WO2019175947A1

WO2019175947A1 - Wireless communication system, different-frequency handover method, base station, and terminal apparatus

Info

Publication number: WO2019175947A1
Application number: PCT/JP2018/009607
Authority: WO
Inventors: 裕明渡辺; 義博河▲崎▼; 高木　淳一
Original assignee: 富士通株式会社
Priority date: 2018-03-13
Filing date: 2018-03-13
Publication date: 2019-09-19

Abstract

[Problem] When a URLLC packet is transmitted between a base station and a terminal apparatus and a GAP period in a different-frequency handover has been set, there may be a case where a delay-related specification provided for the URLLC packet is not met. [Solution] In a different-frequency handover, when a conflict occurs between a processing such as a reception quality measurement in a GAP period and the transmission of a URLLC packet for which a delay-related specification is provided, the delay in transmission of the URLLC packet can be suppressed by performing a cancelation or the like of the GAP period and thereby executing the transmission of the URLLC packet on a priority basis.

Description

Wireless communication system, different frequency handover method, base station, and terminal device

The present disclosure relates to a wireless communication system, a different frequency handover method, a base station, and a terminal device.

In wireless communication, a base station forms a wireless communication area called a cell and performs wireless communication with a terminal device in the wireless communication area. When the terminal device moves to another cell formed by another base station, the connection destination of the terminal device is transferred from the base station to another base station. This process is called handover. When a base station and other base stations use radio signals having different frequencies, a handover between these base stations is particularly called a different frequency handover.

In handover, the terminal apparatus measures the reception quality of a radio signal transmitted from another base station, for example, Signal Interference Ratio (hereinafter referred to as “SIR”). The measured SIR is notified from the terminal device to the base station. Based on the SIR measurement result notified from the terminal device, the base station changes the connection with the terminal device from the base station to another base station as necessary. In the above-described different frequency handover, when a plurality of radio processing circuits are provided in the terminal device, the terminal device simultaneously receives radio signals from other base stations while maintaining communication with the base station, and performs SIR. It is possible to measure. However, when the terminal device has a single wireless processing circuit, a technique is used in which wireless communication with the base station is temporarily suspended and SIR is measured for other base stations during that time. In order to receive radio signals from other base stations and measure the reception quality, a period called measurement gap (Measurement GAP, hereinafter referred to as “GAP period”) is provided. During the GAP period, wireless communication between the terminal device and the base station is temporarily suspended. In the Long Term Evolution (LTE), for example, a time width of several ms is set as the GAP period.

On the other hand, for example, in the communication of the fifth generation mobile communication system (5G), there is communication in which stricter requirements (regulations and allowable values) are set for delays in the radio section than before. For example, in Ultra Reliable and Low Latency Communications (hereinafter referred to as “URLLC”), the delay in the radio section is required to be 0.5 ms or less.

Japanese Unexamined Patent Publication No. 2016-063243 International Publication No. 2015-170579 JP 2006-121172 A

Assume that a packet in which a rule regarding delay is set, for example, a URLLC packet is transmitted between a base station and a terminal device, and a GAP period in a different frequency handover is set. In this case, since the communication between the base station and the terminal device is suspended during the GAP period, there may be a case where the requirement regarding the delay required for the URLLC packet is not satisfied. For example, it is assumed that the base station receives a URLLC packet from the host device immediately before the start time of the GAP period. In this case, if transmission of the URLLC packet is executed after the end of the GAP period, transmission of the URLLC packet is suspended in the base station at least during the GAP period. As a result, there may be a delay that exceeds a regulation relating to the delay.

An object of the present invention is to suppress a packet transmission delay when a process such as reception quality measurement in a GAP period and a packet transmission for which a rule regarding delay is competing in a different frequency handover.

A wireless communication system including a base station and a terminal device that performs wireless communication with the base station, wherein the base station performs a first period from another base station to the terminal device. A packet that is set as a measurement period for measuring the first quality of the first radio signal to the terminal, and that is transmitted from the base station to the terminal device and that defines a rule regarding delay in the radio communication When the base station holds at a time before the start time of the first period, the base station executes a change process for changing the setting of the measurement period, and after the change process, the change The base station transmits the packet to the terminal device within the first period set as the measurement period before the process is executed, and a time point before the start time of the first period At the base station If you do not hold the packet, the terminal device, a radio communication system, characterized by measuring said first quality of the first radio signal in the first period is disclosed.

According to the present invention, it is possible to suppress packet transmission delay when processing such as reception quality measurement in the GAP period competes with transmission of a packet for which a rule relating to delay is defined in different frequency handover. .

It is a figure which shows the radio | wireless communications system containing a base station and a terminal device. It is a hardware block diagram of a terminal device. It is a ladder chart regarding measurement of reception quality in handover. It is a ladder chart about the processing mainly performed in the radio communications system in a GAP period. 10 is a ladder chart for explaining processing for changing a GAP period when transmission of a packet for which a regulation relating to delay is defined competes with processing such as reception quality measurement in the GAP period. It is a figure which shows an example of the method of notifying a change of a GAP pattern to a terminal device. It is a figure which shows the other example of the method of notifying a terminal device of the change of a GAP pattern. It is a hardware block diagram of a base station. It is a functional block diagram of the processor of a base station. It is a functional block diagram of the processor of a terminal device. It is a flowchart of the process performed by the processor of a base station. It is a flowchart of the process performed by the processor of a base station, Comprising: It is a flowchart of the process mainly regarding execution of a GAP sequence. It is a flowchart of the process performed by the processor of a terminal device. It is a flowchart of the process performed by the processor of a terminal device, Comprising: It is a flowchart of the process mainly regarding execution of a GAP sequence. It is a figure which shows a mode that a GAP period is shifted. It is a figure which shows an example of the method of notifying a change of a GAP pattern to a terminal device. It is a flowchart of the process performed by the processor of a base station, Comprising: It is a flowchart of the process mainly regarding execution of a GAP sequence. It is a flowchart of the process performed by the processor of a terminal device, Comprising: It is a flowchart of the process mainly regarding execution of a GAP sequence. It is a figure which shows a mode that a GAP period is shortened. It is a figure which shows an example of the method of notifying a change of a GAP pattern to a terminal device. It is a flowchart of the process performed by the processor of a base station, Comprising: It is a flowchart of the process mainly regarding execution of a GAP sequence. It is a flowchart of the process performed by the processor of a terminal device, Comprising: It is a flowchart of the process mainly regarding execution of a GAP sequence. It is a ladder chart when a terminal device transmits a packet to a base station and a GAP period is canceled. It is a functional block diagram of the processor of a terminal device. It is a flowchart of the process performed by the processor of a terminal device. It is a flowchart of the process performed by the processor of a base station, and is a flowchart of the process performed when the change request signal of a GAP pattern is mainly received from the terminal device.

