GPRS-EDGE Radio Network Optimization
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Description
GPRS Principles
www.huawei.com
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
1
Foreword z
GPRS principle is the basic part of the whole GPRS system and the succeeding products learning.
z
This slide will help us to understand the GPRS system networking and wireless subsystem etc.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page1
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Objectives z
Upon completion of this course, you will be able to:
Know the GPRS system structure
Describe the GPRS important interfaces
Understand the GPRS channel structures
Master the GPRS relevant numbering
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page2
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Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page3
4
Circuit Switch (CS) G
A CS
CS
B H C
I
CS
D
J
E K F
CS
CS
L
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Page4
5
Packet Switch (PS) PS
A
PS
PS
1 1
2
3
1
2
3
C
1
3
2 3
2
2
3 2 1
B
PS
1 2 3
2 1 3
PS
PS
D
PS
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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GSM Development Evolution 3G
2.75 G
ECSD 38.8 Kb/s
2.5 G
HSCSD 14.4 Kb/s
UMTS
384 Kb/s
EGPRS EDGE 59.2 Kb/s
GPRS 21.4 Kb/s
CS
2G
GSM
9.6 Kb/s
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
PS
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What is GPRS and EDGE? z
Abbreviation of General Packet Radio Service.
z
GPRS is an end-to-end packet switching technology provided on the basis of GSM technology.
z
It has much interactive services with the existing GSM circuit switching system.
z
GPRS supports wireless access rate of up to 171.2Kbps.
z
EDGE (Enhanced Data Rates for GSM Evolution)
EGPRS (Enhanced GPRS)
EGPRS supports wireless access rate of up to 473.6Kbps.
ECSD (Enhanced CSD, Enhanced HSCSD-High Speed Circuit Switched Data)
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page7
•GPRS is the abbreviation of General Packet Radio Service. •GPRS network introduces packet switching functional entities in the GSM network to implement data transmission in the packet mode. •GPRS can be regarded as the service expansion based on the GSM network for supporting mobile subscribers access the Internet of other packet data networks via packet data mobile terminal. Making full use of the existing GSM network,small investment and quick rewarding,all of these benefit to protect the existing investment and obtain maximum benefits for the operators.
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GPRS&EDGE Coding Rate Kbps
59.2
60.00
54.4
50.00
GPRS
44.8
EGPRS
40.00
29.6
30.00 22.4
21.4
20.00 13.4
10.00 0.00
17.6
15.6
14.8
9.05
CS-1
8.8
CS-2
CS-3
CS-4
MCS-1
11.2
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
GMSK
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
MCS-7
MCS-8
MCS-9
8PSK
Page8
9
Adjustments to GSM Network
BSS
A
Pb
CS Core Network
PCU Gs Gb
PS Core Network
BSS
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
NSS
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Most Popular GPRS Applications z
E-mail
z
Web Browsing
z
Information Services
z
Moving Images
z
Still Images
z
Remote LAN Access
z
File Transfer
z
Sport Report Public Information Weather Forecast Service Traffic Information
Stock Market
Still Images
Job Despatch
Live News
Moving Bank
Personal Information Service
File Transfer
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Email
Web Browsing
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Advantages and Disadvantages of GPRS z
z
Advantages
Share resource with GSM
High resource utilization
Fast transmission rate
Always on line
Short access time
Disadvantages
Slower data rates in practice than anticipated in theory
Suboptimal modulation technique
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page11
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Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page12
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CS & PS Logic Structure C
GMSC
PSTN
E D CS
B T S
Abis
G-Abis
A
MSC/VLR
TRAU
BSC
PCU
Pb
PS
HLR AUC GPRS Register
Gs Gb
Gr SGSN
BSS Gn Gc
Internet
GGSN Gi
CN Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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GPRS System Structure HLR
SMS-GMSC SMS-IWMSC
MSC/VLR
EIR
SS7 WAP Gateway BSS MS
Gs
BSC
Gd
Gb
Gr
Gf Gn
Gc
Firewall
Gi
GGSN
Abis BTS
Intranet/Internet RADIUS
PCU
SGSN
Gn
GPRS Backbone
Ga
CG
Gi
ATM/DDN/ISDN/Ethernet, etc
X.25 BSS
SGSN
BSC
MS
GGSN
Gb
CNCN-PS
Abis BTS
DNS
BG
PCU
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Other PLMN
Gp
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GPRS MS z
Class A
z
Class B
z
The MS is attached to both GPRS and other GSM services and the MS supports simultaneous operation of GPRS and other GSM services.
The MS is attached on GPRS network and GSM network simultaneously but not enabling circuit switching and packet switching services at the same time. services are selected automatically.
Class C
The MS is attached to either GPRS or other GSM services. Alternate use only. services are selected manually or default selected service.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of PCU (Packet Control Unit) z
Packet wireless resource management function (RLC/MAC protocol function)
z
Wireless resource management functions of GPRS BSS
Circuit paging coordination
G-Abis interface processing function
Function related with GPRS BTS
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of PCU (Packet Control Unit) z
z
Pb interface processing function
LAPD link between BSC and PCU
Layer-3 signaling between BSC and PCU
Gb interface processing function
Data packet relay on wireless interface and Gb interface
Mobility management (cell updating procedure)
Downlink traffic control (wireless QoS guarantee)
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page17
Provides physical and logical data interface out of the BSS for packet data traffic LLC layer PDU segmentation/reassembly of RLC blocks Packet data transfer scheduling ARQ functions Radio channel management function
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Functions of SGSN (Serving GPRS Support Node) z
Packet routing
z
MS Session management
z
Authentication and Ciphering
z
Mobility management
z
Billing information collection
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of GGSN (Gateway GPRS Support Node) z
Interface between GPRS backbone and external PDNs.
z
PDP Conversion and context management
z
IP address assignment management
z
Packet routing to/from SGSNs
z
Billing information collection
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of CG (Charging Gateway) z
Real-time collection of GPRS bills
z
Temporary storage and buffering of GPRS bills
z
Pre-processing of GPRS bills
z
Sending GPRS bills to the billing center
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of MSC/VLR z
When Gs interface is installed, MSC/VLR can support
z
Establishment and maintenance of the association between SGSN and MSC/VLR.
z
z
z
GPRS combined mobility management procedure.
Combined IMSI/GPRS attachment/detachment.
Combined location area/routing area updating.
Circuit paging coordination function.
The wireless resource usage can be greatly improved.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of HLR/AUC z
Saving and updating GPRS subscriber subscription data
z
User authentication
z
Providing location/routing information and processing needed in mobility management and routing, for example:
z
Saving and updating user service SGSN number and address
GPRS user location deletion indication
Whether MS is reachable.
