Radio frequency (RF) spectrum is already dense enough and hard to add more broadband channels to meet the current user demands. Optical free-space communications could be an excellent alternative to the RF communications system, and it provides additional benefits, e.g., large bandwidth, high data rates and reliable communication link. Therefore, free-space optical (FSO) communication system becomes more attractive for the deployment of additional broadband channels, and it fulfils the current user demands of bandwidth-hungry applications. FSO communication links are susceptible to numerous meteorological conditions such as fog, snow, dust, smoke, scintillation and smog. Achieving better connectivity under the above-mentioned severe conditions is a crucial research question. Joint optical-RF communication system is developed to overcome the problems as mentioned earlier. The proposed adaptive optical-RF transmission system is optimized so that the system performance is maximized under all channel conditions. Optimization is achieved over the respective channel mappings, and the total required power by exploiting the proposed algorithm. The mapping schemes of each link are optimally chosen such that the total mutual information is maximized while distributing optimal power to the individual channel. Simulations are performed and verified with the analytical results to validate the proposed design. A comparison of the adaptive joint system (i.e., hybrid FSO-RF) over the non-adaptive system under various weather conditions is provided. From simulation results, the performance gain of more than 1 dB is achieved under the minimum power level. It is, therefore, recommended that the adaptive hybrid FSO-RF communication system is always an optimum solution for all weather conditions.

射频（RF）频谱已经足够密集，很难添加更多的宽带信道来满足当前用户的需求。光学自由空间通信可能是RF通信系统的绝佳替代品，它还提供了其他好处，例如，大带宽，高数据速率和可靠的通信链路。因此，自由空间光（FSO）通信系统对于部署更多的宽带信道变得更具吸引力，并且它满足了当前用户对带宽需求旺盛的应用的需求。FSO通信链接易受多种气象条件的影响，例如雾，雪，灰尘，烟，闪烁和烟雾。在上述严酷条件下实现更好的连接性是至关重要的研究问题。开发联合光学-RF通信系统以克服前面提到的问题。所提出的自适应光学-RF传输系统已经过优化，因此在所有信道条件下系统性能都可以最大化。通过利用提出的算法，可以在各个通道映射以及总所需功率上实现优化。最佳选择每个链路的映射方案，以使总互信息最大化，同时将最佳功率分配给各个信道。进行仿真并用分析结果进行验证，以验证所提出的设计。提供了在各种天气条件下自适应联合系统（即，混合FSO-RF）与非自适应系统的比较。根据仿真结果，在最小功率水平下可获得超过1 dB的性能增益。因此，建议自适应混合FSO-RF通信系统始终是所有天气条件的最佳解决方案。