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So is it 4.5G or LTE-Advanced Pro? Either way, it’s pretty damn quick

Recent technology demo proves a big point

By Simon Rockman, 11 Nov 2015

Huawei's Mobile Broadband Forum While BT and the UK government may think that 10Mbps is plenty of speed, nobody else does it seems, and the mobile world is now gearing up for 1Gbps. In fact, the so-called 4.5G even has an official name, LTE-Advanced Pro.

Whatever it’s called, the ability to increase the bandwidth beyond the 150Mbps of standard 4G comes from three technologies, namely carrier aggregation, more advanced modulation, and an increase in antennas.

Carrier aggregation is up and running on EE and Vodafone now (the networks combined), with typically 20MHz of spectrum from each of two frequencies – say 800MHz and 1800MHz in the case of EE – to provide more bandwidth and up to 300Mbps.

If the two carriers are contiguous you can get better performance. The LTE spec would technically allow lots of carriers to operate, but the cost of the spectrum means most people are looking to four as a sensible limit.

Improving the modulation needs more processing power but Moore's law is our friend here and at least you don’t need to buy any more spectrum.

Going from 64-bit to 256-bit QAM (quadrature amplitude modulation), where out-of-phase carriers are modulated, and increasing the rate of modulation improves the throughput. Infrastructure companies are keen to sell 256QAM kit into operators, and are pushing it hard.

The final element of the increased performance shtick is MIMO, or multiple-input, multiple-output. This uses several antennas so that multiple data streams can be transmitted on the same frequency at the same time with error correction left to sort out the mess. In 4.5G LTE-Advanced Pro this is likely to be four or eight instances. For 5G, look to Massive MIMO with 256 input output channels.

Putting all this together, mobile operators and infrastructure manufacturers are confident of seeing speeds of 1Gbps as entirely possible from the technology.

Huawei and Hong Kong Telecom demonstrated a prototype system producing 900Mbps at Huawei's Mobile Broadband Forum in Hong Kong last week, with all three technologies and a real-world handset running over 200Mbps with just carrier aggregation, and two instances of MIMO.

Putting these high speeds in the hands of users begs the question of what they will be used for; history has shown that unexpected uses always grow up. At the forum last week the examples of self-driving cars and augmented reality headsets were much discussed. We'll see. ®

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