JP3431542B2 - Wireless base station - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio base station using a directional beam antenna or an adaptive array antenna.

[0002]

2. Description of the Related Art In recent years, demand for mobile communication represented by mobile phones, PHS, etc. has increased due to its convenience and multi-functionality, but the number of subscribers has been increasing at a momentum to surpass fixed networks. .

In recent years, with the explosive increase in demand for such wireless communication, channel shortage due to traffic concentration, especially in metropolitan areas, and deterioration of reception quality due to interference due to active frequency reuse have occurred. Getting serious.

Therefore, a technique for increasing the subscriber capacity while maintaining the line quality is expected, and there are many problems such as effective use of a tight frequency resource, cost reduction of infrastructure construction, or effective use of existing infrastructure. There is.

As one of the methods for increasing the subscriber capacity in the existing base station, forming a beam having directivity can be considered. For example, when a sector antenna is used for a base station, it is equivalent to spatially dividing a conventional circular service area into a plurality of small areas,
Assuming that the amount of co-channel interference between base stations can be ignored,
The capacity can be expected to increase by several times the number of sectors.

[0006] Considering further efficient use of space, a plurality of terminal stations existing in a service area are formed by dynamically forming multi-beams spatially orthogonal to each other, and dynamically allocating the terminals. It enables precise channel reuse depending on the individual location and traffic distribution of each.

As one of the effective orthogonal multi-beam forming techniques, a received signal is positively removed from an interfering station in any direction except the same direction, and directivity is given to the interfering station during transmission. There is an adaptive array antenna that has the function of directing nulls.

When an adaptive array antenna is used,
Space division multiplexing by beam directivity can be realized. At the base station, even if the visibility of the propagation path cannot be secured,
Similar directivity control is possible if the direction of arrival and reception of the transmitted / received signal is known.

The outline of the adaptive array antenna will be described below.

The adaptive array antenna is a signal processing method in which an array antenna having a plurality of antenna elements controls the phases and amplitudes of their outputs and synthesizes them.
The beam is directed toward the arrival direction of the desired wave, and the null is directed toward the arrival direction of the interference wave. Controlling and synthesizing the phase and amplitude of the received signal is equivalent to complexly weighting the output of each antenna element as shown in FIG.

At this time, the adaptive array output y is given by the following equation 1.

[0012]

[Equation 1] Note that w and x respectively represent a complex weighting coefficient vector and a complex reception signal vector of each antenna element,

[0013]

[Equation 2]

[0014]

[Equation 3] And Where ^T is the transpose of the matrix.

The weighting coefficient vector is controlled so that the combined signal satisfies a predetermined standard. The optimal weighting coefficient vector is the Wiener-Hopf equation

[0016]

[Equation 4] Is obtained by solving.

However,

[0018]

[Equation 5]

[0019]

[Equation 6] Is.

D represents the reference signal sequence, and * represents the complex conjugate of the elements.

[0021] In addition, E [x ^* x ^T] represents the expected value of x ^* x ^T.

Since an enormous amount of calculation is required to obtain the optimum weighting coefficient vector, a sequential update type adaptive algorithm with a small amount of calculation is often applied in practice.

For example, an LMS (Least Mean) for performing weight control for reducing an error from a known reference signal for each sample.
Square) algorithm is known.

An example of the directivity pattern obtained by the above adaptive processing is shown in FIG. As a model, consider a case where two terminal stations are present and communicating in the service area of one base station.

The signal arrival directions of the terminal station 1 and the terminal station 2 are θ = −20 ° and 80 °, respectively, and the solid line shows the beam pattern for the terminal station 1 and the broken line shows the beam pattern for the terminal station 2.

At this time, in the base station, the desired reception wave power to interference wave power ratio (D / U ratio) when the terminal station 2 or the terminal station 1 is used as an interference station is given by the following equations.

[0027]

[Equation 7]

[0028]

[Equation 8] In the case of transmission, if the preformed transmission beam pattern is as shown in FIG. 2, the terminal station is calculated by subtracting the propagation losses L ₁ and L ₂ of the respective downlinks from the equations (7) and (8). The reception D / U ratio on the side can be predicted.

