paging old2006

PAGING_timer (T3113 in 3GPP TS 44.018)

Guard time for paging initiated from MSC.

i) PAGTIMEFRST1LA First PAGING Attempt, PAGING in one LA. Started: PAGING message is sent to BSC. Stopped: PAGING RESPONSE message is received. Expire: Repetition of paging depending on an exchange property parameter PAGREP1LA .

ii) PAGTIMEREP1LA Second PAGING Attempt, PAGING in one LA. Started: PAGING message is sent to BSC. Stopped: PAGING RESPONSE message is received. Expire: No action.

iii) PAGTIMEFRSTGLOB First PAGING Attempt, Global PAGING. Started: PAGING message is sent to BSC. Stopped: PAGING RESPONSE message is received. Expire: Repetition of paging depending on an exchange property parameter PAGREPGLOB

v) PAGTIMEREPGLOB Second PAGING Attempt, Global PAGING. Started: PAGING message is sent to BSC. Stopped: PAGING RESPONSE message is received. Expire: No action.

Figure 5 Paging

When a call is to be setup to an MS in an area served by the BSS, the MSC sends a PAGING message to the BSC. The BSC will then send PAGING COMMAND to the BTS, serving either all the cells in the BSC or a specific Location Area. The BTS then transmits PAGING REQUESTs on the PCH (downlink CCCH). For more information see Reference [15]

The BTS schedules the transmission to the paging group that the MS belongs to, so the MS only needs to listen to the messages transmitted to its paging group in order to reduce power consumption in idle mode.

The paging message contains enhanced Multi-Level Precedence and Pre-emption service (eMLPP) information. This gives information on whether the MS is allowed to seize channel resources that are already in use by other users in case of congestion. For more information see Reference [11] .

CS Paging for a GPRS attached GPRS/EGPRS MS is done via the SGSN if the Gs interface between the MSC and the SGSN is available and Network Operation Mode 1 is activated. See Reference [15] for more information.

4.2 Paging

There are two types of paging, PS Paging and CS Paging.

4.2.1 CS Paging

When an MS in Class A or Class B mode of operation is attached to both PS and CS, and the Gs interface between MSC and SGSN is available, the MSC sends the pages to the SGSN, via the Gs interface, instead of directly to the BSC. The SGSN knows the location of the MS:

On cell level when the MS is in ready state On RA level when the MS is in idle state or stand-by state

SGSN sends the page to the affected PCU(s) with information of the cell or RA. If the MS is involved in a packet transfer, the PCU sends the page on the control channel associated with the packet transfer, Packet Associated Control Channel (PACCH). Otherwise the page is sent out on PPCH or, if that is not available on PCH. This is Network Operation Mode I.

It is possible to have a network without a Gs interface. In this case the MSC cannot send the page to SGSN. Instead the MSC sends the page directly to the BSC. Which channel to send this paging message on will be depending on whether DTM is supported in a cell or not.

In case DTM is supported in a cell and the MS is in packet transfer mode, the IMSI is used to coordinate that the CS paging message is sent on a channel that is monitored by the MS. By use of IMSI co-ordination also non DTM capable MSs can be reached by a CS page when in packet transfer mode regardless of network operation mode.

In case DTM is not supported in a cell, the CS pages will always be sent on PCH. This is Network Operation Mode II or III. In this case the BSC is unable to check paging messages coming from the MSC and see if the MS is GPRS attached as well. Therefore the BSC will always send those messages on PCH. An MS of class B does not listen to the PCH when in packet transfer mode, therefore pages can be lost.

4.2.2 PS Paging

The SGSN sends a paging request to all BSCs serving the RA where the MS is currently located.

The serving BSC then pages the MS in all cells within the paging area. The PPCH is used if the MPDCH exists in the cells. For those cells not having an MPDCH, the PCH is used instead.

In case PPCH is used it is possible to include more than one page in each 44.060 Packet Paging Request to better utilize the available resources.

Details about paging for GPRS/EGPRS can be found in Reference [11].

4.2.3 Paging Groups and DRX

The Discontinuous Reception (DRX) is a technique implemented in the GPRS/EGPRS traffic system that ensures that the MS is exactly aware of the period of time a paging may be transmitted, thereby allowing the MS to be powered down for a high percentage of the time. This to reduce the power consumption during standby mode. For details see Reference [11].

