HKT wants to use 700-MHz band for underground coverage

HKT 700
Image credit: pisaphotography /

Hong Kong incumbent telco HKT says it has proof that the 700-MHz band can provide mobile coverage in underground train stations without interfering with signals above ground – and wants telecoms regulator OFCA to let cellcos use the band for that purpose.

In Hong Kong, the 700-MHz band is currently authorized only for TV broadcasts. HKT wants to use the band for additional mobile capacity in underground MTR stations to alleviate traffic congestion, but that raises the issue of whether using the 700-MHz band for mobile communications would interfere with TV signals.

HKT says they won’t, offering evidence on Tuesday that 700-MHz signals above ground can’t penetrate all the way down to underground MTR stations – and vice versa.

HKT said it has performed tests at underground platforms of MTR stations in which it tried to detect 700-MHz signals from aboveground, and was unable to detect any. By the same logic, 700-MHz mobile signals inside the stations would not be able to interfere with TV broadcasts outside the stations.

HKT also cited research from Dr. Tsang Kim-fung, an associate professor of City University of Hong Kong, which conducted similar tests for the 900-MHz band. Presenting the study at a seminar organized by the Institution of Engineering and Technology last week, Dr. Tsang said the study found that 900-MHz signals currently transmitted inside the MTR don’t penetrate through to ground level. Consequently, because the 900-MHz and 700-MHz bands have similar propagation characteristics, underground 700-MHz signals would also be unlikely to be detected outside of the MTR.

In light of all this, HKT said it is asking OFCA [PDF] to review the use of the 700-MHz band for mobile communications inside “enclosed locations such as MTR underground platforms and tunnels in order to relieve mobile traffic congestion problems at the MTR as early as possible.”

The announcement is part of HKT’s ongoing effort to pry more spectrum out of OFCA, whom the operator has publicly criticized for being too slow to release additional spectrum, particularly for 5G services.

The independent CA has only just kicked off public consultations in the last few months for new spectrum allocations, the most recent being a plan to release 5G mmWave bands free of charge. The CA plans to release 4,500 MHz worth of new spectrum between 2019 and 2020 for 5G services.

To that end, also on Tuesday, the CA kicked off a new public consultation on its proposal to release 200 MHz of spectrum in the 3.3 GHz band (3.3 – 3.4 GHz) and the 4.9 GHz band (4.83 – 4.93 GHz) for 5G usage, particularly indoor coverage.

The CA said it intends to hold separate auctions for both bands, and that the spectrum usage fee (SUF) for each will reflect “the full market value of the spectrum”.

That’s unlikely to go down well with HKT, who has also complained at length that the CA already charges way too much for spectrum compared to other markets. The operator is also likely to be unimpressed with the proposal by the Commerce and Economic Development Bureau (CEDB) that the SUF for the 3.3/4.9 GHz bands could be paid in annual instalments rather than all at once.

The CA will be accepting comments on the latest proposal until September 26, and aims to finalize everything in time to hold the 3.3/4.9 GHz auctions somewhere in the middle of next year.

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