GO NA37 E1 1 Data Service Performance Optimization Delay-29
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Transcript of GO NA37 E1 1 Data Service Performance Optimization Delay-29
7/28/2019 GO NA37 E1 1 Data Service Performance Optimization Delay-29
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Data Service Performance
Optimization _ Delay
ZTE University
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objectives
In order to understand the data service delay, wehave to know the different types of data services
first. Nowadays, the most common data services
are: mobility management, session management
and typical applications. The following content
analyzes the features of these services and the
reasons for the delay of these services, so as to
help reducing the delay and improving the user experience.
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Contents
Signaling Process Delay
Data Process Delay
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Data Service Protocols
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Mobility Management Process
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GPRS handset mobility management states
There are 3 mobility management states for a GPRS handset,including Idle state, Standby state and Ready state.
From Idle to Ready: logical links are established between the MSand SGSN through activation process to complete the state
conversion;
From Standby to Idle: the handset or SGSN initiates the operationsof deleting the mobility management packets from the MS andSGSN and deleting the PDP packets from the SGSN and GGSN.Or the HLR informs the SGSN to delete the location area
information;
From Standby to Ready: the MS sends LLC PDU data to the SGSNand the SGSN receives the LLC PDU data sent to the MS;
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GPRS handset mobility management states
From Ready to Standby: the MS is converted to Standbystate after cell re-selection when a time-out occurs on thepredefined non-data transmission counter; or the SGSNforced the MS into Standby state; or an exception occurs
in data transmission;
From Ready to Idle, the handset or SGSN initiates theoperations of deleting the mobility management packets
from the MS and SGSN and deleting the PDP packetsfrom the SGSN and GGSN, or the HLR informs the SGSNto delete the location area information;
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Attach Delay
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Attach Delay
After the Attach is started, pay special attentions to the setting of test
interval. The following case may occur on the ZTE equipment in the
exsiting network: the value of uplink extention TBF timer is greater and
uplink delay still exsist, the MS has to release the reserved TBF of last
service first and then send Channel Request on RACH channel, if the
ATTACH test interval is set with a low value. Since the timing of test is
started from the sending of Attach Request, this will lead to waste of time, and the result will be affected.
After the Channel Request is sent, the establishment of uplink TBF willbe started. According to the tests, if One Phase Access function of
TBF is enabled, it will save about 400-500ms. The delay of TBF link
establishment is affected by the link transmission delay and the time of
node processing.
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Differences between One-Phase Access and
Two-Phase Access
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Attach Delay
After the uplink TBF is established, the MS sends the Attach
Request to SGSN, and the network starts to establish
downlink TBF. And after the downlink TBF is established,
the network will send requests to start authentication and
encryption. This process will take about 100ms. It is the
time for establishing the downlink TBF while the uplink TBFis already established.
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Attach Delay
The authentication and encryption in ATTACH isconducted between the terminal and the SGSN. And it will
take no more than 200ms to complete the authentication
and encryption. It is suggested to implement this process,
since it is the foundation for all the services. However, the
authentication and encryption of the other services may becancelled.
After authentication and encryption, the network will send
Attach Accept message. It will take about 300ms if the test
is operated without SGSN crossing.Cons idering al l the above signal ing p rocesses, the
Attach may be completed w ith in 1 to 2 seconds.
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Delay of Session Management
In order to process the PDP packets, each GPRSequipment need one or more PDP addresses.
Each PDP packet may be activated or unactivated
to indicate whether the data is reachable.
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Features of "unactivated"
When the PDP packet is unactivated, the data service tocertain PDP address will be not available. Because there is
neither routing information nor mapping information in the
PDP packet.
After receiving PDP packet with unactivated address, the
GGSN may activate the PDP address if it has the right. If
activation can not be initiated, the GGSN will initiate error
indication automatically.
The user can start PDP activation process to change the
PDP state from unactivated to activated.
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Features of "activated"
When the PDP packet is activated, the data service tocertain PDP address will be available. The PDP packet
contains routing information and mapping information then.
