JP4882790B2 - Communication apparatus and weight update method - Google Patents

Description

  The present invention relates to a communication device and a weight update method.

The multi-antenna technique is a technique for improving communication capacity, frequency utilization efficiency, power consumption, and the like by performing transmission / reception using a plurality of antennas in wireless communication. Even if the number of antennas on either the transmission side or the reception side is one, it is possible to improve the communication quality according to the number of antennas on the other side.
Moreover, there exists MIMO (Multiple Input Multiple Output) as a term regarding the multi-antenna technology. MIMO, when used as a communication term, often refers to a communication scheme in which both the transmission side and the reception side use a plurality of antennas, but may also be used to refer to general multi-antenna technology.

Advantages obtained by the multi-antenna signal processing algorithm include the following four.
(1) Spatial diversity
(2) Synthetic gain
(3) Interference mitigation (Interference Mitigation)
(4) Spatial Multiplexing

The space diversity is to reduce deterioration in communication quality due to the influence of multipath or the like by using spatially separated antennas.
The combined gain increases the ratio of received power and noise from the desired direction by applying a weight using the propagation path information (changes in amplitude and phase) to the signals on the receiving and transmitting antennas. It is to be.

In the interference wave removal, a received signal from each antenna is combined with a weight so as to cancel an incoming signal (interference signal) other than the desired signal. A number of interference signals smaller than the number of receiving antennas can be removed. If the propagation coefficient of the incoming signal is unknown, some learning algorithm must be used.
The spatial multiplexing is a method of establishing a plurality of communication paths simultaneously by applying interference wave cancellation. There are a method in which a single user transmits different signals from a plurality of antennas to increase the communication capacity, and a method in which a plurality of users simultaneously communicate to increase frequency utilization efficiency. The latter method is called SDMA (Space Division Multiple Access).

As a multi-antenna technique that has recently attracted attention, there is OFDM-MIMO using an OFDM (Orthogonal Frequency Division Multiplexing) scheme.
In the OFDM method, a plurality of carrier waves (subcarriers) are arranged on the frequency axis, and the plurality of carrier waves are partially overlapped to improve frequency use efficiency. OFDM is employed in transmission systems such as terrestrial digital broadcasting and wireless LAN.

One important technique in OFDM-MIMO is updating weights.
For example, in the case of the multi-antenna technique, when the ratio of the received power and the noise power from the desired wave direction is increased by the combined gain of (2) above in the multi-antenna technique and strong directivity is directed in the desired wave direction (beam forming) Used.
In beam forming, in addition to directing strong directivity in the desired wave direction, the influence of received signals other than the desired wave can be reduced.

  The weight is generated using the reference signal. For example, in OFDM, since a known signal (pilot signal) is inserted on the reception side and transmission side, the weight can be updated using this pilot signal as a reference signal.

  As weight update algorithms, there are LMS (Least Mean Square) and RLS (Recursive Last-Squares), which are aimed at minimizing error energy.

Since the OFDM pilot signals are arranged at predetermined intervals in the time axis direction, it is possible to sequentially update the weight each time the pilot signal is received.
In steady state (when there is no temporal change in the propagation coefficient), updating the weight more than a certain number of times can converge the weight calculation result and reduce the influence of interference signals and noise signals. it can.

The weight update method is described in Patent Document 1, for example.
FIG. 10 shows a signal arrangement diagram of FIG. This signal arrangement diagram is a signal arrangement of the digital terrestrial television broadcasting system based on the OFDM system. In the figure, the subcarrier arrangement in the carrier-symbol space is shown in which the vertical axis is the symbol direction (time axis direction) i and the horizontal axis is the carrier direction (frequency axis direction) k. In the figure, black circles indicate scattered pilot SP, and white circles indicate data signals (data subcarriers).
In the case of the signal arrangement shown in the figure, for the same SP carrier number kp, the SP signal is repeated at a cycle of 4 symbols.

Patent Document 1 describes a method of updating weights by applying an LMS algorithm.
According to this document, when there is a weight wb _kp (i) updated by using an SP signal at time i of a certain carrier number kp, the next weight update is performed 4 symbols after the same carrier number kp. The weight update value wb _kp (i + 4) is calculated using the SP signal (carrier number kp, time i + 4).
That is, the weight update direction of Patent Document 1 is only the positive direction of the symbol direction (time axis direction), as indicated by the arrow in FIG. In other words, the order of SP signals used for weight update is a simple time order.
JP 2003-174427 A

  Conventionally, appropriate consideration has not been made regarding the order of pilot signals (reference signals) used for weight update, and there has been only a simple forward time axis direction update as described above.

