CN101359926B - Receiver, channel estimation method and apparatus - Google Patents
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Abstract
本发明提供了一种接收机、信道估计方法与装置，其中，信道估计方法包括：对导频信道进行多径搜索，选择出信道窗内能量大于预设条件的径；对所述径进行信道估计；对信道估计得到的信道估计值消除升余弦干扰，得到无升余弦干扰的信道估计值；对所述无升余弦干扰的信道估计值进行升余弦卷积，得到导频信道中所有位置上的径能量。本发明进行信道估计时，不会引入新的噪声，有效保证了LMMSE均衡器的均衡性能；另外，避免了由于存在RC影响，在进行RC卷积时引入径之间的干扰，从而在信道估计值与实际信道值之间产生偏差，进一步保证了LMMSE均衡器的均衡效果。
The present invention provides a receiver, channel estimation method and device, wherein the channel estimation method includes: performing multipath search on the pilot channel, and selecting a path whose energy in the channel window is greater than a preset condition; Estimate; remove the raised cosine interference from the channel estimate obtained by channel estimation to obtain a channel estimate without raised cosine interference; perform raised cosine convolution on the channel estimate without raised cosine interference to obtain all positions in the pilot channel diameter energy. When the present invention performs channel estimation, no new noise will be introduced, effectively ensuring the equalization performance of the LMMSE equalizer; in addition, due to the existence of RC influence, the interference between paths is avoided when performing RC convolution, thereby in channel estimation The deviation between the value and the actual channel value further ensures the equalization effect of the LMMSE equalizer.
Description
Technical Field
The present invention relates to communication technology, and more particularly, to a receiver for eliminating inter-path interference, a channel estimation method using the receiver, and a channel estimation apparatus used in the receiver for channel estimation.
Background
In Wideband Code Division Multiple Access (WCDMA) systems, the multicode signals at the transmitter are orthogonal to each other. However, this orthogonality diminishes or disappears as these signals propagate through a multipath fading channel, and in order to correctly identify the signals, a RAKE receiver is typically introduced at the receiving end to restore the orthogonality of the signals. Because of using the broadband spread spectrum signal, the WCDMA system can distinguish different multipath components in the received signal by using the RAKE receiver, thereby realizing diversity reception, effectively overcoming the influence of multipath fading and improving the receiving performance of the system. However, in the downlink reception of the WCDMA system, due to the inter-symbol interference and multi-user interference caused by multipath, the coherent reception performance of the RAKE receiver is limited, especially in the case of high data transmission rate, such as: when High Speed Downlink Packet Access (HSDPA), the spreading factor is small, which not only reduces the interference rejection of the RAKE receiver, but also greatly reduces the diversity gain introduced by multipath combining. At this time, in order to obtain a more ideal performance, the prior art introduces a Linear Minimum Mean Square Error (LMMSE) technology to realize an LMMSE receiver, an LMMSE equalizer is adopted in the LMMSE receiver to equalize a received signal, the equalization principle of the LMMSE equalizer is that the Mean Square Error between an equalized signal and a transmitted signal is Minimum, and the receiving performance of the LMMSE equalizer is superior to that of the original RAKE receiver because intersymbol interference and multiuser interference caused by multipath are eliminated.
FIG. 1 is a schematic diagram of a WCDMA signal transceiver system in the prior art. At a transmitting end, a transmitting end Root Raised Cosine (RRC) filter filters a signal x (k) and then transmits the signal; transmitting signals through a multipath fading channel superimposed with white Gaussian noise, then reaching an LMMSE receiver at a receiving end, filtering by a receiving end RRC filter in the LMMSE receiver to obtain signals y (k), and respectively sending the signals y (k) to an LMMSE equalizer and a channel estimation device; the channel estimation device carries out channel estimation based on signals y (k), estimates the energy of each path in a fading channel, sends an estimated channel value H channel estimation matrix obtained by estimation to a calculation device, when a plurality of paths exist, the estimated channel value H is represented as a channel estimation matrix H, and simultaneously, the noise function estimation device estimates the Gaussian white noise energy in the channel and estimates the estimated noise energy
Sending to a computing device; the calculating device estimates the value h and the Gaussian white noise energy according to the channel estimation matrix
Calculating to obtain the tap weight w of the LMMSE equalizerdAnd sending the data to an LMMSE equalizer; LMMSE equalizer based on equalization principle for y (k) and wdCarrying out equalization to obtain a signal x' (k); the descrambling/despreading device descrambles and despreads the signal x' (k) to obtain a transmission signal x (k).
