CN102684737B - Method for realizing multi-user spread spectrum broadcasting station based on parallel interference cancellation algorithm - Google Patents
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Abstract
The invention provides a method for realizing a multi-user spread spectrum broadcasting station based on parallel interference cancellation algorithm, which can realize data transmission between a plurality of users and a receiver at the same time under the same frequency. The parallel interference cancellation algorithm is realized on a receiver; and before the algorithm is realized, a code synchronization module of the receiver outputs a spreading code of the current phase position, and a despreading module outputs a primary despreading signal. The parallel interference cancellation algorithm comprises the following steps: firstly, a spreading code is utilized to despread the primary despreading signal for the second time and the cross correlation coefficients of different user spreading codes are worked out at the same time; secondly, all secondary spread spectrum signals that interfere with users are multiplied and added with the corresponding cross correlation coefficients respectively to obtain interference signals; thirdly, the interference signals are subtracted from baseband digital signals to obtain baseband signals without interference; and finally, code synchronization, despreading and carrier synchronization demodulation are performed to the baseband signals without interference so as to obtain the current user data. According to the invention, the processes are carried out concurrently, so that radio station communication and data transmission between a plurality of users and the receiver can be realized in the same frequency band at the same time.
Description
Technical field
The present invention is a kind of multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm, belongs to wireless communication technology field, relates to radio spread spectrum communication technology, multiuser detection, the same research of heterogeneous Carrier Synchronization frequently.
Background technology
Spread spectrum can effectively improve the anti-interference and security performance of communication system by video stretching processing, thereby is rapidly developed, and is widely used in the military field such as military communication, electronic countermeasures, has also obtained paying attention to and application in commercial communication field simultaneously.
Existing wireless spread spectrum broadcasting station mainly adopts point-to-point communication pattern, adopts the modes of polls in the time realizing multi-point communication more, does not realize with frequency multi-point simultaneously.The communication efficiency that has so just reduced spread spectrum receivers, has increased Time Delay of Systems.Therefore urgently develop a kind of implementation method of new multi-user's spread spectrum receivers, realize between multiple users and receiver and communicating in synchronization, same frequency range.
Summary of the invention
The object of the invention is to, by adopting Direct Sequence Spread Spectrum Communication mode to realize the Wireless Data Transmission of multiple users under synchronization, same frequency range, wherein transmitter adopts direct sequence spread spectrum mode to carry out spread spectrum to user data; Receiver adopts Parallel Interference Cancellation method removal multiple access to disturb when realizing multi-user and receives, and employing is carried out carrier synchronization demodulation with the heterogeneous carrier track method of frequency to the carrier wave of multiple Phase Stackings.
The present invention adopts following technological means to realize:
Multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm, is characterized in that comprising the following steps:
1.1. user data is carried out convolutional encoding processing by each transmitter, then with the spreading code distributing, the data after coding are carried out to digital spread spectrum and BPSK(Binary Phase Shift Keying, two-phase PSK) modulation, then send by antenna after up-conversion and filtering processing;
1.2. receiver receives after each subscriber signal that transmitter sends, it is carried out to down-converted, obtain analog if signal, this analog if signal is carried out to controllable gain and amplify processing, deliver to again analog-to-digital conversion sampling A/D chip and sample and obtain digital medium-frequency signal, this digital medium-frequency signal is carried out to Digital Down Convert processing and obtain baseband digital signal;
1.3. baseband digital signal is admitted to a yard synchronization module, by catching and follow the tracks of operation, to realize spreading code synchronous, take a certain road user wherein as active user, all the other a few road users are interference user, utilize Parallel Interference Cancellation algorithm to extract interference signal, and from baseband digital signal, remove the multiple access interference that multiple interference users cause active user's signal, obtain removing the active user's signal after disturbing;
1.4. active user's signal of removing after disturbing is being delivered to carrier synchronization module after synchronous despreading, utilize with the heterogeneous carrier track method of frequency herein and realize the carrier phase accurate tracking demodulation to active user, then adjudicate by bit synchronization and differential decoding processing obtains the data after active user coding, then the user data after coding is carried out to Viterbi decoding obtain active user and receive data;
1.5. by the operation of above-mentioned receiving course multidiameter delay, each road by active user's spreading code carry out despreading, go to disturb, the processing such as carrier synchronization, in synchronization, same frequency, multiple user data are received and are processed.
