Low complexity MAP detection using approximate LLR for CDMA iterative receivers

In this letter, we approximate the log-likelihood ratio (LLR) to find computationally efficient detectors for the iterative receiver in code division multiple access (CDMA) systems. For approximation, a Taylor series of the LLR is considered. One of the well-known detectors is rederived using a first order approximation, while a new detector is found by a second order approximation.