JP4237720B2 - Wireless communication apparatus and wireless communication method - Google Patents

Wireless communication apparatus and wireless communication method Download PDF

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JP4237720B2
JP4237720B2 JP2005083670A JP2005083670A JP4237720B2 JP 4237720 B2 JP4237720 B2 JP 4237720B2 JP 2005083670 A JP2005083670 A JP 2005083670A JP 2005083670 A JP2005083670 A JP 2005083670A JP 4237720 B2 JP4237720 B2 JP 4237720B2
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transmission
wireless communication
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communication terminals
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JP2006270339A (en
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康祐 原田
裕樹 庄木
康彦 田邉
寿久 鍋谷
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株式会社東芝
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  The present invention relates to a technical field of wireless communication, and more particularly to a wireless communication apparatus and a wireless communication method that perform multicast transmission to a plurality of wireless communication terminals.

  When a wireless communication device transmits the same data to a plurality of wireless communication terminals, performing unicast transmission to each wireless communication terminal in turn increases the load on the transmitting terminal and the network, and improves the real-time characteristics of transmission data. It becomes difficult to secure. Therefore, multicast transmission capable of transmitting the same data to a plurality of wireless communication terminals with one transmission is important.

  In multicast transmission, a method in which a wireless communication apparatus efficiently transmits data to a plurality of wireless communication terminals using an adaptive array antenna using a plurality of antenna elements has been studied (for example, Patent Document 1). reference). In this example, when there is only one wireless communication terminal that transmits multicast data, a plurality of wireless communication terminals that transmit multicast data by forming a signal beam directed to only the wireless communication terminal and transmit multicast data are provided. In some cases, a signal beam that simultaneously includes a plurality of wireless communication terminals is formed, and multicast data is transmitted.

By operating in this way, the wireless communication device forms a signal beam individually in the direction of each wireless communication terminal in a manner similar to normal unicast transmission, so that multicast data can be transmitted individually. Data can be efficiently transmitted to a plurality of wireless communication terminals as compared with the case of realizing the multicast function.
JP2003-110696

  However, when the same data is multicast-transmitted to a plurality of wireless communication terminals using an adaptive array antenna using a plurality of antenna elements in this way, a signal beam including a plurality of wireless communication terminals simultaneously is transmitted. In the method of forming and transmitting data, when the positions of the wireless communication terminals are on the opposite side of the wireless communication device or when the number of wireless communication terminals is large, a large signal beam must be formed. On the contrary, there is a problem in that interference is caused to other wireless communication terminals.

  In addition, when the radio communication apparatus performs signal beam forming using an adaptive array antenna, the more the number of radio communication terminals is, the more difficult it is to form an optimal signal beam. For this reason, when a signal beam that is larger than necessary is formed due to the positional relationship of each wireless communication terminal, or when an optimal signal beam cannot be formed due to a large number of wireless communication terminals, the wireless communication device uses the same power. When transmitting, each wireless communication terminal cannot receive at a desired reception power, and the reception characteristics deteriorate, so the transmittable area becomes small. These are serious problems for multicast transmission that may be simultaneously transmitted to wireless communication terminals that exist uniformly in the communication area.

  The present invention has been made in consideration of the above points, and when performing multicast transmission to a plurality of different wireless communication terminals, the wireless communication apparatus efficiently transmits data without degrading reception quality It is another object of the present invention to provide a wireless communication method.

The wireless communication device of the present invention is a wireless communication device that performs multicast transmission to a plurality of different wireless communication terminals, and includes belonging information indicating that the wireless communication device belongs to a group of wireless communication terminals that can receive the multicast transmission. Calculation means for calculating the number of wireless communication terminals to be subjected to multicast transmission based on, a plurality of transmission means each using a plurality of different multicast transmission schemes, and a plurality of wireless communication terminals to be subjected to multicast transmission Any of a plurality of different multicast transmission schemes according to estimation means for estimating a plurality of existing directions, a plurality of antenna elements, the number of wireless communication terminals, the number of antenna elements, and the plurality of directions Selecting means, and corresponding to the selected multicast transmission method, One transmission means of a serial plurality of transmission means, have rows multicast transmission in a wireless communication terminal as the target of the multicast transmission, the plurality of transmission means, at least, form a plurality of signal beams having directivity Beam forming transmission means for performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
The selection means includes
Based on the estimated plurality of directions, the sum of the number of wireless communication terminals that can be considered to be present in the same direction minus 1 for all directions and the number of antenna elements is the target for the multicast transmission. If the number of wireless communication terminals is equal to or less than, select a transmission method by the transmission diversity transmission means,
Based on the plurality of estimated directions, the number of wireless communication terminals that can be regarded as existing in a certain direction minus 1 is calculated for all directions, and the sum of the number of antenna elements is the target of the multicast transmission. If the number is larger than the number of wireless communication terminals, the transmission method by the beamforming transmission means is selected .

