Exit Chart Aided Irregular Convolutional Code Design for Iterative Downlink SDMA Systems using Imperfect Channel State Information

We analyze a precoded and iteratively detected downlink multiuser system employing imperfect Spatio-Temporal Channel Impulse Response at the Transmitters (ST-CIRT) with the aid of Extrinsic Information Transfer (EXIT) charts. A Precoded Iterative DownLink Space Division Multiple Access (PI-DLSDMA) system proposed in our previous research is further improved and shown to be capable of maintaining an infinitesimally low BER, despite using imperfect ST-CIRT. A further novel feature of the PI-DL-SDMA system is that we design an IrRegular Convolutional Code (IRCC) with the aid of EXIT chart analysis for creating an open EXIT tunnel between the inner decoder’s and outer decoder’s EXIT curve at a reduced Eb/N0 value and hence maintain an infinitesimally low BER. Index Terms— SDMA, downlink, iterative, EXIT char