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GPRS

蔡佩倪 2010/10/29. GPRS. Outline. Introduction GSM system architecture GPRS network architecture GPRS/GSM mobile classes GPRS attach procedure PDP context activation GPRS Protocol Stack GPRS channels Summary. Introduction.

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GPRS

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  1. 蔡佩倪 2010/10/29 GPRS

  2. Outline • Introduction • GSM system architecture • GPRS network architecture • GPRS/GSM mobile classes • GPRS attach procedure • PDP context activation • GPRS Protocol Stack • GPRS channels • Summary

  3. Introduction • The General Packet Radio Service (GPRS) is an European Telecommunications Standard Institute (ETSI) standard for packet data transmission using the core GSM (Global System for Mobile Communications) radio access network. • It provides switched packet data transfer to efficiently utilize the radio resources. • It provides a quick session set up and fast data transmission speeds. Supports immediacy (no dial-up connection is necessary) • theoretically supports maximum speeds of up to 171.2 kbps

  4. B BTS other GSM PLMN PSTN PSDN ISDN GSM System Architecture - I VLR MSC G C OMC D VLR Um E B D BSS MSC HLR AUC BSC A C A bis MS F E I R 與固定網路間之介面

  5. GSM System Architecture - II • GSM系統之行動臺(Mobile Station，簡稱MS)是由一「行動話機」及一「客戶識別模組」(Subscirber Identity Module，簡稱SIM)所組成。 • HLR為一大型資料庫，其內主要儲存系統所有行動用戶之相關資料，以做為行動用戶漫遊辨識、記帳之用途。 • 行動交換中心(MSC)是整個 GSM 行動通信系統的中樞，負責行動用戶與行動用戶間之交換接續，及行動用戶與固定網路(如PSTN，ISDN，PSDN等)間之銜接，並與VLR，LR/AUC，EIR等相連接，以取得行動用戶之相關資料。 • 「訪客位置記錄器VLR」主要負責儲存目前漫遊(Roaming)到此一VLR服務區之來訪行動用戶之相關資料，俾使行動用戶漫遊到此一VLR服務區時，仍可繼續享有GSM 行動通信的服務。 • 「設備識別記錄器」(EIR)提供系統經營者具備核對「國際行動台設備識別碼」(IMEI)之能力，以避免讓已遭竊或未經授權之行動台設備進接入其GSM系統。

  6. More about VLR • 訪客位置記錄器(Visitor Location Register, VLR) • 負責儲存目前漫遊(Roaming)到此一VLR服務區之來訪行動用戶之相關資料，包括 • 國際行動用戶識別碼(International Mobile Subscriber Identity, IMSI): 為國際唯一之號碼 (stored in SIM card, sent by phone to BS) • 行動台漫遊號碼( Mobile Subscriber Roaming Number, MSRN) • 行動台最新註冊之位置區(Location Area, LA) • 暫時行動用戶識別碼(Temporary Mobile Subscriber Identity, TMSI): 由VLR指配，較IMSI短，具節省無線資源及保密等優點 • 用戶資料… • 適時向HLR擷取用戶資料 (thru IMSI) • 負責執行認證、位置更新、加密之支援、用戶註冊/解註冊程序、用戶增添服務之處理、IMSI及TMSI（取代IMSI避免被竊取）之管理，可單獨存在亦可與MSC結合在一起。

  7. More about HLR • 本籍位置記錄器(Home Location Register, HLR) • 為一大型資料庫，儲存系統所有用戶之相關資料，做為漫遊辨識、記帳之用，包括 • 行動台ISDN號碼(Mobile Station ISDN Number, MSISDN): 如 886-932123456 • IMSI • 呼叫路由選擇所需之暫時位置訊息(即VLR之ID) • MSRN • 用戶登記資料 • 執行位置註冊 • 提供用戶登記資料給VLR • 提供MSRN給MSC • 認證與加解密之支援 • 與VLR、MSC、AUC間之信號傳送 • 可單獨存在，亦可與其他元件合併。(大多數廠商均將HLR與AUC合併裝設)

  8. GPRS network architecture

  9. GPRS network architecture • The gateway GPRS support node (GGSN) • provides a gateway between the GPRS network and the public packet data network (PDN) or other GPRS networks. • provides authentication and location management functions, connects to the home location register (HLR) by means of the Gc interface, and counts the number of packets transmitted for accurate subscriber billing.

  10. GPRS network architecture • The serving GPRS support node (SGSN) • controls the connection between the network and the mobile station (MS). • provides session management and GPRS mobility management functions such as handovers and paging. It also counts the number of packets routed.

