Digitimes has today reported that Chinese telecommunications equipment and device manufacturer, Huawei Technologies, has announced the completion of LTE Category 11 terminal testing in conjunction with Qualcomm. This standard pushes the maximum download speed of LTE to a theoretical 600 Mbps through a three carrier aggregation technology using 256QAM, or quadrature amplitude modulation. Around the world, many carriers are upgrading LTE technology from Category 4 to Category 6 (with a theoretical maximum download speed of 300 Mbps) with higher Categories still undergoing testing. The pattern we’ve seen around the world is that device manufacturers release a device capable of faster LTE technologies than most carriers of a particular country support, but most customers will use a cell ‘phone for one to three years and perhaps by the middle or end of their contract, networks will have been upgraded.
To explain the fantastic sounding technologies incorporated into LTE Category 11, let me first explain the idea behind “carrier aggregation.” This does not mean your device roams onto a competitor network and loots the bandwidth, but instead it means that the device uses multiple chunks of spectrum. The LTE component carrier signal can have a bandwidth from 1.4 MHz, through 3, 5, 10, 15 or 20 MHz chunks. The wider the bandwidth, the greater the potential bandwidth similar to imagining fluid flowing through a pipe. Modern LTE Categories can bundle two or more separate chunks of spectrum together in order to enhance the performance. And because of how most carriers have spectrum allocated at different points of the spectrum, it’s quite common to see aggregated carriers across multiple frequencies: we may see a carrier joining a 10 MHz chunk of spectrum at say 850 MHz with 5 MHz of 1,900 MHz spectrum. Category 11 LTE allows the device to combine more spectrum, thus creating a wider data pipe into the device and up to those theoretical 600 Mbps transfer speeds. In reality, devices must have a download and an uplink connection and typically have a greater download capacity compared with the upload.
The other part of the LTE Category 11 specification is “quadrature amplitude modulation.” This fantastic sounding technology is not especially new and has been used by cable and satellite television providers for decades. It is a means of combining multiple bit streams by varying the amplitudes of the underlying carrier waves and allowing the receiver to differentiate between each bit stream. Each carrier wave is out of phase with the other by 90 degrees and this is where the quadrature name comes from. The higher the density of bit streams – the higher the number – the less immune the signal is from interference and it will be interesting to see how well Category 11 LTE networks work in the wild. However, it will be some time before devices are launched with this technology and likely even longer before networks around the world are deploying Category 11 masts. There are still relatively few devices and carriers that support Category 9 LTE, with a maximum download speed of 450 Mbps.