JP5627899B2 - Base station and base station communication method - Google Patents

Description

  The present invention relates to a base station and a base station communication method.

  In recent years, studies on LTE (Long Term Evolution) have been promoted in 3GPP, which is a standardization body for mobile communication systems. In LTE, the frequency band of the system is divided into a plurality of resource blocks (RB), and each resource block includes one or more subcarriers (radio communication channels) (for example, 12 subcarriers). In LTE, in principle, resource blocks are allocated to mobile stations every 1 ms subframe.

  As shown in FIG. 4, an LTE communication frame employing the TDD scheme is composed of ten subframes. Each subframe includes an UL subframe for uplink communication from the mobile station to the base station, a DL subframe for downlink communication from the base station to the mobile station, and an UL area for uplink communication in the subframe. (Data reception area) and DL communication area (data transmission area) for downlink communication are classified into Special subframes (hereinafter referred to as “special subframes”). FIG. 5 is a diagram illustrating an example of symbol arrangement in a special subframe. In FIG. 5, the top 9 symbols of the special subframe are DL regions for downlink communication, and the last 2 symbols are UL regions for uplink communication with a guard time of 3 symbols. Note that the symbol arrangement of the special subframe is not limited to the example of FIG. 5, and various settings are defined as shown in the table of FIG.

  Communication between the base station and the mobile station is performed by the above three types of subframes. For example, physical channels such as PDCCH (Physical Downlink Control Channel) and PDSCH (Physical Downlink Shared Channel) are mapped to DL subframes for downlink communication. Among these, in PDSCH, control information such as user data individually sent to each mobile station, paging information uniformly sent to surrounding mobile stations, and SIB (System Information Block) is sent. Also, in the UL subframe for uplink communication, user data is transmitted from each mobile station to the base station, and random access is made from surrounding mobile stations to the base station in a physical channel such as PRACH (Physical Random Access Channel). Such control information is transmitted (see, for example, Non-Patent Document 1).

3GPP TR36.211 (V8.7.0), "Physical Channels and Modulation", May 2009

  In conventional LTE, resource allocation that distinguishes between communication related to control information between a base station and surrounding mobile stations and communication related to user data between the base station and each mobile station is not performed. That is, in conventional LTE, downlink and uplink control information is appropriately allocated to arbitrarily selected DL subframes and UL subframes.

  Such resource allocation in LTE becomes a problem when AAS (Adaptive Antenna System) is introduced. AAS is an array antenna composed of a plurality of antenna elements, wherein the weight of each antenna element is adaptively controlled according to the propagation environment to change the directivity of the radio wave. The adaptive array base station corresponding to AAS uses the antenna weight calculated based on the reference signal transmitted from the mobile station at the time of downlink transmission, so that beam forming or null steering to a desired mobile station is performed. Adaptive control is performed.

  In AAS, a pair of UL subframe and DL subframe is defined, and communication between the base station and the mobile station is preferably performed using the pair. This is because when the base station receives the reference signal transmitted from the mobile station in the UL subframe, the base station can calculate an appropriate transmission weight from the reference signal, so that the downlink in the DL subframe is more efficiently performed. This is because communication can be performed.

  FIG. 7 is a diagram illustrating an example of resource allocation in conventional LTE. In FIG. 7, a subframe 2 that is a UL subframe and a subframe 4 that is a DL subframe are paired. Here, resource blocks 1 to 3 are assigned to mobile station A in subframe 4, but only resource blocks 1 and 2 are assigned to mobile station A in subframe 2. In this case, in the resource block 3 of the subframe 2, random access from surrounding mobile stations is performed on the base station. Therefore, the base station sets an appropriate transmission weight for the mobile station A in the resource block 3 of the subframe 4. It cannot be calculated, and the transmission efficiency of AAS is lowered.

  Similarly, FIG. 8 is a diagram illustrating an example of resource allocation in the conventional LTE. In FIG. 8, subframe 2 that is a UL subframe and subframe 4 that is a DL subframe are paired. Here, resource blocks 4 to 6 are allocated to mobile station B in subframe 2, but only resource blocks 4 to 5 are allocated to mobile station B in subframe 4. In this case, in the resource block 6 of the subframe 4, the base station transmits Paging and SIB to the surrounding mobile stations, and therefore the transmission weight based on the reference signal transmitted from the mobile station in the resource block 6 of the subframe 2 is used. The transmission efficiency of AAS is reduced.

  Accordingly, an object of the present invention made in view of such a point is to provide a base station and a base station communication method capable of resource allocation without reducing AAS transmission efficiency.

