JPWO2007052830A1 - Receiving device, receiving method, matched filter design method, transversal filter coefficient setting method - Google Patents

Abstract

This is a receiving method in which a signal having a known period N on the receiving side is received by a matched filter of N chip signals obtained by the following steps. (1) DFT transform of a signal of period N to obtain an Nth order matrix (c0, c1,... CN-1) t; (2) DFT transform of an arbitrary N chip signal and Nth order The matrix (d0, d1,..., DN-1) t of N and the two matrices obtained in steps (3), (1), and (2) are used to calculate an Nth order matrix (c0 / d0, c1). / D1,... CN−1 / dN−1) t and the Nth order matrix (e0, e1) obtained by performing inverse DFT transform on the Nth order matrix obtained in steps (4) and (3). ,... EN-1) t and (5) determining N chip signals such that e1 is maximized and at least e1 is zero.

Description

  The present invention relates to a receiving apparatus, a receiving method, a matched filter design method, and a transversal filter coefficient setting method.

In wireless communication, radio waves transmitted from a transmitter are received by a receiver. At this time, the receiver must receive the reflected wave reflected by the reflecting object (building, mountain, etc.) unless it is a large plain other than directly receiving the transmitted radio wave as it is. Become.
Therefore, in the receiver, the reflected signal of the main signal is received simultaneously with the main signal (main signal), and an error of the received signal occurs due to the reflected signal. As a result, the transmitted main signal cannot be accurately reproduced on the receiving side.
The reflected wave that causes this error is called a multipath wave. However, this influence cannot be ignored particularly in indoor communication and urban communication.
Therefore, a receiver as shown in FIG. 1 is used. The receiver shown in FIG. 1 includes antennas 11 and 14, a pilot signal receiving unit 12, a multipath characteristic measuring unit 13, a data signal receiving unit 15, a multipath removing unit 16, and a data decoding unit 17. The antennas 11 and 14 may be a single antenna. In this case, the data signal receiving unit 15 may also serve as the pilot signal receiving unit 12.
The communication method can be applied to a communication method such as OFDM (Orthogonal Frequency Division Multiplex).
The operation of the receiver of FIG. 1 will be described. The received wave affected by the multipath is converted into a baseband signal by the data signal receiving unit 15. Since the received signal converted into the baseband signal is affected by the multipath, the multipath removal unit 16 removes the influence of the multipath. The data decoding unit 17 decodes the data from which the multipath effect has been removed.
The pilot signal receiving unit 12 receives the pilot signal simultaneously with the reception of the data signal. Based on the transmitted pilot signal known on the receiving side and the actually received pilot signal, the multipath characteristic measuring unit 13 estimates the multipath characteristic. Based on the estimated multipath characteristic, the multipath removal unit 16 removes the multipath.
Note that the pilot signal is a signal different from the data signal and at least a signal that is distinguished from the data signal. As the pilot signal, a signal having high autocorrelation and low cross-correlation with a data signal or the like is used. In addition, the pilot signal to be transmitted can be informed to the reception side in advance, and can be handled as a known signal in the receiver. As a result, on the receiving side, the multipath characteristic can be estimated by comparing the signal that should be originally received with the signal that is actually received.
In FIG. 1, a multipath using unit 161 may be used instead of the multipath removing unit 16 as shown in FIG. The multipath utilization unit 161 in FIG. 2 does not simply remove the multipath, but from the multipath characteristic measured by the multipath characteristic measurement unit 13 as in RAKE reception, for example, the multipath wave in FIG. MP1, MP2 and MP3 are added in phase with the direct wave. Thereby, a multipath wave can be used.
By the way, in order to add the multipath waves MP1, MP2, and MP3 to the direct wave in phase with the multipath utilization unit 161 in FIG. 2, the multipath characteristic measurement unit 13 accurately calculates the multipath in the baseband region. Need to be measured.
Therefore, a ZCZ (Zero Correlation Zone Sequence) sequence is used for measurement of multipath characteristics (see Patent Document 1).
In general, a ZCZ sequence is generated from a completely complementary sequence, and a one-dimensional sequence that is zero within a certain range of an autocorrelation function and a cross-correlation function is referred to as ZCZ. FIG. 4 shows an example of a complete complementary sequence of order 8, and FIG. 5 shows two ZCZ sequences generated from the complete complementary sequence of order 8 of FIG. It should be noted that two ZCZ sequences are generated from the complete complementary sequence composed of four sets and four from the complete complementary sequence composed of 16 sets. Although the number of “0” needs to be the same for vector A and vector B, it may be any number.
When the signal A shown in FIG. 5 is applied to the matched filter of the signal A, as shown in FIG.
000000080000000
Output
When signal A is applied to the matched filter of signal B, from its output, as shown in FIG.
000000000000000000
Is obtained.
Similarly, when the signal B shown in FIG. 5 is applied to the matched filter of the signal B, from the output,
000000080000000
Output
When signal B is applied to the matched filter of signal A, 000000000000000000 from its output
Is obtained.
In the case where the output of FIG. 6A is obtained, when multipath occurs, the output of the filter as shown in FIG. 7 is obtained.
In FIG. 7, since a multipath signal can be obtained in a time domain without noise, it is possible to accurately obtain a multipath characteristic.
In general, a signal that matches a circuit is a signal obtained by reversing the impulse response in time to form a complex conjugate. It is a response circuit.
For example, a matched filter for a 4-chip signal (−j111) is a circuit with an impulse response of (111j).
Special Table 2002-536870 Publication

However, although such a ZCZ sequence has strict characteristics, there is a problem that codes belonging to the ZCZ sequence are limited.
