Slot error rate performance of DH-PIM with symbol retransmission for optical wireless links

In this paper we introduce the dual-header pulse interval modulation (DH-PIM) technique employing a simple retransmission coupled with a majority decision detection scheme at the receiver. We analytically investigate the slot error rate (SER) performance and compare results with simulated data for the symbol retransmissions rates of three, four and five, showing a good agreement. We demonstrate that the proposed scheme significantly reduces the SER compared with the standard single symbol transmission system, with retransmission rate of five offering the highest code gain of 5 dB

Hybrid Frequency and Phase-Shift Keying Modulation for Energy Efficient Optical Wireless Systems

International audienceIn this letter, we introduce direct-current (DC) offset hybrid frequency and phase-shift keying (DC-FPSK) modulation for Internet-of-Things based on optical wireless systems. For DC-FPSK, non-negative phase-modulated frequency waveforms are generated by combining frequency-shift keying (FSK), phase-shift keying (PSK) and a DC offset. We propose optimal maximum likelihood and sub-optimal receivers for DC-FPSK. The performance is appraised in terms of Euclidean distance, bit-error-rate (BER) performance and energy efficiency. We determine that combining 4-PSK with conventional DC-FSK is the optimal approach to enhance the energy and spectral efficiencies

Bit error performance of diffuse indoor optical wireless channel pulse position modulation system employing artificial neural networks for channel equalisation

The bit-error rate (BER) performance of a pulse position modulation (PPM) scheme for non-line-of-sight indoor optical links employing channel equalisation based on the artificial neural network (ANN) is reported. Channel equalisation is achieved by training a multilayer perceptrons ANN. A comparative study of the unequalised `soft' decision decoding and the `hard' decision decoding along with the neural equalised `soft' decision decoding is presented for different bit resolutions for optical channels with different delay spread. We show that the unequalised `hard' decision decoding performs the worst for all values of normalised delayed spread, becoming impractical beyond a normalised delayed spread of 0.6. However, `soft' decision decoding with/without equalisation displays relatively improved performance for all values of the delay spread. The study shows that for a highly diffuse channel, the signal-to-noise ratio requirement to achieve a BER of 10−5 for the ANN-based equaliser is ~10 dB lower compared with the unequalised `soft' decoding for 16-PPM at a data rate of 155 Mbps. Our results indicate that for all range of delay spread, neural network equalisation is an effective tool of mitigating the inter-symbol interference

Adaptive modulation schemes for optical wireless communication systems

High-speed wireless optical communication links have become more popular for personal mobile applications. This is a consequence of the increasing demand from the personal information service boom. Compared to the radio frequency domain, optical wireless communication offers much higher speeds and bit rates per unit power consumption. As stated by the official infrared standard IrDA optical communication enjoys much lower power consumption than Bluetooth, with an inherent security feature while in Line of Sight (LOS) applications. There are also drawbacks such as the infrared radiation cannot penetrate walls as radio frequencies do and interference from the background contribute to the channel dispersions. Focus on the modulation aspects of the optical wireless communication, this thesis try to improve the channel immunity by utilising optimised modulation to the channel. Modulation schemes such as on off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM) and pulse position and amplitude modulation PAPM schemes have been validated. The combined power and bandwidth requirements suggest that the adaptive modulation schemes can provide reliability when deployed in a real time channel, resulting in improved system performance. As a result, an adaptive modulation technique is proposed. Extensive simulations of severe noise distraction have been carried out to validate the new scheme. The simulation results indicate that the new scheme can provide increased immunity against channel noise fluctuation at a relatively low complexity. The scheme obtained formed a basis to support reliable mobile optical wireless communication applications. The adaptive scheme also takes the real time channel conditions into account, which is different from existing schemes. Guaranteed system performance can be secured without compromising power and bandwidth efficiency. This is also a new approach to realise reliable optical wireless links. Fuzzy logic control module has been developed to match the adaptive pattern

Adaptive modulation schemes for optical wireless communication systems

High-speed wireless optical communication links have become more popular for personal mobile applications. This is a consequence of the increasing demand from the personal information service boom. Compared to the radio frequency domain, optical wireless communication offers much higher speeds and bit rates per unit power consumption. As stated by the official infrared standard IrDA optical communication enjoys much lower power consumption than Bluetooth, with an inherent security feature while in Line of Sight (LOS) applications. There are also drawbacks such as the infrared radiation cannot penetrate walls as radio frequencies do and interference from the background contribute to the channel dispersions. Focus on the modulation aspects of the optical wireless communication, this thesis try to improve the channel immunity by utilising optimised modulation to the channel. Modulation schemes such as on off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM) and pulse position and amplitude modulation PAPM schemes have been validated. The combined power and bandwidth requirements suggest that the adaptive modulation schemes can provide reliability when deployed in a real time channel, resulting in improved system performance. As a result, an adaptive modulation technique is proposed. Extensive simulations of severe noise distraction have been carried out to validate the new scheme. The simulation results indicate that the new scheme can provide increased immunity against channel noise fluctuation at a relatively low complexity. The scheme obtained formed a basis to support reliable mobile optical wireless communication applications. The adaptive scheme also takes the real time channel conditions into account, which is different from existing schemes. Guaranteed system performance can be secured without compromising power and bandwidth efficiency. This is also a new approach to realise reliable optical wireless links. Fuzzy logic control module has been developed to match the adaptive pattern.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Pulse position modulation coding schemes for optical inter-satellite links in free space

The rapid and significant development of communications links between satellites has made it possible to use various applications such as relay voice, video, multimedia, etc. As a result, a great deal of research has been done in this field during the last few years to reduce power consumption and increase transmission reliability. This thesis is concerned with an analysis of intersatellite links in free space, with optical links using laser sources being considered in particular. It includes a literature survey and a thorough theoretical investigation into designing the model of the link in free space. This thesis describes the novel technique of designing the optical receiver that consists of PIN photodiode as a photodetector, Semiconductor optical amplifier (SOA) and a 3rd order Butterworth filter with central decision detection. In addition, it discusses the use of several different coding schemes for use in such links: multiple pulse position modulation (MPPM); digital pulse position modulation (DPPM); Dicode pulse position modulation (Dicode PPM). This novel technique of an optical receiver is investigated and new work is presented in order to examine the noise performance of this optical receiver and hence determine its sensitivity and the number of photons received for a specified error rate. Further new work is carried out to compare these coding schemes in terms of error weightings and coding efficiency through showing how the PCM error rate is affected by false alarm and erasure errors for MPPM, DPPM and Dicode PPM coding 3, 4, 5 and 6 bits of PCM. An original maximum likelihood sequence detector (MLSD) is presented in this thesis in order to perform these comparisons. In addition, computer simulations models (using MCAD) are performed to compare these three coding schemes operating with 3, 4, 5 and 6 bits of PCM in terms of sensitivity and bandwidth efficiency. These comparisons show that MPPM coding 3, 4, 5 and 6 bits of PCM is the appropriate coding scheme to be used in optical inter-satellite links in free space and PCM data rates of 1 Gbit/s.EThOS - Electronic Theses Online ServiceGBUnited Kingdo