WO2016109959A1 - 无线局域网中相位偏移校正的方法和接入点 - Google Patents

无线局域网中相位偏移校正的方法和接入点 Download PDF

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Publication number
WO2016109959A1
WO2016109959A1 PCT/CN2015/070311 CN2015070311W WO2016109959A1 WO 2016109959 A1 WO2016109959 A1 WO 2016109959A1 CN 2015070311 W CN2015070311 W CN 2015070311W WO 2016109959 A1 WO2016109959 A1 WO 2016109959A1
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channel estimation
estimation information
station
phase offset
ofdm symbol
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PCT/CN2015/070311
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English (en)
French (fr)
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刘晟
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华为技术有限公司
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Priority to CN201580071444.7A priority Critical patent/CN107113273A/zh
Priority to PCT/CN2015/070311 priority patent/WO2016109959A1/zh
Publication of WO2016109959A1 publication Critical patent/WO2016109959A1/zh

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes

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  • the present invention relates to the field of wireless communications, and in particular, to a method and an access point for phase offset correction in a wireless local area network.
  • Orthogonal Frequency Division Multiplexing is a multi-carrier modulation technology widely used in fourth-generation cellular communication systems, such as Long-Term Evolution (LTE) and global microwave interconnection. Worldwide Interoperability for Microwave Access (WiMAX) system, etc.
  • WiMAX Worldwide Interoperability for Microwave Access
  • the existing wireless local area network (WLAN) standard based on OFDM technology is composed of gradual evolution of 802.11a, 802.11n, 802.11ac and the like. The utilization of its transmission resources needs to be further improved.
  • the invention provides a method and an access point for phase offset correction in a wireless local area network, which can improve utilization of transmission resources.
  • a method for phase offset correction in a wireless local area network comprising: determining first channel estimation information according to a first orthogonal frequency division multiplexing OFDM symbol in a long training field LTF sent by a station; The second OFDM symbol in the LTF sent by the station determines second channel estimation information; determining a phase offset of the station according to the first channel estimation information and the second channel estimation information; according to the phase offset, The first channel estimation information or the second channel estimation information performs phase offset correction.
  • determining the phase offset of the station according to the first channel estimation information and the second channel estimation information including: according to the first channel The difference between the phase value of the estimated information and the phase value of the second channel estimation information determines the phase offset of the station.
  • the difference between the phase value of the first channel estimation information and the phase value of the second channel estimation information determines the phase offset of the station, including: determining the phase offset ⁇ according to the following formula (1):
  • ⁇ denotes the phase value of the complex number
  • h(f 2k-1 ) is the first channel estimation information determined according to the 2k-1th subcarrier carrying the reference signal transmitted by the station
  • h(f 2k+1) The first channel estimation information determined according to the 2k+1th subcarrier that carries the reference signal sent by the station
  • h(f 2k ) is determined according to the 2kth subcarrier that carries the reference signal sent by the station
  • the second channel estimation information, k takes a positive integer.
  • the difference between the phase value of the first channel estimation information and the phase value of the second channel estimation information determines the phase offset of the station, including: determining the phase offset ⁇ according to the following formula (2):
  • ⁇ denotes the phase value of the complex number
  • h(f 2k-1 ) is the first channel estimation information determined according to the 2k-1th subcarrier carrying the reference signal transmitted by the station
  • h(f 2k+1) The first channel estimation information determined according to the 2k+1th subcarrier that carries the reference signal sent by the station
  • h(f 2k ) is determined according to the 2kth subcarrier that carries the reference signal sent by the station
  • the second channel estimation information, N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the first channel is configured to obtain information about the first channel according to the phase offset Or performing phase offset correction on the second channel estimation information, comprising: using the product of the first channel estimation information and e j ⁇ as a result of phase offset correction, wherein Or using the product of the second channel estimation information and e -j ⁇ as a result of phase offset correction, wherein
  • the Determining the first channel estimation information by the first orthogonal frequency division multiplexing OFDM symbol in the training field LTF comprising: determining the first channel estimation information according to the first reference signal, where the first reference signal is carried in the first OFDM symbol On the 8th-mth subcarrier, 0 ⁇ m ⁇ 7, m and n take a positive integer; determining the second channel estimation information according to the second OFDM symbol in the LTF sent by the station, including: according to the second reference signal The second channel estimation information is determined, and the second reference signal is carried on the 8n-m+4 subcarriers in the second OFDM symbol.
  • a second aspect provides an access point in a wireless local area network, where the access point includes: a first determining module, configured to determine, according to a first orthogonal frequency division multiplexing OFDM symbol in a long training field LTF sent by a station a first channel estimation information, configured to determine second channel estimation information according to the second OFDM symbol in the LTF sent by the station, and a third determining module, configured to use the first channel estimation information and the first The second channel estimation information determines a phase offset of the station; and the processing module is configured to perform phase offset correction on the first channel estimation information or the second channel estimation information according to the phase offset.
  • the third determining module is specifically configured to: determine, according to a difference between a phase value of the first channel estimation information and a phase value of the second channel estimation information The value determines the phase offset of the site.
  • the third determining module is specifically configured to: determine the phase offset amount ⁇ according to the following formula (1) :
  • ⁇ denotes the phase value of the complex number
  • h(f 2k-1 ) is the first channel estimation information determined according to the 2k-1th subcarrier carrying the reference signal transmitted by the station
  • h(f 2k+1) The first channel estimation information determined according to the 2k+1th subcarrier that carries the reference signal sent by the station
  • h(f 2k ) is determined according to the 2kth subcarrier that carries the reference signal sent by the station
  • the second channel estimation information, k takes a positive integer.
  • the third determining module is specifically configured to: determine the phase offset amount ⁇ according to the following formula (2) :
  • ⁇ denotes the phase value of the complex number
  • h(f 2k-1 ) is the first channel estimation information determined according to the 2k-1th subcarrier carrying the reference signal transmitted by the station
  • h(f 2k+1) The first channel estimation information determined according to the 2k+1th subcarrier that carries the reference signal sent by the station
  • h(f 2k ) is determined according to the 2kth subcarrier that carries the reference signal sent by the station
  • the second channel estimation information, N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the processing module is specifically configured to: multiply the first channel estimation information by e j ⁇ As a result of phase offset correction, where Or using the product of the second channel estimation information and e -j ⁇ as a result of phase offset correction, wherein
  • the determining module is specifically configured to: determine the first channel estimation information according to the first reference signal, where the first reference signal is carried on the 8th-m subcarriers in the first OFDM symbol, where 0 ⁇ m ⁇ 7, m and n is a positive integer; the second determining module is specifically configured to: determine the second channel estimation information according to the second reference signal, where the second reference signal is carried on the 8th-m+4 subcarriers in the second OFDM symbol .
  • the method and the access point of the phase offset correction in the WLAN determine the first channel estimation information and the first OFDM symbol and the second OFDM symbol respectively in the LTF sent by the station.
  • the two-channel estimation information is used to determine the phase offset of the station according to the first channel estimation information and the second channel estimation information to perform phase offset correction, thereby obtaining more accurate channel estimation results without introducing additional dedicated calculations.
  • the phase offset OFDM symbol avoids additional overhead and thus improves the utilization of transmission resources.
  • FIG. 1 is a simplified schematic diagram of a WLAN system in accordance with an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of OFDM symbols in a wireless local area network, in accordance with an embodiment of the present invention.
  • FIG. 3 is a schematic flow chart of a method of phase offset correction in a wireless local area network according to an embodiment of the present invention.
  • FIG. 4 is a schematic block diagram of an access point in a wireless local area network in accordance with an embodiment of the present invention.
  • FIG. 5 is a schematic block diagram of an access point in a wireless local area network according to another embodiment of the present invention.
  • FIG. 1 is a simplified schematic diagram of a WLAN system according to an embodiment of the present invention.
  • the system of Figure 1 includes one or more access points AP 101 and one or more stations STA 102.
  • Figure 1 illustrates an access point and two sites as an example.
  • MU-MIMO technology can be used for wireless communication between the access point 101 and the station 102.
  • An AP also referred to as a wireless access point or bridge or hotspot, can access a server or communication network.
  • the STA which may also be referred to as a user equipment, may be a wireless sensor, a wireless communication terminal, or a mobile terminal, such as a mobile phone (or "cellular" phone) that supports WiFi communication functions and a computer with wireless communication capabilities.
  • a mobile phone or "cellular" phone
  • it may be a portable, pocket-sized, handheld, computer-built, wearable, or in-vehicle wireless communication device that supports WiFi communication functions, and exchanges communication data such as voice and data with the wireless access network.
  • Those skilled in the art are aware that some communication devices may have the functions of the above-mentioned access points or sites, and are not limited herein.
  • the IEEE 802.11 standard organization has started the standardization work of the new generation WLAN standard 802.11ax called HEW (High Efficiency WLAN), in which OFDMA (Orthogonal Frequency Division Multiple Access) and Uplink MU-MIMO is the two main key technologies of 802.11ax.
  • HEW High Efficiency WLAN
  • OFDMA Orthogonal Frequency Division Multiple Access
  • Uplink MU-MIMO is the two main key technologies of 802.11ax.