  An object of the present invention is to provide a new technique related to weight update by paying attention to the order of pilots used for weight update.

  The present invention relates to a weight updating unit that performs weight updating based on a received pilot signal in a communication apparatus that performs communication using a communication method in which pilot signals used for weight updating exist at a plurality of positions in the time axis direction, An order control unit that controls the order of pilot signals used for updating the weight of the pilot signal, and the order control unit updates the weight of the pilot signal in the negative direction of the time axis with respect to the pilot signal used for the previous weight update. The order can be controlled as used in

  According to the present invention, the weight update using the pilot signal temporally prior to the pilot signal already used for the weight update can be included in the plurality of weight updates. This makes it possible to update the weight in a direction different from the conventional one.

The communication apparatus includes a reception pilot signal storage unit capable of storing a plurality of pilot signals at different positions on a time axis, and the sequence control unit includes a plurality of pilot signals stored in the reception pilot signal storage unit It is preferable to control the order of pilot signals used for weight update.
By storing pilot signals in the reception pilot signal storage unit, even pilot signals in the negative direction of the time axis can be easily used for weight update.

  The communication system is a communication system that has a plurality of subcarriers in the frequency direction for frequency multiplexing, and includes a pilot subcarrier that becomes a pilot signal in the plurality of subcarriers. In addition, when viewed in a two-dimensional arrangement in the frequency axis direction, the sequence control unit performs weight update using pilot subcarriers in the negative direction in the time axis direction rather than pilot subcarriers used in the previous weight update. This is a combination of negative direction update control and positive direction update control in which weight update is performed using pilot subcarriers in the positive direction in the time axis direction than the pilot subcarrier used in the previous weight update. Is preferred.

By combining the weight update in the negative direction in the time axis direction and the weight update in the positive direction, updating in the positive and negative directions can be performed in the time axis direction. As a result, the number of weight updates per symbol can be increased.
The negative direction and the positive direction include not only a direction parallel to the time axis but also a direction inclined with respect to the time axis.

  Another aspect of the present invention is a method for updating the weights in a communication method in which pilot signals used for weight updating exist at a plurality of positions in the time axis direction, and the pilot signals used for the previous weight updating Weight updating is performed using a pilot signal in the negative direction of the time axis relative to the signal.

  According to the present invention, the weight update using the pilot signal temporally prior to the pilot signal already used for the weight update can be included in the plurality of weight updates. This makes it possible to update the weight in a direction different from the conventional one.

  According to the present invention, it is possible to update the weight in a direction different from the conventional one.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In the present embodiment, WiMAX (Worldwide Interoperability for Microwave Access, IEEE 802.16) will be described as an example of a communication method.

  FIG. 1 shows an OFDM subcarrier arrangement employed in WiMAX. OFDM is a type of frequency multiplexing method, and is a communication method in which digital information is transmitted by applying QAM modulation to a large number of carriers (subcarriers) arranged so as to be orthogonal on the frequency axis.

There are three types of OFDM subcarriers: a data subcarrier (Data Sub-Carrier), a pilot subcarrier (Pilot Sub-Carrier), and a null subcarrier (Null Sub-Carrier).
The data subcarrier is a subcarrier for transmitting data and a control message. The pilot subcarrier is a known signal (pilot signal) on the reception side and the transmission side, and is used for propagation coefficient estimation or as a reference signal for weight update.

  A null subcarrier is a subcarrier in which nothing is actually transmitted, and a guard subband on the low frequency side (guard subcarrier), a guard subband on the high frequency side (guard subcarrier), and a DC subcarrier ( Center frequency subcarrier).

FIG. 2 shows a two-dimensional arrangement of data subcarriers and pilot subcarriers excluding null subcarriers. In FIG. 2, the horizontal axis is the frequency axis, and the vertical axis is the time axis.
1 (1-L) on the horizontal axis in FIG. 2 indicates the subcarrier number. The subcarrier number is a number in which the subcarriers excluding the null subcarrier are numbered in ascending order of frequency. When the number of all subcarriers including null subcarriers is 1024, the total number L of data subcarriers and pilot subcarriers is 840.
K on the vertical axis in FIG. 2 indicates a symbol number. The symbol number is a number assigned to symbols in order of arrival time.

