This week we announced that Telstra continues to keep on top of the wireless technology curve and will launch two ‘Category 4’, or CAT4 devices, for use on our 4G network s later this year – a wi-fi dongle and a handset. What does this mean? Well, that’s a question that needs to be answered on two levels. Firstly, the tech explanation; secondly what this means practically for customers and for Telstra.

What does this mean technically?

CAT 4 devices are rated as capable of 150Mbps peak device downlink speeds. This compares with the CAT3 devices which are rated at 100Mbps peak device downlink speeds. Of course customers will experience slower speeds in real world conditions and it is the combination of the strength of the Next G® network with the new Cat4 device which means Telstra customers can experience the fastest mobile network speed in Australia.

The factors that influence typical user speeds include the following:

  • Technology in use eg 3G: HSPA, HSPA+, or DC-HSPA+; 4G LTE using a Cat 3or Cat4 device
  • The amount or bandwidth of spectrum in use: for 3G: 5 MHz for HSPA and HSPA+; 10 MHz for DC-HSPA+; 4G: typically 10, 15 or 20 MHz depending on location
  • The signal level/quality: this varies depending on distance from the mobile base station and the amount of unwanted signal that might degrade quality
  • The connection from the base station to the network – sometimes called backhaul:  this is a big one! There is no point using the latest wireless technology if the tower or cell is not using a high bandwidth connection back into the core network. In the Telstra network over 93% of the population is served by a base station with 1Gigabit capable backhaul.  These are currently configured at either more than 100 or 200 Mbps per site
  • Other user factors: such as time of day, location of the user, the number of other users on the network and what they are doing

We currently advise customers that the typical download speeds that a customer experiences using a CAT3 device are between 2Mbps – 40Mbps, depending on the above factors.

In our laboratory testing for the new Cat4 devices, we have seen peak device speeds of well over 100 Mbps. So far in live field trials in Perth and Esperance where we have 20MHz of contiguous spectrum, we’ve seen device speeds of over 90Mbps, however the speed a customer typically experiences will be across a broad range, due to the factors I explained above. Suffice to say though, the download speeds a customer experiences using a CAT4 device can be faster than those obtained using a CAT3 device, all other things being equal.

To gain greatest advantage of the faster speeds of a CAT4 device, it needs to be combined with a 4G network offered over 20MHz of contiguous spectrum; this is the widest bandwidth that LTE can use ahead of LTE-Advanced technologies which will come in future years. In some areas of WA, including Perth and Esperance Telstra already has 20MHz of contiguous spectrum in the 1800MHz band so customers in these areas will be the first to be able to experience the speed advantage of a CAT4 device.

What does this mean for customers and for Telstra?

The biggest advantage that outright speeds bring is extra capacity in a wireless network. In reality, as a customer you’re speed is more likely to be limited by the source of the data you are downloading, so in many cases you are not going to notice too much if you’re downloading at 20Mbps or 60Mbps. High def video will still stream well on both speeds, websites will appear to load almost instantaneously. So why is Telstra focussed on bringing the latest technology to our customers?

Each generation of wireless technology is more efficient than the one that precedes it. Much of the reason for this is that as wireless technologies are developed they are designed to deliver faster speeds.

Now the faster you can deliver data, the more capacity you have on your network. To use an analogy, not only can vehicles move faster down a freeway, we are also adding more lanes to the freeway. The two combine to give a more consistent and satisfactory customer experience.

Increased speed also increases capacity because it means that more of our customers can be on the network at one time, and each have the speeds to support what they are doing.

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