CN1269325C - Channel estimation method for WCDMA communication system - Google Patents

Abstract

The invention discloses a channel estimation method for a wideband code division multiple access system. First, descramble and despread the wideband spread spectrum signal input to a RAKE receiver, and then despread it with a spread spectrum code to obtain special physical Control channel and dedicated physical data channel; then calculate the initial channel estimation value, for the continuous dedicated physical control channel symbol string after decorrelation operation, use the algorithm of arithmetic mean to find the channel estimation value Cem at the corresponding moment of the window; finally, Cem compensation The window corresponds to the dedicated physical data channel symbol at time m, and each multipath compensated result is output to the maximum ratio combining module. The method of the present invention overcomes the disadvantages in the prior art that the channel estimation value cannot reflect the channel characteristics when the channel deteriorates, which leads to an increase in the misjudgment rate and poor performance, and can effectively improve the performance in the mobile communication environment, especially at high speeds. The channel estimation accuracy in the mobile communication environment, thus ensuring the high performance of the system.

Description

Channel Estimation Method for Wideband Code Division Multiple Access Communication System

technical field

The present invention relates to a channel estimation method of a wireless communication system, in particular to a channel estimation method of a Wideband Code Division Multiple Access (WCDMA, Wide CDMA) communication system.

Background technique

With the rapid development of mobile communication, people have higher and higher requirements for the quality of mobile communication and the types of services it provides. The proposal and development of the third generation of mobile communication is exactly in line with this demand of people, so it has attracted much attention. . Wideband Code Division Multiple Access (WCDMA, Wide CDMA) is a Radio Transmission Technology (RTT) solution proposed by the ^3rd Generation Partnership Project (3GPP), which can not only provide high-quality voice services , and can provide multimedia services similar to fixed networks.

As shown in Figure 1, in a WCDMA system, in order to improve the uplink quality, some pilot symbols are added to the uplink Dedicated Physical Control Channel (DPCCH) for channel estimation and coherent detection. The transmission of pilot symbols is discontinuous. According to different slot formats, the number of pilot symbols in each slot is between 3 and 8. Therefore, what method is used to accurately estimate the pilot in a slot The channel characteristics corresponding to the symbol segment and the data symbol segment are extremely important to improve the receiving performance of the receiver in a high-speed mobile environment.

At present, the more commonly used channel estimation methods mainly include the following: single-slot average channel estimation method, channel estimation method based on simplified Kalman tracking filter, and multi-slot weighted average channel estimation method (Weighted Multi-Slot Averaging, WMSA) And Iterative Channel Estimation (ICE).

The single-slot average channel estimation method has less pilot symbols and cannot effectively filter out the influence of noise, so its performance is poor no matter in low-speed or high-speed mobile environments. The channel estimation method based on simplified Kalman tracking filter is an improvement of the former, and its performance is improved in low-speed mobile environment, but its performance is still poor in high-speed mobile environment.

The estimation process of the multi-slot weighted average channel estimation method (WMSA, Weighted Multi-SlotAveraging) is as follows: 1) use the single-slot average channel estimation method to obtain the channel estimation value of each time slot; Values are weighted and combined to obtain the channel estimation value of the current time slot. Since the weighted average is performed between multiple time slots, the influence of noise is effectively filtered, so in the case of slow signal fading, this method can obtain good channel estimation performance, but as the channel deteriorates, such as the speed of movement increases, due to The estimated value cannot well reflect the channel characteristics at different periods in the time slot, so the performance deteriorates.