<First embodiment>
FIG. 1 is a diagram illustrating a wireless communication system including a base station and a terminal device. The base station 3a is connected to a host device, for example, the server 2 via the network 1. The server 2 is, for example, an application server. The base station 3a is connected to the terminal device 4 by wireless communication, and transmits and receives data such as packets. In the figure, a base station 3b is another base station arranged in the vicinity of the base station 3a, and forms an adjacent cell with respect to a cell formed by the base station 3a. It is assumed that there are a plurality of base stations 3b. The frequency of the radio signal of at least one base station 3b among the plurality of base stations 3b is different from the frequency of the radio signal of the base station 3a. In addition, when not distinguishing the base station 3a and the base station 3b, it shall be described as “base station 3”.

When the terminal device 4 moves from the cell formed by the base station 3a to the cell formed by the base station 3b, the connection destination of the terminal device 4 is handed over from the base station 3a to the base station 3b. When a handover is executed, prior to the handover, the terminal device 4 performs measurement of signal reception quality, for example, SIR, from another base station 3b that is a candidate for the destination of the handover. Although this embodiment is described using SIR as an example of reception quality, reception quality is not limited to SIR.

FIG. 2 is a hardware configuration diagram of the terminal device 4. The terminal device 4 includes a wireless processing circuit 410, a processor 420, a nonvolatile memory 440, and a volatile memory 450. The wireless processing circuit 410 performs frequency down-conversion, Analog to Digital (AD) conversion, and the like on the wireless signal received by the antenna. Further, the radio processing circuit 410 performs digital to analog (DA) conversion, frequency up-conversion, and the like on the radio signal transmitted from the antenna. When the different frequency handover is executed, the radio processing circuit 410 performs frequency tuning based on the frequency of the received radio signal. The processor 420 executes processing related to communication with the base station 3a, processing related to handover to another base station 3b, and the like. The processor 420 is a hardware processor, and includes a central processing unit (CPU), a micro control unit (MCU), a micro processing unit (MPU), a digital signal processor (DSP), and a field programmable processor (DSP). Circuit (ASIC) is also applicable.

The nonvolatile memory 440 is a computer-readable recording medium. The nonvolatile memory 440 stores a computer program executed by the processor 420 and the like. The non-volatile memory 440 is, for example, Read Only Memory (ROM), Mask Read Only Memory (mask ROM), Programmable Read Only Memory (PROM), Flash Memory, Magnetoresistive Memory Random Memory Random Access Memory. For example, Ferroelectric Random Access Memory (FeRAM). The computer program can be recorded on a storage medium other than the nonvolatile memory 440 and a computer-readable recording medium (excluding a carrier wave). Also, portable recording media such as Digital Versatile Disc (DVD) and Compact Disc Read Only Memory (CD-ROM) in which a computer program is recorded can be distributed. The computer program can be transmitted via a network.

The volatile memory 450 is a computer-readable recording medium. The computer program stored in the nonvolatile memory 440 is loaded into the volatile memory 450. The volatile memory 450 holds data used for arithmetic processing by the processor 420, data that is the result of the arithmetic processing, and the like. The volatile memory 450 is, for example, a Static Random Access Memory (SRAM), a Dynamic Random Access Memory (DRAM), or the like.

FIG. 3 is a ladder chart relating to measurement of reception quality in handover. It is assumed that the reception quality of the radio signal received by the terminal device 4 from the base station 3a, for example, the SIR is lowered in a state where a communication session is established between the base station 3a and the terminal device 4. In this case, in step S10, the terminal device 4 transmits a notification signal indicating that the quality of the received signal has decreased to the base station 3a. In step S11, the base station 3a that has received the notification signal uses information for identifying other base stations 3b arranged around the base station 3a, for example, cell identification (ID) and the other base station 3b. Cell information including frequency information specifying the frequency of the radio signal is notified to the terminal device 4. In addition, the base station 3 a notifies the terminal device 4 of GAP pattern information that specifies a pattern of the reception quality measurement period (hereinafter referred to as “GAP pattern”). The GAP pattern is specified by, for example, the number of GAP periods, the time of each GAP period, the interval between adjacent GAP periods, and the like. In FIG. 3, it is assumed that the set number of GAP periods is 3, the time of each GAP period is 2 ms, and the interval between adjacent GAP periods is 4 ms. The total time of the plurality of GAP periods included in the GAP pattern is based on the time required for the terminal device 4 to measure the SIR for each of the plurality of other base stations 3b and notify the measurement result to the base station 3a. Specified. Moreover, it is preferable that the GAP period is distributed and executed a plurality of times. Note that a series of processing from the start of the first GAP period to the end of the last GAP among the GAP periods executed a plurality of times is called a GAP sequence.

After the GAP sequence is completed, in step S12, the base station 3a determines whether or not to execute handover based on the SIR for the other base station 3b notified from the terminal device 4, and to which base station 3b to perform handover. To decide.

FIG. 4 is a ladder chart about processing executed mainly in the wireless communication system within the GAP period. In the process S13, the base station 3a receives the packet from the network 1 (not shown in FIG. 4) from the server 2, which is a higher-level device. In the following description of the present specification, the “packet” will be described as a packet in which provisions relating to delay are defined, for example, a URLLC packet. In the process S14, the base station 3a holds the received packet in the buffer unit. Next, in process S15, the base station 3a schedules the transmission timing of the packets held in the buffer unit. Here, it is determined that transmission of the packet held in the buffer unit to the terminal device 4 is not completed by the start of the scheduled GAP period thereafter, and the base station 3a suspends transmission of the packet. And

Thereafter, the GAP period is started, and in step S16, the terminal device 4 tunes the frequency of the radio signal that can be received by the radio processing circuit 410 to the frequency of the radio signal from the base station 3b that is a new connection destination candidate. In process S17, the terminal device 4 receives the radio signal from the base station 3b. In step S18, the terminal apparatus 4 measures SIR as the reception quality of the received radio signal. In the process S19, the terminal device 4 transmits the SIR measurement result as a Measurement Report to the base station 3a. In step S20, the terminal device 4 tunes the radio processing circuit 410 to the frequency of the radio signal from the base station 3a in order to resume radio communication with the base station 3a. After the GAP period ends, in step S21, the base station 3a transmits the packet held in the buffer unit to the terminal device 4. Among the processes disclosed in FIG. 4, at least processes S16 to S20 are executed within the GAP period.

