WO2015114784A1

WO2015114784A1 - Wireless communication system, base station, terminal, and processing method

Info

Publication number: WO2015114784A1
Application number: PCT/JP2014/052143
Authority: WO
Inventors: 大介実川
Original assignee: 富士通株式会社
Priority date: 2014-01-30
Filing date: 2014-01-30
Publication date: 2015-08-06
Also published as: JP6183474B2; JPWO2015114784A1

Abstract

A first base station (110) transmits precoded wireless signals. Furthermore, the first base station (110) switches a weight of precoding corresponding to a switch pattern selected from among a plurality of switch patterns having different pattern lengths, and notifies other base stations of the selected switch pattern. A second base station (120) transmits, to a terminal (130) connected to the second base station, wireless signals using a time resource allocated on the basis of the switch pattern notified from the first base station (110). The terminal (130) is connected to the second base station (120), and receives the wireless signals transmitted from the second base station (120).

Description

Wireless communication system, base station, terminal, and processing method

The present invention relates to a wireless communication system, a base station, a terminal, and a processing method.

Conventionally, LTE (Long Term Evolution) is known as a mobile communication standard. In addition, CoMP (Coordinated Multiple-Point transmission and reception) in which a plurality of base stations perform communication in cooperation is known. Further, precoding is known in which beamforming is performed by transmitting weighted signals from a plurality of transmission antennas (see, for example, Patent Documents 1 to 4 below).

International Publication No. 2011/052067 JP 2012-175189 A Special table 2013-52288 gazette Special table 2013-520045 gazette

However, in the above-described prior art, when the first cell performs beam forming considering the influence on the second cell, the weighting factor of the beam forming notified from the terminal of the second cell is set from the second cell to the first cell. Will cause a delay. For this reason, the beam forming of the first cell cannot follow the time variation of the radio channel, and the reception characteristics at the terminal of the second cell may deteriorate.

On the other hand, for example, it is conceivable that a switching pattern of the beamforming weighting factor in the first cell is determined and a time resource that reduces interference from the first cell is allocated to the terminal of the second cell. However, in this case, since the time resource that can be allocated to the terminal of the second cell is limited, the transmission efficiency may be reduced.

In one aspect, an object of the present invention is to provide a wireless communication system, a base station, a terminal, and a processing method that can suppress a decrease in transmission efficiency.

In order to solve the above-described problem and achieve the object, according to one aspect of the present invention, a first base station that transmits a precoded radio signal selects a switching pattern selected from a plurality of switching patterns having different pattern lengths. The precoding weight is switched according to the pattern, the selected switching pattern is notified to another base station, and the second base station uses the time resource allocated based on the switching pattern notified from the first base station. A wireless communication system, a base station, a terminal, and a wireless signal transmitted to a terminal connected to the local station, wherein the terminal is connected to the second base station and receives a wireless signal transmitted from the second base station A processing method is proposed.

According to another aspect of the present invention, a first base station that transmits a precoded radio signal switches the precoding weight according to a switching pattern notified from another base station, and the second base station , Notifying the first base station of a switching pattern selected from a plurality of switching patterns having different pattern lengths, and using a time resource allocated based on the selected switching pattern, wirelessly transmitting to a terminal connected to the own station A radio communication system, a base station, a terminal, and a processing method are proposed in which a signal is transmitted, a terminal is connected to the second base station, and a radio signal transmitted from the second base station is received.

According to one aspect of the present invention, there is an effect that a decrease in transmission efficiency can be suppressed.

FIG. 1A is a diagram illustrating an example of the wireless communication system according to the first embodiment. 1B is a diagram illustrating an example of a signal flow in the wireless communication system illustrated in FIG. 1A. FIG. 1C is a diagram illustrating a modification of the wireless communication system according to the first embodiment. 1D is a diagram illustrating an example of a signal flow in the wireless communication system illustrated in FIG. 1C. FIG. 2A is a diagram illustrating an example of a wireless communication system according to the second embodiment. 2B is a diagram illustrating an example of a signal flow in the wireless communication system illustrated in FIG. 2A. FIG. 3 is a sequence diagram illustrating an example of the operation of the wireless communication system according to the second embodiment. FIG. 4A is a diagram (part 1) illustrating an example of precoding using a double code book. FIG. 4B is a diagram (part 2) illustrating an example of precoding using a double code book. FIG. 4C is a diagram illustrating an example of precoding using a double code book (part 3). FIG. 4D is a diagram illustrating an example of a precoding codebook for 8 transmit antennas. FIG. 4E is a diagram (part 1) illustrating an example of a switching pattern candidate. FIG. 4F is a second diagram illustrating an example of a switching pattern candidate. FIG. 4G is a diagram (part 3) illustrating an example of a switching pattern candidate. FIG. 5A is a diagram illustrating an example of a first TP (connected cell) according to the second embodiment. FIG. 5B is a diagram illustrating an example of a signal flow in the first TP (connected cell) illustrated in FIG. 5A. FIG. 5C is a diagram illustrating an example of a hardware configuration of the first TP. FIG. 6A is a diagram illustrating an example of a second TP (cooperative cell) according to the second embodiment. FIG. 6B is a diagram illustrating an example of a signal flow in the second TP (cooperative cell) illustrated in FIG. 6A. FIG. 7A is a diagram illustrating an example of the first UE. FIG. 7B is a diagram illustrating an example of a signal flow in the first UE illustrated in FIG. 7A. FIG. 7C is a diagram illustrating an example of a hardware configuration of the first UE. FIG. 8 is a flowchart of an example of processing by the first TP according to the second embodiment. FIG. 9 is a flowchart of an example of processing by the second TP according to the second embodiment. FIG. 10A is a diagram illustrating an example of whether or not allocation for each subframe in pattern 1 is possible. FIG. 10B is a diagram illustrating an example of whether or not allocation for each subframe in pattern 3 is possible. FIG. 11 is a diagram of a modification of the wireless communication system according to the second embodiment. FIG. 12 is a sequence diagram illustrating an example of the operation of the wireless communication system according to the third embodiment. FIG. 13A is a diagram illustrating an example of a first TP (connected cell) according to the third embodiment. FIG. 13B is a diagram illustrating an example of a signal flow in the first TP (connected cell) illustrated in FIG. 13A. FIG. 14A is a diagram illustrating an example of a second TP (cooperative cell) according to the third embodiment. FIG. 14B is a diagram illustrating an example of a signal flow in the second TP (cooperative cell) illustrated in FIG. 14A. FIG. 15A is a flowchart (part 1) illustrating an example of processing by the first TP according to the third embodiment. FIG. 15B is a flowchart (part 2) illustrating an example of processing by the first TP according to the third embodiment. FIG. 16 is a flowchart of an example of processing by the second TP according to the third embodiment.

Hereinafter, embodiments of a radio communication system, a base station, a terminal, and a processing method according to the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1A is a diagram illustrating an example of the wireless communication system according to the first embodiment. 1B is a diagram illustrating an example of a signal flow in the wireless communication system illustrated in FIG. 1A. As shown in FIGS. 1A and 1B, the radio communication system 100 according to the first embodiment includes a first base station 110, a second base station 120, and a terminal 130.

The terminal 130 is connected to the second base station 120, for example, and receives a radio signal from the second base station 120. The terminal 130 is a terminal that is affected by reception characteristics due to beamforming (precoding) in the first base station 110. For example, the first base station 110 transmits a radio signal to a terminal different from the terminal 130, and the terminal 130 receives interference due to the radio signal transmitted from the first base station 110. Alternatively, the first base station 110 transmits a radio signal destined for the terminal 130 in cooperation with the second base station 120, and the terminal 130 is transmitted from the first base station 110 and the second base station 120. Each radio signal is received.

<First base station>
The first base station 110 includes a transmission unit 111, a switching unit 112, and a notification unit 113. Transmitter 111 transmits a precoded radio signal. The radio signal transmitted by the transmission unit 111 is a radio signal destined for a terminal connected to the first base station 110, for example. The weight of precoding by the transmission unit 111 is switched by the switching unit 112.

The switching unit 112 selects a switching pattern of the precoding weight by the transmission unit 111 from among a plurality of switching patterns having different pattern lengths. Then, the switching unit 112 notifies the notification unit 113 of the selected switching pattern. The plurality of switching patterns having different pattern lengths are, for example, switching patterns having different repetition cycles when the precoding weight is repeatedly switched with a constant pattern. As an example, the plurality of switching patterns having different pattern lengths are switching patterns having different numbers of types of weights included in the patterns when the precoding weights are repeatedly switched with a constant pattern, for example.

Also, the switching unit 112 switches the precoding weight by the transmission unit 111 according to the selected switching pattern. For example, the weight of precoding by the transmission unit 111 is a weight determined according to a plurality of parameters. In this case, the precoding weight switching pattern is a switching pattern in which the weight is switched by switching at least a part of a plurality of parameters for determining the weight. Further, the plurality of switching patterns of selection candidates of the switching unit 112 are switching patterns having different switching targets among the plurality of parameters.

The notification unit 113 notifies the switching pattern notified from the switching unit 112 to another base station (for example, the second base station 120). Thereby, the notification unit 113 uses, for example, a terminal (for example, a terminal) connected to the second base station 120 using the time resource allocated to the second base station 120 based on the switching pattern selected by the switching unit 112. 130) can transmit a radio signal.

<Second base station>
The second base station 120 includes an acquisition unit 121, an allocation unit 122, and a transmission unit 123. The acquisition unit 121 acquires information indicating the switching pattern selected in the first base station 110 from the first base station 110. Then, the acquisition unit 121 outputs the acquired information to the allocation unit 122.

The allocation unit 122 allocates time resources to the terminal 130 connected to the second base station 120 based on the switching pattern indicated by the information output from the acquisition unit 121. For example, the allocating unit 122 identifies a time resource whose precoding weight in the first base station 110 is a weight with which the reception characteristic in the terminal 130 becomes good based on the switching pattern, and the identified time resource is given to the terminal 130. assign. Then, the allocation unit 122 notifies the transmission unit 123 of the time resource allocated to the second base station 120.

The transmission unit 123 transmits a radio signal to the terminal 130 using the time resource notified from the allocation unit 122.

<Terminal>
The terminal 130 includes a control unit 131 and a receiving unit 132. The control unit 131 performs processing for connecting to the second base station 120. The receiving unit 132 receives the radio signal transmitted from the second base station 120 in the time resource allocated to the terminal 130 by the second base station 120 based on the precoding switching pattern of the first base station 110.

Thus, according to the first embodiment, the first base station 110 can select and notify the second base station 120 of the precoding weight switching pattern of the first base station 110. Accordingly, in the second base station 120, it is possible to allocate time resources that improve the reception characteristics of the terminal 130 in accordance with the beamforming of the first base station 110.

