JP2017152760A - Communication control method, communication system, wireless base station, packet transmission device, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensory quality of a user when the number of wireless terminals connected with a cell suddenly changes.SOLUTION: A communication control method in a communication system including a wireless terminal, a wireless base station for managing a cell which is a communication area the wireless terminal connects, and a packet transmission device capable of transmitting a packet to the wireless terminal via the wireless base station includes the steps of: calculating a change rate of congestion of the cell due to the number of wireless terminals connected with the cell; and performing communication control of the packet depending on the change rate of congestion.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a communication control method, a communication system, a packet transmission device, a radio base station, and a program.

In this specification, the following abbreviations are used.
1xRTT: single carrier Radio Transmission Technology
ACK: Acknowledgement
CCO: Cell Change Order
CDMA: Code Division Multiple Access
CQI: Channel Quality Indicator
CSI: Channel State Information
DS: Differentiated Services
EARFCN: EUTRA Absolute Radio Frequency Channel Number
EDGE: Enhanced Data rates for Global Evolution
EUTRA: Evolved Universal Terrestrial Radio Access
EUTRAN: Evolved Universal Terrestrial Radio Access Network
GERAN: GSM EDGE Radio Access Network
GPS: Global Positioning System
GSM: Global System for Mobile communications
HO: Handover
HRPD: High Rate Packet Data
IP: Internet Protocol
LAN: Local Area Network
LTE: Long Term Evolution
LTE-A: LTE-Advanced
PCI: Physical Cell Identifier
RAT: Radio Access Technology
RRC: Radio Resource Control
RTO: Retransmission Timeout
ssthresh: Slow Start Threshold
TCP: Transmission Control Protocol
TOS: Type of Service
UMTS: Universal Mobile Telecommunications System
UTRAN: Universal Terrestrial Radio Access Network
WAN: Wide Area Network
WiFi: Wireless Fidelity

  With the spread of wireless terminals such as smartphones and tablet terminals, the amount of data traffic for mobile communications has increased rapidly. Introduction is progressing.

  In mobile communication systems such as LTE and LTE-A, a large communication area is configured by distributing a plurality of radio base stations. A communication area managed by a radio base station is called a cell. By giving the antenna directivity, the radio base station can manage a plurality of cells. In addition, by partially overlapping adjacent cells, even when a wireless terminal moves across cells, data communication of the wireless terminal can be continued by the handover (HO) function.

  As an example, the LTE handover function will be described. In LTE, HO occurs when moving from a connected cell to another cell via a radio link. The connected HO source cell is called a source cell, and the HO destination cell is called a target cell. In addition, the state connected to the radio cell is called an active state (RRC_Connected), and the state not connected is called an idle state (RRC_Idle).

  In general, a source cell radio base station performs handover of a radio terminal based on a measurement report transmitted from the radio terminal. Therefore, the source cell radio base station first notifies the radio terminal of the measurement report conditions for detecting the start timing of the handover. The measurement report conditions include a measurement object and a report condition. The measurement target is the frequency (EARFCN) or cell number (PCI) of the wireless cell to be measured. The reporting condition is a trigger condition regarding when measurement information is reported. There are two types of trigger conditions: a predetermined period and an event trigger. However, an event trigger is generally used as a trigger condition for detecting the start timing of handover.

  The source cell radio base station that has received the measurement report transmits a handover request message to the target cell radio base station. The target cell radio base station determines whether or not the requested handover can be accepted. If it is acceptable, the target cell radio base station transmits a message (Handover Request ACK) permitting execution of the handover to the source cell radio base station. When the source cell radio base station receives a message permitting execution of the handover, the source cell radio base station transmits a handover command message to the radio terminal. The radio terminal that has received the handover command message establishes a radio link with the target cell radio base station and transmits a handover complete message to the target cell radio base station.

  An active wireless terminal can smoothly switch wireless cells to be connected by handover. Thereby, even when the wireless terminal moves across wireless cells, the communication interruption time can be minimized. A message exchanged between the radio base stations or between the radio base station and another communication device between the measurement report and the completion of the handover is hereinafter referred to as a “handover message”. The above is the description of the handover function.

  By the way, most of the data traffic received by smartphones and tablet terminals is Internet traffic. A typical communication protocol for Internet traffic is TCP. In TCP, congestion control is performed to adjust the amount of data transmitted by the transmission side according to the congestion state of the network. Basically, when an acknowledgment (ACK) of a transmitted packet is received, the transmission side increases the window size. On the other hand, when the occurrence of congestion such as retransmission timeout is detected, the transmission side decreases the window size.

  Since the communication speed of the wireless terminal is strongly influenced by the wireless congestion level, it is important to perform communication control according to the congestion level. Patent Document 1 discloses a method of estimating a time rate during which radio is used in a wireless LAN as a radio congestion level and controlling the TCP maximum window size based on the radio congestion level. The wireless congestion degree is calculated from packet information in the wireless LAN such as the number of frames. This suppresses TCP packet loss, reduces TCP retransmission, and improves radio frequency usage efficiency. For example, by limiting the TCP window size and controlling so that the wireless congestion level does not become 100%, packet loss and retransmission in the wireless section are reduced.

  Patent Document 2 collects information for determining whether or not the communication accommodated by the base station is congested, and discards the communication by the terminal accommodated in the base station determined to be congested. A technique for calculating a rate and relaying communication of the terminal by a band reduced by the calculated discard rate is described.

  Furthermore, in Patent Document 3, when it is determined that the communication between the information terminal and the information distribution server is congested and the packet loss rate from the information distribution server is increasing, the packet of the distribution data A technique for requesting the information distribution server to change the bit rate from the information terminal is described.

JP 2011-234320 A Japanese Patent Laying-Open No. 2015-0776845 Japanese Patent Laying-Open No. 2015-033095

  The entire disclosure of the above patent document is incorporated herein by reference. The following analysis was made by the present inventors.

  When communication control is performed in consideration of the degree of wireless congestion based on the related technology described above, the user experience is greatly impaired when the degree of cell congestion changes due to a rapid increase or decrease in the number of connected wireless terminals. There is a problem of being. Here, as a factor of the change in the degree of congestion caused by the rapid increase or decrease in the number of connected wireless terminals, there are movements of a large number of users such as movement in public transportation or simultaneous movement in an event venue.

