Hello Charan, 

If we talk about MTech specialisation in communication and signal processing then IITs are really fabulous choices to go for and as you are getting a choice between IIT Indore and IIT Dhanbad then I would recommended going for IIT Indore as it's electronics department as well as the specialisation is really upto mark same as IIT Dhanbad. But the overall rankings and subsequent placements are good in IIT Indore not by any significant difference but with a minimal change than IIT Dhanbad. But the final decision is yours to make. Hope it helped.