The wireless communication device of the present invention is a wireless communication device that performs multicast transmission to a plurality of different wireless communication terminals, and includes belonging information indicating that the wireless communication device belongs to a group of wireless communication terminals that can receive the multicast transmission. Calculation means for calculating the number of wireless communication terminals to be subjected to multicast transmission based on, a plurality of transmission means each using a plurality of different multicast transmission schemes, and a plurality of wireless communication terminals to be subjected to multicast transmission Any of a plurality of different multicast transmission schemes according to estimation means for estimating a plurality of existing directions, a plurality of antenna elements, the number of wireless communication terminals, the number of antenna elements, and the plurality of directions Selecting means, and corresponding to the selected multicast transmission method, One of the plurality of transmission means performs multicast transmission to the wireless communication terminal that is to perform the multicast transmission, and the plurality of transmission means form at least a plurality of directional signal beams. Beam forming transmission means for performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
The selection means includes
The sum of the number of wireless communication terminals that can be regarded as existing in one and the same direction minus the number of antenna elements in all directions and the number of antenna elements is the target of the multicast transmission. If the number is less than the number of wireless communication terminals, select a transmission method by the transmission diversity transmission means,
The sum of the number of wireless communication terminals that can be regarded as existing in one and the same direction minus the number of antenna elements in all directions and the number of antenna elements is the target of the multicast transmission. When the number is larger than the number of wireless communication terminals, the transmission method by the beamforming transmission means is selected .
The wireless communication device of the present invention is a wireless communication device that performs multicast transmission to a plurality of different wireless communication terminals, and includes belonging information indicating that the wireless communication device belongs to a group of wireless communication terminals that can receive the multicast transmission. Calculation means for calculating the number of wireless communication terminals to be subjected to multicast transmission based on, a plurality of transmission means each using a plurality of different multicast transmission schemes, and a plurality of wireless communication terminals to be subjected to multicast transmission Any of a plurality of different multicast transmission schemes according to estimation means for estimating a plurality of existing directions, a plurality of antenna elements, the number of wireless communication terminals, the number of antenna elements, and the plurality of directions Selecting means, and corresponding to the selected multicast transmission method, One of the plurality of transmission means performs multicast transmission to the wireless communication terminal that is to perform the multicast transmission, and the plurality of transmission means form at least a plurality of directional signal beams. Beam forming transmission means for performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
The selection means includes
A value obtained by subtracting the number of wireless communication terminals that can be considered to exist in a certain same direction in the plurality of estimated directions minus the number in all directions from the number of wireless communication terminals to be subjected to the multicast transmission. If the number of antenna elements is equal to or greater than, select a transmission method by the transmission diversity transmission means,
A value obtained by subtracting the number of wireless communication terminals that can be considered to exist in a certain same direction in the plurality of estimated directions minus the number in all directions from the number of wireless communication terminals to be subjected to the multicast transmission. When the number is smaller than the number of antenna elements, a transmission method by the beamforming transmission means is selected.

  According to the wireless communication device and the wireless communication method of the present invention, when multicast transmission is performed with respect to a plurality of different wireless communication terminals, reception quality deteriorates even in a wireless communication terminal that is located away from the wireless communication device. The data can be transmitted efficiently without making it happen.

Hereinafter, a wireless communication apparatus and a wireless communication method according to embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the wireless communication device 100 according to the present embodiment includes at least an antenna unit 101 formed by a plurality of antenna elements, a receiving unit 102, a demodulating unit 103, a terminal number determining unit 104, a modulating unit 105, and a switching unit. A control unit 106, a beam forming unit 107, and a transmission diversity unit 108 are provided.
The receiving unit 102 receives a radio signal via the antenna unit 101, performs necessary processing such as frequency conversion to baseband and AD conversion, and outputs the result to the demodulation unit 103. Further, receiving section 102 outputs N pieces of received signal information received from N (N is a natural number) antenna elements to beam forming section 107. Furthermore, receiving section 102 outputs information indicating which reception signal has the best quality among the N received signals received from the N antenna elements to transmission diversity section 108. Further, when the transmission diversity unit 108 performs transmission diversity by space-time coding, information indicating which reception signal has the best quality is not necessary.

  The demodulator 103 demodulates the received signal input from the receiver 102 and restores the received frame in accordance with the standard of the wireless communication system. As with data transmission, it is desirable to receive data with a plurality of antenna elements at the time of data reception and improve reception quality by weight control and reception diversity. However, only one antenna of the antenna unit 101 is used. It may be.