2, according to the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm described in claim 1, it is characterized in that: the signal amplitude receiving by automatic gain control adjustment before sampling in described 1.2, after sampling, utilize digital controlled oscillator to produce sinusoidal signal signal after sampling is carried out to Digital Down Convert processing, then realize filtering and extraction process by integral comb filter and finite impulse response correction wave filter.
3, according to the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm described in claim 1, it is characterized in that: the code in described 1.3 synchronously comprises the following steps:
3.1 catch by sliding correlation method: first carry out relevant treatment, after filtering, after square detection, integration, send into comparator, in the time that integral result is less than decision threshold, feedback control signal of comparison module input goes to adjust the phase place of local pseudo random sequence code, reenter the relevant treatment of a new round, be acquisition success until the Output rusults of integrator is greater than threshold value, output identification simultaneously enters tracking module;
It is thin synchronous that 3.2 tracking modules adopt incoherent delay lock loop to realize: lock-on signal is divided into two-way and multiplies each other with the local reference signal of half code-element period of lead and lag respectively, carry out square operation by square operation circuit, carry out filtering by low pass filter again, treated two paths of signals is given phase discriminator and is subtracted each other, adjust the phase place of local spreading code according to the result of phase discriminator output, finally make the pseudo random sequence code phase error of transmitting terminal and receiving terminal narrow down to and be less than positive and negative 1/16 code-element period;
3.3 tracking circuits will detect to judge whether PN code synchronization is lost in real time, once detect synchronization loss, proceed to immediately acquisition phase in 3.1 and carry out the synchronizing process of a new round.
4,, according to the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm described in claim 1, it is characterized in that the algorithm of Parallel Interference Cancellation described in 1.3 comprises the following steps:
4.1 utilize tracking module obtain the phase place of current all user's frequency expansion sequences and calculate cross-correlation coefficient, the signal of following the tracks of after despreading are carried out to spread spectrum again simultaneously, are then multiplied by cross-correlation coefficient and obtain interference signal;
4.2 baseband digital signals deduct interference signal and obtain removing the active user's signal after disturbing.
5,, according to the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm described in claim 1, it is characterized in that the heterogeneous carrier track method of same frequency in 1.4 comprises the following steps:
5.1 adopt front 4 groups of phase places local carrier and the despreading output signals that postpone successively to multiply each other simultaneously, and then device sum-product intergrator obtains integral result after filtering, and the Gao of selection integral result mono-tunnel is that final local carrier synchronous demodulation result is exported;
In 5.2 above-mentioned 5.1, process is carried out in real time, once primary carrier phase place changes, integral result variation, adjudicates again, and selecting integral result the highest is that as a result of export on the best Yi of phase matched road.
The present invention is a kind of multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm, compared with prior art, has following obvious advantage and beneficial effect:
In receiver, adopt Parallel Interference Cancellation method to realize the inhibition of disturbing for the mutual multiple access of multiple users.Can make multiple users carry out transfer of data under synchronization, same frequency range by the self-interference of removing system, improve system user capacity and band efficiency.Multi-user is transmitted simultaneously and can be reduced the system delay that traditional polling mode is brought, and each user data transmission time is no longer subject to other user's restriction.
In the use of carrier synchronization module innovation with heterogeneous carrier track method frequently.The carrier phase that the carrier phase stack that the method sends for the multiple users of system and each user arrive receiver by wireless channel is with changes in channel characteristics, tradition phase demodulation module cannot realize the problem that active user's carrier phase is accurately followed the tracks of, the accurate tracking of covert position when the carrier wave postponing successively by local reconstruct multichannel phase place is realized active user, the system that guaranteed is carried out synchronous demodulation accurately.Compared with traditional carrier wave tracing method, so owing to not adding pilot signal and improved the emission effciency of system; Do not adopt phase demodulation module thereby reduced system carrier synchronous settling time.
