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Keywords：Softswitch，power communication system，power plant，application
Abstract.With the power system to achieve "plant network separation"，soft switching technology in the application of power plants more and more attention.At present，part of the power grid，transmission network equipment，fiber optic cable prices cheaper，more and more wide transmission bandwidth.For power generation enterprises，there are transmission equipment within the power plant coverage of the site，temporarily will not change the existing circuit-switched mode.For the power generation enterprises in a very large end node（plant substation voice）has not yet been resolved，soft switching technology can effectively solve the power supply voice switching problems，resulting in more economic benefits，cost savings.
1.Background
Softswitch is the control function entity of the next generation network，which provides the call control and connection control function for the next generation network with real-time service.It is the core of the next generation network call and control.In short，the softswitch is the entity that implements the "call control" function of the traditional PBX，but the traditional "call control" function is combined with the business，and the call control functions required by different services are different，which requires softswitch The provision of call control functions is the basic call control for various services.The basic meaning of softswitch is to separate the call control function from the media gateway.The basic call control function is realized through the software on the server or the network element，including call routing，management control，connection control（establishment session，dismantling session），letter So that interoperability（such as signaling from the 7 to IP signaling）and so on[4].This separation establishes a separate plane for control，switching，and software-programmable functions that enable service providers to freely combine transport services with control protocols to achieve business transfer.All protocols for softswitch are IP-based，and they have the openness and flexibility of all IP-based protocols.Most importantly，the softswitch uses an open application programming interface（API）that simplifies the complexity of the signaling structure and control，and has openness to network technology，access technology，and intelligent services.Allowing the introduction of new services in the exchange mechanism，and the original four switches（long distance，tandem switch），5 switches（local switches）can still be retained through the SS7 link[5]. 2.Softswitch Network Structure Technology
2.1Softswitch Network Structure
Power network to softswitch as the core of the network has three characteristics：First，the use of an open network architecture system，the traditional switch function modules into separate network components，the user can be based on business needs free combination of functional parts Set up the network，the interface between the components of the standardization of the interface can achieve a variety of heterogeneous network interoperability.The second is based on the business-driven network，its function is the separation of business and call control，call and bearer separation，so that business is truly independent of the network，flexible and efficient implementation of the business，the user can configure and define their own business characteristics[6]，Concerned about the network form of the bearer service and the type of terminal，so that the provision of business and application has greater flexibility.Third，based on a unified protocol and packet-based network，because the existing information network，whether it is telecommunications network，computer network or cable network can not be one of the network-based platform to grow information infrastructure[7]，with IP Development，people have recognized that the telecommunications network，computer networks and cable television network will eventually pool to a unified IP network，which is commonly referred to as "triple play" integration trend[8].
The location of the softswitch in the network is divided into media / access layer，transport layer，control layer and service / application layer.The functions of each layer are as follows[9].
（1）media / access layer：to provide a variety of user terminals，user premises network and traditional communication network access to the core network gateway.
（2）transport layer：for a variety of media to provide broadband transmission channel，and the information routing to the destination.
（3）control layer：the main to provide call control，processing functions and protocol functions，business functions and interoperability.
（4）business / application layer：the use of the underlying resources to provide users with a variety of network services and resource management.
2.2External Interface of Softswitch
Softswitch as an open entity，with an external interface must use an open protocol，various interfaces and their use of the protocol as follows. （1）interface between the media gateway（MG）and the softswitch：the media gateway is used for softswitch to carry control，resource control and management of the media gateway.This interface can use the Media Gateway Control Protocol（MGCP），IP Device Control Protocol（IPDC），or H.248 protocol[10].
（2）interface between the signaling gateway（SG）and the softswitch：The signaling gateway is used to transmit the signaling information between the softswitch and the media gateway.This interface can use Signaling Control Transmission Protocol（SCTP）or other similar protocols.
（3）interface between softswitch：to achieve the interaction between different softswitch.This interface can use the Session Initiation Protocol（SIP-T）or H.323 protocol.
（4）interface between softswitch and application / service：provide access to various databases，tripartite application platform，various functions of the server interface，to achieve value-added services，management services and tripartite application support.Such as：· Softswitch and application server interface，you can use the SIP protocol or API（such as Parlay），to provide a tripartite application and a variety of value-added services support functions；· Softswitch and policy server interface，you can use the COPS protocol，The implementation of the network equipment to work on the dynamic intervention；· Softswitch and network management center interface，you can use the SNMP protocol to achieve network management；· Softswitch and intelligent network service control point（SCP）interface，you can use the INAP protocol，To achieve the existing intelligent network business support.
3.Softswitch Technology Advantages
Compared with the traditional switch，the softswitch technology has the following major advantages：
（1）soft switching technology has a lower cost，in the use of the process，the use of open platform and ordinary computer，it is easy to carry out And in the whole process，the price is very cheap，has a greater advantage，and third parties can also easily use the appropriate soft switching equipment，in this case，you can in the corresponding softswitch platform Use the network new business.
