Back when IMT Advanced -- a.k.a. LTE, a.k.a. 4G -- was first formally proposed, the aim was to achieve 1 Gbit/s downlink to stationary/nomadic users. At the time it seemed like a noble dream. Now, amazingly, it is close to reality.
Operators such as Netcom (Norway) and Optus (Australia) have announced successful field trials of gigabit 4G on commercial networks and it looks likely that consumer services will be offered within a year. (See, for example, EE Confirms 1Gbit/s 4G Trials in 2016.)
So what does a gigabit 4G radio look like?
For an operator to offer gigabit 4G requires more spectrum (the most important factor), advanced antenna systems, higher order modulation, and software to make it all work in combination, as outlined below:
- Carrier Aggregation -- at minimum 3 x 20 MHz is needed to reach gigabit speeds and, if the operator has sufficient spectrum, 4 x 20 MHz is preferred. For carriers with limited spectrum assets, the addition of a 20 MHz carriers in the unlicensed 5 GHz band could prove very useful.
- MIMO Antennas -- the big change here is the jump from 2x2 MIMO to 4x4 MIMO on the device (in the higher bands particularly). Base stations can go to 8x8 MIMO, or higher, to offer what is sometimes called full dimension, or 3D, MIMO.
- 256-QAM Modulation -- this requires excellent channel conditions, typically only experienced close to the center of the cell. Effective use of 256-QAM in an outdoor mobile network was considered seriously ambitious only a few years ago, but advances in receiver technology make it more viable.
The user also needs a compatible device. The good news here is that the first Category 16 chipsets are now sampling and the expectation is that first commercial devices will be available towards the end of 2016. These will be high-end devices, for sure, but think about it: a gigabit mobile connection in your hand!
We should also mention the slightly uncomfortable reality: that all this doesn’t necessarily mean you’ll actually experience 1 Gbit/s LTE. In operator circles gigabit speeds are known as the "bling" used to market headline data rates to the public. In practice, the number of users with the right device, in the right conditions, in the right locations, to actually experience 1 Gbit/s (and what smartphone application would even require it?) is likely to be very small.
The more significant benefit from an operator perspective is to use these technologies to increase system capacity, in busy urban locations, to share among more users. This is really how the economics of mobile network technology work, and is what will keep your real-world 5 Mbit/s video stream from buffering or freezing.
This blog is sponsored by Huawei.
— Gabriel Brown, Senior Analyst, Heavy Reading