In FIG. 2, one tile structure is configured by a total of 12 subcarriers, 3 in the symbol direction (time axis direction) and 4 in the frequency axis direction. A tile is a minimum unit for user allocation.
Pilot subcarriers are arranged at the four corners of the tile, and the other subcarriers in the tile are data subcarriers.
As shown in FIG. 2, the tiles are regularly arranged in the time axis direction and the frequency axis direction. As a result, pilot subcarriers exist at a plurality of positions in the frequency axis direction and exist at a plurality of positions in the time axis direction.

  FIG. 3 shows functional blocks of the communication apparatus according to the present embodiment. As this communication apparatus 1, a base station is mainly assumed. The communication device 1 includes a plurality of antenna elements 11 and configures an adaptive array antenna system in which a spatial filtering characteristic is adaptively controlled by a filtering processing unit 14.

The communication device 1 is provided with an RF (Radio Frequency) unit 12 and an FFT unit 13 corresponding to each antenna element 11. The RF unit 12 performs processing such as removal of guard intervals added at the transmission side and A / D conversion. The FFT unit performs processing such as serial / parallel conversion and discrete Fourier transform.
The output (multi-antenna signal) of each FFT unit 13 is given to the filtering processing unit 14. The filtering processing unit 14 adaptively obtains a spatial filtering characteristic corresponding to the propagation environment.

In FIG. 3, in addition to the mobile station (desired station) 2 with which the communication apparatus 1 is trying to communicate, interference stations (mobile stations) 3 and 4 that are interference sources are shown. The total number of desired stations and interfering stations 3 and 4 is M.
The desired station 2 and the interfering stations 3 and 4 respectively perform IFFT units 21, 31, and 41 that perform processing such as parallel / serial conversion and inverse discrete Fourier transform, and processing such as addition of guard intervals and D / A conversion. RF units 22, 32 and 42 and antenna elements 23, 33 and 43 are provided.

  The propagation path between the transmission side communication apparatuses 2, 3, 4 and the reception side communication apparatus 1 is a fading propagation path. When the subcarrier passes through the fading propagation path, its amplitude and phase change. The amount of change varies depending on the position of the subcarrier (time axis direction position and frequency axis direction position).

The filtering processing unit 14 of the receiving-side communication device 1 combines an output signal from each FTT unit corresponding to each antenna element 11 by applying an appropriate weight, extracts a desired signal in each subcarrier, Output as an output signal.
4 shows a filtering model showing the relationship between the desired signal, the output signal, and the received signal (strictly speaking, the signal from the FFT unit 13 corresponding to the antenna element 11 of the communication device 1) in FIG.

In FIG. 4, k indicates a symbol number, and l indicates a subcarrier number. M represents the number of desired signals and interference signals.
The noise signal Z (k, l) is a complex N × 1 vector representing noise in each antenna element 11.
The received signal X (k, l) is a complex N × 1 vector composed of the output from the FFT unit corresponding to each antenna element 11.
The transfer function H _m (k, l) (m = 1 to M) is a complex N × 1 vector in which changes in amplitude and phase that each subcarrier of each signal receives in a fading propagation path with N antenna elements are arranged. is there.
The weight W (k, l) is an N × 1 vector in which complex conjugates of complex weights to be multiplied for each element of the received signal are arranged. In FIG. 4, the superscript H represents a complex conjugate conversion value. Further, in the following, superscript T represents a shift value.

The relationship between the signals in FIG. 4 is expressed as in equations (1) and (2).

The purpose of the filtering processing unit 14 is to estimate only the desired signal S ₁ (k, l) from the received signal X (k, l) affected by the interference signal.
FIG. 5 shows details of the filtering processing unit 14. The filtering processing unit 14 includes a first buffer (reception signal storage unit; reception pilot signal storage unit) 141 that sequentially stores the reception signal X (k, l). Received signal X (k, l) stored in first buffer 141 is applied to weight multiplier 142. The weight multiplying unit 142 multiplies the received signal (data subcarrier) X (k, l) by the weight W (k, l) and combines them to generate an output signal Y (k, l) = W (k, l) ^H X (K, l) is output.

In addition, the received signal (pilot subcarrier) X (k, l) of the first buffer 141 is given to the weight updating unit 143 because it is used to update the weight W (k, l). When the received signal stored in the first buffer 141 is not used by the weight multiplier 142 and the weight updater 143, it is erased as needed.
By accumulating received signals in the first buffer 41, it is possible to easily cope with diversifying weight update directions as in this embodiment.

