LTE (Long Term Evolution)

LTE is the first technology designed explicitly for Next Generation Networking (NGN) and is set to become the de-facto NGN mobile access network standard. It takes advantage of NGN capabilities to provide an always-on mobile data experience comparable to wired networks.

LTE supports peak data rates of more than 100 Mbps on the downlink when using 20 MHz channel bandwidth, two transmit antennas at the base station and two receive antennas at the User Equipment (UE). LTE also supports peak data rates of more than 50 Mbps on the uplink when using a 20 MHz channel bandwidth; and single transmit antennas at the UE and base station.

LTE generates ten to twelve times the throughput on the downlink and eight to ten times the throughput on the uplink relative to 3GPP Release 6.

LTE improves spectrum efficiency as defined relative to Release 6. The uplink and downlink capabilities are two to four times the spectral efficiency of High-Speed Packet Access (HSPA).

LTE has flexible duplex methods. Both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) are valid spectrum allocations and allow LTE to accommodate various channel bandwidths in the available spectrum.

LTE interoperates with W-CDMA, GSM, and CDMA2000 systems. Multimode UEs will support handover to and from these other systems.

Legacy technologies such as HSPA+ and Enhanced EDGE will continue to operate within the new network architecture.  

Downlink Key Features

OFDM based, 15 kHz sub-carrier spacing QPSK, 16QAM, 64QAM modulation Variable RF bandwidth, 1.4 - 20 MHz MIMO in the form of transmit diversity or

spatial multiplexing

Scheduling, link adaptation, HARQ and measurements similar to 3.5G

Uplink Key Features

Single Carrier FDMA, 15 kHz sub-carrier spacing

QPSK, 16QAM, 64QAM modulation Variable RF bandwidth, 1.4 - 20 MHz Scheduling, link adaptation, HARQ and

measurements similar to 3.5G

Random access procedures

TDD/FDD Access - LTE standards support the use of both TDD (Time Domain Duplex) and FDD (Frequency Domain Duplex) from the same set of standards, and with the same air interface characteristics.

Multiple Input Multiple Out (MIMO) - MIMO is an antenna technology that, together with signal processing, can either increase capacity (spatial multiplexing) or signal-to-noise ratio (transmit diversity) in a radio link.

In LTE using 2x2 MIMO with spatial multiplexing, the user data is separated into two data sets each fed to two transmit antennas and received by two receive antennas. Because of multi-path, each data set travels a distinct RF path with different propagation characteristics. The algorithm used to split and recombine the data allows the system to make use of the independence of these two paths in order to improve throughput. The two data streams occupy the same RF channel at the same time. This doubles the data rate possible on the air interface link.