> For the complete documentation index, see [llms.txt](https://gsm.learn-telecom.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://gsm.learn-telecom.com/system-information-messages/system-information-4-si4.md).

# System information-4 (SI4)

CBCH and CBCH related frequency information, LAI, Cell selection parameters and RACH control information are carried by this SI4 message.

![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2FjFtOuWiqnQfURQtogCS4%2Fimage.png?alt=media\&token=014ac1b6-6eda-44b7-94f5-be3f054c45c0)

![](https://1516040574-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2Fg081KOVSE5kjkOj8LvCP%2Fuploads%2F0rJJ34RHGGEgJG0PTvyk%2Fimage.png?alt=media\&token=add634c6-2b5d-41b6-9db2-78862391cea5)