Systems and methods for improved wireless channel estimation
View Patent ↗Systems and methods are disclosed herein to provide improved channel estimation in a wireless data communication system, including but not limited to Multiple Input Multiple Output (MIMO) communication systems. In accordance with one or more embodiments and aspects thereof, a channel estimation system is disclosed that utilizes data payload portions of received wireless packets to calculate estimates of the radio frequency (RF) channel traversed by these packets, and iteratively refines and improves these estimates by selectively utilizing successive received packets according to the application of certain metrics. Such a system may offer improved capabilities such as: more accurate signal reception, reduced bit error ratio, and better reception of short data packets.
1. A system for calculating radio frequency (RF) wireless channel properties for digital communications over a wireless channel, comprising:
a receive processor for receiving information over said wireless channel, converting the information to digital signals, and processing the digital signals;
a channel estimator for calculating a first channel property matrix from said digital signals;
a storage unit containing a plurality of previously computed channel property matrices;
a storage lookup unit operatively coupled to said storage unit that selects at least one second channel property matrix from said plurality of previously computed channel property matrices;
a function for determining whether said first channel property matrix is usable with said at least one second channel property matrix or said at least one second channel property matrix is usable with said first channel property matrix for improving the accuracy of the calculated RF wireless channel properties;
a combination unit for generating a composite channel estimate based on said first and said at least one second channel property matrix; and
an equalizer for using the composite channel estimate to process baseband signals supplied from a plurality of baseband processors to reverse effects of the wireless channel on signals carrying the information over the wireless channel.
2. The system of claim 1 , wherein said function comprises a channel change calculator function for computing a difference between said first and said at least one second channel property matrices, and further wherein said difference computed by said channel change calculator function is operative to determine if said at least one second channel property matrix is usable with said first channel property matrix.
3. The system of claim 1 , wherein said first and said at least one second channel property matrices are wireless channel estimates.
4. The system of claim 1 , wherein said first and said at least one second channel property matrices are channel equalization matrices.
5. The system of claim 1 , wherein said first channel property matrix is normalized to compensate for amplitude variations.
6. The system of claim 2 , wherein said channel change calculator function calculates a channel change metric.
7. The system of claim 1 , wherein said composite channel estimate is a weighted average of said first and said at least one second channel property matrix.
8. The system of claim 1 , wherein said plurality of previously computed channel property matrices is calculated from previously received digital data.
9. The system of claim 1 , further including a storage update unit operatively coupled to said storage unit that updates said plurality of previously computed channel property matrices from the output of said channel property matrix combination unit.
10. The system of claim 1 , wherein said function comprises: a first identifying metric calculator function for computing a first identifying metric on said first channel property matrix, wherein said at least one second channel property matrix comprises a plurality of second candidate channel property matrices, and wherein said first identifying metric is operative to determine if said first channel property matrix is usable with at least one of said plurality of candidate channel property matrices.
11. The system of claim 1 , wherein said at least one second channel property matrix comprises a plurality of candidate channel property matrices, and wherein said function comprises: a selector function for successively selecting one of said plurality of candidate channel property matrices as a selected channel property matrix, and a channel change calculator function for computing a difference between said first channel property matrix and said selected channel property matrix, wherein said difference computed by said channel change calculator function is operative to determine if said selected channel property matrix is usable with said first channel property matrix.
12. A method of calculating a property matrix for a radio frequency (RF) wireless channel, the method comprising the steps of:
receiving RF signals;
converting said RF signals to digital signals;
processing said digital signals;
calculating a first channel property matrix from said digital signals;
retrieving at least one second channel property matrix from a storage medium;
determining whether said first channel property matrix is usable with said at least one second channel property matrix or said at least one second channel property matrix is usable with said first channel property matrix for improving the accuracy of the calculated RF wireless channel properties;
generating, by a combination unit, a composite channel estimate based on said first and said at least one second channel property matrix; and
using, by an equalizer, the composite channel estimate to process baseband signals supplied from a plurality of baseband processors to reverse effects of the wireless channel on signals carrying the information over the wireless channel.
13. The method of claim 12 , wherein determining whether said at least one second channel property matrix is usable with said first channel property matrix comprises calculating a channel change metric using said first and said at least one second channel property matrices, wherein said channel change metric is used to determine if said at least one second channel property matrix is usable in conjunction with said first channel property matrix.
14. The method of claim 12 , wherein said first and said at least one second channel property matrices are calculated using RF channel estimation.
15. The method of claim 12 , wherein said first and said at least one second channel property matrices are calculated using RF channel equalization.
16. The method of claim 12 , further including the step of normalizing said first channel property matrix.
17. The method of claim 12 , further including the step of linearly combining said first and said at least one second channel property matrices.
18. The method of claim 17 , wherein said linear combination is performed by calculating a weighted average of said first and said at least one second channel property matrices.
19. The method of claim 12 , wherein determining whether said first channel property matrix is usable with said at least one second channel property matrix comprises:
calculating a first identifying metric from said first channel property matrix; and
retrieving said at least one second channel property matrix from the storage medium containing a plurality of stored channel property matrices,
wherein said first identifying metric is used to select said at least one second channel property matrix from said plurality of stored channel property matrices.
20. The method of claim 12 , wherein determining whether said at least one second channel property matrix is usable with said first channel property matrix comprises:
calculating a first identifying metric from said first channel property matrix;
retrieving a plurality of channel property matrices using said first identifying matrix;
successively selecting at least one candidate channel property matrix from said plurality of retrieved channel property matrices;
calculating a channel change metric using said first channel property matrix and said at least one candidate channel property matrix; and
using said channel change metric to check if said candidate channel property matrix is usable in conjunction with said first channel property matrix,
wherein said candidate channel property matrix is assigned as said at least one second channel property matrix according to said check.