Android core analysis (16)-Android phone system-Overview

Android phone system overview

First, let alone all the concepts of Android to study the most basic descriptions of the telephone system. Our mobile phone was first used for phone calls, followed by a phone book, followed by PIM, followed by network applications, followed by cloud computing, followed by the idea that our mobile phone can do anything to replace PC. However, the basic functions of a phone call are as follows:

0) dialing, answering, hanging up, sending SMS, network connection, and PIM Management

1) Since telephone operators provide us with additional services such as call waiting and teleconference, how should we manage multiple calls on our mobile phones?

2) When we call, we want to broadcast the incoming call ringtone. When we connect, we need to switch the voice channel. This has dealt with the multimedia system. For example, we have plugged in a headset and connected a Bluetooth headset, how should the system manage and switch?

3) How do I connect to and connect to the linuxsocket channel through PPP when establishing a network path (such as GSM GPRS) for Internet access? How does the system manage data connections?

4) when the AP communicates with the modem, how does one change the AT command into a specific operation function, how does one manage the response sent by the modem to us, how does one manage the AT command channel and Data Channel?

5) how to manage the SIM card phone book?

Android phone system designers must answer the above basic questions about mobile phones. What is the management framework of the design and what concepts are proposed to express it? Therefore, to analyze the phone number of Android, we still need to understand the background of telephone implementation, communication protocols, and general framework.

Back to the basic structure of the telephone system, let's first take a look at the general framework of the telephone module from the air. The figure I provided is a framework of a general smartphone. This framework can summarize the composition of all phone modules, including the Android phone system.

The smart machine architecture is generally an application processor + modem. The application processor and modem are connected using a serial port or USB. To achieve data transmission and control Modem at the same time in a hardware serial port path, the multiplexing protocol (GSM ts07.10) must be implemented ), at the underlying layer, we virtualize two serial ports, one for the CMD channel and the other for the data channel. All telephone control channels are on this channel.

RIL, radio interface layer. This layer is a protocol transfer layer, and the mobile phone framework needs to adapt to multiple types of modem access to the system. For different modem features, the AT command format or response varies, however, this feature cannot be fully considered and compatible during application design. Therefore, when designing a telephone system, the designer establishes a virtual telephone system and sets out standard functions for the virtual telephone system. The upper-layer telephone management is based on these standard functions. RIL converts the Standard Functions of the virtual phone system into the AT commands of the modem in use.

Android designers have designed the telephone system into three parts.

The phone service of andoird is actually a phoneapp. Gsmphone (cdmaphone) is the core object of the phone service. It contains the following related objects.

Our analysis task is to clarify the relationships between these objects and their data transmission relationships. First, we provide the following Android phone system framework to give a brief understanding of the Android phone system, and then analyze the system from the perspective of data flow and the reference relationship of objects. The following figure shows the overall framework of the Android phone system.

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