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.

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