Method of large frequency offset estimation for an OFDM communications system using reference signals

A method of performing carrier frequency offset (CFO) estimation of physical channels in a mobile communications system, the method comprising:

• performing channel estimation of a received signal on a physical channel based on multiple orthogonal frequency division multiplex (OFDM) symbols in one or more reference signals (RSS);
• and
• determining phase rotations Φ and corresponding time differences s between different OFDM symbols in the one or more RSs over an extended phase rotation range greater than +/−π to obtain multiple CFO estimation candidates ƒ0, ƒ1, ƒ2 . . . ƒn within the extended phase rotation range;
• wherein the first CFO estimation candidate ƒ0 corresponds to a base phase rotation value Φ0=Φori where Φori is an original phase rotation value and the additional CFO estimation candidates ƒ1, ƒ2 . . . ƒn within the extended phase rotation range correspond respectively to phase rotation values Φ1, Φ2, . . . Φn=[Φori+/−2 mπ] where m is a positive integer.

A radio equipment in a mobile communications system, the radio equipment comprising:

• a memory storing machine-readable instructions;
• and
• a processor for executing the machine-readable instructions such that, when the processor executes the machine-readable instructions, it configures the radio equipment to:
• perform channel estimation of a received signal on a physical channel based on multiple orthogonal frequency division multiplex (OFDM) symbols in one or more reference signals (RSs);
• determine multiple phase rotations Φ and corresponding time differences s between different OFDM symbols in the one or more RSs over a base phase rotation range comprising +/−π to obtain a first CFO estimation candidate ƒ0;
• and
• extend the base phase rotation range to provide an extended phase rotation range of greater than +/−π to obtain additional CFO estimation candidates ƒ1, ƒ2 . . . ƒn within the extended phase rotation range;
• wherein the first CFO estimation candidate ƒ0 corresponds to a base phase rotation value Φ0=Φori where Φori is an original phase rotation value and the additional CFO estimation candidates ƒ1, ƒ2 . . . ƒn within the extended phase rotation range correspond respectively to phase rotation values Φ1, Φ2, . . . Φn=[Φori+/−2mπ] where m is a positive integer.