تجزیه و تحلیل عملکرد نرخ خطا از لینک نوری بین سیستم عامل های ارتفاع بالا با محو انحراف توسط توزیع هایف

The more reality misalignments model with Hoyt distribution is used to analyze performance for optical links between high altitude platforms. Compared with the recent work in terrestrial FSO, it is proved that the variance ratio have more significant effect on error performance for optical links over long distance. Then, the expression for the pairwise error probability is analyzed and applied to obtain upper bounds on the BER performance for coded optical communications. Simulation results show that coding technique can improve error performance of optical links, but it also can enhance the influences of the variance ratio.

Recently, optical communication systems for high altitude platforms (HAPs) have attracted more interest not just because of many virtues of HAPs compared with terrestrial and satellite communication systems, but because of good channel condition for laser communication in near space [1] and [2]. Owing to the limitation of narrow beam for optical transmission and large distance between two platforms, the spatial tracking requirement of inter-HAPs optical link becomes more stringent. Generally, a model for the FSO communication system with misalignment has been described in [3], [4], [5] and [6], where the variance in the two orthogonal directions is assumed to be identical, i.e. the radial displacement at the receive detector is determined by Rayleigh distribution. However, in the practical systems for HAP optical communication, the drift due to monsoons, temperature and pressure variations results in the platform positional instability [7] and [8]. Hence, for inter-HAPs optical links, the Rayleigh model is not appropriate anymore. Gappmair et al. [9] has extended the conventional model to Hoyt model, and analyzed performance of uncoded terrestrial FSO links over short distance. Xian [10] has investigated the outage probability of inter-satellite optical link without considering the effect of atmospheric turbulence. In this paper, we investigate the error rate performance for inter-HAPs optical links over long distance considering the joint effects of atmospheric turbulence by a gamma–gamma distribution and misalignment fading by Hoyt distribution. Considering the limitation of size and power loss, the probably most promising technique for mitigation of atmospheric disturbances and misalignment fading in inter-HAPs optical link is coding and interleaving [6]. We also discuss the error performance for coded inter-HAPs optical links in the end.

In this paper, we have considered the link performance of the inter-HAPs optical communication system operating over Hoyt distributed misalignment fading in the presence of atmospheric turbulence. We prove that the impact of the variance ratio on the error performance is significant. On the other hand, the divergence angle can help mitigate the influence of variance ratio to some extent. We also have obtained upper bounds on bit-error probability using the transfer function method. It was shown that, we can attain low BER targets for small SNR values using error control coding, while at the same time the influences of the variance ratio become large. Therefore, it is advisable to carefully configure the inter-HAPs optical communications system to make the two variances as close as possible.