The iterative channel estimation (ICE) method is also widely used at present. The corresponding patent has the publication number 1384627 "A Channel Estimation Method for Wideband Code Division Multiple Access System". The weighted average (WMSA) obtains the channel estimation value of the current time slot of each path, compensates and combines the dedicated physical control channel (DPCCH, Dedicated Physical Control Channel), performs hard judgment on the combined result, and takes out the data segment symbol after the judgment as The virtual pilot is fed back to re-estimate the channel for the data segment symbols. In order to improve the accuracy, this process can be iterated multiple times. Because it is based on the multi-slot weighted average (WMSA) method, the channel estimation and compensation of the data segment still only use the information of the pilot part. As the channel deteriorates, the performance of the multi-slot weighted average (WMSA) method becomes worse. , the misjudgment rate of hard decisions increases after merging, which will definitely lead to a decrease in the performance of the method.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art that the channel estimation value cannot reflect the channel characteristics in the case of channel deterioration, resulting in an increase in misjudgment rate and poor performance, in order to propose a method that can effectively improve performance in mobile communication environments, especially in mobile communication environments. It is the channel estimation accuracy in the high-speed mobile communication environment, thereby ensuring a high-performance channel estimation method.

To achieve the above object, the present invention proposes a channel estimation method for wideband code division multiple access system, it is characterized in that, comprises the following steps:

Step 1: Descrambling and despreading the broadband spread spectrum signal input to the RAKE receiver;

The second step: extract the pilot symbols from the current and future time slot (hereinafter referred to as "the next time slot") of the dedicated physical control channel (DPCCH, Dedicated Physical Control Channel) according to the known time slot format; Pilot symbols, each pilot symbol is decorrelated with known pilot symbols to obtain the initial channel estimation value of each pilot symbol; the initial channel estimation value of all pilot symbols in each time slot is arithmetically averaged, Obtain the initial channel estimation value of each time slot;

Step 3: For the pilot part, use a moving window, set the window length to L, and the window covers the channel estimation value of the current pilot symbol in the current time slot and the channel estimation value of the historical L-1 symbols, where the historical symbols The channel estimation value includes not only the channel estimation value of pilot symbols obtained by ideal pilot decorrelation, but also the channel estimation value of non-pilot symbols (see step 5 for the method of calculating the channel estimation value of non-pilot symbols). The average value in the window is the channel estimation value at the corresponding moment in the middle of the window or at a certain suitable moment, and this value is also the channel estimation value finally output by the channel estimation module and used to compensate DPDCH (Dedicated PhysicalData Channel) data. A suitable moment here refers to a certain position in the middle of the window that is biased towards the current moment. The main reason is that when the moving speed is slow, a larger L value will be set, which will require more data memory. In order to take into account hardware resources, you can This consideration is an opportune moment. The biggest difference between this and the prior art is that the window contains both pilot information and non-pilot information. Effectively improve the performance of channel estimation. For non-pilot symbols, first use the result of the previous window and the average value of the channel estimation value of the next time slot as the channel estimation value of the current symbol to compensate the current symbol, and then do Maximal RatioCombining (MRC, Maximal RatioCombining), make a hard decision on the combined result, so that the virtual ideal non-pilot of the current non-pilot symbol is obtained (the so-called virtual means that we do not know it in advance, but we based on For other known information, the value when it is sent by the transmitting end is estimated with a high degree of reliability). The channel estimation value of the current non-pilot symbol is obtained by performing decorrelation operation on the currently received non-pilot symbol with the dummy value. Finally, use the same method as Step 4 to obtain the channel estimation value at the time corresponding to the middle position of the current window or at an appropriate time. Here, there is also an important difference from the prior art. This method not only uses the pilot part information of future time slots, current time slots, and even historical time slots, but also uses the estimated non-guided frequency information contained in the current window. The information of the frequency part further effectively improves the performance of channel estimation.

Step 4: Use the channel estimation value output by the window to perform compensation calculation on the DPDCH (Dedicated Physical Data Channel) at the middle position of the window or at a certain suitable time. The compensated data is combined with all multipaths according to the maximum ratio combination algorithm, and the obtained The result is sent to the decoding module.

