national chung cheng university cellular networks and
TRANSCRIPT
National Chung Cheng UniversityDept. Computer Science & Information Engineering
Cellular Networks and
Mobility Management
Chiang, Wei-Kuo (江為國)
Assistant Professor Department of CSIE National Chung Cheng University Office : EA 311 Phone : 05-2720411~33126 Email : [email protected]
URL : http://www.cs.ccu.edu.tw/~wkchiang/
National Chung Cheng University
National Chung Cheng University
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Outline
Cellular Networks
GSM & Mobility Management
GPRS & Mobility Management
CAMEL
Number Portability
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Wireless Technology Evolution
1G – Analog System
AMPS (Advanced Mobile Phone System) : 中華電信090系統
2G – Digital System
GSM (Global System for Mobile Communication)
900MHz and 1.8GHz (DCS1800)
TDMA Technologies
9.6K bps Data Rate (Shore Message Service; SMS)
歐亞160 Countries, 全球55%市場, 約5億個用戶
CDMA (Code Division Multiple Access)
IS-95: Data Rate 14.4K bps (cdmaOne) IS-95B: Data Rate 64 Kbps
Qualcom
亞太北美市場, 約7,500萬用戶
D-AMPS
又稱IS-136
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備忘稿
第一代行動通訊為AMPS系統,在台灣也就是中華電信的090系統。這個系統提供了類比式的語音服務。
第二代的行動通訊系統改進為提供數位式的語音服務,並提供更嚴密的安全機制。目前較為普遍的三種技術為GSM, CDMA和D-AMPS。 GSM為歐規的系統,採用TDAM和FDMA混和的技術,是目前世界
上使用者最多的系統。
CDMA系統採用code division的技術,佔有亞太北美的市場。
D-AMPS則是改進第一代行動電話系統AMPS,又稱為IS-136。
台灣則是採用歐規的 GSM 系統。
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2.5G
GSM System
High Speed Circuit Switch Data (HSCSD)
Up to 115.2 Kbps
General Packet Radio Service (GPRS)
Up to 171.2 Kbps
Enhanced Data rates for GSM Evolution (EDGE)
改變調變技術
up to 384 Kbps (亦被視為3G技術)
GPRS EDGE
cdma System
cdma 1x
Up to 144 Kbps
Korea
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備忘稿
在第二代和第三代行動通訊系統之間,存在了2.5代的系統。這個2.5代的系統主要是改進原本第二代系統只提供單純的語音服務與少量的數據服務而設計的。因此2.5代的系統並不是一個獨立的系統,它們皆是架構於原本2G
的系統,利用原本2G系統的infrastructure,提供較高速且大量的數據傳輸。
發展2.5G行動通訊(Mobile Technology)技術主要目的是提供較高速的資料傳輸速率。為了使行動通訊的進展是以演化(Evolution)的方式進行,2.5G的系統是基於2G
的系統架構上來開發;而非整套系統重新發展。
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3G
IMT-2000
Year 2000 Ready
Operate at 2000 MHz
Provide 2000K bps Data Rate
3G Data Rate 要求 Vehicular -- 144 Kbps
Pedestrian --- 384 Kbps
Indoor --- 2Mbps
Three Important 3G Technologies Standards
W-CDMA (Wideband CDMA) (歐日系統)
GSM/GPRS/EDGE W-CDMA
cdma2000 (北美系統)
TD-SCDMA (Time Division Synchronize CDMA) (大陸系統)
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備忘稿
第三代通訊系統當初為IMT-2000這個組織所制訂出來的。之所以稱為IMT-2000主要有下列三個原因:希望3G
系統能夠在西元2000年鋪設完成,並將3G頻帶設為2000 MHz且提供2000K bps的資料傳輸率。目前世界上有三個主要的3G技術: (1) 歐日系統的W-CDMA (由3GPP所訂定),延續之前的GSM->GPRS的evolution
path。(2)北美亞太系統的cdma2000 (由3GPP2所制訂) (3) 中國大陸所發展的TDS-CDMA系統。
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From 2G to 3G
From Voice Service to Rich, Interactive Multimedia-
based Personal Communication Service
Permanent Network Connection with High Data Rate
384 Kbps to 2 Mbps
Mobile Access to High-quality Video, Audio, Graphics
and Multimedia as Fixed Internet
Massive Increase in Network Capacity
To Support Billions of Subscribers
Global Roaming
Use Single Terminal to Access Identical Services All
Around the World
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Three Types of Mobility
Terminal Mobility The terminal is connected to the network via
radio interface and move around freely.
Cordless and cellular phones
User Mobility The user can move from one terminal to another
and register for incoming and outgoing calls to
be made to and from this terminal
SIM cards, calling cards
Service Mobility The portfolio of services that a user has
subscribed to follows the user as he/she roams
to different networks.
