JP2008118411A - Radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To average a plurality of time slots and a plurality of subcarriers in a range keeping a coherence property of a propagation path without increasing an operation quantity. <P>SOLUTION: A pilot signal comprised of the plurality of time slots and subcarriers is received, a weighting coefficient is multiplied by a channel estimate value of P(i) pieces on a time base including a t-th time slot and Q(j) pieces on a frequency axis regarding an average range combination of the time base and a frequency axis as an average range set, an averaged channel estimate value is calculated by outputting an added result, a receiving pilot channel compensation value is calculated by conducting the channel compensation of each receiving pilot signal using the averaged channel estimate value, and the channel estimate value with optimum demodulation accuracy is decided by using an inter-signal distance between a transmitting pilot signal point and a receiving pilot channel compensation value signal point. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless reception device.

  A wireless transmission / reception apparatus using an OFDM (Orthogonal Frequency Division Multiplexing) system is adopted as a transmission system for terrestrial digital broadcasting, wireless LAN such as IEEE802.11a, and power line modem.

  In wireless communication using the OFDM method, radio waves transmitted from a base station may be reflected or diffracted by obstacles such as buildings or terrain, and the receiving device may receive the same radio waves from multiple paths (hereinafter referred to as multipath). Call it.) In particular, in order to improve the reception quality at the time of high-speed data transmission, a technique (channel estimation) for estimating the multipath state of the received radio wave more accurately becomes important. As a method for improving channel estimation accuracy in a receiving apparatus of a wireless transmission / reception apparatus using the OFDM method, a method of averaging channel estimation values over a plurality of time slots and a plurality of subcarriers is known (for example, Patent References 1 to 6). By increasing the number of time slots and the number of subcarriers used for averaging, the noise level can be reduced.

  Hereinafter, a conventional method for averaging channel estimation values will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a conventional receiver 100. Referring to FIG. 1, a conventional receiver 100 includes a receiving unit 101, a signal separation unit 102, and a channel estimation unit 103.

  The receiving unit 101 receives a multiplexed signal in which data composed of N (N is a natural number) subcarriers and pilot signals composed of N subcarriers are time-multiplexed within a unit time slot. The receiving unit 101 outputs the received multiplexed signal as a received signal Srx. Here, the receiving unit 101 receives a multiplexed signal over a plurality of time slots.

  The signal separation unit 102 receives the reception signal Srx, separates the pilot signal and the data signal from the reception signal Srx for each time slot, and outputs them as a reception pilot signal Splt and a reception data signal Sdat, respectively.

  Channel estimation section 103 receives received pilot signal Splt, obtains and outputs a channel estimation value Sest per unit subcarrier per unit time slot.

  Here, the averaging ranges on the time axis and the frequency axis are defined as a time averaging range P and a frequency averaging range Q, respectively. At this time, assuming that P is an integer of 0 or more and M or less and Q is an integer of 0 or more and N or less, the processing of the averaging unit 104 will be described below.

The averaging unit 104 receives the channel estimation value Sest as an input. In the averaged channel estimation value vector Sav, as the components of the xth (x is an integer from 0 to M) time slot and the yth (y is an integer from 0 to N) subcarriers,
X-dx, x-dx + 1, ..., x-dx + (P-1)
Time slots and
Y-dy, y-dy + 1,..., Y-dy + (Q−1)
The channel estimation value Sest is multiplied by a weighting coefficient over the subcarriers, and the addition result is output. Dx and dy are integer parts obtained by dividing P and Q by 2 and excluding the first decimal place.

  Demodulation section 105 receives averaged channel estimation value vector Sav and reception data signal Sdat as input, and performs channel compensation of reception data signal Sdat using averaged channel estimation value vector Sav to perform data demodulation processing. Averaging using the weighting factor is performed according to the following equation (1).

… （１）

(1)

In Equation (1), Φ ′ _x (y) represents an averaged channel estimation value corresponding to the xth time slot−yth subcarrier. Φ _x (y) indicates an un-averaged channel estimate corresponding to the x th time slot−y th subcarrier. W _{x ′ and y ′} are weighting factors, and the number of time slots and the number of subcarriers used for averaging are P and Q, respectively.

  A total of (P × Q) channel estimation values are used for the weighted addition of channel estimation values in the xth time slot-yth subcarrier.

FIG. 2 is a conceptual diagram showing an operation of performing addition by multiplying weighting factors. Referring to FIG. 2, the operation for obtaining the weighting coefficient when P = 3, Q = 3, dx = 1, and dy = 1 in the equation (1) is shown. In FIG.
Nine channel estimations corresponding to (x-1) th time slot, xth time slot, (x + 1) th time slot and (y-1) th subcarrier, yth subcarrier, (y + 1) th subcarrier A conceptual diagram for obtaining an averaged channel estimation value in the xth time slot-yth subcarrier using the value is shown.