Subscriber tracing (optional)
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Functions of SMS-GMSC/SMS-IWMSC z
The SMS-GMSC and SMS-IWMSC are connected to the SGSN via the Gd interface to enable GPRS MSs to send and receive SMs over GPRS radio channels.
z
After Gd interface is installed, short messages can be sent via GPRS, which reduces the occupation on SDCCH and cuts down the influence on voice services by SMS services.
z
The operator can select to send SMS via MSC or SGSN. SMS
MS
Gd
SGSN
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
SMS-IWMSC SMS-GMSC Page23
SMS-IWMSC(Interworking MSC For Short Message Service):A function of an MSC capable of receiving a short message from within the PLMN and submitting it to the recipient SC. For example:The MSC forwards the SM to the SMS-IWMSC, which is responsible for processing SMs submitted by the MS. SMS-IWMSC:The SMS Interworking MSC acts as an interface between the PLMN and a Short Message Service Centre (SC) to allow short messages to be submitted from Mobile Stations to the SC. SMS-GMSC(Gateway MSC For Short Message Service):A function of an MSC capable of receiving a short message from an SC, interrogating an HLR for routing information and SMS info, and delivering the short message to the VMSC of the recipient MSFor example:The SMS system submits the message transfer request to the SMS-GMSC, which is responsible for processing delivered SMs. SMS-GMSC:The SMS Gateway MSC (SMS-GMSC) acts as an interface between a Short Message Service Centre and the PLMN, to allow short messages to be delivered to mobile stations from the Service Centre (SC)。
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Functions of BG (Border Gateway) z
BG enables the following protocols necessary for interworking between operators
Security protocol: IPSec and firewall are recommended
Routing protocol: BGP is recommended
Billing protocol: determined by the operators with negotiation; BG might be needed in collecting billing information
z
It is normally based on routers
z
It can be combined with GGSN in physical.
z
BG does not exclusively belong to the GPRS network. Gp GSN PLMN A
R R
R R
BG
BG
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
PLMN B
GSN
Page24
IPsec (IP security) is a standardized framework for securing Internet Protocol (IP) communications by encrypting and/or authenticating each IP packet in a data stream. A protocol for exchanging routing information between gateway host s (each with its own router ) in a network of autonomous system s. BGP is often the protocol used between gateway hosts on the Internet.
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Functions of DNS (Domain Name System) z
The following two types of DNSs may be adopted in the GPRS network:
The DNS between the GGSN and external networks
The DNS on the GPRS backbone network. Provides two types of functions:
a. Resolve the GGSN IP address based on the Access Point Name (APN) in the process of the PDP context activation;
b. Resolve original SGSN IP address based on the original routing area No. in the process of the update of inter-SGSN routing area. DNS Server
z
DNS does not exclusively belong to the GPRS network. SGSN
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
GPRS Backbone
SGSN
Page25
DNS（Domain Name System） The following two types of DNSs may be adopted in the GPRS network: The DNS between the GGSN and external networks: Implements resolution of the domain name of external network, and functions as the ordinary DNS on the Internet. The DNS on the GPRS backbone network. Provides two types of functions: a. Resolve the GGSN IP address based on the Access Point Name (APN) in the process of the PDP context activation; b. Resolve original SGSN IP address based on the original routing area No. in the process of the update of inter-SGSN routing area. The DNS is not a proprietary entity of the GPRS network.
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Functions of RADIUS Server (Remote Authentication Dial In User Service Server) z
It is a protocol used by Remote Access Server's for user Authentication.
z
The RADIUS server stores the authentication and authorization information of subscribers.
z
It also performs subscriber identity authentication in the case of non-transparent access.
z
RADIUS Server does not exclusively belong to the GPRS network.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Contents 3. GPRS Network Interfaces & Protocols 3.1 Interface and Protocol Stack 3.2 Um Interface 3.3 G-abis/Pb Interface 3.4 Gb Interface 3.5 Gs Interface
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Network interface types SGSN SGSN
GPRS backbone network
IP interface
Gi
GGSN GGSN
Gn
PDP network (IP/X.25)
SGSN SGSN
SS7 interface Gc
Gd
Gb Gr Gs
MT TE
Um
A
MSC
HLR
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page29
BSS
SMSGMSC
MS
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Interface in GPRS Network Interface R
Description The reference point between the Mobile Terminal (MT) (for example, mobile phone) and the Terminal Equipment (TE) (for example, the portable computer).
Um
The interface between MS and GPRS network side
Gb
The interface between the SGSN and BSS.
Gc
The interface between the GGSN and HLR (optional).
Gd
The interface between SMS and GMSC The interface between SMS-IWMSC and SGSN
Gi
The reference point between the GPRS and external packet data
Gn
The interface between SGSNs and between SGSN and GGSN in the PLMN.
Gp
The interface between GSNs of different PLMNs.
Gr
The interface between the SGSN and HLR.
Gs
The interface between the SGSN and MSC/VLR (optional).
Gf
The interface between the SGSN and EIR (optional).
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Data transmission plane Application
IP/X.25
IP/X.25
relay
SNDCP LLC RLC
z z
relay
BSSGP
MAC
MAC
Network Service
Physical Layer
Physical Layer
Physical Layer
MS z
RLC
Um
Gb
BSS
MAC: Media Access Control RLC: Radio Link Control LLC: Logical Link Control
z z z
GTP
GTP
SNDCP
LLC
UDP/TCP
UDP/TCP
BSSGP
IP
IP
Network Service
L2
L2
Physical Layer
Physical Layer
Physical Layer
SGSN
IP/X.25
Gn
L2 (MAC)
Physical Layer GGSN
Gi
BSSGP: BSS GPRS Protocol SNDCP: Sub-Network Dependency Convergence Protocol GTP: GPRS Tunneling Protocol
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page31
The Relay function provides buffering and parameter mapping between the RLC/MAC and the BSSGP. For example, on the uplink the RLC/MAC shall provide a TLLI. The Relay function shall then make it available to BSSGP.
32
MS-SGSN signaling plane GMM/SM
GMM/SM
LLC
LLC relay Relay
RLC
RLC
BSSGP
BSSGP
MAC
MAC
Network Service
Network Service
GSM RF
GSM RF
L1bis
L1bis
Um
MS
BSS
z
GMM: GPRS Mobility Management
z
SM: Session Management
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Gb
SGSN
Page32
Um interface: Physical layer: wireless coding/decoding, channel multiplexing and mapping, wireless link control and wireless measurement RLC/MAC: wireless interface media access and link control function LLC:
providing a reliable logic link between MS and SGSN for data transmission. LLC
protocol can support both acknowledged mode and unacknowledged mode. It supports both encryption and decryption modes SNDCP: Layer-3 transmission protocol. As the transition between the network layer and the subnet layer, it implements segmentation/assembling and compression/decompression on IP/X.25 subscriber data GMM/SM: Layer-3 signaling protocol
Gb interface: L1bis: physical transmission layer based on E1 or T1 NS: based on FR; used to transmit BSSGP PDU of the upper layer BSSGP: On the transmission platform, this protocol is used to provide a connectionless link between BSS and SGSN for unacknowledged data transmission; on the signaling platform, it is used to transmit QoS and routing information related with the wireless section; it is also used to process paging requests and implement traffic control on data transmission
33
Contents 3. GPRS Network Interfaces & Protocols 3.1 Interface and Protocol Stack 3.2 Um Interface 3.3 G-abis/Pb Interface 3.4 Gb Interface 3.5 Gs Interface
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page33
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z
SM (Session Management): processes procedure that GPRS MS connects to the external data network.
z
SNDCP (Subnetwork Dependent Convergence Protocol): Multiplexing of several PDPs, compression / decompression and Segmentation of user data.
z
LLC (Logical Link Control ): This layer provides a highly reliable ciphered logical link between an MS and its SGSN.
z
RLC:Segmentation and re-assembly between LLC PDUs and RLC blocks.
z
MAC: defines the procedures that enable multiple mobile stations to share a common transmission medium.
