CN115250125B - RAKE receiver and improved receiving method for satellite communication system - Google Patents
RAKE receiver and improved receiving method for satellite communication system Download PDFInfo
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- CN115250125B CN115250125B CN202210812449.2A CN202210812449A CN115250125B CN 115250125 B CN115250125 B CN 115250125B CN 202210812449 A CN202210812449 A CN 202210812449A CN 115250125 B CN115250125 B CN 115250125B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/1851—Systems using a satellite or space-based relay
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/004—Synchronisation arrangements compensating for timing error of reception due to propagation delay
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
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Abstract
The present invention relates to the field of communications, and in particular, to a RAKE receiver and an improved receiving method for a satellite communication system. Modeling a multipath propagation effect by using a reference signal p in a signal analysis unit, solving a filter coefficient C, multiplying each path of signal by a corresponding coefficient C, and then superposing to obtain an approximate service signal; the traffic signals are then diversity combined in the signal reconstruction unit using the same transversal filter model. The RAKE receiver comprises a signal analysis unit and a signal reconstruction unit; the signal parsing unit includes an FIR transversal filter. The invention avoids the problems of low resolution, error leakage and the like in the prior art based on the equivalent and approximation principle by a signal modeling and reconstruction method, has certain deviation in delay and weighting links, and improves the communication capability of the hidden satellite.
Description
Technical Field
The present invention relates to the field of communications, and in particular, to a RAKE receiver and an improved receiving method for a satellite communication system.
Background
Concealed communication technology:
the novel anti-interference low-interception low-detection LPI/LPD/LPE (Low probability of detection/interference/explication) safe hidden communication technology is a hotspot of the current satellite communication research. Typical burst-mode direct-spread receiver systems and their carrier synchronization techniques are often well-established in application, but are applied in large-delay, large-time-varying narrowband satellite channels, and are difficult to meet the global random access and fast acquisition tracking requirements. The novel safe hidden communication technology is different from the traditional satellite communication technology in that the communication signal can be better hidden from the statistical sense by utilizing the idea of calculation communication through the waveform design and the system technology of the novel signal; the detection method of traditional communication signals such as long-term detection and complex calculation cannot acquire the communication parameters of the my, cannot sense the existence of the wireless signals of the my, and cannot be intercepted and captured in a targeted manner, so that stealth is realized, and the survivability and the safety of the satellite communication of the my are effectively ensured.
Chaos coding technology:
m-sequences are currently widely used as pseudo-random sequences for constructing spread spectrum systems, providing concealment transmission and detection resistance. To further eliminate signal characteristics, a large number of pseudo-random sequences with a certain length and good auto-correlation/cross-correlation properties need to be designed for spreading, while a large number of pseudo-random sequences with a long period and good cross-correlation properties need to be designed for communication parameter control in the randomization process. The conventional pseudo-random sequence has the defects of few primitive polynomials, short sequence periodicity and the like; the study adopts a chaos sequence which is sensitive, bounded and widely distributed at an initial value as a pseudo-random spread spectrum and control sequence. Compared with M sequences and M sequences, the chaotic sequence has Gaussian statistical characteristics and long-term unpredictability, and can bear complex decoding attacks. When the chaotic sequence is adopted for DSSS spread spectrum, the spectrum has better balance characteristic and high detection resistance, so that the method has higher application prospect in the covert communication technology. But the corresponding reception process is also made quite difficult due to the irregularities of the chaotic sequence. One of the problems is that the orthogonality between the spreading sequences is poor, resulting in a large loss of despreading performance, and the disadvantages include despreading residue, low RAKE diversity accuracy, etc.
1. Prior art close to the present invention
The basic structure of a RAKE receiver is shown in fig. 1. In the figure, firstly, the delay, amplitude and phase value of each path are determined by a correlator, then corresponding delay compensation is carried out, despreading is carried out, weighting is carried out according to the measured amplitude and phase value, and finally, each path of signal is combined, thus completing RAKE processing.
