Kucuk, Mehmet Ali; Turk, Kadir

In this letter, an angle-of-arrival (AoA)-based integrated positioning system is proposed that utilizes the standard optical front-end of multi-color visible light communication (MC-VLC). Unlike traditional AoA methods, which rely on specialized receiver architectures, the proposed approach uses the inherent angular dependence of optical filter transmission responses, known as the blue-shift effect, for directly estimating the angle of incidence from the received signal. In this context, an AoA estimation technique is developed by combining eigenvalue decomposition of the MC-VLC channel with regression analysis. Simulation results show that the proposed system achieves millimeter-level positioning accuracy, enabling robust and high-precision indoor localization without additional hardware complexity or cost.

Albayrak, Cenk; Simsek, Cemaleddin; Turk, Kadir

We propose a new early termination method (ETM) with low computational complexity for Luby transform belief propagation (BP) decoder. The proposed method, which we call least reliable messages (LRM) ETM, observes only sign alterations of a small cluster in log-likelihood ratio messages passing between nodes in BP decoder. Simulation results and complexity analyzes show that LRM ETM has quite low computational complexity and small average iteration amounts without any performance degradation compared with conventional ETMs in literature. The method can be applied to code families which can be decoded by BP such as low density parity check codes, polar codes, and Raptor codes.

Simsek, Cemaleddin; Turk, Kadir

As the first theoretically proven capacity-achieving error correction code, polar codes have become a milestone in information theory field, which draw serious attention by its low complexity encoding and decoding structures. For the decoding section, studies are focused on efficient and low complex algorithms based on successive cancellation and belief-propagation (BP) decoders. To reduce computational complexity of BP-based decoders further, early stopping methods that avoid unnecessary iterations can be used. In this letter, we propose a reduced complexity early stopping method for BP-based polar code decoders. The proposed method is based on the hypothesis that observing only a small cluster of information bits polarized to the highest error probabilities is enough to detect successful decoding. Simulation results show that the proposed early stopping criterion significantly reduces the computational complexity of successful decoding detection as well as the total operation numbers of the whole decoding process compared with previous methods in the literature.