Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L25/00—Baseband systems
  • H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
  • H04L25/0202—Channel estimation
  • H04L25/0224—Channel estimation using sounding signals
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B17/00—Monitoring; Testing
  • H04B17/30—Monitoring; Testing of propagation channels
  • H04B17/309—Measuring or estimating channel quality parameters
  • H04B17/345—Interference values
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/0413—MIMO systems
  • H04B7/0417—Feedback systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
  • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
  • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
  • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
  • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
  • H04B7/0621—Feedback content
  • H04B7/0634—Antenna weights or vector/matrix coefficients
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
  • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
  • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
  • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
  • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
  • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
  • H04B7/0636—Feedback format
  • H04B7/0639—Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
  • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity

Definitions

• FIG. 1 is a flowchart illustrating a method of identifying a precoding matrix corresponding to a wireless network channel according to an embodiment of the invention
• the target precoding matrix F may be identified by solving
• the MMSE Capacity Metric exhibited a performance gain of approximately 0.8 decibels (dB) over open loop (i.e., no beamforming) and showed similar performance to optimal closed loop (i.e., beamforming using the theoretical optimal selection criterion).
• Various other selection criteria give performance similar to that of open loop. This performance gain is illustrated in FIG. 2, where packet error rates (PER) for various selection criteria are plotted against SNR for the environment described above, i.e., MMSE decoding with two streams, two transmitting antennas, and two receiving antennas.
• PER packet error rates
• FIG. 3 is a flowchart illustrating a method 300 of identifying a precoding matrix corresponding to a wireless network channel according to an embodiment of the invention.
• method 300 may identify a precoding matrix that increases a capacity of a particular wireless channel using the MMSE Capacity Metric that has just been described.
• the steps of method 300 may be performed by a subscriber station of the wireless network.
• a step 330 of method 300 is to search over all matrices in a matrix codebook (stored in a memory device) using the minimum mean square error metric in order to identify a particular precoding matrix that increases a capacity of the wireless network channel, where the particular precoding matrix has a corresponding matrix index. As an example, this may be accomplished by solving (9).
• a step 410 of method 400 is to identify a metric corresponding to a selection criterion.
• a step 420 of method 400 is to average a channel matrix of every N sub-carriers, where N is greater than 1 and less than or equal to M, in order to create L averaged channel matrices.
• a step 430 of method 400 is to calculate the metric using each one of the averaged channel matrices in order to obtain L averaged metrics for each precoding matrix in the matrix codebook.
• a step 440 of method 400 is to calculate a sum/average of the L averaged metrics over the M sub-carriers for each precoding matrix in the matrix codebook.
• a step 450 of method 400 is to select as the target precoding matrix a particular one of the plurality of precoding matrices that increases the sum/average of the metric.
• L is equal to M divided by N, i.e., each averaged metric contains the same number of contiguous sub-carriers as do all of the other averaged metrics.
• a straight-forward method (for a given codebook) is to compare the metric that was used for precoding matrix selection (the capacity metric, for example) across all bands and ranks.
• a disadvantage of this method is that all matrices in the codebook have to be scanned for all relevant ranks and the metric has to be found for the best matrix, and thus the complexity is high.
• a sub-optimal method but one that eliminates the need to scan all matrices in the codebook, is to approximate the capacity with the best precoding matrix from the codebook using the capacity with optimal precoding matrix without the quantization of the codebook.
• E s is the total transmit energy
• No is the noise energy
• H is the channel matrix
• F is the optimal precoding matrix (without codebook quantization) with the number of columns corresponding to the number of streams.
• the capacity for two streams may also be written as
• the capacity (or any other metric) does not represent the performance of precoding with different ranks with the same reliability, we can use a scaling factor when comparing the metrics for different ranks. For example, if we want to compare rankl precoding and rank 2 precoding for two receive antennas, we will choose rank2 when C 2 > a ⁇ Ci and choose rankl when C 2 ⁇ a ⁇ C ls where Ci and C 2 are as defined above and a is a parameter that can, as an example, be dependent on SNR.
• the calculation requirement for multiple channel instances occurs, for example, when calculating one precoding matrix suitable for multiple bands ("multiple band precoding matrix index"), when calculating a wide-band precoding matrix suitable for any sub-channel, when calculating a long-term precoding matrix suitable for a long time average, or the like.
• An algorithm according to an embodiment of the invention is to choose the matrix which has an increased (e.g., a maximum) accumulated metric over the instances, as follows:
• the addition is done over bands (e.g., different frequency bands in the same time frame; in a long-term precoding matrix the addition is done over frames, e.g., different time frames.
• FIG. 6 is a flowchart depicting a method 600 of identifying, for multiple channel instances, a target precoding matrix from a matrix codebook stored in a memory device and containing a plurality of precoding matrices according to an embodiment of the invention.
• FIG. 7 is a block diagram flowchart 700.
• a step 610 of method 600 is to provide a buffer of Ncodewords metrics according to a size of the matrix codebook.
• a step 620 of method 600 is to calculate a metric of the precoding matrix for each channel instance.