SMS
GMM (GPRS Mobility Management): operates in the signalling plane of GPRS supports mobility management functionality.
SNDCP
z
GMM/SM
Protocol Layer of Um Interface
LLC RLC MAC Physical Link
RF
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page34
GMM (GPRS Mobility Management) This protocol that operates in the signalling plane of GPRS supports mobility management functionality such as GPRS attach, GPRS detach, security, routing area update, location update, roaming, authentication, and selection of encryption algorithms. SM (Session Management) It is the processing procedure that GPRS MS connects to the external data network. The main function is to support the processing of PDP mobile scenario. Logical Link Control (LLC): This layer provides a highly reliable ciphered logical link between an MS and its SGSN. LLC includes functions for the provision of one or more logical link connections discriminated between by means of a DLCI. sequence control, to maintain the sequential order of frames across a logical link connection. detection of transmission, format and operational errors on a logical link connection. recovery from detected transmission, format, and operational errors. notification of unrecoverable errors. flow control. ciphering.
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MM State >GMM context is not established; MS is not reachable. IDLE
Data transmission to and from the mobile subscriber as well as the paging of the subscriber are not possible
STANDBY
>GMM context is established; MS can receive paging but cannot implement data transmission.
The location information in the SGSN MM context contains only the GPRS RAI.
Pages for data or signalling information transfers may be received. It is also possible to receive pages for the CS services via the SGSN. Data reception and transmission are not possible in this state.
>MS can implement data transmission. READY
The MS performs MM procedures to provide the network with the actual selected cell.
SGSN performs the MM on cell level.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page35
The Mobility Management (MM) activities related to a GPRS subscriber are characterised by one of three different MM states.
36
MM State Model READY timer expiry or Force to STANDBY
GPRS Attach
MM State Model of MS
READY
IDLE GPRS Detach
PDU transmission READY timer expiry or Force to STANDBY or Abnormal RLC condition
GPRS Attach
MM State Model of SGSN
IDLE
STANDBY
READY GPRS Detach or Cancel Location
STANDBY PDU reception
Implicit Detach or Cancel Location
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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RLC/MAC Block Generation Subscriber IP packet (N-PDU)
Network Layer
SNDCP PDU(SN-PDU)
SNDCP Layer
LLC Layer
LLC frame
RLC/MAC Layer
Subscriber data
RLC/MAC block
SNDCP head
LLC head
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
LLC FCS
RLC/MAC head
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Physical Channel z
The same as in GSM
z
The same frequency
z
The modulation mode
z
The same TDMA frame definition
z
The same burst pulse definition
z
…
z
The differences between GPRS and GSM
z
The Multi-frame structure
RLC
z
The channel coding
MAC
z
…
Application IP/X25 SNDCP LLC
Physical Layer MS
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
RLC
Relay
BSSGP
Frame relay
MAC Physical Layer
Physical Layer
BSS
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Packet Logic Channels Packet Logic Channel Packet control channel
Packet service channel
PBCCH
PCCCH
PDCCH
BCCH PDTCH/U
TCH
PDTCH/D
PPCH
PRACH
PAGCH
PNCH
PCH, RACH, AGCH,NCH
PACCH PTCCH/U PTCCH/D
SACCH z
The specific type of PDCH (except PRACH) is determined by RLC/MAC head and RLC/MAC control message type. Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page39
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Channel Abbreviation z z z z z z z z z z z z
Packet Data Traffic CHannel Uplink - PDTCH/U Packet Data Traffic CHannel Downlink - PDTCH/D Packet Broadcast Control CHannel - PBCCH Packet Common Control CHannel - PCCCH Packet Dedicated Control Channel - PDCCH Packet Paging CHannel - PPCH Packet Random Access CHannel - PRACH Packet Access Grant CHannel - PAGCH Packet Notification CHannel - PNCH Packet Associated Control CHannel - PACCH Packet Timing advance Control CHannel Uplink - PTCCH/U Packet Timing advance Control CHannel Downlink PTCCH/D
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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PDTCH (Packet Data Traffic CHannel) z
All packet data traffic channels are uni-directional.
Uplink (PDTCH/U) for a mobile
Packet service channel
originated packet transfer.
Downlink (PDTCH/D) for a mobile
PDTCH/U
PDTCH/D
terminated packet transfer.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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PBCCH (Packet Broadcast Control CHannel) z
z
The PBCCH broadcasts parameters used by the MS to access the network for packet transmission operation. The PBCCH also carries the information transmitted via the BCCH to allow circuit switching operation.
Packet control channel
PBCCH
The MS in GPRS attached mode monitors the PBCCH only, if PBCCH is available, otherwise, the BCCH shall be used to broadcast information for packet operation. The existence of the PBCCH in the cell is indicated on the BCCH via SI13.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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PCCCH (Packet Common Control CHannel) z
PPCH
z
PRACH
z
PCCCH
Downlink only, used to allocate one or several PDTCHs.
PNCH
z
Uplink only, used to request allocation of one or several PDTCH/Us or PDTCH/Ds.
PAGCH
z
Downlink only, used to page MS.
PPCH
PRACH
PAGCH
PNCH
Downlink only, used to notify MS of PTM-M call.
If no PCCCH is allocated, the information for packet switching operation is transmitted on the CCCH. If a PCCCH is allocated, it may transmit information for circuit switching operation.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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PDCCH (Packet Dedicated Control Channels) z
PACCH PDCCH
Bi-directional, used to transmit the packet signaling in data transmission.
z
PTCCH/U
PACCH
Used to transmit random access bursts to allow estimation of the timing advance for
PTCCH/U
PTCCH/D
one MS in packet transfer mode. z
PTCCH/D
Used to transmit timing advance updates for several MS. One PTCCH/D is paired with several PTCCH/U's.
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Combinations of Packet Logic Channel Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH Mode 2: PCCCH+PDTCH+PACCH+PTCCH
Mode 3: PDTCH+PACCH+PTCCH
Mode 4: PBCCH+PCCCH (PCCCH=PPCH+PRACH+PAGCH+PNCH）
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
With the increase of traffic, the packet public channel should be configured in the cell. Channel combination mode 1 and mode 2 should be adopted.
In case of small GPRS traffic, GPRS and circuit services share the same BCCH and CCCH in the cell. In this case, only combination mode 3 is needed in the cell.
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Packet Wireless Channel Configurations z
z
Reason of adopting static PDCH
To enable that GPRS MS is constantly online in the cell.
To ensure certain QoS of GPRS services.
Reason of adopting dynamic PDCH
GPRS and GSM share wireless resources. Wireless resources should be adopted in priority; on the other hand, QoS of voice services should be ensured. In a cell, the percentage of packet switching services and the percentage of circuit switching services are constantly changing. Dynamic PDCH is not visible for voice services.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Packet Wireless Channel Configurations z
General principles
The cell should be configured with static PDCH to enable MS to be normally attached on GPRS network as well as certain QoS of GPRS services.
Dynamic PDCH should be configured according to the GPRS traffic forecast, which should be adjusted as TCH or PDCH usable in the operation process according to the cell traffic status.