Accompanying drawing explanation
Fig. 1 (a) is transmitter system block diagram of the present invention;
Fig. 1 (b) is receiver system block diagram of the present invention;
Fig. 2 is automatic gain control flow chart;
Fig. 3 is slippage correlation acquisition method schematic diagram;
Fig. 4 is incoherent delay lock loop tracing schematic diagram;
Fig. 5 is that Parallel Interference Cancellation method realizes schematic diagram;
Fig. 6 is with the heterogeneous carrier track method schematic diagram of frequency;
Embodiment
Below in conjunction with Figure of description, embodiments of the invention are described further:
The present invention is mainly divided into transmitter and receiver two parts, and transmitter mainly completes the coding spread spectrum of user data and modulation sending function, and transmitter system block diagram is as shown in Fig. 1 (a).Receiver will complete multiple the transmitting in same frequency range of same time carried out to accurately reception of while, after analog, numerical portion need to carry out corresponding synchronous despreading, disturb the processing such as removal and synchronous demodulation, to realize separation and the decoding to multiple signals the multichannel superposed signal receiving.Receiver system block diagram is as shown in Fig. 1 (b).
The software realization mode of system can be carried out flexible configuration according to working state of system, and does not need to change hardware configuration.In the time that number of users is less, consider that the inside multiple access interference of system is less, guaranteeing under the condition that data transmission error rate meets the demands, can adopt shorter pseudo random sequence code and single-stage to disturb removal method to improve system bandwidth and data transmission bauds.In the time that number of users is more, for assurance system transmission accuracy rate, can select more complicated pseudo random sequence code and multistage interference removal method.
Receiver first carries out analog down by the radio frequency analog signal receiving and obtains analog if signal, then this analog if signal is carried out to controllable gain amplification, signal amplitude is amplified in the amplitude range of analog-to-digital conversion module requirement, as shown in Figure 2.First carry out signal amplitude discriminating, calculate the absolute value sum of N point signal, the thresholding up and down of result and setting is subtracted each other, the difference signal obtaining is sent into loop filter and carry out loop filtering processing, thereby obtain the control word of controllable amplifier, controllable amplifier is revised multiplication factor according to this control word, realizes the automatic gain control to intermediate-freuqncy signal.
Analog intermediate frequency signal after gain is controlled is delivered to analog-to-digital conversion module again and is obtained digital medium-frequency signal, then after Digital Down Convert, obtains baseband digital signal.First baseband digital signal delivers to a yard synchronization module, realizes thick synchronizing process by slippage correlation acquisition method as shown in Figure 3.Baseband digital signal is divided into two-way, a road as with reference to signal directly by band pass filter, the pseudo random sequence code of the local current phase place of another Lu Xianyu despreading of multiplying each other, and then pass through band pass filter.After filtering, two paths of signals is all by carrying out integration operation according to default integration lengths after square detection computing.The integral result of two paths of signals is compared, if the integral result of despreading road signal reaches certain predetermined value compared with reference arm signal, think that the pseudo random sequence code of local current phase place realized catching to received signal, the timing error of the baseband digital signal pseudo random sequence code phase of now local pseudo random sequence code and reception is in half code-element period.If do not reach preset value, think local pseudo random sequence code do not achieve a butt joint collect mail number catch, now need to readjust the phase place of local spreading code, again carry out aforementioned catch operation until realize catch.
Reception signal after catching is delivered to incoherent delay lock loop tracking module as shown in Figure 4 and is realized thin synchronous to spread spectrum receiving system.Realize the accurate alignment of the local pseudo random sequence code of receiver and transmitter pseudo random sequence code phase, follow the tracks of the change of transmitting terminal pseudo random sequence code phase simultaneously.First input signal is divided into two-way and multiplies each other with the pseudo random sequence code of leading half code-element period, the pseudo random sequence code of half code-element period that lags behind respectively, then do and subtract each other comparison by sending into comparator after band pass filter, square detection, integration respectively, adjust the phase place of local pseudo random sequence code according to comparative result.Because system adopts 8 sampling rates, the result of tracking can make receiving terminal pseudo random sequence code and transmitting terminal pseudo random sequence code phase difference apart from narrowing down in positive and negative 1/16 code-element period.Multiply each other to realize with this pseudo random sequence code and input signal and synchronize despreading.