  • Existing WLAN systems based on the 802.11a, 802.11n, and 802.11ac standards employ OFDM symbols with a length of 4 ⁇ s, including a 0.8 ⁇ s Cyclic Prefix (CP) or Guard Interval (GI).
  • CP Cyclic Prefix
  • GI Guard Interval
  • the 802.11ax standard may support the use of 4 times OFDM symbol length, which does not include CP, and the length of each OFDM symbol is 12.8 ⁇ s.
  • the AP in order to demodulate spatial stream signals from different STAs, the AP needs to obtain the uplink MU by the reference signal carried by the long training field LTF in the uplink packet transmitted by each STA.
  • each of the four subcarriers in each OFDM symbol includes one subcarrier for transmitting a reference signal of a spatial stream
  • each OFDM symbol a plurality of subcarriers are included, and one circle represents one subcarrier, wherein one subcarrier is carried on each of the 8 subcarriers in each OFDM symbol, and the black circle represents the subcarrier carrying the reference signal.
  • the white circle represents the subcarrier that does not carry the reference signal.
  • the CFO and the phase noise will cause a phase offset of the channel estimation on the subcarriers carrying the spatial stream reference signal on different OFDM symbols, thereby reducing the accuracy of the channel estimation, and therefore the phase offset of each spatial stream needs to be performed. Correction.
  • the embodiment of the present invention provides an LTF with 4 times OFDM symbol length and 4 times compression in an indoor application.
  • FIG. 3 shows a schematic flow diagram of a method 200 of phase offset correction in a wireless local area network, which may be performed by an AP, in accordance with an embodiment of the present invention.
  • the method 200 includes:
  • S210 Determine first channel estimation information according to the first orthogonal frequency division multiplexing OFDM symbol in the long training field LTF sent by the station.
  • S220 Determine second channel estimation information according to the second OFDM symbol in the LTF sent by the station.
  • the LTF transmitted by the STA to the AP includes two OFDMs. a symbol: a first OFDM symbol and a second OFDM symbol, and the AP determines the first channel estimation information and the second channel estimation information according to the first OFDM symbol and the reference signal carried in the second OFDM symbol, respectively, according to the first channel estimation information and The second channel estimation information determines a phase offset of the station, and performs phase offset correction on the first channel estimation information or the second channel estimation information according to the phase offset to eliminate the two OFDM symbols in the LTF.
  • the phase offset gives a more accurate channel estimation result.
  • the method for phase offset correction in the WLAN of the embodiment of the present invention determines the first channel estimation information and the second channel estimation information by using the first OFDM symbol and the second OFDM symbol in the LTF transmitted by the station, respectively, according to the first
  • the channel estimation information and the second channel estimation information determine a phase offset of the station to perform phase offset correction to obtain a more accurate channel estimation result without introducing an additional OFDM symbol dedicated to calculating a phase offset.
  • the extra overhead is avoided, which improves the utilization of transmission resources.
  • the AP determines the first channel estimation information according to the first OFDM symbol in the long training field LTF sent by the station. Specifically, the AP receives the first OFDM symbol in the LTF transmitted by the station, where the first OFDM symbol includes a first reference signal for channel estimation, specifically, the 8th-m subcarriers in the first OFDM symbol Carrying the first reference signal, 0 ⁇ m ⁇ 7, m and n taking a positive integer; for example, as shown in FIG. 2, the first reference signal is carried on the 8n-7 subcarriers in the first OFDM symbol, and the AP is configured according to The received first reference signal determines first channel estimation information for the station.
  • the first OFDM symbol includes a first reference signal for channel estimation, specifically, the 8th-m subcarriers in the first OFDM symbol Carrying the first reference signal, 0 ⁇ m ⁇ 7, m and n taking a positive integer; for example, as shown in FIG. 2, the first reference signal is carried on the 8n-7 subcarriers in the first OFDM symbol, and
  • the AP determines second channel estimation information according to the second OFDM symbol in the LTF transmitted by the station. Specifically, the AP receives the second OFDM symbol sent by the station, where the second OFDM symbol includes a second reference signal for channel estimation, specifically, the 8th-m+4 subcarriers in the second OFDM symbol. Carrying the second reference signal, 0 ⁇ m ⁇ 7, m and n taking a positive integer; for example, as shown in FIG. 2, the second reference signal is carried on the 8n-3 subcarriers in the second OFDM symbol, AP The second channel estimation information is determined according to the received second reference signal.
  • the AP determines a phase offset of the station according to the first channel estimation information and the second channel estimation information. Specifically, the phase offset amount may be determined according to a difference between a phase value of the first channel estimation information and a phase value of the second channel estimation information. Since the station carries the reference signal for channel estimation only in part of the subcarriers, when the AP receives the first OFDM symbol and the second OFDM symbol sent by the station, the AP alternately receives the first OFDM symbol and the second OFDM symbol.
  • the subcarrier carrying the reference signal for example, as shown in FIG. 2, the AP alternately receives the subcarriers of the first, second, third, fourth, ...
  • first OFDM symbol and the second OFDM symbol are subcarriers carrying a reference signal.
  • Determining first channel estimation information according to one of the first OFDM symbols carrying the reference signal, and determining second channel estimation information according to one of the second OFDM symbols carrying the reference signal, between the two subcarriers A certain number of subcarriers carrying the reference signal are separated, and a difference is determined according to the phase value of the first channel estimation information and the phase value of the second channel estimation information.
  • another group of first channel estimation information and second channel estimation information are further determined according to the same number of two subcarriers carrying the reference signal, and then according to the phase value of the first channel estimation information and the second channel estimation.
  • the phase value of the information determines another difference, and the phase offset is determined based on the sum of the two differences.
  • the first channel estimation information and the second channel estimation information determined by the adjacent subcarriers carrying the reference signal are taken as an example for description.
  • the AP receives the first OFDM symbol and the second OFDM symbol sent by the station, and alternately receives the first OFDM symbol and the subcarriers carrying the reference signal in the second OFDM symbol, as shown in FIG. Subcarriers of 1, 2, 3...
  • the AP may determine the first channel estimation information and the second channel estimation information according to the reference signals in the subcarriers.
  • the first channel estimation information and the second channel estimation information may be respectively expressed as shown in formula (1):
  • f m is the mth subcarrier including the reference signal received by the AP
  • h(f 2k-1 ) is the first channel estimation information determined according to the reference signal in the subcarrier in the first OFDM symbol received by the AP
  • h(f 2k ) is second channel estimation information determined by the AP according to the reference signal in the received subcarriers in the second OFDM symbol.
  • g(f m ) and The amplitude and phase in the channel parameters determined according to the reference signals included in the mth subcarrier, respectively, ⁇ 1 and ⁇ 2 are common to the channel estimates of the stations on the corresponding subcarriers of the first OFDM symbol and the second OFDM symbol, respectively.
  • ⁇ 1 and ⁇ 2 have a phase shift amount ⁇ due to the influence of CFO and phase noise.
  • the second channel estimation information obtained according to the subcarrier f 2k can be obtained, and the first channel estimation information obtained according to the subcarriers f 2k-1 and f 2k+1
  • equation (2) the relationship, as shown in equation (2):
  • subcarrier f 2k is on the first OFDM symbol
  • subcarriers f 2k-1 and f 2k+1 are on the second OFDM symbol
  • subcarriers f 2k-1 and f 2k+1 are adjacent to subcarrier f 2k
  • ⁇ denotes the phase value of the complex number
  • phase shift amount ⁇ can be obtained by using equations (2) and (3), as shown in equation (4):
  • phase offsets ⁇ may be obtained according to the above formula, and any phase offset may be used.
  • the tie value of the plurality of phase offsets may be used as the phase offset of the station, and the average value ⁇ of all the phase offsets may be determined by the formula (5) as the site Phase offset:
  • N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the phase offset can be obtained by using equations (4) and (5), and the phase offset is calculated by using the received second channel estimation information and two first channel estimation information adjacent thereto.
  • the channel estimation information may be calculated by using any one of the channel estimation information and the two adjacent channel estimation information, that is, the phase offset is calculated by the following formula (7):
  • h(f k ) is the channel estimation information determined according to any received subcarrier carrying the reference signal
  • h(f k-1 ) and h(f k+1 ) are respectively based on h(f k )
  • phase offsets ⁇ may be obtained according to the above formula (7), and any phase may be used.
  • the offset is used as the phase offset of the station.
  • the tie value of multiple phase offsets can be used as the phase offset of the station.
  • the average value ⁇ of all phase offsets can also be determined by equation (8).
  • the phase offset of the site :
  • N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the AP may perform phase offset correction on the first channel estimation information or the second channel estimation information.
  • the first channel estimation information or the second channel estimation information may be multiplied by a phase offset factor to obtain new channel estimation information for the purpose of phase offset correction.
  • the first channel estimation information is multiplied by e j ⁇ to obtain new first channel estimation information, and the new first channel estimation can be expressed as shown in formula (6):
  • the common initial phase of the new first channel estimation information and the second channel estimation information is both ⁇ 2 , eliminating the influence of the phase offset.
  • the second channel estimation information may be multiplied by e - j ⁇ ⁇ to obtain new second channel estimation information, where the common initial phase of the new second channel estimation information and the original first channel estimation information is both ⁇ 1 .
  • the effect of phase shift can also be eliminated.
  • B corresponding to A means that B is associated with A, and B can be determined according to A.