The present invention has been made in view of the above problems, and when receiving a signal with a known period N, a receiving device having characteristics equivalent to those when receiving a ZCZ sequence by receiving with a predetermined matched filter, It is an object of the present invention to provide a reception method, a matched filter design method, and a transversal filter coefficient setting method.

In order to solve the above problems, the present invention employs means for solving the problems having the following characteristics.
According to a first aspect of the present invention, an N-chip (or digit, bit) signal having a known period N on the receiving side is received by an N-chip signal matching filter obtained by the following first to fifth means. This is a featured receiving apparatus.
An _N-th order matrix (c ₀ , c ₁ ,... C _N-1 ) is obtained by DFT-transforming the N-chip signals (a ₀ , a ₁ ,... A _N-1 ) having the known period N. a first means for determining ^t ;
Second to obtain an Nth order matrix (d ₀ , d ₁ ,..., D _N-1 ) t by DFT transforming an arbitrary N-chip signal (b ₀ , b ₁ ,..., B _N-1 ). means,
The matrix element obtained by the first means and the complex conjugate of the matrix element obtained by the second means are multiplied for each corresponding element to obtain an Nth-order matrix (c ₀ / d ₀ , c ₁ / D ₁ ,... C _N−1 / d _N−1 ) third means for determining ^t ,
The Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t obtained by the third means is subjected to inverse DFT transform to obtain an Nth order matrix ( e ₀ , e ₁ ,... e _N−1 ) fourth means for determining ^t ;
Fifth means for obtaining an N-chip signal such that N-th order matrix e ₀ obtained by the fourth means is larger than a predetermined size and at least e ₁ is zero. “T” is a transposed matrix. “/ D” represents a complex conjugate of d.
In the fifth means, there are a plurality of N-chip signals in which the N-th order matrix e ₀ obtained by the fourth means is larger than a predetermined size and at least e ₁ is zero. Here, obtaining an N-chip signal means specifying an arbitrary N-chip signal as a specific N-chip signal so as to satisfy such a condition.
According to a second aspect, in the first aspect, the N-chip signal having the known period N is a preamble signal or a training signal defined by IEEE 802.11.
A third invention is characterized in that, in the first or second invention, the multipath characteristic is measured by receiving an N-chip signal of the known period N on the receiving side.
A fourth aspect of the invention is a receiving method in which an N-chip signal having a known period N on the receiving side is received by an N-chip signal matching filter obtained by the following first to fifth steps.
The _N-th matrix (c ₀ , c ₁ ,... C _N-1 ) ^{t is obtained} by DFT transforming the N chip signals (a ₀ , a ₁ ,... A _N−1 ) having the known period N. A first step for determining
Second to obtain an Nth order matrix (d ₀ , d ₁ ,... D _N-1 ) ^t by DFT transforming an arbitrary N chip signal (b ₀ , b ₁ ,..., B _N-1 ). And the steps
The matrix element obtained in the first step and the complex conjugate of the matrix element obtained in the second step are multiplied for each corresponding element to obtain an Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... c _N−1 / d _N−1 ) a third step for obtaining ^t ;
The Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t obtained by the third step is subjected to inverse DFT transform, and the Nth order matrix (E ₀ , e ₁ ,... E _N−1 ) Fourth step for obtaining ^t ;
In order N of the matrix which has been determined by the fourth step, the e ₀ is greater than a predetermined size, further, a fifth step of obtaining a N chip signals, such as at least e ₁ becomes zero Note, "t" Represents a transposed matrix, and “/ d” represents a complex conjugate of d.
Incidentally, in the fifth step, said N-order matrix e ₀ obtained by the fourth means and greater than a predetermined size, further, the N-chip signal, such as at least e ₁ becomes zero, there are multiple. Here, obtaining an N-chip signal means specifying an arbitrary N-chip signal as a specific N-chip signal so as to satisfy such a condition.
According to a fifth aspect, in the fourth aspect, the N-chip signal having the known period N is a preamble signal or a training signal defined by IEEE 802.11.
A sixth invention is characterized in that, in the fourth or fifth invention, the multipath characteristic is measured by receiving a signal of N chips having the known period N on the receiving side.
In a seventh aspect of the invention, an N-th order matrix (c ₀ , c ₁ ,... C) is obtained by DFT transforming N chip signals (a ₀ , a ₁ ,... A _N−1 ) having a known period N. _N-1 ) a first step for determining ^t ;
Second to obtain an Nth order matrix (d ₀ , d ₁ ,... D _N-1 ) ^t by DFT transforming an arbitrary N chip signal (b ₀ , b ₁ ,..., B _N-1 ). And the steps
The matrix element obtained in the first step and the complex conjugate of the matrix element obtained in the second step are multiplied for each corresponding element to obtain an Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... c _N−1 / d _N−1 ) a third step for obtaining ^t ;
The Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t obtained by the third step is subjected to inverse DFT transform, and the Nth order matrix (E ₀ , e ₁ ,... E _N−1 ) Fourth step for obtaining ^t ;
A fifth step of obtaining an N-chip signal such that e ₀ is larger than a predetermined size in the N-th order matrix obtained by the fourth step and at least e ₁ is zero;
And a step of generating a matched filter for the N-chip signal obtained in the fifth step.
“T” represents a transposed matrix, and “/ d” represents a complex conjugate of d.
According to an eighth aspect of the present invention, there is provided a receiving apparatus characterized in that the receiving side receives the N-chip signal having the known period N by a matched filter designed by the designing method of the seventh aspect.
