SIM900 Circuit Design. Where to connect PWRKEY of SIM900.?

I am designing a circuit for SIM900 with a MCU. I have never designed the circuit for SIM900 so thought of posting question so that someone can review it. As per the datasheet, SIM900 works on power between 3.2v-4.8v. For this I have used LM317 with 150 & 370 resistors. So it will give output voltage of 4.33v. Below is the schematic for it:

VBAT is the output voltage of 4.33v.

Now in SIM900 I have connected TX RX pin to the MCU and have made connection for status and netlight, SIM Card connector. I have connected VBAT and GND. But I am confused with PWRKEY connections. Below is the schematic :

I don't have an idea about PWRKEY. I have a GSM Module and they are using a switch button for it which when pressed connect it to ground. But I do not want this. Is there any alternative for this. Also please review my circuit. Thanks.!

• The ability of an LM317 to to provide the required current during transmit is questionable. Try looking at published designs for the SIM900 (or failing that, seeing what you can learn from SIM800 or SIM808 designs). – Chris Stratton Jul 5 '16 at 6:25
• -1 For not reading the datasheet. The answer can be found in it for more scenarios. – Bence Kaulics Jul 5 '16 at 8:42