[0029]

As described above, in a conventional base station that forms a directional beam or a base station using an adaptive array antenna, at the time of reception, the received signal is transmitted by passing through the antenna and the high frequency circuit. Although the amplitude and the phase change due to the influence of the variation of each element, by performing weighting control on the signal after the distortion, a high-purity output can be obtained.

However, at the time of transmission, even if weighting control for forming an optimum beam pattern is performed by digital signal processing or a low frequency analog circuit,
There is a problem that the transmission beam is not optimally formed due to the influence of variations in the phase and amplitude of each element of the high frequency analog circuit and the antenna located in the subsequent stage.

Specifically, even if an ideal beam as shown in FIG. 2 is formed due to coupling between antenna elements, fluctuations in passing phase due to analog components, insufficient D / A quantization accuracy, etc. As shown in FIG. 3, the beam orthogonality is broken due to the deviation of the beam direction and the null direction, unnecessary radiation is generated to the undesired terminal station, and the reception D / U ratio at each terminal station is deteriorated.

In this case, the predicted value of the D / U ratio actually received by the terminal is given by the following equation.

[0033]

[Equation 9]

[0034]

[Equation 10] In order to prevent this deterioration, the specifications of the high frequency analog circuit and antenna of the transmission system should be made very strict, or the amplitude and phase errors that occur in each element of the transmission system should be detected and calibrated before operation as a base station. A method and a method of correcting the beam deviation after the operation are required.

As a conventional countermeasure, if the specifications of each element are made strict, the design becomes difficult and the manufacturing cost of parts is high, so there is a limit. Further, the method of detecting and calibrating the error between the respective elements has a problem that the accuracy is insufficient due to the influence of temperature characteristics, noise, disturbance and the like.

The present invention has been made to solve such problems.

[0037]

Means for Solving the Problems] To solve the problems described above, no line base station of the present invention is to form a beam pattern
In the wireless base station that wirelessly communicates with the terminal station,
Therefore, the desired power to interference power ratio of the downlink is measured.
This measured value is inserted into the transmitted signal sequence and
The desired wave power vs. the interference wave power reported using the reverse line
A receiving means for receiving the ratio measurement value and this receiving means
Based on the received desired power to interference power ratio measurement
Based on the control means for controlling the beam pattern,
The beam pattern controlled by the control means
A wireless communication means for wirelessly communicating with the terminal station.
The control means is for the direction of arrival of signals from a predetermined terminal station.
Try to form in advance according to a constant transmission weight coefficient vector
Directivity gain obtained from a beam pattern and
To the signal arrival direction from a terminal station other than the fixed terminal station
Calculated from the directivity gain obtained from the beam pattern
The calculated value of the desired wave power to interference wave power ratio of the downlink
Formed with the beam pattern that was about to be formed
Measured at each terminal station via the downlink according to the specified pattern.
Of the desired wave power reported by the uplink after being interfered with
The measured value of the wave power ratio and the transmission weight coefficient vector
Compare the multiple times by changing several times,
In comparison, from the beam pattern that was going to be formed
The transmission weight coefficient that is the closest to the obtained directional gain
It is characterized by selecting a number vector. Also, the present invention
The wireless base station of the
In the wireless base station that communicates, the terminal station goes down
The desired power to interference power ratio of the line is measured and
The measured values are inserted into the transmitted signal sequence and
Receives the reported measurement value of the desired wave power to interference wave power ratio
Receiving means for receiving, and the above-mentioned received by this receiving means
Based on the measured value of the desired wave power to the interference wave power ratio,
Control means for controlling the system pattern and this control means
The controlled beam pattern allows wireless communication with the terminal station.
Wireless communication means for communicating, the control means
Predetermined transmission weight factor for the direction of signal arrival from the terminal station
Beam pattern that was tried to be formed beforehand according to the number vector
Other than the above-mentioned specified terminal station
The beam pattern for the direction of signal arrival from the terminal station of
Location of the downlink calculated from the directional gain obtained from the
The calculated value of the desired wave power to the interference wave power ratio and the actual
The pattern formed by the beam pattern
After going through the downlink line by the
Measurement of desired wave power to interference wave power ratio reported by line
Value and compare while changing the transmission weight coefficient vector
However, above all thresholds defined for each beam
When the transmission weight coefficient vector is obtained, this obtained coefficient
Characterized in that the wireless communication is performed using a number vector
It

With such a configuration, it is possible to calibrate the transmission system in a short time without the labor of tightening the specifications of the high frequency analog circuit and the antenna of the transmission system. Further, according to the present invention, since the information on the receiving state is fed back so as to provide a good environment on the receiving side and the correction is performed accordingly, a more accurate calibration can be performed as compared with the conventional calibration method of adjusting only on the transmitting side. It is possible.

