통신시스템(gprs network)
DESCRIPTION
About GPRS NetworkTRANSCRIPT
Telecommunication Basics(GPRS Network)
Software Engineering Lab - 김영기 책임
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음성 통화 통화, 문자, 이메일 통화, 문자, 멀티미디어, 무선인터넷 초고속 인터넷 초고속 무선 인터넷유,무선간 연동
IS-95 A IS-95 B
GSM GPRS
CDMA-1X
EV-DV
CDMA-1XEV-DO r0
W-CDMA R3
W-CDMA R5
(HSCPA)
CDMA-1XEV-DO rA
W-CDMA R6
(HSUPA)
CDMA-1XEV-DO rB
W-CDMAR7
(HSPA+)
LTEEDGE
UMB
W-CDMAHSPA+Phase2
AMPS
NMT
LTE Advanced
802.15e Wave1(Mobile WiMAX)
802.15e Wave2(Mobile WiMAX)
802.16eWiMAX R1.5
802.16nWiMAX R2.0
GSM track
CDMA track
WiMAX track
What is GPRS ?
GPRS (General Packet Radio Service)
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
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
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
GPRS Architecture
BTS
BSC
UmPSTN
SS7Network
DataNetwork(Internet)
DataNetwork(X.25)
Local areaNetwork
Local areaNetwork
Coperate1Server
Coperate2Server
SMS-GMSC
Gd
HLR/AuCGr
EIR
MAP-F
Router
Router
MSC
Inter-PLMNBackboneNetwork
Gp
Gi.IP
Gi.X.25
Intra-PLMNBackboneNetwork
(IP Based)
GdGr
Gs
Gb
Gn
Serving GPRSSupport Node(SGSN)
BorderGateway (BG)
Point-To-MultipointService Center
(PTM-SC)
Gn
Gateway GPRSSupport Node
(GGSN)
GSM to GPRS
Interfaces
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
Protocol Stack
GPRS Control Plane Protocol Stack
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
LLC
GMM/SM
GSM RF
Um Gb
MAC
RLC
LLCRelay
GSM RF
NetworkService
MAC
RLC BSSGP
L1bis
BSSGP
NetworkService
LLC
GMM/SM
L1bis
MS BSS (PCU) SGSN
Protocol Stack
GPRS Traffic Protocol Stack
IP/X.25
LLC
SNDCP
GSM RF
Application
Um GnGb
MAC
RLC
IP/X.25
GTP
L1
L2
LLC
GSM RF
Frame RelayMAC
RLC BSSGP
L1bis
BSSGP
Frame Relay
LLC
SNDCP GTP
L1bis L1
L2
IP
MS BSS (PCU) SGSN GGSN Gi
IP
UDP/TCP UDP/TCP
END
NODE
X.25IP
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 √ √
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
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
Other Elements
Entity Functionality
BG(Border Gateway)
Not defined within GPRS
Routes packets from SGSN/GGSN of one operator to a SGSN/GGSN of an other
operator
Provides protection against intruders from external networks
DNS(Domain Name Server)
Translates addresses from ggsn1.oper1.fi-format to 123.45.67.98 format
Charging Gateway Collects charging information from SGSNs and GGSNs
PTM-SC(Point to Multipoint-Service Center)
PTM Multicast (PTM-M)
- Downlink broadcast, No subscription, No Ciphered
PTM Group call (PTM-G)
- Closed or open groups, Down/Up link, Ciphered
Geographical area limitation
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
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
Logical Channels
Mapped by the MAC to physical channels
Control channels for control, synchronization and signalingCommon/Dedicated/Broadcast
Packet Traffic ChannelsEncoded speech/Encoded data
Packet Data Logical Channels
PDTCHPDCCHPCCCH PBCCH
Traffic Channels
[Up]
PDTCH/DPDTCH/HPACCHPTCCH/DPTCCH/UPBCCHPACCHPTCCH/DPTCCH/UPTCCH/U
Control Channels
[Down] [Down] [Down][Down] [Down] [Down][Up] [Up][Up/Down]
PPCH = Packet Paging ChannelPAGCH = Packet Access Grant ChannelPNCH = Packet Notification ChannelPACCH = Packet Associated Control ChannelPTCCH = Packet Timing Advance Control Channel
PCCCH = Packet Common Control ChannelPBCCH = Packet Broadcast Control ChannelPDCCH = Packet Dedicated Control ChannelPDTCH = Packet Traffic ChannelPRACH = Packet Random Access Channel
Up = Uplink DirectionDown = Downlink Direction
