CN111786917B - Channel estimation method, receiver and storage medium - Google Patents
Channel estimation method, receiver and storage medium Download PDFInfo
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- CN111786917B CN111786917B CN202010768857.3A CN202010768857A CN111786917B CN 111786917 B CN111786917 B CN 111786917B CN 202010768857 A CN202010768857 A CN 202010768857A CN 111786917 B CN111786917 B CN 111786917B
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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
- H04L25/0202—Channel estimation
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- H—ELECTRICITY
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- 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
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- H—ELECTRICITY
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- H04B17/00—Monitoring; Testing
- H04B17/30—Monitoring; Testing of propagation channels
- H04B17/309—Measuring or estimating channel quality parameters
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Abstract
The embodiment of the application provides a channel estimation method, a receiver and a storage medium. The method comprises the following steps: receiving a pilot signal; acquiring a power delay spectrum PDP of a pilot signal; detecting whether a target path exists in the PDP, wherein the target path is a main path comprising a direct path; and when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimation value of each subframe in the frequency offset change period. According to the technical scheme provided by the embodiment of the application, whether the current channel environment is subjected to the Rice distribution is judged, and the Doppler spread parameters are estimated through the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period at the moment under the condition that the current channel is subjected to the rice distribution, so that the accuracy of channel estimation is improved, the error rate is further reduced, and the throughput of the system is improved.
Description
Technical Field
The embodiment of the application relates to the technical field of wireless communication, in particular to a channel estimation method, a receiver and a storage medium.
Background
After the data is transmitted by the transmitting end, the data reaches the receiving end through the propagation of the wireless channel, and various interference factors in the wireless channel can influence the transmitted data, so that the received data is balanced by adopting a channel estimation scheme, and the influence of the wireless channel is overcome to recover the data.
In the related art, channel estimation is performed in the following manner: the channel is assumed to be subject to a rayleigh fading model, for which channel estimation is then performed, such as estimating doppler spread parameters based on a U-shaped spectrum and a 0-order bessel function.
Disclosure of Invention
The embodiment of the application provides a channel estimation method, a receiver and a storage medium. The technical scheme is as follows:
in one aspect, an embodiment of the present application provides a channel estimation method, where the method includes:
receiving a pilot signal;
acquiring a power delay profile (Power Delay Profile, PDP) of the pilot signal;
detecting whether a target path exists in the PDP, wherein the target path is a main path comprising a direct path;
and when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
In another aspect, the present application provides a receiver, the receiver comprising:
a receiving unit for receiving a pilot signal;
a processing unit for:
PDP of the pilot signal is obtained;
detecting whether a target path exists in the PDP, wherein the target path is a main path comprising a direct path;
and when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
In yet another aspect, embodiments of the present application provide a receiver, the receiver including a processor, a memory storing a computer program loaded and executed by the processor to implement the channel estimation method as described in one aspect.
In yet another aspect, embodiments of the present application provide a computer readable storage medium having a computer program stored therein, the computer program being loaded and executed by a processor to implement a channel estimation method as described in one aspect.
In yet another aspect, embodiments of the present application provide a computer program product comprising computer instructions stored in a computer-readable storage medium, the computer instructions being read from the computer-readable storage medium by a processor of a computer device, the computer instructions being executed by the processor to cause the computer device to perform the channel estimation method provided in the above aspect or various alternative implementations of the aspect.
The technical scheme provided by the embodiment of the application can bring beneficial effects at least including:
after receiving the pilot signal, determining whether the current channel environment obeys Rayleigh distribution based on whether a main path containing a direct path exists in the PDP of the pilot signal, if the main path containing the direct path exists in the PDP, determining that the current channel environment does not obey Rayleigh distribution but obeys the Lees distribution, and estimating Doppler expansion parameters through the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period at this time, thereby improving the accuracy of channel estimation, further reducing the error rate and improving the throughput of a system.
Drawings
Fig. 1 is a schematic diagram of a wireless communication system provided in one embodiment of the present application;
fig. 2 is a flow chart of a channel estimation method provided in one embodiment of the present application;
fig. 3 is a flowchart of a channel estimation method according to another embodiment of the present application;
FIG. 4 is a schematic diagram of a PDP provided by an embodiment of the present application;
FIG. 5 is a schematic representation of power spectral density provided by one embodiment of the present application;
fig. 6 is a flowchart of a channel estimation method according to another embodiment of the present application;
FIG. 7 is a block diagram of a receiver provided in one embodiment of the present application;
fig. 8 is a block diagram of a receiver according to another embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the embodiments of the present application will be described in further detail below with reference to the accompanying drawings.