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

[0046]

[0047]

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration example of a terminal station and a base station of the wireless communication system according to the embodiment of the present invention. First, with respect to the terminal station, the duplexer 102 located after the antenna 101 switches between transmission and reception, and a reception signal is obtained from the receiver 103 through the demodulation unit 104 and the signal identification unit 105.

At the same time, after demodulation, the reception D / U ratio measuring section 106 calculates interference component power including noise obtained by subtracting the desired signal power from the received signal power, and measures the power ratio.

After that, the transmission sequence creation unit 107 inserts the measured value of the reception D / U ratio and the transmission value is transmitted from the transmitter 108.

Next, regarding the base station, the antennas 111 to 1
The signal received by 13 is the duplexer located in the subsequent stage.
Transmission / reception is switched by 114 to 116, and the signals are input to the adaptive array processing unit via receivers 117 to 119.

The adaptive array processing section includes a reception weight coefficient vector calculation section 125, multipliers 120 to 122 and an adder 123.
And its output is determined by the signal identifying unit 124 to obtain an uplink signal.

This adaptive array processing section is provided for each uplink (N) and independently forms orthogonal beams. The calculated weighting coefficient vector at the time of reception is stored in the memory 127.
Stored in.

Simultaneously with the signal judgment of the adaptive array output, the reception D / of the terminal station inserted in the uplink signal burst is detected.
The U ratio measurement value is extracted by the detection unit 126 and the measurement value is also stored in memory.
Store in 127.

After that, the transmission weight coefficient vector adjustment unit 128
At the weight coefficient vector at the time of reception of each uplink stored in memory 127, and by using the D / U measured value, detecting a difference between the predicted D / U ratio preformed transmit beam Then
Adjust the transmit weighting factor vector.

The transmission adaptive array section is composed of a distributor 129 for distributing the downlink signal input to each array element and multipliers 130 to 132 for multiplying the corrected transmission weight coefficient vector, and each of the N downlink circuits. A quadrature beam is independently formed with respect to the signal input, and transmitted through the transmitters 133 to 135.

[0058] ADAPTIVE Buare processing <br/> management of the base station shown in Figure 1, after passing through the receiver 117 to 119, are also possible in the process according to the analog signal, and the receiver 117 to 119 A / D converter The digital signal processing may be performed by assuming that the digital signal processing is included.

Next, the operation of this system will be described with reference to the flowchart of FIG.

First, the transmission weighting coefficient vector W _{o, N} corresponding to the initial N beams is determined (step 11), and the following procedure is tried M times to adjust the weighting coefficient vector (step 13).

[0061] Step 15 to 17 operation in each terminal station, and the other is an operation of the base station. After the directional beam is formed and transmitted by the base station (step 14), the terminal station receives and detects the signal (step 15).

The terminal station measures the reception D / U ratio after processing such as frequency conversion and synchronization adjustment (step 16).

As a method of measuring the reception D / U ratio, for example,
In the base station, a different known reference signal sequence is formed in advance for each of a plurality of beams to be formed, and in each terminal station, the reference signal sequence is detected, and the desired wave power and the interference wave power are calculated, thereby receiving D There is a method to estimate the / U ratio.

Specifically, as shown in FIG. 6, first, the correlator 201
At, the received signal and the reference signal are correlated. As a result, the complex delay profile h (τ; t) of the desired signal remaining after the interference signal is removed is extracted. 2 with squarer 202
The desired signal power D in the received signal is obtained by multiplying and adding.

Next, the convolver 203 creates a replica γ ′ of the received signal by convolving the measured delay profile h (τ; t) with the transmission sequence (reference signal). At this time,
The noise and interference signal components included in the received signal are the received signal γ
And the replica γ ′, the difference signal γ−γ ′ is obtained by the adder 204, and squared by the squarer 205 to obtain the interference signal power U.

