CN1708142A - Method for realizing infomration channel estimation in orthogonal frequency division multiplexing system - Google Patents

Abstract

The invention discloses a method for realizing channel estimation in an orthogonal multiplex frequency division multiplexing system. In the method, firstly, the receiving end obtains the frequency domain receiving signal received by the subcarrier where the pilot frequency is located according to the received time domain receiving signal ; According to the received signal in the frequency domain received on the pilot subcarrier of the same OFDM symbol, the time domain channel information at the OFDM symbol is obtained; the time domain channel information is used to estimate the frequency domain channel information at the subcarrier where the data symbol is located. The solution of the present invention solves the problem of relatively large performance loss when the existing channel estimation solution is used in a system with a rapidly changing channel environment and a channel with a large delay. The solution of the present invention makes it possible to obtain better performance under the condition that the channel environment changes rapidly, and effectively improves the performance of the actual channel estimation in the high-delay channel and OFDM system, and strengthens the applicability of the data communication system to the channel environment. Thus, the data transmission efficiency of the actual system is improved.

Description

A Method for Realizing Channel Estimation in Orthogonal Multiplex Frequency Division Multiplexing System

technical field

The present invention relates to Orthogonal Multiplexing Frequency Division Multiplexing (OFDM) technology, more precisely, relates to a method for realizing channel estimation in OFDM system.

Background technique

OFDM technology is a frequency division multiplexing technology capable of transmitting high-speed data services. On the one hand, compared with traditional single-carrier technology, OFDM technology can provide higher spectrum efficiency by using a simple equalization algorithm; on the other hand, in In a system using OFDM, there is no need to allocate a wide guard bandwidth between adjacent carriers like traditional frequency division multiplexing (FDM), so that mutual interference between subcarriers can be avoided, thereby saving bandwidth. .

At present, OFDM technology has been widely used in existing communication systems, and this technology has been embodied in the wireless local area network standard 802.11a, and the fixed wireless access standard 802.16a. In addition, in the mobile wireless communication access system, the wireless access network of the Third Generation Partnership Project (3GPP) and the physical layer of IEEE 802.20 are also considering using OFDM technology to build a mobile wireless communication access with higher frequency efficiency. into the system.

Figure 1 shows a typical network diagram of a frequency cellular multiplexing system. Among them, two radio network controllers (RNC), that is, RNC1 and RNC2 are connected to the core network (CN), and some base stations (BS) are respectively connected to the two RNCs, wherein BS1, BS2 and BS3 are connected to RNC1, BS4, BS5 and BS6 are connected to RNC2, and two mobile stations (MS), namely MS1 and MS2 maintain wireless connection with these base stations. Figure 2 shows a typical omni-directional antenna multiplexing mode in a cell, referred to as a cell multiplexing mode for short, and Figure 3 shows a typical 120-degree directional antenna multiplexing mode in a cell, referred to as a sector multiplexing mode for short. The data transmission system using OFDM technology has the following advantages:

1) It has strong fault tolerance to multipath delay extension. As shown in Figure 4, an OFDM symbol includes two parts in the time domain: the data part and the cyclic prefix part. The cyclic prefix part is generated cyclically at the end of the _data part. The time is T _cp . The fault tolerance of OFDM technology is manifested in: compared with the duration Ts of an OFDM symbol, the duration of the typical channel impulse response is very small, and only occupies a small part of Ts, so it can be increased by adding a smaller cyclic prefix, namely T _cp to completely overcome the interference between signals caused by multipath.

2) It has strong fault tolerance to frequency selective fading. OFDM technology can recover digital signals carried by strongly fading sub-carriers by using redundant schemes such as channel coding.

3) A simple equalization algorithm is adopted. Since OFDM technology uses the frequency domain to transmit signals, and the role of the channel in the frequency domain is represented by simple multiplication, so that the data transmission system using OFDM technology only needs a simple single-tap equalizer when performing signal equalization. .

4) Compared with FDM technology, OFDM technology has higher spectral efficiency.

Although the data transmission system using OFDM technology has the above advantages, but in order to fully reflect the above advantages in the actual application of the system, and more importantly, to make the system work normally, the following key technologies must be solved: frequency synchronization, symbol synchronization , frame synchronization, channel estimation and equalization, etc. These key technologies are closely related to the actual use environment of the system, and also closely related to the network configuration requirements of the system.

The purpose of channel estimation in the above key technology is: the receiver obtains the frequency domain channel information of the data transmitted by the transmitter through channel estimation. After obtaining the frequency-domain channel information, the receiver can perform equalization and other processing according to the frequency-domain channel information to obtain corresponding data. Therefore, channel estimation technology is an important prerequisite for the receiver to obtain data correctly.

