Carrier Interferometry Ofdm System Signal Detection

Carrier interferometry orthogonal frequency division multiplexing (CI/OFDM) has gained a great deal of attention recently because of its good bit error rate (BER) and low peak-to-average power ratio (PAPR) performance. In this dissertation, we will introduce a complete equivalent implementation model of CI/OFDM system. Based on this model and matrix operations, we investigate the signal-to-noise ratio (SNR) of CI/OFDM for two linear detection methods as zero forcing (ZF) and minimum mean square error (MMSE) equalization. According to the capacity comparison between CI/OFDM and OFDM, we find that the BER and PAPR advantage of CI/OFDM over the traditional OFDM are at the cost of low capacity. Based on the BER simulation results in two typical channels and theoretical analysis, we reveal the suitable application scenarios for CI/OFDM system, the more frequently the channel deep fades occur, the more significant the BER advantage of CI/OFDM over OFDM is.Cognitive radio (CR) has been proposed as a promising technology to solve the paradox between spectrum scarcity and spectrum underutilization. The choice of the PHY layer data transmission scheme is a significant design decision when implementing a CR system. To be specific, the technique must be sufficiently agile to enable CR users the ability to transmit in a licensed band while not interfering with the licensed users (LUs). In this paper, we improve the traditional CI/OFDM system and propose to apply non-contiguous CI/OFDM (NC-CI/OFDM) as a new data transmission scheme for CR context. Computer simulation results confirm that the proposed NC-CI/OFDM system can bring desirable BER performance and low PAPR compared with the traditional NC-OFDM.Compare to the traditional cyclic prefix (CP) OFDM system, zero-padding OFDM (ZP-OFDM) system can ensure symbol recovery regardless of the occurrence of channel deep fades. In this paper, we combine CI/OFDM with ZP-OFDM to propose an enhanced CI/OFDM system which is named ZP-CI/OFDM. We introduce the system model of ZP-CI/OFDM and analyze its transmit-received signal using the knowledge of multi-path fading channel. We consider three kinds of signal detection schemes based on different received signal models, which are MMSE detection in frequency domain, MMSE detection in time domain and nonlinear detection. We also compare the complexity of the three kinds of signal detection schemes. Finally, according to performance simulation results, we confirm that the proposed ZP-CI/OFDM system is a wireless transmission technology with high power efficiency.