With the acceleration of the pace of the construction of smart grid by the State Grid Corporation and the large-scale input of new energy, the importance of real-time deployment of power supply and demand is becoming more and more obvious, and at the same time, the real-time control of the power communication network has put forward higher requirements. The development of power grid makes all kinds of business will get rapid development, especially the data business is showing explosive growth trend, the business demand presents more and more bandwidth, more and more particles, more and more flexible way of bandwidth provision, circuit transmission performance and reliability requirements are more and more high, make the current SDH-based communication network is difficult to meet the development of the grid on the demand for communication. Therefore, it is of great significance to study and apply advanced and mature ASON technology to accelerate the construction of a strong communication network compatible with it, to meet the needs of the development of informationization of the company system, to improve the level of application of the communication service of the company system, and to provide reliable guarantee for the production, operation and management of the power grid.

1 ASON technology

1.1 ASON concept

ASON is an automatic switching transport network (ASTN) based on SDH optical network and optical transport network (OTN), which is a dynamic, automatic switching transport network, where the user dynamically initiates the service request, the network element automatically calculates and selects the path, and realizes the connection establishment, restoration, and dismantling through the signaling control, and integrates the switching and transport into a new generation of optical network. According to ITU-TG.8080 recommendation, ASON architecture is generally divided into transmission plane, control plane and management plane 3 parts, as shown in Figure 1.

Transport plane for the user from an endpoint bidirectional or unidirectional transparent information transfer, but also to transmit some control and network management information, including transport network elements (cross-connect devices and links), which carries the exchanged entities, such as optical connections. In addition, the transport plane has a hierarchical structure that supports multi-granularity optical switching technology, with devices interconnected by physical interfaces PI.

The control plane consists of optical connection controllers OCC, which are connected to each other through the network node interface NNI, and is the most characteristic core part of the ASON system, which consists of the routing, signaling forwarding, and resource management and other functional modules, and the signaling network that transmits the control signaling information, to complete the functions of the call control and connection control, etc. The control plane is a hierarchical structure that supports multi-granularity optical switching technology. Control level through the use of interfaces, protocols and signaling systems, dynamic exchange of optical network topology information, routing information and other control signaling, to achieve the dynamic establishment and removal of optical channels and dynamic allocation of network resources, but also in the event of a failure of the connection to restore it.

The main features of the management plane are the distribution of management functions and intelligence. The traditional optical transport network management system is replaced by a new type of multi-plane management structure based on the transport plane, control plane and signaling network, constituting an integrated optical network management scheme that combines centralized management with distributed intelligence, and combines the maintenance and management needs for the operator (management plane) with the dynamic service needs for the user (control plane).ASON's management plane and control plane technology ASON's management plane and control plane technology complement each other, and can realize dynamic configuration of network resources, performance detection, fault management and route planning and other functions. The network management module in the management plane connects the optical connection controller and switch through the network management interface NMI-A of the control plane and the network management interface NMI-T of the transmission network respectively. The services connecting the user and the ASON network contain data from the two planes of transmission and control, and the user communicates with the two planes through the physical interface and the user network interface UNI, respectively.

1.2 ASON Connection Methods

Through the transmission plane, control plane and management plane, ASON supports three types of connections: permanent connection, switched connection and soft permanent connection. Permanent connections, also known as provisioned connections, are done by the network management system or manually. A switched connection is any connection established at the request of an end user, i.e., between connected end nodes through a signaling/control plane, including the dynamic exchange of signaling messages between signaling units within the control plane. The introduction of switched connections is at the heart of the entire ASON, and it is with the introduction of switched connections that the optical network is characterized by intelligence. The soft permanent connection is a user-to-user connection, in which the user-to-network portion of the end-to-end connection is a permanent connection established through the network management system, while the network portion of the end-to-end connection is a switched connection established through the control plane, and the establishment of this connection is in between the first two, which is a kind of segmented hybrid connection, in which the connection establishment request is initiated by the management plane and set up by the control plane. initiated by the control plane and set up by the control plane.The structure diagrams of the 3 connection methods are shown in Figs. 2 to 4.

