  Visible light communication (VLC)-based beacon systems, which usually
transmit identification (ID) information in small-size data frames are applied
widely in indoor localization applications. There is one fact that flicker of
LED light should be avoid in any VLC systems. Current flicker mitigation
solutions based on run-length limited (RLL) codes suffer from reduced code
rates, or are limited to hard-decoding forward error correction (FEC) decoders.
Recently, soft-decoding techniques of RLL-codes are proposed to support
soft-decoding FEC algorithms, but they contain potentials of high-complexity
and time-consuming computations. Fortunately, non-RLL direct current
(DC)-balance solutions can overcome the drawbacks of RLL-based algorithms,
however, they meet some difficulties in system latency or inferior
error-correction performances. Recently, non-RLL flicker mitigation solution
based on Polar code has proved to be an optimal approach due to its natural
equal probabilities of short runs of 1's and 0's with high error-correction
performance. However, we found that this solution can only maintain the DC
balance only when the data frame length is sufficiently long. Accordingly,
short beacon-based data frames might still be a big challenge for flicker
mitigation in such non-RLL cases. In this paper, we introduce a flicker
mitigation solution designed for VLC-based beacon systems that combines a
simple pre-scrambler with a Polar encoder which has a codeword smaller than the
previous work 8 times. We also propose a hardware architecture for the proposed
compact non-RLL VLC receiver for the first time. Also, a 3-bit soft-decision
filter is introduce to enable soft-decoding of Polar decoder to improve the
performance of the receiver.
