JP6133920B2 - Base station apparatus, radio signal control method, and computer program - Google Patents

Description

  The present invention relates to a base station apparatus, a radio signal control method, and a computer program.

  In the time division duplex (TDD) system of wireless communication, the time slot of the signal (UL signal) of the link (Uplink: UL) in the direction from the terminal device to the base station device, and the base station Switching to the time slot of the link (Downlink: DL) signal (DL signal) in the direction from the device to the terminal device occurs. For example, standardization work is being advanced by 3GPP (3rd Generation Partnership Project) In a wireless communication system (LTE system) called LTE (Long Term Evolution), a TDD LTE system called TD-LTE is known (see, for example, Non-Patent Documents 1, 2, and 3). Then, a switching time (Guard Period: GP) is provided when switching from a DL signal time slot to a UL signal time slot.

3GPP (3rd Generation Partnership Project), TS36.331, “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio Resource Control (RRC); Protocol specification”, V12.1.0 (2014-03) 3GPP (3rd Generation Partnership Project), TS36.211, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation”, V12.1.0 (2014-03) 3GPP (3rd Generation Partnership Project), TS36.213, “Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures”, V12.3.0 (2014-09)

  In the TD-LTE described above, the shorter the GP, the more time resources that can be used for communication increase, but there is a high possibility that a collision between the DL signal and the UL signal occurs due to a delay in communication between the base station apparatus and the terminal apparatus. Become. Since the delay in communication between the base station apparatus and the terminal apparatus may differ for each base station apparatus, it is desirable to set a GP suitable for each base station apparatus.

  The present invention has been made in consideration of such circumstances, and sets a switching time between a DL signal time slot and a UL signal time slot suitable for each base station apparatus in the TDD scheme of wireless communication. An object of the present invention is to provide a base station apparatus, a radio signal control method, and a computer program.

(1) One aspect of the present invention is a base station apparatus that performs radio communication with a terminal apparatus using a time division duplex method, and the base station apparatus transmits to the terminal apparatus in the past “uplink radio frames for downlink radio frames. A delay time information acquisition unit that acquires delay time information based on a history of “frame transmission timing correction value” , and based on the acquired delay time information, a downlink signal time slot and an uplink signal time slot; A base station apparatus comprising: a radio signal control unit that determines a switching time between and an information transmission unit that transmits information about the determined switching time to the terminal device.
(2) According to one aspect of the present invention, in the base station apparatus according to (1), the delay time information acquisition unit is a random access channel signal received from the terminal apparatus by the base station apparatus. The base station apparatus acquires the delay time information based on the transmission timing correction value transmitted to the terminal apparatus with respect to the access channel signal.
(3) One aspect of the present invention is the base station apparatus according to any one of (1) and (2), wherein the delay time information acquisition unit is configured to provide coverage of the base station apparatus based on the transmission timing correction value. A base station device that calculates a round trip delay time distribution for a terminal device located therein, determines a representative round trip delay time based on the calculated round trip delay time distribution, and uses the determined representative round trip delay time as the delay time information It is.
(4) In one aspect of the present invention, in the base station device according to any one of (1) to (3), the radio signal control unit updates the switching time according to a change amount of the delay time information. It is a base station apparatus that determines whether or not to perform.
(5) According to one aspect of the present invention, in the base station device of any one of (1) to (3), the switching time update process is executed when a state of the base station device satisfies a predetermined condition The base station apparatus.

(6) One aspect of the present invention is a radio signal control method for a base station apparatus that performs radio communication with a terminal apparatus using a time division duplex method, and the base station apparatus has transmitted to the terminal apparatus in the past. Delay time information acquisition step for acquiring delay time information based on the history of `` transmission timing correction value of uplink radio frame for downlink radio frame '' , and the base station apparatus, based on the acquired delay time information, A radio signal control step for determining a switching time between a downlink signal time slot and an uplink signal time slot, and the base station device transmits information on the determined switching time to the terminal device. And an information transmission step.

