The performance of optical wireless OOK, 2-PPM and spread spectrum under the effects of multipath dispersion and artificial light interference

Abstract

Indoor wireless infrared transmission systems are mainly affected by ambient light‐induced shot noise, multipath dispersion and the interference produced by artificial light sources. In this paper, spread spectrum techniques are proposed to combat multipath dispersion and artificial light interference. The bit error rate performance of the spread spectrum technique under the combination of these detrimental effects are studied and compared with that of OOK and 2‐PPM. A novel analysis is derived to provide a simplified common analytical platform to facilitate the comparison among the three modulation schemes. Bit error rate analyses for OOK, PPM and spread spectrum taking into account the combined effects of multipath dispersion and artificial light interference are derived for the first time. Analytical, simulation and experimental results of bit error rate versus optical signal‐to‐noise ratio are then presented. The results show that spread spectrum techniques are very robust to multipath dispersion and artificial light interference. Copyright © 2000 John Wiley & Sons, Ltd.

Wireless Optical Communications Through the Turbulent Atmosphere: A Review

“…Although, many modulation techniques have been proposed, from non-coherent to coherent schemes, there is marked trend to favor the use of intensity-modulation direct-detection (IM/DD) scheme because it hides the high-frequency nature of the optical carrier thanks to its equivalent baseband model (Barry, 1994). Another reason to prefer the IM/DD scheme is the relatively low design complexity of the receiver system, when comparing to coherent systems, and because the photodetector is many times larger than the optical wavelength it exhibits a high degree of immunity to multipath fading (Wong et al, 2000). Among the most widespread intensity-modulation schemes for optical communications, namely on-off keying (OOK) and pulse position modulation (PPM), Chan (1982) noted that the PPM scheme is the most suitable for FSO owing to the fact that it does not rely on a threshold value to apply optimal detection.…”

Wireless Optical Communications Through the Turbulent Atmosphere: A Review

“…Although, many modulation techniques have been proposed, from non-coherent to coherent schemes, there is marked trend to favor the use of intensity-modulation direct-detection (IM/DD) scheme because it hides the high-frequency nature of the optical carrier thanks to its equivalent baseband model (Barry, 1994). Another reason to prefer the IM/DD scheme is the relatively low design complexity of the receiver system, when comparing to coherent systems, and because the photodetector is many times larger than the optical wavelength it exhibits a high degree of immunity to multipath fading (Wong et al, 2000). Among the most widespread intensity-modulation schemes for optical communications, namely on-off keying (OOK) and pulse position modulation (PPM), Chan (1982) noted that the PPM scheme is the most suitable for FSO owing to the fact that it does not rely on a threshold value to apply optimal detection.…”

Hybrid pulse position modulation and binary phase shift keying subcarrier intensity modulation for free space optics in a weak and saturated turbulence channel

“…Therefore, the electrical signal at the output of the photodetector in one symbol period is defined as [2,24] it RI…”

“…At the receiver, detection is carried out by choosing the index of the slot containing the maximum received signal in a symbol; hence, the conditional slot error rate (SER) is obtained as [23,24] …”

Recent developments in indoor optical wireless systems

“…Considering bandwidth efficiency, 2-PPM and BPSK have equal bandwidth requirements, being twice that needed for OOK. Thus, OOK emerges as the most suitable modulation scheme among binary modulation schemes, but at high data rates (>10 Mbps) it suffers from a large power penalty, because of multipath dispersion [14].…”

Wireless Optical Communications Through the Turbulent Atmosphere: A Review

“…Although, many modulation techniques have been proposed, from non-coherent to coherent schemes, there is marked trend to favor the use of intensity-modulation direct-detection (IM/DD) scheme because it hides the high-frequency nature of the optical carrier thanks to its equivalent baseband model (Barry, 1994). Another reason to prefer the IM/DD scheme is the relatively low design complexity of the receiver system, when comparing to coherent systems, and because the photodetector is many times larger than the optical wavelength it exhibits a high degree of immunity to multipath fading (Wong et al, 2000). Among the most widespread intensity-modulation schemes for optical communications, namely on-off keying (OOK) and pulse position modulation (PPM), Chan (1982) noted that the PPM scheme is the most suitable for FSO owing to the fact that it does not rely on a threshold value to apply optimal detection.…”

Hybrid pulse position modulation and binary phase shift keying subcarrier intensity modulation for free space optics in a weak and saturated turbulence channel

“…Therefore, the electrical signal at the output of the photodetector in one symbol period is defined as [2,24] it RI…”

“…At the receiver, detection is carried out by choosing the index of the slot containing the maximum received signal in a symbol; hence, the conditional slot error rate (SER) is obtained as [23,24] …”

Recent developments in indoor optical wireless systems

“…Considering bandwidth efficiency, 2-PPM and BPSK have equal bandwidth requirements, being twice that needed for OOK. Thus, OOK emerges as the most suitable modulation scheme among binary modulation schemes, but at high data rates (>10 Mbps) it suffers from a large power penalty, because of multipath dispersion [14].…”

Wireless Optical Communications Through the Turbulent Atmosphere: A Review

“…Although, many modulation techniques have been proposed, from non-coherent to coherent schemes, there is marked trend to favor the use of intensity-modulation direct-detection (IM/DD) scheme because it hides the high-frequency nature of the optical carrier thanks to its equivalent baseband model (Barry, 1994). Another reason to prefer the IM/DD scheme is the relatively low design complexity of the receiver system, when comparing to coherent systems, and because the photodetector is many times larger than the optical wavelength it exhibits a high degree of immunity to multipath fading (Wong et al, 2000). Among the most widespread intensity-modulation schemes for optical communications, namely on-off keying (OOK) and pulse position modulation (PPM), Chan (1982) noted that the PPM scheme is the most suitable for FSO owing to the fact that it does not rely on a threshold value to apply optimal detection.…”

Hybrid pulse position modulation and binary phase shift keying subcarrier intensity modulation for free space optics in a weak and saturated turbulence channel

“…Therefore, the electrical signal at the output of the photodetector in one symbol period is defined as [2,24] it RI…”

“…At the receiver, detection is carried out by choosing the index of the slot containing the maximum received signal in a symbol; hence, the conditional slot error rate (SER) is obtained as [23,24] …”

Recent developments in indoor optical wireless systems

“…Considering bandwidth efficiency, 2-PPM and BPSK have equal bandwidth requirements, being twice that needed for OOK. Thus, OOK emerges as the most suitable modulation scheme among binary modulation schemes, but at high data rates (>10 Mbps) it suffers from a large power penalty, because of multipath dispersion [14].…”