  The technique described in Patent Document 1 determines a window size as congestion control using an actual measurement value of a time rate at which radio is used as the degree of cell congestion. Therefore, when the number of wireless terminals increases or decreases rapidly, dynamic flow control cannot be performed on the wireless base station that relays data transmission to the wireless terminals. For example, when the number of wireless terminals increases rapidly, the degree of cell congestion increases rapidly, and the wireless communication speed per wireless terminal decreases rapidly. At this time, if the data flow rate to the radio base station is not reduced, the buffer in the radio base station overflows, that is, packet loss occurs, resulting in a decrease in the perceived speed and an increase in the completion time of transmission of application data. On the other hand, when the number of wireless terminals rapidly decreases, the degree of cell congestion is rapidly reduced, and the wireless communication speed per wireless terminal increases rapidly. At this time, there is a risk that the buffer will run out because there is no data to be transmitted to the wireless terminal. As a result of these, there is a problem that the user experience quality is greatly impaired.

  In addition, the techniques described in Patent Documents 2 and 3 also control communication by paying attention to a congestion situation at a certain point in time, a communication discard rate, a packet loss rate, and the like. It is difficult to prevent a decrease in the user experience quality when the degree rapidly increases or decreases.

  Therefore, it becomes a problem to improve the user's quality of experience when the number of wireless terminals connected to the cell changes suddenly. An object of the present invention is to provide a communication control method, a communication system, a radio base station, a packet transmission device, and a program that contribute to solving the problem.

  A communication control method according to a first aspect of the present invention includes a radio terminal, a radio base station that manages a cell that is a communication area to which the radio terminal is connected, a packet to the radio terminal via the radio base station. A communication control method in a communication system including a packet transmitting apparatus capable of transmitting, the step of calculating a change rate of congestion of the cell due to the number of wireless terminals connected to the cell, and according to the change rate of the congestion And performing communication control of the packet.

  A communication system according to a second aspect of the present invention includes a radio base station that manages a cell that is a communication area to which a radio terminal is connected, and a packet transmitter that can transmit packets to the radio terminal via the radio base station. And. The radio base station calculates a rate of change in congestion of the cell due to the number of radio terminals connected to the cell. The packet transmission device performs communication control of the packet according to the change rate of the congestion.

  A radio base station according to a third aspect of the present invention is a radio base station that manages a cell that is a communication area to which a radio terminal is connected, and is configured to prevent congestion of the cell due to the number of radio terminals connected to the cell. A congestion degree calculation unit for calculating a rate of change and a packet transmission apparatus capable of transmitting packets to the wireless terminal via the radio base station perform communication control of the packet according to the rate of change of the congestion. And a transmission unit for requesting.

  A packet transmission device according to a fourth aspect of the present invention is a packet transmission device capable of transmitting a packet to the wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected. Change rate of congestion of the cell due to the number of wireless terminals connected to the cell, or a receiving unit that receives a request for communication control of the packet according to the change rate from the radio base station, and change of the congestion A packet transmission control unit that controls communication of the packet according to a rate or the request.

  A packet transmission device according to a fifth aspect of the present invention is a packet transmission device capable of transmitting a packet to the wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected. A receiving unit that receives information on the load on the cell due to the number of wireless terminals connected to the cell from the radio base station, and calculates a change rate of the congestion of the cell based on the information on the load. And a packet transmission control unit for performing communication control of the packet.

  The program according to the sixth aspect of the present invention relates to the cell resulting from the number of radio terminals connected to the cell with respect to a computer provided in a radio base station that manages a cell that is a communication area to which the radio terminal is connected. Processing for calculating the rate of change of congestion of the packet, and performing packet communication control according to the rate of change of congestion for a packet transmission device capable of transmitting packets to the wireless terminal via the wireless base station So as to execute the requesting process. The program can also be provided as a program product recorded on a non-transitory computer-readable storage medium.

  According to the communication control method, the communication system, the radio base station, the packet transmission device, and the program according to the present invention, it is possible to improve the user's quality of experience when the number of radio terminals connected to the cell changes suddenly.

It is a block diagram which illustrates the composition of the radio base station concerning one embodiment. It is a block diagram which illustrates the composition of a packet transmission device according to an embodiment. 1 is a configuration example of a communication system according to a first embodiment. It is a block diagram which shows the structural example of the wireless base station of 1st Embodiment. It is a block diagram which shows the structural example of the packet transmission apparatus of 1st Embodiment. It is a flowchart which shows the operation example of the radio base station of 1st Embodiment. It is a flowchart which shows the operation example 1 of the packet transmission apparatus of 1st Embodiment. It is a flowchart which shows the operation example 2 of the packet transmission apparatus of 1st Embodiment. It is a block diagram which shows the structural example of the wireless base station of 2nd Embodiment. It is a block diagram which shows the structural example of the packet transmission apparatus of 2nd Embodiment. It is a flowchart which shows the operation example of the radio base station of 2nd Embodiment. It is a flowchart which shows the operation example of the packet transmission apparatus of 2nd Embodiment. It is a block diagram which shows the structural example of the wireless base station of 3rd Embodiment. It is a block diagram which shows the structural example of the packet transmission apparatus of 3rd Embodiment. It is a flowchart which shows the operation example of the radio base station of 3rd Embodiment. It is a flowchart which shows the operation example of the packet transmission apparatus of 3rd Embodiment. It is a block diagram which shows the structural example of the wireless base station of 4th Embodiment. It is a block diagram which shows the structural example of the packet transmission apparatus of 4th Embodiment. It is a flowchart which shows the operation example of the wireless base station of 4th Embodiment. It is a flowchart which shows the operation example of the packet transmission apparatus of 4th Embodiment.

  First, an outline of one embodiment will be described. Note that the reference numerals of the drawings attached to this summary are merely examples for facilitating understanding, and are not intended to limit the present invention to the illustrated embodiment.

