2G Cellular Data Networks

1 2 General Mobility Issues 2G Cellular Data Networks Registration and Authentication User Locate local service provider access point Obtain network access Service provider Locate mobile user within network for MS-terminated connections Authenticate user access rights Handoff Users move between service access points Service maintained when changing attachment point (location) Roaming Handoff between service providers Elaborate authentication and accounting 3 4 Standard Mobile (RFC 2002) User Connects to router by LAN or point-to-point connection Sends s containing source and destination addresses Receives s to (possibly temporary) dedicated address address = network number.host number Router Forwards to next hop according to routing protocol Routing tables locate host by NETWORK NUMBER 132.4.16.X X=1, 2, 3,..., 254 Internet protocol supporting host mobility Maintains TCP connections as host changes location Supports authentication Mobile host maintains single long-term address Version 4 address and address format are unaffected Routing tunnel replaces standard routing 138.27.192.87 132.4.16.X X=1, 2, 3,..., 254 Router 1 2 3 Router 1 2 3 138.27.192.Y Y=1, 2, 3,..., 254 138.27.192.Y Y=1, 2, 3,..., 254 Router 1 2 3 138.27.192.87 Router 1 2 3

5 6 Mobile Basic Idea Mobile Entities Similar to Call forwarding Mail forwarding at post office Mobile Node Permanent address Usual home service router Finds mobile service routers when roaming Home router and mobile service router coordinate s Sent to usual home router Forwarded by home router to mobile service router Forwarded to Mobile Node Mobile Node (MN) Host or router that can change its point of attachment Home Address Permanent address assigned to MN Correspondent Node (CN) Node that sends s to MN home address Home Agent (HA) Maintains table of registered mobile nodes Forwards s addressed to mobile node Foreign Agent (FA) Delivers s between MN and HA Mobility Agent HA or FA supporting mobility Care-of-Address (COA) FA address used to identify current location of MN 7 8 Mobile Service Definitions Agent Discovery Principle Connection Services Agent Discovery Care-of-Address Discovery Registration Principle Delivery Services Encapsulation Tunneling Decapsulation Roaming and Handoff Change of Foreign Agent Route Optimization Mobility Agents broadcast availability Home Agents (HA) Foreign Agents (FA) Mobile Node (MN) looks for Local router services when connected to home network Foreign Agent (FA) services when connected to foreign network FA advertises services

9 10 Care-of-Address Discovery Registration Mobile Node (MN) Requests service from Foreign Agent (FA) Foreign Agent Assigns Care-of-Address (COA) to MN FA can have 1 or more available COAs Usually FA assigns same COA to all MNs Foreign Agent Requests Mobile support from MN s Home Agent Home Agent Agrees to provide Mobile support MN Registers COA with its HA HA forwards s to FA Datagrams for MN arrive at HA MN requests service from FA MN registers with FA and HA FA forwards request to HA FA informs MN of status HA accepts or rejects 11 12 Establishment of Service in Mobile Principle Delivery Services MN in home network Encapsulation Enclose inside second Inner header: addressed from CN to MN Outer header: addressed from HA to COA Tunneling Path taken by encapsulated From HA to FA Decapsulation FA opens encapsulated FA forwards original to MN FA to MN forwarding works at DATA LINK LAYER Standard routing would return to Home Network MN in foreign network

13 14 Mobile End-to-End Delivery Roaming and Hand-Off From: HA address From: CN address To: FA COA Address To: MN Home Address Standard MN FA From: CN address To: MN Home Address DATA DATA Encapsulated HA Standard CN Roaming MN Moves to new attachment point (network) Requires change of FA Multiple bindings Multiple COAs old + new Avoid loss Avoid too frequent registrations HA Forwards each packet to multiple COAs MN Receives packet at one COA Route optimization after reconnection From: CN address To: MN Home Address DATA 15 16 Change of Foreign Agent CN HA FA old FA new MN Encapsulated Encapsulated registration MN changes location Home agent is bottleneck Increases network load Triangle Routing registration ACK update ACK Encapsulated Encapsulated

