Testing Telstra 4G In Sydney Train Tunnels

Testing Telstra 4G In Sydney Train Tunnels

Part of Telstra’s announcement today of its 4G network expansion plans was the claim that there was now 4G coverage in the main train tunnel between Central and North Sydney. As a confirmed train broadband addict, I had to test this. The verdict? Sometimes the 4G is better in the tunnels than above ground, and sometimes it’s non-existent.

The claim by Telstra COO Brendon Riley in a media release was unequivocal:

Our network expansion kicks off in Sydney today where we’re introducing some of the world’s fastest mobile internet speeds to customers visiting iconic Bondi Beach and to underground rail passengers travelling on the North Shore line between Central and North Sydney stations, helping our customers stay connected and entertained on their commute.

On reading this, I was more than a little sceptical. All three mobile networks (Telstra, Optus and Vodafone) have said that 3G coverage has been available on this stretch of railway since early July. My own daily experience as a commuter suggests that while the coverage is much improved (and I’m grateful for that), there are still definite gaps where no signal can be had. Could the newer 4G network equipment fill them in?

My testing methodology was simple. I boarded a train at Central and travelled to North Sydney, a route which rapidly goes underground to Town Hall, stays entirely underground to Wynyard, continues through a tunnel before emerging into the outdoors on the Sydney Harbour Bridge, arrives at Milsons Point, and then passes into a minor tunnel to enter North Sydney. On arrival, I switched platforms and did the same journey in reverse.

My 4G testing device was the standard postpaid 4G Wi-Fi hotspot. I monitored this throughout both trips to see which network it was connected to; the screen tells you whether you’re on the basic 3G network, the enhanced DC-HSPA option, or the super-fast 4G. The device always seeks out the fastest option before falling back to slower alternatives.

So how did it perform? On the first journey from Central to North Sydney, there was no point when it didn’t indicate 4G availability. It was actually better in the tunnel between Town Hall and Wynyard than in the open air on the Harbour Bridge (where it dropped to one bar), but it never vanished outright.

However, on arrival at North Sydney, the device changed to DC-HSPA, and remained resolutely on that network or basic 3G for the entire return leg. Clearly there should be 4G signal in that area; I’d seen it myself on the journey north 10 minutes earlier. But this time around, my hotspot didn’t want to know

For a basic indication of performance (and to check if the network indicators were trustworthy), I also ran speed tests using Speedtest.net where I could on each leg (via my notebook connected to the hotspot). This turned out to mean I ran several tests on the journey north, but none on the return; the slower DC-HSPA option kept timing out whenever I tried testing on the way back, so I never got a full set of figures. Here are the numbers I did collect (higher is better for downloads and uploads; lower is better for ping tests):

Location Ping (ms) Download (Mb/s) Upload (Mb/s)
Town Hall-Wynyard tunnel 100 3.43 2.42
Wynyard platform 136 19.45 5.61
Wynyard-Milsons Point tunnel 55 31.27 5.30
Sydney Harbour Bridge 118 5.04 7.77
Milsons Point platform 58 33.33 14.86
Milsons Point-North Sydney tunnel 73 27.27 13.03
North Sydney platform (3G) 120 4.79 2.96

If you assumed performance would be better outdoors (on the bridge) than underground, you’d be wrong; the tunnel stretches had stronger results. On the North Sydney platform, the 3G speeds are notably lower than 4G, but still acceptable. Note however that the first listed test is on a 4G connection but with very slow speeds. Variability is to be expected when you’re testing speed in a moving vehicle.

We can draw two conclusions from this brief test. Firstly, there is definitely 4G coverage available throughout the tunnels between Central and North Sydney, so customers with a 4G device can potentially get better data services. However, as with any mobile service, performance isn’t guaranteed and your speeds and availability can vary very widely, even in what is for all practical purposes the same location. In places on my return journey, the claimed connectivity was so poor in practice that I couldn’t actually browse web sites or do anything else useful.

No-one is being asked to pay a premium for 4G (apart from the initial equipment), so I don’t see a case for massive consumer rage. We’re also coming from a situation where no connection at all in a tunnel has been the norm, so every improvement is welcome. 4G has hit the CityRail tunnel network, but I wouldn’t assume you can stream data non-stop from your seat just yet. Let’s hope it improves further in the future.

