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EP-4489359-B1 - METHOD AND APPARATUS FOR ESTIMATING FREQUENCY OFFSET IN WIRELESS COMMUNICATION SYSTEM

EP4489359B1EP 4489359 B1EP4489359 B1EP 4489359B1EP-4489359-B1

Inventors

  • SON, Youngwook
  • KIM, HYEONJUN
  • LEE, JUNG WOON
  • JEON, HYUNBAE

Dates

Publication Date
20260513
Application Date
20240703

Claims (12)

  1. An operating method of a receiver (100; 200) that communicates with a transmitter (100; 200) through a frequency band, the operating method comprising: detecting (S101; S403) a signal received from the transmitter (100; 200) at a plurality of sub-bands constituting the frequency band; determining (S103; S405) first frequency offsets for the signal at reception sub-bands at which the signal has been detected among the plurality of sub-bands; determining (S105; S407) second frequency offsets by calibrating carrier frequency offsets based on a distance of each of the reception sub-bands from a center frequency of the frequency band; and determining (S107; S409) a third frequency offset for the frequency band based on the second frequency offsets, wherein the determining (S107; S409) of the third frequency offset comprises determining the third frequency offset by performing weighted averaging on the second frequency offsets based on weights corresponding to an amplitude of the signal measured at each of the reception sub-bands.
  2. An operating method of a receiver (100; 200) that communicates with a transmitter (100; 200) through a frequency band, the operating method comprising: detecting (S101; S403) a signal received from the transmitter (100; 200) at a plurality of sub-bands constituting the frequency band; determining (S103; S405) first frequency offsets for the signal at reception sub-bands at which the signal has been detected among the plurality of sub-bands; determining (S105; S407) second frequency offsets by calibrating carrier frequency offsets based on a distance of each of the reception sub-bands from a center frequency of the frequency band; and determining (S107; S409) a third frequency offset for the frequency band based on the second frequency offsets, wherein the determining (S107; S409) of the third frequency offset comprises: re-constructing (S315) in-phase/quadrature, I/Q, vectors for each of the reception sub-bands by using an amplitude of the signal measured at each of the reception sub-bands and the second frequency offsets; obtaining a vector for the frequency band by combining the I/Q vectors; and determining the third frequency offset by calculating a phase of the vector for the frequency band.
  3. The operating method of claim 1 or 2, wherein the signal comprises a training sequence that is periodically repeated in a time domain, and the determining (S103; S405) of the first frequency offsets comprises determining the first frequency offset based on periodicity of the training sequence.
  4. The operating method of claim 3, wherein the determining (S103; S405) of the first frequency offsets comprises determining the first frequency offset by extracting (S203; S309; 505) phase information for each of the plurality of sub-bands from the training sequence by using an auto-correlation function, ACF.
  5. The operating method of any one of claims 1 to 4, wherein the distance of each of the reception sub-bands from the center frequency of the frequency band corresponds to a magnitude of an index of each of the reception sub-bands.
  6. The operating method of any one of claims 1 to 5, further comprising: receiving data from the transmitter (100; 200) by using the third frequency offset.
  7. The operating method of any one of claims 1 to 6, wherein a bandwidth of the frequency band is 320 MHz, and a bandwidth of each of the plurality of sub-bands is 20 MHz.
  8. An operating method of a receiver (100; 200) that communicates with a transmitter (100; 200) through a frequency band, the operating method comprising: detecting (S101; S403) a signal received from the transmitter (100; 200) at a plurality of sub-bands constituting the frequency band, , wherein the signal for each sub-band is detected (S201) based on an auto-correlation function, ACF, and a cross-correlation function, CCR; determining (S103; S405) first frequency offsets for the signal at reception sub-bands at which the signal has been detected among the plurality of sub-bands; determining (S105; S407) second frequency offsets by calibrating carrier frequency offsets based on a distance of each of the reception sub-bands from a center frequency of the frequency band; calculating (S203) phase information based on a ACF result of each sub-band; calibrating (S205) phase information based on a frequency position of the sub-band; re-constructing (S207) an in-phase/quadrature, I/Q, vector based on the absolute value of the ACF and the calibrated phase information; and combining (S209) I/Q vectors of sub-bands at which the signal has been detected, and determining (S211) a third frequency offset by calculating phase information of one combined vector.
  9. The operating method of claim 4, wherein the ACF corresponds to a delay equal to a sample repetition period of the training sequence.
  10. The operating method of claim 9, further comprising: obtaining a calibrated carrier frequency offset, CFO, value by reversely calibrating (S507) a sampling clock offset, SCO; and re-constructing (S509) an in-phase/quadrature, I/Q, value for each sub-band using the calibrated CFO value.
  11. The operating method of any one of claims 1 to 10, further comprising: splitting (S501) a wideband channel into sub-bands.
  12. A receiver for communicating with a transmitter (100; 200) through a frequency band, the receiver (100; 200) comprising: a radio frequency integrated circuit, RFIC, (120); and a processor (110) configured to perform the method of any one of claims 1 to 11, and wherein the signal received from the transmitter (100; 200) is received through the RFIC (120).

