WO2016049817A1 - 信道估计方法、通信节点及通信系统 - Google Patents

信道估计方法、通信节点及通信系统 Download PDF

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WO2016049817A1
WO2016049817A1 PCT/CN2014/087807 CN2014087807W WO2016049817A1 WO 2016049817 A1 WO2016049817 A1 WO 2016049817A1 CN 2014087807 W CN2014087807 W CN 2014087807W WO 2016049817 A1 WO2016049817 A1 WO 2016049817A1
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field
spatial stream
subcarrier
subcarriers
communication node
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PCT/CN2014/087807
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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 CN201480073641.8A priority Critical patent/CN105917713B/zh
Priority to EP14903031.4A priority patent/EP3177083B1/en
Priority to PCT/CN2014/087807 priority patent/WO2016049817A1/zh
Priority to KR1020177007257A priority patent/KR101938100B1/ko
Priority to JP2017516853A priority patent/JP2017535141A/ja
Publication of WO2016049817A1 publication Critical patent/WO2016049817A1/zh
Priority to US15/448,915 priority patent/US10057087B2/en

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
    • H04L25/0232—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols by interpolation between sounding signals
    • 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
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/261—Details of reference signals
    • H04L27/2613—Structure of the reference signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0204—Channel estimation of multiple channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00—Baseband systems
    • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
    • H04L25/0202—Channel estimation
    • H04L25/0224—Channel estimation using sounding signals
    • H04L25/0228—Channel estimation using sounding signals with direct estimation from sounding signals
    • H04L25/023—Channel estimation using sounding signals with direct estimation from sounding signals with extension to other symbols
    • 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
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
    • H04L27/2692—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with preamble design, i.e. with negotiation of the synchronisation sequence with transmitter or sequence linked to the algorithm used at the receiver
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems

Definitions

  • Embodiments of the present invention relate to a wireless communication technology, and in particular, to a channel estimation method, a communication node, and a communication system.
  • Wireless Local Area Network (English: Wireless Local Access Network, WLAN) based on Orthogonal Frequency Division Multiplexing (OFDM) is gradually evolved from 802.11a, 802.11n, 802.11ac, etc. composition.
  • 802.11n and 802.11ac already support single-user multiple-input multiple-output (English: Single User Multiple-Input Multiple-Output, SU-MIMO), and 802.11ac also supports downlink multi-user multiple input and multiple output (English: Multi- User Multiple-Input Multiple-Output, referred to as MU-MIMO.
  • MU-MIMO Multi- User Multiple-Input Multiple-Output
  • the IEEE 802.11 standard organization has started the standardization work of the new generation WLAN standard 802.11ax called High Efficiency WLAN (HEW), in which Orthogonal Frequency Division Multiple Access (English: Orthogonal Frequency) Division Multiple Access (OFDMA) and uplink MU-MIMO are the two key technologies of 802.11ax.
  • HEW High Efficiency WLAN
  • OFDMA Orthogonal Frequency Division Multiple Access
  • OFDMA Orthogonal Frequency Division Multiple Access
  • OFDMA Orthogonal Frequency Division Multiple Access
  • uplink MU-MIMO uplink MU-MIMO
  • SU-MIMO and MU-MIMO multiple spatial streams are transmitted in parallel by MIMO, and the receiving end needs to obtain the estimation of the MIMO channel first, so that each spatial stream can be demodulated and received.
  • an access point (English: Access Point, abbreviated as AP) can be used to demodulate signals from different stations (English: Station, abbreviated as STA), and can be sent through the uplink packet preamble sent by each STA.
  • the High Efficiency Long Training Field (HE-LTF) is used to obtain the channel estimation of the uplink MU-MIMO.
  • HE-LTF High Efficiency Long Training Field
  • Figure 1 is a schematic diagram of a prior art HE-LTF scheme.
  • Each of the available subcarriers of each OFDM symbol carries a reference signal, and sequentially adopts subcarrier (English: Sub-carrier) interleaving to sequentially correspond to different spatial streams, wherein the available subcarriers are at most Subcarriers other than the zero-frequency subcarrier, the guard subcarrier for suppressing adjacent channel leakage, and the like are removed in the MIMO transmission band.
  • the number of subcarriers corresponding to each spatial stream in one OFDM symbol is M/N, where M is the number of available subcarriers, and each spatial stream sequentially corresponds to a different subcarrier in each OFDM symbol, and before The subcarriers corresponding to the corresponding spatial streams in one OFDM symbol are staggered by the position of one subcarrier. Therefore, after N OFDM symbols, the subcarriers corresponding to each spatial stream traverse the positions of all available subcarriers, and the subcarriers corresponding to each spatial stream are orthogonal to each other. In this way, by using the reference signals carried by the subcarriers corresponding to each spatial stream in the HE-LTF, the channel estimation of the corresponding spatial stream on each available subcarrier can be obtained.
  • the distribution pattern of the positions of the subcarriers corresponding to the spatial streams in the nth OFDM symbol of the HE-LTF is defined as ⁇ (n), wherein the positions of the subcarriers corresponding to the different spatial streams are different.
  • the symbol distribution, the distribution pattern of the positions of the subcarriers corresponding to the spatial streams in the next OFDM symbol may be expressed as ⁇ (n+1), where “+1” indicates the subcarrier corresponding to each spatial stream in the OFDM symbol The position moves forward or backward by the position of one subcarrier.
  • the distribution pattern of the positions of the subcarriers corresponding to the spatial streams in the N OFDM symbols is ⁇ (1), ⁇ (2), ⁇ , ⁇ (N). ).
  • the existing OFDM system-based WLAN system uses an OFDM symbol length of 4 us.
  • the 802.11ax standard supports OFDM symbol lengths of 4 times or longer.
  • the use of 4 times OFDM symbol length means that the length of each OFDM symbol is 16 us respectively.
  • the length of the HE-LTF reaches 128 us when transmitting 8 spatial streams, and the overhead thereof It can reach 4.3% ⁇ 12.8%, and the resource utilization rate is low.
  • Embodiments of the present invention provide a channel estimation method, a communication node, and a communication system, which reduce signaling overhead and improve resource utilization while ensuring channel estimation performance.
  • a first aspect of the present invention provides a channel estimation method, the method comprising:
  • the preamble includes at least a first field and a second field, where the subcarriers of the orthogonal frequency division multiplexing OFDM symbol of the first field are used to carry the first a reference signal, the first reference signal is a determination signal known to both the second communication node and the first communication node, and the subcarrier of the OFDM symbol of the second field is used for Containing useful information; the useful information is physical layer control information, and/or data;
  • a first channel estimate for each spatial stream on all subcarriers within the multiple input multiple output MIMO transmission band is obtained.
  • each subcarrier in each OFDM symbol of the first field and the second field sequentially corresponds to a different spatial stream, and subcarriers in the same position in different OFDM symbols The corresponding spatial streams are different.
  • each of the OFDM symbols of the first field and the second field sequentially corresponds to a different spatial stream group, and the same position of the different OFDM symbols
  • the spatial stream groups corresponding to the carriers are different, and the spatial stream group includes K spatial streams; in the first field, the K spatial streams of each spatial stream group are orthogonally transformed, and sequentially a subcarrier transmission corresponding to the spatial stream group of K OFDM symbols in a field; in the second field, the K spatial streams of each spatial stream group are orthogonally transformed, in turn by the Subcarrier transmission corresponding to the spatial stream group of K OFDM symbols in the two fields.
  • the subcarriers are subcarriers other than the guard subcarriers that are used to suppress adjacent channel leakage in the MIMO transmission band.
  • the using the first field and the second field of the preamble to obtain a first of each spatial stream on all subcarriers in a multiple input multiple output MIMO transmission frequency band Channel estimation includes:
  • a first channel estimate for each spatial stream on all subcarriers within the MIMO transmission band is obtained by combining channel estimates for the corresponding subcarriers in the first and second fields of each spatial stream.
  • an embodiment of the present invention provides a channel estimation method, where the method includes:
  • the preamble includes at least a first field and a second field, and the subcarriers of the orthogonal frequency division multiplexed OFDM symbol of the first field are used to carry a first reference signal, where a reference signal is a determination signal known to both the first communication node and the second communication node, and the subcarriers of the OFDM symbol of the second field are used to carry useful information; the useful information is physical layer control information, and/or data;
  • a signal packet including the preamble is transmitted to the second communication node.