The channel estimation values in each time slot and each subcarrier are each input to a multiplication unit and multiplied by a weighting factor. For example, the fifth multiplication unit 115 multiplies the channel estimation value of the y-th subcarrier in the x-th time slot by the weighting factors W _{x and y} . The channel estimation values of the same y-th subcarrier and the channel estimation values in the (x−1) th time slot and the (x + 1) th time slot adjacent to the xth time slot include the fourth multiplier 114 and the sixth In each of the multipliers 116, the weighting factors _{Wx, (y-1)} and the weighting factors _{Wx, (y + 1)} are multiplied.

  Outputs from the fourth multiplier 114, the fifth multiplier 115, and the sixth multiplier 116 are added by the second adder 122. The output of the second addition unit 122 corresponds to the weighted addition value of the channel estimation value over the (x−1) th time slot, the xth time slot, and the (x + 1) th time slot regarding the yth subcarrier.

  Similarly, the weighted addition value of the channel estimation value over the (x−1) th time slot, the xth time slot, and the (x + 1) th time slot in the (y−1) th subcarrier adjacent to the yth subcarrier is 1 is output from the adder 121. Further, the weighted addition value of the channel estimation values over the (x−1) th time slot, the xth time slot, and the (x + 1) time slot in the other (y + 1) th subcarrier adjacent to the yth subcarrier is third. Output from the adder 123.

  Outputs from the first adder 121, the second adder 122, and the third adder 123 are added by the fourth adder 124. The output of the fourth adder 124 is the (x-1) th time slot, the xth time slot, the (x + 1) th time slot, the (y-1) th subcarrier, the yth subcarrier, and the (y + 1) th time slot. Corresponds to the weighted sum of channel estimates across subcarriers. The average channel estimation value vector Sav is generated by the above processing.

JP 2005-328312 A JP 2004-364094 A JP 2004-253894 A JP 2003-069530 A JP 2001-268048 A JP 2000-124965 A

  In the conventional receiver 100, if the channel estimation values are averaged over the coherent time and coherent band of the propagation path, the channel estimation accuracy is degraded because the channel fluctuation cannot be regarded as constant within the averaging range. . Therefore, in order to suppress noise while maintaining high channel estimation accuracy, it is necessary to average channel estimation values over a plurality of time slots and a plurality of subcarriers within a range in which the coherence of the propagation path is maintained. Desired. The weighting factor can be changed according to the propagation environment. When changing the weighting factor according to the propagation environment, the time component of the weighting factor is set depending on the maximum Doppler frequency or the like, and the frequency component of the weighting factor is set depending on the delay spread or the like. Therefore, in the conventional example, it is recommended to measure the Doppler frequency, the delay spread, and the like and set the number of time slots and the number of subcarriers used for averaging or the weighting factor according to the propagation path.

  In the above-described method, in order to obtain the channel estimation value with high accuracy, it is necessary to maintain the coherence of the propagation path over the time slot range and the subcarrier range in which the channel estimation value is averaged. In order to average a plurality of time slots and a plurality of subcarriers within a range in which the coherence of the propagation path is maintained, estimation of a Doppler frequency, a delay spread, and the like is required. Particularly in delay spread estimation, it is necessary to obtain a delay profile using IFFT (Inverse Fourier Transform) or cross-correlation, which may increase the amount of calculation.

In order to solve the above problems, the present invention
A pilot signal composed of M (M is a natural number) time slots and N (N is a natural number) subcarriers is input as a received pilot signal,
Channel estimation means for obtaining a channel estimation value per unit time slot and per unit subcarrier;
A plurality of different average ranges P (1), P (2),..., P (U) on the time axis (P (1), P (2),..., P (U)) Is a natural number less than or equal to M satisfying P (1) <P (2) <... <P (U). U is a natural number.) Time slots and a plurality of different average ranges Q (1), Q on the frequency axis (2), ..., Q (V) (Q (1), Q (2), ..., Q (V) is less than or equal to N satisfying Q (1) <Q (2) <... <Q (V) A natural number. V is a natural number.) A combination of average ranges on the time axis and the frequency axis composed of subcarriers is defined as the first to (U * V) average range set, and the (i * V + j) average range. For the set (i is a natural number less than or equal to U, j is a natural number less than or equal to V), the (i * V + j) -th average channel estimation vector t (t is Integers less than or equal to M) P (i) consecutive on the time axis including the tth time slot and sth subcarriers as s time slot s (s is an integer greater than or equal to 0 and less than or equal to N) subcarrier components Averaging means for multiplying the Q (j) continuous, total (P (i) * Q (j)) channel estimation values on the frequency axis including a weighting factor and outputting the addition result;
The received pilot signal and the first to (U * V) average channel estimation value vectors are input, and the received pilot signal is averaged by the k-th (k is a natural number equal to or less than (U * V)). First to (N * M) signal points obtained by performing channel compensation with a channel estimation value vector are k-th received pilot channel compensation vectors, and transmission pilot signal points that are transmission signal points of the received pilot signal; Using the calculation result of the inter-signal distance with each of the first to (N * M) signal points in the kth received pilot channel compensation vector, the optimum channel estimation value used for channel compensation of the data part is determined and output. And demodulation accuracy measuring means.

