If you are resigning, there is no compensation that you can get under the Indian labour laws.
It does not matter on the fact that you have been working for 15 years you have contributed to the financials of the company. That was a part of your job and it was your duty to have done your work properly. The compensation that you will get is the ones listed above and nothing.
However, if you do not resign, and you are terminated by the company or you retrenched, you would be entitled to compensation for this. In case of termination, you would be entitled to reinstatement if the termination is not for a valid cause or for any misconduct under the standing orders. in case of retrenchment, you will get retrenchment compensation of 15 days for every year work. Further, retrenchment can only be done in reverse order of which means they can retrench you only after they have retrenched others who have joined after you.