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Vehicle-to-Vehicle (V2V) Communication is one of the most promising application opportunities of Visible Light Communication (VLC). This paper suggests a novel transmission technique for VLC-V2V applications, called 2x2 Differential Transmission (2x2 DT). This transmission method exhibits excellent common-mode optical noise rejection performance. This beneficiary property is presented first with simulation results and later with real-life urban traffic measurement as well. After the promising simulation results, a demonstrational automotive-grade VLC-V2V link is presented and investigated for evaluation purposes. The link does not contain electrical filters, optical filters nor optical lenses, hence link costs are kept low and versatility is preserved. With our proposed 2x2 differential solution, both the transmission quality and common-mode optical noise rejection performance is outstanding. Due to the increased sensitivity of the differential VLC transmission regarding crosstalk between channels, a method is suggested for crosstalk reduction for high-quality differential transmission. more...

Polarization effects of channels such as turbulent free space and optical fibers can deteriorate the quality of polarization-sensitive communication schemes, for example, quantum key distribution. The exact nature of the channel is problematic to determine, and most theoretical results are based on approximations. We introduce a general model with probabilistic polarization angle rotation and analyze the average error it causes in terms of the moments of the probability distribution. For a small rotation angle variance, an inequality between distributions’ errors is considered based on their kurtosis values and potentially higher-order central moments. An upper bound is determined for the error probability, holding for all practically interesting scenarios. more...

Future passive optical network (PON) designs with 5G have been expected to provide simultaneous multiple wireless signals to the end-users. In this regard, this paper for the first time proposes and experimentally demonstrates the simultaneous transmission of baseband 4-pulse amplitude modulation (4-PAM), and radiofrequency (RF) filter bank multicarrier (FBMC), and universal filter orthogonal frequency division multiplexing (UF-OFDM) signals in a PON. A single optical wavelength from a laser source is used to demonstrate the signal transmission over a PON. The proposed system applies in one wavelength using one laser source for the PON. In contrast with conventional on-off keying (OOK) modulation format, 4-PAM modulation format can provide double bandwidth efficiency. Due to the property of high suppression for out of band emission, UF-OFDM and FBMC are considered as potential 5G modulation formats. In the optical line terminal (OLT), the composite signal consisting of 4-PAM, FBMC, and UF-OFDM is designed, generated, and transmitted using optical intensity modulation. The received signal is extracted in the optical network unit (ONU) and demodulated using digital signal processing techniques. Each of the above-mentioned modulation formats mentioned above is designed with a 2 Gbps data rate constituting a total of 6 Gbps aggregate data rate. The bit error rate (BER) and error vector magnitude (EVM) values have been measured after 25 km fiber length. Measurement results show EVM values below 12.5 % as a figure of merit as proposed by 3GPP LTE for 16 QAM modulation. more...

In Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communication links, Visible Light Communication (VLC) solutions have a unique deployment opportunity. This paper introduces an effective common-mode noise rejection technique for V2V-VLC. Transmission measurement results are presented, regarding the noise cancellation efficiency and improvements due to the proposed 2-by-2 differential VLC transmission method. Our promising results have shown, that not only did this arrangement excel in case of common-mode noise rejection, but it also has the inherent design property that the amount of rejection does not significantly depend on the modulation frequency of the noise source. Measurements were made with industrial automotive-grade LED lighting equipment. more...

This paper demonstrates a hybrid radio over multimode fibre and free space optics (RoMMF-FSO) system that can be used to extend the transmission range of the fourth generation long-term evolution (4G-LTE) signal in access networks. A single mode filtering technique (SMFT) is used to enhance 4G-LTE performance. The proposed scheme is evaluated in terms of the system transfer function, laser beam profile, and error vector magnitude (EVM). We show that using SMFT increases the RoMMF-FSO system bandwidth by 2 GHz and improves the received optical power by 13.6 dB. Moreover, the proposed system enhances the EVM by 4%. The measured results show that by using a 1 km MMF instead of a 1 km SMF will marginally increase the measured EVM from ~6.6% to ~7% with a 0.2 dB power penalty with respect to the LTE EVM limit of 12.5% as is specified for 16-quadrature amplitude modulation. The proposed system is validated practically under atmospheric turbulence conditions to mimic the outdoor environment. Measured EVM results are verified theoretically through transmitting LTE signals with turbulent using log-normal model. We also show that for a FSO link span of 500 m to meet the EVM target of 12.5% the SNR power penalties are ~2 dB and ~11 dB for Rytov variance of 1.2 × 10-4 and 0.1, respectively, compared with no turbulence. more...

We report the sampling rate dependency of a single-bit quantum random number generation scheme using a filtered and amplified source of amplified spontaneous emission (ASE). The quality of randomness is measured by the number of passed NIST statistical randomness tests. The number decreases for almost all cases when increasing the sampling rate. We apply a simple self-delay XOR post-processing technique, drastically improving the quality for low sampling rates. However, sampling rates higher than the analog bandwidth of the sampled intensity fluctuations are found to be ineligible for the generation scheme. more...

