This application relates to the field of communications technologies, and in particular, to a data sending method, a channel estimation method, and apparatuses thereof.
With rapid development of network technologies and mobile devices, a wireless local area network (Wireless Local Area Network, WLAN for short) technology based on the Institute of Electrical and Electronics Engineers (Institute of Electrical and Electronics Engineers, IEEE for short) 802.11 standard gains considerable development and wide application. There are mainly 802.11, 802.11b/g/a, 802.11n, 802.11ac, and 802.11ax that is in formulation. An orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM for short) technology is used as a core technology at a physical layer in the standards other than 802.11 and 802.11b.
In coherent detection of an OFDM system, channel estimation needs to be performed. Channel estimation refers to a process in which a parameter of a channel passed through by a transmit signal is obtained by performing estimation according to a received signal by using a criterion. In the 802.11n and 802.11ac standards, a multiple-input multiple-output (Multi-input Multi-output, MIMO for short) technology is used to improve a channel capacity, increase a system scope, and improve reliability. A received signal is a superposed signal of multiple transmit signals, where these transmit signals are simultaneously transmitted by multiple transmit antennas and almost synchronously reach a receive antenna. Therefore, a channel estimation algorithm of a MIMO system is more complex than that of a single-antenna system. To correctly identify multiple transmit signals in one superposed signal, channel features of multiple parallel channels from transmit antennas to a same receive antenna need to be estimated by using a channel estimation algorithm.
A common ground shared by the foregoing WLAN standards in which the OFDM technology is used as a core technology is that a method for generating a long training field (Long Training Field, LTF for short) that can be used for channel estimation is specified for a physical layer, and the LTF includes one or more symbols. The symbol is, for example, an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexing, OFDM for short) symbol. A long training sequence (Long Training Sequence, LTS for short) may be carried in a frequency domain of the symbol.
In a MIMO scenario, if the LTF includes only one symbol, after receiving the symbol, a receive end cannot distinguish between symbols corresponding to multiple spatial flows, and therefore, cannot perform channel estimation.
Therefore, to implement MIMO channel estimation, in the 802.11n standard, in a high throughput long training field (High Throughput LTF, HT-LTF for short), a single symbol is extended in a time domain by using an orthogonal code word. As shown in
It may be seen from
In the 802.11ac standard, a very high throughput long training field (Very HT-LTF, VHT-LTF for short) is generated by using the same method, and channel estimation is performed on multiple spatial flows in a MIMO scenario by using the generated VHT-LTF.
The foregoing method for generating an LTF is simple. However, system overheads are relatively high. For example, when an access point (Access Point, AP for short) simultaneously sends eight spatial flows, eight symbols need to be sent in each spatial flow, which causes a relatively low system throughput.
This application provides a data sending method, a channel estimation method, and apparatuses thereof to resolve a technical problem in the prior art that a method for generating a long training field causes relatively high system overheads.
A first aspect of this application provides a data sending method, including:
performing Fourier transform on a first time domain sequence to obtain a first frequency domain sequence, where the first time domain sequence is a sequence with an autocorrelation property;
determining, according to a maximum multipath delay of a system transmission channel, bandwidth of the channel, and a subcarrier quantity NFFT, a maximum quantity of spatial flows that can be supported by a single symbol;
determining, in a parameter configuration table according to a total quantity of spatial flows, a cyclic shift parameter corresponding to each spatial flow, where the cyclic shift parameter represents a time sequence shift value of the first time domain sequence;
obtaining a long training field LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter; and
sending the LTF and indication information to each receive end, where the indication information includes a number of a spatial flow allocated to each receive end.
With reference to the first aspect, in a first possible implementation manner of the first aspect, the indication information further includes symbol data of each receive end, and the symbol quantity is obtained by performing the following step:
determining the symbol quantity according to the total quantity of spatial flows and the maximum quantity of spatial flows.
With reference to the first aspect or the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the method further includes:
determining, in the parameter configuration table according to the total quantity of spatial flows, an orthogonal mapping matrix corresponding to each spatial flow; and
the obtaining a long training field LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter includes:
obtaining the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix.
With reference to the first aspect, the first possible implementation manner of the first aspect, or the second possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
With reference to the third possible implementation manner of the first aspect, in a fourth possible implementation manner of the first aspect, the obtaining the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix includes:
obtaining a second frequency domain sequence of each spatial flow according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix;
performing inverse Fourier transform on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow; and
adding up second time domain sequences corresponding to all the spatial flows, to obtain the LTF.
With reference to any one of the first aspect, or the first possible implementation manner of the first aspect to the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner of the first aspect, the determining, according to a maximum multipath delay of the channel, bandwidth of the channel, and a subcarrier quantity NFFT, a maximum quantity of spatial flows that can be supported by a single symbol includes:
dividing the subcarrier quantity NFFT by the bandwidth to obtain an inverse discrete Fourier transform IDFT period of an orthogonal frequency division multiplexing OFDM symbol; and
dividing the IDFT period by the maximum multipath delay to obtain the maximum quantity of spatial flows that can be supported by a single symbol.
With reference to any one of the first aspect, or the first possible implementation manner of the first aspect to the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner of the first aspect, a length of the first time domain sequence is N, and N is a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block; and
a length of the first frequency domain sequence is the subcarrier quantity NFFT.
A second aspect of this application provides a channel estimation method, including:
receiving a long training field LTF and indication information that are sent by a transmit end, where the indication information includes a number of a spatial flow allocated to a receive end;
obtaining a total quantity of spatial flows and a maximum quantity of spatial flows that can be supported by a single symbol;
determining, in a parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, a cyclic shift parameter corresponding to the spatial flow, where the cyclic shift parameter represents a time sequence shift value of a first time domain sequence, and the first time domain sequence is a sequence with an autocorrelation property; and
determining, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, a length N of the first time domain sequence, the number of the spatial flow, and the received LTF, a frequency domain channel estimation value corresponding to the spatial flow.
With reference to the second aspect, in a first possible implementation manner of the second aspect, the method further includes:
determining, in the parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, an orthogonal mapping matrix corresponding to the spatial flow; and
the determining, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, a length N of the first time domain sequence, the number of the spatial flow, and the received LTF, a frequency domain channel estimation value corresponding to the spatial flow includes:
determining, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the number of the spatial flow, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the first possible implementation manner of the second aspect, in a second possible implementation manner of the second aspect, the determining, according to the cyclic shift parameter, the maximum quantity of spatial flows that can be supported by a single symbol, the first time domain sequence, the length N of the first time domain sequence, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow includes:
determining a window function according to the cyclic shift parameter, the maximum quantity of spatial flows that can be supported by a single symbol, and the length N of the first time domain sequence;
merging the received LTF according to the number of the spatial flow and the orthogonal mapping matrix;
obtaining a second estimated time domain sequence according to an LTF obtained after the merging;
performing Fourier transform on the second estimated time domain sequence to obtain a first estimated frequency domain sequence;
extracting, from the first frequency domain sequence, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end;
performing inverse Fourier transform on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence;
processing the at least one third time domain sequence and the first time domain sequence by using the window function, to obtain at least one fourth estimated time domain sequence; and
separately performing Fourier transform on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the second aspect, the first possible implementation manner of the second aspect, or the second possible implementation manner of the second aspect, in a third possible implementation manner of the second aspect, the length N of the first time domain sequence is specifically a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block is the length N.
