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.

In networks where stations are equally likely to transmit to one another, simple slotted ALOHA is not an appropriate form of multiple access protocol as messages meant for different stations can collide in the common channel. In this paper the performance of a single channel slotted ALOHA network is compared to that o f a CDMA ALOHA network where each of the station is assigned a different spreading code with which to receive messages, and thus effectively possesses its own private 'virtual channel'.

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It has been shown in [l] that the throughput-delay performance of a CDMA ALOHA network, where each station is assigned a spreading code so that each effectively has its own 'virtual channel', and where channel sensing and collision detection are also used, is much better than that of a simple CSMA-CD network. Such a system, however, is difficult to implement. A simpler system that may provide good performance and that is easy to implement is a CDMA ALOHA network with just channel sensing. The channel sensing can be provided by a simple correlator and threshold device. In this paper, the performance of such a network is investigated, and some comparisons are made with those of the simple CSMA-CD network and the CDMA ALOHA network with both channel sensing and collision detection. It is shown that when the CDMA-CS network is stable, its performance is not much worse than that of a CDMA-CS/CD network, and much better than that of a simple single channel CSMA-CD system. I.