  • determining B from A does not mean that B is only determined based on A, and that B can also be determined based on A and/or other information.
  • the size of the sequence numbers of the above processes does not mean the order of execution, and the order of execution of each process should be determined by its function and internal logic, and should not be taken to the embodiments of the present invention.
  • the implementation process constitutes any limitation.
  • the method for phase offset correction in the WLAN of the embodiment of the present invention determines the first channel estimation information and the second channel estimation information by using the first OFDM symbol and the second OFDM symbol in the LTF transmitted by the station, respectively.
  • the channel estimation information and the second channel estimation information determine the phase offset of the station to perform phase offset correction, thereby obtaining more accurate channel estimation results without introducing an additional OFDM symbol dedicated to calculating the phase offset. , avoiding extra overhead, which can improve the utilization of transmission resources.
  • phase offset correction in a wireless local area network is described in detail above with reference to FIG. 1 to FIG. 3, and the phase offset correction in the wireless local area network according to the embodiment of the present invention will be described below with reference to FIG. Incoming AP.
  • FIG. 4 shows a schematic block diagram of an access point 300 in a wireless local area network according to an embodiment of the present invention, the access point 300 comprising:
  • the first determining module 310 is configured to determine, according to the first orthogonal frequency division multiplexing OFDM symbol in the long training field LTF sent by the station, the first channel estimation information;
  • a second determining module 320 configured to determine second channel estimation information according to the second OFDM symbol in the LTF sent by the station;
  • a third determining module 330 configured to determine a phase offset of the station according to the first channel estimation information and the second channel estimation information
  • the processing module 340 is configured to perform phase offset correction on the first channel estimation information or the second channel estimation information according to the phase offset.
  • the LTF transmitted by the STA to the AP includes two OFDMs.
  • the first OFDM symbol and the second OFDM symbol the AP determines, by the first determining module 310, the first channel estimation information according to the reference signal carried in the first OFDM symbol; and the second determining module 320 is configured according to the second OFDM symbol.
  • the reference signal determines the second channel estimation information.
  • the processing module 340 performs phase offset correction on the first channel estimation information or the second channel estimation information, eliminating two sites in the LTF.
  • the phase offset on the OFDM symbol results in a more accurate channel estimation result.
  • the access point in the WLAN of the embodiment of the present invention determines the first channel estimation information and the second channel estimation information by using the first OFDM symbol and the second OFDM symbol in the LTF sent by the station, respectively, according to the first channel.
  • the estimation information and the second channel estimation information determine the phase offset of the station to perform phase offset correction, thereby obtaining more accurate channel estimation results without introducing an additional OFDM symbol dedicated to calculating the phase offset, avoiding Additional overhead can increase the utilization of transmission resources.
  • the AP determines, by using the first determining module 310, the first channel estimation information according to the first OFDM symbol in the LTF sent by the station.
  • the first determining module 310 of the AP receives the first OFDM symbol in the LTF transmitted by the station, where the first OFDM symbol includes a first reference signal for channel estimation, and specifically, may be in the first OFDM symbol.
  • the first reference signal is carried on the 8th-m subcarriers, 0 ⁇ m ⁇ 7, and m and n take positive integers; for example, as shown in FIG. 2, the eighth n-7 subcarriers in the first OFDM symbol are carried on the first carrier.
  • a reference signal, the AP determines the first channel estimation information of the station according to the received first reference signal.
  • the AP determines, by the second determining module 320, the second channel estimation information according to the second OFDM symbol in the LTF sent by the station.
  • the second determining module 320 of the AP receives the second OFDM symbol sent by the station, where the second OFDM symbol includes a second reference signal for channel estimation, specifically, the 8th in the second OFDM symbol.
  • Carrying the second reference signal on -m+4 subcarriers, 0 ⁇ m ⁇ 7, m and n taking positive integers; for example, as shown in FIG. 2, carrying the 8n-3 subcarriers in the second OFDM symbol
  • the second reference signal the AP determines the second channel estimation information according to the received second reference signal.
  • the third determining module 330 of the AP determines the phase offset of the station according to the first channel estimation information and the second channel estimation information. Specifically, the phase offset amount may be determined according to a difference between a phase value of the first channel estimation information and a phase value of the second channel estimation information. Since the station carries the reference signal for channel estimation only in part of the subcarriers, when the AP receives the first OFDM symbol and the second OFDM symbol sent by the station, the AP alternately receives the first OFDM symbol and the second OFDM symbol.
  • the subcarriers carrying the reference signal for example, as shown in FIG. 2, the AP alternately receives the first, second, third, respectively, in the first OFDM symbol and the second OFDM symbol. 4...
  • subcarriers which are subcarriers carrying a reference signal. Determining first channel estimation information according to one of the first OFDM symbols carrying the reference signal, and determining second channel estimation information according to one of the second OFDM symbols carrying the reference signal, between the two subcarriers A certain number of subcarriers carrying the reference signal are separated, and a difference is determined according to the phase value of the first channel estimation information and the phase value of the second channel estimation information. Similarly, another group of first channel estimation information and second channel estimation information are further determined according to the same number of two subcarriers carrying the reference signal, and then according to the phase value of the first channel estimation information and the second channel estimation. The phase value of the information determines another difference, and the phase offset is determined based on the sum of the two differences.
  • the first channel estimation information and the second channel estimation information determined by the adjacent subcarriers carrying the reference signal are taken as an example for description.
  • the AP receives the first OFDM symbol and the second OFDM symbol sent by the station, and alternately receives the first OFDM symbol and the subcarriers carrying the reference signal in the second OFDM symbol, as shown in FIG. Subcarriers of 1, 2, 3...
  • the AP may determine the first channel estimation information and the second channel estimation information by the first determining module 310 and the second determining module 320, respectively, according to the reference signals in the subcarriers.
  • the first channel estimation information and the second channel estimation information may be respectively expressed as shown in formula (1), wherein fm is the mth subcarrier including the reference signal received by the AP, h(f 2k-1 ) a first channel estimation information determined according to a reference signal in a subcarrier in the first OFDM symbol received by the AP; h(f 2k ) is a first determined by the AP according to the reference signal in the subcarrier in the received second OFDM symbol Two channel estimation information.
  • ⁇ 1 and ⁇ 2 are common to the channel estimates of the stations on the corresponding subcarriers of the first OFDM symbol and the second OFDM symbol, respectively.
  • the second channel estimation information obtained according to the subcarrier f 2k can be obtained, and the first channel estimation information obtained according to the subcarriers f 2k-1 and f 2k+1
  • the relationship is as shown in the formula (2), in which the subcarrier f 2k is on the first OFDM symbol, the subcarriers f 2k-1 and f 2k+1 are on the second OFDM symbol, and the subcarriers f 2k-1 and f 2k+1 is the two subcarriers adjacent to the subcarrier f 2k , and ⁇ denotes the phase value of the complex number.
  • the relationship shown in the formula (3) can be obtained, and the phase shift amount ⁇ can be obtained by using the formulas (2) and (3), such as a formula ( 4) shown.
  • phase offsets ⁇ may be obtained according to the above formula, and any phase offset may be used.
  • the tie value of the plurality of phase offsets may be used as the phase offset of the station, and the average value ⁇ of all the phase offsets may be determined by the formula (5) as the site Phase offset, where N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the phase offset can be obtained by using equations (4) and (5), and the phase offset is calculated by using the received second channel estimation information and two first channel estimation information adjacent thereto.
  • the channel estimation information may be calculated by using any channel estimation information and two adjacent channel estimation information, that is, the phase offset is calculated by using equation (7), where h(f k ) is received according to Any one of the channel estimation information determined by the subcarriers carrying the reference signal, h(f k-1 ) and h(f k+1 ) are respectively subcarriers carrying the reference signal adjacent to h(f k ) Determined channel estimation information.
  • phase offsets ⁇ may be obtained according to the above formula (7), and any phase may be used.
  • the offset is used as the phase offset of the station.
  • the tie value of multiple phase offsets can be used as the phase offset of the station.
  • the average value ⁇ of all phase offsets can also be determined by equation (8).
  • the phase offset of the site where N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the processing module 340 of the AP may perform phase offset correction on the first channel estimation information or the second channel estimation information according to the phase offset. Specifically, the processing module 340 may multiply the first channel estimation information or the second channel estimation information by a phase offset factor to obtain new channel estimation information for the purpose of phase offset correction. For example, the processing module 340 multiplies the first channel estimation information by the phase offset factor e j ⁇ to obtain new first channel estimation information, which may be expressed as shown in equation (6).
  • the common initial phase of the new first channel estimation information and the original second channel estimation information is both ⁇ 2 , eliminating the influence of the phase offset.
  • the second channel estimation information may be multiplied by the phase offset factor e -j ⁇ to obtain new second channel estimation information, where the new initial channel phase information and the original initial channel estimation information have a common initial phase.
  • the effect of phase shift can also be eliminated.
  • B corresponding to A means that B is associated with A, and B can be determined according to A.
  • determining B from A does not mean that B is only determined based on A, and that B can also be determined based on A and/or other information.
  • phase offset corrected access point 300 in a wireless local area network may correspond to 200 performing the method in the embodiment of the present invention, and the above and other operations of the respective modules in the access point 300 and The functions of the respective methods in FIG. 1 to FIG. 3 are respectively implemented for the sake of brevity, and are not described herein again.
