通过c++来实现电信部门的电信计费系统，能够实现对本地通话和长途通话的统计

这是一个优秀的Telcom公司开发的Q921商用协议栈，已在很多项目中使用并验证。实现了完整的Q921 LAPB和LAPD协议栈-This is an excellent Telcom developed Q921 commercial protocol stack has been used in many projects and verify. To achieve a complete Q921 LAPB and LAPD protocol stack

Wonderful decription about the Base Station Sub System of GSM. Their construction,working, types,methodoligiegs.Good source document for Telcom Engineer

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