  In other words, in order to solve the above-mentioned problem, the present invention is a channel estimation device used for a radio receiver, which is a channel estimation device used for a radio receiver, and includes a plurality of time slots and subcarriers. A pilot signal consisting of (frequency) is received, and the combination of the average ranges of the time axis and the frequency axis is set as an average range set, and P (i) on the time axis including the tth time slot and Q on the frequency axis (J) Multiplying the channel estimation values by the weighting coefficient, and outputting the addition result to obtain an average channel estimation value. Using the average channel estimation value, channel compensation is performed for each received pilot signal and reception is performed. Obtain the pilot channel compensation value, and determine the channel estimation value with the best demodulation accuracy using the inter-signal distance between the transmission pilot signal point and the reception pilot channel compensation value signal point.In addition, a received pilot signal to be subjected to channel compensation in the average range of the time slot and the frequency slot in the weighting factor multiplication process using a different average channel estimation value by shifting either one of the time slot and the frequency slot. If a point is included, the weighting factor is set to zero.

  According to the present invention, it is possible to average a plurality of time slots and a plurality of subcarriers within a range in which the coherence of the propagation path is maintained without increasing the amount of calculation.

[First Embodiment]
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. FIG. 3 is a block diagram illustrating the configuration of the receiver 10 of this embodiment. Referring to FIG. 3, the receiver 10 includes a reception unit 1, a signal separation unit 2, a channel estimation unit 3, an averaging unit 4, a demodulation accuracy measurement unit 5, and a demodulation unit 6. ing. When the receiving unit 1 specifies one time slot, the receiving unit 1 writes a multiplexed signal in which data composed of N (N is a natural number) subcarriers and pilot signals composed of N subcarriers are time-multiplexed. Receive for each subcarrier. The receiving unit 1 receives the multiplexed signal in M (M is a natural number of 1 or more) time slots. The receiving unit 1 outputs the received multiplexed signal as a received signal _SRX .

The signal separator 2 receives the received signal S _RX and separates the pilot signal and the data signal from the received signal S _RX . The signal separation unit 2 outputs the separated signals as a reception pilot signal _SPLT and a reception data signal SDAT, respectively. The channel estimation unit 3 receives the received pilot signal _SPLT , and obtains and outputs a channel estimation value _SEST per unit subcarrier per unit time slot.

The averaging unit 4 receives the channel estimation value S _EST and inputs a plurality of different average ranges P (1), P (2),..., P (U) time slots on the time axis and a plurality of frequency ranges on the frequency axis. Average range Q (1), Q (2),..., Q (V) subcarriers different from each other, the combination of the average ranges on the time axis and the frequency axis is the first to (U × V) average ranges Set.

Here, P (1), P (2),..., P (U) are
P (1) <P (2) <... <P (U)
It is assumed that the natural number is less than or equal to M and U is a natural number.

Q (1), Q (2), ..., Q (V)
A natural number equal to or less than N satisfying Q (1) <Q (2) <... <Q (V), and V is a natural number.

  With respect to the (i × V + j) average range set (i is a natural number less than or equal to U, j is a natural number less than or equal to V), the tth (t is 0 or more) of the (i × V + j) average channel estimation value vector M or less) time slot-sth (where s is an integer of 0 or more and N or less) subcarriers, P (i) consecutive on the time axis including the tth time slot, and the sth subcarrier Q (j) on the frequency axis including the total (P (i) × Q (j)) channel estimation values are multiplied by a weighting factor, and the result of addition is output.

  Next, the operation related to the averaging of the present embodiment will be described using the equation (2).

… （２）

(2)

In the equation (2), dt and ds are integer parts obtained by dividing P (i) and Q (j) by 2 and excluding the first decimal place. For example,
Average range P (U) on the time axis = 3
Average range on frequency axis Q (V) = 3
And the average range set is
First average range set: ((P (i), Q (j)) = (1, 1)
Second average range set: ((P (i), Q (j)) = (2, 1)
Third average range set: ((P (i), Q (j)) = (3, 1)
Fourth average range set: ((P (i), Q (j)) = (1, 2)
Fifth average range set: ((P (i), Q (j)) = (2, 2)
Sixth average range set: ((P (i), Q (j)) = (3, 2)
Seventh average range set: ((P (i), Q (j)) = (1, 3)
Eighth average range set: ((P (i), Q (j)) = (2, 3)
Ninth average range set: ((P (i), Q (j)) = (3, 3)
It is.