The terminal number determination unit 104 determines and grasps the number of wireless communication terminals to which the wireless communication apparatus 100 performs multicast transmission. The number of wireless communication terminals is grasped using the Internet Group Management Protocol (IGMP) which is a TCP / IP standard. The wireless communication terminal uses IGMP to notify the wireless communication device 100 that it belongs to the multicast group, and the terminal number determination unit 104 assigns each of the subscribed wireless communication terminal addresses for each multicast group. And managing the number of subscribed wireless terminals. Even when the wireless communication device 100 does not include a multicast router function, the terminal number determination unit 104 can grasp the number of subscribed wireless terminals by IGMP snooping information from the wireless communication terminal to the multicast router. is there. That is, the wireless communication device 100 may be able to determine the number of wireless communication terminals subject to multicast transmission by some determination without receiving a notification from the wireless communication terminal. If wireless communication apparatus 100 has affiliation information indicating that it belongs to a group of wireless communication terminals that can receive multicast transmission, terminal number determination section 104 performs multicast transmission based on this affiliation information. The number of target wireless communication terminals can be calculated.
Here, the number-of-terminals determination unit 104 uses IGMP to grasp the number of wireless communication terminals targeted for multicast transmission. However, any other means can be used as long as the number of wireless communication terminals targeted for multicast transmission can be grasped. A method may be used.

Modulation section 105 receives and modulates transmission data. The switching control unit 106 modulates using either the beam forming unit 107 or the transmission diversity unit 108 based on the number of wireless communication terminals to which the wireless communication apparatus 100 performs multicast transmission, which is input from the terminal number determination unit 104. The transmission control for transmitting the transmitted data is performed. In addition, the switching control unit 106 grasps and manages the number of wireless communication terminals targeted for multicast transmission. The switching control unit 106 performs switching to the beam forming unit 107 when it is determined to perform transmission by beam forming, and switches to the transmission diversity unit 108 when it is determined to perform transmission by transmission diversity. The switching operation of the switching control unit 106 will be described later with reference to FIG.
The beam forming unit 107 replicates N output signals from the switching control unit 106 based on information such as N received signals received from N antenna elements input from the receiving unit 102 in order to perform transmission beam forming. Alternatively, each divided signal is multiplied by a weight, and necessary processing such as DA conversion or frequency conversion is performed on a radio signal to a predetermined frequency, and then transmitted to a wireless communication terminal that is a multicast transmission target via the antenna unit 101. . Details of the beam forming unit 107 will be described later with reference to FIGS.

  The transmission diversity unit 108 receives the antenna unit 101 based on the information input from the reception unit 102 and indicating which reception signal has the best quality among the N reception signals received from the N antenna elements. Among the plurality of antenna elements, an antenna element that is expected to be multicast-transmitted with a transmission characteristic is estimated, and an antenna element to be transmitted is selected each time. In addition, the transmission diversity unit 108 also performs necessary processing such as frequency conversion on the D / A conversion and the radio signal to a predetermined frequency, and then transmits it to the radio communication terminal to be multicast transmission via the antenna unit 101. It is also possible to use space-time coding in the transmission diversity unit 108. Details of the transmission diversity unit 108 in this case will be described later with reference to FIG.

Next, the beam forming unit 107 will be described with reference to FIGS.
As shown in FIG. 2, the beamforming unit 107 includes a transmission weight control unit 201, a number of multipliers 202 equal to the number of antenna elements, and a transmission processing unit 203.

  The beamforming unit 107 divides or duplicates the transmission signal output from the switching control unit 106 into series signals of the number of antenna elements, and then inputs these series signals to the transmission weight control unit 201. Transmission weight control section 201 determines N transmission weight coefficients, inputs each weight coefficient to each multiplier 202, and multiplies each series signal by each weight coefficient. The transmission processing unit 203 performs DA conversion and frequency conversion on a radio signal to a predetermined frequency, which are processes necessary for other transmissions, and then outputs each series signal to each antenna element.

  For example, as shown in FIG. 3, the transmission weight control unit 201 controls the weight coefficient so as to form a directional signal beam for a wireless communication terminal that performs multicast transmission. At this time, for example, control is performed based on a reception weight coefficient calculated when data is received from each wireless communication terminal, but a directional transmission beam can be formed for each wireless communication terminal. For example, the weight coefficient may be controlled using any information. For example, in the transmission weight control unit 201, the transmission side may determine the weight unilaterally. In this case, the weight coefficient is determined without referring to the reception signal from the reception unit 102.

Next, the transmission diversity unit 108 will be described with reference to FIG. FIG. 4 shows a case where the transmission diversity unit 108 performs transmission using space-time coding instead of normal transmission diversity.
In this case, the transmission diversity unit 108 includes a space-time coding unit 401 and a transmission processing unit 402. The space-time coding unit 401 performs space-time coding by performing a temporal order change of transmission signal sequences, inversion of positive and negative, complex conjugate processing, and the like. The transmission processing unit 402 performs other transmission processing, such as DA conversion and frequency conversion on a radio signal to a predetermined frequency, and then simultaneously performs a multicast transmission target wireless communication terminal from each antenna element of the antenna unit 101. Send data to. Here, according to the space-time coding method, transmission is not always performed using all antenna elements.

  In multicast transmission, unlike in unicast transmission, it is often difficult to estimate antenna elements that are transmitted with better characteristics in normal transmission diversity. A method of performing transmission diversity is effective.

