Entropy of BTZ black hole and its spectrum by quantum radial geodesics   behind horizons
  In the framework of thermal quantization of radial geodesics completely confined behind the horizons we calculate the entropy of BTZ black hole in agreement with the Bekenstein--Hawking relation. Particles in the BTZ black hole occupy the only quantum ground level. The quantization allow us to find a linear dependence of black hole mass versus its orbital momentum. 
V.V.Kiselev