Fixed network optimization and evolution
The fixed telephone network has played a huge and irreplaceable role in promoting the development of society, bringing great convenience to people's communication. However, just as fixed-line alternative letters and telegrams at the time, various emerging communication methods began to be accepted. Under the new situation, fixed-line operators operating PSTN are facing increasingly severe challenges. First, the booming of the Internet has subverted the traditional telecom business model. Internet-based voice value-added services are rapidly developing. PSTN voice services are increasingly being shunted by other methods such as VoIP, instant messaging, etc., especially traditional long-distance calls. The business is most affected by IP phones. Second, with the popularity of monthly and one-way charging for mobile voice services, the replacement of fixed networks by mobile networks has become more serious, resulting in a decline in the number of fixed network users and fixed voice services, and the simple voice service is far from satisfactory. The needs of users, diversified, personalized and interactive business are the trend of the times. Third, from the fixed telephone network itself, the TDM network faces many problems, including: as the business volume declines, the equipment utilization rate decreases; the equipment models are large, the network access time is long, the aging rate is high, and the failure rate is high; Lack of spare parts, there are potential safety hazards, and manufacturers' support is weak. The profit margin of fixed voice services has become smaller and smaller. Operators' efforts can only delay the decline of fixed-line revenues, and they cannot fundamentally change this trend. There is an urgent need to find new ways of sustainable development through a series of The network transformation and update means can be implemented and implemented to optimize the fixed voice network economically and rationally, improve the market response capability, meet the diversified business needs of current users, and achieve energy saving and emission reduction. 2 fixed voice network optimization To study the optimization of fixed voice networks, it is necessary to consider the following factors to formulate the overall idea of ​​network optimization. a) Network evolution trends. It conforms to the evolution trend of network broadband and enhances the business opening capability of the network. b) Network architecture design. Step-by-step flat-end network structure is implemented to reduce the transfer of existing long-distance traffic. c) Energy conservation and emission reduction. Pushing the end office as the unit, the entire equipment scale will be retired, achieving better energy saving and emission reduction effects. d) Light enters and exits copper. Promote scale retreat from the user side distribution cable to the interoffice backbone cable. e) Resource utilization. It is necessary to further improve the efficiency of resource utilization in the PSTN end office. The optimization of the fixed voice network is mainly for the TDM network, especially the TDM end office. In combination with the existing problems, the optimization methods of the TDM end office mainly have two major categories: one is non-IP transformation, which mainly includes the reduction and withdrawal of the board. The other is the IP transformation, including the AG package, the new AG and the FTTx transformation. 2.1 Non-IP transformation optimization method This type of transformation is only the adjustment and optimization of the existing network TDM. The modified end office equipment is still the TDM end office and does not support the IP interface. 2.1.1 Rewinding and reducing volume This method is mainly for the end office with lower installation rate, removing the idle user board and the relay board, reducing the capacity of the equipment in the network, thereby achieving the purpose of reducing the occupation and power consumption. The main measures are: priority reduction according to the order of the whole rack and the whole machine frame; for large-scale switching equipment, the port is “last-to-front†adjustment; for the whole racks such as Bell and Nortel, the whole machine frame is difficult to reduce. The switching device is implemented by reducing the format of the user interface board; empty the whole module, the whole frame, and the whole rack as much as possible, especially near the end of the rack. When using this method, there are several situations that need attention. a) For plates that have been used for a long period of time, if they are used in the past, there is a possibility of increasing maintenance costs and reducing the stability and safety of the system. b) If the port density of the old and old boards is too low, and the slots are also occupied, it will cause waste. c) Some equipment chassis are full. If you want to use the original board, you need to add a box. 2.1.2 Withdrawal of the head This method mainly transforms the end office into a module office of the same model, and hangs it to other end offices; the equipment cable and the outgoing copper cable maintain the status quo, no need for line cutover, only data adjustment, after the cutover transformation is completed, the mother The machine head is powered off. When using this method, there are several situations that need attention. a) Need to merge with the same model, otherwise it is not compatible. b) The quality of the end user board equipment and lines required to be modified is good. c) Small capacity combination, otherwise it exceeds the control module processing range. d) The S1240 needs to be added with a new cabinet. The cutover is complicated and is not recommended. 