The ninth invention has N branch circuits, and each branch circuit has coefficients x ₁ , x ₂ ,..., X _N−1 , x _{N respectively} , and cascaded to the coefficient multipliers. And a delay circuit set so as to be different from each other by the time slot of the input signal, and further, a coefficient setting method of a transversal filter for synthesizing signals from each of N branches branched by an adder In
When a known N-chip signal is supplied to the input terminal of the transversal filter, 2N-1 signals output in time series from the transversal filter,
The coefficient x ₁ , x ₂ ,... Of the coefficient unit is set so that the signal output at the center time is larger than a predetermined magnitude, and at least the signal output at the time adjacent to the signal is zero. .., X _N−1 , x _N are set.
A tenth aspect of the invention is a receiving apparatus characterized in that the known N-chip signal is received on the receiving side by a transversal filter having a coefficient set in the ninth aspect.
The eleventh invention is provided with a plurality of transversal filters whose coefficients are set by the method of the ninth invention,
Simultaneously supplying the known N-chip signals to the plurality of transversal filters;
The receiving apparatus is characterized in that outputs of the plurality of transversal filters are added and output.
A twelfth aspect of the invention is the receiving apparatus according to any one of the ninth to eleventh aspects of the invention, wherein the known N-chip signal is a preamble signal or a training signal defined by IEEE 802.11. .
The thirteenth invention has N branch circuits, and each branch circuit has coefficients x ₁ , x ₂ ,... X _N−1 , x _N , respectively, and cascades the coefficient multipliers. In a transversal filter coefficient setting method for synthesizing signals from N branches branched by an adder, the delay circuit is set so as to be different for the time slot of the input signal. ,
An impulse signal that has passed through a multipath line having a multipath is supplied to an input terminal of the transversal filter, and 2N-1 signals output in time series from the transversal filter,
The coefficient x ₁ , x ₂ ,... Of the coefficient unit is set so that the signal output at the center time is larger than a predetermined magnitude, and at least the signal output at the time adjacent to the signal is zero. .., X _N−1 , x _N are set.
A fourteenth aspect of the invention is a receiving apparatus characterized in that an arbitrary signal that has passed through the multipath line on the receiving side is received by a transversal filter whose coefficients are set by the method of the thirteenth aspect.
A fifteenth aspect of the present invention provides a plurality of transversal filters whose coefficients are set by the method of the thirteenth aspect of the invention,
Applying an arbitrary signal via the multipath line simultaneously to the plurality of transversal filters,
The receiving apparatus is characterized in that outputs of the plurality of transversal filters are added and output.

  According to the present invention, when a signal having a known period N is received, a reception device and a reception method having characteristics equivalent to those obtained when a ZCZ sequence is received by a filter representing a ZCZ characteristic by being received by a predetermined matched filter. A matching filter design method and a transversal filter coefficient setting method can be provided.

FIG. 1 is a diagram for explaining a receiving apparatus (part 1).
FIG. 2 is a diagram for explaining the receiving apparatus (part 2).
FIG. 3 is a diagram for explaining multipath at a radio frequency.
FIG. 4 is a diagram for explaining an example of a completely complementary series.
FIG. 5 is a diagram for explaining an example of a ZCZ sequence.
FIG. 6 is a diagram for explaining the output of the matched filter (when there is no multipath).
FIG. 7 is a diagram for explaining the output of the matched filter (in the case of multipath).
FIG. 8 shows one method for obtaining the cross-correlation function of two signals.
FIG. 9 is a diagram for explaining the case of a 4-chip signal.
FIG. 10 is a diagram for explaining a 4-row, 4-column DFT matrix.
FIG. 11 is a diagram for explaining a 4-row, 4-column inverse DFT matrix.
FIG. 12 is a diagram for explaining a frequency domain matrix and its frequency position.
FIG. 13 is a diagram for explaining a time-domain matrix and its pulse positions.
FIG. 14 is a diagram (No. 1) for explaining the setting that provides the same characteristics as when a ZCZ sequence is received.
FIG. 15 is a diagram (part 1) for explaining the case of a 16-chip signal.
FIG. 16 is a diagram (No. 2) for explaining the setting that provides the same characteristics as when a ZCZ sequence is received.
FIG. 17 is a diagram (part 2) for explaining the case of a 16-chip signal.
FIG. 18 is a diagram for explaining a transversal filter for a 3-chip input signal.
FIG. 19 is a diagram for explaining the setting of the coefficients of the transversal filter.
FIG. 20 is a diagram for explaining a transversal filter for a 5-chip input signal.
FIG. 21 is a diagram for explaining the noise suppression filter.
FIG. 22 is a diagram for explaining the multipath inverse filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11, 14 Antenna 12 Pilot signal (training signal) receiving part 13 Multipath characteristic measurement part 15 Data signal receiving part 16 Multipath removal part 17 Data decoding part 161 Multipath utilization part 21 Input terminal 22-24 Coefficient 25, 26 Delay circuit 27, 33, 426 Adder 321-325, 421-425 Filter

(Design of filter using DFT matrix)
“N-chip signal A (... A _N−1 , a ₀ , a ₁ ,..., A _N−1 , a ₀ ...)” And N-chip signal B (b ₀ , A cross-correlation function with b ₁ ,... b _N−1 ) will be described with reference to FIG.
In the following description, the case of “N-chip signal A of period N (... A ₀ , a ₁ ,... A _N−1 ,...)” Will be mainly described. However, in the present invention, in place of “N-chip signal A (... A ₀ , a ₁ ,... A _N−1 ...) Having a period _N , a pseudo-periodic signal having a finite period is used. It may be. In this specification, the term “periodic signal” includes pseudo-periodic signals. “N-chip signal A (... A ₀ , a ₁ ,... A _N-1 ...)” Of pseudo period N is “the main body of signal A (a ₀ , a ₁ ,... A part of the latter half of the main body of the signal A is added before “a _N−1 ” ”, and a part of the first half of the signal A is added after the main body of the signal A (the first half or the second half). Or a signal added only to the Further, a pilot signal or a training signal can be used as the _N- chip signal A (... A ₀ , a ₁ ,... A _N−1 .
