Broadband networks crisscross China

May 1, 1996

Broadband networks crisscross China

China is accelerating its fiber-optic infrastructure development and deployment to attain worldwide technological parity in broadband services, networks and infrastructure during the next five years

david F. Romero

national semiconductor

Backed by the government`s ambitious plans and finances for economic development and communications infrastructure deployment, China is expected to become the largest telecommunications market during the remainder of this decade. Having completed its eighth five-year plan in 1995, the world`s most-populous nation is embarking on its most-aggressive infrastructure deployment agenda to date.

The country`s two primary goals for the telecommunications transmission portion of the ninth five-year plan (1996 to 2000) are:

Connect the less economically developed inland provinces with the economic "growth engines" along the eastern coast of China.

Attain a level of self-sufficiency in the development and manufacture of Synchronous Digital Hierarchy (SDH) equipment that will be deployed along the fiber backbones to establish the communications lifeline of the country.

The fibering of the eastern provinces served as the primary deployment focus from 1991 to 1995 to accommodate their high population densities. These provinces include the major industrial centers of Guangdong, Jiangsu and Shanghai. Additional infrastructure is scheduled for these areas from 1996 to 2000. However, the current plan focuses mainly on a matrix backbone with eight primary east/west fiber routes intersecting eight primary north/south routes via more than 60 major network nodes (see figure).

Nationwide fiber

This fiber mesh, comprising more than 100,000 kilometers of fiber-optic cable, will cross every province and provide connectivity to every provincial capital and major population center in China. Of this total, 70,000 km are scheduled for deployment along routes entirely within provincial boundaries, with the remaining 30,000 km for the interprovincial network. These planned fiber links are gauged to spur growth in the rural provinces to the west. In turn, the links are expected to reverse the increasing disparity in standard of living and income between residents of coastal and inland provinces.

China`s Ministry of Posts and Telecommunications (MPT), the organization within the government that is responsible for planning and deploying the telecommunications infrastructure, is also expected to flatten the hierarchical structure of the network. In the past, three levels of network infrastructure existed: an interprovincial transport network, an intraprovincial transport network and a local transport or access network. The new hierarchy spells out two levels of infrastructure: a single, long-distance transport network (effectively consolidating the interprovincial and intraprovincial transport networks) and the local access network. In addition, more efforts are projected to focus on fiber-ring architectures within the access networks to obtain higher communications reliability and flexibility.

Other fiber projects

Although the magnitude of the MPT`s plan is massive, other fiber-optic cable deployment activity is also occurring in China. The China United Telecommunications Corp. (China Unicom), a recently formed competitive network provider, is planning to install more than 22,000 km of fiber cabling along 10 major routes during the next five years. In addition, many provinces have derived their own fiber deployment plans during the ninth five-year plan which, according to Chinese Government departmental estimates, could easily bring the nation`s total installation of fiber-optic cabling by the end of this decade to approximately 300,000 km.

Most of the fiber-optic cable installed during this five-year plan is expected to contain 36 fibers, compared to the typical core counts of 24 during the last five-year plan. The new cabling specifies singlemode fiber operating at 1550 nanometers and conforming to ITU-T Recommendation G.652. It is well-suited to handle SDH rates to 2.48 gigabits per second.

However, in anticipation of future requirements along certain high-growth routes, especially along the east coast, the optical cables might consist of dispersion-shifted fiber conforming to ITU-T Recommendation G.653. This singlemode fiber, which provides low-dispersion and low-attenuation characteristics centered at 1550 nm, is better suited to SDH systems at line rates to 10 Gbits/sec and higher. Although no development activity within China for SDH systems currently runs at this line rate, the dispersion-shifted fiber networks would easily accommodate the higher speeds.


With little or no existing legacy cabling in place, practically no fiscal disincentive stands in the way of installing the most advanced equipment available along these new routes. Therefore, the MPT plans to rapidly migrate the class of equipment to be developed and deployed from plesiochronous digital hierarchy (PDH)-based equipment to SDH-based systems. The ongoing deployment of PDH systems, with line rates of 34, 140 and 565 Mbits/sec, is foreseen to be replaced by SDH systems at line rates of 155, 622 and 2488 Mbits/sec (STM-1, STM-4 and STM-16, respectively).

Three classes of SDH equipment-- repeaters, terminal multiplexers and add/drop multiplexers--are expected to run at these line rates. The terminal and add/drop multiplexers are figured to handle the PDH tributary rates of 2 to 140 Mbits/sec to provide connectivity to the infrastructure put in place during the previous five-year plans. The STM-4 and STM-16 SDH systems might also be configured to provide both STM-1 tributary interfaces--where appropriate--and add/drop multiplexers into the new portions of the access network consisting of STM-1 systems.

The deployment of SDH systems within China is not new. Considerable installation of foreign-designed and -manufactured systems has taken place during the last few years. The installation of imported systems should continue during the current plan. However, as foreign-designed but locally manufactured SDH systems become available from some of the recently established domestic and foreign joint ventures, these systems will be widely deployed.

China`s ultimate goal regarding SDH systems, however, is to be fully self-sufficient, as it is now with PDH equipment. The Wuhan Research Institute, a part of the MPT, has developed and currently manufactures a high percentage of the PDH systems deployed within China. In fact, the institute has established a strong export market for PDH systems in other parts of Asia.

Much SDH development activity occurred at several research and development centers within the MPT during the last five-year plan in support of China`s goal. As the current plan unfolds, these systems are expected to receive high MPT acceptance for deployment along the fiber-mesh backbone. This deployment represents the typical network installation pattern of most emerging countries with regulated telecommunications environments, such as in India and Brazil.

When the eighth five-year plan concluded last December, China reached a national telephone line density of 3.65% (3.65 telephones per 100 people). This density exceeded the goal by 1%. The teledensity goals for the current plan are to attain a national figure of 10% to 40% in urban centers. Clearly, this goal is a major driver for the aggressive fiber-optic cabling plans within China.

However, China is also looking to provide advanced broadband services commensurate with a growing middle class. For example, a broadband multimedia information network is being built in Guangzhou. This network, planned for completion this year, is expected to provide end-to-end connectivity for a configuration of multimedia computers exchanging voice, video and data communications. Plans call for extending this information network to the entire province by the year 2000.

Moreover, several national, provincial and municipal videoconferencing networks are in various stages of construction. Because China is so large, installing videoconferencing centers is an economically viable alternative to travel. This would provide remote users--typically government entities and businesses--with a means of communication that is more effective than telephone alone. Consequently, urban centers have also been networked. Zhejiang province, for example, located along the east coast near Shanghai, has put into operation 78 videoconferencing centers that provide connections for 73 cities, counties and townships to the provincial government as well as to the national videoconferencing network.

China has also been hit by Internet fever. China`s information highway, known as Chinanet, was launched last June. Growth has been strong, although the number of subscribers totals fewer than 3000. However, the MPT`s current five-year plan hopes to deploy 500,000 Internet terminals by the year 2000. u

David F. Romero is strategic marketing manager for broadband transmission support products at National Semiconductor in South Portland, ME. His Internet address is [email protected].

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