  FIG. 1 is a block diagram illustrating a configuration of a radio base station 3 according to an embodiment. The radio base station 3 is a radio base station that manages a cell that is a communication area to which a radio terminal is connected (for example, a radio base that manages a radio cell 4-1 that is a communication area to which the radio terminal 5-1 in FIG. 3 is connected). Station 3-1). Referring to FIG. 1, the radio base station 3 transmits a packet to the radio terminal via the radio base station 3 and a congestion degree calculation unit 36 that calculates a change rate of the congestion of the cell due to the number of radio terminals connected to the cell. And a transmission unit 38 that requests a packet transmission apparatus (for example, the packet transmission apparatus 1 in FIG. 3) that can transmit the packet to perform communication control according to a change rate of congestion.

  FIG. 2 is a block diagram illustrating the configuration of the packet transmission device 1 according to an embodiment. The packet device 1 can transmit a packet to a wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected (for example, a wireless communication area to which the wireless terminal 5-1 in FIG. 3 is connected). A packet can be transmitted to the wireless terminal 5-1 through the wireless base station 3-1 managing the cell 4-1. Referring to FIG. 2, the packet transmission device 1 receives, from a radio base station, a rate of change in cell congestion caused by the number of radio terminals connected to the cell or a packet communication control request according to the rate of change. And a packet transmission control unit 18 that performs packet communication control in accordance with the congestion change rate or the request.

  Note that the packet transmission device 1 receives a cell load information from the radio base station that is caused by the number of radio terminals connected to the cell from the radio base station, and calculates a cell congestion change rate based on the load information. And a packet transmission control unit 18 that performs packet communication control according to the calculated rate of change.

  According to one embodiment, since communication control is performed dynamically according to the rate of change (or degree of change) of congestion caused by the number of wireless terminals, even if the degree of congestion changes suddenly, wireless communication is performed. Buffer overflow and buffer depletion at the base station can be suppressed, and as a result, user experience quality can be improved.

  Hereinafter, embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted unless necessary for clarifying the description.

<Embodiment 1>
A communication system according to the first embodiment will be described with reference to the drawings.

[Constitution]
FIGS. 3A and 3B are diagrams illustrating a configuration example of a communication system in the present embodiment. The communication system includes a wireless communication system at least in part. In the present embodiment, LTE will be described as an example of a radio communication system. Referring to FIGS. 3A and 3B, the communication system includes a packet transmission device 1, a network 2, radio base stations 3-1 to 3-2, and radio cells 4-1 to 4-2. And wireless terminals 5-1 to 5-2. The present invention can be applied to both the radio base station 3-1 and 3-2, and is therefore referred to as a radio base station 3 when it is not necessary to distinguish between radio base stations. Similarly, the wireless cells 4-1 to 4-2 and the wireless terminals 5-1 to 5-2 are referred to as a wireless cell 4 and a wireless terminal 5, respectively. In addition, the number of each component of FIG. 3 (a), (b) is an example, for example, the radio base station 3 may have three or more. FIG. 3B omits the depiction of the radio base station 3-2 and the radio cell 4-2. The radio terminal 5 can perform handover between the radio cells 4-1 and 4-2.

  In FIG. 3A, the packet transmission device 1 may be a wireless terminal other than the wireless terminals 5-1 and 5-2, for example, or may be a content transmission device such as a server that distributes content to the wireless terminal 5. There may be. Further, the packet transmission device 1 may be a relay device installed in the network 2 as shown in FIG.

  The packet transmission device 1 transmits a packet addressed to the wireless terminal 5 to the wireless terminal 5. The packet transmission to the wireless terminal 5 may be performed in response to a request from the wireless terminal 5. When the packet transmission device 1 is a content transmission device, the content transmission device divides the content data and transmits it to the wireless terminal 5 as packets. The content data is data such as video and audio.

  The network 2 is a network in which the packet transmission device 1 and the wireless base station 3 are connected, and the packet transmitted by the packet transmission device 1 can be carried to the wireless base station 3. The network 2 may include a core network or a wide area network (WAN) such as an IP network. The packet transmission device 1 may be located inside the network 2 or may be located outside.

  The radio base station 3 manages the radio cell 4 and transmits the packet arriving from the packet transmission device 1 via the radio to the connected radio terminal 5 (downlink communication). Note that communication in the direction from the wireless terminal 5 to the wireless base station 3 (uplink communication) can also be performed via wireless.

  The radio cell 4 is a communication area connectable with the radio base station 3 and is managed by the radio base station 3. Note that the radio cell 4 managed by the radio base station 3 may not be one or two cells as shown in FIGS. 3A and 3B, but may be three or more cells.

  The wireless terminal 5 receives a packet transmitted from the packet transmission device 1 via the wireless base station 3. In addition, the radio terminal 5 reports a measurement report for detecting the start timing of handover, CSI including CQI indicating radio quality, and the like according to an instruction from the radio base station 3.

  FIG. 4 is a block diagram illustrating a configuration example of the radio base station 3 in the present embodiment.

  Referring to FIG. 4, the radio base station 3 includes a congestion degree calculation unit 31. Although not shown in FIG. 4, the radio base station 3 performs a function of receiving downlink channel reception quality information such as CQI from the radio terminal 5 and assigns radio resources to the radio terminal 5 such as frequency blocks. A scheduling function, a function of storing packets addressed to the wireless terminal 5 received via the network 2 in a buffer, a function of transmitting packets stored in the buffer to the wireless terminal 5 and the like are also included. These functions are equivalent to those of a radio base station generally used in a radio communication system, and the configuration and operation thereof are publicly known.

  The congestion degree calculation unit 31 calculates a cell load due to the number of wireless terminals. More specifically, the congestion degree calculation unit 31 calculates the latest and future number of wireless terminals. Further, the congestion degree calculation unit 31 calculates a change rate of congestion from the calculated cell load. Furthermore, the congestion degree calculation unit 31 transmits a transmission rate control request notification to the packet transmission device 1 based on the change rate of the congestion.

  5A and 5B are block diagrams illustrating a configuration example of the packet transmission device 1 in the present embodiment.

  Referring to FIG. 5, the packet transmission device 1 includes a packet transmission control unit 11. Although not shown in FIG. 5, the packet transmission device 1 also includes a functional block for causing the packet transmission device 1 to function as a node that transmits a packet to the wireless terminal 5. For example, the packet transmission device 1 includes a function of receiving a request from the wireless terminal 5 and a function of storing packets addressed to the wireless terminal 5 in advance. Further, the packet transmission device 1 may have a function of relaying packets between other nodes and the radio base station 3.

