통신시스템(Gprs network)

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About GPRS Network

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통신시스템(Gprs network)

  1. 1. Telecommunication Basics (GPRS Network) Software Engineering Lab - 김영기 책임
  2. 2. Remember Again !!! 1G 2G 3G 3.5G 4G WiMAX track 802.15e Wave1 802.15e Wave2 802.16e 802.16n (Mobile WiMAX) (Mobile WiMAX) WiMAX R1.5 WiMAX R2.0 CDMA-1X CDMA-1X CDMA-1XCDMA track EV-DO r0 EV-DO rA EV-DO rB UMB AMPS IS-95 A IS-95 B CDMA-1X EV-DVGSM track EDGE LTE LTE Advanced NMT GSM GPRS W-CDMA W-CDMA W-CDMA W-CDMA W-CDMA R5 R6 R7 HSPA+ R3 (HSCPA) (HSUPA) (HSPA+) Phase2음성 통화 통화, 문자, 이메일 통화, 문자, 멀티미디어, 무선인터넷 초고속 인터넷 초고속 무선 인터넷 유,무선간 연동
  3. 3. What is GPRS ? GPRS (General Packet Radio Service)  General = Not restricted to GSM use  Packet Radio = Enable Packet mode communication over air  Service = Not System, Existing BSS (Partially also NSS) infrastructure is used Part of GSM phase 2+ Required many new network elements into NSS Provides connections to external packet data networks (Internet, X.25) Benefits Resources are reserved only when needed and charged accordingly Connection setup times are reduces Enables new services opportunities
  4. 4. GPRS Characteristics GPRS uses packet switched resource allocation Resource allocated only when data is to be sent/received Flexible channel allocation One to eight time slots Available resources shared by active users Up and Down link channels reserved separately GPRS and circuit switched GSM services can use same time slots alternatively Traffic characteristics suitable for GPRS Intermittent, busty data transmissions Frequent transmissions of small volumes of data Infrequent transmission of larger volumes of data
  5. 5. GPRS Architecture BSC BTS PSTN Um MSC Gb HLR/AuC SMS-GMSC Gr Gr Gd Serving GPRS Support Node(SGSN) Gs Gd SS7 Coperate1 Gn Network Server Border EIR Intra-PLMN Gateway (BG) Backbone MAP-FInter-PLMN Gp Network Backbone (IP Based) Gateway GPRS Network Support Node Local area Router Gn (GGSN) Gi.IP Data Network Network Point-To-Multipoint (Internet) Service Center (PTM-SC) Coperate2 Server Gi.X.25 Data Router Network (X.25) Local area Network
  6. 6. GSM to GPRS
  7. 7. Interfaces
  8. 8. Radio Interface Protocols 2 Plane User plane Control Plane 3 Layers Layer 1 : Physical (PHY) Layer 2 : Data Link Media Access Control (MAC) Radio Link Control (RLC) Packet Data Convergence Protocol (PDCP) Layer 3 : Radio Resource Control (RRC) for lu mode Radio Resource (RR) for A/Gb mode
  9. 9. Protocol Stack GPRS Control Plane Protocol Stack GMM/SM GMM/SM LLC LLC LLC Relay RLC RLC BSSGP BSSGP MAC MAC Network Network Service Service GSM RF GSM RF L1bis L1bis MS BSS (PCU) SGSN Um Gb GMM/SM (New in GPRS) GPRS Mobility Management and Session Management GPRS Attach/Detach PDP Context 구성 및 해제 GPRS 단말 위치 갱신 – Routing Area Update/Location Update 인증 Radio Resource Assign
  10. 10. Protocol Stack GPRS Traffic Protocol StackApplication IP/X.25 IP/X.25 E X.25 N SNDCP SNDCP GTP GTP IP D LLC LLC LLC UDP/TCP UDP/TCP N RLC RLC BSSGP BSSGP IP IP O MAC MAC Frame Relay Frame Relay L2 L2 D E GSM RF GSM RF L1bis L1bis L1 L1 MS BSS (PCU) SGSN GGSN Gi Um Gb Gn
  11. 11. Assignment of functions Function MS BSS SGSN GGSN HLR Network Access Control Registration √ Authentication and Authorization √ √ √ Admission Control √ √ √ Message Screening √ Charging Data Collection √ √ Packet Routing & Transfer Relay √ √ √ √ Routing √ √ √ √ Addressing Translation and Mapping √ √ √ Encapsulation √ √ √ Tunneling √ √ Compression √ Ciphering √ √ √ Mobility Management √ √ √ √ Logical Link Management Logical Link Establishment √ √ Logical Link Maintenance √ √ Logical Link Release √ √ Radio Resource Management Um Management √ √ Cell Selection √ √ Um-T ranx √ √ Path Management √ √
  12. 12. Gateway GPRS Support Node Typically located at one of the MSC sites One (or few) per operator Main functions Interface to external data networks Resembles to a data network router Forwards end user data to right SGSN Converts the GPRS packets from SGSN to the PDP format Routes mobile originated packets to right destination Converts PDP addresses change to GSM addresses of the destination user Filters end user traffic Collects charging information for data network usage Data packets are not sent to MS unless the user has activated the PDP address Performs authentication Many-to-many relations among SGSNs & GGSNs
