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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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