The IEEE 802.11a protocol provides channel estimation techniques. Specifically, the frame structure in the 802.11a system is shown in Figure 5. The beginning of each frame includes a preamble symbol (Preamble), followed by a data OFDM symbol of indefinite length. The data OFDM symbol includes user data and signaling. The pilot allocation scheme of 802.11a is shown in Figure 6 . In the physical layer options of 802.11a and 802.16a, Preamble is used for channel estimation. Specifically, since the receiver knows the data carried by each subcarrier of the Preamble transmitted by the transmitter, the channel condition experienced by each subcarrier of the Preamble can be obtained by using the received Preamble, and the channel environment changes slowly In the case of , the channel condition experienced by each subcarrier of the Preamble can be regarded as the channel condition experienced by the subcarrier corresponding to the data OFDM symbol corresponding to the Preamble.

That is to say, the solution provided by the 802.11 protocol is to approximate the channel condition of the data OFDM symbol to the channel condition of the corresponding Preamble. For this scheme, if the channel environment in the system changes quickly, this approximation will bring a large error. In addition, because the relative motion between the receiver and the transmitter will cause changes in the channel environment, it is said that , this solution will have certain limitations when applied to a system where the channel environment changes rapidly. The channel of the current mobile wireless communication system often changes quickly, and it is obviously not suitable to adopt the above-mentioned solution in the mobile wireless communication system.

In addition, although pilot subcarriers are introduced in the 802.11a OFDM implementation to track channel changes, to correct the channel conditions experienced by each subcarrier of the Preamble, and use the corrected channel conditions as the corresponding data OFDM symbols The channel value of the subcarrier, but this correction cannot fully reflect the rapid change of the channel, and will still cause a large performance loss.

In order to solve the shortcomings of the above solutions, the industry proposes a time-frequency grid-point pilot allocation mode, which is shown in FIG. 7 . The pilot OFDM symbols in this mode, that is, Preamble, are evenly distributed on the time-frequency plane. Therefore, using the pilot OFDM symbols to track channel changes can solve the problem of channel environment changes to a certain extent.

At present, in a proposal Tdoc R1-030780 submitted by Siemens to 3GPP RAN1, a specific pilot allocation mode, a corresponding channel estimation method, and corresponding simulation results are proposed. Specifically, this method uses two one-dimensional interpolation methods. First, three Lagrangian interpolations are performed in the time domain, and then seven Lagrangian interpolations are performed in the frequency domain to obtain the time-frequency plane of the transmitted data. Channel conditions for subcarriers. The simulation results provided by Siemens show that compared with the ideal channel estimation, Siemens' channel estimation scheme has a performance loss of 0.5-0.7dB for PA3, PB3, and VA30 channels. For VB30 channel, there is even a floor at BLER=0.13. Therefore, if the channel is a long-delay channel, using the Siemens channel estimation method will show a large performance loss.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a method for implementing channel estimation in an OFDM system, so as to reduce the performance loss of the receiver when performing channel estimation.

To achieve the above object, the technical solution of the present invention is achieved in that a method for realizing channel estimation in an OFDM system comprises the following steps:

a. The receiving end obtains the frequency domain receiving signal received by the subcarrier where the pilot frequency is located according to the received time domain receiving signal;

b. Obtain the time-domain channel information at the OFDM symbol according to the received signal in the frequency domain received on the pilot subcarrier of the same OFDM symbol;

c. Estimate frequency-domain channel information at the subcarrier where the data symbol is located by using the obtained time-domain channel information.

Described step b comprises the following steps:

b1. Obtain the time domain channel response at the OFDM symbol according to the received signal in the frequency domain received on the pilot subcarrier located on the same OFDM symbol;

b2. Extract corresponding time-domain channel information from the obtained time-domain channel response.

Said step b1 comprises the following steps:

b11. According to the received signal in the frequency domain and the frequency domain signal on the pilot subcarrier in the corresponding OFDM symbol transmitted by the transmitting end, obtain the frequency domain channel response at the corresponding pilot subcarrier on the corresponding OFDM symbol;

b12. Obtain the time-domain channel response of the pilot subcarrier at the corresponding OFDM symbol according to the frequency-domain channel response.

The step b2 includes: according to the delay extension supported by the system, determine the truncation range from the time domain channel response obtained in step b1, obtain the time domain channel value corresponding to the truncation range in the time domain channel response, and use 0 The truncated time-domain channel value in the time-domain channel response is replaced.

The step b2 includes: determining more than one strongest path in the time-domain channel by analyzing the time-domain channel response at OFDM symbols in continuous time, obtaining the time-domain channel value corresponding to the strongest path, and replacing the time-domain channel value with 0 The unselected time-domain channel values in the above-mentioned time-domain channel response.

The step b2 includes: determining the truncation range by analyzing the time-domain channel response at OFDM symbols in continuous time, obtaining the time-domain channel value corresponding to the truncation range in the time-domain channel response, and replacing the time-domain channel with 0 Unselected time-domain channel values in the response.

Said step c comprises the following steps:

c11. By interpolating and estimating the time domain channel information at the OFDM symbol containing the pilot subcarrier, obtaining the time domain channel information at the OFDM symbol adjacent to the OFDM symbol containing the pilot subcarrier and containing data;

c12. Inverse Fourier transform is performed on the time-domain channel information at the OFDM symbol containing data to obtain corresponding frequency-domain channel information.

