Leaky feeder radiating coaxial cable has served Australian underground mines reliably for decades as a voice-grade communications backbone. It cannot, however, carry what autonomous loaders, tele-remote drilling rigs and live underground video now demand — and the transition from leaky feeder to underground LTE is reshaping how communications networks are designed below surface.
Why Leaky Feeder Hits a Hard Ceiling
Leaky feeder works by radiating and receiving RF signal along slots cut into a coaxial cable strung through drives and declines, amplified at intervals to overcome cable loss. It was purpose-built for two-way radio voice traffic and typically tops out well under 1 Mbps of usable data throughput — adequate for voice and basic telemetry, but nowhere near what an autonomous haulage guidance system or a tele-remote drill operator streaming live video needs, which routinely requires tens of Mbps with low, consistent latency. No amount of retuning turns leaky feeder into a broadband bearer; the physics of the medium caps it.
Decline Network Topology for Underground LTE
An underground LTE network replaces or augments leaky feeder with small cell radio nodes distributed through the decline and drives, each fed by fibre backhaul running back to a surface or near-surface core. Node spacing depends on frequency band and tunnel geometry, but a well-planned Australian decline network typically places small cells every 150-300 metres in main haulage drives, tighter in areas with sharp bends or significant equipment clutter that attenuates signal. Every small cell's fibre backhaul run needs to survive the same harsh underground conditions as the mine's power and ventilation services — rated cabling, robust containment, and route diversity where the decline layout allows it.
- Backhaul fibre should follow a ring or redundant-path topology where decline geometry permits, rather than a single daisy-chained run where one cable fault blacks out every node downstream of it.
- Refuge chambers need coverage from at least two independent nodes on separate backhaul paths — a refuge chamber that loses all communications during the exact emergency it exists for is a critical design failure.
- Power for underground small cells typically comes from the mine's existing low-voltage reticulation, with local UPS battery backup sized for the site's emergency response time assumptions, not just a nominal 15-30 minutes.
Design takeaway: Stage the transition — run LTE and legacy VHF/leaky-feeder in parallel during commissioning, extending and validating LTE coverage level by level, rather than a single cutover that leaves the mine without a proven fallback communications path if the new network underperforms in its first weeks.
Integration With Autonomous Haulage and Tele-Remote Systems
The underground LTE network isn't just a data pipe — for autonomous haulage and tele-remote operations it's a safety-critical control link, and needs to be engineered with that in mind: guaranteed minimum bandwidth reservations for guidance and control traffic (via QoS prioritisation at the LTE core), documented failover behaviour when a vehicle moves out of coverage (typically an automatic, controlled stop), and coordination with the mine's broader digital backbone described elsewhere in this series for autonomous haulage networks specifically.
Frequently Asked Questions
Why can't leaky feeder support autonomous underground haulage?
Leaky feeder (radiating coaxial cable) was designed for voice-grade two-way radio, typically delivering well under 1 Mbps of effective throughput. Autonomous loader guidance, tele-remote drilling and live video feeds need consistent, low-latency bandwidth in the tens of Mbps, which leaky feeder's architecture cannot deliver regardless of how it's tuned.
Can LTE and legacy leaky-feeder radio run in the same underground mine at once?
Yes, and most Australian transitions do this deliberately — running LTE and VHF/leaky-feeder in parallel during the changeover period so voice communications and safety systems have a proven fallback while the LTE network is progressively extended and validated level by level.
What redundancy do refuge chambers need for underground LTE coverage?
Refuge chambers should have coverage from at least two independent small cells or repeater nodes fed from separate backhaul paths, since a refuge chamber losing all communications during an emergency defeats its purpose — this typically means avoiding a single daisy-chained fibre run as the only backhaul path to chamber-adjacent nodes.