METHOD FOR A JOINT TIME-FREQUENCY SYNCHRONIZATION OF USER EQUIPMENT IN NB-IOT NETWORKS

摘要

The invention discloses a method for a joint time-frequency synchronization of User Equipment in NB-IoT Networks already connected to a serving cell obtaining an optimal time-frequency offset estimation. The objective to provide a procedure that permits optimized time-frequency synchronization of a UE, whereby quantities already known to the UE are used to operate the UE power efficiently and with a better performance will be solved by a method comprising the following stages:- demodulating a received NB-IoT subframe Rm with regard to a pre-computed reference NB-IoT subframe Bm derived from information of the serving cell, and storing Wm in matrix W;- computing a metric Vm(f,t) and recursively combining it with Wm, resulting in a new metric Um(f,t);- recursively computing a reference value Sm over Wm;- comparing the metric Um(f,t) with the Sm, whereas- if a normalized value of Um(f,t)/Sm does not exceed a threshold Kthres(m), stages 1 to 5 of the method are recursively repeated up to a maximum number Mmax have been demodulated, otherwise- if the normalized value of Um(f,t)/Sm exceeds the threshold Kthres(m), arg-max values with regard to the discrete frequency offset values f ∈F and the discrete time offset;values t ∈T are computed based on the values of Um(f,t) obtaining an optimal value of the time-frequency offset estimate.