17 18 FA Route Optimization HA Roaming Under Route Optimization (2a) Encapsulated s (5) (4) Binding Update (2b) Warning (3) Binding Request (1) 19 20 Voice/Data Interfaces in Cellular Network Data over AMPS Voice on AMPS Serial Data on Analog AMPS Modem Voice on Analog Telephone Voice on Digital Telephone Serial Data on ISDN Voice on TDMA, GSM, CDMA Serial Data on Analog Modem Analog Local Loop 300-3300 Hz Digital Local Loop (ISDN) 64 kbps (DS-0) Serial Data in Digital Frame Circuit Mode Network provides dedicated point-to-point SVC connections and charges for time and distance of connection T1/E1 Digital Concentrator Public Switched Telephone Network (PSTN) T1/E1 Digital Concentrator Packet Data Frame Relay, ATM, Frame Relay, ATM, Packet Data in CDPD/GPRS/EDGE Frame Frame Relay, ATM, Packet Mode Network provides packet forwarding over one-to-many SVC connections and charges for packet volume digital bits digital bits modem digital bits modem modem modulated (analog) data modulated (analog) data POTS Network analog channels (300-3300 Hz) AMPS Network analog channels (300-3300 Hz) PSTN

21 22 Cellular Circuit Mode Data Services Cellular Packet Mode Data Services User makes dial-up call to Internet Service Provider (ISP) ISP digital bits modem digital bits digital bits ISDN digital channel (64 kbps) POTS Network analog channel (300-3300 Hz) Cellular Network digital voice/data circuit mode channels (9.6-19.2 kbps) modem PSTN Datagrams Datagrams Cellular Network digital voice/data circuit mode channels and packet mode forwarding (19.2 kbps - 2 Mbps) Cellular service provider acts directly as ISP AMPS: CDPD GSM: GPRS / EDGE Internet Datagrams digital bits 23 24 Cellular Data Terminals wwan Services for Cellular Technology Laptop with integrated cellular modem Smartphone with integrated cellular modem Laptop using cellular phone as modem d-amps (IS-136) Circuit mode data over voice channel Cellular Digital Packet Data (CDPD) End-of-life GSM Native circuit mode data channel General Packet Radio Service (GPRS) Enhanced Data Rates for GSM Evolution (EDGE) Evolution path 3G CDMA Circuit mode data over voice channel IS-95B Evolution path 3G

25 26 Cellular Digital Packet Data (CDPD) Packet Mode data on AMPS frequencies Shares radio frequency channels with voice calls AMPS and d-amps compatible First service 1993 Considered 2.5G enhancement Infrastructure additions to AMPS technology Data channel equipment in cellular network Internal or external modem in mobile station routing Exchange standard s with Internet Internal CDPD network Implements Mobile to tunnel s Full duplex transmission up to 19.2 kbps Base System (BS) CDPD Network Architecture Internal CDPD Tunneling BS CELL Public Land Mobile Network PLMN Base Transceiver Mobile Switching Site (BTS) Center (MSC) MDBS BTS Base Station Controller (BSC) BSS Base Station Subsystem CLUSTER MD-IS PSTN Internet (IS) Standard Routing F-ES 27 28 CDPD System Architecture Elements Mobile Data Base Station (MDBS) Mobile End Station () Mobile Data Base Station (MDBS) Data forwarding function in Base Transceiver Site (BTS) Intermediate Station (IS) Standard network routers, switches, gateways Mobile Data Intermediate Station (MD-IS) Data forwarding function in Mobile Switching Center (MSC) Fixed End System (F-ES) MDBS IS MD-IS IS F-ES Data forwarding function in Base Transceiver Site (BTS) Manages data streams for all s in one cell Transmits and receives digital data in AMPS channels Forward channel Announces channel availability to CDPD MDBS transmits data to all Provides ACK or NACK responses to packets Reverse direction MDBS receives data from upstream radio downstream radio IS MDBS IS MD-IS F-ES

29 30 Mobile Data Intermediate Stations (MD-IS) Located in Mobile Switching Center (MSC) Manages interface between CDPD and Internet Handles TCP/ to CDPD protocol conversion Mobility Management using Mobile Protects upstream elements from mobility issues Mobility management MD-ISs exchange location information about roamers Mobile Network Location Protocol (MNLP) Home MD-IS Default gateway for at home Home Agent (HA) for roaming Attached MD-IS Foreign Agent (FA) for roaming Network Data Link TCP SNDCP MDLP MAC Physical (Radio) MDLP MAC Physical (Radio) CDPD Protocol Layers MDLP TCP Data Link Physical CDPD Networking Tunnel Data Link Data Link Physical Physical End-to-End Transport SNDCP MDLP TCP Data Link Data Link Physical Physical Internet MDBS IS MD-IS IS Data Link Physical TCP Data Link End-to-end transport of TCP segments Internet hops perform standard routing and forwarding CDPD hops implement Mobile MD-IS performs tunneling to MD-IS to MDBS to routing by address + phone number Physical F-ES 31 32 Physical Medium Access MAC Protocol Access Control in CDPD Transmits over AMPS analog frequency channels Transfers data packets on unused voice channels Unused AMPS frequencies or d-amps time slots Sniff and hop Base stations broadcast advertise available channels Mobile station listens for idle channels Works well with excess network capacity Digital Sense Multiple Access/Collision Detect (DSMA/CD) Contention-based access among CDPD s Exploits forward/reverse frequency pairing Device senses the transmit medium Listens for Idle flag in forward channel f 1 :busy flag f 2 : voice f 3 :idle flag f 4 : packet data f 3 :ACK/NACK If medium is Idle Device sends data in reverse channel Waits for ACK from MDBS in forward channel Collision transmission from multiple sources MDBS returns Decode Failure flag Random back-off period before trying again Maximum transmit time of about 1 second per transmission

