Frequency offset correction in narrowband machine-to-machine

Abstract

A method in a node is disclosed. The method comprises receiving a signal, and obtaining a first oversampled received signal by sampling the received signal according to a symbol rate. The method further comprises estimating a first frequency offset based on the first oversampled received signal, the first frequency offset estimated using an estimation range limited to one of a bandwidth of the received signal or the symbol rate of the received signal, and obtaining a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1. The method further comprises estimating a true frequency offset based on the first frequency offset estimate and the second oversampled received signal.

1 - 25 . (canceled) 
     
     
         26 . A method in a node, comprising:
 receiving a signal;   obtaining a first oversampled received signal by sampling the received signal according to a symbol rate;   estimating a first frequency offset based on the first oversampled received signal, the first frequency offset estimated using an estimation range limited to one of a bandwidth of the received signal or the symbol rate of the received signal;   obtaining a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1;   correcting the first frequency offset by using the second oversampled received signal to extend the estimation range outside of the signal bandwidth of the received signal or the symbol rate of the received signal; and   estimating a true frequency offset based on the corrected first frequency offset and the second oversampled received signal.   
     
     
         27 . The method of  claim 26 , wherein the node comprises one of a wireless device or a network node. 
     
     
         28 . The method of  claim 26 , further comprising:
 determining a set of candidate aliased frequency offsets corresponding to the corrected first frequency offset.   
     
     
         29 . The method of  claim 28 , wherein estimating the true frequency offset based on the corrected first frequency offset and the second oversampled received signal comprises:
 generating a plurality of signals, each of the plurality of generated signals comprising a noise-free received signal with a frequency offset applied, the applied frequency offset comprising one of the determined set of candidate aliased frequency offsets corresponding to the estimated first frequency offset;   comparing one or more of the generated signals to the second oversampled received signal; and   determining one of the applied frequency offsets to be the true frequency offset based at least in part on the comparison of one or more of the generated signals to the second oversampled received signal.   
     
     
         30 . The method of  claim 28 , wherein estimating the true frequency offset based on the corrected first frequency offset and the second oversampled received signal comprises:
 generating a noise-free received signal without a frequency offset applied;   applying an element-wise multiplication of the second oversampled received signal with a complex conjugate of the generated noise-free received signal to generate a new signal; and   determining an aliased frequency offset within the determined set of candidate aliased frequency offsets to be the true frequency offset, wherein the aliased frequency offset determined to be the true frequency offset is an aliased frequency offset within the determined set of candidate aliased frequency offsets that is most similar to the generated new signal.   
     
     
         31 . The method of  claim 26 , further comprising estimating a time offset before estimating the first frequency offset as part of a cell search procedure. 
     
     
         32 . The method of  claim 26 , further comprising using the determined true frequency offset to correct the received signal to enable reception of subsequent information. 
     
     
         33 . The method of  claim 32 , wherein the subsequent information comprises one or more of:
 a cell identity;   a frame number;   broadcast information; and   a data transmission.   
     
     
         34 . A node, comprising:
 a memory storing instructions; and   a processor configured to execute the instructions to:
 receive a signal; 
 obtain a first oversampled received signal by sampling the received signal according to a symbol rate; 
 estimate a first frequency offset based on the first oversampled received signal, the first frequency offset estimated using an estimation range limited to one of a bandwidth of the received signal or the symbol rate of the received signal; 
 obtain a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1; 
 correct the first frequency offset by using the second oversampled received signal to extend the estimation range outside of the signal bandwidth of the received signal or the symbol rate of the received signal; and 
 estimate a true frequency offset based on the corrected first frequency offset and the second oversampled received signal. 
   
     
     
         35 . The node of  claim 34 , wherein the node comprises one of a wireless device or a network node. 
     
     
         36 . The node of  claim 34 , wherein the processor is further configured to execute the instructions to:
 determine a set of candidate aliased frequency offsets corresponding to the corrected first frequency offset.   
     
     
         37 . The node of  claim 36 , wherein the processor is further configured to execute the instructions to:
 generate a plurality of signals, each of the plurality of generated signals comprising a noise-free received signal with a frequency offset applied, the applied frequency offset comprising one of the determined set of candidate aliased frequency offsets corresponding to the estimated first frequency offset;   compare one or more of the generated signals to the second oversampled received signal; and   determine one of the applied frequency offsets to be the true frequency offset based at least in part on the comparison of one or more of the generated signals to the second oversampled received signal.   
     
     
         38 . The node of  claim 34 , wherein the processor is further configured to execute the instructions to:
 generate a noise-free received signal without a frequency offset applied;   apply an element-wise multiplication of the second oversampled received signal with a complex conjugate of the generated noise-free received signal to generate a new signal; and   determine an aliased frequency offset within the determined set of candidate aliased frequency offsets to be the true frequency offset, wherein the aliased frequency offset determined to be the true frequency offset is an aliased frequency offset within the determined set of candidate aliased frequency offsets that is most similar to the generated new signal.   
     
     
         39 . The node of  claim 34 , wherein the processor is further configured to execute the instructions to:
 estimate a time offset before estimating the first frequency offset as part of a cell search procedure.   
     
     
         40 . The node of  claim 34 , wherein the processor is further configured to execute the instructions to:
 use the estimated true frequency offset to correct the received signal to enable reception of subsequent information.   
     
     
         41 . The node of  claim 40 , wherein the subsequent information comprises one or more of:
 a cell identity;   a frame number;   broadcast information; and   a data transmission.   
     
     
         42 . A non-transitory computer-readable medium storing a program code executable by a network device, wherein the execution of the program code causes the network device to perform operations comprising:
 receiving a signal;   obtaining a first oversampled received signal by sampling the received signal according to a symbol rate;   estimating a first frequency offset based on the first oversampled received signal, the first frequency offset estimated using an estimation range limited to one of a bandwidth of the received signal or the symbol rate of the received signal;   obtaining a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1;   correcting the first frequency offset by using the second oversampled received signal to extend the estimation range outside of the signal bandwidth of the received signal or the symbol rate of the received signal; and   estimating a true frequency offset based on the corrected first frequency offset and the second oversampled received signal.   
     
     
         43 . The non-transitory computer-readable medium of  claim 42 , further comprising:
 determining a set of candidate aliased frequency offsets corresponding to the corrected first frequency offset.   
     
     
         44 . The non-transitory computer-readable medium of  claim 43 , wherein estimating the true frequency offset based on the corrected first frequency offset and the second oversampled received signal comprises:
 generating a plurality of signals, each of the plurality of generated signals comprising a noise-free received signal with a frequency offset applied, the applied frequency offset comprising one of the determined set of candidate aliased frequency offsets corresponding to the estimated first frequency offset;   comparing one or more of the generated signals to the second oversampled received signal; and   determining one of the applied frequency offsets to be the true frequency offset based at least in part on the comparison of one or more of the generated signals to the second oversampled received signal.   
     
     
         45 . The non-transitory computer-readable medium of  claim 43 , wherein estimating the true frequency offset based on the corrected first frequency offset and the second oversampled received signal comprises:
 generating a noise-free received signal without a frequency offset applied;   applying an element-wise multiplication of the second oversampled received signal with a complex conjugate of the generated noise-free received signal to generate a new signal; and   determining an aliased frequency offset within the determined set of candidate aliased frequency offsets to be the true frequency offset, wherein the aliased frequency offset determined to be the true frequency offset is an aliased frequency offset within the determined set of candidate aliased frequency offsets that is most similar to the generated new signal.