JP2013168696A - Radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio communication system that can adaptively adjust timing when data transmitted in coordination reaches a terminal.SOLUTION: In a radio communication system according to the invention, a radio station receives data from a gateway, and delivers duplicate data of the received data to other radio stations if it is necessary to coordinate with the other radio stations in operation to transmit the received data to a terminal. Further, the radio station has a function to transmit the received data to a destination terminal thereof in coordination with the other radio stations, and a function to transmit a test signal to the destination terminal directly and also via the other radio stations. The terminal, on the basis of the reception result of the test signal, measures a relative transmission delay time which is the difference between reception time when it directly receives data destined for the terminal from a radio station having received the data from the gateway and reception time when it receives the data via the other radio stations, and notifies a transmission source radio station of the test signal of the relative transmission delay time.

Description

  The present invention relates to a wireless communication system in which a plurality of communication devices cooperate to transmit a signal.

  In recent years, construction of a high-speed wireless communication system has been demanded due to high demand for high-speed communication. As one technique for improving the wireless transmission speed, a technique in which a plurality of wireless stations cooperate to perform signal transmission has been conventionally known.

  For example, Patent Document 1 listed below describes a technique related to a mode in which radio stations belonging to a plurality of different radio systems such as cognitive radio cooperate, specifically, a method of distributing packets to each radio system according to QoS. ing.

  Patent Document 2 below describes a method for improving the throughput of the entire communication system by distributing loads to a plurality of radio frequency channels.

  As for a form in which a plurality of wireless stations cooperate, there are cases where cooperation is performed between wireless stations belonging to different wireless systems, and there are cases where cooperation is performed between a plurality of wireless stations belonging to the same wireless system. These conventional techniques include the following common operations. In common operation, when data addressed to a terminal is generated in a higher-level distribution device (server) that accommodates each wireless station, the distribution device first distributes the data addressed to the terminal to each wireless station that performs the cooperative operation. To do. Each wireless station that has received the data addressed to the terminal from the distribution apparatus transmits the received data to the terminal through a wireless link. Information such as the channel state of each route is collected in advance in the distribution device, and data may be distributed on each route based on the information.

JP 2009-141438 A JP 2006-313993 A

  In the prior art, a distribution device that mainly uses radio stations transmits different data to each of the associated radio stations. That is, the distribution apparatus divides data into a plurality of blocks and determines a block to be transmitted from each wireless station, and transmits a block to be transmitted from the wireless station to the terminal. However, it is not always good to transmit different data from each wireless station. Depending on the environment, such as when the terminal is moving fast, data may not be received successfully from some transmitting stations. Therefore, it is desired to realize a configuration that can select an appropriate cooperative transmission mode according to the environment.

  In addition, when a plurality of radio stations transmit different data parts, a control signal for notifying the receiving side (terminal) of the data part transmitted by each base station is required, but for efficient signal transmission Requires a method for efficiently notifying (transmitting) this control signal.

  In addition, it is desirable that the rate at which data is transmitted from a plurality of radio stations is adaptively changed according to the propagation environment, and at this time, it is possible to control the data so that the data arrives almost simultaneously from each radio station. Is desired.

  Further, when a plurality of radio stations transmit different data portions, data from one base station may be delayed depending on the traffic situation and the situation of the connection link between the radio stations. For this reason, it is desirable to provide a configuration for performing retransmission control so that data arrives almost simultaneously from each wireless station and a method for notifying the terminal of information related to retransmission control.

  In addition, when a plurality of wireless stations transmit different data portions, it is desired to provide a method for guaranteeing the maintenance of predetermined communication quality in cooperative transmission.

  In addition, in wireless transmission, the connection state of some links among the links with a plurality of wireless stations that perform cooperative transmission may deteriorate rapidly. Therefore, it is desired to realize a configuration that can maintain communication quality even in such a case.

  In addition, it is desired to realize a configuration that can flexibly perform cooperative control when a terminal performs handover between cells.

  Also, in an environment in which a coordinated radio station (each radio station that performs coordinated transmission) and a terminal have multiple antennas, it is desired to realize a configuration in which the coordinated radio station can transmit signals within a range in which the receiving station can separate spatially multiplexed signals.

  In addition, when a plurality of radio stations transmit signals in cooperation with each other in cellular radio communication, the configuration can be expanded while maintaining the functions of the 3GPP (Third Generation Partnership Project) -LTE (Long Term Evolution) system, which is an international standard system Realization of is desired.

  The present invention has been made in view of the above, and an object of the present invention is to provide a wireless communication system that can adaptively adjust the timing at which data transmitted in cooperation from a plurality of wireless stations arrives at a terminal.

  In order to solve the above-described problems and achieve the object, the present invention is a wireless communication system including a plurality of wireless stations, a gateway that accommodates the plurality of wireless stations, and a terminal that communicates with the wireless stations. When the wireless station receives data from the gateway and needs to cooperate with another wireless station in the transmission operation of the received data to the terminal, the other wireless station cooperates with the duplicate data of the received data. A function of transmitting the received data to the destination terminal in cooperation with the other wireless station, and transmitting a test signal for transmission delay measurement directly to the destination terminal A function of transmitting via another wireless station, the terminal is based on the reception result of the test signal, the data addressed to itself is the wireless station that acquired the data from the gateway Measure the relative transmission delay time, which is the difference between the reception time when receiving directly and the reception time when receiving via another wireless station, and further use the measured relative transmission delay time as the source wireless station of the test signal It is characterized by notifying to.

  According to the present invention, a terminal measures a difference in arrival time of data transmitted from each wireless station using a test signal transmitted from a wireless station that performs cooperative transmission, and notifies the wireless base station of the measurement result. Therefore, each wireless station that performs coordinated transmission can adjust the data transmission timing based on the measurement result notified from the terminal, and there is an effect that the data arrival timing to the terminal can be adjusted adaptively.

FIG. 1 is a diagram of a configuration example and an operation outline of the wireless communication system according to the first embodiment. FIG. 2 is a diagram of a configuration example and an operation outline of the wireless communication system according to the first embodiment. FIG. 3 is a sequence diagram illustrating a cooperation control procedure according to the first embodiment. FIG. 4 is a diagram illustrating a configuration example of a radio station that realizes the cooperative control according to the first embodiment. FIG. 5 is a diagram illustrating an example of a data division method in the cooperative wireless station. FIG. 6 is a diagram illustrating an example of a sequence number attached to the header of data divided by the cooperation wireless station. FIG. 7 is a diagram illustrating an example of a signal transmission operation from the cooperative wireless station to the terminal. FIG. 8 is a diagram illustrating an example of a signal transmission operation from the cooperative wireless station to the terminal. FIG. 9 is a diagram illustrating a configuration example of a terminal that receives data transmitted in cooperation. FIG. 10 is a diagram illustrating a configuration example of a control signal instructing a data division method. FIG. 11 is a diagram illustrating an example of the data dividing operation. FIG. 12 is a diagram illustrating a control signal transmitted from the cooperative wireless station to the terminal together with the divided data. FIG. 13 is a diagram illustrating a data combining operation in the terminal. FIG. 14 is a diagram illustrating an example of a control signal transmitted from the main radio station to the sub radio station when there are three linked radio stations. FIG. 15 is a diagram illustrating an example of a control signal transmitted from each cooperative wireless station to a terminal when there are three cooperative wireless stations. FIG. 16 is a diagram illustrating a data division / transmission operation in the radio station when the number of data bits is changed for each transmission. FIG. 17 is a diagram illustrating a data integration operation in the terminal when the number of data bits changes for each transmission. FIG. 18 is a diagram illustrating an example of retransmission control in the wireless communication system according to the third embodiment. FIG. 19 is a sequence diagram showing a retransmission control operation. FIG. 20 is a diagram for explaining a retransmission operation by the radio station according to the third embodiment. FIG. 21 is a diagram illustrating an example of a method for defining a data portion. FIG. 22 is a diagram illustrating an example of transmission control when there are three wireless stations performing cooperative transmission. FIG. 23 is a diagram for explaining a retransmission operation when there are three linked wireless stations. FIG. 24 is a diagram illustrating an example of a transmission control operation in the wireless communication system according to the fourth embodiment. FIG. 25 is a sequence diagram illustrating an example of a data transmission procedure when three wireless stations perform cooperative transmission. FIG. 26 is a diagram illustrating an example of a notification method when the control information related to the data division ratio is notified for each frame. FIG. 27 is a diagram illustrating an example of a method in which the cooperative wireless station notifies the terminal station of the data division ratio. FIG. 28 is a diagram illustrating an example of a correspondence table between data division ratios and index numbers. FIG. 29 is a sequence diagram illustrating a control procedure when the cooperative wireless station performs cooperative transmission in the wireless communication system according to the sixth embodiment. FIG. 30 is a diagram illustrating a control procedure when the cooperative wireless station performs divided data transmission. FIG. 31 is a diagram illustrating an example of a control signal transmitted from the terminal to each cooperative wireless station when there are two cooperative wireless stations. FIG. 32 is a diagram illustrating an example of a control signal transmitted from the terminal to each cooperative wireless station when there are three cooperative wireless stations. FIG. 33 is a diagram illustrating an operation example of data transmission in the wireless communication system according to the sixth embodiment. FIG. 34 is a diagram illustrating an example of control for selecting whether to perform cooperative control led by a cooperative wireless station or cooperative control led by a terminal. FIG. 35 is a diagram illustrating an example of control for selecting whether to perform cooperative control led by a cooperative wireless station or cooperative control led by a terminal. FIG. 36 is a diagram illustrating a relative delay measurement operation in the case where there are two linked wireless stations. FIG. 37 is a sequence diagram showing a relative delay measurement operation. FIG. 38 is a diagram for explaining the cooperative transmission operation in the wireless communication system according to the eighth embodiment. FIG. 39 is a diagram for explaining a cooperative transmission operation in the wireless communication system according to the ninth embodiment. FIG. 40 is a diagram illustrating an example of a table indicating a correspondence relationship between the division ratio and the maximum number of layers for each cooperative wireless station. FIG. 41 is a diagram for explaining the cooperative transmission operation in the wireless communication system according to the ninth embodiment. FIG. 42 is a diagram illustrating an example of a utilization form of cooperative transmission described in the first to ninth embodiments. FIG. 43 is a flowchart illustrating a procedure for the cooperative wireless station to select a transmission mode. FIG. 44 is a diagram showing a user plane protocol stack in the LTE scheme. FIG. 45 is a diagram illustrating a protocol stack for applying the cooperative transmission control described in Embodiments 1 to 11 to the 3GPP LTE scheme. FIG. 46 is a diagram illustrating a configuration example of a radio station according to the twelfth embodiment. FIG. 47 is a diagram illustrating a configuration example of a terminal according to the twelfth embodiment.

  Embodiments of a wireless communication system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  In the following embodiments, a method for transmitting data to a terminal in cooperation with a plurality of wireless stations is disclosed. Each embodiment may be described using the terms “base station” and “terminal”, but the disclosed data transmission method is applicable to any radio station other than “base station” and “terminal”. is there. In each embodiment, a radio station that performs data transmission in cooperation with another radio station will be referred to as a “cooperative radio station”.

Embodiment 1 FIG.
FIG. 1 and FIG. 2 are diagrams showing a configuration example and an outline of operation of the radio communication system according to the present embodiment. As shown in the figure, the wireless communication system of the present embodiment includes a gateway connected to an upper network and a wireless station connected to the gateway, and the wireless station and the terminal station are connected via a wireless transmission path (wireless link). To communicate. The gateway and each wireless station are connected by a wired transmission path.