In-line and reflective semiconductor optical amplifiers (SOA and RSOA) can be effectively utilized as external optical intensity modulators. However the limited modulation bandwidth affects the application possibilities, because next generation access networks desire high trans- mission speed. Bandwidth enhancement can be achieved by means of optical equalization thanks to the chirping char- acteristics of semiconductor optical amplifier. The limited modulation transfer function can be combined with the converted phase modulation transfer function. Investiga- tion of optical filter with optimal slope is a crucial chal- lenge in this approach. The presented simulations describe the slope dependence of the modulation band. The model can take into account the different type of realizable opti- cal filters. However there is a trade-off between modula- tion efficiency and modulation bandwidth due to the extra insertion loss of the set-off optical filter. In the paper theo- retical and simulation investigations are presented with the result of improved modulation bandwidth. more...

In the BB84 quantum key distribution (QKD) protocol, the communicating parties do a quantum bit error rate (QBER) test to determine whether there is an eavesdropper trying to gain information about the secret key. However, the QBER is not only influenced by the eavesdropper’s strategies, but also by the imperfections of the physical devices and the channel through which the quantum states propagate. We developed a simple channel model with error parameters describing the channel and the potential polarization switching in the transmitter, to see how those effects influence the QBER in a polarization-qubit BB84 implementation. Certain well-defined probabilistic channel models are compared to see which is responsible for the highest error probability. more...

In this paper we have investigated a mm-wave Radio-over-Fibre access network solution. After basic transmission quality assessments two methods are suggested to overcome the poor modulation characteristics of the reflective semiconductor amplifier and decrease the error rate in uplink direction. Device parameters have been optimized, namely the uplink-downlink power budget and RSOA bias current. more...

The paper experimentally investigates indoor visible light communication (VLC) channels. The disturbances come from the light bulbs and other VLC systems. The paper demonstrates that the noisiest light bulbs are the fluorescent lamps which emit high frequency disturbances. Different light bulbs are examined to make an optimal carrier choice for the transmitted signal. In the next part of the paper several modulation schemes and two kinds of detector systems are compared. The paper represents also the advantages and disadvantages of receiver constructions with and without a lens. The optimum modulation for different application is investigated. more...

Universal Filtered Orthogonal Frequency Division Multiplexing (UF-OFDM) modulation format is considered as a potential candidate for future wireless 5G due to its features of better spectral efficiency and lower spectral side lobes compared to the cyclic prefix OFDM (CP-OFDM). In this paper, we demonstrate the generation of the UF-OFDM signal for 5G millimeter-wave (mm-wave) small cell radio access network (RAN). The data rate is 3.2 Gbps for 16 quadrature amplitude modulation (QAM) with a bandwidth of 1.25 GHz. The system performance is evaluated by bit error rate (BER) measurements. By varying the power of driving UF-OFDM signal to the MZM the optimum modulation point is determined. more...

In this paper, we propose a new technique for synchronization and channel estimation in M-QAM OFDM radio over fiber (RoF) system by using constant amplitude zero auto-correlation (CAZAC) sequence based training preamble. Delay and correlate method is used to identify the training sequence in the received signal vector and to correct the symbol timing offset. For an optimum demodulation of OFDM signal, optimum down sampling offset position has to be identified before applying symbol timing algorithm. To solve this issue, we present the iterative method of finding optimum down sampling offset position. We show that the training preamble used for synchronization can also be applied to estimate the channel response using averaging technique. Moreover, we used the least square estimation based channel estimation method using pilot subcarriers and compare the results with training preamble based estimation. more...

In this paper, we focus on the study of large bandwidth wireless signal transmission following a 60 GHz standard over a multimode fiber link used to cover optical distribution for the last mile. To reduce the multimode effects within the fiber, a single mode fiber is first added to play a role of mode filter, and then replaced by a Mandrel as a filter. Error vector magnitude (EVM) is used as a metrics to analyze the signal degradation. Simulation results are confirmed by measurements. The EVM of the RoF links on single mode fiber, multimode fiber with and without filtering are compared. more...

In this paper, we propose a hybrid radio over multi-mode/single-mode fibre and free space optics (RoMMF/SMF-FSO) system to enhance the 4th generation-long term evolution (4G-LTE) signal performance when used in local area access networks. A single mode fibre pigtailed gradient index lens is used to minimise the modal effect of the optical link at different turbulence strengths. The proposed system is characterised in terms of the system transfer function, error vector magnitude (EVM), and optical launch power (OLP). Results demonstrate the robustness of the proposed scheme in terms of increased available passband bandwidth by 2 GHz and improving the transmission shape by reducing the system transfer function ripple by more than 5 dB. Successful transmission of the 4G-LTE signal is achieved over a MMF/SMF-FSO channel with a 1.5 dB power penalty under the higher turbulence level (i.e., Rytov variance of 0.1). more...