Circuit switching services can seize the channel used by GPRS services.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Mapping of Packet Logic Channel z
A radio block is a 4-normal-burst sequence that carries a RLC/MAC PDU (Protocol Data Unit). 25
0
B0
B1
B2 T B3
B4
B5 I B6
51
B7
B8 T B9
B10 B11 I
456 bits
01234 567
012 34 567 01234 567
01234 56 7
I = Idle frame T = Frame used for PTCCH B0 ~ B11 = Radio blocks
1 TDMA frame
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Mapping of Packet Logic Channel 0
BCCH 0
50
F S B B B B C C C C F S C C C C C C C C F S C C CC C C C C F S C C C C C C C C F S C C C C C C C C
I
1 12
PDCH
2 B0
B1
B2 T B3
51
25
B4
B5 I B6
B7
B8 T B9
B10 B11 I
3 25
TCH
4T T T T T T T T T T T TSTT T T T T T T T T T T I 5 6 7
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Transmission Principle of Data Packet on Um Interface Subscriber IP packet
SNDCP PDU
LLC PDU
RLC/MAC block N B
N B
N B
N B
Physical layer
B0 B1 B2 T B3 B4 B5 I B6 B7 B8 T B9 B10 B11 I Subscriber data
SNDCP head
LLC head
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
LLC FCS
RLC/MAC head
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Allocation of Wireless Packet Resources TS 0
B0
B1
B2
B3
B4
B5
B6
B7
B8
B9
B1 0
B1 1
TS 1
B0
B1
B2
B3
B4
B5
B6
B7
B8
B9
B1 0
B1 1
TS 2
B0
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
MS1 z
MS2
MS3
Wireless resource allocation and wireless transmission adopt the wireless block (BLOCK) as the basic unit.
z
Each PDCH can be used by several MSs; each MS can use multiple PDCHs at the same time.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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52
Basic Conceptions about Radio Block z
USF(Uplink State Flag) is sent in all downlink RLC/MAC blocks and indicates the owner or use of the next uplink Radio block on the same timeslot.
z
The USF field is three bits in length DL
U
=1 SF
U
=1 SF
……
……
B0
I
F=1 US
U
B B1 1
=1 SF
10
T
B
F=2 US
F=2 US
B 9T
8
F=3 US
B7
I
F=3 US
F=3 US
5 I B B6
T F=3
F=4 US
U
US
B4
T B3
F=4 US
=4 SF
B2
B1
UL
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
I
B0
I
USF=1
MS1
USF=2
MS2
USF=3
USF=4
MS3
MS4
Page52
The USF field is three bits in length and eight different USF values can be assigned, except on PCCCH, where the value '111' (USF=FREE) indicates that the corresponding uplink Radio block contains PRACH.
53
Basic Conceptions about Radio Block z
TBF (Temporary Block Flow)
A Temporary Block Flow (TBF) is a physical connection used by the two RR entities（the RR entity of the MS and that of the BSS） to support the unidirectional transfer of LLC PDUs on packet data physical channels.
A TBF is temporary and is maintained only for the duration of the data transfer.
z
TFI (Temporary Flow Identity)
Each TBF is assigned a Temporary Flow Identity (TFI) by the network.
The TFI field is five bits in length.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page53
The same TFI value may be used concurrently for TBFs in opposite directions. The TFI is assigned in a resource assignment message that precedes the transfer of LLC frames belonging to one TBF to/from the MS. The same TFI is included in every RLC header belonging to a particular TBF as well as in the control messages associated to the LLC frame transfer (e.g. acknowledgements) in order to address the peer RLC entities.
54
Contents 4. GPRS Wireless Subsystem 4.1 Packet Channels 4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control 4.5 Network Control Modes
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page54
55
Medium Access Modes z
Uplink resource allocation mode
Dynamic allocation (supported by all MSs and all networks)
The mobile station detecting an assigned USF value for each assigned PDCH and block or group of four blocks that it is allowed to transmit on that PDCH.
Fixed allocation (supported by all MSs and all networks)
Fixed bit mapping is adopted to determine the allocated blocks in the allocation period without an assigned USF.
Extended dynamic allocation (optional for the network)
The mobile station detecting an assigned USF value for any assigned PDCH allowing the mobile station to transmit on that PDCH and all higher numbered assigned PDCHs in the same block or group of four blocks.
z
Downlink resource allocation mode
Dynamic allocation and fixed allocation.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page55
Three medium access modes are supported: Dynamic Allocation characterised by that the mobile station detecting an assigned USF value for each assigned PDCH and block or group of four blocks that it is allowed to transmit on that PDCH; Extended Dynamic Allocation characterised by the mobile station detecting an assigned USF value for any assigned PDCH allowing the mobile station to transmit on that PDCH and all higher numbered assigned PDCHs in the same block or group of four blocks Fixed Allocation characterised by fixed allocation of radio blocks and PDCHs in the assignment message without an assigned USF. Fixed Allocation may operate in half duplex mode, characterised by that downlink and uplink TBF are not active at the same time. Half duplex mode is only applicable for multislot classes 19 to 29.
Either the Dynamic Allocation medium access mode or Fixed Allocation medium access mode shall be supported by mobile stations and all networks that support GPRS. The support of Extended Dynamic Allocation is optional for the network. The Dynamic Allocation and Fixed Allocation modes shall be supported in all mobile stations. The support of Extended Dynamic Allocation is mandatory for mobile stations of multislot classes 22, 24, 25 and 27. The support of Extended Dynamic Allocation for mobile stations of all other multislot classes are optional and shall be indicated in the MS Radio Access Capability.
In the case of a downlink transfer, the term medium access mode refers to the measurement time scheduling, for the MS to perform neighbour cell power measurements
56
Contents 4. GPRS Wireless Subsystem 4.1 Packet Channels 4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control 4.5 Network Control Modes
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page56
57
MS Multi-TS Ability z
Concept of MS multi-TS ability
Types
Type 1: Non-simultaneous TRX
Type 2: Simultaneous TRX
the multi-TS ability level is 1-29; the bigger the level, the stronger the multi-TS ability.
z
1~12 (Type 1),up to 4 timeslots in any direction
13~18 (Type 2),ranges between 3~8 timeslots
19~29 (Type 1)
BSS allocates resources according to the MS multi-TS ability, requested QoS and current resource configuration.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Contents 4. GPRS Wireless Subsystem 4.1 Packet Channels 4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control 4.5 Network Control Modes
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page58
59
Power Control z
Power control can improve the spectrum usage and system capacity as well as reduce MS power consumption.
z
As there is no continuous bi-directional connection in the packet data transmission process, GPRS power control is very complicated.
z
Uplink power control includes open-loop and close-loop power control.
z
About downlink power control, there is no specific definition in protocol. It lies on the BTS and its algorithm needs information about downlink, so downlink power control needs MS sends channel quality reports to BTS.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Contents 4. GPRS Wireless Subsystem 4.1 Packet Channels 4.2 Medium Access Modes 4.3 MS Multi-TS Ability 4.4 Power Control 4.5 Network Control Modes
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page60
61
Network Control Modes z
During the network controlled cell re-selection, the network may request measurement reports from the MS and control its cell re-selection. Hence, three types of mode are defined as follows:
z
NC0: Normal MS controls
NC1: MS control with measurement reports
NC2: Network control
The network subsystem must support NC0 and should gradually support NC1 and NC2.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page61
During the network controlled cell re-selection, the network may request measurement reports from the MS and control its cell re-selection. Hence, three types of mode are defined as follows: NC0: Normal MS controls. The MS shall perform autonomous cell re-selection. NC1: MS control with measurement reports. The MS shall send measurement reports to the network. The MS shall perform autonomous cell re-selection. NC2: Network control. The MS shall send measurement reports to the network. The MS shall not perform autonomous cell re-selection.