  In the wireless communication system having the above configuration, when data is transmitted from the upper network side to a terminal under the wireless station, each cooperative wireless station (in the case of the system configuration shown in FIGS. 1 and 2, the wireless stations 1 and 2 are used). The same data is distributed to. As described above, in the wireless communication system according to the present embodiment, a configuration in which the conventional system divides data in a server (distribution device) on the network and distributes different data portions to each wireless station has been adopted. On the other hand, one of the features is that the same data is distributed to the cooperative radio station. In the wireless communication systems shown in the second and subsequent embodiments, the same data is similarly distributed to the cooperative wireless stations.

  As a method of distributing the same data to each cooperative wireless station, for example, as shown in FIG. 1, a gateway on the network copies the data and transmits it to a plurality of wireless stations 1 and 2 under its control. Further, as shown in FIG. 2, the data received by the wireless station 1 that has received data from the gateway may be redistributed (duplicated and transmitted) to the wireless station 2. When the method shown in FIG. 2 is applied, for example, when the gateway determines that the same data distribution to a plurality of radio stations (cooperative radio stations) is necessary, the gateway receives one of the cooperating radio stations from the upper network. The cooperative wireless station that transfers the received data and instructs redistribution to the cooperative wireless station, and receives the data from the gateway transmits the duplicate data of the received data to the other cooperative wireless stations. In addition, any method for distributing the same data to a plurality of wireless stations may be used. For convenience, in FIGS. 1 and 2, only the wireless stations 1 and 2 that perform cooperative transmission to the illustrated terminal are illustrated, but in reality, other wireless stations that do not perform cooperative transmission are also accommodated in the gateway. Has been.

  A wireless station to which the same copied data is distributed (a wireless station that performs cooperative transmission) is a wireless station that can perform wireless communication with a destination terminal of the distributed data. When the gateway replicates data (when the operation shown in FIG. 1 is performed), the gateway determines a wireless station (cooperating wireless station) to cooperate before starting replication. When a wireless station redistributes received data to another wireless station (when the operation shown in FIG. 2 is performed), the wireless station that has received the data addressed to the terminal from the gateway performs cooperative transmission before starting redistribution. The wireless station to be performed (data redistribution destination) is determined, or the gateway determines the wireless station that performs cooperative transmission. In the latter case, the gateway determines a wireless station that cooperatively transmits data addressed to a certain terminal, notifies the determination result to one of the determined wireless stations, transmits the data, and receives the data. The wireless station distributes data to the wireless station indicated by the notification content from the gateway. When the operation shown in FIG. 2 is performed, the gateway transfers the received data from the upper network to any one of the subordinate radio stations without determining whether or not to perform cooperative transmission using a plurality of radio stations. The wireless station that has received data from the gateway may determine whether to transmit data in cooperation with other wireless stations. A method for determining a wireless station that performs cooperative transmission in a gateway or a wireless station is not particularly defined.

  Each cooperative wireless station (wireless stations 1 and 2) receiving the same data distribution selects an appropriate data portion from the received data and transmits it to the terminal. Thus, high wireless transmission efficiency can be realized by each cooperative wireless station selecting an appropriate data portion and transmitting a signal to the terminal.

  When this embodiment is applied, the amount of transmission data on the wired network is larger than that of a system to which a conventional configuration is applied, but the allowable transmission rate of the wired network is sufficiently larger than that of a wireless link and much on a wired network. Even if the data is transmitted, it is not usually a large cost. On the other hand, since the radio stations 1 and 2 hold all the data, it is possible to perform transmission control in which an appropriate data portion is selected according to the environment and transmitted with low delay. There are many other advantages when the control operation as shown in FIGS. 1 and 2 is applied. Details thereof will be described later.

  As described above, in the wireless communication system according to the present embodiment, the wireless stations 1 and 2 (cooperating wireless stations) that have received the same data distribution select an appropriate data portion from them and transmit it to the subordinate terminals. It is characterized by.

  FIG. 3 is a sequence diagram showing the cooperation control procedure of the present embodiment, and shows an example in which the wireless stations 1 and 2 cooperate with each other and transmit data received from the higher level network to the terminal. This sequence corresponds to the operation outline shown in FIG. FIG. 4 is a diagram illustrating a configuration example of a radio station that realizes the cooperative control of the present embodiment. The configuration shown in FIG. 4 can be applied to both the radio stations 1 and 2 (main radio station and sub radio station).

  As shown in FIG. 4, the radio station according to the present embodiment includes a data receiving unit 41 that receives data from the gateway, a buffer 42 that holds data received by the data receiving unit 41, and a buffer 42 that holds the data. A transmission mode selection unit 43 that selects a transmission mode of data being transmitted (how data is transmitted in cooperation with other radio stations), and buffers transmission data according to the selection result in the transmission mode selection unit 43 42, a data selection unit 44 to be taken out, a control information reception unit 45 for receiving control information transmitted from a terminal or another wireless station, a control information determination unit 46 for determining control information to be transmitted to the terminal, and a data selection unit And a data / control information transmitting unit 47 that transmits the data received from the control information determining unit 46 and the control information received from the control information determining unit 46 to the terminal. In the case of the system configuration shown in FIG. 2, in the wireless station that has received the data, for example, the data receiving unit 41 redistributes the received data to another wireless station (another wireless station that performs cooperative transmission).

  In the cooperation control shown in FIG. 3, first, the wireless stations 1 and 2 receive the same data from the gateway (step S31). Data transmitted from the gateway is received by the data receiver 41 of each cooperative wireless station (wireless stations 1 and 2) and stored in the buffer 42. Further, the radio stations 1 and 2 receive, as control information, a report regarding the current channel state, channel quality, moving speed, and the like from the terminal (step S32). This control information is received by the control information receiving unit 45 of each cooperative wireless station. The channel state and channel quality are the channel state and channel quality for the downlink channel (downlink channel) that is the direction from the radio station to the terminal.

  Next, Steps S33 and S34 are executed, and any one of the cooperative wireless stations has a plurality of cooperative transmission modes in which a mode (cooperative transmission mode) for transmitting data from each cooperative wireless station is determined in advance. Choose from. FIG. 3 shows a case where the wireless station 1 selects the cooperative transmission mode. In this case, the cooperative wireless station that does not select the cooperative transmission mode (becomes wireless station 2 in FIG. 3) uses the control information received from the terminal in step S32 as the cooperative wireless station that selects the cooperative transmission mode ( Wireless station 1) (step S33), and wireless station 1 uses cooperative transmission mode based on control information received directly from the terminal and control information received from the terminal via another cooperative wireless station (wireless station 2). Is selected (step S34). The control information transmitted from the wireless station 2 is received by the control information receiving unit 45 of the wireless station 1, and in the wireless station 1, the transmission mode is selected by the transmission mode selection unit 43. In the following description, the cooperative wireless station that selects the cooperative transmission mode is referred to as “main wireless station” or “main cooperative wireless station”, and the other cooperative wireless stations are referred to as “sub wireless station” or “sub cooperative wireless station”. "

  After selecting the transmission mode, the radio station 1 as the main radio station next notifies the sub radio station (radio station 2) of the selected transmission mode and related information (transmission timing, data division method, etc.) (steps). S35). In this process, the transmission mode determination unit 43 of the wireless station 1 transmits information on the selection result (transmission mode) and related information to the wireless station 2, and the wireless station 2 transmits these information to the control information reception unit 45. Receive. Each cooperative wireless station (wireless stations 1 and 2) transmits necessary control information and data to the terminal according to the transmission mode selected by the main cooperative wireless station (steps S36 to S39). Control information to be transmitted to the terminal is generated by the control information determination unit 46 of each cooperative radio station, and data is generated by the data selection unit 44. The generated control information and data are transmitted from the data / control information transmission unit 47 to the terminal. Here, the control information transmitted from each cooperative radio station to the terminal is related information (transmission timing, data division method, etc.) of the transmission mode selected by the main radio station. Receives data transmitted from the associated wireless station.

  As a more preferable transmission mode selection mode, a mode of selecting from the following two transmission modes is particularly effective.

(Transmission mode A: Division data transmission mode)
Each cooperative wireless station divides data and transmits different data portions.
(Transmission mode B: Same data transmission mode)
The same data is transmitted from each cooperative radio station.

  Transmission mode A is particularly effective when the terminal is stationary and the channel state does not change. This is because the channel quality notified by the terminal does not change much with time, and the terminal can stably receive the divided data. In this case, high wireless transmission efficiency can be realized by transmitting different data from each cooperative wireless station.

  On the other hand, the transmission mode B is particularly effective when the terminal is moving at high speed. In this case, although the channel environment of the terminal is easy to change and data may not be received, a diversity effect can be obtained by transmitting the same data from each cooperative radio station (two radio stations in this embodiment). Can do. It should be noted that the timing at which each cooperative radio station transmits data may be the same or different. In addition, each cooperative wireless station may transmit data at the same frequency or at different frequencies. When the terminal has a plurality of antennas, even if the radio stations 1 and 2 transmit data at the same frequency, data from each cooperative radio station can be received simultaneously. Further, when the radio stations 1 and 2 transmit data at different frequencies, the data can be individually received using a frequency filtering technique that has been widely known. As described above, the configuration in which the wireless stations 1 and 2 cooperate to select the transmission mode according to the environment enables efficient data transmission.

  When the transmission mode A (data division transmission mode) is used, the wireless station 1 notifies the wireless station 2 of a sequence number assignment method for the divided data. There are mainly the following two methods for assigning sequence numbers to data.

(Linkage sequence number assignment)
A series of sequence numbers is divided by a plurality of radio stations, and a set of sequences divided by each radio station is added to a data packet and transmitted.
(Independent sequence number assignment)
A sequence number is independently assigned to a data packet at each wireless station and transmitted.

  When coordinated sequence number allocation is used, compared with the case where independent sequence number allocation is used, coordinated transmission processing on the transmission side (cooperative radio station side) is complicated, but each data part on the reception side (terminal) The processing load for the joining operation is reduced. On the other hand, when the independent sequence number assignment is used, the processing on the transmission side is not complicated, but the combination processing on the reception side is complicated and the processing load increases. Which one is used may be fixed by the system, or may be selected adaptively according to the state (load state, etc.) of the radio station or terminal.

  FIG. 5 is a diagram illustrating an example of a data dividing method in each cooperative wireless station, and illustrates a data dividing method in each cooperative wireless station (wireless stations 1 and 2) when using transmission mode A and cooperative sequence number assignment. ing. In this figure, all data is divided into 8 blocks, and sequence numbers 1 to 8 are assigned to each block. Further, a data portion that each wireless station is responsible for transmission is extracted from the data, and transmitted from each wireless station. FIG. 6 is a diagram illustrating an example of a sequence number assigned to the header of data divided by each cooperative wireless station. As shown in the figure, a sequence number can be assigned to each data portion by writing the sequence number in the header portion of the divided data.

  7 and 8 are diagrams illustrating an example of a signal transmission operation from the cooperative wireless station to the terminal, and show specific examples of control information and data transmitted from the wireless station to the terminal. FIG. 7 shows the operation when the transmission mode A is used, and FIG. 8 shows the operation when the transmission mode B is used. In the operations shown in FIGS. 7 and 8, first, the radio station A (main radio station) uses, as control information, information identifying radio resources used for data transmission and the transmission mode (transmission mode A or B), and Information on the sequence number assignment method is transmitted to the terminal. Next, the terminal that has received the control information identifies the transmission mode (transmission mode A or B) and the sequence number assignment method, and receives data at the specified radio resource position. Many methods for specifying a radio resource by a control signal have been conventionally known, and any method may be used.