Figure 5 shows that Parallel Interference Cancellation method realizes schematic diagram, below Yi Yi road subscriber signal A be that example describes the implementation of algorithm in detail.After the baseband digital signal r (n) receiving is caught and followed the tracks of by the spreading code with local party A-subscriber (being called for short PNA), carry out preliminary despreading, obtain the PNA of current phase place simultaneously from tracking module.Same other several signals carry out similar processing and obtain respectively the spreading code (being called for short PNB) of the current phase place of party B-subscriber and the spreading code (being called for short PNC) of the current phase place of C user.Sequence cross-correlation coefficient formulas:
Wherein, A is the identical number in the corresponding position of two sequences; D is the different number in the corresponding position of two sequences.The correlation matrix that utilizes formula (1) can calculate each frequency expansion sequence of current phase place is:
Utilize formula (2) can calculate the cross-correlation coefficient ρ between PNA and PNB
aB, the cross-correlation coefficient ρ between PNB and PNC
bC, the cross-correlation coefficient ρ between PNA and PNC
aC.By secondary spread-spectrum signal B1 and ρ
aBmultiply each other, obtain the interference of party B-subscriber to party A-subscriber; Secondary spread-spectrum signal C1 and ρ
bCmultiply each other, obtain the interference of C user to party A-subscriber.Above-mentioned two interference signals are added and can obtain current B and the multiple access interference of C user to party A-subscriber's formation:
X＝ρ
ABB1+ρ
BCC1 （3）
To receive signal r (n) deducts this multiple access and disturbs the signal A2 after obtaining disturbing, A2 is delivered to follow-up trapping module and again carry out the subsequent treatment such as synchronous despreading, demodulation filtering, so just realized the multi-use family Interference Cancellation operation to user A.The operation that system is carried out similar party A-subscriber to B and C user simultaneously realizes parallel processing, and in the time that the more interference of number of users is comparatively strong, receiving system can adopt multistage Interference Cancellation operation, the error code causing to reduce internal system self-interference.
Figure 6 shows that with the heterogeneous carrier track method schematic diagram of frequency, utilize this part to realize the carrier signal of multichannel user Phase Stacking is carried out to synchronous demodulation.What native system adopted is 8 sampling rates, be that each carrier cycle has 8 phase places, rear 4 phase places and above 4 phase place phase difference of pi phase places, can remove the impact of the phase place of falling π because system has adopted differential coding, and before only adopting so local, half period 4 phase places are carried out carrier phase tracking.4 tunnel local carrier signal a, b, c, d that local generation initial phase successively decreases successively, multiply each other respectively at despread signal y (n), carry out corresponding amplitude and phase place correction by filter successively afterwards, pass through again integrator, wherein integration period=processing gain × sample rate, integral result is delivered to comparator and compare judgement, select the Gao of judgement integral result mono-tunnel as the best Yi of phase matched road, i.e. final local carrier synchronous demodulation result output.Said process carries out in real time, if changed because the larger variation of transmitting terminal or wireless channel causes receiving terminal carrier phase, and integral result variation, carrier synchronization module is mated best Yi road and is carried out synchronous demodulation with regard to again adjudicating selected phase.
