3GPP LTE technologies

To reach the higher data rates and faster connection times LTE contains a new radio interface and access network compared to the previous cellular systems. During 3GPP organized workshops it was agreed that the technology solution chosen for the LTE air interface uses Orthogonal Frequency Division Multiplexing (OFDM) and to reach the agreed data levels, Multiple Input Multiple Output (MIMO) technologies together with high rate modulation were agreed. These new technologies enable LTE to operate more efficiently with respect to the use of spectrum, and also to provide the much higher data rates that are being required.

OFDM (Orthogonal Frequency Division Multiplex) 

 OFDM-based technology has been incorporated into LTE because it can achieve the targeted high data rates with simpler implementations involving relatively low cost and power-efficient hardware. It is good to notice that OFDMA is used in the downlink of LTE but for the uplink Single Carrier-Frequency Division Multiple Access (SC-FDMA) technology is used. SC-FDMA is technically similar to OFDMA but it suits better for handheld devices because it is less demanding on battery power.

MIMO (Multiple Input Multiple Output)

Today’s mobile networks are very noisy environments. Without noise, an infinite amount of information could be transmitted over a finite amount of spectrum. To minimize the effects of noise and to increase the spectrum utilization and link reliability, LTE uses MIMO technique to send the data. The basic idea of MIMO is to use multiple antennas at receiver end and use multiple transmitters when sending the data. Before sending the data, the transmitter converts serial bit streams output by the source into multiple parallel sub streams. Then transmitter sends them via different transmit antennas using the same time slot and the same frequency band. After receiving data, the receiver separates out the original sub streams from the mixed signals using the non-correlation of signals on multiple receive antennas caused by multipath in the transmission. This leads to significant increases in achievable data rates and throughput.

SAE (System Architecture Evolution)

With the very high data rate and low latency requirements for 3G LTE, it is necessary to evolve the system architecture to enable the improved performance to be achieved. One change is that a number of the functions previously handled by the core network have been transferred out to the periphery. Essentially this provides a much "flatter" form of network architecture. In this way latency times can be reduced and data can be routed more directly to its destination. 

SAE - The Core Network for LTE