High efficiency long training field symbol transmission for multiple transmission streams
地域：
St. Michael
摘要
Embodiments described herein provide a system for transmitting high efficiency long term training field (HE-LTF) symbols for multiple wireless spatial streams over a wireless channel. An advanced P-matrix design is used to construct HE-LTF symbols that are processed by a receiver such that channel properties such as channel estimates or carrier phase error are determined prior to receiving all HE-LTF symbols. Tone multiplexing of wireless spatial stream is also used to transmit multiple spatial streams based on an assignment of sets of spatial streams to sets of tones available for transmission, increasing the throughput of the transmission system. The advanced P-matrix design and tone multiplexing are used in combination to achieve calculate channel properties before receiving all HE-LTF symbols while minimizing power fluctuation among the high efficiency short training field symbol and the HE-LTF symbols.
說(shuō)明書(shū)
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This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/732,893, filed Sep. 18, 2018, which is hereby incorporated by reference herein in its entirety.
This disclosure relates to high efficiency long training field (HE-LTF) symbols in wireless communication systems, and specifically, HE-LTF symbol generation for multiple transmission streams.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the inventors hereof, to the extent the work is described in this background section, as well as aspects of the description that does not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted to be prior art against the present disclosure.
Various techniques such as massive multiple input multiple output (MIMO) or millimeter wave have been proposed to address an increasing demand for increased data throughput and higher speeds in wireless communications systems. Moreover, access points compliant with emerging wireless communications standards, such as IEEE 802.11ax, will also need to initiate an increased number of transmission spatial streams in order to serve increased numbers of user devices.
權(quán)利要求
What is claimed is:1. A system for transmitting High Efficiency Long Training Field (HE-LTF) symbols to a receiver over a wireless channel, the system comprising:a transmitter configured to transmit a total number of HE-LTF symbols corresponding to an LTF mapping matrix for determining a plurality of wireless channel properties of the wireless channel over which the HE-LTF symbols are transmitted by the transmitter; and control circuitry coupled to the transmitter, the control circuitry configured to:determine a portion of the LTF mapping matrix for calculating, at a receiver, a wireless channel property of the plurality of wireless channel properties based on a subset of the HE-LTF symbols mapped by the portion, wherein the subset of the HE-LTF symbols mapped by the portion is less than the total number of HE-LTF symbols to be transmitted; and assemble, based at least on the determined portion of the LTF mapping matrix, the subset of the HE-LTF symbols mapped by the portion of the LTF mapping matrix. 2. The system for transmitting HE-LTF symbols of claim 1 , wherein the control circuitry is configured to determine the portion of the LTF mapping matrix by concatenating a portion of a fixed matrix with a zero matrix, wherein a position of the portion of the fixed matrix in the portion of the LTF mapping matrix corresponds to the spatial stream and wherein the fixed matrix associated with a standard LTF mapping matrix. 3. The system for transmitting HE-LTF symbols of claim 2 , wherein the LTF mapping matrix is an R-matrix representative of a training matrix for determining carrier phase error accumulated over the transmitted HE-LTF symbols, and wherein the transmitter is further configured to transmit HE-LTF symbols mapped by the R-matrix over one or more pilot tones in the wireless channel. 4. The system for transmitting HE-LTF symbols of claim 3 , wherein, for HE-LTF symbols mapped by the R-matrix transmitted over the pilot tone, the control circuitry being configured to assemble the HE-LTF symbols mapped by the R-matrix by aligning the portion of the fixed matrix within a subset of rows of the R-matrix for application, at the receiver, of an inverse of the fixed matrix and a pseudo inverse of a channel response matrix to the R-matrix to obtain carrier phase error associated with the spatial stream. 5. The system for transmitting HE-LTF symbols of claim 2 , wherein the LTF mapping matrix is a P-matrix representative of a training matrix for determining at least a channel estimate of the spatial stream, wherein the transmitter is further configured to transmit HE-LTF symbols mapped by the P-matrix over one or more data tones in the wireless channel. 6. The system for transmitting HE-LTF symbols of claim 5 , wherein, for HE-LTF symbols mapped by the P-matrix transmitted over the data tone, the control circuitry is configured to assemble the HE-LTF symbols mapped by the P-matrix by interleaving the portion of the fixed matrix diagonally for application, at the receiver, of an inverse of the fixed matrix at the position of the portion of the fixed matrix in the P-matrix to determine the channel estimate of the spatial stream after receiving a subset of the transmitted HE-LTF symbols. 7. The system for transmitting HE-LTF symbols of claim 1 , wherein the HE-LTF symbols are transmitted over a plurality of wireless spatial streams and wherein the control circuitry is further configured to assign a subset of the wireless spatial streams to a set of tones in the wireless channel. 