  FIG. 9 is a diagram illustrating a configuration example of a terminal that receives data transmitted in cooperation. This terminal includes a signal receiving unit 91 that receives a signal via an antenna, a channel state measuring unit 92 that measures a downlink channel state and quality, and control information that indicates a channel state measurement result and a data reception result. Control information determination / transmission unit 93 that performs generation (control information parameter determination) and transmission, data reception units 94 and 95 that extract transmission data for each opposing radio station from the signal received by the signal reception unit 91, The control information is extracted from the signal received by the signal receiving unit 91, the control information receiving unit 96 for decoding the content, and the data extracted by the data receiving units 94 and 95 are combined and transmitted from the opposite radio station side. A data combining unit 97 for reproducing the original data.

  In the terminal shown in FIG. 9, the signal receiving unit 91 receives signals from the radio stations 1 and 2, and the control information receiving unit 96 decodes the control signal included in the received signal so that the transmission mode (A or A B) is identified. In addition, the data receiving units 94 and 95 individually extract data from the radio stations 1 and 2. Further, in the case of the transmission mode A, the data combining unit 97 confirms the sequence numbers of the signals transmitted from the radio stations 1 and 2 and integrates the data by arranging the sequence numbers of the signals. On the other hand, in the transmission mode B, the data combining unit 97 receives data individually received from the radio stations 1 and 2 according to a combining method such as maximum ratio combining, thereby improving the signal reception quality.

  As described above, in the wireless communication system according to the present embodiment, the same data addressed to the terminal (all data addressed to the terminal) is distributed to the cooperative wireless stations (wireless stations 1 and 2) that transmit the data addressed to the terminal in a coordinated manner. Then, each cooperative radio station that has received the same data distribution transmits the divided data from each cooperative radio station (shares and transmits different data portions) and the same data from each cooperative radio station. An appropriate transmission mode is selected from the transmission mode B for transmitting (all data) and data is transmitted to the terminal. In addition, the transmission mode used at the time of data transmission is notified to the terminal as control information. This makes it possible to realize appropriate data transmission according to the environment (such as the movement status and movement speed of the terminal, and the respective channel conditions between each linked radio station and the terminal), and efficient data transmission from the network side to the terminal. Can be done automatically. Further, the data is divided according to the sequence number assignment method negotiated between the cooperative wireless stations, and the terminal rearranges the data according to the sequence number assignment method, thereby integrating the data signals divided by the cooperative wireless stations. Thereby, the terminal can integrate the data from each cooperation radio station by simple rearrangement based on the sequence number. In particular, when the coordinated sequence number assignment described with reference to FIGS. 5 and 6 is used, the terminal can combine data by rearranging only the sequence numbers without being aware of the transmitting radio station, and a particularly simple order. Sorting can be performed.

Embodiment 2. FIG.
In the present embodiment, a case will be described in which the independent sequence number assignment method is applied to data in the coordinated transmission control described in the first embodiment.

  When performing data transmission using transmission mode A (divided data transmission mode) and independent sequence number assignment in the wireless communication system described in the first embodiment, first the wireless station 1 of the main wireless station to the wireless station 2 of the sub wireless station In response to this, the control signal shown in FIG. 10 is transmitted. This control signal includes, as control information, a division start position indicating a data position at which data division is started, a division cycle T (bit), a division ratio R, a radio station ID in charge of the first half, and a radio station ID in charge of the second half. It is. The division start position can be shared between wireless stations by specifying a data number such as an IP packet number or its bit position. It is assumed that the sequence number is assigned in advance, and each wireless station is aware of the contents (using independent sequence number assignment).

  When the wireless station 2 that has received the control signal shown in FIG. 10 recognizes the division start position, the wireless station 2 grasps the data division method based on the division period T and the division ratio R. Further, by decoding the wireless station ID in charge of the first half and the wireless station ID in charge of the second half, the data portion (data block) in charge of transmission by itself (wireless station 2) is recognized. Upon recognizing the control contents, the radio station 2 divides the entire data series in a T-bit cycle as shown in FIG. 11, and further divides each block of the T bits into a ratio of R: 1-R. The wireless station 2 adds a header to which a sequence number is independently assigned for each wireless station and transmits the data portion that is responsible for transmission among the divided data portions. The wireless station 1 also divides the data in the same procedure, and transmits the data part that is responsible for transmission with a header assigned a sequence number.

  FIG. 12 is a diagram illustrating a control signal transmitted from the cooperative wireless station to the terminal together with the divided data (data block after being divided according to the control information). As shown in the figure, this control signal includes information (sequence allocation method) indicating a sequence number allocation method (cooperation or independent), a division period T (bit), a division ratio R, and a cooperative radio of the transmission source of this control signal. Information on the data portion (first half or second half) that the station is responsible for transmission is included. By receiving this control signal, the terminal recognizes the sequence number assignment method and the data division method.

  FIG. 13 is a diagram illustrating a data combining operation in the terminal. As illustrated, the terminal first combines the data portion received from the wireless station 1 according to the sequence number, and similarly combines the data portion received from the wireless station 2. Since the terminal confirms the information contained in the control signal transmitted together with the data and grasps the division period T and the division ratio R of the received data, the terminal then divides the combined data into a certain number of bits. Thus, the data portions from the associated wireless stations (wireless stations 1 and 2) are alternately arranged. Here, the data obtained by combining the data portions received from the radio station 1 is divided into TR bits (T × R bits). On the other hand, the data obtained by combining the data portions received from the radio station 2 is divided every T (1-R) bits. By such a method, data can be integrated at the terminal.

Although FIGS. 10 to 13 have been described on the assumption that two wireless stations cooperate, the same concept can be extended to a case where three or more wireless stations cooperate. As an example, a case where three wireless stations 1 to 3 cooperate to transmit data will be described. FIG. 14 is a diagram illustrating an example of a control signal (control signal transmitted from the main radio station to the sub radio station) used when there are three linked radio stations. When the radio station 1 is the main radio station, the radio station 1 determines the transmission mode, and when the transmission mode A is selected, the control illustrated in FIG. 14 for the radio stations 2 and 3 that are the sub radio stations. Send a signal. This control signal includes a division start position, the number of data divisions N, the number of bits of the first division part (division part 1), the number of bits of the second division part (division part 2), and the third division part ( The number of bits of the divided part 3) and the radio station ID in charge of each divided part are included as control information. The lower part of FIG. 14 shows, as an example, the relationship between each divided portion and the number of bits of each divided portion when the division number N is 3. Each sub-radio station (radio stations 2 and 3) and main radio station (radio station 1) that have received this control signal grasps the divisions that are responsible for transmission by checking each control information contained therein. Then, the divided data portion is transmitted to the terminal. FIG. 15 shows an example of a control signal transmitted from each cooperative radio station (radio stations 1, 2 and 3) to the terminal. This control signal includes information on the sequence allocation method, the number of divisions N, the number of bits B _{1 to} B _{N of} each divided portion, and the data portion (divided portion) that the cooperative radio station that is the transmission source of this control signal is responsible for transmission. Contains. The terminal receives this control signal and confirms each control information contained therein, thereby recognizing the sequence number assignment method and the data division method. Based on this control signal, the terminal receives and rearranges the data portion transmitted from each cooperative radio station, thereby integrating the cooperatively transmitted data. Thus, the present invention can also be applied to a case where three or more wireless stations cooperate to transmit data in a divided manner.

  So far, it has been assumed that each wireless station periodically transmits data having the same number of bits. However, the number of bits of data transmitted through the wireless link may be different for each transmission. For example, when the radio station adaptively changes the modulation / coding rate according to the channel state with the terminal, the number of bits of data for each transmission may change depending on the modulation scheme used. . Here, the number of data bits for each transmission may change over time, or may change for each transmission at a different frequency. In addition, the number of bits may change in transmission to different spatial regions.

  FIG. 16 is a diagram illustrating a data division / transmission operation in the radio station when the number of data bits is changed for each transmission. In the example illustrated in FIG. 16, the wireless stations 1 and 2 divide data at a T-bit period, and further divide T-bit data at a ratio of R: 1−R. After that, each wireless station once combines the data parts that it is responsible for transmission (corresponding to the data blocks 1601 and 1602 shown in the figure), and adaptively determines the modulation / coding rate according to the channel state, Determine the bit size. When each wireless station determines the bit size for each transmission, the wireless block divides the combined block (data blocks 1601 and 1602) with the determined bit size, and further, a header 1603 for each divided block (divided data). ˜1607 are added, and the sequence number is written in the header and transmitted to the terminal.

  FIG. 17 is a diagram showing the data integration operation in the terminal when the number of data bits changes for each transmission. The procedure for combining the data divided in the procedure shown in FIG. 16 and returning it to the original data is shown. Show. As shown in the figure, the terminal arranges the data received from the radio station 1 in order of the sequence numbers and combines them to obtain a data block 1701. Further, the data block 1701 is divided for each TR bit. Similarly, the data received from the radio station 2 are arranged and combined in the order of their sequence numbers to form a data block 1702, and further divided every T (1-R) bits. Finally, the data is integrated by alternately arranging the divided data (TR-bit data block and T (1-R) -bit data block) from the radio stations 1 and 2.

  As described above, in the cooperative transmission method of the present embodiment, when cooperative wireless stations (wireless stations 1 and 2) transmit data in a divided manner, each cooperative wireless station assigns a sequence number independently, and the sequence number is included in the header. The written divided data and an appropriate control signal are transmitted to the data destination terminal. Thus, the terminal rearranges and combines the received divided data according to the sequence numbers added to the headers, and further rearranges the divided data into blocks each having a predetermined bit according to the received control information. Thus, the original transmission data can be restored by integrating the divided transmission data.

Embodiment 3 FIG.
In this embodiment, a retransmission control method applicable to the radio communication system described in Embodiments 1 and 2 will be described.

  In the first and second embodiments, the case where a plurality of wireless stations cooperate to transmit divided data has been described. However, there are cases where the terminal cannot correctly receive part or all of the data from the cooperation wireless station. Therefore, in this embodiment, a retransmission control method in the case where data is retransmitted in such a situation will be described.

  FIG. 18 is a diagram illustrating an example of retransmission control in the wireless communication system according to the present embodiment. FIG. 18 illustrates retransmission control when the wireless stations 1 and 2 operate as cooperative wireless stations and transmit the data portion # 1 and the data portion # 2 in the divided data transmission mode (transmission mode A). FIG. 19 is a sequence diagram showing the retransmission control operation of FIG.

  Here, data portions # 1 and # 2 shown in FIGS. 18 and 19 are the same as those described in the first and second embodiments (TR bit data portion, T (1-R) bit data portion). Yes, part of the divided data. However, the terminal may not be able to correctly receive the data parts # 1 and # 2. Therefore, for example, when the data portion # 2 cannot be correctly received, in the wireless communication system of the present embodiment, the terminal transmits to the wireless station 1 (main wireless station) the data portion # 2 that has not been correctly received. Request. In this case, the terminal transmits a “transmission request for another divided portion” to the wireless station 1 in order to request transmission of a portion different from the already transmitted data portion. When the wireless station 1 receives the “transmission request for another divided portion”, the wireless station 1 transmits a data portion (data portion # 2) other than the already transmitted data portion to the terminal. At this time, a control signal indicating transmission of the data portion corresponding to the “transmission request for other divided portion” is also transmitted. The terminal that has received the control signal and the data recognizes from the received control signal that the data portion # 2 corresponding to the “request signal of other divided portion” transmitted before is transmitted from the radio station 1, All data is received by integrating with the already received data part # 1.