As shown in FIG. 4, the packet held in the buffer unit of the base station 3a is held in the base station 3a and transmission is suspended until the subsequent GAP period ends. Therefore, packet transmission is delayed for at least the time corresponding to the GAP period.

For example, in 5G packets, the specification specifies that the delay in the wireless communication section is 0.5 ms or less. If the length of the GAP period is 2 ms, for example, if the packet reaches the base station 3a before the GAP period and transmission to the terminal device 4 is suspended until the GAP period ends, at least A delay of 2 ms occurs, and the requirement regarding the delay required in the specification is not satisfied.

In the present embodiment, when transmission of a packet in which a regulation regarding delay is defined in this way and processing such as reception quality measurement in the GAP period compete, packet transmission is performed by changing the setting of the GAP period. Can be preferentially executed.

FIG. 5 is a ladder chart for explaining the process of changing the GAP period when the transmission of a packet for which the regulation relating to delay is defined competes with the process of measuring the reception quality in the GAP period.

In the process S22, the base station 3a receives the packet from the server 2 which is a host device. In the process S23, the base station 3a holds the received packet in the buffer unit. In the process S24, the base station 3a performs scheduling regarding the transmission timing of the packet held in the buffer unit. For example, when the GAP period is set, the base station 3a determines whether or not the regulations regarding the packet delay are satisfied even if transmission of the packet is executed after the end of the GAP period. For example, when the delay allowable value is 0.5 ms and the GAP period is 2 ms, it is determined that the rule regarding the packet delay is not satisfied. In this case, in step S26, the base station 3a cancels the set GAP period, and reschedules packet transmission so that the packet is transmitted in the canceled period. In step S25, the base station 3a transmits to the terminal device 4 a change notification indicating that the GAP period has been canceled, that is, the GAP pattern has been changed. The terminal device 4 recognizes that the setting of the GAP period has been canceled by the change notification, and the processes S16 to S20 disclosed in FIG. 4 are not executed in the canceled GAP period.

In step S27, the base station 3a transmits the packet to the terminal device 4 at the rescheduled timing.

FIG. 6 is a diagram illustrating an example of a method for notifying the terminal device 4 of the change of the GAP pattern. The GAP period defined by the GAP pattern notified in the process S11 of FIG. 3 is assumed to be from time T1 to time T2 in the figure. If the packet is held in the buffer unit before the start of the GAP period and the packet transmission is performed while avoiding the GAP period, the base station 3a Cancel the GAP period setting. Then, as shown in the process S25 of FIG. 5, the base station 3a notifies the terminal device 4 of the change of the GAP pattern. This notification is executed using, for example, a Physical Downlink Control Channel signal (hereinafter referred to as “PDCCH signal”). In FIG. 6, the PDCCH signal includes cancellation information indicating that the setting for setting the period from time T1 to time T2 as the GAP period is cancelled. Moreover, the allocation resource information which specifies the radio | wireless resource used for the radio | wireless communication between the terminal device 4 and the base station 3a is contained in a PDCCH signal. By transmitting this PDCCH signal to the terminal device 4, the terminal device 4 recognizes that the setting of the GAP period scheduled thereafter is canceled. And based on the allocation resource information contained in a PDCCH signal, transmission / reception of the packet between the base station 3a and the terminal device 4 is performed.

FIG. 7 is a diagram illustrating another example of a method for notifying the terminal device 4 of a change in the GAP pattern. FIG. 6 discloses an example in which cancellation information indicating that the setting of the next GAP period is canceled in the PDCCH signal and allocation resource information for specifying a radio resource are included. In the example shown in FIG. 7A, the allocation resource information is included in the PDCCH signal, while the information corresponding to the cancellation information is not included in the PDCCH signal. In this case, the terminal device 4 may recognize that the setting of the GAP period is canceled based on the allocation resource information included in the PDCCH signal. As a comparative example, FIG. 7B shows a case where the setting of the GAP period is not canceled. Since the setting of the GAP period is not canceled, the terminal device 4 measures the reception quality of the radio signal from the other base station 3b in the GAP period as scheduled. Therefore, radio resources are not allocated to radio communication between the base station 3a and the terminal device 4, and allocation resource information is not included in the PDCCH signal. In other words, when the allocation resource information is included in the PDCCH signal, it indicates that the setting of the GAP period is implicitly canceled.

FIG. 8 is a hardware configuration diagram of the base station 3. The base station 3 includes a wireless processing circuit 310, a processor 320, a nonvolatile memory 340, a volatile memory 350, and a network interface circuit 360. The wireless processing circuit 310 performs down conversion, AD conversion, and the like on the wireless signal received by the antenna. The wireless processing circuit 310 performs DA conversion, up-conversion, and the like on the wireless signal transmitted from the antenna. The processor 320 executes processing related to packet transmission / reception with the server 2, processing related to packet transmission / reception with the terminal device 4, setting of a GAP pattern, handover, and the like. The processor 320 is a hardware processor, and an FPGA or an ASIC can be applied in addition to a CPU, MCU, MPU, and DSP.

The nonvolatile memory 340 is a computer-readable recording medium. The nonvolatile memory 340 stores a computer program executed by the processor 320 and the like. The nonvolatile memory 340 is, for example, a ROM, mask ROM, PROM, flash memory, MRAM, ReRAM, FeRAM, or the like. The computer program can be recorded on a storage medium other than the non-volatile memory 340 and a computer-readable recording medium (except for a carrier wave). In addition, portable recording media such as DVDs and CD-ROMs on which computer programs are recorded can be distributed. The computer program can be transmitted via a network.

