Patent Publication Number: US-2015072701-A1

Title: Wireless system control device and control method

Description:
REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to Japanese Patent Application No. 2012-107727, filed on May 9, 2012, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a wireless system control device and a wireless system control method. 
     BACKGROUND ART 
     The standards body of 3GPP (Third Generation Partnership Project) proposes a standard of LTE (Long Term Evolution) as a transition technology between the third generation mobile phone (3G) and the fourth generation mobile phone (4G). LTE specifications have been published as E-UTRAN (Evolved Universal Terrestrial Radio Access Network). 
     With the spread of smart phones in recent years, the number of mobile terminals connecting to a high-speed mobile network, such as an E-UTRAN network, is increasing, and traffic accommodated to the high-speed mobile network is growing. This causes shortage of network resources in the high-speed mobile network. 
     Then, techniques have been studied, with which part of traffic that cannot be accommodated to the high-speed mobile network is redirected (offloaded) from the high-speed mobile network to another network, such as the Internet. In SIPTO (Selected IP Traffic Offload) described in 3GPP TS23.401 V10.5.0″ section 4.3.15, as searched on Sep. 27, 2011 on the Internet &lt;URL: http://www.3gpp.org/ftp/Specs/archive/23_series/23.401/23401-a50.zip&gt;, as a selection method for another network, a technique is presented that selects a transfer device in another network geographically close to the base station to which a user terminal is connecting. 
     SUMMARY OF THE INVENTION 
     Problems to be Solved 
     When offloading the traffic in a high-speed mobile network, quality of service (QoS) provided to the traffic should be considered even in an offloaded network. Subscribers of the high-speed mobile network use communication services for the high-speed mobile network., expecting quality of service for the high-speed mobile network (for example, up to 100 Mbps) to which they connect. 
     Therefore, the traffic flowing through the high-speed mobile network can be not only traffic that does not require high quality of service, such as a mail or a file download, but also traffic that requires a high quality of service, such as video conferencing or a game. 
     Here, if traffic is offloaded from the high-speed mobile network without considering a quality level of service required for the traffic, a service delivery provided for the traffic may cause a problem (e.g., a video freezes during video conferencing) to make the user feel dissatisfied with communication services. 
     That is, in order for a network to properly provide quality of service requested by traffic, only part of the network through which the traffic passes cannot be at a high level of quality, but the entire network (End to End) through which the traffic passes needs to be at a high level of quality. For example, even when traffic has passed through a high-speed mobile network, as a result of being offloaded from the high-speed mobile network to another network having low quality, communication quality in the offloaded network serves as a bottleneck to degrade communication quality provided to the traffic. 
     Then, the present invention is mainly intended to solve the problems described above, and, while reducing congestion in a wireless system, to provide appropriate quality of service for traffic passing through the wireless system. 
     Solution to Problems 
     In order to solve the above problems, the present invention is characterized to include: a storage means that, for traffic caused by a connection request for wireless communication, stores request quality which is quality of service of communication networks required for the traffic, and delivery quality which is quality of service delivered by each of the communication networks; a quality-obtaining means that, for the traffic caused by the connection request, obtains the request quality associated with the traffic from the storage means, and, for each of the communication networks on a route through which the traffic caused by the connection request passes, obtains the delivery quality for said communication network from the storage means; and a determining means that, when the delivery quality obtained satisfies the request quality obtained, allows a connection to each of the communication networks associated with the delivery quality obtained, and, when the delivery quality obtained does not satisfy the request quality obtained, disallows a connection to each of the communication networks associated with the delivery quality obtained. Other means will be described later. 
     Advantageous Effects of the Invention 
     According to the present invention, while the congestion in a wireless system is reduced, appropriate quality of service can be provided for traffic passing through the wireless system. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  are block diagrams showing a wireless system according to an embodiment of the present invention.  FIG. 1A  shows a data plane and  FIG. 1B  shows a control plane. 
         FIG. 2  is a block diagram showing two types of traffic routes according to an embodiment of the present invention. 
         FIGS. 3A and 3B  are explanatory diagrams indicating communication quality of traffic, according to an embodiment of the present invention.  FIG. 3A  indicate a status before offloading, and  FIG. 3B  indicates a status after offloading. 
         FIGS. 4A and 4B  are block diagrams showing hardware configurations of units which constitute a wireless system according to an embodiment of the present invention.  FIG. 4A  shows an external transfer unit and  FIG. 4B  shows a control unit. 
         FIG. 5  is a block diagram showing a control unit according to an embodiment of the present invention. 
         FIGS. 6A and 6B  are diagrams showing request quality data of traffic according to an embodiment of the present invention.  FIG. 6A  shows traffic quality data and  FIG. 6B  shows an acceptable quality data. 
         FIGS. 7A to 7C  are diagrams showing delivery quality data of network according to an embodiment of the present invention.  FIG. 7A  shows data processed by a network quality processing unit,  FIG. 7B  shows data processed by an estimated quality processing unit, and  FIG. 7C  shows data processed by an external quality processing unit. 
         FIG. 8  is a flowchart showing a process of obtaining actual measured data of delivery quality according to an embodiment of the present invention. 
         FIG. 9  is a flowchart showing a traffic route determination process according to an embodiment of the present invention. 
