Shrinkage based covariance estimators:
- Ledoit and Wolf 1.
- Improved Ledoit and Wolf estimator using the Rao-Blackwell theorem 2.
- Oracle approximating shrinkage estimator 2.
1 Ledoit, O., & Wolf, M., A well-conditioned estimator for large-dimensional covariance matrices, Journal of Multivariate Analysis, 88(2), 365–411 (2004). http://dx.doi.org/10.1016/s0047-259x(03)00096-4.
2 Chen, Y., Wiesel, A., Eldar, Y. C., & Hero, A. O., Shrinkage algorithms for mmse covariance estimation, IEEE Transactions on Signal Processing, 58(10), 5016–5029 (2010). http://dx.doi.org/10.1109/tsp.2010.2053029.