In the step c11, the receiving end interpolates and estimates the time-domain channel information at adjacent OFDM symbols containing pilot subcarriers as follows: 2 ^l -1 logarithmic Lagrangian interpolation method is used for interpolation estimation .

Said step c comprises the following steps:

c21. Obtain corresponding frequency domain channel information according to the time domain channel information at the OFDM symbol containing the pilot subcarrier;

c22. According to the obtained frequency domain channel information at the OFDM symbol containing the pilot subcarrier, estimate the frequency domain channel information at the OFDM symbol adjacent to the OFDM symbol containing the pilot subcarrier and containing data.

In the step c21, the OFDM symbols containing pilot subcarriers are OFDM symbols with dense pilot subcarriers.

The step c22 is: directly use the obtained frequency-domain channel information at the OFDM symbol containing the pilot subcarrier as the frequency-domain channel information at the OFDM symbol adjacent to the OFDM symbol and containing data.

The step c22 is: modify the obtained frequency-domain channel information at the OFDM symbol containing the pilot subcarrier, and use the corrected frequency-domain channel information as an OFDM symbol adjacent to the OFDM symbol and containing data channel information in the frequency domain.

The step c22 is: interpolating and estimating the channel information in the frequency domain at the OFDM symbol containing the pilot subcarrier to obtain the channel information in the frequency domain at the OFDM symbol adjacent to the OFDM symbol and containing data.

The interpolation estimate is: use 2 ^l -1 Lagrange interpolation method or 1 Lagrangian interpolation algorithm for interpolation estimation.

According to the solution of the present invention, the receiving end obtains the frequency domain received signal received by the subcarrier where the pilot frequency is located according to the received time domain received signal, and then obtains the frequency domain received signal according to the received frequency domain received signal on the pilot subcarrier located in the same OFDM symbol The time-domain channel information at the corresponding pilot subcarrier on the OFDM symbol, and then estimate the frequency-domain channel information at the subcarrier where the data symbol is based on the time-domain channel information, so that in the case of rapid channel environment changes and high delay can achieve better performance. The solution of the invention strengthens the applicability of the data communication system to the channel environment, improves the performance of the actual channel estimation in the OFDM system, and thus improves the data transmission efficiency of the actual system.

Description of drawings

Fig. 1 is a networking diagram of a typical frequency cellular multiplexing system;

Figure 2 is a schematic diagram of a typical cell omni-directional antenna multiplexing method;

FIG. 3 is a schematic diagram of a typical 120-degree directional antenna multiplexing mode in a cell;

Fig. 4 is a schematic diagram of OFDM symbols;

FIG. 5 is a schematic diagram of a frame structure provided by 802.11a;

FIG. 6 is a schematic diagram of a pilot allocation scheme of 802.11a;

FIG. 7 is a schematic diagram of a pilot grid point method;

FIG. 8 is a schematic flow diagram of transmitting OFDM symbols at the transmitting end;

FIG. 9 is a schematic flow diagram of a receiver receiving OFDM symbols;

Fig. 10 is a schematic diagram of the distribution relationship between pilot OFDM symbols and data OFDM symbols;

FIG. 11 is a schematic structural diagram of a pilot OFDM symbol;

FIG. 12 is a schematic structural diagram of a data OFDM symbol;

Fig. 13 is a schematic diagram of numbering fragments of OFDM symbols in the scheme of the present invention;

FIG. 14 is a schematic diagram of a process of channel estimation at the receiving end in an embodiment of the present invention;

Fig. 15 is a flow chart of the first processing mode in the solution of the present invention;

FIG. 16 is a schematic diagram of a pilot allocation mode of a pilot grid point;

Fig. 17 is a processing flowchart based on pilot grid points in the first processing mode of the present invention;

Fig. 18 is a flowchart of the second processing mode in the solution of the present invention;

Figure 19 is a schematic diagram of the distribution of irregular pilot OFDM symbols and data OFDM symbols;

Fig. 20 is a flow chart of the third processing mode in the solution of the present invention;

Fig. 21 is a schematic diagram of channel estimation performance simulation obtained by adopting the solution of the present invention under the condition of Vehicle A channel and 30kmph when the number of truncated paths is 32;

Fig. 22 is a schematic diagram of channel estimation performance simulation obtained by adopting the solution of the present invention under the condition of Vehicle A channel and 60kmph when the number of truncated paths is 32;

Fig. 23 is a schematic diagram of channel estimation performance simulation obtained by adopting the scheme of the present invention under the condition of Vehicle B channel and 30kmph when the number of truncated paths is 160.

Detailed ways

In the solution of the present invention, the receiving end first needs to receive the OFDM symbols transmitted by the transmitting end, and then perform channel estimation on the received OFDM signals.