33 34 Special CDPD Protocols SNDCP Subnetwork Dependent Convergence Protocol Maps user s to an MDLP channel Session services SAR (Segmentation and Reassembly) uses SNDCP as tunnel to MD-IS MDLP Mobile Data Link Protocol Framing Destination addressing Encrypted address used as MAC layer address Logical Link Control (LLC) functions Error control and flow control CDPD MAC DSMA-CD Manages channel access Manages collision detection and packet retry process in Home System F-ES places TCP segment into addressed to Network Entity Identifier (NEI) Standard address for Assigned by CDPD service provider routed through Internet to Home MD-IS Home MD-IS tunnels to via MDBS SNDCP Opens ports to for session service Encrypts Encrypted form of NEI is Temporary Equipment Identifier (TEI) Performs SAR (Segmentation and Reassembly) Passes segments to MDLP MDLP Builds data link frame Addressed to TEI Includes frame sequencing, flow control, and error control fields Passes MDLP frame to TCP/ for transmission to MDBS 35 36 Mobility and Tunneling Mobility and Tunneling Entire CDPD system is one Internet domain Controlled by one MD-IS Acts as an Internet subnet End-to-end tunnel (SNDCP and MDLP over TCP/) covers service area TEI in MDLP packets permits mobile MAC-layer addressing Telephone number permits mobile physical layer addressing Handoff moves between cells or between clusters End-to-end tunnel still covers service area MDLP frames forwarded to new MDBS within TCP/ frames Mobility handled by telephone mobility MDLP frames still addressed to same TEI Internal CDPD Tunneling Internal CDPD Tunneling IS Mobile Switching Center (MSC) IS Mobile Switching Center (MSC) MDBS Base Station Controller (BSC) Internet (IS) MD-IS F-ES Standard Routing handoff MDBS Base Station Controller (BSC) Internet (IS) MD-IS F-ES Standard Routing

37 38 Roaming Mobile Station and Fixed Station Connects to network in non-home system Registers with local (attachment) MD-IS Attachment MD-IS Exchanges location data with Home MD-IS Mobile Network Location Protocol (MNLP) Assigns roamer Subnetwork Point of Attachment (SNPA) address Functions as Mobile Foreign Agent (FA) Home MD-IS Functions as Mobile Home Agent (HA) F-ES Addresses TCP segment to NEI Routed through Internet to Home MD-IS Home MD-IS tunnels to attachment MD-IS using SNPA Attachment MD-IS tunnels to via MDBS, SNDCP, MDLP Home 1 Subdomain IS MDBS MD-IS IS F-ES Subdomain 5 3 2 4 MDBS IS MD-IS IS 39 40 in Roaming Subdomain and F-ES in Home Subdomain with Roaming Roaming 8 1 MDBS 2 7 IS Subdomain 3 4 5 5 6 MD-IS IS F-ES 4 1 Roaming Home 12 6 1 1 MDBS 2 2 IS 5 11 3 3 4 10 Subdomain 4 9 MD-IS 5 8 IS F-ES Subdomain Subdomain 2 MDBS IS MD-IS 3 IS MDBS IS MD-IS 6 7 IS