  Furthermore, as shown in FIG. 19, when the terminal successfully integrates the data portions # 1 and # 2, the terminal sends a signal indicating that all data has been successfully received (ACK for all data reception) to the wireless station 1 and Transmit to the radio station 2. The wireless station 1 and the wireless station 2 that have received this ACK delete the corresponding data portion stored in the buffer (the data portion whose normal reception has been confirmed by the reception of the ACK). In this way, by transmitting “ACK for all data reception” from the terminal to the radio stations 1 and 2 as a control signal, the amount of data stored in the buffer in each cooperative radio station can be reduced, and the buffer size in the radio station can be reduced. Can be miniaturized.

  FIG. 19 shows a case in which “transmission request of other divided parts” and “ACK indicating successful reception of all data” are used at the same time, but “ACK indicating successful reception of all data”. Can also be applied to cases where the “transmission request for other divided parts” is not transmitted. For example, even when the data portions are correctly received from the wireless stations 1 and 2, the terminal notifies the wireless stations 1 and 2 as “control signal” of “ACK indicating successful reception of all data”. As a result, the wireless stations 1 and 2 can delete the corresponding data portion stored in the buffer.

  Since “ACK indicating successful reception of all data” is notified to the wireless station that transmitted only a part of the data portion (each wireless station that transmitted T-bit data in cooperation), conventional wireless transmission This is different from ACK. The ACK in the conventional wireless transmission is transmitted to confirm the receipt of data to the wireless station that transmitted the data. On the other hand, “ACK indicating successful reception of all data” in the present embodiment notifies that the terminal has received all data including the part where the wireless station is not transmitting data. To do. Therefore, this is a new control signal for notifying the second wireless station of the receipt notification of the data portion received from the first wireless station.

  Further, instead of notifying each cooperative radio station of “ACK indicating successful reception of all data” from the terminal as a control signal, it may be notified as a control signal how far the terminal has received the data. . For example, the terminal notifies each cooperative radio station of the last sequence number at which all data has been received, and each cooperative radio station deletes the data portion corresponding to the sequence number smaller than the notified sequence number from the buffer. . In this way, this embodiment also includes notifying each cooperative radio station of the final sequence number at which the terminal has received all the data.

  In addition, instead of notifying each cooperative wireless station from the terminal as “ACK indicating that all data has been successfully received” as a control signal, each cooperative wireless station counts the elapsed time with a timer from the data transmission time, It is also possible to delete the accumulated data after a predetermined time from the buffer. In this way, the present embodiment also includes deleting accumulated data including an untransmitted data portion (a portion that is not in charge of transmission) based on the elapsed time.

  FIG. 20 is a diagram for explaining a retransmission operation by the radio station according to the present embodiment, in which a data part (data part # 1) transmitted first by radio station 1 and "transmission request for other divided parts" are received. The relationship of the data part (data part # 2) transmitted corresponding to is shown. When the data portion # 1 is the first half of the T-bit data after being divided, the data portion # 2 becomes the remaining second half of the data. In order to clearly define the range of other data parts (other divided parts), information on the target data range T1 (bit) is shared between each cooperative radio station and the terminal. This information can be updated by transmitting and receiving control signals between the cooperative radio station and the terminal. In addition, in the wireless standard, the data range T1 (bits) may be shared as a fixed number of bits. The data range T1 (bit) may be matched with the frame time. In this case, the “transmission request for other divided portion” is another data portion corresponding to the data portion transmitted in the frame.

  When the wireless station 1 transmits a data portion corresponding to the “transmission request for other divided portion” (data portion # 2 in the example of FIG. 20), the amount of data (number of bits) that the wireless station 1 can transmit at one time ) And the amount of data (number of bits) transmitted by the wireless station 2 at one time may be different. In this case, the radio station 1 may change the data format so as to match the data amount of one time of the radio station 1 by subdividing or combining the “other data portions” to be transmitted. When the data format is changed in this way, the wireless station 1 notifies the terminal of the data format or data format used as control information. The terminal receives a signal according to the received control information.

  FIG. 21 is a diagram illustrating an example of a method for defining a data portion. FIG. 21 shows an example in which the data part # 1 and the data part # 2 are defined in units of frames. In a wireless communication system to which such a definition method is applied, after the wireless station 1 transmits the data portion # 1 of the frame u and receives a “transmission request for another divided portion”, the wireless station 1 Data portion # 2 is transmitted. On the other hand, when the wireless station 1 receives the ACK indicating that the reception of all the data is successful after transmitting the data portion # 1 of the frame u, the wireless station 1 transmits the frame u + 1. Start. As described above, when an “ACK request indicating that all the data in the frame has been received” is received from the terminal until the “request for transmission of another divided portion” is received, the remaining data portion of the frame is transmitted. In this manner, simple control can be achieved by handling “transmission request of other divided portions” in units of frames. It is also a feature of this embodiment that the terminal transmits an ACK indicating that all data has been successfully received. With this configuration, the cooperative radio station can confirm the reception of all data and can move to the control of the next frame at the same time.

  The series of retransmission control described can be realized by the terminal having the configuration shown in FIG. 9 and the radio station having the configuration shown in FIG. In the terminal, the data receiving units 94 and 95 determine whether the reception is successful or unsuccessful. If the reception is unsuccessful, the control information determining / transmitting unit 93 transmits a “transmission request signal for other data portion”. When the control information receiving unit 45 receives the request signal, the wireless station recognizes that it is a “transmission request signal of another data portion” in the transmission mode selection unit 43 and stores it in the buffer 42 in the data selection unit 42. Extract necessary data from existing data. In addition, the control information determination unit 46 generates a control signal indicating that the data part corresponding to the “transmission request signal of other data part” is transmitted, and the generated data and the control signal are transmitted to the data / control information transmitting unit 47. Send to the terminal via.

  By the retransmission control described in the present embodiment, the terminal can receive all data from the wireless station 1 even when the connection state with the wireless station 2 is poor. If the retransmission control according to the present embodiment is not applied, if the state of any one of the radio links between the cooperative radio station and the terminal is deteriorated, the terminal cannot receive all data, and the communication quality is greatly deteriorated. . It is extremely important in operation to always guarantee communication quality, and services that cannot guarantee communication quality have a big problem in practical use. On the other hand, when this control is used, even when the channel state changes suddenly and the connection with the radio station 2 becomes poor, the radio station 1 transmits the data that the radio station 2 originally should transmit, thereby Can support. Thus, the use of retransmission control according to the present embodiment can solve the problem of communication quality degradation in cooperative transmission.

  Further, in the first embodiment, the configuration in which the same data is distributed to the cooperative wireless station has been described. However, in this configuration, the cooperative wireless station stores the same data in the buffer, and receives the “transmission request for other divided parts”. The requested data portion can be transmitted with extremely low delay. As described above, the configuration in which the same data is distributed to the cooperative wireless station can cope with transmission of other data portions with low delay. Note that the retransmission control described in this embodiment may be used in combination with a conventional method (a method in which a terminal requests retransmission to a radio station that has transmitted data that has failed to be received). In this case, the terminal makes a retransmission request to the wireless station 2 (the transmission source wireless station of the data that failed to be received), and further transmits a “transmission request for another divided portion” to the wireless station 1. The wireless stations 1 and 2 both transmit the data portion corresponding to the requested content (in the case of the example shown in FIG. 18, this is the data portion 2), so that the terminal can more reliably identify the data portion requested for retransmission. Can receive.

  Similar transmission control can be applied to cooperative transmission by three or more radio stations. FIG. 22 is a diagram illustrating an example of transmission control when there are three wireless stations performing cooperative transmission. In the control operation shown in FIG. 22, the radio stations 1, 2, and 3 transmit data portions # 1, # 2, and # 3, respectively, but the terminal designates a portion that cannot be received, and the data portion Request transmission of #n (n = 1, 2, 3) to a wireless station (for example, wireless station 1) that has received data normally. The wireless station that has received the transmission request for the data portion #n transmits the data portion #n specified by the request signal to the terminal. At this time, a control signal indicating that the signal of data portion #n has been transmitted to the terminal is also transmitted. The terminal recognizes from the control signal that data portion #n has been transmitted and receives the data. By such control, the terminal can receive all data even when there are three or more wireless stations performing cooperative transmission.

  FIG. 23 is a diagram for explaining the retransmission operation when there are three cooperative wireless stations, and shows the operation when the wireless station 1 is in charge of transmitting the data portion # 1. The upper part shows the data (data part # 1) transmitted first by the wireless station 1, and the lower part shows the data part (data part # 2) transmitted by the wireless station 1 when a transmission request for the data part # 2 is received from the terminal. Is shown.

  Here, the terminal makes a transmission request to the wireless station 1, but may make a similar transmission request to another cooperative wireless station. However, as a more preferable form, it is desired that the main radio station and the sub radio station are determined among the linked radio stations, and the main radio station is responsible for the communication quality of data transmission at the terminal. In such a configuration, the terminal preferentially transmits a “transmission request signal for another data portion” to the main radio station. Thus, it is also one of the features that a radio station responsible for guaranteeing communication quality with the terminal is provided in the linked radio station. Another feature is that the terminal preferentially transmits a “transmission request for another divided portion” to a specific radio station.

  As described above, in the wireless communication system according to the present embodiment, when a part of the data transmitted in cooperation is not received, the terminal transmits the data that could not be received so as to transmit the data that could not be received. The request was made to another cooperative radio station different from the original radio station. Thereby, the problem of communication quality degradation in cooperative transmission can be solved.

Embodiment 4 FIG.
In the present embodiment, in the retransmission control described in the third embodiment, a more preferable mode when a terminal makes a retransmission request to a cooperative radio station is disclosed.

  In the third embodiment, the case where the wireless station 1 transmits another data portion in response to the “transmission request for other divided portion” received from the terminal has been described. However, there are various methods for transmitting the other data portion. is there. These will be described with reference to FIGS.

  FIG. 24 is a diagram illustrating an example of a transmission control operation in the wireless communication system according to the present embodiment. In the operation in which the wireless stations 1 to 3 perform cooperative transmission, the wireless stations 1 to 3 perform the data portion # in one frame. An example in which the wireless station 1 retransmits the data portion # 2 in response to a request from the terminal after transmitting 1 to # 3, respectively. In FIG. 24, 241 to 249 are sequence numbers added to the divided data transmitted from each cooperative wireless station to the terminal.

  In the operation shown in FIG. 24, first, the wireless station 1 transmits the data portion # 1 (divided data 241, 244, 247), and the wireless station 2 transmits the data portion # 2 (divided data 242, 245, 248). The wireless station 3 transmits data portion # 3 (divided data 243, 246, 249). Each radio station transmits each piece of divided data that it is responsible for transmission in ascending order of sequence number. For example, the wireless station 1 transmits in the order of the divided data 241 → the divided data 244 → the divided data 247. Thereafter, it is assumed that the wireless station 1 is requested to transmit the data portion # 2 from the terminal. At this time, the wireless station 1 that has received the transmission request for the data portion # 2 transmits the requested data portion # 2 in the same order as that transmitted from the wireless station 2 before that (in order from the smallest sequence number). However, the data may be transmitted in the reverse order (the divided data 248, the divided data 245, and the divided data 242 may be transmitted in this order).