         FIG. 10  is a flow chart showing an offloading determination process according to an embodiment of the present invention. 
         FIGS. 11A and 11B  are explanatory diagrams showing a handover route for a normal route according to an embodiment of the present invention.  FIG. 11A  shows a route before a handover and  FIG. 11B  shows a route after the handover. 
         FIG. 12  is a flowchart showing a process of determining a handover route for a normal route according to an embodiment of the present invention. 
         FIGS. 13A and 13B  are explanatory diagrams showing a handover route for offloading according to an embodiment of the present invention.  FIG. 13A  shows a route before a handover and  FIG. 13B  shows a route after the handover. 
         FIG. 14  is a flowchart showing a handover route determination process for offloading according to an embodiment of the present invention. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     Hereinafter, a description will be given in detail of an embodiment of the present invention, with reference to drawings. 
       FIG. 1  is a block diagram showing a wireless system. Hereinafter, in the present embodiment, an example will be shown for a wireless system that applies an E-UTRAN by 3GPP. Therefore, E-UTRAN terms (e.g., UE, User Equipment, for a user terminal) described in 3GPP TS23.401 V10.5.0″ section 4.3.15, as searched on. Sep. 27, 2011 on the Internet &lt;URL: http://www.3gpp.org/ftp/Specs/archive/23_series/23401/23401-a50.zip&gt;will be additionally used in the description. On the other hand, the wireless system according to the present embodiment may be applied to a wireless system using a standard other than. the one by the 3GPP, such as a system in which a base station is provided for wireless LAN communication. 
     Data plane of the wireless system in  FIG. 1A . is configured with user terminals  1 , base stations  2  ( 2   a,    2   b ), user transfer units  3  ( 3   a,    3   b ), external transfer units  4  ( 4   a ,  4   b ), and mobile networks  5  ( 5   a,    5   b ), with connections as illustrated. 
     The user terminal (UE, User Equipment)  1  is a terminal as an endpoint of a connection through which traffic of user data flows, and communicates, end. to end, with a peer terminal  5   z  as the other endpoint of the connection (see  FIG. 2 ). 
     Each of the base stations (eNB, E-UTRAN Node B)  2  ( 2   a,    2   b ) directly connects to the user terminal  1  to accommodate the user terminal  1 . The identifier of each of the base stations  2  ( 2   a,    2   b ) is, for example, TAI (Tracking Area Index), ECGI (E-UTRAN Cell Global Identifier), or the like. 
     The user transfer units (SGW, Serving Gateway)  3  ( 3   a,    3   b ) are transfer units that handle user data, to relay traffic (such as voice calls) between the user terminals  1 . 
     The external transfer units (PGW: PDN Gateway)  4  ( 4   a,    4   b ) are gateways located at respective boundaries for connecting to the external Internet, a corporate intranet, or the like. 
     It should be noted that as a transfer unit (gateway) on a route of traffic between the user terminal  1  and the peer terminal  5   z,  not only the user transfer units  3  ( 3   a,    3   b ) and the external transfer units  4  ( 4   a,    4   b ), but also an LGW (Local Gateway), a BNG (Broadband Network Gateway), or the like, which is arranged between a wireless system network (e.g., Radio Access Network, Core Network) and the mobile networks  5  ( 5   a,    5   b ), may be used. 
     The mobile networks (PDN, Packet Data Network)  5  ( 5   a,    5   b ) are networks that accommodate a router  5   y  and the peer terminal  5   z  in  FIG. 2 . 
     The router (RT, Router)  5   y  is a router that depends on an APN (Access Point Name) which is an identifier of each of the mobile networks  5  ( 5   a,    5   b ). 
     The peer terminal (CN, Corresponding Node)  5   z  is a communication partner of the user terminal  1 . 
     A control plane of the wireless system in  FIG. 1B  is configured to include control units  6  ( 6   a,    6   b ) connected to the data plane (base stations  2  ( 2   a,    2   b ), user transfer units  3  ( 3   a,    3   b )), and an operation unit  6   z,  a subscriber server  7  and a DNS server  8  that are connected to the control unit  6 . Note that each control unit  6  ( 6   a,    6   b ) may be accommodated in the same housing with other units (the operation unit  6   z,  the subscriber server  7 , the DNS server  8 , and the like). 
     The control units (MME, Mobile Management Entity)  6  ( 6   a,    6   b ) are access gateways that manage network controls of data plane in  FIG. 1A . 
     The operation unit (OAM, Operation Administration and Maintenance)  6   z  is a unit for performing operation management and maintenance of the data plane in  FIG. 1A . 
     The subscriber server (HSS, Home Subscriber Server)  7  manages subscription information about the mobile networks  5  ( 5   a,    5   b ) to which the user terminals  1  subscribe. 
     The DNS (Directory Name Service) server  8  provides a service to identify an IP address (resolve name) associated with the domain name, using a domain name of FQDN (Fully Qualified Domain Name) as a search key. Therefore, the DNS server  8  is registered in advance, for an FQDN which can be inputted as a search key, with a device of the FQDN (or a set of devices on a route passing through the device). 
       FIG. 2  is a block diagram showing two types of routes of traffic. As a route of the traffic flowing from the user terminal  1  to the peer terminal  5   z,  there are two types of routes: a normal route and an offloaded route. 
