Abstract
In this paper, the peak-to-average power ratio (PAPR) reduction problem with tone injection (TI) in the direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) system is investigated, which is formulated as a tough integer combinatorial optimization problem. Since it is a challenging task to find the global optimal solution, the branch-and-bound method (BBM), which is extensively employed to deal with the NP-hard problem, is introduced to solve this problem. By splitting the superior branches and pruning the inferior branches, the close optimal solution is obtained. Simulation results reveal that the proposed BBM-based TI method has superior PAPR reduction and bit error rate (BER) performance compared with some existing algorithms. The proposed algorithm ensures a relatively low peak value, and thus provides an important benchmark in performance evaluations relative to other existing algorithms targeting at the same problem.
Highlights
Owing to the advantages of huge bandwidth, unlicensed frequency, immune to electromagnetic interference and high security, visible light communications (VLC) system has attracted considerable attention recently
The signals with high peak-to-average power ratio (PAPR) passing through power amplifier and light emitting diode (LED) [5] emitter can result in a nonlinear distortion
For the proposed branch-and-bound method (BBM) method, it can be efficiently solved by the interior-point method, which has a complexity of O(C × max(( N 2 -1)3, ( N 2 -1)2 (N -2), F )) in solving the PAPR optimization problem (8), where C denotes the number of steps, N 2 -1 represents the dimension of the variable ω, N -2 is the number of constraints and F is the cost in evaluating the first and the second derivatives of the objective and constraint functions [17]
Summary
Owing to the advantages of huge bandwidth, unlicensed frequency, immune to electromagnetic interference and high security, visible light communications (VLC) system has attracted considerable attention recently. Unlike radio frequency (RF) communications, VLC with white light emitting diodes (LEDs) can provide both illumination and communication simultaneously, and has the merit of high efficiency, long life, low cost and power consumption. An exponential nonlinear companding technique is proposed in [7] for VLC OFDM systems, which reduces the PAPR by compressing large signals and expanding the small signals simultaneously. Both methods mentioned above can result in the BER performance degradation caused by the nonlinear distortion of signals. Simulation results validate that the proposed BBM scheme can achieve a superior PAPR reduction performance compared with the existing TI schemes
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