Design And Implementation Multiple RFID Tags Wireless Network

In recent years,with the rapid development of the Internet of Things technology,the Internet of Things has become the next stage of the goal of researchers.However,the Internet of Things at this stage has many shortcomings.With the rapid increase of Io T devices,the maintenance cost and power consumption of the devices have become more prominent.Backscattering technology is expected to become a key technology to solve this problem.The passive tags in the backscattering system can communicate with the base station by reflecting the radio frequency signal,which greatly reduces the power consumption of the node.However,due to power limitation,path loss and other reasons,most existing passive tags are difficult to achieve long-distance transmission,which limits the development of backscattering systems.At the same time,with the rapid increase in the number of Io T devices,it also brings new demands and challenges.Current researches on backscatter communication systems are mostly focused on the scenario of one tag,and the problem of parallel transmission of multiple tags needs to be further resolved.In order to solve these problems,this paper proposes a backscatter communication system in a multi-tag scenario.First of all,in the system,a new type of tunnel diode-based backscatter amplifier is used in the tag.This amplifier can amplify and reflect the radio frequency signal with extremely low power consumption,so it can effectively increase the communication distance.Using the characteristics of the backscatter amplifier,a circuit is built at the label to realize FSK modulation.The circuit includes a DC bias module and a modulation module containing a single-chip microcomputer.After experimental testing,the maximum bit transmission rate of the tag reaches 4Kbps,and the transmission distance can reach 13 meters.Compared with ordinary passive tags,the communication distance is significantly improved.Then,this paper proposes a backscatter communication system network protocol based on the combination of time division multiplexing and frequency division multiplexing.The protocol supports 256 tag devices to access the network,and supports the dynamic allocation of time slots and channel resources.A wake-up receiver is added to the tag to solve the problem of multi-user time synchronization and tag reception.After that,this article uses the USRP B200 software radio hardware platform and GNU Radio software platform to build a prototype system.Experimental tests show that this system can support 256 tags at the same time when the bit rate is 1Kbps,and the transmission distance of tags can reach more than ten meters.Compared with the existing backscatter communication system,the transmission distance and the number of supporting equipment have been greatly improved.It verified the feasibility of our scheme based on time division multiplexing and frequency division multiplexing.The main work of this paper is as follows:1.Conducting research work on tunnel diode backscatter amplifier and backscatter modulation technology,using independent components to build a modulation circuit,and realizing FSK modulation.2.A backscatter communication system combining time division multiplexing and frequency division multiplexing is proposed.And the time synchronization problem in time division multiplexing is solved by using wake-up receivers in the tags.3.To verify the performance of the backscatter communication system proposed in this thesis,the GNU Radio software platform is used to build the base station and the system prototype platform.