SIM800C 无信号却能上网，求牛人解答

这是我联网的过程

 SIM900 POWER ON
Time:2017-03-27 14:56:15
Time:2017-03-27 14:56:20
SIM900 SEND:[AT
]
SIM900 RECV:[A]
SIM900 SEND:[AT
]
]IM900 RECV:[AT
SIM900 SEND:[AT
]
SIM900 RECV:[AT
OK
]
SIM900 SEND:[ATE0
]
SIM900 RECV:[ATE0
OK
]
SIM900 SEND:[AT+CPIN?
]
SIM900 RECV:[
+CPIN: READY

OK
]
SIM900 SEND:[AT+CSQ
]
SIM900 RECV:[
+CSQ: 0,0

OK

SMS Ready
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
Time:2017-03-27 14:56:25
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,2

OK
]
SIM900 SEND:[AT+CREG?
]
1IM900 RECV:[

OK
]
SIM900 SEND:[AT+CREG?
]
SIM900 RECV:[
+CREG: 0,1

OK
]
SIM900 SEND:[AT+IFC=0,0
]
SIM900 RECV:[
OK
]
SIM900 SEND:[AT+CGATT?
]
SIM900 RECV:[
+CGATT: 0

OK
]
SIM900 SEND:[AT+CGATT?
]
SIM900 RECV:[
+CGATT: 0

OK
]
SIM900 SEND:[AT+CGATT?
]
SIM900 RECV:[
+CGATT: 1

OK
]
SIM900 SEND:[AT+CIPMODE=1
]
SIM900 RECV:[
OK
]
Time:2017-03-27 14:56:30
SIM900 SEND:[AT+CSTT
]
SIM900 RECV:[
OK
]
SIM900 SEND:[AT+CIICR
]
SIM900 RECV:[
OK
]
SIM900 SEND:[AT+CLTS=1
]
SIM900 RECV:[
OK
]
SIM900 SEND:[AT+CCLK?
]
SIM900 RECV:[
+CCLK: "04/01/05,04:35:22+32"

OK
]
SIM900 SEND:[AT+CIFSR
]
SIM900 RECV:[
10.180.181.235
]
SIM900 SEND:[AT+CIPSTART="TCP","123.232.100.4",2319
]
SIM900 RECV:[
OK
]
SIM900 RECV:[
CONNECT
]
SIM800 CONNECT OK
Time:2017-03-27 14:56:36

在联网之前，查询CSQ结果为0，0，但是最后的时候却能连上网，而且功能正常，谁知道这是怎么了

http://bbs.21ic.com/icview-1639138-1-1.html

注册需要时间，建议开机25秒后查询

SIM800在开机启动后一定时间内才能注册网络，通常是通过判断AT+CREG的返回值来确定网络是否成功注册后在检测当前网络信号强度