  • the access point in the WLAN of the embodiment of the present invention determines the first channel estimation information and the second channel estimation information by using the first OFDM symbol and the second OFDM symbol in the LTF sent by the station, respectively, according to the first channel.
  • the estimation information and the second channel estimation information determine the phase offset of the station to perform phase offset correction, thereby obtaining more accurate channel estimation results without introducing an additional OFDM symbol dedicated to calculating the phase offset, avoiding Additional overhead can increase the utilization of transmission resources.
  • an embodiment of the present invention further provides an access point 400 in a wireless local area network, including a processor 410, a memory 420, and a bus system 430.
  • the processor 410 and the memory 420 are connected by a bus system 430 for storing instructions for executing instructions stored by the memory 420.
  • the memory 420 stores the program code, and the processor 410 can call the program code stored in the memory 420 to perform the following operations: determining the first channel estimation information according to the first orthogonal frequency division multiplexing OFDM symbol in the long training field LTF sent by the station.
  • the first channel estimation information and the second channel estimation information determine a phase offset of the station; and the phase offset correction is performed on the first channel estimation information or the second channel estimation information according to the phase offset.
  • the access point in the WLAN of the embodiment of the present invention determines the first channel estimation information and the second channel estimation information by using the first OFDM symbol and the second OFDM symbol in the LTF sent by the station, respectively, according to the first channel.
  • the estimation information and the second channel estimation information determine the phase offset of the station to perform phase offset correction, thereby obtaining more accurate channel estimation results without introducing an additional OFDM symbol dedicated to calculating the phase offset, avoiding Additional overhead can increase the utilization of transmission resources.
  • the processor 410 may be a central processing unit ("CPU"), and the processor 410 may also be other general-purpose processors, digital signal processors (DSPs). , an application specific integrated circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, and the like.
  • the general purpose processor may be a microprocessor or the processor or any conventional processor or the like.
  • the memory 420 can include read only memory and random access memory and provides instructions and data to the processor 410. A portion of the memory 420 may also include a non-volatile random access memory. For example, the memory 420 can also store information of the device type.
  • the bus system 430 may include a power bus, a control bus, a status signal bus, and the like in addition to the data bus. However, for clarity of description, various buses are labeled as bus system 430 in the figure.
  • each step of the foregoing method may be completed by an integrated logic circuit of hardware in the processor 410 or an instruction in a form of software.
  • the steps of the method disclosed in the embodiments of the present invention may be directly implemented as a hardware processor, or may be performed by a combination of hardware and software modules in the processor.
  • the software module can be located in a conventional storage medium such as random access memory, flash memory, read only memory, programmable read only memory or electrically erasable programmable memory, registers, and the like.
  • the storage medium is located in the memory 420, and the processor 410 reads the information in the memory 420 and completes the steps of the above method in combination with its hardware. To avoid repetition, it will not be described in detail here.
  • the processor 410 may call the program code stored in the memory 420 to perform the following operations: determining the difference according to a phase value of the first channel estimation information and a phase value of the second channel estimation information. The phase offset of the site.
  • the processor 410 may call the program code stored in the memory 420 to perform the following operations: determining the phase offset ⁇ according to the formula (4), where ⁇ denotes the phase value of the complex number, h( f 2k-1 ) is the first channel estimation information determined according to the received 2k-1th subcarrier carrying the reference signal sent by the station, and h(f 2k+1 ) is the first transmitted according to the received station 2k+1 the first channel estimation information determined by the subcarrier carrying the reference signal, h(f 2k ) is the second channel estimation determined according to the received 2kth subcarrier carrying the reference signal sent by the station Information, k takes a positive integer.
  • the processor 410 may call the program code stored in the memory 420 to perform the following operations: determining the phase offset ⁇ according to the formula (5), where ⁇ denotes a phase value of the complex number, h( f 2k-1 ) is the first channel estimation information determined according to the received 2k-1th subcarrier carrying the reference signal sent by the station, and h(f 2k+1 ) is the first transmitted according to the received station 2k+1 the first channel estimation information determined by the subcarrier carrying the reference signal, h(f 2k ) is the second channel estimation determined according to the received 2kth subcarrier carrying the reference signal sent by the station information, N is the number of subcarriers of the first OFDM symbol, Indicates an integer and k takes a positive integer.
  • the processor 410 may call the program code stored in the memory 420 to perform the following operation: the product of the first channel estimation information and e j ⁇ is used as a result of the phase offset correction, wherein Or using the product of the second channel estimation information and e -j ⁇ as a result of phase offset correction, wherein
  • the processor 410 may call the program code stored in the memory 420 to perform the following operations: determining the first channel estimation information according to the first reference signal, where the first reference signal is carried in the first OFDM symbol On the 8th-mth subcarrier, 0 ⁇ m ⁇ 7, m and n take a positive integer; the second channel estimation information is determined according to the second reference signal, where the second reference signal is carried in the second OFDM symbol On the 8th-m+4 subcarriers.
  • the access point 400 in the wireless local area network may correspond to the access point 300 in the wireless local area network in the embodiment of the present invention, and may correspond to performing in the method 200 according to an embodiment of the present invention.
  • the above-mentioned and other operations and/or functions of the respective modules in the access point 400 in the WLAN are respectively implemented in order to implement the respective processes of the respective methods in FIG. 1 to FIG. 3, and are not described herein again for brevity.
  • the access point in the WLAN of the embodiment of the present invention determines the first channel estimation information and the second channel estimation information by using the first OFDM symbol and the second OFDM symbol in the LTF sent by the station, respectively, according to the first channel.
  • Estimating information and second channel estimation information determine the phase of the site
  • the bit offset is used for phase offset correction to obtain more accurate channel estimation results without introducing additional OFDM symbols dedicated to calculating the phase offset, avoiding additional overhead and thus improving the utilization of transmission resources. rate.
  • the disclosed systems, devices, and methods may be implemented in other manners.
  • the device embodiments described above are merely illustrative.
  • the division of the unit is only a logical function division.
  • there may be another division manner for example, multiple units or components may be combined or Can be integrated into another system, or some features can be ignored or not executed.
  • the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.
  • each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.
  • the functions may be stored in a computer readable storage medium if implemented in the form of a software functional unit and sold or used as a standalone product.
  • the technical solution of the present invention which is essential or contributes to the prior art, or a part of the technical solution, may be embodied in the form of a software product, which is stored in a storage medium, including
  • the instructions are used to cause a computer device (which may be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention.
  • the storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like, which can store program codes.