  The weight update unit 143 updates the weights by an update process using pilot subcarriers included in the received signal, and outputs the updated weights to the second buffer 144. Details of the update process will be described later.

  The second buffer (update weight storage unit) 144 has weights W (k, l) ((k, l) = (1, 1), (1, 4),. 1, L),... Are sequentially stored. The update weight in the second buffer 144 is erased as needed when it is not used in the weight interpolation unit 145 described later.

The weight interpolation unit 145 interpolates the weight W (k, l) at the data subcarrier position using the weight at the pilot subcarrier position, and gives the weight W (k, l) to the weight multiplication unit 142. .
FIG. 6 shows an example of weight interpolation. In the example of FIG. 6, linear interpolation is performed in tile units. Specifically, by performing the calculation shown in FIG. 6A on the weights W ₁ , W ₄ , W ₉ , and W ₁₂ at the pilot subcarrier positions of the tile shown in FIG. Weights W ₂ , W ₃ , W ₅ , W ₆ , W ₇ , W ₈ , W ₁₀ , W ₁₁ at the subcarrier position are calculated.
By performing this calculation for all tiles, weights at all data subcarrier positions can be calculated.

[Weight update processing by weight update unit]
The weight update unit 143 according to the present embodiment is configured to update weights using the RLS algorithm. However, other algorithms such as an LMS algorithm or an SMI algorithm may be used.

The weight update unit 143 uses a pilot subcarrier X (k, l) in a received signal, a corresponding desired signal reference signal (pilot subcarrier) S (k, l), and a weight update parameter P. Thus, the current weight W (k _prev , l _prev ) is updated to a new weight W (k, l).

The weight update arithmetic expression by the RLS algorithm is as the following expressions (3) and (4). Note that the weight update unit 143 also calculates an update value P _{next of the} parameter P used in Expression (4). The update calculation formula of P is as the following formula (5).

As shown in FIG. 5, among the values used in the equations (3) to (5), the pilot subcarrier X (k, l) is acquired from the first buffer 141 via the order control unit 146. . Further, the reference signal (pilot subcarrier) S (k, l) of the desired signal is generated by the reference signal generation unit 147 and given to the weight update unit 143. The weight update parameter P (N × N matrix) is stored in the third buffer (weight update parameter storage unit) 148, and the weight update unit 143 acquires the parameter P from the third buffer 148. The parameter P _next updated by the weight updating unit 143 is updated and stored in the third buffer 148 and used as the parameter P for the next weight update.

  Moreover, (alpha) in said Formula (4) (5) is a forgetting factor, and takes the value between 0-1. By adjusting the value of α, it is possible to adjust the follow-up characteristic to the variation of the transfer function in the frequency axis direction and the time axis direction.

[Weight update order control]
As described above, the weight updating unit 143 acquires the received signal (pilot subcarrier) X (k, l) from the first buffer 141 via the order control unit 146.
The order controller 146 separates and extracts pilot subcarriers from the received signal stored in the first buffer 141.
Then, order control section 146 controls the order of pilot subcarriers used by weight update section 143 for weight update. Specifically, order control section 146 rearranges the separated pilot subcarriers in the order used for weight update. Then, order control section 146 provides the rearranged pilot subcarriers to weight update section 143 in the rearranged order.

  Here, as will be described later, the order control unit 146 may perform control so that pilot subcarriers located in the negative direction on the time axis are used for weight updating relative to the pilot subcarriers used for previous weight updating. . In order to perform such negative direction update control, it is necessary to acquire pilot subcarriers that are temporally previous. In the present embodiment, the first buffer 141 stores a predetermined period of past (a predetermined number of symbols). Since subcarriers are accumulated, negative direction update control can be easily performed.

  Note that the order control unit 146 has a rearrangement rule (update order rule) for one or more pilot subcarriers. Note that the rearrangement rule (update order) can be dynamically changed according to the propagation environment.

  An example of the update order rule is shown in FIG. In this rule, first, updating in the direction D1 in FIG. 7 is performed. That is, in the same subcarrier (same subcarrier number = 1), a plurality of pilot subcarriers (1, 1) to (k, 1) existing in the time axis direction are targeted in order from the pilot subcarrier having the smallest symbol number. To update the weight (positive direction update control D1 in the time axis direction).