Therefore, for example, even if there is a delay in communication between the first base station 110 and the second base station 120, the relationship between the precoding of the first base station 110 and the scheduling of the second base station 120 is Adjustments can be made following time variations. For this reason, the reception characteristic in the terminal 130 connected to the second base station 120 can be improved.

Also, the precoding weight of the first base station 110 can be switched by a switching pattern selected from a plurality of switching patterns having different pattern lengths (repetition periods). This makes it possible to shorten the repetition period of the precoding weight according to the antenna configuration, the wireless environment, and the like. For this reason, the freedom degree of the scheduling in the 2nd base station 120 improves, and the fall of transmission efficiency can be suppressed.

<Selection of switching pattern based on terminal moving speed>
For example, the terminal 130 may notify the first base station 110 of the moving speed of the terminal 130. In this case, the terminal 130 can notify the moving speed to the first base station 110 via the second base station 120, for example. The moving speed may be, for example, a numerical value indicating a specific moving speed [m / sec], or may be information indicating the moving speed in stages (for example, “low speed” and “high speed”). Information indicating whether the vehicle is stopped or moving may be used.

In this case, the switching unit 112 of the first base station 110 selects a precoding weight switching pattern based on the moving speed of the terminal 130 notified from the terminal 130. Accordingly, the first base station 110 can perform beam forming by selecting a switching pattern having a pattern length corresponding to the moving speed for the terminal 130 connected to the second base station 120.

For example, when the moving speed of the terminal 130 is relatively high, the time variation of the relationship between the precoding weight of the first base station 110 and the reception characteristics at the terminal 130 is large. For this reason, for example, when the moving speed of the terminal 130 is relatively high, among the plurality of parameters that determine the precoding weight of the first base station 110, there are many parameters that greatly affect the reception characteristics at the terminal 130. Become.

On the other hand, when the moving speed of the terminal 130 is relatively high, the switching unit 112 selects a switching pattern having a relatively long pattern length among the plurality of switching patterns, thereby increasing more types of weights. Beam forming can be performed while switching. Therefore, the second base station 120 can perform scheduling with higher reception characteristics, and can suppress a decrease in reception characteristics at the terminal 130.

Also, when the moving speed of the terminal 130 is relatively low (including stoppage), the time variation of the relationship between the precoding weight of the first base station 110 and the reception characteristics at the terminal 130 is small. For this reason, for example, when the moving speed of the terminal 130 is relatively low, among the plurality of parameters that determine the precoding weight of the first base station 110, there are few parameters that greatly affect the reception characteristics at the terminal 130. Become.

In contrast, when the moving speed of the terminal 130 is relatively low, the switching unit 112 selects a switching pattern having a relatively short pattern length from among the plurality of switching patterns. Thereby, the repetition cycle of the precoding weight can be shortened. For this reason, the freedom degree of the scheduling with respect to the terminal 130 in the 2nd base station 120 improves, and the fall of the transmission efficiency with respect to the terminal 130 can be suppressed.

<Selection of switching pattern based on antenna interval of first base station>
For example, the switching unit 112 of the first base station 110 may select a precoding weight switching pattern based on intervals between a plurality of antennas from which the transmission unit 111 transmits radio signals. Accordingly, the first base station 110 can perform beam forming by selecting a switching pattern having a pattern length corresponding to the interval between a plurality of antennas.

For example, when the antenna interval of the first base station 110 is relatively wide, the time variation of the relationship between the precoding weight of the first base station 110 and the reception characteristics at the terminal 130 is large. For this reason, for example, when the antenna interval of the first base station 110 is relatively wide, the reception characteristics at the terminal 130 among the plurality of parameters that determine the precoding weight of the first base station 110 are greatly affected. More parameters are given.

In contrast, when the antenna interval of the first base station 110 is relatively wide, the switching unit 112 selects a switching pattern having a relatively long pattern length among the plurality of switching patterns. Thereby, beam forming can be performed while switching more types of weights. Therefore, the second base station 120 can perform scheduling with higher reception characteristics, and can suppress a decrease in reception characteristics at the terminal 130.

Also, when the antenna interval of the first base station 110 is relatively narrow, the time variation of the relationship between the precoding weight of the first base station 110 and the reception characteristics at the terminal 130 is small. Therefore, for example, when the antenna interval of the first base station 110 is relatively narrow, the reception characteristics at the terminal 130 among the plurality of parameters that determine the precoding weight of the first base station 110 are greatly affected. Fewer parameters to give.

In contrast, when the antenna interval of the first base station 110 is relatively narrow, the switching unit 112 selects a switching pattern having a relatively short pattern length from among the plurality of switching patterns. Thereby, the repetition cycle of the precoding weight can be shortened. For this reason, the freedom degree of the scheduling in the 2nd base station 120 improves, and the fall of the transmission efficiency with respect to the terminal 130 can be suppressed.

<Multiple parameters that determine precoding weight>
As described above, the precoding weight by the first base station 110 is a weight determined according to a plurality of parameters, for example. The plurality of parameters may be parameters that the terminal 130 selects and notifies to the second base station 120 according to the channel estimation result based on the radio signal from the first base station 110. In this case, the plurality of parameters may include, for example, a plurality of parameters having different notification periods by the terminal 130.

Also, the second base station 120 notifies the first base station 110 of parameters different from the switching target among the plurality of parameters notified from the terminal 130 based on the switching pattern notified from the first base station 110. May be. In this case, the first base station 110 can perform precoding with a weight according to the parameter notified from the second base station 120 and the parameter to be switched according to the selected switching pattern.

Further, in this case, the second base station 120 notifies only the parameter different from the switching target among the plurality of parameters notified from the terminal 130 to the first base station 110, and the switching target of the plurality of parameters The parameter may not be notified. Thereby, the communication amount between the 1st base station 110 and the 2nd base station 120 can be reduced.

(Modification of Radio Communication System According to First Embodiment)
FIG. 1C is a diagram illustrating a modification of the wireless communication system according to the first embodiment. 1D is a diagram illustrating an example of a signal flow in the wireless communication system illustrated in FIG. 1C. 1C and 1D, the same reference numerals are given to the same parts as those shown in FIGS. 1A and 1B, and the description thereof is omitted.

1A and 1B, a case has been described in which the first base station 110 determines and notifies the second base station 120 of a precoding weight switching pattern. On the other hand, as shown in FIGS. 1C and 1D, the second base station 120 may determine and notify the first base station 110 of a precoding weight switching pattern.

<First base station>
For example, the first base station 110 includes an acquisition unit 141 instead of the notification unit 113 illustrated in FIGS. 1A and 1B. The acquisition unit 141 acquires information indicating the switching pattern selected in the second base station 120 from the second base station 120. Then, the acquisition unit 141 outputs the acquired information to the switching unit 112. The switching unit 112 switches the weight of precoding performed by the transmission unit 111 according to the switching pattern indicated by the information output from the acquisition unit 141.

<Second base station>
The second base station 120 includes a notification unit 151 instead of the acquisition unit 121 illustrated in FIGS. 1A and 1B. The notification unit 151 selects a switching pattern of precoding weights by the first base station 110 from a plurality of switching patterns having different pattern lengths. Then, the notification unit 151 transmits information indicating the selected switching pattern to the first base station 110. Further, the notification unit 151 notifies the allocation unit 122 of the selected switching pattern. The allocation unit 122 allocates time resources to terminals connected to the second base station 120 based on the switching pattern indicated by the information output from the notification unit 151.

In this way, the second base station 120 may select and notify the first base station 110 of the switching pattern of the precoding weight of the first base station 110. Also in this case, it is possible to improve reception characteristics in the terminal 130 connected to the second base station 120, similarly to the configurations shown in FIGS. 1A and 1B. In addition, the degree of freedom of scheduling in the second base station 120 is improved, and a decrease in transmission efficiency can be suppressed.

(Embodiment 2)
(Radio communication system according to the second embodiment)
FIG. 2A is a diagram illustrating an example of a wireless communication system according to the second embodiment. 2B is a diagram illustrating an example of a signal flow in the wireless communication system illustrated in FIG. 2A. As illustrated in FIGS. 2A and 2B, the radio communication system 200 according to the second embodiment includes a first UE 201, a first TP 211, and a second TP 212. Also, the wireless communication system 200 may include a second UE 202.

Each of the first TP 211 and the second TP 212 is a TP (Transmission Point) that performs wireless communication. Each of the first TP 211 and the second TP 212 is, for example, an eNB (evolved Node B). The cell 221 is a cell (communication range) of the first TP 211. The cell 222 is a cell (communication range) of the second TP 212.

Further, the first TP 211 and the second TP 212 are connected by, for example, an X2 interface. In the communication using the X2 interface between the first TP 211 and the second TP 212, for example, a delay of about 20 [ms] occurs.

Each of the first UE 201 and the second UE 202 is a UE (User Equipment: user terminal) capable of wireless communication with the first TP 211 and the second TP 212, for example. In the example illustrated in FIGS. 2A and 2B, the first UE 201 is located in the cell 221 and is connected to the first TP 211. The second UE 202 is located in the cell 222 and is connected to the second TP 212.

The first UE 201 periodically reports a PMI (Precoding Matrix Indicator) based on the channel estimation result of the cell 221 to the first TP 211. The PMI reporting period by the first UE 201 can be arbitrarily set, for example, from {2, 5, 10, 16, 20, 32, 40, 64, 80, 128, 160} [ms]. It is also possible to turn off PMI reporting by the first UE 201.

The radio communication system 100 shown in FIGS. 1A and 1B can be realized by the radio communication system 200 shown in FIGS. 2A and 2B, for example. In this case, the first base station 110 shown in FIGS. 1A and 1B can be realized by the second TP 212 shown in FIGS. 2A and 2B, for example. The second base station 120 shown in FIGS. 1A and 1B can be realized by the first TP 211 shown in FIGS. 2A and 2B, for example. The terminal 130 shown in FIGS. 1A and 1B can be realized by the first UE 201 shown in FIGS. 2A and 2B, for example.

In the radio communication system 200, for example, coordinated beamforming (CB) is performed in which beamforming (BF) level cooperation is performed between the first TP211 and the second TP212. For example, the second TP 212 performs beam forming (precoding) so as to form a null point in the direction of the first UE 201 connected to the first TP 211 in cooperation with the first TP 211.