With reference to any one of the second aspect, or the first possible implementation manner of the second aspect to the third possible implementation manner of the second aspect, in a fourth possible implementation manner of the second aspect, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
A third aspect of this application provides a data sending apparatus, including:
a processing unit, configured to: perform Fourier transform on a first time domain sequence to obtain a first frequency domain sequence, where the first time domain sequence is a sequence with an autocorrelation property; determine, according to a maximum multipath delay of a system transmission channel, bandwidth of the channel, and a subcarrier quantity NFFT, a maximum quantity of spatial flows that can be supported by a single symbol; determine, in a parameter configuration table according to a total quantity of spatial flows, a cyclic shift parameter corresponding to each spatial flow, where the cyclic shift parameter represents a time sequence shift value of the first time domain sequence; and obtain a long training field LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter; and
a sending unit, configured to send the LTF and indication information to each receive end, where the indication information includes a number of a spatial flow allocated to each receive end.
With reference to the third aspect, in a first possible implementation manner of the third aspect, the processing unit is further configured to determine a symbol quantity according to the total quantity of spatial flows and the maximum quantity of spatial flows.
With reference to the third aspect or the first possible implementation manner of the third aspect, in a second possible implementation manner of the third aspect, the processing unit is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows, an orthogonal mapping matrix corresponding to each spatial flow; and obtain the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix.
With reference to the third aspect, the first possible implementation manner of the third aspect, or the second possible implementation manner of the third aspect, in a third possible implementation manner of the third aspect, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
With reference to the third possible implementation manner of the third aspect, in a fourth possible implementation manner of the third aspect, the processing unit is specifically configured to: obtain a second frequency domain sequence of each spatial flow according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix; perform inverse Fourier transform on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow; and add up second time domain sequences corresponding to all the spatial flows, to obtain the LTF.
With reference to any one of the third aspect, or the first possible implementation manner of the third aspect to the fourth possible implementation manner of the third aspect, in a fifth possible implementation manner of the third aspect, the processing unit is specifically configured to: divide the subcarrier quantity NFFT by the bandwidth to obtain an inverse discrete Fourier transform IDFT period of an orthogonal frequency division multiplexing OFDM symbol; and divide the IDFT period by the maximum multipath delay to obtain the maximum quantity of spatial flows that can be supported by a single symbol.
With reference to any one of the third aspect, or the first possible implementation manner of the third aspect to the fifth possible implementation manner of the third aspect, in a sixth possible implementation manner of the third aspect, a length of the first time domain sequence is N, and N is a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block; and a length of the first frequency domain sequence is the subcarrier quantity NFFT.
A fourth aspect of this application provides a channel estimation apparatus, including:
a receiving unit, configured to receive a long training field LTF and indication information that are sent by a transmit end, where the indication information includes a number of a spatial flow allocated to a receive end; and
a processing unit, configured to: obtain a total quantity of spatial flows and a maximum quantity of spatial flows that can be supported by a single symbol; determine, in a parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, a cyclic shift parameter corresponding to the spatial flow, where the cyclic shift parameter represents a time sequence shift value of a first time domain sequence, and the first time domain sequence is a sequence with an autocorrelation property; and determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, a length N of the first time domain sequence, the number of the spatial flow, and the received LTF, a frequency domain channel estimation value corresponding to the spatial flow.
With reference to the fourth aspect, in a first possible implementation manner of the fourth aspect, the processing unit is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, an orthogonal mapping matrix corresponding to the spatial flow; and determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the number of the spatial flow, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the first possible implementation manner of the fourth aspect, in a second possible implementation manner of the fourth aspect, the processing unit is configured to: determine a window function according to the cyclic shift parameter, the maximum quantity of spatial flows that can be supported by a single symbol, and the length N of the first time domain sequence; merge the received LTF according to the number of the spatial flow and the orthogonal mapping matrix; obtain a second estimated time domain sequence according to an LTF obtained after the merging; perform Fourier transform on the second estimated time domain sequence to obtain a first estimated frequency domain sequence; extract, from the first frequency domain sequence, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end; perform inverse Fourier transform on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence; process the at least one third time domain sequence and the first time domain sequence by using the window function, to obtain at least one fourth estimated time domain sequence; and separately perform Fourier transform on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the fourth aspect, the first possible implementation manner of the fourth aspect, or the second possible implementation manner of the fourth aspect, in a third possible implementation manner of the fourth aspect, the length N of the first time domain sequence is specifically a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block is the length N.
With reference to any one of the fourth aspect, or the first possible implementation manner of the fourth aspect to the third possible implementation manner of the fourth aspect, in a fourth possible implementation manner of the fourth aspect, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
A fifth aspect of this application provides a transmit-end device, including:
a processor, configured to: perform Fourier transform on a first time domain sequence to obtain a first frequency domain sequence, where the first time domain sequence is a sequence with an autocorrelation property; determine, according to a maximum multipath delay of a system transmission channel, bandwidth of the channel, and a subcarrier quantity NFFT, a maximum quantity of spatial flows that can be supported by a single symbol; determine, in a parameter configuration table according to a total quantity of spatial flows, a cyclic shift parameter corresponding to each spatial flow, where the cyclic shift parameter represents a time sequence shift value of the first time domain sequence; and obtain a long training field LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter; and
a transmitter, configured to send the LTF and indication information to each receive end, where the indication information includes a number of a spatial flow allocated to each receive end.
With reference to the fifth aspect, in a first possible implementation manner of the fifth aspect, the processor is further configured to determine a symbol quantity according to the total quantity of spatial flows and the maximum quantity of spatial flows.
With reference to the fifth aspect or the first possible implementation manner of the fifth aspect, in a second possible implementation manner of the fifth aspect, the processor is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows, an orthogonal mapping matrix corresponding to each spatial flow; and obtain the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix.
With reference to the fifth aspect, the first possible implementation manner of the fifth aspect, or the second possible implementation manner of the fifth aspect, in a third possible implementation manner of the fifth aspect, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
With reference to the third possible implementation manner of the fifth aspect, in a fourth possible implementation manner of the fifth aspect, the processor is specifically configured to: obtain a second frequency domain sequence of each spatial flow according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix; perform inverse Fourier transform on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow; and add up second time domain sequences corresponding to all the spatial flows, to obtain the LTF.