The network subsystem must support NC0 and should gradually support NC1 and NC2.
62
Network Control Modes MS
NC0
MS
NC1
The MS shall send measurement reports to the network
The MS shall perform autonomous cell re-selection
The MS shall perform autonomous cell re-selection
NC2 MR The
BTS
MS Cell re-selection
MS
shall
not
perform autonomous cell re-selection
command
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page62
63
Contents 1. GPRS System Overview 2. GPRS Architecture 3. GPRS Network Interfaces & Protocols 4. GPRS Wireless Subsystem 5. GPRS Location Area
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Relationship among Location Areas SGSN1 SGSN2 BSC1 BSC3
BSC2 CELL CELL
CELL CELL CELL
CELL CELL CELL
RA2 CELL RA1
RA3 LA1
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
LA2
Page64
65
LAI (Location Area Identification) z
MCC：Mobile Country Code, it consists of 3 digits. For example: The MCC of China is "460"
z
MNC：Mobile Network Code, it consists of 2 digits. For example: The MNC of China Mobile is "00"
z
LAC：Location Area Code, it is a two bytes hex code. The value 0000 and FFFF is invalid
z
For example: 460008C90
MCC
MNC
LAC
Location Area Identification
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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RAI z
Routing area is the sub-set of the location area. In special cases, the two areas are equal
z
The division of the routing area is related with traffic distribution and SGSN processing ability
MCC
MNC
LAC
RAC
Location Area Identification Routing Area Identification
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page66
67
CGI z
CI (Cell Identity): This code uses two bytes hex code to identify the radio cells within a LAI.
z
RAC is only unique when presented together with LAI.
z
CI is only unique when presented together with LAI or RAI.
z
CGI = MCC+MNC+LAC+{RAC}+CI
MCC
LAC
MNC
RAC
CI
Location Area Identification Routing Area Identification CGI
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page67
68
Relationship among location areas z
LAI MCC+ MNC+ LAC
LAI
z
RAI
MCC+ MNC+ LAC+RAC RAI
z
CGI /CellID
MCC+ MNC+ LAC+{RAC}+CI CGI
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Page68
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Summary z
GPRS System Overview
z
GPRS Architecture
z
GPRS Network Interfaces & Protocols
z
GPRS Wireless Subsystem
z
GPRS Location Area
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
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Thank you www.huawei.com
71
GPRS EDGE Mobile Management Algorithm www.huawei.com
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
72
Foreword z
GPRS Mobility Management is a GPRS signaling protocol that handles mobility issues such as roaming, authentication and selection of encryption algorithms. It is important to enable the network to keep track the current location of the MS in order for the paging to be performed smoothly. With the proper setting of the GMM parameters, we can shorten the access delay of the MS.
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page1
73
References z
GBSS8.1 BSC6000 Feature Description
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page2
74
Objectives z
Upon completion of this course, you will be able to:
Understand the GPRS Mobility Management procedure
Familiar with the GMM state model
Understand the cell reselection algorithm
Recognize the cell update and routing area update flow
Realize the GMM related parameters
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page3
75
Contents 1. Overview of GPRS Mobile Management 2. Location Update 3. GPRS Cell Selection & Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page4
76
Overview for GPRS Mobile Management z
The main purpose of the mobility management is to keep track of the user’s current location. Thus, the paging can be performed.
z
MS perform cell selection and reselection when it moves around the coverage area. It also sends the location update message to the SGSN so that the network can be always aware of the MS’s current location.
z
There are 3 states exist in the GPRS mobility management and different location information is available in each state (please see the following figure – MM State).
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page5
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GMM State > GMM context is not established; MS is not reachable. IDLE
Data transmission to and from the mobile subscriber as well as the paging of the subscriber are not possible
STANDBY
> GMM context is established; MS can receive paging but cannot implement data transmission.
The location information in the SGSN MM context contains only the GPRS RAI.
Pages for data or signalling information transfers may be received. It is also possible to receive pages for the CS services via the SGSN. Data reception and transmission are not possible in this state.
> MS can implement data transmission. READY
The MS performs MM procedures to provide the network with the actual selected cell.
SGSN performs the MM on cell level.
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page6
.
78
GMM State Model READY timer expiry or Force to STANDBY
GPRS Attach
MM State Model of MS
READY
IDLE GPRS Detach
PDU transmission READY timer expiry or Force to STANDBY or Abnormal RLC condition
GPRS Attach
MM State Model of SGSN
IDLE
STANDBY
READY
STANDBY PDU reception
GPRS Detach or Cancel Location
Implicit Detach or Cancel Location
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z
z
z
z
Page7
By performing GPRS attach, the MS gets into READY state and if the MS does not transmit any packet for a long period of time until the READY timer is expired, the MS will get into STANDBY state. It is possible to transmit data only if the MS is in READY state, thus the MS in STANDBY state can switch back to the READY state, if a PDU transmission occurs and in the same way, at READY state if the GPRS detach is performed, the MS will be back into IDLE state and all PDP context will be deleted. In STANDBY state, the MS sends the location update message seldom, so its location is not known exactly and the paging is necessary for every downlonk packet, resulting in a delivery delay. In READY state, the MS updates its location frequently. Consequently the MS‘s location is known precisely and no paging delay during delivery downlonk packet. Howeverm this consumes much more the uplink radio capacity and battery of the MS.
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GMM State vs Location Information z
During GMM IDLE state, MS is detached from GPRS. Thus MS can not receive paging nor data transmission.
z
During GMM STANDBY state, MS is attached to the GPRS network and it will perform routing area update (RAU), MScontrolled cell reselection and monitor paging. It only report RA changes.
z
During GMM READY state/ packet transfer mode, MS will perform both routing area update (RAU) and cell update (both MS-controlled and Network-controlled cell reselection). It report the cell changes and RA changes.
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page8
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Contents 1. Overview of GPRS Mobile Management 2. Location Update 2.1 Relationship between Cell, Routing Area & Location Area 2.2 LAI, RAI, CGI 2.3 Signaling flow for Cell Update, RA Update & LA Update
3. GPRS Cell Selection & Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Relationship among Location Areas SGSN1 SGSN2 BSC1 BSC3
BSC2 CELL CELL
CELL CELL CELL
CELL CELL CELL
RA2 CELL RA1
RA3 LA1
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z z z
LA2
Page10
When MS across Location Area border, LAU & RAU is necessary When MS moves within same LA and across Routing Area boarder, RAU is necessary When MS moves within the same LA and RA, cell update may be needed may be needed. It depends on the current state of the MS. a) READY state: MS updates the location every cell change. This strategy ensures that the accurate location of the MS is always known and packet data can be delivered faster as no paging procedure is necessary. However the MS battery is drained more and uplink radio capacity is wasted for cell updates. b) STANDBY state: MS updates the location only when the MS moves to a new routing area (RA). In this strategy, when data packet is sent to the MS, paging is required in order to find out the current location of the MS. Thus, uplink capacity will be wasted for paging response and every downlink packet requires paging of the mobile delay.