At this time, the second TP 212 switches the precoding weight of the second TP 212 according to a switching pattern selected from among a plurality of switching patterns having different pattern lengths, and notifies the first TP 211 of the selected switching pattern. For example, when a candidate for a switching pattern is known between the first TP 211 and the second TP 212, the second TP 212 transmits the identification information (ID) of the selected switching pattern to the first TP 211, and selects the switching pattern selected. 1TP211 can be notified. Alternatively, the second TP 212 may directly notify the first TP 211 of the selected switching pattern.

On the other hand, the first TP 211 allocates to the first UE 201 a subframe in which interference from the second TP 212 is reduced in the first UE 201 based on the switching pattern notified from the second TP 212. For example, the first TP 211 acquires, from the first UE 201, a PMI that causes less interference from the second TP 212 in the first UE 201.

Then, the first TP 211 assigns to the first UE 201 a subframe in which the beam forming in the second TP 212 is beam forming corresponding to the PMI acquired from the first UE 201. The beam forming corresponding to the PMI includes, for example, beam forming by the same PMI as the acquired PMI and beam forming by the PMI that is close (for example, closest) to the acquired PMI.

As a result, for example, even if there is a delay in communication between the first TP 211 and the second TP 212, it is possible to follow the scheduling in the first TP 211 with respect to the beamforming state in the second TP 212 and suppress interference in the first UE 201. . Further, it is possible to shorten the repetition period of the precoding weight in the second TP 212 according to the antenna configuration, the wireless environment (for example, the moving state of the first UE 201), and the like. For this reason, the freedom degree of the scheduling in 1st TP211 improves, and the fall of transmission efficiency can be suppressed.

Also, when there are a plurality of first UEs 201 and cooperative control is performed for each of the plurality of first UEs 201, the first TP 211 assigns different frequency resources to the plurality of first UEs 201, respectively. And 2nd TP212 determines the switching pattern of precoding about each of several 1st UE201, and performs switching of precoding about each of several 1st UE201.

(Operation of Radio Communication System According to Second Embodiment)
FIG. 3 is a sequence diagram illustrating an example of the operation of the wireless communication system according to the second embodiment. In the radio communication system 200 shown in FIGS. 2A and 2B, for example, the operation shown in FIG. 3 is performed. In the example illustrated in FIG. 3, the first UE 201 is connected to the first TP 211. Further, it is assumed that the second UE 202 is being connected to the second TP 212.

First, the first TP 211 and the second TP 212 wirelessly transmit a DL (Down Link) reference signal (step S301). Wireless transmission of the DL reference signal by step S301 is periodically performed by each of 1st TP211 and 2nd TP212, for example. The DL reference signal wirelessly transmitted in step S301 is received by the first UE 201.

Next, the first UE 201 measures the cell reception level and the moving speed based on the DL reference signal wirelessly transmitted in step S301 (step S302). The cell reception level is, for example, the received power of the DL reference signal in the first UE 201 for each of the first TP 211 and the second TP 212. The cell reception level is, for example, RSRP (Reference Signal Received Power: reference signal reception power) for each of the first TP 211 and the second TP 212.

The moving speed is the moving speed of the first UE 201 measured based on the temporal variation of the reception result of the DL reference signal. However, the moving speed is not a strict moving speed, and may be a stepped speed such as “low speed” or “high speed”.

Next, the first UE 201 notifies the first TP 211 of moving speed information indicating the moving speed measured in step S302 and RSRP (step S303). Next, the first TP 211 determines a cooperative TP that performs cooperative control with the own station based on the RSRP notified in step S303 (step S304). In the example illustrated in FIG. 3, it is assumed that the RSRP for the second TP 212 is good and the second TP 212 is determined as the cooperative TP in step S304.

Next, the first TP 211 performs transmission of a cooperative control application for applying cooperative control to the second TP 212 determined as the cooperative TP in step S304 and notification of the moving speed information transmitted in step S303 (step S305). .

Next, the second TP 212 determines a coordinated control RB (Resource Block: resource block) and a precoding switching pattern (step S306). The cooperative control RB is a radio resource (for example, a frequency resource) used for communication performed by the second TP 212 in cooperation with the first TP 211. The determination of the RB for cooperative control is performed based on the scheduling situation in the second TP 212, for example.

The switching pattern is a precoding weight switching pattern used by the second TP 212 in the cooperative control RB. The switching pattern is determined based on, for example, the antenna configuration (for example, antenna interval) of the second TP 212 and the moving speed information notified in step S305. In the example illustrated in FIG. 3, it is assumed that “pattern 3” is determined as the switching pattern.

Next, the second TP 212 notifies the first TP 211 of the cooperative control RB information indicating the cooperative control RB determined in step S306 and the switching pattern ID indicating the switching pattern determined in step S306 (step S307).

Meanwhile, the first UE 201 measures CSI (Channel State Information) of the first TP 211 and the second TP 212 (step S308). CSI includes PMI. Next, the first UE 201 notifies the first TP 211 of the CSI of the first TP 211 and the second TP 212 measured in step S308 (step S309).

Next, the first TP 211 notifies the second TP 212 of the CSI of the second TP 212 among the CSI notified in step S309 (step S310). Here, in the example shown in FIG. 3, the ID indicating “pattern 3” is notified in step S307. In “pattern 3”, only α is a switching target (see, for example, FIG. 4G). Therefore, the first TP 211 may notify only W ₁ and Y of W ₁ , Y, and α that are elements of PMI included in the CSI of the second TP 212 in step S310.

Next, the second TP 212 generates a precoding matrix based on the precoding switching pattern determined in step S306 and the PMI of the second TP 212 included in the CSI notified in step S310 (step S311). Next, 2nd TP212 performs the scheduling which allocates the radio | wireless resource in an own cell to UE (for example, 2nd UE202) of an own cell (step S312).

Next, the second TP 212 transmits the PDSCH (Physical Downlink Shared Physical Channel: physical downlink shared channel), which has been precoded by the precoding matrix generated in step S311, to the second UE 202 based on the scheduling result in step S312. (Step S313). In the example illustrated in FIG. 3, step S313 is PDSCH transmission in a subframe in which precoding is performed in which the interference level with the first UE 201 is reduced.

On the other hand, the first TP 211 generates a precoding matrix based on the PMI included in the CSI of the first TP 211 notified in step S309 (step S314). Next, based on the switching pattern notified by step S307, 1st TP211 performs the scheduling which allocates the sub-frame with small interference from 2nd TP212 to 1st UE201 (step S315). In the example illustrated in FIG. 3, the first TP 211 allocates a subframe in which step S <b> 313 is performed to the first UE 201.

Next, the first TP 211 transmits the PDSCH that has been pre-coded using the pre-coding matrix generated in step S314 to the first UE 201 based on the scheduling result in step S315 (step S316). Accordingly, the PDSCH transmission in step S316 is performed in the same subframe as the PDSCH transmission in step S313.

Thereby, the first TP 211 can transmit the PDSCH to the first UE 201 in a subframe in which precoding is performed by the second TP 212 to reduce the interference level with the first UE 201.

(Precoding with double codebook)
4A to 4C are diagrams illustrating an example of precoding using a double codebook. In LTE Rel-8 (eg TS36.211 V8.9.0), a codebook for 2 transmit antennas and 4 transmit antennas was specified. In LTE Rel-10 (for example, TS36.213 V10.11.0, R1-105011), a codebook for 8 transmitting antennas was specified.

In particular, the specification of the codebook for 8 transmitting antennas is called a double codebook or a dual codebook because two kinds of codebooks are used to reduce the feedback amount of CSI. .

In addition, in LTE Rel-12, the introduction of an extended codebook for four transmitting antennas is under consideration. A configuration similar to that of the 8Tx double codebook of Rel-10 is assumed.

Thus, for example, in LTE Rel-10 and Rel-12, a double codebook (dual codebook) using two kinds of codebooks for precoding is being studied. For example, precoding using a double code book can be applied to precoding of the second TP212.

The antenna array 401 in FIG. 4A shows an example of a cross polarized antenna array. Each antenna of the antenna array 401 is composed of two ULA (Uniform Linear Array) antennas having different polarities.

The antenna set 411 is each ULA in the −45 ° direction of each antenna of the antenna array 401. The antenna set 412 is each ULA in the + 45 ° direction in each antenna of the antenna array 401.

The beam grid 421 is a beam grid corresponding to each code book in the antenna set 411. The beam grid 422 is a grid of beams corresponding to each code book in the antenna set 412.

In the double codebook, control information overhead can be reduced by introducing two kinds of codebooks that share the directional beam in the ULA and the phase adjustment control between the ULAs. For example, the precoding codebook W in the second TP 212 has a hierarchical structure of W ₁ and W ₂ as shown by the following equation (1), for example.

W ₁ is a wideband common precoding matrix including candidates of a plurality of DFT (Discrete Fourier Transform) beams (b) for ULA as elements. Each of the

beam grids

421 and 422 is adjusted by, for example, W ₁ .

W ₂ is a precoding matrix for each subband and layer including, as elements, a selection vector (Y) for selecting a DFT beam in W ₁ and a phase adjustment coefficient (α) for performing phase adjustment between ULAs. . The phase difference between the beams of the

beam grids

421 and 422 is adjusted by, for example, W ₂ .

W ₁ and W ₂ are, for example, elements of the PMI that are notified from the first UE 201 to the first TP 211 and are elements having different notification cycles.

A beam grid 431 illustrated in FIG. 4B is a diagram illustrating an example of a grid of each beam selected by W ₁ . In the example shown in FIG. 4B, the beam grid 431 is a beam grid corresponding to Index # 0 to # 15. A beam grid 432 illustrated in FIG. 4C is a diagram illustrating an example of a grid of each beam selected by W ₂ when, for example, Index # 1 is selected by W ₁ .

In the double codebook shown in FIGS. 4A to 4C, the time fluctuations of the optimum values of W ₁ , Y, and α, which are the elements of the precoding weight of the second TP 212, differ from each other depending on the device configuration and environment.

First, W ₁ that is a precoding matrix including a plurality of ULA beams constituting a cross polarization antenna will be described. When the interval between the transmission antennas of the second TP 212 is narrow, since the fading correlation of each transmission antenna is high, the optimal value of W ₁ mainly depends on the position of the first UE 201, and the time variation of the optimal value of W ₁ is small. On the other hand, when the interval between the transmission antennas of the second TP 212 is wide, since the fading correlation of each transmission antenna is low, the optimal value of W ₁ mainly depends on the fading variation, and the time variation of the optimal value of W ₁ is large.

Next, a selection vector Y that is one element of W ₂ that is a precoding matrix for selecting any one of the plurality of beams indicated by W ₁ and performing phase adjustment between ULAs will be described. When the interval between the transmission antennas of the second TP 212 is narrow, since the fading correlation of each transmission antenna is high, the optimal value of W ₂ mainly depends on the position of the first UE 201 and the time variation of the optimal value of W ₂ is small. On the other hand, when the interval between the transmission antennas of the second TP 212 is wide, since the fading correlation of each transmission antenna is low, the optimal value of W ₂ mainly depends on the fading variation, and the time variation of the optimal value of W ₂ is large.