(7) According to one aspect of the present invention, an uplink to a downlink radio frame transmitted from the base station apparatus to the terminal apparatus in the past is transmitted to a computer of the base station apparatus that performs radio communication with the terminal apparatus using a time division duplex method. Delay time information acquisition step for acquiring delay time information based on the history of “radio frame transmission timing correction value”, and downlink signal time slot and uplink signal time slot based on the acquired delay time information A computer program for executing a radio signal control step for determining a switching time between and an information transmission step for transmitting information on the determined switching time to the terminal device.

  According to the present invention, it is possible to set the switching time between the DL signal time slot and the UL signal time slot suitable for each base station apparatus in the wireless communication TDD system.

It is a block diagram which shows the base station apparatus 1 which concerns on one Embodiment of this invention. It is a figure which shows the structural example of the hardware which implement | achieves the base station apparatus 1 shown in FIG. It is a flowchart which shows the example of the radio | wireless signal control method which concerns on one Embodiment of this invention. It is a schematic sequence chart concerning a RACH signal. It is explanatory drawing of "TA command." It is a figure which shows the structural example of SSF of TD-LTE. It is a figure explaining the SSF determination method concerning one embodiment of the present invention. It is a figure which shows the structural example of the SSF determination table which concerns on one Embodiment of this invention. It is a flowchart which shows the other example of the radio | wireless signal control method which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, TD-LTE will be described as an example of a TDD wireless communication system.

  FIG. 1 is a configuration diagram illustrating a base station apparatus 1 according to an embodiment of the present invention. FIG. 1 shows a configuration related to a radio signal control function among configurations of a TD-LTE base station apparatus. In FIG. 1, the base station apparatus 1 includes a delay time information acquisition unit 11, a radio signal control unit 12, and an information transmission unit 13. The delay time information acquisition unit 11 acquires delay time information about a delay time in communication between the base station apparatus 1 and a terminal apparatus that wirelessly communicates with its own base station apparatus 1.

  The radio signal control unit 12 determines “Special Subframe Configuration: SSF” based on the delay time information acquired by the delay time information acquisition unit 11. SSF is a parameter for specifying GP. The information transmission unit 13 transmits the SSF determined by the radio signal control unit 12 to the terminal device.

  FIG. 2 is a diagram illustrating a configuration example of hardware that realizes the base station apparatus 1 illustrated in FIG. 1. In FIG. 2, the base station apparatus 1 includes a wireless communication unit 21, a communication unit 22, a CPU 23, and a storage unit 24. These units are configured to exchange data. The wireless communication unit 21 performs wireless communication with the terminal device. The communication unit 22 communicates with other devices via the backbone network. The CPU 23 controls the base station device 1. This control function is realized by the CPU 23 executing a computer program. The storage unit 24 stores a computer program executed by the CPU 23 and various data. The storage unit 24 stores a wireless signal control program 31. The functions of the respective units of the base station apparatus 1 shown in FIG. 1 are realized by the CPU 23 shown in FIG. 2 executing a radio signal control program 31 stored in the storage unit 24.

[Example of wireless signal control method]
FIG. 3 is a flowchart showing an example of a radio signal control method according to the present embodiment. With reference to FIG. 3, the example of operation | movement of the base station apparatus 1 shown in FIG. 1 is demonstrated.

(Step S <b> 101) The delay time information acquisition unit 11 acquires delay time information about a delay time in communication between a terminal device that wirelessly communicates with its own base station device 1 and the base station device 1. Here, a method for acquiring the delay time information will be described.

  In the present embodiment, the delay time information acquisition unit 11 acquires delay time information based on the history of UL timing correction values (TA command (Timing Advance command)). In TD-LTE, when starting communication between a terminal device (User Equipment: UE) and a base station device (eNodeB: eNB), a RACH (Random Access CHannel) signal is used. The RACH signal is used to synchronize the UL signal between the terminal device and the base station device. The base station apparatus transmits “TA command” to the terminal apparatus according to the RACH signal received from the terminal apparatus.

