What is the benefit of adding zeros subcarriers in frequency-domain OFDM signal?

1. What is the purpose of using zero padding before the Ifft stage in OFDM?
2. What is subcarrier in OFDM?
3. What prevents the subcarriers in orthogonal frequency division multiplexing OFDM from interfering with each other?
4. How to calculate number of subcarriers in OFDM?

What is the purpose of using zero padding before the Ifft stage in OFDM?

The zero padding is there to minimize the effect of multipath. Short explanation: over the air signal gets convoluted with channel response, this blurs the signal and redistribute its energy through a wider frequency range than the original.

What is subcarrier in OFDM?

Subcarriers in cellphones, LTE 4G and 5G NR

Cellphone data uses subcarriers in OFDM and OFDMA arrangements to transmit data from the base station to the handset. In LTE, each subcarrier is spaced 15 kHz apart. These subcarriers are combined in groups of 12 to form a single resource block.

What prevents the subcarriers in orthogonal frequency division multiplexing OFDM from interfering with each other?

Both OFDM and OFDMA divided a channel into subcarriers through a mathematical function known as an inverse fast Fourier transform (IFFT). The spacing of the subcarriers is orthogonal, so they will not interfere with one another despite the lack of guard bands between them.

How to calculate number of subcarriers in OFDM?

If you divide the channel bandwidth (20 MHz) by the subcarrier bandwidth (312.5 kHz) you will see that 802.11a/g comprises 64 subcarriers.