Related terms related to the embodiments of the present application are explained first.
Rayleigh fading channel: a statistical model of a radio signal propagation environment in which a probability density function of an envelope of a signal after passing through a radio channel follows a Rayleigh distribution. The rayleigh fading model is suitable for the case where there is no direct signal between the transmitter and the receiver, such as short wave channels reflected by the ionosphere and troposphere, and in urban environments where buildings are dense.
The probability density function of the Rayleigh distribution is expressed by the following formula:
σ 2 is the power of the multipath signal component.
Rice fading channel: a statistical model of the radio signal propagation environment in which the probability density function of the envelope of the signal after it has passed through the radio channel obeys the Rice distribution. The rayleigh fading model is suitable for the situation that direct signals exist between a transmitter and a receiver, such as a high-speed railway channel environment and the like.
The probability density function of the rice distribution is expressed by the following formula:
r is the envelope of a sinusoidal signal plus a narrow-band Gaussian random signal, A is the peak value of the amplitude of the main signal, sigma 2 Is the power of the multipath signal component, J 0 (. Cndot.) is a modified 0 th order Bessel function of the first type.
Doppler spread: due to multipath propagation, the transmitter transmits at a frequency f 0 The signal received by the receiver is a signal synthesized by a plurality of sub-path signals with different arrival directions, doppler frequencies of the sub-paths with different arrival directions are different, and the multipath signal synthesized by each sub-path signal is a transmitting signal in [ f ] 0 -max，f 0 +max]The spread in the frequency range, i.e. the doppler spread.
Direct diameter: there is no path blocked by an object between the transmitter and the receiver, the power is usually larger, and in the case of a direct path, the current channel environment obeys the rice distribution.
Referring to fig. 1, a schematic diagram of a wireless communication system provided in an embodiment of the present application is shown. The wireless communication system may be a long term evolution (Long Term Evolution, LTE) system, a fifth generation (5th Generation,5G) system, or other system that may occur in the future. The wireless communication system includes: a transmitter 11, and a receiver 12.
The transmitter 11 is for transmitting pilot signals. The transmitter 11 includes, but is not limited to: user Equipment (UE), relay station, base station, etc. The receiver 12 is configured to receive pilot signals transmitted by the transmitter. The receiver 12 includes, but is not limited to: UE, relay station, base station, etc.
When the channel estimation method is used for estimating an uplink channel, in the uplink channel, if the transmitter 11 transmitting the pilot signal is a UE, the receiver 12 is a base station or a relay station, and if the transmitter 11 transmitting the pilot signal is a relay station, the receiver 12 is a base station or a last hop relay station. When the channel estimation method is used for estimating an uplink channel, in a downlink channel, if the transmitter 11 transmitting a pilot signal is a base station, the receiver 12 is a terminal or a relay station, and if the transmitter 11 transmitting a pilot signal is a relay station, the receiver 12 is a terminal or a next hop relay station.
In the embodiment of the present application, only the channel estimation method is used to estimate the uplink channel, and the transmitter 11 is a base station, and the receiver 12 is a terminal.
In the related art, when the channel does not conform to the rayleigh fading model, for example, when a direct signal exists, the channel conforms to the rice fading model, and the channel estimation method provided by the related art is adopted for channel estimation, the accuracy of channel estimation is lower.
Based on this, the embodiment of the application provides a channel estimation method, after receiving a pilot signal, whether the current channel environment obeys the rayleigh distribution is determined based on whether a main path including a direct path exists in the PDP of the pilot signal, if the main path including the direct path exists in the PDP, the current channel environment is determined not to obey the rayleigh distribution, but obeys the rice distribution, and at the moment, the doppler spread parameters are estimated by not adopting the channel estimation method provided by the related technology, but estimating the doppler spread parameters through the maximum value and the minimum value in the frequency offset estimated values of each subframe in the frequency offset change period, so that the accuracy of channel estimation is improved, the error rate is further reduced, and the throughput of the system is improved.
Referring to fig. 2, a flow chart of a channel estimation method according to an embodiment of the present application is shown, and the method is applied to the receiver 12 in fig. 1. The method comprises the following steps:
in step 201, a pilot signal is received.
The receiving end receives the pilot signal sent by the sending end. A pilot signal is a signal transmitted for measurement or monitoring purposes within a telecommunications network, typically a single frequency, also referred to as a reference signal.
Step 202, obtain the PDP of pilot signal.