1.3 ASON Networking Factors

1.3.1 Network Latitude

Network dimension is a key factor to be considered for ASON networking. For an ideal mesh network, there needs to be a certain degree of connectivity between the nodes, and each node should preferably have more than three physical connection directions. Only the network in a certain degree of connectivity conditions, the entire network in the mesh recovery utilization and other aspects can be better advantage.

1.3.2 Type of service

ASON network can provide mesh recovery function, which enables operators to find a balance between bandwidth utilization and service recovery time. Usually, data services have lower latency requirements compared to voice services, making data-dominated networks more suitable for adopting ASON technology.

1.3.3 DCN Realization Methods

It is recommended to prioritize the in-band mode, because the in-band mode does not require the construction of a new DCN network, and the security of the DCN network is closely related to the link redundancy of the DCN physical layer, because the DCN topology in the in-band mode is exactly the same as that of the optical transmission network. The optical transmission network topology has a high degree of link redundancy, so the in-band approach also has good security. If the out-of-band approach is used, it must be ensured that the link redundancy of the DCN network is not lower than that of the optical transmission network topology; otherwise, the out-of-band approach does not have any other advantages except for cost enhancement.

1.3.4 Service Size

The service volume is usually one of the main considerations for selecting the topology when organizing the network. In the case of small business volume, the ring connection shows better bandwidth utilization. However, for large service volumes, the demand for large service volumes between nodes can make the direct physical pipes between nodes provided by the mesh network to be effectively filled and show better bandwidth utilization.

1.3.5 Interconnection

An important goal of ASON networking is to realize interconnection and interoperability of services in multi-vendor environments, so the equipment is required to comply with mainstream protocols and signaling standards. For better interoperability and management, the introduction of too many protocols should be avoided.

1.4 Technical Advantages of ASON

Compared with traditional optical networks, ASON has the following technical advantages:

1) It realizes dynamic allocation during optical network communication, and can dynamically adjust the provided broadband according to the feedback information implemented by users;

2) As ASON technology is characterized by bi-directionality, it can have good monitoring and protection capabilities for optical networks and has the advantage of distributed processing;

3) It can realize independent control of data network elements optical layer network elements, effectively linking the data service and information system of the optical network, and can make the network elements have intelligence;

4) strong network expansion capability, ASON with automatic discovery and add network nodes, can greatly reduce the workload brought about by large-scale network expansion;

5) high network security, ASON network using mesh network structure, not subject to node failure and fiber breakage problems, while ASON also provides a variety of protection and recovery mechanisms for different levels of business to provide the appropriate level of protection and recovery methods to ensure the safe and stable operation of the power grid;

6) high utilization of network resources, ASON introduces a recovery mechanism, making the bandwidth occupied by the protection is 20% to 30% less than that of SDH, which improves the utilization of resources to a certain extent.

2 Qinghai Electric Power Communication Transmission Network Status

2.1 Network Structure

Qinghai electric power communication network is mainly composed of Huawei, ZTE, ECI optical transmission equipment, its network is mainly ring with chain structure, has built four fiber optic double ring network, including the core backbone fiber optic ring network transmission bandwidth of 10 G, the backbone fiber optic ring network transmission bandwidth of 2.5 G. The core backbone communication sites are mostly more than one set of MSTP equipment, business scheduling complex.

2.2 Problems

At present, the following problems exist in the organization of the network:

1) Low utilization rate of ring network resources, and cross-ring communication sites become network bottlenecks. Core communication sites built with multiple sets of MSTP equipment, service transfer needs to be realized through the ODF/DDF interconnection between the equipment, circuit scheduling is done manually, the workload is large and prone to errors; low network utilization, multiplexing segment protection can only achieve 50% bandwidth utilization.

2) Single protection and recovery mechanism, poor support for new services. Traditional SDH can only provide ring network protection, and cannot provide different protection and recovery methods according to different customer needs; it cannot realize end-to-end automatic configuration.