  Originally, the wireless station 2 should transmit the data portion # 2, but if the transmission rate between the wireless station 2 and the terminal is slower than expected, the time required until all the data portion # 2 arrives at the terminal. become longer. In such a case, there is a possibility that the terminal can receive the divided data 242 and the divided data 245 from the wireless station 2, but cannot receive the divided data 248. Therefore, if the wireless station 1 transmits the divided data 248 → the divided data 245 → the divided data 242 in this order, the terminal receives the divided data 248 from the wireless station 1, and when the terminal receives the data portion # 2 (the divided data 242 , 245, 248) can be received. As a result, before the wireless station 1 transmits all the data portion # 2, the terminal transmits an ACK (ACK indicating that all data has been successfully received) to the wireless stations 1 to 3, and the wireless station 1 Can stop the transmission of data portion # 2 on the way. Note that all data here refers to all data in one frame. If such a retransmission control operation is applied, since the terminal receives all the divided data even if the wireless station 1 does not transmit all the divided data of the data portion # 2, the received divided data (need to be transmitted) (Non-partitioned data) can be prevented from being retransmitted from the wireless station 1 to the terminal, and the time until the start of transmission of the next frame can be shortened to improve wireless transmission efficiency.

  FIG. 25 is a sequence diagram illustrating an example of a data transmission procedure when three wireless stations perform cooperative transmission, and illustrates the sequence of operations described with reference to FIG.

  In the transmission procedure shown in FIG. 25, first, the wireless stations 1, 2, and 3 transmit data portions # 1, # 2, and # 3, respectively, according to the divided data transmission mode. For example, when the terminal cannot receive a part of the data portion #n (n = 1, 2, 3), the terminal requests the wireless station 1 as the main wireless station to transmit the data portion #n. When the terminal requests the wireless station 1 to transmit the data portion #n, the terminal also requests the transmission order of the divided data of the data portion #n according to a pre-defined format. In accordance with a request from the terminal, the wireless station 1 transmits the divided data of the data portion #n in an appropriate format among several formats preliminarily defined for the data transmission order. Further, the wireless station 1 notifies the terminal of the format number that defines the transmission order or order of the divided data by the control signal. The terminal grasps the data transmission order of the data portion #n by analyzing the control signal transmitted together with the data portion #n requested to be transmitted, and receives the data. When the terminal receives all the divided data, the terminal transmits an ACK signal indicating that all the data has been received to each cooperative radio station. The ACK signal may be transmitted before the wireless station 1 has completely transmitted the data portion # 2. When the wireless station 1 receives the ACK signal from the terminal before completing the transmission of the data portion #n, the wireless station 1 stops the transmission of the data portion #n. By canceling data transmission in the middle, unnecessary data transmission can be reduced and wireless transmission efficiency can be improved. In addition, interference with surroundings can be reduced.

  In the present embodiment, the case where retransmission is performed in the divided data unit from the larger sequence number to the smaller sequence number (when retransmission is performed in the reverse order of the first transmission order) has been described. A method of transmitting the last bit (or symbol) to the first bit of the frame in units or information bit units in order is also possible. Even in this case, even if the wireless station is in the process of retransmitting, the terminal transmits an ACK after completing the reception of all data, so the wireless station can stop data transmission and send unnecessary data. The wireless transmission efficiency can be improved by reducing the amount of interference, and interference with the surroundings can be reduced.

  As described above, in the wireless communication system according to the present embodiment, the wireless station that retransmits data in response to a request from the terminal performs the reverse order of the retransmission data when it was previously transmitted from another wireless station. It was decided to send in. Thereby, it is possible to prevent the amount of data to be retransmitted from being increased more than necessary, thereby improving the radio transmission efficiency and reducing interference to the surroundings.

Embodiment 5 FIG.
In this embodiment, a method for controlling a data division part transmitted by each wireless station in units of frames in the wireless communication system described in Embodiments 1 to 4 will be described. In the present embodiment, it is assumed that the wireless stations 1 and 2 of the wireless communication system perform cooperative transmission as shown in FIG. 1 or FIG.

  In a state where the radio stations 1 and 2 of the radio communication system described in the first to fourth embodiments perform cooperative transmission in the transmission mode A (divided data transmission mode), the radio station 1 has a certain frame (assumed to be a frame u). ) Is completed earlier than the wireless station 2, the wireless station 1 may start transmitting the data portion (divided data) in the next frame u + 1 earlier than the wireless station 2. Thereby, compared with the case where the wireless station 1 waits for the data transmission of the frame u + 1 until the wireless station 2 completes the transmission of the data portion of the frame u, this method can perform data transmission more flexibly. As a result, radio resources can be used efficiently and radio transmission efficiency can be improved.

  Further, the cooperative wireless station may change the data division ratio between the wireless stations for each frame. For example, when the wireless station 1 completes data transmission in the frame u faster than the wireless station 2, the wireless station 1 transmits data at a higher rate than the current (frame u) when transmitting the next frame u + 1. It can be said that it is possible. Therefore, in the next frame u + 1, it can be said that transmitting data at a higher division ratio R is more suitable for matching the arrival times of the data portions from the radio stations 1 and 2.

  In this way, changing the data division ratio in units of frames notifies the control information (corresponding to the division ratio R shown in FIG. 12) of the control signal shown in FIG. 12 in units of frames. Can be realized.

  FIG. 26 is a diagram illustrating an example of a control signal notification method in the case of notifying control information regarding the data division ratio for each frame. When changing the data division ratio for each frame, as shown in FIG. 26, the division ratio R (control information related to the data division ratio) is notified for each frame. Further, since other control information (control information related to the sequence number assignment method and control information related to the division period / transmission portion) need not be changed for each frame, it is notified in a cycle longer than the frame. As described above, in the control operation for changing the data division ratio for each frame, the division ratio R or information corresponding thereto is notified in units of frames, and other control information related to data division is also notified in a longer cycle. This is one of the features of the wireless communication system according to the embodiment. Thereby, it can prevent that the control information transmitted to a terminal from a cooperation radio station increases more than necessary. Note that control information regarding the data division ratio is not transmitted every frame, but may be transmitted every several frames. Also in this case, other control information is transmitted at a longer cycle. Further, when it is determined that the data division ratio needs to be changed, control information related to the data division ratio may be transmitted.

  In addition, the division ratio R is not always notified as control information related to the “data division ratio”, but as shown in FIG. 27, the initial value (R0) of the division ratio R is notified in the first frame, and the previous frame is transmitted in the previous frame. Only the difference value (ΔR1, ΔR2,...) Of the ratio from the frame may be notified as the control signal. If this configuration is used, the amount of data to be notified can be reduced compared to the case where the value of the division ratio is notified for each frame.

  It is also possible to reduce the amount of control information by standardizing the correspondence between a representative value related to the data division ratio R and the index number and notifying the corresponding index number. In this case, the linked wireless station and the terminal hold the table information shown in FIG. 28 in advance. FIG. 28 is a diagram illustrating an example of a correspondence table between the data division ratio R and the index number. Thus, the control information amount can be reduced by the configuration in which the index number is notified as the control information related to the data division ratio R. Further, it is also possible to notify only a change in the number of index numbers with respect to the previous frame in a continuous frame. For example, only the index number changes of +1, 0, and −1 are performed with respect to the previous frame. This uses the property that the division ratio tends to be a similar value in a continuous frame. In this case, the amount of control information can be further reduced.

  Further, it is more desirable to change the control information related to data division for each terminal. This is because the appropriate data division ratio changes depending on the location of the terminal. Therefore, it is more preferable that the main cooperative radio station determines an appropriate data division ratio for each terminal in accordance with the channel state notification from each terminal.

  As described above, in the wireless communication system of the present embodiment, the data division ratio (the ratio of the amount of data transmitted from each cooperative wireless station to the terminal) is changed in units of frames, so that efficient wireless transmission can be realized.

Embodiment 6 FIG.
In this embodiment, a radio communication system that performs cooperative transmission control different from those in Embodiments 1 to 5 will be described.

  In Embodiments 1 to 5, the main radio station in the coordinated radio station determines the coordinated transmission method based on the state (channel state or channel quality) of each radio link between each coordinated radio station and the terminal. A wireless communication system has been shown. On the other hand, this embodiment shows a wireless communication system in which a terminal determines a cooperative transmission method such as a transmission mode and a data division method and notifies the cooperative wireless station as a control signal.

  FIG. 29 is a sequence diagram illustrating a control procedure when the cooperative wireless station performs cooperative transmission in the wireless communication system of the present embodiment. As shown in the figure, in the wireless communication system of the present embodiment, when the same data is distributed to the wireless stations 1 and 2 that perform cooperative transmission, one of the cooperative wireless stations sends the data information to the terminal. Notice. For example, the radio station 1 as the main radio station notifies the data information. The data information includes information indicating that the data addressed to the terminal is held, and information on the associated radio station holding the same data (in this example, information on the radio stations 1 and 2. This information is transmitted. Only information on cooperative wireless stations other than the cooperative wireless station to be connected) may be included. In the case of a system configuration in which the main radio station redistributes the data signal received from the higher-order gateway to the sub radio station (the configuration in FIG. 2 described above), the radio station 1 (main radio station) transmits the data signal to the sub radio station. Re-delivery is also performed. Further, the wireless stations 1 and 2 transmit channel state measurement reference signals through wireless links, respectively, and the terminal measures the channel state using the reference signals. Then, the terminal determines an appropriate transmission mode based on the measurement result (channel state with the wireless stations 1 and 2), and notifies the wireless stations 1 and 2 of control information # 1 and # 2 indicating the determined transmission mode. .

  As a more preferable transmission mode selection mode, a mode in which the terminal selects one of the following two transmission modes is particularly effective as in the first to fifth embodiments in which the transmission mode is determined on the cooperative radio station side. .

(Transmission mode A: Division data transmission mode)
Each cooperative wireless station divides data and transmits different data portions.
(Transmission mode B: Same data transmission mode)
The same data is transmitted from each cooperative radio station.

  When the terminal transmits control information indicating the transmission mode A to the associated wireless station, the terminal also transmits control information regarding a data division method. FIG. 30 shows a control procedure when the cooperative wireless station performs divided data transmission. In this case, the terminal measures the channel state using the reference signal, determines an appropriate data division method based on the channel state with the wireless stations 1 and 2, and notifies the wireless stations 1 and 2. The radio stations 1 and 2 divide the data based on the control information from the terminal, and transmit data portions # 1 and # 2 to the terminal, respectively. When the radio stations 1 and 2 transmit data portions # 1 and # 2, respectively, control information indicating that the data is data divided according to the control information of the terminal is transmitted to the terminal. Based on the control information, the terminal recognizes and receives the data portion transmitted from the wireless stations 1 and 2 and finally integrates to receive all data. When all the data is received, the terminal transmits an ACK signal to the radio stations 1 and 2. Actually, after measuring the channel state with the radio stations 1 and 2 using the reference signal, the terminal determines the transmission mode based on the channel state, and when the transmission mode A is selected, the channel state further The data division method is determined based on the above. When transmission mode A is selected, control information indicating transmission mode A and control information indicating a data division method are transmitted to radio stations 1 and 2. When the transmission mode B is selected, control information indicating the transmission mode B is transmitted to the radio stations 1 and 2. The operation after the terminal determines the transmission mode and the data division method and transmits control information indicating the determination result to each cooperative wireless station (data transmission from the cooperative wireless station to the terminal) is the wireless communication according to the first to fifth embodiments. It is the same as the system.