The power delay profile is used to describe the dispersion of the channel over time. Since the pilot signal arrives at the receiver at different times via different paths, a phenomenon of signal time spread is caused, and a power delay profile is used to describe this phenomenon.
After receiving the pilot signal, the receiving end firstly carries out channel estimation on the received pilot signal to obtain the channel response of the pilot signal in the frequency domain, and then carries out Fourier transformation on the channel response of the pilot signal in the frequency domain to obtain the channel response of the pilot signal in the time domain. And then, acquiring a power delay spectrum of the pilot signal in at least two time slots according to the channel response of the pilot signal in the time domain.
Step 203, detecting whether the PDP includes a target path.
The target diameter is a main diameter including a direct diameter. The direct path is strong in power, and is also called as rice path because the channel model follows the rice distribution in the case where there is a direct path.
Optionally, the receiver detects whether the target path is included in the PDP by the following substeps:
in step 203a, M maximum paths are selected from the PDP according to the power of the paths included in the PDP, M being a positive integer.
Optionally, the receiver sorts the paths included in the PDP in order of power from high to low, and then selects a path with power of M bits before among the paths included in the PDP according to the sorting result as M maximum paths. The value of M is set experimentally or empirically, and M is illustratively 3.
And 203b, obtaining signal-to-noise ratio parameters corresponding to the M maximum paths according to the signal-to-noise ratios corresponding to the M maximum paths respectively.
The signal-to-noise ratio is the ratio between the power of the maximum path and the noise power, expressed in decibels. Optionally, the receiver acquires noise power and power of M maximum paths from the PDP, and then calculates signal-to-noise ratios corresponding to the M maximum paths respectively according to the acquired noise power and the power of M maximum paths.
Optionally, the signal-to-noise ratio parameter is a parameter associated with the signal-to-noise ratio, such as a signal-to-noise ratio variance, a parameter obtained based on the signal-to-noise ratio variance, and the like. In the embodiments of the present application, the signal-to-noise ratio parameter is merely described as an example of the signal-to-noise ratio variance, which is a parameter for measuring the degree of deviation between a random variable and its mathematical expectation (i.e., average). Optionally, the receiver obtains the signal-to-noise ratio variance corresponding to the M maximum paths according to the signal-to-noise ratios corresponding to the M maximum paths respectively. Illustratively, the receiver calculates the variance s for the M largest diameters by the following formula 2 ：
Wherein x is i And the signal to noise ratio of the ith maximum path in the M maximum paths is represented, i is a positive integer less than or equal to M, and x is the average value of the signal to noise ratios of the M maximum paths.
And 203c, detecting whether a target path exists in the PDP according to the signal-to-noise ratio parameters corresponding to the M maximum paths.
And when the signal-to-noise ratio parameter is the signal-to-noise ratio variance, the receiver detects whether the target path exists in the PDP according to the signal-to-noise ratio variance corresponding to the M maximum paths. Optionally, when the signal-to-noise ratio variance corresponding to the M maximum paths is smaller than a first threshold value, determining that a target path exists in the PDP. And when the signal-to-noise ratio variance corresponding to the M maximum paths is larger than a first threshold value, determining that no target path exists in the PDP. The value of the first threshold is set according to experiments or experience, which is not limited in the embodiment of the present application.
In this embodiment of the present application, the receiver selects M maximum paths from the PDP in each time slot for the pilot signal, calculates signal-to-noise ratios corresponding to the M maximum paths, and determines the maximum paths as target paths, that is, main paths including direct paths, when there are maximum paths for indicating that variance of signal-to-noise ratio variation is smaller than a first threshold.
Optionally, after obtaining the PDP of the pilot signal, the receiving end performs accumulation filtering on the PDP to obtain a filtered PDP.
Optionally, before selecting the M maximum paths, the receiver performs cyclic shift on the filtered power delay profile, and then selects the M maximum paths according to the power of the paths included in the PDP. By the method, the situation that the paths at the forefront and the last paths in the power delay spectrum cannot be screened is avoided.
And 204, when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
When the target path exists in the PDP, determining that the current channel environment obeys the rice distribution, and at the moment, assuming that the channel environment obeys the Rayleigh distribution, and adopting a corresponding channel estimation method to perform channel estimation, the problem of lower accuracy of the channel estimation can be caused. In the embodiment of the application, whether the target path exists in the PDP is detected before channel estimation, so that the current channel environment is judged to obey Rayleigh distribution or rice distribution, and different channel estimation schemes are adopted to carry out channel estimation, so that the accuracy of channel estimation is improved, and the error rate is reduced.
