Telstra has warned the federal government that incoming satellite-to-mobile voice services won’t adequately support triple zero calls until low earth orbit constellations reach a “critical mass”.
The telco included the warning in a response to a parliamentary committee inquiring into the universal outdoor mobile obligation (UOMO), saying it wished to “augment” advice it had previously given to the government.
Framing it as “additional information to assist” the inquiry, Telstra told the committee that timing the start of the obligations to the availability of one or more LEOsat constellations was “insufficient”.
Building on previous advice that it has given to the government that 5G non-terrestrial network standards were still in an early stage of development, the carrier said that terrestrial and non-terrestrial networks needed to be integrated to carry SMS, voice and data reliably.
Pointing to its other statutory obligations, including for emergency calls, it warned that until LEOsat constellation densities reached a “critical mass”, they would not be able to sustain calls of adequate duration to serve first responders and mobile users in distress.
“Until a satellite constellation reaches a critical mass of satellites, which will be different for each constellation based on the spectrum band(s) they operate on, size of spot beams, volume of end users supported per spot beam, etc, contiguous calls of several to tens of minutes will not be possible,” Telstra wrote.
“This is of particular relevance to emergency calls, where in some call cases, after the call is transferred to the ESO [emergency services organisation], the caller is required to stay on the call for a lengthy duration while the ESO provides advice, or seeks updates from the caller.”
The carrier pointed to the example of when emergency call operators and first responders might need to provide life-saving instructions to callers in distress, such as instructions for cardiopulmonary resuscitation or CPR.
Telstra then repeated the call it has previously made, and which is echoed by its rival mobile network operators, to delay the start of the UOMO obligations.
“The intent of the UOMO can only be realised once a full ecosystem is ready, including a critical mass of satellites, ground infrastructure, interworking between celestial and terrestrial networks, customer devices, chipsets for the devices and extensive end-to-end testing. We expect the is to be late 2028 at the earliest,” it said.
Telstra has some experience with LEOsat service impacting its voice calling services in the context of emergency calls.
The carrier operates a network of around 200 small cell mobile base stations in remote areas using Eutelsat’s OneWeb LEOsat constellation for backhaul.
The switch from using geostationary backhaul to the LEOsat constellation triggered a 43 percent jump in number of mobile tower outages causing “significant community impact”, from 3614 in 2024 to 5221 in 2025.
At the time, Telstra cited coverage gaps in the LEOsat constellation gap as the cause of outages.
The gaps caused the base stations to lose their ability to provide triple zero calls for periods of 10 to 15 minutes twice per day.
It’s understood that, on average, the gaps cause the small cell base stations to be unavailable for placing calls for around 30 to 35 minutes each day.
The Department of Communications sought more information about the base stations after an apparent triple zero communication failure incident involving one of the base stations at Tirranna Springs in Queensland late last year.
In that incident Jil Wilson, the owner of the roadhouse at Tirranna Springs, told iTnews that voice dropouts were the key cause of her difficulties when using her local mobile base station to call an ambulance to help a staff member who received burn injuries late last September.
Early this year, Telstra quietly stopped migrating its remote small cell mobile base stations onto low earth orbit satellite backhaul until its constellation provider, Eutelsat OneWeb, could get more craft into service.
Telstra chief executive Vicki Brady revealed the decision at the carrier’s half-year results presentation in February.
“We have rolled it out to a relatively small number of sites to date. That rollout is not going further right now as we work out what is the right balance to find here. It does provide real benefits much more capacity, much better performance in terms of data over those sites,” Brady said.