  If the terminal cannot receive data correctly, the retransmission control described in Embodiments 3 and 4 may be performed, or known retransmission control may be performed.

  FIG. 31 is a diagram illustrating an example of a control signal transmitted from the terminal to each cooperative wireless station (wireless stations 1 and 2) when there are two cooperative wireless stations. The control signal shown in FIG. 31 includes a division start position indicating a data position at which data division is started, a division cycle T (bit), a division ratio R, a radio station ID in charge of the first half, a radio station ID in charge of the second half, And a sequence allocation method indicating a sequence number allocation method (cooperation or independent). The division start position is information specifying a data number such as an IP packet number or its bit position. With this information, the division start position can be shared between cooperative wireless stations. In addition, each cooperative radio station that has received the control signal shown in FIG. 31 from the terminal decodes the radio station ID that is in charge of the first half and the radio station ID that is in charge of the second half, so (Divided data) can be recognized. Further, the data division method can be grasped by deciphering the division period T and the division ratio R. Furthermore, by deciphering the sequence allocation method, it is possible to recognize the sequence number allocation method (cooperative sequence number allocation or independent sequence number allocation) to the divided data.

FIG. 32 is a diagram illustrating an example of a control signal transmitted from the terminal to each cooperative wireless station (wireless stations 1, 2, 3) when there are three cooperative wireless stations. The control signal shown in FIG. 32 includes a division start position indicating a data position at which data division is started, a division number N, the number of bits B _{1 to} B _N of each divided portion, and a radio station in charge of transmission of each divided portion. A radio station ID and a sequence number assignment method are included. The lower part of FIG. 32 shows, as an example, the relationship between each divided portion and the number of bits of each divided portion when the division number N is 3. As in the case of the two linked wireless stations, the divided start position can be shared between the linked wireless stations by the divided start position. 32 receives the control signal shown in FIG. 32 from the terminal, the radio station of the radio station in charge of the division number N, the bit numbers B _{1 to} B _N of each division part, and the transmission of each division part. By decoding the ID, it recognizes the data portion that it is responsible for transmission. Further, the method of assigning sequence numbers to the divided data is recognized by decoding the sequence assignment method.

The control signal transmitted from the terminal to the cooperative wireless station may be transmitted for each frame. When the transmission is performed for each frame, the terminal can change the data division ratio (the ratio of the amount of data transmitted by each cooperation wireless station) between the cooperation wireless stations for each frame. In addition, it is also possible to adopt a configuration in which the terminal notifies only information relating to the data division ratio in units of frames, and other control information (information relating to the sequence number assignment method, division period / transmission part) is notified in a longer period than the frame. . The “information about the data division ratio” is the division ratio R in the case of the control signal shown in FIG. 31 or information corresponding thereto. In the case of the control signal shown in FIG. B _{1 to} B _N or information corresponding thereto. With such a configuration, it is possible to efficiently notify only the division ratio R that needs to be changed in a short cycle to the cooperative radio station. It should be noted that information regarding the data division ratio may be transmitted every several frames instead of every frame. Further, it may be transmitted when it is determined that the data division ratio needs to be changed.

  As described above, when a configuration is adopted in which the terminal determines the cooperative transmission method and notifies each cooperative wireless station of the determination result, cooperative transmission is performed without communicating a control signal between the wireless stations performing the cooperative transmission. Yes. FIG. 33 is a diagram illustrating an operation example of data transmission in the wireless communication system according to the present embodiment. In the illustrated wireless communication system, the wireless stations 1 and 2 are wireless stations of different networks or wireless communication systems. For example, when the wireless station 1 is a cellular network base station and the wireless station 2 is a wireless LAN access point, a standard for communicating control signals with each other is not defined. In such a case, it is difficult for the wireless stations 1 and 2 to perform cooperative transmission in the conventional technique. On the other hand, if this embodiment is applied, even when it is difficult to directly transmit and receive control signals between the radio stations 1 and 2, the terminal specifies a transmission data portion and performs radio resource control. Cooperative transmission can be performed by implementing the section. In other words, a mechanism that distributes the same data to each cooperative wireless station via a gateway that accommodates each cooperative wireless station, and information on the wireless station to which the same data is distributed (information on the wireless station that performs cooperative transmission) If a function for notifying a wireless station is provided, cooperative transmission can be realized even in a wireless communication system in which direct communication between wireless stations performing cooperative transmission is impossible.

  As described above, the configuration shown in the present embodiment can be flexibly introduced into the conventional heterogeneous network without requiring mutual control between the heterogeneous networks. Therefore, it is also a great advantage that the terminal can be practically accepted by specifying a transmission data portion and performing a part of radio resource control.

  Further, the cooperation control described in the present embodiment and the cooperation control described in the first to fifth embodiments can be selected adaptively. For example, when the wireless stations 1 and 2 are adjacent base stations belonging to the same cellular network, Embodiments 1 to 5 in which cooperative control is performed via a wired network between the wireless stations 1 and 2 can be used. it can. On the other hand, when the wireless station 1 is a cellular network base station and the wireless station 2 is a wireless LAN access point, the terminal determines the transmission mode and the data division method as in this embodiment. preferable. Therefore, depending on the form of the wireless station to be linked, it is selected whether to perform cooperative transmission led by the cooperative wireless station in cooperative control between the cooperative wireless stations or to perform cooperative transmission led by the terminal in accordance with an instruction from the terminal.

  FIG. 34 is a diagram illustrating an example of control for selecting whether to perform cooperative control led by a cooperative wireless station or cooperative control led by a terminal. In the control procedure shown in FIG. 34, first, the wireless stations 1 and 2 notify the terminal of belonging network information (network information to which the transmission source wireless station of this information belongs). Next, the terminal determines a cooperation control method (terminal initiative or wireless station initiative) based on the belonging network information notified from each wireless station, and uses control information # 1 and # 2 indicating the determination result (cooperation control method). Transmit to radio stations 1 and 2. Thereafter, the wireless stations 1 and 2 perform cooperative control according to the cooperative control method indicated by the received control information. FIG. 35 is a diagram illustrating different examples of control for selecting whether to perform cooperative control led by a cooperative wireless station or cooperative control led by a terminal. In the control procedure shown in FIG. 35, first, the wireless station 2 as the sub wireless station notifies the belonging network information to the wireless station 1 as the main wireless station. Next, the wireless station 1 determines the cooperation control method based on the notified information (the belonging information of the wireless station 2), and transmits control information indicating the determination result to the terminal. The terminal that has received the control information performs the control described in the present embodiment or the first to fifth embodiments according to the cooperative control method indicated by the control information. As described above, it is possible to adaptively select whether the cooperative control between the cooperative wireless stations is performed by the cooperative wireless station or the terminal.

Embodiment 7 FIG.
In the present embodiment, a data division method in the cooperative transmission control described in the first to sixth embodiments will be described.

  In the previous embodiment, examples of the control signal format transmitted / received between the linked wireless stations or between the wireless station and the terminal have been disclosed in FIGS. 10, 12, 14, 15, 31, and 32. These control signal formats include a radio station ID as control information as information for specifying a radio station in charge of each portion of the divided data. In contrast, in the present embodiment, a radio communication system that does not need to be notified by including information for specifying a radio station in charge of each part of divided data in a control signal will be described. Specifically, a wireless communication system that eliminates the need for notification of information for identifying the wireless station that is responsible for each part of the divided data by determining the wireless station that is responsible for each part according to a predetermined rule Will be described.

  For example, it is determined in advance that a wireless station with a small wireless station ID is in charge of the first half of the data among the linked wireless stations. In this case, it is not necessary to notify the relationship between the radio station ID and the data portion in charge in the control signal. It is only necessary for the associated wireless stations to know each other's wireless station ID in advance. In this case, each wireless station can recognize the divided data to be handled by notifying only the data division method. When there are two linked wireless stations, the division start position, division period, and division ratio (see FIGS. 10 and 31) may be notified by a control signal. Further, when there are three or more cooperative wireless stations, the division start position, the number of divisions, and the number of bits of each divided portion (see FIGS. 14 and 32) may be notified by a control signal. As a result, transmission efficiency can be improved.

  In addition, when there are two linked radio stations, it is determined in advance that the main radio station is in charge of the first data portion and the cooperating sub radio station is in charge of the second data portion. There is no need to notify the relationship between the wireless station ID and the data portion in charge by a control signal. Also in this case, if only the data division method (division start position, division period, division ratio) is notified by the control signal, each radio station can recognize the data portion in charge.

  In addition, a simple method of allocating wireless station IDs that shortens the original wireless station ID between the wireless stations that cooperate can be used. For example, when the original wireless station ID is an IP address, a long bit number is required, but when there are three linked wireless stations, a simple wireless station of 2 bits (00, 01, 10, 11). An ID is assigned to the three cooperative radio stations and a control signal is transmitted. With such a configuration, it is possible to reduce the amount of control signal necessary for notification of the wireless station ID and improve transmission efficiency.

Embodiment 8 FIG.
In this embodiment, cooperative transmission by a plurality of wireless stations in a form different from those in Embodiments 1 to 7 will be described. In the present embodiment, the radio communication system shown in FIG. 2 is assumed.

  When a plurality of wireless stations perform cooperative transmission control, it is important to measure the relative delay of signals transmitted from each wireless station in order to maintain transmission quality. Here, the relative delay refers to the terminal when the main radio station receives the data signal from the higher-level device (gateway) and then redistributes the data signal to the sub radio station and transmits it to the terminal via the sub radio station. And the arrival time at the terminal when directly transmitted to the terminal. This relative delay includes all effects such as a network delay between the wireless stations 1 and 2, a processing delay, and a propagation delay in the wireless link.

  In order to measure this relative delay, in the radio communication system according to the present embodiment, as shown in FIGS. 36 and 37, radio station 1 as the main radio station transmits test signal # 1 to the terminal, and the terminal Then, grasp the arrival time. Separately, the radio station 1 transmits a test signal # 2 to the radio station 2 via the network, and when the radio station 2 receives the test signal # 2 from the radio station 1, the radio station 2 transmits the signal to the terminal. The terminal grasps the reception time difference between the test signals # 1 and # 2 as a relative delay, and notifies the wireless stations 1 and 2 of information indicating the relative delay (delay time difference information) as the control information # 1 and # 2. The wireless stations 1 and 2 that have received the delay time difference information can perform cooperative transmission control in consideration of the notified relative delay. For convenience of explanation, in FIG. 37, the timing at which the radio station 1 transmits the test signals # 1 and # 2 is shifted, but the radio station 1 transmits the test signals # 1 and # 2 at the same time. Is desirable. If the transmission time information is written in the test signals # 1 and # 2 and transmitted, it is not always necessary to transmit the test signals # 1 and # 2 at the same time. The amount of transmission data can be suppressed.

  An example of cooperative transmission control is shown. For example, in cooperative transmission in the transmission mode B in which the wireless stations 1 and 2 transmit the same data, there is a form in which the wireless station 1 delays the transmission start timing of the divided data toward the terminal by a relative delay. When the wireless station 1 transmits data with a delay, the terminal can receive data from the wireless station 1 and the wireless station 2 almost simultaneously. As a result, the terminal can easily combine the received signals from the radio stations 1 and 2. When the reception timings from the radio stations 1 and 2 are different, the terminal must store the data received from the radio station 1 in the memory for a predetermined time, and requires a lot of memory. On the other hand, if the method of the present embodiment is used, the amount of memory required by the terminal can be reduced.

