Minimal Noise Variance Decoder for Uncoordinated Multiple Access in VLC

Abstract

Abstract-In a visible light communications system (VLC), light sources are responsible for both illumination, communications and positioning. These light sources inevitably interfere each others at the receiver. To retain the appealing advantage that VLC systems can reuse existing lighting infrastructure, using an extra network to control or synchronize the light sources should be avoided. This paper proposes an uncoordinated multiple access scheme for VLC systems with positioning capability. The proposed scheme does not require a central unit to coordinate the transmission of the transmitters. Transmitters can be asynchronous with one another and with the receiver. Each transmitter is allocated a unique codeword with L chips for a system with up totransmitters where L is prime. Due to the linear growth in complexity with respect to number of transmitters, our proposed scheme is feasible for systems with large numbers of transmitters. Our novel decoder can minimize the effect of additive Gaussian noise at the receiver side. Simulation results show that the proposed decoder outperforms zero-forcing decoder.

Sinusoidal-Based Multiple Access Scheme for Visible Light Decentralized Asynchronous Systems

“…3) Simulation results are obtained and have shown that the proposed scheme significantly outperforms existing schemes in the literature in terms of the BER and system throughput when they are applied to a DAS. This paper improves the preliminary result in [1] and has the following significant differences: i) This paper proposes a novel scheme, in which receivers can obtain an unbiased channel estimate per each codeword duration despite the transmit data randomness. Channel estimation rate is therefore much higher than the rate allowed in [1].…”

“…This paper improves the preliminary result in [1] and has the following significant differences: i) This paper proposes a novel scheme, in which receivers can obtain an unbiased channel estimate per each codeword duration despite the transmit data randomness. Channel estimation rate is therefore much higher than the rate allowed in [1]. Simulation results in this paper illustrate a case that a received vector with length equal to 34 is sufficient for good channel estimation.…”

“…Simulation results in this paper illustrate a case that a received vector with length equal to 34 is sufficient for good channel estimation. In contrast, the scheme in [1] can achieve similar performance if the received vector length is 2311. Therefore, the scheme in this paper significantly reduces the length by 85%.…”

“…Therefore, the scheme in this paper significantly reduces the length by 85%. ii) The work in this paper goes beyond the work in [1] by proposing a new estimator which has a lower computational complexity, without any performance degradation in comparison to the proposed estimator in [1]. iii) New analytical results for our new proposed scheme are derived in this paper (see Section IV).…”

Indoor Localization Using Multi-Color Fingerprinting

“…Almost all of them are based on the underlying assumption that the receiver can differentiate among light sources: this can be realized by having the LEDs working in a transmission multiplexing scheme such as Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA), which are common technologies. Discussions of the advantage and disadvantage of these multiple access schemes for VLC can be found in [14].…”