The received spread spectrum signal may be expressed as:
where x (k) is the transmitted baseband spread spectrum signal, a l ，θ l ，d l The amplitude, phase and delay of path l, respectively. In RAKE receiving process, through the cross-correlation operation of local reference signal and r (k), each path has a corresponding Sinc curve whose peak position, amplitude and phase reflect a l ，θ l ，d l The SNR maximized step gain can be obtained by graphically processing the parameters.
2. Problems of the prior art
In practical application, the parameter estimation method based on the cross-correlation operation has some defects, and mainly comprises the following steps:
1. because the Sinc curve has a wider main lobe, the time delay resolution is not high, and paths with similar time delay are difficult to identify;
2. when d l When the sampling period is not integral multiple, the Sinc curve has larger distortion, so that a is difficult to measure l ，θ l ，d l ；
3. Higher side lobes exist in the cross-correlation curve, so that curve confusion corresponding to weaker multipath is easy to occur, and error combination is caused.
For these reasons, the cross-correlation curve cannot accurately reflect the shape of the channel impulse response, and there is a relatively obvious difference between the two, see fig. 2 and 3, and the cross-correlation curve at this time cannot accurately reflect the characteristics of the channel impulse response, so that the corresponding RAKE processing gain is lower than the expected value, and the receiving performance is lower.
Therefore, when the parameters of the multipath channel are identified by the cross-correlation method, the problems of low resolution, error and leakage and the like exist due to the influences of the main lobe width, side lobes and the like of the Sinc-type curve, and certain deviation exists in delay and weighting links, so that the merging effect is lower than an expected value.
Disclosure of Invention
First, the present invention solves the problems
In order to improve the sensitivity of the hidden signal, the invention provides a RAKE receiver for improving diversity combining gain and an improved receiving method, which improve the communication capacity of the hidden satellite.
The technical scheme of the invention is as follows:
the invention provides a method for improving the receiving of a RAKE of a satellite communication system, which comprises the following steps:
1. modeling the FIR transverse filter model by using a reference signal p in a signal analysis unit, solving the coefficient C of the FIR transverse filter, multiplying each path of signal by the corresponding coefficient C, and finally superposing to obtain an approximate service signal;
1.1 first, y (k) is divided into L paths through step-by-step unit delay, and the FIR transverse filter uses a local pilot reference signal y and a filter polynomial coefficient C, C= [ C ] 0 ,C 1 ,...,C L-1 ]Approximating the reference signal p in the received signal to generate a p', and adjusting C by an algorithm 0 、C 1 、C 2 、……C L-1 Filter coefficients such that err is as small as possible;
constructing an active ingredient in p (k) by y (k), taking the number of taps as L, and having
Err (k) in the above formula is a part of p (k) that cannot be modeled;
1.2 solving the FIR transversal filter coefficient C (k) in the above formula according to a least square criterion method, wherein k=0, 1, 2 … … L-1;
1.3 multiplying each signal by a corresponding coefficient C (k), k=0, 1, 2, …, L-1, and finally adding up to obtain an approximate service signal x (k).
2. The same model is used in the signal reconstruction unit to diversity combine the service signals.
And (3) performing delay compensation and amplitude weighting on the subsequent service signal x (k) divided into L paths, and finally superposing to finish RAKE processing. The time delay compensation method comprises the following steps: the delay compensation of the path delay is small, and the delay compensation of the path delay is large, so that the total delay of each path is the same after compensation.
A second aspect of the present invention provides a RAKE receiver comprising a signal parsing unit and a signal reconstruction unit; the signal analysis unit comprises an FIR transverse filter, is used for modeling a multipath propagation effect by using a reference signal p and applying a transverse filter model to solve a filter coefficient C, and is used for multiplying each path of signal by a corresponding coefficient C and then superposing the signals to obtain an approximate service signal; the signal reconstruction unit is used for carrying out diversity combination on the service signals by utilizing the model constructed in the signal analysis unit.
