JP2018026711A - QoS control system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a QoS control system and method, capable of ensuring low delay property of a preferential type flow without adding a function to a radio base station.SOLUTION: A QoS control system 100 having a transfer function is disposed between an eNB 20 and an EPC 10. The QoS control system 100 includes: a congestion detection section 150 for analyzing a TCP packet to be transferred and detecting occurrence of packet loss in a radio section; a bandwidth control section 110 for controlling to narrow a bandwidth of a best effort type flow when packet loss occurs.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a QoS control technique in a mobile network.

  With the development of IoT (Internet of Things), the concept of Tactile Internet that conveys human skin sensations and reactions over a network has been proposed. The Tactile Internet is required to have low latency on the order of milliseconds. In order to realize a network with such strict delay requirements, it is necessary to review the network architecture.

  A method called Mobile Edge Computing has been proposed as a network architecture for realizing low-latency communication. Mobile Edge Computing aims to reduce the communication delay between the server and the terminal by deploying servers and applications in the data center near the terminal. To achieve Mobile Edge Computing with ETSI ISG MEC A framework has been proposed (see Non-Patent Document 1).

  As a specific implementation technique of Mobile Edge Computing, as shown in Non-Patent Document 2, in the S1 interface section connecting eNB (evolved Node B) and EPC (Evolved Packet Core) defined in 3GPP, S1 By adding a packet transmission / reception function to the bearer, a server or an application deployed in a data center near the terminal can communicate with the terminal via the S1 interface.

"Mobile-Edge Computing-Introductory Technical White Paper", ETSI ISG MEC, 2014 "Intel NEV SDK Product Brief", Intel White Paper, [online], [searched July 14, 2016], Internet <URL: https: //networkbuilders.intel.com/docs/Intel_Wireless_Product_Brief_for_IDF_v8.pdf>

  When Mobile Edge Computing is realized by the technique shown in Non-Patent Document 2, it is possible to communicate with a data center near the terminal and shorten the physical propagation delay related to communication. However, in addition to the propagation delay, there is a queuing delay due to congestion in addition to the propagation delay, and the radio band in the wireless section is limited in the mobile network. Cheap.

  In order to realize low-delay communication, it is necessary to distinguish between a best-effort flow with a mild delay condition and a priority-type flow with a severe delay condition, and to prevent the priority flow from staying even when congestion occurs in a wireless section.

  As a means for realizing such control, there is a QoS (Quality of Service) control technology, and by incorporating a QoS control function into an eNB or Mobile Edge Computing platform, control without retaining a priority flow is possible.

  However, in the QoS control defined in 3GPP, it is defined that the eNB performs QoS control in units of bearers established between the EPC and the terminal. In the method shown in Non-Patent Document 2, since the best effort type flow and the priority type flow are mixed in the bearer, the eNB is required to identify these flows and perform QoS control, but the implementation exceeds the specifications of 3GPP. Therefore, it is necessary to add a new function to the eNB. In addition, the bearer established between eNB and EPC is comprised by the combination of several bearers, such as a S1 bearer and a radio bearer.

  As a direction for solving such a problem, it is not realistic from the viewpoint of cost to add functions to all existing eNBs deployed in the mobile network. For this reason, introducing QoS control into the Mobile Edge Computing platform instead of the eNB is considered as a solution.

  However, since the Mobile Edge Computing platform cannot directly grasp the congestion state of the wireless section, detection of the congestion state becomes an issue. In addition, there is a possibility that the bandwidth usage rate in the wireless section may be lowered when excessive control is applied when bandwidth is limited for the best effort flow at the time of congestion.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a QoS control system and method capable of ensuring low latency of a priority flow without adding a function to a radio base station. Is to provide.

  In order to achieve the above object, the present invention provides a TCP that is provided between a radio base station and a core network in a mobile network that includes a radio base station and a core network and in which a priority flow and a best effort flow are mixed. A QoS control system having a packet transfer function, a packet loss detecting means for analyzing a TCP packet to be transferred to detect occurrence of a packet loss in a wireless section, and a bandwidth of a best effort flow when a packet loss occurs And a band control means for controlling the frequency to be narrow.