Here, as the reference signal sequence, it is desirable to use code bit sequences orthogonal to each other, whereby the interference signal can be strongly suppressed after the correlation processing for obtaining the delay profile.

It is also possible to transmit a signal that does not include a desired signal at the same transmission timing from the base station and estimate the interference signal power U from the received signal power at the terminal station.

Normally, in the speech channel, in its frame format, there is a redundant bit sequence irrelevant to the information signal. For example, it corresponds to a preamble or a unique word used for recognizing a terminal station or for synchronization or demodulation.

Therefore, when the measured value of the received D / U ratio is transmitted from each terminal to the base station, the measured value of the received D / U ratio is transmitted to the redundant part of the uplink communication channel at the terminal station. insert and transmits transmit during time each, or every predetermined period (step 17).

On the other hand, in the base station, the time at which the reception D / U ratio measurement value is transmitted from the terminal station is known, and the position and the encoding method in which the information of the reception D / U ratio measurement value is included in the frame are included. Can be easily detected because it is also predetermined.
(Step 18).

With this configuration, the reception D / required for calibration can be obtained without degrading the frame efficiency of the transmission signal sequence.
The U ratio measurement value can be transmitted in the uplink.

In addition, to insert the reception D / U ratio measurement value,
An uplink control channel may be used instead of the call channel. Again, it is desirable to use the redundant part in the control channel as in the above.

Further, the number of bits may be large depending on the encoding when inserting the reception D / U ratio into the frame. In such a case, the bit is transmitted at the immediately preceding time. By encoding and transmitting only the difference information from the received D / U ratio measurement value, the required number of bits can be reduced.

[0074] weight coefficient vector W _i of each receiving D / U ratio measured values detected and the _time, after storing the _N in the memory 127 (step 19), the initial weighting factors have been stored previously in memory 127 Shift the phase and amplitude of the vector (step 20),
A new weight coefficient vector W _{i + 1, N} is obtained (step 21).

After that, the transmission beam is formed by the new weighting coefficient vector, and the trial is repeated. After the weighting factor adjustment described above has been repeated for a given number of trials M (step
13), referring to all the received D / U ratio measurement values stored in the memory, the D / U when forming the ideal transmit beam pattern
Select the weighting coefficient vector Do that and the nearest value as the ratio predicted value
(Step 23), and output W _out after calibration (step 24).

The method of determining the weighting coefficient vector will be described below.

The beam forming unit of the base station uses the values of the reception D / U ratios of all downlinks predicted from the directivity gains of the transmission beams that have been formed in advance, and the terminal stations actually passing through the downlinks. The transmission weighting coefficient vector is adjusted so as to minimize the difference between the reception D / U ratio values of all the terminal stations that have been calculated in step 1 and then reported by the uplink.

Specifically, the phase and the amplitude of the initial weighting coefficient vector are changed by the determined widths Δθ and Δp for each trial of the flowchart, and the weighting coefficient vector is updated. Measure the reception D / U ratio.

From the result for the transmission beam of the M pattern, it is possible to know the tendency of the directional pattern change with respect to the phase / amplitude change of the weighting coefficient vector. Finally, from all the weight coefficient vector groups stored in memory,
Select the optimal weighting factor vector.

As the evaluation function, for example,

[0081]

[Equation 11] The weighting coefficient vector that minimizes is output.

In order to adjust a different error for each element, this M requires the number of samples given by the following equation.

[0083]

[Equation 12] In the above-described optimization calibration method, as the number of array elements in the base station increases, the amount of calculation increases exponentially and becomes unrealistic. When there are a large number of terminals and a large number of orthogonal beams are formed, the number of array elements must be increased when a degree of freedom that can compensate for that is required, and the same problem occurs.

Since it is often difficult to find the optimum weighting coefficient that minimizes the difference between the predicted D / U ratio and the reception D / U ratio, it is necessary to calculate the optimum weighting coefficient from the line design including a margin.
Desired D / U ratio P _j (j = 1,
2, ....., N) is set for each beam, and the reception D / U ratio is the threshold P.
It is effective to adjust the transmission weighting coefficient vector so that it becomes _j or less.