As can be seen from the processing procedure of the LMMSE receiver in FIG. 1 on the received signal, the tap weight w of the LMMSE equalizerdFrom the channel estimate h and the Gaussian white noise energyAnd determining that the difference between the channel estimation value h and the actual channel value directly influences the performance of the LMMSE equalizer, and the more the channel estimation approaches the actual channel condition, the better the equalization effect of the LMMSE equalizer is. Therefore, how to perform channel estimation and obtain a channel estimation value that approximates to an actual channel value is very critical.
The traditional channel estimation method carries out channel fading estimation on the path position of a pilot channel directly according to a multipath search indication. As shown in fig. 2, which is a schematic structural diagram of a conventional channel estimation apparatus, a flow of performing channel estimation is as follows: when a multipath searching module detects that a path exists in a Pilot Channel, the multipath searching module sends multipath searching indication information to a Common Pilot Channel (CPICH) descrambling and despreading module, wherein the multipath searching indication information comprises the initial path position and Channel length information of the Pilot Channel needing Channel estimation, and the initial path position is the initial position of the Channel, so that a Channel window needing Channel estimation can be obtained by combining the Channel length, and therefore the termination position of the Channel window can also be obtained; the CPICH descrambling and despreading module is used for descrambling and despreading at each path position in the channel window in sequence to obtain a pilot symbol; the division module divides the pilot frequency symbol obtained by descrambling and despreading by the transmitted pilot frequency symbol to obtain a channel estimation value and transmits the channel estimation value to a Finite long Impulse Response (FIR) filter; the FIR filter carries out front and back smoothing treatment on the received channel estimation value; because a power weighting factor is multiplied on the pilot signal at the transmitting end, the current channel estimation value and the actual channel estimation value have a power weighting factor difference, and the power weighting factor processing module divides the signal processed by the FIR filter by the power weighting factor to obtain the channel estimation value CE of each path position in the channel window.
When the traditional channel estimation method is adopted for channel estimation, the path energy of all positions in a channel window is considered, and because the path energy of some positions is weaker and the signal-to-noise ratio of the positions with weaker energy is generally lower, larger noise is introduced when the traditional channel estimation method is used for channel estimation, so that the equalization performance of the LMMSE equalizer is influenced, and the equalization performance of the LMMSE equalizer is reduced.
In order to overcome the performance degradation of an LMMSE equalizer caused by introducing larger noise in the traditional channel estimation method, in the prior art, 1/4 chips are taken as precision, a single path with a signal-to-noise ratio reaching a preset threshold value is selected from a channel window detected by a multi-path searching module, and then the channel estimation is carried out on the single path by adopting the traditional channel estimation method; because the equivalent channel to be estimated is the convolution of the actual channel with the receiving RRC filter and the sending RRC filter, the two RRC filters are connected in series and are equivalent to a raised cosine filter, the parameter matrix of the raised cosine filter is represented by RC, the estimated channel estimation value is convolved with RC to obtain the channel estimation of all phase points in a channel window, and the precision of the phase points is also 1/4 chips. In consideration of complexity, the number of taps in a chip of the equalizer is generally 2 or 1, and channel estimation at the chip level is required to be 1 or 1/2, so that the convolved channel estimation value with 1/4 chip accuracy is downsampled to obtain a channel estimation value at the chip level or 1/2 chip level.
The inventor discovers that in the process of implementing the invention: compared with the conventional channel estimation method, the method for performing channel estimation on a single path selected by using 1/4 chips as the precision avoids the performance reduction of the LMMSE equalizer caused by introducing noise, but because the estimated channel estimation value is mixed with the influence of RC, the estimated channel estimation value is convolved with the RC at the moment, and further interference between the paths is introduced, which can cause the deviation between the channel estimation value obtained after convolution and an actual channel value, so that the equalization effect of the LMMSE equalizer is reduced, and particularly when two paths with stronger energy and a distance less than 1 chip exist in a channel, the channel estimation effect is worse because the interference between the paths generated by the RC is larger.