  11. GPRS network architecture • Functions of the packet control unit (PCU) • converting packet data into a format that can be transferred over the air interface • managing radio resources • implementing quality of service (QoS) measurements

  12. GPRS/GSM mobile classes • Class A (GSM/GPRS) • Class A mobiles can attach to the GPRS and GSM network simultaneously. • Class B (GSM/GPRS) • This class is similar to class A with the exception that Class B mobile phones will not support simultaneous traffic. • Most GPRS mobile devices are Class B. • Class C (GSM or GPRS) • This class of mobile phones will have both GSM and GPRS functionality but will attach to only one network at a time.

  13. GPRS Routing Example 1

  14. GPRS Routing Example 2

  15. GPRS Routing Example 3

  16. The GPRS attach procedure • A GPRS attach is a GPRS mobility management (GMM) process that is always initiated by the mobile phone. • Depending on the settings of the mobile phone, the GPRS attach may be performed every time the phone is powered on, or it may be initiated manually by the user.

  17. The GPRS attach procedure

  18. PDP context activation • A PDP context activates a packet communication session with the SGSN. • During the activation procedure, the mobile phone either provides a static IP address or requests a temporary one from the network. • It also specifies the access point name (APN) with which it wants to communicate. • The mobile requests a desired quality of service (QoS) and a network service access point identifier (NSAPI).

  19. PDP context activation

  20. GPRS Protocol Stack

  21. Transmitting the packet data units

  22. GPRS logical channels • Logical channels are pre-defined functions supported by frames within a physical channel. • GPRS physical channels generally carry two types of information: control signaling for establishing and maintaining a GPRS service, and user data traffic. • GPRS logical channels can be classified as packet control channels and packet traffic channels.

  23. GPRS logical channels

  24. GPRS logical channels • PBCCH (packet broadcast control channel) • is used to broadcast packet data system information to all GPRS mobiles in a cell. • The PBCCH might not be present for certain channel combinations, in which case the BCCH will be used to broadcast packet system information.

  25. GPRS logical channels • PCCCH (packet common control channel) • a set of logical channels used for common signaling between the mobile station and the base station. (PRACH, PPCH, PAGCH, PNCH) • PRACH (packet random access channel) • is used only in uplink to initiate uplink transfer. • PPCH (Packet Paging Channel) • is used to page a mobile prior to downlink packet transfer.

  26. GPRS logical channels • PAGCH (packet access grant channel) • is used in the packet transfer establishment phase to send resource assignment messages to a mobile prior to packet transfer. • PNCH (packet notification channel) • is used to send a point-to-multipoint multicast notification to a group of mobiles prior to point-to-multipoint multicast packet transfer.

  27. GPRS logical channels • PTCH (packet traffic channel) • PDTCH (packet data traffic channel) • is allocated for data transfer. • It is dedicated temporarily to one or a group of mobiles for multicast applications. • PACCH (packet associated control channel) • is used to convey signaling information related to a given mobile • PTCCH (packet timing advance control channel)

  28. GPRS physical channels • Radio channels of GPRS are the same as GSM TDMA frame = 4.615ms Timeslot 1 2 3 4 5 6 7 8 Frequency 1 Frequency 2 … … … … Frequency 124

  29. GPRS physical channels • The physical channel dedicated to packet data traffic is called a packet data channel (PDCH). • The logical channels are mapped over physical channels using the technique of “multiframing.” • The GPRS multiframe length is 52 TDMA frames, and it is organized into 12 blocks of 4 consecutive TDMA frames, plus 4 idle frames.

  30. The 52-multiframe structure

  31. 52-multiframe for four time slots

  32. Mapping logical channels tophysical channels

  33. Mapping logical channels tophysical channels • Example on downlink • Example on uplink

  34. Resource allocation GSM only GPRS only GSM only GSM & GPRS GPRS only

  35. Summary • GPRS technology adds packet-switching capability to GSM • PCU, GGSN, SGSN • Time slot, frame • 1 TDMA frame = 8 Time slot • 52-multiframe structure • 12 Radio blocks

  36. References • Agilent Understanding General Packet Radio Service (GPRS) http://cp.literature.agilent.com/litweb/pdf/5988-2598EN.pdf • S. Emmanuel, S. Patrick, P. Pierre-Jean, GPRS for Mobile Internet, Artech House, 2003. • Kai-Wei Ke, Chen-Nien Tsai, and Ho-Ting Wu, “Performance analysis for hierarchical resource allocation in multiplexed mobile packet data networks,” Computer Networks, Vol. 54, Issue 10, 2010, pp. 1707-1725. • General Packet Radio Service (GPRS) Overview http://www.pcs.csie.ntu.edu.tw/course/pcs/2007/reference/08_GPRS_Overview.pdf • 廖宏祥，鐘嘉德。整合分封無線服務(GPRS)簡介。暨大電子雜誌。http://beaver.dlc.ncnu.edu.tw/projects/emag/show.aspx?dataId=98d2571b-481d-483b-8804-f64ed720c38b • 邱弘斌。行動網際網路技術與應用上課投影片。

  37. THANK YOU Q & A

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