First, the process of transmitting OFDM symbols at the transmitting end is briefly described. The transmitter first multiplexes the pilot symbols and data symbols according to the multiplexing method of the pilot symbols and data symbols on the time-frequency plane to generate a frequency domain signal for transmission, and then performs Fourier transform on the frequency domain signal Inverse transformation, digital-to-analog conversion and other processes, and emit the final generated electromagnetic signal. The processing procedure is shown in FIG. 8 .

For the receiving end, after receiving the signal transmitted by the transmitting end, it first performs data sampling on the electromagnetic signal received from the channel; then according to the acquired synchronization information, performs OFDM symbols on the received sampling data in the time domain Extraction, Fourier transform and demultiplexing to form the received pilot symbols and data symbols; then use the received pilot symbols and the pilot symbols transmitted by the transmitter at the corresponding time-frequency positions for channel estimation to obtain the time-frequency plane The channel information in the frequency domain at the time-frequency point where the data is carried on the network. The processing procedure is shown in FIG. 9 .

In the following, the process of channel estimation by the receiving end using the received OFDM symbols including pilot subcarriers in the scheme of the present invention will be further described in detail with reference to the accompanying drawings and specific embodiments.

Specifically, there are three processing methods for channel estimation at the receiving end. The first processing method is: the receiving end first obtains the corresponding frequency domain receiving signal according to the received time domain receiving signal of the subcarrier where the pilot frequency is located; then, according to Obtain the time-domain channel response at the OFDM symbol from the frequency-domain signal received on the pilot subcarrier of the same OFDM symbol; and obtain channel information such as delay and attenuation of the path from the time-domain channel response; Then, according to the time-domain channel information at the OFDM symbol containing the pilot subcarrier, and using a specific interpolation algorithm, the time-domain channel information at the OFDM symbol containing data is estimated; after that, according to the time-domain channel information at the OFDM symbol containing data The domain channel information obtains the frequency domain channel information at the OFDM symbol, that is, the frequency domain channel information at the corresponding subcarrier carrying data.

The second processing method also first obtains the time domain channel information at the OFDM symbol containing the pilot subcarrier according to the time domain received signal of the received pilot subcarrier, the difference is that after obtaining the time domain channel information of the OFDM symbol containing the pilot subcarrier After the time-domain channel information at the OFDM symbol, the corresponding frequency-domain channel information is obtained according to the information, and then the frequency-domain channel information at the OFDM symbol containing data is obtained according to the frequency-domain channel information.

The third processing method is similar to the second processing method, both of which first obtain the frequency domain channel information at the OFDM symbol containing the pilot subcarriers. The difference from the second processing method is that according to the When the frequency domain channel information at the OFDM symbol of the carrier is obtained, the frequency domain channel information at the OFDM symbol containing the pilot subcarrier can be directly used as the frequency domain channel information at the OFDM symbol adjacent to the OFDM symbol and Frequency-domain channel information at OFDM symbols containing data. For the third processing manner, the OFDM symbols containing pilot subcarriers used for channel estimation are preferably those OFDM symbols with dense pilot subcarriers.

Obviously, the above-mentioned first processing method is similar to the second processing method, the difference is: the first processing method first estimates the OFDM symbol containing data after obtaining the time-domain channel information at the OFDM symbol containing the pilot subcarrier The time-domain channel information at the location, and then obtain the corresponding frequency-domain channel information according to the time-domain channel information; the second processing method obtains the time-domain channel information at the OFDM symbol containing the pilot subcarrier, and first obtains the corresponding frequency domain channel information, and then estimate the frequency domain channel information at the OFDM symbol containing data according to the frequency domain channel information. Therefore, the first processing manner will be described in detail below only with a specific embodiment.

In this embodiment, OFDM symbols adopt regular distribution of pilot OFDM symbols and data OFDM symbols in the time domain as the pilot allocation mode, and the receiving end uses the first processing method to perform channel estimation based on this allocation mode.

Firstly, the distribution mode adopted by the OFDM symbols in this embodiment will be described. A specific implementation of this mode is shown in Fig. 10, where there are n data OFDM symbols between two adjacent pilot OFDM symbols. Same as the prior art, the length of the pilot OFDM symbol can be the same as the length of the data OFDM symbol, and it can also be different, and the pilot OFDM symbol and the data OFDM symbol are also composed of a cyclic prefix part and a data part, and the cyclic prefix part is composed of a data part The end loop generation of , where the length of the cyclic prefix part and the data part is the number of sampling points occupied by this part. The structure of the pilot OFDM symbol is shown in Figure 11, where the length of the cyclic prefix part is Np _{, cp} , and the length of the data part is Np _{, data} ; the structure of the data OFDM symbol is shown in Figure 12, where the cyclic prefix The length of the part is N _d,cp and the length of the data part is N _{d data} .

