SC-FDMA (Single Carrier Frequency Division Multiple Access) is indeed used in LTE systems for the uplink transmission. It offers advantages like a lower peak-to-average power ratio (PAPR), improved coverage in the presence of interference, and efficient spectral usage. In the LTE uplink, SC-FDMA divides the available frequency bandwidth into subcarriers allocated to users, enabling efficient and reliable communication from user devices to the network.
Has SC-FDMA been used as a multiple access scheme in LTE systems?
Yes, SC-FDMA (Single Carrier Frequency Division Multiple Access) has indeed been used as a multiple access scheme in LTE (Long-Term Evolution) systems. SC-FDMA is a key component of the uplink (UL) transmission scheme in LTE.
Here’s a detailed explanation of how SC-FDMA is employed in LTE systems:
Introduction to SC-FDMA:
SC-FDMA is a modulation scheme used for transmitting data in the uplink of LTE networks. It is often referred to as “Single Carrier” because it operates on a single carrier frequency.
Why SC-FDMA in Uplink:
In LTE, different multiple access schemes are used for the uplink (transmitting from the user device to the base station) and the downlink (transmitting from the base station to the user device).
SC-FDMA is chosen for the uplink because it has certain advantages over other schemes like OFDMA (Orthogonal Frequency Division Multiple Access), which is used in the downlink.
One primary advantage is that SC-FDMA has a lower peak-to-average power ratio (PAPR), making it more suitable for power-constrained devices like mobile phones.
How SC-FDMA Works:
SC-FDMA divides the available frequency bandwidth into a series of subcarriers.
Each subcarrier is assigned to a user or a user group, and they transmit their data using these subcarriers.
Unlike OFDMA, where subcarriers are orthogonal (non-overlapping), SC-FDMA subcarriers have a specific overlap, which reduces the PAPR.
SC-FDMA uses a discrete Fourier transform (DFT) at the transmitter to convert the time-domain signals into the frequency domain for transmission.
Advantages of SC-FDMA:
Lower PAPR: As mentioned earlier, SC-FDMA has a lower PAPR compared to OFDMA, which is crucial for power efficiency in the uplink.
Better coverage: SC-FDMA provides better coverage in the presence of interference and is more resilient to frequency-selective fading.
Improved spectral efficiency: SC-FDMA allows for efficient use of the available spectrum, which is essential for accommodating a large number of users in a cellular network.
LTE Uplink Frame Structure:
In LTE, the uplink frame structure consists of various time slots and subframes where user data is transmitted using SC-FDMA.
The scheduling of users and allocation of SC-FDMA resources are managed by the base station (eNodeB) to ensure fair and efficient use of the uplink spectrum.
SC-FDMA is the multiple access scheme of choice for the uplink transmission in LTE systems due to its lower PAPR, better coverage, and spectral efficiency advantages. It plays a crucial role in enabling efficient and reliable communication from mobile devices to the cellular network infrastructure.