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This paper constructs a model for Optical Spatial Modulation Orthogonal Frequency Division Multiplexing (O-SM-OFDM). It investigates the effects of different power allocation schemes on bit error ratio (BER) performance. The experiment is based on an optical 2 × 1 SM-OFDM system with symmetrical link geometry. Effects introduced by the particular properties of intensity modulation (IM) that the signal has to be real valued and positive are considered in this study. In this work we assume direct current (DC) biased optical communication and take into account light-emitting diode (LED) non-linearities. We consider the information bits that are encoded in the spatial domain in SM and the bits in quadrature amplitude (QAM) modulated signal separately. The former are the “spatial domain bits”, and the latter are the “signal domain bits”. The optical transmit powers are varied while the total transmit power is kept constant and power imbalances between the different transmitters are created in order to be able to study the trade-off between the accuracy of detecting the spatial domain bits and the signal domain bits. It is shown that transmission power imbalance between transmitters can improve the detection accuracy of the spatial domain bits as expected. However, this will reduce the receiver signal to noise ratio (SNR) of the signals with weaker power. As a consequence, signal domain BER increases, which compromises the BER improvement of spatial domain bits. In this context, the relationship between power imbalance, BER performance and minimum SNR required to achieve a certain BER level are investigated. The optimal point of transmission power difference is determined via computer simulations.
|Title of host publication||Proc. of the Vehicular Technology Conference (VTC Spring)|
|Place of Publication||Yokohama, Japan|
|Publisher||Institute of Electrical and Electronics Engineers (IEEE)|
|Publication status||Published - 1 May 2012|