For all the combinations, weighting multiplication and addition are performed, and first average channel estimation value vector S _AV (1) to ninth average channel estimation value vector S _AV (9) are output.

  A weighted addition process performed by the averaging unit 4 when the average range set (P (i), Q (j)) = (3, 3) will be described with reference to FIG. In this case, ds and dt described above are both 1. FIG. 4 uses all nine channel estimates corresponding to (t−1), t, (t + 1) time slots and (s−1), s, (s + 1) subcarriers, The conceptual diagram which calculates | requires the average channel estimated value in the sth subcarrier of a t-th time slot is shown.

The channel estimation values in each time slot and each subcarrier are each input to a multiplication unit and multiplied by a weighting factor. For example, in the fifth multiplication unit 15, the channel estimation value corresponding to the t-th time slot and the sth subcarrier is multiplied by the weighting factor _{Wt, s} . The channel estimation values corresponding to the (t−1) th and (t + 1) th time slots adjacent to the same sth subcarrier and adjacent to the tth time slot include the fourth multiplication unit 14 and the sixth multiplication unit 16, respectively. , W _{(t−1), s} and W _{(t + 1), s} are multiplied.

  Outputs from the fourth multiplier 14, the fifth multiplier 15, and the sixth multiplier 16 are added by the second adder 22. The output of the second adder 22 corresponds to the average value of the channel estimation values over the (t−1), t, and (t + 1) time slots for the sth subcarrier.

  Similarly, the weighted addition value of the channel estimation value over the (t−1), t, and (t + 1) time slots in the (s−1) th subcarrier adjacent to the sth subcarrier is the third adder 23. And the weighted sum of the channel estimation values over the (t−1), t, (t + 1) time slots in the other (s−1) th subcarrier adjacent to the sth subcarrier is 1 is output from the adder 21.

  Outputs from the first adder 21, the second adder 22, and the third adder 23 are added by the fourth adder 24. The output of the fourth adder 24 is the channel estimation value over three (s−1), s, and s + 1) subcarriers and three (t−1), t, and (t + 1) time slots. Corresponds to the weighted addition value.

The same processing as described above is performed for the other average range sets. In the first to ninth average range sets, channel estimation values obtained by performing weighted addition in the t-th time slot to the s-th subcarrier are respectively 1 average channel estimation value vector S _AV (1) to 9th average channel estimation value vector S _AV (9) are output.

In demodulation accuracy measuring section 5, first average channel estimation value vector S _AV (1) to ninth average channel estimation value vector S corresponding to the same time slot and subcarrier as the received pilot signal to be subjected to channel compensation. Channel compensation of the received pilot signal is performed using each of _AV (9).

Next, the first to (N * M) signal points obtained by channel compensation of the received pilot signal with the h-th (h is a natural number of 9 or less) averaged channel estimation value vector S _AV (h) are obtained. , The h th received pilot channel compensation vector. Then, the inter-signal distance between the transmission pilot signal point that is the transmission signal point of the reception pilot signal and each of the first to (N * M) signal points in the h-th reception pilot channel compensation vector is calculated.

  Based on the calculation result, for each of the first to (N * M) signal points, the averaged channel corresponding to the component having the minimum inter-signal distance in the first to ninth received pilot channel compensation vectors. The component of the estimated value vector is output as the optimum channel estimated value used for channel compensation of the data part.

  Based on the above, it is possible to perform channel compensation of data using the channel estimation value with the best channel estimation accuracy among the averaged channel estimation values obtained by setting multiple averaging ranges in time slots and subcarriers It is.

[Second Embodiment]
The second embodiment of the present invention will be described below. The configuration of the receiver 10 in the second embodiment is the same as that in the first embodiment. In the second example, the processing in the demodulation accuracy measuring unit 5 is different from that in the first embodiment. Therefore, in the following description, it demonstrates corresponding to the difference with 1st Embodiment.

In the first embodiment described above, the first to ninth average channel estimation value vectors S _AV (1) to (9) corresponding to time slots and subcarriers, which are the same as the received pilot signal to be subjected to channel compensation, are respectively used. Is used to compensate the channel of the received pilot signal.

If in the production of averaging channel estimation values, and sets the average range of time slots and subcarriers together 1, the noise component in the averaged channel estimate vector S _AV is equal to the noise component in the received pilot signal.