First, (1) DFT transform of “N-chip signals A (a ₀ , a ₁ ,... A _N−1 )” of period N is performed, and an N-order matrix (c ₀ , c ₁ ,. ..C _N-1 ) ^t is generated.
Next, (2) DFT transform of “N-chip signal B (b ₀ , b ₁ ,... B _N−1 )” and frequency domain N-order matrix (d ₀ , d ₁ ,... D _N−1 ) ^t is generated. “T” represents a transposed matrix.
Next, (3) the elements of the N-th order matrix (c ₀ , c ₁ ,... C _N-1 ) ^t and the N-th order matrix (d ₀ , d ₁ ,... D _N-1 ) ^t The complex conjugate of the elements is multiplied for each corresponding element to generate an Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t . . Note that “/ d” represents the complex conjugate of d.
(4) where, N following matrix in the frequency domain _{(c 0 / d 0, c} 1 / d 1, ··· c N-1 / d N-1) When the inverse DFT transform a ^t, the signal of period N It is possible to obtain a cross-correlation function between (a ₀ , a ₁ ,... A _N−1 ) and N chip signals (b ₀ , b ₁ ,... B _N−1 ).
Next, a reception apparatus and reception method having characteristics equivalent to those when a ZCZ sequence is received by receiving a known training signal (which may be a pilot signal) and receiving it with a predetermined matched filter will be described.
In order to facilitate understanding, a 4-chip signal will be described with reference to FIG. In FIG. 9, it is assumed that the known training signal is a 4-chip signal (0.5-0.5 0.5 1.5) with a period of 4T. T is a time slot of each signal. When this 4-chip signal (0.5-0.50.5 1.5) is DFT transformed by the fourth-order DFT matrix shown in FIG. 10, (1j0-j) ^t in FIG. 9A is obtained. .
On the other hand, with respect to an arbitrary 4-chip periodic signal (xyzw), the matrix shown in FIG.
Next, similarly to FIG. 8, the matrix shown in FIG. 9C is obtained from the complex conjugate of the matrix of FIG. 9A and the matrix of FIG. 9B.
When the matrix of FIG. 9C is subjected to inverse DFT transform using the fourth-order DFT inverse matrix illustrated in FIG. 11, the matrix illustrated in FIG. 9D is obtained.
Here, the frequency position of (c ₀ , c ₁ , c ₂ , c ₃ ) ^t obtained by performing DFT conversion on the 4-chip time-axis signals (a ₀ , a ₁ , a ₂ , a ₃ ) As shown in FIG. 12, it is as shown in FIG. That is, the frequency axis coefficient c ₀ represents the magnitude of the direct current frequency number component at frequency zero (C), and the frequency axis coefficient c ₁ represents the magnitude of the frequency component adjacent to the right side (D). , the coefficient c ₃ of the frequency axis, (C) represents the magnitude of the frequency frequency components to the left of (B), the coefficient c ₂ of the frequency axis represents the magnitude of the outside of the frequency number components (a , E).
Note that if Δf is the reciprocal of the time slot (Δf = 1 / T) of the signals of the time axis signals (a ₀ , a ₁ , a ₂ , a ₃ ), the whole has a band of 4Δf.
Similarly, when the time axis signal of FIG. 9D obtained by performing inverse DFT transform on the frequency axis signal of FIG. 9C is (e ₀ , e ₁ , e ₂ , e ₃ ), The time position is as shown in FIG. That is, the time axis coefficient e ₀ represents the magnitude of the signal at the center time t ₀ (C), and the time axis coefficient e ₁ represents the magnitude of the signal at the right adjacent time (D). The axis coefficient e ₃ represents the signal magnitude at the time on the left of (C) (B), and the time axis coefficient e ₂ represents the signal magnitude at the outside time (A, E). ).
Therefore, as shown in FIG. 13B, by increasing the C component and setting the B and D components to zero, it is possible to obtain the same characteristics as when a ZCZ sequence is received. If the B and D components are zero, the same characteristics as when the ZCZ sequence is received can be obtained, so there is no need to worry about the components A and E here.
The case of FIG. 9D will be specifically described. When the fourth-order column vector shown in FIG. 9D is (A, B, C, D) ^t , in order to obtain the same characteristics as when the ZCZ sequence is received, FIG. ) As shown in
A = xy + z + 3w is increased,
B = −x + y + 3z + w is zero,
As for C = x + 3y + z−w, it does n’t matter,
Let D = 3x + y−z + w be zero.
Regarding B and D, if expressed in mathematical formulas,
-X + y + 3z + w = 0 (1)
3x + y-3 + w = 0 (2)
It becomes.
Therefore, a 4-chip signal (xyzw) is set so as to increase A = x−y + z + 3w while satisfying the expressions (1) and (2).
Therefore, by receiving a 4-chip signal (1/2 -1/2 1/2 3/2), which is a known training signal, with a matched filter of the 4-chip signal (xyzw) set in this way, As shown in FIG. 13B, the same characteristics as when a ZCZ sequence is received can be obtained.
Next, a 4-chip periodic signal (xyzw) that satisfies the expressions (1) and (2) and increases A = xy + z + 3w will be considered.
From formula (1) and formula (2),
x = z (3)
And y + 2z + w = 0 (4)
Can be obtained.
Since there are four unknowns and two equations, x, y, z, and w cannot be determined uniquely.
However, although it cannot be determined uniquely, it can be said that there is a degree of freedom. Therefore, there are an infinite number of 4-chip periodic signals (xyzw) so as to increase A = x−y + z + 3w while satisfying the expressions (1) and (2).