With reference to any one of the fifth aspect, or the first possible implementation manner of the fifth aspect to the fourth possible implementation manner of the fifth aspect, in a fifth possible implementation manner of the fifth aspect, the processor is specifically configured to: divide the subcarrier quantity NFFT by the bandwidth to obtain an inverse discrete Fourier transform IDFT period of an orthogonal frequency division multiplexing OFDM symbol; and divide the IDFT period by the maximum multipath delay to obtain the maximum quantity of spatial flows that can be supported by a single symbol.
With reference to any one of the fifth aspect, or the first possible implementation manner of the fifth aspect to the fifth possible implementation manner of the fifth aspect, in a sixth possible implementation manner of the fifth aspect, a length of the first time domain sequence is N, and N is a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block; and a length of the first frequency domain sequence is the subcarrier quantity NFFT.
With reference to any one of the fifth aspect, or the first possible implementation manner of the fifth aspect to the sixth possible implementation manner of the fifth aspect, in a seventh possible implementation manner of the fifth aspect, the transmit-end device is a wireless local area network access point or a station.
A sixth aspect of this application provides a receive-end device, including:
a receiver, configured to receive a long training field LTF and indication information that are sent by a transmit end, where the indication information includes a number of a spatial flow allocated to a receive end; and
a processor, configured to: obtain a total quantity of spatial flows and a maximum quantity of spatial flows that can be supported by a single symbol; determine, in a parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, a cyclic shift parameter corresponding to the spatial flow, where the cyclic shift parameter represents a time sequence shift value of a first time domain sequence, and the first time domain sequence is a sequence with an autocorrelation property; and determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, a length N of the first time domain sequence, the number of the spatial flow, and the received LTF, a frequency domain channel estimation value corresponding to the spatial flow.
With reference to the sixth aspect, in a first possible implementation manner of the sixth aspect, the processor is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, an orthogonal mapping matrix corresponding to the spatial flow; and determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the number of the spatial flow, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the first possible implementation manner of the sixth aspect, in a second possible implementation manner of the sixth aspect, the processor is configured to: determine a window function according to the cyclic shift parameter, the maximum quantity of spatial flows that can be supported by a single symbol, and the length N of the first time domain sequence; merge the received LTF according to the number of the spatial flow and the orthogonal mapping matrix; obtain a second estimated time domain sequence according to an LTF obtained after the merging; perform Fourier transform on the second estimated time domain sequence to obtain a first estimated frequency domain sequence; extract, from the first frequency domain sequence, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end; perform inverse Fourier transform on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence; process the at least one third time domain sequence and the first time domain sequence by using the window function, to obtain at least one fourth estimated time domain sequence; and separately perform Fourier transform on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the sixth aspect, the first possible implementation manner of the sixth aspect, or the second possible implementation manner of the sixth aspect, in a third possible implementation manner of the sixth aspect, the length N of the first time domain sequence is specifically a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block is the length N.
With reference to any one of the sixth aspect, or the first possible implementation manner of the sixth aspect to the third possible implementation manner of the sixth aspect, in a fourth possible implementation manner of the sixth aspect, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
With reference to any one of the sixth aspect, or the first possible implementation manner of the sixth aspect to the fourth possible implementation manner of the sixth aspect, in a fifth possible implementation manner of the sixth aspect, the receive-end device is a station or a wireless local area network access point.
One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:
In the embodiments of this application, Fourier transform is performed on a first time domain sequence with an autocorrelation property to obtain a first frequency domain sequence; a maximum quantity of spatial flows that can be supported by a single symbol is determined according to a maximum multipath delay of a channel, bandwidth of the channel, and a subcarrier quantity; then, a cyclic shift parameter corresponding to each spatial flow is determined in a parameter configuration table according to a total quantity of spatial flows, where the cyclic shift parameter represents a time sequence shift value of the first time domain sequence; and then, an LTF is obtained according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter. Therefore, in the embodiments, a sequence with an autocorrelation property is used as a sequence used for an LTF. Then, symbols used for spatial flows in a multi-spatial-flow scenario are distinguished by using different cyclic shift parameters. Two spatial flows may be distinguished by performing at least one time of shift. Therefore, for eight spatial flows, only a maximum of four symbols need to be sent in each spatial flow. Therefore, according to the methods in the embodiments, channel estimation may be implemented, where a quantity of symbols that need to be sent in each spatial flow is less than a quantity of symbols that are sent in the prior art, so as to reduce system overheads, and in particular, reduce system overheads in a parameter configuration with a relatively large quantity of subcarriers and a relatively long guard interval.
Embodiments of this application provide a data sending method, a channel estimation method, and apparatuses thereof to resolve a technical problem in the prior art that a method for generating a long training field causes relatively high system overheads.
To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following clearly describes the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are merely a part rather than all of the embodiments of this application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments of this application without creative efforts shall fall within the protection scope of this application.
The station mentioned in this specification may also be referred to as an access terminal, a system, a subscriber unit, a subscriber station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communications device, a user agent, a user apparatus, UE (User Equipment, user equipment), or the like. The station may be a cellular phone, a cordless phone, a SIP (Session Initiation Protocol, Session Initiation Protocol) phone, a WLL (Wireless Local Loop, wireless local loop) station, a PDA (Personal Digital Assistant, personal digital assistant), a handheld device having a wireless communication function, a computing device, or another processing device connected to a wireless modem.
In addition, the wireless local area network access point in this specification may be an independent access point that uses a WLAN (Wireless Local Area Network, wireless local area network) technology; or may be integrated into an existing base station, for example, integrated into: a BTS (Base Transceiver Station, base transceiver station) in GSM (Global System for Mobile Communications, Global System for Mobile Communications) or CDMA (Code Division Multiple Access, Code Division Multiple Access); or may be integrated into an NB (NodeB, NodeB) in WCDMA (Wideband Code Division Multiple Access, Wideband Code Division Multiple Access); or may be an eNB or an eNodeB (evolved Node B, evolved NodeB) in LTE (Long Term Evolution, Long Term Evolution), or a relay station or an access point, or a base station device in a future 5G network; or the like.
In addition, the character “/” in this specification generally indicates an “or” relationship between the associated objects.
This embodiment provides a data sending method that is used for interaction between a station and an access point. When an access point or a station needs to send data, the following method steps are performed. As shown in
Step 101: Perform Fourier transform on a first time domain sequence to obtain a first frequency domain sequence, where the first time domain sequence is a sequence with an autocorrelation property.
Step 102: Determine, according to a maximum multipath delay of a system transmission channel, bandwidth of the channel, and a subcarrier quantity NFFT, a maximum quantity of spatial flows that can be supported by a single symbol.
Step 103: Determine, in a parameter configuration table according to a total quantity of spatial flows, a cyclic shift parameter corresponding to each spatial flow, where the cyclic shift parameter represents a time sequence shift value of the first time domain sequence.