2.3 Feasibility Analysis of Introducing ASON

2.3.1 Business Development Requirements

The generation of ASON technology is actually the demand of the rapid development of data services. At present, Qinghai electric power communication network business from ordinary 2 M small granular business gradually evolved into 155 M/622 M large granular data business, the traditional SDH ring with chain is difficult to meet the needs of business development, and strive to find a new way of organizing the network, and ASON networking can better solve this situation.

2.3.2 Communication Station Optical Cable Dimension

Sufficient fiber optic cable resources is the physical basis for the realization of ASON, generally speaking, if the communication station has three or more fiber optic cable dimension direction, the introduction of ASON can really play its advantages. For the current Qinghai electric power communication network structure, you can choose the core backbone communication station to build ASON network, Xining, Haixi region, the main communication station has reached three and more fiber optic cable dimension direction, "Twelfth Five-Year Plan" period through the infrastructure, technical reform projects continue to improve the communication between the site of the fiber optic cable resources, to lay the foundation for the construction of the ASON network. The foundation is laid for the construction of ASON network.

2.4 ASON transmission network introduction method and level analysis

The application of ASON should be considered separately according to the different characteristics of backbone transmission network and metropolitan transmission network, and different construction plans should be adopted. The introduction of ASON in the backbone transmission network, can consider the "bottom-up" plan, that is, the first in the local network scope of the introduction of ASON, and gradually through the use of UNI interfaces or NNI interfaces will be more than one local ASON island interconnections, and ultimately to achieve the entire network intelligent optical network deployment. According to the existing operating equipment and optical cable resources, Qinghai Power Communication Network firstly considers the construction of ASON MAN in Xining area and Haixi area, and then considers the upgrading and transformation of newly-built 10 G optical transmission equipments in Haidong area and Huanghua area to form ASON MAN and construct OTN backbone transmission network of Qinghai Power Grid, and then gradually extends it to aggregation layer and access layer, and ultimately realizes the intelligent optical network.

3 Qinghai Power Communication Network ASON Network Construction Planning

3.1 Principles of Networking

3.1.1 Node Selection

The selection of ASON nodes is mainly based on the consideration of the node's business flow traffic, the type of bearer service, cable routing and other factors. To select nodes with complex service flow, large service flow, and many fiber optic cable dimensions.

3.1.2 Structure Selection

The backbone network adopts MESH networking mode: if the MAN has 3-dimensional optical direction, it adopts full MESH mode; if it does not have 3-dimensional optical direction, it adopts the transition mode of ring network.

At this stage, only ring network is considered for ASON equipment networking, and when the optical cable conditions have mesh network, ASON intelligent control plane function can be opened in due course to form intelligent mesh network and realize automatic switching function.

3.1.3 Equipment Selection

According to the communication network development planning and intelligent optical network networking research, given the current SDH equipment and ASON equipment, the price difference is relatively small, Qinghai Power Grid in the future equipment construction process in the non-terminal 330 kV substation, hub 110 kV substation transmission equipment selection of equipment with ASON function.

3.2 Network Planning

According to the current status quo of Qinghai electric power communication fiber optic cable resources, combined with the communication development plan, the current western ring network communication sites in Haixi area are selected to form ASON ring network and ASON mesh network in Xining urban area, so as to satisfy the demand of multi-level, multi-capacity level and large span. The newly operated OSN3500 series equipment in the 2011 agricultural network renovation project in the central and western regions already has part of the ASON network functions, and the smooth upgrade of equipment with existing ASON functions to the ASON network can be considered. The initial planning of Qinghai electric power communication ASON network is shown in Figure 5.

4 Conclusion

Although the existing power communication network is basically SDH technology, ASON technology has greatly changed the concept and operation mode of the traditional transmission network, which has had a profound impact on its development, and intelligence will be an inevitable trend in the development of power communication network. The introduction and construction of ASON communication network must be a gradual process, in order to ensure network security and stability on the basis of building a new type of intelligent communication network, the innovation and upgrading of the power communication network are of great significance.