The MS population is divided into a set of paging groups. The group which an MS belongs to is known by both the MS and the BSC and is calculated based on International Mobile Subscriber Identity (IMSI) and DRX parameters. The DRX parameters are negotiated between the MS and the SGSN during the GPRS Attach Procedure. The maximum DRX period is 64 seconds and the minimum is 'no DRX'.

4.4 Paging

MFRMS is, as mentioned before, the multiframe period and defines the transmission interval of paging messages to the same paging group. Together with AGBLK, MFRMS indicates how many different paging groups exist. A higher value of MFRMS means more battery saving in the MSs. However, a specific paging group would then appear less frequently, making call set-up times for mobile terminating calls longer. See the following example:

Example:

If the number of CCCH blocks within a multiframe is 9 and AGBLK is set to 0, there are nine different paging groups within a 51 frame multiframe. If MFRMS is set to

five, there will be 5 * 9 = 45 different paging groups totally, spread out over five multiframes. At most, MFRMS can be equal to nine, which consequently would mean 81 different paging groups (using a non-combined BCCH, see Table 3). In this case the mobile listens to its own paging group every ninth 51-frame multiframe, which means approximately every 2.1 seconds (9 * 235.4 ms).

The advantage with a higher value is a lower MS battery consumption in idle mode. The drawback is that the average call setup time for mobile terminated calls slightly increases. The impact of MFRMS on the battery consumption may differ for different mobiles. The trade-off between low battery consumption and short call set up times for mobile terminated calls has to be done based on the operators preferences.

If many pages are discarded in the BTS, which can by detected by the counters PAGETOOOLD and PAGPCHCONG, decreasing MFRMS or not using combined BCCH can lower the number of discarded pages in a cell.

Recommended setting of AGBLK is 0, unless any of the cases in Section 3.7.1 is fulfilled.

Parameter ATT should always be set to YES so that the system is alerted when the mobile powers on or off. This will prevent unnecessary pagings of the mobile when it is no longer available.

Table 14 Paging Parameters

Parameter name Default value

Recommended value

Value range Unit

PAGTIMEFRST1LA 4

2 to 10 seconds

PAGTIMEFRSTGLOB 4

2 to 10 seconds

PAGREP1LA 2

0, 1, 2, 3

PAGREPGLOB 0

0, 1

PAGTIMEREP1LA 7

2 to 10 seconds

PAGTIMEREPGLOB 7

2 to 10 seconds

LATAUSED 0

0, 1

PAGLATA 0

0, 1

PAGREPCT1LA 2

0, 1, 2, 3

PAGTIMEREPLATA 7

2 to 10 seconds

3.7 Paging

3.7.1 Paging Groups

After an MS tunes to the BCCH carrier and decodes the system information data, it performs an evaluation, taking into account the IMSI number, that determines to which paging group it belongs. The particular method by which an MS determines to which paging group it belongs, and hence, which particular CCCH block of the available blocks on the paging channel that is to be monitored, is defined in 3GPP TS 45.002. When there are no paging messages to be transmitted to MSs in a certain paging group, dummy pagings will be sent instead. The MS stays in sleep mode to minimise power consumption in the time gap between when its own paging group occurs. This is illustrated in Figure 4 . However, the MS must still read the BCCH data sent by the serving cell at least every 30 seconds.

To even-out uneven paging load on the paging groups, the BTS can on it's own initiative decide to use extended paging. Extended Paging is performed when one paging group still have remaining pages to be sent after the normal transmission time for this paging group. If the next-but-one paging group after the normal paging group has spare paging capacity, this capacity can be used to transmit pages that was not possible to be transmitted in it's normal paging group.

For example, if there are five pages queuing to be transmitted in paging group 1 and only four pages can be transmitted at the normal transmission of paging group 1. Before transmitting the four pages in paging group 1, the BTS will check if there is remaining capacity in paging group 3 to be used by the remaining page in paging group 1. If this is the case, the Paging Request sent in paging group 1 will be marked with Extended Paging making all mobiles belonging to paging group 1 also listening to paging group 3. Then, at transmission of paging group 3, the remaining page in paging group 1 will be sent.