Exporting content and services to visited locations
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Cellular Networks (1/3)
A cellular network employs many small radio
cells of limited coverage to cover a large area.
Advantages about the use of small cells
A mobile phone is always close to a network
transceiver, and therefore needs less
transmission power.
Channels can be reused in different cells, so
the capability of a network increases as the
cell size shrinks.
The first cellular network used analog radio
interfaces
Walkie-talkies (as early as 1950s)
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Cellular Networks (2/3)
Widespread deployment of analog cellular
networks began in the early 1980s (1G)
A lack of standardization
Many countries had their own systems
AMPS in USA, C-450 in Germany, RTMS in
France
Roaming was very limited
2G cellular networks appeared in the early
1990s
Digital transmission and higher capability
Encrypted digital transmission ensured much
better privacy
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Cellular Networks (3/3)
GSM is one of the best-known 2G networks
D-AMPS and IS-95 (USA), PDC (Japan)
The level of standardization was much better
than 1G systems
3G cellular networks (the beginning of 2000s)
Multimedia communications and mobile internet
UMTS is one of the most prominent
2.5G cellular networks (between 2G and 3G)
Use the existing frequency bands and radio
interface of 2G networks
But offer 3G capacity and services
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Outline
Cellular Networks
GSM & Mobility Management
GPRS & Mobility Management
CAMEL
Number Portability
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GSM History
GSM started
1982 in Groupe Special Mobile of the European
Conference of Postal and Telecom. Admin. (CEPT)
GSM transferred
In 1988 CEPT transferred all GSM
standardization activities to ETSI
ETSI kept the acronym GSM but changed the
official name to Global System for Mobile Comm.
To ensure standardization on a more international scale
ETSI created 3GPP with other worldwide standard
bodies in 1998
3GPP responsible for all GSM spec.
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GSM Architecture (1)
MSC
BSC
BSC
GMSC
HLR
VLR
MS – mobile station
BTS – base transceiver station
BSC – base station controller
MSC – mobile switching center
GMSC – Gateway MSC
HLR – home location register
VLR – visited location register
External – other GSM or fixed networks
External
MS
BTS
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GSM Architecture (2)
3 main components in GSM MS (mobile station)
BSS (base station subsystem)
Manages the radio resources
BSC and BTS
NSS (network switching subsystem)
The core network part of GSM
MSC: a telephony switch
VLR: holds the subscribe data for visiting
subscribers
HLR: holds the subscriber information,
including information about the VLR to which
a subscriber is currently attached
GMSC: connected to other networks
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Mobility Management (1/2)
Mobility management
Since terminals can move around in cellular
networks or even from one network to another
The network must have some way of locating and
alerting the terminal when a call comes in
GSM networks were divided into location areas
A location area typically covers several radio
cells
Each location area has a unique identifier (LAI)
that is transmitted on a special channel in all
the cells in the location area
Each terminal monitors this channel
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Mobility Management (2/2)
When the terminal detects a change in the
broadcast LAI
It knows it has crossed into another location
area’s radio cell
At this time, it request a location update
If the new location area is served by the same MSC
and VLR, then the VLR registers the move
If served by another MSC and VLR, then the mobile
subscriber info is moved from the old to the new
VLR. The HLR is also updated so that is can route
all incoming calls to the new MSC and VLR.
Figure 4.4
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GSM Location Updates
MSCBSC
BSC
HLR
VLR
MS
BTS
MSC
VLR
Location Area A
Location Area B
3
1
2
4
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GSM Handover / Handoff
It is also possible that a mobile terminal will
move from one cell to another while in
conversation (mid-call)
A mobile terminal continually monitors the
quality of the radio signal from the current
cell, but also from surrounding cells
The network monitors the radio signals from the
mobile terminals
Handover or handoff
The mobile terminal detached in real time from
the radio channel of the old cell and attached
to the new channel in the new cell
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GSM Connection Services
GSM Most Important Connection Services
Basic voice 13 Kbps codec
Half-rate voice 6.5 Kbps codec
CSD/Circuit-switched data 9.6 Kbps
Less suitable
Transmission speed < 56Kbps (telephony modem)
Connection to be set up, charged the same as voice
SMS/Short message service 160 characters
Cell broadcast 93 characters
USSD – service data between terminal and HLR
Note: voice modems do not work with GSM
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Outline
Cellular Networks
GSM & Mobility Management
GPRS & Mobility Management
CAMEL
Number Portability
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GPRS Overview (1/2)
GPRS (General Packet Radio Service) Allows the GSM radio infrastructure to be used
for packet-based data communications
GPRS is typically deployed by operators that already have a GSM network; it is implemented as an extension of the existing GSM infrastructure
GPRS uses exactly the same frequencies and
radio technology as GSM, but it uses the GSM
channels in a different way
A GSM voice call occupies a specific time slot for its entire duration; GPRS occupies time slots only when a packet is sent or received, and a GPRS terminal can use any number of the eight time slot in a frequency channel.