41 42 General Packet Radio Service (GPRS) GSM Circuit Mode and GPRS Packet Mode Data Provides packet mode data access for GSM -based architecture Considered 2.5G enhancement s separated from circuit mode traffic at cluster Packet Control Unit (PCU) Packet mode function in BSC to handle s Circuit mode voice/data routed to MSC Forwarded to other MSC or PSTN Packet mode data is routed to Serving GPRS Support Node (SGSN) Forwarded to Internet or X.25 PSDN PCU to SGSN runs over Frame Relay Mobility management Circuit mode traffic uses PSTN / PLMN routing Packet mode traffic uses routing 43 44 MS MS Base System (BS) Base System (BS) GPRS System Architecture Public Land Mobile Network PLMN Base Transceiver Site (BTS) BTS Base Station Controller (BSC) Packet Control Unit (PCU) Mobile Switching Center (MSC) Frame Relay PSTN GPRS Backbone () Gateway GPRS Support Node (GGSN) GPRS Support Nodes Serving GPRS Support Node (SGSN) Packet-switched version of MSC Handles packets to / from Mobile Stations (MS) Handles MS mobility management Gateway GPRS Support Node (GGSN) Interfaces SGSNs to external networks Maintains routing information Exterior gateway for GPRS network Address mapping ( mobility) Routes incoming s to appropriate PCU BSS Base Station Subsystem Serving GPRS Support Node (SGSN) Internet

45 46 GPRS Terminal Classes GPRS System Elements Class A terminal Supports simultaneous GPRS and GSM voice services Class B terminal Supports GPRS or GSM voice service at one time Monitor (on hold) one channel and operate second channel simultaneously Class C terminal Supports only one service at a time 47 48 GPRS System Elements GPRS System Architecture BTS BSC HLR VLR BSS SGSN GGSN CG CDR BG SOG AUC Base Transceiver Site Base Station Controller Home Location Register Visitor Location Register Base Station Subsystem Serving GPRS Support Node Gateway GPRS Support Node Charging Gateway Call Detail Record Border Gateway Service Order Gateway Authentication Center MS MS MS BS BS BS BTS BTS BTS PLMN - 1 SGSN BSC MSC SGSN BSC MSC PLMN - 2 SGSN BSC MSC GPRS Backbone GPRS Backbone PSTN Border Gateway GPRS Backbone Border Gateway GGSN Internet GGSN

49 50 GPRS Architecture Protocol Stack GPRS Protocol Structure 1 MS to BSS Tunnel BSS to SGSN Tunnel MS to SGSN Tunnel From Internet or X.25 SGSN to GSSN Tunnel Fixed-system application sends data to MS s or X.25 packets Basic hops Internet GGSN SGSN BSS MS GGSN SGSN GTP TCP/UDP L2 L1 SGSN GTP TCP/UDP L2 L1 GGSN Standard user s from Internet GPRS Tunneling Protocol (GTP) GTP header added to user Call Data Records (CDR) for billing Handles call failure Standard TCP/ and infrastructure protocols 51 52 SGSN-to-MS Tunnel GPRS Protocol Structure 2 SGSN to BSS GPRS Protocol Structure 3 SNDCP LLC SNDCP LLC BSSGP NW L1bis GTP TCP/ UDP L2 L1 Sub-Network Dependent Convergence Protocol (SNDCP) SNDCP header Encapsulates GTP + user s Provides Session services SAR (Segmentation and Reassembly) Maps user s to LLC channel Logical Link Control (LLC) LLC header Flow control Error control Link control BSSGP NW L1bis BSS SNDCP LLC BSSGP NW L1bis SGSN GTP TCP/ UDP L2 L1 Map LLC packets to BSSGP Base Station System GPRS Protocol (BSSGP) Processes routing and QoS information Routing layer for Frame Relay signaling Call setup / control signaling over Frame Relay Maps BSSGP signaling to Frame Relay signaling Frame Relay packets MS BSS SGSN

53 54 GPRS Protocol Structure 4 GPRS Connection Process BSS to MS SNDCP LLC RLC MAC RF MS RLC BSSGP MAC MAC RF RF BSS Radio Link Control (RLC) MS-to-BSS Logical Link Control Flow control, error control, link control Media Access Control (MAC) Between MS and BSS Controls access to GPRS GSM Radio Frequency (RF) MS allocated 1 to 8 GSM time slots 18 kbps per time slot 18 kbps to 144 kbps 55 56 GPRS Connection Process MS switches on and sends GPRS attach request User Registration 1 Associate PLMN address with Packet Data Protocol (PDP) address PDP address Static or dynamic or X.25 address PLMN address International Mobile Subscriber ID (IMSI) Authentication BSC queries Home Location Registers (HLR) 2 HLR updates Visitor Location Registers (VLR) 3 Call Admission Control (CAC) 4 Determines required network resources Grants resources if available Routing hop-by-hop or X.25-PLP delivery Routing tables in GSN (GGSN or SGSN) Address conversion / VC mapping GSN handles compression and encryption Enhanced Data Rates for GSM Evolution (EDGE) Standard: GPRS-136HS Formally defined as 3G enhancement to GPRS Considered 2.75G enhancement Uses enhanced modulation technique Transmits 60 kbps in each time slot 8 slots 60 kbps/slot = 480 kbps Uses 384 kbps for user data Planned (but not relevant) CDPD Gateway d-amps Gateway using Voice Over (Vo)