Optionally, the receiver estimates the doppler spread parameter based on the difference between the maximum and minimum values.
Illustratively, the receiver estimates the doppler spread parameter fd by the following formula:
fd＝(fmax-fmin)/2；
wherein fmax is the maximum value of the frequency offset estimation value of each subframe in the frequency offset change period; fmin is the minimum value of the frequency offset estimation values of each subframe in the frequency offset change period.
Optionally, when there is no target path in the PDP, the receiver uses N effective paths in the PDP of the pilot signal in the current slot, and estimates the doppler spread parameter based on the U-shaped spectrum and the 0-order bezier correlation, N being a positive integer. When the target path does not exist in the PDP, determining that the current channel environment obeys Rayleigh distribution, using N effective paths of the pilot signal in the PDP in the current time slot, and estimating Doppler spread parameters based on the U-shaped spectrum and 0-order Bessel correlation.
In summary, after receiving the pilot signal, the technical solution provided in the embodiment of the present application determines whether the current channel environment obeys the rayleigh distribution based on whether the pilot signal has a main path including a direct path in the PDP in a plurality of time slots, if the PDP has a main path including a direct path, it is determined that the current channel environment does not obey the rayleigh distribution, but obeys the rice distribution, at this time, the doppler spread parameter is estimated by the maximum value and the minimum value in the frequency offset estimation value of each subframe in the frequency offset variation period, so as to improve the accuracy of channel estimation, further reduce the error rate, and improve the throughput of the system.
Referring to fig. 3, a flow chart of a channel estimation method according to another embodiment of the present application is shown. The method is also applicable to the receiver 12 in fig. 1. The method comprises the following steps:
in step 301, a pilot signal is received.
Step 302, a PDP of a pilot signal is acquired.
Step 303, detecting whether a target path exists in the PDP.
The target diameter is a main diameter including a direct diameter.
And 304, when the target path exists in the PDP, determining the effective paths with the number of samples from the target path being larger than a third threshold value in the effective paths except the target path as Rayleigh paths.
The third threshold value is set experimentally or empirically, which is not limited in this embodiment of the present application. Because the leakage power exists in the direct path, the leakage power of the direct path can be prevented from being misjudged as the Rayleigh path by screening the number of samples, and the accuracy of the channel estimation result is improved.
Referring in conjunction to fig. 4, a schematic diagram of a power delay profile is shown in accordance with one embodiment of the present application. In the power delay spectrum, a path having a number of samples from the target path smaller than a third threshold value is regarded as an invalid rayleigh path, and a path having a number of samples from the target path greater than or equal to the third threshold value is regarded as an effective rayleigh path.
In step 305, the power of the target path and the power of the rayleigh path are obtained.
And 306, performing channel estimation based on the Rayleigh path to obtain a first estimated value when the ratio of the power of the target path to the power of the Rayleigh path is smaller than or equal to a second threshold value.
The second threshold value is set experimentally or empirically, and this is not limited in the examples of the present application. When the ratio between the power of the target path and the power of the Rayleigh path is smaller than the second threshold value, the fact that the power of the main path including the direct path is not quite different from the power of the Rayleigh path is indicated, at the moment, channel estimation needs to be carried out by using the target path and the Rayleigh path respectively, and finally, the final Doppler expansion parameters are obtained according to the channel estimation results of the target path and the Rayleigh path.
Optionally, the receiver performs channel estimation to obtain the first estimated value by: the receiver carries out channel estimation through a 0-order Bessel function to obtain a first estimated value.
Step 307, determining a second estimated value based on the maximum value and the minimum value in the frequency offset estimated values of each subframe in the frequency offset change period of the target path.
Optionally, the receiver calculates a difference between a maximum value and a minimum value in each subframe in the frequency offset variation period; and then determining a second estimated value according to the difference between the maximum value and the minimum value. Illustratively, the receiver performs channel estimation to obtain the second estimated value pshift by the following formula:
Pshift＝(fmax-fmin)/2；
wherein fmax is the maximum value of the frequency offset estimated values of all subframes in the frequency offset change period, and fmin is the minimum value of the frequency offset estimated values of all subframes in the frequency offset change period.
Step 308, estimating the Doppler spread parameter according to the first estimated value and the second estimated value.
Optionally, the receiver determines the doppler spread parameter based on the product parameter between the adjustment factor and the second estimate and the first estimate.