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GPRS Overview (2/2)
Multislot class of the GPRS terminal
The maximum number of time slots that a
terminal can handle
The more time slots a terminal can use, the
higher the data communication rate it provides
Few terminals of multislot class 8
More complex, more energy consuming, high network load
Asymmetric in use of time slots
4(downlink)+1(uplink), 3+1, 2+2, 2+1, 1+1
13.4 Kbps per time slot
In practice most terminals does not support
more than multislot class 4
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GPRS Architecture (1/2)
MSC
BSC
GMSC
HLR
VLR
BTS, MSC, VLR, HLR – software updates
PCU – Packet Control Unit
SGSN – Serving GPRS Support Node
GGSN – Gateway GPRS Support Node
PSTN, GSMMS
BTS
Internet
SGSN GGSN
PCU
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GPRS Architecture (2/2)
SGSN
Similar to MSC function in GSM, except that the
SGSN is a router rather than a switch
Handles location updates and handovers
Needs to be connected to the HLR
Also connected to the MSC and VLR covering the same cells
To allow combined location management for dual-mode terminals
Several BSC can be connected to one SGSN
GGSN
Acts as the gateway to external packet networks
Several SGSN can be connected to one GGSN
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GPRS System
Packet Switching Technology
Based on GSM Cellular Network
High Data Speed
21.4 Kbps per Time Slot
Up to 8 Time Slots
Physical Channel for Data Transmission
Assigned on Demand
Can Be Shared with Other Users
GPRS
External
Data
Network
PSTN
HLR
SGSN GGSN
GbGn Gi
GSM
PCU
BSS
Gateway
MSC/VLRVisited
MSC/VLR
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備忘稿 GPRS (General Packet Radio Server)有別於GSM,是一種
packet-switched的電信網路。GPRS的技術使用了GSM的存取網路( cellular access network),所以只需昇級骨幹網路(core network)就可以提供高速的資料傳輸。GPRS之所以可以提供較高的傳輸速率的原因就是在於可以同時使用多個時槽(time slots),最多可以達八個,也就是可以達到 171.2Kpbs的傳輸速度。
我們以GPRS為例子來簡介2.5的系統。GPRS和GSM彼此共用infrastructure。也就是在BSS部分,GSM和GPRS網路並沒有太大的差別。只有當資料要傳至核心網路的時候,BSS中的PCU會判斷所傳輸的資料為語音或是數據。若是語音傳輸,PCU會將資料傳輸至原本GSM的核心網路。若是數據傳輸,則PCU會將資料傳輸至GPRS的核心網路。在骨幹網路上則是多了兩個元件: GGSN 以及SGSN,而骨幹網路則完全是以packet-switched的網路為主。
目前台灣的GPRS手機多半為雙模(dual mode),同時兼具GSM與GPRS的功能。
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GPRS Logical Architecture
other PLMN
MSC/VLR HLR
EIR
SGSN
GGSN
GGSN
SGSN
PDN TE
SMS-GMSC
SMS-IWMSC
MS BSSGiGn
Gn Gp
Gb
Gd
Um
GcGrGs
Gf
CE
D
A
Signalling &
Data Transfer
Signalling
GPRS Logical Architecture
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備忘稿
既然利用現有的GSM網路就可以升級至GPRS,因此要了解GPRS
就必須先熟悉GSM網路如何運作。當GSM手機撥號時,訊號的傳遞是先連上 BTS,再繼續傳到 BSC 以及 MSC。MSC 主要是做各個網路間交換的功能,將傳送進來的撥號信號交換到另一個 MSC 或公眾有線電話 (PSTN) ,來進行整個連線的建立。GPRS的網路架構是在現有的GSM 網路架構上,再增加兩個新的網路設備節點,分別為SGSN (Serving GPRS Support Node) 以及 (GGSN) Gateway
GPRS Support Node 。SGSN 與 GGSN 具有封包 Packet 的處理與傳送功能。
簡單的說,SGSN 的角色是去維護HLR(儲存手機profile的資料庫);而GGSN主要是負責外部網路以及內部網路 資料的傳送,就像是(gateway)的角色。,主要是提供行動(Mobility)的管理。
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SGSN and GGSN
IP based
Network
SGSN GGSNHLR
Serving GPRS Support Node. Mobility Management (Location
Update, Paging etc.)
. Access Control & Security
(Authentication, Ciphering)
. BSS Queue Management
. GSM Circuit-Switched Interactions
. Operation Data, such as Billing Info.
Gateway GPRS Support Node. Interworking between PDN and
GPRS PLMN
. Packet Screening
. Routing Tables about Attached
GPRS Subscribers
. Address Mapping
. PDU Tunneling
. Operation Data, such as Billing Info.
