MWEB recently landed itself in hot water with the Advertising Standards Authority of South Africa over a Huawei B315 router which was called an “LTE-Advanced” product.
According to the complaint, the router does not support LTE-Advanced standards, as it is only rated as a Category 4 LTE device.
This gives it download speeds of up to 150Mbps.
MWEB agreed to pull the advertising, but did not admit that it made a mistake or that the advertising was misleading.
This raised the question: When does a device really support LTE-Advanced?
What LTE-Advanced means
The answer comes from the standards released by the 3rd Generation Partnership Project (3GPP), which define the capabilities of networks and devices.
LTE (Long Term Evolution) is defined in 3GPP Release 8, which makes provision for user equipment categories 1 through 5, usually abbreviated in the form “LTE Cat. 5”.
This is what initially indicates if a device is LTE or LTE-Advanced. If a device has an equipment category lower than Cat. 6, like the Huawei B315, it is not LTE-Advanced.
The major difference between networks and devices that support LTE-Advanced – also called LTE-A – and LTE is a feature called carrier aggregation.
Carrier aggregation refers to the ability of the network or device to combine capacity – bandwidth – which may be scattered over the radio frequency spectrum.
For example, a mobile operator in South Africa may have spectrum in the 900MHz, 1,800MHz, and 2,100MHz frequency bands.
Previously, when a phone connected to a network, it would connect in only one of these bands. The device would have access to the maximum bandwidth available in that band, which was always smaller than 20MHz.
With carrier aggregation, bandwidth across multiple frequencies can be combined to give devices access to chunks of bandwidth larger than 20MHz, which means faster speeds.
LTE with carrier aggregation, or LTE-Advanced, is defined in 3GPP Release 10.
The standard adds another three categories of devices which can use the carrier aggregation capabilities of LTE-Advanced – from Cat. 6 to Cat. 8.
Any device rated as LTE Cat. 6 or greater may therefore be classified as an LTE-Advanced device.
If a retailer does not list the user equipment category, you can look for mentions of carrier aggregation (CA). Subsequent 3GPP releases allow for three or more carriers to be aggregated, which is sometimes abbreviated “3CA” or “4CA”.
The Snapdragon X20 modem which comes with Qualcomm’s Snapdragon 845 chip supports LTE Cat. 18, for instance, which allows carrier aggregation of up to five 20MHz channels. This is defined in 3GPP Release 13.
Is carrier aggregation all you need?
There is a debate whether the mere support of carrier aggregation should qualify a network to be called LTE-Advanced, however.
This is particularly relevant in South Africa due to spectrum constraints networks face.
Samsung told MyBroadband that by default its devices require a network to support Category 6 LTE, and for the total combined bandwidth to exceed 20MHz, before they will display the “4G+” icon.
Networks in South Africa frequently don’t have over 20MHz of aggregated bandwidth available, though.
As a result, one network asked Samsung to reduce the combined bandwidth requirement for the 4G+ icon to display to 15MHz, which Samsung approved.
“Samsung’s global policy regarding the display of the LTE/LTE-A/4G/4G+ network icon is that the network icon display is operator-configurable upon official request and Samsung approval,” it said.
MIMO and modulation
In addition to carrier aggregation, the LTE category also indicates whether a device supports multiple-input and multiple-output (MIMO) antenna configurations, along with higher-order modulation schemes like 256 quadrature amplitude modulation (QAM).
It should be noted that even though a device’s modem might support 4×4 MIMO, its antenna layout would also have to be designed to support the technology.
In smartphones, you must look for explicit mention of MIMO and can’t assume it from the device category.
While South Africa’s mobile operators have only recently started testing 256 QAM in their live networks, it does help improve network performance and may be a specification you want to look out for in future.
Support for 256 QAM is defined from 3GPP Release 12, with LTE categories ranging from Category 13 to Category 16.
Qualcomm has released a series of videos explaining carrier aggregation, 4×4 MIMO, and 256 QAM using the metaphor of reducing traffic on highways congested by truck traffic.
They are embedded below.