Disclosure of Invention
The technical problem to be solved by the embodiment of the invention is as follows: the interference between paths introduced when the channel estimation value is convoluted with an RC system due to the mixed RC influence is eliminated, so that the deviation between the convoluted channel estimation value and an actual channel due to the interference between the paths is avoided, and the equalization effect of the LMMSE equalizer is improved.
According to an embodiment of the present invention, a channel estimation method is provided, including:
performing multi-path search on a pilot channel, and selecting a path with energy in a channel window larger than a preset condition;
performing channel estimation on the path;
raised cosine interference is eliminated from a channel estimation value obtained by channel estimation, and a channel estimation value without raised cosine interference is obtained;
and performing raised cosine convolution on the channel estimation value without raised cosine interference to obtain path energy at all positions in the pilot channel.
According to another aspect of the present invention, there is provided a channel estimation apparatus, including:
the multipath searching module is used for performing multipath searching on the pilot channel;
the selection module is used for selecting paths with energy larger than a preset condition from a channel window searched by the multipath;
the channel estimation module is used for carrying out channel estimation on the paths with the energy larger than the preset condition;
the restoring module is used for eliminating raised cosine interference on a channel estimation value obtained by channel estimation;
and the convolution module is used for performing raised cosine convolution on the channel estimation value without raised cosine interference obtained after raised cosine interference is eliminated.
According to another embodiment of the present invention, a receiver is provided, which includes a root raised cosine filter, a channel estimation device, a noise power estimation device, a weight calculation device, an equalizer, and a descrambling and despreading device, wherein the channel estimation device includes:
the multipath searching module is used for performing multipath searching on the pilot channel;
the selection module is used for selecting paths with energy larger than a preset condition from a channel window searched by the multipath;
the channel estimation module is used for carrying out channel estimation on the paths with the energy larger than the preset condition;
the restoring module is used for eliminating raised cosine interference on a channel estimation value obtained by channel estimation;
and the convolution module is used for performing raised cosine convolution on the channel estimation value without raised cosine interference obtained after raised cosine interference is eliminated.
When the embodiment of the invention carries out channel estimation, only the path with the energy in the selected channel window larger than the preset condition is carried out channel estimation, no new noise is introduced, and the equalization performance of the LMMSE equalizer is effectively ensured; in addition, after RC influence on the channel estimation value estimated by the traditional channel estimation method is eliminated, the channel estimation value is convolved, interference between paths caused by the RC influence and the RC convolution is avoided, the channel estimation value is closer to an actual channel value, and the equalization effect of the LMMSE equalizer is effectively guaranteed.
The technical solutions of the embodiments of the present invention are further described in detail with reference to the accompanying drawings and embodiments.
Drawings
Fig. 1 is a schematic structural diagram of a WCDMA signal transceiving system in the prior art.
Fig. 2 is a schematic structural diagram of a conventional channel estimation apparatus in the prior art.
Fig. 3 is a flowchart of a channel estimation method according to an embodiment of the present invention.
Fig. 4 is a flowchart of another embodiment of the channel estimation method of the present invention.
FIG. 5 is a schematic diagram of energy extraction according to the embodiment of FIG. 4.
Fig. 6 is a schematic structural diagram of a channel estimation device according to an embodiment of the present invention.
Fig. 7 is a schematic structural diagram of an embodiment of the receiver of the present invention.
Detailed Description
The embodiment of the invention carries out channel estimation on the paths with the energy in the channel window larger than the preset condition, and carries out RC convolution after RC interference is eliminated on the channel estimation value, thereby obtaining the path energy at all positions in the pilot channel.
As shown in fig. 3, a flow chart of an embodiment of the channel estimation method of the present invention is shown, which includes the following steps:
and 102, performing channel estimation on the paths with energy meeting preset conditions.