     The normal route is a route that passes through in the order of the user terminal  1 , the base station  2   a,  a relay network  9   d,  the user transfer unit  3   a,  a core network  9   a,  the external transfer unit  4   a,  a relay network  9   c,  the router  5   y , and the peer terminal  5   z.    
     The offloaded route is a route that passes through in the order of the user terminal the base station  2   a,  the relay network  9   d,  the user transfer unit  3   a , the external transfer unit  4   b,  an Internet  9   b,  the router  5   y,  and the peer terminal  5   z.    
     The relay network  9   c  is, for example, a network where a VLAN (Virtual Local Area Network) connection is established between the external transfer unit  4   a  and the router  5   y,  and for establishing this, the external transfer unit  4   a  holds IP address information of the router  5   y.  Note that as the relay network  9   c , a network, which is run by a provider different from the provider of the core network  9   a,  may be routed. 
     The relay network  9   d  is, for example, a RAN (Radio Access Network). 
     According with an increase of traffic to the core network  9   a  and/or the relay network  9   c,  the user transfer unit  3   a  can redirect part of the traffic flowing through the normal route to the offloaded route, to reduce congestion in the core network  9   a  and/or the relay network  9   c.  However, simply redirecting any traffic to the offloaded route without qualification may be able to achieve reducing congestion, but as an adverse effect, traffic such as video conferencing that requires high quality may be sometimes interrupted due to low quality of the offloaded route. 
     Therefore, the control device  6  determines, for each traffic flowing through the normal route, whether or not to allow the traffic being offloaded to the offloaded route (hereinafter, offloading determination) (details of the determination process will be described later in  FIG. 10  etc.). This allows mail traffic or the like, which can flow without a problem even on the offloaded route, to be offloaded, and disallows traffic such as video conferencing to be offloaded, to suppress the aforesaid adverse effect. 
       FIGS. 3A and 3B  are explanatory diagrams indicating communication quality of traffic. These indicate quality of service guaranteed for each route through which the traffic passes from the user terminal  1  to the peer terminal  5   z.    
       FIG. 3A  indicates a state of mail traffic before offloading. Traffic of video conferencing and mail traffic pass through the normal routes in  FIG. 2 , respectively. 
     As flowing through the normal route, traffic of video conferencing can receive, from the user terminal  1  to the external transfer unit  4 , a high-quality service provided with the E-UTRAN by 3GPP and further receive, from the external transfer unit  4  to the peer terminal  5   z,  a high-quality service provided by the provider of the relay network  9   c.  That is, traffic of video conferencing can receive a high-quality service, end to end, to allow the video conferencing to be serviced smoothly. 
     Mail traffic can also receive a high-quality service, end to end, as well as the traffic of video conferencing. However, as the relay network  9   c  is congested, part of the traffic flowing through the normal route needs to be offloaded to the offloaded route. 
       FIG. 3B  indicates a state of the mail traffic after offloading. The traffic of video conferencing passes through the normal route in  FIG. 2 , and the mail traffic is offloaded so as to pass through the offloaded route in  FIG. 2 . Considering the communication quality required for each traffic, the control unit  6  disallows the traffic of video conferencing to be offloaded, and allows the mail traffic to be offloaded. 
     The mail traffic passes through the Internet  9   b,  to which the mail traffic is offloaded, to cause end-to-end communication quality degraded. However, since the user does not suffer inconvenience so much even if a mail arrives late by the unit of several seconds, the user can be kept free from suffering inconvenience. 
     The traffic of video conferencing is exempted from offloading to continuously receive a high-quality service, end to end. 
       FIGS. 4A and 4B  are block diagrams showing hardware configurations of units that constitute the wireless system. In  FIGS. 4A and 4B , the external transfer unit  4  and the control unit  6  are illustrated, and other devices in the wireless system also have similar hardware configurations. 
     Each unit in the wireless system is configured as a computer having a CPU (Central Processing Unit)  91 , a memory  92 , a UIF (User Interface)  93 , and an NWIF (NetWork Interface)  99 . 
     The CPU  91  executes a program retrieved from the memory  92  for configuring each processing unit. 
     The memory  92  stores, along with the program for each processing unit, data used by each processing unit. 
     The UIF  93  is an interface for connecting input and output devices (keyboard, mouse, display, and the like) for inputting and outputting each data stored in the memory  92 . 
     The NWIF  99  is an interface for relaying data to be exchanged with other units. 
     In the external transfer unit in  FIG. 4A , the user transfer unit  3 , the mobile network  5  (routers  5   y ), and the operation unit  6   z  are shown as an example of those connected from the NWIF  99 . 
     In the control unit  6  in  FIG. 4B , the base station  2 , the user transfer unit  3 , the subscriber server  7 , the DNS server  8 , and the operation unit  6   z  are shown as an example of those connected from the NWIF  99 . 
       FIG. 5  is a block diagram showing the control unit  6 . As described in  FIGS. 2 ,  3 A and  3 B, the control unit  6  is configured to allow traffic to pass through a transfer unit which is selected, depending on the result of the offloading determination by an offloading determination unit  53 , either by a normal route selection unit  61  that selects a transfer unit through which the normal route is established, or an offloaded route selection unit  62  that selects a transfer unit through which the offloaded route is established. 
