Why is the mobile phone delayed in receiving text messages?

The reasons for "delay" in SMS reception are as follows: (1) Mobile phone SMS memory overflows. After the mobile phone terminal's short message storage is full, SMS cannot be received normally. After the short message space is cleared, short message delivery delays will occur. . If the user cannot clear the SMS memory space in time, the phone will still be in a "memory overflow state" after the SMS center resends it multiple times, which will cause a "delay" of more than an hour in receiving SMS messages. (2) The mobile phone is turned off and is not in the service area. Due to wireless reasons, coverage reasons, mobile phone and other reasons, the network cannot page the user when sending text messages. It can also be said that "the mobile phone is not in the service area". In this case, the SMS center needs to send the SMS through the SMS resending mechanism. If the mobile phone is still "out of service area" after the SMS center resends it multiple times, it will cause a "delay" of more than one hour in receiving SMS messages. (3) Network problems In addition, network problems such as HLR, MSC, and SMS center will also cause "delay" problems in receiving SMS messages. However, compared with the first two types, the proportion of "delay" in SMS reception caused by network problems is not large. (4) Mobile phone or user card failure. Mobile phone or user card performance problems cause the inability to receive text messages accurately and timely.