  According to the present invention, the priority flow is affected by the best-effort flow by detecting congestion in the radio section and limiting the bandwidth of the best-effort flow without adding a function to the radio base station. Thus, packets can be prevented from staying in the radio base station, and as a result, communication with a low priority delay flow can be realized.

The figure explaining the outline | summary of a radio | wireless communications system The figure explaining the congestion detection function of a QoS control system The figure explaining the detection method of the 1st packet loss The figure explaining the detection method of the 2nd packet loss The figure explaining the calculation method of the limit data amount of the band limitation Configuration diagram of QoS control system Configuration diagram of bandwidth controller The figure explaining operation of a band control part The figure explaining operation | movement of a TCP data packet process part The figure explaining operation | movement of a TCPACK packet process part The figure explaining an example of the management data of a flow management part The figure explaining operation of the congestion detection part The figure explaining an example of the management data of a quality control part

  A radio communication system according to the present embodiment will be described with reference to FIG. FIG. 1 is a configuration diagram illustrating an outline of a wireless communication system according to the present invention.

  The present invention is intended for a mobile network such as the well-known LTE (Long Term Evolution), and FIG. 1 will be described by taking LTE as an example. The network configuration in LTE includes an EPC 10 as a core network and an eNB 20 as a radio base station that accommodates the terminal 1. The EPC 10 is connected to one or more external networks including the Internet 30 and includes a gateway with the external network. As is well known, when the terminal 1 communicates with the Internet 30, a flow related to the communication is formed between the radio bearer 41 formed between the terminal 1 and the eNB 20, and between the eNB 20 and the EPC 10. Pass the S1 bearer 42.

  In the present invention, it is assumed that a Mobile Edge Computing platform (hereinafter referred to as “MEC platform”) 50 for realizing low-latency communication is provided. The MEC platform 50 is disposed between the eNB 20 and the EPC 10 and in the vicinity of the eNB 20. An application 60 that provides a service to the terminal 1 is connected to the MEC platform 50. The MEC platform 50 provides a packet transmission / reception function for the S1 bearer, thereby enabling communication between the terminal 1 and the application 60 deployed in the vicinity of the terminal 1.

  As shown in FIG. 1, the present invention performs QoS control on two flows with different priorities, a priority flow and a best effort flow, which are mixed in the bearers 41 and 42 between the eNB 20 and the EPC 10. It is characterized by incorporating the QoS control system 100 into the MEC platform 50. That is, the QoS control system 100 is disposed in the S1 interface section. The control target of the QoS control system 100 is a TCP (Transmission Control Protocol) flow located in the transport layer of the OSI (Open Systems Interconnection) reference model.

  A priority flow is formed between the terminal 1 and the application 60 by the MEC platform 50. The best effort flow is basically formed between the terminal 1 and the Internet 30, but it should be noted that a best effort flow may be formed between the terminal 1 and the application 60. In the present embodiment, for simplicity of explanation, it is assumed that the best effort flow is formed only between the terminal 1 and the Internet 30 as shown in FIG.

  The MEC platform 50 has a function of performing signal processing and packet processing unique to a mobile network such as an S1 bearer in order to realize Mobile Edge Computing. On the other hand, the QoS control system 100 handles only TCP flow processing, and packet distribution processing and the like are processed by the MEC platform 50. In other words, the TCP flow to be processed in the QoS control system 100 includes not only the TCP flow between the terminal 1 and the Internet 30 but also the TCP flow between the terminal 1 and the application 60. In FIG. 2 and subsequent figures, the description of the application 60 is omitted for the sake of simplicity.

  The QoS control system 100 according to the present invention has a congestion detection function and a bandwidth control function. The congestion detection function is a function of detecting a congestion state in a wireless section based on TCP packet sequence number analysis. The bandwidth control function is a function for performing bandwidth control on the best effort flow in order to avoid the congestion state when the congestion state is detected.

  An outline of the congestion detection function of the QoS control system 100 will be described with reference to FIG. In the congestion detection function, the reachability of the packet is confirmed from the sequence number of the TCP packet and the ACK information of the ACK packet. When the arrival confirmation by the ACK information cannot be obtained, a packet loss has occurred and it is considered that the wireless section is congested. Since there is a time difference due to the NW delay in the return of ACK, a time difference is provided between the analysis phases of (1) TCP packet processing and (2) ACK packet processing (each analysis phase is a fixed time determined in advance). Also, by recording the transfer data amount of the TCP packet, the data amount when congestion occurs is grasped.