     The normal route selection unit  61  can be implemented, for example, by a technique described in Non-Patent Document “TS 29.303” at section 5.3 “Procedures for Discovering and Selecting a PGW and SGW”. 
     The offloaded route selection unit  62  can be implemented, for example, by a technique described in Non-Patent Document “TS 29.303” at section 5.6 “GW Selection for SIPTO”. 
     Non-Patent Document “TS 29.303” can be obtained online as “3GPP TS 29.303 V11.0.0”, as searched on Apr. 5, 2012, from the Internet &lt;URI; http://www.3gpp.org/ftp/Specs/archive/29_series/29.303/29303-b00.zip&gt;. 
     Note that the main difference between the normal route selection unit  61  and the offloaded route selection unit  62  is an input parameter (FQDN) to the DNS server  8  which both selectors call. 
     The FQDN of the offloaded route selection unit  62  includes identification information (e.g., identification information of devices that are geographically closer to the base station  2  to which the user terminal  1  connects) of devices (base station  2 , transfer unit etc.) through which the offloaded route is established. Here, for loadbalancing purpose, the offloaded route selection unit  62  may randomly select devices from candidate devices through which the route can. be established. 
     The FQDN of the normal route selection unit  61  does not include identification information of devices through which the normal route is established, and the default transfer unit is selected by the DNS server  8 . 
     Hereinafter, a description will be given in detail of the components used for offloading determination in the offloading determination unit  53 . The offloading determination unit  53  allows offloading when delivery quality  52  of the network is greater than request quality  51  of the traffic, and disallows offloading when the delivery quality  52  is less than the request quality  51 . 
     Note that when the request quality  51  of the traffic and the delivery quality  52  of the network. are equal, offloading may be either allowed or disallowed. 
     First, in order to obtain the request quality  51 , the control device  6  includes a request quality processing unit  11 , traffic quality data  12 , and allowable quality data  13  (see  FIGS. 6A and 6B  for details). 
     Next, in order to obtain the delivery quality  52 , the control device  6  includes a network quality processing unit  21 , a network association data  22 , network quality determination data  23 , estimated quality processing unit  31 , estimated quality association data  32 , estimated quality determination data  33 , an external quality processing unit  41 , external quality association data  42 , and external quality determination data  43  (see  FIGS. 7A-7C  for details). 
       FIGS. 6A and 6B  are block diagrams showing the request quality data of traffic.  FIG. 6A  shows, as traffic quality data  12 , an example using the data shown in “Table 6.1.7: Standardized QCI characteristics” in 3GPP TS 23.203. The 3GPP TS 23.203 can be obtained online as “3GPP TS 23.203 V11.5.0”, as searched on Apr. 5, 2012, from the Internet &lt;URL: http://www.3gpp.org/ftp/Specs/archive/23_series/23.203/23203-b50.zip&gt;. 
     The traffic quality data  12  is constructed, for each QCI (QoS Class Identifier) that is information to identify quality of service, in association with information indicating whether or not the QCI has a guaranteed bit rate (GBR), the priority of the QCI, specific parameters of quality of service requested by traffic (delay (Packet Delay), loss rate (Packet EL Rate)), and specific information of traffic service(s) that apply(ies) the QCI. 
     It should be noted, as an example of parameters of quality of service, the delay and the loss rate are listed, but the policy, such as which one of these two should be used and which one should be given priority, may be inputted in advance by a provider of a wireless system. Further, as parameters of quality of service, parameters other than the delay and the loss rate (such as bandwidth) may be used alone or in combination with the two parameters. 
     The acceptable quality data  13  in  FIG. 6B  shows quality of service which. the user requests from (allows) an offloaded network. The acceptable quality data  13  is associated, for each QCI, with parameters (delay, loss rate) of quality of service. It should be noted that the acceptable quality data  13  is desirable to be created for each user or a user group having the same attribute (such as contracts with the same fee structure). 
     The offloading determination unit  53  uses, as the request quality  51  used for offloading determination, parameters of quality of service for identification, based on at least one parameter among the parameters of quality of service in the traffic quality data  12  and the parameters of quality of service in the acceptable quality data  13 . 
     For example, the request quality  51  may be a parameter of quality of service in the acceptable quality data  13 , or may be a result of a specific operation (minimum value operation, average value operation) inputted with a parameter of quality of service in the traffic quality data  12  and a parameter of quality of service in the acceptable quality data  13 . 
     In addition, an interval subject to the parameter(s) of quality of service, which is/are defined in the traffic quality data  12  and/or the acceptable quality data  13 , may be a route from the external transfer unit  4  to the mobile network  5 , or may be a route from a device other than the external transfer unit  4  (such as the base station  2 ) to the mobile network  5 . 
     Further, the parameter(s) of quality of service may be the maximum value requested. (allowed), or may be an average value, 
       FIGS. 7A-7C  are diagrams showing delivery quality data of network. The offloading determination unit  53  uses, as the delivery quality  52  used for offloading determination, parameters of quality of service for identification, based on at least one parameter among parameters of quality of service, which are defined with respective identification data of quality (network quality identification data  23 , estimated quality identification data  33 , external quality identification data  43 ). 
       FIG. 7A  shows network association data  22  and the network quality identification data  23  processed by the network quality processing unit  21 . 