  The packet transmission control unit 11 receives a transmission rate control request notification from the wireless base station 3 and adjusts the transmission rate to the wireless terminal 5 using the request notification.

  In the present embodiment, transmission rate control is performed as communication control according to the congestion change rate.

[Operation]
Next, an operation example of the radio base station 3 of the present embodiment will be described using the flowchart of FIG.

  The radio base station 3 calculates the latest cell load L_CUE (k) and future cell load L_EUE (k) due to the number of radio terminals from the following formulas (1) and (2) (step S101).

  L_CUE (k) = N_CUE (k) (1)

  L_EUE (k) = L_CUE (k) + N_RxHOREQ (k) −N_TxHOREQ (k) (2)

  Here, k is an identification number of the measurement times and represents the number of measurements. N_CUE (k) represents the number of connected wireless terminals. N_RxHOREQ (k) represents the number of HO Requests received most recently, and N_TxHOREQ (k) represents the number of HO Requests transmitted most recently. Specifically, the number of HO Requests transmitted / received within 100 ms, the number of HO Requests for which handover has not been completed among the transmitted / received HO Requests, and the like can be considered. The number of future wireless terminals can be calculated from equation (2).

  Next, the radio base station 3 calculates the change rate ΔL_UE (k) of the congestion degree from the following equation (3) (step S102).

  ΔL_UE (k) = (L_EUE (k) −L_CUE (k)) / L_CUE (k) (3)

  Next, the radio base station 3 determines whether or not the degree of congestion increases rapidly based on the following equation (4) (step S103). Th_L_UE_UP is a threshold value (> 0) for determining a rapid increase.

  ΔL_UE (k)> Th_L_UE_UP Expression (4)

  When Expression (4) is satisfied (step S103, Yes), the radio base station 3 transmits a transmission rate decrease request notification to the packet transmission device 1 (step S104). Here, the wireless terminal that is the target of the transmission rate reduction request is a wireless terminal that is accommodated in the wireless cell 4 in the future.

  On the other hand, when Expression (4) is not satisfied (Step S103, No), the wireless base station 3 determines whether or not the congestion degree is rapidly reduced based on Expression (5) below (Step S105).

  ΔL_UE (k) <Th_L_UE_DOWN ... Formula (5)

  Th_L_UE_DOWN is a threshold value (<0) for determining a sudden decrease.

  When Expression (5) is satisfied (step S105, Yes), the radio base station 3 transmits a transmission rate increase request notification to the packet transmission device 1 (step S106). As in step 104, the wireless terminal that is the target of the transmission rate increase request is a wireless terminal that will be accommodated in the wireless cell 4 in the future.

  The radio base station 3 may calculate the change rate ΔL_UE (k) of the degree of congestion using the difference between L_EUE (k) and L_CUE (k) instead of calculating the ratio as in Expression (3).

  In addition, when the execution interval of the flowchart of FIG. 6 is as short as about 10 ms, the radio base station 3 may use the number of connected radio terminals as a calculation method of L_CUE (k) and L_EUE (k). In this case, Formula (6) and Formula (7) are used instead of Formula (1) and Formula (2).

  L_CUE (k) = L_CUE (k−1) (6)

  L_EUE (k) = N_CUE (k) (7)

  Further, as exception processing, when L_CUE (k) or L_EUE (k) is a small value (for example, 0), processing that does not transmit a request notification may be inserted.

  In addition to this embodiment, the wireless terminal to be counted for N_CUE (k) may be the wireless terminal 5 whose data size stored in the buffer is a predetermined value or more, or a packet of specific traffic is stored in the buffer. The stored wireless terminal 5 may be used, or the wireless terminal 5 may simply be active (RRC_Connected).

  Also, the radio base station 3 replaces N_TxHOREQ (k) (number of HO Request transmissions) used in the calculation of L_EUE (k) with a measurement report transmitted from the radio terminal for detecting the HO start timing. May be. Alternatively, the radio base station 3 may determine the position of the radio terminal 5 from the Doppler frequency of the radio terminal 5 or the measurement report, determine whether or not to implement the handover, and count as N_TxHOREQ (k). Alternatively, if the radio base station 3 can acquire the GPS information of the radio terminal 5, it may determine whether or not to perform handover from the GPS position information and may count as N_TxHOREQ (k).

  In addition, when the radio base station 3 calculates L_CUE (k) and L_EUE (k), the radio base station 3 weights with the data size of each radio terminal accumulated in the buffer as in the following equations (8) and (9). May be.

  L_CUE (k) = Σ {BUF (i) / TH_BUF} (8)

  L_EUE (k) = L_CUE (k) + N_RxHOREQ (k) −Σ {BUF (i_TxHOREQ) / TH_BUF}... (9)

  Where Σ is the sum, i is the identification number of the wireless terminal, BUF (i) is the buffer size of the wireless terminal 5 whose identification number is i, TH_BUF is the correction coefficient, and i_TxHOREQ is the terminal of the terminal that transmitted the HO Request Represents an identification number.

  As a notification method from the radio base station 3 to the packet transmission device 1, for example, the following three methods are conceivable. The radio base station 3 transmits a notification for each radio terminal. However, if it is the 1st method shown below, the wireless base station 3 may transmit a notification collectively for every cell. In the case of batch transmission in cell units, the radio base station 3 also transmits radio terminal identification information for distinguishing radio terminals that will be accommodated in the radio cell 4 in the future.

  The first method is a method for generating dedicated packet data for the wireless base station 3 to transmit notification information.

  The second method is a method in which the radio base station 3 writes notification information in a specific area of an existing layer of an existing packet transmitted from the radio base station 3 to the packet transmission device 1. The existing packet refers to a TCP ACK response packet or the like. The specific area refers to an unused area of the IP header. Specifically, it refers to the Reserved Bits, Options field, Padding field, etc. of the TOS field and DS field.

  The third method is a method of introducing a tunneling protocol to an existing packet transmitted from the radio base station 3 to the packet transmitter 1 and adding notification information to the header information of the tunneling protocol in which the radio base station 3 is introduced. It is.

