  Space-time coding techniques have become common-place in wireless
communication standards as they provide an effective way to mitigate the fading
phenomena inherent in wireless channels. However, the use of Space-Time Block
Codes (STBCs) increases significantly the optimal detection complexity at the
receiver unless the low complexity decodability property is taken into
consideration in the STBC design. In this letter we propose a new
low-complexity decodable rate-1 full-diversity 4 x 4 STBC. We provide an
analytical proof that the proposed code has the Non-Vanishing-Determinant (NVD)
property, a property that can be exploited through the use of adaptive
modulation which changes the transmission rate according to the wireless
channel quality. We compare the proposed code to existing low-complexity
decodable rate-1 full-diversity 4 x 4 STBCs in terms of performance over
quasi-static Rayleigh fading channels, detection complexity and Peak-to-Average
Power Ratio (PAPR). Our code is found to provide the best performance and the
smallest PAPR which is that of the used QAM constellation at the expense of a
slight increase in detection complexity w.r.t. certain previous codes but this
will only penalize the proposed code for high-order QAM constellations.