For ease of description, the OFDM symbols shown in Figure 10 are numbered according to the following numbering rules:

Numbering of the pilot OFDM symbols: number the pilot OFDM symbols sequentially according to the time sequence of transmission, wherein the number of the pilot OFDM symbols transmitted first is smaller;

The natural numbers of n data OFDM symbols between adjacent pilot OFDM symbols: sequentially numbered from 1 to n, wherein the number of data OFDM symbols transmitted first is smaller;

Number of data OFDM symbols: Multiply the number of pilot OFDM symbols adjacent to itself and transmitted before itself by the number of data OFDM symbols between adjacent pilot OFDM symbols, and then add the number of data OFDM symbols between the adjacent pilot OFDM symbols Natural numbering between adjacent pilot OFDM symbols.

The numbering fragments of a section of OFDM symbols using the above numbering rules are shown in Figure 13. In the figure, k-1, k, k+1 and k+2 are the numbers of pilot OFDM symbols; n*(k-1)+1 ...n*(k-1)+n is the number of data OFDM symbols between pilot OFDM symbols k-1 and k; n*k+1...n*k+n is pilot OFDM symbols k and k The number of data OFDM symbols between +1; n*(k+1)+1...n*(k+1)+n is the number of data OFDM symbols between pilot OFDM symbols k+1 and k+2 serial number.

Based on the above numbers, assuming that the frequency-domain signal carried by the i-th subcarrier of the k-th pilot OFDM symbol is D _{k, i} , then the frequency-domain signal sequence carried by the k-th pilot OFDM symbol is (D _{k, 0} , Dk _{, 1} , ..., _{Dk, Np, data} ).

Based on the above-mentioned pilot allocation mode, the receiver uses the first processing method to perform channel estimation as shown in Figure 14, and its specific processing process is shown in Figure 15, corresponding to the following steps:

Step 1501. Obtain the channel response in the time domain of the pilot OFDM symbol according to the received time domain pilot OFDM symbol.

Since in the pilot allocation mode adopted in this embodiment, OFDM symbols include pilot OFDM symbols and data OFDM symbols, wherein, pilot OFDM symbols only include pilot subcarriers, and data OFDM symbols only include data, therefore, in the above In the first processing method, the time-domain channel response at the OFDM symbol is obtained according to the frequency-domain signal received on the pilot subcarrier located in the same OFDM symbol, which in this embodiment is received according to the pilot OFDM symbol The frequency domain signal acquires the time domain channel response at the pilot OFDM symbol.

If the time-domain signal sequence received by the kth pilot OFDM symbol is (S _{k, 0} ′, S _{k, 1} ′, ..., S _{k, Np, data} ′), after Fourier transform, such as fast Fourier transform (FFT ), the obtained frequency-domain received signal sequence is (D _{k, 0} ′, D _{k, 1} ′, ..., D _{k, Np, data} ′), since the frequency-domain signal sequence carried by the kth pilot OFDM symbol is (D _{k, c} , D _{k, 1} ,..., D _{k, Np, data} ), so the frequency-domain channel response at the kth pilot OFDM symbol is $(\frac{{\mathrm{D.}}_{k,0}^{\′}}{{\mathrm{D.}}_{k,0}},\frac{{\mathrm{D.}}_{k,1}^{\′}}{{\mathrm{D.}}_{k,1}},\·\·\·,\frac{{\mathrm{D.}}_{k,N_{p,\mathrm{data}}}^{\′}}{{\mathrm{D.}}_{k,N_{p,\mathrm{data}}}}),$ It is abbreviated as (C _{k, 0} ^p , C _{k, 1} ^p , ..., C _{k, Np, data} ^p ). Perform inverse Fourier transform on the obtained frequency domain responses (C _{k, 0} ^p , C _{k, 1} ^p , ..., C _{k, Np, data} ^p ), such as inverse fast Fourier transform (IFFT), to obtain the kth The time-domain channel response of the channel at the pilot OFDM symbol is abbreviated as (c _{k, 0} ^p , ck _{, 1} ^p , . . . , c _{k, Np, data} ^p ).

Step 1502, extracting time-domain channel information at the pilot OFDM symbol according to the time-domain channel response at the pilot OFDM symbol. The time-domain channel information includes path delay, path attenuation, and the like.

After obtaining the time-domain channel response at the pilot OFDM symbol, in order to reduce channel noise, it is necessary to analyze the information to obtain effective channel information.

There are two ways to acquire channel information, one is the simple truncation method, which can be used when the channel delay range of the wireless transmission environment is known; the other is an adaptive channel information extraction method.

For the simple truncation method, the truncation range can be determined according to the time delay extension supported by the system. For example, assuming that the delay of the channel is at most N sampling points, the pilot OFDM symbol obtained in step 1502 can be directly Time-domain channel response (c _{k, 0} ^p , c _{k, 1} ^p ,..., c _{k, Np, data} ^p ) is truncated, and the range of truncation is slightly larger than the number of sampling points corresponding to the maximum delay of the channel, for example, The truncation range is N', and N'≥N. The time-domain channel at the kth pilot OFDM symbol obtained at this time is (c _{k, 0} ^p , c _{k, 1} ^p ,..., c _{k, N′} ^p , 0,..., 0), where the The number is N _{p, data} -N'.