Step 104: Obtain an LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter.
Step 105: Send the LTF and indication information to each receive end, where the indication information includes a number of a spatial flow allocated to each receive end.
In step 101 in this embodiment of this application, the first time domain sequence is a sequence with an autocorrelation property. For example, the first time domain sequence may be a Zadoff-Chu sequence, a Frank sequence, a Golomb multiphase sequence, or a Chirp sequence.
Optionally, the first time domain sequence is a sequence with an ideal autocorrelation property, for example, a Zadoff-Chu sequence.
However, a length N of the first time domain sequence is specifically determined by a quantity of consecutive available subcarriers of the channel. Preferably, a value of N is the quantity of consecutive available subcarriers.
For example, a channel includes 256 subcarriers. It is assumed that subcarrier numbers are {−128, −127, . . . −123, −122, . . . −2, −1, 0, 1, 2, . . . 122, 123, . . . 127}, where numbers of available subcarriers are {−120, . . . −1} and {1, . . . 120}, and the rest are empty subcarriers. It may be seen that a quantity of consecutive available subcarriers is 120, and therefore, a value of N may be 120.
In another possible implementation manner, the length N may also be determined by a quantity of subcarriers included in a resource block (Resource Block, RB for short). A value of N is the quantity of subcarriers included in an RB.
For example, a channel includes 256 subcarriers. It is assumed that subcarrier numbers are {−128, −127, . . . −123, −122, . . . −2, −1, 0, 1, 2, . . . 122, 123, . . . 127}, where numbers of available subcarriers are {−120, . . . −1} and {1, . . . 120}, and the rest are empty subcarriers. Each RB includes 24 subcarriers in a frequency domain. There are 10 RBs in total. Therefore, a value of N may be 24.
For ease of description, the first time domain sequence is denoted as {xn}, n=0, . . . , N−1. Then, step 101 is performed: perform Fourier transform on a first time domain sequence to obtain a first frequency domain sequence. The Fourier transform may be specifically, for example, fast Fourier transform (Fast Fourier Transform, FFT for short). After the Fourier transform is performed on the first time domain sequence, a length of an obtained frequency domain sequence is also N. Then, the obtained frequency domain sequence is used for bit complement according to locations of consecutive available subcarriers, and a location of an empty subcarrier is complemented with a bit to obtain the first frequency domain sequence. Therefore, the length of the first frequency domain sequence is the subcarrier quantity NFFT of the channel. Next, a specific implementation manner of step 102 is described: determine, according to a maximum multipath delay of a channel, bandwidth of the channel, and a subcarrier quantity NFFT, a maximum quantity of spatial flows that can be supported by a single symbol. The maximum quantity of spatial flows that can be supported by a single symbol indicates MIMO channel estimation, of a maximum quantity of multiplexed spatial flows, supported by a single symbol.
In a possible implementation manner, step 102 includes: dividing the subcarrier quantity NFFT by the bandwidth to obtain an inverse discrete Fourier transform (Inverse Discrete Fourier Transform, IDFT for short) period of an OFDM symbol; and dividing the IDFT period by the maximum multipath delay to obtain the maximum quantity of spatial flows that can be supported by a single symbol.
There may also be specifically multiple manners of obtaining the maximum multipath delay of the channel. In a first manner, a type of the system transmission channel, for example, an outdoor channel or an indoor channel, is determined according to a current operation mode of a system, for example, an indoor or outdoor operation mode; and according to a determined channel type, a delay of a channel model corresponding to the channel type is obtained and used as the maximum multipath delay.
In a second manner, the maximum multipath delay may be determined according to a cyclic prefix (Cyclic Prefix, CP for short) of a data frame. For example, a length of the CP is directly used as the maximum multipath delay.
It should be noted that step 101 and step 102 are not sequential, and may be simultaneously performed.
Further, a quantity of required symbols, that is, a symbol quantity, may be determined according to the total quantity of spatial flows and the maximum quantity of spatial flows supported by a single symbol. For example, the maximum quantity of spatial flows supported by a single symbol is 4, and the total quantity of spatial flows is 8. Therefore, the total quantity of required symbols is 2.
Next, an implementation manner of step 103 is described. First, the parameter configuration table is described. The parameter configuration table may be specifically configured in a system or agreed on in a protocol. A same parameter configuration table is used on a transmit end and a receive end. The parameter configuration table may include the following items: a total quantity of spatial flows, a number of a spatial flow, and a cyclic shift parameter. Further, the parameter configuration table further includes an orthogonal mapping matrix. Further, the parameter configuration table may further include a symbol quantity. In other words, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows. Further, the parameter configuration table further includes a correspondence between the orthogonal mapping matrix and each spatial flow within the total quantity of spatial flows. Further, the parameter configuration table further includes a correspondence between the total quantity of spatial flows and the symbol quantity.
Specifically, as shown in Table 1, Table 1 is a parameter configuration table of an example in which a total quantity Nss of spatial flows is 1 to 8 and a maximum quantity of spatial flows supported by a single symbol is 4, where M indicates a symbol quantity, iss indicates a number of a spatial flow, vi
In actual application, the cyclic shift parameter vi
Certainly, the first time domain sequence may also be divided into another quantity of segments. For example, when the total quantity of spatial flows is 3, the first time domain sequence may also be divided into three segments. Shift may either not be performed on a spatial flow 0, and therefore, the cyclic shift parameter is 0. For a spatial flow 1, because the spatial flow 1 needs to be distinguished from the spatial flow 0, shift needs to be performed on the first time domain sequence. Then, the spatial flow 1 may be represented by a sequence obtained after the first time domain sequence is circularly shifted by one segment, that is, circularly shifted by one third of an IDFT period of a symbol. Therefore, the cyclic shift parameter is 1. For a spatial flow 2, because the spatial flow 2 needs to be distinguished from the spatial flows 0 and 1, cyclic shift needs to be performed on the first time domain sequence. Then, the spatial flow 2 may be represented by a sequence obtained after the first time domain sequence is circularly shifted by two segments, that is, circularly shifted by two thirds of the IDFT period of a symbol. Therefore, the cyclic shift parameter is 2.
Therefore, in actual application, specific expression forms of the cyclic shift parameter may be different.
In Table 1, when the total quantity of spatial flows is greater than 4, because the first time domain sequence obtained after being shifted for the fourth time is the same as a case in which the first time domain sequence is not shifted, a spatial flow 0 and a spatial flow 4 cannot be distinguished. Therefore, the orthogonal mapping matrix is used to further distinguish between different spatial flows.
It should be noted that step 103 and the foregoing step 101 to step 102 are not sequential, and may be simultaneously performed.
After step 101 to step 103 are performed, step 104 is performed: obtain an LTF according to the first frequency sequence, the maximum quantity of spatial flows, and the cyclic shift parameter.
