Anamalamudi, Sangi, Alkatheiri, Bin Muhaya, and Liu
158
7.6 LiFi Networks
With the increasing demand for wireless data communication, the existing wireless
spectrum below 10 GHz (cm‐wave communication) has become congested and insufficient. The Federal Communication Commission (FCC) has come up with different
alternatives to minimize this challenge. One is to opportunistically re‐use the available
spread spectrum (below 10 GHz) through Software defined radio (SDR) and Cognitive
radio networks. The other alternative is to consider the radio spectrum above 10 GHz
(mm‐wave communication) and provide wireless network connectivity through visible
light communication. However, the higher frequencies (f ) result in increased path
loss (L) based on the Friis free space equation (L ∝ f2). Furthermore, blockage and
shadowing in terrestrial communication are more difficult to overcome at higher frequency‐based radio communication. Consequently, radio devices need to be designed
to enhance the probability of line‐of‐sight (LoS) through beam forming techniques and
by using cells with small radius (~50 m) [23]. The design of small cells is not an issue
from a system capacity perspective, because reducing cell sizes has been the major contribution for enhanced system performance in existing cellular communications. On the
other hand, usage of higher frequencies for terrestrial communication has become a
practical option. However, one drawback is that the challenge to provide supporting
infrastructure for smaller cells becomes an important consideration.
Light Fidelity (LiFi) is a bidirectional, high‐speed and fully networked optical wireless
communication technology that works in a similar way to WiFi. LiFi is a form of visible
light communication and a subset of optical wireless communications (OWC). LiFI can
be a complement to RF communication (WiFi or cellular networks), or even a replacement in the context of data broadcasting. LiFi takes the concept of visible light communication (VLC) further through light emitting diodes (LEDs) to realize the fully
networked wireless systems. Synergies harnessed as luminaries become LiFi at the cells,
resulting in enhanced wireless capacity providing the necessary connectivity to realize
the Internet‐of‐Things, and contributing to the key performance indicators for the fifth
generation of cellular systems (5G). Visible light communication makes use of “off‐the‐
shelf ” white light emitting diodes (LEDs) that are used for solid‐state lighting (SSL) as
signal transmitters and off‐the‐shelf p‐intrinsic‐n (PIN) photodiodes (PDs) or avalanche
photo‐diodes (APDs) as signal receivers [24]. This shows that VLC communication
enables the system that illuminates and concurrently it provides broadband wireless
data connectivity.
When the illumination is not desired in the uplink, then the infrared (IR) LEDs or
indeed RF would be the viable solutions. In visible light communication, the application
information is being carried by the intensity (power) of the light. This clearly shows that
the information‐carrying signal has to be real valued and strictly positive. State‐of‐the‐
art traditional digital modulation schemes for Radio Frequency (RF) communication
use complex valued and bipolar signals. Modifications are certainly necessary where
there will be a rich body of knowledge on modified multi‐carrier modulation techniques
such as OFDM for intensity modulation (IM) and direct detection (DD). The data rates
of 3.5 Gb/s have been reported from a single LED. It is noteworthy that visible light
communication is not subject to fast fading effects, as the wavelength is significantly
smaller than the detector area. Although the link‐level demonstrations are important
steps to prove that VLC is a viable technique to help in mitigating the spectrum
158
7.6 LiFi Networks
With the increasing demand for wireless data communication, the existing wireless
spectrum below 10 GHz (cm‐wave communication) has become congested and insufficient. The Federal Communication Commission (FCC) has come up with different
alternatives to minimize this challenge. One is to opportunistically re‐use the available
spread spectrum (below 10 GHz) through Software defined radio (SDR) and Cognitive
radio networks. The other alternative is to consider the radio spectrum above 10 GHz
(mm‐wave communication) and provide wireless network connectivity through visible
light communication. However, the higher frequencies (f ) result in increased path
loss (L) based on the Friis free space equation (L ∝ f2). Furthermore, blockage and
shadowing in terrestrial communication are more difficult to overcome at higher frequency‐based radio communication. Consequently, radio devices need to be designed
to enhance the probability of line‐of‐sight (LoS) through beam forming techniques and
by using cells with small radius (~50 m) [23]. The design of small cells is not an issue
from a system capacity perspective, because reducing cell sizes has been the major contribution for enhanced system performance in existing cellular communications. On the
other hand, usage of higher frequencies for terrestrial communication has become a
practical option. However, one drawback is that the challenge to provide supporting
infrastructure for smaller cells becomes an important consideration.
Light Fidelity (LiFi) is a bidirectional, high‐speed and fully networked optical wireless
communication technology that works in a similar way to WiFi. LiFi is a form of visible
light communication and a subset of optical wireless communications (OWC). LiFI can
be a complement to RF communication (WiFi or cellular networks), or even a replacement in the context of data broadcasting. LiFi takes the concept of visible light communication (VLC) further through light emitting diodes (LEDs) to realize the fully
networked wireless systems. Synergies harnessed as luminaries become LiFi at the cells,
resulting in enhanced wireless capacity providing the necessary connectivity to realize
the Internet‐of‐Things, and contributing to the key performance indicators for the fifth
generation of cellular systems (5G). Visible light communication makes use of “off‐the‐
shelf ” white light emitting diodes (LEDs) that are used for solid‐state lighting (SSL) as
signal transmitters and off‐the‐shelf p‐intrinsic‐n (PIN) photodiodes (PDs) or avalanche
photo‐diodes (APDs) as signal receivers [24]. This shows that VLC communication
enables the system that illuminates and concurrently it provides broadband wireless
data connectivity.
When the illumination is not desired in the uplink, then the infrared (IR) LEDs or
indeed RF would be the viable solutions. In visible light communication, the application
information is being carried by the intensity (power) of the light. This clearly shows that
the information‐carrying signal has to be real valued and strictly positive. State‐of‐the‐
art traditional digital modulation schemes for Radio Frequency (RF) communication
use complex valued and bipolar signals. Modifications are certainly necessary where
there will be a rich body of knowledge on modified multi‐carrier modulation techniques
such as OFDM for intensity modulation (IM) and direct detection (DD). The data rates
of 3.5 Gb/s have been reported from a single LED. It is noteworthy that visible light
communication is not subject to fast fading effects, as the wavelength is significantly
smaller than the detector area. Although the link‐level demonstrations are important
steps to prove that VLC is a viable technique to help in mitigating the spectrum