82
Relationship among Location Areas z
LAI
MCC+ MNC+ LAC LAI
z
RAI
MCC+ MNC+ LAC+RAC RAI
z
CGI /CellID
MCC+ MNC+ LAC+{RAC}+CI CGI
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page11
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Contents 1. Overview of GPRS Mobile Management 2. Location Update 2.1 Relationship between Cell, Routing Area & Location Area 2.2 LAI, RAI, CGI 2.3 Signaling flow for Cell Update, RA Update & LA Update
3. GPRS Cell Selection & Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page12
84
LAI (Location Area Identification) z
MCC：Mobile Country Code, it consists of 3 digits. For example: The MCC of China is "460"
z
MNC：Mobile Network Code, it consists of 2 digits. For example: The MNC of China Mobile is "00"
z
LAC：Location Area Code, it is a two bytes hex code. The value 0000 and FFFF is invalid
z
For example: 460008C90
MCC
MNC
LAC
Location Area Identification
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page13
85
RAI (Routing Area Identification) z
Routing area is the sub-set of the location area. In special cases, the two areas are equal.
z
The division of the routing area is related with traffic distribution and SGSN processing ability
MCC
MNC
LAC
RAC
Location Area Identification Routing Area Identification
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page14
86
CGI (Cell Global Identity) z
CI (Cell Identity): This code uses two bytes hex code to identify the radio cells within a LAI.
z
RAC is only unique when presented together with LAI.
z
CI is only unique when presented together with LAI or RAI.
z
CGI = MCC+MNC+LAC+{RAC}+CI
MCC
LAC
MNC
RAC
CI
Location Area Identification Routing Area Identification CGI
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page15
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Contents 1. Overview of GPRS Mobile Management 2. Location Update 2.1 Relationship between Cell, Routing Area & Location Area 2.2 LAI, RAI, CGI 2.3 Signaling flow for Cell Update, RA Update & LA Update
3. GPRS Cell Selection & Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Cell Update Flow MS
Old Cell
Uplink LLC-PDU
New Cell PDU (CGI) in BSSGP-PDU
[MS ID]
RLC Radio Block
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
1.
2.
3.
4.
5.
6.
7.
SGSN SGSN received and recorded the cell update
SGSN send the subsequence service to MS through the new cell
Page17
When the MS moves from one cell to another within the same RA and LA, cell update procedure will happen during the READY state. During the READY state/ packet transfer state, MS will keep monitor its current location and cell reselection will happen. When MS discover another better cell according to its own measurement. The MS stops listening to the old cell and start to read the necessary SYSINFO in the new cell. MS make an access in the new cell and send a cell update to the SGSN (transparent to the PCU). SGSN will obtain the cell update (cell change information) from the uplink LLCPDU and record the cell update information and discovers that there was already an ongoing downlink packet transfer. SGSN will then sends a Flush message to the respective PCU. The Flush message contains the addresses to both the old and new cell as well as the MS identity. The PCU check whether it is responsible for the new cell. In that case all the buffered frames/ the subsequence service will be moved to a queue towards the new cell. The PCU assign new resources to the MS in the new cell and transmission is restarted. If the PCU is not responsible for the new cell, it will delete all the frames destined to the MS ang leave the retransmission to higher layers.
89
Intra-SGSN Routing Area Update Flow MS
BSS ROUTING AREA UPDATE REQUEST [Old RAI, old P-TMSI, update type]
SGSN ROUTING AREA UPDATE REQUEST [Old RAI, old P-TMSI, update type, new CI]
SECURITY FUNCTIONS (optional)
ROUTING AREA UPDATE ACCEPT [P-TMSI, P-TMSI signature]
ROUTING AREA UPDATE COMPLETE [P-TMSI] optional]
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
1.
z
z
Page18
When MS moves to new RA, it sends RA update request including the RAI of the old RA to its assigned SGSN. When the message arrives at the BSS, the BSS adds the CI of the new cell. Based on the RAI and CI data, SGSN can derived the new RAI. Intra-SGSN routing area update: The MS has moved to an RA, assigned to the same SGSN as the old RA. In this case, the SGSN knows already all necessary user profile, and can assign a new packet temporary mobile subscriber identity (P-TMSI) to the user without the need to inform other network elements. Security function: authentication and ciphering/encrpytion
90
Inter-SGSN Routing Area Update Flow MS
BSS
New SGSN
Old SGSN
GGSN
HLR
ROUTING AREA UPDATE REQUEST [Old RAI, old P-TMSI, update type]
PDP CTT REQ PDP CTT ACK [GGSN address] PDP CONTEXT UPDATE PDP CONTEXT UPDATE ACK
DATABASE UPDATE ROUTING AREA UPDATE ACCEPT
INSERT SUBCRIBER DATA
ROUTING AREA UPDATE COMPLETE
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z
z
z
z
Page19
Inter-SGSN routing area update: In this case, the MS has moved to an RA, assigned to a different SGSN, thus, the new SGSN does not have the user profile of the MS. The new SGSN contacts the old SGSN and requests the PDP context of the user. After receiving the PDP context of the user, the new SGSN informs the involved network elements, GGSN about the new PDP context of the user HLR about the user’s new SGSN HLR cancels the MS information context in the old SGSN and loads the subscriber data to the new SGSN. New SGSN acknowledges to the MS The old SGSN is requested to transmit the undelivered data to the new SGSN.
91
Contents 1. Overview of GPRS Mobile Management 2. Location Update 3. GPRS Cell Selection & Reselection 3.1 Cell Reselection Algorithm 3.2 Parameter for Cell Reselection 3.3 Type of Cell Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page20
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GPRS Cell Reselection Algorithm z
If no PBCCH exists, the GPRS cell selection & reselection is basically the same as GSM cell selection & reselection (C1, C2):
C2 = C1 + CRO – TO*H(PT-T)
when PT=/31
C2 = C1 – CRO
when PT=31
C1 = RLA_C – RxLev_Acc_Min – Max((MS_TXPWR_MAX_CCCH – P), 0)
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
1. 2. 3.
Page21
C1 = RLA_C - RxLev_Access_Min - Max((MS_TxPwr_MAX_CCH - P), 0) C2 = C1 + CRO - TO * H(PT-T) when PT=/31 C2 = C1 - CRO when PT= 31
93
GPRS Cell Reselection Algorithm z
If no PBCCH exists, the GPRS cell selection & reselection is basically the same as GSM cell selection & reselection (C1, C2) excepts for the following conditions: a) When MS in STANDBY mode,
Cell reselection within the same RA/LA: C2(nei) > C2 (serving) for t>5s
Cell reselection between different RA/LA: C2(nei) > C2 (serving) + CRH for t>5s
b) When MS in READY mode,
Cell reselection within the same RA/LA: C2(nei) > C2 (serving) + CRH for t>5s
Cell reselection between different RA/LA: C2(nei) > C2 (serving) + CRH for t>5s
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
1. 2. 3.
