Android-based Smart Phone Telephony System Design And Implementation

With the development of wireless communication technology and mobile terminaltechnology, today’s smart phones include many functions, such as voice, images, data,Internet and other integrated functions.Android has withstood the test of the market, andoccupies a larger market share, a industry chain with the Android platform as the core hasgradually formed from the chip manufacturers, mobile phone manufacturers to a varietyof application development companies, Internet companies.It is because of the opensource of Android source code, major mobile phone manufacturers reduce theirdevelopment costs and rapidly launch the Android smart phone products with their owncharacteristics.Telephony as the basic communication function is the core of the phone, the phonewithout the basic communication capabilities, such as call, SMS and mobile Internet, willlose its own meaning. In the Android phone customization process, the scope and contentof Telephony involves widely, and because of its inherent complexity of communication,as well as greater environmental and hardware relevance,Telephony has always beenimportant and difficult in the development of Android smartphones. If we can in-depthstudy Telephony features and principles, we will solve the problems encountered in theAndroid phone customization development process better, and will improve the stabilityand performance of the system, make our products more competitive.Android Telephony system needs to adapt to many types of baseband module toaccess to the system, such as GSM baseband module, CDMA baseband module,3Gbaseband module. The baseband modules are implemented in a very different way due tothe different communication technology, even if two baseband modules with the samecommunication technology, because of the different manufacturer, there are manydifferences for the implementation ways.for example, the AT command format orinitialization sequence may vary. The differences between Baseband modules can not becompletely considered when designing Android Telephony, so RIL (Radio InterfaceLayer) is added to Android Telephony as the hardware abstraction layer to mask thesedifferences. RIL’s quality affect the overall performance of mobile communicationscapabilities.This paper firstly introduces the Android and smart phone Architecture, explains theAndroid development and compilation environment. Then analyzes the AndroidTelephony system framework, introduces the location of each layer and its functions indetails, expecially focuses on the the operating mechanism and the key businessprocesses of sub-modules of RIL layer. Then the design method of the Vendor RILrealization library named Td RIL is described in detail, Together with modem AT manualand the related communication protocols, voice call, SMS and3G online data services areimplemented. In final, test and verify android operating system’s3G related functions.