Recent advancements in multiple-input-multiple-output (MIMO) has proved that it tends to achieve a spectral efficiency of tens or even higher of bits/Hz. The Large Area Synchronized (LAS) space-time spreading codes have an Interference Free Window (IFW) where both the auto-correlation and cross-correlation become zero. Combining MIMO with LAS codes can effectively take advantage of multipath delay spread and random fading. In this paper, we show that by using the Turbo Product Codes (TPC) and space interleaving in such a system, even the simple decorrelating detection method can detect the multi-antenna signals in effect and achieve very high spectral efficiency with finite-complexity which is feasible to realize in practice.