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Abstract

本发明实施例涉及无线局域网中相位偏移校正的方法和接入点。该方法包括：根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息；根据该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量；根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正。本发明实施例的无线局域网中相位偏移校正的方法和接入点，不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。

Description

无线局域网中相位偏移校正的方法和接入点 技术领域
本发明涉及无线通信领域，尤其涉及无线局域网中相位偏移校正的方法和接入点。
背景技术
正交频分复用(Orthogonal Frequency Division Multiplexing，OFDM)技术是一种多载波调制技术，广泛应用于第四代蜂窝通信系统中，如长期演进(Long-Term Evolution，LTE)、全球微波互联接入(Worldwide Interoperability for Microwave Access，WiMAX)系统等。现有基于OFDM技术的无线局域网(Wireless local Access Network，简称WLAN)标准由逐步演进的802.11a、802.11n、802.11ac等版本组成。其传输资源的利用率还需要进一步的提高。
发明内容
本发明提供了一种无线局域网中相位偏移校正的方法和接入点，能够提高传输资源的利用率。
第一方面，提供了一种无线局域网中相位偏移校正的方法，该方法包括：根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息；根据该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量；根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正。
结合第一方面，在第一方面的第一种可能的实现方式中，该根据该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量，包括：根据该第一信道估计信息的相位值和该第二信道估计信息的相位值的差值确定该站点的相位偏移量。
结合第一方面的第一种可能的实现方式，在第一方面的第二种可能的实现方式中，该根据该第一信道估计信息的相位值和该第二信道估计信息的相位值的差值确定该站点的相位偏移量，包括：根据下面的公式(1)确定该相位偏移量Δθ：
Figure PCTCN2015070311-appb-000001
其中，∠表示求复数的相位值，h(f2k-1)为根据该站点发送的第2k-1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k+1)为根据该站点发送的第2k+1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k)为根据该站点发送的第2k个承载了参考信号的子载波确定的该第二信道估计信息，k取正整数。
结合第一方面的第一种可能的实现方式，在第一方面的第三种可能的实现方式中，该根据该第一信道估计信息的相位值和该第二信道估计信息的相位值的差值确定该站点的相位偏移量，包括：根据下面的公式(2)确定该相位偏移量Δθ：
Figure PCTCN2015070311-appb-000002
其中，∠表示求复数的相位值，h(f2k-1)为根据该站点发送的第2k-1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k+1)为根据该站点发送的第2k+1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k)为根据该站点发送的第2k个承载了参考信号的子载波确定的该第二信道估计信息，
Figure PCTCN2015070311-appb-000003
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000004
表示取整数，k取正整数。
结合第一方面的第二种或第三种可能的实现方式，在第一方面的第四种可能的实现方式中，其特征在于，该根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正，包括：将该第一信道估计信息与ejΔθ的乘积作为相位偏移校正的结果，其中
Figure PCTCN2015070311-appb-000005
或将该第二信道估计信息与e-jΔθ的乘积作为相位偏移校正的结果，其中
Figure PCTCN2015070311-appb-000006
结合第一方面或第一方面的第一种至第四种可能的实现方式中的任一种可能的实现方式，在第一方面的第五种可能的实现方式中，该根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息，包括：根据第一参考信号确定该第一信道估计信息，该第一参考信号承载在该第一OFDM符号中的第8n-m个子载波上，0≤m≤7，m和n取正整数；该根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息，包括：根据第二参考信号确定该第二信道估计信息，该第二参考信号承载在该第二OFDM符号中的第8n-m+4个子载波上。
第二方面，提供了一种无线局域网中的接入点，该接入点包括：第一确定模块，用于根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；第二确定模块，用于根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息；第三确定模块，用于根据该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量；处理模块，用于根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正。
结合第二方面，在第二方面的第一种可能的实现方式中，该第三确定模块具体用于：根据该第一信道估计信息的相位值和该第二信道估计信息的相位值的差值确定该站点的相位偏移量。
结合第二方面的第一种可能的实现方式，在第二方面的第二种可能的实现方式中，该第三确定模块具体用于：根据下面的公式(1)确定该相位偏移量Δθ：
Figure PCTCN2015070311-appb-000007
其中，∠表示求复数的相位值，h(f2k-1)为根据该站点发送的第2k-1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k+1)为根据该站点发送的第2k+1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k)为根据该站点发送的第2k个承载了参考信号的子载波确定的该第二信道估计信息，k取正整数。
结合第二方面的第一种可能的实现方式，在第二方面的第三种可能的实现方式中，该第三确定模块具体用于：根据下面的公式(2)确定该相位偏移量Δθ：
Figure PCTCN2015070311-appb-000008
其中，∠表示求复数的相位值，h(f2k-1)为根据该站点发送的第2k-1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k+1)为根据该站点发送的第2k+1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k)为根据该站点发送的第2k个承载了参考信号的子载波确定的该第二信道估计信息，
Figure PCTCN2015070311-appb-000009
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000010
表示取整数，k取正整数。
结合第二方面的第二种或第三种可能的实现方式，在第二方面的第四种 可能的实现方式中，该处理模块具体用于：将该第一信道估计信息与ejΔθ的乘积作为相位偏移校正的结果，其中
Figure PCTCN2015070311-appb-000011
或将该第二信道估计信息与e-jΔθ的乘积作为相位偏移校正的结果，其中
Figure PCTCN2015070311-appb-000012
结合第二方面或第二方面的第一种至第四种可能的实现方式中的任一种可能的实现方式，在第二方面的第五种可能的实现方式中，其特征在于，该第一确定模块具体用于：根据第一参考信号确定该第一信道估计信息，该第一参考信号承载在该第一OFDM符号中的第8n-m个子载波上，0≤m≤7，m和n取正整数；该第二确定模块具体用于：根据第二参考信号确定该第二信道估计信息，该第二参考信号承载在该第二OFDM符号中的第8n-m+4个子载波上。
基于上述技术方案，本发明实施例的无线局域网中相位偏移校正的方法和接入点，通过站点发送的LTF中的第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
附图说明
为了更清楚地说明本发明实施例的技术方案，下面将对本发明实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本发明的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1是根据本发明实施例的WLAN系统的简单示意图。
图2是根据本发明实施例的无线局域网中OFDM符号的示意图。
图3是根据本发明实施例的无线局域网中相位偏移校正的方法的示意性流程图。
图4是根据本发明实施例的无线局域网中的接入点的示意性框图。
图5是根据本发明另一实施例的无线局域网中的接入点的示意性框图。
具体实施方式
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行 清楚、完整地描述，显然，所描述的实施例是本发明的一部分实施例，而不是全部实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动的前提下所获得的所有其他实施例，都应属于本发明保护的范围。
图1为一个本发明实施方式的WLAN系统的简单示意图。图1的系统包括一个或者多个接入点AP101和一个或者多个站点STA102，图1以一个接入点和两个个站点为例。接入点101和站点102之间可以采用MU-MIMO技术进行无线通信。
AP，也可称之为无线访问接入点或桥接器或热点等，其可以接入服务器或通信网络。
STA，还可以称为用户设备，可以是无线传感器、无线通信终端或移动终端，如支持WiFi通讯功能的移动电话(或称为“蜂窝”电话)和具有无线通信功能的计算机。例如，可以是支持WiFi通讯功能的便携式、袖珍式、手持式、计算机内置的，可穿戴的，或者，车载的无线通信装置，它们与无线接入网交换语音、数据等通信数据。本领域技术人员知道，一些通信设备可能同时具有上述接入点或者站点的功能，在此不予限制。
目前IEEE 802.11标准组织已经启动了称之为HEW(High Efficiency WLAN，高效率无线局域网)的新一代WLAN标准802.11ax的标准化工作，其中，OFDMA(正交频分多址Orthogonal Frequency Division Multiple Access)和上行MU-MIMO是802.11ax的两项主要的关键技术。现有基于802.11a、802.11n和802.11ac标准的WLAN系统，所采用的OFDM符号长度为4μs，其中包括0.8μs的循环前缀(Cyclic Prefix，简称CP)或保护间隔(Guard Interval，简称GI)。为了提高OFDMA的效率，802.11ax标准可能支持采用4倍OFDM符号长度，此时不包括CP，每个OFDM符号的长度为12.8μs。