  Moreover, the example of different cooperation transmission control is shown. As shown in FIG. 38, when data is stored in the wireless station 1 and the wireless stations 1 and 2 execute cooperative transmission in transmission mode A in which different portions of the stored data are divided, wireless with a short delay time is used. Station 1 transmits the first half of the divided data, and radio station 2 having a long delay time transmits the second half of the divided data. Since the terminal needs the first half of the data earlier, the wireless station 1 transmits the first half of the signal (data 1, 2, 3 in FIG. 38) for which low delay transmission is required. On the other hand, the radio station 2 transmits the latter half signal (data 4, 5, 6 in FIG. 37) in which the delay is allowed.

  Moreover, the example of different cooperation transmission control is shown. For example, when two communications such as voice and e-mail with different allowable delay amounts are provided to a terminal, communication data with a short allowable delay (such as voice) is transmitted from the wireless station 1 to the terminal, and communication with a long allowable delay is performed. Data (such as mail) is transmitted from the wireless station 2 to the terminal. Thus, communication quality can be maintained by determining a radio station to be transmitted for each communication based on the measured relative delay.

  This embodiment can be used in combination with any of Embodiments 1 to 7 described above. In particular, in the combination with Embodiment 6 in which the terminal determines and notifies the data division method, the terminal determines the data division method based on the relative delay and notifies the cooperative wireless station, thereby improving the transmission efficiency.

  As described above, in this embodiment, the terminal measures the relative delay of the signal transmitted from the cooperative base station, and notifies the cooperative base station of the relative delay information. Thereby, each cooperative radio station can determine data to be transmitted from each cooperative radio station based on the notified relative delay information, and can maintain high signal quality in consideration of delay.

Embodiment 9 FIG.
In this embodiment, a form different from Embodiments 1 to 8 of cooperative transmission by a plurality of wireless stations is disclosed.

  In recent wireless communication, in order to accommodate high-speed wireless communication, a configuration in which a transmission / reception station uses a plurality of antennas is often used. A system in which a transmitting / receiving station includes a plurality of antennas is called a MIMO (Multi-Input Multi-Output) system, and the MIMO system is widely known to be capable of spatially multiplexing a plurality of signals.

  In general, a receiving station having an M antenna can receive and receive a maximum of M spatially multiplexed signals. However, it is difficult to properly separate and receive M + 1 or more spatially multiplexed signals. Therefore, when a plurality of radio stations perform cooperative transmission to a terminal having an M antenna using the same time frequency, a configuration in which M or less signals are simultaneously transmitted is preferable.

  In order to realize such a state, in this embodiment, as shown in FIG. 39, the terminal transmits control information 3601 and 3602 to wireless stations 1 and 2, respectively. These pieces of control information are information indicating the number of spatially multiplexed signals that can be used to the maximum by the wireless stations 1 and 2. The radio stations 1 and 2 set the number of spatially multiplexed signals within the range of the number of spatially multiplexed signals indicated by the control information 3601 and 3602, respectively, and transmit them to the terminal.

For example, when the number of antennas M of the terminal is 2,
Maximum number of spatially multiplexed signals indicated by control information 3601 = N1
Maximum number of spatially multiplexed signals indicated by control information 3602 = N2
Then,
(N1, N2) = (1,1), (2,0), (0,2), (1,0), (0,1)
Are used as the “information regarding the maximum number of spatially multiplexed signals that can be used”.

  When each radio station transmits a signal to a terminal within the range of the number of spatially multiplexed signals (N1, N2), the number of signals received simultaneously by the terminal is M or less. Thus, the terminal notifies the information regarding the number of spatially multiplexed signals that can be used to the maximum to a plurality of radio stations, whereby the number of spatially multiplexed signals can be controlled to an appropriate value.

  In addition, the terminal can periodically update the information on the number of spatially multiplexed signals that can be used to the maximum by notifying control information 3601 and 3602 periodically. By such control, the number of spatially multiplexed signals can be set flexibly according to the environment.

  The “maximum number of spatially multiplexed signals that can be used” described above may be the number of spatially multiplexed signals. Also in this case, the number of signals simultaneously received by the terminal is M or less. The number of spatially multiplexed signals may be called the number of layers.

  The control information 3601 and 3602 can be defined in a table format together with the division ratio R as shown in FIG. In FIG. 40, a terminal with M = 4 antennas is assumed, and the terminal can receive a total of four layers from the associated wireless station. In FIG. 40, the table is created in consideration of the fact that a radio station that transmits more data portions requires a larger number of layers. Thus, by creating a table that combines the transmission data amount and the required number of layers, the amount of control information transmitted from the terminal to each cooperative wireless station can be reduced. It is also a feature of the wireless communication system of the present embodiment that a table is created by combining the amount of data handled by the wireless station and the number of layers.

  Also, unlike the configuration shown in FIG. 39, the wireless stations 1 and 2 know the number of antennas of the terminal in advance, and the number of layers used by the wireless stations 1 and 2 is determined by cooperative control between the wireless stations 1 and 2. It can also be determined. In this case, as shown in FIG. 41, the wireless stations 1 and 2 notify the terminal of the number of used layers using control information 3801 and 3802, respectively. At this time, using the table shown in FIG. 40, it is also possible to notify the number of layers and the data portion assigned to each radio station from the radio stations 1 and 2 to the terminal. The table shown in FIG. 40 can also be used when the radio station 1 (main radio station) determines the number of layers to use and notifies the radio station 2 (sub radio station). In this way, by holding a table in which only the necessary combinations related to the number-of-layers information and the data portion assigned to each wireless station are held, control information can be notified to the terminal efficiently.

  The table of FIG. 40 shows the correspondence between the data amount and the number of layers, but it is not necessary to create a table as long as it is a control method having a relationship with the data amount and the number of layers. For example, when the data amount or the data ratio is determined, a configuration that limits the number of layer candidates according to the value is also possible. When transmitting to a terminal having 4 antennas, if the data ratio handled by the radio station 1 is 50% or less, the number of layer candidates is limited to 1 and 2, and the data ratio handled by the radio station 1 is 50%. If it is larger, the radio station 1 (main radio station) can determine the number of layer candidates as 1, 2, 3, and 4. In addition, any control method may be used as long as it is related to the data amount and the number of layers. As described above, a method of changing the number of layer candidates by notifying the data ratio or the data amount is also one of the characteristics of the wireless communication system of the present embodiment. As described above, a configuration in which the radio station 1 can support a higher number of layers according to an increase in the amount of data transmitted by the radio station 1 is preferable.

  As described above, in the wireless communication system according to the present embodiment, when the cooperative wireless station and the terminal have a plurality of antennas and perform spatial multiplexing transmission, the terminal station is in a channel state with each cooperative wireless station. Based on the above, the number of multiplexing (maximum number of spatially multiplexed signals) permitted to be used by each cooperative radio station is determined, or the number of multiplexing is determined by the main radio station. Thereby, the cooperative transmission control in the radio communication system described in the first to eighth embodiments can be applied to the MIMO system.

Embodiment 10 FIG.
In the present embodiment, an example of the utilization mode of the cooperative transmission disclosed in the first to ninth embodiments is disclosed.

  FIG. 42 is a diagram illustrating an example of a utilization mode of cooperative transmission disclosed in the first to ninth embodiments. In the system configuration shown in FIG. 42, the radio stations 1 and 2 are adjacent to each other, the area where the terminal can communicate with both of the radio stations 1 and 2 is the cooperation area, and the terminal is one of the radio stations 1 and 2. The area where only communication is possible is the non-cooperation area. When the terminal is located in the cooperation area, the wireless stations 1 and 2 perform cooperative transmission to the terminal. On the other hand, when the terminal is located in the non-cooperation area, the wireless station supporting the non-cooperation area where the terminal is located transmits data alone to the terminal.

  Here, consider the case where the terminal starts moving from the cell of the radio station 1 and moves to the cell of the radio station 2 as shown in the figure. In this case, the terminal moves from the single support area of the wireless station 1 (non-cooperative area under the control of the wireless station 1) to the single support area of the wireless station 2 via the cooperative support area of the wireless stations 1 and 2. At this time, the cooperative transmission control shown in the first to ninth embodiments is applied in the cooperative support area by the wireless stations 1 and 2. In such control, each of the wireless stations 1 and 2 notifies the terminal of information indicating single support / cooperative support as a control signal, and recognizes whether the terminal is single support or cooperative support based on the control signal. If the control signal indicates single support, the terminal follows conventional radio control. On the other hand, when the control signal indicates cooperation support, the terminal performs the control operation described in the first to ninth embodiments.

  In the example shown in FIG. 42, when the terminal moves from the cell of the radio station 1 to the cell of the radio station 2, the ratio of data handled by the radio station 1 is gradually lowered as the position of the terminal approaches the radio station 2. Gradually increase the percentage of data handled by station 2. This control is because the communication quality between the radio station 1 and the terminal decreases as the terminal moves, and conversely, the communication quality between the radio station 2 and the terminal increases. As described above, in the vicinity of the cell boundary, two wireless stations that perform cooperative transmission transmit different portions of data, respectively, and gradually change the ratio of data to be transmitted, thereby smoothly supporting handover.

  In addition, in the international standard LTE (Long Term Evolution) in 3GPP (Third Generation Partnership Project), handover between cells is a hard handover that switches instantaneously, and one radio station (base station) always supports a terminal. . Further, in the third generation mobile communication system W-CDMA, soft handover is supported, but in this system, each radio station transmits the same data. On the other hand, the present embodiment is greatly different in that a plurality of radio stations transmit different data portions. By transmitting different data portions, higher communication capacity can be realized.

  In addition, when moving from the cell of the radio station 1 to the cell of the radio station 2, a new soft handover function in which each radio station transmits a different data portion by gradually decreasing the ratio of the data portion handled by the radio station 1 Is possible. Such a handover has not been considered in conventional mobile communication systems.

  Further, when the terminal moves in the cooperation support area, the wireless link connection state with one of the wireless stations 1 and 2 may be rapidly deteriorated. Even in such an environment, if radio transmission control based on the retransmission control described in the third embodiment is performed, communication quality can always be guaranteed. Therefore, by applying the retransmission control shown in the third embodiment, even when the propagation state with one radio station changes suddenly, the other radio station supports data transmission, and thus provides a stable service. it can.

  As described above, according to the present embodiment, it is possible to realize a wireless communication system that supports a new type of soft handover, and it is possible to realize wireless communication quality that is more efficient and stable than in the past.

Embodiment 11 FIG.
In the present embodiment, an example of a utilization mode of cooperative transmission by a plurality of radio stations described in the first or sixth embodiment is disclosed.

  In the first and sixth embodiments, it has been described that when the wireless stations 1 and 2 perform cooperative transmission, it is possible to select a transmission mode B that transmits the same data. Can be provided according to the environment.

(Transmission mode B1)
The radio stations 1 and 2 transmit the same data incoherently.
After receiving data from the radio stations 1 and 2 individually, the terminal improves signal quality based on signal synthesis such as maximum ratio synthesis.

(Transmission mode B2)
The radio stations 1 and 2 transmit the same data using a distributed space-time code at the same time frequency.
As a typical distributed space-time code, there is a configuration in which the STBC (Space Time Block Code) code is applied with the radio stations 1 and 2 regarded as different transmission antennas. The reception method of the STBC code is widely known, and the terminal may use any method.