Note that the movement width (movement width in the time direction) of one forward direction update control D1 may be an arbitrary length, but may be, for example, a symbol length for one frame (subframe) or less. .
In WiMAX, one basic frame includes an uplink subframe and a downlink subframe, and the base station receives the uplink subframe. This uplink subframe is composed of 15 symbols. Therefore, it is preferable that the movement width in one forward direction update control D1 is a maximum of 15 symbols.

  When the forward direction update control D1 is performed and the pilot subcarrier (k, 1) of a predetermined symbol number = k is reached, the update in the frequency direction D2 is performed next. That is, the pilot subcarrier (k, 4) that moves from the position (k, 1) in the frequency axis direction and is next in the frequency axis direction is used for weight update (first frequency axis direction update control D2). Note that the movement width of the first frequency axis direction update control D2 is equal to three subcarriers.

  After the first frequency axis direction update control D2, the update is performed in the direction D3 in FIG. That is, in the same subcarrier (same subcarrier number = 4), a plurality of pilot subcarriers (k, 4) to (1, 4) existing in the time axis direction are targeted in order from the pilot subcarrier having the largest symbol number. To update the weight (negative direction update control D3 in the time axis direction).

  The moving width (moving width in the time direction) of one negative direction update control D3 may be an arbitrary length, but a maximum symbol length (15 symbols) for one frame (subframe) is preferable. .

When the negative direction update control D3 is performed and the pilot subcarrier (1, 4) having the smallest symbol number 1 is reached, the update is performed in the direction D4 in FIG. That is, it moves in the time axis direction from the position (1, 4), and the next pilot subcarrier (1, 5) in the frequency axis direction is used for weight update (second frequency axis direction update control D4). Note that the movement width of the second frequency axis direction update is one subcarrier.
After the second frequency axis direction update control D4, the forward direction update control D1 is performed, and the above process is repeated. If updating in the D4 direction cannot be performed, updating may be performed in the same manner using the next k symbols that are temporally after the symbol number k.

In the above rule, the four update controls of the positive direction update control D1, the first frequency direction update control D2, the negative direction update control D3, and the second frequency direction update control D4 are combined. By performing the positive direction update control D1 and the negative direction update control D3 as in the above rule, the number of weight updates per symbol becomes very large compared to the case of only the positive direction update control D1. As a result, an appropriate weight can be obtained at high speed.
Further, by combining the frequency direction update control D2 and D4, it is possible to easily set many pilot symbols as weight update targets.

In the rule of FIG. 7, the update performed by moving in the time axis direction is performed more than the update performed by moving in the frequency axis direction. Therefore, when considering the cross-correlation of propagation coefficients at the position of each subcarrier, if the cross-correlation between subcarriers in the time axis direction is larger than the cross correlation in the frequency axis direction, an appropriate weight is given early. Is obtained.
Moreover, even if the correlation coefficient in the time axis direction is large, it is difficult to increase the number of weight updates in the simple positive update control D1, but the correlation coefficient is reduced by combining the negative update control D3. It can be updated many times in the larger direction (time axis direction).

Here, the cross-correlation of propagation coefficients may be larger in the frequency axis direction and larger in the time axis direction. For example, when the mobile station that is the communication partner of the base station is moving at high speed, the propagation environment changes from moment to moment, so the cross-correlation in the time axis direction becomes lower and the cross-correlation in the frequency direction becomes relatively lower. Will be bigger.
On the other hand, when the mobile station is slow or stopped, there is almost no change in the propagation environment even if the time changes, so the cross-correlation becomes larger in the time axis direction.

  Thus, when the cross-correlation of propagation coefficients is large in the time axis direction, weight updating is easier to converge when weight updating is performed in the axial direction, and appropriate weights can be calculated at high speed. .

FIG. 8 shows a second example of the update order rule.
In the example of FIG. 8, weight updating is performed with reference to a tile that is the minimum unit of user allocation. That is, tile updating is performed in units of tile columns arranged in the time axis direction, and weight updating is performed separately for each tile column in the frequency axis direction. This also applies to the example of FIG.

More specifically, in the example of FIG. 8, the weight update is performed as follows. That is, the weights are updated in the order of W1, W12, W4, and W9 for one tile, and the weights are updated in the same order for the subsequent tiles.
The movement D11 from W1 to W12 and the movement D13 from W4 to W9 are positive oblique direction update controls that perform movement in both the frequency axis direction and the time axis direction. The movement D12 from W12 to W4 is negative direction update control, and the movement D14 from W9 to the next tile W1 is positive direction update control.
In the update controls D11 to D14, the positive oblique direction update controls D11 and D13, the negative direction update control D12, and the positive direction update control D14 are combined.

