  Targeting always the best achievable bit error rate (BER) performance in
iterative receivers operating over multiple-input multiple-output (MIMO)
channels may result in significant waste of resources, especially when the
achievable BER is orders of magnitude better than the target performance (e.g.,
under good channel conditions and at high signal-to-noise ratio (SNR)). In
contrast to the typical iterative schemes, a practical iterative decoding
framework that approximates the soft-information exchange is proposed which
allows reduced complexity sphere and channel decoding, adjustable to the
transmission conditions and the required bit error rate. With the proposed
approximate soft information exchange the performance of the exact soft
information can still be reached with significant complexity gains.