  Next, the switching operation of the switching control unit 106 will be described with reference to FIG. FIG. 5 is a flowchart illustrating a case where the switching control unit 106 determines whether to switch to the beam forming unit 107 or the transmission diversity unit 108. Here, it is assumed that multicast transmission is performed for multicast group A.

  When the switch control unit 106 is notified of a multicast transmission request addressed to the multicast group A, the switch control unit 106 selects the number of wireless communication terminals that are subscribed to the multicast group A from the managed information, that is, multicast transmission. The number of target wireless communication terminals is checked (step S501). Then, the switching control unit 106 compares the number of wireless communication terminals targeted for multicast transmission with the number of transmitting antenna elements (step S502). If the number of wireless communication terminals targeted for multicast transmission is greater than or equal to the number of antenna elements for transmission, the process proceeds to step S503. On the other hand, if the number of wireless communication terminals targeted for multicast transmission is smaller than the number of antenna elements for transmission, step S504 is performed. Proceed to

  In step S503, the switching control unit 106 selects the transmission method by the switching transmission diversity in the transmission diversity unit 108, and performs transmission. In step S504, the switching control unit 106 switches to the beam forming unit 107, selects a method for generating and transmitting a beam by directivity control, and performs transmission.

According to the wireless communication apparatus of the present embodiment, when multicast transmission is performed, if the beam can be clearly generated and transmitted to each wireless communication terminal by directivity control, the effect of beam forming is large. In each wireless communication terminal, reception performance can be improved by beam forming. On the other hand, in the wireless communication device of the present embodiment, when the beam cannot be clearly generated for each wireless communication terminal, the effect of beam forming is weakened, and conversely, the reception performance is lowered. By performing transmission diversity transmission, it is possible to improve reception performance in each wireless communication terminal. That is, data can be transmitted efficiently.
As a result, it also leads to expansion of the multicast transmission range, and data can be transmitted to a wireless communication terminal far from the wireless communication device without increasing the transmission power, so that power consumption can be reduced. It becomes.

  In general, in multicast transmission, an acknowledgment signal (ACK signal) cannot be expected unlike unicast transmission, and it is difficult to know whether or not each wireless communication terminal has received it properly. For this reason, this embodiment is also effective in that it is possible to improve the reception performance and expand the transmission range without performing the determination to increase the transmission power and the determination to perform retransmission.

(Second Embodiment)
The wireless communication device 600 of this embodiment is different only in that a terminal direction estimation unit 601 is added to each device portion of the wireless communication device 100 of the first embodiment. In the present embodiment, the switching control unit 106 makes the switching threshold value of the beamforming unit 107 or the transmission diversity unit 108 variable. This switching threshold value corresponds to the number of wireless communication terminals or antenna elements to be multicast transmission checked in step S501 of FIG. That is, the switching control unit 106 determines whether to use the beam forming unit 107 or the transmission diversity unit 108 by the operation according to the flowchart in which the number of wireless communication terminals or the number of antenna elements is changed to the switching threshold in FIG. . However, the variable control of the switching threshold is reversed depending on which is set as the switching threshold. Details will be described later with reference to FIGS. Of the device portions of the wireless communication device 600 shown in FIG. 6, the same portions as those of the wireless communication device 100 are denoted by the same reference numerals, and the description thereof is omitted.
The terminal direction estimation unit 601 estimates the direction in which each wireless communication terminal that has joined the multicast group grasped and managed by the switching control unit 106 exists. As a method for estimating the direction in which the wireless communication terminal exists, a method that the wireless communication device itself estimates, such as a method for estimating the position direction of the wireless communication terminal by estimating the arrival direction of the radio wave transmitted by the wireless communication terminal For example, the method of grasping the position and direction of the wireless communication terminal by receiving the position and direction information of its own wireless communication terminal calculated using the position detection function in the GPS system or the wireless LAN system, for example. Any other means or method may be used as long as it can be estimated.

  The position / direction information of each wireless communication terminal estimated by the terminal direction estimation unit 601 is notified to the switching control unit 106. This notification is performed as needed or periodically, and the information is updated each time. The switching control unit 106 determines whether each wireless communication terminal exists in the same direction for each multicast group based on the notified position / direction information of the wireless communication terminal.

Next, refer to FIG. 7A, FIG. 7B, and FIG. 7C for determining whether each wireless communication terminal exists in the same direction for each multicast group performed by the switching control unit 106. To explain.
As shown in FIG. 7A, it is assumed that the angle between the wireless communication terminal 701 and the wireless communication terminal 702 calculated based on the position / direction information of the wireless communication terminal is θ 1 . 7 the angle theta 1 in the example of (a) is smaller than the threshold angle α indicating whether or not the same direction, the switching control unit 106 wireless communication terminal 701 and the radio communication terminal 702 is present in the same direction judge. Further, since the other angles θ 2 to θ 4 are larger than the threshold angle α, the switching control unit 106 determines that the wireless communication terminal 701, the wireless communication terminal 702, the wireless communication terminal 703, and the wireless communication terminal 704 are in the same direction. Is determined not to exist. Here, the threshold angle α may be a fixed value or a variable value. The threshold angle α depends on the performance of the beam forming unit 107 and the number of antenna elements. For example, the threshold angle α having a larger value can be adopted as the performance of the beam forming unit 107 is excellent and the number of wireless communication terminals belonging to the multicast group is smaller than the number of antenna elements.

