The universal availability of LEDs, license-free deployment and data rate of Gbps order, makes LiFi an attractive and inexpensive choice for indoor communications. However, LiFi suffers from a major drawback of blockage. As a result its throughput fluctuates spatially, consequently stand-alone LiFi can not guarantee the QoS. On the other hand, WiFi can support moderate data rates with more ubiquitous coverage. As LiFi and WiFi operate in non-overlapping spectrums and while LiFi can support high data rates when the receiver is in direct LoS, WiFi can support moderate data rates with more ubiquitous coverage. Therefore, coexistence of LiFi and WiFi technologies to form a heterogeneous LiFi WiFi network (HLWN) is suggested. It has been shown that a HLWN provides higher system throughput as compared to standalone LiFi or WiFi networks. Further, an appropriately designed HLWN can support higher data rate, better user satisfaction, outage performance, and lower handover rates.
Billions of IoT devices require connection, and RF communication is saturating day by day. Further, pervasive IoT requires a large density of connections, ubiquitous coverage, high aggregate bandwidth, sustainable energy resources, and a high level of security with simple, low power, low complex, inexpensive, energy-efficient communication technology due to the IoT devices' power limitations and hardware constraints. LiFi as an enabler for IoT communication can address these challenges by providing RF interference-free green communication along with huge unlicensed spectrum (no recurring cost), indoor positioning, energy autonomy through energy harvesting, inherent security, and many more yet to explore and research.
Indoor positioning has been a topic of growing interest for the past few years. The demand for accurate location-based services (LBS) increased together with the growing popularity of smartphones. Conventional indoor positioning systems based on radio-wave techniques deliver positioning accuracies from tens of centimeters to a few meters. LED-based indoor positioning system using visible light communication (VLC) technology reuses current lighting infrastructures, thus can be deployed easily and fast inside buildings where LEDs are used for lighting. Moreover, it will not generate radio-frequency (RF) interference, and therefore could be used in RF radiation restricted environments such as hospitals and mines, etc. Hence, the VLC-based indoor positioning technique will be a strong competitor for future indoor positioning systems.
Vehicular communication is a growing area of communication between vehicles and it includes roadside communication infrastructure. Wireless communications are making possible sharing of information through real time communications between vehicles and infrastructure. This has led to applications to increase safety of vehicles and communication between passengers and the Internet, like Vehicle-to-vehicle (V2V) communication enables vehicles to wirelessly exchange information about their speed, location, and heading. This technology behind V2V communication allows vehicles to broadcast and receive messages, creating a 360-degree awareness of other vehicles in proximity.
Physical layer security (PLS) is a technique implemented on the bottom (physical) layer of the network stack. Unlike conventional security mechanisms (such as access control, pasword protection and end-to-end encryption ), it relies on the channel characterization of the communication medium. The growing demand for high connectivity, reliability and data rates in the fifth generation (5G) of communication networks and beyond, the importance of physical layer security in wireless communication systems has been increased. The security threats due to the broadcast nature of wireless media in the presence of active or passive Eavesdropper may lead to the transmitted information leakage. Various PLS techniques in radio frequency (RF) such as beamforming, friendly jamming , artificial noise(AN), relaying etc. are adopted. Data privacy and confidentiality with the unprecedented data traffic demand are the major concerns in RF for both indoor as well as outdoor scenarios. As, visible light communication (VLC) has gained much attention due its various beneficial features including its inherent security features over RF in indoor scenarios, PLS is equally important for VLC specifically in some scenarios such as classrooms, meeting rooms, libraries,shopping malls, railway stations and aircrafts.
CSK: The VLC modulation scheme, which modulates the optical power of the red, green and blue (RGB) lights of trichromatic LED (TLED) keeping total power constant, is known as color shift keying (CSK). RGB LEDs are usually preferred over phosphor-coated LEDs for communication purposes as they support wavelength modulations and have low latency. Constant total output power reduces the imminent human health complications. The complexity of CSK is more than OOK but less than O-OFDM. LiFi4IoT indoor scenarios can utilize CSK and its modified versions to support moderate data rates with low complexity.
O-OFDM : The requirement of real and unipolar signals to drive LEDs for intensity modulation using OFDM has led to various optical-OFDM techniques. Some of the O-OFDM techniques are DC-biased optical OFDM (DCO-OFDM), asymmetrically clipped optical OFDM (ACO-OFDM), Flip-O-OFDM, O-OFDM with pulse shaping, Precoded O-OFDM, FHT based O-OFDM, O-OFDM with different subcarrier modulation schemes (PAM, CSK). O-OFDM and its medium access version O-OFDMA can be used for high spectral efficiency with an increased data rate to support a large number of high-speed consumer multimedia.
Green communication is the need of the hour. With the advent of new applications, energy and high-speed communication is surging rapidly. The use of solar panel as a receiver serves both of these purposes. It is a well-known fact that solar panel can be used as an energy harvester and everyday improvement has increased the efficiency, making it a valuable addition to technology. With new innovative business models, it is expected that this power will be able to generate enough revenue which will finally make the solar-panel-based communication almost free of cost. The potential market of this technology is India, South East Asia and Africa. Due to the very small dimension of the conventional free space receivers, the optical system requires a very complex system design for alignment and beam tracking between transmitter and receiver. With a solar panel as a receiver, this problem can be simplified to a great extent. Since the receiving area is bigger than the conventional receivers, mechanical control is very much simplified.
There is extensive ongoing research activity related to underwater communications. The targetted points are increasing the distance and bandwidth while reducing the energy consumption of underwater devices, with the aim of increasing the network lifetime. Also, the areas focus on how to prevent ship collisions.