如图1所示，在上行MU-MIMO中，AP为了解调来自不同STA的空间流信号，需要通过各个STA发射的上行分组中的长训练字段LTF所承载的参考信号，来获得上行MU-MIMO信道的估计。当传输数据的OFDM符号长度为原来的4倍长度时，由于室内应用时信道频域变化很缓慢，室内应用中通常采用4倍压缩的LTF方案，即当空间流的个数Nss＝1至4时，只有一个OFDM符号，当Nss＝5至8时，包含两个OFDM符号。另外，每个OFDM符号中每4个子载波中包括一个用于传输某个空间流的参考信号的子载波， 通过该4倍压缩的LTF可以直接获得1/4的子载波上的信道估计，由于室内应用时信道频域变化很缓慢，因此可以再通过对前述1/4的子载波上的信道估计进行内插，获得该空间流的其余3/4的子载波上的信道估计。例如，如图2所示，当空间流的个数Nss＝5至8时，STA发送的LTF包含两个OFDM符号，分别为第一OFDM符号和第二OFDM符号。在每个OFDM符号中，包括多个子载波，一个圆圈代表一个子载波，其中，每个OFDM符号中每8个子载波中有一个子载波上承载参考信号，黑色圆圈代表承载了参考信号的子载波，白色圆圈代表了没有承载参考信号的子载波。在AP接收该STA发送的两个OFDM符号时，会分别收到如图2所示的第1、2、3、4等承载了参考信号的子载波，AP根据这些承载了参考信号的子载波确定信道估计。
在上行MU-MIMO中，空间流可能来自不同的STA，尽管理想情况下STA的载波频率和AP的载波频率完全相同，但由于STA和AP的本地振荡器存在微小的频率波动和相位噪声，因此实际系统中AP与STA之间存在一定的载波频率偏移CFO。由于不同STA的本地振荡器各不相同，因此不同空间流的CFO和载波的相位噪声各不相同。在室内应用的场景下，由于采用了4倍压缩的LTF方案，当Nss＝5至8时，包含两个OFDM符号，承载空间流参考信号的子载波分布在两个不同的OFDM符号上。此时，CFO和相位噪声将造成不同的OFDM符号上承载该空间流参考信号的子载波上的信道估计出现相位偏移，从而降低信道估计的精度，因此需要对各个空间流的相位偏移进行校正。
为此，本发明实施例提供了一种室内应用中采用4倍OFDM符号长度和4倍压缩的LTF时，当Nss＝5至8，STA发送的LTF两个OFDM符号时，在不增加开销情况下，对各空间流的信道估计进行有效的相位偏移校正的方法。
图3示出了根据本发明实施例的无线局域网中相位偏移校正的方法200的示意性流程图，该方法200可以由AP执行。如图3所示，该方法200包括：
S210，根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；
S220，根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息；
S230，根据该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量；
S240，根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正。
具体地，对于室内的应用场景，由于室内信道的频域变化很缓慢，可以采用4倍压缩LTF的方法，当空间流个数Nss＝5至8时，STA向AP发送的LTF包括两个OFDM符号：第一OFDM符号和第二OFDM符号，AP根据第一OFDM符号和第二OFDM符号中承载的参考信号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量，根据该相位偏移量，对第一信道估计信息或者第二信道估计信息进行相位偏移校正，消除该站点在LTF中两个OFDM符号上的相位偏移，获得更加精确的信道估计结果。
因此，本发明实施例的无线局域网中相位偏移校正的方法，通过站点发送的LTF中第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
在S210中，AP根据站点发送的长训练字段LTF中的第一OFDM符号确定第一信道估计信息。具体地，AP接收站点发送的LTF中的第一OFDM符号，该第一OFDM符号中包括用于信道估计的第一参考信号，具体地，可以在第一OFDM符号中的第8n-m个子载波上承载该第一参考信号，0≤m≤7，m和n取正整数；例如图2所示，在第一OFDM符号中的第8n-7个子载波上承载该第一参考信号，AP根据接收到的该第一参考信号确定该站点的第一信道估计信息。
在S220中，AP根据该站点发送的LTF中的第二OFDM符号确定第二信道估计信息。具体地，AP接收站点发送的第二OFDM符号，该第二OFDM符号中包括用于信道估计的第二参考信号，具体地，可以在该第二OFDM符号中的第8n-m+4个子载波上承载该第二参考信号，0≤m≤7，m和n取正整数；例如图2所示，在该第二OFDM符号中的第8n-3个子载波上承载该第二参考信号，AP根据接收到的该第二参考信号确定第二信道估计信息。
在S230中，AP根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量。具体地，可以根据第一信道估计信息的相位值和第二信道估计信息的相位值的差值确定相位偏移量。由于站点只在部分子载波中承载用于信道估计的参考信号，AP接收该站点发送的第一OFDM符号和第二OFDM符号时，会交替接收到该第一OFDM符号和该第二OFDM符号中承载了参考信号的子载波，例如，如图2所示，AP会交替接收到分别位于第一OFDM符号和第二OFDM符号中的第1、2、3、4…的子载波，这些子载波均为承载了参考信号的子载波。根据第一OFDM符号中的一个承载了参考信号的子载波确定第一信道估计信息，根据第二OFDM符号中的一个承载了参考信号的子载波确定第二信道估计信息，这两个子载波之间间隔了一定数量的承载参考信号的子载波，根据该第一信道估计信息的相位值和该第二信道估计信息的相位值确定一个差值。同样地，再根据相距同样数量的两个承载参考信号的子载波确定另一组第一信道估计信息和第二信道估计信息，再根据该第一信道估计信息的相位值和该第二信道估计信息的相位值确定另一个差值，根据这两个差值之和确定相位偏移量。
例如，根据LTF中第一OFDM符号上的一个承载了参考信号的子载波确定第一信道估计信息，再根据第二OFDM符号上的一个承载了参考信号的子载波确定第二信道估计信息，这两个子载波之间间隔了2个承载了参考信号的子载波，计算该第一信道估计信息的相位值和该第二信道估计信息的相位值，确定一个相位值的差值；同样地，再根据两个承载了参考信号的子载波分别确定第一信道估计信息和第二信道估计信息，并计算第一信道估计信息的相位值和第二信道估计信息的相位值的差值，这两个子载波之间也间隔了2个承载参考信号的子载波。根据两个相位值的差值确定相位偏移量。
可选地，作为一个实施例，如图2所示，以相邻的承载了参考信号的子载波确定的第一信道估计信息和第二信道估计信息为例进行说明。具体地，AP接收该站点发送的第一OFDM符号和第二OFDM符号，交替接收该第一OFDM符号和该第二OFDM符号中承载了参考信号的子载波，如图2所示，分别接收编号为1、2、3…的子载波。根据子载波中的参考信号，AP可以确定第一信道估计信息和第二信道估计信息。该第一信道估计信息和该第二信道估计信息可以分别表示为如公式(1)所示：
Figure PCTCN2015070311-appb-000013
其中，fm为AP接收的第m个包括参考信号的子载波，h(f2k-1)为根据AP接收的第一OFDM符号中的子载波中的参考信号确定的第一信道估计信息；h(f2k)为AP根据接收的第二OFDM符号中的子载波中的参考信号确定的第二信道估计信息。g(fm)和
Figure PCTCN2015070311-appb-000014
分别为根据第m个子载波中包括的参考信号确定的信道参数中的幅度和相位，θ1和θ2分别为站点在第一OFDM符号和第二OFDM符号的相应子载波上的信道估计的公共初始相位，由于CFO和相位噪声的影响，θ1和θ2存在相位偏移量Δθ，这里以Δθ＝θ2-θ1为例进行说明。
在本发明实施例中，根据公式(1)，可以得到根据子载波f2k得到的第二信道估计信息，与根据子载波f2k-1和f2k+1得到的第一信道估计信息之间的关系，如公式(2)所示：
Figure PCTCN2015070311-appb-000015
其中，子载波f2k在第一OFDM符号上，子载波f2k-1和f2k+1在第二OFDM符号上，子载波f2k-1和f2k+1是与子载波f2k相邻的前后两个子载波，∠表示求复数的相位值。
在本发明实施例中，由于室内信道频域变化很慢，因此可以得到公式(3)：
Figure PCTCN2015070311-appb-000016
利用公式(2)和(3)即可得到相位偏移量Δθ，如公式(4)所示：
Figure PCTCN2015070311-appb-000017
可选地，在本发明实施例中，由于第一OFDM符号和第二OFDM符号均包括多个子载波，即可根据上述公式求出多个相位偏移量Δθ，可以将任意一个相位偏移量作为该站点的相位偏移量，可以将多个相位偏移量的平局值作为该站点的相位偏移量，也可以通过公式(5)确定所有相位偏移量的平均值Δθ作为该站点的相位偏移量：
Figure PCTCN2015070311-appb-000018
其中，
Figure PCTCN2015070311-appb-000019
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000020
表示取整数，k取正整数。
在本发明实施例中，可以利用公式(4)和(5)得到相位偏移量，该相位偏移量是以接收的第二信道估计信息与其前后相邻的两个第一信道估计信息计算得到的，可选地，也可以通过任意一个信道估计信息与其前后两个相邻的信道估计信息计算得到，即通过下面的公式(7)计算相位偏移量：
Figure PCTCN2015070311-appb-000021
其中，h(fk)为根据接收的任意一个承载了参考信号的子载波确定的信道估计信息，h(fk-1)和h(fk+1)分别为根据与h(fk)相邻的承载了参考信号的子载波确定的信道估计信息。
可选地，在本发明实施例中，由于第一OFDM符号和第二OFDM符号均包括多个子载波，即可根据上述公式(7)求出多个相位偏移量Δθ，可以将任意一个相位偏移量作为该站点的相位偏移量，可以将多个相位偏移量的平局值作为该站点的相位偏移量，也可以通过公式(8)确定所有相位偏移量的平均值Δθ作为该站点的相位偏移量：
Figure PCTCN2015070311-appb-000022
其中，
Figure PCTCN2015070311-appb-000023
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000024
表示取整数，k取正整数。
在S240中，根据该相位偏移量，AP可以对该第一信道估计信息或第二信道估计信息进行相位偏移校正。具体地，可以将该第一信道估计信息或第二信道估计信息乘以相位偏移因子获得新的信道估计信息，达到相位偏移校正的目的。例如，将第一信道估计信息乘以ejΔθ获得新的第一信道估计信息，该新的第一信道估计即可表示如公式(6)所示：
Figure PCTCN2015070311-appb-000025
该新的第一信道估计信息和第二信道估计信息的公共初始相位均为θ2，消除了相位偏移的影响。可选地，也可以将第二信道估计信息乘以e-jΔθ获得新的第二信道估计信息，该新的第二信道估计信息和原第一信道估计信息的公共初始相位均为θ1，同样可以消除了相位偏移的影响。
应理解，在本发明实施例中，“与A相应的B”表示B与A相关联，根据A可以确定B。但还应理解，根据A确定B并不意味着仅仅根据A确定B，还可以根据A和/或其它信息确定B。
应理解，在本发明的各种实施例中，上述各过程的序号的大小并不意味着执行顺序的先后，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本发明实施例的实施过程构成任何限定。
因此，本发明实施例的无线局域网中相位偏移校正的方法，通过站点发送的LTF中的第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