  FIG. 4 is a schematic sequence chart relating to the RACH signal. A signal transmission procedure related to the RACH signal will be described with reference to FIG.

(Step S1) A base station apparatus (eNB) alert | reports a RACH related parameter with a broadcast signal with respect to the terminal device (UE) in coverage (coverage) Cov.

(Step S2) The terminal apparatus (UE) transmits a RACH signal using the broadcasted RACH related parameters.

(Step S3) The base station apparatus (eNB) transmits “TA command” to the terminal apparatus (UE) that has transmitted the RACH signal.

(Step S4) The terminal apparatus (UE) transmits a UL data signal using the “TA command” received from the base station apparatus (eNB).

FIG. 5 is an explanatory diagram of “TA command”. In FIG. 5, the UL timing correction value “N _TA × T _S [seconds]” by the “TA command” is a DL radio frame (DL Radio Frame) when the terminal device transmits a UL radio frame (UL Radio Frame). ) Is a transmission timing correction value of the UL radio frame. T _S is "1/30720000" seconds. As N _TA , for example, “N _TA = TA × 16, where TA is any integer from 0 to 1282” is used. With this UL timing correction value (TA command), timing correction from 0 to 670 [microseconds] is possible. This is because the UL signal can be synchronized with respect to the terminal device in the range of about 0 to 100 [km] as the radius of the coverage size converted into the round-trip delay time between the base station device and the terminal device. It corresponds to.

The delay time information acquisition unit 11 is based on the “TA command” transmitted from the base station apparatus 1 to the terminal apparatus with respect to the RACH signal at the time of initial access among the RACH signals received from the terminal apparatus in the past. A round-trip delay time distribution (round-trip delay time distribution) is calculated for the terminal devices within the coverage of the base station apparatus 1. The delay time information acquisition unit 11 determines a representative round trip delay time based on the round trip delay time distribution. The representative round trip delay time is an example of delay time information. The following examples are given as representative round trip delay times.
(Example of representative round trip delay time) 95% tile value in round trip delay time distribution.
(Example 2 of representative round trip delay time) The longest round trip delay time in the round trip delay time distribution.
(Example 3 of representative round trip delay time) The maximum number of round trip delay times in the round trip delay time distribution.
(Example 4 of representative round trip delay time) Average value of round trip delay time in round trip delay time distribution.

  Note that the “TA command” is also transmitted to the terminal device for the RACH signal at the time of loss of synchronization. However, “TA command” at the time of loss of synchronization is a difference value from the previous “TA command”. When processing is performed in consideration of the difference value, the “TA command” at the time of loss of synchronization may be used for calculation of the round-trip delay time distribution.

Returning to FIG.
(Step S <b> 102) The wireless signal control unit 12 determines the SSF based on the delay time information acquired by the delay time information acquisition unit 11. FIG. 6 is a diagram illustrating a configuration example of the TD-LTE SSF. In FIG. 6, when switching from the DL signal time slot “DL Subframe” to the UL signal time slot “UL Subframe”, the “SP Subframe” switches from the DL signal to the UL signal between “DL Subframe” and “UL Subframe”. Is provided. The “SP Subframe” has a DL signal time slot “D”, a GP time slot “G”, and a UL signal time slot “U”. In the “SP Subframe” in the example of FIG. 6, nine SSF values “0 to 8” having different ratios of time slots “D”, “G”, and “U” are provided. The SSF value “0 to 4” has one UL signal time slot “U”. The SSF value “5 to 8” has two time slots “U” of the UL signal.