     The network association data  22  is data, for each external transfer unit  4 , associating a mobile network  5  to be connected to the external transfer unit  4  with the APN of the mobile network  5 , and is notified from the operation unit  6   z . For example, the first line of the network association data  22  indicates that a mobile network  5   a  is connected to an external transfer unit  4   a,  and the mobile network  5   a  is associated with a name “APN1”. 
     The network quality identification data  23  is data that for each APN of the mobile network  5  connected (offloaded) from the external transfer unit  4 , defines the parameters (delay, loss rate) of quality of service provided by the mobile network  5 . 
     The network quality processing unit  21  uses one of a first to third settings as exemplified below to set parameters of quality of service in the network quality identification data  23 . Note that data in the network association data  22  and data other than those of quality of service in the network quality identification data  23  are, as they are network configuration data, inputted in advance by the administrator or the like. 
     Hereinafter, a description will be given of each setting in conjunction with a cost of acquisition of the configuration data and accuracy of data. For example, (the control unit  6  of) a provider of inexpensive communication services may arrange quality identification data, having a lower cost of data acquisition but lower accuracy of data, while (the control unit  6  of) a provider of expensive communication services may arrange quality identification data, having a higher cost of data acquisition but higher accuracy of data. 
     The first setting is to input by an administrator a representative value of quality of service to be used in common to all the APNs. Since only inputting a single parameter is required, this setting is superior in terms of a cost of data acquisition. Further, time and effort may be reduced in obtaining actual quality of service to allow the offloading determination of the present embodiment to be widely implemented, even when. an. offloaded network is managed in a different mode (another company, another country, or the like). 
     The second setting is to input by an administrator values of quality of service for each APN. The administrator inputs values of quality of service for each APN, based on the knowledge obtained by referring to specifications in an equipment catalog, or the like. This setting balances between a cost of data acquisition and accuracy of data. 
     The third setting is to receive and set actual measured data of values of quality of service (see  FIG. 8  for details) for each APN from the operation unit  6   z . A cost of data acquisition is high but accuracy of data is superior, therefore disadvantages can be reduced such that even with quality of service being poor in practice in an offloaded network, the gateway is wrongly selected for offloading. 
       FIG. 7B  shows estimated quality association data  32  and estimated quality identification data  33  processed by the estimated quality processing unit  31 . 
     The estimated quality association data  32  is data that, for each APN identified by an ID, associates a character string of the APN with a word indicating estimated quality identified from the character string. The word indicating the estimated quality is, for example, a word included in the character string of the APN. The word indicating the estimated quality is, for example, a character string representing a type of network, such as “internet”, a character string representing a type of service, such as “voice”, or the like. 
     The estimated quality identification data  33  is data that, for each word that indicates estimated quality, defines parameters (delay, loss rate) of its quality of service. 
     The estimated quality processing unit  31 , from an APN of the mobile network  5  included on the offloaded route of traffic, identifies the word indicating the estimated quality of the APN with reference to the estimated quality association data  32 , and then obtains quality of service associated with the estimated quality with reference to the estimated quality identification data  33 . Therefore, the estimated quality processing unit  31  receives and registers input of data contents in the estimated quality association data  32  and the estimated quality identification data  33  in advance from the administrator. 
     For example, when an APN on the offloaded route of traffic is APN1=“voice.mnc012.mcc214.gprs,” the estimated quality processing unit  31  refers to the estimated quality association data  32  to set the estimated quality to “voice”, since the APN1 includes a character of “voice.” Then, referring to the line having the estimated quality of “voice” in the estimated quality identification data  33 , the estimated quality processing unit  31  estimates that quality of service of the APN1 is “delay=100 ms, loss rate=10̂ −6.” 
       FIG. 7C  shows an external quality association data  42  and an external quality identification data  43  processed by the external quality processing unit  41 . 
     The external quality association data  42  is data that associates a QCI (left column) indicating quality of service of an offloading network with an external QCI (External Network QoS Index) indicating quality of service of an offloaded network. Note that a DSCP (DiffServ Code Point) value associated with the external QCI is added to packets flowing through the offloaded network. 
     The external quality identification data  43  is data that, for each external QCI, defines parameters (delay, loss rate) of its quality of service. Each of these parameters may be an upper limit value of quality, or may be an average value. 
     Here, the offloading network is, for example, each of “3GPP” networks in  FIG. 3A , and the offloaded network is, for example, the relay network  9   c  or the Internet  9   b  in  FIG. 3B . 
     The external quality processing unit  41 , based on the QCI (“1”, or the like) of traffic identified from the traffic quality data  12 , identifies an associated external QCI (“a”, or the like) from the external quality association data  42 , and then, from the identified external QCI, obtains parameters (delay of “80,” and loss rate of “10̂−3,” or the like) of quality of service with reference to the external quality identification data  43 . 
     Thus, each quality of service corresponds to one another even between different networks, then it can be expected that quality of service of the offloaded network is equivalent to quality of service of the offloading network, which allows gaining highly accurate delivery quality  52 . 
       FIG. 8  is a flowchart showing a process of obtaining actual measured data of delivery quality. 
     In S 201 , the operation unit  6   z  transmits to the external transfer unit  4  a measurement request (QoS Measurement Req) which is a command that requests information about quality of service. 