（2）the user's choice has a diversity.The traditional switch in the use of the process，generally by a business to provide the appropriate software and hardware maintenance and development，system updates and all other business，so that makes the user's choice of space significantly reduced，making the user did not The corresponding initiative，especially in the follow-up maintenance costs and no corresponding options，but the softswitch technology can solve this problem，the use of softswitch technology，you can establish a unified，standard onion space，And in the use of the process，the user can be independent of the supplier's choice，for the application of the software is extremely beneficial.（3）has a high reliability.Users in the process of network group，the use of soft switching technology can be fully functional software classification，all assigned to the corresponding backbone network，in the process，mainly based on the computer as a platform for system programming Processing，so that the network will become more secure and reliable. References
[1].Xing Yanxia.et al.Softswitch technology and network convergence.Mobile Communications，2005，Vol.29（6）.
[2].Liu Weihong.et al.Softswitch technology in power communication network.Zhejiang University，2008.
[3].Guo Jinghong，Cai Bin，Gao Yun，et al.Next generation network and its power development strategy during the "Eleventh Five-Year" period.Power System Communications，2006，Vol.27（10）.
[4].Qiang Lei.et al.Softswitch based on the next generation network networking technology.Beijing：People's Posts and Telecommunications Press，2005.
[5].Peng Qingqing，Xiang Li，Lu Changyan，et al.National Electric Power Dispatching Data Network.Power System Automation，2004，Vol.28（8）.
[6].Gao Longhua，Wang Li.et al.Application of Softswitch Technology in Power Communication Network.Modern Communications，2003，Vol.（5）.
[7].Li Wenyaoet al.Study on Functional Structure Model of Next Generation Network.China Journal of Data Communications，2003，Vol.（3）.
[8].Wang Jun，Zhang Jianwu.et al.PSTN network and NGN network interoperability.Modern Communications，2003，Vol.（3）.
[9].Chalie.et al.Research on the Combination of Softswitch Network and Existing Network.JOURNAL OF BEIJING UNIVERSITY OF POSTS AND TELECOM，2004，Vol.27（3）.
[10]Ye Wenchao.Discussion on Some Problems of Network Using NGN Technology.Telecommunications Science，2003，Vol.（5）.
（作者單位：1State Grid Hubei Electric Power Company Huanglongtan Hydropower Plant，Shiyan 442000，China）
Abstract.With the power system to achieve "plant network separation"，soft switching technology in the application of power plants more and more attention.At present，part of the power grid，transmission network equipment，fiber optic cable prices cheaper，more and more wide transmission bandwidth.For power generation enterprises，there are transmission equipment within the power plant coverage of the site，temporarily will not change the existing circuit-switched mode.For the power generation enterprises in a very large end node（plant substation voice）has not yet been resolved，soft switching technology can effectively solve the power supply voice switching problems，resulting in more economic benefits，cost savings.
1.Background
Softswitch is the control function entity of the next generation network，which provides the call control and connection control function for the next generation network with real-time service.It is the core of the next generation network call and control.In short，the softswitch is the entity that implements the "call control" function of the traditional PBX，but the traditional "call control" function is combined with the business，and the call control functions required by different services are different，which requires softswitch The provision of call control functions is the basic call control for various services.The basic meaning of softswitch is to separate the call control function from the media gateway.The basic call control function is realized through the software on the server or the network element，including call routing，management control，connection control（establishment session，dismantling session），letter So that interoperability（such as signaling from the 7 to IP signaling）and so on[4].This separation establishes a separate plane for control，switching，and software-programmable functions that enable service providers to freely combine transport services with control protocols to achieve business transfer.All protocols for softswitch are IP-based，and they have the openness and flexibility of all IP-based protocols.Most importantly，the softswitch uses an open application programming interface（API）that simplifies the complexity of the signaling structure and control，and has openness to network technology，access technology，and intelligent services.Allowing the introduction of new services in the exchange mechanism，and the original four switches（long distance，tandem switch），5 switches（local switches）can still be retained through the SS7 link[5]. 2.Softswitch Network Structure Technology
2.1Softswitch Network Structure
Power network to softswitch as the core of the network has three characteristics：First，the use of an open network architecture system，the traditional switch function modules into separate network components，the user can be based on business needs free combination of functional parts Set up the network，the interface between the components of the standardization of the interface can achieve a variety of heterogeneous network interoperability.The second is based on the business-driven network，its function is the separation of business and call control，call and bearer separation，so that business is truly independent of the network，flexible and efficient implementation of the business，the user can configure and define their own business characteristics[6]，Concerned about the network form of the bearer service and the type of terminal，so that the provision of business and application has greater flexibility.Third，based on a unified protocol and packet-based network，because the existing information network，whether it is telecommunications network，computer network or cable network can not be one of the network-based platform to grow information infrastructure[7]，with IP Development，people have recognized that the telecommunications network，computer networks and cable television network will eventually pool to a unified IP network，which is commonly referred to as "triple play" integration trend[8].