  Next, an operation example of the packet transmission device 1 according to the present embodiment will be described with reference to the flowchart of FIG.

  The packet transmission device 1 determines whether or not the notification received from the wireless base station 3 is a transmission rate reduction request (step S201). If it is a decrease request (step S201, Yes), the packet transmission device 1 suppresses the transmission rate to the corresponding wireless terminal 5 (step S202). On the other hand, if the request is an increase request (No at Step S201), the packet transmission device 1 increases the transmission rate to the corresponding wireless terminal 5 (Step S203).

  A transmission rate control method performed by the packet transmission device 1 will be described with a specific example.

  A case where the communication protocol is TCP will be described. When suppressing the transmission rate, the packet transmission device 1 reduces the window size by a predetermined rate. On the other hand, when increasing the transmission rate, the packet transmission device 1 increases the window size by a predetermined rate. By reducing the window size, the number of packets that can be transmitted at one time is reduced.

  As another method, when the transmission rate is suppressed, the packet transmission device 1 increases the TCP retransmission timer (RTO). On the other hand, when increasing the transmission rate, the packet transmission device 1 decreases the RTO. By setting the RTO to a large value, the retransmission interval can be increased.

  As another method, when the transmission rate is suppressed, the packet transmission device 1 sets ssthresh for determining the TCP state to a value smaller by a predetermined ratio. On the other hand, when increasing the transmission rate, the packet transmission device 1 sets ssthresh to a value larger by a predetermined percentage. By setting ssthresh to a small value, the TCP state in which the window size can be exponentially increased by receiving the ACK on the TCP transmission side becomes longer.

  A method for controlling the transmission rate when the application can be identified as a moving image will be described with a specific example. When the transmission rate is suppressed, the packet transmission device 1 reduces the image quality of the moving image. On the other hand, when increasing the transmission rate, the packet transmission device 1 increases the image quality of the moving image. Here, the image quality refers to the number of pixels and the number of frames. When the image quality is lowered, the packet transmission device 1 reduces at least one of the number of pixels and the number of frames. Alternatively, when the transmission rate is suppressed, the packet transmission device 1 lowers the pacing target value. On the other hand, when increasing the transmission rate, the packet transmission device 1 increases the pacing target value. A combination of pacing start and stop may be used. Here, pacing is a technique for changing the amount of transmission according to traffic conditions and suppressing video playback stop and unnecessary traffic transmission.

  Further, the operation of the packet transmission device 1 of the present embodiment may be as follows. That is, as shown in the flowchart of FIG. 8, in response to the transmission rate request notification received from the radio base station 3, a confirmation response may be transmitted to the radio base station 3 after performing the transmission rate control ( Steps S211, S212). Alternatively, the packet transmission device 1 may determine whether to follow the transmission rate request notification received from the radio base station 3 in consideration of its own state. In this case, the packet transmission device 1 transmits an acknowledgment to the radio base station 3 when the transmission rate is controlled.

  In the communication system according to the present embodiment, the radio base station obtains the cell load caused by the radio terminal, calculates the change rate of the congestion degree from the obtained cell load, and packetizes the transmission rate control request based on the calculated change rate. Send to the transmitter. Further, the packet transmission apparatus controls the transmission rate according to the request. According to such a configuration, the communication system can dynamically respond to a sudden change in the number of wireless terminals connected to the cell, and can improve the quality of experience of the user.

<Embodiment 2>
Next, a communication system according to the second embodiment will be described with reference to the drawings.

[Constitution]
FIG. 9 is a block diagram illustrating a configuration example of the radio base station 3 in the present embodiment.

  Referring to FIG. 9, the radio base station 3 includes a congestion degree calculation unit 32. Although not shown in FIG. 9, the radio base station 3 may have other functional blocks as in the first embodiment.

  Similar to the congestion degree calculation unit 31 of the first embodiment, the congestion degree calculation unit 32 calculates a cell load due to the number of wireless terminals. Further, the congestion degree calculation unit 32 calculates the change rate of the congestion from the calculated cell load in the same manner as the congestion degree calculation unit 31 of the first embodiment. In addition, the congestion degree calculation unit 32 transmits information regarding the calculated change rate of congestion to the packet transmission device 1.

  FIGS. 10A and 10B are block diagrams illustrating a configuration example of the packet transmission device 1 according to the present embodiment.

  Referring to FIG. 10, the packet transmission device 1 includes a packet transmission control unit 12. Although not shown in FIG. 10, the packet transmission device 1 may have other functional blocks as in the first embodiment.

  The packet transmission control unit 12 receives information related to the congestion change rate from the radio base station 3 and adjusts the transmission rate to the radio terminal 5 based on the congestion change rate.

[Operation]
Next, an operation example of the radio base station 3 of this embodiment will be described using the flowchart of FIG. The flowchart of this embodiment differs from the first embodiment in that steps S103 to S106 are deleted from the flowchart of FIG. 6 and step S111 is added.

  The radio base station 3 transmits information on the calculated congestion change rate ΔL_UE (k) to the packet transmission device 1 (step S111).

  Note that, as in steps S103 and S104 in the flowchart of FIG. 6, it is determined whether the degree of congestion increases rapidly and / or decreases rapidly. If the congestion level rapidly increases or decreases, the radio base station 3 executes step S111. Thus, the change rate of congestion may be transmitted to the packet transmission device 1.

  Next, an operation example of the packet transmission device 1 of the present embodiment will be described using the flowchart of FIG. The flowchart of the present embodiment is different from the first embodiment in that step S201 is deleted from the flowchart of FIG. 7 and steps S211 to S212 are added.

  The packet transmission device 1 determines whether the degree of congestion increases rapidly from the above-described equation (4) using the information regarding the change rate of congestion received from the radio base station 3 (step S211). When Expression (4) is satisfied (step S211, Yes), the packet transmission device 1 suppresses the transmission rate to the corresponding wireless terminal 5 (step S202). On the other hand, when Expression (4) is not satisfied (Step S211, No), the packet transmission device 1 determines whether or not the degree of congestion is drastically reduced from Expression (5) described above (Step S212). When Expression (5) is satisfied (step S212, Yes), the packet transmission device 1 increases the transmission rate to the corresponding wireless terminal 5 (step S203).

