be transmitted is multiplied by the spreading sequence, and the multiplication result is used for modulating the pulse to obtain a pulse sequence, which is called a burst. And obtaining the number of the slice occupied by the current burst (the number range of the slice in the figure is [0,1,2,3 ]) according to the pseudo-random sequence, determining which section of the symbol is occupied by the burst in the waiting position information to correspond to the numbered slice, and then placing the burst into the corresponding slice to finish modulation.
Therefore, the invention adopts the position demodulation soft decision method of the BPM-BPSK receiver, and the demodulation numerical value information is converted into the numerical value representation of the position information by processing the demodulation results of the corresponding slices in the two sections, so that the soft decision can be carried out, and the demodulation performance of the receiver is improved.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention and not for limiting it, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that: the technical scheme of the invention can be modified or replaced by the same, and the modified technical scheme cannot deviate from the spirit and scope of the technical scheme of the invention.
Claims (6)
1. A method for soft decision for position demodulation of a BPM-BPSK receiver, comprising the steps of:
step 1, demodulating front and rear sections of a currently received symbol simultaneously to obtain two demodulation results;
step 2, summing the two demodulation results and obtaining a difference;
step 3, performing correlation operation on the sum and difference results;
step 4, performing soft decision operation by using the correlation operation result, the channel estimation result and the noise estimation result;
and 5, quantifying the soft decision operation result.
2. The soft decision method for position demodulation of a BPM-BPSK receiver according to claim 1, wherein the process of obtaining two demodulation results in step 1 is as follows: obtaining the number of the section where the modulation signal of the current symbol is located according to the pseudo-random sequence agreed at the two ends of the receiving and transmitting, and taking out the two signals corresponding to the number of the section in the front and rear sections of the currently received symbol according to the front and rear sections divided by the BPM modulation mode, carrying out demodulation or despreading processing corresponding to the modulation of the transmitting end to obtain two demodulation results, and marking as D l And D r ，D l And D r And respectively corresponding to the demodulation results of the front section and the rear section.
3. The method for soft decision of position demodulation of a BPM-BPSK receiver according to claim 2, wherein the specific formula of summing and differencing the two demodulation results in step 2 is as follows:
D s ＝D l +D r
D d ＝D l -D r
wherein D is l And D r Demodulation results corresponding to the front section and the rear section respectively, D s Representing the sum of the front-section and back-section demodulation results, D d Representing the difference between the front-stage and back-stage demodulation results.
4. The soft decision method for position demodulation of a BPM-BPSK receiver as claimed in claim 3, wherein the correlation operation in step 3 has the following specific expression:
wherein abs () is an absolute value operation, D cor Representing the result of the correlation operation.
5. The soft decision method for position demodulation of a BPM-BPSK receiver as claimed in claim 4, wherein the calculation formula for performing the soft decision operation in step 4 using the correlation operation result, the channel estimation result, and the noise estimation result is as follows:
D 0 ＝(D cor -(+chan_est)) 2
D 1 ＝(D cor -(-chan_est)) 2
the modulation scheme of BPM is assumed to be: if the corresponding code bit is 0, burst is positioned at the front section; if the corresponding code bit is 1, burst is located in the latter stage, where D cor Representing the result of the correlation operation, D dem Representing the current noise situationUnder the condition, the quantification result of the credibility is differentiated by positive and negative, D 0 Indicating D with current reception after reaching the current receiving end through the channel under the condition of assuming that the coding bit is 0 cor Proximity of (3); d (D) 1 Shows the D with the current receiving end after the current receiving end is reached through the channel under the condition of assuming the coding bit is 1 cor And +chan_est and-chan_est each represent a theoretical value of the demodulation result.
6. The soft decision method for position demodulation of a BPM-BPSK receiver according to claim 1, wherein the specific process of quantizing the soft decision operation result in step 5 is as follows: setting the quantization bit width to N, D dem Is rounded and +2 (N-1) Post-limiting to [0:2 ] N -1]In the range, as a soft decision output of demodulation, wherein a closer to 0 indicates a greater probability that the demodulation result is 0; the closer to 2 N -1 indicates a greater probability of demodulation result being 1.
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