Compared with the prior art, the channel estimation method of the present invention makes full use of the estimated non-pilot information many times, fully utilizes all available information in a limited moving window, and effectively , significantly improving the performance of the channel estimation module. Using the channel estimation method described in the invention, the channel estimation value of each symbol position in a time slot can be obtained more accurately than the prior art, and can reflect the channel at different times in a time slot when the channel fading is slow or fast Therefore, the receiving performance of the communication system can be greatly improved. Simulation results show that no matter when the moving speed is slow or fast, the performance of the channel estimation method described in the present invention is obviously improved compared with the channel estimation performance of the prior art.

Description of drawings

Fig. 1 is the frame structure of WCDMA system uplink dedicated physical channel (DPCH, Dedicated PhysicalChannel);

Fig. 2 is a schematic diagram of an existing multi-slot weighted average channel estimation method.

Fig. 3 is a block diagram of implementing the channel estimation method of the present invention.

Fig. 4 is a flow chart of the channel estimation method of the present invention.

Fig. 5 is a flowchart of an iterative algorithm in the channel estimation method of the present invention.

Fig. 6 is a schematic diagram of the moving window arithmetic mean method in the channel estimation method of the present invention.

Fig. 7 is a schematic diagram of a method for calculating channel estimation values of non-pilot symbols in the channel estimation algorithm of the present invention.

Detailed ways

The implementation of the technical solution will be further described in detail below in conjunction with the accompanying drawings. According to these drawings, those skilled in the art can easily realize the present invention.

The present invention mainly proposes a channel estimation method for WCDMA system uplink channel based on moving window arithmetic mean which fully utilizes pilot frequency and non-pilot frequency information, so as to improve the receiving performance of the communication system in the mobile environment.

Fig. 1 is the frame structure of the WCDMA system uplink dedicated physical channel (DPCH); in order to distinguish the data field in the DPDCH and the data field in the DPCCH, the data field in the DPCCH is specially identified as a non-pilot field.

Fig. 2 is a schematic diagram of a multi-slot weighted average channel estimation algorithm in the prior art. In this specific method, the multi-slot weighted average channel estimation method is used to calculate the channel estimation value of time slot 2. The specific process is: firstly, the channel estimation value of each pilot symbol in the time slot is arithmetically averaged to obtain the channel estimation value of time slot 1 respectively. , 2, 3 and 4 channel estimates, and then perform weighted average among adjacent four time slots according to the weights corresponding to each time slot in the figure, to obtain the final channel estimate of time slot 2, namely

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; E.</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; /</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}{\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>$

是时隙2的最终信道估计值，E_i，α_i分别是各时隙内算术平均得到的信道估计值和进行多时隙加权平均时各时隙对应的权值。现有技术中的迭代信道估计法，就是用

去补偿时隙2中的非导频数据，然后经过最大比合并、硬判决得到虚拟的已知非导频数据，再与解扩后的DPCCH中的非导频符号做解相关运算，得到非导频符号的信道估计值，从而得到整个时隙2的所有符号的信道估计值，再经过多时隙加权平均得到各个时隙的信道估计，该方法比普通的多时隙加权平均方法性能略好。In the formula

is the final channel estimation value of time slot 2, E _i , α _i are the channel estimation value obtained by the arithmetic mean in each time slot and the weight value corresponding to each time slot when multi-slot weighted averaging is performed, respectively. The iterative channel estimation method in the prior art is to use

To compensate the non-pilot data in time slot 2, and then obtain the virtual known non-pilot data through maximum ratio combination and hard decision, and then perform decorrelation operation with the non-pilot symbols in the despread DPCCH to obtain the non-pilot data The channel estimation value of the pilot symbols is used to obtain the channel estimation value of all symbols in the entire time slot 2, and then the channel estimation of each time slot is obtained through multi-slot weighted average. This method has slightly better performance than the ordinary multi-slot weighted average method.

