Research On NB-IOT Coverage Enhancement And Low Power Consumption Technology

In recent years,the Internet of Things(Io T)has become a very popular topic.Although many Io T communication technologies have appeared,the Io T technology has always lacked a unified standard.Therefore,3GPP introduced the Narrowband Internet of Things(NB-IOT)in Release 13.NB-IOT is a low power wide area network technology with deep coverage,low power,low cost and massive connections.In the field of Internet of Things applications,NB-IOT has been widely concerned,NB-IOT is considered one of the most promising technologies in the field of Internet of Things.This thesis studies the coverage enhancement performance of NB-IOT.Firstly,the two main coverage enhancement technologies,namely power spectrum density(PSD)boosting and repetitions,are analyzed.Compared with GPRS,the NB-IOT uplink PSD can be improved by about 7d B.Doubling the number of repetitions can obtain the signal to noise ratio(SNR)gain of about 3 d B.Then,the coverage performance of the 15 k Hz and 3.75 k Hz subcarrier spacing is evaluated during Single-tone transmission based on the NB-IOT uplink shared channel simulation platform.The simulation results show that the maximum coupling loss(MCL)level of 164 d B can be achieved,which represents 20 d B coverage enhancement compared to GPRS when the NPUSCH repeats 32 and 8 times at 15 k Hz and 3.75 k Hz Single-tone transmission respectively.This thesis also studies the NB-IOT uplink data rate and link adaptation.First,the effect of PSD boosting and repetitions on the data rate,the data rate of the Cat-NB2 terminal and the data rates of NB-IOT under different coverage enhancement levels is studied.The simulation results show that the PHY layer data rates of NB-IOT under three coverage levels are 21.12 kbps,2.56 kbps and 0.31 kbps,respectively.Since NB-IOT supports repetition to enhance coverage,the link adaptation of NB-IOT should be considered at least two dimensions of MCS level and repetition times.Meanwhile,the low complexity requirements of NB-IOT should also be considered.This thesis proposes a simple and effective link adaptive algorithm.Firstly,the MCS level is selected according to the packet size.Then,the determined number of repetitions should be the minimum value that meets the block error rate.The simulation results show that the proposed link adaptation method can reduce transmission time and consume less resources.From the perspective of low power circuit design,this thesis studies low power design techniques to reduce the power consumption of NB-IOT terminal chips.Firstly,the component of power consumption,NB-IOT low power mode and various low power techniques is analyzed.Then,based on the Hummingbird E203 processor,multi-voltage,clock gating and operand isolation are used.Multi-voltage technology reduces circuit power consumption by using lower power supply voltage for some modules while meeting circuit performance requirements.Clock gating reduces the clock signal toggle rate to reduce circuit power consumption.Operand isolation reduces chip power consumption by reducing the combinational logic toggle rate.The result shows that after using low power design technology,although the area has increased by 28%,the power consumption has decreased by 55%.