Contrasting space-time schemes for MIMO FSO systems with non-coherent modulation

International audienc

A Comprehensive Modeling of Vehicle-To-Vehicle Based VLC System under Practical Considerations, an Investigation of Performance, and Diversity Property

In this work, a vehicle-to-vehicle (V2V) visible light communications (VLC) model for two practical scenarios, is proposed. In scenario 1, the random lateral shift of vehicles and the deterministic longitudinal separation between two communicating vehicles are considered, whereas in scenario 2, longitudinal separation between two vehicles is considered to be random, and lateral shift of vehicles is considered to be deterministic. To this end, we emphasize comprehensive modeling of the practical characteristics of the considered V2V-VLC system, such as random path loss due to the random mobility of the vehicle, random lateral shift and random longitudinal separation of the vehicle. Moreover, we analyze the performance of the proposed V2V-VLC model in terms of different metrics under the consideration of a novel channel model. Considering our findings, it is observed that the random lateral shift of the vehicle and the random longitudinal separation between two vehicles have a significant impact on the V2V-VLC system performance. Further, at a distance of 40 m, for example, the path loss penalties for moderate and dense fog weather scenarios are 2 and 3 dB, respectively, compared with the clear weather. Furthermore, the combined impact of path loss and atmospheric turbulence affects the V2V-VLC performance significantly

Self-Synchronizing Pulse Position Modulation With Error Tolerance

Pulse position modulation (PPM) is a popular signal modulation technique which converts signals into M-ary data by means of the position of a pulse within a time interval. While PPM and its variations have great advantages in many contexts, this type of modulation is vulnerable to loss of synchronization, potentially causing a severe error floor or throughput penalty even when little or no noise is assumed. Another disadvantage is that this type of modulation typically offers no error correction mechanism on its own, making them sensitive to intersymbol interference and environmental noise. In this paper, we propose a coding theoretic variation of PPM that allows for significantly more efficient symbol and frame synchronization as well as strong error correction. The proposed scheme can be divided into a synchronization layer and a modulation layer. This makes our technique compatible with major existing techniques such as standard PPM, multipulse PPM, and expurgated PPM as well in that the scheme can be realized by adding a simple synchronization layer to one of these standard techniques. We also develop a generalization of expurgated PPM suited for the modulation layer of the proposed self-synchronizing modulation scheme. This generalized PPM can also be used as stand-alone error-correcting PPM with a larger number of available symbols