Channel estimation is only carried out on the selected path with the energy meeting the preset condition, new noise is not introduced, and the balance performance of the LMMSE equalizer is effectively ensured;
103, eliminating RC influence on a channel estimation value obtained by channel estimation to obtain a channel estimation value of a corresponding path without RC interference;
and 104, convolving the channel estimation value of the corresponding path without the RC interference with the parameter matrix of the RC filter to obtain path energy at all positions in the pilot channel.
After RC influence on the channel estimation value estimated by the channel is eliminated, the channel estimation value is convolved, so that the phenomenon that due to the RC influence, interference between paths is introduced when RC convolution is carried out, and therefore deviation is generated between the channel estimation value and an actual channel value is avoided, the channel estimation value is closer to the actual channel value, and the equalization effect of the LMMSE equalizer is further guaranteed.
Fig. 4 is a flowchart of another embodiment of the channel estimation method of the present invention, which includes the following steps:
Due to the effect of the RC system on multipath, which is not an impulse response of a single path in practice, the path with stronger energy still has larger energy at a path position less than one chip away from the path. When multipath searching is carried out, the phase points at 3/4 chips are deleted from left and right for the path position where the selected signal-to-noise ratio reaches the preset threshold. In the paths which are searched by the multipath and meet the preset condition, because the subsequent steps of the scheme can remove the interference of an RC system and restore the energy of a single path, the channel estimation values of two sides of the main path are kept, which is favorable for more accurately simulating the channel. When the interference of an RC system is removed, the inversion of an RC matrix must meet the condition of diagonal dominance, and if the interference is removed by selecting phase point paths in 1/2 chips on the left and right of a main path, the matrix is easy to be ill-conditioned and unable to be inverted. Therefore, in the present embodiment, two phase points on the left and right sides of the main path are selectively deleted, that is: the phase points in 1/2 chips on the left and right of the main path are deleted, three phase points on the left and right of the secondary path are deleted, one phase point is 1/4 chips, and four phase points are arranged in one chip.
Further, three phase points on the left and right of the major axis may be deleted, and two phase points on the left and right of the minor axis may be deleted. However, since the main path has the strongest energy, the deletion of the left and right phase points can preserve more energy of the main path than the deletion of the left and right phase points, which is beneficial to obtaining more accurate channel estimation values.
Wherein, the energy greater than the preset condition may specifically be: the energy or the signal-to-noise ratio is larger than a preset threshold value, or the ratio of the energy on the path to the energy on the minimum path is larger than a preset value.
And step 204, performing channel estimation on each path of which the energy meets the preset condition to obtain a channel estimation value CE. Specifically, the conventional channel estimation apparatus as shown in fig. 2 is employed for channel estimation.
In step 205, due to RC interference between paths, there is interference from other paths to the current path on the channel estimation value of each path obtained in step 204, and since the RC parameters are known, the RC influence is eliminated from the channel estimation value CE by using the least square method, and the multipath estimation CE' without RC influence is obtained.
Assuming that the path positions searched by the multipath are: p1, P2, P3, P4, P5, P6, P7 and P8; the delay difference between the paths is: <math> <mrow> <msub> <mi>τ</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>j</mi> </mrow> </msub> <mo>=</mo> <munderover> <mi>Σ</mi> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mn>8</mn> </munderover> <munderover> <mi>Σ</mi> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> <mo>;</mo> <mi>ji</mi> </mrow> <mn>8</mn> </munderover> <mrow> <mo>(</mo> <msub> <mi>P</mi> <mi>i</mi> </msub> <mo>-</mo> <msub> <mi>P</mi> <mi>j</mi> </msub> <mo>)</mo> </mrow> <mo>;</mo> </mrow></math> the channel estimates on each path obtained from step 204 are: CE1，CE2，CE3，CE3，CE4，CE5，CE6，CE7，CE8(ii) a After the RC influence is eliminated, the channel estimation values without RC influence on each path are obtained as follows: CE'1，CE’2，CE’3，CE’3，CE’4，CE’5，CE’6，CE’7，CE’8；
RC is the filter parameter matrix of RRC convolutional RRC, the RC effect can be eliminated by the following equation:
the above matrix equation can be abbreviated as: RC · CE' + n ═ CE, where n is the noise figure at each radial position described above.