When the switching control unit 106 determines that a terminal exists in the same direction, the switching control unit 106 changes a value used for the switching threshold value of the beam forming unit 107 and the transmission diversity unit 108. When the switching threshold is set corresponding to the number of transmitting antenna elements, the number of switching thresholds is increased by one as there is one wireless communication terminal determined to be in the same direction. In other words, the number of switching thresholds is increased by one by the number calculated for all the directions around the wireless communication device 600 minus the number of wireless communication terminals that can be regarded as existing in a certain direction.
In FIG. 7A, the switching threshold value is increased by 1 to (the number of transmitting antenna elements + 1), and in FIGS. 7B and 7C, the switching threshold value is increased by 2 and (the number of transmitting antenna elements + 2). ). That is, if there is one other wireless communication terminal in the same direction as a certain wireless communication terminal, the same effect as when the number of antenna elements of the wireless communication apparatus 600 is increased by one is obtained. In this case, the switching control unit 106 changes the number of antenna elements in step S502 of FIG. 5 to “number of antenna elements + 1” and “number of antenna elements for transmission + 2”. In this embodiment, this number and the number of terminals are changed. To determine which of the beam forming unit 107 and the transmission diversity unit 108 to use.
Conversely, if it is determined that the terminal no longer exists in the same direction due to movement of the wireless communication terminal, withdrawal from the multicast group, or the like, each time the number of switching thresholds increased is restored. Here, since it is determined for each multicast group whether or not they exist in the same direction, a switching threshold also exists for each multicast group.

  When the switching threshold is set corresponding to the number of wireless communication terminals, the number of switching thresholds is decreased by one as there is one wireless communication terminal determined to be in the same direction. That is, in FIG. 7A, the switching threshold is decreased by 1 to (number of wireless communication terminals−1), and in FIG. 7B and FIG. 7C, the switching threshold is decreased by 2 and (number of wireless communication terminals). -2). That is, if there is one other wireless communication terminal in the same direction as a certain wireless communication terminal, the same effect as that obtained when one wireless communication terminal belonging to the multicast group is reduced can be obtained. In this case, the switching control unit 106 changes the number of wireless communication terminals in step S502 of FIG. 5 to “number of wireless communication terminals−1” and “number of wireless communication terminals−2”. And the number of antenna elements may be compared to determine which of the beam forming unit 107 and the transmission diversity unit 108 to use. However, in this embodiment, a case where the switching threshold is set corresponding to the number of transmitting antenna elements will be described below.

  Further, the switching control unit 106 stores which wireless terminal the angle between the wireless communication terminals when the switching threshold is increased. This angle is referred to when the switching threshold is decreased. Details of this will be described later with reference to FIG.

  When a multicast transmission request is notified, the number of multicast communication target wireless communication terminals is compared with the corresponding multicast group switching threshold, and if the number of multicast communication target wireless communication terminals is equal to or greater than the switching threshold, transmission diversity is performed. Switch to the unit 108, select a transmission method by transmission diversity, and perform transmission. On the other hand, when the number of wireless communication terminals subject to multicast transmission is less than the switching threshold, the beam switching unit 107 is switched to select a method for generating and transmitting a beam by directivity control and performing transmission.

Next, an operation for increasing the switching threshold and an operation for decreasing the switching threshold will be described with reference to FIGS. 8 and 9, respectively. Here, it is assumed that the number-of-terminals determination unit 104 determines that the number of wireless communication terminals targeted for multicast transmission in the wireless communication apparatus 600 is M. Of the steps in the flowchart of FIG. 9, the same steps as those in the flowchart of FIG. 8 are denoted by the same reference numerals, and description thereof is omitted.
<Switching threshold increase>
First, for example, the switching control unit 106 sets i = 1 at M angles θ i (i = 1,..., M; M is a natural number of 2 or more) between the terminals (step S801), and the terminal direction estimation unit 601 calculates and estimates the angle theta 1 (step S802). Here, the angle θ i is an angle formed by the direction in which two wireless communication terminals are measured, measured from the wireless communication device 600, and is the i th of the M wireless communication terminals numbered in order. The angle between the wireless communication terminal and the i + 1th wireless communication terminal (where M + 1 is replaced with 1).

Angle theta 1 determines whether less or not than the threshold angle alpha (step S803). The switching control unit 106, if the angle theta 1 is determined to be smaller than the threshold angle α proceeds to step S804, the other hand, if the angle theta 1 is determined to be the threshold angle α or the process proceeds to step S805.

