Frequency offset correction in narrowband machine-to-machine

A node, comprising:

• one or more processors, the one or more processors configured 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;
• determine, based on the estimated first frequency offset, a set of possible aliased frequency offsets corresponding to the estimated first frequency offset;
• obtain a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1;
• and
• estimate a true frequency offset based on the second oversampled received signal,
• wherein in estimating the true frequency offset based on the second oversampled received signal, the one or more processors are further configured 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 possible 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 possible aliased frequency offsets that is most similar to the generated new signal.

A computer program product comprising instructions stored on non-transitory computer-readable media which, when executed by one or more processors, perform the acts of:

• 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;
• determining, based on the estimated first frequency offset, a set of possible aliased frequency offsets corresponding to the estimated first frequency offset;
• obtaining a second oversampled received signal by sampling the received signal according to N times the symbol rate, wherein N is greater than 1;
• and
• estimating a true frequency offset based on the second oversampled received signal,
• wherein estimating the true frequency offset based on 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 possible 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 possible aliased frequency offsets that is most similar to the generated new signal.