  In the communication system according to the present embodiment, the radio base station obtains the cell load caused by the radio terminal, calculates the change rate of the congestion degree from the obtained cell load, and sends the calculated change rate to the packet transmitting apparatus. The packet transmission apparatus controls the transmission rate according to the change rate. According to such a configuration, the communication system can dynamically respond to a sudden change in the number of wireless terminals connected to the cell, and can improve the quality of experience of the user. Further, according to the present embodiment, it is possible to reduce the load on the radio base station side as compared with the first embodiment by determining the control content of the transmission rate according to the rate of change on the packet transmitting device side. It becomes possible.

<Embodiment 3>
Next, a communication system according to a third embodiment of the present invention will be described with reference to the drawings.

[Constitution]
FIG. 13 is a block diagram illustrating a configuration example of the radio base station 3 in the present embodiment.

  Referring to FIG. 13, the radio base station 3 includes a congestion degree calculation unit 33. Although not shown in FIG. 13, the radio base station 3 may have other functional blocks as in the first embodiment.

  Similar to the congestion degree calculation unit 31 of the first embodiment, the congestion degree calculation unit 33 calculates a cell load due to the number of wireless terminals. In addition, the congestion degree calculation unit 33 transmits information regarding the calculated cell load to the packet transmission device 1.

  FIGS. 14A and 14B are block diagrams illustrating a configuration example of the packet transmission device 1 according to the present embodiment.

  Referring to FIG. 14, the packet transmission device 1 includes a packet transmission control unit 13. Although not shown in FIG. 14, the packet transmission device 1 may have other functional blocks as in the first embodiment.

  The packet transmission control unit 13 receives information on the cell load from the radio base station 3, and calculates the change rate of the congestion of the cell load. Further, the packet transmission control unit 13 adjusts the transmission rate to the wireless terminal 5 based on the change rate of congestion.

[Operation]
Next, an operation example of the radio base station 3 of the present embodiment will be described using the flowchart of FIG. The flowchart of this embodiment differs from the first embodiment in that steps S102 to S106 are deleted from the flowchart of FIG. 6 and step S121 is added.

  The radio base station 3 transmits information L_EUE (k) related to the cell load caused by the calculated number of radio terminals to the packet transmission device 1 (step S121).

  Next, an operation example of the packet transmission device 1 of the present embodiment will be described using the flowchart of FIG. In the flowchart of this embodiment, step S201 is deleted from the flowchart of FIG. 7, and steps S211 to S212 of FIG. 12 of the second embodiment and step S221 are newly added. Is different.

  The packet transmission device 1 calculates the change rate ΔL_UE (k) of the congestion degree from the above-described equation (3) using the future cell load received from the radio base station 3 (step S221). The packet transfer apparatus 1 uses L_EUE (k−1) reported last time as L_CUE (k) for calculating ΔL_UE (k).

  In the present embodiment, the radio base station 3 transmits only information related to the future cell load L_EUE (k) to the packet transmission device 1. However, the radio base station 3 may also transmit information regarding the latest cell load L_CUE (k) to the packet transmission device 1 together. In this case, the packet transmission device 1 may calculate the change rate ΔL_UE (k) of the congestion degree from the equation (3) using the received L_CUE (k).

  In the communication system according to the present embodiment, the radio base station obtains the cell load caused by the radio terminal, and sends the obtained cell load to the packet transmission apparatus. Further, the packet transmission device calculates a change rate of the congestion degree from the cell load, and controls the transmission rate according to the calculated change rate. According to such a configuration, the communication system can dynamically respond to a sudden change in the number of wireless terminals connected to the cell, and can improve the quality of experience of the user. In addition, according to the present embodiment, the process of calculating the change rate of the congestion degree from the cell load and the process of determining the control content of the transmission rate according to the change rate are performed on the side of the packet transmission device, so that the second Compared with the embodiment, the load on the radio base station side can be further reduced.

<Embodiment 4>
Next, a communication system according to a fourth embodiment will be described with reference to the drawings.

[Constitution]
In the present embodiment, an example is assumed in which, in addition to LTE, RATs other than LTE such as WiFi coexist as a wireless communication system. In this embodiment, a wireless terminal 5 connected by LTE is assumed.

  FIG. 17 is a block diagram illustrating a configuration example of the radio base station 3 in the present embodiment.

  Referring to FIG. 17, the radio base station 3 includes a congestion degree calculation unit 34. Although not shown in FIG. 17, the radio base station 3 may have other functional blocks as in the first embodiment.

  Similar to the congestion degree calculation unit 31 of the first embodiment, the congestion degree calculation unit 34 calculates a cell load due to the number of wireless terminals. Further, the congestion degree calculation unit 34 calculates the change rate of the congestion from the calculated cell load in the same manner as the congestion degree calculation unit 31 of the first embodiment. Furthermore, the congestion degree calculation unit 34 transmits a communication control request notification to the packet transmission device 1 based on the change rate of the congestion. Specifically, a transmission rate control request and a request for switching a communication path to another RAT, that is, WiFi.

  18A and 18B are block diagrams illustrating a configuration example of the packet transmission device 1 according to the present embodiment.

  Referring to FIG. 18, the packet transmission device 1 includes a packet transmission control unit 14. Although not shown in FIG. 18, the packet transmission device 1 may have other functional blocks as in the first embodiment.

  The packet transmission control unit 14 receives a communication control request notification from the wireless base station 3, and uses the request notification to control communication with the wireless terminal 5. Specifically, the packet transmission control unit 14 controls the transmission rate and switches the communication path to RAT other than LTE, that is, WiFi.

  In the present embodiment, unlike the first to third embodiments, communication path switching control is performed in addition to transmission rate control as communication control according to the change rate of congestion.

[Operation]
Next, an operation example of the radio base station 3 of the present embodiment will be described using the flowchart of FIG. The flowchart of the present embodiment is different from the first embodiment in that step S104 is deleted from the flowchart of FIG. 6 and step S131 is added.

  When the calculated congestion change rate ΔL_UE (k) satisfies the equation (4) (step S103, Yes), the wireless base station 3 transmits a connection request to another RAT to the packet transmission device 1 (step S131). ).

