This letter deals with turbo equalization for coded data transmission over intersymbol interference (ISI) channels. We propose a message-passing algorithm that uses the expectation propagation rule to convert messages passed from the demodulator and decoder to the equalizer and computes messages returned by the equalizer by using a partial Gaussian approximation (PGA). We exploit the specific structure of the ISI channel model to compute the latter messages from the beliefs obtained using a Kalman smoother/equalizer. Doing so leads to a significant complexity reduction compared to the initial PGA implementation. Results from Monte Carlo simulations show that the proposed approach leads to a significant performance improvement compared to state-of-the-art turbo equalizers and allows for trading performance with complexity.
Zhang, C., Wang, Z., Manchón, C. N., Sun, P., Guo, Q., & Fleury, B. H. (2016). Turbo Equalization Using Partial Gaussian Approximation. I E E E Signal Processing Letters, 23(9), 1216-1220. https://doi.org/10.1109/LSP.2016.2581841