A third aspect of the invention provides a RAKE receiving system that includes a RAKE receiver.
The invention has the advantages that:
the method of the invention avoids the problems of low resolution, error leakage and the like in the prior art by the signal modeling and reconstruction method based on the equivalent and approximation principle, has certain deviation in delay and weighting links, and improves the hidden communication capability.
Drawings
Fig. 1: the RAKE receiver architecture principle in the prior art;
fig. 2: impulse response of the channel;
fig. 3: cross-correlation curves;
fig. 4: a Rake receiving system;
fig. 5: the Rake receiver structure of the invention is schematically shown;
fig. 6: a signal analysis module structure schematic diagram;
fig. 7: FIR filter structure schematic diagram;
fig. 8: schematic diagram of signal reconstruction module;
fig. 9: an improved RAKE receiving unit.
Detailed Description
The invention is described in further detail below with reference to the accompanying drawings.
Referring to fig. 4, the invention provides a satellite communication Rake receiving system, which comprises AGC, field intensity detection, sampling unit, short code PNG, short code searching, mapping, long code PNG, symbol synchronization, rake receiver, local pilot signal sequence transmitter, despreading, de-differencing, de-interleaving, de-scrambling, decoding and other components.
After symbol synchronization is carried out on a received signal, the received multipath signal contains a pilot frequency field p and effective information x. As shown in fig. 5, the signal analysis unit uses the reference signal p to model the multipath propagation effect by using a transversal filter model, and solves the filter coefficient C, and the signal reconstruction unit uses the same model to diversity-combine the service signal, thereby improving the receiving sensitivity of the hidden signal.
The structure of the signal analysis unit is shown in fig. 6, where p is a reference signal in the received signal, and y is a local pilot reference signal. In the signal analysis unit, a FIR transversal filter is constructed, which uses the local pilot reference signal y and the filter polynomial coefficients C (C= [ C ] 0 ,C 1 ,...,C L-1 ]) Approximating the reference signal p in the received signal to generate a p', adjusting C by an algorithm 0 、C 1 、C 2 、……C L-1 And filter coefficients such that err is as small as possible. The FIR filter structure is shown in fig. 7.
Constructing an active ingredient in p (k) by y (k), taking the number of taps as L, and having
Err (k) in the above equation is a part of p (k) that cannot be modeled.
The FIR transversal filter coefficients C (k), k=0, 1, 2 … … L-1 are solved by the least squares criterion method. If L is greater than the delay spread of the channel, the first term on the right of the above equation will contain all the active components in p (k), err (k) being the inactive component such as noise, according to the orthogonal principle.
According to the obtained FIR transversal filter coefficient C and the FIR filter structure, it can be seen that the signal transmission process, that is, the effect of forming x (k) in the RAKE receiver by y (k) output by the transmitter through the multipath channel, can be equivalent to the following operations, by dividing y (k) into L paths through step-by-step unit delay, multiplying each path by a corresponding coefficient C (k), k=0, 1, 2, …, L-1, and finally superposing to obtain the approximate x (k). I.e. an FIR filter that equates the multipath channel to L taps.
Therefore, when diversity and combining are performed on the subsequent service signals x (k), the inverse operation can be performed on the x (k) based on the model: and the method is divided into L paths for delay compensation and amplitude weighting, and finally overlapped to finish RAKE processing. The method for compensating the time delay is that the time delay compensation with large path time delay is small, and the time delay compensation with small path time delay is large, so that the total time delay of each path is the same after the time delay compensation.
The principle of the corresponding signal reconstruction unit is shown in fig. 8, where the modified RAKE processing outputs z (k), k=0, 1, 2, …, L-1.
The scheme for improving diversity combining gain proposed by the invention is shown in fig. 9.