For this reason, the reception pilot channel compensation point obtained after channel compensation may coincide with the transmission pilot signal point, and it may be determined that the channel compensation accuracy is the best when averaging is not performed. In the second embodiment, on the received pilot signals, the time slot in the averaging channel estimate vector S _AV, or be to at least one different values of subcarriers, performs channel estimation with higher accuracy.

The demodulation accuracy measuring unit 5 calculates the y-th subcarrier component of the xth time slot in the received pilot signal for the yth (s = y) subcarrier component of the x + 1 (t = x + 1) time slot. Channel compensation is performed using each of the averaged channel estimation value vectors S _AV (1) to (9).

Next, the demodulation accuracy measuring unit 5 performs first to (N *) channel compensation of the received pilot signal with the h-th (h is a natural number of 9 or less) averaged channel estimation value vector S _AV (h). The signal point of M) is set as the h-th received pilot channel compensation vector. Then, the inter-signal distance between the transmission pilot signal point that is the transmission signal point of the reception pilot signal and each of the first to (N * M) signal points in the h-th reception pilot channel compensation vector is calculated.

  Based on the calculation result, the demodulation accuracy measuring unit 5 has the smallest inter-signal distance in the first to ninth received pilot channel compensation vectors for each of the first to (N * M) signal points. A component of the averaged channel estimation value vector corresponding to the component is output as an optimum channel estimation value used for channel compensation of the data part.

By the configuration and operation of the second embodiment, erroneous selection of the optimum averaging range that occurs when both the time slot and subcarrier average ranges are set to 1, and the first to ninth average channel estimation value vectors S are avoided. It is possible to perform data channel compensation using the best channel estimation value among _AV (1) to (9).

  In the configuration and operation of the second embodiment, channel compensation of the received pilot signal is performed using the average channel estimation value shifted by one time slot for the received pilot signal. As long as the value is within the range in which the value is maintained, the shift amount on the time axis may be set to another value. Further, an average channel estimation value shifted on the frequency axis may be used as long as the coherence on the frequency axis is maintained.

[Third Embodiment]
The third embodiment of the present invention will be described below. The configuration of the receiver 10 in the third embodiment is the same as that in the first embodiment. The third embodiment described below is different from the first example in the processing in the averaging unit 4. Therefore, in 3rd Embodiment, it demonstrates corresponding to a difference with 1st Embodiment.

In the first embodiment described above, in the weighted addition of the averaging unit 4, generation of the first to ninth average channel estimation value vectors S _AV (1) to (9) from the t-th time slot to the s-th subcarrier component In FIG. 5, averaging is performed including the xth time slot-yth subcarrier component to be subjected to channel compensation in the received pilot signal.

In this case, the number of channel estimates is less used for averaging, averaging channel estimate vector S _AV is, the x time slot in the received pilot signal S _PLT of interest to perform channel compensation - component of the y subcarrier Get closer to. As a result, there are cases where it is determined that the channel compensation accuracy is good when the inter-signal distance between the reception pilot channel compensation point obtained by channel compensation and the transmission pilot signal point approaches 0 and the average range is reduced. is there.

In the third embodiment, in the multiplication process of the weighting factor in the averaging unit 4, the average range of the time slot and the subcarrier includes the xth time slot of the received pilot signal _SPLT to be subjected to channel compensation—the yth subcarrier. Are included, the weight coefficient W _{x, y} corresponding to the xth time slot-yth subcarrier is set to zero. Then, an average channel estimation value is generated. In the third embodiment, the optimum average range can be appropriately selected even when the number of channel estimation values used for averaging decreases. Thereby, it is possible to perform data channel compensation using the best channel estimation value among the averaged channel estimation values.

[Fourth Embodiment]
The fourth embodiment of the present invention will be described below. The configuration of the receiver 10 in the fourth embodiment is the same as that in the first embodiment. In the fourth embodiment, the processing in the demodulation accuracy measuring unit 5 is different from that in the first embodiment. Therefore, in the fourth embodiment, description will be made corresponding to the difference from the first embodiment.

In the best mode of the present invention, the first average channel estimation value vector S _AV (1) to the ninth average channel estimation corresponding to the same time slot and subcarrier as the received pilot signal subject to channel compensation. Channel compensation of the received pilot signal is performed using each of the value vectors S _AV (9).

In the process of obtaining the average channel estimation value, if the average range of time slots and subcarriers includes the component of the xth time slot-yth subcarrier of the received pilot signal _SPLT to be subjected to channel compensation, the average When the number of channel estimation values used for conversion decreases, the averaged channel estimation value approaches the xth time slot-yth subcarrier component of the received pilot signal _{SPLT that} is the target of channel compensation.