  Details of packet loss detection in the congestion detection function of the QoS control system 100 will be described with reference to FIGS. The method shown in FIG. 3 or 4 is used for detecting the packet loss. The method shown in FIG. 3 performs congestion detection by analyzing the ACK sequence number, and FIG. 4 performs congestion detection by analyzing the ACK + SACK sequence number. 3 and 4 are both examples of one packet loss, but the packet loss determination result shows that the ACK sequence number analysis results in 3 packet loss and the ACK + SACK sequence number analysis results in 1 packet loss. The latter is more accurate. . In the present invention, ACK + SACK sequence number analysis is used in principle, but if the TCP flow to be analyzed does not support the SACK option, the ACK sequence number analysis method is used.

An overview of the bandwidth control function of the QoS control system 100 will be described. First, in the congestion detection function, the analysis result is recorded as statistical data as the data amount x _i when the packet loss occurs and the packet loss number y _i .

  Then, in the bandwidth control function, based on the recorded statistical data, a limit data amount for preventing congestion in the wireless section is determined by any of the following methods.

(1) The minimum value of the data amount x _i × the safety coefficient is set as the limited data amount. Here, the safety coefficient is a correction value for making the value smaller than the minimum data amount in which packet loss occurs, such as 0.9.
(2) Treat the relationship between the amount of data and the number of packet losses as a linear function, and use the x-axis intercept. That is, the coefficient of the linear function y = ax + b is obtained by the following least square method, and x = −b / a × safety coefficient is set as the limit data amount. The safety factor is the same as (1) above. An image of this method is shown in FIG.

  The bandwidth control is performed by limiting the maximum data amount that can be transmitted in the same time interval as the analysis phase shown in FIG. 2 to the limited data amount determined by the above information.

  Next, a QoS control system according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 6, the QoS control system 100 according to the present embodiment includes a bandwidth control unit 110, a TCP data packet processing unit 120, a flow management unit 130, a TCPACK packet processing unit 140, and a congestion detection unit 150. And a quality management unit 160.

  As shown in FIG. 7, the bandwidth control unit 110 includes a classifier 111 that distributes the storage destination queue based on the priority class of the TCP packet received from the upper network, a priority queue 112 that stores the TCP packet of the priority class, A BE queue 113 that stores a TCP packet of the best effort class, a bandwidth control function unit 114 that controls output of the TCP packet from the BE queue 113 by an algorithm such as a token bucket policer or a shaper, and a TCP packet by scheduling based on a priority class A scheduler 115 for output and an overall control unit (not shown) are provided.

  As shown in FIG. 8, the overall control unit of the bandwidth control unit 110 reads the data amount and the packet loss number data from the quality management unit 160 (step S1), and calculates a limit data amount for preventing the above-described congestion. (Step S2), the limited data amount to be limited per unit time calculated is set in the bandwidth control function unit 114 (Step S3). Here, it should be noted that the band control target by the band control function unit 114 is a best-effort flow, as is apparent from FIG.

  Packets from the upper network are passed to the TCP data packet processing unit 120 via the bandwidth control unit 110. As shown in FIG. 9, the TCP data packet processing unit 120 identifies a TCP flow (step S11), and the TCP data packet information of the flow management unit 130 includes a TCP flow ID, a sequence number, the number of bytes, and reception time information. It is recorded (step S12). The TCP flow ID is an ID that can uniquely identify a TCP flow calculated by hash calculation from an IP address, a TCP port number, or the like. The packet processed by the TCP data packet processing unit 120 is transferred to the lower network.

  On the other hand, as shown in FIG. 10, the TCP ACK packet processing unit 140 identifies a TCP flow from the lower network (step S21), and the ACK sequence number, SACK sequence number, and reception time information are stored in the flow management unit 130. Are recorded in the TCPACK packet information (steps S22 and S23). The packet processed by the TCPACK packet processing unit 140 is transferred to the upper network.

  An example of management data in the flow management unit 130 is shown in FIG. As described above, the flow management unit 130 manages the TCP data packet information recorded by the TCP data packet processing unit 120 and the TCPACK packet information recorded by the TCPACK packet processing unit 140.