Fig. 3 is the implementation block diagram of the channel estimation method of the present invention, which has illustrated the position of the modules of the channel estimation method of the present invention to be implemented in the whole WCDMA RAKE receiver. In this example, the AD converter 301 converts the analog signal input to the receiver into a digital signal and sends it to the descrambling and despreading module 304. The multipath scrambling code descrambles and despreads the input signal, and sends each multipath signal after descrambling and despreading to its corresponding channel estimation and compensation module 305, and the channel estimation and compensation module 305 calculates each symbol of DPCCH respectively Compensate the dedicated channel DPDCH for the channel estimation value at the corresponding time, output the compensated signals of each path to the maximum ratio combination module 306 for maximum ratio combination, and finally input the combined signal into the deinterleaving/decoder 307 for decoding Interleave and decode to obtain the original signal transmitted by the transmitter. The position of the channel estimation method proposed in the present invention in the implementation block diagram is the channel estimation and compensation module 305 .

Fig. 4 is a flow chart of the channel estimation method of the present invention, which illustrates the preparatory work that should be done before implementing the channel estimation method of the present invention, and the whereabouts of the processing results after completion.

This logic flow starts at step 401 and ends at step 404 .

Step 401 performs descrambling and despreading on the broadband spread spectrum signal input to the RAKE receiver. Because the signal received by the RAKE receiver is scrambled and spread, it needs to be descrambled first with the corresponding scrambling code, that is, the scrambling code is multiplied by the conjugate of the received signal, and then it is despread with the spreading code , to obtain DPCCH (Dedicated Physical Control Channel, dedicated physical control channel) and DPDCH (Dedicated Physical Data Channel dedicated physical data channel), which is the preparation work for the following steps, and only the signal after descrambling and despreading can be used for further channeling estimated processing.

Enter step 402 in order to calculate the initial channel estimation value. Extract the pilot symbols from the current and future time slot (hereinafter referred to as "the next time slot") of the dedicated physical control channel (DPCCH, Dedicated Physical Control Channel) according to the known time slot format; for the extracted pilot symbols, Each pilot symbol is decorrelated with the known pilot symbols to obtain the initial channel estimation value of each pilot symbol; the arithmetic average of the initial channel estimation values of all pilot symbols in each time slot is obtained to obtain the channel estimation value of each time slot The initial channel estimate of .

Enter step 403 sequentially, for the continuous DPCCH symbol strings that have undergone decorrelation operations, move the window symbol by symbol one by one, and use the algorithm of arithmetic mean to obtain the channel estimation value CEm at the corresponding moment of the window. This step is the core part of this method. Figure 5 will do a very specific and detailed description.

Enter step 404 in sequence, use the CEm compensation window obtained in step 403 to correspond to the DPDCH symbol at time m. The results after each multipath compensation are output to the maximum ratio combining module.

Fig. 5 is a flowchart of an iterative algorithm in the channel estimation method of the present invention, which illustrates in detail the calculation flow of the channel estimation method of the present invention. This figure is the core part of the channel estimation method involved in the present invention, that is, how to use both pilot and non-pilot information to obtain the most accurate channel estimation method through a moving window. Figure 5 is a detailed flow chart of the method, which is step 403 refinement. The logic flow starts at step 501 and ends at step 512 .

Step 501, from all the symbols of the descrambled and despreaded current slot and the next slot obtained in step 402, from the first symbol of the current slot to the last symbol of the current slot, symbol by symbol Sent to step 502, one enters the next symbol after going through the whole process of Fig. 5 .

Step 502, judge whether the current symbol Sn delivered by step 501 is the first non-pilot symbol in the current time slot according to the known time slot format (Slot Format), if it is stepping to step 506, if not stepping to 503.

Step 503, judge whether the current symbol Sn is a pilot symbol according to the known time slot format, if yes, go to step 505.1, if not, go to step 507.

Step 504, generate a pilot sequence according to the known time slot format for use in step 505.1.

In step 505, a decorrelation operation is performed on the received symbol and the known symbol (or the estimated symbol), and the decorrelation operation is actually multiplication, that is, the symbol is removed. The known symbol in step 505.1 is the symbol corresponding to the current position in the pilot symbol sequence locally generated in step 504 according to the known time slot format. The known symbols in step 505.2 are actually estimated through steps 507, 508, 509, and 510, because in general, under the comparison of the physical channel BER of DPCCH, the estimated symbols can be approximately used as known symbols for decorrelation operation. Step 511 after step 505 operation.