  • an embodiment of the present invention provides a second communications node, where the second communications node includes:
  • An acquiring module configured to acquire a preamble in a signal packet sent by the first communications node, where the preamble includes at least a first field and a second field, and the subcarriers of the orthogonal frequency division multiplexing OFDM symbol of the first field And configured to carry a first reference signal, where the first reference signal is a determining signal that is known by both the second communications node and the first communications node, and the subcarriers of the OFDM symbol of the second field are used for carrying Information; the useful information is physical layer control information, and/or data;
  • a channel estimation module configured to obtain, by using the first field and the second field of the preamble acquired by the acquiring module, a first channel estimate of each spatial stream on all subcarriers in a multiple input multiple output MIMO transmission frequency band.
  • each subcarrier in each OFDM symbol of the first field and the second field sequentially corresponds to a different spatial stream, and subcarriers in the same position in different OFDM symbols The corresponding spatial streams are different.
  • each subcarrier in each of the OFDM symbols of the first field and the second field sequentially corresponds to a different spatial stream group, and the same position in different OFDM symbols
  • the spatial stream groups corresponding to the carriers are different, and the spatial stream group includes K spatial streams; in the first field, the K spatial streams of each spatial stream group are orthogonally transformed, and sequentially a subcarrier transmission corresponding to the spatial stream group of K OFDM symbols in a field; in the second field, the K spatial streams of each spatial stream group are orthogonally transformed, The subcarriers corresponding to the spatial stream group of the K OFDM symbols in the second field are transmitted.
  • the subcarrier is a subcarrier other than the guard subcarrier for removing adjacent frequency carrier in the MIMO transmission band and for suppressing adjacent channel leakage.
  • the channel estimation module is specifically configured to:
  • a first channel estimate for each spatial stream on all subcarriers within the MIMO transmission band is obtained by combining channel estimates for the corresponding subcarriers in the first and second fields of each spatial stream.
  • an embodiment of the present invention provides a first communications node, where the first communications node includes:
  • a determining module configured to determine a preamble in the signal packet; wherein the preamble includes at least a first field and a second field, and the subcarrier of the orthogonal frequency division multiplexing OFDM symbol of the first field is used to carry the first reference a signal, the first reference signal is a determination signal known to both the second communication node and the first communication node, and the subcarrier of the OFDM symbol of the second field is used to carry useful information; the useful information is physical Layer control information, and/or data;
  • a sending module configured to send, to the second communications node, a signal packet including the preamble.
  • an embodiment of the present invention provides a second communications node, where the second communications node includes:
  • a transceiver configured to acquire a preamble in a signal packet sent by the first communications node, where the preamble includes at least a first field and a second field, and the subcarrier of the orthogonal frequency division multiplexing OFDM symbol of the first field And configured to carry a first reference signal, where the first reference signal is a determining signal that is known by both the second communications node and the first communications node, and the subcarriers of the OFDM symbol of the second field are used for carrying Information; the useful information is physical layer control information, and/or data;
  • a processor configured to obtain, by using the first field and the second field of the preamble obtained by the transceiver, a first channel estimate for each spatial stream on all subcarriers in a multiple input multiple output MIMO transmission frequency band.
  • each subcarrier in each OFDM symbol of the first field and the second field sequentially corresponds to a different spatial stream, and subcarriers in the same position in different OFDM symbols The corresponding spatial streams are different.
  • each of the OFDM symbols of the first field and the second field sequentially corresponds to a different spatial stream group, and the same position of the different OFDM symbols
  • the spatial stream groups corresponding to the carriers are different, and the spatial stream group includes K spatial streams; in the first field, the K spatial streams of each spatial stream group are orthogonally transformed, and sequentially a subcarrier transmission corresponding to the spatial stream group of K OFDM symbols in a field; in the second field, the K spatial streams of each spatial stream group are orthogonally transformed, in turn by the Subcarrier transmission corresponding to the spatial stream group of K OFDM symbols in the two fields.
  • the subcarrier is a subcarrier other than the guard subcarrier for removing adjacent frequency carrier in the MIMO transmission band and for suppressing adjacent channel leakage.
  • the processor is specifically configured to:
  • the second field is Reloading and modulating the payload information to generate a second reference signal corresponding to each subcarrier of each OFDM symbol of the second field;
  • a first channel estimate for each spatial stream on all subcarriers within the MIMO transmission band is obtained by combining channel estimates for the corresponding subcarriers in the first and second fields of each spatial stream.
  • an embodiment of the present invention provides a first communications node, where the first communications node includes:
  • a processor configured to determine a preamble in the signal packet; wherein the preamble includes at least a first field and a second field, and the subcarrier of the orthogonal frequency division multiplexing OFDM symbol of the first field is used to carry the first reference a signal, the first reference signal is a determination signal known to both the second communication node and the first communication node, and the subcarrier of the OFDM symbol of the second field is used to carry useful information; the useful information is physical Layer control information, and/or data;
  • a transmitter configured to send, to the second communications node, a signal packet including the preamble.
  • an embodiment of the present invention provides a communications system, where the communications system includes:
  • the second communication node provided by any of the foregoing third aspects, and the first communication node provided by the foregoing fourth aspect.
  • the HE-LTF in the signal packet is composed of two parts, and the first part of each OFDM symbol subcarrier is used to carry the reference signal, and the second part is used to carry the reference signal.
  • the subcarrier of the OFDM symbol does not carry the reference signal, but is used to carry the useful information. Therefore, the overhead actually used for channel estimation is only the first field, since the number of OFDM symbols in the first field is smaller than the number of spatial streams, therefore, Compared with the prior art, the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • FIG. 1 is a schematic diagram of a prior art HE-LTF scheme
  • FIG. 2 is a flowchart of a channel estimation method according to an embodiment of the present invention.
  • FIG. 13 is another flowchart of a channel estimation method according to an embodiment of the present invention.
  • FIG. 14 is still another flowchart of a channel estimation method according to an embodiment of the present invention.
  • FIG. 15 is a schematic structural diagram of a second communication node according to an embodiment of the present disclosure.
  • FIG. 16 is a schematic structural diagram of a first communication node according to an embodiment of the present disclosure.
  • FIG. 17 is another schematic structural diagram of a second communication node according to an embodiment of the present disclosure.
  • FIG. 18 is another schematic structural diagram of a first communication node according to an embodiment of the present invention.
  • FIG. 19 is a schematic structural diagram of a communication system according to an embodiment of the present invention.
  • the 802.11ax signal packet is composed of a preamble and a data field.
  • the preamble includes a legacy preamble (English: Legacy Preamble) and a HEW preamble.
  • the HEW preamble is a specific preamble of the 802.11ax packet, and includes at least a signaling field and a training field.
  • the signaling field is used for transmission Physical layer control information
  • the training field includes functions for automatic gain control, providing reference signals for channel estimation
  • HE-LTF is part of the training field.
  • the preamble of the signal packet sent by the first communication node to the second communication node includes at least a first field and a second field, where the number of OFDM symbols of the first field is smaller than that of the spatial stream.
  • the number, and the sum of the number of OFDM symbols of the first field and the second field is not greater than the number of spatial streams.
  • the first field of each OFDM symbol carries a reference signal, and the reference signal is a determining signal that is known by both the first communications node and the second communications node, and typically uses two-phase phase shift keying.
  • the second field does not carry the reference signal for each subcarrier of the OFDM symbol. It is used to transmit useful information, which may be all or part of the physical layer control information, and/or all or part of the data transmitted by the signal packet.
  • useful information may be all or part of the physical layer control information, and/or all or part of the data transmitted by the signal packet.
  • the first field and the second field may be respectively understood as a first part and a second part of the HE-LTF field, such that the HE-LTF field in the present invention has
  • channel estimation also has the function of transmitting all or part of physical layer control information, and/or all or part of the data.
  • the first field may also be understood as a HE-LTF field
  • the second field is understood as a part or all of a signaling field, and or a part or all of a data field, such that the second field in the present invention
  • the function of transmitting all or part of the physical layer control information, and/or all or part of the data there is also the function of providing a reference signal for channel estimation together with the first field.
  • FIG. 2 is a flowchart of a channel estimation method according to an embodiment of the present invention. As shown in FIG. 2, the channel estimation method provided by the embodiment of the present invention includes:
  • Step 201 Acquire a preamble in a signal packet sent by the first communications node, where the preamble includes at least a first field and a second field, where the subcarriers of each orthogonal frequency division multiplexing OFDM symbol of the first field are used by Carrying a first reference signal, the first reference signal is a determination signal known to both the second communication node and the first communication node, and the subcarrier of each OFDM symbol of the second field is used to carry useful information.
  • the useful information is physical layer control information, and/or data;
  • the preamble first field and the second field to obtain each spatial stream.
  • the execution subject of the embodiment of the present invention may be a communication node in a wireless communication system, such as a second communication node, and the second communication node communicates with the first communication node.
  • the first communication node may be, for example, a STA, a user equipment, or an access point
  • the second communication node may be, for example, a STA, an access point, or a user equipment.