The adjustment factor is associated with at least one of: signal to noise ratio, channel delay spread, K factor value. Where the K factor value refers to the ratio of the main signal power (direct signal) to the variance of the multipath component. Optionally, the receiver stores a correspondence relationship, where the correspondence relationship includes correspondence relationships between different signal-to-noise ratios, different channel delay spreads, different K factor values, and different adjustment factors, and after the receiver obtains the current signal-to-noise ratio and the current channel delay spread, the receiver queries the correspondence relationship to obtain the corresponding adjustment factor.
The product parameter between the adjustment factor and the second estimate is determined based on the product between the adjustment factor and the second estimate. Optionally, the product parameter between the adjustment factor and the second estimate value refers to the product between the adjustment factor and the second estimate value.
Optionally, the receiver obtains a product between the adjustment factor and the second estimated value, and determines a sum of the product and the first estimated value as the doppler spread parameter. The above-mentioned estimation process of the doppler spread parameter is expressed by the following formula:
fd＝fd1+factor*pshift；
wherein fd1 is a first estimated value, factor is an adjustment factor, and pshift is a second estimated value.
And 309, when the ratio between the power of the target path and the power of the Rayleigh path is greater than the second threshold value, determining the Doppler spread parameter according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
When the ratio between the power of the target path and the power of the Rayleigh path is larger than a second threshold value, the main path power containing the direct path is higher, the power of the Rayleigh path is weaker, the received signal is mainly the signal transmitted by the direct path, at the moment, the Rayleigh path is ignored, and the target path is directly adopted to estimate Doppler expansion parameters. Specific implementation of estimating the doppler spread parameter by using the target path refers to step 304, and will not be described herein.
The steps 306 to 308 and 309 are parallel technical schemes. In one possible implementation, the receiver performs steps 301-308. In another possible implementation, the receiver performs steps 301-305, 309.
Referring to fig. 5 in combination, when the direct path exists, the position of the frequency offset is 0 after the frequency offset adjustment is close to the position of the direct path, so that the gravity center of the power spectrum is not located at the central position of the U-shaped power spectrum, but is located at the F position in fig. 5, the gravity center of the power spectrum after the frequency offset adjustment is close to the strong power direct path, and if the doppler spread estimation result obtained by performing doppler spread parameter estimation based on the 0-order bessel function is smaller. Therefore, in the embodiment of the application, different channel estimation methods are adopted to perform channel estimation on the target path and the Rayleigh path respectively, and finally, the Doppler expansion parameters which are finally estimated are determined according to the channel estimation results of the target path and the Rayleigh path, so that the accuracy of channel estimation can be improved.
In summary, after receiving the pilot signal, the technical solution provided in the embodiment of the present application determines whether the current channel environment obeys the rayleigh distribution based on whether the pilot signal has a main path including a direct path in the PDP in a plurality of time slots, if the PDP has a main path including a direct path, it is determined that the current channel environment does not obey the rayleigh distribution, but obeys the rice distribution, at this time, the doppler spread parameter is estimated by the maximum value and the minimum value in the frequency offset estimation value of each subframe in the frequency offset variation period, so as to improve the accuracy of channel estimation, further reduce the error rate, and improve the throughput of the system.
And when the ratio between the power of the target path and the power of the Rayleigh path is smaller than a second threshold value, adopting different channel estimation methods to respectively carry out channel estimation on the target path and the Rayleigh path, and finally determining the finally estimated Doppler spread parameters according to the channel estimation results of the target path and the Rayleigh path, thereby improving the accuracy of channel estimation.
The Rayleigh path is also screened by the number of samples, so that the leakage power of the direct path can be prevented from being misjudged as the Rayleigh path, and the accuracy of the channel estimation result is improved.
Referring to fig. 6, a flowchart of a channel estimation method according to an embodiment of the present application is shown. The method comprises the following steps:
in step 601, a pilot signal is received.
In step 602, channel estimation is performed on the pilot signal to obtain a frequency domain channel response.
In step 603, fourier transform is performed on the frequency domain channel response to obtain a time domain channel response.
Step 604 filters the time domain channel response.
Step 605, calculate the PDP in each slot.
Step 606, accumulate and filter the PDP.
In step 607, the PDP is cyclically shifted.
Step 608, statistics of noise power of noise area in PDP.
In step 609, N effective paths and M maximum paths are selected according to the power of each path in the PDP.
In step 610, signal-to-noise ratios corresponding to the M maximum paths are calculated.
In step 611, the variances corresponding to the M maximum paths are calculated according to the signal-to-noise ratios corresponding to the M maximum paths.
Step 612, determining whether there is a rice path (i.e., a main path including a direct path).