As one of the solutions, there is a 4-chip signal (1-3 1 1). Therefore, if a 4-chip signal (0.5-0.5 0.5 1.5) with a period of 4 is received by the filter that matches the 4-chip signal (1-3 1 1), FIG. ) A signal as shown on the right can be obtained.
In the case of a 4-chip periodic signal (1 −3 1 1), A = 8, B = 0, C = −8, and D = 0. So, check this.
Using the matched filter of the 4-chip signal (1-3 1 1), which is the 4-chip signal (xyzw), as a reception filter, the signal “3” at the rear of the periodic signal (1 −1 1 3) is added in front, A signal to the signal (3 1 -1 1 3 1-1) to which “1-1” of the front signal is added later is referred to as a periodic signal (1 −1 1 3). ).
Then, 3 4 -9 0 8 0 -8 -14 -1 is obtained. The underlined portion is obtained as a result of the expressions (1) and (2).
In this way, when a signal with a known period N is received, a receiving device and a receiving method having characteristics equivalent to those when a ZCZ sequence is received can be obtained by receiving with a predetermined matched filter.
So far, the case of a 4-chip signal has been described. Next, the case of a 16-chip signal will be described with reference to FIG.
(1) First, the time base signal which is a known training signal period _{16 (··· a 0, a 1} , a 2 ··· a 15 ···) time domain signal in _{(a 0, a} 1, a ₂ ... A ₁₅ ) is generated using a 16th order DFT matrix and a 16th order matrix (c ₀ , c ₁ ,... C ₋₂ c ₋₁ ) ^t is generated.
(2) Next, a 16th-order matrix (d ₀ , d ₁ ,..., D ₋₁ ) ^t is generated by DFT transforming an arbitrary 16-chip signal (b ₀ , b ₁ ,... B ₋₁ ). To do.
(3) Next, from the complex conjugate of the 16th order matrix (c ₀ , c ₁ ,... C ₋₁ ) ^t and the 16th order matrix (d ₀ , d ₁ ,... D ₋₁ ) ^t , A 16th-order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C ₋₁ / d ₋₁ ) ^t is generated. Note that “/ d” represents the complex conjugate of d.
(4) Next, a 16th-order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C ₋₁ / d ₋₁ ) ^t is subjected to inverse DFT transform to obtain a signal (a ₀ , matrix (e ₀ , e ₁ ,... e ₋ representing a cross-correlation function between a ₁ ,... a _N−1 ) and N chip signals (b ₀ , b ₁ ,... b _N−1 ). ₂ , e ₋₁ ) ^t is generated. In contrast, consider the same manner as FIG. 13 (B), to increase the signal level of e _0, to zero signal level of ambient e _0.
For example, FIG. 16 shows a case where e ₋₃ , e ₋₂ , e ₋₁ , e ₁ , e ₂ , and e ₃ are set to zero.
Next, a signal A (a ₀ a ₁ a ₂ a ₃ ... A ₁₃ a ₁₄ a ₁₅ ) having a period 16 on the time axis will be described as an example.
A signal A (a ₀ a ₁ a ₂ a ₃ ... A ₁₃ a ₁₄ a ₁₅ ) having a period 16 on the time axis will be described with reference to FIG. FIG. 17A shows a 16-chip signal A (a ₀ a ₁ a ₂ a ₃ ... A ₁₃ a ₁₄ a ₁₅ ).
FIG. 17B is a pseudo-periodic signal of the signal A (a ₀ a ₁ a ₂ a ₃ ... A ₁₃ a ₁₄ a ₁₅ ), and the signal (a _{16-m 2} ... A ₁₅ a ₀ a ₁ a ₂ a ₃ ·· a ₁₃ a ₁₄ a ₁₅ a ₀ · a _m1-1 ). The signal of FIG. 17B is the signal before the signal A in the signal A (a ₀ a ₁ a ₂ a ₃ ... A ₁₃ a ₁₄ a ₁₅ ) on the time axis shown in FIG. Signal A is added to the _second half of signal A (m ₂ pieces), and after signal A is added to the first half of signal A (m ₁ pieces). This signal is shown in FIG. As described above, e ₀ is equal to or larger than a predetermined size, and e ₁ , e ₂ , e ₃ , e ₄ , e ₋₂ , and e ₋₁ are set to zero (other components are not minded). The 16-chip signals (b ₀ , b ₁ ,... B ₋₁ ) are received by a matched filter.
As a result, the signal A on the time axis can be received as shown in FIG. Therefore, the multipath characteristic can be measured by the signal A on the time axis. Note that FIG. 17C shows a case where m ₁ = 4 and m ₂ = 2. Since multipath occurs after a direct wave, it is preferable that m ₁ > m ₂ .
As a known 16-chip signal, a preamble signal or a training signal defined by IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, or the like can be used.
In FIG. 16, N chip signals (b ₀ , b ₁ ,..., B _N− satisfying the condition that e ₋₃ , e ₋₂ , e ₋₁ , e ₁ , e ₂ , and e ₃ are set to zero. ₁ ) was obtained, but in addition to this condition, a condition for keeping the signal level constant may be added.
In this case, in addition to the conditions of e ₋₃ = 0, e ₋₂ = 0, e ₋₁ = 0, e ₁ = 0, e ₂ = 0, e ₃ = 0,
b ₀ ² + b ₁ ² +... + b _N−1 ² = constant (= r ² )
N chip signals (b ₀ , b ₁ ,..., B _N−1 ) satisfying the above are obtained.
(Design of filter without using DFT matrix)
Here, the design of a filter that can obtain the same characteristics as when a ZCZ sequence is received without using a DFT matrix will be described.
