Why is SC-FDMA used for uplink transmissions in LTE?
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 .
What is SC-FDMA in LTE?
SC-FDMA is a hybrid modulation scheme that combines the low peak-to-average ratio (PAR) of traditional single-carrier formats such as GSM with the multipath resistance and in-channel frequency scheduling flexibility of orthogonal frequency-division multiplexing (OFDM). Acronyms galore: LTE history and context.
Why LTE uses OFDMA for downlink and SC-FDMA for uplink?
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.
Why SC-FDMA is single carrier?
SC-FDMA (Singe Carrier FDMA) presents the benefit of a single carrier multiplexing of having a lower Peak-to-average Power Ratio. On SC-FDMA before applying the IFFT the symbols are pre coded by a DFT (Discrete Fourier Transform). This way each subcarrier after de IFFT will contain part of each symbol.
How does SC-FDMA differ from OFDMA?
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.
Which modulation technique is used in LTE for uplink transmission?
LTE devices use QPSK, 16QAM and 64QAM to modulate data and control information. The eNodeB supports all of these modulation techniques for the Down Link direction. However, 64QAM is optional in the Uplink direction.
What is the advantage of using SC-FDMA in the uplink?
SC-FDMA has drawn great attention as an attractive alternative to OFDMA, especially in the uplink communications where lower peak-to-average power ratio (PAPR) greatly benefits the mobile terminal in terms of transmit power efficiency and reduced cost of the power amplifier.
Why SC-FDMA has low PAPR?
SC-FDMA spreads the energy of one subcarrier over all subcarriers before the IFFT. This way spectral nulls in the channel is reduced with averaging. Hence, PAPR is reduced.
Why OFDM is not suitable for uplink transmission for LTE?
Unfortunately OFDM has a high peak to average ratio. While this is not a problem for the base station where power is not a particular problem, it is unacceptable for the mobile. As a result, LTE uses a modulation scheme known as SC-FDMA – Single Carrier Frequency Division Multiplex which is a hybrid format.
What is the difference between Ofdma and SC-FDMA?
What is the highest modulation scheme that is used in LTE?
One of the LTE features introduced in Rel-12 is the support for higher order modulation, that is 256QAM for DL data transmission to enhance the spectral efficiency and the system throughput.
What is the advantage of using single carrier frequency division multiple access SC-FDMA in the uplink?
