LTE stands for Long Term Evolution. It is the technology that superseded GSM (2G), and UMTS (3G) as a packet switched network. The main driver by 3GPP was to consolidate its pre-decessor technologies as well as and offer faster data rates to enhance user experience. Thus For these reasons, initial requirements for peak data rates were 100Mbps in DL and 50Mbps in UL with low latency of 10-20ms. In summary LTE was developed to:
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The multiple access technique utilized is OFDM (Orthogonal Frequency Division Multiplex) in the downlink and SC-FDMA (Single Carrier - Frequency Division Multiple Access) in the uplink. This modulation technique allows for many subcarriers to be close together, hence making the system robust to interference as well as . This technique also allows for improving spectral efficiency. As a result, more data can be sent in the same frequency bandwidth - which also translates to faster data rates. OFDMA supports various modulation schemes from BPSK, QPSK, 16QAM to 64QAM. Peak to Average Power Ratio is a main challenge of OFDM, thus in the uplink SC-FDMA is utilized.
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