In order to facilitate understanding, the case of the filter of FIG. 18 will be described for the signal (1 1 −1) of 3 chips. In the present invention, as shown in FIGS. 18 and 20, the branch circuit has N branches, and each branch circuit includes a coefficient unit and a delay circuit cascaded to the coefficient unit. A filter that synthesizes the signals from the N branches branched by the adder is called a transversal filter.
The transversal filter of FIG. 18 includes an input terminal 21, a coefficient unit (coefficient x ₁ ) 22, a coefficient unit (coefficient x ₂ ) 23, a coefficient unit (coefficient x ₃ ) 24, a delay circuit (τ delay) 25, a delay circuit ( 2τ delay) 26 and an adder 27. Note that τ is a delay time corresponding to the time slot time of the signal to be processed.
A known three-chip signal (1 1 −1) applied to the input terminal 21 is sequentially sent from its output terminal to x ₃ (t ₀ ), x ₂ + x ₃ (t ₀ + T) as shown in FIG. ), X ₁ + x ₂ −x ₃ (t ₀ + 2T), x ₁ −x ₂ (t ₀ + 3T), and −x ₁ (t ₀ + 4T) are output.
Generally speaking, in the case of a transversal filter with N branches supplied with N chip signals, 2N-1 time-series signals are output from the transversal filter.
Therefore, in order to obtain the same characteristics as when the ZCZ sequence is received, as shown in FIG. 19, the value of the central time point (t ₀ + 2T) is increased and the time point adjacent to the central time point is increased. The magnitudes of (t ₀ + T) and time (t ₀ + 3T) are set to zero, and the magnitudes of time (t ₀ ) and time (t ₀ + 4T) are ignored.
In other words,
x ₂ + x ₃ = 0 (3)
x ₁ −x ₂ = 0 (4)
The filter coefficients x ₁ , x ₂ and x ₃ are set so as to increase x ₁ + x ₂ −x ₃ while satisfying the expressions (3) and (4).
That is, in this case, if x1 = x2 = −x3, when a known 3-chip signal (1 1 −1) is received, an output equivalent to that when a ZCZ sequence is received can be obtained. .
The case of a 5-chip signal will be described with reference to FIG. When a known 5-chip signal (1 1 1 -1 1) is applied to the input terminal of the transversal filter of FIG. 20, from the output terminal, as shown in FIG. 20, x ₅ (t ₀ ), x ₄ , + x ₅ (t ₀ + T), x ₃ + x ₄ + x ₅ (t ₀ + 2T), x ₂ + x ₃ + x ₄ −x ₅ (t ₀ + 3T), x ₁ + x ₂ + x ₃ −x ₄ + x ₅ ( t ₀ + 4T), x ₁ + x ₂ −x ₃ + x ₄ (t ₀ + 5T), x ₁ −x ₂ + x ₃ (t ₀ + 6T), −x ₁ + x ₂ (t ₀ + 7T), x ₁ (t ₀ + 8T) ) Is output.
Therefore, in order to obtain the same characteristics as when the ZCZ sequence is received, as shown in FIG. 19, the value of the time point (t ₀ + 4T) is increased, and the time point (t ₀ + 3T) and the time point (t ₀ ). The magnitude of + 5T) is set to zero, and the magnitudes of the time point (t ₀ ) and the time point (t ₀ + 4T) are ignored.
In other words,
x ₂ + x ₃ + x ₄ −x ₅ = 0 (5)
x ₁ + x ₂ −x ₃ + x ₄ = 0 (6)
The coefficients x ₁ , x ₂ , x ₃ , x ₄ and x ₅ of the transversal filter are set so as to increase x ₁ + x ₂ + x ₃ −x ₄ + x ₅ while satisfying the expressions (5) and (6). Set.
However, since there are few equations for determining the coefficient for the required coefficient, the solution is indefinite.
Therefore, since there are many coefficients x ₁ , x ₂ , x ₃ , x ₄ and x ₅ of such a transversal filter, a known 5-chip signal (1 1 1 -1 1) is received, There are many filters that can obtain the same output as when receiving a ZCZ sequence.
Note that the number of chips of the input signal and the number of filters are preferably the same. However, the number of processing chips of the filter may be larger than the number of chips of the input signal.
As a known signal, a 16-chip preamble signal or a training signal defined by IEEE802.11a, IEEE802.11b, IEEE802.11g, or the like can be used.
(Noise suppression filter)
A noise suppression filter in which a number of filters having the same function that can obtain an output equivalent to that when receiving a ZCZ sequence when a known signal is received will be described with reference to FIG.
FIG. 21 includes a known signal A and a noise suppression filter 32. The noise suppression filter 32 includes filters 321 to 325 and an adder 33 that can obtain an output equivalent to that when a ZCZ sequence is received. Filters 321 to 325 are different filters.
As described above, when a known 5-chip signal (1 1 1 -1 1) is received, there are many filters that can obtain an output equivalent to that when a ZCZ sequence is received.
Therefore, when a known 5-chip signal (1 1 1 -1 1) is received, it is simultaneously received by the filters 321 to 325, which can obtain an output equivalent to that when the ZCZ sequence is received, and is added to the adder. Add at 33. Thereby, SN ratio can be improved.
That is, even if noise is added to the signal between the known signal A and the noise suppression filter 32, the signal is output from the filters 321 to 325 in the same phase, but the noise is randomly generated from the filters 321 to 325. Since the signal is output with a correct phase, the SN ratio of the added signal is improved.
As described above, a noise suppression filter is configured by forming N filters for obtaining a ZCZ output for a given signal and adding the N filter outputs.
Since the output of this noise suppression filter is equivalent to the output when the ZCZ sequence is received, the multipath characteristic can be measured by this noise suppression filter.
(Multi-pass inverse filter)
The multipath inverse filter is a filter that converts a signal that has passed through the multipath line into an original signal (a signal that is not affected by the multipath line).
