Spatial Coupling In Turbo Equalization

In this paper we consider spatial coupling in turbo equalization and demonstrate that the code design trade-off between the performance in waterfall and error floor regions can be avoided. We introduce three coupling schemes and compare their performances, where the first method introduces coupling between the encoder and the channel, while the second uses a spatially coupled (SC) code. In the third scheme we use both a coupled code and couple between the code and the channel. We show by computer simulations that, with spatial coupling, we can have good performance in both the error floor and the waterfall region with reasonable decoding latency by using a window decoder. We show this for both the maximum a posteriori (MAP) and linear minimum mean square (MMSE) equalizers.