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備忘稿
GSM網路中,一個BSC同時連接許多BTS,BSC與BTS 的所在區域即組成一個服務區域。GPRS網路增加節點SGSN,會佈設在網路內的各個服務區域內,SGSN負責紀錄在服務區域內有哪些使用者,並且更新使用者的資訊到HLR上。同時也負責使用者的認證、計費、以及存取的控制。若是使用者傳送的是屬於封包的資料,經由BSC的判斷,會將封包的資料傳給 SGSN,由SGSN做封包的交換與傳輸。
GGSN中,第一個G是指 Gateway,代表 GGSN 是GPRS與外界網路(IP Network)的一個閘道,所以GGSN工作便是將外界網路的封包傳送進GPRS網路,或將GPRS網路內的封包傳出到外界的網際網路上。
GGSN與SGSN的連線主要是GTP(GPRS Tunneling Protocol)穿隧技術。
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GPRS MM/SM
Mobility Management
Attach
Detach
Security
Routing Area Update
Session Management
PDP Context Activation
PDP Context Deactivation
PDP Context Modification
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備忘稿
在GPRS運作中,主要分別兩大主要的程序:行動管理(Mobility
Management) 與議程管理(Session Management)。
行動管理主要發生在手機與SGSN之間,當手機開機、關機以及位置更改的時候,必須通知網路(發送一個 routing area update),以便後續的位置追蹤。另外,行動管理中也包含和安全性相關的程序
。這些程序皆由SGSN負責處理。
議程管理大部分是發生於手機與GGSN之間,主要管理手機和外界網路的連結。當手機執行完 PDP Context Activation 的程序後,手機便取得一個IP address並能夠和外界網路相溝通(或是決定使用者的QoS level)。SGSN和GGSN皆須涉入議程管理的程序中。
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GPRS Data Transfer
MS Sends Packet, Destined to Another MS’s PDP Address, to SGSN.
SGSN Delivers Packets to GGSN.
GGSN Determines the SGSN where MS Registered by Checking the
PDP Context Corresponding to PDP Address.
GGSN Tunnels the PDU to SGSN Using GPRS Tunneling Protocol
(GTP).
SGSN Receives and Decapsulates the Packet, and Delivers to MS.
BSS SGSN GGSNGPRS
Backbone IP Network
SGSN
BSS
Internet
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GGSN Function
Manage the addressing of GPRS subscribers GGSN manages the pool of IP addresses
Keeps track of the current SGSN that a
subscriber is attached to
In most cases IP addresses subscribers have are
dynamically assigned from a pool
This IP address assignment is done by GGSN
GGSN routes packets to the right SGSN through
IP tunnels Tunneling means that an IP packet destined for
a certain subscriber is put in the payload of
another IP packet that has as address the SGSN
that the subscriber is attached to
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GPRS Mobility
GPRS network is divided into routing areas
GSM network is divided into location areas
To facilitate the interworking between GSM and
GPRS, a routing area is always the same as, or
a subset of a location area
Why?
GSM location updates automatically imply routing
area updates. This avoids the need for duplicate
updates and saving signaling overhead
An incoming GSM call can be paged in the GPRS
routing area, which is smaller than the location
area. This results in less use of radio resources for
paging.
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GPRS Connection Model
GPRS Connection States
Idle: MS is detached from GPRS, no mobility
management, SGSN & HLR have no updated routing
information
When the subscriber performs a detach, power off, or switching to GSM mode
Ready: sending or receiving data, handles
handover (cell tracking)
When sending or receiving data
Standby: MS is attached to GPRS, but not
sending or receiving packets. MS can receives
paging requests, routing area updates
When no data has been sent or received for a certain period
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GPRS State Transitions
IDLE READY STANDBY
GPRS AttachREADY timer expiry or
Force to STANDBY
PDU transmission
IDLE READY STANDBY
GPRS Attach
GPRS Attach Reject orCancel Location
READY timer expiry,
Force to STANDBY, orAbnormal RLC Condition
PDU reception
GPRS Detach, Implicit Detach, or Cancel Location
IDLE READY STANDBY
IDLE READY STANDBY
GPRS Detach,RAU Reject,
GPRS Detach,RAU Reject or
GPRS Attach Reject
(b) SGSN MM States for GPRS(b) SGSN MM States for GPRS
(a) MS MM States for GPRS(a) MS MM States for GPRS
The state of a GPRS subscriber is maintained
both in the terminal and in the network
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References
Modeling GPRS Mobility Management
Mechanism
Lin, Y.-B. and Yang, S.-R. “A Mobility
Management Strategy for GPRS,” IEEE
Transactions on Wireless Communications, vol.
2, no. 6, November 2003.
Pending Patent: Lin, Y.-B., Yang, S.-R., and
Feng, V. W.-S. “Mobility Management Method and
System for Wireless Data Networks” (with
CCL/ITRI).