上文中结合图1至图3，详细描述了根据本发明实施例的无线局域网中相位偏移校正的方法，下面将结合图4，描述根据本发明实施例的无线局域网中相位偏移校正的接入点AP。
图4示出了根据本发明实施例的无线局域网中接入点300的示意性框图，该接入点300包括：
第一确定模块310，用于根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；
第二确定模块320，用于根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息；
第三确定模块330，用于根据该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量；
处理模块340，用于根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正。
具体地，对于室内的应用场景，由于室内信道的频域变化很缓慢，可以采用4倍压缩LTF的方法，当空间流个数Nss＝5至8时，STA向AP发送的LTF包括两个OFDM符号：第一OFDM符号和第二OFDM符号，AP通过第一确定模块310根据第一OFDM符号中承载的参考信号，确定第一信道估计信息；通过第二确定模块320根据第二OFDM符号中承载的参考信号，确定第二信道估计信息。再通过第三确定模块330根据第一信道估计信息和 第二信道估计信息确定该站点的相位偏移量，根据该相位偏移量，处理模块340对第一信道估计信息或者第二信道估计信息进行相位偏移校正，消除该站点在LTF中两个OFDM符号上的相位偏移，获得更加精确的信道估计结果。
因此，本发明实施例的无线局域网中的接入点，通过站点发送的LTF中的第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
在本发明实施例中，AP通过第一确定模块310根据站点发送的LTF中的第一OFDM符号确定第一信道估计信息。具体地，AP的第一确定模块310接收站点发送的LTF中的第一OFDM符号，该第一OFDM符号中包括用于信道估计的第一参考信号，具体地，可以在第一OFDM符号中的第8n-m个子载波上承载该第一参考信号，0≤m≤7，m和n取正整数；例如图2所示，在第一OFDM符号中的第8n-7个子载波上承载该第一参考信号，AP根据接收到的该第一参考信号确定该站点的第一信道估计信息。
在本发明实施例中，AP通过第二确定模块320根据该站点发送的LTF中的第二OFDM符号确定第二信道估计信息。具体地，AP的第二确定模块320接收站点发送的第二OFDM符号，该第二OFDM符号中包括用于信道估计的第二参考信号，具体地，可以在该第二OFDM符号中的第8n-m+4个子载波上承载该第二参考信号，0≤m≤7，m和n取正整数；例如图2所示，在该第二OFDM符号中的第8n-3个子载波上承载该第二参考信号，AP根据接收到的该第二参考信号确定第二信道估计信息。
在本发明实施例中，AP的第三确定模块330根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量。具体地，可以根据第一信道估计信息的相位值和第二信道估计信息的相位值的差值确定相位偏移量。由于站点只在部分子载波中承载用于信道估计的参考信号，AP接收该站点发送的第一OFDM符号和第二OFDM符号时，会交替接收到该第一OFDM符号和该第二OFDM符号中承载了参考信号的子载波，例如，如图2所示，AP会交替接收到分别位于第一OFDM符号和第二OFDM符号中的第1、2、3、 4…的子载波，这些子载波均为承载了参考信号的子载波。根据第一OFDM符号中的一个承载了参考信号的子载波确定第一信道估计信息，根据第二OFDM符号中的一个承载了参考信号的子载波确定第二信道估计信息，这两个子载波之间间隔了一定数量的承载参考信号的子载波，根据该第一信道估计信息的相位值和该第二信道估计信息的相位值确定一个差值。同样地，再根据相距同样数量的两个承载参考信号的子载波确定另一组第一信道估计信息和第二信道估计信息，再根据该第一信道估计信息的相位值和该第二信道估计信息的相位值确定另一个差值，根据这两个差值之和确定相位偏移量。
例如，根据LTF中第一OFDM符号上的一个承载了参考信号的子载波确定第一信道估计信息，再根据第二OFDM符号上的一个承载了参考信号的子载波确定第二信道估计信息，这两个子载波之间间隔了2个承载了参考信号的子载波，计算该第一信道估计信息的相位值和该第二信道估计信息的相位值，确定一个相位值的差值；同样地，再根据两个承载了参考信号的子载波分别确定第一信道估计信息和第二信道估计信息，并计算第一信道估计信息的相位值和第二信道估计信息的相位值的差值，这两个子载波之间也间隔了2个承载参考信号的子载波。根据两个相位值的差值确定相位偏移量。
可选地，作为一个实施例，如图2所示，以相邻的承载了参考信号的子载波确定的第一信道估计信息和第二信道估计信息为例进行说明。具体地，AP接收该站点发送的第一OFDM符号和第二OFDM符号，交替接收该第一OFDM符号和该第二OFDM符号中承载了参考信号的子载波，如图2所示，分别接收编号为1、2、3…的子载波。根据子载波中的参考信号，AP通过第一确定模块310和第二确定模块320可以分别确定第一信道估计信息和第二信道估计信息。该第一信道估计信息和该第二信道估计信息可以分别表示为如公式(1)所示，其中，fm为AP接收的第m个包括参考信号的子载波，h(f2k-1)为根据AP接收的第一OFDM符号中的子载波中的参考信号确定的第一信道估计信息；h(f2k)为AP根据接收的第二OFDM符号中的子载波中的参考信号确定的第二信道估计信息。g(fm)和
Figure PCTCN2015070311-appb-000026
分别为根据第m个子载波中包括的参考信号确定的信道参数中的幅度和相位，θ1和θ2分别为站点在第一OFDM符号和第二OFDM符号的相应子载波上的信道估计的公共初始相位，由于CFO和相位噪声的影响，存在相位偏移量Δθ， Δθ＝θ2-θ1。
在本发明实施例中，根据公式(1)，可以得到根据子载波f2k得到的第二信道估计信息，与根据子载波f2k-1和f2k+1得到的第一信道估计信息之间的关系，如公式(2)所示，其中，子载波f2k在第一OFDM符号上，子载波f2k-1和f2k+1在第二OFDM符号上，子载波f2k-1和f2k+1是与子载波f2k相邻的前后两个子载波，∠表示求复数的相位值。
在本发明实施例中，由于室内信道频域变化很慢，因此可以得到公式(3)所示的关系，并利用公式(2)和(3)即可得到相位偏移量Δθ，如公式(4)所示。
可选地，在本发明实施例中，由于第一OFDM符号和第二OFDM符号均包括多个子载波，即可根据上述公式求出多个相位偏移量Δθ，可以将任意一个相位偏移量作为该站点的相位偏移量，可以将多个相位偏移量的平局值作为该站点的相位偏移量，也可以通过公式(5)确定所有相位偏移量的平均值Δθ作为该站点的相位偏移量，其中，
Figure PCTCN2015070311-appb-000027
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000028
表示取整数，k取正整数。
在本发明实施例中，可以利用公式(4)和(5)得到相位偏移量，该相位偏移量是以接收的第二信道估计信息与其前后相邻的两个第一信道估计信息计算得到的，可选地，也可以通过任意一个信道估计信息与其前后两个相邻的信道估计信息计算得到，即通过公式(7)计算相位偏移量，其中，h(fk)为根据接收的任意一个承载了参考信号的子载波确定的信道估计信息，h(fk-1)和h(fk+1)分别为根据与h(fk)相邻的承载了参考信号的子载波确定的信道估计信息。
可选地，在本发明实施例中，由于第一OFDM符号和第二OFDM符号均包括多个子载波，即可根据上述公式(7)求出多个相位偏移量Δθ，可以将任意一个相位偏移量作为该站点的相位偏移量，可以将多个相位偏移量的平局值作为该站点的相位偏移量，也可以通过公式(8)确定所有相位偏移量的平均值Δθ作为该站点的相位偏移量，其中，
Figure PCTCN2015070311-appb-000029
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000030
表示取整数，k取正整数。
在本发明实施例中，根据该相位偏移量，AP的处理模块340可以对该第一信道估计信息或第二信道估计信息进行相位偏移校正。具体地，处理模块340可以将该第一信道估计信息或第二信道估计信息乘以相位偏移因子获 得新的信道估计信息，达到相位偏移校正的目的。例如，处理模块340将第一信道估计信息乘以相位偏移因子ejΔθ获得新的第一信道估计信息，该新的第一信道估计即可表示如公式(6)所示。该新的第一信道估计信息和原第二信道估计信息的公共初始相位均为θ2，消除了相位偏移的影响。可选地，也可以将第二信道估计信息乘以相位偏移因子e-jΔθ获得新的第二信道估计信息，该新的第二信道估计信息和原第一信道估计信息的公共初始相位均为θ1，同样可以消除了相位偏移的影响。
应理解，在本发明实施例中，“与A相应的B”表示B与A相关联，根据A可以确定B。但还应理解，根据A确定B并不意味着仅仅根据A确定B，还可以根据A和/或其它信息确定B。
另外，本文中术语“和/或”，仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
应理解，根据本发明实施例的无线局域网中相位偏移校正的接入点300可对应于执行本发明实施例中的方法的200，并且接入点300中的各个模块的上述和其它操作和/或功能分别为了实现图1至图3中的各个方法的相应流程，为了简洁，在此不再赘述。
因此，本发明实施例的无线局域网中的接入点，通过站点发送的LTF中的第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
如图5所示，本发明实施例还提供了一种无线局域网中的接入点400，包括处理器410、存储器420和总线系统430。其中，处理器410和存储器420通过总线系统430相连，该存储器420用于存储指令，该处理器410用于执行该存储器420存储的指令。该存储器420存储程序代码，且处理器410可以调用存储器420中存储的程序代码执行以下操作：根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；根据该站点发送的该LTF中的第二OFDM符号确定第二信道估计信息；根据 该第一信道估计信息和该第二信道估计信息确定该站点的相位偏移量；根据该相位偏移量，对该第一信道估计信息或该第二信道估计信息进行相位偏移校正。
因此，本发明实施例的无线局域网中的接入点，通过站点发送的LTF中的第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
应理解，在本发明实施例中，该处理器410可以是中央处理单元(Central Processing Unit，简称为“CPU”)，该处理器410还可以是其他通用处理器、数字信号处理器(DSP)、专用集成电路(ASIC)、现成可编程门阵列(FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件等。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。
该存储器420可以包括只读存储器和随机存取存储器，并向处理器410提供指令和数据。存储器420的一部分还可以包括非易失性随机存取存储器。例如，存储器420还可以存储设备类型的信息。
该总线系统430除包括数据总线之外，还可以包括电源总线、控制总线和状态信号总线等。但是为了清楚说明起见，在图中将各种总线都标为总线系统430。
在实现过程中，上述方法的各步骤可以通过处理器410中的硬件的集成逻辑电路或者软件形式的指令完成。结合本发明实施例所公开的方法的步骤可以直接体现为硬件处理器执行完成，或者用处理器中的硬件及软件模块组合执行完成。软件模块可以位于随机存储器，闪存、只读存储器，可编程只读存储器或者电可擦写可编程存储器、寄存器等本领域成熟的存储介质中。该存储介质位于存储器420，处理器410读取存储器420中的信息，结合其硬件完成上述方法的步骤。为避免重复，这里不再详细描述。
