Design method of dual network dual standby based on Android platform

(3) Application framework layer.

Android application development is based on frameworks and components, which provide a variety of advanced building blocks that you need to use when creating your application, so in this layer, developers have full access to the framework API when developing the application. Calling many of the components that come with Android itself, you can also develop new components and put them into the application framework for yourself and other applications to call. Such modules greatly improve the development efficiency of the application.

(4) Application layer.

Android itself includes some core applications developed by Java, such as desktop, SMS transceiver, calendar, phone address book, browser, E-mail client, etc. Developers can also develop more unique features on this basis. Android apps, such as special effects cameras, players, charging photo frames, and more.

3. 1 Android dual network dual standby implementation

The scheme of implementing the dual-network dual-standby mechanism by adding a set of radio interface layer RIL supporting CDMA in GSM single-mode state is shown in Figure 3.

Figure 3 Android dual network dual standby phone part structure

In PhoneAPP, a new GSMPhone and a CDMAPhone correspond to two frameworks (different CallTracker) and RIL (different RIL), respectively, to achieve single-mode dual-network dual standby improvement.

In the figure, CallLiST is mainly used to manage the switching between two phones, so as to avoid a series of interface display errors such as hanging one call but causing another to end. The CallList module manages two calls and all calls to both phones, storing all calls for both phones through a CallList table. The upper interface calls this CallList table to handle the switching of the two phones. In the framework, a new CallList class is used to store multiple phones of the phone for display on the upper layer.

The CallList class contains methods such as attached(), detach(), update(), clear(), get-CurrentCall(), getDefault(). Make the Calls of the two Phones under control. When you hang it, delete it from the table and add it to the table when you call it.

When the upper layer is displayed, as long as the last call to the Call in the CallList is called, there will be no interface error.

In the dual-network dual-standby module with GSM network and CDMA network, since the code of the CDMA part has changed a lot, the original CallTracker is only used by GSM. Here, it is changed to CallTracker and GsmCallTracker to abstract the CallTracker base class. It can also be used by CDMA; GSMCall becomes GsmCall, which is more consistent with the uniform naming rules; in addition, the startup part of pppd is also placed from the Java framework layer to the RIL layer.

3. 2 Android RIL layer improvements

In the Android system, RIL is a local implementation of the telephone system. It provides an abstraction layer between the Android phone service (android. telephony) and the radio hardware. It is mainly responsible for the transmission and response analysis of AT commands, which is also the basis for the implementation of the telephone service. In addition, RIL is responsible for the reliable transmission of data. So RIL plays a central role in the Android phone section. The design of the program mainly involves the modification of the following four parts of the RIL:

(1) Since the solution maintains two RIL instances, the RIL instance manager needs to be responsible for connecting with the android telephony through the socket. Each RIL instance provides a dedicated communication channel for the SIM-side communication service for the respective SIM card.

(2) Radio Service Arbitration Manager, which is a newly added module in the dual-network dual-standby scheme. It is mainly used to arbitrate voice and short message services for each RIL instance. MODEM to proceed.

(3) RIL Event Dispatcher, which is used to allocate RIL request and AMSS events to the communication service management module for processing.

(4) Radio Service Manager, the Android call application first needs to obtain the call service from the framework layer through the subsystem information, and then each SIM card subsystem will be mapped to a specific RIL instance ID, service management. The ID of the RIL instance will be used to identify the parameters of the DSS API in the subsystem ID.

3. 3 Android dual network dual standby call mechanism implementation

The implementation of Android system phone service is based on RIL. RIL in Android single mode is similar to TI and other platforms. It uses Google's default reference interface, which is to open the modem side or USB virtual serial port to send to the modem side. The AT command is used to perform actual wireless communication. For example, the upper layer of the UI sends a RIL_REQUEST_DIAL request to the RIL layer. When receiving the request, the RIL layer sends an "AT***" command to the modem through the serial port to initiate a call. Of course, the function that actually implements the call is the modem side. At this point, it has nothing to do with Android. The working principle of the Android platform RIL and modem is shown in Figure 4.

Figure 4 How RIL and modem work

Calls are built on top of the basic architecture of the telephone service.

The main user interface related to the call is actually based on the ITelephony interface to implement the "Phone" service in the Phone application, and the access interface is provided through the TelephonyManager. This service internally accesses the RIL through the GSMPhone / CDMAPhone obtained by PhonyFactory, providing services such as dialing, connecting, hanging up, and holding calls. The structure of the Android dual-network dual standby call part is shown in Figure 5.

Figure 5 android dual network dual standby call part structure

The implementation of the dual-network dual-standby call part of the Android system mainly involves several key data structures from GSMPhone/CDMAPhone to the corresponding RIL path, namely GSMCall /CDMACall, CallNotifiter, GSMConnection /CDMAConnection, CallTracker and so on.

Both GSMCall and CDMAPhone inherit the Call base class, providing basic call control structure and call status, such as Hold, Active, etc. Each connected GSMCall / CDMACall has one or more (conference call) GSMConnection / CDMAConnection structure. Used to maintain related information such as call duration. CallTracker is the core of the call module, which provides call-related interfaces such as calls, hang-ups, and more. GSMPhone / CDMAPhone has an instance of CallTracker and encapsulates the corresponding interface. This interface is implemented by calling CommandsInterface in GSMPhone / CDMAPhone, that is, the submitted RIL package.

In addition, the CallTracker maintains the current GSMCall and CDMACall lists, keeps track of all call statuses, and provides management of call status such as outgoing calls. The way to implement tracking is pollCallsWhenSafe, which gets the list of currently active calls through the getCurrentCalls interface of CommandsInterface. The underlying implementation of this operation is AT + CLCC (different Modem implementations may be different), which is the primary interface for getting a list of call states from Modem. The callback is done by ENENT_ POLL _ CALLS-RESULT. The callback function is handlePollCalls, which is the core method for getting the actual call information in the modem, and the meaning of the Tracker. handlePollCalls completes the actual tracking function, and updates the information of the Call list according to the status of Outgoing, Incomming, Active, Hold, etc. reported by the bottom layer. The state transition of each call during its life cycle can be reflected in the Call-Tracker, and will be reflected in the Call-Tracker. These changes are promptly notified to their followers, that is, to implement the Phone application.

4 Results analysis

Based on the Android operating system, the dual-network dual-standby function module design utilizes Android's universal system architecture and device-independent application development platform to realize the frame design and upper-layer Phone application design of the dual-network dual-standby single-pass system. The improved Android system platform supports both GSM and CDMA networks for simultaneous standby, which greatly facilitates many users who have two mobile phone cards and are not on the same network. Figure 6 is a state diagram of simultaneous standby of GSM and CDMA dual networks on the Android system platform.

Figure 6 GSM and CDMA dual network simultaneous standby interface

5 Conclusion

Utilize Android's original system architecture and itself contain some Java core applications, and add a new set of CDMA-enabled RIL to realize dual-network dual standby design based on Android platform, so that one mobile phone maintains two independent RILs at the same time. Support GSM and support CDMA, respectively, separate processing of dual SIM cards, greatly facilitating the majority of Android mobile phone users. As a smartphone operating system that is currently highly anticipated, dual-network dual standby will surely win a broader development space and more supporters, and will also lay a solid foundation for future development. Although some of the design of this program is still not perfect, many details have yet to be resolved. However, with the continuous upgrade of Android version and the continuous enrichment of Android applications, the dual-network dual-standby design based on Android platform will continue to improve and develop.