(Transmission mode B3)
The radio stations 1 and 2 transmit the same data coherently at the same time frequency.
Coherent transmission is disclosed, for example, in the document “P. Larsson and R. Hu,“ Large-scale cooperative relaying network with optimal coherent combining under aggregate relay power constraints, ”Proc. Of FTC, 2003.”.

(Transmission mode B4)
The radio stations 1 and 2 transmit signals encoded by applying different encoding methods to the same data. The terminal receives data from the radio stations 1 and 2 individually, and then performs decoding processing using the encoded data from the radio stations 1 and 2. There are various application methods of different encoding methods, but a method of adding different redundant bits, a method of using different encoding rates, a method of performing different convolution operations, and the like are also included.

  The transmission mode B1 is particularly suitable when the radio stations 1 and 2 transmit signals using different time frequencies. The transmission mode B2 is suitable when the radio stations 1 and 2 transmit signals using the same time frequency. Transmission mode B3 is suitable when the moving speed of the terminal is sufficiently low and the channel state changes very slowly. Also, the transmission mode B4 can be used in the same environment as the transmission mode B1, and although the amount of calculation at the receiving station is large, a coding gain is obtained, so that better reception characteristics than the transmission mode B1 can be obtained. Therefore, in an environment where the receiving station can tolerate the amount of calculation, the system is superior to the transmission mode B1.

  Therefore, in the wireless communication system according to the present embodiment, when the transmission mode B is used, the transmission modes B1, B2, and B3 are further appropriately used according to the environment. In order to realize this configuration, the terminal measures the channel state with the wireless stations 1 and 2 and the fluctuation state thereof, and notifies the wireless stations 1 and 2 of the channel state. FIG. 43 is a flowchart showing a transmission mode selection procedure in the cooperative wireless station, and shows a transmission mode selection procedure when the wireless stations 1 and 2 are cooperative wireless stations. First, it is determined whether or not to transmit at the same time frequency in the cooperative control between the wireless stations 1 and 2. When transmitting at a different time frequency (in the case of “No”), the transmission mode B1 is selected. On the other hand, when transmitting at the same time frequency (in the case of “Yes”), the channel fluctuation state in the terminal is further observed, and when the channel fluctuation state is slow (in the case of “Yes”), the transmission mode B3 is set. When the channel change state is early (in the case of “No”), the transmission mode B2 is selected.

  Thus, radio transmission efficiency can be improved by selecting an appropriate transmission mode according to the cooperation control state and the channel state in the terminal.

Embodiment 12 FIG.
In this embodiment, a configuration for applying the cooperative transmission control described in Embodiments 1 to 11 to the international standard 3GPP LTE scheme is disclosed.

  In cellular wireless communication, the international standard 3GPP LTE system is often applied, and it is important to perform function expansion while supporting the conventional standard in a form that extends the configuration of the conventional LTE system. Therefore, in this embodiment, a method for smoothly introducing a cooperation function between radio stations (base stations) into the LTE scheme will be described.

  FIG. 44 is a diagram showing a user plane protocol stack in the LTE scheme. This protocol stack is based on the document “3GPP TS 36.300 V9.2.0“ EUTRA and EUTRAN overall description, Stage 2. ””.

  In the protocol stack shown in FIG. 44, the PDCP (Packet Data Convergence Protocol) layer compresses / decompresses the header of the IP packet and encrypts the data to realize efficient use of the bandwidth. The RLC (Radio Link Control) layer performs conversion to a data format transmitted on the radio link. In the MAC (Medium Access Control) layer, multiplexing with data of other users is performed. In the physical (PHY: Physical Layer) layer, processing for generating actual transmission data such as modulation and coding is performed. Transmission data generated in the physical layer is transmitted to the radio link.

  FIG. 45 is a diagram illustrating a protocol stack for applying the cooperative transmission control described in Embodiments 1 to 11 to the 3GPP LTE scheme. As shown in the figure, by newly adding a function of performing data extraction in the base station (eNB: evolved node B), and further adding a function of combining data on the terminal (UE: User Equipment) side, A new cooperative control function can be supported while supporting the conventional function.

  FIG. 46 is a diagram illustrating a configuration example of a radio station configuring the radio communication system according to the present embodiment. More specifically, the cooperative transmission control described in the first to eleventh embodiments is applied to the 3GPP LTE scheme. The example of a structure is shown.

  When receiving the IP packet in the IP network, the base station having the configuration shown in FIG. 46 executes header compression of the IP packet, PDCP numbering, and the like in the PDCP layer. Furthermore, data buffering is performed in the newly inserted buffer / data extraction unit, and only data having the PDCP number to be transmitted by the base station is extracted from the data of the kth terminal (terminal #k). The extracted data is transmitted through the RLC / MAC layer and the PHY layer through the radio link in the same manner as in the conventional LTE configuration.

  When the necessary data portion is extracted by the buffer data extraction unit, the data division control unit instructs data to be extracted. The data division control unit communicates control information regarding the division method with a cooperative base station (another base station that cooperates to transmit data) via the X2 interface, and determines an appropriate division method. It is also possible to determine the data division method (according to the determination result at the terminal) in the form described in the sixth embodiment, that is, according to the control information from the terminal. In this case, the uplink control channel receiving unit receives control information transmitted from the terminal. In order to support different data division for each terminal, the buffer / data extraction unit, the data division control unit, and the uplink control channel reception unit are configured for each terminal.

  In this way, by adding only the function of extracting the data of the PDCP number required for cooperative transmission to the base station compatible with the conventional LTE scheme, the base station can be newly added without losing the function of the conventional LTE scheme. Station cooperation function (cooperation transmission function) can be added. When it is desired to support only the conventional LTE scheme, the base station supporting the terminal transmits all PDCP packets to the lower layer in the buffer data extraction unit. In this case, the cooperative base station discards all PDCP packets. When base station cooperative transmission is performed, a packet having a part of PDCP numbers is notified to a lower layer.

  FIG. 47 is a diagram illustrating a configuration example of a terminal that receives data from a radio station configuring the radio communication system according to the present embodiment, and the cooperative transmission control described in the first to eleventh embodiments is applied to the 3GPP LTE scheme. An example of the configuration is shown.

  The terminal configured as shown in FIG. 47 processes the signal received through the radio link in the PHY layer / MAC layer / RLC layer in the same manner as a conventional LTE terminal. At this time, the downlink control channel analysis unit decodes the control signal transmitted from the wireless station, so that only one of the wireless stations 1 and 2 transmits the signal, or the wireless stations 1 and 2 transmit the signal in cooperation. Is determined. When the downlink control channel analysis unit determines that a plurality of radio stations (radio stations 1 and 2) perform cooperative transmission, each data reception unit (data reception unit from radio station 1, data reception unit from radio station) A data receiving unit) individually receives signals from the radio stations 1 and 2, extracts data with PDCP numbers transmitted from the respective radio stations, and outputs the extracted data to the data combining unit. The data combining unit checks the PDCP number of each data input from the data receiving unit, rearranges each data in the order of the numbers, and combines them. Further, in order to perform the retransmission control (retransmission request) shown in the third embodiment, the absence of the PDCP number is confirmed, information necessary for the retransmission request is generated, and transmitted from the uplink control channel transmission unit. The data combined in the data combining unit is transferred to the IP layer via the PDCP layer in the same manner as a conventional LTE terminal.

  In this way, by adding a new data combining unit and downlink control channel analyzing unit to a terminal corresponding to the conventional LTE scheme, the terminal can have a new base station cooperation function without losing the LTE scheme function. Can support.

  As described above, the radio station (base station) and the terminal according to the present embodiment have the same functions as the conventional ones except for newly added functions, and need not be changed. As a result, the same manufacturing process as the LTE method can be used, and cost reduction can be realized from the viewpoint of capital investment. In addition, it is possible to share parts with the conventional LTE system, which is beneficial from the viewpoint of mass production.

  In terms of performance, even when the propagation state between one base station and the terminal deteriorates rapidly, the other base station can support the terminal by the base station cooperation function. As a result, it is possible to realize more stable signal quality than the LTE system supported by only one base station. In the MIMO system, each base station and terminal can establish a plurality of links using good spatial channels. As a result, wireless transmission efficiency can be improved by base station cooperation. Also, in an environment where there is a sufficient number of terminals that one base station can support, a higher transmission rate can be supported by base station cooperation. As described above, the cooperative transmission control performed in the wireless communication according to the present invention can greatly contribute to the realization of highly efficient wireless transmission.

Embodiment 13 FIG.
You may use combining transmission control shown in Embodiment 1-12 suitably. In the first to twelfth embodiments, control information from the terminal to the associated radio station (channel state and channel quality shown in FIG. 3, transmission mode information shown in FIG. 29, data division method shown in FIG. 30, etc.) Is mainly transmitted, but all the control information is transmitted from the terminal to one wireless station (for example, the wireless station 1), and the wireless station 1 that has received the control information receives the other cooperative wireless communication. You may comprise so that it may transmit to a station via a wired network.

  In the first to twelfth embodiments, each cooperative radio station individually receives downlink control information (information indicating a division method applied to data when data is transmitted) from the cooperative radio station to the terminal. Although the case of transmitting was mainly described, one wireless station (for example, wireless station 1) receives control information from the cooperative wireless station via a wired network, and control information of all the cooperative transmitting stations from the wireless station 1 to the terminal. May be sent.

  Moreover, although Embodiment 1-12 mainly demonstrated the case where each cooperation radio station was arrange | positioned in a different position, a cooperation radio station may be arrange | positioned in the same position. The cooperative radio station may be a sector that supports only an area in a specific direction. Therefore, cooperative transmission between sectors is also included in the present invention.

  In the first to twelfth embodiments, the control method may be described using “frame”. However, any parameter indicating time such as “time slot”, “subframe”, “time symbol”, and “time sample” may be used. It does not matter. In addition, the wireless control method may be described using the term “division ratio”, but any information that can estimate the division ratio may be notified instead of directly reporting the division ratio.

  As described above, the wireless communication system according to the present invention is useful for a wireless communication system in which a plurality of wireless stations cooperate to transmit data to one terminal, and in particular, the cooperative wireless stations have different data portions. It is suitable for a radio communication system in a form in charge of transmission.

1, 2 Radio stations 41, 94, 95 Data receiving unit 42 Buffer 43 Transmission mode selecting unit 44 Data selecting unit 45, 96 Control information receiving unit 46 Control information determining unit 47 Data / control information transmitting unit 91 Signal receiving unit 92 Channel state Measurement unit 93 Control information determination / transmission unit 97 Data combination unit

Claims (1)

A wireless communication system including a plurality of wireless stations, a gateway that accommodates the plurality of wireless stations, and a terminal that communicates with the wireless stations,
The radio station is
When it is necessary to cooperate with other wireless stations in receiving data from the gateway and in the operation of transmitting the received data to the terminal, the duplicate data of the received data is distributed to the other wireless stations, A function of transmitting the received data to the destination terminal in cooperation with the other radio station, and transmitting a test signal for transmission delay measurement directly to the destination terminal and via the other radio station A function to transmit,
The terminal
Based on the reception result of the test signal, the difference between the reception time when the data addressed to itself is received directly from the wireless station obtained from the gateway and the reception time when the data is received via another wireless station. A wireless communication system, wherein a certain relative transmission delay time is measured, and further, the measured relative transmission delay time is notified to a transmission source radio station of the test signal.

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