The CCCH blocks are also used to send access grant messages on the AGCH to the MS. The structure of the CCCH regarding paging messages and access grant messages is controlled by the two parameters AGBLK and MFRMS .

In each downlink non-combined BCCH 51 frame multiframe there are nine different CCCH blocks and in the combined BCCH/SDCCH there are three different CCCH blocks. AGBLK is the number of reserved CCCH blocks for the AGCH. The remaining CCCH blocks (9 - AGBLK, for non-combined BCCH and 3 - AGBLK, for combined BCCH) are used as PCH and AGCH.

Access grant messages are given priority over paging messages even if no CCCH blocks are reserved for the AGCH, that is when AGBLK = 0. Therefore no reservation of blocks is needed. However,AGBLK must be >0 in the following cases:

if System information 7 or 8 have to be sent, see further Section 3.8 . if a Cell broadcast channel (CBCH) is configured on a SDCCH/8 in the cell, see

further Section 3.9 . if Voice Group Call Service (VGCS) is used in th cell. Then notifications sent on

NCH will need at least one block reserved for AGCH, see further Section 3.10.

It is futher recommended to set AGBLK > 0 in the following cases:

if GPRS/EGPRS is active and System Information 2bis andSystem Information 2ter are sent, see further Section 3.11 .

if GSM to UMTS cell reselection is active and System Information 2bis and System Information 2ter are sent, see Reference [8].

if both GSM to UMTS cell reselection and GPRS/EGPRS is active and System Information 2bis or System Infromation 2ter are sent, see further Section 3.11 and Reference [8].

Table 3 The Relation between MFRMS, AGBLK, Number of Paging Groups and Time between Transmission of Each Paging Group

MFRMS

Time between transmission

of each paging group

Number of paging groups, Combined BCCH

Number of paging groups, non combined

BCCH

AGBLK = 0 AGBLK = 1 AGBLK = 0 AGBLK = 1

2 0.47 sec 6 4 18 16

3 0.71 sec 9 6 27 24

4 0.94 sec 12 8 36 32

5 1.18 sec 15 10 45 40

6 1.41 sec 18 12 54 48

7 1.65 sec 21 14 63 56

8 1.89 sec 24 16 72 64

9 2.12 sec 27 18 81 72

The BTS has one paging queue for each paging group. The length of the paging queues vary between 6 and 14 depending on the number of paging queues in use. The length of the paging queues is calculated as:

Length of paging queue = 14 - (PQmax/10), where PQmax is equal to the number of paging groups -1.

3.7.2 Paging Strategies

The paging procedure in the Ericsson GSM System is managed by the MSC. (The description of the paging parameters and the different paging strategies refers to the Ericsson MSC, HLR and VLR.) Different paging strategies are possible, e.g. not to send any second paging or to send the second paging as global paging. An operator can control the paging procedure with parameter settings in the MSC.

The paging attempts, including both the first and the repeated attempts, is either local or global depending on whether or not the Location Area Identity is stored in the VLR, see Figure 5 in Appendix A. Local pagings are performed only within one location area whereas global pagings are performed within a whole MSC service area. A second paging may be initiated if no response from the MS is received before a first timer expires.

The timer is called PAGTIMEFRST1LA for local pagings and PAGTIMEFRSTGLOB for global pagings.

If the first paging was a local paging the PAGREP1LA parameter defines whether or not a second paging shall be initiated and, in that case, if it shall be local or global. After the second paging has been sent, the MSC waits for the PAGTIMEREP1LA timer, indicating a local second paging, or PAGTIMEREPGLOB,

indicating a global second paging, to expire before it concludes that the paging attempt was unsuccessful.

If the first paging was a global paging and no response was received before the first timer expired, the PAGREPGLOB parameter will define whether a second global paging will be initiated. If the second global paging is sent, the MSC will wait for the PAGTIMEREPGLOB timer to expire before it considers the MS unreachable.

There are a number of counters related to the Idle Mode Behaviour.

TOTPAG Number of paging messages received from the MSC.

TOTCONGPAG

Number of discarded paging messages due to lack of capacity in the BSC, or due to congestion in the BSC paging queues, or due to no Data Link Individual is available for a paging request taken from the paging queue.

PAGPCHCONG Number of discarded paging messages due to full Paging Queue in the BTS.