In step S804, the switching control unit 106 increases the number of switching thresholds by one. In step S805, the value of i is incremented by 1, and preparation for comparing the next angle θ i + 1 and the threshold angle α is made. Next, the terminal direction estimation unit 601 determines whether or not the value of i after being increased in step S805 is greater than M−1, which is one less than the number of angles between the terminals (step S806). ). For example, when the unit is radians, the angle θ M may be calculated by θ M = 2π− (θ 1 +... + Θ M−1 ). When i = M, the wireless communication is performed as in step S802. There is no need to estimate the angle θ M using the direction of arrival of the radio wave transmitted by the communication terminal, the position detection function in the GPS system or the wireless LAN system, or the like.

  If the value of i is greater than M−1, all the angles to be determined have been determined, so that the switching threshold is determined and the operation for increasing the switching threshold is terminated and the switching threshold is determined (step S806). On the other hand, when the value of i is equal to or less than M−1, there is an angle that has not been determined yet, so the process returns to step S802 (step S806).

  When it is known that the wireless communication terminal is used in a fixed manner, the operation of increasing the switching threshold value may be performed only once at the beginning when each wireless communication terminal joins the multicast group. Usually, since the wireless communication terminal is considered to move, it is desirable for the wireless communication apparatus 600 to periodically perform the “switching threshold increase” operation.

<Switching threshold reduction>
In addition to the operation of increasing the switching threshold as described above, the switching threshold may be decreased. This is because when the wireless communication terminal leaves the multicast group or the wireless communication terminal is moving, the wireless communication terminals that have been determined to be in the same direction are then separated in the same direction. This is because it may not be determined. When there are wireless communication terminals that are no longer in the same direction, the switching threshold must be decreased. Specifically, for example, this is performed according to a flowchart shown in FIG.
First, the switching control unit 106 sets i = 1 at the angle θ i (step S801), and determines whether or not the angle θ 1 is obtained by raising the switching threshold according to the flowchart of FIG. 8 (step S901). . That is, the angle theta 1 is, for example, whether the angle is determined theta 1 <alpha by the operation of FIG. 8 to the most recent past is determined. If the angle theta 1 is intended to raise the switching threshold the process proceeds to step S802, the case the angle theta 1 is not intended to raise the switching threshold the process proceeds to step S805.

Angle theta 1 estimated in step S802 determines whether larger or not than the threshold angle alpha (step S902). When the switching control unit 106 determines that the angle θ 1 is larger than the threshold angle α, the process proceeds to step S903, whereas when it determines that the angle θ 1 is equal to or smaller than the threshold angle α, the process proceeds to step S805. In step S903, the switching control unit 106 decreases the number of switching thresholds by one.

In step S805 and subsequent steps, the value of i is incremented by 1, and preparation for comparing the next angle θ i + 1 with the threshold angle α is performed, and steps S901, S802, S902, and S903 are performed until i = M−1. Even when the wireless communication terminal withdraws from the multicast group, the switching threshold may be decreased corresponding to the withdrawn wireless communication terminal in the same manner as the operation illustrated in FIG.

  According to the wireless communication device of the present embodiment, when there are wireless communication terminals in the same direction, it is possible to transmit to a plurality of wireless communication terminals with the same beam. The effect of beam forming can be expected even in a wireless communication terminal. Even in such a case, more optimal multicast transmission is possible by performing transmission by beam forming.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a block diagram of a wireless communication apparatus according to a first embodiment of the present invention. The block diagram of the beam forming part of FIG. FIG. 3 is a diagram illustrating an example of a beam pattern when the wireless communication apparatus of FIG. 1 performs beam forming. The block diagram of the transmission diversity part of FIG. The flowchart which shows the switching operation | movement of the switching control part of FIG. The block diagram of the radio | wireless communication apparatus which concerns on the 2nd Embodiment of this invention. 6A is a diagram illustrating a case where the switching control unit in FIG. 6 determines two wireless communication terminals in the same direction, and FIG. 6B is a diagram illustrating a case where the switching control unit in FIG. The figure which shows the case where it determines with the same direction, (c) is the figure which shows the case where the switching control part of FIG. 6 determines three wireless communication terminals to be the same direction. The flowchart which shows the operation | movement which the switching control part of FIG. 6 increases a switching threshold value. The flowchart which shows the operation | movement which the switching control part of FIG. 6 reduces a switching threshold value.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Wireless communication apparatus, 101 ... Antenna part, 102 ... Reception part, 103 ... Demodulation part, 104 ... Terminal number determination part, 105 ... Modulation part, 106 ... Switching control part, 107 ... Beam forming part, 108 ... Transmission diversity part , 201 ... transmission weight control unit, 202 ... multiplier, 203, 402 ... transmission processing unit, 401 ... space-time coding unit, 600 ... wireless communication device, 601 ... terminal direction estimation unit, 701 to 710 ... wireless communication terminal

Claims (10)