The volatile memory 350 is a computer-readable recording medium. The computer program stored in the non-volatile memory 340 is loaded into the volatile memory 350. The volatile memory 350 holds data used for arithmetic processing by the processor 320, data that is the result of the arithmetic processing, and the like. The volatile memory 350 is, for example, SRAM or DRAM.

The network interface circuit 360 is an interface device with the network 1.

FIG. 9 is a functional block diagram of the processor 320 of the base station 3. The processor 320 includes a reception unit 321, a transmission unit 322, a radio resource allocation unit 323, a handover processing unit 324, a measurement result processing unit 325, a higher device side reception unit 326, a higher device side transmission unit 327, a buffer unit 328, and a scheduling unit 329. , GAP pattern setting unit 330 and GAP control unit 331.

The receiving unit 321 demodulates and decodes the signal received from the terminal device 4. The transmission unit 322 modulates and encodes a signal transmitted to the terminal device 4. The radio resource allocation unit 323 allocates radio resources used in radio communication performed with the terminal device 4. The handover processing unit 324 performs processing related to handover to another base station 3b. For example, when a notification regarding the reception quality is transmitted from the terminal device 4, the handover processing unit 324 is transmitted from the cell ID that identifies the other base station 3b arranged in the vicinity or the other base station 3b. The terminal device 4 is notified of frequency information indicating the frequency of the radio signal. In addition, the handover processing unit 324 notifies the terminal device 4 of information indicating the GAP pattern set by the GAP pattern setting unit 330. Thereafter, the terminal device 4 performs reception quality measurement, and the measurement result processing unit 325 receives the reception quality measurement result transmitted from the terminal device 4. Then, based on the received reception quality measurement result, the handover processing unit 324 determines whether or not to execute handover and performs processing related to handover execution. The upper apparatus side receiving unit 326 receives a packet from the upper apparatus, for example, the server 2 via the network interface circuit 360. The higher-level device side transmission unit 327 transmits the packet to the higher-level device via the network interface circuit 360. The buffer unit 328 is a buffer that holds packets received from the host device. For example, when the host device side receiving unit 326 receives a packet from the host device, the packet is temporarily held in the buffer unit 328. The scheduling unit 329 schedules the transmission timing of the packet held in the buffer unit 328 to the terminal device 4. When scheduling a packet transmission, the scheduling unit 329 performs scheduling in consideration of the data amount of the packet held in the buffer unit 328, whether or not a rule regarding delay is defined for the packet. In addition, when a GAP pattern has already been determined, the scheduling unit 329 performs scheduling in consideration of the GAP period. The GAP pattern setting unit 330 sets a GAP pattern when the handover processing unit 324 receives a notification regarding reception quality from the terminal device 4, and notifies the handover processing unit 324 of the set GAP pattern. The GAP pattern setting unit 330 also executes a process for changing the GAP pattern once set. In this case, the GAP pattern setting unit 330 notifies the handover processing unit 324 of the change contents. The GAP control unit 331 performs processing related to execution of the GAP sequence.

FIG. 10 is a functional block diagram of the processor 420 of the terminal device 4. The processor 420 functions as a reception unit 421, a transmission unit 422, a reception quality notification unit 423, a reception quality measurement unit 424, a tuning unit 425, and a GAP control unit 426.

The receiving unit 421 performs demodulation and decoding of the signal received from the base station 3a. The transmission unit 422 modulates and encodes a signal transmitted to the base station 3a. The reception quality notification unit 423 transmits a notification signal to the base station 3a when the reception quality of the radio signal from the base station 3a is lowered, for example, when the SIR becomes a predetermined value or less. The notification signal may include the measured SIR value, or may include information indicating that the SIR has become equal to or less than a predetermined value. The reception quality measurement unit 424 measures the reception quality of radio signals from the base station 3a, and measures the reception quality of radio signals from other base stations 3b during the GAP period. The reception quality measuring unit 424 notifies the measured reception quality to the base station 3a. The tuning unit 425 tunes the reception frequency of the wireless processing circuit 410. For example, in the GAP period, in order to receive a radio signal having a frequency different from the frequency of the radio signal from the base station 3a, the reception frequency of the radio processing circuit 410 is tuned. The GAP control unit 426 controls the reception quality measurement unit 424, the tuning unit 425, and the like so that the GAP sequence is executed based on the GAP pattern notified from the base station 3a.

FIG. 11 is a flowchart of processing executed by the processor 320 of the base station 3a. The process flow is started in process S30, and in process S31, the handover processing unit 324 determines whether a reception quality notification signal is received from the terminal device 4. If it is determined that the notification signal has been received (Yes in process S31), the process flow proceeds to process S32. If it is not determined that the notification signal has been received (No in process S31), the process flow repeats process S31. .

In process S32, the handover processing unit 324 determines whether the reception quality of the radio signal in the terminal device 4 is equal to or less than the specified value based on the received notification signal. If it is determined that the reception quality is not more than the specified value (Yes in process S32), the process flow proceeds to process S33, and if it is not determined that the reception quality is not more than the specified value (No in process S32), the process is performed. The flow returns to process S31. In step S33, the GAP pattern setting unit 330 sets a GAP pattern. In step S <b> 34, the handover processing unit 324 notifies the terminal device 4 of cell information related to the other base station 3 b and GAP pattern information indicating the GAP pattern set by the GAP pattern setting unit 330. In process S35, the GAP control unit 331 executes the GAP sequence based on the GAP pattern set in process S33. Thereafter, the process flow ends in process S36.

FIG. 12 is a flowchart of processing executed by the processor 320 of the base station 3a, and mainly shows processing related to execution of the GAP sequence. The flowchart shown in FIG. 12 corresponds to the details of the process S35 in the process flow disclosed in FIG. The process flow is started in process S40, and in process S41, the buffer unit 328 determines whether the packet addressed to the terminal device 4 is held in the buffer unit 328. When it is determined that the packet is held in the buffer unit 328 (Yes in process S41), the process flow proceeds to process S42, and when it is not determined that the packet is held in the buffer unit 328 (No in process S41). ) Repeats the process S41 in the process flow. In process S42, the scheduling unit 329 schedules the packet transmission timing in consideration of the GAP pattern, that is, in consideration that the specific period is set as the GAP period. In process S43, the scheduling unit 329 determines whether the delay requirement required for the packet is satisfied based on the scheduled transmission timing of the URLLC. If it is determined that the delay rule is satisfied (Yes in process S43), the process flow proceeds to process S46. If it is not determined that the delay rule is satisfied (No in process S43), the process flow proceeds to process S44. .