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GPRS/UMTS Architecture
BSS: Base Station Subsystem
BTS: Base Transceiver Station
GGSN: Gateway GPRS Support Node
MS: Mobile Station
Node B: Base Station
RNC: Radio Network Controller
SGSN: Serving GPRS Support Node
UTRAN: UMTS Terrestrial Radio Access Network
Data
NetworkSGSN GGSN
Core Network
(packet-switched service domain)
RNC
Node B
UTRAN
UMTS MS
BSC
BTS
BSS
GPRS MS
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BSC1/RNC1 BSC2/RNC2 BSC3/RNC3 BSC4/RNC4
C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24
SGSN2
URA1 URA2 URA3 URA4 URA5 URA6 URA7 URA8 URA9 URA10
RA1 RA2 RA3 RA4 RA5 RA6
SGSN1
UMTS
only
In GPRS, the SGSN tracks the cell and RA of an MS.
In UMTS, for an MS
the SGSN tracks the RA, and
the RNC tracks the cell and the URA.
GPRS/UMTS Mobility Management (MM)
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In the cell tracking mode, if allocated a channel for packet transmission, the
MS is in the power active mode;
otherwise, the MS is in the power saving mode.
In the URA tracking or RA tracking mode, the
MS is in the power saving mode.
URA trackingcell tracking RA tracking
power saving modepower
active mode
*
UMTS Power Saving (PS)
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cell
tracking
URA
tracking
RA
tracking
RA
tracking
cell
tracking
MS tracking in GPRS MS tracking in UMTS
T1 T2 T3
Transitions T1, T2 and T3 in GPRS/UMTS MM are
determined by inactivity timers/counters.
Transition T4 in UMTS PS is also determined by the
inactivity timer mechanism.
power savingpower active
MS power operation in UMTS
T4
Inactivity Timer/Counter for GPRS/UMTS MM and PS
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State Machine for GPRS MM
In READY state, the MS is tracked by the SGSN
at the cell level.
In STANDBY state, the MS is tracked by the
SGSN at the RA level.
IDLE READY STANDBY
GPRS AttachREADY timer expiry or
Force to STANDBY
PDU transmission
IDLE READY STANDBY
GPRS Attach
GPRS Attach Reject orCancel Location
READY timer expiry,
Force to STANDBY, orAbnormal RLC Condition
PDU reception
GPRS Detach, Implicit Detach, or Cancel Location
IDLE READY STANDBY
IDLE READY STANDBY
GPRS Detach,RAU Reject,
GPRS Detach,RAU Reject or
GPRS Attach Reject
(b) SGSN MM States for GPRS(b) SGSN MM States for GPRS
(a) MS MM States for GPRS(a) MS MM States for GPRS
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SGSN
Location update
RA Tracking
RA changed
Low paging cost
High location update cost
High paging cost
Low location update cost
SGSN
Location update
Cell Tracking
RA
Cell changed
Location Update vs. Paging
Transitions between cell and RA trackings
determine the location update and paging
signaling costs.
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READY Timer Mechanism
3GPP TS 23.060 proposed the READY Timer (RT)
approach, where an RT threshold T is defined.
t4
tp
time
the end of
the previous
packet transmission
t0 t1
the beginning of
the next
packet transmission
. . . . .t1 t2 t3 ti ti+1 ti+2 ti+3
. . . .ti+4 ti+5
Cell Updates RA Updates
......
tNc
Ready timer T
expiration
Drawbacks of the RT approach
The RT approach has a major fallacy that the RT
timers in both the MS and the SGSN are
independent and thus may lose synchronization.
When the MS mobility rate changes from time to
time, the RT timer can not adapt to the change.
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READY Counter Mechanism
To resolve the drawbacks of the RT approach, they
propose the READY Counter (RC) approach.
In the RC approach, an RC counter counts the
number of cell movements in the packet idle period.
If the number of movements reaches a threshold K,
then the MS is switched from cell tracking to RA
tracking.
tm,4
tp
time
the end of
the previous
packet transmission
t0
t1
the beginning of
the next
packet transmission
. . . . .tm,1
tm,2
tm,3
tm,K
tm,K+1
tm,K+2
tm,K+3
. . . .tm,K+4
tm,K+5
K Cell Updates Nu-K RA Updates
......
Threshold K
tm,Nc
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Mix two types of user mobility patterns Type I pattern: mobility rate λm’ = 1/500min
Type II pattern: mobility rate λm’’ = 1/5min
Consider 1,000,000 packet idle periods with mean 100min, in which Type I pattern is exercised with probability 0.5, and
Type II pattern is exercised with probability 0.5.
Let the expected signaling cost of location update and paging in a packet idle period be
CT’ for Type I pattern, and CT’’ for Type II pattern.