Firstly, modeling a multipath propagation effect by using a reference signal p in a signal analysis unit, solving a filter coefficient C, multiplying each path of signal by a corresponding coefficient C, and finally superposing to obtain an approximate service signal; the traffic signals are then diversity combined in the signal reconstruction unit using the same model.
Claims (4)
1. A method for RAKE improved reception in a satellite communication system, the method comprising the steps of:
(1) Modeling the FIR transverse filter model by using a reference signal p in a signal analysis module, solving the coefficient C of the FIR transverse filter, multiplying each path of signal by the corresponding coefficient C, and finally superposing to obtain an approximate service signal;
1.1 first, y (k) is divided into L paths through step-by-step unit delay, and the FIR transverse filter uses a local pilot reference signal y and a filter polynomial coefficient C, C= [ C ] 0 ,C 1 ,...,C L-1 ]Approximating the reference signal p in the received signal to generate a p', and adjusting C by an algorithm 0 、C 1 、C 2 、……C L-1 Filter coefficients such that err is as small as possible;
constructing an active ingredient in p (k) by y (k), taking the number of taps as L, and having
Err (k) in the above formula is a part of p (k) that cannot be modeled;
1.2 solving the FIR transversal filter coefficient C (k) in the above formula according to a least square criterion method, wherein k=0, 1, 2 … … L-1;
multiplying each path of signal by corresponding coefficient C (k), wherein k=0, 1, 2, … and L-1, and finally superposing to obtain an approximate service signal x (k);
(2) The same FIR transverse filter model is utilized in a signal reconstruction module to carry out diversity combination on service signals;
and dividing the subsequent service signal x (k) into L paths for delay compensation and amplitude weighting, and finally superposing to finish RAKE processing.
2. The RAKE improved reception method of claim 1, wherein the method of delay compensation is: the delay compensation of the path delay is small, and the delay compensation of the path delay is large, so that the total delay of each path is the same after compensation.
3. A RAKE receiver for implementing the RAKE improved reception method of claim 1 or 2, characterized in that the RAKE receiver comprises a signal parsing unit and a signal reconstruction unit; the signal analysis unit comprises an FIR transverse filter, is used for modeling a multipath propagation effect by using a reference signal p and applying a transverse filter model to solve a filter coefficient C, and is used for multiplying each path of signal by a corresponding coefficient C and then superposing the signals to obtain an approximate service signal; the signal reconstruction module is used for carrying out diversity combination on the service signals by utilizing the model constructed in the signal analysis unit.
4. A RAKE reception system comprising the RAKE receiver of claim 3.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101119130A (en) * | 1999-08-23 | 2008-02-06 | 高通股份有限公司 | Adaptive channel estimation in a wireless communication system |
| CN101188436A (en) * | 2006-11-10 | 2008-05-28 | 英飞凌科技股份公司 | Receiver |
| CN102111182A (en) * | 2009-12-25 | 2011-06-29 | 中国电子科技集团公司第五十研究所 | Self-adaptive UWB Rake receiver, self-adaptive UWB Rake receiving method and UWB wireless communication system |
| CN107154813A (en) * | 2016-03-06 | 2017-09-12 | 南京理工大学 | Adaptive Rake receivers and method of reseptance |
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Patent Citations (4)
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| CN101119130A (en) * | 1999-08-23 | 2008-02-06 | 高通股份有限公司 | Adaptive channel estimation in a wireless communication system |
| CN101188436A (en) * | 2006-11-10 | 2008-05-28 | 英飞凌科技股份公司 | Receiver |
| CN102111182A (en) * | 2009-12-25 | 2011-06-29 | 中国电子科技集团公司第五十研究所 | Self-adaptive UWB Rake receiver, self-adaptive UWB Rake receiving method and UWB wireless communication system |
| CN107154813A (en) * | 2016-03-06 | 2017-09-12 | 南京理工大学 | Adaptive Rake receivers and method of reseptance |
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