Claims (3)
1. the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm, is characterized in that comprising the following steps:
1.1. user data is carried out convolutional encoding processing by each transmitter, then with the spreading code distributing, the data after coding are carried out to digital spread spectrum BPSK(Binary Phase Shift Keying, two-phase PSK) modulation, then send by antenna after up-conversion and filtering processing;
1.2. receiver receives after each subscriber signal that transmitter sends, and it is carried out to down-converted, obtains analog if signal, this analog if signal is carried out to controllable gain and amplify and process, to adjust the signal amplitude receiving; Delivering to modulus conversion chip samples and obtains digital medium-frequency signal again, utilize digital controlled oscillator to produce sinusoidal signal the signal after sampling is carried out to Digital Down Convert processing, then carry out filtering and extraction by integral comb filter and finite impulse response correction wave filter, obtain baseband digital signal;
1.3. baseband digital signal is admitted to a yard synchronization module, by catching and follow the tracks of operation, to realize spreading code synchronous, take a certain road user wherein as active user, all the other a few road users are interference user, utilize Parallel Interference Cancellation algorithm to extract interference signal, and from baseband digital signal, remove the multiple access interference that multiple interference users cause active user's signal, obtain removing the active user's signal after disturbing;
(1) trapping module adopts sliding correlation method, the steps include: first to carry out relevant treatment, after filtering, after square detection, integration, send into comparator, in the time that integral result is less than decision threshold, feedback control signal of comparison module input goes to adjust the phase place of local pseudo random sequence code, reentering the relevant treatment of a new round, is acquisition success until the Output rusults of integrator is greater than threshold value, and output identification simultaneously enters tracking module;
(2) tracking module adopts incoherent delay lock loop to realize carefully synchronously: lock-on signal is divided into two-way and multiplies each other with the local reference signal of half code-element period of lead and lag respectively, carry out square operation by square operation circuit, carry out filtering by low pass filter again, treated two paths of signals is given phase discriminator and is subtracted each other, adjust the phase place of local spreading code according to the result of phase discriminator output, finally make the pseudo random sequence code phase error of transmitting terminal and receiving terminal narrow down to and be less than positive and negative 1/16 code-element period;
Tracking circuit will detect to judge whether PN code synchronization is lost in real time, once detect synchronization loss, proceeds to immediately 1.3(1) in acquisition phase carry out the synchronizing process of a new round;
1.4. active user's signal of removing after disturbing is being delivered to carrier synchronization module after synchronous despreading, utilize with the heterogeneous carrier track method of frequency herein and realize the carrier phase accurate tracking demodulation to active user, then adjudicate by bit synchronization and differential decoding processing obtains the data after active user coding, then the user data after coding is carried out to Viterbi decoding obtain active user and receive data;
1.5. by the operation of above-mentioned receiving course multidiameter delay, each road adopts that active user's spreading code carries out despreading, goes to disturb, carrier synchronization processes, and synchronization, same frequency receive and process multiple user data.
2. the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm according to claim 1, is characterized in that the algorithm of Parallel Interference Cancellation described in 1.3 comprises the following steps:
2.1 utilize tracking module obtain the phase place of current all user's frequency expansion sequences and calculate cross-correlation coefficient, the signal of following the tracks of after despreading are carried out to spread spectrum again simultaneously, are then multiplied by cross-correlation coefficient and obtain interference signal;
2.2 baseband digital signals deduct interference signal and obtain removing the active user's signal after disturbing.
3. the multi-user's spread spectrum receivers implementation method based on Parallel Interference Cancellation algorithm according to claim 1, is characterized in that the heterogeneous carrier track method of same frequency in 1.4 comprises the following steps:
3.1 adopt front 4 groups of phase places local carrier and the despreading output signals that postpone successively to multiply each other simultaneously, and then device sum-product intergrator obtains integral result after filtering, and the Gao of selection integral result mono-tunnel is that final local carrier synchronous demodulation result is exported;
In 3.2 above-mentioned 3.1, process is carried out in real time, once primary carrier phase place changes, integral result variation, adjudicates again, and selecting integral result the highest is that as a result of export on the best Yi of phase matched road.
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| CN112187298A (en) * | 2019-07-05 | 2021-01-05 | 中兴通讯股份有限公司 | Communication anti-interference detection method and device |
| CN110940857A (en) * | 2019-12-13 | 2020-03-31 | 西安锐驰电器有限公司 | Spectrum parameter detection method |
| CN112187338B (en) * | 2020-09-17 | 2022-06-07 | 中国电子科技集团公司第三十八研究所 | Two-stage processing interference cancellation system and method for asynchronous CDMA system |
| CN113225104B (en) * | 2021-04-12 | 2022-07-01 | 中国电子科技集团公司第三十八研究所 | Method and system for capturing multi-user burst spread spectrum signal in asynchronous communication system |
| CN113507548A (en) * | 2021-07-09 | 2021-10-15 | 郑州琼佩电子技术有限公司 | Signal anti-interference system for image processing |
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