Comparison of RC and RT (1)
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In RC (E[tp] = 100min, E[tm’] = 500min, E[tm’’] = 5min) the lowest C
T’ is expected when K ≥ 2
the lowest CT’’ is expected when K = 0
good performance can be expected when K = 1 or 2
In RT (E[tp] = 100min, E[tm’] = 500min, E[tm’’] = 5min) the best threshold value for C
T’ occurs when T > 100min
the best threshold value for CT’’ occurs when T < 5min
no T value will satisfy both patterns
Comparison of RC and RT (2)
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They proposed READY Counter (RC) to
resolve the fallacies of READY Timer (RT).
They devised an adaptive algorithm dynamic
RC (DRC) to reduce the net cost of location
update and paging.
They proposed analytic and simulation
models to investigate RT, RC and DRC.
They provided numerical examples to show
how to select appropriate operation
parameters.
Summary
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Outline
Cellular Networks
GSM & Mobility Management
GPRS & Mobility Management
CAMEL
Number Portability
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CAMEL Overview
Customized Applications for Mobile Network Enhanced Logic
CAMEL: IN for mobile networks (both GSM and GPRS)
ETSI Standards
Why not done by ITU-T?
IN CS-2 & CS-3 includes features support mobile networks
ITU-T specifications must have a worldwide scope and not
be biased toward European standards such as GSM.
ETSI found the CS-2/CS-3 standards are insufficiently
specific for GSM
WIN (Wireless IN) for ASNI-41 (US)
Different protocols
Almost identical architectures, and similar concepts
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CAMEL Architecture (1/2) IN vs CAMEL
In most uses of IN, the SSF, SCF and SRF belong the same
service provider
CAMEL: home network, visited network, interrogating network
A CAMEL service is executed in an SCF in the home network of the subscriber, but where the service is triggered depends on the location of mobile terminal.
HLR: as a special kind of SDF from the IN viewpoint
MAP (Mobile AP): the protocol used to access the HLR
MSC~HLR, SCF~HLR
CAP (CAMEL Application Part): adapted version of INAP
SSF~SCF, SRF~SCF
CAMEL simplifies the call model (compared with IN CS-2)
CAMEL BCSM almost identical to IN
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CAMEL Architecture (2/2)
CAMEL Call Control
Home (A)
Mobile originated Mobile terminated
gsmSCF
Visited
MSC
gsmSSF
O-BCSM
Home (B)
gsmSCF
Interrogating
GMSC
gsmSSF
T-BCSM
Visited
MSC
gsmSSF
T-BCSM
AB
Service is executed in an SCF in the home network
Service is triggered
-an outgoing call: visited network’s MSC
-an incoming call: interrogating network’s GMSC or visited network’s MSC
The interrogating network is usually the home network
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Triggering the CAMEL Services
CAMEL Subscription Information (CSI)
Contents
TDP List (DP to be armed)
SCF address (SS7 address of SCF)
Service key (service to be invoked when DP is met)
Default call handling (error handling, SCF not reached)
Others: DP criteria, CAMEL capability handling, CSI
state, notification flag
CSI Types
O-CSI (outgoing CSI) – held in visited network VLR
T-CSI (terminating CSI) – held in interrogating network
GMSC
VT-CSI (visited terminating CSI) – held in visited
network VLR
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Why we need CAMEL ?
Prepaid subscription with roaming
Many operators implement their prepaid accounts
on a service node with a specialized database
Such prepaid implementations based service
nodes or local IN systems do not allow the
subscriber to place calls in other networks
No standardized interface that lets the MSC in a visited network consult a service node in the home network
The only interface defined in GSM for roaming is between the HLR and VLR, for location management
CAMEL lets the MSC consult the SCF in the home
network
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CAMEL Prepaid with Roaming
SSF SCF
Home networkVisited network
VLR
Subscriber
Place outgoing call
CAMEL?
O-CSI found
(1)
CAMEL(2)
Start O-BCSM
Collected_Info
initialDP
Check creditCreditsufficient
Continue for x sec.
(3)
(4)
Complete call setup
Time expired
time expired event
Update creditCreditinsufficient
(5)
Clear call
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CAMEL Standardization CAMEL Phase 1 (1996)
based on IN CS-1 (ETSI CS-1 Core INAP)
routing, number translation, screening, user
interaction, charging, ...
