GPRS(General Packet Radio Service)目前仍是行動通訊的主流，其核心網路主要是包括SGSN(Serving GPRS Support Node),GGSN(Gateway GPRS Support Node)兩大部分，透過此兩大部分可以來進行訊息傳遞和封包轉換，就算是3G行動網路系統，其核心網路也是參照GPRS網路發展而來的。

本論文的目的就是利用現成的伺服器和網路卡，以Linux作業系統為核心，修改現有OpenGGSN所提供的開放式GGSN與SGSNEmu的原始碼，再加上本論文新研發的手機模擬器(Mobile Station Emulator-MS Emu)以經濟而有效地發展出GPRS核心網路系統研發平台以做為GPRS之基礎。根據此平台可以來研究GPRS訊息傳遞，如:建立/回應PDP(Packet Data Protocal)請求等，或者實際上傳遞IP封包，透過Ethereal網路分析軟體可以來了解GPRS封包轉換的程序。

根據此論文中所開發的平台，了解到真實GPRS網路實際運作的情形，然後再更進一步去修改它，使它可適用於3G WCDMA，無線都會網路及其他多擷取網路，成為更有價值的研究發展平台。

This thesis presents a discussion of using off-the-shelf server hardware and network interface cards and OpenGGSN source codes to cost-effectively build a GPRS core network emulation system. Using this emulation system, a research on GPRS message communication flow was carried out. This includes GPRS attach request, activate PDP (Packet Data Protocol) context request, create PDP context request, create PDP context response and data packet delivery. A discussion of utilizing a network protocol analyzer called ‘Ethereal’ to analyze and visualize GPRS message/data packets flow within this system is also presented. Finally, problems encountered with OpenGGSN and solutions are also discussed.

This research produces two products: the YZU GPRS core network emulation system and a Linux-based GGSN prototype. The former includes a Mobile Station Emulator (MSemu) that can cost-effectively emulate multiple Mobile Stations. MSemu is a new product of this research.

With appropriate modifications, this emulation system can be extended to 3G cellular network, wireless local/metropolitan area networks and other multiple access networks, to become a very valuable research and development platform.

第一章 緒論 ………………………………………………………… 1
1.1 研究動機與目的 ……………………………………… 1
1.2 研究方法 ………………………………………………… 2
1.3 各章提要 ………………………………………………… 2
第二章 GPRS相關技術背景探討 ………………………………… 3
2.1 GPRS系統架構 ………………………………………… 3
2.2 GPRS 協定架構 ………………………………………… 4
2.2.1 傳輸層 ………………………………………………… 5
2.3.1 訊號層 ………………………………………………… 6
2.3 GPRS 傳送資料程序 ………………………………… 7
2.3.1 GPRS attach …………………………………………… 7
2.3.2 PDP context 程序 ……………………………………… 9
2.2.3 封包繞送與位址轉換 ………………………………… 12
2.3.4 GPRS detach ………………………………………… 14
第三章 OpenGGSN: Open Source GPRS 核心網路 ……………… 15
3.1 OpenGGSN介紹 ……………………………………… 15
3.2 OpenGGSN架構 ……………………………………… 16
3.2.1 GGSN架構 …………………………………………… 17
3.2.2 SGSNEmu架構 ………………………………………… 18
第四章 GPRS 核心網路之模擬與測試 ………………………… 21
4.1 模擬系統平台架構 ……………………………………… 21
4.2 模擬系統平台細節 ……………………………………… 23
4.2.1 MS Emu ……………………………………………… 23
4.2.2 SGSNEmu ……………………………………… 25
4.2.3 GGSN及Computer 1 on Internet ………………… 25
4.3 模擬測試流程 …………………………………………… 25
4.3.1 MS Emu-SGSNEmu間的模擬測試 ………………… 26
4.3.2 SGSNEmu-GGSN- Computer 1 on Internet間的模 擬測試 ……………………………………… 31
第五章 分析結果及探討 ………………………………………… 36
5.1 MS Emu-SGSNEmu介面 ………………………………… 37
5.2 MS Emu-SGSNEmu-GGSN介面………………………… 39
5.3 GGSN-Computer 1 on Internet介面……………………… 43
5.4 Delete PDP Context Request …………………………… 45
5.5 模擬系統的封包繞送與位址轉換 ……………………… 46
5.6 Computer 1 on Internet-MS Emu間的封包傳送………… 47
第六章 結論與未來發展 ………………………………………… 49
6.1 結論 …………………………………………………… 49
6.2 未來發展 ………………………………………………… 50
參考文獻 …………………………………………………………………… 51
附錄A ……………………………………………………………………… 52
附錄B ……………………………………………………………………… 57
附錄C ……………………………………………………………………… 60

[1] OpenGGSN- Open Source GPRS Core Network, http://www.openggsn.org/.
[2] Yi-Bing Lin and I. Chlamtac, ”Wireless and Mobile Network Architectures ”, John Wiley & Sons, Inc, 2001.
[3] 3GPP.3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Service(GPRS); Service description; Stage 2(Release 6). Technical Specification 3GPP TS 23.060 version 6.4.0 (2004-03).
[4] J. Eberspacher, et al, “ GSM Switching, Services and Protocols, 2e“, John Wiley & Sons, 2001.
[5] Sanders, Geoffrey,“ GPRS Networks ”, Wiley, 2003.
[6] Virtual Point-to-Point(TUN) and Ethernet(TAP) device, Maxim Krasnyansky & Maksim Yevmenkin, http://vtun.sourceforge.net/tun/.
[7] 3GPP.3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Service(GPRS);GPRS Tunneling Procotol(GTP) across the Gn and Gp interface(Release 6). Technical Specification 3GPP TS 29.060 version 6.5.0 (2004-06).
[8] W.Richard Stevens, ”UNIX Network Programming: The Sockets Networking API, 3e ”, Addison-Wesley, 2004.