57 58 Short Message Service (SMS) SMS in GSM Architecture Transmission of short text messages Up to 160 bytes of alphanumeric data 160 English ASCII characters 16-bit unicode for non-english alphabets 80 characters GSM permits message concatenation SMSC IWMSC GMSC Supported by GSM, d-amps, and CDMA Out-of-band signaling SMS sent over signaling channel not traffic channel SMS can be sent during a voice call Short messages do not create a heavy traffic load SME SMSC SME: Short Messaging Entity SMSC: Short Message Service Center GMSC: Gateway Message Service Center IWMSC: Interworking Message Service Center 59 60 SMS Nodes SMS Delivery to MS Short Messaging Entity (SME) Any entity that can receive or send short messages Fixed network element Mobile Station Another service center Short Message Service Center (SMSC) Store and forwarding of SMS between SME and MS Gateway Message Service Center (GMSC) Receives SMS from SMSC Interrogates HLR for routing information Delivers SMS to MSC for destination SME Interworking Message Service Center (IWMSC) Receives SMS from MSC Delivers SMS to appropriate SMSC for forwarding SME SMSC HLR MSC VLR BSS SMS Submit Delivery Report Route Request Route SMS Forward Delivery Report User Info ACK SMS Forward ACK User Info ACK Page ACK SMS Forward ACK MS

61 62 High Speed Circuit Switched Data (HSCSD) Circuit Switched Data (CSD) 14.4 kbps circuit mode data connection in 2G GSM User data replaces digitized voice in 1 time slot High Speed Circuit Switched Data (HSCSD) 2.5G enhancement Up to 8 slots (full user frame) allocated to one data channel Up to 115.2 kbps Transparent data transmission User data stream can contain signaling to network Allows dynamic reconfiguration of data connection (data rate, QoS) HSCSD data frames carry data sub-stream numbers Maintains order of transmission over GSM Non-transparent data transmission Only user data in data stream No signaling or reconfiguration LLC functions performed by GSM protocols 2.5G Cellular Video Video conferencing MS-to-MS or MS-to-PC audio / video connection Video conference Technology demonstrated in 1926 Commercial systems available since 1964 AT&T lost $250 million (in 1965 dollars) on Picture Phone Personal feel of cellular call may overcome customer resistance Live video streaming TV broadcasting to telephones Video-on-Demand (VOD) 63 64 Protocol Options for Digital Video Protocol Options for Cellular Digital Video Digital multimedia streaming options for fixed terminals Circuit-switched technology Compressed video over 64 kbps ISDN High quality video over B-ISDN (ATM-based) networks Used by corporate networks and news reporting Not widely adopted by home users Packet-switched technology based H.323 protocol for video call (also used in Voice Over ) Widely implemented Digital multimedia streaming options for mobile terminals Packet-switched technology Video over H.323 over cellular (GPRS/EDGE/UTMS) Circuit-switched technology Compressed video over High Speed Circuit Switched Data (HSCSD) Cellular Fine for non-real-time services with bursty data Web browsing SMS/MMS Cannot provide QoS required for non-bursty video Low transmission delay and jitter Traffic and mobility variations make delay highly variable HSCSD provides Dedicated channel with no delay variation High availability Stable bit rate for constant bit rate (CBR) video data

65 66 3G-324M Protocol for Video 3G-324M Functions Defines required services for multimedia calls Call set-up Call routing Frame structure Frame multiplexing Voice and image coordination Call security Specifies profiles for existing standards H.223 Multiplexing and De-multiplexing H.245 Call Control H.263 Video Codec H.223 Multiplexing Protocol Divides the HSCSD channel into subchannels Assigns subchannels to voice, audio, control, and data Segmentation and Reassembly (SAR) Provides low delay and low overhead Determines procedures depending on system error rate H.245 Control Protocol Procedures for setting up and controlling video calls Control message definitions and structures Error control and flow control for digital video packets H.263 Video Coding Encoding procedures for video channels Mandates widely used standard codecs Permits optional codecs such as MPEG-4 67 3G-324M System Architecture Camera Screen Microphone Speaker Video Codec Audio Codec Multiplexer and Demultiplexer Transparent 64 kbps synchronous link HSCSD Operating System Call Control (H.245) (H.223) Call Signaling Dialing number Call acceptance Establishing bearer channel Call Control Exchange terminal capabilities Determine session master Open audio and video logical channels