SC Sub-carrier

In wireless communication systems, sub-carrier refers to a technique used in multicarrier modulation schemes, such as orthogonal frequency-division multiplexing (OFDM). Sub-carriers are closely spaced, narrowband channels that collectively form the overall transmission bandwidth. Each sub-carrier carries a modulated signal, and the combination of multiple sub-carriers allows for efficient data transmission.

SC (Single Carrier) refers to a modulation scheme where data is transmitted using a single continuous carrier wave. In contrast, multicarrier modulation schemes divide the available frequency spectrum into multiple sub-carriers, each carrying a portion of the total data. The use of sub-carriers provides several advantages over single-carrier modulation, including improved spectral efficiency, robustness against multipath fading, and the ability to combat interference.

In SC systems, the entire data stream is modulated onto a single carrier frequency. The modulation scheme used can vary depending on the specific system requirements and standards. Some commonly used modulation schemes for SC include phase-shift keying (PSK), amplitude-shift keying (ASK), and quadrature amplitude modulation (QAM).

One key characteristic of SC modulation is that it is susceptible to frequency-selective fading. This means that different frequencies within the transmission bandwidth experience varying levels of attenuation and phase shifts due to multipath propagation. To mitigate the effects of frequency-selective fading, equalization techniques are employed at the receiver to compensate for the channel distortion.

Compared to SC, multicarrier modulation schemes like OFDM divide the data into multiple parallel streams, which are then modulated onto different sub-carriers. These sub-carriers are closely spaced, typically orthogonal to each other, and overlap in frequency to utilize the available spectrum efficiently. Each sub-carrier can be modulated independently, allowing for greater flexibility and robustness against frequency-selective fading.

OFDM has gained significant popularity in various wireless communication standards, such as Wi-Fi (IEEE 802.11) and Long-Term Evolution (LTE), due to its ability to combat multipath fading, improve spectral efficiency, and support high data rates. However, SC modulation still finds application in certain scenarios where the simplicity of a single-carrier system outweighs the benefits offered by multicarrier modulation.

In summary, SC sub-carrier refers to the use of a single continuous carrier wave to transmit data, while multicarrier modulation schemes like OFDM employ multiple closely spaced sub-carriers to improve spectral efficiency and combat frequency-selective fading. The choice between SC and multicarrier modulation depends on the specific requirements of the communication system.