  As shown in FIG. 12, the congestion detection unit 150 reads the TCP data packet information and the TCP ACK packet information from the flow management unit 130 (step S31), and the sequence number of the recorded TCP data packet is determined for each TCP flow. It is determined whether the reception confirmation by ACK has been taken (steps S32 to S34). However, since the ACK packet may not be transmitted immediately due to the Delayed ACK, the TCP data packet recorded at the end of the TCP flow is excluded from analysis (step S32).

  In the determination of reception confirmation, if the sequence number of the TCP data packet is smaller than the ACK sequence number, it is assumed that the reception confirmation has been obtained (step S33). It is also assumed that the reception confirmation has been obtained when the SACK sequence numbers # 1 to #N include the sequence number of the TCP data packet (step S34). If none of them corresponds, it is considered that a packet loss has occurred, and the number of packet losses in the quality management unit 160 is counted up (+1) (step S35). Moreover, the congestion detection unit 150 records the total number of bytes described in the TCP data packet information as the data amount of the quality management unit 160 (step S36). Finally, each processed data is deleted from the flow management unit 130 (step S37). An example of management data managed by the quality management unit 160 is shown in FIG.

  The bandwidth control unit 110 classifies the packets into a best effort type flow and a priority type flow based on a predetermined policy, and performs queuing by dividing the packets into a priority queue 112 and a BE queue 113, respectively. In the bandwidth control, the data amount used in the bandwidth limiting function unit 114 is determined by one of the two methods described above using the data amount of the quality management unit 160 and the statistical data of the number of packet losses.

  In the above description, the upper network and the lower network are the lower network on the terminal 1 side as viewed from the QoS control system 100, and the communication partner side of the terminal 1, that is, the Internet 30 and the application 60 side is the upper network. I want to be.

  Thus, according to the radio communication system according to the present embodiment, the priority flow is detected by detecting congestion in the radio section and limiting the bandwidth of the best effort flow without adding a function to the eNB 20. However, it is possible to prevent packets from staying in the eNB 20 due to the influence of the best effort flow, and as a result, the priority flow can realize communication with low delay.

  Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this. For example, in the above embodiment, LTE defined by 3GPP has been described as a mobile network, but the present invention can also be applied to mobile networks based on other architectures.

10 ... EPC
20 ... eNB
DESCRIPTION OF SYMBOLS 30 ... Internet 41 ... Radio bearer 42 ... S1 bearer 50 ... MEC (Mobile Edge Computing) platform 100 ... QoS control system 110 ... Bandwidth control part 110
DESCRIPTION OF SYMBOLS 120 ... TCP data packet processing part 130 ... Flow management part 140 ... TCPACK packet processing part 150 ... Congestion detection part 160 ... Quality management part

Claims (5)

A QoS control system comprising a radio base station and a core network and having a TCP packet transfer function arranged between the radio base station and the core network in a mobile network in which a priority flow and a best effort flow are mixed. ,
Packet loss detection means for analyzing the TCP packet to be transferred and detecting the occurrence of packet loss in the wireless section;
A QoS control system comprising: bandwidth control means for controlling the bandwidth of a best effort flow to be narrowed when a packet loss occurs. The QoS control system according to claim 1, wherein the packet loss detection unit detects occurrence of a packet loss based on a sequence number and an ACK number of a TCP packet to be transferred. The QoS control system according to claim 1, wherein the packet loss detection unit detects occurrence of a packet loss based on a sequence number and an ACK number of a TCP packet to be transferred and a sequence number of a SACK option. The mobile network includes a platform having a packet transmission / reception function for a bearer formed between the radio base station and the core network,
The QoS control system according to any one of claims 1 to 3, wherein the QoS control system is arranged on the platform. In a mobile network including a radio base station and a core network and having a priority type flow and a best effort type flow mixed together, a QoS control system arranged between the radio base station and the core network performs QoS control for transferring a TCP packet. A QoS control method to perform,
The packet loss detection means of the QoS control system analyzes the TCP packet to be transferred and detects the occurrence of the packet loss in the wireless section,
A QoS control method, characterized in that the bandwidth control means of the QoS control system performs control so as to narrow the bandwidth of the best effort flow when packet loss occurs.

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