  FIG. 9 shows a third example of the update order rule. In FIG. 9, the weight is updated in the order of W1, W9, W4, and W12 for one tile T1, and the weight is updated in the order of W4, W12, W1, and W9 for the next tile T2 in the time axis direction. I do. Hereinafter, this order is repeated alternately for subsequent tiles.

9, the movement D21 of the tile T1 from W1 to W9, the movement D23 of the tile T1 from W4 to W12, the movement D24 of the tile T1 from W12 to the tile T2, and the movement D25 of the tile T2 from W4 to W12. , And the movement of the tile T2 from W1 to W9 is forward update control.
On the other hand, the movement D22 of the tile T1 from W9 to W4 and the movement D26 of the tile T2 from W12 to W1 are negative oblique direction update control. This negative oblique direction update control can be said to be negative direction update control involving movement in the frequency axis direction.
As described above, the negative direction update control may involve movement in the frequency axis direction.

Note that the update order rules are not limited to those described above, and various combinations including at least negative direction update control are possible. Further, the movement width in one update control can be set freely.
Furthermore, in the above example, one pilot subcarrier is used for updating only once, but may be used for updating a plurality of times. There may also be pilot subcarriers that are not used for updating.

  The present invention is not limited to the embodiment described above, and various modifications can be made without departing from the spirit of the present invention. For example, the present invention is not limited to WiMAX but can be applied to, for example, an apparatus for digital terrestrial broadcasting.

It is a figure which shows the subcarrier structure of OFDM. It is a frequency-time two-dimensional array of subcarriers. It is a block diagram of a communication apparatus. It is a figure which shows the simplified spatial filtering model. It is a block diagram of a filtering process part. It is explanatory drawing of the weight interpolation method. It is a figure which shows the 1st example of a weight update order rule. It is a figure which shows the 2nd example of a weight update order rule. It is a figure which shows the 3rd example of a weight update order rule. It is a figure which shows the subcarrier arrangement | positioning in terrestrial digital broadcasting. It is a figure which shows the conventional weight update direction.

Explanation of symbols

1: Communication device (base station) 2: Desired station 3: Interfering station 4: Interfering station 11: Antenna element 12: RF unit 13: FFT unit 14: Filtering processing unit 141: First buffer (received pilot signal storage unit) 142 : Weight multiplication unit 143: weight update unit 144: second buffer (update weight storage unit) 145: weight interpolation unit 146: sequence control unit 147: reference signal generation unit 148: third buffer (weight update parameter storage unit)

Claims (4)

In the communication apparatus pilot signal used for weight update of the receive beam in a communication device constituting a multi-antenna system performs communication by a communication system that exist in more than the position of the time axis direction,
A weight updating unit for updating weights based on the received pilot signal;
An order controller for controlling the order of pilot signals used for updating weights;
With
The weight update unit calculates the weight at the position of the pilot signal by updating the weight updated in the previous weight update based on the pilot signal used for the update,
The order control unit is capable of controlling the order so that a pilot signal in the negative direction of the time axis is used for weight update with respect to a pilot signal used for the previous weight update. A reception pilot signal storage unit capable of storing a plurality of pilot signals at different positions on the time axis;
The communication apparatus according to claim 1, wherein the order control unit controls the order of pilot signals used for weight update for a plurality of pilot signals stored in the received pilot signal storage unit. The communication scheme is a communication scheme that includes a plurality of subcarriers in the frequency direction for frequency multiplexing and includes pilot subcarriers that serve as pilot signals in the plurality of subcarriers.
When the subcarrier arrangement is viewed in a two-dimensional arrangement in the time axis direction and the frequency axis direction, the sequence control unit is
Negative direction update control in which weight update is performed using pilot subcarriers in the negative direction in the time axis direction relative to the pilot subcarrier used in the previous weight update;
The forward direction update control in which weight update is performed using pilot subcarriers in the positive direction in the time axis direction relative to the pilot subcarrier used in the previous weight update, and control is combined. The communication apparatus according to 1 or 2. In the communication system pilot signals used to update the weights of the receive beam in the system of multi-antenna is present in the plurality of positions in the time axis direction, the weights are updated in the previous weight updating, based on the pilot signal to be used for updating A method of calculating a weight at the position of the pilot signal by updating,
A weight updating method, wherein weight updating is performed using a pilot signal in a negative direction of a time axis relative to a pilot signal used for updating a previous weight.

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