  • subcarriers in the embodiments of the present invention refer to subcarriers other than the guard subcarriers for removing adjacent-channel leakage in the MIMO transmission band.
  • the first communication node determines a preamble in the signal packet and transmits a signal packet including the preamble to the second communication node.
  • the preamble includes at least a first field and a second field, where a subcarrier of each orthogonal frequency division multiplexing OFDM symbol of the first field is used to carry a first reference signal, where the first reference signal is A determination signal is known by both the communication node and the first communication node, and the subcarrier of each OFDM symbol of the second field is used to carry useful information.
  • the second communication node After acquiring the preamble in the signal packet sent by the first communication node, the second communication node obtains the first channel estimation of each spatial stream on all subcarriers in the MIMO transmission frequency band by using the first field and the second field And then the second communication node uses the first channel estimate to demodulate the signal transmitted by the first communication node.
  • the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • Each subcarrier in each OFDM symbol of the first field and the second field corresponds to a different spatial stream, and the spatial streams corresponding to the subcarriers in the same position in different OFDM symbols are different.
  • the subcarriers corresponding to the spatial streams in each OFDM symbol are orthogonal to each other.
  • the channel estimation of each spatial stream on its corresponding subcarrier can be directly obtained, and the useful information carried by the second field is In other words, it is equivalent to transmitting in the form of OFDMA.
  • the subcarrier corresponding to each spatial stream cannot traverse all subcarrier positions in the MIMO transmission band in the entire first field and the second field.
  • ⁇ 1 and ⁇ 2 are selected such that all subcarriers corresponding to each spatial stream in the first field and the entire first field and the second field are distributed as uniformly as possible throughout the MIMO transmission band.
  • the first field and the second field each have only one OFDM symbol, which are respectively represented by LTF-1 and VLTF-1, and the distribution patterns of the positions of the subcarriers corresponding to the spatial streams are respectively used (1).
  • the first field of the HE-LTF has two OFDM symbols LTF-1 and LTF-2, and the distribution patterns of the positions of the subcarriers corresponding to the spatial streams are ⁇ (1) and ⁇ ( 3)
  • the positions of the corresponding subcarriers in LTF-1 and LTF-2 are respectively expressed as:
  • “1” and “0” respectively indicate that the spatial stream has and does not correspond to the subcarrier at the location, and therefore, the location of the corresponding subcarrier of the spatial stream 1 in the first field is: 1, 0, 1, 0. 1,1,0,1,0,1,0,1,0, ⁇ , that is, uniformly dispersed throughout the MIMO transmission band; the position of the corresponding subcarrier of the spatial stream 1 in the second field is exactly complementary: 0, 1,0,1,0,1,0,1,0,1,0,1,0,1, ⁇ , therefore, the subcarriers corresponding to spatial stream 1 in the two fields are combined, and the subcarrier corresponding to spatial stream 1 is in the whole In one field and the second field, all subcarrier positions in the MIMO transmission band are traversed.
  • the ordinates in Figures 3 and 4 also show the positional distribution of the corresponding subcarriers of the spatial streams in the entire first field and the second field, wherein the symbol " ⁇ " in Figures 3 and 4 indicates the spatial stream in phase. There should be a corresponding subcarrier at the location.
  • L 2
  • the first field and the second field each have only one OFDM symbol, LTF-1 and VLTF-1, respectively, using spatial stream subcarrier distribution patterns ⁇ (1) and ⁇ (3).
  • the position of the subcarrier corresponding to spatial stream 1 in LTF-1 is: 1,0,0,0,1,0,0,0,1,0,0,0, ⁇ , ie
  • the position of the corresponding subcarrier in the first field and the second field is: 1,0,1,0,1,0,1,0,1,0,1,0 , hehe.
  • the symbol "x" in FIG. 5 indicates that the spatial stream does not have a corresponding subcarrier at the corresponding position.
  • the positions of the subcarriers corresponding to the two-field spatial stream 1 are: 1,0,0,0,0,0,1,0,0,0,0,0, ⁇ and 1,0,1,0,0, 0,1,0,1,0,0,0,0, ⁇ , in contrast to FIG. 7, the positions of the subcarriers corresponding to the first field and the second field spatial stream 1 are: 1,0,1,0, respectively. 0,0,1,0,1,0,0,0, ⁇ and 1,0,0,0,0,0,1,0,0,0,0,0, ⁇ .
  • N 6
  • L 4
  • the position of the corresponding subcarrier in the entire first field and the second field of the spatial stream 1 is: 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 0, ⁇ .
  • each of the OFDM symbols of the first field and the second field sequentially corresponds to a different spatial stream.
  • each subcarrier in each OFDM symbol of the first field and the second field may sequentially correspond to a different spatial stream group.
  • Each subcarrier in each OFDM symbol of the first field and the second field sequentially corresponds to a different spatial stream group, and the spatial stream groups corresponding to the subcarriers in the same position in different OFDM symbols are different, and the spatial stream group includes K spatial streams.
  • the K spatial streams of each spatial stream group are orthogonally transformed, and are sequentially transmitted by subcarriers corresponding to the spatial stream group of K OFDM symbols in the first field; in the second field, The K spatial streams of each spatial stream group are orthogonally transformed, and are sequentially transmitted by subcarriers corresponding to the spatial stream group of K OFDM symbols in the second field.
  • the subcarriers corresponding to each spatial stream group in each OFDM symbol are orthogonal to each other, and at the same time, the spatial streams in each spatial stream group at the transmitting end are orthogonally transformed, and the K OFDM symbols are sequentially corresponding to the spatial stream group.
  • the subcarriers are transmitted, so that the receiving end can decompose each spatial stream in each spatial stream group from the K OFDM symbols through the orthogonal transform, and therefore, each spatial stream in each spatial stream group is also mutually Orthogonal.
  • channel estimates for each spatial stream on its corresponding subcarrier can be obtained directly.
  • the spatial streams 1, 2 form a spatial stream A group, and the spatial streams 3, 4 constitute a spatial stream B group.
  • the spatial stream A group corresponds to the sub-carriers of the odd-numbered position
  • the spatial stream B group corresponds to the sub-carriers of the even-numbered position
  • the spatial stream A group corresponds to subcarriers of odd positions. Therefore, taking the spatial stream A group as an example, combining the subcarriers corresponding to the spatial streams 1 and 2 in the two fields, the subcarriers corresponding to the spatial streams 1 and 2 traverse the MIMO transmission band in the entire first field and the second field. All subcarrier locations within.
  • the spatial streams 1, 2 form a spatial stream A group
  • the spatial streams 3, 4 constitute a spatial stream B group
  • the spatial streams 5, 6 constitute a spatial stream C group.
  • the position numbers of the subcarriers corresponding to the spatial streams A, B, and C are: 1, 4, 7, ..., 2, 5, 8, ..., and 3, 6, respectively.
  • the position numbers of the subcarriers corresponding to the spatial streams A, B, and C are: 2, 5, 8, ..., 3, 6, 9, ..., And 1, 4, 7... Therefore, taking the spatial stream A group as an example, combining the subcarriers corresponding to the spatial streams 1 and 2 in the two fields, The positions of the corresponding subcarriers of the subcarriers corresponding to the spatial streams 1 and 2 in the entire first field and the second field are: 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0 , hehe.
  • VLTF-2, VLTF-3, VLTF-4, spatial streams 1, 2 form a spatial stream A group, spatial streams 3, 4 constitute a spatial stream B group, and spatial streams 5, 6 constitute a spatial stream C group.
  • the position numbers of the subcarriers corresponding to the spatial streams A, B, and C are: 1, 4, 7, ..., 2, 5, 8, ..., and 3, 6, respectively.
  • the position numbers of the subcarriers corresponding to the spatial streams A, B, and C are: 2, 5, 8, ..., 3, 6, respectively.
  • the position numbers of the subcarriers corresponding to the spatial streams A, B, and C are respectively: 6, 9..., 1, 4, 7..., and 2, 5, 8...
  • the subcarriers corresponding to the spatial streams 1 and 2 traverse the MIMO transmission band in the entire first field and the second field. All subcarrier locations within.
  • the spatial streams 1 and 2 form a spatial stream A group
  • the spatial streams 3 and 4 form a spatial stream B group
  • the spatial streams 5 and 6 form a spatial stream C group
  • the spatial streams 7 and 8 constitute a spatial stream D group.
  • the position numbers of the subcarriers corresponding to the spatial stream A group, the B group, the C group, and the D group are: 1, 5, 9, ..., 2, 6, 10, ..., 3 7, 11, ..., and 4, 8, 12...; in the two OFDM symbols in the second field, the position numbers of the subcarriers corresponding to the spatial streams A, B, C, and D are respectively: 3 , 7, 11..., 4, 8, 12..., 1, 5, 9..., and 2, 6, 10... Therefore, taking the spatial stream A group as an example, combining the subcarriers corresponding to the spatial streams 1 and 2 in the two fields, the subcarriers corresponding to the spatial streams 1 and 2 traverse the MIMO transmission band in the entire first field and the second field. All subcarrier locations within.