In step S44, the GAP control unit 331 notifies the terminal device 4 that the setting of the next GAP period is canceled by transmitting a change notification of the GAP pattern. In step S45, the GAP control unit 331 sets the packet transmission schedule again based on the cancellation of the setting of the next GAP period.

In process S46, the transmission unit 322 transmits the packet to the terminal device 4 based on the transmission schedule set in process S42 or the transmission schedule reset in process S45. Thereafter, the process flow ends in process S47.

FIG. 13 is a flowchart of processing executed by the processor 420 of the terminal device 4. The process flow is started in process S50, and in process S51, the reception quality notifying unit 423 determines whether the reception quality of the radio signal from the base station 3a has deteriorated. If it is determined that the reception quality of the radio signal has decreased (Yes in process S51), the process flow proceeds to process S52. If it is not determined that the reception quality of the radio signal has decreased (No in process S51), the process proceeds to step S52. The flow repeats the process S51.

In process S52, the reception quality notification unit 423 transmits a notification signal about the reception quality to the base station 3a. In step S53, the GAP control unit 426 determines whether the cell information related to the other base station 3b and the GAP pattern information indicating the GAP pattern have been received from the base station 3a. The cell information includes a cell ID that specifies the other base station 3b and frequency information that specifies the frequency of the radio signal of the other base station 3b. The GAP pattern information includes information indicating the start time of the GAP sequence, the number of GAP periods included in the GAP sequence, the length of each GAP period, the interval between GAP periods, and the like. If it is determined in step S53 that cell information and GAP pattern information have been received (Yes in step S53), the process flow proceeds to step S54, and if it is not determined that cell information and GAP pattern information have been received (step S53). No), the process flow returns to the process S51. In process S54, the GAP control unit 426 executes the GAP sequence based on the GAP pattern information. Thereafter, the process flow ends in process S55.

FIG. 14 is a flowchart of processing executed by the processor 420 of the terminal device 4, and is mainly a flowchart of processing related to execution of the GAP sequence. The flowchart shown in FIG. 14 corresponds to the details of the process S54 in the process flow disclosed in FIG. The process flow starts in process S60, and in process S61, the GAP control unit 426 determines whether a GAP pattern change notification signal is received from the base station 3a. If it is determined that a change notification signal has been received (Yes in process S61), the process flow proceeds to process S62. If it is not determined that a change notification signal has been received (No in process S61), the process flow is process S64. Proceed to

When the process flow proceeds to process S62, the GAP control unit 426 cancels the setting of the next GAP period based on the change notification signal in process S62. In step S63, the reception unit 421 receives a packet from the base station 3a using the assigned radio resource.

On the other hand, when the process flow proceeds to process S64, the tuning unit 425 tunes the radio processing circuit 410 to the frequency of the radio signal of the other base station 3b in the GAP period in process S64. In process S65, the reception quality measuring unit 424 measures the reception quality of the radio signal of the other base station 3b. In step S66, the reception quality notification unit 423 notifies the measured reception quality to the base station 3a.

After step S63 or step S66, in step S67, the GAP control unit 426 determines whether the GAP sequence has ended. If it is determined that the GAP sequence has been completed (Yes in process S67), the process flow ends in process S68. If it is not determined that the GAP sequence has been completed (No in process S67), the process flow is performed in process S61. Return to.

Thus, the first embodiment has been disclosed. In the first embodiment, when the packet transmission and the processing such as reception quality measurement in the GAP period compete, the setting of the GAP period is canceled and the packet transmission is preferentially executed.

<Second embodiment>
In the first embodiment, an example in which the setting of the GAP period is canceled in order to give priority to packet transmission is disclosed, but in the second embodiment, an example in which the GAP period is shifted is disclosed. FIG. 15 is a diagram illustrating how the GAP period is shifted. Since the processing S10, the processing S11, and the processing S12 are the contents disclosed in FIG. 3, the description thereof is omitted here.

In process S70, the base station 3a receives a packet from the server 2 before the GAP period # 2 is started. The base station 3a decides to change the GAP pattern, that is, shift the GAP period # 2 scheduled thereafter to the rear in order to satisfy the provisions regarding the packet delay. In step S71, the base station 3a notifies the terminal device 4 of the change of the GAP pattern. Thereafter, in step S72, the base station 3a transmits the packet to the terminal device 4. After the packet is transmitted, the shifted GAP period # 2 begins.

As described above, also in the second embodiment, the GAP pattern is changed so that the packet transmission is executed with priority, and the provisions regarding the packet delay can be satisfied.

FIG. 16 is a diagram illustrating an example of a method for notifying the terminal device 4 of a change in the GAP pattern. At the time before the start of the GAP period, the packet is held in the buffer unit 328, and when the packet transmission is scheduled so as to avoid the GAP period, it is determined that the requirement regarding the delay required for the packet is not satisfied. If so, the GAP period is shifted backwards. In this case, the base station 3 a transmits a GAP pattern change notification to the terminal device 4. This change notification can be executed using, for example, a PDCCH signal, as in the first embodiment. In FIG. 16, the PDCCH signal includes shift information indicating that the setting of the GAP period whose start time is time T1 is changed and the start of the GAP period is set at time T3 after time T1. The shift amount is a time corresponding to, for example, 2 slots. Moreover, the allocation resource information which specifies the radio | wireless resource used for the radio | wireless communication between the terminal device 4 and the base station 3a is contained in a PDCCH signal. By transmitting this PDCCH signal to the terminal apparatus 4, the terminal apparatus 4 recognizes that the start timing of the GAP period scheduled thereafter is shifted. And based on the allocation resource information contained in a PDCCH signal, transmission / reception of the packet between the base station 3a and the terminal device 4 is performed.

FIG. 17 is a flowchart of processing executed by the processor 320 of the base station 3a, and mainly shows processing related to execution of the GAP sequence. Processes other than process S73 are the same as those already disclosed in FIG. In FIG. 12, the terminal device 4 is notified in step S44 that the setting of the next GAP period is cancelled. In FIG. 17, in step S73, the next GAP period is shifted backward by a predetermined time. Is notified to the terminal device 4. The information indicating the shift amount is included in, for example, a PDCCH signal as described in FIG.