8. The system for transmitting HE-LTF symbols of claim 7 , wherein the control circuitry is further configured to cyclically shift the rows of the LTF mapping matrix a predetermined number of times such that each tone of the set of tones is associated with a cyclically shifted LTF mapping matrix by shifting the rows of a predetermined LTF mapping matrix cyclically by a number corresponding to a modulo of a tone number over which the shifted LTF mapping matrix is transmitted. 9. A method for transmitting High Efficiency Long Training Field (HE-LTF) symbols to a receiver over a wireless channel, the method comprising:determining a portion of an LTF mapping matrix for calculating, at a receiver, a wireless channel property of the plurality of wireless channel properties based on a subset of a total number of the HE-LTF symbols mapped by the portion, wherein the subset of the HE-LTF symbols mapped by the portion is less than the total number of HE-LTF symbols to be transmitted; assembling, based at least on the determined portion of the LTF mapping matrix, the subset of the HE-LTF symbols mapped by the portion of the LTF mapping matrix; and transmitting the subset of HE-LTF symbols corresponding to the LTF mapping matrix for determining a plurality of wireless channel properties of the wireless channel over which the HE-LTF symbols are transmitted by a transmitter. 10. A system for channel estimation based on High Efficiency Long Training Field (HE-LTF) symbols transmitted to a receiver over a wireless channel by a transmitter over a plurality of tones, the system comprising:control circuitry coupled to the transmitter, the control circuitry configured to:assign, based on a modulo operation applied to tone indices corresponding to the plurality of tones, a plurality of wireless spatial streams to the plurality of tones, wherein a subset of the plurality of tones is separated by one or more tones unassigned to the subset of the plurality of tones; and generate, based on the assigned plurality of wireless spatial streams, the HE-LTF symbols for estimating, at the receiver, the wireless channel having bandwidth coherency within the plurality of tones; and the transmitter configured to transmit, over the plurality of tones, the generated HE-LTF symbols for interpolation of a channel estimate matrix corresponding to the one or more tones unassigned to the subset of the unassigned tones. 11. The system for channel estimation of claim 10 , the control circuitry further configured to select an HE mode associated with a maximum number of tones available for transmission of the HE-LTF symbols, wherein the number of the plurality of tones is the maximum number of tones. 12. The system for channel estimation of claim 11 , wherein the control circuitry is configured to select the HE mode by selecting a 4xHE-LTF mode having the maximum number of tones available for transmission of the HE-LTF symbols. 13. The system for channel estimation of claim 11 , wherein the control circuitry is configured to select the HE mode by selecting a 2xHE-LTF mode having half of the maximum number of tones available for transmission of the HE-LTF symbols. 14. The system for channel estimation of claim 11 , the control circuitry further configured to:select a first tone-select mode; and in response to selecting the first tone-select mode, divide the maximum number of tones into four subsets of tones available for transmission of the HE-LTF symbols. 15. The system for channel estimation of claim 14 , wherein the control circuitry is further configured to:determine, based on the tone-select mode, a minimum number of the number of wireless spatial streams assignable to each subset of the four subsets of the plurality of tones; and distribute a remaining number i of wireless spatial streams, calculated based on the minimum number, evenly among i subsets of the four subsets. 16. The system for channel estimation of claim 10 , the control circuitry further configured to select a tone-select mode indicative of a maximum number of subsets of wireless spatial streams transmittable over the plurality of tones. 17. The system for channel estimation of claim 10 , wherein the control circuitry is configured to generate a P-matrix having a first amount of rows of a pre-defined matrix, wherein the first amount corresponds to the number of the subset of wireless spatial streams to be transmitted over the subset of the plurality of tones. 18. The system for channel estimation of claim 10 , wherein the transmitter is further configured to transmit a spatial mapping matrix associated with a mapping of a channel response matrix to the plurality of wireless spatial streams over the plurality of tones, the spatial mapping matrix having a number of rows associated with a number of antennas at the transmitter and a number of columns associated with a number of the plurality of wireless spatial streams. 19. The system for channel estimation of claim 18 , wherein the control circuitry is further configured to generate the spatial mapping matrix based on a portion of the spatial mapping matrix, wherein the portion has the number of rows associated with the number of antennas at the transmitter and a number of columns corresponding to the number of the subset of wireless spatial streams to be transmitted over the subset of the plurality of tones. 20. The system for channel estimation of claim 10 , wherein the control circuitry is further configured to, for a plurality of users, transmit HE-LTF symbols associated with a first user of the plurality of users on a first tone and transmit HE-LTF symbols associated with a second user of the plurality of users on a second tone.
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