  • FIG. 13 is another flowchart of a channel estimation method according to an embodiment of the present invention.
  • the channel estimation method shown in FIG. 13 is that, based on the method shown in FIG. 2, the access point uses the first reference signal carried by the first field and the useful information carried by the second field to obtain each Spatial flow
  • a scheme for estimating a first channel on all subcarriers in a MIMO transmission band is defined.
  • the channel estimation method provided by the embodiment of the present invention includes:
  • a preamble in a signal packet sent by the first communications node where the preamble includes a first field and a second field, where subcarriers of each orthogonal frequency division multiplexing OFDM symbol of the first field are used.
  • Carrying a first reference signal the first reference signal is a determination signal that is known by both the second communication node and the first communication node, and the subcarrier of each OFDM symbol of the second field is used to carry the useful information;
  • the useful information is physical layer control information, and/or data;
  • Step 901 can refer to the explanation and description of step 201 in the method embodiment shown in FIG. 2.
  • the first communication node may be, for example, a STA, a user equipment, or an access point
  • the second communication node may be, for example, a STA, an access point, or a user equipment.
  • the second communication node obtains a channel estimate of each spatial stream on a corresponding subcarrier in the first field by using a reference signal carried by the first field of the preamble; since the number of OFDM symbols of the first field is smaller than the number of spatial streams Therefore, it is necessary to obtain a second channel estimate of each spatial stream on all subcarriers in the MIMO transmission band by interpolation, wherein the interpolation can adopt various types of interpolation algorithms mature in the existing signal processing techniques.
  • the second communication node uses the above steps to obtain each spatial stream in the MIMO transmission frequency A second channel estimate on all subcarriers in the band, demodulation (such as constellation demapping, etc.) and decoding processing on the second field, and obtaining useful information carried by the second field.
  • the second field for transmitting physical layer control information generally BPSK modulation and convolutional coding with a coding rate of 1/2 are used, in which the receiver streams all subcarriers in the MIMO transmission band from each spatial stream.
  • the channel estimation on the subcarrier corresponding to each spatial stream is taken out, and the signal of each spatial stream is BPSK demodulated and channel decoded to obtain physical layer control information bits carried by the second field.
  • the information bits obtained by the demodulation and decoding process are re-encoded and modulated (such as constellation mapping) by using the same modulation and coding scheme, and the reference signals corresponding to the sub-carriers of the second field are generated. It is also possible to directly utilize the hard decision output of the second field demodulation process and perform remodulation using the same modulation method. Still taking the second layer to transmit physical layer control information as an example, since BPSK modulation and convolutional coding with a coding rate of 1/2 are adopted, even if the signal to noise ratio is low, the decoding can be successfully performed. Therefore, the receiver is decoded and then re-encoded.
  • the reference signal obtained by the modulation method has no difference compared with the reference signal directly transmitted by the transmitting end, so that the present invention can ensure the performance of the channel estimation is the same as that of the prior art while obtaining the benefit of greatly reducing the overhead.
  • the reference signal corresponding to each sub-carrier of the second field can be obtained by directly demodulating the hard-decision output re-modulation, thereby simplifying the operation of the channel estimation.
  • FIG. 14 is still another flowchart of a channel estimation method according to an embodiment of the present invention.
  • the channel estimation method provided by the embodiment of the present invention includes:
  • a preamble in the signal packet wherein the preamble includes a first field and a second a field, the subcarrier of each orthogonal frequency division multiplexing OFDM symbol of the first field is used to carry a first reference signal, where the first reference signal is determined by both the first communication node and the second communication node.
  • a signal, a subcarrier of each OFDM symbol of the second field is used to carry useful information; the useful information is physical layer control information, and/or data;
  • the execution body of the embodiment of the present invention may be the first communication node.
  • the first communication node may be, for example, a user equipment or an access point
  • the second communication node may be, for example, an access point or a user equipment.
  • the user equipment After determining the preamble in the uplink packet, the user equipment sends an uplink packet including the preamble to the access point, where the preamble includes a first field and a second field, and each orthogonal frequency division of the first field
  • the subcarriers that multiplex the OFDM symbols are used to carry reference signals, and the subcarriers of each OFDM symbol of the second field are used to carry useful information.
  • the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • FIG. 15 is a schematic structural diagram of a second communication node according to an embodiment of the present invention.
  • the second communication node 11 provided by the embodiment of the present invention includes:
  • the obtaining module 1101 is configured to obtain a preamble in a signal packet sent by the first communications node, where the preamble includes at least a first field and a second field, and the OFDM symbol of the first field is OFDM symbol
  • the carrier is configured to carry a first reference signal, where the first reference signal is a determining signal that is known by both the second communications node and the first communications node, and the subcarriers of the OFDM symbol of the second field are used to carry Useful information; the useful information is physical layer control information, and/or data;
  • the channel estimation module 1102 is configured to obtain, by using the first field and the second field of the preamble acquired by the acquiring module, a first channel estimate of each spatial stream on all subcarriers in a multiple input multiple output MIMO transmission frequency band.
  • the second communication node 11 provided by the embodiment of the present invention may be used to implement the technical solution of the method embodiment shown in FIG. 2, and the implementation principle thereof is similar, and details are not described herein again.
  • the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • each subcarrier in each OFDM symbol of the first field and the second field sequentially corresponds to a different spatial stream, and spatial streams corresponding to subcarriers in the same position in different OFDM symbols are different.
  • each of the OFDM symbols of the first field and the second field The subcarriers are sequentially corresponding to a different spatial stream group, and the spatial stream groups corresponding to the subcarriers in the same position in different OFDM symbols are different, and the spatial stream group includes K spatial streams; in the first field, each The K spatial streams of the spatial stream group are orthogonally transformed, and are sequentially transmitted by subcarriers corresponding to the spatial stream group of K OFDM symbols in the first field; in the second field, each space The K spatial streams of the stream group are orthogonally transformed, and are sequentially transmitted by subcarriers corresponding to the spatial stream group of K OFDM symbols in the second field.
  • the subcarrier is a subcarrier other than the guard subcarrier for removing adjacent frequency carrier in the MIMO transmission band and for suppressing
  • the channel estimation module 1102 is configured to: obtain, by using the first reference signal carried by the first field, a channel estimation of each spatial stream on a corresponding subcarrier in the first field;
  • a first channel estimate for each spatial stream on all subcarriers within the MIMO transmission band is obtained by combining channel estimates for the corresponding subcarriers in the first and second fields of each spatial stream.
  • FIG. 16 is a schematic structural diagram of a first communication node according to an embodiment of the present invention. As shown in FIG. 16, the first communication node 12 provided by the embodiment of the present invention includes:
  • a determining module 1201 configured to determine a preamble in the signal packet, where the preamble includes at least a first field and a second field, where the subcarriers of the orthogonal frequency division multiplexing OFDM symbol of the first field are used to carry the first a reference signal, the first reference signal is a determination signal known to both the second communication node and the first communication node, and the subcarrier of the OFDM symbol of the second field is used to carry useful information; Physical layer control information, and/or data;
  • the sending module 1202 is configured to send, to the second communications node, a signal packet including the preamble.
  • the user equipment 12 provided by the embodiment of the present invention may be used to implement the technical solution of the method embodiment shown in FIG. 14 , and the implementation principle thereof is similar, and details are not described herein again.
  • the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • FIG. 17 is another schematic structural diagram of a second communication node according to an embodiment of the present invention. As shown in FIG. 17, the second communication node 17 provided by the embodiment of the present invention includes:
  • the transceiver 1701 is configured to acquire a preamble in a signal packet sent by the first communications node, where the preamble includes at least a first field and a second field, and the OFDM of the first field is a sub-frequency division multiplexed OFDM symbol
  • the carrier is configured to carry a first reference signal, where the first reference signal is a determining signal that is known by both the second communications node and the first communications node, and the subcarriers of the OFDM symbol of the second field are used to carry Useful information; the useful information is physical layer control information, and/or data;
  • the processor 1702 is configured to obtain, by using the first field and the second field of the preamble acquired by the transceiver 1701, a first channel estimate of each spatial stream on all subcarriers in a multiple input multiple output MIMO transmission frequency band.
  • the second communication node 17 provided by the embodiment of the present invention may be used to implement the technical solution of the method embodiment shown in FIG. 2, and the implementation principle thereof is similar, and details are not described herein again.
  • the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • each subcarrier in each OFDM symbol of the first field and the second field sequentially corresponds to a different spatial stream, and spatial streams corresponding to subcarriers in the same position in different OFDM symbols are different.