The multipath inverse filter can be designed in the same manner as “designing a filter not using a DFT matrix”. That is, by applying a signal (original signal + multipath signal; here, known) as a known N-chip signal to the transversal filter of FIGS. An inverse filter can be designed.
By the way, in the “design of the filter not using the DFT matrix”, a known N chip (3 or 5 chip) signal is applied to the transversal filter. However, in this multipath inverse filter, a signal whose impulse has passed through a multipath line is used as a known N-chip signal.
For example, when the multipath characteristic of the line is (1, -0.5, 0.25j, 0), when an impulse is transmitted to the multipath line, the receiving side sequentially receives 1, -0.5, 0. .25j, 0 signal is received. Therefore, when the multipath characteristic of the line is (1, -0.5, 0.25j, 0), the signal (1, -0.5, 0.25j, 0) is used as a known N chip signal. Apply to transversal filter.
In this way, by applying a signal through which the impulse has passed through the multipath line to the transversal filter and designing the filter in the same manner as “designing a filter not using the DFT matrix”, the signal through which the impulse has passed through the multipath line is used. On the other hand, it is possible to obtain a filter that can obtain the same characteristics as when a ZCZ sequence is received.
In principle, the original impulse can be output by receiving the impulse signal via the multipath line by the multipath inverse filter.
Further, a plurality of the multipath inverse filters may be provided in parallel as in FIG.
For example, a plurality of multipath inverse filters provided in parallel can be configured as shown in FIG. The multipath inverse filter 42 in FIG. 22 includes filters 421 to 425 and an adder 426.
Here, a case where the multipath characteristic of the line is (1, −0.5, 0.25j, 0) as a result of measuring the multipath characteristic using the noise suppression filter will be described.
The filters 421 to 425 are different filters that are applied with signals (1, -0.5, 0.25j, 0) as input signals and that output the same as when receiving a ZCZ sequence.
Thus, transmits a signal _{A (a 0 a 1 a 2} a 3 ·· a 13 a 14 a 15), the multi-path circuits, the input terminals of the multipath inverse filter 42, the signal _A (a ₀ a 1 a ₂ a ₃ ... A ₁₃ a ₁₄ a ₁₅ ), a signal affected by multipath is supplied to each signal a _{0 to} a ₁₅ .
That, _{a 0 is, a 0, -0.5a 0, 0.25ja} 0, 0 , and the
a ₁ becomes a ₁ , −0.5a ₁ , 0.25ja ₁ , 0,
...
a ₁₅ becomes a ₁₅ , −0.5a ₁₅ , 0.25ja ₁₅ , 0, and is supplied to the multipath inverse filter 42.
The filters 421 to 425 are different filters that are applied with signals (1, -0.5, 0.25j, 0) and output as outputs when the ZCZ sequence is received. 425,
a ₀ , −0.5a ₀ , 0.25ja ₀ , 0,
_{a 1, -0.5a 1, 0.25ja 1} , 0,
...
_{a 15, -0.5a 15 /2,0.25ja 15,} 0
Is applied,
a ₀ , a ₁ , a ₂ , a ₃ ,... a ₁₃ , a ₁₄ , a ₁₅ are sequentially output.
That is, the multipath inverse filter 42 can eliminate the influence of multipath.
The multipath inverse filter 42 can be applied to both fixed communication and mobile communication. In the case of fixed communication, a multipath inverse filter is created by measuring multipath characteristics in advance (or at regular intervals).
In the case of mobile communication, a multipath characteristic measurement signal (for example, pilot signal, training signal) is transmitted in parallel with the signal to be transmitted or before and after the signal to be transmitted, and the measured multipath characteristic is obtained each time. use. Note that a multi-pass inverse filter that has been calculated offline and stored in the memory in advance may be selected and used.
In addition, when transmitting a multipath characteristic measurement signal in parallel with a signal to be transmitted, signals that can be separated from each other on the reception side are used.
The multipath in the above description is not limited to the case where the signal is generated on the wireless line, but may be the case where the signal is generated on a wired line. Furthermore, if generalized and a linear transmission system, multipath measurement can be performed in the same manner.
In the specification of the present application, the modulation signal is expressed as “chip” on the assumption that it is used in the spread spectrum communication method, but it can be used in other than the spread spectrum communication method. In this case, “chip” is understood to mean “bit”, “symbol”, etc., which are modulation signals.
Although the best mode for carrying out the invention has been described above, the present invention is not limited to the embodiment described in the best mode. Modifications can be made without departing from the spirit of the present invention.
This international application claims priority based on Japanese Patent Application No. 2005-318711 filed on November 1, 2005, and the entire contents of Patent Application No. 2005-318711 are incorporated herein by reference.

Claims (15)

An N-chip signal having a known period N on the receiving side is received by a matched filter of N-chip signals obtained by the following first to fifth means.
An _N-th order matrix (c ₀ , c ₁ ,... C _N-1 ) is obtained by DFT transforming the N-chip signals (a ₀ , a ₁ ,. a first means for determining ^t ;
Second to obtain an Nth order matrix (d ₀ , d ₁ ,... D _N-1 ) ^t by DFT transforming an arbitrary N chip signal (b ₀ , b ₁ ,..., B _N-1 ). means,
The matrix element obtained by the first means and the complex conjugate of the matrix element obtained by the second means are multiplied for each corresponding element to obtain an Nth-order matrix (c ₀ / d ₀ , c ₁ / D ₁ ,... C _N−1 / d _N−1 ) third means for determining ^t ,
The Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t obtained by the third means is subjected to inverse DFT transform to obtain an Nth order matrix ( e ₀ , e ₁ ,... e _N−1 ) fourth means for determining ^t ,
In order N of the matrix obtained by the fourth means, the e ₀ is greater than a predetermined size, further, it noted fifth means obtains the N chip signals, such as at least e ₁ becomes zero, "t" is transposed “/ D” represents a complex conjugate of d. 2. The receiving apparatus according to claim 1, wherein the N-chip signal having the known period N is a preamble signal or a training signal defined by IEEE 802.11. 3. The receiving apparatus according to claim 1, wherein a multipath characteristic is measured by receiving an N-chip signal having the known period N on the receiving side. A receiving method of receiving N chip signals having a known period N on the receiving side with a matched filter of N chip signals obtained by the following first to fifth steps.
