2-D Optical-CDMA Modulation With Hard-Limiting for Automotive Time-of-Flight LiDAR

Abstract

In this proof-of-principle paper, the application of 2-D optical code-division multiple-access (OCDMA) modulation to long-range automotive time-of-flight (ToF) light detection and ranging (LiDAR) is studied. The regulations and physical constraints that govern the design parameters are reviewed. Using 2-D carrier-hopping prime codes (CHPCs), the modulation model and a novel 2-D hard-limiting decoder are designed and validated with OptiSystem TM simulations. Based on the design parameters, the 2-D CHPCs have six times as many distinct sequences (for sensor identification) as 1-D code sequences. Analytical and simulation studies show that the proposed 2-D OCDMA modulation model can eliminate the near-far (power) problem and support more LiDAR sensors with distinctive ToF tags, greater interference robustness for more simultaneous ToF measurements, and better performance than the 1-D counterparts. The simulation results show that the 2-D model can support four times as many simultaneous emitting sensors without false detections as the 1-D model. In summary, the 2-D OCDMA modulation has more benefits and is more cost efficient overall, even though it is more complex.

A Novel Cycloidal Scanning LiDAR Sensor Using Risley Prism and Optical Orthogonal Frequency-Division Multiple Access for Aerial Applications

“…In that case, they are refracted at different angles depending on the location, making it possible to measure more locations simultaneously. Optical CDMA (OCDMA) and OOFDMA technology can eliminate mutual interference even when multiple LiDARs operate simultaneously [37]- [39], [41], [64], [70], [71]. In LiDAR sensors, the challenge of multipath or mutual interference arises when laser pulses encounter obstacles that cause reflection or scattering.…”

“…The proposed LiDAR incorporates a variable FoV function that adjusts the scanning pattern and density of the point cloud to correspond to different sizes, distances, and distributions of objects. The proposed LiDAR employs multiple pulses generated by special coding techniques, rather than a single pulse, to ensure that only the pulses it emits are distinguishable, eliminating mutual interference [34], [35], [37]- [39], [71], [78]. However, coding techniques in optics can only use the presence of light, limiting them to represent only zeros and positives, unlike RF, which can represent negative numbers.…”

Coded Pulse Stream LiDAR Based on Optical Orthogonal Frequency-Division Multiple Access

“…LiDAR systems that use a single laser pulse are subject to similar limitations, regardless of the chosen transmission method. Researchers have explored coded pulses using randomized or optical code division multiple access (OCDMA) techniques to overcome these limitations [9], [10], [11]. This method transmits a coded laser pulse stream with unique codes to distinguish each measurement location.…”

“…This study presents a new LiDAR that utilizes optical orthogonal frequency division multiple access (OOFDMA) to generate a laser pulse stream, as illustrated in Figure 1. The proposed LiDAR employs pulse stream generated by special coding techniques, rather than a single pulse, to ensure that only the pulses it sends are distinguishable, eliminating mutual interference [9], [10], [11], [14], [15], [16], [17]. However, coding techniques in optics can only use the presence of light, limiting them to represent only zeros (''0''s) and positives (''+1''s), unlike RF which can represent negative numbers (''−1''s).…”

Overcoming the limitations of 3D sensors with wide field of view metasurface-enhanced scanning lidar

“…35 In this scheme, strongly inspired by code division multiple access (CDMA) multiplexing technique from telecommunication theory, different pixels are modulated with different sequences, and the sequence family satisfies orthogonality conditions to avoid cross talk between pixels. From this point, research on this topic has focused on comparing and optimizing the modulation sequences, 36,37 proposing more complex sequence generation using wavelength division, 38 implementing hardware solutions to optimize the processing time, 39 or on considering this technique to ensure the robustness to interference from other lidars. 40 As for the experimental demonstration of this technique, implementations have only been made in kilohertz scanning devices, 41 hence using codes that were not compatible with fast scanning.…”