  13. 13. Serving GPRS Support Node Functionally connected with BSC, physically can be at MSC or BSC site One for few BSCs or one (or few) per every BSC One SGSN can support BSCs of several MSC sites Main functions Delivers data packets to mobile stations & vice-versa Authenticates GPRS mobiles / Maintain user profile Handles mobile’s registration in GPRS network Handles mobile’s mobility management / Packet Routing, Transfer Relays MO and MT data traffic TCP/IP header compression, V.42bis data compression, error control MS- SGSN (ARQ) Collect charging information of air interface usage
  14. 14. Other Elements Entity Functionality  Not defined within GPRS BG  Routes packets from SGSN/GGSN of one operator to a SGSN/GGSN of an other (Border Gateway) operator  Provides protection against intruders from external networks DNS  Translates addresses from ggsn1.oper1.fi-format to 123.45.67.98 format (Domain Name Server) Charging Gateway  Collects charging information from SGSNs and GGSNs  PTM Multicast (PTM-M) - Downlink broadcast, No subscription, No Ciphered PTM-SC  PTM Group call (PTM-G) (Point to Multipoint-Service Center) - Closed or open groups, Down/Up link, Ciphered  Geographical area limitation
  15. 15. GPRS Backbones GPRS Backbones Enables communication between GPRS Support Nodes based on private IP Network IPv6 is the ultimate protocol IPv4 can be used as an intermediate solution Intra-PLMN backbone Connect GPRS Support Nodes of one operator Operator decides the network architecture LAN, Point-to-Point links, ATM, ISDN, … Inter-PLMN backbone Connects GPRS operators via BGs Provides international GPRS roaming Operators decide the backbone in the roaming agreement
  16. 16. Physical Channels FDMA + TDMA Defined by timeslot (0~7) and Radio frequency channel Shared Basic Physical Sub Channel Shared among several users (up to 8) Uplink Stage Flag (USF) controls multiple access Dedicated Basic Physical Sub Channel One user support Packet Data Channel (PDCH) Dedicated to packet data traffic from logical channels (Refer Next Slide) Control User data
  17. 17. Logical Channels Mapped by the MAC to physical channels Control channels for control, synchronization and signaling Common/Dedicated/Broadcast Packet Traffic Channels Encoded speech/Encoded data Packet Data Logical Channels Traffic Channels Control Channels PCCCH PBCCH PDCCH PDTCHPTCCH/U PTCCH/U PTCCH/D PACCH PBCCH PTCCH/U PTCCH/D PACCH PDTCH/H PDTCH/D [Up] [Down] [Down] [Down] [Down] [Up/Down] [Down] [Up] [Up] [Down] PCCCH = Packet Common Control Channel PPCH = Packet Paging Channel Up = Uplink Direction PBCCH = Packet Broadcast Control Channel PAGCH = Packet Access Grant Channel Down = Downlink Direction PDCCH = Packet Dedicated Control Channel PNCH = Packet Notification Channel PDTCH = Packet Traffic Channel PACCH = Packet Associated Control Channel PRACH = Packet Random Access Channel PTCCH = Packet Timing Advance Control Channel
  18. 18. Control Channels Packet Common Control Channel (PCCCH) Paging (PPCH) Random Access (PRACH) Grant (PAGCH) Packet Notification (PNCH) Packet Broadcast Control Channel (PBCCH) Frequency correction channels Synchronization channel (MS freq. vs. BS) Broadcast control channel for general information on the base station Packet broadcast channels Broadcast parameters that MS needs to access network for packet transmission
  19. 19. Packet Traffic Channels TCH Traffic Channels (TCH) Encoding of speech or user data Channels are either predetermined multiplexed or multiplexing determined by MAC Full rate / Half rate On both SBPSCH and DBPSCH Modulation techniques GMSK (Gaussian Minimum Shift Keying) = MSK + Gaussian filter 8-PSK
  20. 20. GPRS Mobile Types A/Gb mode Class Description  Simultaneous GPRS and conventional GSM operation Class A  Supports simultaneous circuit switched and GPRS data transfer  Can be attached to both GPRS and conventional GSM services simultaneously  Can listen circuit switched and GPRS pages (via GPRS) Class B  Supports either circuit switched calls or GPRS data transfer but not simultaneous communication  Most common for handsets today  Alternatively attached in GPRS or conventional GSM  No simultaneous operation Class C  ‘GPRS only’ mobiles also possible (e.g. for telemetric applications)  E.g. expansion cards for laptops lu mode Mode Description CS/PS  Same as Class A in A/Gb mode PS  MS can only operate packet switched services CS  MS can only operate circuit switched services
