中文摘要：

为实现一个Android平台的网络电话，提出一个基于PJSIP堆栈的VoIP系统设计方案。该方案符合Android NDK开发规范，即上层使用Java语言开发，下层采用纯c语言的PJSIP库开发其协议栈，并使用JNI连接上下两部分。在此叙述了PJSIP的原理，并以此为出发点，分析并设计了一个具体的VoIP系统。最后通过测试，该方案能很好地完成会话的发起、应答、通信，以及会话的注销等功能，达到了设计要求。

英文摘要：

To realize a VoIP for Android platform, a design scheme of VoIP system based on PJSIP protocol stack is proposed. The system meets the Android NDK development specifications, which is developed by Java language in application layer and developed by C in Android framework layer. The PJSIP principle is described, and as a starting point to design a specific VoIP system. The system can meet the design requirements through a test.