FIG. 18 is a flowchart of processing executed by the processor 420 of the terminal device 4, and is mainly a flowchart of processing related to execution of the GAP sequence. Processes other than the process S74 are the same as those already disclosed in FIG. In FIG. 14, the setting of the next GAP period is canceled in the process S62, but in FIG. 18, the next GAP period is shifted backward by a predetermined time in the process S74.

As described above, the second embodiment has been disclosed. Also in the second embodiment, packet transmission can be preferentially executed when the packet transmission competes with processing such as reception quality measurement in the GAP period.

<Third embodiment>
In the third embodiment, when the packet addressed to the terminal device 4 is held in the base station 3a, the timing for transmitting the packet is secured by shortening the GAP period.

FIG. 19 shows how the GAP period is shortened. Processes other than the process S75 are the same as the process contents already disclosed in FIG. In FIG. 19, the base station 3a receives a packet from the server 2 before the start of the GAP period # 2. In this case, the base station 3a changes the GAP pattern so as to shorten the GAP period # 2 scheduled thereafter in order to satisfy the provisions regarding the packet delay, and changes the GAP pattern to the terminal device 4 in step S75. Notice. With this change, the start time of the GAP period # 2 is delayed by a predetermined time. In step S <b> 72, the base station 3 a transmits the packet to the terminal device 4. After the packet is transmitted, the GAP period # 2, which is shortened and changed so that the start time is delayed, starts.

As described above, also in the third embodiment, the GAP pattern is changed so that the packet transmission is executed with priority, and the provisions regarding the packet delay can be satisfied.

FIG. 20 is a diagram illustrating an example of a method for notifying the terminal device 4 of a change in the GAP pattern. It is assumed that the packet is held in the buffer unit 328 at a time before the start of the GAP period. In this case, when scheduling of packet transmission is performed while avoiding the GAP period, if it is determined that the request regarding the delay required for the packet is not satisfied, it is determined to change the GAP pattern so as to shorten the GAP period. Then, the base station 3a notifies the terminal device 4 of the change of the GAP pattern. This notification can be executed using, for example, a PDCCH signal in the same manner as in the first and second embodiments. In FIG. 20, in the PDCCH signal, the setting of the GAP period starting at time T1 is changed, the length of the GAP period is shortened by a length corresponding to, for example, 2 slots, and the start of the GAP period is set at time T3. Abbreviated information indicating that it is to be performed. Moreover, the allocation resource information which specifies the radio | wireless resource used for the radio | wireless communication between the terminal device 4 and the base station 3a is contained in a PDCCH signal. By transmitting this PDCCH signal to the terminal device 4, the terminal device 4 recognizes that the setting of the GAP period scheduled thereafter has been changed. And based on the allocation resource information contained in a PDCCH signal, transmission / reception of the packet between the base station 3a and the terminal device 4 is performed.

As shown in FIG. 19, when the length of the GAP period # 2 is shortened, the length of the GAP period # 3 is increased so as to compensate for the total length of the GAP periods included in the GAP sequence. The GAP pattern may be changed so that the

FIG. 21 is a flowchart of processing executed by the processor 320 of the base station 3a, and mainly shows processing related to execution of the GAP sequence. Processes other than the process S76 are the same as those already disclosed in FIG. In FIG. 12, the terminal device is notified in step S44 that the setting of the next GAP period is cancelled. In FIG. 21, in step S76, the next GAP period is shortened and the start time of the GAP period is set backward. Is notified to the terminal device 4 that it is delayed by a predetermined time. The information indicating the shortening amount is included in, for example, a PDCCH signal as described in FIG.

FIG. 22 is a flowchart of processing executed by the processor 420 of the terminal device 4, and is mainly a flowchart of processing related to execution of the GAP sequence. Processes other than the process S77 are the same as the process contents already disclosed in FIG. In FIG. 14, the setting of the next GAP period is canceled in the process S62, but in FIG. 22, the next GAP period is shortened by a predetermined time in the process S77.

As described above, the third embodiment has been disclosed. Also in the third embodiment, when packet transmission and reception quality measurement in the GAP period compete, it is possible to suppress delay in packet transmission.

<Fourth embodiment>
In the first to third embodiments, packet transmission from the base station 3a to the terminal device 4, that is, so-called downlink communication has been described. In the fourth embodiment, packets from the terminal device 4 to the base station 3a are described. Transmission, so-called uplink communication will be described. Even when the terminal device 4 transmits a packet to the base station 3a, contention between the packet transmission and processing such as reception quality measurement in the GAP period may occur. In this case, the terminal device 4 can preferentially execute packet transmission by canceling the setting of the GAP period.

FIG. 23 is a ladder chart when the terminal device 4 transmits a packet to the base station 3a and the GAP period is canceled. In the process S80, the packet to be transmitted is held in the buffer unit of the terminal device 4. Further, in step S81, the terminal device 4 performs scheduling on the transmission timing of the packet held in the buffer unit. Then, when packet transmission is scheduled after the next scheduled GAP period, it is determined whether or not a rule regarding packet delay is satisfied. If it is determined that the delay rule is not satisfied, in step S82, the terminal device 4 transmits a GAP pattern change request to the base station 3a. The change request can be executed using, for example, a Physical Uplink Control Channel signal (hereinafter referred to as “PUCCH signal”). In step S83, the base station 3a notifies the terminal device 4 that the GAP pattern is to be changed. As a result, the setting of the GAP period is cancelled, and in step S84, scheduling is performed again regarding packet transmission. In step S85, a packet is transmitted from the terminal device 4 to the base station 3a based on the rescheduling result.

As described above, even in packet transmission from the terminal device 4 toward the base station 3a, when packet transmission and processing such as reception quality measurement in the GAP period compete, the setting of the GAP period is canceled to cancel the packet. Transmission can be executed with priority.

FIG. 24 is a functional block diagram of the processor 420 of the terminal device 4. In addition to the reception unit 421, the transmission unit 422, the reception quality notification unit 423, the reception quality measurement unit 424, the tuning unit 425, and the GAP control unit 426 disclosed in FIG. It functions as the request unit 429.