It should be noted that if Table 1 is used as an example, when the total quantity of spatial flows is less than or equal to 4, the orthogonal mapping matrix is not required for distinguishing between the spatial flows. However, when the total quantity of spatial flows is greater than 4, the orthogonal mapping matrix is required for further distinguishing between the spatial flows.
Therefore, optionally, the method further includes: determining, in the parameter configuration table according to the total quantity of spatial flows, an orthogonal mapping matrix corresponding to each spatial flow. Step 104 specifically includes: obtaining the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix.
In this embodiment, for example, with reference to the orthogonal mapping matrix, step 104 specifically includes: obtaining a second frequency domain sequence of each spatial flow according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix; performing inverse Fourier transform on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow; and adding up the second time domain sequences corresponding to all the spatial flows, to obtain the LTF. The second frequency domain sequence of each spatial flow includes frequency domain sequences of all symbols of each spatial flow. In other words, a quantity of obtained second frequency domain sequences is the same as a quantity of symbols included in a spatial flow. Correspondingly, a quantity of second time domain sequences is corresponding to a quantity of second frequency domain sequences.
When no reference needs to be made to the orthogonal mapping matrix, the orthogonal mapping matrix may be deleted from the foregoing steps.
Optionally, after the LTF is obtained in step 104, step 105 is performed: send the LTF and indication information to each receive end, where the indication information includes a number of a spatial flow allocated to each receive end. Further, the indication information further includes a symbol quantity of each receive end.
That the LTF is sent to each receive end may be specifically that the LTF is sent together with data of each spatial flow. The indication information may be specifically indicated by using an information bit in a downlink/an uplink resource indication field. For example, the symbol quantity is indicated by using 1 bit, a start number of a spatial flow allocated to each receive end is indicated by using 3 bits, and the total quantity of spatial flows allocated to each receive end is indicated by using 3 bits. For example, when the total quantity of spatial flows is 8, spatial flows allocated to the uth user are spatial flows 4 to 6. It can be learned by searching the parameter configuration table shown in Table 1 that when the total quantity of spatial flows is 8, the symbol quantity is 2. Therefore, a bit for the symbol quantity may be indicated by {1}, bits for a start number of a spatial flow may be indicated by {1, 0, 0}, and bits for a quantity of spatial flows allocated to the uth user may be indicated by {0, 1, 1}. Certainly, in actual application, the indication information may also be sent to each receive end in another manner.
Optionally, the transmit end sends the LTF and the indication information to each receive end, so that each receive end performs channel estimation.
The following describes how to perform channel estimation on a receive end side. As shown in
Step 201: Receive an LTF and indication information that are sent by a transmit end, where the indication information includes a symbol quantity of each receive end and a number of a corresponding spatial flow allocated to each receive end.
Step 202: Obtain a total quantity of spatial flows and a maximum quantity of spatial flows that can be supported by a single symbol.
Step 203: Determine, in a parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, a cyclic shift parameter corresponding to the spatial flow, where the cyclic shift parameter represents a time sequence shift value of a first time domain sequence, and the first time domain sequence is a sequence with an autocorrelation property.
Step 204: Determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, a length N of the first time domain sequence, the number of the spatial flow, and the received LTF, a frequency domain channel estimation value corresponding to the spatial flow.
That the transmit end further sends the indication information to each receive end is described in the foregoing. Correspondingly, the receive end performs step 201: receive an LTF and indication information. The symbol quantity and the number of the spatial flow corresponding to each receive end may be obtained according to bit information in an indication bit of the indication information.
A possible implementation manner of step 202 is the same as a specific manner of the foregoing step 102. Therefore, details are not described herein.
In another possible implementation manner, step 202 is specifically: receiving the total quantity of spatial flows sent by the transmit end and the maximum quantity of spatial flows that can be supported by a single symbol.
In step 203, the first time domain sequence is the same as the sequence used in step 101. Generally, which sequence the first time domain sequence is specifically is configured in a system. Therefore, the transmit end and the receive end use a same first time domain sequence by default. Alternatively, that both the transmit end and the receive end use a same first time domain sequence that is agreed on in a protocol.
The length of the first time domain sequence is N. Optionally, a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block is the length N. Generally, both the transmit end and the receive end agree on, by default, that the length N of the first time domain sequence is the quantity of consecutive available subcarriers of the channel or the quantity of subcarriers included in a resource block. Therefore, both the transmit end and the receive end determines the length N according to this rule.
Next, step 203 is performed: determine, in a parameter configuration table according to the total quantity of spatial flows and a number of the spatial flow, a cyclic shift parameter corresponding to the spatial flow.
The parameter configuration table is the same as a parameter configuration table used by the transmit end. A concept of the cyclic shift parameter is the same as that described above.
Next, step 204 is performed.
Optionally, the method further includes: determining, in the parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, an orthogonal mapping matrix corresponding to the spatial flow. A concept of the orthogonal mapping matrix is the same as that described above.
Therefore, step 204 specifically includes: determining, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the number of the spatial flow, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow.
Optionally, a possible implementation manner of step 204 is: determining a window function according to the cyclic shift parameter, the maximum quantity of spatial flows, and the length N; merging the received LTF according to the number of the spatial flow and the orthogonal mapping matrix; obtaining a second estimated time domain sequence according to an LTF obtained after the merging; performing Fourier transform on the second estimated time domain sequence to obtain a first estimated frequency domain sequence; extracting, from the first estimated frequency domain sequence, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end; perform inverse Fourier transform on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence; processing the at least one third estimated time domain sequence and the first time domain sequence by using the window function, to obtain at least one fourth estimated time domain sequence; and separately performing Fourier transform on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow.
The window function may have multiple forms, for example, a rectangular window, a triangular window, Hanning window, Hamming window, and Gaussian window.
It should be noted that a process of performing windowing processing by using the window function and performing merging processing on the received LTF may be described as the foregoing. Merging processing is performed before windowing processing; or windowing processing may be performed before merging processing.
It may be seen from the foregoing description that according to this embodiment of the present application, a sequence with an autocorrelation property is used as a sequence used for an LTF, and then LTFs used by spatial flows in a multi-spatial-flow scenario are distinguished by using different cyclic shift parameters, so that channel estimation can be implemented with less symbols sent in each spatial flow than those in the prior art, so as to reduce system overheads.
The following separately uses several specific examples to describe specific implementation processes of the data sending method and the channel estimation method in this embodiment.
The system is in an outdoor operation mode, the channel is an outdoor channel and applied in downlink transmission. It is assumed that a bandwidth BW=20 MHz, a subcarrier quantity is NFFT=256, and subcarrier numbers are {−128, −127, . . . −123, −122, . . . −2, −1, 0, 1, 2, . . . 122, 123, . . . 127}, where numbers of available subcarriers are {−120, . . . −1} and {1, . . . 120}, and the rest are empty subcarriers.
