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We explore the performance and hardware complexity tradeoffs associated with performing iterative multiple- input multiple-output (MIMO) detection using a sphere decoder and a low-density parity-check (LDPC) decoder. Iterations are performed both within the LDPC decoder as well as via an outer iteration loop through which refined soft information is fed back from the LDPC decoder to a MIMO detector. A hardware architecture and associated implementation results on Xilinx Virtex-5 field programmable gate array for a 4 x 4 QPSK MIMO system are presented. The system offers a performance improvement of approximately 1 dB over systems without the outer iteration loop, and provides an information bit throughput that ranges from 60 to 300 megabits per second when a length 1944 rate 1/2 LDPC code is used.