China's PDT network rolls out

Networks based on China’s indigenously developed Police Digital Trunking standard are being deployed across the country.

The history of China Police’s mission-critical communications dates back to the 1990s. Back then, the agency trialled various technologies including conventional analog, MPT1327 analog trunking and TETRA, in an attempt to set up a nationwide standard across different provinces and cities using the police force’s proprietary 350 MHz frequency range. However, after 20 years of trials and practice, the overall development of the 350 MHz communication network was not even and uniform. MPT1327 had been adopted by majority county-level cities as a mainstream technology, while TETRA had been adopted by a number of province-level municipalities, provincial capitals and developed coastal cities. In addition, an IP-based analog trunking system was used by a few provinces as an experiment.

During those years, analog trunking played a major role and greatly enhanced the capability of China Police’s mission-critical communications. But with drawbacks such as the low efficiency of spectrum usage, low capacity, inadequate functionality and weak encryption, the development of analog trunking was very limited and finally abandoned. On the other hand, Euro-American developed countries had begun to upgrade their technology from analog to digital trunking. TETRA attracted extensive attention from a number of cities in China and since 2006 was successfully brought in by Beijing, Shanghai, Shenzhen and Jinan. Compared with analog trunking, TETRA has a series of excellent features such as high-quality clear voice, high efficiency of spectrum usage and fast data transmission. This advanced digital trunking technology was put to good use by security agencies during the 2008 Beijing Olympics and 2010 Shanghai World Expo.

Nevertheless, TETRA was still not a perfect option for China’s police. TETRA began in Europe, where the population density, especially in the cities, is much higher, producing high traffic within comparatively small regions. In China, the majority of population is scattered over vast regions… where radio coverage must be wide but where traffic is expected to be much lower than in big cities such as Beijing and Shanghai. To have a nationwide network, China’s police wanted to have much wider coverage but with the same amount of investment. A self-developed encryption algorithm was also a major consideration. TETRA was terminated as an official digital trunking standard for China Police in May 2014. However, TETRA is vibrant in mass transit rail, ports and airports in China.

The birth of PDT

The Information and Telecommunication Bureau of the Chinese Ministry of Public Security (ITBMPS) made the decision to undertake research with the aim of developing a Chinese-owned trunking standard. “The actual conditions in China are different from other countries. Neither analog trunking nor TETRA is the answer to the national standard for China Police. It is the only and inevitable option for us to develop our own digital trunking standard,” said an ex-chief official of ITBMPS.

In April 2008, ITBMPS initiated research into a Police Digital Trunking (PDT) standard. In August 2008, the Chinese Police Wireless Telecom Technology Specialist Panel was established and called for a meeting with Chinese manufacturers to formulate the standard. At this meeting, Shenzhen-based Hytera, one of the top five global PMR enterprises at that time, was designated as the leader of the group to drive the entire development.

In October 2011, ITBMPS released the trial version of the General Specification of the PDT standard to kick off the testing. In 2013, ITBMPS released the final version of the General Specification and certified the planning for construction of a nationwide PDT network. At this point, the first Chinese digital trunking standard with independent intellectual property rights came into reality. Development is led by the PDT Association, which has a membership comprising both Chinese and international entities.

The PDT Standard meets the specific needs of China’s public safety sector and seamlessly interfaces with the current police geographic information system (GIS) dispatching platform. In addition, it is intended to provide features such as wide coverage, flexible networking, efficient dispatching, high-quality voice and data transmission, and secure encryption. “The invention of PDT will greatly improve the development pace and strength of the Chinese police telecom industry. It will also provide a solution that is more suitable for Chinese police operation,” the official added.

In fact, the whole concept is forward-looking. “The PDT standard is compatible with international standards. This could help Chinese PMR enterprises explore international markets and attract foreign PMR enterprises to join the PDT competition in China market, which would be beneficial in bringing down the manufacturing costs and improving product performance as well as elevating product competitiveness,” said Yelin Jiang, vice president of Hytera.

Implementation

As the leader of the PDT Standard development master group, Hytera has achieved a number of important milestones, such as: the first PDT application for China Police (for the Shenzhen Immigration Inspection Station); the first PDT application for a provincial capital (Harbin Traffic Police); the first multiple city connection (Xinjiang Province); and the first application for a province-level municipality (Chongqing City).

According to figures from the PDT Association, as of November 2016, 30 provinces, cities and municipalities had begun construction of PDT networks. More than 280 PDT systems and 6000 sets of PDT base stations, as well as 400,000 PDT terminal units, have been deployed by China Police. According to forecasts, the total value of PDT network construction in China will be between US$2–3 billion, with construction to peak during 2017–19. And even as that rollout takes place, the PDT Association has begun formulating the next-generation broadband trunking standard for China Police.

Images courtesy Hytera.

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