• 专利附录
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  • 权利要求
  • 类似技术
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  • 优先权
    • 专利摘要:
    An apparatus for estimating a channel using an adaptive filter configured to be used very effectively in a demodulator of a wireless communication system, and a control method thereof. The apparatus for estimating a channel using the adaptive filter includes an apparatus for updating the coefficients of the adaptive filter in a direction of minimizing an imaginary term when representing a channel characteristic as a complex envelope.
    公开号:KR20000046036A
    申请号:KR1019980062711
    申请日:1998-12-31
    公开日:2000-07-25
    发明作者:배상민
    申请人:윤종용；삼성전자 주식회사；
    IPC主号:
    专利说明:

    Channel Estimation Device in Wireless Communication System and Its Control Method
    BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel estimating apparatus used in a radio communication system and a control method thereof, and more particularly, to an apparatus for estimating a channel using an adaptive filter so as to be used effectively in a demodulator of a wireless communication system and a control method thereof. It is about.
    Fading channel information in the IS-95 CDMA system is estimated by measuring the strength of a pilot signal in which all data values are set to "0". At this time, in order to remove user data included in the received signal and to increase the accuracy of the estimated value of the channel included in the pilot signal, an integral integral value fixed to the period of the Walsh orthogonal code is fixed. do. For this simple integration function, the IS-95 system is implemented with hardware of a first order infinite impulse response filter, and the configuration thereof is as follows.
    FIG. 1 illustrates a block diagram of a channel estimator applied to an IS-95 (Interim Standard-95) Code Division Mutiple Access (CDMA) system. Referring to FIG. 1, an inverse signal for outputting a despread signal by multiplying an in-phase and quadrature sampled received signal (I, Q) by a PN code (pseudo noise code) A channel estimator 12 for estimating a channel by integrating a spreader 10 and a signal output from the despreader 10 to a predetermined integral value, and an output of the channel estimator 12 and an inverse of the channel estimator 12. And a multiplier 14 for multiplying the spread signal and outputting the channel estimated despread signal, and an orthogonal spreader 16 for multiplying and orthogonally spreading the signal output from the multiplier 14 and an orthogonal code. In this case, the orthogonal code is a Walsh orthogonal code (walsh-code).
    However, the conventional channel estimating apparatus having the configuration as shown in FIG. 1 has a problem in that it is not adaptively operated when the doppler frequency of the fading channel varies according to the moving speed of the terminal. That is, there is a problem that the channel estimator 12 is composed only of the hardware of the IIR filter, and thus only the integral integer number is fixed, so that the channel estimator 12 is affected by the integral value. For example, if the integral value of the IIR filter is too large, it will not be able to follow the change of channel characteristics when moving at high speed, and if the value is too small, performance will be degraded because it is easily affected by noise, not the channel environment. There was a problem.
    Accordingly, an object of the present invention is to provide an adaptive channel estimating apparatus and a control method for finding and compensating an accurate channel environment by adaptively changing characteristics according to a movement (movement) speed of a terminal or a change of a channel environment. .
    Another object of the present invention is a channel estimating apparatus and control using an adaptive filter having a structure for accurately estimating channel characteristics and compensating for the channel in an optimal state even if the characteristics of a channel change with time in a demodulator of a communication system. In providing a method.
    It is still another object of the present invention to provide an adaptive channel tracking apparatus and control method including an adaptive filter counter that obtains an optimal channel estimation coefficient adaptively to channel characteristics that change over time.
    In order to achieve the above object, the present invention provides a channel estimation apparatus and method using an adaptive filter, characterized in that the coefficient of the adaptive filter is updated in a direction in which the imaginary term is minimized when the characteristic of the channel is represented by a complex envelope. do.
    According to an embodiment of the present invention, a channel estimating apparatus includes a PN code (I-PN, Q-) corresponding to a sample received in-phase signal and an in-phase & quadri-phase sampled received signal (I, Q). A complex PN despreader that outputs a complex despread signal by multiplying each PN), and integrates the complex despread in-phase signal and quad-phase signal for a predetermined time to extract only pilot signals that are primary channel estimates. An adaptive filter and a complex transformation for adaptively filtering the extracted in-phase and quad-phase pilot signals to a filtering coefficient to generate channel estimates of the in-phase and quad-phase and complex-converting the generated channel estimates A cross product of the in-phase and quad-phase pilot signals and the channel estimates of the in-phase and quad-phase and the difference value An adaptive filter coefficient generator for supplying filter coefficients to be minimized to the adaptive filter and the complex transform unit, and the adaptive filtered and complex-converted signal to each of the complex PN despread in-phase signal and quad-phase signal, And orthogonal code despreaders that sequentially multiply the orthogonal codes to produce despread orthogonal codes with channel fading compensation.