Specifically, the adaptive channel information extraction method is through the time-domain channel response (c _{k, 0} ^p , c _{k, 1} ^p , ..., c _{k, Np, data} ^p ) to analyze, and select a part of the strongest path as the effective path, the selected effective path does not have to be continuous. For example, (c _{k, i0} ^p , c _{k, i1} ^p , . . . , c _{k, i, i} ^p ) may be selected as valid channel information for this period of time. After the effective channel information is determined, the unselected time-domain channel values in the time-domain channel response of the pilot OFDM symbols are replaced with 0, so that the time-domain channel information of the pilot OFDM symbols can be obtained.

In addition, the above adaptive channel information extraction method can also be simplified, for example, truncation can be incorporated into the method. The simplified method is called an adaptive truncation method. Specifically, the method first needs to determine the truncation length N'. When determining N', the time-domain channel response ( c _{k, 0} ^p , c _{k, 1} ^p ,..., c _{k, Np, data} ^p ) are analyzed to determine the area where the energy is concentrated, and the length corresponding to this area is taken as N', which is The determined truncation length, obtain all the time domain channel values corresponding to N' before, and then use 0 to replace the time domain channel response at the pilot OFDM symbol that is not selected, that is, all time domain channel values after N' , thus determining the time-domain channel information.

Step 1503, using the time-domain channel information at the adjacent pilot OFDM symbols and using a specific interpolation algorithm to estimate the time-domain channel information at the data OFDM symbols.

After obtaining the time-domain channel information (c _k,0 ^p , c _k,1 ^p ,…, _ck,N′ ^p ,0,…,0) at the pilot OFDM symbol, we can further estimate The time-domain channel information of the channel at the data OFDM symbol (c _{s, 0} ^d , c _{s, 1} ^d , ..., c _{s, N′} ^d , 0, ..., 0), where s is the number of the data OFDM symbol.

Specifically, c _k*n+j can be estimated by using (..., c _{k-1, i} ^p , c _{k, i} ^p , c _{k+1, i} ^p , c _{k+2, i} ^p , ...), The value of _i ^d , where j is the natural number in those data OFDM symbols between two adjacent pilot OFDM symbols.

The value of c _{k*n+j, i} ^d can be estimated by 2l-1 Lagrangian interpolation, and the typical estimation formula is:

${\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\overset{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

Among them, c _{k+m, i} ^p represents the time domain channel value at the i-th sampling point at the k+m pilot OFDM symbol, c _{k*n+j, i} ^d represents the k*n+j data The time-domain channel value at the i-th sampling point at the OFDM symbol, n represents the number of data OFDM symbols between two adjacent pilot OFDM symbols.

When a Lagrangian interpolation is used, that is, linear interpolation, the above formula can be simplified as:

${\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span>$

Among them, c _{k, i} ^p represent the time-domain channel value at the i-th sampling point at the k-th pilot OFDM symbol, c _{k*n+j, i} ^d represent the k-th data OFDM symbol at the k*n+j-th The time-domain channel value at the i sampling point, n represents the number of data OFDM symbols between two adjacent pilot OFDM symbols.

2l-1 logarithmic Lagrangian interpolation can also be used, and the typical estimation formula is as follows:

$\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\underset{\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}}{\overset{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\frac{\underset{\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; l</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{\mathrm{<span\; class="notranslate">\; l</span>}}{\mathrm{<span\; class="notranslate">\; \&Pi;</span>}}}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; q</span>}<span\; class="notranslate">\; )</span>}{<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

Among them, c _{k+m, i} ^p represents the time domain channel value at the i-th sampling point at the k+m pilot OFDM symbol, c _{k*n+j, i} ^d represents the k*n+j data The time-domain channel value at the i-th sampling point at the OFDM symbol, n represents the number of data OFDM symbols between two adjacent pilot OFDM symbols.

Similarly, when a logarithmic Lagrangian interpolation is used, that is, a logarithmic linear interpolation, the above formula can be simplified as:

$\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; *</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; ln</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; )</span>$

Among them, c _{k, i} ^p represent the time-domain channel value at the i-th sampling point at the k-th pilot OFDM symbol, c _{k*n+j, i} ^d represent the k-th data OFDM symbol at the k*n+j-th The time-domain channel value at the i sampling point, n represents the number of data OFDM symbols between two adjacent pilot OFDM symbols.

Through any of the above formulas, the value of (c _{s, 0} ^d , c _{s, 1} ^d , ..., c _{s, N′} ^d ) can be estimated, and N _{d, data} -N′ 0s are added behind it, then (c _{s, 0} ^d , c _{s, 1} ^d , ..., c _{s, N′} ^d , 0, ..., 0) can be obtained.

Step 1504, using the obtained time-domain channel information at the data OFDM symbol to obtain frequency-domain channel information at the data OFDM symbol.

Specifically, it is the time-domain channel response (c _{s, 0} ^d , c _{s, 1} ^d , ..., c _{s, N′} ^d , 0, ..., 0 ) to perform IFFT to obtain the frequency domain response (C _{s, 0} ^d , C _{s, 1} ^d , ..., C _{s, Nd, data} ^d ) of the channel at the sth data OFDM symbol.