The buffer unit 427 is a buffer that holds a packet transmitted to the base station 3. The packet is held in the buffer unit 427 before being transmitted to the base station 3. The scheduling unit 428 performs scheduling related to transmission of packets held in the buffer unit 427. The transmission unit 422 transmits the packet held in the buffer unit 427 at the transmission timing determined by the scheduling unit 428. The change request unit 429 determines whether or not a rule related to a delay required for the packet is satisfied when the packet is transmitted at the transmission timing determined by the scheduling unit 428. If it is not determined that the delay rule is satisfied, the change request unit 429 transmits a change request signal for requesting the change of the GAP pattern, for example, canceling the next scheduled GAP period, to the base station 3a.

When the base station 3a determines to change the GAP pattern based on the change request signal, for example, to cancel the next GAP period, the scheduling unit 428 executes scheduling again. Then, the change request unit 429 transmits the packet at the transmission timing newly determined by the scheduling unit 428.

FIG. 25 is a flowchart of processing executed by the processor 420 of the terminal device 4. The processing flow is started in step S90, and in step S91, the buffer unit 427 determines whether a packet is held in the buffer unit 427. If it is determined that the packet is held (Yes in process S91), the process flow proceeds to process S92. If it is not determined that the packet is held (No in process S91), the process flow is process S98. Proceed to

When the process flow proceeds to process S92, the scheduling unit 428 sets a transmission schedule of packets held in the buffer unit 427 in consideration of the GAP pattern in process S92. In step S93, when the change request unit 429 transmits a packet according to the transmission schedule determined in step S92, the change request unit 429 determines whether the delay requirement required for the packet is satisfied. If it is determined that the delay rule is satisfied (Yes in process S93), the process flow proceeds to process S97. If it is not determined that the delay rule is satisfied (No in process S93), the process flow proceeds to process S94. .

When the process flow proceeds to process S94, the change request unit 429 transmits a change request signal requesting to cancel the setting of the next GAP period to the base station 3a in process S94. In process S95, the change request unit 429 receives a notification indicating that the setting of the next GAP period is canceled from the base station 3a. In step S <b> 96, the scheduling unit 428 sets the transmission schedule of the packets held in the buffer unit 427 again. In step S97, the transmission unit 422 transmits the packet to the base station 3a based on the transmission schedule set in step S96, that is, the reset transmission schedule. If it is determined in step S93 that the delay rule is satisfied (Yes in step S93), the transmission unit 422 transmits a packet to the base station 3a based on the transmission schedule set in step S92 in step S97. To do.

On the other hand, when the process flow proceeds from process S91 to process S98, the tuning unit 425 tunes the radio processing circuit 410 to the frequency of the radio signal of the other base station 3b in the GAP period in process S98. In process S99, the reception quality measuring unit 424 measures the reception quality of the radio signal of the other base station 3b. In step S100, the reception quality notification unit 423 notifies the measured reception quality to the base station 3a. The process flow ends in process S101 after process S97 or after process S100.

FIG. 26 is a flowchart of processing executed by the processor 320 of the base station 3, and is a flowchart of processing executed mainly when a GAP pattern change request signal is received from the terminal device 4.

The processing flow is started in step S110, and in step S111, the GAP control unit 331 determines whether a GAP pattern change request signal is received from the terminal device 4. If it is determined that a change request signal has been received (Yes in process S111), the process flow proceeds to process S112. If it is not determined that a change request signal has been received (No in process S111), the process flow is process S115. Proceed to

In process S112, the GAP pattern setting unit 330 determines to cancel the setting of the next GAP period based on the change request signal. In step S113, the GAP control unit 331 notifies the terminal device 4 that the setting of the next GAP period is cancelled. Thereafter, in process S <b> 114, the reception unit 321 receives a packet from the terminal device 4.

In process S115, the GAP control unit 331 determines whether the GAP sequence has ended. If it is determined that the GAP sequence has ended (Yes in process S115), the process flow ends in process S116. If it is not determined that the GAP sequence has ended (No in process S115), the process flow proceeds to process S111. Return.

As described above, the uplink packet transmission from the terminal device 4 has been disclosed as the fourth embodiment. Also in the fourth embodiment, when the terminal device 4 competes with packet transmission and processing such as reception quality measurement in the GAP period, the packet transmission is preferentially executed by canceling the setting of the GAP period. Is possible. In the fourth embodiment, an example of canceling the set GAP period is disclosed, but this is an example of changing the GAP pattern. As disclosed in the second and third embodiments, a method of shifting the GAP period backward and a method of shortening the GAP period are also applicable in the fourth embodiment.

DESCRIPTION OF SYMBOLS 1 Network 2

Server

3, 3a, 3b Base station 4 Terminal device 310 Wireless processing circuit 320 Processor 340 Non-volatile memory 350 Volatile memory 360 Network interface circuit 410 Wireless processing circuit 420 Processor 440 Non-volatile memory 450 Volatile memory 321 Receiving part 322 Transmission unit 323 Radio resource allocation unit 324 Handover processing unit 325 Measurement result processing unit 326 Upper device side reception unit 327 Upper device side transmission unit 328 Buffer unit 329 Scheduling unit 330 GAP pattern setting unit 331 GAP control unit 421 Reception unit 422 Transmission unit 423 Reception quality notification unit 424 Reception quality measurement unit 425 Tuning unit 426 GAP control unit 427 Buffer unit 428 Scheduling unit 429 Change request unit