Steps 614-620 are performed when it is determined that the rice diameter exists, and step 613 is performed when it is determined that the rice diameter does not exist.
Step 613, estimating Doppler spread parameters based on the U-shaped spectrum and the 0-order Bessel function.
Step 614 distinguishes between rice paths and rayleigh paths.
In step 615, a ratio between the power of the rice path and the power of the rayleigh path is calculated.
Step 616, determining whether the ratio is greater than a second threshold.
Step 617 is performed when the ratio is determined to be greater than the second threshold value, and steps 618-620 are performed when the ratio is determined to be less than or equal to the second threshold value.
Step 617 estimates doppler spread parameters using the rice path.
At step 618, a first estimate is obtained using the rayleigh path.
Step 619, a second estimate is obtained using the rice diameter.
Step 620, obtaining the finally estimated doppler spread parameter according to the first estimated value and the second estimated value.
The following is an apparatus embodiment of the present application, and for parts of the apparatus embodiment that are not described in detail, reference may be made to the technical details disclosed in the method embodiment described above.
Referring to fig. 7, a block diagram of a receiver provided in an exemplary embodiment of the present application is shown. The receiver may be implemented as all or part of the terminal by software, hardware or a combination of both. The receiver includes: a receiving unit 701 and a processing unit 702.
The receiving unit 701 is configured to receive a pilot signal.
The processing unit 702 is configured to:
acquiring a power delay spectrum PDP of the pilot signal;
detecting whether a target path exists in the PDP, wherein the target path is a main path comprising a direct path;
and when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
In summary, after receiving the pilot signal, the technical solution provided in the embodiment of the present application determines whether the current channel environment obeys the rayleigh distribution based on whether the pilot signal has a main path including a direct path in the PDP in a plurality of time slots, if the PDP has a main path including a direct path, it is determined that the current channel environment does not obey the rayleigh distribution, but obeys the rice distribution, at this time, the doppler spread parameter is estimated by the maximum value and the minimum value in the frequency offset estimation value of each subframe in the frequency offset variation period, so as to improve the accuracy of channel estimation, further reduce the error rate, and improve the throughput of the system.
In an alternative embodiment provided based on the embodiment shown in fig. 7, the processing unit 702 is configured to:
selecting M maximum paths from the PDP according to the power of paths included in the PDP, wherein M is a positive integer;
acquiring signal-to-noise ratio parameters corresponding to the M maximum paths according to the signal-to-noise ratios respectively corresponding to the M maximum paths;
and detecting whether the target path exists in the PDP according to the signal-to-noise ratio parameters corresponding to the M maximum paths.
Optionally, the processing unit 702 is configured to:
acquiring signal-to-noise ratio variances corresponding to the M maximum paths according to the signal-to-noise ratios corresponding to the M maximum paths respectively;
and detecting whether the target path exists in the PDP according to the signal-to-noise ratio variance corresponding to the M maximum paths.
Optionally, the processing unit 702 is configured to:
when the signal-to-noise ratio variance corresponding to the M maximum paths is smaller than a first threshold value, determining that the target paths exist in the PDP;
and when the signal-to-noise ratio variance corresponding to the M maximum paths is greater than or equal to the first threshold value, determining that the target path does not exist in the PDP.
In an alternative embodiment provided based on the embodiment shown in fig. 7, the processing unit 702 is configured to:
and determining the Doppler spread parameter according to the difference between the maximum value and the minimum value.
In an alternative embodiment provided based on the embodiment shown in fig. 7, the processing unit 702 is configured to:
when the target path exists in the PDP, acquiring the power of the target path and the power of a Rayleigh path;
and when the ratio between the power of the target path and the power of the Rayleigh path is larger than a second threshold value, executing the step of determining the Doppler spread parameter according to the maximum value and the minimum value in the frequency offset estimation value of each subframe in the frequency offset change period.
Optionally, the processing unit 702 is further configured to:
when the ratio between the power of the target path and the power of the Rayleigh path is smaller than or equal to the second threshold value, using the Rayleigh path and carrying out channel estimation based on a U-shaped spectrum and a 0-order Bessel function to obtain a first estimated value;
determining a second estimated value based on the maximum value and the minimum value in the frequency offset estimated values of all subframes of the target path in the frequency offset change period;
and determining the Doppler spread parameter according to the first estimated value and the second estimated value.
Optionally, the processing unit 702 is configured to:
determining the Doppler spread parameter based on a product parameter between an adjustment factor and the second estimate and the first estimate;
wherein the adjustment factor is associated with at least one of: signal to noise ratio, channel delay spread, K factor value. Optionally, the processing unit 702 is configured to:
obtaining a product between the adjustment factor and the second estimated value;
and determining the sum of the product and the first estimated value as the Doppler spread parameter.
