A simple yet effective scheme is proposed to improve the detection capability of multiple-input multiple-output (MIMO) symbol detectors in wireless communication systems at low signal-to-noise ratio (SNR). The proposed scheme is to change the metric calculation adaptively to the channel SNR, grounded on the fundamental relationship between the detection capability and the bit-error rate (BER) performance with respect to the channel SNR. An efficient hardware architecture implementing the

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... d scheme is also presented to show its applicability in a practical sense and it is proven that the architecture induces only a negligible hardware overhead compared to the state-of-the-art MIMO symbol detector. Experimental results show that the proposed scheme can indeed increase the detection capability effectively without degrading the BER performance noticeably. Keywords-adaptive metric calculation; multiple-input multiple-output (MIMO); sphere decoding; wireless communications I. II. MIMO SYMBOL DETECTION This section describes the model of MIMO communication systems and how to detect MIMO symbols transmitted through the channel. A. System Model Considering a spatially multiplexed N T × N R MIMO communication system, the equivalent baseband system model can be modeled as