High efficiency long training field symbol transmission for multiple transmission streams
摘要
說(shuō)明書(shū)
Under the current IEEE 802.11ax standard, the receiver will multiply the received signal by a Hermitian of the 16×16 P-matrix to obtain the channel estimates for the 16 spatial streams. The application of the Hermitian of the P-matrix is referred to herein as an “undo P” operation. This operation, in order to be done in a short amount of time to obtain channel estimates necessary to process the data symbols immediately after receiving the preamble, requires a complicated receiver architecture to accomplish all of the arithmetic operations within the time available. As more transmission streams are used, the amount of arithmetic operations also increases. For example, transmitting 32 streams requires a 32×32 P-matrix on which the receiver is required to perform an undo P using another 32×32 matrix within the same time required for transmitting 16 streams or any number of streams.
Phase roll estimation, calculated by the receiver to refine both timing and channel estimates, also requires the determination of channel estimates of all spatial streams. In the current standard, phase roll estimation, like channel estimation, cannot be calculated until all HE-LTF symbols have been received. As the number of streams transmitted increases, the time that phase roll estimation is calculated is delayed further. Due to similar time constraints, QR decomposition operations to further process channel estimates, channel smoothing, channel interpolation, and other operations requiring the receipt of all LTF symbols, become increasingly difficult to implement when number of streams increase.