  1. A wireless communication device that performs multicast transmission to a plurality of different wireless communication terminals,
    Calculating means for calculating the number of wireless communication terminals to be subjected to multicast transmission based on belonging information indicating belonging to a group of wireless communication terminals capable of receiving multicast transmission;
    A plurality of transmission means each using a plurality of different multicast transmission methods;
    Estimating means for estimating a plurality of directions in which a plurality of wireless communication terminals to be subjected to the multicast transmission exist;
    A plurality of antenna elements;
    Selecting means for selecting any one of a plurality of different multicast transmission schemes according to the number of wireless communication terminals, the number of antenna elements, and the plurality of directions;
    Corresponding to the multicast transmission method wherein the selected, have rows one transmission unit, the multicast transmission to the wireless communication terminal as the target of the multicast transmission of the plurality of transmission means,
    The plurality of transmission means include at least beam forming transmission means for forming a plurality of directional signal beams and performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity ,
    The selection means includes
    Based on the estimated plurality of directions, the sum of the number of wireless communication terminals that can be considered to be present in the same direction minus 1 for all directions and the number of antenna elements is the target for the multicast transmission. If the number of wireless communication terminals is equal to or less than, select a transmission method by the transmission diversity transmission means,
    Based on the plurality of estimated directions, the number of wireless communication terminals that can be regarded as existing in a certain direction minus 1 is calculated for all directions, and the sum of the number of antenna elements is the target of the multicast transmission. comprising radio when communication is larger than the number of terminals, the beam forming transmission means radio communications device you and selects a transmission scheme according.
  2. A wireless communication device that performs multicast transmission to a plurality of different wireless communication terminals,
    Calculating means for calculating the number of wireless communication terminals to be subjected to multicast transmission based on belonging information indicating belonging to a group of wireless communication terminals capable of receiving multicast transmission;
    A plurality of transmission means each using a plurality of different multicast transmission methods;
    Estimating means for estimating a plurality of directions in which a plurality of wireless communication terminals to be subjected to the multicast transmission exist;
    A plurality of antenna elements;
    Selecting means for selecting any one of a plurality of different multicast transmission schemes according to the number of wireless communication terminals, the number of antenna elements, and the plurality of directions;
    One transmission means of the plurality of transmission means corresponding to the selected multicast transmission method performs multicast transmission to a wireless communication terminal to be subjected to the multicast transmission,
    The plurality of transmission means include at least beam forming transmission means for forming a plurality of directional signal beams and performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
    The selection means includes
    The sum of the value added by 1 as the number of wireless communication terminals that can be regarded as existing in the same direction in the plurality of estimated directions and the number of antenna elements is the target of the multicast transmission. If the number is less than the number of wireless communication terminals, select a transmission method by the transmission diversity transmission means,
    The sum of the number of wireless communication terminals that can be regarded as existing in one and the same direction minus the number of antenna elements in all directions and the number of antenna elements is the target of the multicast transmission. A radio communication apparatus that selects a transmission method by the beamforming transmission means when the number is larger than the number of radio communication terminals .
  3. A wireless communication device that performs multicast transmission to a plurality of different wireless communication terminals,
    Calculating means for calculating the number of wireless communication terminals to be subjected to multicast transmission based on belonging information indicating belonging to a group of wireless communication terminals capable of receiving multicast transmission;
    A plurality of transmission means each using a plurality of different multicast transmission methods;
    Estimating means for estimating a plurality of directions in which a plurality of wireless communication terminals to be subjected to the multicast transmission exist;
    A plurality of antenna elements;
    Selecting means for selecting any one of a plurality of different multicast transmission schemes according to the number of wireless communication terminals, the number of antenna elements, and the plurality of directions;
    One transmission means of the plurality of transmission means corresponding to the selected multicast transmission method performs multicast transmission to a wireless communication terminal to be subjected to the multicast transmission,
    The plurality of transmission means include at least beam forming transmission means for forming a plurality of directional signal beams and performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
    The selection means includes
    The value obtained by subtracting 1 from the number of wireless communication terminals to be subjected to the multicast transmission as the number of wireless communication terminals that can be considered to exist in a certain same direction in the plurality of estimated directions is the antenna element. If the number is more than the number, select the transmission method by the transmission diversity transmission means,
    A value obtained by subtracting the number of wireless communication terminals that can be considered to exist in a certain same direction in the plurality of estimated directions minus the number in all directions from the number of wireless communication terminals to be subjected to the multicast transmission. When the number is smaller than the number of antenna elements, the radio communication apparatus selects a transmission method by the beamforming transmission means .
  4. The transmission diversity transmission means, wireless communication apparatus according to any one of claims 1 to 3, characterized in that performing the space-time coding.
  5. The said calculation means acquires the said affiliation information using the Internet group management protocol (Internet Group Management Protocol) , and calculates the said wireless communication terminal number from this affiliation information. Item 5. The wireless communication device according to any one of Item 4 .
