Abstract
Due to high peak-to-average-power ratio (PAPR) and low spectral-efficiency, the conventional Fast Fourier Transform based orthogonal frequency division multiplexing (OFDM) is losing its place to the other multicarrier modulation schemes. Alternatively, the wavelet treated multiple-input multiple-output (MIMO)-OFDM is gaining its popularity in realization of futuristic 5G networks due to proffering high spectral-efficiency, low-cost and low phase-noise. Subsequently, this work demonstrates a RF transmission system in S-band employing $2 \times 2$ MIMO-OFDM using orthogonal- and biorthogonal-wavelets with diverse phase shift keying modulation (PSK) schemes. Among the available MIMO configurations, the authors implement spatial diversity as it promises good reliability in noisy links [11] . However, the distribution of Wavelet-OFDM (W-OFDM) signals over a radio over fibre (RoF) link is critically affected by the optical sub-system non-linearity. So, the simplest $2 \times 2$ Alamouti’s space-time block code (STBC) is implemented in this work to overcome this non-linearity and to realize a less-complex detection. The work is further extended to realize an adaptive MIMO-RoF system employing W-OFDM scheme to adjust itself to a suitable available phase shift keying strategy as per the link-situation to retain an optimal balance of link-quality and spectral-efficiency.
Highlights
An unprecedented demand for a reliable high-speed wireless access is being observed
The results suggest the substantial compensation of frequency-selective fading and optical sub-system non-linearity as compared to the conventional orthogonal frequency division multiplexing (OFDM)
A 2 × 2 Alamouti coded Wavelet-OFDM-multiple-input multiple-output (MIMO)-RF transmission over fibre is demonstrated in this work to produce small side-lobes, low peak-to-average power ratio (PAPR) together with high powerefficiency by incorporating diverse wavelets
Summary
An unprecedented demand for a reliable high-speed wireless access is being observed. A suitable link-adaptation strategy must be adopted via adaptive-selection of the modulation parameters, transmission-rate and transmit power in accordance with the channel fluctuations to realize a spectral-efficient RoF link with high link-reliability. These parameters are selected under some quality of services (QoS) constraints as per the channel state information (CSI) [11]. To realize a reliable RF transmission over RoF link with high spectral-efficiency, the authors implement wavelet employed MIMO-OFDM strategy with link-adaptive capability as per the situation of the wireless-link in this work. The work is extended by evaluating the performance of the reported system for different wavelets under the impact of optical non-linearity in terms of power-penalty measurements i.e. Eb/No (normalized signal-to-noise ratio) requirements to achieve a defined threshold BER. The proposed work is structured as: Section I describes the earlier reported work to be aware about the recent developments and requirements for realizing a spectral-and powerefficient RoF link to meet the demands of fifth-generation telecommunication industry; Section II highlights the major contribution of the proposed work; Section III describes the working principal of the proposed system briefly; Section IV presents the system description and its adaptive property in detail; Section V discusses about the result outcomes and is followed by the concluding part
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