     In S 202 , the external transfer unit  4 , as a response to the measurement request in S 201 , sends a measurement response (QoS Measurement Res) to the operation unit  6   z.    
     In S 203 , the external transfer unit  4 , for the measurement request in S 201  performs quality measurement (QoS Measurement) with the mobile network  5  (router  5   y ). The quality measurement means, for example, to execute a ping command for the measurement, based on measurement messages (echo request message, echo reply message) transmitted and received between the external transfer unit  4  and the mobile network  5 . 
     Delay of actual measured data is a result of the division by  2  of an average time since an echo request message is transmitted until, an echo reply message is received. 
     Loss rate of the actual measured data is calculated as (number of echo request messages that have not received echo reply messages) (total number of echo request messages transmitted). 
     Setting values of the measurement (address of respective nodes for transmitting and receiving measurement messages, number of echo request messages to transmit, and the like) may be set remotely from other device (operation unit  6   z,  control unit  6 , or the like), or may be set locally from an input means connected to the unit itself. 
     In S 204 , the operation unit  6   z  transmits to the external transfer unit  4  a measurement result request (QoS Information Req) which is a command that requests information about quality of service measured in S 203 . 
     In S 205 , the external transfer unit  4  transmits to the operation unit  6   z  a measurement result response (QoS Information Res) that includes the information about quality of service measured in S 203 . 
     In S 206 , the operation unit  6   z  transmits to the control unit  6  a measurement report (QoS InfoInsert Req) that includes the information about quality of service measured which is obtained in S 205 . 
     In S 207 , the control device  6  returns a measurement report response (QoS InfoInsert Res), 
     The respective processings in S 201  to S 207  described above may be executed not only in the sequence shown as an example in  FIG. 8  but also in sequences variously modified. 
     For example, since quality of service is the data that varies as time passes, a measurement request in S 201  may be transmitted repeatedly at predetermined time intervals to allow information about most recent quality of service to be measured multiple times. 
     In addition, respective response messages in S 202 , S 205 , S 207  may be omitted to proceed to the next process after waiting a predetermined time, without waiting for the arrival of those response messages. 
     Further, the external transfer unit  4  may skip the respective message processing in S 202 , S 203  and, in response to a measurement request in S 201 , transmit the measurement result response in S 205 . 
       FIG. 9  is a flowchart showing a traffic route determination process. 
     In S 11 , the user terminal  1  transmits a connection request (Attach Request), which includes the ID of the base station  2  geographically close to itself, to the base station  2  to be connected. The base station  2  notifies the control unit  6  of the ID of the user terminal  1  and the ID of the base station  2 . 
     In S 12 , the control unit  6  performs terminal authentication (Authentication) for the user terminal  1  in S 11 . To do that, the control unit  6  obtains authentication data of the user terminal  1  from the subscriber server  7 . 
     In S 13 , the control unit  6  transmits an update request (ULR, Update Location Request) of updating the connection position of the user terminal  1  to the subscriber server  7 . 
     In S 14 , in response to S 13 , the subscriber server  7  transmits an update response (ULA, Update Location Ack), which includes subscriber data (Subscriber data), to the control device  6 . The update response includes: the APN that indicates the mobile network  5  which the user of the user terminal  1  subscribes to (can use); information whether or not SIPTO offloading is allowed for the APN (SIPTO allowed); and the QCI provided by the mobile network  5  of the APN. 
     In S 15 , the offloading determination unit  53  in the control unit  6  performs offloading determination (see  FIG. 10  for details). 
     In S 16 , based on the results of the offloading determination in S 15 , the control unit  6  transmits to the DNS server  8  a GW request of requesting a transfer unit (GW) on the route the traffic, for which a connection request has been made in S 11 , passes through. 
     Note that when offloading is allowed in S 15 , FQDNs included in the GW request in S 16  are the default APN obtained in S 14  as well as the APN of the base station  2  included in the connection request in S 11 . 
     On the other hand, when offloading is disallowed. in S 15 , the GW request in S 16  does not specify a particular device (specifies the default APN obtained in S 14  as an FQDN). 
     In S 17 , the DNS server  8 , in response to the GW request in S 16 , transmits a GW response to the control unit  6 . The GW response includes an IP address of the transfer unit (user transfer unit  3 , external transfer unit  4 ) associated with the FQDNs included in the GW request in S 16 . 
     In S 18 , the control unit  6 , for each transfer unit specified in the GW response in S 17 , instructs connection establishment (Connection establishment) of the route the traffic of the user data passes through. In this connection establishment, quality of service is applied that is indicated by the QCI included in the update response in S 14 . For details of the connection establishment that specifies the QCI, Section 5.3.2.1 in “3GPP TS23.401 V10.5.0” section 4.3.15, as searched on Sep. 27, 2011 on the Internet &lt;URL: http://www.3gpp.org/ftp/Specs/archive/23_series/23.401/23401-a50.zip&gt;may be referred to, for example. 
       FIG. 10  is a flowchart showing an offloading determination process. 
     In S 101 , the offloading determination unit  53 , based on the “SIPTO allowed” in the update response obtained in S 14 , determines whether or not the user terminal  1  in S 11  is allowed to use offloaded routes. If the result is YES (allowed) in S 101 , the process proceeds to S 102  in order to perform offloading determination. If the result is NO (disallowed) in S 101 , the process proceeds to S 106  without referring to quality of service at all to perform the offloading determination, because any offloaded route is not available. 