2.2 IP transformation and optimization method This method includes modifying the existing TDM equipment, adding the AG encapsulation mode of the IP uplink port, and adding a device such as an AG or a PON supporting the IP port to replace the TDM. 2.2.1 AG package this way The VoIP main control board or the main control box is added to replace the narrowband main control module of the original switching device, and the modified end office is connected to the softswitch or IMS. The device cable and the outgoing copper cable maintain the status quo, and no line cutover is required. Data adjustment, power off the system rack and the public board after the cutover is completed. When using this method, there are several situations that need attention. a) Require the user board equipment and line quality. b) After the transformation, the voice service can still only be provided. c) The cost is higher, 40~86 yuan/line. d) Less than 500 gate areas are not applicable, and it is necessary to expand softswitch or implement IMS access. 2.2.2 Creating an AG Mode This mode is mainly used for areas where voice requirements are dominant. A new AG can choose to replace existing TDM equipment in the core equipment room or in the equipment room near the user side. Among them, close to the user side machine room, it is beneficial to realize the light in and out of the trunk cable. 2.2.3 FTTx mode The FTTx transformation method mainly combines the broadband upgrade speed increase and the optical entry copper retreat project, and realizes the access of the original user by moving the access device downward, and the new device uplinks to the soft switch or the IMS system. FTTx includes FTTB/C and FTTH. a) The FTTB/C mode retains the cable from the transfer box to the user terminal. The degree of light entering the copper is higher, and the user can retain the original terminal, so the user basically does not feel the impact before and after the cutover. b) The FTTH mode has the highest degree of optical retreat, and the user can retain the original narrowband voice terminal or a broadband voice terminal. 2.3 Fixed voice network optimization summary In terms of economic benefits, in addition to the reduction of the board and the withdrawal of the head, the investment recovery period of other transformation methods has exceeded 10 years. Among them, due to the operability of the reduction of capacity and the reduction of capacity, in the case of limited funds, operators are more suitable to adopt the optimization method of reducing the capacity of the board to reduce the energy consumption of the equipment and improve the network installation rate; At the time, considering the evolution of the future technology and the cooperation with the light into the copper, the FTTx transformation method can be adopted more. For the FTTx retrofit, it is recommended to implement the retrofit for the TDM end office where the following conditions exist. a) Equipment with high failure rate, insufficient technical support, and potential safety hazards. b) Equipment with severe aging of copper cables in the covered area and poor line quality. c) Equipment that has been in operation for more than 15 years in the network. d) Equipment with relatively high energy consumption for equipment operation. e) Devices with a low capacity and quantity of equipment. f) Equipment with a large footprint in the equipment room. g) Equipment with a low installed rate. 3 The next evolution of fixed voice networks 3.1 The evolution direction of the fixed voice network The needs of users determine the future direction of fixed voice networks. Whether the bearer service uses the telecommunication network or the Internet, there is still debate. Overall, the driving force for the future evolution of fixed voice networks comes from the following two aspects. a) Business provision. The telecommunications business mainly includes three major categories: basic and supplementary services, intelligent services and multimedia services. Among them, the first two types of services are mainly provided by the telecommunication network, while the multimedia services, IMS and the Internet can be provided. The service types and service experiences provided by the Internet are better than the IMS. The so-called "cloud management" concept proposes to reflect the other direction of the future telecommunication business to a certain extent, but it is still in the concept stage, and it is a subversive change for the network, business and operation management of existing telecommunication operators. Cut into the telecommunications business from the Internet. It is difficult to form an industrial scale in a short period of time. b) Evolution of equipment and network architecture. With the continuous development of communication technology, from traditional TDM to softswitch, it gradually develops to IMS. From the perspectives of standardization degree, protocol type, service type, access, terminal, energy consumption and interface openness, IMS is a recent The technical standards that are seen are the most mature, the industry support is the best, and commercial technology has been obtained; the equipment and architecture of fixed and mobile networks are evolving to IMS. In general, from the perspective of the two aspects of the current fixed-line evolution, IMS is a relatively clear evolution direction. 3.2 Service and implementation under IMS 3.2.1 Overview of services under IMS The services in IMS are mainly divided into three categories: basic and supplementary services, traditional intelligent services, and new IMS services. a) The supplementary services mainly include calling number identification display/restriction/override, call forwarding/waiting/holding, three-party calling, outgoing call restriction, DND service, abbreviated dialing, hotline service, alarm clock, lockout service, and fax service. b) Traditional intelligent services mainly include VPN, prepaid, No.1, mobile H code translation, Yueling and card services. This type of business has both national and local businesses and even local deployments. c) IMS new services, including multimedia phones, ring tones, color images, conferences, instant messaging, unified centrex, click-to-dial, converged one-way, converged video (IPTV), IP call center (IPCC), interactive voice and video response system (IVDR), etc. Among the above services, the first and second types belong to the services already provided by the existing network, and the third type is the special services provided in the IMS environment. 