IIIT Hyderabad Publications |
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Spectrum Sensing of FBMC Signals in 5G and Cognitive RadiosAuthor: Keesara Upender Date: 2018-07-23 Report no: IIIT/TH/2018/53 Advisor:Sachin Chaudhari AbstractOrthogonal frequency division multiplexing (OFDM) has been a dominant technology in several wireless standards such as LTE-A, WiMAX and WLAN. However, OFDM might be a misfit for next generation wireless communication systems (5G) and cognitive radios. OFDM suffers from drawbacks such as out of band radiation (due to high side lobe power), tight synchronization and loss in spectral efficiency. As a result of these disadvantages, OFDM is not going to be a default contender for 5G. In the recent past, many researchers have proposed filter bank multicarrier (FBMC) as a replacement for OFDM in 5G and cognitive radios. FBMC uses well designed bank of filters that has less side lobe power resulting in minimal out-of-band radiation so that the requirement of tight synchronization is relaxed in FBMC. This has a great advantage in machine-to-machine (M2M) communication and IoT. Spectrum is a very scarce resource but unfortunately it is underutilized. Cognitive radio (CR) is one of the solutions to exploit the underutilized spectrum. Spectrum sensing is an important enabler for efficient use of spectrum and interference management in 5G and CR setting. In the spectrum sensing literature, there are no detection schemes available for FBMC signal except conventional energy detector. Hence, there is a need for feature detection techniques to efficiently detect FBMC signal. In this work, we propose a spectrum sensing scheme to detect FBMC signal in the presence of noise. Autocorrelation analysis of FBMC signal is carried out at each stage of FBMC signal generation. It is found that FBMC samples are correlated at last but one stage of FBMC signal generation. However, the autocorrelation value is zero for non-zero lag values at the last stage of FBMC signal generation. A modification is proposed to the received FBMC signal to retrieve the lost autocorrelation property of FBMC signal. With this modification, autocorrelation value at the lag equal to the number of subcarriers is non-zero. This autocorrelation property is used to design a detector for FBMC signal. The distribution of the test statistic of the proposed detector is derived under noise-only scenario so that the threshold of the detector can be obtained. The performance analysis of the proposed autocorrelation detector is carried out for different non-idealities such as multipath channel, noise uncertainty and no frame-synchronization (time). Next, the performance of the proposed detector is compared with that of energy detector. Finally, the proposed detector is combined with the energy detector to increase the robustness of overall detection. Full thesis: pdf Centre for Communications |
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