It is assumed that Nss is a total quantity of transmitted spatial flows, a total of Nu users share the entire bandwidth, and Nss,u is a quantity of spatial flows transmitted to the uth user, where u=0, 1, . . . Nu−1. It is assumed that a transmit end is an AP.
A first time domain sequence with an ideal autocorrelation property is obtained. A length of the first time domain sequence is that N=120. The first time domain sequence may be indicated by {xn}, n=0, . . . , N−1.
N-point Fourier transform is performed on the first time domain sequence, and an obtained frequency domain sequence is indicated by {Xd}=FFT[xn], d=0, . . . , N−1. Therefore, a first frequency domain sequence
may be indicated by {0, 0, 0, 0, 0, 0, 0, 0, X0, . . . X119, 0, X0, . . . , X119, 0, 0, 0, 0, 0, 0, 0}. That is, a length of the first frequency domain sequence is the subcarrier quantity, 256 in this embodiment.
In this embodiment, the channel is an outdoor channel, and a maximum multipath delay τmax=3.2 us of the channel is obtained by using an outdoor channel model. An IDFT period
of a symbol may be obtained according to the bandwidth BW=20 MHz and the subcarrier quantity NFFT=256. A single symbol can support MIMO channel estimation of a maximum of
multiplexed spatial flows.
Optionally, a quantity M=┌Nss/iss_max┐ of symbols that need to be sent may be further calculated, where ┌ ┐ is a roundup function.
In the parameter configuration table shown in Table 1, a cyclic shift parameter vi
A second frequency domain sequence of each spatial flow is obtained according to the first frequency domain sequence {Lk}, the maximum quantity iss_max of spatial flows, the cyclic shift parameter vi
The second frequency domain sequence Lk,mi
Then, inverse Fourier transform is performed on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow. For example, inverse Fourier transform is performed on the second frequency domain sequence Lk,mi
Finally, the second time domain sequences corresponding to all the spatial flows are added up, to obtain the LTF.
For example, the LTF actually sent by the AP may be indicated by
where ltfn,m indicates the LTF.
Correspondingly, the following uses the uth user as an example to describe a process of implementing channel estimation by a receive end. The receive end is, for example, a station.
A maximum quantity of spatial flows, for example, the maximum quantity of spatial flows received from the transmit end, is obtained.
The first time domain sequence is obtained, where a length of the first time domain sequence is N. In this embodiment, the length N is specifically a quantity of consecutive available subcarriers, that is, 120. The first time domain sequence is still indicated by {xn}.
The LTF and the indication information are received, where the indication information includes a symbol quantity M of each receive end and a spatial flow iss allocated to each receive end. Further, for example, the symbol quantity M is determined as 2 according to bit information in a downlink resource indication field, and the spatial flows iss allocated to the uth user are spatial flows 4 to 6.
In the parameter configuration table shown in Table 1, the cyclic shift parameter vi
The frequency domain channel estimation value corresponding to the spatial flow is determined according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the orthogonal mapping matrix, and the received LTF.
Specifically, a possible implementation manner of obtaining the frequency domain channel estimation value corresponding to the spatial flow is: determining a window function according to the cyclic shift parameter vi
The foregoing example is still used. For the uth user, values of iss are 4, 5, and 6.
The received LTF {ym} is merged according to the number iss of the spatial flow and the orthogonal mapping matrix Pi
CP removal processing is performed on the LTF yi
Then, NFFT-point Fourier transform is performed on the second estimated time domain sequence to obtain a first estimated frequency domain sequence Yi
Next, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end is extracted from the first estimated frequency domain sequence Yi
Next, N-point inverse Fourier transform is performed on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence. The foregoing two second estimated frequency domain sequences {Yk
Then, the at least one third estimated time domain sequence and the first time domain sequence are processed by using the foregoing determined window function, to obtain at least one fourth estimated time domain sequence. Specifically, two fourth estimated time domain sequences may be indicated by
where left sides of the equations separately indicate two fourth estimated time domain sequences, and right sides of the equations indicate operational formulas. A cross-correlation operation is performed on the third estimated time domain sequence and the first time domain sequence, and then, a windowing operation is performed by using the window function.
Next, N-point Fourier transform is separately performed on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow. Specifically, N-point Fourier transform is performed on {hr
In this embodiment, the system is in an indoor operation mode, the channel is an indoor channel, and a maximum multipath delay of the channel is determined as τmax=0.8 us by using an indoor channel model, which is different from example 1. Therefore, a maximum number of spatial flows supported by a single HTF symbol is
A quantity M of symbols that need to be sent by the transmit end is 1. In addition, in this case, settings of the parameter configuration table may be shown as Table 2.
In this embodiment, specific steps are the same as those in example 1, except that the foregoing parameters and the parameter configuration table are different from those in example 1.
For the channel estimation process of the receive end in this embodiment, specific steps are the same as those in the foregoing example 1, except that the foregoing parameters and the parameter configuration table are different from those in example 1. Therefore, details are not described herein.
In this embodiment, a subcarrier quantity is NFFT=512, which is different from example 1. It is assumed that subcarrier numbers are {−256, −255, . . . −226, −225, . . . −2, −1, 0, 1, 2, . . . 225, 226, . . . 255}, where numbers of available subcarriers are {−225, . . . −2} and {2, . . . 225}, and the rest are empty subcarriers.
Therefore, in this case, the length N is 224. A first frequency domain sequence
may be indicated by
An IDFT period of an OFDM symbol is
A maximum quantity of spatial flows supported by a single symbol is
A quantity M of symbols that need to be sent by the transmit end is 1. In this embodiment, settings of the parameter configuration table may be shown as Table 3.
In this embodiment, specific steps are the same as those in example 1, except that the foregoing parameters and the parameter configuration table are different from those in example 1.
For the channel estimation process of the receive end in this embodiment, specific steps are the same as those in the foregoing example 1, except that the foregoing parameters and the parameter configuration table are different from those in example 1. Therefore, details are not described herein.
In this embodiment, the transmit end is, for example, a station and is applied in uplink transmission, and the receive end is, for example, an AP, which is different from example 1. In this embodiment, uplink data transmission is scheduled by the AP. The AP first sends a next or next several uplink resource indications to the station. It is assumed that in the uplink resource indication, a total of Nu users are set to share the entire bandwidth during this time of uplink transmission, where Nss is a total quantity of transmitted spatial flows, and Nss,u is a quantity of spatial flows transmitted by the uth user, and u=0, 1, . . . Nu−1. Other steps are the same as those in the foregoing example 1.
For a process of performing channel estimation by the receive end, in step 203 in this embodiment, a symbol quantity M and a spatial flow corresponding to the receive end are determined according to indication information, which is different from example 1. The spatial flow corresponding to the receive end is specifically a spatial flow separately transmitted by the Nu users. The indication information is specifically obtained from the uplink resource indication sent by the AP. Other steps are the same as those in the foregoing example 1.