  Next, an operation example of the packet transmission device 1 of the present embodiment will be described using the flowchart of FIG. The flowchart of this embodiment is different from that of the first embodiment in that steps S201 and S202 are deleted from the flowchart of FIG. 7 and steps S231 to 234 are added.

  The packet transmission device 1 determines whether or not the notification received from the radio base station 3 is a connection request to another RAT (step S231). When it is a connection request to another RAT (step S231, Yes), the packet transmission device 1 performs connection processing to the other RAT of the corresponding wireless terminal 5, that is, connection processing to WiFi (step S232). Packet transmission to the wireless terminal 5 is transmitted from another RAT (step S233). On the other hand, when the request is not a connection request to another RAT (step S231, No), the packet transmission device 1 determines whether or not it is a transmission rate increase request (step S234). When it is a request to increase the transmission rate (step S234, Yes), the packet transmission device 1 increases the transmission rate to the corresponding wireless terminal 5 (step S203).

  Further, in this embodiment, after connecting to another RAT, the subsequent wireless terminal packet transmission is performed from the other RAT. However, LTE and RAT (WiFi) other than LTE may be used together.

  In the present embodiment, the wireless base station 3 transmits a connection request to the other RAT to the packet transmission device 1. However, the wireless base station 3 sends a connection request to the other RAT to the corresponding wireless terminal 5. You may send it. For example, the radio base station 3 can use a message instructing one of Inter-RAT handover, CCO, and Redirection to instruct the radio terminal 5 to connect to another RAT cell.

  Inter-RAT handover is, for example, handover from LTE (EUTRAN) to UMTS (UTRAN), GSM (GERAN), CDMA2000 1xRTT, or CDMA2000 HRPD. Inter-RAT handover can specify a target RAT, radio resources of the RAT, and the like by a MobilityFromEUTRACommand message.

  Similarly, CCO is RAT switching from LTE (EUTRAN) to GSM (GERAN). RAT switching by CCO can specify a target RAT (that is, GERAN), a radio resource of the RAT, and the like by a MobilityFromEUTRACommand message.

  Redirection is, for example, switching from LTE (EUTRAN) to UMTS (UTRAN), GSM (GERAN), CDMA2000 1xRTT, or CDMA2000 HRPD. For switching by Redirection, the target RAT and frequency (RedirectedCarrierInfo) can be specified by the RRCConnectionRelease message.

  Or you may implement by introduce | transducing a new apparatus and the wireless base station 3 corresponding also to WiFi communication.

  In the present embodiment, connection to another RAT is performed as communication path switching control, but connection to another cell may be performed. Here, the other cells include cells of different radio base stations, cells different depending on the directional antenna, or cells having different frequencies.

  Further, in the present embodiment, the communication control performed by the radio base station 3 is determined. However, a configuration for determining by the packet transmission device 1 may be adopted as in the second or third embodiment.

  In the present embodiment, as communication control according to the change rate of congestion, in addition to transmission rate control, communication path switching control is also performed, so that it is more flexible than the first to third embodiments. Communication control becomes possible, and the quality of experience of the user when the number of wireless terminals connected to the cell changes suddenly can be further improved.

<Other embodiments>
As mentioned above, although several embodiment of this invention was described, this invention is not limited to said embodiment.

Further, the above-described wireless base station, packet transmission device, and wireless terminal can be realized by hardware, software, or a combination thereof. In addition, the above-described radio base station, packet transmission device, and radio terminal control method can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.
Moreover, about each said embodiment, you may implement | achieve with the communication apparatus provided with the function of the wireless base station 3 and the packet transmission apparatus 1 in one apparatus.

  As mentioned above, although several embodiment of this invention was described, this invention is not limited to said embodiment, A various change and combination are possible in the range which does not deviate from the summary of this invention already described. Of course.