In order to solve the above-described problems, the base station according to the first invention
A base station that performs communication by allocating at least a part of a communication frame to a mobile station,
The communication frame includes an uplink subframe for uplink communication from the mobile station, a downlink subframe for downlink communication to the mobile station paired with the uplink subframe, and data transmission to the mobile station An area, and at least one special subframe including the data transmission area and a data reception area from the mobile station divided in the time direction,
In the special subframe, the data transmission area is an area for transmitting downlink control information to surrounding mobile stations, the data reception area is allocated as an area for receiving uplink control information from the surrounding mobile stations, and An allocating unit that allocates communication related to user data with a mobile station to the uplink subframe and the downlink subframe paired with the uplink subframe;
A calculation unit that calculates a transmission weight for the downlink subframe that is paired with the uplink subframe based on the signal received in the uplink subframe;
A transmission / reception unit that transmits the downlink control information in the data transmission region, receives the uplink control information in the data reception region, and transmits the user data to the mobile station by adaptive array control based on the transmission weight; , Bei to give a,
The downlink control information is characterized in paging and system information der Rukoto.

  As described above, the solution of the present invention has been described as an apparatus. However, the present invention can be realized as a method, a program, and a storage medium storing the program, which are substantially equivalent thereto, and the scope of the present invention. It should be understood that these are also included.

For example, the base station communication method according to the second aspect of the present invention, which is realized as a method,
A communication method of a base station that performs communication by allocating at least a part of a communication frame to a mobile station,
The communication frame includes an uplink subframe for uplink communication from the mobile station, a downlink subframe for downlink communication to the mobile station paired with the uplink subframe, and data transmission to the mobile station An area, and at least one special subframe including the data transmission area and a data reception area from the mobile station divided in the time direction,
In the special subframe, the data transmission area is an area for transmitting downlink control information to surrounding mobile stations, the data reception area is allocated as an area for receiving uplink control information from the surrounding mobile stations, and Allocating communication related to user data with a mobile station to the uplink subframe and the downlink subframe paired with the uplink subframe;
A calculation step of calculating a transmission weight for the downlink subframe paired with the uplink subframe based on the signal received in the uplink subframe;
A transmission / reception step of transmitting the user data to the mobile station by transmitting the downlink control information in the data transmission area, receiving the uplink control information in the data reception area, and adaptive array control based on the transmission weight; , have a,
The downlink control information is characterized in paging and system information der Rukoto.

  ADVANTAGE OF THE INVENTION According to this invention, the resource allocation which does not reduce the transmission efficiency of AAS is attained by allocating the communication regarding the control information between a base station and the surrounding mobile station to a special sub-frame.

FIG. 1 is a functional block diagram of a base station according to an embodiment of the present invention. FIG. 2 is a diagram illustrating an example of resource allocation according to an embodiment of the present invention. FIG. 3 is an operation flowchart of the base station shown in FIG. FIG. 4 is a diagram illustrating an example of a communication frame configuration in LTE. FIG. 5 is a diagram illustrating an example of the symbol arrangement of the special subframe. FIG. 6 is a diagram illustrating an example of setting special subframes. FIG. 7 is a diagram illustrating an example of resource allocation in conventional LTE. FIG. 8 is a diagram illustrating an example of resource allocation in conventional LTE.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an adaptive array base station 1 according to an embodiment of the present invention. The adaptive array base station 1 includes an array antenna ANT, a radio communication unit 10 (transmission / reception unit), an AAS processing unit 20 including a weight calculation unit 21 and a weight addition unit 22, a baseband processing unit 30, a scheduler 40, A radio resource allocation unit 50 (allocation unit). The radio communication unit 10, the AAS processing unit 20, and the baseband processing unit 30 are configured by interface devices / circuits suitable for the LTE system, and the scheduler 40 and the radio resource allocation unit 50 are configured by a suitable processor such as a CPU. It is what is done. Details of each part will be described below.

  The radio communication unit 10 converts the radio signal received by the array antenna ANT from the frequency of the carrier wave to the baseband frequency and outputs the generated signal to the weight calculation unit 21 as a reception system process. Further, as a transmission system process, the radio communication unit 10 converts a baseband frequency signal from the weight addition unit 22 into a carrier frequency and transmits it to the mobile station through the array antenna ANT by adaptive array control.

  In the AAS processing unit 20, the receiving weight calculation unit 21 performs adaptive signal processing on the signal input from the wireless communication unit 10 and outputs the signal to the baseband unit 30. Specifically, the weight calculation unit 21 obtains for each antenna element of the array antenna ANT using the reference signal (Reference Signal) transmitted from the mobile station through the UL subframe and other known information as the adaptive signal processing. From the phase information or the like, a transmission weight (phase / amplitude weighting for each antenna element) for the DL subframe paired with the UL subframe is calculated so as to obtain a high transmission gain for the mobile station. On the other hand, the transmission-system weight addition unit 22 adds the transmission weight obtained by the weight calculation unit 21 to the signal input from the baseband unit 30 and outputs the signal to the radio communication unit 10.