In this embodiment, an orthogonal frequency division multiple access (Orthogonal Frequency Division Multiple Access, OFDMA for short) transmission method is used, which is different from example 1. Each RB includes 24 subcarriers in a frequency domain. There are 10 RBs in total that are separately {−120, . . . , −97}, {−96, . . . , −73}, . . . , {73, . . . , 96}, and {97, . . . , 120}.
It is assumed that Nssr is a total quantity of spatial flows transmitted on bandwidth of the rth RB, where r=0, 1, . . . 9. A total of Nur users share this RB. Nss,ur is a quantity of spatial flows transmitted to the uth user on the bandwidth of the rth RB, where u=0, 1, . . . , Nur−1.
Therefore, in this case, the length N of the first time domain sequence is a quantity of subcarriers included in an RB, that is 24. A first frequency domain sequence
of the rth RB may be indicated by
A quantity of symbols that need to be sent is
where ┐ ┐ is a roundup function. In other words, in this embodiment, a total quantity Nss of spatial flows is a maximum value of the total quantity Nssr of spatial flows transmitted in each RB.
In a parameter configuration table shown in Table 4, a cyclic shift parameter vi
First, a second frequency domain sequence of each spatial flow in the rth RB is obtained according to the first frequency domain sequence {Lkr}, the maximum quantity iss_max of spatial flows, the cyclic shift parameter vi
The second frequency domain sequence Lk,mi
Then, inverse Fourier transform is performed on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow. For example, inverse Fourier transform is performed on the second frequency domain sequence Lk,mi
Finally, the second time domain sequences corresponding to all spatial flows in each RB are added up to obtain the LTF.
For example, the LTF actually sent by the AP may be indicated by
where ltfn,m indicates the LTF.
Correspondingly, the following uses the uth user of the rth RB as an example to describe a process of implementing channel estimation by the receive end. The receive end is, for example, a station.
Different from example 1, the length N is a quantity of subcarriers included in an RB, that is, 24.
A symbol quantity M and a spatial flow allocated to the uth user of the rth RB are determined according to the indication information.
In the parameter configuration table shown in Table 4, the cyclic shift parameter vi
A window function is determined according to the cyclic shift parameter vi
The received LTF {ym} is merged according to the number issr of the spatial flow and the orthogonal mapping matrix Pi
The LTF yi
Then, NFFT-point Fourier transform is performed on the second estimated time domain sequence to obtain a first estimated frequency domain sequence Yi
Next, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end is extracted from the first estimated frequency domain sequence Yi
Next, N-point inverse Fourier transform is performed on the second estimated frequency domain sequence {Yk
Then, the third estimated time domain sequence yn
where a left side of the equation indicates the fourth estimated time domain sequence, and a right side of the equation indicates an operational formula. A cross-correlation operation is performed on the third estimated time domain sequence and the first time domain sequence, and then, a windowing operation is performed by using the window function.
Next, N-point Fourier transform is separately performed on the fourth estimated time domain sequence to obtain a frequency domain channel estimation value corresponding to the spatial flow. Specifically, N-point Fourier transform is performed on ht
In this embodiment, the transmit end is, for example, a station and is applied in uplink transmission, and the receive end is, for example, an AP. Generally, uplink data transmission is scheduled by the AP, and the AP first sends a next or next several uplink resource indications in a downlink frame, which is different from example 1. It is assumed that in the uplink resource indication, a total quantity of spatial flows transmitted on bandwidth of the rth RB is set to Nssr during this time of uplink transmission, where r=0, 1, . . . 9. A total of Nur users share this RB. Nss,ur is a quantity of spatial flows transmitted by the uth user on bandwidth of the rth RB, where u=0, 1, . . . Nu−1. Remaining steps are the same as those in example 5.
For a process of performing channel estimation by the receive end, in step 203 in this embodiment, an LTF quantity M and a spatial flow corresponding to the receive end are determined according to the indication information, which is different from example 4. The spatial flow corresponding to the receive end is specifically a spatial flow issr separately transmitted by each user on the bandwidth of the rth RB. The indication information is specifically obtained from the uplink resource indication sent by the AP. Remaining steps are the same as those in example 5.
Based on a same invention concept, an embodiment of this application further provides a data sending apparatus. For definitions of related terms and specific implementation of the data sending apparatus shown in
As shown in
Optionally, the processing unit 301 is further configured to determine a symbol quantity according to the total quantity of spatial flows and the maximum quantity of spatial flows.
Optionally, the processing unit 301 is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows, an orthogonal mapping matrix corresponding to each spatial flow; and obtain the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix.
With reference to the foregoing embodiments, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
Optionally, the processing unit 301 is specifically configured to: obtain a second frequency domain sequence of each spatial flow according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix; perform inverse Fourier transform on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow; and add up second time domain sequences corresponding to all the spatial flows, to obtain the LTF.
With reference to the foregoing embodiments, the processing unit 301 is specifically configured to: divide the subcarrier quantity NFFT by the bandwidth to obtain an inverse discrete Fourier transform IDFT period of an orthogonal frequency division multiplexing OFDM symbol; and divide the IDFT period by the maximum multipath delay to obtain the maximum quantity of spatial flows that can be supported by a single symbol.
With reference to the foregoing embodiments, a length of the first time domain sequence is N, and N is a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block; and a length of the first frequency domain sequence is the subcarrier quantity NFFT.
Changing manners and specific examples of the data sending method in the foregoing embodiment of
Based on a same invention concept, this embodiment further provides a transmit-end device such as a wireless local area network access point or a station. For definitions of related terms and specific implementation of the transmit-end device shown in
As shown in
Optionally, the processor 401 is further configured to determine a symbol quantity according to the total quantity of spatial flows and the maximum quantity of spatial flows.
Optionally, the processor 401 is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows, an orthogonal mapping matrix corresponding to each spatial flow; and obtain the LTF according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix.
With reference to the foregoing embodiments, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
Optionally, the processor 401 is specifically configured to: obtain a second frequency domain sequence of each spatial flow according to the first frequency domain sequence, the maximum quantity of spatial flows, the cyclic shift parameter, and the orthogonal mapping matrix; perform inverse Fourier transform on the second frequency domain sequence to obtain a second time domain sequence corresponding to each spatial flow; and add up second time domain sequences corresponding to all the spatial flows, to obtain the LTF.
With reference to the foregoing embodiments, the processor 401 is specifically configured to: divide the subcarrier quantity NFFT by the bandwidth to obtain an inverse discrete Fourier transform IDFT period of an orthogonal frequency division multiplexing OFDM symbol; and divide the IDFT period by the maximum multipath delay to obtain the maximum quantity of spatial flows that can be supported by a single symbol.
With reference to the foregoing embodiments, a length of the first time domain sequence is N, and N is a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block; and a length of the first frequency domain sequence is the subcarrier quantity NFFT.
