Precoded Optical Spatial Modulation for Indoor Visible Light Communications

• This paper proposes a precoded optical space-domain index modulation scheme for indoor visible light communications, which is based on optimization of the minimum Euclidean distance in optical spatial modulation (OSM) with real-valued modulation constellations. We find that the precoding matrix design can be formulated as a non-convex quadratically constrained quadratic program (QCQP) problem, whose solution is generally intractable. To tackle this problem, we first consider the case of two optical transmit antennas (Nt = 2) in precoded OSM and derive the closed-form solution for arbitrary M-order pulse amplitude modulation (PAM). Based on the derived solutions and the error vector reduction method, we then propose a low-complexity iterative (LCI) algorithm to identify the precoding matrix for the cases of Nt > 2. To strike a flexible complexity-BER (bit error rate) tradeoff, we propose a successive convex approximation (SCA)-assisted matrix-based optimization method to transform the non-convex QCQP problem into a series of linear convex subproblems, which can easily be solved by low-complexity solvers. Simulation results show that these proposed algorithms are capable of substantially improving the system error performance compared with conventional OSM systems. Besides, the symbol-based SCA algorithm is introduced and it outperforms the matrix-based SCA and the suboptimal LCI algorithm in terms of the BER.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Telekommunikation (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Telecommunications (hsv//eng)

Nyckelord

Convex optimization

index modulation

precoding

spatial modulation

visible light communication

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