In this case, there may be a plurality of sets of weighting coefficient vectors that satisfy the conditions, and an appropriate one may be selected from them.

FIG. 5 shows a flowchart of the second calibration method using the reception D / U ratio threshold value.

The procedure is almost the same as the calibration method of FIG.
If the D / U ratio measurement values detected at the base station are all threshold values P _j or more (step 38 ), the calibration is terminated at that point (step 41).

As a result, a solution can be obtained without trying all cases for phase / amplitude adjustment, and the amount of calculation and the time required for calibration can be shortened.

With the system configuration and the calibration method described above, in the adaptive array antenna and the base station forming a plurality of directional beams, the calibration of the transmission system, which is expected to be difficult with the conventional technique, can be performed inexpensively and easily. It produces an effect called Ru can be done accurately.

The above embodiment is processing for one directional beam, and it is necessary to perform parallel processing by using a plurality of CPUs in order to form a plurality of beams. But,
When using a few high-speed CPUs, etc., time-division processing for beam forming and calibration does not change the effect.

[0091] The above embodiment applies the adaptive array antenna in the base station, has been considered the case of forming a Cartesian beam into a plurality of terminal stations, the present invention is simply a base station using an array antenna, It is also applicable when forming a plurality of directional beams that do not perform null control.

Furthermore, the present invention can be applied to the case where there is only one terminal station and the directivity gain of the beam is simply improved. At this time, the D /
The U ratio is equivalent to C / N (carrier power to noise power ratio).

The calibrated beam has a pattern in which the maximum gain direction matches the direction in which the terminal station is located, and the C / N becomes maximum.

Next, a wireless communication system according to the second embodiment of the present invention will be described.

The calibration method of this embodiment is characterized in that a pseudo terminal station is used in order to estimate the error of the transmission beam pattern.

Here, the pseudo terminal station is a terminal which can be moved or stopped by designating its position on the side of the base station, and the distance from the base station is kept constant and the distance attenuation of the radio wave is performed at each terminal. It is effective to easily optimize the initial transmission beam pattern because the terminals are aligned and the directions of all terminals are predetermined.

Further, since it is not necessary for the downlink to include information, a long reference signal sequence can be transmitted regardless of frame efficiency, and the estimation accuracy of the D / U ratio can be improved.

As described above, in the wireless communication system of the present embodiment, the position of the pseudo terminal station is known in the base station,
When a plurality of pseudo terminal stations are used, it is possible to expect an effect that a desired transmission beam can be calibrated in a short time by designating the position of the terminal station each time so that the number of trials is reduced.

Furthermore, since the propagation loss depending on the position of the terminal station can be accurately approximated, it is possible to more accurately estimate the reception D / U ratio at each terminal station that can be predicted from the transmission beam from the base station. Become.

Further, particularly when limited to the communication system adopting the time division duplex system (TDD), since the same frequency is used for transmission and reception, if the interval between transmission and reception is very short, the radio wave environment at the time of reception and transmission will be different. There is a high correlation.

Paying attention to this point, the weighting coefficient vector forming the receiving antenna pattern having the highest D / U ratio obtained at the time of the immediately preceding reception is stored, and this same weighting coefficient vector is also used at the time of transmission. As a result, an ideal initial beam pattern with a high D / U ratio can be obtained.

In recent years, as a new point-to-point service using wireless, wireless local
A subscriber wireless communication system called a loop (WLL) is drawing attention and is being studied for its introduction.

This is a service that mainly provides high-quality communication to fixed subscribers, but has the advantage that the infrastructure can be constructed easily and inexpensively as compared with a wired system. The present invention can be applied not only to mobile terminals as terminal stations but also to wireless infrastructure using semi-fixed terminals such as WLL.

At this time, since the position of the terminal or the direction viewed from the base station can be estimated with a certain degree of accuracy, the optimum transmission beam pattern can be determined without applying the remote-control calibration method using the pseudo terminal. effective.

[0105]

As described above, the radio base of the present invention
The station can calibrate the deviation between the transmission beam to be formed and the actually formed transmission beam easily and in a short time, as compared with the strict specification design and the calibration method which are difficult in the conventional technique.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a wireless communication system according to an embodiment of the present invention.