FIG. 7 is a diagram for explaining an SSF determination method according to an embodiment of the present invention. A delay time occurs in communication between the base station apparatus (eNB) and the terminal apparatus (UE). If the GP is shorter than the delay time, the possibility of collision between the DL signal and the UL signal increases. When the GP satisfies the following expression (1), collision between the DL signal and the UL signal can be prevented.
GP ≧ “DL transmission delay time” + “UL transmission delay time” + “DL-UL switching time” (1)
However, the DL transmission delay time is a transmission delay time from the base station device (eNB) to the terminal device (UE). The UL transmission delay time is a time based on the transmission delay time from the terminal device (UE) to the base station device (eNB). The DL-UL switching time is the time required for switching the radio signal transmission / reception operation of the terminal device (UE). The DL-UL switching time includes a time when the terminal device (UE) switches the DL signal reception operation from on to off and a time when the terminal device (UE) switches the UL signal transmission operation from off to on.

  In general, the coverage and device configuration of each base station device (eNB) are different. For this reason, each of DL transmission delay time and UL transmission delay time may differ for every base station apparatus (eNB). From this, it is preferable that the lower limit value of GP in the above formula (1) (the value on the right side of the formula (1)) is a value suitable for each base station apparatus. In the present embodiment, the radio signal control unit 12 determines the SSF of its own base station apparatus 1 based on the delay time information acquired by the delay time information acquisition unit 11.

  FIG. 8 is a diagram illustrating a configuration example of the SSF determination table according to the present embodiment. The SSF determination table in FIG. 8 corresponds to the SSF in FIG. The SSF determination table of FIG. 8 stores the maximum allowable delay time (maximum allowable delay time) value for each of the SSF values “0 to 8”. The maximum allowable delay time stored in the “UL 1 Symbol” column corresponds to SSF values “0 to 4” having one UL signal time slot “U” in “SP Subframe”. The maximum allowable delay time stored in the “UL 2 Symbol” column corresponds to SSF values “5 to 8” having two time slots “U” of the UL signal in “SP Subframe”. However, (alpha) is DL-UL switching time of the terminal device in which the said SSF determination table is used. The DL-UL switching time is set in the radio signal control unit 12 in advance.

  The wireless signal control unit 12 has an SSF determination table. The radio signal control unit 12 includes a representative round trip delay time that is the delay time information acquired by the delay time information acquisition unit 11, a DL-UL switching time of the terminal device set in the radio signal control unit 12 in advance, and “SP Based on the designation of the number (one or two) of time slots “U” in “Subframe”, the SSF value of its own base station apparatus 1 is selected from the SSF determination table. In this selection, the SSF value corresponding to the designation of the number of time slots “U” in “SP Subframe”, and the DL-UL switching of the terminal apparatus set in advance in the wireless signal control unit 12 in the representative round trip delay time The SSF value that is the minimum maximum allowable delay time that allows the time obtained by adding the time is selected. For example, when the representative round-trip delay time is “100 microseconds (μs)” and the designation of the number of time slots “U” in “SP Subframe” is 1, the maximum allowable delay time is “117 + α. The SSF value “2” which is (μs) ”is selected.

Returning to FIG.
(Step S103) The information transmission unit 13 transmits the SSF value, which is the determination result of the radio signal control unit 12, to the terminal device. The terminal apparatus configures “SP Subframe” corresponding to the SSF value received from the base station apparatus 1. In the base station apparatus 1, the radio signal control unit 12 configures “SP Subframe” corresponding to the SSF value transmitted to the terminal apparatus.

  According to the above-described embodiment, the GP of the base station apparatus 1 is set according to the delay time information based on the “UL timing correction value (TA command)” transmitted from the base station apparatus 1 to the terminal apparatus in the past. can do. Thereby, in TD-LTE, the effect that the GP between the time slot of DL signal and the time slot of UL signal suitable for each base station apparatus 1 can be set is acquired.

  In addition, as the delay time information, any one of the above-described representative round trip delay times 1 to 4 may be acquired. For example, when the 95% tile value in the round trip delay time distribution of Example 1 of the representative round trip delay time is acquired as the delay time information, a peculiar round trip delay time that is too large is excluded and is within the coverage of the base station apparatus 1. Many terminal devices can be covered. In addition, the above-described representative round trip time examples 1 to 4 may be selectively used according to the radio frequency band used by the base station apparatus 1 or the location of the base station apparatus 1. For example, for the base station device 1 located in an area where the terminal device is located locally, the maximum number of round-trip delay times in the round-trip delay time distribution of Example 3 of the representative round-trip delay time may be used. Can be mentioned.