The least square error that can be obtained using the least squares method is the smallest when the components of the error vector have the same variance and the components are uncorrelated. For the above equation to eliminate the inter-path RC interference, the sum of the squares of the errors is minimized by the criterion of least squares, i.e.:
and minimum. The number of the unknown parameters CE' to be solved is equal to the number of the equations, and the solution can be obtained by a least square method as follows: CE ═ RC-1CE；
The RC matrix is further inverted to obtain the channel estimation CE' of the path at each position before RC influence. Because the RC matrix is a real symmetric matrix, the RC matrix can be inverted by using gaussian-seidel (Gauss-Siedel) inversion, gaussian elimination decomposition inversion or cholesky decomposition inversion, etc., so as to obtain the path channel estimation value CE' at the corresponding position where the RC interference is eliminated.
And step 206, convolving the channel estimation value CE' of the path without RC interference with the parameter matrix of the RC filter to obtain path energy at all positions in the pilot channel.
Fig. 5 is a schematic diagram of energy interception according to the present invention. Wherein, FIG. 5-1 shows the energy of CE' at each path position before convolution, assuming that the channel length is L; FIG. 5-2 shows the energy of the RC filter at the corresponding path position, assuming that the channel length is M; fig. 5-3 shows the energy length of the convolution of the channel estimation CE' with the RC filter parameter matrix, where the channel length is L + M, and a larger energy portion of the channel length L is cut out from the convolution in order to retain the entire energy as much as possible.
In step 208, the accuracy of the channel estimate obtained in step 207 is 1/4 chips, and since the equalizer tap is generally one or two samples within one chip, the required channel estimate should also be one or two samples within one chip, and for this reason, the channel estimate at all positions in the pilot channel is downsampled to obtain a channel estimate CE' of one chip or 1/2 chips.
In step 209, a channel estimation matrix is generated from the channel estimation value CE'.
In addition, the number of equations may be increased to make the number of equations larger than the number of unknowns, and the Minimum Mean Square Error (MMSE) or other least squares methods are used to eliminate the RC influence on the channel estimation value CE, so as to obtain the multipath estimation CE' without the RC influence.
Assume that the path positions searched by the multipath are, according to the energy, as follows in sequence through step 201 and step 202: p1, P2, P3, P4, P5, P6, P7 and P8, wherein only the radial positions P1 and P2 satisfy the preset condition in step 203, one of the radial positions P3, P4, P5, P6, P7 and P8 is selected to perform channel estimation, and if P3 is selected, the channel estimation value CE of the radial positions P1, P2 and P3 is used to perform channel estimation1，CE2And CE3To restore the channel estimation values CE 'of the radial positions P1 and P2 for eliminating RC influence'1And CE'2. The RC effect can be eliminated by the following equation:
by means of least squares <math> <mrow> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mrow> <mi>CE</mi> <mo>′</mo> </mrow> <mn>1</mn> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mrow> <mi>CE</mi> <mo>′</mo> </mrow> <mn>2</mn> </msub> </mtd> </mtr> </mtable> </mfenced> </mrow></math> The channel estimation matrix H' of (a) is:
can be obtained by MMSE method <math> <mrow> <mfenced open='[' close=']'> <mtable> <mtr> <mtd> <msub> <mrow> <mi>CE</mi> <mo>′</mo> </mrow> <mn>1</mn> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mrow> <mi>CE</mi> <mo>′</mo> </mrow> <mn>2</mn> </msub> </mtd> </mtr> </mtable> </mfenced> </mrow></math> The channel estimation matrix H' of (a) is:
wherein,
as noise energy, I3Is an identity matrix.
As shown in fig. 6, which is a schematic structural diagram of an embodiment of the channel estimation apparatus of the present invention, the channel estimation apparatus includes a multipath searching module 301, a selecting module 302, a channel estimation module 303, a restoring module 304, and a convolution module 305, which are connected in sequence. The multipath searching module 301 is configured to perform multipath searching on a pilot channel; the selection module 302 is configured to select a path with energy greater than a preset condition from a channel window searched by a multipath; the channel estimation module 303 is configured to perform channel estimation on a path with energy greater than a preset condition; the restoring module 304 is configured to eliminate RC interference for a channel estimation value obtained by channel estimation; the convolution module 305 is configured to perform RC convolution on the RC interference-free channel estimation value obtained after the RC interference is eliminated.