Step 506, just step into this step when step 502 receives the first non-pilot symbol, this step obtains all pilot symbols of the next time slot from the output result of 402, and then uses according to known time slot format The known pilot sequence is obtained, and the decorrelation operation is performed on the pilot symbols of the next time slot one by one, and then the CE _next-slot is obtained by averaging the results after the decorrelation operation. Finally, save the CEnext-slot, because it will be used when estimating all non-pilot symbols.

Step 507, as shown in Figure 7, simply calculate the average value of CE _m-1 and CE _next-slot to obtain the pre-channel estimated value C'n of the current non-pilot symbol, that is, C'n=(CE _n-1 +CE _next-slot )/2. Among them, CE _m-1 is the result obtained from the previous symbol S _n-1 through the entire process in FIG. 5 , and CE _next-slot is the result obtained in step 506 . FIG. 7 is a schematic diagram of solving the pre-channel estimation value of the current non-pilot symbol, which is a graphical illustration of step 507. C'n will be used to estimate the original symbol of Sn at the transmitter.

Step 508, use C'n to compensate Sn to obtain the compensated current non-pilot symbol S'n.

Step 509, combining the S'n in all multipaths by the maximum ratio combination method to obtain the combined symbol S'n-source.

就是发射端原符号Sn-source的估计值。Step 510, making a hard decision on S'n-source, ${\hat{S}}_{\mathrm{no}-\mathrm{source}}=(S\text{'}\mathrm{no}-\mathrm{source}\&Greater\; Equal;0)?1:-1,$ So

is the estimated value of the original symbol Sn-source at the transmitter.

Step 511, judge whether the current symbol Sn is a pilot symbol according to the known time slot format, if the selection switch points to the left to receive the output result of 505.1, if not, select the switch to point to the right to receive the output result of 505.2.

Step 512, as shown in Figure 6, move the window so that the window covers Cn-L+i.....Cn, calculate the arithmetic mean value of the channel estimation value in the window, and obtain the final channel estimation value at time m corresponding to the window CEm, namely $\mathrm{CEm}=\frac{1}{L}\underset{i=1}{\overset{L}{\mathrm{\&Sigma;}}}{C}_{\mathrm{no}-L+i},$ Among them, m>=n-int(L-1)/2, int is an integer rounded down, L is the window length, L takes a value of 6-60 according to the moving speed, the slower the speed, the larger the value of L, and L can be It is determined based on the moving speed estimated by Doppler frequency offset. When m=n-int(L-1)/2, time alignment during compensation will have the best performance, but for slow fading, that is, when L is relatively large, a large hardware storage space will be required, so generally ( A compromise value between n-int(L-1)/2, n). CEm is the final channel estimation value at time m, which will be used to make final compensation for DPDCH (Dedicated Physical Data Channel), and the compensation result can be sent to the decoder after MRC (Maximal RatioCombining) decoding.

Claims (3)

1, a kind of channel estimation methods that is used for broadband CDMA system is characterized in that, may further comprise the steps:

Step 1: the wideband spread-spectrum signal to the input RAKE receiver carries out descrambling and de-spreading, obtains Dedicated Physical Control Channel and Dedicated Physical Data Channel respectively;

Step 2: calculate channel estimation value: in the current of Dedicated Physical Control Channel and next time slot, take out frequency pilot sign according to known time slot format; To the frequency pilot sign that extracts, each frequency pilot sign and known pilot symbols are carried out the decorrelation computing, obtain the channel estimation value of each frequency pilot sign;