  As a result, the inter-signal distance between the reception pilot channel compensation point obtained by channel compensation and the transmission pilot signal point approaches 0, and it is determined that the channel compensation accuracy is good when the average range is reduced. There is a case.

In the fourth embodiment, in the generation of the average channel estimation value by the demodulation accuracy measuring unit 5, the xth time slot of the received pilot signal _SPLT to be subjected to channel compensation is within the time slot and subcarrier averaging range. The y-th subcarrier component is not included. An average channel estimation time slot or at least one of subcarriers is equal to or greater than (P (i) +1) time slots or (Q (j) +1) subcarriers or more with respect to the received pilot signal. Shift in the positive direction.

Using the (x + (P (i) +1)) time slot−y-th subcarrier component or the xth time slot− (y + (Q (j) +1)) subcarrier component of the averaged channel estimation value Then, channel compensation of the xth time slot-yth subcarrier component in the received pilot signal _SPLT is performed. In the fourth embodiment, the time slot or subcarrier of the average channel estimation value is shifted in the positive direction with respect to the received pilot signal, but may be in the negative direction.

Next, the demodulation accuracy measuring unit 5 performs first to (N *) channel compensation of the received pilot signal with the h-th (h is a natural number of 9 or less) averaged channel estimation value vector S _AV (h). M) signal points are set as the h-th received pilot channel compensation vector, and transmission pilot signal points that are transmission signal points of the received pilot signal and the first to (N * M) -th received pilot channel compensation vectors. The distance between signals with each signal point is calculated. Then, using the calculation result of the inter-signal distance, an average channel estimation value vector that provides the minimum inter-signal distance is selected and output as an optimum channel estimation value used for channel compensation of the data part.

  With the configuration and operation described above, the receiver 10 according to the fourth embodiment can more appropriately select an optimal average range that occurs when the number of channel estimation values used for averaging decreases. Then, it is possible to perform data channel compensation using the best channel estimation value among the averaged channel estimation values.

[Fifth Embodiment]
The fifth embodiment of the present invention will be described below. The configuration of the receiver 10 in the fifth embodiment is the same as that in the first embodiment. In the fifth embodiment, the processing in the demodulation accuracy measuring unit 5 is different from that in the first example. Therefore, in the fifth embodiment, description will be made corresponding to the difference from the first example.

In the first embodiment described above, on the received pilot signals, the time slot in the averaging channel estimate vector S _AV or, as at least one subcarrier are different values, the first averaged channel estimate At least one of each time slot or subcarrier of vector S _AV (1) to ninth average channel estimation value vector S _AV (9) is shifted by 1 in the positive direction with respect to received pilot signal _SPLT . .

This operation avoids erroneous selection of the optimum averaging range that occurs when both the time slot and subcarrier average ranges are set to 1. In the first embodiment, the shift direction of the average channel estimation value with respect to the received pilot signal _SPLT is selected from time slots and subcarriers. The optimal shift direction may depend on the propagation environment.

In the fifth embodiment, the demodulation accuracy measuring unit 5, on the received pilot signal, and when the only time slot in the averaging channel estimate vector S _AV different values, when only a different value subcarriers, respectively A reception pilot channel compensation point is generated.

Next, the inter-signal distance between the reception pilot channel compensation point and the transmission pilot signal point that is the transmission signal point of the reception pilot signal _SPLT is calculated. Thereafter, channel compensation of the received data signal is performed using the averaged channel estimation value that provides the minimum distance between signals.

  In the receiver 10 of the fifth embodiment, even when the channel variation of either time or frequency is severe due to the above-described configuration and operation, even when coherence is not maintained between one time slot or one subcarrier, It is possible to perform channel compensation of data using a channel estimation value that provides the best demodulation accuracy.

FIG. 1 is a block diagram showing a configuration of a conventional receiver. FIG. 2 is a diagram illustrating a conventional weighted addition process of channel estimation values. FIG. 3 is a block diagram illustrating the configuration of the receiver in the embodiment of the invention. FIG. 4 is a diagram showing a weighted addition process of channel estimation values in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Receiver 1 ... Reception part 2 ... Signal separation part 3 ... Channel estimation part 4 ... Averaging part 5 ... Demodulation accuracy measurement part 6 ... Demodulation part 11 ... 1st multiplication part 12 ... 2nd multiplication part 13 ... 3rd multiplication Unit 14 ... fourth multiplier 15 ... fifth multiplier 16 ... sixth multiplier 17 ... seventh multiplier 18 ... eighth multiplier 19 ... ninth multiplier 21 ... first adder 22 ... second adder 23 ... third adder 24 ... fourth adder 100 ... receiver 101 ... receiver 102 ... signal separator 103 ... channel estimator 104 ... averager 105 ... demodulator 111 ... first multiplier 112 ... second multiplier 113 ... 3rd multiplication part 114 ... 4th multiplication part 115 ... 5th multiplication part 116 ... 6th multiplication part 117 ... 7th multiplication part 118 ... 8th multiplication part 119 ... 9th multiplication part 121 ... 1st addition part 122 ... 2nd addition part 123 ... 3rd addition part 124 ... 4th addition part P ... Time averaging range Q ... Frequency average Range