  The baseband processing unit 30 demodulates the signal input from the weight calculation unit 21 as reception system processing, separates the demodulation result for each mobile station, and outputs the result to the scheduler 40. Further, the baseband processing unit 30 outputs a symbol sequence of transmission data to the mobile station input from the radio resource allocation unit 50 to the weight addition unit 22 as a transmission system process.

  The scheduler 40 sets mobile stations to which resource blocks are allocated from the received data for each mobile station input from the baseband processing unit 30. Specifically, the scheduler 40 sets a mobile station to which resource blocks are allocated according to the received signal quality for each resource block reported from the mobile station, channel state information (CQI), or the amount of data to be transmitted.

  The radio resource allocation unit 50 allocates radio resources to the mobile station set by the scheduler 40. As described above, LTE subframes employing the TDD scheme include UL subframes for uplink communication from a mobile station to a base station, DL subframes for downlink communication from a base station to a mobile station, and sub The frame is classified into a special subframe in which a UL area (data reception area) for uplink communication and a DL area (data transmission area) for downlink communication exist in the frame. Here, the radio resource allocation unit 50 allocates communication related to control information between the base station and the surrounding mobile stations, such as downlink Paging / SIB and uplink PRACH, to the special subframe. Moreover, the radio | wireless resource allocation part 50 allocates the communication regarding the user data between each separate mobile station to a UL subframe and DL subframe used as a pair. Note that when the radio resource allocation unit 50 allocates communication of a plurality of mobile stations to a pair of UL subframes and DL subframes, the communication to each mobile station is performed at the same frequency in the UL subframes and DL subframes. Resource allocation is performed as in a band (resource block).

  FIG. 2 is a diagram illustrating an example of resource block allocation by the radio resource allocation unit 50. In FIG. 2, Paging / SIB is assigned to the DL area of subframe 1 which is a special subframe, and PRACH is assigned to the UL area. Further, in the UL subframe (subframe 2) and DL subframe (subframe 4) which are paired, communication to mobile station A and mobile station B is transmitted to resource blocks 1 to 3 and resource blocks 4 to 6, respectively. Assigned. With this assignment, when the base station receives the reference signal transmitted from the mobile station A and the mobile station B in the subframe 2 that is the UL subframe, the base station can appropriately transmit the reference signal for the subframe 4 that is the DL subframe. The transmission weight can be calculated. Moreover, since communication regarding control information between the base station and surrounding mobile stations can be performed in a specific subframe, such communication does not reduce the efficiency of AAS communication.

  The radio resource allocating unit 50 performs symbol mapping (amplitude and phase allocation) according to a modulation scheme for transmission data including control information to the mobile station and user data, and a baseband processing unit Output to 30.

  FIG. 3 is an operation flowchart of the base station 1 shown in FIG. When receiving the radio signal from the mobile station via the array antenna ANT, the radio communication unit 10 converts the received radio signal from the frequency of the carrier wave to the baseband frequency, and outputs the generated signal to the weight calculation unit 21 (step S101). ). The weight calculation unit 21 can obtain a high transmission gain for the mobile station from the phase information obtained for each antenna element of the array antenna ANT using the reference signal transmitted from the mobile station and other known information. A transmission weight is calculated (step S102). Specifically, the weight calculation unit 21 is paired with the UL subframe so as to obtain a high transmission gain for the mobile station based on a reference signal or the like transmitted from the mobile station through the UL subframe. A transmission weight for the DL subframe is calculated. The baseband processing unit 30 demodulates the signal input from the weight calculation unit 21, separates the demodulation result for each mobile station, and outputs the result to the scheduler 40 (step S103).

  The scheduler 40 sets the mobile station to which the resource block is allocated from the received data for each mobile station input from the baseband processing unit 30 (step S104). The radio resource allocation unit 50 allocates radio resources to the mobile station set by the scheduler 40 (Step S105). Here, the radio resource allocation unit 50 allocates communication regarding control information between the base station and the surrounding mobile stations to the special subframe. Moreover, the radio | wireless resource allocation part 50 allocates the communication regarding the user data between each separate mobile station to a UL subframe and DL subframe used as a pair.