  • each subcarrier in each OFDM symbol of the first field and the second field corresponds to a different spatial stream group, and the spatial stream groups corresponding to the subcarriers in the same position in different OFDM symbols are different.
  • the spatial stream group includes K spatial streams; in the first field, K spatial streams of each spatial stream group are orthogonally transformed, and sequentially by the K OFDM symbols in the first field Subcarrier transmission corresponding to the spatial stream group; in the second field, the K spatial streams of each spatial stream group are orthogonally transformed, and sequentially by the K OFDM symbols in the second field
  • the subcarrier is a subcarrier other than the guard subcarrier for removing adjacent frequency carrier in the MIMO transmission band and for suppressing adjacent channel leakage.
  • processor 1702 is specifically configured to:
  • a first channel estimate for each spatial stream on all subcarriers within the MIMO transmission band is obtained by combining channel estimates for the corresponding subcarriers in the first and second fields of each spatial stream.
  • FIG. 18 is another schematic structural diagram of a first communication node according to an embodiment of the present invention. As shown in FIG. 18, the first communication node 18 provided by the embodiment of the present invention includes:
  • the processor 1801 is configured to determine a preamble in the signal packet, where the preamble includes at least a first field and a second field, where the subcarrier of the Orthogonal Frequency Division Multiplexing OFDM symbol of the first field is used to carry the first a reference signal, the first reference signal is a determination signal known to both the second communication node and the first communication node, and the subcarrier of the OFDM symbol of the second field is used to carry useful information; Physical layer control information, and/or data;
  • the transmitter 1802 is configured to send a signal packet including the preamble to the second communication node.
  • the first communication node 18 provided by the embodiment of the present invention may be used to perform the technical solution of the method embodiment shown in FIG. 14 , and the implementation principle thereof is similar, and details are not described herein again. Compared with the prior art, the technical solution provided by the embodiment of the present invention greatly reduces signaling overhead and improves resource utilization.
  • FIG. 19 is a schematic structural diagram of a communication system according to an embodiment of the present invention.
  • the communication system 13 provided by the embodiment of the present invention includes: a second communication node 131 and a first communication node 132; wherein the second communication node 131 can be provided by any embodiment of the present invention.
  • the second communication node 11; the first communication node 132 can employ the first communication node 12 provided by any embodiment of the present invention.
  • the foregoing program may be stored in a computer readable storage medium, and the program is executed when executed.
  • the foregoing steps include the steps of the foregoing method embodiments; and the foregoing storage medium includes: a medium that can store program codes, such as a ROM, a RAM, a magnetic disk, or an optical disk.

Abstract

本发明实施例提供一种信道估计方法、通信节点及通信系统，其中，所述方法包括：获取第一通信节点发送的信号分组中的前导；前导至少包括第一字段和第二字段，第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，第一参考信号为第二通信节点和第一通信节点均已知的确定信号，第二字段的OFDM符号的子载波用于承载有用信息；有用信息为物理层控制信息，和/或数据；使用第一字段和第二字段，获得每个空间流在多输入多输出传输频带内所有子载波上的第一信道估计。本发明实施例提供的技术方案，在保证信道估计性能的同时，降低了信令开销，提高了资源利用率。

Description

信道估计方法、通信节点及通信系统 技术领域
本发明实施例涉及无线通信技术，尤其涉及一种信道估计方法、通信节点及通信系统。
背景技术
基于正交频分复用技术(英文：Orthogonal Frequency Division Multiplexing，简称：OFDM)的无线局域网(英文：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。其中，802.11n和802.11ac已经支持单用户多输入多输出(英文：Single User Multiple-Input Multiple-Output，简称：SU-MIMO)，802.11ac还支持下行多用户多输入多输出(英文：Multi-User Multiple-Input Multiple-Output，简称：MU-MIMO)。目前IEEE 802.11标准组织已经启动了称之为高效率无线局域网(英文：High Efficiency WLAN，简称：HEW)的新一代WLAN标准802.11ax的标准化工作，其中，正交频分多址(英文：Orthogonal Frequency Division Multiple Access，简称：OFDMA)和上行MU-MIMO是802.11ax的两项主要的关键技术。在SU-MIMO和MU-MIMO中，多个空间流通过MIMO方式并行传输，接收端需要首先获得MIMO信道的估计，才能对各个空间流进行解调等接收处理。例如，在上行MU-MIMO中，接入点(英文：Access Point，简称：AP)为了解调来自不同站点(英文：Station，简称：STA)的信号，可以通过各个STA发送的上行分组前导中的高效率长训练字段(英文：High Efficiency Long Training field，简称：HE-LTF)来获得上行MU-MIMO的信道估计。
图1为一种现有的HE-LTF方案的示意图。在该现有方案中，HE-LTF包含N个OFDM符号，其中，N为空间流的个数(当实际的空间流数为大于1的奇数时，N为实际的空间流数+1；当实际的空间流数为1时，N＝1)。每个OFDM符号的可用子载波均承载参考信号，并采用子载波(英文：Sub-carrier)交织的方式依次对应不同的空间流，其中，可用子载波至多为 MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波等以外的子载波。具体来说，一个OFDM符号中每个空间流对应的子载波数为M/N，其中M为可用子载波数，每个空间流在每个OFDM符号中依次对应不同的子载波，且与前一个OFDM符号中相应空间流对应的子载波错开一个子载波的位置。因此，经过N个OFDM符号后，每个空间流对应的子载波遍历所有的可用子载波的位置，且每个空间流对应的子载波相互正交。这样，利用HE-LTF中每个空间流对应的子载波承载的参考信号，就能获得相应空间流在每个可用子载波上的信道估计。
为了便于表述，本发明中将HE-LTF的第n个OFDM符号中各空间流对应的子载波的位置的分布图案定义为Ψ(n)，其中，不同空间流对应的子载波的位置用不同的符号区分，则下一个OFDM符号中各空间流对应的子载波的位置的分布图案可以表示为Ψ(n+1)，其中，“+1”表示该OFDM符号中各空间流对应的子载波的位置前移或后移一个子载波的位置。这样，在图1所示的现有HE-LTF方案中，N个OFDM符号中各空间流对应的子载波的位置的分布图案依次为Ψ(1),Ψ(2),Λ,Ψ(N)。
现有基于OFDM技术的WLAN系统所采用的OFDM符号长度为4us，为了支持室外应用及提高OFDMA的性能，802.11ax标准支持采用4倍或更长的OFDM符号长度。采用4倍OFDM符号长度，意味着每个OFDM符号的长度分别为16us，例如，对于典型的长度为1～3ms的WLAN分组，当传输8个空间流时HE-LTF的长度达到128us，其开销可达4.3％～12.8％，资源利用率低。
发明内容
本发明实施例提供一种信道估计方法、通信节点及通信系统，在保证信道估计性能的同时，降低了信令开销，提高了资源利用率。
本发明的第一个方面提供一种信道估计方法，所述方法包括：
获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承 载有用信息；所述有用信息为物理层控制信息，和/或数据；
使用所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
在第一方面的第一种可能的实现方式中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。