The _N-th matrix (c ₀ , c ₁ ,... C _N-1 ) ^{t is obtained} by DFT transforming the N chip signals (a ₀ , a ₁ ,... A _N−1 ) having the known period N. A first step for
Second to obtain an Nth order matrix (d ₀ , d ₁ ,... D _N-1 ) ^t by DFT transforming an arbitrary N chip signal (b ₀ , b ₁ ,..., B _N-1 ). Steps,
The matrix element obtained in the first step and the complex conjugate of the matrix element obtained in the second step are multiplied for each corresponding element to obtain an Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... c _N−1 / d _N−1 ) Third step for obtaining ^t ,
The Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t obtained by the third step is subjected to inverse DFT transform, and the Nth order matrix (E ₀ , e ₁ ,... E _N−1 ) Fourth step for obtaining ^t ;
In order N of the matrix obtained by the fourth step, the e ₀ is greater than a predetermined size, further, a fifth step of obtaining a N chip signals, such as at least e ₁ becomes zero Note, "t" Represents a transposed matrix, and “/ d” represents a complex conjugate of d. 5. The reception method according to claim 4, wherein the N-chip signal having the known period N is a preamble signal or a training signal defined by IEEE 802.11. 6. The receiving method according to claim 4, wherein a multipath characteristic is measured by receiving a signal of N chips of the known period N on the receiving side. An _N-th order matrix (c ₀ , c ₁ ,... C _N-1 ) ^t is obtained by DFT-transforming N chip signals (a ₀ , a ₁ ,... A _N-1 ) having a known period N. A first step to find,
Second to obtain an Nth order matrix (d ₀ , d ₁ ,... D _N-1 ) ^t by DFT transforming an arbitrary N chip signal (b ₀ , b ₁ ,..., B _N-1 ). And the steps
The matrix element obtained in the first step and the complex conjugate of the matrix element obtained in the second step are multiplied for each corresponding element to obtain an Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... c _N−1 / d _N−1 ) a third step for obtaining ^t ;
The Nth order matrix (c ₀ / d ₀ , c ₁ / d ₁ ,... C _N−1 / d _N−1 ) ^t obtained by the third step is subjected to inverse DFT transform, and the Nth order matrix (E ₀ , e ₁ ,... E _N−1 ) Fourth step for obtaining ^t ;
A fifth step of obtaining an N-chip signal such that e ₀ is larger than a predetermined size in the N-th order matrix obtained by the fourth step and at least e ₁ is zero;
Generating a matched filter for the N-chip signal obtained in the fifth step.
“T” represents a transposed matrix, and “/ d” represents a complex conjugate of d. 8. A receiving apparatus, wherein a receiving side receives an N-chip signal of the known period N by a matched filter designed by the method described in claim 7. N branch circuits, each branch circuit having a coefficient x ₁ , x ₂ ,..., X _N−1 , x _N and a signal inputted in cascade to the coefficient multiplier And a delay circuit set so as to be different from each other by a time slot, and a coefficient setting method for a transversal filter for synthesizing signals from each branch branched into N by an adder.
When a known N-chip signal is supplied to the input terminal of the transversal filter, 2N-1 signals output in time series from the transversal filter,
The coefficient x ₁ , x ₂ ,... Of the coefficient unit is set so that the signal output at the center time is larger than a predetermined magnitude, and at least the signal output at the time adjacent to the signal is zero. .. A coefficient setting method for a transversal filter, characterized in that x _N-1 and x _N are set. 10. A receiving apparatus, wherein the known N-chip signal is received by a transversal filter in which coefficients are set by the method according to claim 9 on the receiving side. A plurality of transversal filters having coefficients set by the method described in claim 9 are provided,
Simultaneously supplying the known N-chip signals to the plurality of transversal filters;
A receiving apparatus, wherein outputs of the plurality of transversal filters are added and output. The receiving apparatus according to claim 9, wherein the known N-chip signal is a preamble signal or a training signal defined by IEEE 802.11. N branch circuits, each branch circuit having a coefficient x ₁ , x ₂ ,..., X _N−1 , x _N and a signal inputted in cascade to the coefficient multiplier And a delay circuit set so as to be different from each other by a time slot, and a coefficient setting method for a transversal filter for synthesizing signals from each branch branched into N by an adder.
An impulse signal that has passed through a multipath line having a multipath is supplied to an input terminal of the transversal filter, and 2N-1 signals output in time series from the transversal filter,
The coefficient x ₁ , x ₂ ,... Of the coefficient unit is set so that the signal output at the center time is larger than a predetermined magnitude, and at least the signal output at the time adjacent to the signal is zero. .. A coefficient setting method for a transversal filter, characterized in that x _N-1 and x _N are set. 14. A receiving apparatus, wherein a receiving side receives an arbitrary signal that has passed through the multipath line by a transversal filter in which a coefficient is set by the method according to claim 13. A plurality of transversal filters having coefficients set by the method described in claim 13 are provided.
Applying an arbitrary signal via the multipath line simultaneously to the plurality of transversal filters,
A receiving apparatus, wherein outputs of the plurality of transversal filters are added and output.

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