The Algorithm Design Of NB-IoT's Baseband OFDM Modem

The Narrow Band Internet of Things(NB-IoT)is a newborn narrowband wireless communication technology specially for the Internet of Things(IoT)applications,which can coexist with the existing Long Term Evolution(LTE)therefore be embedded directly in the existing cellular communication network to achieve smooth network upgrades and dramatic deployment cost reduction.Due to the fact,it has sized immense attention from the IoT industry and achieved rapid development,and has various industrial applications includes industrial construction,smart cities,and agricultural environments.However,as the research survey shows,compared with other narrowband wireless communication technologies,the NB-IoT technology is far from sufficient development.The current NB-IoT chip products on the market are rather scarce while posses disadvantages in power consumption and chip cost compared to other narrowband wireless communication technologies.These have greatly obstructed the prevalence of NB-IoT's application.Meanwhile,becasue of the high technical threshold in the tech-development of the NB-IoT chip design,most of the current research in the NB-IoT field focus on NB-IoT's application layer,and there is rare reported relevant research on baseband design which is most critical to NB-IoT's chip design.In view of this,a design research work on the baseband OFDM modem,one of the essential parts of NB-IoT technology,has been completed in this paper which mainly includes the following:1.The analysis of the NB-IoT protocol and analysis of related technology theories.The principle of OFDM and SC-FDMA has been analyzed.The system architecture of NB-IoT end,the signal channels along with the frame structure of uplink and downlink have been studied according to NB-IoT's protocol.the baseband signal generation mechanisms and procedures are clarified.2.The implementation of the physical layer downlink baseband OFDM demodulation algorithm.The derivation of the baseband OFDM signal generation principle has been completed.The system architecture of the demodulator has been proposed and the design of its modules have been carried out.an experimental verification platform has been built with relevant Keysight instrument and demodulation algorithm verification has been completed.3.The implementation of the physical layer uplink baseband SC-FDMA modulation algorithm.The derivation of the baseband SC-FDMA signal generation principle has been completed.The system architecture of the modulator has been proposed and the design of its modules have been carried out.the corresponding demodulation algorithm has been designed based on which the verification of modulator has been implemented.4.The research on the synchronization and the under-sampling technique.Based on NB-IoT's frame structure,a cyclic-prefix-based symble synchronization technology is proposed and its algorithm design along with the feasibility verification is accomplished.A method of reducing the baseband hardware overhead and power consumption by decreasing the sampling frequency has been explored.Sequentially,the simulation verification of its viability have been implemented.The NB-IoT physical layer baseband OFDM modem designed in this thesis has the capacity of demodulating the NB-IoT downlink OFDM baseband signal and generating Single-tone/ Multi-tones SC-FDMA baseband modulation for the NB-IoT uplink.It creates a condition to improve NB-IoT's baseband circuit performance and to reduce its hardware overhead and power consumption,lays a solid foundation for the further NB-IoT's baseband chip design and implementation,and provides a beneficial reference for other's NB-IoT technical development.