Earlier this month, Russian network operator Yota reported it had launched the world’s first commercial LTE-Advanced network, using equipment supplied by Huawei. The network comprises 13 base stations in Moscow and Yota has reported downlink data at up to 300Mbit/s. However, Yota has admitted that it will not have terminals available until 2013 and the network is essentially for test purposes at the moment.
While the basic LTE system (first defined in 3GPP Release 8) is often referred to in the media as 4G technology, actually LTE-Advanced is the first member of the GSM/UMTS/LTE family of standards to satisfy the International Telecommunication Union (ITU) requirements of 4G, for example by achieving a peak downlink user data throughput of more than 1Gbps.
LTE-Advanced builds on the same underlying radio interface as LTE, including an Orthogonal Frequency-Division Multiple Access (OFDMA) downlink and Single-Carrier Frequency Division Multiple Access (SC-FDMA) uplink. The first version of LTE-Advanced, defined in 3GPP Release 10, includes a number of new developments to improve the performance of LTE, including:
Carrier Aggregation: Basic LTE can operate in bandwidths ranging from 1.4MHz to 20MHz. LTE-Advanced allows for up to five sets of LTE carriers to be combined to achieve a total bandwidth of up to 100MHz.
Enhanced multi-antenna techniques: LTE-Advanced supports Multiple Input Multiple Output (MIMO) antenna configurations up to 8×8 (i.e. 8 transmitting antennas and 8 receiving antennas) on the downlink and 4×4 on the uplink, to achieve increased throughput in good signal conditions.
Relay Nodes: Heterogeneous Networks (or “HetNets”) comprising a wide variety of cell sizes will become increasingly important as LTE networks are deployed. Relay Nodes will form an important component of these networks by boosting the coverage and capacity towards the edge of cells, by relaying signals to and from a donor base station over a radio connection.
These developments achieve a number of benefits, including greater spectral efficiency, improved performance towards the edge of cells, support of a greater number of simultaneous active users, and an increase in user data throughput to 3Gbps in the downlink and 1.5Gbps in the uplink.
A variety of further developments are planned for LTE-Advanced in forthcoming releases, including cognitive radio, higher order modulation, complex antenna arrays and intense frequency use through advanced HetNets. I will look at these in more detail in future posts.