Turbo equalisation for the Enhanced GPRS system

The iterative receiver structures can often improve the performance with a reasonable level of complexity. In this paper, we study iterative equalisation technique, i.e., turbo equalisation (TE), which enables to improve the performance by signal processing means in the receiver – without altering any other part of the system. TE is based on the feedback information from the channel decoder into the equaliser. That information is used as a priori information in the equaliser to start a new iteration, which provides more reliable decisions. The performance evaluation for Enhanced General Packet Radio System (EGPRS) shows that TE is beneficial for 8-PSK modulation in particular giving 2 dB gain with one extra iteration. However, TE requires soft-in-softout (SISO) decoder to be used, since the feedback information from the decoder should contain reliability information.