可选地，作为一个实施例，处理器410可以调用存储器420中存储的程序代码执行以下操作：根据该第一信道估计信息的相位值和该第二信道估计信息的相位值的差值确定该站点的相位偏移量。
可选地，作为一个实施例，处理器410可以调用存储器420中存储的程 序代码执行以下操作：根据公式(4)确定该相位偏移量Δθ，其中，∠表示求复数的相位值，h(f2k-1)为根据接收的该站点发送的第2k-1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k+1)为根据接收的该站点发送的第2k+1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k)为根据接收的该站点发送的第2k个承载了参考信号的子载波确定的该第二信道估计信息，k取正整数。
可选地，作为一个实施例，处理器410可以调用存储器420中存储的程序代码执行以下操作：根据公式(5)确定该相位偏移量Δθ，其中，∠表示求复数的相位值，h(f2k-1)为根据接收的该站点发送的第2k-1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k+1)为根据接收的该站点发送的第2k+1个承载了参考信号的子载波确定的该第一信道估计信息，h(f2k)为根据接收的该站点发送的第2k个承载了参考信号的子载波确定的该第二信道估计信息，
Figure PCTCN2015070311-appb-000031
N为该第一OFDM符号的子载波个数，
Figure PCTCN2015070311-appb-000032
表示取整数，k取正整数。
可选地，作为一个实施例，处理器410可以调用存储器420中存储的程序代码执行以下操作：将所述第一信道估计信息与ejΔθ的乘积作为相位偏移校正的结果，其中
Figure PCTCN2015070311-appb-000033
或将所述第二信道估计信息与e-jΔθ的乘积作为相位偏移校正的结果，其中
Figure PCTCN2015070311-appb-000034
可选地，作为一个实施例，处理器410可以调用存储器420中存储的程序代码执行以下操作：根据第一参考信号确定该第一信道估计信息，该第一参考信号承载在该第一OFDM符号中的第8n-m个子载波上，0≤m≤7，m和n取正整数；根据第二参考信号确定该第二信道估计信息，该第二参考信号承载在该第二OFDM符号中的第8n-m+4个子载波上。
应理解，根据本发明实施例的无线局域网中的接入点400可对应于本发明实施例中的无线局域网中的接入点300，并可以对应于执行根据本发明实施例的方法200中的相应主体，并且无线局域网中的接入点400中的各个模块的上述和其它操作和/或功能分别为了实现图1至图3中的各个方法的相应流程，为了简洁，在此不再赘述。
因此，本发明实施例的无线局域网中的接入点，通过站点发送的LTF中的第一OFDM符号和第二OFDM符号，分别确定第一信道估计信息和第二信道估计信息，根据第一信道估计信息和第二信道估计信息确定该站点的相 位偏移量来进行相位偏移校正，获得更加精确的信道估计结果，而不需要引入额外的专门用于计算相位偏移量的OFDM符号，避免了额外的开销，从而能够提高传输资源的利用率。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本发明的范围。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的系统、装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统、装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本发明各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。
所述功能如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本发明的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)执行本发明各个实施例所述方法的全部或部分步骤。而前 述的存储介质包括：U盘、移动硬盘、只读存储器(ROM，Read-Only Memory)、随机存取存储器(RAM，Random Access Memory)、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应所述以权利要求的保护范围为准。

Claims (12)

  1. 一种无线局域网中相位偏移校正的方法，其特征在于，包括：
    根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；
    根据所述站点发送的所述LTF中的第二OFDM符号确定第二信道估计信息；
    根据所述第一信道估计信息和所述第二信道估计信息确定所述站点的相位偏移量；
    根据所述相位偏移量，对所述第一信道估计信息或所述第二信道估计信息进行相位偏移校正。
  2. 根据权利要求1所述的方法，其特征在于，所述根据所述第一信道估计信息和所述第二信道估计信息确定所述站点的相位偏移量，包括：
    根据所述第一信道估计信息的相位值和所述第二信道估计信息的相位值的差值确定所述站点的相位偏移量。
  3. 根据权利要求2所述的方法，其特征在于，所述根据所述第一信道估计信息的相位值和所述第二信道估计信息的相位值的差值确定所述站点的相位偏移量，包括：
    根据下面的公式(1)确定所述相位偏移量Δθ：
    Figure PCTCN2015070311-appb-100001
    其中，∠表示求复数的相位值，h(f2k-1)为根据所述站点发送的第2k-1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k+1)为根据所述站点发送的第2k+1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k)为根据所述站点发送的第2k个承载了参考信号的子载波确定的所述第二信道估计信息，k取正整数。
  4. 根据权利要求2所述的方法，其特征在于，所述根据所述第一信道估计信息的相位值和所述第二信道估计信息的相位值的差值确定所述站点的相位偏移量，包括：
    根据下面的公式(2)确定所述相位偏移量Δθ：
    Figure PCTCN2015070311-appb-100002
    其中，∠表示求复数的相位值，h(f2k-1)为根据所述站点发送的第2k-1 个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k+1)为根据所述站点发送的第2k+1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k)为根据所述站点发送的第2k个承载了参考信号的子载波确定的所述第二信道估计信息，
    Figure PCTCN2015070311-appb-100003
    N为所述第一OFDM符号的子载波个数，
    Figure PCTCN2015070311-appb-100004
    表示取整数，k取正整数。
  5. 根据权利要求3或4所述的方法，其特征在于，所述根据所述相位偏移量，对所述第一信道估计信息或所述第二信道估计信息进行相位偏移校正，包括：
    将所述第一信道估计信息与ejΔθ的乘积作为相位偏移校正的结果，其中
    Figure PCTCN2015070311-appb-100005
    或
    将所述第二信道估计信息与e-jΔθ的乘积作为相位偏移校正的结果，其中
    Figure PCTCN2015070311-appb-100006
  6. 根据权利要求1至5中任一项所述的方法，其特征在于，所述根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息，包括：
    根据第一参考信号确定所述第一信道估计信息，所述第一参考信号承载在所述第一OFDM符号中的第8n-m个子载波上，0≤m≤7，m和n取正整数；
    所述根据所述站点发送的所述LTF中的第二OFDM符号确定第二信道估计信息，包括：
    根据第二参考信号确定所述第二信道估计信息，所述第二参考信号承载在所述第二OFDM符号中的第8n-m+4个子载波上。
  7. 一种无线局域网中的接入点，其特征在于，包括：
    第一确定模块，用于根据站点发送的长训练字段LTF中的第一正交频分复用OFDM符号确定第一信道估计信息；
    第二确定模块，用于根据所述站点发送的所述LTF中的第二OFDM符号确定第二信道估计信息；
    第三确定模块，用于根据所述第一信道估计信息和所述第二信道估计信息确定所述站点的相位偏移量；
    处理模块，用于根据所述相位偏移量，对所述第一信道估计信息或所述第二信道估计信息进行相位偏移校正。
  8. 根据权利要求7所述的接入点，其特征在于，所述第三确定模块具体用于：
    根据所述第一信道估计信息的相位值和所述第二信道估计信息的相位值的差值确定所述站点的相位偏移量。
  9. 根据权利要求8所述的接入点，其特征在于，所述第三确定模块具体用于：
    根据下面的公式(1)确定所述相位偏移量Δθ：
    Figure PCTCN2015070311-appb-100007
    其中，∠表示求复数的相位值，h(f2k-1)为根据所述站点发送的第2k-1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k+1)为根据所述站点发送的第2k+1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k)为根据所述站点发送的第2k个承载了参考信号的子载波确定的所述第二信道估计信息，k取正整数。
  10. 根据权利要求8所述的接入点，其特征在于，所述第三确定模块具体用于：
    根据下面的公式(2)确定所述相位偏移量Δθ：
    Figure PCTCN2015070311-appb-100008
    其中，∠表示求复数的相位值，h(f2k-1)为根据所述站点发送的第2k-1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k+1)为根据所述站点发送的第2k+1个承载了参考信号的子载波确定的所述第一信道估计信息，h(f2k)为根据所述站点发送的第2k个承载了参考信号的子载波确定的所述第二信道估计信息，
    Figure PCTCN2015070311-appb-100009
    N为所述第一OFDM符号的子载波个数，
    Figure PCTCN2015070311-appb-100010
    表示取整数，k取正整数。
  11. 根据权利要求9或10所述的接入点，其特征在于，所述处理模块具体用于：
    将所述第一信道估计信息与ejΔθ的乘积作为相位偏移校正的结果，其中
    Figure PCTCN2015070311-appb-100011
    或
    将所述第二信道估计信息与e-jΔθ的乘积作为相位偏移校正的结果，其中
    Figure PCTCN2015070311-appb-100012
  12. 根据权利要求7至11中任一项所述的接入点，其特征在于，
    所述第一确定模块具体用于：
    根据第一参考信号确定所述第一信道估计信息，所述第一参考信号承载在所述第一OFDM符号中的第8n-m个子载波上，0≤m≤7，m和n取正整数；
    所述第二确定模块具体用于：
    根据第二参考信号确定所述第二信道估计信息，所述第二参考信号承载在所述第二OFDM符号中的第8n-m+4个子载波上。
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