Optimization and Evolution of Traditional Fixed Voice Network

1 Research background

With the advancement of technology and the development of social needs, the telephone network is constantly evolving. Various new technologies and new equipment are applied in the network. The telephone network is becoming more efficient and flexible. The fixed telephone network has played a huge and irreplaceable role in the process of promoting social development, bringing great convenience to people's communication. However, just as fixed-line telephones replaced letters and telegraphs at that time, various emerging communication methods began to be gradually accepted by people. Under the new situation, fixed-line operators operating PSTN are facing increasingly severe challenges.

First, the vigorous development of the Internet has subverted the traditional telecommunications business model. The Internet-based voice value-added services are developing rapidly. PSTN voice services are increasingly diverted by other communication methods such as VoIP and instant messaging, especially traditional long-distance calls. The business is most affected by IP phones.

Second, with the popularization of monthly subscriptions and one-way charges for mobile voice services, the replacement of fixed networks by mobile networks is becoming more and more serious, resulting in the continuous decline in the number of fixed network users and fixed voice services, and pure voice services are far from satisfactory The needs of users, diversified, personalized and interactive integration services are the general trend.

Third, from the perspective of the fixed telephone network itself, the TDM network is facing many problems, including: with the decline in business volume, the utilization rate of equipment is reduced; there are many equipment models, long network access time, aging, and a high failure rate; There is a lack of spare parts, there are hidden safety risks, and the support of manufacturers is weakened; switches generally have the problems of large footprint and high energy consumption. Compared with soft switching (or IMS) equipment, TDM equipment of the same size consumes more than 35% of energy and 60% of the occupied area of ​​the equipment room. With the advancement of optical fiber copper retreat and broadband speedup, TDM end offices only support narrowband For copper access, the requirements for its transformation are becoming more urgent. The fixed softswitch network also appears to be unable to cope with the interoperability of different manufacturers, the ability to provide multimedia services, and the convergence of fixed and mobile networks.

The profit space for fixed voice services is getting smaller and smaller. Operators' efforts can only delay the decline in fixed-line revenue, but cannot fundamentally change this trend. There is an urgent need to find new ways of sustainable development-through a series of Operational implementation of network transformation and updating methods to optimize the fixed voice network economically and reasonably, improve market responsiveness, meet the diversified business needs of current users, and achieve energy conservation and emission reduction.

2 Research on optimization of fixed voice network

The optimization of the fixed voice network needs to consider the following factors to formulate the overall idea of ​​network optimization.

a) Network evolution trend. It conforms to the trend of network broadband evolution and enhances the network's business opening capabilities.

b) Network architecture design. Gradually realize the end-to-end flat network structure and reduce the transfer of existing long-distance traffic.

c) Energy saving and emission reduction. Promote the end-bureau as the unit, withdraw the entire scale of equipment from the network to achieve better energy-saving and emission-reduction effects.

d) Light advances and retreats from copper. Promote the large-scale withdrawal from the distribution cable on the user side to the backbone cable between the offices.

e) Resource utilization. To further improve the efficiency of the PSTN end office resource use in the network.

The optimization of the fixed voice network is mainly aimed at the TDM network, especially the TDM end office. Combining with the existing problems, there are two main types of optimization methods for the TDM end office: one is the non-IP transformation, which mainly includes the withdrawal of the board and the reduction of capacity. Head-to-head, etc .; the other category is IP transformation, including AG packaging, new AG, and FTTx transformation.

2.1 Non-IP transformation and optimization methods

This type of transformation is only the adjustment and optimization of the existing network TDM. The transformed end office equipment is still a TDM end office and does not support IP interfaces.

2.1.1 Volume reduction

This method is mainly aimed at the end office with a low installation rate, removing idle user boards and relay boards to reduce the capacity of the equipment on the network, so as to achieve the purpose of reducing floor space and power consumption.