Further, a bus architecture (represented by a bus 400) is shown in
A user interface such as a keypad, a display, a speaker, a microphone, or a joystick may be further provided depending on a property of the receive-end device.
The processor 401 is responsible for managing the bus 400 and general processing. The memory 404 may be configured to store data used by the processor 401 when performing an operation. Further, the parameter configuration table is stored in the memory 404.
Changing manners and specific examples of the data sending method in the foregoing embodiment of
Based on a same invention concept, this embodiment provides a channel estimation apparatus. As shown in
Optionally, the processing unit 502 is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, an orthogonal mapping matrix corresponding to the spatial flow; and determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the number of the spatial flow, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow.
Optionally, the processing unit 502 is configured to: determine a window function according to the cyclic shift parameter, the maximum quantity of spatial flows that can be supported by a single symbol, and the length N of the first time domain sequence; merge the received LTF according to the number of the spatial flow and the orthogonal mapping matrix; obtain a second estimated time domain sequence according to an LTF obtained after the merging; perform Fourier transform on the second estimated time domain sequence to obtain a first estimated frequency domain sequence; extract, from the first frequency domain sequence, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end; perform inverse Fourier transform on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence; process the at least one third time domain sequence and the first time domain sequence by using the window function, to obtain at least one fourth estimated time domain sequence; and separately perform Fourier transform on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the foregoing embodiments, the length N of the first time domain sequence is specifically a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block is the length N.
With reference to the foregoing embodiments, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
Changing manners and specific examples of the channel estimation method in the foregoing embodiment of
Based on a same invention concept, this embodiment provides a receive-end device. As shown in
Optionally, the processor 602 is further configured to: determine, in the parameter configuration table according to the total quantity of spatial flows and the number of the spatial flow, an orthogonal mapping matrix corresponding to the spatial flow; and determine, according to the cyclic shift parameter, the maximum quantity of spatial flows, the first time domain sequence, the length N of the first time domain sequence, the number of the spatial flow, the orthogonal mapping matrix, and the received LTF, the frequency domain channel estimation value corresponding to the spatial flow.
Optionally, the processor 602 is configured to: determine a window function according to the cyclic shift parameter, the maximum quantity of spatial flows that can be supported by a single symbol, and the length N of the first time domain sequence; merge the received LTF according to the number of the spatial flow and the orthogonal mapping matrix; obtain a second estimated time domain sequence according to an LTF obtained after the merging; perform Fourier transform on the second estimated time domain sequence to obtain a first estimated frequency domain sequence; extract, from the first frequency domain sequence, at least one second estimated frequency domain sequence corresponding to locations and a quantity that are of consecutive available subcarriers and corresponding to the receive end; perform inverse Fourier transform on the at least one second estimated frequency domain sequence to obtain at least one third estimated time domain sequence; process the at least one third time domain sequence and the first time domain sequence by using the window function, to obtain at least one fourth estimated time domain sequence; and separately perform Fourier transform on the at least one fourth estimated time domain sequence to obtain the frequency domain channel estimation value corresponding to the spatial flow.
With reference to the foregoing embodiments, the length N of the first time domain sequence is specifically a quantity of consecutive available subcarriers of the channel or a quantity of subcarriers included in a resource block is the length N.
With reference to the foregoing embodiments, the parameter configuration table includes a correspondence between the cyclic shift parameter and each spatial flow within the total quantity of spatial flows.
Further, a bus architecture (represented by a bus 600) is shown in
A user interface such as a keypad, a display, a speaker, a microphone, or a joystick may be further provided depending on a property of the receive-end device.
The processor 602 is responsible for managing the bus 600 and general processing. The memory 604 may be configured to store data used by the processor 602 when performing an operation. For example, the parameter configuration table is stored in the memory 604.
Changing manners and specific examples of the channel estimation method in the foregoing embodiment of
One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:
In the embodiments of this application, Fourier transform is performed on a first time domain sequence with an autocorrelation property to obtain a first frequency domain sequence; a maximum quantity of spatial flows that can be supported by a single symbol is determined according to a maximum multipath delay of a channel, bandwidth of the channel, and a subcarrier quantity; then, a cyclic shift parameter corresponding to each spatial flow is determined in a parameter configuration table according to a total quantity of spatial flows, where the cyclic shift parameter represents a time sequence shift value of the first time domain sequence; and then, an LTF is obtained according to the first frequency domain sequence, the maximum quantity of spatial flows, and the cyclic shift parameter. Therefore, in the embodiments, a sequence with an autocorrelation property is used as a sequence used for an LTF. Then, symbols used for spatial flows in a multi-spatial-flow scenario are distinguished by using different cyclic shift parameters. Two spatial flows may be distinguished by performing at least one time of shift. Therefore, for eight spatial flows, only a maximum of four symbols need to be sent in each spatial flow. Therefore, according to the methods in the embodiments, channel estimation may be implemented, where a quantity of symbols that need to be sent in each spatial flow is less than a quantity of symbols that are sent in the prior art, so as to reduce system overheads, and in particular, reduce system overheads in a parameter configuration with a relatively large quantity of subcarriers and a relatively long guard interval.
A person skilled in the art should understand that the embodiments of this application may be provided as a method, a system, or a computer program product. Therefore, this application may use a form of hardware only embodiments, software only embodiments, or embodiments with a combination of software and hardware. Moreover, this application may use a form of a computer program product that is implemented on one or more computer-usable storage media (including but not limited to a disk memory, an optical memory, and the like) that include computer-usable program code.
This application is described with reference to the flowcharts and/or block diagrams of the method, the device (system), and the computer program product according to the embodiments of this application. It should be understood that computer program instructions may be used to implement each process and/or each block in the flowcharts and/or the block diagrams and a combination of a process and/or a block in the flowcharts and/or the block diagrams. These computer program instructions may be provided for a general-purpose computer, a dedicated computer, an embedded processor, or a processor of any other programmable data processing device to generate a machine, so that the instructions executed by a computer or a processor of any other programmable data processing device generate an apparatus for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.
These computer program instructions may be stored in a computer readable memory that can instruct the computer or any other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory generate an artifact that includes an instruction apparatus. The instruction apparatus implements a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.
These computer program instructions may be loaded onto a computer or another programmable data processing device, so that a series of operations and steps are performed on the computer or the another programmable device, thereby generating computer-implemented processing. Therefore, the instructions executed on the computer or the another programmable device provide steps for implementing a specific function in one or more processes in the flowcharts and/or in one or more blocks in the block diagrams.
Apparently, a person skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. This application is intended to cover these modifications and variations of this application provided that these modifications and variations of this application fall within the scope of protection defined by the following claims and their equivalent technologies.
This application is a continuation of International Application No. PCT/CN2014/085635, filed on Aug. 30, 2014, the disclosure of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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Parent | PCT/CN2014/085635 | Aug 2014 | US |
Child | 15443360 | US |