Optionally, the processing unit 702 is further configured to: and when the target path exists in the PDP, determining an effective path with the number of samples, which is larger than a third threshold value, from the target paths in the effective paths except the target path as a Rayleigh path.
In an alternative embodiment provided based on the embodiment shown in fig. 7, the processing unit 702 is further configured to: and when the target path does not exist in the PDP, using N effective paths of the pilot signal in the PDP of the current time slot, and estimating the Doppler spread parameter based on a U-shaped spectrum and a 0-order Bessel function, wherein N is an integer larger than M.
It should be noted that, when the apparatus provided in the foregoing embodiment performs the functions thereof, only the division of the foregoing functional modules is used as an example, in practical application, the foregoing functional allocation may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules, so as to perform all or part of the functions described above. In addition, the apparatus and the method embodiments provided in the foregoing embodiments belong to the same concept, and specific implementation processes of the apparatus and the method embodiments are detailed in the method embodiments and are not repeated herein.
Fig. 8 is a schematic structural view of a terminal according to an exemplary embodiment.
The terminal 800 comprises a transmitter 801, a receiver 802 and a processor 803. The processor 803 may also be a controller, represented in fig. 8 as "controller/processor 803". Optionally, the terminal 800 may further comprise a modem processor 805, wherein the modem processor 805 may comprise an encoder 806, a modulator 807, a decoder 808, and a demodulator 809.
In one example, the transmitter 801 conditions (e.g., analog converts, filters, amplifies, and upconverts, etc.) the output samples and generates an uplink signal, which is transmitted via an antenna to the access network device described in the above embodiments. On the downlink, the antenna receives the downlink signal transmitted by the access network device in the above embodiment. Receiver 802 conditions (e.g., filters, amplifies, frequency downconverts, digitizes, etc.) the received signal from the antenna and provides input samples. In modem processor 805, an encoder 806 receives traffic data and signaling messages to be sent on the uplink and processes (e.g., formats, encodes, and interleaves) the traffic data and signaling messages. A modulator 807 further processes (e.g., symbol maps and modulates) the encoded traffic data and signaling messages and provides output samples. A demodulator 809 processes (e.g., demodulates) the input samples and provides symbol estimates. A decoder 808 processes (e.g., deinterleaves and decodes) the symbol estimates and provides decoded data and signaling messages that are transmitted to the terminal 800. The encoder 806, modulator 807, demodulator 809, and decoder 808 may be implemented by a composite modem processor 805. These elements are handled according to the radio access technology employed by the radio access network (e.g., the access technology of LTE and other evolved systems). Note that, when the terminal 800 does not include the modem processor 805, the above-described functions of the modem processor 805 may also be performed by the processor 803.
The processor 803 controls and manages the actions of the terminal 800 for executing the processing procedure performed by the terminal 800 in the above-described embodiment of the present disclosure. For example, the processor 803 is further configured to perform the steps on the terminal side in the above method embodiments, and/or other steps of the technical solutions described in the embodiments of the present disclosure.
Further, the terminal 800 may also include a memory 804, the memory 804 for storing program codes and data for the terminal 800.
Those skilled in the art will appreciate that the structure shown in fig. 8 is not limiting and that more or fewer components than shown may be included or certain components may be combined or a different arrangement of components may be employed.
In an exemplary embodiment, there is also provided a computer readable storage medium having stored therein a computer program loaded and executed by a processor of a terminal to implement the channel estimation method in the above-described method embodiment.
Alternatively, the above-mentioned computer readable storage medium may be a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a magnetic tape, a floppy disk, an optical data storage device, or the like.
In an exemplary embodiment, there is also provided a computer program product comprising computer instructions stored in a computer readable storage medium, the computer instructions being read from the computer readable storage medium by a processor of a computer device, the computer instructions being executed by the processor to cause the computer device to perform the channel estimation method provided in the above aspect or in various alternative implementations of the aspect.
It should be understood that references herein to "a plurality" are to two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a exists alone, A and B exist together, and B exists alone. The character "/" generally indicates that the context-dependent object is an "or" relationship. The terms "first," "second," and the like, as used herein, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another.
The foregoing embodiment numbers of the present application are merely for describing, and do not represent advantages or disadvantages of the embodiments.
