Patent Document 1 discloses a configuration in which, when mobile stations are unevenly distributed, base stations and a higher-level control station work together to adjust the coverage area of the base stations to reduce the state in which communication cannot be performed. In this configuration, each of the base stations collects information on the number of mobile stations, as well as the state of the mobile stations (busy, reception standby, power-off after location registration), in the service area of the base station, and the higher-level control station receives communication traffic information from the base stations, identifies the limit of the traffic density and, based on the information, supplies control information for adjusting the communication support range (coverage area) of the base stations.
Patent Document 2 discloses a configuration in which a management system is provided. When a change in the load status is notified from an IPGW (Internet Protocol GateWay) that has the load measurement unit for measuring the number accesses to the IPGW and the load of the CPU, the management system issues an instruction to the mobile subscriber center (MSC) to allow a mobile terminal to access, not a near IPGW, but a lightly loaded IPGW.
Patent Document 3 discloses a radio network system that has a node selection information management function unit connected, directly or indirectly, to all of multiple base control stations and multiple base stations. This node selection information management function unit acquires traffic load information on all base control stations and transmits information on call connection destination priority, which is best for the entire network system, to each base station.
Non Patent Document 1 proposes a technology called OpenFlow. OpenFlow identifies communications as end-to-end flows and performs path control, failure recovery, load balancing, and optimization on a per-flow basis. An OpenFlow switch, which functions as a forwarding node, operates according to the flow table to which information is added, and whose contents are updated, by the OpenFlow controller according to the OpenFlow protocol. The flow table includes flow entries each of which is a set of a packet matching rule, which identifies a packet, and an action for outputting a packet to a particular port, discarding a packet, or rewriting the header of a packet. When a matching entry is found, the OpenFlow switch performs processing for the received packet according to the action described in the entry. When a matching entry is not found, the OpenFlow switch notifies the OpenFlow protocol that a packet has been received.
Non Patent Document 2 is a specification prepared by the OpenFlow Consortium. The detail of the functions of the counters provided by the OpenFlow switch is described in “3.2 Counters” on page 4 of the specification. The function of the OpenFlow controller to collect statistical information, recorded by the counter function described above, from the OpenFlow switches is described in “4.1.1 Controller-to-Switch” on page 9 of the specification (see the item “Read-State”).
Patent Document 1:
    Japanese Patent Kokai Publication No. JP2003-111133APatent Document 2:    Japanese Patent Kokai Publication No. JP2001-069176APatent Document 3:    Japanese Patent Kokai Publication No. JP2008-236037ANon Patent Document 1:    Nick McKeown and seven other authors, “OpenFlow: Enabling Innovation in Campus Networks”, [online], [Searched on Jul. 17, 2009], Internet <URL: http://www.openflowswitch.org//documents/openflow-wp-latest.pdf>Non Patent Document 2:    OpenFlow Switch Specification” Version 0.9.0. (Wire Protocol 0x98) [Searched on Dec. 7, 2009], Internet <URL: http://www.openflowswitch.org/documents/openflow-spec-v0.9.0.pdf>