Next, the phase adjustment coefficient α which is one element of W ₂ will be described. Since the fading correlation between ULAs having different polarities is uncorrelated, the optimum value of α depends on fading fluctuation, and the time fluctuation of the optimum value of α is large.

FIG. 4D is a diagram illustrating an example of a precoding codebook for 8 transmit antennas. For example, in LTE Rel-10, the specification of a precoding codebook for 8 transmitting antennas is defined. This precoding code book is defined for each spatial multiplexing number (rank) in LTE TS36.213 v10.11.0 (7.2.4). Also, according to the first PMI (i1 = {0,..., 15}) and the second PMI (i2 = {0,..., 15}), the precoding codebook W ⁽¹ for rank1 shown in the table 440 of FIG. 4D is used. ⁾ _{m and n} are defined.

For example, in a typical CoMP CB scheme, rank1 precoding is applied in a cooperative cell in order to form a sharp null directivity for the UE. The above-described precoding codebook can also be expressed as, for example, the following equation (2). In the following equation (2), in e _i is (i + 1) -th only elements 1, a selection vector is remaining elements are zero.

(Candidate switching pattern)
4E to 4G are diagrams illustrating examples of switching pattern candidates. Switching patterns 451 to 453 shown in FIGS. 4E to 4G respectively indicate patterns 1 to 3 that are switching patterns of precoding weight coefficients of the second TP 212.

The switching pattern 451 (pattern 1) is a switching pattern for switching the precoding elements W ₁ and W ₂ (Y, α) of the _second TP 212 for each subframe. Therefore, the switching pattern 451 indicates repetition of 16 × 16 = 256 precoding elements.

The switching pattern 452 (pattern 2) is a switching pattern for switching the precoding elements Y and α of the second TP 212 for each subframe. Therefore, the switching pattern 452 indicates repetition of 4 × 4 = 16 precoding elements.

The switching pattern 453 (pattern 3) is a switching pattern for switching the precoding element α of the second TP 212 for each subframe. Therefore, the switching pattern 453 indicates repetition of four precoding elements.

For example, the first TP 211 and the second TP 212 share the switching patterns 451 to 453 (switching patterns 1 to 3) as switching pattern candidates. Then, the first TP 211 selects one of the switching patterns from the switching patterns 451 to 453, and notifies the second TP 212 of the switching pattern ID indicating the selected switching pattern.

(First TP according to the second embodiment)
FIG. 5A is a diagram illustrating an example of a first TP (connected cell) according to the second embodiment. FIG. 5B is a diagram illustrating an example of a signal flow in the first TP (connected cell) illustrated in FIG. 5A. As illustrated in FIGS. 5A and 5B, the first TP 211 includes a reception antenna 501, a reception RF unit 502, an uplink control signal demodulation unit 503, a cooperative TP determination unit 504, a wired I / F unit 505, and a switching pattern. A memory 506.

Also, the first TP 211 includes a precoding matrix matching unit 507, a user scheduler 508, a data signal generation unit 509, and a precoding codebook memory 510. Further, the first TP 211 includes a precoding matrix generation unit 511, a precoding unit 512, a reference signal generation unit 513, a physical channel multiplexing unit 514, a transmission RF unit 515, and a transmission antenna 516.

The reception antenna 501 receives an uplink signal (uplink reception signal) transmitted wirelessly, and outputs the received signal to the reception RF unit 502. The reception RF unit 502 performs reception RF processing on the signal output from the reception antenna 501. The reception RF processing includes, for example, frequency conversion from an RF (Radio Frequency: high frequency) band to a baseband band. Reception RF section 502 outputs a signal obtained by the reception RF processing to uplink control signal demodulation section 503.

The uplink control signal demodulation unit 503 demodulates the uplink control signal included in the signal output from the reception RF unit 502. Uplink control signal demodulation section 503 outputs RSRP from the UE (for example, first UE 201) included in the signal obtained by demodulation to cooperative TP determination section 504. Further, uplink control signal demodulation section 503 outputs movement speed information indicating the movement speed of the UE (for example, first UE 201) included in the signal obtained by demodulation to wired I / F section 505.

Further, uplink control signal demodulating section 503 outputs PMI included in the signal obtained by demodulation to wired I / F section 505, precoding matrix matching section 507, and precoding matrix generating section 511. For example, the uplink control signal demodulating unit 503 may output only the non-switching target element of W ₁ , Y, and α, which are PMI elements of the second TP 212 (neighboring cell), to the wired I / F unit 505. . Further, uplink control signal demodulating section 503 may output only the switching target element of W ₁ , Y, and α, which are PMI elements of second TP 212 (neighboring cell), to precoding matrix matching section 507.

Also, the uplink control signal demodulation section 503 outputs the PMI of the first TP 211 (own cell) to the precoding matrix generation section 511. The switching target and non-switching target elements in the PMI of the second TP 212 (neighboring cell) can be determined based on the switching pattern of the second TP 212 stored in the switching pattern memory 506, for example.

The coordinated TP determination unit 504 determines a coordinated TP that performs coordinated communication with the own cell based on the RSRP output from the uplink control signal demodulation unit 503. In the example illustrated in FIGS. 5A and 5B, the cooperative TP determination unit 504 determines the second TP 212 as the cooperative TP. The cooperative TP determination unit 504 outputs a cooperative control application for applying for cooperative control to the second TP 212 determined as the cooperative TP to the wired I / F unit 505.

The wired I / F unit 505 is a wired communication interface (for example, X2 interface) that performs wired communication with the second TP 212. For example, the wired I / F unit 505 transmits the moving speed information and PMI output from the uplink control signal demodulation unit 503 to the second TP 212. In addition, the wired I / F unit 505 transmits the cooperative control application output from the cooperative TP determination unit 504 to the second TP 212.

Also, the wired I / F unit 505 receives the switching pattern ID indicating the switching pattern of the precoding weight of the second TP 212 (neighboring cell) transmitted from the second TP 212, and sends the received switching pattern ID to the switching pattern memory 506. Output. Also, the wired I / F unit 505 receives the cooperative control RB information transmitted from the second TP 212 and outputs the received cooperative control RB information to the user scheduler 508.

The switching pattern memory 506 stores the switching pattern ID of the second TP 212 (peripheral cell) output from the wired I / F unit 505.

Based on the switching pattern indicated by the switching pattern ID of the second TP 212 stored in the switching pattern memory 506, the precoding matrix matching unit 507 derives a PMI (element) indicating the precoding weight of the second TP 212 in each subframe. . Further, the precoding matrix matching unit 507 collates the derived PMI in each subframe with the PMI (report value from the UE) of the second TP 212 output from the uplink control signal demodulation unit 503.

Then, the precoding matrix collation unit 507 notifies the user scheduler 508 of the subframe in which each collated PMI matches among the subframes as a collation result. Thereby, the beam forming (precoding) in the second TP 212 can notify the user scheduler 508 of a subframe in which beam forming based on the PMI requested by the first UE 201 is performed. However, the subframe notified by the precoding matrix matching unit 507 is not limited to the subframe in which the matched PMIs match. For example, the subframe notified by the precoding matrix matching unit 507 may be a subframe in which the difference between the matched PMIs is the smallest, or a subframe in which the difference between the matched PMIs is a difference equal to or less than a predetermined value. Good.

The user scheduler 508 performs scheduling for allocating the resource block indicated by the RB information for cooperative control output from the wired I / F unit 505 to the cooperative communication based on the collation result notified from the precoding matrix collation unit 507. Then, the user scheduler 508 outputs the scheduling result to the data signal generation unit 509.

For example, the user scheduler 508 allocates, to the first UE 201, a subframe notified as a matching result from the precoding matrix matching unit 507 among the resource blocks indicated by the RB information for cooperative control. Thereby, the subframe in which the beamforming in the second TP 212 becomes the beamforming based on the PMI requested by the first UE 201 can be assigned to the first UE 201.

The data signal generation unit 509 generates a data signal to be transmitted to the UE (for example, the first UE 201) based on the scheduling result output from the user scheduler 508, and outputs the generated data signal to the precoding unit 512.

The precoding code book memory 510 stores a code book indicating combinations of precoding weights performed by the first TP 211.

The precoding matrix generation unit 511 generates a precoding matrix used for precoding in the precoding unit 512 and outputs the generated precoding matrix to the precoding unit 512. The precoding matrix generation unit 511 generates the precoding matrix based on, for example, the PMI of the own cell output from the uplink control signal demodulation unit 503 and the codebook stored in the precoding codebook memory 510. Is called.

The precoding unit 512 precodes the data signal output from the data signal generation unit 509 based on the precoding matrix output from the precoding matrix generation unit 511. Then, precoding section 512 outputs the precoded data signal to physical channel multiplexing section 514.

The reference signal generation unit 513 generates a downlink reference signal (RS: Reference Signal), and outputs the generated reference signal to the physical channel multiplexing unit 514. The reference signal output by the reference signal generation unit 513 is, for example, the DL reference signal shown in FIG.

The physical channel multiplexing unit 514 multiplexes the data signal output from the precoding unit 512 and the reference signal output from the reference signal generation unit 513 by physical channel processing. Then, the physical channel multiplexing unit 514 outputs a signal (multiplexed signal) obtained by multiplexing to the transmission RF unit 515.

The transmission RF unit 515 performs transmission RF processing on the signal output from the physical channel multiplexing unit 514. The transmission RF processing includes, for example, frequency conversion from a baseband band to an RF band. The transmission RF unit 515 outputs a signal subjected to transmission RF processing to the transmission antenna 516. The transmission antenna 516 wirelessly transmits the signal (downlink transmission signal) output from the transmission RF unit 515.

The acquisition unit 121 illustrated in FIGS. 1A and 1B can be realized by the wired I / F unit 505, for example. 1A and 1B can be realized by, for example, a precoding matrix matching unit 507 and a user scheduler 508. The transmission unit 123 illustrated in FIGS. 1A and 1B can be realized by the transmission RF unit 515 and the transmission antenna 516, for example.

FIG. 5C is a diagram illustrating an example of a hardware configuration of the first TP. The first TP 211 shown in FIGS. 5A and 5B can be realized by, for example, the communication device 530 shown in FIG. 5C. The communication device 530 includes a CPU 531, a memory 532, a wireless communication interface 533, and a wired communication interface 534. The CPU 531, the memory 532, the wireless communication interface 533, and the wired communication interface 534 are connected by a bus 539.

