wireless communications
Optical wireless communications (OWC) has witnessed a revival recently among researchers in both academia and industry. The main reason for this resurgence is the exhausted radio-frequency (RF) spectrum, which is getting too crowded to handle the increasingly high demand for data rates. The optical band offers an opportunity to relieve the RF spectrum by accommodating part of the load. Other reasons behind the interest in OWC include relatively simple deployment, unlicensed bandwidth, high data rate, and dense spatial reuse. Practical outdoor applications include free-space optical communication for backhaul links between base-stations, and for ground-to-satellite/satellite-to-ground and inter-satellite communication. Indoor applications include visible-light communication to establish Light-Fidelity (LiFi) access and positioning, and enables combining illumination and communication functionalities using LED fixtures. Several works in the literature studied OWC from theoretical and practical perspectives, and demonstrated the capability of this technology to achieve high data rates.
This Best Readings section presents papers on optical wireless communications that cover several fronts, including information theoretic aspects, communication theoretic aspects, and implementation aspects. While the following list is by no means exhaustive, it highlights papers that could constitute a starting point for researchers interested in this area.
Broadband wireless internet market is booming. We know that broadband wireless works on RF spectrum which is very scarse resource. Moreover due to increase in number of subscribers for wireless networks, spectrum congestion has become a bottlenack. Moreover licensing requirements as well as un-suitability of certain RF bands have pioneered the developed of optical wireless communication system. Unlike conventional wireless system which operates using RF waves, optical wireless system works either using infrared waves or light waves.
Optical wireless system operates using wavelength ranging from 1330 nm to 1550 nm. These are most common wavelength used in optical fiber system. It requires Line of Sight communication between transmitter and receiver.
Difference between Short range and Long range optical wireless
Based on the distance and data rate specifications, optical wireless system is divided into short range and long range optical wireless systems. Moreover short range transmission system is further divided into directed system and diffused system. In directed system line of sight (LOS) is must while in diffused LOS is not needed. Following table compares these two and mentions difference between short range and long range optical wireless system types.
Advantages of Optical Wireless System
Following are the advantages of optical wireless system:
- It is immune to interference.
- It is highly secure as optical waves do not penetrate the walls.
- It provides higher data rate due to huge bandwidth available on fiber cable.
- As it operates using ISM unlicensed bands, license related issues are not required to be tackled with.
- Optical wireless network is used as best complement technology along with RF based wireless network.
- Data transfer rate of upto 10 Gbps can be achieved.
- It can cover distance of upto 1000 meters.
- It can make use of cheaper optical fiber cables and components.
Disadvantages of Optical Wireless System
Following are the disadvantages of optical wireless system:
- Break in the optical line of sight link leads to huge loss of data.
- Moreover atmospheric conditions can lead to link failures. The typical examples are dense smoke, kites, birds, rain etc.