Design And Implementation Of Ambient Backscatter Communication System Based On Adaptive Modulation Tag

Ambient Backscatter Communication(Am BC)transmits data by backscattering the surrounding RF signals.Its biggest advantage is extremely low power consumption,and it can perform backscatter communication with u W level of power consumption.It is one of the key technologies for the future development of passive Internet of Things(Io T)wireless communication technology.The existing ambient backscatter communication system has the following problems: the communication rate is high,but the communication distance is short; the communication distance is long,but the communication rate is low.In order to solve this problem,this paper proposes a Lo Ra signal source ambient backscatter communication system based on tag adaptive modulation to achieve a low power consumption,long-distance,high-speed environmental backscatter communication system.Firstly,for the application scenario of short-distance and high-speed communication in the Internet of Things,this thesis proposes an amplitude modulation(ASK)and demodulation scheme for Lo Ra signal source ambient backscatter communication system.The system modeling,receiver algorithm design and simulation,prototype verification system design and implementation of the scheme are mainly studied.Specifically,the system modeling and simulation based on the electromagnetic wave free-space loss are carried out to verify the correctness of the scheme and algorithm,and the theoretical BER performance of the system is analyzed; a software radio platform-based backscatter receiver is built,a u W level backscatter tag is designed,and a prototype system for amplitude modulated environment backscatter communication is implemented.The experiment proves that the scheme can achieve the communication rate of 5Mbps within the distance of 5m.Secondly,for the application scenario of long-distance and low-speed communication in the Internet of Things,this thesis proposes a frequency shift modulation(FSK)and demodulation scheme for Lo Ra signal source ambient backscatter communication system.The system modeling,receiver algorithm design and simulation,prototype verification platform design and implementation of this scheme are mainly studied.Specifically,we modeled and simulated the FSK modulation system using the first harmonic component of the square wave,verified the correctness of the scheme and algorithm,designed the demodulation algorithm of the ambient Lo Ra signal,and analyzed the theoretical BER performance of the system; built a software radio-based backscatter receiver and implemented a prototype system for FSK modulated ambient backscatter communication.The simulation results show that the scheme can achieve 3.9kbps communication rate at 3km communication distance from the tag to the receiver,and the experimental results of the prototype verification system prove that the scheme is feasible.Furthermore,aiming at the problem that the existing ambient backscatter communication system cannot take into account either the communication distance or data rate,this thesis proposes the Tag adaptive modulation mechanism base on amplitude modulation and demodulation scheme and the frequency shift modulation and demodulation scheme for two application scenarios of short-distance high-speed and long-distance low-speed.The downlink design of the system and the design of tag adaptive modulation mechanism are mainly studied.The design of the downlink includes frequency selection,modulation scheme,data format design and communication timing protocol,etc.The design of tag adaptive modulation mechanism is mainly based on CQI(Channel Quality Indication)feedback to achieve dynamic adjustment of the system parameters such as modulation mode,signal bandwidth,and transmit power.