The LTE system works

How LTE actually works?

In LTE system, it uses two different types of air interfaces (radio links), one for downlink which the signal travels from tower to device, and one for uplink which the signal travels from device to tower. In LTE, it utilizes the optimal way to do wireless connections both ways and this utilization makes a better optimized network and better battery life on LTE devices.

Figure: Verizon Cell Tower

For the downlink,                                                                                              LTE uses an orthogonal frequency division multiple access (OFDMA) air interface as opposed to the CDMA and TDMA air interfaces. OFDMA mandates that MIMO (multiple in, multiple out) is used. The stability of the connection will increases and latency will also get decrease tremendously by having MIMO that devices have multiple connections to a single cell. However, there is a significant disadvantage in MIMO that the noise caused by the antenna being so close to each other on smaller phones and this may cause LTE performance to drop. 

For the uplink,                                                                                                   LTE uses the discrete Fourier transform spread orthogonal frequency division multiple access (DFTS-OFDMA) scheme of generating a single carrier frequency division multiple access (SC-FDMA) signal. Why SC-FDMA better for uplink? This is because it has a better peak-to-average power ratio over OFDMA for uplink. LTE-enabled devices, in order to conserve battery life, typically don’t have a strong and powerful signal going back to the tower. Therefore, a lot of the benefits of normal OFDMA would be lost with a weak signal. Despite SC-FDMA is still a MIMO system and LTE uses a SC-FDMA 1×2 configuration, where the 1 there represent an antenna on the transmitting device while the 2 means there are two antennas on the base station for receiving.