A CPU 531 (Central Processing Unit) controls the entire communication device 530. The memory 532 includes, for example, a main memory and an auxiliary memory. The main memory is, for example, a RAM (Random Access Memory). The main memory is used as a work area for the CPU 531. The auxiliary memory is, for example, a nonvolatile memory such as a magnetic disk, an optical disk, or a flash memory. Various programs for operating the communication device 530 are stored in the auxiliary memory. The program stored in the auxiliary memory is loaded into the main memory and executed by the CPU 531.

The wireless communication interface 533 is a communication interface that performs communication with the outside of the communication device 530 (for example, the first UE 201) wirelessly. The wireless communication interface 533 is controlled by the CPU 531.

The wired communication interface 534 is a communication interface that communicates with the outside of the communication device 530 (for example, the second TP 212 and the host device) by wire. The wired communication interface 534 is controlled by the CPU 531.

The reception antenna 501, the reception RF unit 502, the uplink control signal demodulation unit 503, the transmission RF unit 515, and the transmission antenna 516 shown in FIGS. 5A and 5B can be realized by the wireless communication interface 533, for example. The wired I / F unit 505 illustrated in FIGS. 5A and 5B can be realized by the wired communication interface 534, for example. The switching pattern memory 506 and the precoding codebook memory 510 shown in FIGS. 5A and 5B can be realized by the memory 532, for example.

The uplink control signal demodulating unit 503, the cooperative TP determining unit 504, the precoding matrix matching unit 507, the user scheduler 508, and the data signal generating unit 509 shown in FIGS. 5A and 5B can be realized by the CPU 531, for example. The precoding matrix generation unit 511, the precoding unit 512, the reference signal generation unit 513, and the physical channel multiplexing unit 514 illustrated in FIGS. 5A and 5B can be realized by the CPU 531, for example.

(Second TP according to the second embodiment)
FIG. 6A is a diagram illustrating an example of a second TP (cooperative cell) according to the second embodiment. FIG. 6B is a diagram illustrating an example of a signal flow in the second TP (cooperative cell) illustrated in FIG. 6A. As illustrated in FIGS. 6A and 6B, the second TP 212 includes a wired I / F unit 601, a cooperative control resource determination unit 602, and a switching pattern determination unit 603.

Also, the second TP 212 includes a switching pattern memory 604, a user scheduler 605, a data signal generation unit 606, a precoding codebook memory 607, a precoding matrix generation unit 608, and a precoding unit 609. The second TP 212 includes a reference signal generation unit 610, a physical channel multiplexing unit 611, a transmission RF unit 612, and a transmission antenna 613.

The wired I / F unit 601 is a wired communication interface (for example, an X2 interface) that performs wired communication with the first TP 211. For example, the wired I / F unit 601 outputs the cooperative control application transmitted from the first TP 211 to the cooperative control resource determining unit 602. Also, the wired I / F unit 601 outputs the movement speed information transmitted from the first TP 211 to the switching pattern determination unit 603. Also, the wired I / F unit 601 outputs the non-switching target PMI of the second TP 212 (own cell) transmitted from the first TP 211 to the precoding matrix generation unit 608.

Further, the wired I / F unit 601 transmits the RB information for cooperative control output from the cooperative control resource determination unit 602 to the first TP 211. Further, the wired I / F unit 601 transmits the switching pattern ID output from the switching pattern determination unit 603 to the first TP 211.

The cooperative control resource determination unit 602 determines a radio resource to be used for cooperative control with the first TP 211 based on the cooperative control application from the first TP 211 output from the wired I / F unit 601. For example, the cooperative control resource determination unit 602 acquires a wireless resource that can be used for cooperative control with the first TP 211 from the user scheduler 605, and determines a wireless resource to be used for cooperative control with the first TP 211 based on the acquired wireless resource. . The cooperative control resource determination unit 602 outputs cooperative control RB information indicating the determined radio resource to the wired I / F unit 601. Also, the cooperative control resource determination unit 602 notifies the user scheduler 605 of the determined radio resource.

The switching pattern determination unit 603 determines the switching pattern of the precoding weight in the second TP 212 based on the moving speed information output from the wired I / F unit 601. In addition, the switching pattern determination unit 603 may determine a switching pattern of precoding weights in the second TP 212 based on intervals between a plurality of antennas (transmission antennas 613) through which the second TP 212 transmits radio signals. The intervals between the plurality of antennas (transmission antennas 613) are stored in the memory of the second TP 212, for example. The switching pattern determination unit 603 outputs a switching pattern ID indicating the determined switching pattern to the wired I / F unit 601 and the switching pattern memory 604.

The switching pattern memory 604 stores the switching pattern ID output from the switching pattern determination unit 603.

The user scheduler 605 performs scheduling for assigning the radio resource notified from the cooperative control resource determination unit 602 to the cooperative communication. Then, the user scheduler 605 outputs the scheduling result to the data signal generation unit 606.

The data signal generation unit 606 generates a data signal to be transmitted to the UE (for example, the second UE 202) based on the scheduling result output from the user scheduler 605, and outputs the generated data signal to the precoding unit 609.

The precoding code book memory 607 stores a code book indicating combinations of precoding weights performed by the second TP 212.

The precoding matrix generation unit 608 generates a precoding matrix used for precoding in the precoding unit 609, and outputs the generated precoding matrix to the precoding unit 609. The generation of the precoding matrix related to the cooperative communication is based on, for example, the non-switching target PMI output from the wired I / F unit 601 and the switching target PMI based on the switching pattern ID stored in the switching pattern memory 604. Done. Generation of a code book stored in the precoding codebook memory 607 and a precoding matrix related to communication other than cooperative communication is performed based on the codebook stored in the precoding codebook memory 607, for example.

The precoding unit 609 performs precoding of the data signal output from the data signal generation unit 606 based on the precoding matrix output from the precoding matrix generation unit 608. Precoding section 609 then outputs the precoded data signal to physical channel multiplexing section 611.

The reference signal generator 610 generates a downlink reference signal (RS) and outputs the generated reference signal to the physical channel multiplexer 611. The reference signal output by the reference signal generation unit 610 is, for example, the DL reference signal shown in FIG.

The physical channel multiplexing unit 611 multiplexes the data signal output from the precoding unit 609 and the reference signal output from the reference signal generation unit 610 by physical channel processing. Then, physical channel multiplexing section 611 outputs a signal (multiplexed signal) obtained by multiplexing to transmission RF section 612.

The transmission RF unit 612 performs transmission RF processing on the signal output from the physical channel multiplexing unit 611. The transmission RF processing includes, for example, frequency conversion from a baseband band to an RF band. The transmission RF unit 612 outputs a signal subjected to transmission RF processing to the transmission antenna 613. The transmission antenna 613 is a plurality of antennas that wirelessly transmit signals (downlink transmission signals) output from the transmission RF unit 612.

1A and 1B can be realized by a transmission RF unit 612 and a transmission antenna 613, for example. The switching unit 112 illustrated in FIGS. 1A and 1B can be realized by, for example, the switching pattern determination unit 603, the switching pattern memory 604, and the precoding matrix generation unit 608. The notification unit 113 illustrated in FIGS. 1A and 1B can be realized by the wired I / F unit 601, for example.

The hardware configuration of the second TP 212 is the same as the hardware configuration of the first TP 211. For example, the second TP 212 can be realized by the communication device 530 illustrated in FIG. 5C. In this case, the physical channel multiplexing unit 611, the transmission RF unit 612, and the transmission antenna 613 illustrated in FIGS. 6A and 6B can be realized by the wireless communication interface 533 illustrated in FIG. 5C, for example.

The wired I / F unit 601 shown in FIGS. 6A and 6B can be realized by, for example, the wired communication interface 534 shown in FIG. 5C. The switching pattern memory 604 and the precoding codebook memory 607 shown in FIGS. 6A and 6B can be realized by the memory 532 shown in FIG. 5C, for example.

The cooperative control resource determination unit 602, the switching pattern determination unit 603, the user scheduler 605, and the data signal generation unit 606 shown in FIGS. 6A and 6B can be realized by the CPU 531 shown in FIG. 5C, for example. Moreover, the precoding matrix generation unit 608, the precoding unit 609, and the reference signal generation unit 610 illustrated in FIGS. 6A and 6B can be realized by the CPU 531 illustrated in FIG. 5C, for example.

(First UE)
FIG. 7A is a diagram illustrating an example of the first UE. FIG. 7B is a diagram illustrating an example of a signal flow in the first UE illustrated in FIG. 7A. As illustrated in FIGS. 7A and 7B, the first UE 201 includes a reception antenna 701, a reception RF unit 702, a data signal demodulation unit 703, and a channel estimation unit 704. Further, the first UE 201 includes an RSRP calculation unit 705, a moving speed estimation unit 706, a precoding codebook memory 707, a PMI selection unit 708, an uplink control signal generation unit 709, a transmission RF unit 710, and a transmission antenna 711. And comprising.

The reception antenna 701 receives a downlink signal (downlink reception signal) transmitted wirelessly, and outputs the received signal to the reception RF unit 702. The reception RF unit 702 performs reception RF processing on the signal output from the reception antenna 701. The reception RF processing includes, for example, frequency conversion from the RF band to the baseband. Reception RF section 702 outputs a signal obtained by the reception RF processing to data signal demodulation section 703 and channel estimation section 704.

The data signal demodulator 703 demodulates the data signal included in the signal output from the reception RF unit 702, and outputs the data obtained by the demodulation.

The channel estimation unit 704 performs channel estimation for each base station (cell) based on the DL reference signal included in the signal output from the reception RF unit 702. Channel estimation section 704 outputs the result of channel estimation to RSRP calculation section 705, movement speed estimation section 706, and PMI selection section 708.

RSRP calculation section 705 calculates RSRP for each base station based on the result of channel estimation output from channel estimation section 704. Then, RSRP calculation section 705 outputs the calculated RSRP to uplink control signal generation section 709.

The moving speed estimation unit 706 estimates the moving speed of the first UE 201 based on the time variation of the channel estimation result output from the channel estimation unit 704. Then, the movement speed estimation unit 706 outputs movement speed information indicating the estimated movement speed to the uplink control signal generation unit 709.

The precoding codebook memory 707 stores a PMI (codebook) corresponding to a combination of precoding weights performed by the first TP 211 and the second TP 212. The PMI selection unit 708 selects, from the PMIs stored in the precoding codebook memory 707, a PMI for which the channel estimation result output from the channel estimation unit 704 is good for each base station. Then, the PMI selection unit 708 outputs the selected PMI to the uplink control signal generation unit 709.