    1 is a block diagram of a channel estimator being applied in an IS (Interim Standard) -95 Code Division Mutiple Access (CDMA) system.
    2 is a block diagram of a channel estimating apparatus using an adaptive filter according to an embodiment of the present invention.
    Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to obscure the subject matter of the present invention.
    2 is a block diagram of a channel estimating apparatus using an adaptive filter according to an embodiment of the present invention. In the configuration of the embodiment of the present invention shown in FIG. 2, after complex-pN despreading of the in-phase signal I and the quad-phase signal Q received and digitally sampled, as in the conventional method, It is configured in the form of additional adaptive filtering on the pilot signals Ri and Rq having channel characteristics remaining after the user data component is removed by integrating a predetermined time (ai, aq).
    Referring to FIG. 2, the complex PN despreader 20 is a multiplier 22 and 24 that multiplies each of the in-phase signal I and the quad-phase signal Q by the I-PN code and the Q-PN codes, respectively. ) And (26, 28), an adder 30 that adds the outputs of the multipliers 22, 24, and an adder 32 that adds the output of the multipliers 26, 28; Consists of. The complex PN despreader 20 having the configuration described above multiplies each of the received in-phase signal I and the quad-phase signal Q by the I-PN code and the Q-PN code and adds the results, respectively. The phase-corrected complex despread signal is outputted to the output node, respectively, with the first and second integrators 34 and 36 in the channel estimator 23, the in-phase data path (IDAPA) and the quadraple. Each feeds a quadri-phase data path (QDAPA).
    The first and second integrators 34 and 36 respectively integrate the ai and aq of the complex despread signals for a predetermined time, respectively, to provide in-phase and quadra with channel characteristics remaining after user data components are removed. Only phase pilot signals Ri and Rq are supplied to one side of the first and second adaptive filters 37 and 38 and the multipliers 40 and 42 respectively connected to the output node.
    Accordingly, when the envelope of the fading channel is expressed as “Fi + jFq” in the complex domain, the complex PN despeading 20 and the first and second integrators 34, shown in FIG. After 36), the user data components are removed, leaving only the pilot signal components Ri and Rq for channel estimation. This component is equal to the primary estimate of Fi and Fq, respectively, since the pilot signal has any known value ("+1", "-1" for digital communication). The mathematical expression in the case where the fading component is to be compensated using the channel estimation value as described above is expressed by Equations 1 and 2 below.
    I data: Si (Fi + jFq) (Ri-jRq) = Si [FiRi + FqRq + j (FqRi-FiRq)]
    Ｑ data: Si (Fi + jFq) (Ri-jRq) = Sq [FiRi + FqRq + j (FqRi-FiRq)]
    In Equations 1 and 2, Si and Rq are user data carried on I and Q channels.
    When the fading channel is accurately estimated, Ri and Rq become Fi and Fq, respectively, so that the imaginary terms are eliminated in Equations 1 and 2 so that only the real term remains, so that accurate restoration of Si and Sq is achieved. However, when the characteristics of the fading channel change in time according to the moving speed of the terminal, it is difficult to obtain an accurate channel estimate by simply integrating ai and aq by a certain amount. Therefore, there is a need to adaptively filter according to the characteristics of the fading channel.
    The first and second adaptive filters 37 and 38 of FIG. 2 are filter coefficients that are varied by adapting the in-phase pilot signals Ri and Rq, which are the primary channel estimates, to the characteristics of the channel. Filtering according to (Hi) (Hq) has a function to output a true channel estimates (Fi) and (Fq), the most suitable filter coefficient for this is the first adaptive filter coefficient generator shown in FIG. 46 and the output of the second adaptive filter counter 48.
