LTE UE category allows network to operate with terminals with different data capabilities as well as allows market to differentiate between low end devices with lower data capabilities against high-end devices with higher data rates. This differentiations determines price or UEs in many cases.
In LTE not all UEs support all categories and also terminals from an earlier release does not support features introduced in later version of 3GPP releases. For example a release 8 UE does not support features like carrier aggregation which was introduced in Release 10.
So during connection setup, UE needs to indicate network about what 3GPP release it supports as well as the capabilities it support withing the specific release.
3GPP release 8/9 UE can have 5 different categories, Category 1 support minimum set of functionality while category 5 UE has maximum data rate and supports full set of features. In release 10 features such as carrier aggregation and uplink spatial multiplexing are added. So from release 10 three new UE categories are added. and the maximum number of component carriers and degree of spatial multiplexing supported, both in uplink and downlink, are signalled separately from the category number. A release-10 terminal may therefore declare itself as, for example, category 4 but capable of uplink spatial multiplexing. So UE categories 1-5 have different meaning in Release 10 when compared with Release 8/9.
For backward compatibility purpose Release 10 UE has to declare both Release 8/9 capabilities and Release 10 capabilities.
LTE UE Categories
|Downlink peak rate|
|Uplink peak rate (Mbit/s)||5||25||50||50||75||50||150||1500|
Maximum downlink modulation: 64 QAM
Maximum uplink modulation: 16QAM (Category 1-4 and 6), 64QAM (Category 5 and 7)