---
title: SIM (Cellular)
description: >-
  Test USSD flows, SMS messaging, and cellular network registration on real SIM
  cards using an on-premise Cellular agent and physical slots.
sidebarTitle: USSD
lastUpdated: "2026-09-09"
---

> **For AI agents:** the complete documentation index is at [llms.txt](/llms.txt). Append `.md` to any page URL for its markdown version.

The Cellular channel tests cellular networks, USSD flows, and SMS messaging on real SIM cards. Tests run on physical SIMs inside your on-premise **Cellular agent**.

## Quickstart

Create your first SIM test in four steps.

<Steps>
  <Step>
    **Create the test.** Open the **Tests** section for your product, click **+ Create new test**, choose **Classic**, and pick the **Cellular** channel. Name the test.
  </Step>
  <Step>
    **Add steps.** Build the flow with cellular actions: send a USSD command and assert the response, or send and receive an SMS. Save the test.
  </Step>
  <Step>
    **Run it on a SIM.** Click **Run** on the test's row, then pick a SIM in a Cellular agent slot on the [run confirmation](/executions/run) page and launch.
  </Step>
  <Step>
    **Read the result.** Open the execution under **Executions** to see status, the USSD or SMS responses, and timing.
  </Step>
</Steps>

<Info>
  Cellular covers data communication, USSD menu flows, and SMS send/receive. These are all part of one channel, not separate test types.
</Info>

<Tip>
  See [Cellular tests (USSD & SMS)](/tests/cellular) for a complete guide to authoring USSD menus, SMS flows, and handling network-initiated USSD pushes.
</Tip>

## Cellular tests

**Common actions:** send and receive SMS, navigate USSD menus, check network registration and signal, and test data connectivity.

## SIM cards

Physical GSM/3G/4G/5G SIM cards installed in the Cellular agent's slots. Each SIM reports:

- IMSI (International Mobile Subscriber Identity)
- Phone numbers (national and international format)
- Slot position in the agent
- Firmware version
- Registration status on the network
- Signal strength
- APN (Access Point Name) configuration
- Telecom operator
- Gateway (the agent controlling it)
- 24-hour test usage

See [Statuses](/equipment/statuses) for SIM statuses, network registration states, and signal levels.

## The Cellular agent

A specialized device that holds multiple SIM cards and runs tests on real cellular networks.

- Executes tests on physical SIM cards
- Handles USSD menu flows and SMS messaging
- Monitors network registration and signal strength
- Manages APN configurations for each SIM

### SIM slots

A Cellular agent contains multiple slots, each holding one SIM card:

- Slot ID (e.g. `agent-uuid-0`, `agent-uuid-1`)
- Position (numeric index: 0, 1, 2, etc.)
- Current SIM (empty, or the installed SIM)
- Active flag (is the slot currently operational)
- Firmware version

Each slot reports the status and registration status of its installed SIM independently.