FIG. 2 is a diagram showing an ideal transmission beam pattern.

FIG. 3 is a diagram showing an actually determined transmission beam pattern.

FIG. 4 is a flowchart showing a calibration method of the present invention.

FIG. 5 is a flowchart showing a second calibration method of the present invention.

FIG. 6 is a diagram showing a method of measuring a reception D / U ratio.

FIG. 7 is a diagram showing a configuration of a conventional adaptive array antenna.

[Explanation of symbols]

101, 111-113 ... Antenna 102, 114-116 ... Duplexer 103, 117-119 ... Receiver 104 ... Demodulator 105, 124 ... Signal identification section 106… Reception D / U ratio measurement section 107 ... Transmission sequence creation unit 108, 133 ~ 135 ... Transmitter 120-122, 130-132 ... Multiplier 123, 204 ... Adder 125 ... Weighted sequence vector calculator 126… D / U ratio measurement value detector of terminal station 1 127 ... Memory 128 ... Transmission weight sequence vector adjustment unit 129 ... Distributor 201 ... Correlator 202, 205 ... Squarer 203 ... Folding device

Front page continuation (72) Inventor Shuichi Obayashi 1 Komukai Toshiba-cho, Kouki-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center Co., Ltd. (56) Reference JP-A-9-200115 (JP, A) JP-A-8 -237729 (JP, A) JP 2000-174678 (JP, A) International Publication 97/020400 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 7/24-7 / 26 102 H04Q 7/00-7/38

Claims (2)

(57) [Claims] 1. A beam pattern is formed to wirelessly communicate with a terminal station.
In a wireless base station that performs communication, the terminal station determines the desired power to interference power ratio of the downlink.
Measured and this measured value is inserted into the transmitted signal sequence
The desired wave power to interference reported using the uplink
Receiving means for receiving the measured value of the wave power ratio, and the desired wave power to the interference wave received by the receiving means
Control the beam pattern based on the measured power ratio
And the beam pattern controlled by this control means
Wireless communication means for wirelessly communicating with the terminal station, wherein the control means has a predetermined transmission weight in a signal arrival direction from a predetermined terminal station.
The beam pattern that was to be formed in advance according to the coefficient vector
Directivity gain obtained from a turn and the predetermined terminal station
Other than the beam pattern for the signal arrival direction from terminal stations other than
Downlink calculated from directional gain obtained from turns
Calculated value of desired wave power to interference wave power ratio of
The pattern formed by the beam pattern that was about to be created
After being measured at each terminal station via the downlink line
Of the desired wave power to interference wave power ratio reported by the
Change the measured value and the transmission weighting coefficient vector a plurality of times
By comparing the plurality of times, the beam that was being formed within the plurality of comparisons
Before the value is closest to the directional gain obtained from the pattern
Note that the transmission weighting coefficient vector is selected.
Line base station . 2. A beam pattern is formed to wirelessly communicate with a terminal station.
In a wireless base station that performs communication, the terminal station determines the desired power to interference power ratio of the downlink.
Measured and this measured value is inserted into the transmitted signal sequence
The desired wave power to interference reported using the uplink
Receiving means for receiving the measured value of the wave power ratio, and the desired wave power to the interference wave received by the receiving means
Control the beam pattern based on the measured power ratio
And the beam pattern controlled by this control means
Wireless communication means for wirelessly communicating with the terminal station, wherein the control means has a predetermined transmission weight in a signal arrival direction from a predetermined terminal station.
The beam pattern that was to be formed in advance according to the coefficient vector
Directivity gain obtained from a turn and the predetermined terminal station
Other than the beam pattern for the signal arrival direction from terminal stations other than
Downlink calculated from directional gain obtained from turns
Calculated value of desired wave power to interference wave power ratio of
The pattern formed by the beam pattern that was about to be created
After being measured at each terminal station via the downlink line
Of the desired wave power to interference wave power ratio reported by the
Compare the measured value with the transmission weighting coefficient vector
Compared with the above, the transmission becomes equal to or higher than all the thresholds defined for each beam.
When the weighting coefficient vector is obtained, the obtained coefficient vector
Characterized in that the wireless communication is performed by using a module.
Line base station .