The foregoing description of the exemplary embodiments of the present application is not intended to limit the invention to the particular embodiments disclosed, but on the contrary, the intention is to cover all modifications, equivalents, alternatives, and alternatives falling within the spirit and scope of the invention.
Claims (12)
1. A method of channel estimation, the method comprising:
receiving a pilot signal;
acquiring a power delay spectrum PDP of the pilot signal;
selecting M maximum paths from the PDP according to the power of paths included in the PDP, wherein M is a positive integer; acquiring signal-to-noise ratio variances corresponding to the M maximum paths according to the signal-to-noise ratios corresponding to the M maximum paths respectively; detecting whether a target path exists in the PDP according to the signal-to-noise ratio variance corresponding to the M maximum paths, wherein the target path is a main path comprising a direct path;
and when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
2. The method of claim 1, wherein the detecting whether the target path exists in the PDP according to the signal-to-noise ratio variance corresponding to the M maximum paths comprises:
when the signal-to-noise ratio variance corresponding to the M maximum paths is smaller than a first threshold value, determining that the target paths exist in the PDP;
and when the signal-to-noise ratio variance corresponding to the M maximum paths is greater than or equal to the first threshold value, determining that the target path does not exist in the PDP.
3. The method of claim 1 wherein said determining doppler spread parameters based on maximum and minimum values of frequency offset estimates for each subframe in a frequency offset variation period comprises:
and determining the Doppler spread parameter according to the difference between the maximum value and the minimum value.
4. The method of claim 1, wherein before determining the doppler spread parameter from the maximum value and the minimum value of the frequency offset estimates of each subframe in the frequency offset variation period, further comprises:
when the target path exists in the PDP, acquiring the power of the target path and the power of a Rayleigh path;
and when the ratio between the power of the target path and the power of the Rayleigh path is larger than a second threshold value, executing the step of determining the Doppler spread parameter according to the maximum value and the minimum value in the frequency offset estimation value of each subframe in the frequency offset change period.
5. The method according to claim 4, wherein the method further comprises:
when the ratio between the power of the target path and the power of the Rayleigh path is smaller than or equal to the second threshold value, using the Rayleigh path and carrying out channel estimation based on a U-shaped spectrum and a 0-order Bessel function to obtain a first estimated value;
determining a second estimated value based on the maximum value and the minimum value in the frequency offset estimated values of all subframes of the target path in the frequency offset change period;
and determining the Doppler spread parameter according to the first estimated value and the second estimated value.
6. The method of claim 5, wherein said estimating the doppler spread parameter from the first estimate and the second estimate comprises:
determining the Doppler spread parameter based on a product parameter between an adjustment factor and the second estimate and the first estimate;
wherein the adjustment factor is associated with at least one of: signal to noise ratio, channel delay spread, K factor value.
7. The method of claim 6, wherein the step of providing the first layer comprises,
obtaining a product between the adjustment factor and the second estimated value;
and determining the sum of the product and the first estimated value as the Doppler spread parameter.
8. The method according to any one of claims 4-7, wherein before the obtaining the power of the target path and the power of the rayleigh path, further comprising:
and when the target path exists in the PDP, determining an effective path with the number of samples, which is larger than a third threshold value, from the target paths in the effective paths except the target path as a Rayleigh path.
9. The method according to any one of claims 1 to 7, further comprising:
and when the target path does not exist in the PDP, using N effective paths of the pilot signal in the PDP of the current time slot, and determining the Doppler spread parameter based on a U-shaped spectrum and a 0-order Bessel function, wherein N is an integer larger than M.
10. A receiver, the receiver comprising:
a receiving unit for receiving a pilot signal;
a processing unit for:
acquiring a power delay spectrum PDP of the pilot signal;
selecting M maximum paths from the PDP according to the power of paths included in the PDP, wherein M is a positive integer; acquiring signal-to-noise ratio variances corresponding to the M maximum paths according to the signal-to-noise ratios corresponding to the M maximum paths respectively; detecting whether a target path exists in the PDP according to the signal-to-noise ratio variance corresponding to the M maximum paths, wherein the target path is a main path comprising a direct path;
and when the target path exists in the PDP, determining Doppler spread parameters according to the maximum value and the minimum value in the frequency offset estimated value of each subframe in the frequency offset change period.
11. A receiver comprising a processor and a memory, the memory storing a computer program that is loaded and executed by the processor to implement the channel estimation method of any of claims 1 to 9.
12. A computer readable storage medium, characterized in that the computer readable storage medium has stored therein a computer program, which is loaded and executed by a processor to implement the channel estimation method according to any of claims 1 to 9.
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