     In S 102 , the offloading determination unit  53  (quality-obtaining means) obtains the request quality  51  of the traffic (user), as described in the traffic quality data  12  in  FIG. 6A  and the acceptable quality data  13  in  FIG. 6B . 
     In S 103 , the offloading determination unit  53  (quality-obtaining means) obtains the delivery quality  52  of the network, as described in the network quality identification data  23 , the estimated quality identification data  33 , and the external quality identification data  43  in  FIGS. 7A-7C , respectively. 
     Here, in order to guarantee quality of service, end to end, it is desirable, as the delivery quality  52  for the traffic passing through multiple networks (a first network, a second network, a third network, ---), to calculate values indicating quality of service, end to end, as exemplified below. 
     Delivery quality  52  (delay)=(Delay value in the first network)+(Delay value in the second network)+(Delay value in the third network)+--- 
     Delivery quality  52  (loss rate)=1−(Transfer success rate in the first network)×(Transfer success rate in the second network)×(Transfer success rate in the third network)×---, where Transfer success rate=(1−Loss rate of the network). 
     Delivery quality  52  (bandwidth)=MIN ((bandwidth of the first network), (bandwidth of the second network), (bandwidth of the third network), ---), where MIN is a function to calculate the minimum value among multiple arguments. 
     In S 104 , the offloading determination unit  53  determines whether the delivery quality in S 103  satisfies the request quality in S 102  to perform offloading determination. When it meets this determination criteria (YES at S 104 ), offloading is allowed and the process proceeds to S 105 . When it does not meet this determination criteria (NO at S 104 ), offloading is disallowed and the process proceeds to S 106 . 
     For example, when the delivery quality  52  (Delay column in the network quality identification data  23 ) in S 103  is “Delay=150 ms,” offloading is allowed for each traffic service having the request quality  51  of “Delay ≦in 150 ms” in S 102  (QCIs 1, 2, 3, 5, 7 are applicable in the traffic quality data  12 ). 
     Or when the delivery quality  52  (Loss rate column in the network quality identification data  23 ) in S 103  is “Loss rate=10̂6,” offloading is allowed for each traffic service having the request quality  51  of “Loss rate ≦10̂−6” in  5102  (QCIs 4, 5, 6, 8, 9 are applicable in the traffic quality data  12 ). 
     In S 105 , the offloaded route selection unit  62  determines (allow offloading) that the offloaded route will be the route the traffic passes through. 
     In S 106 , the normal route selection unit  61  determines (disallow offloading) that the normal route will be the route the traffic passes through. Note that, as described in  FIG. 9 , the determination result in S 105  or  5106  is reflected to the FQDN included in the GW request in S 16 . 
     With the processes described hereinabove using  FIGS. 1A-10 , a connection is established that corresponds to quality of service each traffic requests, end to end, from the user terminal  1  to the peer terminal  5   z.  In the description hereinafter using  FIGS. 11A-14 , a description will be given of an example in which, after the connection is established, a base station  2  ( 2   a,    2   b ) that accommodates the user terminal  1  is switched (handed over) to another. 
       FIGS. 11A and 11B  are explanatory diagrams showing a handover route of the traffic flowing through the normal route. The user terminal  1  will hand over the connection from the base station  2   a  to the base station  2   b.    
     In a state before the handover in  FIG. 11A , the normal route for flowing the traffic passes through the user terminal  1 , the base station  2   a,  the user transfer unit  3   a,  the external transfer unit  4   a,  the mobile network  5  in this order. 
     In a state after the handover in  FIG. 11B , the normal route for flowing the traffic passes through the user terminal  1 , the base station  2   b,  the user transfer unit  3   a,  the external transfer unit  4   a,  the mobile network  5  in this order. 
     Therefore, with the handover, the normal route on the upstream side (the user terminal  1 , the base station  2  ( 2   a,    2   b ), the user transfer unit  3  ( 3   a,    3   b )) is changed, but the normal route on the downstream side (user transfer unit  3  ( 3   a ,  3   b ), the external transfer unit  4  ( 4   a,    4   b ), the mobile network  5 ) is unchanged. In other words, GWs of transfer units on the downstream side (user transfer unit  3  ( 3   a,    3   b ), external transfer unit  4  ( 4   a,    4   b )) are reselected (GW relocation) with the handover. 
     That is, the control unit  6  needs to change the connection of the normal route on the upstream side to a new route after the handover, but can take over the state before the handover, as is, for the connection of the normal route on the downstream side, without disconnecting the old connection and establishing a new connection. This can suppress service interruption due to disconnection of the connection. 
       FIG. 12  is a flowchart showing a process of determining a handover route for the normal route in  FIG. 11A . 
     In S 21 , the user terminal  1  starts an update of position information (TAU, Tracking Area Update) associated with the handover (HO, Hand Over). 
     In S 22 , the user terminal  1  transmits a HO request (Tracking Area Update request) in S 21  to the base station  2   b  of the handover destination. The base station  2   b  notifies the control device  6   b  of the HO request in S 22 . Hereinafter, the control unit  6   b  receiving the notification, in order to newly perform mobility management of the user terminal  1 , takes over the information about the user terminal  1  from the control unit  6   a,  which has been performing the mobility management before the handover. 