The uplink control signal generation unit 709 receives an uplink control signal including the RSRP output from the RSRP calculation unit 705, the movement speed information output from the movement speed estimation unit 706, and the PMI output from the PMI selection unit 708. Generate. Then, uplink control signal generation section 709 outputs the generated uplink control signal to transmission RF section 710.

The transmission RF unit 710 performs transmission RF processing on the signal output from the uplink control signal generation unit 709. The transmission RF processing includes, for example, frequency conversion from a baseband band to an RF band. The transmission RF unit 710 outputs a signal subjected to transmission RF processing to the transmission antenna 711. The transmission antenna 711 wirelessly transmits the signal (uplink transmission signal) output from the transmission RF unit 710.

1A and 1B can be realized by, for example, the reception antenna 701 and the reception RF unit 702.

It should be noted that the same configuration as that of the first UE 201 shown in FIGS. 7A and 7B can be applied to the second UE 202 shown in FIGS. 2A and 2B.

FIG. 7C is a diagram illustrating an example of a hardware configuration of the first UE. The first UE 201 shown in FIGS. 7A and 7B can be realized by the communication device 730 shown in FIG. 7C, for example. The communication device 730 includes a CPU 731, a memory 732, a user interface 733, and a wireless communication interface 734. The CPU 731, the memory 732, the user interface 733, and the wireless communication interface 734 are connected by a bus 739.

The CPU 731 controls the entire communication device 730. The memory 732 includes, for example, a main memory and an auxiliary memory. The main memory is, for example, a RAM. The main memory is used as a work area for the CPU 731. The auxiliary memory is a non-volatile memory such as a magnetic disk or a flash memory. Various programs for operating the communication device 730 are stored in the auxiliary memory. The program stored in the auxiliary memory is loaded into the main memory and executed by the CPU 731.

The user interface 733 includes, for example, an input device that receives an operation input from the user, an output device that outputs information to the user, and the like. The input device can be realized by a key (for example, a keyboard) or a remote controller, for example. The output device can be realized by, for example, a display or a speaker. Further, an input device and an output device may be realized by a touch panel or the like. The user interface 733 is controlled by the CPU 731.

The wireless communication interface 734 is a communication interface that performs communication with the outside of the communication device 730 (for example, the first TP 211) wirelessly. The wireless communication interface 734 is controlled by the CPU 731.

The control unit 131 shown in FIGS. 1A and 1B can be realized by the CPU 731 and the wireless communication interface 734, for example.

The reception antenna 701, the reception RF unit 702, the transmission RF unit 710, and the transmission antenna 711 shown in FIGS. 7A and 7B can be realized by the wireless communication interface 734, for example. The precoding codebook memory 707 shown in FIGS. 7A and 7B can be realized by the memory 732, for example. The data signal demodulator 703, the channel estimator 704, the RSRP calculator 705, the moving speed estimator 706, the PMI selector 708, and the uplink control signal generator 709 shown in FIGS. 7A and 7B are realized by the CPU 731 and the memory 732, for example. can do.

(Process by 1st TP concerning Embodiment 2)
FIG. 8 is a flowchart of an example of processing by the first TP according to the second embodiment. The first TP 211 performs, for example, each step shown in FIG. First, the first TP 211 transmits a DL reference signal (step S801). Next, the first TP 211 receives the RSRP of the first TP 211 and the second TP 212 (each TP) and the moving speed information of the first UE 201 from the first UE 201 (step S802).

Next, the first TP 211 determines whether or not the cooperative TP candidate (second TP 212) satisfies the CoMP application condition (step S803). The determination in step S803 can be made based on the RSRP of the second TP 212 received in step S802, for example. When the cooperative TP candidate does not satisfy the CoMP application condition (step S803: No), the first TP 211 ends the series of processes.

In step S803, when the cooperative TP candidate satisfies the CoMP application condition (step S803: Yes), the first TP 211 sends the second TP 212 the cooperative control application and the moving speed information of the first UE 201 received in step S802. Transmit (step S804). Next, the first TP 211 receives the RB information for cooperative control for the first UE 201 and the switching pattern ID from the second TP 212 (step S805).

Next, the first TP 211 receives the CSI of the first TP 211 and the second TP 212 from the first UE 201 (step S806). Next, the first TP 211 transmits the CSI of the second TP 212 received in step S806 to the second TP 212 (step S807). Next, the first TP 211 generates a precoding matrix based on the CSI of the first TP 211 received in step S806 (step S808).

Next, the first TP 211 determines whether or not the switching pattern indicated by the switching pattern ID received in step S805 is the pattern 3 (step S809). When the switching pattern is pattern 3 (step S809: Yes), the first TP 211 selects a subframe in which the report value (PMI) from the first UE 201 matches the application value of the second TP 212 with respect to α as the precoding element. Specify (step S810).

In step S809, when the switching pattern is not pattern 3 (step S809: No), the first TP 211 determines whether the switching pattern is pattern 2 (step S811). When the switching pattern is pattern 2 (step S811: Yes), the first TP 211 has a sub-value in which the report value (PMI) from the first UE 201 matches the application value of the second TP 212 with respect to α and Y as precoding elements. A frame is specified (step S812).

If the switching pattern is not pattern 2 in step S811, that is, if the switching pattern is pattern 1 (step S811: No), the first TP 211 proceeds to step S813. That is, the first TP 211 specifies a subframe in which the report value (PMI) from the first UE 201 matches the application value of the second TP 212 with respect to α, Y, and W ₁ that are precoding elements (step S813).

Next, the first TP 211 transmits the PDSCH to the first UE 201 in the subframe specified in any of Steps S810, S812, and S813 (Step S814), and ends the series of processes. In Steps S810, S812, and S813, if there is no subframe in which the report value (PMI) from the first UE 201 matches the application value of the second TP 212, the first TP 211 returns to, for example, Step S803.

(Process by 2nd TP concerning Embodiment 2)
FIG. 9 is a flowchart of an example of processing by the second TP according to the second embodiment. The second TP 212 performs, for example, each step shown in FIG. First, the second TP 212 transmits a DL reference signal (step S901). Next, it is assumed that the second TP 212 receives the cooperative control application and the moving speed information of the first UE 201 from the first TP 211 (step S902). Next, 2nd TP212 determines RB for cooperative control based on the cooperative control application received by step S902 (step S903).

Next, the second TP 212 determines whether the antenna interval of the transmission antennas of the second TP 212 is narrower than a predetermined interval (step S904). The predetermined interval can be, for example, half the wavelength of the radio signal. When the antenna interval is narrower than the predetermined interval (step S904: Yes), the second TP 212 determines to apply the pattern 3 to the precoding of the second TP 212 (step S905).

In step S904, when the antenna interval is not narrower than the predetermined interval (step S904: No), the second TP 212 determines whether or not the moving speed of the first UE 201 is slower than the predetermined speed (step S906). The determination in step S906 can be made based on the moving speed information received in step S902, for example. When the moving speed is slower than the predetermined speed (step S906: Yes), the second TP 212 determines to apply the pattern 2 to the precoding of the second TP 212 (step S907).

In step S906, when the moving speed is not slower than the predetermined speed (step S906: No), the second TP 212 determines to apply the pattern 1 to the precoding of the second TP 212 (step S908).

Next, the second TP 212 transmits, to the first TP 211, cooperative control RB information indicating the cooperative control RB determined in step S903, and the switching pattern ID (step S909). The switching pattern ID is a switching pattern ID indicating a precoding switching pattern determined in any one of steps S905, S907, and S908.

Next, the second TP 212 receives the CSI of the second TP 212 from the first TP 211 (step S910). Next, the second TP 212 determines whether or not the switching pattern determined in any of steps S905, S907, and S908 is pattern 3 (step S911).

In step S911, when the switching pattern is pattern 3 (step S911: Yes), the second TP 212 proceeds to step S912. That is, the 2TP212 includes α is the precoding element of each sub-frame based on the pattern 3, Y included in the 2TP212 the CSI received at step S910, with W ₁ generates a precoding matrix (step S912 ).

In step S911, when the switching pattern is not pattern 3 (step S911: No), the second TP 212 determines whether or not the switching pattern is pattern 2 (step S913). When the switching pattern is pattern 2 (step S913: Yes), the second TP 212 proceeds to step S914. That is, the second TP 212 generates a precoding matrix using the precoding elements α and Y for each subframe based on the pattern 2 and W ₁ included in the CSI of the second TP 212 received in step S910 (step S914).

In step S913, when the switching pattern is not pattern 2, that is, when the switching pattern is pattern 1 (step S913: No), the second TP 212 proceeds to step S915. That is, the 2TP212 is precoding elements of each sub-frame based on the pattern 1 alpha, Y, to generate a precoding matrix by using W ₁ (step S915).

Next, the second TP 212 transmits the PDSCH to the UE (for example, the second UE 202) subordinate to the second TP 212 (step S916), and ends the series of processes. In step S916, the second TP 212 transmits the PDSCH using the precoding matrix generated in any of steps S912, S914, and S915.

(Whether or not each subframe can be assigned)
FIG. 10A is a diagram illustrating an example of whether or not allocation for each subframe in pattern 1 is possible. For example, when pattern 1 is selected as the switching pattern for the precoding weight of the second TP 212 in step S306 in FIG. 3, all combinations of W ₁ , Y, and α that are elements of the precoding weight W are switched. . Therefore, there are 256 precoding weights W (0) to (255).

Therefore, as shown in the table 1010 in FIG. 10A, the repetition of the precoding weight in the second TP 212 is every 256 subframes. Further, in each of the first UE 201 and the second UE 202, the table 1010 indicates the subframe in which the precoding weight (beamforming) of the second TP 212 is optimal as “OK”, and indicates the other subframes as “NG”. Yes.

Therefore, if the optimal value of the precoding weight of the second TP 212 in the first UE 201 is W (0), the number of subframes in which the precoding weight of the second TP 212 is W (0) is one in 256 subframes. Similarly, if the optimal value of the precoding weight of the second TP 212 in the second UE 202 is W (3), the number of subframes in which the precoding weight of the second TP 212 is W (3) is one in 256 subframes.

In the example shown in FIG. 10A, when the number of UEs is 2, as an example, transmission to the UE is possible only in 2 subframes of 256 subframes.

FIG. 10B is a diagram illustrating an example of whether or not allocation for each subframe in pattern 3 is possible. For example, when the pattern 3 is selected as the switching pattern of the precoding weight of the second TP 212 in step S306 of FIG. 3, only α of W ₁ , Y, and α, which are elements of the precoding weight W, is switched. It is done. For this reason, there are four precoding weights W (0) to (3). For this reason, as shown in the table 1010 of FIG. 10B, the repetition of the precoding weight in the second TP 212 is every four subframes.

