A few days ago, the Hong Kong-Zhuhai-Macao Bridge, a super sea-crossing project jointly built by Guangdong, Hong Kong and Macao, was opened. The opening ceremony was held in Zhuhai, Guangdong on the morning of the 23rd. It is not only the longest sea-crossing bridge in the world, but also one of the most technically complex, construction requirements and standards in the history of Chinese transportation. It is hailed as the "Seven Wonders of the New World" by the British "Guardian".

But, you know what?

Behind the most complex project, there is also a feat of communication engineering--

• In the subsea immersed tube tunnel with a depth of more than 40 meters on the Hong Kong-Zhuhai-Macao Bridge, the 4G network signal on the mobile phone is still full, and the voice and video communication is smooth.

The bridge, the undersea tunnel and the east-west artificial island have achieved 4G signal coverage in the whole process, and the 4G network test results of the three operators of telecom, mobile and Unicom are all excellent.

How is this level of communication network tempered?

The mobile communication infrastructure of the main project of the Hong Kong-Zhuhai-Macao Bridge was constructed by China Tower Corporation and has passed the network acceptance tests of China Telecom, China Mobile and China Unicom. The engineering solution is divided into four parts according to the main body: cross-sea bridge coverage scheme, undersea tunnel coverage scheme, artificial island coverage scheme and connection line coverage scheme.

The mobile phone mobile communication system consists of three parts: mobile stations (such as mobile phones), base stations BS (antennas, radio signal receiving, transmitting equipment and base station controllers, etc.), switching networks (mobile switches, inter-regional relay transmission equipment, etc.). No matter how close the mobile stations are, they cannot communicate directly and need to access and forward through the base station and the mobile switching center. Therefore, whether the mobile station can receive the radio signal depends on the signal coverage of the base station in the area.

China Telecom, China Mobile and China Unicom have their own operating networks and wireless frequency bands. In the past, mobile infrastructure was built and operated independently, resulting in a waste of resources. In 2014, in order to reduce the repeated construction of towers and related infrastructure in the telecommunications industry, improve the investment efficiency of the industry, and further promote resource conservation and environmental protection from the mechanism, the three major operators jointly funded the establishment of China Tower Corporation and benefited from it.

It can be seen that the tower company to cover the network, can take into account the three operators of the network and frequency bands, to avoid waste of resources, improve efficiency.

Bridge main body coverage scheme

The bridge section of the bridge has a total of 43 gantry, and it is on these gantry that the base station antenna is installed.

However, due to the different distances between the bridge gantry, the shortest distance between the two gantry is 50 meters and the longest is 2813 meters, and the antenna hanging height is also limited. In order to ensure the ultra-long distance coverage, the designers have conducted many on-site surveys and investigations. Through on-site simulation, careful discussion and on-site demonstration together with antenna manufacturers, it is proposed to use a unified procurement of 33 degrees, 21dBi high gain narrow beam antenna to cover several of the ultra-long-distance gantry sections, and finally achieve full coverage of the bridge section of the public network signal.

All public network equipment such as pole, antenna, RRU, distribution box, fiber splitting box and other equipment are set on the door frame. Three new 3-meter poles will be built for each portal frame, and one 3-meter pole will be allocated to each operator for hanging antennas and RRU. A pair of antennas are installed in front of and behind each 3-meter pole. The antenna is about 8 meters high from the bridge deck and is covered by back-to-back installation. Four new 1-meter poles will be built for each portal frame, one 1-meter pole will be allocated for each operator to hang RRU, and the remaining one 1-meter pole will be used for hanging distribution box and fiber distribution box.

Tunnel Coverage Scheme

In life, when a vehicle (especially a train) passes through a longer tunnel, the signal often disappears. So, in the subsea immersed tube tunnel with a depth of more than 40 meters of the Hong Kong-Zhuhai-Macao Bridge, how is the signal full grid achieved?

The total length of the tunnel section of the Hong Kong-Zhuhai-Macao Bridge is 6.7 kilometers, covering a total of 13.4 kilometers of upper and lower lanes. The upstream and downstream tunnels are covered by leaky cable logarithmic periodic antennas, and the construction method is that mobile has a single leaky cable, and Telecom Unicom shares a set of logarithmic periodic antennas.

These technical solutions do not seem to be high, but we would like to remind you in particular:

Behind the most technically complex project in the history of Chinese transportation is also a super-difficult communication project.

Communication construction is extremely difficult, not easy

As mentioned above, the bridge project includes three coverage scenarios: bridge main body, tunnel and artificial island. In addition to the large scale of construction, each scenario brings great difficulty to the design and construction of the communication scheme because of its own project requirements.

Bridge body:

The construction conditions are bad, the sea surface weather is particularly unstable, it is necessary to overcome the influence of high temperature and strong wind, and the safety measures are particularly strict; the bridge connects the three places on both sides of the strait, the sea level signal is not easy to control, the diffuse reflection is serious, and the interference is strong. The construction personnel need to overcome the vertigo caused by the reflection of the water surface, and the safety measures are particularly strict.

Tunnel in the Sea:

The requirements for the protection of finished decorations are very high, and high-value decorations such as enamel steel plates must not be touched during the construction process, which is difficult to construct.

gongbei connecting line tunnel:

There are many attachments on the inner wall and the space is narrow, which has high requirements on the volume and performance of communication equipment. The working surface is extremely narrow and the construction environment is extremely harsh.

Artificial Island:

The management unit has very high requirements for aesthetics, and the erection of any equipment requires repeated verification and discussion by various departments, which will affect the construction efficiency.

In addition, this project requires too many coordination units, the construction quality and safety management requirements are too high, the design changes are too complicated, and the overall construction span of the project is too long.

Therefore, while lamenting this super century project, please do not ignore the communication builders behind it. It was they who overcame all the difficulties and got through the road that reached the signal full grid behind the super project.

Tunnel Mobile Signal Coverage Solution Shenzhen Century Hengrui Taobao Century Hengrui Technology