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Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Divya S Pillai <91891495+divipillai@users.noreply.github.com>

Author: 3 people

doc/app/sm_cellular_modem.rst

@@ -204,7 +204,7 @@ The controlling chip runs a Zephyr application, which uses Zephyr's native IP st
    * System mode is not configured. See the `%XSYSTEMMODE`_ command in the AT command Reference Guide for more details.
 
 User pipes for AT commands
-===========================
+==========================
 
 Zephyr's cellular modem driver provides **user pipes** for sending AT commands to the modem while PPP is active.
 User pipes are additional CMUX channels (DLC channels 3 and 4) that the host application can use for modem configuration, DFU/FOTA, or other AT command operations.
@@ -216,13 +216,13 @@ User pipes are available only when the modem driver has all CMUX channels open.
 This occurs after the following conditions are met:
 
 * CMUX has been started with ``AT+CMUX=0``.
-* The network interface is brought up with ``net_if_up()``, which opens CMUX channels, attaches to the network, and opens the PPP connection.
+* The network interface is activated with ``net_if_up()``, which opens the CMUX channels, connects to the network, and establishes the PPP connection.
 
-When the network interface is brought down with ``net_if_down()``, PPP is closed and user pipes become unavailable.
+When the network interface is deactivated with ``net_if_down()``, the PPP connection is closed and user pipes become unavailable.
 
 .. important::
 
-   User pipes are NOT available when PPP is closed.
+    User pipes are not available when PPP is closed.
    The modem driver is designed so that ``net_if_up()`` opens all CMUX channels, including user pipes, and ``net_if_down()`` closes them.
 
 The DLC channel callback notifies the host application when a user pipe opens or closes.
@@ -234,7 +234,7 @@ User pipes allow the host application to send AT commands while maintaining an a
 Common use cases include:
 
 * Configuring eDRX and PSM settings (``AT+CEDRXS``, ``AT+CPSMS``).
-* Performing modem firmware updates via ``AT#XFOTA`` or DFU commands.
+* Performing modem firmware updates using ``AT#XFOTA`` or DFU commands.
 * Querying modem status and diagnostics.
 * Managing SMS or other modem features not exposed through the PPP interface.
 * Temporarily pausing PPP for maintenance operations.