  The radio resource allocating unit 50 performs symbol mapping corresponding to the modulation scheme on the transmission data including control information to the mobile station and user data, and outputs the generated symbol sequence to the baseband processing unit 30 (step S106). ). The baseband processing unit 30 outputs the symbol sequence of the transmission data to the mobile station input from the radio resource allocation unit 50 to the weight addition unit 22 (step S107). The weight addition unit 22 adds the transmission weight obtained by the weight calculation unit 21 to the signal input from the baseband unit 30, and outputs the signal to the radio communication unit 10 (step S108). The radio communication unit 10 converts the baseband frequency signal from the weight adding unit 22 into a carrier frequency, and transmits it to the mobile station through the array antenna ANT by adaptive array control (step S109).

  According to the present embodiment, the radio resource allocation unit 50 allocates communication related to control information between the base station and the surrounding mobile stations to the special subframe. Therefore, it is possible to allocate resources without reducing the AAS transmission efficiency without the downlink Paging / SIB or the uplink PRACH interfering with user data for individual mobile stations. In addition, by assigning transmission / reception of control information to special subframes, mobile stations around the base station need only receive special subframes at predetermined intervals during paging, thereby reducing power consumption of the mobile stations. It becomes possible to do.

  Moreover, the radio | wireless resource allocation part 50 allocates the communication regarding the user data between each separate mobile station to a UL subframe and DL subframe used as a pair. For this reason, since communication with an individual mobile station can be performed using an appropriate transmission weight, the transmission efficiency of AAS can be increased. In addition, when the radio resource allocation unit 50 allocates communication of a plurality of mobile stations to the paired UL subframe and DL subframe, the communication with respect to each mobile station is performed at the same frequency in the UL subframe and the DL subframe. Resource allocation is performed as in a band (resource block). Thereby, the transmission efficiency of AAS can be increased even for a plurality of mobile stations.

  Although the present invention has been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications and corrections based on the present disclosure. Therefore, it should be noted that these variations and modifications are included in the scope of the present invention. For example, the functions included in each component, each step, etc. can be rearranged so that there is no logical contradiction, and multiple components, steps, etc. can be combined or divided into one It is.

  For example, when there are a plurality of special subframes in one communication frame, the radio resource allocation unit 50 can transmit downlink control information such as the same Paging / SIB in each DL region of the plurality of special subframes. As a result, the base station can transmit control information more reliably to surrounding mobile stations.

DESCRIPTION OF SYMBOLS 1 Adaptive array base station 10 Wireless communication part 20 AAS process part 21 Weight calculation part 22 Weight addition part 30 Baseband process part 40 Scheduler 50 Radio | wireless resource allocation part ANT Array antenna

Claims (2)

A base station that performs communication by allocating at least a part of a communication frame to a mobile station,
The communication frame includes an uplink subframe for uplink communication from the mobile station, a downlink subframe for downlink communication to the mobile station paired with the uplink subframe, and data transmission to the mobile station An area, and at least one special subframe including the data transmission area and a data reception area from the mobile station divided in the time direction,
In the special subframe, the data transmission area is an area for transmitting downlink control information to surrounding mobile stations, the data reception area is allocated as an area for receiving uplink control information from the surrounding mobile stations, and An allocating unit that allocates communication related to user data with a mobile station to the uplink subframe and the downlink subframe paired with the uplink subframe;
A calculation unit that calculates a transmission weight for the downlink subframe that is paired with the uplink subframe based on the signal received in the uplink subframe;
A transmission / reception unit that transmits the downlink control information in the data transmission region, receives the uplink control information in the data reception region, and transmits the user data to the mobile station by adaptive array control based on the transmission weight; , equipped with a,
The downlink control information, said base station paging and system information der Rukoto. A communication method of a base station that performs communication by allocating at least a part of a communication frame to a mobile station,
The communication frame includes an uplink subframe for uplink communication from the mobile station, a downlink subframe for downlink communication to the mobile station paired with the uplink subframe, and data transmission to the mobile station An area, and at least one special subframe including the data transmission area and a data reception area from the mobile station divided in the time direction,
In the special subframe, the data transmission area is an area for transmitting downlink control information to surrounding mobile stations, the data reception area is allocated as an area for receiving uplink control information from the surrounding mobile stations, and Allocating communication related to user data with a mobile station to the uplink subframe and the downlink subframe paired with the uplink subframe;
A calculation step of calculating a transmission weight for the downlink subframe paired with the uplink subframe based on the signal received in the uplink subframe;
A transmission / reception step of transmitting the user data to the mobile station by transmitting the downlink control information in the data transmission area, receiving the uplink control information in the data reception area, and adaptive array control based on the transmission weight; , have a,
The downlink control information, the communication method comprising paging and system information der Rukoto.

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