Asset impairment Process in SAP - Urgent

Hi SAP Guru...

from 2013 on wards, My client want to use Asset Impairment Process. How to do this in SAP ???

I have gone through different Post and all are bits and Pieces not Complete.

Can someone Guide me this. and explain the complete process and config steps..

1. Some says Unplanned depreciation

2. some says create New transaction types.

The expected Gl entry is

Asset Impairment Loss Dr.

Accumulated Impairment Loss Cr.

Depreciation is based on Useful Life.

Thanks....