在第一方面的第二种可能的实现方式中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。
在第一方面的第三种可能的实现方式中，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
在第一方面的第四种可能的实现方式中，所述使用所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计包括：
使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
第二方面，本发明实施例提供一种信道估计方法，所述方法包括：
确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第一通信节点和第二通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
向所述第二通信节点发送包括所述前导的信号分组。
第三方面，本发明实施例提供一种第二通信节点，所述第二通信节点包括：
获取模块，用于获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为所述第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
信道估计模块，用于使用所述获取模块获取的所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
在第三方面的第一种可能的实现方式中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。
在第三方面的第二种可能的实现方式中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依 次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。
在第三方面的第三种可能的实现方式中，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
在第三方面的第四种可能的实现方式中，所述信道估计模块，具体用于：
使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
第四方面，本发明实施例提供一种第一通信节点，所述第一通信节点包括：
确定模块，用于确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
发送模块，用于向所述第二通信节点发送包括所述前导的信号分组。
第五方面，本发明实施例提供一种第二通信节点，所述第二通信节点包括：
收发器，用于获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为所述第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
处理器，用于使用所述收发器获取的所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
在第五方面的第一种可能的实现方式中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。
在第五方面的第二种可能的实现方式中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。
在第五方面的第三种可能的实现方式中，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
在第五方面的第四种可能的实现方式中，所述处理器，具体用于：
使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承 载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
第六方面，本发明实施例提供一种第一通信节点，所述第一通信节点包括：
处理器，用于确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
发送器，用于向所述第二通信节点发送包括所述前导的信号分组。
第七方面，本发明实施例提供一种通信系统，所述通信系统包括：
上述第三方面提供的任意一种第二通信节点，及上述第四方面提供的第一通信节点。
在本发明实施例提供的信道估计方法、通信节点及通信系统中，信号分组中的HE-LTF由两部分组成，第一部分每个OFDM符号的子载波用于承载参考信号，第二部分每个OFDM符号的子载波并不承载参考信号，而是用于承载有用信息，因此，实际用于信道估计的开销只是第一字段，由于第一字段中的OFDM符号数小于空间流的数目，因此，与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
附图说明
图1为一种现有的HE-LTF方案的示意图；
图2为本发明实施例提供的信道估计方法的流程图；
图3为本发明实施例中第一字段和第二字段中各空间流(N＝2)对应的子载波的位置的分布图；
图4为本发明实施例中第一字段和第二字段中各空间流(N＝4)对应的子载波的位置的分布图；
图5为本发明实施例中第一字段和第二字段中各空间流(N＝4)对应的子载波的位置的另一分布图；
图6为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的分布图；
图7为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的另一分布图；
图8为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的又一分布图；
图9为本发明实施例中第一字段和第二字段中各空间流(N＝4)对应的子载波的位置的又一分布图；
图10为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的再一分布图；
图11为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的还一分布图；
图12为本发明实施例中第一字段和第二字段中各空间流(N＝8)对应的子载波的位置的分布图；
图13为本发明实施例提供的信道估计方法的另一流程图；
图14为本发明实施例提供的信道估计方法的又一流程图；
图15为本发明实施例提供的第二通信节点的结构示意图；
图16为本发明实施例提供的第一通信节点的结构示意图；
图17为本发明实施例提供的第二通信节点的另一结构示意图；
图18为本发明实施例提供的第一通信节点的另一结构示意图；
图19为本发明实施例提供的通信系统的结构示意图。
具体实施方式
802.11ax信号分组由前导和数据字段两部分组成；其中，前导包括传统前导(英文：Legacy Preamble)和HEW前导；HEW前导是802.11ax分组特定的前导，至少包括信令字段和训练字段等部分，其中，信令字段用于传输 物理层控制信息，训练字段包括用于自动增益控制、为信道估计提供参考信号等功能，HE-LTF即是训练字段的一部分。
在本发明实施例提出的信道估计方法中，第一通信节点发送给第二通信节点的信号分组的前导至少包括第一字段和第二字段，所述第一字段的OFDM符号数小于空间流的数目，且所述第一字段和第二字段的OFDM符号数之和不大于空间流的个数。其中，第一字段每个OFDM符号的子载波均承载参考信号，所述参考信号为第一通信节点和第二通信节点均已知的确定信号，典型地可采用二相相移键控(英文：Binary Phase Shift Keying，简称：BPSK)、四相相移键控(英文：Quadrature Phase Shift Keying，简称：QPSK)等调制符号；第二字段每个OFDM符号的子载波并不承载参考信号，而是用于传输有用信息，所述有用信息可以是物理层控制信息的全部或一部分，和/或，所述信号分组传输的数据的全部或一部分。
在本发明实施例提出的信道估计方法中，可以将所述第一字段和第二字段分别理解为HE-LTF字段的第一部分和第二部分，这样，本发明中HE-LTF字段除了具有为信道估计提供参考信号的功能外，还具有传输全部或部分物理层控制信息、和/或，全部或部分数据的功能。同时，也可以将所述第一字段理解为HE-LTF字段，而将第二字段理解为信令字段的一部分或全部，和或，数据字段的一部分或全部，这样，本发明中第二字段除了具有传输全部或部分物理层控制信息、和/或全部或部分数据的功能外，还具有与所述第一字段一起为信道估计提供参考信号的功能。
本领域普通技术人员可以理解：上述两种理解方式的本质是相同的，无论按照那种方式理解，都不影响本发明所提出的技术方案的实施。
图2为本发明实施例提供的信道估计方法的流程图。如图2所示，本发明实施例提供的信道估计方法，包括：
201、获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的每个正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的每个OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
202、使用所述前导第一字段及所述第二字段，获得每个空间流在 MIMO传输频带内所有子载波上的第一信道估计。
本发明实施例的执行主体可以是无线通信系统中的通信节点，例如第二通信节点，且第二通信节点与第一通信节点之间进行通信。可选的，所述第一通信节点例如可以是STA、用户设备或接入点，所述第二通信节点例如可以是STA、接入点或用户设备。
可以理解，本发明实施例中所述的子载波，是指MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
第一通信节点确定信号分组中的前导，并向第二通信节点发送包括所述前导的信号分组。其中，所述前导至少包括第一字段和第二字段，所述第一字段的每个正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的每个OFDM符号的子载波用于承载有用信息。第二通信节点获取第一通信节点发送的信号分组中的前导后，使用所述第一字段及所述第二字段，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计；然后，第二通信节点使用所述第一信道估计解调第一通信节点发送的信号。
由于第二字段每个OFDM符号的子载波并不承载参考信号，而是用于传输有用信息，实际用于信道估计的开销只是第一字段，由于第一字段中的OFDM符号数小于空间流的数目，因此，与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
在具体的实施例中，例如：空间流的个数N，第一通信节点发送的信号分组中总共包含L个OFDM符号，其中，第一字段和第二字段分别包含L1和L2个OFDM符号，即，L1+L2＝L，其中，L≤N。所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。这样，每个OFDM符号中各空间流对应的子载波相互正交，对于信道估计而言，可以直接获得各空间流在其对应的子载波上的信道估计，对第二字段承载的有用信息而言，相当于采用OFDMA的方式进行传输。
如果将所述第一字段和第二字段的各OFDM符号中各空间流对应的子载波的位置的分布图案的集合分别表示为π1和π2，而将图1所示子载波交织方 案中N个OFDM符号中各空间流对应的子载波的位置的分布图案的集合表示为Φ，则π1和π2均是Φ的子集，而它们之间的交集为空，即π1∩π2＝φ，其中φ表示空集。特别地，当L＝N时，π1∪π2＝Φ，即每个空间流对应的子载波在整个第一字段和第二字段中遍历MIMO传输频带内所有的子载波位置。
当L<N时，每个空间流对应的子载波在整个第一字段和第二字段中不能遍历MIMO传输频带内所有的子载波位置。优选地，π1和π2的选择应使得每个空间流在所述第一字段和整个第一字段和第二字段中对应的所有子载波，尽可能均匀分散在整个MIMO传输频带内。图3为本发明实施例中第一字段和第二字段中各空间流(N＝2)对应的子载波的位置的分布图。图4为本发明实施例中第一字段和第二字段中各空间流(N＝4)对应的子载波的位置的分布图。显然，在图3和图4所示实施例中：L＝N。
在图3所示实施例中，第一字段和第二字段均只有一个OFDM符号，分别用LTF-1和VLTF-1表示，各空间流对应的子载波的位置的分布图案分别采用Ψ(1)、Ψ(2)，即有：π1＝{Ψ(1)}、π2＝{Ψ(2)}、π＝Φ＝{Ψ(1),Ψ(2)}。
在图4所示实施例中，HE-LTF的第一字段有两个OFDM符号LTF-1和LTF-2，各空间流对应的子载波的位置的分布图案分别为Ψ(1)与Ψ(3)，第二字段也有两个OFDM符号VLTF-1、VLTF-2，各空间流对应的子载波的位置的分布图案分别为Ψ(2)与Ψ(4)。因此，在该实施例中，π1＝{Ψ(1),Ψ(3)}、π2＝{Ψ(2),Ψ(4)}、π＝Φ＝{Ψ(1),Ψ(2),Ψ(3),Ψ(4)}。以空间流1为例，其对应的子载波在LTF-1和LTF-2中的位置分别表示为：