CAMEL Phase 2 (1997)
based on IN CS-1 (ETSI CS-1R Core INAP)
extended call model
user interactions with SRF
interaction with GSM supplementary services
CAMEL Phase 3 (1999)
3GPP R99, 3GPP R4
support GPRS
CAMEL Phase 4
Many IN CS-2 Capabilities (e.g., mid-call announcement)
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CAMEL Phase 1 Architecture
CAMEL Phase 1
Roaming leg
HLR gsmSCF
GMSC
gsmSSF
MSC
gsmSSFVLR
Home Network
Interrogating Network Visited Network
Incoming line
Forwarded leg
MAP
MAP
MAPCAP CAP
MO call - Outgoing leg(or Forwarding leg)
MS
MAP
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CAMEL Phase 2
CAMEL Phase 2 Architecture
Roaming leg
HLR gsmSCF
GMSC
gsmSSF
MSC
gsmSSFVLR
gsmSRF
Home Network
Interrogating Network Visited Network
Home/Interrogating/Visited Network
Incoming line
Forwarded leg
MAP
MAP
MAPCAP CAP
CAP
MO call - Outgoing leg(or Forwarding leg)
MS
MAP
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CAMEL Phase 3
CAMEL Phase 3 Architecture
Roaming leg
HLR gsmSCF
GMSC
gsmSSF
MSC
gsmSSFVLR
gsmSRF
Home Network
Interrogating Network Visited Network
Home/Interrogating/Visited Network
Incoming line
Forwarded leg
MAP
MAP
MAPCAP CAP
CAP
MAP
SGSN
gprsSSF
CAP
MAP
SMSC
MAP
MO call - Outgoing leg(or Forwarding leg)
MAP
MS
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CAMEL Phase 3 for GPRS
Extensions in CAMEL Phase 3
CAMEL phase 3 enables an SCF in the subscriber’s
home network to control
GPRS Mobility Management
Activation of PDP Contexts
CAMEL services for GPRS are triggered by
an SSF associated with the SGSN that the subscriber
is attached to
Two new state models for GPRS:
Attach-Detach state
Tracks the mobility management
PDP Context state
Represents the establishing PDP contexts process
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CAMEL Attach-Detach State
2 states & 4 detection points
Intra-SGSN Location Update
the terminal stays attached
can send notification only
DP only EDP-N
Inter-SGSN Location Update
the terminal detaches from old SGSN
and then attaches to the new
the HLR is notified of the move
DP can be TDP-R
mobility management can be suspended
and controlled by service logic in the
SCF
Detached
AttachedAD_Exception
Attach
User- or network
initiated detach
Attach request
Detach
Intra SGSN Routeing
area update
Inter SGSN Routeing area update
Change of Position
GPRS Session
(location update DP)
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CAMEL PDP-Context State
Before a subscriber can send or
receive data, the GGSN must set
up a PDP Context.
The state model is started for each
activated PDP context.
A request to send or receive data
causes the state transitions from
Idle to PDP_Cotext_Setup.
When GGSN has set up OK, it
notifies SGSN that data
transmission can begin. This
causes a transition.
Change-of-position-context DP
moves from one routing area to
another
Idle
PDP_Context_Setup
Change of
Position context
C_Exception
PDP_Context_Established
Change of Position Context
PDP Context Est.
PDP ContextDisconnection
PDP Context Est. Ack.
Routeing area update
User or networkinitiated disc.
Routeing area update
PDP ContextSetup Ack.
PDP ContextSetup Req.
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Enhancements for GSM It allows the SCF to control the sending of short message
SMS (short message services)
Terminal submit messages to MSC;
Store and forward;
Receive in destination terminal
Transported on a signaling channel, and do not
involve the setup of a call.
It notifies SCF when GSM supplementary services is
started in the MSC
MSC-based supplementary services (programmed in MSC)
can interfere with CAMEL services.
It controls mobility management (from the SCF)
VLR notifies SCF of attach, detach, location-update
events for a subscriber.
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CAMEL Phase 4 O-BCSM
O_Null & Authorise_Origination_Attempt_Collect_Info O_Exception
Collected_Info
Route_Select_Failure
O_Busy
O_No_Answer
O_Abandon
O_Alerting
Routing
Analysed_Information
Analyse_Information
invalid_information
O_alerting_failure
O_routing_failure
O_Term_Seized
O_AnswerBasic Call transition
O_Disconnect O_active_failure
O_Mid_Call
O_Active
O_Mid_CallO_Change_Of_Position
O_Change_Of_Position
Source: 3GPP TS 23.078 V5.1.0
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CAMEL Phase 4 T-BCSM
T_Null
Terminating Call Handling
T_Exception
Terminating_Attempt_Authorised
T_Answer
T_Busy
T_No_Answer
T_Abandon
T_Disconnect
T_active_failure
T_call_handling_failure
T_Alerting
Call_Accepted
Call_rejected
T_Active
T_Mid_Call
T_Mid_Call
T_ Change_Of_Position
T_ Change_Of_Position
Basic Call transition
Source: 3GPP TS 23.078 V5.1.0
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Mobile-Specific Services
Mobile networks have specific characteristics
Calling a mobile phone is equivalent to calling a
person, whereas calling a fixed phone is calling a
location
Service Examples:
SMS (Short Messaging)
Whereas voice services are synchronous, short
messaging is an asynchronous way of comm.