In the channel estimation apparatus shown in fig. 6, the selection module 302 may specifically include a measurement unit 3021 and a selection unit 3022, where the measurement unit 3021 is connected to the multipath searching module 301, and is configured to measure energy or a signal-to-noise ratio of an inner diameter of a channel window searched by the multipath searching module 301, and further, the measurement unit 3021 may further select a path with strongest energy in the channel window and a path with stronger energy in the remaining paths in sequence; the selecting unit 3022 is connected to the channel estimating module 303, and configured to select a path with energy in a channel window greater than a preset condition according to a measurement result of the measuring unit 3021, and send the path to the channel estimating module 303. The channel estimation apparatus of this embodiment can be used to implement the channel estimation method of the embodiment shown in fig. 3.
Further, the selecting module may further include a deleting unit 3023, disposed between the measuring unit 3021 and the selecting unit 3022, for deleting two phase points on the left and right of the main path with the strongest energy and three phase points on the left and right of the minor path with the stronger energy, which are selected by the selecting unit 3021.
In addition, the channel estimation apparatus shown in fig. 6 may further include an information storage module 306, connected to the selection unit 3022, for storing condition information of paths with energy greater than a preset condition, for example: the energy is greater than a preset value A, or the signal-to-noise ratio is greater than a preset value B, or the ratio of the energy to the minimum path energy is greater than a preset value C; specifically, the selecting unit 3022 is configured to compare the energy or signal-to-noise ratio of the primary path and the secondary path sent by the measuring unit 3021 with the corresponding condition information in the information storage module 306, and select a path with energy greater than a preset condition in the channel window.
Further, the channel estimation apparatus provided in the embodiment of the present invention may further include a parameter storage module 307, which is respectively connected to the restoring module 304 and the convolution module 305, and configured to store the RC filter parameter matrix; specifically, the restoring module 304 is configured to obtain a parameter matrix of the RC filter from the parameter storage module 307, and perform product calculation on an inverse matrix of the parameter matrix of the RC filter and a channel estimation value obtained by channel estimation to eliminate RC interference on the channel estimation value obtained by channel estimation; the convolution module 305 is configured to obtain an RC filter parameter matrix from the parameter storage module 307, and perform raised cosine convolution on the RC filter parameter matrix and the channel estimation value without RC interference.
Referring to fig. 6 again, the channel estimation apparatus according to the embodiment of the present invention may further include a down-sampling module 308, configured to down-sample the path energy at all positions in the pilot channel obtained after the RC convolution. Furthermore, the channel estimation apparatus may further include a matrix generation module 309, configured to generate a channel estimation matrix according to the channel estimation value of 1/2 chips obtained by downsampling. The channel estimation apparatus of this embodiment can be used to implement the channel estimation method of the embodiment shown in fig. 4.
Referring to fig. 7, which is a schematic structural diagram of an embodiment of the receiver of the present invention, the receiver of the embodiment includes an RRC filter, a channel estimation device, a weight calculation device, an equalizer, a descrambling and despreading device, and a noise power estimation device connected to the weight calculation device, which are connected in sequence, and an output end of the RRC filter is further connected to an input end of the equalizer. The channel estimation apparatus may adopt the channel estimation apparatus of any embodiment shown in fig. 6, specifically, an output end of the RRC filter is connected to the multipath searching module 301 in the channel estimation apparatus, and an output end of the convolution module 305 or the down-sampling module 308 in the channel estimation apparatus is connected to an input end of the weight calculation apparatus.
