Umts Access Control

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UMTS Access Control

Content

UMTS System Information Broadcasting

UMTS PagingUMTS Random AccessUMTS RRC Connection Setup and Release

Access Failed Case

System Broadcasting The system information broadcasted oer the BC! channel mainly includes the follo"ing

contents#

Public $and Mobile %et"or& 'P$M%( I)* location area '$A(* route area 'RA( Information on the timers and counters related to the Radio Resource Control 'RRC(

connections

Configuration information of the UTRA% registration area 'URA(

Cell selection and reselection parameters

Parameters for configuring the common channels* such as FAC!* PC!* and RAC!

Information on the uplin& interference related to the au+iliary po"er control

U, measurement control message oer the idle or common channel

Parameters of the ad-acent cell

System information Master information bloc& 'MIB(

Schedule bloc& 'SB(

System information bloc& 'SIB(

SIB.* SIB/* SIB0* SIB1* SIB2* SIB..* SIB..bis* SIB.34
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Scheduling leels of the SIBS

SIB Bloc&


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System broadcasting


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SIB05SIB6


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Parameters in SIB0 and SIB6 are related to the cell selection and cell reselection4 SIB0 containsinformation re7uired by the U, in Idle mode4 SIB6 contains information re7uired by the U, in Connected4If SIB6 is not sent* the U, in Connected mode can also receie SIB04

SIB1 and SIB8 are mainly used to configure the common transport channels and common physicalchannels4 SIB1 contains the parameters of the au+iliary common control channels in I),$ mode9 SIB8contains the parameters of the common physical channels or shared physical channels in connectedmode4 The U, in Idle mode uses SIB19 the U, in connected mode uses SIB84 If SIB8 does not e+ist* the

U, in the connected mode also uses SIB14


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SIB2

SIB2 is the system information bloc& that is updated periodically4 The timer of SIB2 is calculated

as follo"s#

,+piration timer : MA;'0/*SIB


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SIB..bis

>aiting Time After U, Sending RRC C?%%,CTI?%S,TUP R,@U,ST Message


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Ma+imum %umber of Retransmissions of the RRCC?%%,CTI?% R,@U,ST Message


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UMTS Paging

Paging Flo"


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PAI% TP, .

>hen the U, is in the Idle* or URA


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Page Indicator

The U, -udges "hether the net"or& is paging itself by monitoring its o"n PI4 ,ach PIC! frame cancontain the PI of multiple U,s4 The more the parameter %p* the larger the transmit po"er of the PIC! "illbe4

Paging ?ccasionFor saing po"er* the U, in the Idle or PC! state monitors the PIC! channel in the )iscontinuous

Reception ')R;( mode4 In the )R; mode* the U, monitors the PI once eery )R; period4 That is* each

U, has its o"n paging occasion 'P?(4 The U, monitors each PIC! frame in the corresponding SF% and

finds its o"n PI in the frame according to the calculated PI4 Therefore* the R%C fills in the PI in the

message transmitted oer the PIC! channel according to the paging occasion of the U,4 )R; period

:/&frames


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)R; cycle length coefficient

>hen the U, is in the Idle mode* the R%C calculates D in the )R; period according to Dcs* Dps*

and )R; Cycle $ength Coefficient in the paging message from the C%4

For paging messages from the CS domain* D : Min'Dcs*Dps(

For paging messages from the PS domain* if the C% adds )R; Cycle $ength Coefficient

to the paging message* D : Min 'Dcs* Dps* )R; Cycle $ength Coefficient(4If the C% does not add )R;Cycle $ength Coefficient to the paging message* D : Min'Dcs*Dps(4

>hen the U, is in the PC! state* the R%C calculates D in the )R; period according to Dcs* Dps*

DUtran* and )R; Cycle $ength Coefficient in the paging message from the C%4

For paging messages from the CS domain* D : Min'Dcs*DUtran(

For paging messages from the PS domain* if the C% adds )R; Cycle $ength Coefficient

to the paging message* D : Min 'Dps* DUtran* )R; Cycle $ength Coefficient(4 If the C% does not add)R; Cycle $ength Coefficient to the paging message* D : Min'Dps*DUtran(4


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PAI% TP, /

>hen the U, is in the )C! or FAC! state* the UTRA% initiates the paging process and sends a paging

message of PAI% TP, / oer the )CC! channel4 The UTRA% configures paging cause in themessage4 After the U, in the )C! or FAC! state receies the message of PAI% TP, /* it starts the

paging reception process and reports paging cause and paging record type identifier to the upper layer4


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UMTS Random AccessPRAC! Structure

Preamble Part

The preamble part of PRAC! is 6E8 chips long4 It is obtained by repeating the .8chip signature for /18

times and then processed "ith RPAC! preamble scrambling4

Message Part


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ChanneliGed code of PRAC! message part

