README.md
1# Cellular Call<a name="EN-US_TOPIC_0000001105379632"></a>
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3- [Introduction](#section117mcpsimp)
4- [Directory Structure](#section127mcpsimp)
5- [Constraints](#section131mcpsimp)
6- [Repositories Involved](#section204mcpsimp)
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8## Introduction<a name="section117mcpsimp"></a>
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10The cellular call module provides basic call services on carrier networks, including 2G/3G circuit switched \(CS\) calls and 4G/5G IP multimedia subsystem \(IMS\) calls \(including VoLTE/VoWIFI/VoNR voice, video, and conference calls\). It also supports domain selection and handover between CS and IMS calls, as well as emergency calls. This module is compatible with mainstream modem chip platforms.
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12The following figure shows the architecture of the cellular call module.
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14**Figure 1** Architecture of the cellular call module<a name="fig970511919486"></a>
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19The cellular call module consists of three layers:
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211. Cellular call management layer \(CellularCallService\): consists of CellularCallRegister, CellularCallProxy, and CellularCallHandler. CellularCallRegister provides the function of registering an observer for call information changes; CellularCallProxy functions as a proxy for implementing external APIs of CellularCallService; CellularCallHandler processes callback events reported by the RIL Adapter.
222. Cellular call service layer \(CellularCallStub\): consists of CSControl, IMSControl, CellularCallConfig, and CellularCallSupplement. CSControl implements CS call control; IMSControl implements IMS call control; CellularCallConfig implements call information configuration; CellularCallSupplement implements supplementary services.
233. Cellular call connection layer \(Connection\): consists of BaseConnection, ConfigRequest, and SupplementRequest. BaseConnection implements the call session connection function; ConfigRequest implements configuration requests; SupplementRequest implements supplementary service requests.
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25## Directory Structure<a name="section127mcpsimp"></a>
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27```
28/base/telephony/cellular_call # Cellular call module
29├─ BUILD.gn # Build script (gn)
30├─ README.md # Readme
31├─ services
32│ ├─ common # Tools
33│ ├─ connection # Connection layer
34│ ├─ control # Control service layer
35│ └─ manager # Management layer
36├─ sa_profile # SA profile
37├─ ohos.build # Build code
38└─ test # Test code
39```
40
41## Constraints<a name="section131mcpsimp"></a>
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43- Programming language: C++
44- Software constraints: This module must work with the telephony core service \(core\_service\) and Call Manager \(call\_manager\).
45- Hardware constraints: The accommodating device must be equipped with a speaker or earphone, a headset, and a modem and a SIM card capable of independent cellular communication.
46
47>**Note:**
48>APIs for the cellular call service are not exposed externally. They are directly called by the Call Manager.
49
50## Repositories Involved<a name="section204mcpsimp"></a>
51
52[Telephony Subsystem](https://gitee.com/openharmony/docs/blob/master/en/readme/telephony.md)
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54**telephony_cellular_call**
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56[telephony_core_service](https://gitee.com/openharmony/telephony_core_service/blob/master/README.md)
57
58[telephony_call_manager](https://gitee.com/openharmony/telephony_call_manager/blob/master/README.md)
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