Specifically, the RRC filter is configured to receive a transmission signal transmitted through a multipath fading channel superimposed with white gaussian noise, filter the received signal, and send the filtered signal to the multipath searching module 301 in the equalizer and the channel estimation device respectively;
the channel estimation apparatus performs channel estimation based on the filtered signal by using the method shown in fig. 3 or fig. 4, and estimates the estimated channel estimation value, that is: the path energy or the channel estimation matrix at all positions in the pilot channel is sent to a weight calculation device;
the noise power estimation device estimates the Gaussian white noise energy in the channel and sends the estimated noise energy to the calculation device;
the calculating device calculates according to the channel estimation value sent by the channel estimation device and the noise energy sent by the noise power estimation device to obtain a tap weight of the equalizer and sends the tap weight to the equalizer;
and the equalizer equalizes the filtered signals sent by the RRC filter and the tap weight value of the equalizer according to an equalization principle, and sends equalized signals obtained after equalization to a descrambling and despreading device. The equalizer is an LMMSE equalizer;
the descrambling and despreading device descrambles and despreads the balanced signal to obtain an original transmission signal transmitted by the transmitter.
When the embodiment of the invention carries out channel estimation, only the path with the energy in the selected channel window larger than the preset condition is carried out channel estimation, no new noise is introduced, and the equalization performance of the LMMSE equalizer is effectively ensured; in addition, after RC influence on the channel estimation value estimated by the traditional channel estimation method is eliminated, the channel estimation value is convoluted, so that interference between paths caused by the RC influence during RC convolution is avoided, deviation is generated between the channel estimation value and an actual channel value, and the equalization effect of the LMMSE equalizer is further ensured.
Finally, it should be noted that: the above examples are only for illustrating the technical solutions of the present invention, and are not to be construed as limiting the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art will understand that: modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention.
Claims (11)
1. A channel estimation method, comprising the steps of:
performing multi-path search on a pilot channel, and selecting a path with energy in a channel window larger than a preset condition;
performing channel estimation on the path;
raised cosine interference is eliminated from a channel estimation value obtained by channel estimation, and a channel estimation value without raised cosine interference is obtained;
and performing raised cosine convolution on the channel estimation value without raised cosine interference to obtain path energy at all positions in the pilot channel.
2. The channel estimation method according to claim 1, wherein the condition that the energy is greater than the predetermined energy is specifically: the energy is larger than a preset value, or the signal-to-noise ratio is larger than a preset value, or the ratio of the energy to the minimum path energy is larger than a preset value.
3. The channel estimation method according to claim 1 or 2, wherein the performing a multipath search on the pilot channel and selecting a path with energy in a channel window greater than a preset condition comprises: performing multi-path search on a pilot channel, selecting a main path with the strongest energy from the paths obtained by the multi-path search operation, and deleting two or three phase points on the left and right of the main path; selecting a minor path with the strongest energy from the positions of other paths, deleting two or three phase points at the left and right of the minor path, and sequentially selecting and deleting two or three phase points at the left and right of a plurality of minor paths; and selecting a path with energy larger than a preset condition from the selected main path and the plurality of secondary paths.
4. The channel estimation method according to claim 3, wherein the step of eliminating raised cosine interference from the channel estimation value obtained by channel estimation specifically comprises: and solving the product of the inverse matrix of the raised cosine filter parameter matrix and the channel estimation value obtained by channel estimation by adopting a least square method, and eliminating raised cosine interference of the channel estimation value.
5. The channel estimation method according to any of claims 1 to 4, wherein after obtaining the path energy at all positions in the pilot channel, the method further comprises:
down-sampling the path energy at all positions in the pilot channel to obtain a channel estimation value of 1/2 chips;
and generating a channel estimation matrix according to the 1/2 chip channel estimation value.
6. A channel estimation device, comprising:
the multipath searching module is used for performing multipath searching on the pilot channel;
the selection module is used for selecting paths with energy larger than a preset condition from a channel window searched by the multipath;
the channel estimation module is used for carrying out channel estimation on the paths with the energy larger than the preset condition;
the restoring module is used for eliminating raised cosine interference on a channel estimation value obtained by channel estimation;
and the convolution module is used for performing raised cosine convolution on the channel estimation value for eliminating raised cosine interference, which is obtained after the raised cosine interference is eliminated.