Page22
C1 = RLA_C - RxLev_Access_Min - Max((MS_TxPwr_MAX_CCH - P), 0) C2 = C1 + CRO - TO * H(PT-T) when PT=/31 C2 = C1 - CRO when PT= 31
94
Cell Reselection in Standby Mode
RA 2 RA 1 CC2>BC2＋CRH
AC2>BC2 Cell B Cell A
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Cell C
Page23
95
Cell Reselection in Ready Mode RA 1 BC2>AC2＋CRH Cell A Cell B
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Page24
96
GPRS Cell Reselection Algorithm z
If PBCCH exists, new cell selection & reselection algorithm (C31, C32) is applicable: C31(s) = RLA_P(s) – HCS_THR(s)
(Serving cell)
C31(n) = RLA_P(n) – HCS_THR(n) – GPRS_TO(n)*H(GPRS_PENALTY_TIME-T)*L(n)
(Neighbor cell)
C31
= signal threshold criterion
RLA_P
= actual received level of the GPRS cell
HCS_THR
= signal level threshold of cell reselection of HCS GPRS
GPRS_TO
= GPRS temporary offset
L = 0; when PRIORITY_CLASS (s) = PRIORITY_CLASS (n) L = 1; when PRIORITY_CLASS (s) =/ PRIORITY_CLASS (n) Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z
z
z z
Page25
C31 = signal threshold criterion/ signal level threshold criterion of HCS and is used to judge whether to adopt preference cell reselection HCS_THR = Hierarchical Cell Structure signal level threshold of cell reselection of HCS GPRS. It is broadcast on PBCCH of the service cell. RLA_P = Received level of the GPRS cell TO = Temporary offset given to the neighbor when the neighbor cell’s PRIORITY_CLASS is different from the PRIORITY_CLASS of the serving cell
97
GPRS Cell Reselection Algorithm z
If PBCCH exists, new cell selection & reselection algorithm (C31, C32) is applicable: C32(s) = C’1
(Serving cell)
C32(n) = C’1 + GPRS_RESELECT_OFF – GPRS_TO*H(GPRS_PENALTY_TIME – T) * (1-L)
(Neighbor cell)
H(X GPRS_PENALTY_TIME H(X>0) = 1; T < GPRS_PENALTY_TIME L = 0; when PRIORITY_CLASS (s) = PRIORITY_CLASS (n) L = 1; when PRIORITY_CLASS (s) =/ PRIORITY_CLASS (n)
C’1 = RxLev – GPRS_Acc_Level_Min – Max( (GPRS_MS_TXPWR_MAX_CCH – P), 0) Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z
z
z
Page26
C32 = Perfection of C2 applied to GSM. It applies the offset and the delay value to the cell reselection which needs execution of cell update program or route update program. When the PBCCH channel does not exist in the service cell, the MS will execute cell reselection according to the C2 algorithm. T = timer with initial value =0. When a cell is recorded by the MS into the 6 strongest cell, the counter corresponding to this cell, T will begin to count at a precision of one TDMA frame (4.62ms). When this cell is removed from the 6 strongest cell list, the timer is reset. GPRS TO = temporary offset, which counts from the counter T. T to the
98
GPRS Cell Reselection Algorithm z
In additional, it is necessary to consider the routing area for the serving cell and adjacent cell:
When MS in STANDBY mode, and within the same RA C32’(n) = C32(n)
When MS in READY mode, and within the same RA C32’(n) = C32(n) - CELL_RESELECT_HYSTERESIS
When MS in READY or STANDBY mode, with different RA C32’(n) = C32(n) - RA_RESELECT_HYSTERESIS
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z
Page27
C32’(n) = Final calculated/ actual value of the C32 criterion after consider the routing area of the serving cell and neighbor cell.
99
Cell Reselection Trigger Condition Cell reselection triggering condition:
z
With C1, C2 criterion
With C’1, C31, C32 criterion
1
C1 < 0
C’1 < 0
2
Downlink signaling failure
Downlink signaling failure
3
Serving cell is barred
Serving cell is barred
4
Random access attempt is
Random access attempt is unsuccessful
unsuccessful after MAX_RETRANS
after MAX_RETRANS
Better neighbor cell detected:
Better cell with the highest C32 among:
Same RA: C2(n) > C2(s) for t>5s
(a) Highest PRIORITY_CLASS, C31>=0
Dif RA: C2(n) > C2(s)+CRH for t>5
(b) All cell, if no cell fulfils C31 criterion
5
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Contents 1. Overview of GPRS Mobile Management 2. Location Update 3. GPRS Cell Selection & Reselection 3.1 Cell Reselection Algorithm 3.2 Parameter for Cell Reselection 3.3 Type of Cell Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Network Control Mode z
Cell Attribute -> GPRS Attributes
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z z
z z
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Parameter Name: Network Control Mode Description: In the cell reselection required by the network, the network requests the MS to send measurement reports to control its cell reselection. There are three network control modes. nc0: Normal MS control. The MS performs automatic cell reselection.nc1: MS control with measurement reports. The MS sends measurement reports to the network and performs automatic cell reselection.nc2: Network control. The MS sends measurement reports to the network but does not perform automatic cell reselection. GUI Value Range: [nc0,nc1,nc2] Default Value: nc0
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Parameter for GPRS Cell Reselection z
Network Control Mode (NCO)
Mode
Definition
Whether the MS send the M.R
MS mode
Cell Selection Mode
NC0
Normal MS Control Mode
No
Ready & Standby
Controlled by MS
NC1
MS Control with M.R Mode
Yes
Only Ready
Controlled by MS
NC2
Network Control Mode
Yes
Only Ready
Controlled by network
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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z
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NC0: MS performs autonomous cell reselection without sending measurement reports to the network. NC1: MS performs autonomous cell reselection and sends measurement reports to network. NC2: Network controls cell reselection and MS sends measurement reports to the network.
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Support NC2 z
Cell Attributes -> Other Attributes
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z z z
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Parameter Name: Support NC2 Description: This parameter specifies whether the cell supports the Network Control 2 (NC2) function. In NC2, the MS reports the measurement report of the reference cell and neighbor cells to the BSC. The BSC controls cell reselection (including normal reselections and loadbased reselections) of the MS. GUI Value Range: [No,Yes] Default Value: No
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NC2 Support in External Neighbour Cell z
BSC6000 -> Configure 2G External Cell
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z z
z z
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Parameter Name: NC2 Support in External Neighbour Cell Description: This parameter specifies whether the GSM external cell supports NC2. GUI Value Range: [Not Support,Support] Default Value: Not Support
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Parameter for GPRS Cell Reselection z
Cell Attributes -> GPRS Attributes -> Advanced -> Ps Other Parameters
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z z
z z
z z
z z
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Parameter Name: Cell Urgent Reselection Allowed Description: This parameter specifies whether enabling the critical cell reselection algorithm is allowed. GUI Value Range: [Forbid,Permit] Default Value: Permit Parameter Name: Cell Load Reselection Allowed Description: This parameter specifies whether enabling the cell load-based reselection algorithm is allowed. GUI Value Range: [Forbid,Permit] Default Value: Permit Parameter Name: Cell Normal Reselection Allowed Description: This parameter specifies whether enabling the normal cell reselection algorithm is allowed. GUI Value Range: [Forbid,Permit] Default Value: Permit
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Support NACC z
Cell Attributes -> Other Attributes
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z z
z z
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Parameter Name: Support NACC Description: This parameter specifies whether the cell support the Network Assisted Cell Change (NACC) function.In network control mode NC0, NC1, or NC2, when the MS is in the packet transmission mode, the network informs the MS of the system information about neighbor cells in advance. Therefore, the cell reselection of the MS is accelerated. GUI Value Range: [No,Yes] Default Value: No
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Contents 1. Overview of GPRS Mobile Management 2. Location Update 3. GPRS Cell Selection & Reselection 3.1 Cell Reselection Algorithm 3.2 Parameter for Cell Reselection 3.3 Type of Cell Reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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GPRS Cell Reselection Type z
There are 3 type of cell reselections:
MS controlled cell reselection
Network controlled cell reselection
Network assisted cell reselection
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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MS-Controlled Cell Reselection z
MS-Controlled Cell Reselection
MS periodically measures the RX levels of all the BCCH carriers of the serving cell and its neighboring cells.