[Another example of wireless signal control method]
Next, another example of the operation of the base station apparatus 1 shown in FIG. 1 will be described with reference to FIG. FIG. 9 is a flowchart showing another example of the radio signal control method according to the present embodiment.

(Step S201) The base station apparatus 1 determines execution of the SSF update process. An example of a method for determining execution of the SSF update process is given below.

(Example 1 of determination method of execution of SSF update process)
It is determined whether it is a predetermined timing for executing the SSF update process. For example, the SSF update process is executed at a constant cycle.

(Example 2 of determination method of execution of SSF update process)
It is determined whether the status of its own base station apparatus 1 satisfies a condition for executing the SSF update process. For example, the statistical value of the traffic load of the base station apparatus 1 is calculated at a constant cycle, and the SSF update process is executed when the change amount of the statistical value is equal to or greater than a predetermined threshold. As the traffic load, for example, the number of terminal devices connected can be mentioned. Alternatively, a statistical value of the resource usage amount of the base station apparatus 1 is calculated at a constant cycle, and the SSF update process is executed when the change amount of the statistical value is equal to or greater than a predetermined threshold.

(Step S202) As a result of the determination in step S201, when the SSF update process is executed, the process proceeds to step S203, and when the SSF update process is not executed, the process returns to step S201.

(Step S <b> 203) The delay time information acquisition unit 11 acquires delay time information about a delay time in communication between the base station apparatus 1 and a terminal apparatus that wirelessly communicates with its own base station apparatus 1. The method for acquiring the delay time information is the same as step S101 in FIG. 3 described above.

(Step S204) The radio signal control unit 12 determines the SSF based on the delay time information acquired by the delay time information acquisition unit 11. This SSF determination method is the same as step S102 in FIG. 3 described above.

(Step S205) The wireless signal control unit 12 determines whether to update the SSF. In this SSF update determination, the SSF value that is the determination result in step S204 is compared with the already set SSF value, and if both are different, it is determined that the SSF is updated. Alternatively, the representative round trip delay time that is the delay time information acquired in step S203 of the current SSF update process is compared with the representative round trip delay time that is the delay time information acquired in step S203 of the previous SSF update process. The SSF may be determined to be updated when the difference between the two is equal to or greater than a predetermined threshold.

  As a result of the determination in step S205, if the SSF is updated, the process proceeds to step S206. If the SSF is not updated, the process returns to step S201.

(Step S206) The information transmission unit 13 transmits the SSF value, which is the determination result of the radio signal control unit 12, to the terminal device. The terminal apparatus configures “SP Subframe” corresponding to the SSF value received from the base station apparatus 1. In the base station apparatus 1, the radio signal control unit 12 configures “SP Subframe” corresponding to the SSF value transmitted to the terminal apparatus.

(Step S207) The base station apparatus 1 determines the end of the radio signal control process of FIG. As a result of this determination, if the process is to be terminated, the radio signal control process of FIG. 9 is terminated. If not, the process returns to step S201.

  According to the other example of the radio signal control method of FIG. 9 described above, the SSF can be updated appropriately.

  Note that an SSF value that is the maximum maximum allowable delay time may be set as an initial value of the SSF value for the base station apparatus 1.

  In the other example of the radio signal control method of FIG. 9 described above, the base station apparatus 1 determines to perform the SSF update process in step S201, but another apparatus different from the base station apparatus 1 is the base station apparatus 1. The base station apparatus 1 may be instructed to execute the SSF update process by judging the execution of the SSF update process. For example, a center station that manages a plurality of base station apparatuses 1 may determine that the SSF update process of the base station apparatus 1 under its management is executed and instruct the base station apparatus 1 to execute the SSF update process. Can be mentioned.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the specific structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

  For example, the delay time information acquisition unit 11 may limit the “TA command” used for calculating the round-trip delay time distribution under a predetermined condition. For example, the time zone in which “TA command” is transmitted to the terminal device may be limited. Or you may limit the area where the terminal device which transmitted "TA command" exists. Those limitations may be determined according to the usage status (the usage time zone change status, the usage zone change status, etc.) regarding the coverage of the base station apparatus 1.