A part or all of the above embodiment may be described as in the following supplementary notes, but is not limited thereto.
(Appendix 1)
This is as in the communication control method according to the first aspect.
(Appendix 2)
Calculating the rate of change of congestion using the number of wireless terminals connected to the cell;
The communication control method according to attachment 1.
(Appendix 3)
Calculating a rate of change of the congestion using a message exchanged between the wireless terminal and the wireless base station for handover,
The communication control method according to Supplementary Note 2, wherein
(Appendix 4)
The radio base station includes a buffer for storing the packet,
Calculating the rate of change of the congestion taking into account the size of the packets stored in the buffer;
The communication control method according to attachment 3.
(Appendix 5)
The wireless terminal to be controlled by the communication control includes a wireless terminal accommodated in the cell both before and after the change of the congestion,
The communication control method according to attachment 1.
(Appendix 6)
The communication control is control of a transmission rate of the packet.
The communication control method according to attachment 1.
(Appendix 7)
The communication control is control for changing a communication path of the packet.
The communication control method according to attachment 1.
(Appendix 8)
The control of the transmission rate is a control for suppressing the transmission rate when the change rate of the congestion is larger than a predetermined threshold value.
The communication control method according to attachment 6.
(Appendix 9)
The transmission rate control is a control to increase the transmission rate when the change rate of the congestion is smaller than a predetermined threshold.
The communication control method according to attachment 6.
(Appendix 10)
The control for suppressing the transmission rate is a control for reducing the transmission window size of the communication protocol by a predetermined rate.
The communication control method according to attachment 8.
(Appendix 11)
The control for increasing the transmission rate is control for increasing the transmission window size of the communication protocol by a predetermined rate.
The communication control method according to attachment 9.
(Appendix 12)
The control for suppressing the transmission rate is a control for increasing the retransmission timer of the communication protocol.
The communication control method according to attachment 8.
(Appendix 13)
The control for increasing the transmission rate is control for decreasing the retransmission timer of the communication protocol.
The communication control method according to attachment 9.
(Appendix 14)
The control for suppressing the transmission rate is a control for reducing a threshold value serving as a reference for determining the transmission window size of the communication protocol when congestion occurs by a predetermined ratio.
The communication control method according to attachment 8.
(Appendix 15)
The control for increasing the transmission rate is a control for increasing a threshold value serving as a reference for determining the transmission window size of the communication protocol when congestion occurs by a predetermined ratio.
The communication control method according to attachment 9.
(Appendix 16)
The control for suppressing the transmission rate is control for reducing the image quality of the moving image.
The communication control method according to attachment 8.
(Appendix 17)
The control for increasing the transmission rate is control for increasing the image quality of the moving image.
The communication control method according to attachment 9.
(Appendix 18)
When the change rate of the congestion is larger than a predetermined threshold, the communication path of the packet data is changed.
The communication control method according to attachment 7.
(Appendix 19)
The change of the communication path is to select another cell.
The communication control method according to attachment 7.
(Appendix 20)
The change of the communication path is to select another radio access method (RAT).
The communication control method according to attachment 7.
(Appendix 21)
The communication system according to the second aspect is as described above.
(Appendix 22)
The radio base station generates dedicated packet data and requests the packet transmission device to control communication of the packet.
The communication system according to attachment 21.
(Appendix 23)
The radio base station uses the existing packet header to request communication control of the packet from the packet transmission device.
The communication system according to attachment 21.
(Appendix 24)
The radio base station introduces a tunneling protocol and requests the packet transmission apparatus to control communication of the packet.
The communication system according to attachment 21.
(Appendix 25)
The packet transmission device transmits an acknowledgment to the radio base station when performing communication control of the packet in response to the request,
The communication system according to any one of appendices 21 to 24.
(Appendix 26)
As in the radio base station according to the third aspect.
(Appendix 27)
As in the packet transmission device according to the fourth aspect.
(Appendix 28)
A radio base station that manages a cell that is a communication area to which a radio terminal is connected,
A congestion degree calculation unit for calculating a change rate of congestion of the cell due to the number of wireless terminals connected to the cell;
A transmission unit that transmits the rate of change of congestion to a packet transmission device capable of transmitting packets to the wireless terminal via the wireless base station,
A wireless base station characterized by that.
(Appendix 29)
A radio base station that manages a cell that is a communication area to which a radio terminal is connected,
A congestion degree calculation unit for calculating the load of the cell due to the number of wireless terminals connected to the cell;
A transmission unit that transmits information indicating the load to a packet transmission device capable of transmitting a packet to the wireless terminal via the wireless base station,
A wireless base station characterized by that.
(Appendix 30)
A program according to the sixth aspect.
(Appendix 31)
For a computer provided in a packet transmission device capable of transmitting a packet to the wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected,
A rate of change in congestion of the cell due to the number of radio terminals connected to the cell, or a process of receiving a request for communication control of the packet according to the rate of change from the radio base station;
Performing a communication control of the packet according to the change rate of the congestion or the request,
A program characterized by that.
(Appendix 32)
For a computer provided in a packet transmission device capable of transmitting a packet to the wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected,
Processing for receiving from the radio base station information related to the load on the cell due to the number of radio terminals connected to the cell;
Calculating a change rate of congestion of the cell based on the information about the load, and performing a process of performing communication control of the packet according to the calculated change rate,
A program characterized by that.

  It should be noted that the entire disclosure of the above patent document is incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiment can be changed and adjusted based on the basic technical concept. Further, various combinations or selections of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible within the scope of the entire disclosure of the present invention. is there. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea. In particular, with respect to the numerical ranges described in this document, any numerical value or small range included in the range should be construed as being specifically described even if there is no specific description.

DESCRIPTION OF SYMBOLS 1 Packet transmitter 2 Network 3, 3-1, 3-2 Wireless base station 4-1, 4-2 Wireless cell 5-1, 5-2 Wireless terminal 11-14, 18 Packet transmission control part 16 Receiving part 31- 34, 36 Congestion degree calculator 38 Transmitter

Claims (10)

Communication control in a communication system including a wireless terminal, a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected, and a packet transmission device that can transmit a packet to the wireless terminal via the wireless base station A method,
Calculating a rate of change in congestion of the cell due to the number of wireless terminals connected to the cell;
Performing communication control of the packet according to the change rate of the congestion,
A communication control method characterized by the above. Calculating the rate of change of congestion using the number of wireless terminals connected to the cell;
The communication control method according to claim 1. Calculating a rate of change of the congestion using a message exchanged between the wireless terminal and the wireless base station for handover,
The communication control method according to claim 2. The communication control is control of a transmission rate of the packet.
The communication control method according to claim 1. The communication control is control for changing a communication path of the packet.
The communication control method according to claim 1. A radio base station that manages a cell that is a communication area to which a radio terminal is connected;
A packet transmission device capable of transmitting a packet to the wireless terminal via the wireless base station,
The radio base station calculates the rate of change in congestion of the cell due to the number of radio terminals connected to the cell,
The packet transmission device performs communication control of the packet according to a change rate of the congestion.
A communication system characterized by the above. A radio base station that manages a cell that is a communication area to which a radio terminal is connected,
A congestion degree calculation unit for calculating a change rate of congestion of the cell due to the number of wireless terminals connected to the cell;
A transmission unit that requests a packet transmission device capable of transmitting a packet to the wireless terminal via the wireless base station to perform communication control of the packet according to a change rate of the congestion,
A wireless base station characterized by that. A packet transmission device capable of transmitting a packet to the wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected;
A rate of change in congestion of the cell due to the number of radio terminals connected to the cell, or a reception unit that receives a request for communication control of the packet according to the rate of change from the radio base station;
A packet transmission control unit that performs communication control of the packet according to the change rate of the congestion or the request,
A packet transmitter characterized by the above. A packet transmission device capable of transmitting a packet to the wireless terminal via a wireless base station that manages a cell that is a communication area to which the wireless terminal is connected;
A receiving unit for receiving, from the radio base station, information related to the load on the cell caused by the number of radio terminals connected to the cell;
A packet transmission control unit that calculates a change rate of congestion of the cell based on the information on the load, and performs communication control of the packet according to the calculated change rate;
A packet transmitter characterized by the above. For a computer provided in a wireless base station that manages a cell that is a communication area to which a wireless terminal is connected,
Processing to calculate the rate of change of congestion of the cell due to the number of wireless terminals connected to the cell;
A process for requesting a packet transmission apparatus capable of transmitting a packet to the wireless terminal via the wireless base station to perform communication control of the packet according to the change rate of the congestion is executed.
A program characterized by that.

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