sim900a pdp deactivate

Hi to all,

I am using SIM900A for my project.In this i am facing some issues.

They are,

1.In Debug only 5 to 10 minutes i am connecting GPRS connection after that i am getting PDP DEACT.If i restart my microcontroller then again it works only for 5 to 10 minutes and it goes to PDP DEACT.I dont know why?

2.Some times CONNECT FAIL also came.What it means?

I am trying like this.
>>AT+CREG?
<< wait for responce
>>AT+CIPSTATUS
<<wait for responce
>> AT+CSTT(here iam using APN)
<<wait for responce
>>AT+CIICR(Bring wireless connection)
<<wait for responce
>>AT+CIFSR
<<wait for responce
>>AT+CIPSTART(IP address)
<<wait for responce



Please guide me to solve my issues

thanks in advance...