Questions Downlink OFDMA in LTE

1. Why do we use OFDMA in downlink?
2. Why do we use OFDMA in LTE?
3. How OFDMA operate in 4G lte communication?
4. What is the difference between OFDMA and SC-FDMA why OFDMA is not used in both the directions?

Why do we use OFDMA in downlink?

Downlink OFDMA allows multiple data frames to be transmitted in a single data unit to multiple stations, thus amortizing preamble overhead and medium contention overhead, leading to higher aggregated network throughput.

Why do we use OFDMA in LTE?

LTE is also known as 4G. OFDMA provides optimal spectral efficiency as well as variable bandwidth and provision for many independent channels. This is achieved in a remarkably simple method, using the fast Fourier transform and inverse fast Fourier transform.

How OFDMA operate in 4G lte communication?

OFDM is a form of transmission that uses a large number of closely spaced carriers that are modulated with low rate data. Normally these signals would be expected to interfere with each other, but by making the signals orthogonal to each another there is no mutual interference.

What is the difference between OFDMA and SC-FDMA why OFDMA is not used in both the directions?

SC-FDMA system is less sensitive to frequency offset compared to the OFDM system. SC-FDMA is widely used in LTE subscriber terminals in the transmit path and variant OFDMA is used in the eNodeB downlink(or receive path of LTE subscriber). OFDM is referred to as multicarrier modulation.