1,0,0,0,1,0,0,0,1,0,0,0,Λ，和0,0,1,0,0,0,1,0,0,0,1,0,Λ
其中，“1”和“0”分别表示该空间流在该位置有和没有对应的子载波，因此，空间流1在第一字段的对应的子载波的位置为：1,0,1,0,1,0,1,0,1,0,1,0,Λ，即均匀分散在整个MIMO传输频带内；空间流1在第二字段的对应的子载波的位置正好与之互补：0,1,0,1,0,1,0,1,0,1,0,1,Λ，因此，合并这两个字段中空间流1对应的子载波，空间流1对应的子载波在整个第一字段和第二字段中即遍历MIMO传输频带内所有的子载波位置。
图3和图4中纵坐标也表示了各空间流在整个第一字段和第二字段中的对应子载波的位置分布，其中，图3和图4中的符号“●”表示空间流在相 应位置有对应的子载波。
图5为本发明实施例中第一字段和第二字段中各空间流(N＝4)对应的子载波的位置的另一分布图。在该实施例中L＝2，第一字段和第二字段均只有一个OFDM符号，即LTF-1和VLTF-1，分别采用空间流子载波分布图案Ψ(1)和Ψ(3)。以空间流1为例，空间流1对应的子载波在LTF-1中的位置为：1,0,0,0,1,0,0,0,1,0,0,0,Λ，即每间隔3个子载波空位出现一次，在整个第一字段和第二字段中对应的子载波的位置为：1,0,1,0,1,0,1,0,1,0,1,0,Λ。其中，图5中的符号“×”表示空间流在相应位置没有对应的子载波。
图6为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的分布图。图7为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的另一分布图。图6和图7分别示出了L＝3时的两个不同实施例。这两个实施例均选取π＝{Ψ(1),Ψ(3),Ψ(5)}，区别是π1和π2不同，以空间流1为例，图6中第一字段和第二字段空间流1对应的子载波的位置分别为：1,0,0,0,0,0,1,0,0,0,0,0,Λ和1,0,1,0,0,0,1,0,1,0,0,0,Λ，图7则与之反，第一字段和第二字段空间流1对应的子载波的位置分别为：1,0,1,0,0,0,1,0,1,0,0,0,Λ和1,0,0,0,0,0,1,0,0,0,0,0,Λ。
图8为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的又一分布图。在该实施例中N＝6，L＝4，其中π1＝{Ψ(1),Ψ(4)}、π2＝{Ψ(2),Ψ(5)}。因此，以空间流1为例，第一字段和第二字段空间流对应的子载波的位置分别为：
1,0,0,1,0,0,1,0,0,1,0,0,Λ，和0,1,0,0,1,0,0,1,0,0,1,0,Λ，
空间流1在整个第一字段和第二字段中对应的子载波的位置为：1,1,0,1,1,0,1,1,0,1,1,0,Λ。
在上述具体的实施例中，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流。可选的，第一字段和第二字段的每个OFDM符号中的每个子载波可以依次对应一个不同的空间流组。仍以空间流的个数N举例进行说明：第一通信节点发送的信号分组中总共包含L个OFDM符号，其中，第一字段和第二字段分别包含L1和L2个OFDM符号，即，L1+L2＝L，其中，L≤N，L1＝mK，L2＝nK，K≥2。第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流 组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流。在第一字段中，每个空间流组的K个空间流经过正交变换，依次由第一字段中的K个OFDM符号的与该空间流组对应的子载波传输；在第二字段中，每个空间流组的K个空间流经过正交变换，依次由第二字段中的K个OFDM符号的与该空间流组对应的子载波传输。
这样，每个OFDM符号中各空间流组对应的子载波相互正交，同时，在发射端各空间流组中的空间流经过正交变换，依次由K个OFDM符号的与该空间流组对应的子载波发送，因此接收端经过所述正交变换，即可从所述K个OFDM符号中分解出各空间流组中的各个空间流，因此，各空间流组中的各空间流也是相互正交的。这样，对于信道估计而言，可以直接获得各空间流在其对应的子载波上的信道估计。
图9为本发明实施例中第一字段和第二字段中各空间流(N＝4)对应的子载波的位置的又一分布图。在该实施例中，m＝1，n＝1，K＝2，因此第一字段和第二字段均有两个OFDM符号，即LTF-1、LTF-2和VLTF-1、VLTF-2，空间流1、2组成空间流A组，空间流3、4组成空间流B组。在第一字段中的两个OFDM符号中，空间流A组对应奇数位置的子载波，空间流B组对应偶数位置的子载波；在第二字段中的两个OFDM符号中，空间流A组对应偶数位置的子载波，空间流B组对应奇数位置的子载波。因此，以空间流A组为例，合并这两个字段中空间流1和2对应的子载波，空间流1和2对应的子载波在整个第一字段和第二字段中即遍历MIMO传输频带内所有的子载波位置。
图10为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的再一分布图。在该实施例中，m＝1，n＝1，K＝2，因此第一字段和第二字段均有两个OFDM符号，即LTF-1、LTF-2和VLTF-1、VLTF-2，空间流1、2组成空间流A组，空间流3、4组成空间流B组，空间流5、6组成空间流C组。在第一字段中的两个OFDM符号中，空间流A组、B组和C组对应的子载波的位置序号分别为：1、4、7…，2、5、8…，和3、6、9…，在第二字段中的两个OFDM符号中，空间流A组、B组和C组对应的子载波的位置序号分别为：2、5、8…，3、6、9…，和1、4、7…。因此，以空间流A组为例，合并这两个字段中空间流1和2对应的子载波， 空间流1和2对应的子载波在整个第一字段和第二字段中对应的子载波的位置为：1,1,0,1,1,0,1,1,0,1,1,0,Λ。
图11为本发明实施例中第一字段和第二字段中各空间流(N＝6)对应的子载波的位置的还一分布图。在该实施例中，m＝1，n＝2，K＝2，因此第一字段有两个OFDM符号，即LTF-1、LTF-2，第二字段有4个OFDM符号，即VLTF-1、VLTF-2、VLTF-3、VLTF-4，空间流1、2组成空间流A组，空间流3、4组成空间流B组，空间流5、6组成空间流C组。在第一字段中的两个OFDM符号中，空间流A组、B组和C组对应的子载波的位置序号分别为：1、4、7…，2、5、8…，和3、6、9…，在第二字段中的VLTF-1、VLTF-2符号中，空间流A组、B组和C组对应的子载波的位置序号分别为：2、5、8…，3、6、9…，和1、4、7…，在第二字段中的VLTF-3、VLTF-4符号中，空间流A组、B组和C组对应的子载波的位置序号分别为：3、6、9…，1、4、7…，和2、5、8…。因此，以空间流A组为例，合并这两个字段中空间流1和2对应的子载波，空间流1和2对应的子载波在整个第一字段和第二字段中即遍历MIMO传输频带内所有的子载波位置。
图12为本发明实施例中第一字段和第二字段中各空间流(N＝8)对应的子载波的位置的分布图。在该实施例中，m＝1，n＝1，K＝2，因此第一字段和第二字段均有两个OFDM符号，即LTF-1、LTF-2和VLTF-1、VLTF-2，空间流1、2组成空间流A组，空间流3、4组成空间流B组，空间流5、6组成空间流C组，空间流7、8组成空间流D组。在第一字段中的两个OFDM符号中，空间流A组、B组、C组和D组对应的子载波的位置序号分别为：1、5、9…，2、6、10…，3、7、11…，和4、8、12…；在第二字段中的两个OFDM符号中，空间流A组、B组、C组和D组对应的子载波的位置序号分别为：3、7、11…，4、8、12…，1、5、9…，和2、6、10…。因此，以空间流A组为例，合并这两个字段中空间流1和2对应的子载波，空间流1和2对应的子载波在整个第一字段和第二字段中即遍历MIMO传输频带内所有的子载波位置。
图13为本发明实施例提供的信道估计方法的另一流程图。图13所示的信道估计方法，是在图2所示方法的基础上，对接入点使用所述第一字段承载的第一参考信号及所述第二字段承载的有用信息，获得每个空间流在 MIMO传输频带内所有子载波上的第一信道估计的方案进行了限定，如图13所示，本发明实施例提供的信道估计方法，包括：
901、获取第一通信节点发送的信号分组中的前导；其中，所述前导包括第一字段和第二字段，所述第一字段的每个正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的每个OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
902、使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
903、通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
904、使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
905、采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
906、使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
907、通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
步骤901可以参照图2所示方法实施例中针对步骤201的解释和说明。
可选的，所述第一通信节点例如可以是STA、用户设备或接入点，所述第二通信节点例如可以是STA、接入点或用户设备。第二通信节点通过使用前导的第一字段承载的参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；由于第一字段的OFDM符号数小于空间流的个数，因此，需要通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计，其中，内插可以采用现有信号处理技术中成熟的各类内插算法。
然后，第二通信节点利用上述步骤获得的每个空间流在MIMO传输频 带内所有子载波上的第二信道估计，对所述第二字段解调(如星座去映射等操作)和解码处理，获取所述第二字段承载的有用信息。以第二字段用于传输物理层控制信息为例，通常采用BPSK调制和编码速率为1/2的卷积编码，在该步骤中，接收机从每个空间流在MIMO传输频带内所有子载波上的信道估计中，取出每个空间流对应的子载波上的信道估计，对每个空间流的信号进行BPSK解调和信道解码，获得第二字段承载的物理层控制信息比特。
接着，对上述解调和解码处理获得的信息比特，采用相同的调制编码方式，重新进行编码和调制(如星座映射等操作)，生成所述第二字段的各子载波对应的参考信号。也可以直接利用第二字段解调过程的硬判决输出，采用相同的调制方式进行重新调制。仍以第二字段传输物理层控制信息为例，由于采用BPSK调制和编码速率为1/2的卷积编码，即使信噪比很低也可以成功解码，因此，采用接收端解码后再重新编码和调制的方式获得的参考信号，与发射端直接发送的参考信号相比，没有任何区别，因此可以保证本发明在获得开销大大降低的好处的同时，信道估计的性能与现有技术相同。当信噪比较高时，可以直接利用解调硬判决输出重新调制的方式来获得第二字段各子载波对应的参考信号，从而简化信道估计的操作。
然后，第二通信节点使用所述第二字段的各子载波对应的参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；由于第一字段和第二字段所采用的空间流子载波分布图案互不重叠，因此，当L＝N时，接收机合并每个空间流在第一和第二字段相应子载波上的信道估计，就能获得每个空间流在MIMO传输频带内所有子载波上的信道估计；当L<N时，接收机合并每个空间流在第一和第二字段相应子载波上的信道估计后，进一步采用二次内插，即可获得每个空间流在MIMO传输频带内所有子载波上的信道估计。至此，第二通信节点就可以使用上行信道估计解调用户设备发送的信号。
图14为本发明实施例提供的信道估计方法的又一流程图。如图14所示，本发明实施例提供的信道估计方法，包括：
1001、确定信号分组中的前导；其中，所述前导包括第一字段和第二 字段，所述第一字段的每个正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第一通信节点和第二通信节点均已知的确定信号，所述第二字段的每个OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
1002、向所述第二通信节点发送包括前导的信号分组。
本发明实施例的执行主体可以是第一通信节点。可选的，所述第一通信节点例如可以是用户设备或接入点，所述第二通信节点例如可以是接入点或用户设备。用户设备在确定上行分组中的前导后，向接入点发送包括所述前导的上行分组，其中，所述前导包括第一字段和第二字段，所述第一字段的每个正交频分复用OFDM符号的子载波用于承载参考信号，所述第二字段的每个OFDM符号的子载波用于承载有用信息。与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