  21. 21. Service Types Point-to-Point Internet access by user Point-to-Multipoint Delivery of information (e.g. news) to multiple locations or interactive conference applications IP Multimedia Subsystem Simultaneous access to multiple different types of real-time and non-real-time traffic IMS provides synchronization between such components
  22. 22. Mobility Management (1/2) 3 different state Data can only be transmitted in the ACTIVE state State Description  No logical PDP context activated  No network address (IP) registered for the terminal IDLE  No routing of external data possible  Only multicast messages to all GPRS handsets available  Only routing area is known - RA is defined by operator  allows individual optimizations STANDBY  When downlink data is available, packet paging message is sent to routing area  Upon reception, MS sends it’s cell locations to the SGSN and enters the ACTIVE state  SGSN knows the cell of the MS ACTIVE  PDP contexts can be activated/deactivated  Can remain in this state even if not data is transmitted (controlled by timer)
  23. 23. Mobility Management (2/2) Mobility Management Message Cell update When MS changes the cell within a Routing Area in READY state Routing Area update When MS changes the cell between Routing Area in READY or STANDBY state Two types of Routing Area Updates from MS’s point of view only one type Intra-SGSN Routing Area Update Inter-SGSN Routing Area Update Periodic Routing Area updates are applicable
  24. 24. PDP Contexts Packet Data Protocol (PDP) Session Logical tunnel between MS and GGSN Anchored GGSN for Session PDP activities Activation GGSN에게 단말의 존재를 알림 GPRS Data 수신/전송을 위해 (Session 이용을 위해), 반드시 IP 할당이 필요하며, IP 주소 등을 할당하는 과장 Modification Deactivation
  25. 25. PDP Context Procedures MS initiated MS BSS SGSN GGSN Activate PDP Context Request Create PDP Context Request Create PDP Context Response Activate PDP Context Accept GGSN initiated MS BSS SGSN GGSN Packet from ext. nw. PDU Notification Request PDU Notification Response Activate PDP Context Activation Activate PDP Context Request Create PDP Context Request Create PDP Context Response Activate PDP Context Accept
  26. 26. GPRS Call Scenario 1 GPRS Attach Previous MS SGSN HLR/AuC SGSN BSS Packet Channel Request Packet Uplink Assignment RLC Block (attach request) Attach Request Send Authentication Info. Packet Control Acknowledgment Authentication and Send Authentication Info RR Ciphering Request Packet Downlink Assignment RLC blocks (Authentication and Ciphering Request) Packet Downlink Ack Packet Channel Request Packet Uplink Assignment RLC blocks (Authentication and Ciphering Response) Packet Uplink Ack Authentication and Ciphering Response Update GPRS Location Packet Control Cancel Location Acknowledgement Cancel Location RR Insert Subscriber Data Insert Subscriber Data RR Update GPRS Location RR Attach Accept RLC blocks (Attach accept) Packet Downlink Ack Packet Downlink Reponses Packet Uplink Assignment RLC blocks (Attach complete) Packet Uplink Ack Attach Complete Packet Control Acknowledgement
  27. 27. GPRS Call Scenario 2 GPRS/GSM Attach Previous Previous MSC HLR MSC HLR MS BSS SGSN /VLR /AuC /AuC /VLR Attach Request Send Authentication Info Send Authentication Info RR Authentication and Ciphering Request Authentication and Ciphering Response Update GPRS Location Cancel Location Cancel Location RR Insert Subscriber Data Insert Subscriber Data RR Update GPRS Location RR Update Location Request Update Location Cancel Location Cancel Location RR Insert Subscriber Data Insert Subscriber Data RR Update Location RR Update Location Accept Attach Accept Attach Complete
  28. 28. GPRS Call Scenario 3 RA update New Old HLR MS SGSN SGSN GGSN BSS Routing Area Update Request SGSN Context Request SGSN Context Response Authentication and Ciphering Authentication and Ciphering SGSN Context Acknowledge Forward Buffered PDUs Update PDP Context Request Update PDP Context Response Update GPRS Location Cancel Location Insert Subscriber Data Insert Subscriber Data RR Update Subscriber Data RR Routing Area Update Accept Routing Area Update Complete
  29. 29. [별첨] GSM vs. GPRS Email via GSM Email via GPRS Auth. Auth. Server Server GSM PSTN Internet GPRS Internet Email EmailUser Modem Modem Server Virtual Authenticated Server GPRS Path to Email Data Tunnel Server Initial Call Process Time (s) Initial Call Process Time (s)GSM Call 4 GPRS Call 4Train Model 30 Login and Authenticate 11Login and Authenticate 11 Download mail 180Download mail 180 Total 3min 45s Total 3min 45s Subsequent CallSubsequent Call Not applicable – Permanent Virtual 0Repeat Above 3min 45s Circuit

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