Therefore, if the optimal value of the precoding weight of the second TP 212 in the first UE 201 is W (0), the number of subframes in which the precoding weight of the second TP 212 is W (0) is one in four subframes. Similarly, if the optimal value of the precoding weight of the second TP 212 in the second UE 202 is W (3), the number of subframes in which the precoding weight of the second TP 212 is W (3) is one in four subframes.

In the example shown in FIG. 10B, when the number of UEs is 2, as an example, transmission to the UE is possible in 128 subframes of 256 subframes. For this reason, for example, the transmission efficiency becomes higher than the example shown in FIG. 10A.

As shown in FIGS. 10A and 10B, a plurality of switching patterns having different pattern lengths can be selectively used. Thereby, for example, by selecting the pattern 1 having a long pattern length, the precoding weight W of the second TP 212 can be switched to many values, so that scheduling with higher reception characteristics is possible (see FIG. 10A). ).

Also, for example, by selecting the pattern 3 having a short pattern length, the repetition period of the precoding weight W of the second TP 212 can be shortened. As a result, the time resources that can be allocated to the first UE 201 in the first TP 211 are increased, and the degree of scheduling freedom is improved. For this reason, even if the first TP 211 adopts a method of periodically switching precoding weights in a constant pattern, a decrease in transmission efficiency can be suppressed.

(Modification of Radio Communication System According to Second Embodiment)
FIG. 11 is a diagram of a modification of the wireless communication system according to the second embodiment. In FIG. 11, the same parts as those shown in FIGS. 2A and 2B are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIG. 11, in the wireless communication system 200, JT (Joint Transmission) in which the first TP 211 and the second TP 212 simultaneously transmit the same data to the first UE 201 may be performed. Then, in JT, the second TP 212 cooperates with the first TP 211 to perform beam forming (precoding) so that reception characteristics are improved in the first UE 201 connected to the first TP 211.

In this case, based on the switching pattern notified from the second TP 212, the first TP 211 allocates to the first UE 201 a subframe in which the reception characteristics from the second TP 212 in the first UE 201 are good. For example, the first TP 211 obtains, from the first UE 201, a PMI in which the reception characteristics from the second TP 212 in the first UE 201 are favorable. Then, the first TP 211 allocates to the first UE 201 a subframe in which the beam forming in the second TP 212 is beam forming corresponding to the PMI acquired from the first UE 201.

Thereby, for example, even if there is a delay in communication between the first TP 211 and the second TP 212, the scheduling in the first TP 211 can follow the beam forming state in the second TP 212. For this reason, it is possible to improve reception characteristics in the first UE 201. Further, it is possible to shorten the repetition period of the precoding weight in the second TP 212 according to the antenna configuration, the wireless environment (for example, the moving state of the first UE 201), and the like. For this reason, the freedom degree of the scheduling in 1st TP211 improves, and the fall of transmission efficiency can be suppressed.

As described above, according to the second embodiment, the second TP 212 can select and notify the first TP 211 of the switching pattern of the precoding weight of the second TP 212. Thereby, in 1st TP211, according to the beamforming of 2nd TP212, allocation of the time resource from which the receiving characteristic of 1st UE201 becomes favorable is attained.

Therefore, for example, even if there is a delay in the communication between the second TP 212 and the first TP 211, the relationship between the precoding of the second TP 212 and the scheduling of the first TP 211 can be adjusted following the time variation of the radio channel. For this reason, it is possible to improve reception characteristics in the first UE 201 connected to the first TP 211.

Also, the precoding weight of the second TP 212 can be switched by a switching pattern selected from a plurality of switching patterns having different pattern lengths (repetition periods). This makes it possible to shorten the repetition period of the precoding weight according to the antenna configuration, the wireless environment, and the like. For this reason, the freedom degree of the scheduling in 1st TP211 improves, and the fall of transmission efficiency can be suppressed.

(Embodiment 3)
The third embodiment will be described with respect to differences from the second embodiment. In the second embodiment, the case where the second TP 212 determines the switching pattern of the precoding weight of the second TP 212 and notifies the first TP 211 of the switching pattern has been described. On the other hand, in the third embodiment, a case will be described in which the first TP 211 determines and notifies the second TP 212 of the switching pattern of the precoding weight of the second TP 212.

(Operation of Wireless Communication System According to Third Embodiment)
FIG. 12 is a sequence diagram illustrating an example of the operation of the wireless communication system according to the third embodiment. In the radio communication system 200 according to the third embodiment, for example, the operation illustrated in FIG. 12 is performed. In the example illustrated in FIG. 12, it is assumed that the first UE 201 is being connected to the first TP 211. Further, it is assumed that the second UE 202 is being connected to the second TP 212.

Steps S1201 to S1204 shown in FIG. 12 are the same as steps S301 to S304 shown in FIG. However, in step S1204, the first TP 211 determines a precoding switching pattern in addition to the determination of the cooperative TP (step S1204). In step S1204, for example, the first TP 211 can determine the switching pattern based on the moving speed information received in step S1203. Further, the first TP 211 can determine the switching pattern based on the antenna interval information indicating the interval between the transmission antennas of the second TP 212. The antenna interval information can be acquired by receiving from the second TP 212, for example.

Next, the first TP 211 transmits, to the second TP 212 determined as the cooperative TP in step S1204, the cooperative control application for applying cooperative control and the switching pattern ID indicating the switching pattern determined in step S1204 (step S1205). . Next, the second TP 212 determines the RB for cooperative control (step S1206). Next, the second TP 212 notifies the first TP 211 of the cooperative control RB information indicating the cooperative control RB determined in step S1206 (step S1207).

Steps S1208 to S1216 shown in FIG. 12 are the same as steps S308 to S316 shown in FIG. However, in step S1211, the second TP 212 generates a precoding matrix based on the switching pattern indicated by the switching pattern ID received in step S1205 (step S1211).

In step S1215, the first TP 211 performs scheduling for assigning a subframe with small interference from the second TP 212 to the first UE 201 based on the switching pattern determined in step S1204 (step S1215).

(First TP according to the third embodiment)
FIG. 13A is a diagram illustrating an example of a first TP (connected cell) according to the third embodiment. FIG. 13B is a diagram illustrating an example of a signal flow in the first TP (connected cell) illustrated in FIG. 13A. 13A and 13B, the same parts as those shown in FIGS. 5A and 5B are denoted by the same reference numerals, and the description thereof is omitted.

As shown in FIGS. 13A and 13B, the first TP 211 according to the third embodiment includes a switching pattern determination unit 603 in addition to the configurations shown in FIGS. 5A and 5B. The switching pattern determination unit 603 is the same as the switching pattern determination unit 603 shown in FIGS. 6A and 6B, for example.

The uplink control signal demodulator 503 outputs the moving speed information indicating the moving speed of the first UE 201 included in the signal obtained by the demodulation to the switching pattern determination unit 603. The wired I / F unit 505 receives the antenna interval information transmitted from the second TP 212 and outputs the received antenna interval information to the switching pattern determination unit 603. In addition, the wired I / F unit 505 transmits the switching pattern ID output from the switching pattern determination unit 603 to the second TP 212.

The switching pattern determination unit 603 determines a switching pattern of precoding weights in the second TP 212 based on the moving speed information output from the uplink control signal demodulation unit 503. Also, the switching pattern determination unit 603 may determine a switching pattern of precoding weights in the second TP 212 based on the antenna interval information output from the wired I / F unit 505.

The switching pattern determination unit 603 outputs a switching pattern ID indicating the determined switching pattern to the wired I / F unit 505 and the switching pattern memory 506. The switching pattern memory 506 stores the switching pattern ID of the second TP 212 (peripheral cell) output from the switching pattern determination unit 603.

The notification unit 151 illustrated in FIGS. 1C and 1D can be realized by the switching pattern determination unit 603 and the wired I / F unit 505 illustrated in FIGS. 13A and 13B, for example.

(Second TP according to the third embodiment)
FIG. 14A is a diagram illustrating an example of a second TP (cooperative cell) according to the third embodiment. FIG. 14B is a diagram illustrating an example of a signal flow in the second TP (cooperative cell) illustrated in FIG. 14A. 14A and 14B, the same parts as those shown in FIGS. 6A and 6B are denoted by the same reference numerals, and description thereof is omitted. As illustrated in FIGS. 14A and 14B, the second TP 212 according to the third embodiment may be configured to omit the switching pattern determination unit 603 illustrated in FIGS. 6A and 6B.

The wired I / F unit 601 transmits antenna interval information indicating the antenna interval of the transmission antenna 613 of the second TP 212 to the first TP 211. The antenna interval information is stored, for example, in the memory of the second TP 212 (for example, the memory 532 shown in FIG. 5C).

Also, the wired I / F unit 601 receives the switching pattern ID transmitted from the first TP 211 and outputs the received switching pattern ID to the switching pattern memory 604. The switching pattern memory 604 stores the switching pattern ID output from the wired I / F unit 601.

The acquisition unit 141 illustrated in FIGS. 1C and 1D can be realized by, for example, the wired I / F unit 601 illustrated in FIGS. 14A and 14B.

(Process by 1st TP concerning Embodiment 3)
FIG. 15A and FIG. 15B are flowcharts illustrating an example of processing by the first TP according to the third embodiment. The first TP 211 performs, for example, the steps shown in FIGS. 15A and 15B. Steps S1501 to S1503 shown in FIG. 15A are the same as steps S801 to S803 shown in FIG.

In step S1503, when the cooperative TP candidate satisfies the CoMP application condition (step S1503: Yes), the first TP 211 determines whether the antenna interval of the transmission antennas of the second TP 212 is smaller than the predetermined interval (step S1504). . The determination in step S1504 can be made based on the antenna interval information received from the second TP 212, for example. The antenna interval information may be received from the second TP 212 before each step shown in FIGS. 15A and 15B, or may be received immediately before step S1504.

In step S1504, when the antenna interval is narrower than the predetermined interval (step S1504: Yes), the first TP 211 determines to apply the pattern 3 to the precoding of the second TP 212 (step S1505). When the antenna interval is not narrower than the predetermined interval (step S1504: No), the first TP 211 determines whether the moving speed of the first UE 201 is slower than the predetermined speed (step S1506). The determination in step S1506 can be made based on the moving speed information received in step S1502, for example. When the moving speed is slower than the predetermined speed (step S1506: Yes), the first TP 211 determines to apply the pattern 2 to the precoding of the second TP 212 (step S1507).

In step S1506, when the moving speed is not slower than the predetermined speed (step S1506: No), the first TP 211 determines to apply the pattern 1 to the precoding of the second TP 212 (step S1508).