The location of the softswitch in the network is divided into media / access layer，transport layer，control layer and service / application layer.The functions of each layer are as follows[9].
（1）media / access layer：to provide a variety of user terminals，user premises network and traditional communication network access to the core network gateway.
（2）transport layer：for a variety of media to provide broadband transmission channel，and the information routing to the destination.
（3）control layer：the main to provide call control，processing functions and protocol functions，business functions and interoperability.
（4）business / application layer：the use of the underlying resources to provide users with a variety of network services and resource management.
2.2External Interface of Softswitch
Softswitch as an open entity，with an external interface must use an open protocol，various interfaces and their use of the protocol as follows. （1）interface between the media gateway（MG）and the softswitch：the media gateway is used for softswitch to carry control，resource control and management of the media gateway.This interface can use the Media Gateway Control Protocol（MGCP），IP Device Control Protocol（IPDC），or H.248 protocol[10].
（2）interface between the signaling gateway（SG）and the softswitch：The signaling gateway is used to transmit the signaling information between the softswitch and the media gateway.This interface can use Signaling Control Transmission Protocol（SCTP）or other similar protocols.
（3）interface between softswitch：to achieve the interaction between different softswitch.This interface can use the Session Initiation Protocol（SIP-T）or H.323 protocol.
（4）interface between softswitch and application / service：provide access to various databases，tripartite application platform，various functions of the server interface，to achieve value-added services，management services and tripartite application support.Such as：· Softswitch and application server interface，you can use the SIP protocol or API（such as Parlay），to provide a tripartite application and a variety of value-added services support functions；· Softswitch and policy server interface，you can use the COPS protocol，The implementation of the network equipment to work on the dynamic intervention；· Softswitch and network management center interface，you can use the SNMP protocol to achieve network management；· Softswitch and intelligent network service control point（SCP）interface，you can use the INAP protocol，To achieve the existing intelligent network business support.
3.Softswitch Technology Advantages
Compared with the traditional switch，the softswitch technology has the following major advantages：
（1）soft switching technology has a lower cost，in the use of the process，the use of open platform and ordinary computer，it is easy to carry out And in the whole process，the price is very cheap，has a greater advantage，and third parties can also easily use the appropriate soft switching equipment，in this case，you can in the corresponding softswitch platform Use the network new business.
（2）the user's choice has a diversity.The traditional switch in the use of the process，generally by a business to provide the appropriate software and hardware maintenance and development，system updates and all other business，so that makes the user's choice of space significantly reduced，making the user did not The corresponding initiative，especially in the follow-up maintenance costs and no corresponding options，but the softswitch technology can solve this problem，the use of softswitch technology，you can establish a unified，standard onion space，And in the use of the process，the user can be independent of the supplier's choice，for the application of the software is extremely beneficial.（3）has a high reliability.Users in the process of network group，the use of soft switching technology can be fully functional software classification，all assigned to the corresponding backbone network，in the process，mainly based on the computer as a platform for system programming Processing，so that the network will become more secure and reliable. References
[1].Xing Yanxia.et al.Softswitch technology and network convergence.Mobile Communications，2005，Vol.29（6）.
[2].Liu Weihong.et al.Softswitch technology in power communication network.Zhejiang University，2008.
[3].Guo Jinghong，Cai Bin，Gao Yun，et al.Next generation network and its power development strategy during the "Eleventh Five-Year" period.Power System Communications，2006，Vol.27（10）.
[4].Qiang Lei.et al.Softswitch based on the next generation network networking technology.Beijing：People's Posts and Telecommunications Press，2005.
[5].Peng Qingqing，Xiang Li，Lu Changyan，et al.National Electric Power Dispatching Data Network.Power System Automation，2004，Vol.28（8）.
[6].Gao Longhua，Wang Li.et al.Application of Softswitch Technology in Power Communication Network.Modern Communications，2003，Vol.（5）.
[7].Li Wenyaoet al.Study on Functional Structure Model of Next Generation Network.China Journal of Data Communications，2003，Vol.（3）.
[8].Wang Jun，Zhang Jianwu.et al.PSTN network and NGN network interoperability.Modern Communications，2003，Vol.（3）.
[9].Chalie.et al.Research on the Combination of Softswitch Network and Existing Network.JOURNAL OF BEIJING UNIVERSITY OF POSTS AND TELECOM，2004，Vol.27（3）.
[10]Ye Wenchao.Discussion on Some Problems of Network Using NGN Technology.Telecommunications Science，2003，Vol.（5）.
（作者單位：1State Grid Hubei Electric Power Company Huanglongtan Hydropower Plant，Shiyan 442000，China）