The state can be changed from unactivated to activated
only when the GPRS equipment is at Standby or Ready
mode.
The user can start PDP activation process to change the
PDP state from unactivated to activated. If deactivation
process is started or the state of mobility management is
changed to Idle, the PDP state will be changed fromactivated to unactivated.
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MS Session Management Model
activate
Do not activate
activate
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Standard PDP Activation
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Analysis of PDP Activation Delay
The handset sends Activate PDP Context Requestmessage to the SGSN via the BSC.
The delay in this period mainly consists of air interface
transmission time, Abis transmission time, BSC/PCU
process time, and GB transmission time. It will takeabout 100ms.
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Analysis of PDP Activation Delay
After receiving the Activate PDP Context Requestmessage, the SGSN will initiate authentication and
encryption.
But, this function is optional. It is recommended to close
this function, since the authentication and encryptionhave been already executed in the Attach process. It
will save about 100ms if this function is closed.
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Analysis of PDP Activation Delay
SGSN sends Create PDP Context Request to GGSN: The contents include PDP type, PDP address, APN network
access point, mark of NSAPI network layer access node, MSISDN
terminal number, QoS service quality, Selection Mode, Charging
Characteristics and PDP Configuration Options.
After processing the request, the GGSN will send CreatePDP Context Response,
including the PDP address, PDP Configuration Options and QoS
service quality.
The delay in this process mainly includes Gn interfacetransmission delay and GGSN processing time. Since the
Gn interface uses wire line transmission and the GGSN
processing speed is very fast , this delay is only about
10ms.
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Analysis of PDP Activation Delay
After receiving the Create PDP Context Responsemessage, the SGSN will process this message as Activate
PDP Context Accept and send it to the handset.
The content includes the PDP type, PDP address, QoS service
quality, wireless priority and PDP Configuration Options.
This delay mainly consists of air interface transimissiontime, Abis transimission time, BSC/PCU process time, and
GB transimission time. According to previous experience,
the delay is about 100ms.
Cons idering all the above facto rs, the PDP activat ion delay m ay be control led win thin 400ms.
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Contents
Signaling Process Delay Data Process Delay
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WAP webpage browsing delay
The process of WAP webpage browsing mainly includesPS Attach, PDP activation, WAP gateway connection,
WAP relocation and WAP responsing. Because this
process belongs to data service process, our analysis
will mainly focus on the upper protocol contents.
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Signaling Flow
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Analysis on WAP webpage browsing delay
WAP gateway connection: There are only 2 signalings in the process of WAP
gateway connection. Normally, it takes only 400ms for
the two signalings. However, same data of other
protocols may be involved in this process, such asSSDP, NBNS and IGMP. It is suggested to turn off
some related services on the computer, so as to avoid
the delay caused by those protocol data. Generally, it
takes about 400ms to complete WAP gateway
connection.
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Analysis on WAP webpage browsing delay
WAP relocation: When using tools to do the test, the user needs to input
the gateway address manually. The WAP website may
feed back a new address for the handset to visit. And in
these cases, the WAP relocation is needed. Generally,WAP relocation process takes about 100ms.
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Analysis on WAP webpage browsing delay
The WAP page responsing process includes visiting newWAP address and sending the WAP webpage data.
The process of visiting new WAP address includes the request and
response for visiting. It generally takes about 800ms.
The process of sending the WAP webpage data mainly refers to
sending the data segment. The delay in this process is related withthe total amount of the data (mainly the size of the webpage) and
the size of the data segment. Generally, it takes about dozens of
ms to send one segment.
For example, it takes about 1500ms
for the WAP page response process
when the handset is visiting the WAP
homepage address of CMCC.
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Analysis on WAP webpage browsing delay
WAP log-in succeeded: after the downloading of WAP webpage is completed, the handset will
confirm the WAP log-in again and apply for ending
the session. This generally takes about dozens of
ms.
Cons ider ing al l the above factors , the WAP log-in p rocess general ly
may take 4 second s. And i t may be contro l led w i th in 3 seconds
under bet ter con di t ions.
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