The paper proposes three different multiplexing methods that can be applied in a Visible Light Communication-based indoor-positioning system. Our solutions realize the positioning algorithms via simple means which do not influence the light sources' performance significantly. The measurement results show that the proposed procedures are suitable for precise indoor-positioning applications. more...

We propose unequal sideband intensity based modulation scheme called vestigial sideband scheme (VSB) for the radio over fiber system (RoF) using concatenated Mach-Zehnder modulator (MZM) and phase modulator (PM). This scheme can be generated with proper adjustment of the modulation indexes of the modulators. MZM-PM configuration can also be used for generating single sideband (SSB) and carrier suppressed double sideband (CS-DSB) schemes. However, SSB scheme suffers from low signal to noise ratio (SNR) due to the strong dc component present in the detected signal. CS-DSB scheme cannot deliver the vector signal without modifying the phase and frequency at the receiver. Proposed VSB scheme can compensate chromatic dispersion (CD) of the RoF link as well as can deliver the vector signal without modification of the carrier frequency and phase at the receiver. We provide the theoretical analysis of the MZM-PM configuration. We illustrate the behaviour of harmonic distortion due to the CD in dispersive RoF link. Finally, we provide the comparison of symbol error rate of the proposed VSB scheme using 4QAM modulation format with DSB and SSB schemes. Simulation results show that VSB scheme can provide better performance than DSB and SSB scheme in dispersive RoF link. more...

In this paper, the method of generating optical single sideband (OSSB) scheme for radio over fiber (RoF) system using concatenated electro-optic amplitude modulator (AM) and phase modulator (PM) is presented. We provide the theoretical analysis of this configuration. With the proper control of parameters of the modulators, optical carrier to sideband ratio (OCSR) equal to 0 dB for OSSB scheme can be achieved in AM-PM configuration without the need of tunable optical filter. We illustrate through the numerical simulation the optimum values of AM dc bias and PM modulation index required to verify the proposed method. more...

This paper proposes an optimum hybrid radio over multi-mode fiber and free space optics (RoMMF-FSO) system to enhance the last mile bottleneck issues of wireless communication systems. Single mode fiber (SMF) and gradient index (GRIN) lenses are used as mode filtering techniques to optimize the system performance by mitigating the modal effects produced by multimode optical fiber networks. We characterize the system based on the beam profile, transfer function, and error vector magnitude (EVM) measurements. The results reveal that both techniques can improve the EVM performance significantly by ~19% and ~30% using a SMF filter and SMF-GRIN lenses, respectively. Furthermore, the analysis of the obtained measurements show the SMF-GRIN lenses is more effective than SMF only with lower EVM values and negligible difference in the optical launch power. more...

The omnipresence of LEDs for illumination provides unique opportunities for indoor localization. Signals transmitted by the LEDs can be used to determine the position of a person or object within a room with high precision. The requirements of such applications are different from high speed VLC systems. One of the commonly employed methods for VLC-based localization is optical tracking and imaging while the other is based on trilateration/triangulation. However, in both the methods it is critical that the user device is able to recover signals from each luminaire separately. In order to achieve this, a number of processing methods and devices can be chosen, which will be elaborated in this chapter. Practical implications including the required modifications/additions on the illumination infrastructure to enable positioning are also covered. more...

The filter bank multicarrier (FBMC) modulation format is considered as a potential candidate for future wireless 5G due to its feature of high suppression for out-of-band emissions, which allows combining multiple sub-bands with very narrow band-gaps, and hence increases the overall wireless transmission capacity. In this paper, we experimentally demonstrate the generation of multi sub-bands FBMC signals at millimeter-wave (mm-wave) for radio-over-fiber (RoF) systems. The designed multi sub-bands FBMC system consists of 5 sub-bands of 800 MHz with inter sub-band gaps of 781.25 kHz. The composite 5 sub-bands FBMC signal is generated with no band-gap between dc to the first sub-band to preserve the bandwidth of the system. Each FBMC sub-band consists of 1024 sub-carriers and is modulated with uncorrelated data sequences. The aggregate FBMC signal is carried optically by externally modulating a free running laser and is converted to millimeter waves (mm-waves) by photomixing with another free running laser at a frequency offset of 53 GHz. At the receiver, the received electrical mm-wave signal is down-converted to an intermediate frequency (IF) and then post-processed using digital signal processing (DSP) techniques. With the use of the simple recursive least square (RLS) equalizer in the DSP receiver, the achieved aggregate data rate is 8 Gbps and 12 Gbps for 16 quadrature amplitude modulation (QAM), and 64 QAM, respectively with a total bandwidth of 4.2 GHz. The system performance is evaluated by measuring error vector magnitude (EVM) and bit error rate (BER) calculations. more...