    On the other hand, a cross producer composed of multipliers 40, 42, and subtractor 44 is a cross product of the input and output signals of the first and second integrators 34, 36. The difference value DEF is generated and supplied to the first and second adaptive filter coefficient generators 46 and 48, respectively. Each of the first and second adaptive filter coefficient generators 46 and 48 is configured with an appropriate adaptive filtering algorithm in a direction such that the difference value DEF output from the subtractor 44 is minimized. The filter coefficients Hi and Hq in the first and second adaptive filters 37 and 38 are updated. That is, each of the first and second adaptive filter coefficient generators 46 and 48 determines the filter coefficients Hi and Hq in the first and second adaptive filters 37 and 38 for each channel. The filter coefficients Hi and Hq are updated to minimize the absolute value of the difference between the signal and the estimated values Ei and Eq.
    The designed signal of each channel may be represented by the following Equations 3 and 4 as imaginary terms of Equation 1 or 2 described above.

    The difference between the signals Ei and Eq output from the first and second adaptive filters 37 and 38, respectively, is defined as an error function εi and εq to be minimized. To be together.

    The error functions εi and εq can be represented as linear functions of adaptive filter coefficients, and algorithms of least mean square error or recursive least square, which are well known in the art. Adaptive filtering algorithm such as can be selected and used.
    On the other hand, the complex converter 49 for inputting the output values Ei, Eq, which are second-filtered by the first and second adaptive filters 37 and 38, is complex-converted to a value of "Ei + jEq". The multipliers 50 and 54 are respectively provided on the in-phase data path IDAPA and the quad-phase data path QDAPA to compensate for channel fading components.
    As described above, the present invention has an advantage of improving reliability of reconstructed data by adaptively estimating channel characteristics by adaptively estimating channel characteristics even when channel characteristics change with time in a demodulator of a communication system requiring channel estimation. .
    权利要求:
    Claims (6)
    [1" claim-type="Currently amended] In the channel estimation apparatus of a wireless communication system,
    A complex despreader that complexly despreads the sampled and received in-phase channel signal and quad-phase channel signal and outputs them as a complex envelope signal;
    The complex despread in-phase and quad-phase channel signals are adaptive filters, respectively, according to predetermined filter coefficients;
    And an adaptive filter controller for updating the filter coefficients of the adaptive filters in a direction of minimizing the imaginary term of the complex envelope, and compensating the fading channel of the complex envelope signals by complex converting the adaptive filtered value. An apparatus for estimating channels in a wireless communication system.
    [2" claim-type="Currently amended] 2. The apparatus of claim 1, further comprising adaptive filter coefficient generators for obtaining a imaginary term of a complex envelope by inputting and outputting signals to the adaptive filters and updating the filter coefficients of the adaptive filters so that their values are minimized. Channel estimation apparatus of a wireless communication system, characterized in that.
    [3" claim-type="Currently amended] 3. The apparatus of claim 2, wherein each of the adaptive filter coefficient generators is implemented by an algorithm of least mean square error or cyclic least square.
    [4" claim-type="Currently amended] The channel of a wireless communication system according to claim 1, wherein an integrator of a predetermined length is further connected between the output node of the complex despreader and the adaptive filters to supply first estimated pilot signals to the adaptive filters. Estimator.
    [5" claim-type="Currently amended] In the channel estimation method using an adaptive filter,
    Generating a primary channel estimation signal by integrating the complex despread in-phase and quad-phase channel signals as integrators of a predetermined length, respectively,
    Generating a secondary channel estimation signal by adaptively filtering the primary channel estimated signals to predetermined filter coefficients to generate a secondary estimated channel signal;
    An adaptive filtering coefficient generation process of updating the adaptive filter coefficients before and after the adaptive filtering to minimize the imaginary term value of the complex envelope calculated by cross-production;
    And complexly converting the adaptive filtered values to multiply the complex despread in-phase and quad-phase channel signals to compensate for channel fading.
    [6" claim-type="Currently amended] 6. The method of claim 5, wherein the adaptive filter coefficient generating process is a minimum mean square error algorithm or a cyclic least square algorithm.
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    同族专利:
    公开号 | 公开日
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    1998-12-31|Application filed by 윤종용, 삼성전자 주식회사
    1998-12-31|Priority to KR1019980062711A
    1998-12-31|Priority claimed from KR1019980062711A
    2000-07-25|Publication of KR20000046036A
    2001-02-01|Application granted
    2001-02-01|Publication of KR100279720B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1019980062711A|KR100279720B1|1998-12-31|Channel Estimation Device in Wireless Communication System and Its Control Method|
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