Description

BACKGROUND Aspects of the inventive concept relate to a method and apparatus for determining a frequency offset so as to improve communication performance. As an example of wireless communication, a wireless local area network (WLAN) is technology that connects two or more devices by using a wireless signal transmission method. A WLAN may be based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. The 802.11 standard has evolved into 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac, 802.11ax, etc., and is capable of supporting a transmission rate of up to 1 Gbyte/s based on orthogonal frequency division multiplexing (OFDM). In 802.11ac, data may be simultaneously transmitted to multiple users through multiuser multi-input multi-output (MU-MIMO). In 802.11ax, also called high efficiency (HE), orthogonal frequency division multiple access (OFDMA) as well as MU-MIMO is also applied to implement multiple access by splitting available subcarriers and providing the split subcarriers to users. Accordingly, a WLAN system, to which 802.11ax is applied, may effectively support communication in dense areas and outdoors. 802.11be, also called extremely high throughput (EHT), seeks to support a 6-GHz unlicensed frequency band, to support various bandwidths per channel, to introduce hybrid automatic repeat and request (HARQ), and to support up to 16x16 MIMO. Accordingly, next-generation WLAN systems are expected to effectively support low latency and high-speed transmission such as new radio (NR), which is 5th generation (5G) technology. Recently, new technologies capable of supporting a bandwidth of up to 640 MHz per channel in 802.11be have been proposed to increase spectral efficiency and the transmission rate. In wireless communication systems, a difference may occur between a carrier frequency of a transmission signal transmitted by a transmitter and a carrier frequency of a reception signal recognized by a receiver. Due to such a difference, the receiver may calculate a frequency offset and match the carrier frequency of the transmission signal to the carrier frequency of the reception signal. In wideband wireless communication systems, due to various factors, a difference may occur between a carrier frequency of a transmission signal transmitted by a transmitter and a carrier frequency of a reception signal recognized by a receiver. Therefore, there is a need for a method of determining a frequency offset by taking into account various factors. CN 114 338 325 A discloses a carrier frequency offset and sampling frequency offset determination method and device. SUMMARY Aspects of the inventive concept provide a method and apparatus for determining a frequency offset so as to improve communication performance. The invention is set out in the appended set of claims. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which: FIG. 1 is a diagram illustrating a wireless communication system according to an embodiment;FIG. 2 illustrates a block diagram of a wireless communication device according to an embodiment;FIG. 3A illustrates a block diagram of a wireless communication device according to an embodiment;FIG. 3B is a diagram for describing a sampling clock offset (SCO);FIG. 3C illustrates a carrier frequency offset (CFO) and an SCO in a frequency domain;FIG. 3D illustrates an embodiment of calibrating deviation due to an SCO effect from a CFO for each of 16 sub-bands with respect to a reception signal having a bandwidth of 320 MHz in a wideband channel;FIG. 4 illustrates an operation procedure of a wireless communication device according to an embodiment;FIG. 5A illustrates an operation procedure of a wireless communication device according to an embodiment;FIG. 5B illustrates an operation procedure of a wireless communication device at an mth sub-band, according to an embodiment;FIG. 5C illustrates an operation of a wireless communication device at each sub-band and a method of combining a plurality of sub-bands, according to an embodiment;FIG. 6 illustrates a method of detecting a reception signal at a sub-band, obtaining a synchronization timing, and determining a frequency offset based on the synchronization timing and the reception signal, according to an embodiment;FIG. 7 illustrates an operation procedure of a wireless communication device according to an embodiment;FIG. 8 illustrates signals that are processed by a wireless communication device, according to an embodiment;FIGS. 9A and 9B illustrate frequency offsets in which an SCO effect is not calibrated in an additive white Gaussian noise (AWGN) channel;FIGS. 9C and 9D illustrate frequency offsets in which an SCO effect is calibrated in an AWGN channel, according to an embodiment;FIGS. 9E and 9F illustrate frequency offsets in which an SCO effect is not calibrated in a fading channel, according to an embodiment;