Addressing Multi-User Interference in Vehicular Visible Light Communications: A Brief Survey and an Evaluation of Optical CDMA MAC Utilization in a Multi-Lane Scenario

Abstract

Visible Light Communications (VLC) are developing as an omnipresent solution for inter-vehicle communications. Based on intensive research efforts, the performance of vehicular VLC systems has significantly improved in terms of noise resilience, communication range, and latencies. Nevertheless, in order to be ready for deployment in real applications, solutions for Medium Access Control (MAC) are also required. In this context, this article provides an intensive evaluation of several optical CDMA MAC solutions and of their efficiency in mitigating the effect of Multiple User Interference (MUI). Intensive simulation results showed that an adequately designed MAC layer can significantly reduce the effects of MUI, ensuring an adequate Packet Delivery Ratio (PDR). The simulation results showed that based on the use of optical CDMA codes, the PDR can be improved from values as low as 20% up to values between 93.2% and 100%. Consequently, the results provided in this article show the high potential of optical CDMA MAC solutions in vehicular VLC applications, reconfirm the high potential of the VLC technology in inter-vehicle communications, and emphasize the need to further develop MAC solutions designed for such applications.

Iterative Equalization and Decoding over an Additive White Gaussian Noise Channel with ISI Using Low-Density Parity-Check Codes

“…Firstly, a summary of existing SISO equalization algorithms derived from classical equalization methods according to the maximum a posteriori (MAP) or minimum meansquare error (MMSE) criterion is presented. In this respect, we referred to [4,5,[16][17][18][19][20][21][22][23][24][25][26][27].…”

“…Code division multiple access (CDMA) systems need to regard the interference caused by multiple users. In this respect, in [26], the iterative handling for CDMA is described. In addition, the principles of turbo equalization can be used in the issue of linear precoding or precoding multiantenna systems [27].…”

Driving toward Connectivity: Vehicular Visible Light Communications Receiver with Adaptive Field of View for Enhanced Noise Resilience and Mobility

“…Regardless of these unfriendly conditions, VLC has made impressive progress, achieving a performance that was difficult to imagine before. Thus, today's vehicular VLC prototypes can provide a high resilience to optical interference [19][20][21], including the interference generated by multiple VLC transmitters [22]; decent data rates; and communication ranges of up to almost 200 m [23], indicating that this technology is almost ready for real-life implementation [24][25][26]. Although substantial strides have been made in advancing vehicular VLC technology, its specific challenges require further research efforts.…”

Experimental Demonstration of a Visible Light Communications System Based on Binary Frequency-Shift Keying Modulation: A New Step toward Improved Noise Resilience

“…Nevertheless, in many cases, the VLC receiver is exposed to other sources of light, not just to the VLC transmitter. In vehicular applications, the VLC receiver can be exposed to multi-user interferences (MUI) [25,26], but it can also be exposed to a multitude of other light sources (artificial and natural) [9]. Among all optical noise sources, sunlight is considered to be the most disruptive, as it can reach intensities that can go above 65,000 µW/cm 2 .…”