A Highly Reliable Radio Communication System for Wireless Sensor and Actuator Networks

The reliability of Wireless Sensor and Actuator Networks (WSANs) is an essential aspect of wireless communications. To achieve a robust communication, the reliability of Filter Bank Multicarrier (FBMC) modulation that uses Offset Quadrature Amplitude Modulation (OQAM) is enhanced by spreading as done in the process of Code Division Multiple Access (CDMA). Although, the spectral efficiency is downscaled by the spreading code length, the Bit Error Ratio (BER) of the system is significantly improved by spreading in time or frequency domain.

In this dissertation, a highly reliable WSAN based on spread FBMC is introduced. The selection of FBMC is based on its ability to solve some drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) such as the need of the Cyclic Prefix (CP) and the high Out-Of-Band (OOB) emissions. After the implementation of Frequency Spreading (FS) and Time Spreading (TS) on FBMC, the effects of using different industrial channel models are discussed. It is proven by simulations that real and complex variants of spread FBMC can be used to establish a reliable communication between different nodes of the network.

The joint effect of quantization and clipping of the Analog-to-Digital Converter (ADC) for spread FBMC is also discussed in this thesis. It is shown that an optimal clipping level for the received signal maximizes the Signal-to-Quantization Noise power Ratio (SQNR). Depending on the ADC resolution, an optimal range of clipping levels can be used to minimize the BER.

Subsequently, the performance of spread FBMC in uplink and full-sized downlink under several types of jamming is investigated. When the transmission is attacked by White Gaussian Noise (WGN) methods such as Barrage Noise Jamming (BNJ) and Partial Band Jamming (PBJ), it is proven that spread FBMC outperforms spread OFDM variants. When tone jamming is implemented using time-invariant schemes such as All Tone Jamming (ATJ), Multitone Jamming (MTJ), and Random Multitone Jamming (RMTJ), spread FBMC usually outperforms spread OFDM variants. 

However, it is shown that spreading is less effective as the number of targeted resource blocks decreases when the system is targeted by some time-variant tone jamming techniques such as Sweep Multitone Jamming (SMTJ) and Random Frequency Hopping Jamming (RFHJ). When a Carrier Frequency Offset (CFO) is present between the system and the jamming signal, it is shown that spreading, alongside the improvement of the system robustness, decreases the sensitivity of both OFDM and FBMC to the CFO.

A practical implementation of FS-FBMC using the Universal Serial Radio Peripheral (USRP) is also done to verify how the robustness of the FBMC transmission is enhanced by spreading. In addition to the reliability enhancement, it is proven that spreading can be applied to overcome the high Error Vector Magnitude (EVM) of the In-phase/Quadrature (I/Q) demodulator when the received signal power is low.


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