Next, the first TP 211 transmits to the second TP 212 a cooperative control application and a switching pattern ID indicating a switching pattern determined in any of steps S1505, S1507, and S1508 (step S1509). Next, the first TP 211 receives RB information for cooperative control for the first UE 201 from the second TP 212 (step S1510).

Steps S1511 to S1519 shown in FIG. 15B are the same as steps S806 to S814 shown in FIG. In steps S1514 and S1516, the first TP 211 determines the switching pattern determined in any of steps S1505, S1507, and S1508.

(Process by 2nd TP concerning Embodiment 3)
FIG. 16 is a flowchart of an example of processing by the second TP according to the third embodiment. The second TP 212 performs, for example, each step shown in FIG. First, the second TP 212 transmits a DL reference signal (step S1601). Next, it is assumed that the second TP 212 receives the cooperative control application and the switching pattern ID from the first TP 211 (step S1602).

Next, the second TP 212 determines a cooperative control RB based on the cooperative control application received in step S1602 (step S1603). Next, the second TP 212 transmits cooperative control RB information indicating the cooperative control RB determined in step S1603 to the first TP 211 (step S1604).

Steps S1605 to S1611 shown in FIG. 16 are the same as steps S910 to S916 shown in FIG. However, in steps S1606 and S1608, the second TP 212 determines the switching pattern indicated by the switching pattern ID received in step S1602.

Thus, according to Embodiment 3, the first TP 211 can select and notify the second TP 212 of the switching pattern of the precoding weight of the second TP 212. Thereby, in 1st TP211, according to the beamforming of 2nd TP212, allocation of the time resource from which the receiving characteristic of 1st UE201 becomes favorable is attained.

Therefore, for example, even if there is a delay in the communication between the second TP 212 and the first TP 211, the relationship between the precoding of the second TP 212 and the scheduling of the first TP 211 can be adjusted following the time variation of the radio channel. For this reason, it is possible to suppress interference in the first UE 201 connected to the first TP 211.

As described above, according to the wireless communication system, the base station, the terminal, and the processing method, it is possible to suppress a decrease in transmission efficiency.

For example, in Rel-11 of LTE (for example, TR36.819 V11.2.0), technical studies are performed assuming cooperation between a plurality of sectors configured by the same base station and cooperation between a base station and an RRH. The specification was formulated.

In addition, LTE Rel-12 (for example, 3GPP RP-130847), as an extended CoMP technology, a technical study was performed assuming cooperation between multiple base stations connected by a non-ideal backhaul line with transmission delay. ing. The above-described CB and the like can be applied to these CoMP technologies as an example.

DESCRIPTION OF SYMBOLS 100,200 Wireless communication system 110 1st base station 111,123 Transmission part 112 Switching part 113,151 Notification part 120 2nd base station 121,141 Acquisition part 122 Assignment part 130 Terminal 131 Control part 132 Reception part 201 1st UE
202 2nd UE
211 1st TP
212 2nd TP
221, 222 cell 401

antenna array

411, 412 antenna set 421, 422, 431, 432

beam grid

440, 1010 table 451 to 453

switching pattern

501, 701

reception antenna

502, 702 reception RF unit 503 uplink control signal demodulation unit 504 cooperative

TP Determination unit

505, 601 Wired I /

F unit

506, 604 Switching pattern memory 507 Precoding

matrix matching unit

508, 605

User scheduler

509, 606 Data

signal generation unit

510, 607, 707

Precoding codebook memory

511, 608 Precoding

matrix Generation unit

512, 609

Precoding unit

513, 610 Reference

signal generation unit

514, 611 Physical

channel multiplexing unit

515, 612, 710 Transmission RF unit 16,613,711 transmitting antenna 530,730 communication device 531,731 CPU
532, 732

Memory

533, 734 Wireless communication interface 534

Wired communication interface

539, 739 Bus 602 Cooperative control resource determination unit 603 Switching pattern determination unit 703 Data signal demodulation unit 704 Channel estimation unit 705 RSRP calculation unit 706 Movement speed estimation unit 708 PMI selection 709 Uplink control signal generator 733 User interface

Claims

A first base station that transmits a precoded radio signal, wherein the precoding weight is switched according to a switching pattern selected from a plurality of switching patterns having different pattern lengths, and the selected switching pattern is transferred to another base station. A first base station notifying to,
A second base station that transmits a radio signal to a terminal connected to the local station using a time resource allocated based on the switching pattern notified from the first base station;
A terminal connected to the second base station and receiving a radio signal transmitted from the second base station;
A wireless communication system comprising:
The precoding weight is a weight according to a plurality of parameters,
The plurality of switching patterns are switching patterns that switch at least a part of the plurality of parameters, and are switching patterns in which parameters to be switched among the plurality of parameters are different.
The wireless communication system according to claim 1.
The plurality of parameters are parameters that the terminal selects and notifies to the second base station based on a channel estimation result based on a radio signal from the first base station. Wireless communication system.
The second base station notifies the first base station of a parameter different from the switching target among the plurality of parameters notified from the terminal based on the switching pattern notified from the first base station. ,
The first base station performs the precoding with a weight according to the parameter notified from the second base station and the parameter to be switched to be switched according to the selected switching pattern.
The wireless communication system according to claim 3.
The terminal notifies the moving speed of the terminal to the first base station via the second base station;
The first base station selects the switching pattern based on a moving speed notified from the terminal.
The wireless communication system according to any one of claims 1 to 4, characterized in that:
The radio communication according to any one of claims 1 to 5, wherein the first base station selects the switching pattern according to an interval between a plurality of antennas that transmit the precoded radio signals. system.
A transmitter for transmitting a precoded radio signal;
A switching unit that switches the precoding weight by a switching pattern selected from a plurality of switching patterns having different pattern lengths;
By notifying the other base station of the switching pattern selected by the switching unit, the other base station using the time resource allocated based on the selected switching pattern to the other base station. A notification unit for transmitting a radio signal to a terminal connected to the station;
A base station comprising:
The selected switching pattern from another base station that transmits a precoded radio signal and switches the precoding weight according to a switching pattern selected from a plurality of switching patterns having different pattern lengths. An acquisition unit for acquiring information indicating
Based on the information acquired by the acquisition unit, an allocation unit that allocates time resources to terminals connected to the own station;
A transmitter for transmitting a radio signal to the terminal using the time resource allocated by the allocator;
A base station comprising:
The first base station that transmits a precoded radio signal, the selection notified from the first base station that switches the precoding weight according to a switching pattern selected from a plurality of switching patterns having different pattern lengths A control unit connected to a second base station that transmits a radio signal using a time resource allocated based on the switched pattern;
In a time resource allocated based on the switching pattern, a receiving unit that receives a radio signal transmitted from the second base station;
A terminal comprising:
A processing method by a base station that transmits a precoded radio signal,
The precoding weight is switched by a switching pattern selected from a plurality of switching patterns having different pattern lengths,
A terminal connected to the other base station by using the time resource allocated to the other base station based on the selected switching pattern by notifying the selected switching pattern to the other base station. Send a radio signal to
A processing method characterized by the above.
A processing method by a base station,
The selected switching pattern from another base station that transmits a precoded radio signal and switches the precoding weight according to a switching pattern selected from a plurality of switching patterns having different pattern lengths. To get information about
Based on the acquired information, time resources are allocated to terminals connected to the own station,
Transmitting a radio signal to the terminal using the allocated time resource;
A processing method characterized by the above.
A terminal processing method,
The first base station that transmits a precoded radio signal, the selection notified from the first base station that switches the precoding weight according to a switching pattern selected from a plurality of switching patterns having different pattern lengths Connected to a second base station that transmits a radio signal using a time resource allocated based on the switched pattern,
In a time resource allocated based on the switching pattern, a radio signal transmitted from the second base station is received.
A processing method characterized by the above.
A first base station for transmitting a precoded radio signal, wherein the first base station switches the precoding weight according to a switching pattern notified from another base station;
A switching pattern selected from among a plurality of switching patterns having different pattern lengths is notified to the first base station, and a radio signal is transmitted to a terminal connected to the own station using a time resource allocated based on the selected switching pattern. A second base station that transmits
A terminal connected to the second base station and receiving a radio signal transmitted from the second base station;
A wireless communication system comprising:
The second base station acquires information indicating intervals of a plurality of antennas that transmit the precoded radio signal by the first base station, and selects the switching pattern based on the acquired information. The wireless communication system according to claim 13.
A transmitter for transmitting a precoded radio signal;
An acquisition unit that acquires information indicating the selected switching pattern from another base station that transmits a radio signal to the terminal using a time resource allocated based on the switching pattern selected from a plurality of switching patterns having different pattern lengths When,
A control unit that switches the weight of the precoding according to the information acquired by the acquisition unit;
A base station comprising:
Among a plurality of switching patterns having different pattern lengths to a first base station that transmits a precoded radio signal and switches the precoding weight according to a switching pattern notified from another base station. A notification unit for notifying the switching pattern selected from
Based on the selected switching pattern, an allocating unit that allocates time resources to terminals connected to the own station;
A transmitter for transmitting a radio signal to the terminal using the time resource allocated by the allocator;
A base station comprising:
Among a plurality of switching patterns having different pattern lengths to a first base station that transmits a precoded radio signal and switches the precoding weight according to a switching pattern notified from another base station. A control unit connected to a second base station that transmits a radio signal to a terminal connected to the own station, using a time resource allocated based on the selected switching pattern,
In a time resource allocated based on the switching pattern, a receiving unit that receives a radio signal transmitted from the second base station;
A terminal comprising:
A processing method by a base station that transmits a precoded radio signal,
Obtaining information indicating the selected switching pattern from another base station that transmits a radio signal to the terminal using a time resource allocated based on the switching pattern selected from a plurality of switching patterns having different pattern lengths,
The precoding weight is switched according to the acquired information.
A processing method characterized by the above.
A processing method by a base station,
Among a plurality of switching patterns having different pattern lengths to a first base station that transmits a precoded radio signal and switches the precoding weight according to a switching pattern notified from another base station. Notify the switching pattern selected from
Based on the selected switching pattern, time resources are allocated to terminals connected to the own station,
Transmitting a radio signal to the terminal using the allocated time resource;
A processing method characterized by the above.
A terminal processing method,
Among a plurality of switching patterns having different pattern lengths to a first base station that transmits a precoded radio signal and switches the precoding weight according to a switching pattern notified from another base station. A switching pattern selected from the above, using a time resource allocated based on the selected switching pattern, connected to a second base station that transmits a radio signal to a terminal connected to the own station,
In a time resource allocated based on the switching pattern, a radio signal transmitted from the second base station is received.
A processing method characterized by the above.