Through the above steps, when the distribution of pilot OFDM symbols and data OFDM symbols in the regular time domain is used as the pilot allocation mode, the first processing method is used for channel estimation.

Of course, this process can also be used in other pilot allocation modes, for example, for channel estimation in the pilot allocation mode based on pilot grid points. The specific process is similar to the above process, so only it will be processed below A brief description of the process. A pilot allocation mode based on pilot grid points is shown in FIG. 16 . Based on the pilot allocation mode, the specific flow of the first processing method is shown in Figure 17, corresponding to the following steps:

Step 1701, the receiving end obtains the frequency-domain reception signal of the subcarrier where the pilot frequency is located according to the received time-domain reception signal.

Step 1702, according to the received signal in the frequency domain received on the pilot subcarrier of the same OFDM symbol, obtain the channel response in the time domain at the corresponding OFDM symbol.

Step 1703. Obtain time domain channel information from the time domain channel response. The time-domain channel information may be path delay, path attenuation, and the like.

Step 1704, according to the time-domain channel information at the OFDM symbol containing the pilot subcarrier, and using a specific interpolation algorithm, estimate the time-domain channel information at the OFDM symbol adjacent to the OFDM symbol and containing data.

Step 1705: Obtain frequency domain channel information at the corresponding subcarrier carrying data according to the time domain channel information at the OFDM symbol containing data.

The first processing method has been described in detail above. Since the second processing method is basically similar to the first processing method, only a brief description will be given of the channel estimation process using the second processing method. Still taking the distribution of pilot OFDM symbols and data OFDM symbols in the regular time domain as the pilot allocation mode as an example, the specific process of channel estimation is shown in Figure 18, corresponding to the following steps:

Step 1801. Obtain the channel response in the time domain of the pilot OFDM symbol according to the received time domain pilot OFDM symbol.

This process is the same as step 1501 in the above processing method.

Step 1802, extract time-domain channel information at the pilot OFDM symbol from the time-domain channel response of the channel at the pilot OFDM symbol. The time-domain channel information includes path delay, path attenuation, and the like.

This process is also the same as step 1502 in the above processing method.

Step 1803, using the obtained time-domain channel information at the pilot OFDM symbol to obtain frequency-domain channel information at the corresponding pilot OFDM symbol.

Step 1804, using the frequency-domain channel information at the adjacent pilot OFDM symbols, and using an interpolation method to estimate the frequency-domain channel information at the data OFDM symbols.

The interpolation method used in step 1804 may be a 2l-1 Lagrangian interpolation method.

Next, the above-mentioned third processing mode will be described by taking the distribution of irregular pilot OFDM symbols and data OFDM symbols as a pilot allocation mode as an example.

The distribution of irregular pilot OFDM symbols and data OFDM symbols is shown in Figure 19. The number of data OFDM symbols contained between every two adjacent OFDM symbols can be different. This pilot allocation mode is more suitable for channel A slow-changing situation. For this pilot allocation mode, since the OFDM symbols include pilot OFDM symbols and data OFDM symbols, and the pilot OFDM symbols only contain pilot subcarriers, and the data OFDM symbols only contain data, the receiving end adopts the third The processing method is specifically to estimate the frequency domain channel information of the data OFDM symbols according to the pilot OFDM symbols. The processing process is as shown in Figure 20, and specifically includes the following steps:

Step 2001. Obtain the channel response in the time domain of the pilot OFDM symbol according to the received time domain pilot OFDM symbol.

Step 2002, extracting time-domain channel information at the pilot OFDM symbol according to the time-domain channel response at the pilot OFDM symbol. The time-domain channel information includes path delay, path attenuation, and the like.

Step 2003, using the obtained time-domain channel information at the pilot OFDM symbol to obtain the frequency-domain channel information at the pilot OFDM symbol.

Step 2004, directly use the obtained frequency-domain channel information at the pilot OFDM symbol as the frequency-domain channel information of the data OFDM symbol between the pilot OFDM symbol and the next pilot OFDM symbol.

Of course, it is also possible to modify the obtained frequency-domain channel information at the pilot OFDM symbol, and use the corrected frequency-domain channel information as the frequency of the data OFDM symbol between the pilot OFDM symbol and the next pilot OFDM symbol. Domain channel information.

The solution of the present invention can achieve better performance in the case of channel environment changes and high delay. Specifically, through the solution of the present invention, compared to the ideal channel estimation, when the number of truncated paths is 32, the channel estimation results of Vehicle A channel and 30kmph are shown in Figure 21, and the performance loss is less than 0.3dB; Vehicle The channel estimation results of channel A and 60kmph are shown in Figure 22, and the performance loss is less than 1.1dB. When the number of truncated paths is 160, in the case of Vehicle B channel and 30kmph, as shown in Figure 23, the channel estimation obtained by using the scheme of the present invention has a performance loss of less than 0.7dB compared to the ideal channel estimation.