Claims (10)

A channel estimation device used in a radio receiver,
A pilot signal composed of M (M is a natural number) time slots and N (N is a natural number) subcarriers is input as a received pilot signal, and channel estimation values per unit time slot and per unit subcarrier are obtained. Channel estimation means;
A plurality of different average ranges P (1), P (2),..., P (U) (P (1) to P (U) on the time axis are set as P (1) < P (2) <... <natural number less than or equal to M satisfying P (U)) and a plurality of different average ranges Q (1), Q (2),..., Q (V) (Q (1) to Q (V) are combinations of average ranges on the time axis and the frequency axis, which are composed of subcarriers (N or less natural numbers satisfying Q (1) <Q (2) <... <Q (V)). Is the first to (U × V) average range set, and (i is a natural number less than U, j is a natural number less than V), (i × V + j) ) Of the average channel estimation value vector of s (t is an integer not less than 0 and not more than M) time slot s (s is an integer not less than 0 and not more than N). As a carrier component, P (i) continuous on the time axis including the t-th time slot and Q (j) continuous on the frequency axis including the s-th subcarrier, total (P (i) × Q (j)) averaging means for multiplying channel estimation values by weighting factors and outputting the addition results;
The received pilot signal and the first to (U × V) average channel estimation value vectors are input, and the received pilot signal is averaged by the k-th (k is a natural number equal to or less than (U × V)). First to (N × M) signal points obtained by channel compensation with a channel estimation value vector are k-th received pilot channel compensation vectors, and transmission pilot signal points that are transmission signal points of the received pilot signal; The optimum channel estimation value used for channel compensation of the data part is determined and output using the calculation result of the inter-signal distance with each of the first to (N × M) signal points in the k-th received pilot channel compensation vector. A channel estimation apparatus comprising: demodulation accuracy measuring means. The demodulation accuracy measuring means is
The channel compensation of the received pilot signal is performed using an averaged channel estimation value vector corresponding to a time slot and a subcarrier that is the same as the received pilot signal to be subjected to channel compensation. The channel estimation apparatus described. The demodulation accuracy measuring means is
The channel compensation of the received pilot signal is performed on the received pilot signal to be subjected to channel compensation using an averaged channel estimation value vector in which at least one of a time slot and a subcarrier is different. Item 2. The channel estimation device according to Item 1. The averaging means comprises:
The channel estimation apparatus according to any one of claims 1 to 3, wherein the weighting coefficient corresponding to a time slot and a subcarrier of the received pilot signal to be subjected to channel compensation is set to 0. The demodulation accuracy measuring means is
The averaging range in the generation of the averaged channel estimation value does not include the time slot and subcarrier component corresponding to the received pilot signal to be subjected to channel compensation.
The channel estimation apparatus according to claim 1, wherein channel compensation of the received pilot signal is performed by shifting at least one of a time slot and a subcarrier of the average channel estimation value vector. The demodulation accuracy measuring means is
For the received pilot signal subject to channel compensation, using an averaged channel estimation value vector with different time slots in the same subcarrier, and an averaged channel estimation value vector with different subcarriers in the same time slot, 5. The channel estimation apparatus according to claim 1, wherein channel compensation of the received pilot signal is performed and one of the demodulation accuracy is selected. A channel estimation method used in a radio receiver, comprising:
A channel estimation step for inputting a pilot signal composed of M time slots and N subcarriers as a received pilot signal, and obtaining a channel estimation value per unit time slot and per unit subcarrier;
Using the channel estimation value as input, a plurality of different average ranges P (1), P (2),..., P (U) time slots on the time axis and a plurality of different average ranges Q (1 ), Q (2),..., Q (V) subcarriers, the combination of the average ranges on the time axis and the frequency axis is the first to (U × V) average range set, and the (i × For the average range set of V + j), as a component of the tth time slot and s subcarriers of the (i × V + j) averaged channel estimation value vector, continuous P (on the time axis including the tth time slot is used. i) and continuous Q (j) on the frequency axis including the s-th subcarrier, the total (P (i) × Q (j)) channel estimation values are multiplied by a weighting factor and added. An averaging step to output the results;
The received pilot signal and the first to (U × V) averaged channel estimation value vectors are input, and the received pilot signal is obtained by channel compensation with the kth averaged channel estimation value vector. ˜ (N × M) signal points are k-th received pilot channel compensation vectors, and transmission pilot signal points that are transmission signal points of the received pilot signals, and first to first in the k-th received pilot channel compensation vectors. And a demodulation accuracy measuring step for determining and outputting an optimum channel estimation value used for channel compensation of the data part using a calculation result of the inter-signal distance with each of (N × M) signal points. Estimation method. A wireless transmission system used for wireless communication,