The main measures are: priority to reduce the load in the order of the whole rack and the whole frame; for large-scale switching equipment, the port is adjusted "last to the front"; for the whole rack and the whole frame such as Bell and Nortel, it is difficult to reduce the load Switching equipment is carried out by reducing the user interface board; try to free up the entire module, the entire frame, and the entire rack, especially the rack near the end.

When using this method, there are several situations that need attention.

a) For the plates with long service life, if the old ones are used, there is the possibility of increasing maintenance costs and reducing the stability and safety of the system.

b) If the port density of some old boards is too low, it will cause waste if the slots are also occupied.

c) The slot of the frame of some equipment is full. If you want to use the old original card, you need to add a frame, and you need to invest another.

2.1.2 Withdrawal

This method is mainly to transform the end office into a modular office of the same model and download it to other end offices; the equipment cable and the outgoing copper cable maintain the status quo, no line cutover is required, only data adjustment is performed, and the mother The head of the bureau was turned off and the service was cancelled.

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) It is required that the transformed end office user board equipment and lines are of good quality.

c) Small-capacity combination, otherwise it exceeds the processing range of the control module.

d) S1240 needs to add a new cabinet, and the cutover is complicated, so it is not recommended.

2.2 Optimization method of IP transformation

This method includes the transformation of existing TDM equipment, the addition of AG encapsulation methods for IP upstream ports, and the replacement of TDM with new equipment that supports IP ports such as AG and PON.

2.2.1 AG packaging

In this method, a new VoIP main control board or main control frame is added to replace the narrowband main control module of the original switching equipment, and the modified end office is connected to the soft switch or IMS. Only data adjustment is performed, and the system rack and public board are powered off after the cutover transformation is completed.

When using this method, there are several situations that need attention.

a) The user board equipment and line quality are required to be good.

b) After the transformation, it can still only provide voice services.

c) The cost is relatively high, 40 ~ 86 yuan / line.

d) The area of ​​less than 500 gates is not applicable. At the same time, it needs to expand the softswitch or implement IMS access.

2.2.2 New AG mode

This method is mainly used in areas where voice demand is the main factor. New AGs can choose to replace existing TDM equipment in the core computer room or the computer room close to the user side. Among them, close to the user-side computer room is conducive to the optical cable entry and exit of the backbone cable.

2.2.3 FTTx method

The FTTx transformation method mainly combines broadband upgrade and speed-up and the optical copper entry and exit project. The original users are accessed by moving down the access equipment, and the new equipment is upstream connected to the softswitch or IMS system. FTTx includes FTTB / C and FTTH.

a) The FTTB / C method retains the cable from the junction box to the user terminal, and the degree of optical entry and exit is relatively high, and the user can retain the original terminal, so the user can hardly feel the impact before and after the cutover.

b) The FTTH mode has the highest degree of optical access and copper retreat. The user can keep the original narrowband voice terminal or use a broadband voice terminal.

2.3 Optimization summary of fixed voice network

From the point of view of economic benefits, except for the withdrawal of the board and volume reduction and the merger of the heads, the investment recovery period of other transformation methods is more than 10 years. Among them, due to the greater operability of the board reduction and capacity reduction, under the circumstances of limited funds, operators are more suitable to adopt the optimization method of board reduction and capacity reduction to reduce equipment energy consumption and increase the network installation rate; At this time, considering the evolution of future technologies and the cooperation with the optical system, the FTTx transformation method can be adopted more. For FTTx transformation, it is recommended that the TDM end office with the following conditions be given priority to implement transformation.

a) Equipment with high failure rate, insufficient technical support, and potential safety hazards.

b) Equipment with severe copper aging and poor line quality in the coverage area.

c) Equipment with a service life of more than 15 years on the network.

d) Equipment with relatively high energy consumption for equipment operation.

e) Equipment with a low proportion of equipment capacity and quantity.

f) Equipment with a large floor area in the machine room.

g) Equipment with low installed rate.

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