The spectrum spreading code used by the control part of PRAC! is cc : Cch*/18*m4 "here m :

.8Hs .14 The spectrum spreading code used by the data part of PRAC! is cd :Cch*SF*m4 "here SF:/18*

./3* 86* 0/ are the spectrum spreading factor of the data part* m : SFHs5.84

s'E less than s bigger than .1( is the serial number of the signature used by the PRAC!

preamble part among all .8 PRAC! preamble signatures4

%umber of bits carried in PRAC! message s spectrum spreading factor#

Random Access Process of Physical $ayer

Select an aailable access slot

Select a signature

Set the preamble retransmission counter The U, calculates the initial transmit po"er of preamble

If the U, fails to receie* in the )$ access slot corresponding to the slot that sends the U$ access

preamble* the positie or negatie response 'AI : . nor J.( corresponding to the selected signature onAIC!* Increase the transmit po"er of random access preamble by one PRStep4

If the U, receies* in the )$ access slot corresponding to the slot that sends the U$ access

preamble* the positie response corresponding to the selected signature on AIC!* then the U, sends themessage part of random access4

RAC! access slot set


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RAC! Subchannel

PRAC!5AIC! timing relation


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UMTS RRC Connection Setup and ReleaseRRC Connection Setup


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RRC Connection Setup


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,stablishing a RRC Connection oer a )edicatedTransport channel

>hen receiing the RRC C?%%,CTI?% R,@U,ST message from a U,* the R%C specifies the

channel oer "hich the RRC connection is to be established according to the parameter InitRrc?n)ch4

If the parameter InitRrc?n)ch is set to E 'Forced to )C! and Using %ormal Speed

Signaling( or . 'Forced to )C! and Using .048Dbps signaling(* or 1'Forced to )C! and using /24/Dbps(*the R%C establishes the RRC connection oer the )C! channel4

If the parameter InitRrc?n)ch is set to 0 '%ot Forced* Using 046Dbps Signaling on Cell

)C! State( or 6 '%ot Forced* Using .048&bps Signaling on Cell)C! State(* or 8'%ot Forced* Using/24/Dbps Signaling on Cell)C! State(* the R%C selects to establish the RRC connection oer the )C!according to the establishment cause in the RRC C?%%,CTI?% R,@U,ST message4

,stablishing a RRC Connection oer a Common Transport

channel

>hen receiing the RRC C?%%,CTI?% R,@U,ST message from a U,* the R%C specifies the

channel oer "hich the RRC connection is to be established according to the parameter InitRrc?n)ch4

If the parameter InitRrc?n)ch is set to / 'Forced to FAC!(* the R%C establishes the RRC

connection oer the FAC! channel4


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If the parameter InitRrc?n)ch is set to 0 * 6* or 8* the R%C establishes the RRC connection

according to the establishment cause4 If there is only a signaling process* instead of setting upserices'for e+ample* the alue of establishment cause is registration (* R%C "ill select common channelto bear signaling4

>ireless $in& Setup Failure

If the radio lin& setup fails* the R%C sends the RRC C?%%,CTI?% R,K,CT message to the U, and fills

in >ait Time in the message4 The parameter >ait Time specifies the duration 'from the reception of the

RRC C?%%,CTI?% R,K,CT message to the time of sending access re7uest( during "hich the U, has

to "ait4

Failure to Receie RRC Connection Setup ResponseFrom U,

If R%C hanLt receied RRC C?%%,CTI?% S,TUP C?MP$,T, for "aiting 1 seconds from the first

transmitting of RRC C?%%,CTI?% S,TUP* the RRC connection setup fails4 The U, is still in idle mode4

Releasing the RRC Connection The connection carrying serices data or %AS signaling is released normally4

The %ode B detects radio lin& failure4

The R%C monitors the R$C connection failure4

The U, in the )C! or FAC! state sends C,$$ UP)AT, message4 The alue of AM


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Access Failed Case)escription

Customer complained that it "as difficult to access the net"or& in office* and it "as too long to "ait4Analysis

The drie test sho"s that the receiing leel of U, is normal4 Besides* there is no alarm related to

hard"are4

The Performance Management System'PMS( soft"are of %odeB sho"s the statistics of

accessing4 A large amount of re-ection of access is found* "hich occupied the demodulation resource*causing the long time to "ait for a call connection4

Preamble


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Use the signaling trace tools of ?MCR* R%C didnLt receie the NRRC Connection Re7uestO message4 Use

the BMC TRAC,* find NRach CRC ,rrorO4So* "e ma&e a conclusion that the Preamble Threshold is too

big "hich result in the message transmit po"er is ery lo"* and %odeB cannot receie the message4

Solution

Solution

Change the Preamble Threshold#/6dB/.dB

Constant alue#/.dB.3dB

Result

Test again* ma&e a call ./E times* all the calls are successful4

Access Failed Case


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Umts Access Control

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