Claims

A wireless communication system having a base station and a terminal device that performs wireless communication with the base station, and performs a different frequency handover,
The base station sets the first period as a measurement period for measuring the first quality of the first radio signal from another base station to the terminal device,
A case where the base station holds a packet transmitted from the base station to the terminal device and for which a rule regarding delay in the wireless communication is defined at a time before the start time of the first period The base station performs a change process for changing the setting of the measurement period,
After the change process, before the change process is executed, the base station transmits the packet to the terminal device within the first period set as the measurement period,
When the base station does not hold the packet at a time before the start time of the first period, the terminal device measures the first quality of the first radio signal in the first period. A wireless communication system.
When the second quality of the second radio signal from the base station to the terminal device falls below a predetermined value, the terminal device measures the first quality of the first radio signal;
The terminal device notifies the base station of the measured first quality of the first radio signal;
The radio according to claim 1, wherein the base station determines whether to perform a handover from the base station to the other base station based on the first quality notified from the terminal device. Communications system.
When the base station holds the packet at a time before the start time of the first period, the base station transmits the packet to the terminal device at a first timing outside the first period. Performing scheduling for the transmission of the packets, such as
If the regulation is not satisfied when the packet is transmitted to the terminal device at the first timing, the change process is executed for the measurement period,
After the change process, before the change process is executed, the base station transmits the packet to the terminal apparatus at a second timing within the first period set as the measurement period. The wireless communication system according to claim 1 or 2.
If the rule is satisfied even if the packet is transmitted to the terminal device at the first timing, the base station does not execute the change process for the measurement period and transmits the packet at the first timing. The wireless communication system according to claim 3, wherein the wireless communication system transmits to the terminal device.
The change process includes a cancel process for canceling the setting with the first period as the measurement period, a shift process for shifting the measurement period to a second period after the first period, and the measurement period. The wireless communication system according to any one of claims 1 to 4, wherein the wireless communication system is at least one of a shortening process for shortening the time.
The base station
When executing the cancellation process, prior to the start of the first period, the terminal device is notified that the setting with the first period as the measurement period is canceled,
When performing the shift process, before the start of the first period, to notify the terminal device shift time information indicating a shift time to shift the measurement period,
The shortening time information indicating a shortening time for shortening the measurement period is notified to the terminal device before the start of the first period when the shortening process is executed. Wireless communication system.
The base station
The radio resource information for specifying radio resources used for transmitting the packet is notified to the terminal device before the start of the first period when the change process is executed. The wireless communication system according to 1.
The first radio signal has a first frequency;
The second radio signal has a second frequency;
The radio communication system according to any one of claims 2 to 7, wherein the different frequency handover is executed between the base station and the other base station.
The terminal device includes a wireless module;
The radio module is tuned to the second frequency when the terminal apparatus performs the radio communication with the base station, and the terminal apparatus adjusts the first quality of the first radio signal of the other base station. The wireless communication system according to claim 8, wherein when the measurement is performed, the wireless communication system is tuned to the first frequency.
A different frequency handover method using a radio communication system having a base station and a terminal device that performs radio communication with the base station,
The base station sets the first period as a measurement period for measuring the first quality of the first radio signal from another base station to the terminal device,
A case where the base station holds a packet transmitted from the base station to the terminal device and for which a rule regarding delay in the wireless communication is defined at a time before the start time of the first period The base station performs a change process for changing the setting of the measurement period,
After the change process, before the change process is executed, the base station transmits the packet to the terminal device within the first period set as the measurement period,
When the base station does not hold the packet at a time before the start time of the first period, the terminal device measures the first quality of the first radio signal in the first period. A different frequency handover method characterized by the above.
When the second quality of the second radio signal from the base station to the terminal device falls below a predetermined value, the terminal device measures the first quality of the first radio signal;
The terminal device notifies the base station of the measured first quality of the first radio signal;
The base station determines whether to perform a handover from the base station to the other base station based on the first quality notified from the terminal device. Frequency handover method.
When the base station holds the packet at a time before the start time of the first period, the base station transmits the packet to the terminal device at a first timing outside the first period. Performing scheduling for the transmission of the packets, such as
If the regulation is not satisfied when the packet is transmitted to the terminal device at the first timing, the change process is executed for the measurement period,
After the change process, before the change process is executed, the base station transmits the packet to the terminal apparatus at a second timing within the first period set as the measurement period. The different frequency handover method according to claim 10 or 11.
If the rule is satisfied even if the packet is transmitted to the terminal device at the first timing, the base station does not execute the change process for the measurement period and transmits the packet at the first timing. It transmits to the said terminal device. The different frequency handover method of Claim 12 characterized by the above-mentioned.
The change process includes a cancel process for canceling the setting with the first period as the measurement period, a shift process for shifting the measurement period to a second period after the first period, and the measurement period. 14. The different frequency handover method according to claim 10, wherein at least one of the shortening processes for shortening the time is performed.
The base station
When executing the cancellation process, prior to the start of the first period, the terminal device is notified that the setting with the first period as the measurement period is canceled,
When performing the shift process, before the start of the first period, to notify the terminal device shift time information indicating a shift time to shift the measurement period,
The shortening time information indicating a shortening time for shortening the measurement period is notified to the terminal device before the start of the first period when the shortening process is executed. Different frequency handover method.
A base station that performs wireless communication with a terminal device,
The base station sets the first period as a measurement period for measuring the first quality of the first radio signal from another base station to the terminal apparatus, and is transmitted from the base station to the terminal apparatus A change to change the setting of the measurement period when the base station holds a packet that has a rule regarding delay in the wireless communication at a time before the start time of the first period A setting unit for executing processing;
After the changing process, before the changing process is executed, the base station transmits the packet to the terminal device within the first period set as the measurement period. ,
When the base station does not hold the packet at a time before the start time of the first period, the terminal device measures the first quality of the first radio signal in the first period. Base station characterized by
When the terminal device notifies the base station of the first quality of the measured first radio signal, the base station sends another base station based on the first quality notified from the terminal device. The base station according to claim 16, further comprising a handover processing unit that determines whether to perform handover to the station.
When the base station holds the packet at a time before the start time of the first period, the base station transmits the packet to the terminal device at a first timing outside the first period. A scheduling unit for performing scheduling related to transmission of the packet,
If the regulation is not satisfied when the packet is transmitted to the terminal device at the first timing, the change process is executed for the measurement period,
After the change process, before the change process is executed, the base station transmits the packet to the terminal apparatus at a second timing within the first period set as the measurement period. The base station according to claim 16 or 17.
If the rule is satisfied even if the packet is transmitted to the terminal device at the first timing, the packet is transmitted to the terminal device at the first timing without executing the changing process for the measurement period. The base station according to claim 18, wherein:
A terminal device that performs wireless communication with a base station,
A notification is received from the base station that the first period is set as a measurement period for measuring the first quality of the first radio signal from another base station to the terminal device. When the base station holds a packet transmitted to the terminal device and for which a rule relating to delay in the wireless communication is defined, at a time before the start time of the first period, A control unit that receives a change notification for changing the setting of the measurement period from the base station;
A receiving unit for receiving the packet transmitted from the base station within the first period;
A measurement unit that measures the first quality of the first radio signal during the first period when the base station does not hold the packet at a time before the start time of the first period. A terminal device characterized by the above.