Why SC-FDMA is used in uplink?

SC-FDMA is preferred for LTE uplink mainly due to its advantage of having low peak-to-average power ratio (PAPR) during signal transmission. It is found that by increasing spreading factor symbol error rate is reduced for SC-FDMA system and for spreading factor of 64 for SNR=20 dB, SER is of the order of 10 -4 .

Why LTE uses OFDMA for DL and SC-FDMA for UL?

In LTE, the OFDMA is used as downlink and SCFDMA as uplink modulation schemes; with OFDM as the basic building block. OFDMA is used for achieving high spectral efficiency in communication system; whereas, SC-FDMA for uplink multiple access scheme in LTE system.

Which modulation techniques are used for uplink and downlink in LTE?

While LTE’s downlink uses OFDM, the uplink uses a different modulation scheme known as single-carrier frequency-division multiplexing (SC-FDMA).

Why LTE uses OFDMA for downlink and SC-FDMA for uplink?

LTE uses OFDM as the basic signal format – OFDMA in the downlink and SC-FDMA in the uplink with various modulation formats. OFDM forms the basic signal format used within 4G LTE. Higher order modulation is used to achieve the higher data rates: the modulation order being determined by the signal quality.

What are the differences between OFDMA and SC-FDMA?

The most obvious difference between the two schemes is that OFDMA transmits the four QPSK data symbols in parallel, one per subcarrier, while SC-FDMA transmits the four QPSK data symbols in series at four times the rate, with each data symbol occupying a wider M x 15 kHz bandwidth.

How does OFDM differ from OFDM and OFDMA differ from OFDM?

OFDMA stands for orthogonal frequency division multiplexing access. It is an extension of OFDM. The difference is that OFDMA is multi-user where OFDM is single-user. It has 3x higher throughput than single-user OFDM for short packets of data or multiple endpoints.

Does 5G use OFDM?

The 5G New Radio (NR) standard uses OFDM on both the uplink and downlink. The NR specification is designed with a high degree of flexibility to cover a diverse set of applications.

Why do we use OFDM?

Immunity to selective fading: One of the main advantages of OFDM is that is more resistant to frequency selective fading than single carrier systems because it divides the overall channel into multiple narrowband signals that are affected individually as flat fading sub-channels.

How does OFDMA work?

OFDMA is a multi-user version of OFDM enabling concurrent AP communication (uplink & downlink) with multiple clients by assigning subsets of subcarriers, called Resource Units (RUs) to the individual clients. OFDMA allows multiple users with varying bandwidth needs to be served simultaneously.

What is difference between OFDM and OFDMA?

How OFDMA works in LTE?

LTE uses a pre-coded version of OFDM called Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink. This is to compensate for a drawback with normal OFDM, which has a very high Peak to Average Power Ratio (PAPR). A low PAPR also improves coverage and the cell-edge performance.