# System Information Messages

- [System information-1(SI1)](https://gsm.learn-telecom.com/system-information-messages/system-information-1-si1.md): Cell ARFCN, RACH parameters required to access the system by MS and hopping related information are sent in this SI message.
- [System information-2(SI2)](https://gsm.learn-telecom.com/system-information-messages/system-information-2-si2.md): Neighbour BCCH frequencies and PLMN information are sent in this SI. MS uses these frequencies for signal strength measurements required for handover.
- [System information-2bis(SI-2bis)](https://gsm.learn-telecom.com/system-information-messages/system-information-2bis-si-2bis.md): RACH control and BCCH extension on neighbor cells
- [System information-2ter(SI-2ter)](https://gsm.learn-telecom.com/system-information-messages/system-information-2ter-si-2ter.md): Information of BCCH extended allocated on which neighbor cells are provided in this SI. Broadcasted optionally on BCCH by the network to all the MSs.
- [System information-2 Quarter (SI-2Quater)](https://gsm.learn-telecom.com/system-information-messages/system-information-2-quarter-si-2quater.md): 3G neighbor cell related information
- [System information-3 (SI3)](https://gsm.learn-telecom.com/system-information-messages/system-information-3-si3.md): Carry following : 1. LAI of the current location area, 2. Cell identity, 3. Control channel information required to calculate paging group, 4. Cell options to achieve good performance in the cell, 5.
- [System information-4 (SI4)](https://gsm.learn-telecom.com/system-information-messages/system-information-4-si4.md): CBCH and CBCH related frequency information, LAI, Cell selection parameters and RACH control information are carried by this SI4 message.
- [System information-5 (SI5)](https://gsm.learn-telecom.com/system-information-messages/system-information-5-si5.md): It carries neighbor cell informations. In active mode, MS sends measurement reports in the uplink and output power/timing advance information in the downlink (on SACCH). Also gets BCCH carrier related
- [System information-6 (SI6)](https://gsm.learn-telecom.com/system-information-messages/system-information-6-si6.md): Information on LAI, cell options, Cell identity and PLMN permitted or not is transmitted on this SI.
- [System information-7 (SI7)](https://gsm.learn-telecom.com/system-information-messages/system-information-7-si7.md): Cell re-selection parameters needed by MS are sent on this SI.
- [System information-8 (SI8)](https://gsm.learn-telecom.com/system-information-messages/system-information-8-si8.md): Cell re-selection parameters needed by MS are sent on this SI.
- [System information-9 (SI9)](https://gsm.learn-telecom.com/system-information-messages/system-information-9-si9.md): Scheduling related some of the informations are sent on this SI.
- [System information-13 (SI13)](https://gsm.learn-telecom.com/system-information-messages/system-information-13-si13.md): Carry GPRS related information needed for PS call.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://gsm.learn-telecom.com/system-information-messages.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.