CW-SIC (Codeword level SIC)

Last updated on Mar 21, 2023

CW-SIC (Codeword level Successive Interference Cancellation) is a technique used in wireless communication systems to improve spectral efficiency by allowing multiple users to share the same channel. It is a type of interference cancellation technique that is used to separate the signals of different users sharing the same frequency band.

In wireless communication systems, multiple users share the same frequency band to transmit and receive data. This can result in interference between the signals of different users, which can degrade the performance of the system. To address this issue, various interference cancellation techniques have been developed, such as frequency hopping, spread spectrum, and SIC.

CW-SIC is a technique that allows multiple users to transmit and receive data on the same channel by using a unique code for each user. These codes are known as codewords, and they are used to modulate the data of each user. The codewords are designed to be orthogonal, which means that they have no correlation with each other. This ensures that the signals of different users can be separated from each other.

The basic principle behind CW-SIC is to cancel the interference caused by the signals of other users. In a wireless communication system, the signals of different users are combined at the receiver. This results in interference between the signals, which makes it difficult to extract the data of each user. With CW-SIC, the receiver uses the unique codewords of each user to separate their signals.

The process of CW-SIC involves several steps. The first step is to receive the combined signal from all users on the channel. The receiver then performs a demodulation process to extract the codeword of each user from the combined signal. This process is known as initial demodulation. Once the codeword of each user has been extracted, the receiver uses it to cancel the interference caused by the signals of other users. This is done by subtracting the interference caused by the codeword of each user from the combined signal. The receiver then repeats this process for all users on the channel, until the signals of all users have been separated.

CW-SIC can be implemented using different algorithms, such as the Maximum Likelihood (ML) algorithm, the Minimum Mean Square Error (MMSE) algorithm, and the Linear Minimum Mean Square Error (LMMSE) algorithm. These algorithms are used to optimize the process of interference cancellation, by minimizing the error between the received signal and the estimated signal.

One of the advantages of CW-SIC is that it can improve the spectral efficiency of wireless communication systems. By allowing multiple users to share the same channel, CW-SIC can increase the number of users that can be supported by the system, without requiring additional bandwidth. This can result in significant cost savings for service providers, as they can serve more users with the same resources.

Another advantage of CW-SIC is that it can improve the quality of service for users. By separating the signals of different users, CW-SIC can reduce the interference between the signals, which can improve the signal-to-noise ratio (SNR) of the received signal. This can result in better performance for users, such as higher data rates and improved voice quality.

However, there are also some limitations to CW-SIC. One of the main limitations is that it requires accurate knowledge of the channel conditions. This is because the interference cancellation process depends on the channel coefficients between the transmitter and receiver of each user. Any errors in the estimation of these coefficients can result in degraded performance of the system.

Another limitation of CW-SIC is that it requires a high computational complexity. This is because the receiver has to perform multiple iterations of the interference cancellation process for each user. This can result in a high processing delay, which can impact the real-time performance of the system.

In conclusion, CW-SIC is a powerful interference cancellation technique that can significantly improve the spectral efficiency and quality of service in wireless communication systems. It allows multiple users to share the same channel by using unique codewords for each user, which are designed to be orthogonal. The receiver then uses these codewords to separate the signals of different users, by cancelling the interference caused by the signals of other users.