Is Push-to-Talk Over Cellular (PoC) or a Repeater/DAS the Better Fix for Radio Dead Zones on a Singapore Construction Site?

PoC (push-to-talk over cellular, running on LTE) is the right fix when the dead zone is a coordination problem across an open or scattered site and the telco signal there is already decent. A UHF repeater — and eventually a DAS once the structure closes in — is the right fix wherever the dead zone sits inside enclosed volume the public mobile network doesn't reach either: basements, core walls, tunnel headings, plant rooms. On most Singapore sites with real duration or basement scope, the answer ends up being both: PoC for site-wide and off-site coordination, a dedicated UHF channel for the safety-critical comms that have to work inside concrete. That's not a preference for radio — during the active build, the permanent cellular infrastructure the finished building will eventually have usually isn't there yet either.

What is PoC, and how is it different from a UHF two-way radio?

PoC is a push-to-talk app or ruggedised handset running a VoIP call over the telco's own LTE or 5G network — every transmission leaves the site as a data packet and depends entirely on that network's coverage, capacity and priority at that spot. A conventional two-way radio transmits UHF RF (400–470 MHz for the DMR and analog gear used on almost every Singapore site) directly to a repeater or DAS antenna the contractor owns and controls, with no carrier, SIM or data plan in the path. That difference — whose network you're borrowing versus whose network you own — is what decides which one survives a dead zone.

Why doesn't PoC automatically solve a dead zone the way a repeater does?

Because a dead zone question assumes there's a signal worth talking over, and PoC only has one if the mobile network already reaches that spot. On a completed, occupied building that's often true — Singapore's COPIF framework requires developers to set aside Mobile Deployment Space so telcos can fit indoor DAS, so a handed-over building usually has reasonable in-building 4G. An active construction site is usually the opposite: that telco DAS is fit-out infrastructure, installed toward the end of the programme, not during the shell-and-core phase when excavation, basement pours and core walls are exactly the enclosed, unfinished volumes killing coverage. A raw concrete core blocks a telco's LTE signal at least as hard as it blocks UHF, and usually harder — the frequency term of free-space path loss alone costs a cellular signal near 1900 MHz roughly 12.5 dB more than UHF at 450 MHz for the same obstruction (20·log₁₀(1900/450) = 12.5 dB; see why cellular DAS coverage figures don't transfer to UHF radio), before counting the extra depth an outdoor macro cell has to punch through that a purpose-built repeater doesn't.

A few figures worth keeping in view when comparing the two paths:

• −95 dBm: the design threshold Suneast works to for reliable UHF DMR voice at the portable.

• 40 W / +46 dBm repeater against a 4 W / +36 dBm portable — the uplink, not the downlink, is usually the limiting path, a large part of why a raw structure with no fitted-out cellular network struggles just as much on PoC.

• 10 dB standard and 15 dB mission-critical fade margin, layered on top of that threshold.

• 4.5 dB/100 m: typical half-inch coax feeder loss at 450 MHz for a repeater's backbone — infrastructure a PoC deployment doesn't need at all.

When is a repeater/DAS clearly the better call?

Whenever the site has enclosed volume the public network hasn't reached yet: basement boxes, tunnel drives, deep plant rooms, or the confined spaces where Singapore's Workplace Safety and Health framework expects a working means of communication between an entrant and a standby person (see keeping radio coverage working through tunnels and deep excavation works). It's also the better call whenever the programme runs long enough — most sites above roughly 30 floors or with meaningful basement scope, the same threshold our repeater-sizing piece works through — to justify a system that doesn't depend on telco congestion, a dropped SIM bill, or a network outage during an incident. A repeater is a one-time mobilisation the contractor controls end to end.

When does PoC make more sense?

Short-duration works, largely outdoor or low-rise sites, and any job where the real requirement is reaching subcontractors, suppliers or head office off-site rather than covering a structure's interior. PoC also wins when ground-level mobile coverage is already solid and the workforce is spread across a wide, open compound rather than stacked inside concrete — repeater coverage doesn't help two teams on opposite ends of a large site talk to each other if neither is inside the dead zone in the first place.

Does either option need an IMDA licence?

A PoC handset rides on the telco's own licensed spectrum under the telco's licence, so the site doesn't need its own radio station licence for PoC traffic. A UHF repeater and any private channel behind it does — under IMDA's Localised Radio-Communication Station Licence or Localised Private Network Licence framework, the tiers we break down in IMDA licence tiers by channels, users and power. Confirm the current fee schedule and lead time with IMDA before committing to a programme date, since licensing runs in parallel with mobilisation, not after it.

Can PoC and a UHF repeater run on the same site?

Yes, and on any site with real basement or high-rise scope this is the common answer rather than the exception: PoC for wide-area and cross-site coordination, UHF DMR through a repeater for the safety-critical channel that has to work inside concrete regardless of telco load. The two can be bridged through a gateway, but every bridge adds latency and a single point of failure, so most Singapore sites simply run both networks in parallel and train supervisors on which channel carries a life-safety call.

Related questions

Does a PoC radio fleet still work if the mobile network gets congested during an incident? Not reliably — PoC calls share the network with every other data user on site, and an emergency is exactly when everyone reaches for a phone at once; a dedicated UHF channel doesn't compete for that capacity.

Is renting PoC handsets cheaper than installing a repeater for a short job? Usually, for work measured in weeks rather than years — PoC is a recurring per-handset SIM cost with no mobilisation lead time, while a repeater is a capital purchase amortised over the whole programme, so the crossover point comes down to duration and how much enclosed volume the site has.

Will a PoC app work in a lift shaft or stairwell the way a UHF radio does? No better than the phone signal already there, which on an unfinished structure is usually worse than a properly designed UHF link, since neither the telco's indoor DAS nor a repeater exists yet in those spaces unless someone has specifically installed one.

Suneast designs, licenses and installs the UHF repeater and DAS side of this decision for Singapore construction sites — surveying which zones the public network already reaches, sizing the repeater and antenna plan against both budgets, and handling the IMDA application, so the site isn't relying on a network it doesn't control for the one channel that has to work when something goes wrong.