Saturday, 14 April 2018

NTT Docomo's Underground LTE Small Cells with possibility to deploy 5G in future


NTT Docomo has announced that they have developed a prototype of manhole type base station for the first time in Japan. They will be used in locations where there is no other infrastructure available in vicinity to host base stations. The antenna is installed at a depth of 10 cm under the ground, with a fiber connection to the radio equipment and the power supply are drawn from the ground by the underground buried piping. The service area is about 90 m radius. 

Based on this, I am not sure if this is a complete small cell or just a remote radio head. I am inclined to think that this is a complete base station as its a standard LTE base station as per the specifications.


Manhole type base station specification (Sapporo verification station)
methodFDD-LTE
frequency1.5 GHz band (BAND 21)
Bandwidth15 MHz
MIMO compatible2 × 2 MIMO
Downlink modulation scheme256 QAM
Maximum ThroughputDL: 150 Mbps / UL: 37.5 Mbps
Size (buried part)70 cm × 70 cm × 70 cm
Device sizeAbout 29 cm × about 17 cm × about 7.5 cm
weightApproximately 15 kg
Specification of manhole cover (Sapporo Verification Bureau)
sizeDiameter 64.8 cm · thickness 5 cm
weightApproximately 27 kg
Load bearing capacity25 tons

The output power is not specified but base stations can easily fit within 15 kgs.

I have written about underground small cell here and here, which was about Swisscom, Ericsson & Kathrein trying it in Switzerland. I have also written about how the Japanese operator KDDI is trying to cover similar locations using lamp posts here. Its good to see Docomo trying something new.

As per the announcement, DoCoMo will work to improve the communication environment to areas where it was difficult to establish a base station, aiming for full-scale operation within the year 2018, and will continue to consider the application of future technologies to 5G in parallel.

From what I have heard, some antenna manufacturers are working on trying to convert the manhole cover in to an antenna. Its going to be a big challenge though.

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