     In S 23 , the control unit  6   b  of the takeover destination transmits a takeover request (context request) for requesting information required for the connection of the user terminal 1 (S 18 ) to the control unit  6   a  of the takeover source. 
     In S 24 , the control unit  6   a,  in response to the request in S 23 , transmits to the control unit  6   b  a takeover response (context response) inclusive of the connection information. This connection information, in addition to the update response (APN, SIPTO allowed, QCI) in S 14 , includes the GW response (IP address of the transfer unit) in S 17 . 
     In S 25 , terminal authentication (Authentication) is performed in the same way as in S 12 . 
     In S 26 , offloading determination is performed in the same way as in S 12 , and as a result, offloading may be disallowed (normal route is selected). 
     S 27  and S 28  are the name resolution process (GW request, GW response) by the DNS server  8  in the same way as S 16 , S 17 . 
     In S 29 , the control unit  6   b  performs GW reselection (GW relocation), as described in  FIG. 11B . 
       FIGS. 13A and 13B  are explanatory diagrams showing a handover route of the traffic flowing through the offloaded route. As in  FIGS. 11A and 11B , the user terminal  1  will hand over the connection from the base station  2   a  to the base station  2   b.  Here, according to a transition from the state before the handover in  FIG. 13A  to a state after the handover in  FIG. 13B , transfer units (user transfer unit  3  ( 3   a,    3   b ), external transfer unit  4  ( 4   a,    4   b )) the offloaded route passing through are changed. 
     Therefore, unlike  FIGS. 11A and 11B , GW reselection cannot be performed, and then the connection of the offloaded route needs to be changed end to end. 
       FIG. 14  is a flowchart showing a handover route determination process for offloading in  FIGS. 13A and 13B . Hereinafter, the same steps in  FIG. 12  and  FIG. 14  have the same reference numerals, and a description will be given by focusing on differences between the two flowcharts. 
     S 21  to S 25  perform the same processing in both flow charts. 
     In S 26  in  FIG. 14 , as a result of the offloading determination, offloading (select the offloaded route) is allowed. 
     In S 28   b,  the control unit  6   b  transmits a message of not performing a GW reselection (newly selects a transfer unit which is different from the transfer unit that has been in connection before the handover), as a GW change (Serving GW change indication) to the control unit  6   a.    
     In S 29   a,  the control unit  6   b  implements a new connection establishment (Connection establishment) shown in  FIG. 13B . 
     In S 29   b,  the control device  6   a  disconnects the unnecessary connection shown in  FIG. 13A . 
     In the present embodiment described as above, the offloading determination unit  53  in the control device  6  ( 6   a,    6   b ) compares the request quality  51  and the delivery quality  52  to perform offloading determination to determine whether or not the traffic is redirected to an offloaded route. This disallows traffic, which has the request quality  51  higher than the delivery quality  52  and then the offloaded route cannot satisfy the request quality  51 , to be redirected to the offloaded route, to provide a communication service to the user without any impact such as degradation of quality of service. Further, this allows traffic, which has the request quality  51  lower than the delivery quality  52  and then even the offloaded route can satisfy the request quality  51 , to be redirected to the offloaded route, to reduce congestion in the wireless system. 
     Here, regarding a level of the communication quality (the request quality  51 , the delivery quality  52 ), quality parameters such as “Delay” and “Loss rate” indicate the higher communication quality as the quality index value becomes smaller. On the other hand, quality parameters such as “Bandwidth” indicate the higher communication quality as the quality index value becomes larger. 
     Thus, sufficient communication quality is provided to allow both the user of the traffic flowing through the normal route and the user of the traffic flowing through the offloaded route to use the traffic service, and this can suppress all of the cost of customer service being increased due to the user complaining to the provider, business opportunities being lost due to the user switching the service contract to other provider, and the offering price of communication services being lowered. 
     Furthermore, even with various delivery quality  52 , the delivery quality  52  can be identified from various data such as the network quality identification data  23 , the estimated quality identification data  33 , and the external quality identification data  43  to allow the offloading determination to be performed at a low cost and with high accuracy. 
     Note that the present invention is not limited to the embodiments described as above, and includes various modifications. For example, the above-described embodiments are described in detail in order to better illustrate the present invention and are not intended to be limited to include all the configurations described. 
     In addition, a part of the configuration of one embodiment may be replaced with the configuration of another embodiment, or the configuration of another embodiment may be added to the configuration of one embodiment. 
     Further, a part of the configuration of each embodiment may be deleted, or added/replaced with other configuration(s). Furthermore, each of the configurations, functions, processing units, processing means, and the like as described above may be implemented partially or entirely in hardware, such as by designing with (a) integrated circuit(s). 
     Moreover, each of the configurations and the functions as described above may be implemented in software, by a processor interpreting and executing a program to implement each function. 
     Information such as programs to implement respective functions, tables, and files may be stored in a memory, a recording device such as a hard disk and an SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD card, and a DVD. 
     In addition, control lines and information lines are shown for those required for explanation, and all control lines and information lines are not shown for the products. In practice, almost all configurations may be considered to be connected to each other.