图15为本发明实施例提供的第二通信节点的结构示意图。如图15所示，本发明实施例提供的第二通信节点11，包括：
获取模块1101，用于获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为所述第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
信道估计模块1102，用于使用所述获取模块获取的所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
本发明实施例提供的第二通信节点11可以用于执行图2所示方法实施例的技术方案，其实现原理类似，在此不再赘述。与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
可选的，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。可选的，所述第一字段和第二字段的每个OFDM符号中的每个 子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。可选的，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
可选的，所述信道估计模块1102，具体用于：使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
图16为本发明实施例提供的第一通信节点的结构示意图。如图16所示，本发明实施例提供的第一通信节点12，包括：
确定模块1201，用于确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
发送模块1202，用于向所述第二通信节点发送包括所述前导的信号分组。
本发明实施例提供的用户设备12可以用于执行图14所示方法实施例的技术方案，其实现原理类似，在此不再赘述。与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
图17为本发明实施例提供的第二通信节点的另一结构示意图。如图17所示，本发明实施例提供的第二通信节点17，包括：
收发器1701，用于获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为所述第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
处理器1702，用于使用所述收发器1701获取的所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
本发明实施例提供的第二通信节点17可以用于执行图2所示方法实施例的技术方案，其实现原理类似，在此不再赘述。与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
可选的，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。可选的，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。可选的，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
可选的，所述处理器1702，具体用于：
使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
图18为本发明实施例提供的第一通信节点的另一结构示意图。如图18所示，本发明实施例提供的第一通信节点18，包括：
处理器1801，用于确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
发送器1802，用于向所述第二通信节点发送包括所述前导的信号分组。
本发明实施例提供的第一通信节点18可以用于执行图14所示方法实施例的技术方案，其实现原理类似，在此不再赘述。与现有技术相比，本发明实施例提供的技术方案极大地降低了信令开销，提高了资源利用率。
图19为本发明实施例提供的通信系统的结构示意图。如图19所示，本发明实施例提供的通信系统13，包括：第二通信节点131及第一通信节点132；其中，所述第二通信节点131可以采用本发明任意实施例所提供的 第二通信节点11；所述第一通信节点132可以采用本发明任意实施例所提供的第一通信节点12。
本领域普通技术人员可以理解：实现上述方法实施例的全部或部分步骤可以通过程序指令相关的硬件来完成，前述的程序可以存储于一计算机可读取存储介质中，该程序在执行时，执行包括上述方法实施例的步骤；而前述的存储介质包括：ROM、RAM、磁碟或者光盘等各种可以存储程序代码的介质。
最后应说明的是：以上各实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述各实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明各实施例技术方案的范围。

Claims (19)

  1. 一种信道估计方法，其特征在于，包括：
    获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
    使用所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
  2. 根据权利要求1所述的方法，其特征在于，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。
  3. 根据权利要求1所述的方法，其特征在于，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。
  4. 根据权利要求1所述的方法，其特征在于，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
  5. 根据权利要求1所述的方法，其特征在于，所述使用所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计包括：
    使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
    通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
    使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第 二字段承载的有用信息；
    采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
    使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
    通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
  6. 一种信道估计方法，其特征在于，包括：
    确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第一通信节点和第二通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
    向所述第二通信节点发送包括所述前导的信号分组。
  7. 一种第二通信节点，其特征在于，包括：
    获取模块，用于获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为所述第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
    信道估计模块，用于使用所述获取模块获取的所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
  8. 根据权利要求7所述的第二通信节点，其特征在于，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。
  9. 根据权利要求7所述的第二通信节点，其特征在于，所述第一字段 和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。
  10. 根据权利要求7所述的第二通信节点，其特征在于，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
  11. 根据权利要求7所述的第二通信节点，其特征在于，所述信道估计模块，具体用于：
    使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一字段中对应子载波上的信道估计；
    通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
    使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
    采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
    使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
    通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
  12. 一种第一通信节点，其特征在于，包括：
    确定模块，用于确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信 节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
    发送模块，用于向所述第二通信节点发送包括所述前导的信号分组。
  13. 一种第二通信节点，其特征在于，包括：
    收发器，用于获取第一通信节点发送的信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为所述第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
    处理器，用于使用所述收发器获取的所述前导的第一字段和第二字段，获得每个空间流在多输入多输出MIMO传输频带内所有子载波上的第一信道估计。
  14. 根据权利要求13所述的第二通信节点，其特征在于，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流，不同OFDM符号中相同位置的子载波对应的空间流均不相同。
  15. 根据权利要求13所述的第二通信节点，其特征在于，所述第一字段和第二字段的每个OFDM符号中的每个子载波依次对应一个不同的空间流组，不同OFDM符号中相同位置的子载波对应的空间流组均不相同，所述空间流组包括K个空间流；在所述第一字段中，每个空间流组的K个空间流经过正交变换，依次由所述第一字段中的K个OFDM符号的与所述空间流组对应的子载波传输；在所述第二字段中，每个空间流组的所述K个空间流经过正交变换，依次由所述第二字段中的K个OFDM符号的与所述空间流组对应的子载波传输。
  16. 根据权利要求13所述的第二通信节点，其特征在于，所述子载波为MIMO传输频带内除去零频子载波、用于抑制邻道泄漏的保护子载波以外的子载波。
  17. 根据权利要求13所述的第二通信节点，其特征在于，所述处理器，具体用于：
    使用所述第一字段承载的第一参考信号，获得每个空间流在所述第一 字段中对应子载波上的信道估计；
    通过内插获得每个空间流在MIMO传输频带内所有子载波上的第二信道估计；
    使用所述第二信道估计对所述第二字段进行解调和解码，获取所述第二字段承载的有用信息；
    采用与所述解调和解码操作相同的调制编码方式，对所述第二字段承载的有用信息重新进行编码和调制，生成所述第二字段的各OFDM符号的各子载波对应的第二参考信号；
    使用所述第二字段的各OFDM符号的各子载波对应的第二参考信号，获得每个空间流在所述第二字段中对应子载波上的信道估计；
    通过合并每个空间流在所述第一字段及第二字段中对应子载波上的信道估计，获得每个空间流在MIMO传输频带内所有子载波上的第一信道估计。
  18. 一种第一通信节点，其特征在于，包括：
    处理器，用于确定信号分组中的前导；其中，所述前导至少包括第一字段和第二字段，所述第一字段的正交频分复用OFDM符号的子载波用于承载第一参考信号，所述第一参考信号为第二通信节点和所述第一通信节点均已知的确定信号，所述第二字段的OFDM符号的子载波用于承载有用信息；所述有用信息为物理层控制信息，和/或数据；
    发送器，用于向所述第二通信节点发送包括所述前导的信号分组。
  19. 一种通信系统，其特征在于，包括：
    如权利要求7-11任一所述的第二通信节点，及如权利要求12所述的第一通信节点。
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