Step 3: in all symbol strings for the current time slots of continuous Dedicated Physical Control Channel through the decorrelation computing and next time slot, from first symbol of current time slots S1, till last symbol SL of current time slots, be total to L symbol, symbol ground moving window one by one, L is length of window, for the pilot tone in the current time slots, the pilot frequency sequence of learning according to time slot format carries out participating in the window arithmetic average after the decorrelation and obtains channel estimation value CEm; For the non-pilot tone of current time slots, first pilot average value CE with next time slot _Next-slotWith nearest channel estimation results CE _M-1Ask the pre-channel estimation value C ' n of average this non-frequency pilot sign of conduct, C ' n is carried out channel compensation and maximum ratio merging, according to the hard decision result after merging this non-pilot tone is carried out decorrelation then, the result after the decorrelation participates in the window arithmetic average and obtains channel estimation value CEm; Wherein subscript m is a channel estimation value index in time, and n is a Dedicated Physical Control Channel symbol index in time;

Step 4: with the corresponding m constantly of the channel estimation value CEm backoff window Dedicated Physical Data Channel symbol constantly that step 3 obtains, the result after each multipath compensation exports to high specific and merges module.

2, the channel estimation methods that is used for broadband CDMA system according to claim 1 is characterized in that, described step 3 specifically realizes by following steps:

In all symbols for the current time slots behind the descrambling and de-spreading and next time slot, from first symbol of current time slots S1, till last symbol SL of current time slots, enter following flow process a symbol of a symbol, previous symbol is imported next symbol after finishing whole flow process again;

Whether, be first non-frequency pilot sign in current time slots, subscript n is a Dedicated Physical Control Channel symbol index in time, if step to step (5), steps to step (2) if not according to known time slot format if (1) differentiating current sign Sn;

(2) differentiate according to known time slot format whether current sign Sn is frequency pilot sign,, step to step (6) if not if step to step (4);

(3) generate pilot frequency sequence according to known time slot format;

(4) symbol and the known symbol that receive are done the decorrelation computing, wherein known symbol is the symbol of step (3) according to corresponding current location in the local sequence of pilot symbols that produces of known time slot format;

(5) obtain all frequency pilot signs of next time slot, use according to known time slot format again and obtain known pilot sequence, the frequency pilot sign of next time slot is done the decorrelation computing one by one, the decorrelation calculated result is averaged obtains CE then _Next-slot, at last with CE _Next-slotPreservation is got up;

(6) by CE _M-1And CE _Next-slotSimply average and obtain the pre-channel estimation value C ' n of current non-frequency pilot sign, i.e. C ' n=(CE _M-1+ CE _Next-slot)/2; CE wherein _M-1Be the result who obtains through whole flow process by previous symbol Sn-1, CE _Next-slotBe the result who tries to achieve in step (5);

(7) use current non-frequency pilot sign S ' n after C ' n compensation Sn is compensated;

(8) method that the S ' n in all multipaths is merged with high specific merges the symbol S ' n-source after obtaining merging;

(9) S ' n-source is done hard decision, ${\hat{S}}_{n-\mathrm{soursce}}=(S\text{'}n-\mathrm{souscrce}\&GreaterEqual;0)$ 1:-1,

It is exactly the estimated value of the former symbol Sn-source of transmitting terminal;

(10) symbol that the non-frequency pilot sign Sn-source of the Dedicated Physical Control Channel that receives and step (9) are estimated Do the decorrelation computing;

(11) differentiate according to known time slot format whether current sign Sn is frequency pilot sign, if selector switch points to the output result of left side receiving step (4), selector switch points to the output result of the right receiving step (10) if not;

(12) ask the arithmetic mean value, obtain the m final channel estimation value CEm constantly of window correspondence, promptly $\mathrm{CEm}=\frac{1}{L}\underset{i=1}{\overset{L}{\mathrm{\&Sigma;}}}{C}_{n-L+i},$ M＞=n-int (L-1)/2 wherein, int is downward round numbers, i is an interim cyclic variable of asking average computation to use.

3, the channel estimation methods that is used for broadband CDMA system according to claim 2, it is characterized in that, in the described step (12), L is different and different according to translational speed, span is 6-60, the slow more L value of speed is big more, estimates that according to Doppler frequency deviation the translational speed that obtains decides.

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