• a step 630 of method 600 is to accumulate the metrics of each precoding matrix to the metric in the buffer. Steps 620 and 630 are performed for each precoding matrix in the matrix codebook.
• a step 640 of method 600 is to identify as the target precoding matrix a particular one of the plurality of precoding matrices that yields a desired (e.g., a maximal) accumulated metric.
• the target precoding matrix here is simply the matrix preferred by the subscriber station.
• the subscriber station may then communicate this preference to a base station that may, in turn, select the subscriber station's preferred matrix (or another matrix) as the precoding matrix.
• step 630 comprises performing an addition over a plurality of bands, e.g., different frequency bands (groups of adjacent subcarriers ) in the same time frame.
• step 630 comprises performing an addition over a plurality of frames, e.g., different time frames.
• capacity values may be used for CINR reporting because in 802.16e the CINR for MIMO is based on MIMO capacity.
• the WiMAX standard requires, or will require in the future, that a MIMO-capable mobile station with maximum likelihood (ML) receiver implementation shall support averaged CINR reports based on capacity.
• the mobile station shall report AVG CINRd B according to the following calculations:
• AVG_CINR (1B 101og 10 (e c(Jj1H » - 1), Q S) where C d, y
• ⁇ 2 is an estimate of the noise power (defined below)
• H is the channel response matrix (referred to earlier herein simply as the channel matrix)
• H H is the channel response matrix after having been operated on by a Hermitian transpose operator.
• An extension of this method is to calculate C reg ion(d, y
• the WiMAX standard (specifically, IEEE 802.16 REV2 D8) specifies that the noise power shall be averaged over a region (of OFDM sub-carriers x OFDM symbols) in order to reduce its variance, as follows:
• Embodiments of the invention significantly reduce the amount of memory required, thus enhancing network performance.
• embodiments of the invention calculate the capacity using only a single iteration, thus eliminating the need to keep all of the pilots in memory. This simplified calculation is possible because trace(R"H p ) and abs(det(H p J) are nearly constant over a small region
• trace and determinant (and noise power) terms are changing in time and in frequency, in certain environments (such as low mobility environments) it is possible to find a local time/frequency region in which the variations of these terms are small enough that an average value of each term in that region may be found.
• Using (18) allows the averaging of the trace, determinant, and noise power terms to be done using a single iteration. For example, a mobile station may receive a pilot, estimate its channel, calculate the associated "trace,” “det,” and noise power terms, and then discard the pilot without the need to keep it in memory. Instead, only accumulated (or average) "trace,” “det,” and “noise power” need to be stored in memory, and these three terms are used to calculate the capacity.
• FIG. 8 illustrates the location of clusters 820 within a frame 810.
• Frame 810 is further partitioned into regions such as a region 835 in which the approximation of (18) may be implemented.
• Each cluster 820 is made up of eight pilots 821, half of which (those depicted as white circles) are transmitted from a first transmit antenna and half of which
• a second transmit antenna (those depicted as black circles) are transmitted from a second transmit antenna.
• This pilot structure is defined by the 802.16e standard and helps the receiver to estimate the channel matrix H.) Also illustrated are a time axis 850 and a frequency axis 860.
• Region 835 is an example of a region of a single cluster (or 14 subcarriers) over several OFDM symbols (e.g. all symbols in frame 810).
• the black and white circles represent pilots-subcarriers (as mentioned previously) and every rectangle is a region of 14 tones (in the frequency axis) over 2 symbols (in the time axis).
• the rectangle is also called a cluster (i.e., cluster 820), which includes 14 x 4 subcarriers among which are 8 pilot subcarriers.
• the pre-defined region in which (16), (17), and (18) are calculated is an area of N x M clusters, where the maximum value of M depends on the frame length (in symbols) and the maximum value of N depends on the fast Fourier transform (FFT) bandwidth.
• FFT fast Fourier transform
• a step 910 of method 900 is to receive a plurality of pilot tones.
• a step 930 of method 900 is to perform a trace operation and a determinant operation on each one of the plurality of channel response matrices (or function thereof— see above) in order to obtain a plurality of traces and a plurality of determinants.
• performing the trace operation comprises solving trace(R"H p ) , where p is an index of the pilot tones, H is the channel response matrix, and H H is the channel response matrix after having been operated on by a Hermitian transpose operator.
• performing the determinant operation comprises solving det(H ⁇ ), where, once again,/? is the index of the pilot tones and H is the channel response matrix.
• a step 940 of method 900 is to find an average value of the plurality of traces, an average value of the absolute value of the plurality of determinants, and an average value of the plurality of noise power terms.
• finding an average value of the plurality of traces comprises solving where P represents
• finding an average value of the absolute value of the plurality of determinants comprises solving
• P represents a total number of the pilot tones in the selected region.
• a step 950 of method 900 is to represent the capacity of the wireless network channel as a function of the average value of the plurality of traces, the average value of the absolute value of the plurality of determinants, and the average value of the plurality of noise power terms.
• a step 960 of method 900 is to find a solution of the function.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Physics & Mathematics (AREA)
• Mathematical Physics (AREA)
• Quality & Reliability (AREA)
• Electromagnetism (AREA)
• Power Engineering (AREA)
• Mobile Radio Communication Systems (AREA)
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• Error Detection And Correction (AREA)

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• 2009
  • 2009-09-23 US US12/586,620 patent/US8411783B2/en not_active Expired - Fee Related
• 2010
  • 2010-09-02 CN CN201080043204.3A patent/CN102577155B/zh not_active Expired - Fee Related
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