  6. A wireless communication method for performing multicast transmission to a plurality of different wireless communication terminals,
    Calculating the number of wireless communication terminals to be subjected to multicast transmission based on affiliation information indicating belonging to a group of wireless communication terminals capable of receiving multicast transmission;
    Prepare multiple transmission methods that use multiple different multicast transmission methods,
    Estimating a plurality of directions where there are a plurality of wireless communication terminals to be subjected to the multicast transmission,
    Depending on the number of wireless communication terminals, the number of antenna elements, and the plurality of directions, any one of a plurality of different multicast transmission methods is selected,
    Corresponding to the multicast transmission method wherein the selected, have rows multicast transmission to a target wireless communication terminal to perform the multicast transmission,
    The plurality of transmission means are at least:
    Beam forming transmission means for forming a plurality of directional signal beams and performing multicast transmission;
    Transmission diversity transmission means for performing multicast transmission by transmission diversity ,
    Selecting any one of the plurality of different multicast transmission schemes includes:
    Based on the estimated plurality of directions, the sum of the number of wireless communication terminals that can be considered to be present in the same direction minus 1 for all directions and the number of antenna elements is the target for the multicast transmission. If the number of wireless communication terminals is equal to or less than, select a transmission method by the transmission diversity transmission means,
    Based on the plurality of estimated directions, the number of wireless communication terminals that can be regarded as existing in a certain direction minus 1 is calculated for all directions, and the sum of the number of antenna elements is the target of the multicast transmission. is greater than the radio communication terminal number made, radio communications how to characterized in that to select the transmission mode by the beam forming transmission means.
  7. A wireless communication method for performing multicast transmission to a plurality of different wireless communication terminals,
    Calculating the number of wireless communication terminals to be subjected to multicast transmission based on affiliation information indicating belonging to a group of wireless communication terminals capable of receiving multicast transmission;
    Prepare multiple transmission methods that use multiple different multicast transmission methods,
    Estimating a plurality of directions where there are a plurality of wireless communication terminals to be subjected to the multicast transmission,
    Depending on the number of wireless communication terminals, the number of antenna elements, and the plurality of directions, any one of a plurality of different multicast transmission methods is selected,
    Corresponding to the selected multicast transmission method, perform multicast transmission to the wireless communication terminal to be subjected to the multicast transmission,
    The plurality of transmission means include at least beam forming transmission means for forming a plurality of directional signal beams and performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
    Selecting any one of the plurality of different multicast transmission schemes includes:
    The sum of the number of wireless communication terminals that can be regarded as existing in one and the same direction minus the number of antenna elements in all directions and the number of antenna elements is the target of the multicast transmission. If the number is less than the number of wireless communication terminals, select a transmission method by the transmission diversity transmission means,
    The sum of the number of wireless communication terminals that can be regarded as existing in one and the same direction minus the number of antenna elements in all directions and the number of antenna elements is the target of the multicast transmission. A radio communication method characterized by selecting a transmission method by the beamforming transmission means when the number is larger than the number of radio communication terminals.
  8. A wireless communication method for performing multicast transmission to a plurality of different wireless communication terminals,
    Calculating the number of wireless communication terminals to be subjected to multicast transmission based on affiliation information indicating belonging to a group of wireless communication terminals capable of receiving multicast transmission;
    Prepare multiple transmission methods that use multiple different multicast transmission methods,
    Estimating a plurality of directions where there are a plurality of wireless communication terminals to be subjected to the multicast transmission,
    Depending on the number of wireless communication terminals, the number of antenna elements, and the plurality of directions, any one of a plurality of different multicast transmission methods is selected,
    Corresponding to the selected multicast transmission method, perform multicast transmission to the wireless communication terminal to be subjected to the multicast transmission,
    The plurality of transmission means include at least beam forming transmission means for forming a plurality of directional signal beams and performing multicast transmission, and transmission diversity transmission means for performing multicast transmission by transmission diversity,
    Selecting any one of the plurality of different multicast transmission schemes includes:
    A value obtained by subtracting the number of wireless communication terminals that can be considered to exist in a certain same direction in the plurality of estimated directions minus the number in all directions from the number of wireless communication terminals to be subjected to the multicast transmission. If the number of antenna elements is equal to or greater than, select a transmission method by the transmission diversity transmission means,
    A value obtained by subtracting the number of wireless communication terminals that can be considered to exist in a certain same direction in the plurality of estimated directions minus the number in all directions from the number of wireless communication terminals to be subjected to the multicast transmission. When the number is smaller than the number of antenna elements, a transmission method by the beamforming transmission unit is selected.
  9. The radio communication method according to any one of claims 6 to 8, wherein the transmission diversity transmission means performs space-time coding.
  10. Calculating the number of wireless communication terminals means obtaining the affiliation information using an Internet Group Management Protocol and calculating the number of wireless communication terminals from the affiliation information. The wireless communication method according to any one of claims 6 to 9 , wherein:
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