The above descriptions are only preferred embodiments of the solutions of the present invention, and are not intended to limit the protection scope of the present invention.

Claims (14)

1, a kind of method that realizes channel estimating in orthogonal multi-path frequency-division duplicating system is characterized in that this method may further comprise the steps:

A. receiving terminal obtains the frequency domain received signal that pilot tone place subcarrier receives according to the time domain received signal that receives;

B. according to being positioned at the frequency domain received signal that receives on the pilot sub-carrier of same orthogonal multi-path frequency-division duplicating OFDM symbol, obtain the time domain channel information at this OFDM symbol place;

C. utilize the frequency domain channel information at the subcarrier place, time domain channel information data estimator symbol place that obtains.

2, method according to claim 1 is characterized in that, described step b may further comprise the steps:

B1. according to being positioned at the frequency domain received signal that receives on the pilot sub-carrier of same OFDM symbol, obtain the time domain channel reaction at this OFDM symbol place;

B2. from the time domain channel reaction that obtains, extract corresponding time domain channel information.

3, method according to claim 2 is characterized in that, described step b1 may further comprise the steps:

B11. according to described frequency domain received signal, and the frequency-region signal on the pilot sub-carrier in the corresponding OFDM symbol of transmitting terminal emission, the frequency domain channel reaction of obtaining corresponding pilot sub-carrier place on the corresponding OFDM symbol;

B12. obtain the time domain channel reaction of corresponding OFDM symbol place pilot sub-carrier according to described frequency domain channel reaction.

4, method according to claim 2, it is characterized in that, described step b2 comprises: according to the time delay expansion that system supported, from the time domain channel reaction that step b1 obtains, determine the scope of blocking, obtain this and block scope corresponding time domain channel value in described time domain channel reaction, and replace the time domain channel value that quilt is clipped in the described time domain channel reaction with 0.

5, method according to claim 2, it is characterized in that, described step b2 comprises: the time domain channel reaction at the OFDM symbol place by analyzing continuous time, determine in the time domain channel most powerful path of one or more, obtain the pairing time domain channel value of described most powerful path, and replace not selected time domain channel value in the described time domain channel reaction with 0.

6, method according to claim 2, it is characterized in that, described step b2 comprises: the scope of blocking is determined in the time domain channel reaction at the OFDM symbol place by analyzing continuous time, obtain this and block scope corresponding time domain channel value in described time domain channel reaction, and replace not selected time domain channel value in the described time domain channel reaction with 0.

7, method according to claim 1 is characterized in that, described step c may further comprise the steps:

C11. estimate by the time domain channel information at the OFDM symbol place that comprises pilot sub-carrier is carried out interpolation, obtain adjacent and comprise the time domain channel information at the OFDM symbol place of data with the described OFDM symbol that comprises pilot sub-carrier;

C12. the time domain channel information at the OFDM symbol place that comprises data is carried out inverse fourier transform, obtain corresponding frequency domain channel information.

8, method according to claim 7, it is characterized in that among the described step c11 that described receiving terminal carries out interpolation to time domain channel information adjacent and that comprise the OFDM symbol place of pilot sub-carrier and is estimated as: adopt 2l-1 logarithm lagrange-interpolation to carry out interpolation and estimate.

9, method according to claim 1 is characterized in that, described step c may further comprise the steps:

C21. obtain corresponding frequency domain channel information according to the time domain channel information that comprises the OFDM symbol place of pilot sub-carrier;

C22. according to the frequency domain channel information at the OFDM symbol place that comprises pilot sub-carrier of gained, estimate adjacent and comprise the frequency domain channel information at the OFDM symbol place of data with the described OFDM symbol that comprises pilot sub-carrier.

10, method according to claim 9 is characterized in that among the described step c21, and the described OFDM symbol that comprises pilot sub-carrier is the intensive OFDM symbol of pilot sub-carrier.

11, method according to claim 9, it is characterized in that described step c22 is: directly with the frequency domain channel information at the OFDM symbol place that comprises pilot sub-carrier of gained as adjacent with described OFDM symbol and comprise the frequency domain channel information at the OFDM symbol place of data.

12, method according to claim 9, it is characterized in that, described step c22 is: the frequency domain channel information to the OFDM symbol place that comprises pilot sub-carrier of gained is revised, and with revised frequency domain channel information as adjacent with described OFDM symbol and comprise the frequency domain channel information at the OFDM symbol place of data.

13, method according to claim 9, it is characterized in that, described step c22 is: the frequency domain channel information at the OFDM symbol place that comprises pilot sub-carrier is carried out interpolation estimate, obtain adjacent with described OFDM symbol and comprise the frequency domain channel information at the OFDM symbol place of data.

14, according to claim 7 or 13 described methods, it is characterized in that described interpolation is estimated as: adopt 2l-1 lagrange-interpolation or 1 Lagrange's interpolation algorithm to carry out interpolation and estimate.

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