3.2.2 Service Implementation under IMS Under the IMS architecture, all services can be implemented by setting the corresponding AS. However, for the inheritance of traditional intelligent services, considering the consistency of services and the difficulty of network cutover, the following three methods are generally adopted. Method 1: The voice path returns to the existing tandem office to trigger the intelligent service. The call of the IMS domain is routed to the fixed network tandem office through the MGCF, and the intelligent service is triggered by the tandem office to the existing intelligent network SCP. In this way, the technical difficulty is low. The service triggering and service control are implemented by the tandem office and the SCP of the existing network respectively, but the IM-MGW to the gateway needs to occupy a large voice port. Method 2: Implemented by IMS-SSF. This method simplifies the IMS user service flow, and the IM-SSF is responsible for completing the conversion of the INAP/CAP/SIP protocol to the IMS SIP protocol, and completing the service triggering, and the service control is still completed by the SCP. In this way, there is no need to call back to the tandem office, so there is no need to additionally occupy the port resources of the IM-MGW to the gateway, but it is necessary to complete the docking test of the IM-SSF and the provincial or even the local SCP, which is technically more difficult. Method 3: Create a new AS platform to replace the existing SCP device. The service triggering and service control in this mode are implemented in the IMS. There is no voice path, but the traditional intelligent services in the province are deployed in the province or even locally. The business logic is different. Therefore, the new AS is fully inherited. 3.3 Evolution Strategy of Fixed Voice Network 3.3.1 General steps for the evolution of a fixed voice network In view of the current situation that the fixed voice network TDM and softswitch coexist, the evolution of the fixed voice network can follow the following steps. The first step is to use the PSTN network as an opportunity to deploy the IMS network on a large scale to control the expansion of the fixed network softswitch to form a TDM+softswitch+IMS network architecture. The second step: TDM users basically complete the migration to IMS, form the network architecture of IMS+ softswitch, and realize the flattening of the network. The third step: After the upgrade of the fixed network softswitch equipment, the whole access to the IMS network, IMS becomes the only core control network of the fixed network. 3.3.2 TDM Device Evolution Strategy After the IMS is introduced, the existing TDM devices evolve to the IMS in the following two modes. a) After the AG is encapsulated, it is connected to the IMS core network. b) Through the FTTx transformation, all the TDM equipments are retired. There is no additional requirement for the existing TDM switch in the FTTx transformation mode, and the AG package method requires the device manufacturer to provide a specific package solution. At present, among the mainstream manufacturers, Nokia Siemens, Bell and ZTE have provided mature AG packaging solutions. 3.3.3 Softswitch Equipment Evolution Strategy 3.3.3.1 Softswitch End Office Evolution Strategy Currently, there are two ways for the softswitch end office to evolve to IMS. a) AGCF+H.248 AG mode. Modify the softswitch SS to AGCF, or create a new AGCF, and the AG remains unchanged. b) SIP AG mode. The interface protocol of the softswitch AG is upgraded from H.248 to SIP, and the softswitch SS is no longer used. From the perspectives of standardization degree, commercial maturity, business capability, and difficulty of transformation, the current AGCF+H.248 AG method has certain advantages. Currently, the IMS commercial network deployed in China mainly adopts such methods. 3.3.3.2 Evolutionary Policy of the Softswitch Switching Station The softswitch tandem SS is transformed into MGCF, and the TG evolves into IM-MGW for voice intercommunication between IMS and other China Unicom networks. 3.3.3.3 SDC Evolution Strategy SDC is mainly used to centrally store user's service attribute data when the fixed network is intelligent. It is similar to the HSS function in IMS. Therefore, SDC also has the possibility of evolving to HSS. However, the user data structure, authentication mode, interface protocol, etc. of the SDC device itself are different from those of the HSS, and the resources available on the software are limited; the HSS of most manufacturers is developed based on a new hardware platform such as ATCA, and the SDC is hardware. The model is relatively old, the processing capacity is limited, and subsequent support and maintenance are more difficult. Therefore, the significance of SDC hardware upgrade to HSS is not significant. Therefore, when evolving to IMS, SDC adopts the following strategies. a) The coexistence phase between IMS and fixed network softswitch, SDC only serves the fixed network softswitch. b) When the fixed network softswitch needs to evolve to AGCF, the data in the SDC is migrated to the HSS, and the SDC is gradually retired. 4 Conclusion After IMS is defined as the next development direction of the fixed voice network, the optimization of the fixed voice network can be summarized as the realization of network slimming by measures such as the reduction of capacity and the gradual migration to the target through IMS replacement of TDM. As a new technology, IMS introduces many aspects of network construction and maintenance, such as service, network, support, transmission and supporting. Therefore, the preparation of operators in the early stage of IMS construction is very important, and during IMS construction, it needs Handle the network division and interconnection of softswitch and IMS to ensure the stable and healthy development of the fixed voice network. Desktop Power Adapter,Hp All-In-One Desktop Power Adapter 90W,Laptop Power Adapter Charger,Hp Desktop Power Adapter Guang Er Zhong(Zhaoqing)Electronics Co., Ltd , http://www.cnadaptor.com