  In this paper, the spectral efficiency of permutation modulation-based
multiple input multiple output (MIMO) visible light communication is improved
using systematically designed, multiweight codeword matrices. Soft-decision,
low-complexity detection schemes are then designed for the receiver and
compared with the maximum likelihood (ML) detection method. Bit error rate
(BER) results show the soft-decision detection algorithm is able to decode the
transmitted information without knowledge of the channel state information.
This enables the mobile receiver decode information while within the field of
view of the transmitter unit. The BER results also show a close match with the
ML detection in some codebooks and the performance of the soft-decision decoder
is evaluated for different positions of the receiver in an indoor environment.
