  We report on the MIT Epoch of Reionization (MITEoR) experiment, a pathfinder
low-frequency radio interferometer whose goal is to test technologies that
improve the calibration precision and reduce the cost of the high-sensitivity
3D mapping required for 21 cm cosmology. MITEoR accomplishes this by using
massive baseline redundancy, which enables both automated precision calibration
and correlator cost reduction. We demonstrate and quantify the power and
robustness of redundancy for scalability and precision. We find that the
calibration parameters precisely describe the effect of the instrument upon our
measurements, allowing us to form a model that is consistent with $\chi^2$ per
degree of freedom < 1.2 for as much as 80% of the observations. We use these
results to develop an optimal estimator of calibration parameters using Wiener
filtering, and explore the question of how often and how finely in frequency
visibilities must be reliably measured to solve for calibration coefficients.
The success of MITEoR with its 64 dual-polarization elements bodes well for the
more ambitious Hydrogen Epoch of Reionization Array (HERA) project and other
next-generation instruments, which would incorporate many identical or similar
technologies.