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
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
GPRS Mobile Types
A/Gb mode
lu mode
Class Description
Class A Simultaneous GPRS and conventional GSM operation
Supports simultaneous circuit switched and GPRS data transfer
Class B
Can be attached to both GPRS and conventional GSM services simultaneously
Can listen circuit switched and GPRS pages (via GPRS)
Supports either circuit switched calls or GPRS data transfer but not simultaneous communication
Most common for handsets today
Class C
Alternatively attached in GPRS or conventional GSM
No simultaneous operation
‘GPRS only’ mobiles also possible (e.g. for telemetric applications)
E.g. expansion cards for laptops
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
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
Mobility Management (1/2)
3 different state
Data can only be transmitted in the ACTIVE state
State Description
IDLE
No logical PDP context activated
No network address (IP) registered for the terminal
No routing of external data possible
Only multicast messages to all GPRS handsets available
STANDBY
Only routing area is known
- RA is defined by operator allows individual optimizations
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
ACTIVE
SGSN knows the cell of the MS
PDP contexts can be activated/deactivated
Can remain in this state even if not data is transmitted (controlled by timer)
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
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
PDP Context Procedures
MS initiated
GGSN initiated
Activate PDP Context Request
Create PDP Context Request
Create PDP Context Response
Activate PDP Context Accept
MS BSS GGSNSGSN
MS BSS GGSNSGSN
Packet from ext. nw.PDU Notification Request
PDU Notification Response
Activate PDP Context Activation
Activate PDP Context RequestCreate PDP Context Request
Create PDP Context Response
Activate PDP Context Accept
GPRS Call Scenario 1
GPRS Attach
MS BSS HLR/AuCSGSN
PreviousSGSN
Packet Channel Request
Packet Uplink Assignment
RLC Block (attach request)Attach Request
Send Authentication Info.
Send Authentication Info RRPacket Control
Acknowledgment Authentication andCiphering 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
Packet ControlAcknowledgement
Authentication andCiphering Response Update GPRS Location Cancel Location
Cancel Location RRInsert Subscriber Data
Insert Subscriber Data RR
Update GPRS Location RRAttach 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
GPRS Call Scenario 2
GPRS/GSM Attach
MS BSS
HLR/AuCSGSN
MSC/VLR
PreviousMSC/VLR
PreviousHLR/AuC
Attach RequestSend Authentication Info
Send Authentication Info RR
Authentication and Ciphering Request
Authentication and Ciphering Response
Update GPRS LocationCancel 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
GPRS Call Scenario 3
RA update
MS BSSHLRNew
SGSNOld
SGSN GGSN
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
[별첨] GSM vs. GPRS
Initial Call Process Time (s)
GSM Call 4
Train Model 30
Login and Authenticate 11
Download mail 180
Total 3min 45s
Subsequent Call
Repeat Above 3min 45s
Initial Call Process Time (s)
GPRS Call 4
Login and Authenticate 11
Download mail 180
Total 3min 45s
Subsequent Call
Not applicable – Permanent Virtual Circuit
0
Email via GSM Email via GPRS
User Modem ModemEmailServer
EmailServer
GSM PSTN Internet GPRS Internet
Auth.Server
Auth.Server
VirtualGPRS
Data Tunnel
AuthenticatedPath to Email
Server