With no PBCCH configured, MS calculates C2 value.
With PBCCH configures, MS calculates C31/C32 value.
Based on the calculated value, MS decided whether to reselect a new serving cell.
z
Also call as autonomous cell reselection.
Parameter setting:
Support NC0/ NC1 to YES
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Network-Controlled Cell Reselection z
Network-Controlled Cell Reselection
MS periodically sends measurement reports to the BSC based on the parameters in the SYSINFO broadcast in the cell.
Based on the measurement reports and neighboring cell load, BSC sends a cell change command to the MS if all conditions are met, leading the MS to a suitable cell.
z
Parameter setting:
Support NC2 to YES
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Network-Controlled Cell Reselection (NC2) MS
BSS PACKET MEASUREMENT REPORT PACKET ENHANCED MEASUREMENT REPORT NC2 Cell Reselection Algorithm
PACKET NEIGHBOR CELL DATA
PACKET CELL CHANGE ORDER
PACKET CELL CHANGE FAILURE
[P-TMSI] optional]
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
1.
2.
3.
4.
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MS in the GMM Ready mode state periodically sends PACKET MEASUREMETN REPORT to the BSC. After receive the MR, NSC process the MR. According to the NC2 cell reselection algorithm, BSC determines whether to perform cell reselection. If BSC determines to initiate a cell reselection, it send PACKET CELL CHANGE ORDER to MS to instruct MS to reselect the target cell. If NACC support, PACKET NEIGHBOR CELL DATA containing SYSINFO will be sent before the PACKET CELL CHANGE ORDER so that the reselection can be accelerated. If cell reselection fails, MS sends PACKET CELL CHANGE FAILURE message to BSC. After receive this message, BSC subtracts CELL PENALTY LEVEL from the RxLev of the target cell.
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NC2 Cell Reselection Algorithm z
The NC2 cell reselection algorithm follows the priority sequence in descending order of:
Urgent reselection algorithm
Load reselection algorithm
Normal reselection algorithm
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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z
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Urgent reselection is based on the receive quality of the radio link on the Um interface. If BER increases, the possible reason is that the signal level is too low or there is interference on the channel. In the network, load in some cells are heavy and some are light. To balance the load in these cells, load reselection is performed. In load reselection procedure, MS in heavy-loaded cell are directed to light-loaded cell. MS in neighbouring cell should not be reselected to the heavy-loaded cell. Normal reselection is based on Receive Level. When urgent reselection an load reselection are not met, normal reseelction is started to handover MS to a neighboring cell with higher signal strength if the RxLev (serving cell) < [Min Access Level Threshold]
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NC2 Cell Reselection Algorithm Begin
Measure RxLev & RxQual MS in the MR
[Cell Urgent Reselection Allowed]?
Yes
No
[Cell Load Reselect Allowed]?
MS RxQual deterioration ratio > [MS Rx Qual Worsen Threshold]
Yes
No
Yes
No
[Cell Normal Reselect Allowed]?
Channel multiplexing rate>[Load Reselect Start Thres]
Yes
Any MS RxLev load reselection -> normal reselection Each type of reselection have different trigger condition.
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NC2 Cell Reselection Algorithm Continue
Trigger urgent cell reselection and select cell with the highest priority in cell list.
For GSM Cell
For FDD Cell
RxLev>MAX(RxLev(s), [Min_Acc_Level_Thres])+ [Cell Reselect Hyst] AND non-congestion state
Ec/No>[PS FDD EcNo Quality Thres] or RSCP>[PS FDD RSCP Quality Thres]
For TDD Cell
No
No
RSCP>[PS FDD RSCP Quality Thres] No
End Yes
Yes
Yes
No
Cell reselection successful?
[Cell Penalty Level] given to target cell with [cell Penalty Last Time]
Yes
End
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
z
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The priority of the target cell is determined by receive level and the characteristics information such as cell type, cell priority, support for EDGE, and load status. Different cell type will need to fulfill the specified condition to be the candidate cell. When cell reselection fails, penalty is given to the target cell. If penalty time within [Cell Penalty Last Time (s)], [Cell Penalty Level] is subtracted from the receive level of the target cell.
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NC2 Cell Reselection Algorithm z
Each NC2 cell reselection algorithm contains three NC2 cell reselection type: Cell
Serving cell
Reselection &Target cell
Condition
Type
position
Intra-BSC
Same BSC
Highest priority in the cell list.
Inter-BSC
Different BSC,
RxLev (Ext nei) = RxLev (n) – MAX(2, [Cell
both GSM cell
Reselection Hyst/2])
GSM to
Serving cell is
For FDD cell : Ec/No>[PS FDD EcNo Quality Thres]
UTRAN
GSM cell, target or RSCP>[PS FDD RSCP Quality Thres] cell is UTRAN
For TDD cell: RSCP>[PS TDD RSCP Quality Thres]
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Intra-BSC cell reselection: Serving cell and target cell are controlled by same BSC. The selected target cell is the one that has highest priority in the cell list.
Inter-BSC cell reselection: Serving cell and target are in different BSC and both is GSM cell. The priority for the external neighbouring cell is lower. Thus, RxLev (Ext nei) = RxLev (n) – external cell reselection offset RxLev (Ext nei) = RxLev (n) – MAX(2, [Cell Reselection Hyst/2])
GSM to UTRAN cell reselection: Serving cell is GSM cell and target cell is UTRAN cell. The 3G MR and the 2G/3G cell priority strategy should be processed during the cell reselection. For FDD cell: Ec/No>[PS FDD EcNo Quality Thres] or RSCP>[PS FDD RSCP Quality Thres] For TDD cell: RSCP>[PS TDD RSCP Quality Thres] [2G/3G Cell Reselection Strategy] : Preference for 2G cell, Preference for 3G cell
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Network-Assisted Cell Reselection z
Network-Assisted Cell Reselection
It is also known as NACC, Network Assisted Cell Change.
MS originates a cell change notification (CCN) procedure, and the BSC sends the system information (SYSINFO) about the neighboring cell to the MS before the cell reselection.
NACC accelerates the cell reselection and shortens the service disruption time during cell reselection.
z
Parameter setting:
Support NC0/ NC1/ NC2 to YES
Support NACC to YES
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Network Assisted Cell Change (NACC) z
Purposes:
MS is able to request BSC to send the target cell’s SYSINFO during the cell reselection.
z
Advantages:
According to the SYSINFO, MS accelerates the packet service access in the target cell.
Reduce the period of packet service disruption during a cell reselection .
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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Network Assisted Cell Change (NACC)
Receive System information of cell B before reselection
Cell A
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Cell B
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Network Assisted Cell Change (NACC) z
MS can initiate an NACC procedure only when autonomous cell reselection is triggered:
z
In NC0/ NC1 mode and packet transfer mode:
C1
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