Testing Telstra 4G In Sydney Train Tunnels


  • I’d much prefer a solid, but slower signal, which is consistent throughout the trip. The difference between 3Mb/s and 31Mb/s is not that relevant while on the train (given the sort of use normal people have), but dropping in an out is annoying.
    Rather than feeding the marketing that implies the fastest peak speed is best, might it be possible for testing to focus on what is a reasonable speed, but how consistent the signal is? That might focus on other issues, such as how many other wifi hotspots and phones are turned on in the same carriage trying working on the same wifi band, or how many hotspots or phones are trying to get a signal out through the metal train carriage to the nearest tower.

  • 4G I wish!! You should try getting 3G on the Blue mts line through western Sydney! Its so bad especially around Blacktown its hardly worth pulling my phone out of my pocket. Different parts of the carriage get better signal I just need to find the sweet spot. My wife says I’ll find the sweet spot if I keep looking hard enough… any suggestions??

  • Wonder when this is going to roll out to other lines? Even 2G on the Illawarra line between the start of the tunnel and Central is still noticeably absent. (And likely all the way up to Bondi too, but I’ve never actually taken the train up that far)

  • The reporting in today’s Fairfax papers suggests that the LTE coverage is yet to be fully deployed:

    “It will extend services into Sydney’s rail tunnel between Central and North Sydney stations for commuters and in Melbourne up to 20 kilometres from the city.” future tense suggests that it’s yet to be fully deployed.

    Also, regarding pricing:

    “”Because we are seeing such demand for it and very importantly, the LTE carries information about half the cost of previous technologies”

    • The direct quote from Telstra said it launched yesterday. That’s what I went with. (And you can read the Fairfax quote that way too.) The Canberra Times comment is about Telstra’s costs, not consumer costs.

  • I find the connection to be more stable regardless of fast or slow speeds between Hornsby and the city if I use the 4G wifi device over my iPads built in Telstra sim. That said, surfing the web on the train is still a horrible experience. If you have something urgent and work related, get off the train and sit on the platform for a bit.

  • There is a definite blind spot on the Sydney Harbour Bridge. I’ve noticed this commuting to and from the North Shore for work by bus. I have a iPhone 3GS, used to be on Virgin (Optus) and it would without fail drop out and struggle to reconnect to the 3G network, eventually stumping for 2G or Edge, at about or around the pylon for the Bridge Climb, which is about a 1/3 of the way across the bridge heading northbound. The same effect happens heading southbound. I’m on Telstra now and it goes down to about 1 bar, sometimes drops out too. It’s very odd.

  • Just curious, have there been more updates to coverage with the other carriers (optus) as well? Since they added the tunnels i’ve been getting signal all the way up the north shore line… even in the black-area between pymble and turramurra (even though I still don’t get signal at pymble station itself).

    Dad uses amaysim so he’s on the optus network as well, he’s noticed its getting better too…

  • Once a Telstra 3G/4G device has connected in any 3G mode it will not automagically go back to 4G mode in the same session, even if tehre is good 4G signal available. You need to end the 3G session ans start anew one to establish a 4G connectionunless…. so that’s why your trip from Nth Sydney to Central was 3G only. Having connected to 3G on the North Sydney Plaftorm, you would have needed to drop tehs ession and start again once you were at Milson’s Point to get 4G.

    From my own experience over the past year, with a 320u 3G/4G device, If I am holding a 4G connection on atrain coming coming south into North Sydney, it will generally hold up at the platform and through at least to to the tunnel mouth at the south side of the bridge..

  • there is features on the network which will be deployed by carriers which will force the 4G subscriber to go get off the 3G horse and onto 4G.
    as the comments above suggest, when you have active data session based on standard 3GPP practices the device will remain on 3G until such point you stop browing, so the connection on 3G is idle, then only then will it move to 4G.
    you could have just locked the device on 4G only to get around this issue.

    • Again (and ignoring the insult), I’ve regularly seen the device switch from 4G to 3G and then back again. (I had stopped browsing between tests, so what’s reflected is variable network performance. (And locking to 4G would be pointless in any practical context.)

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