  In the above-described embodiment, TD-LTE is used as an example of the TDD wireless communication system. However, the present invention is also applicable to other TDD wireless communication systems other than TD-LTE.

Further, a computer program for realizing the functions of the base station apparatus 1 described above may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Good. Here, the “computer system” may include an OS and hardware such as peripheral devices.
“Computer-readable recording medium” means a flexible disk, a magneto-optical disk, a ROM, a writable nonvolatile memory such as a flash memory, a portable medium such as a DVD (Digital Versatile Disk), and a built-in computer system. A storage device such as a hard disk.

Further, the “computer-readable recording medium” means a volatile memory (for example, DRAM (Dynamic DRAM) in a computer system that becomes a server or a client when a program is transmitted through a network such as the Internet or a communication line such as a telephone line. Random Access Memory)), etc., which hold programs for a certain period of time.
The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line.
The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 1 ... Base station apparatus, 11 ... Delay time information acquisition part, 12 ... Radio signal control part, 13 ... Information transmission part, 21 ... Wireless communication part, 22 ... Communication part, 23 ... CPU, 24 ... Memory | storage part, 31 ... Wireless Signal control program

Claims (7)

A base station device that performs radio communication with a terminal device using a time division duplex method.
A delay time information acquisition unit that acquires delay time information based on a history of "transmission timing correction value of an uplink radio frame for a downlink radio frame" transmitted by the base station device to the terminal device in the past;
A radio signal control unit that determines a switching time between a downlink signal time slot and an uplink signal time slot based on the acquired delay time information;
An information transmission unit that transmits information about the determined switching time to the terminal device;
A base station apparatus. The delay time information acquisition unit is based on the transmission timing correction value transmitted to the terminal device for the random access channel signal at the time of initial access among the random access channel signals received by the base station device from the terminal device. Obtaining the delay time information;
The base station apparatus according to claim 1. The delay time information acquisition unit calculates a round trip delay time distribution for a terminal device within the coverage of the base station device based on the transmission timing correction value, and represents a representative round trip time distribution based on the calculated round trip delay time distribution. A delay time is determined, and the determined representative round trip delay time is used as the delay time information;
The base station apparatus of any one of Claim 1 or 2. The wireless signal control unit determines whether or not to update the switching time according to a change amount of the delay time information;
The base station apparatus of any one of Claim 1 to 3.   The base station apparatus according to any one of claims 1 to 4, wherein the switching time update process is executed when a state of the base station apparatus satisfies a predetermined condition. A radio signal control method of a base station apparatus that performs radio communication with a terminal apparatus by a time division duplex method,
A delay time information acquisition step in which the base station apparatus acquires delay time information based on a history of "transmission timing correction value of an uplink radio frame for a downlink radio frame" that the base station apparatus has transmitted to the terminal device in the past;
A radio signal control step in which the base station device determines a switching time between a time slot of a downlink signal and a time slot of an uplink signal based on the acquired delay time information;
An information transmission step in which the base station device transmits information about the determined switching time to the terminal device;
A wireless signal control method. To the base station device computer that communicates wirelessly with the terminal device in a time division duplex system,
A delay time information acquisition step of acquiring delay time information based on a history of "transmission timing correction value of an uplink radio frame for a downlink radio frame" transmitted by the base station device to the terminal device in the past;
A radio signal control step of determining a switching time between a downlink signal time slot and an uplink signal time slot based on the acquired delay time information;
An information transmission step of transmitting information about the determined switching time to the terminal device;
A computer program for running.

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