# A Review-Unguided Optical Communications: Developments, Technology Evolution, and Challenges
## 3 Hybrid RF-FSO Systems Techniques and Their Advanced Achievements
### FSOC for WiMAX
However, this is because the organization will employ more people and set up a larger space for base station activity than for other areas. This type of WiMAX-based customizability makes it easy for a system administrator to reduce the costs and meet the requirements/demands of customers [161; 162]. Military tactical communications, disaster management, and search/rescue operations require an immediate internet/communication connectivity which is possible only with WiMAX's kind of data access [162]. A WiMAX base station can also function as a leading mobile node which eases the way to solve all the coordination issues of group handover. The leading mobile node combines several handover processes out of the group of mobile nodes into one, which might eliminate the 'clash of range request' at the base station and decrease the 'delay/latency' in the network. Furthermore, this also copes with communication security-crack issues by dealing with local communication when a suitable target base station is not available to make a handover. VoIP can be used to implement voice applications over the Internet [163]. Finally, the IP network carries out different features, such as gathering 'calls' and 'gateways', into an open virtual network (OVN) and to the events associated with them. WiMAX facilitates various classes of services with a good QoS for VoIP [152]. Telemedicine is an evolved healthcare technology based on information and communications technology. To connect to telemedicine, hardware and software are required for both the expert/doctor and patient side. All necessary and important medical devices can be connected via a WiMAX connection [164]. Via a WiMAX-enabled telemedicine system, the preparation of patients, operation guidance, medical pictures, consultations, and other associated facts would be exchanged with clinical doctors and specialists in real time to examine the information, make a diagnosis, interact/engage with the patient, and recommend the proper care/medicines through a video consultation with the patient's terminal. Telemedicine allows a specialist/doctor and the patient to be visible and talk to each other, though they are separated by thousands of kilometers [153]. In a smart power grid network, so many smart electricity meters and other wireless electronic equipment/sensors give a large amount of measurement data/information [165]. Reliable, safe, effective, and durable data communications with the power grid is important. WiMAX offers the flexibility of many network service configurations so that WiMAX can be adapted for applications specific to this kind of need. WiMAX technology can provide support for multipoint networks and provides multirotor interoperability between products. WiMAX-based architecture can be deployed to have complete control over traffic-management tools/systems [165]. All the advantages of FSO communication technology can be adopted to WiMAX networks. An architecture proposed to have a wide coverage WiMAX network supported by FSO communication link is shown in Figure 26, where a WiMAX base station is physically connected to the Internet (backbone network). This station is also connected to other WiMAX stations via an FSO link that facilitates high-speed data transfer. In addition, every base station provides backbone data, accessed via the FSO link, and to all its local users via WiMAX access within its coverage. Thus, the physical connection of every base station to the backbone Internet is avoided and the FSO linked base stations can be mobile platforms. An FSO communication link from a WiMAX base station to a local tower within its coverage, for high-speed data delivery, is also possible. In the proposed FSO-WiMAX architecture, only one base station accesses the data from the Internet (backbone network) and it delivers the same access to all neighbor towers via FSO communication links. The connections and data access to local users (homes, civic/business buildings, corporate offices, mobile clients, etc.)