MTK6577 signal dropping problem

I have (4.0 inch S9920 Android 4.1 3G Smart Phone MTK6577 Dual Core 1GHz WiFi GPS 12MP Camera – White):
Phone picture: http://www.pokit.org/get/img/a1ca62b705c1adad2061fb3639d8d987.png
Phone specifications: http://www.pokit.org/get/img/ec0e7c49193e46bac39fc2ac293d5b15.png
Software details: http://www.pokit.org/get/img/2b9aecdf2b20d29a506667b0285d8b0b.png

Problem is when I put phone on sleep signal is dropping. After few times acting like that, I don’t get that kind of notification, but I can’t call, or receive a call.

But when phone is on charger everything is fine.


Phone is unusable because of this error

Is there any solution?! I routed it using tutorial on this forum, and tried to increase CPU min from 250Mhz to 750Mhz or more, but it didn’t solve my problem.