A pilot signal consisting of M time slots and N subcarriers is input as a received pilot signal,
Channel estimation means for obtaining a channel estimation value per unit time slot and per unit subcarrier;
Using the channel estimation value as input, a plurality of different average ranges P (1), P (2),..., P (U) time slots on the time axis and a plurality of different average ranges Q (1 ), Q (2),..., Q (V) subcarriers, the combination of the average ranges on the time axis and the frequency axis is the first to (U × V) average range set, and the (i × For the average range set of V + j), as a component of the tth time slot and s subcarriers of the (i × V + j) averaged channel estimation value vector, continuous P (on the time axis including the tth time slot is used. i) and continuous Q (j) on the frequency axis including the s-th subcarrier, the total (P (i) × Q (j)) channel estimation values are multiplied by a weighting factor and added. An averaging means for outputting the results;
The received pilot signal and the first to (U × V) averaged channel estimation value vectors are input, and the received pilot signal is obtained by channel compensation with the kth averaged channel estimation value vector. ˜ (N × M) signal points are k-th received pilot channel compensation vectors, and transmission pilot signal points that are transmission signal points of the received pilot signals, and first to first in the k-th received pilot channel compensation vectors. And a demodulation accuracy measuring means for determining and outputting an optimum channel estimation value used for channel compensation of the data part using a calculation result of a distance between signals with each of (N × M) signal points. Transmission system. Wireless receiver
A channel estimation process for inputting a pilot signal composed of M time slots and N subcarriers as a received pilot signal, and obtaining a channel estimation value per unit time slot and per unit subcarrier;
Using the channel estimation value as input, a plurality of different average ranges P (1), P (2),..., P (U) time slots on the time axis and a plurality of different average ranges Q (1 ), Q (2),..., Q (V) subcarriers, the combination of the average ranges on the time axis and the frequency axis is the first to (U × V) average range set, and the (i × For the average range set of V + j), as a component of the tth time slot and s subcarriers of the (i × V + j) averaged channel estimation value vector, continuous P (on the time axis including the tth time slot is used. i) and continuous Q (j) on the frequency axis including the s-th subcarrier, the total (P (i) × Q (j)) channel estimation values are multiplied by a weighting factor and added. An averaging process to output the results;
The received pilot signal and the first to (U × V) average channel estimation value vectors are input, and the received pilot signal is averaged by the k-th (k is a natural number equal to or less than (U × V)). First to (N × M) signal points obtained by channel compensation with a channel estimation value vector are k-th received pilot channel compensation vectors, and transmission pilot signal points that are transmission signal points of the received pilot signal; The optimum channel estimation value used for channel compensation of the data part is determined and output using the calculation result of the inter-signal distance with each of the first to (N × M) signal points in the k-th received pilot channel compensation vector. A wireless receiver program for executing demodulation accuracy measurement processing. A channel estimation device used in a radio receiver,
A plurality of pilot signals configured corresponding to M time slots and N subcarriers are used as reception pilot signals, and each time slot and one subcarrier are based on the reception pilot signals. Channel estimation means for obtaining a channel estimation value of
When the channel estimation value is input, a plurality of different time slots on the time axis are specified as an average range time slot, and a plurality of different subcarriers on the frequency axis are specified as an average range subcarrier, the average A combination of a range time slot and the average range subcarrier is an average range set,
An average channel estimation value vector is calculated for the average range set, and P consecutive time slots on the time axis including the t-th time slot of the average channel estimation vector and a frequency axis including the s-th subcarrier Averaging means for multiplying P × Q channel estimation values by a weighting factor as the above consecutive Q subcarriers and components to obtain a multiplication value and outputting a result obtained by adding the multiplication values respectively;
The received pilot signal and the averaged channel estimation value vector are input, and a signal point obtained by performing channel compensation on the received pilot signal with the kth averaged channel estimation value vector is defined as a kth received pilot channel compensation vector. And used for the channel compensation of the data part using the calculation result of the inter-signal distance between the transmission pilot signal point that is the transmission signal point of the reception pilot signal and each of the signal points in the kth reception pilot channel compensation vector. A channel estimation apparatus comprising: demodulation accuracy measuring means for determining an optimum channel estimation value.

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