7. The channel estimation device according to claim 6, further comprising:
the parameter storage module is used for storing a raised cosine filter parameter matrix;
the reduction module is used for solving the product of the inverse matrix of the raised cosine filter parameter matrix and the channel estimation value obtained by channel estimation so as to eliminate raised cosine interference on the channel estimation value obtained by channel estimation;
and the convolution module is used for performing raised cosine convolution on the channel estimation value for eliminating raised cosine interference and the raised cosine filter parameter matrix.
8. The channel estimation device according to claim 6 or 7, further comprising:
the down-sampling module is used for down-sampling the path energy at all positions in the pilot channel obtained after raised cosine convolution;
and the matrix generating module is used for generating a channel estimation matrix according to the 1/2 chip channel estimation value obtained by down-sampling.
9. A receiver comprises a root raised cosine filter, a channel estimation device, a noise power estimation device, a weight calculation device, an equalizer and a descrambling and despreading device, and is characterized in that the channel estimation device comprises:
the multipath searching module is used for performing multipath searching on the pilot channel;
the selection module is used for selecting paths with energy larger than a preset condition from a channel window searched by the multipath;
the channel estimation module is used for carrying out channel estimation on the paths with the energy larger than the preset condition;
the restoring module is used for eliminating raised cosine interference on a channel estimation value obtained by channel estimation;
and the convolution module is used for performing raised cosine convolution on the channel estimation value without raised cosine interference obtained after raised cosine interference is eliminated.
10. The receiver of claim 9, wherein the channel estimation device further comprises:
the parameter storage module is used for storing a raised cosine filter parameter matrix;
the reduction module is used for solving the product of the inverse matrix of the raised cosine filter parameter matrix and the channel estimation value obtained by channel estimation so as to eliminate raised cosine interference on the channel estimation value obtained by channel estimation;
and the convolution module is used for performing raised cosine convolution on the channel estimation value for eliminating raised cosine interference and the raised cosine filter parameter matrix.
11. The receiver according to claim 9 or 10, wherein the channel estimation device further comprises:
the down-sampling module is used for down-sampling the path energy at all positions in the pilot channel obtained after raised cosine convolution;
and the matrix generating module is used for generating a channel estimation matrix according to the 1/2 chip channel estimation value obtained by down-sampling.
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| CN101527583B (en) * | 2009-04-17 | 2012-11-14 | 中山大学 | WCDMA downlink channel parameter estimation method |
| CN101753173B (en) * | 2009-11-03 | 2013-04-17 | 华为终端有限公司 | Receiving method and equipment under long time delay extended channel |
| CN101753489B (en) * | 2009-11-03 | 2012-10-03 | 华为终端有限公司 | Communication channel estimating method and device |
| CN101895311B (en) * | 2010-06-18 | 2013-08-07 | 华为技术有限公司 | Signal-receiving method and receiver |
| CN102457324B (en) * | 2010-10-29 | 2015-12-16 | 中兴通讯股份有限公司 | A kind of frequency division duplex system descending multi-user multipath beam form-endowing method and device |
| CN102736069B (en) * | 2012-07-02 | 2014-04-09 | 北京理工大学 | Direct wave interference suppression method |
| CN104243367B (en) * | 2013-06-14 | 2018-03-30 | 晨星半导体股份有限公司 | Receiving device and method for accelerating equalization convergence speed |
| US10524161B2 (en) * | 2014-08-20 | 2019-12-31 | Qualcomm Incorporated | Delay spread estimation and utilization |
| DE102015109752B4 (en) * | 2015-06-18 | 2019-05-23 | Intel IP Corporation | Apparatus and method for generating channel estimation coefficients for channel estimation filtering |
| CN106559366B (en) * | 2016-11-25 | 2019-08-06 | 西安烽火电子科技有限责任公司 | Multipath fading signal diversity based on multidiameter fading channel merges method of reseptance |
| CN108234365B (en) * | 2018-02-26 | 2024-08-06 | 福建京奥通信技术有限公司 | WCDMA repeater downlink channel parameter estimation system and method |
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| CN1780277A (en) * | 2004-11-18 | 2006-05-31 | 中兴通讯股份有限公司 | Channel evaluation and evaluating device for orthogonal frequency division duplex telecommunication system |
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