Tunnel cell phone coverage enhancement report
一、Field description
The tunnel section (1.4 km) has enhanced mobile coverage，The optical fiber wireless repeater station one tow two scheme is adopted.
The topology of the system scheme design is as follows:
Check the pipe gallery site and the actual situation of installation and implementation as follows:
There is no firewall or fire door in the middle of the 1.4km corridor from the north entrance of the tunnel to the south entrance of the tunnel, and the whole passage is very straight.
The outdoor antenna (flat plate antenna) faces south.
The MU repeater is located at the head of the north entrance pipe gallery, in the same position as the RU repeater 1. The RU repeater 2 is located at the tail of the 1.4 km pipe corridor.
The indoor distribution of the two RU repeaters is the same,There is a main feeder line from the two sections to the middle, about 70 meters apart，An indoor antenna is coupled to cover the signal in the middle of the channel. As shown in the picture below:
This image can be double-clicked to enlarge.
二、Adjust and test
Both the MU and RU repeater 1 are connected to the indoor and outdoor cables, and the optical fiber and power cables are connected，The RU repeater 2 is not connected to optical fiber and is not powered.Therefore, you can only perform upper computer commissioning on the MU and RU repeater 1, and test the coverage signal.
三、Rectification instructions
1、The optical fiber between RU repeater 1 and RU repeater 2 must be connected through a black round tail connector (FC/UPC).
2、The power supply for RU repeater 2 must be installed properly.
3、Turn the outdoor antenna 90 degrees to face east, toward the base station.
The source signal transmitted directly from the base station can be obtained by this adjustment, and the working input signal and output signal of the equipment can be enhanced by more than 5dB.
4、Adjust the position of the RU repeater（Very important）
At present, the two RU repeater are at both ends of the 1.4km pipe corridor, and the indoor feeder lines of each RU repeater are above 600 meters, according to the 50-12 coaxial cable loss parameters, the line loss of 600 meters reaches 60dBm (1000 power), and the line loss of 300 meters is 30dBm, equal to 1 watt.
Rectification method: The two RU repeaters are moved to the middle part of each indoor feeder line, and the two RU repeaters are moved to the middle part of the original antenna ANT5 and ANT6 in the equipment room. The output of the equipment adopts a cavity two-power splitter to output signals to the left and right sides respectively. Pay attention to the coupler marked yellow in the figure. The eight couplers need to change the original direction and switch the input and output ports.
Double click the image to enlarge it
Please see the chart below:
5、Coupler parameter adjustment
Due to the situation of the construction ladder on the site, we only see 10DB coupler after ascending the bridge at the first antenna ATN1 position of the RU repeater 2, and the nearby host should use a coupler with a large value to ensure that the signal strength of each working port of the antenna distributed down is balanced, rather than the near strong and far weak situation.
First out of the host is a cavity two-power divider, divided into two main lines, the main line from near to far each way of the 4 couplers should be used 20DB, 15DB, 10DB and 5DB, 4 couplers value from large to small use.