Like email
Location Services
The network knows approximately where a subscriber is
located
Mobile Payment Services
Mobile phone – carry it with you, linked to an account
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CAMEL – SMS (1/2)
SMS Interworking MSC
replays outgoing messages to other networks
SMS Gateway MSC
a gateway for incoming messages from another
network
SMSC (SMS Center)
store and forward messages
SMPP (Short Message Peer-to-Peer Protocol)
CAMEL cannot look inside messages
MSC
SMSGMSC
SMSIW-MSC
SMSC
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CAMEL – SMS (2/2)
CAMEL SMS State Model
Like the BCSM, this state model runs in the SSF
associated with the MSC.
Triggers are activated by CSI in the VLR.
SMS Analyse &Routing
SMS_ExceptionSMS Null & Start &Authorize
DP SMS_Collected_Info
DP O_SMS_Submitted
DP O_SMS_Failure
O_SMS_Exception
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Location Services (1/2)
Mobile phones tend to travel with their owners
Location-based services
emergency calls
finding facilities (e.g., hotel, restaurants,
police stations, ...)
location-based charging, e.g. special home-zone
tariffs
locating friends, children, ...
tracking vehicles
games
GSM and GPRS networks do not offer any
protocol to query a user’s location
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Location Services (2/2)
Positioning techniques to increase precision
Cell identifier: hundred meters
Measurements on the radio interface
GPS-assisted positioning: difficult in building
GSM generic positioning functions: LMU (location measurement unit)
Co-located in the BTS
SMLC (serving mobile location center)
Calculates the position from measurement
GMLC (gateway mobile location center)
Acts as the point through which external client applications can request
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Location Service Example
Location-based charging
Home-Zone Service MS initiates a call
MSC triggers home-zone service
SCF requests the location of the MS from the GMLC
GMLC directs the request to the SMLC, which
determines the position of the MS
GMLC provides location information to the SCF
If the subscriber is in his/her home zone, the
SCF instructs the MSC to complete the call
using home-zone tariffs.
LMU
Home-zone service
gsmSCF
MSC
gsmSSF
GMLC
(1)
(2)
(3)
(5)
(4)
(6)
(4)SMLC
BSC
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Mobile Payment Service
Mobile e-commerce
Industrial payment solutions
Dual-slot terminals
Bluetooth
IN-based (CAMEL-based) payments
Mobile payment with CAMEL
gsmSCF
MSC
gsmSSF
(1)
(2)
(3)
(6)
(4)
(4)
Beverage 1: dial 123456Beverage 2: dial 123457Beverage 3: dial 123458
gsmSDF
(5)
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References
ITU-T Recommendation, Series Q.1200
Q.12x0 ~ Q.12x9
3GPP Specifications
TS 23.078, “Customized Applications for Mobile
network Enhanced Logic (CAMEL) Phase 4 – Stage 2”
3GPP
http://www.3gpp.org/
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Outline
Cellular Networks
GSM & Mobility Management
GPRS & Mobility Management
CAMEL
Number Portability
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Types of Number Portability
Service Provider Number Portability (SPNP) The ability to change the service provider
while keeping the same phone number
Location Number Portability (LNP) The ability to change the subscriber’s fixed
service location while keeping the same phone
number
Service Number Portability (SNP) The ability to change the subscribed services
while keeping the same phone number
from plain old telephone service to ISDN
NP/ ENUM Address for RoutingA list of URI
Number for NamingE.164 Number
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Four of SPNP Schemes (1/2)
ALL Call Query (ACQ)
Most efficient
New
Network
Old
Network
Orig.
Network
Donor
Network
Internal
NPDB
Central
NPDB
1 2
3
Number
Ported
Query on Release (QoR)
Reserved one-by-one
Released one-by-one
New
Network
Old
Network
Orig.
Network
Donor
Network
Internal
NPDB
Central
NPDB
3 4
5
Number
Ported
1 2
RFC 3482Number Portability in the Global Switched Telephone Network (GSTN) : An Overview
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Four of SPNP Schemes (2/2)
Call Dropback
Reserved one-by-one
Released one-by-one
New
Network
Old
Network
Orig.
Network
Donor
Network
Internal
NPDB
Central
NPDB
1 4
3
Number
Ported
Onward Routing
Two call segments
Least efficient
New
Network
Old
Network
Orig.
Network
Donor
Network
Internal
NPDB
Central
NPDBNumber
Ported
14
2
5
3
2
RFC 3482Number Portability in the Global Switched Telephone Network (GSTN) : An Overview
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GSTN NP Implementations
NP Database Queries
Switch-to-NPDB
IN/AIN INAP or GSM MAP over TCAP
STP-to-NPDB
examined ISUP IAM to perform NP translations
NP supported
US: across the wireline/wireless boundary
Europe: only within wireline or wireless domain
Avoid caller confusion about call charge
SPNP Schemes chosen
Onward Routing: Austria,France,UK,Italy,Japan,
All Call Query: US,Germany,Denmark,Finland,
OR for short-term and ACQ for long-term: Norway,Sweden
Mobile All-IP Networking LaboratoryDepartment of Computer Science & Information Engineering
Any Question?
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