PAGETOOOLD

Number of paging messages that have been discarded due to too long queueing delay in the BTS. At the point when a page is taken from the paging queue, its age is calculated and compared to the parameter AGE-OF-PAGING (default set to 5 seconds in Ericsson BSS). If it is too old, it is discarded and PAGETOOLD is incremented.

NLAPAG1LOTOT Number of first page attempts to an LA.

NLAPAG2LOTOT Number of repeated page attempts to an LA.

NLAPAG1RESUCC

Number of page responses to first page to an LA.

NLAPAG2RESUCC

Number of page responses to repeated page to an LA.

NLALOCTOT Total number of LU attempts in the LA.

NLALOCSUCC Number of successful LUs in the LA.

MFRMS is also used by the MS to determine downlink signalling failure in idle mode (Reference [8]). The downlink signalling failure criterion is based on the downlink signalling failure counter DSC. When the MS camps on a cell, DSC shall be initialised to a value equal to the nearest integer to 90/N where N is the MFRMS parameter for that cell. Thereafter, whenever the MS attempts to decode a message in its paging subchannel; if a message is successfully decoded DSC is increased by 1, (however never beyond the nearest integer to 90/N), otherwise DSC is decreased by 4. When

DSC reaches 0, a downlink signalling failure shall be declared. A downlink signalling failure shall result in cell reselection

MFRMS is also used by the MS to control monitoring of received BCCH carrier level (Reference [8]). Whilst in idle mode an MS shall continue to monitor all BCCH carriers as indicated in the BCCH allocation list (BA list). A running average of received level in the preceding 5 to

Max{5, ((5*N+6) div 7)*MFRMS/4}

seconds shall be maintained for each carrier in the BCCH allocation. N is the number of non-serving cell BCCH carriers in BA.

4.4 Paging

MFRMS is, as mentioned before, the multiframe period and defines the transmission interval of paging messages to the same paging group. Together with AGBLK, MFRMS indicates how many different paging groups exist. A higher value of MFRMS means more battery saving in the MSs. However, a specific paging group would then appear less frequently, making call set-up times for mobile terminating calls longer. See the following example:

Example:

If the number of CCCH blocks within a multiframe is 9 and AGBLK is set to 0, there are nine different paging groups within a 51 frame multiframe. If MFRMS is set to five, there will be 5 * 9 = 45 different paging groups totally, spread out over five multiframes. At most, MFRMS can be equal to nine, which consequently would mean 81 different paging groups (using a non-combined BCCH, see Table 3). In this case the mobile listens to its own paging group every ninth 51-frame multiframe, which means approximately every 2.1 seconds (9 * 235.4 ms).

The advantage with a higher value is a lower MS battery consumption in idle mode. The drawback is that the average call setup time for mobile terminated calls slightly increases. The impact of MFRMS on the battery consumption may differ for different mobiles. The trade-off between low battery consumption and short call set up times for mobile terminated calls has to be done based on the operators preferences.

If many pages are discarded in the BTS, which can by detected by the counters PAGETOOOLD and PAGPCHCONG, decreasing MFRMS or not using combined BCCH can lower the number of discarded pages in a cell.

Recommended setting of AGBLK is 0, unless any of the cases in Section 3.7.1 is fulfilled.

Parameter ATT should always be set to YES so that the system is alerted when the mobile powers on or off. This will prevent unnecessary pagings of the mobile when it is no longer available.

PAGREP1LA

Type: Numeral

Range: 0 to 3

Unit: -

Default: 2

Command: DBTSP:TAB=AXEPARS, SETNAME=GSMMMSC.

O&M: -

Comments:Repeated paging in one location area.

The parameter is optional.

This parameter defines in case of mobile terminating calls how the paging in one location area is repeated.

0 Paging in one location area

is not repeated.

1 Paging in one location area is repeated with either TMSI or IMSI.


is repeated with IMSI.

3 Paging is repeated as global paging with IMSI.

Note This parameter is only defined for Ericsson MSCs.

PAGREPGLOB

Type: Numeral

Range: 0 to 1

Unit: -

Default: 0

Command: DBTSP:TAB=AXEPARS, SETNAME=GSMMMSC.

O&M: -

Comments:Repeated global paging.


This parameter defines how the global paging is repeated if the first paging attempt was global.

0 Global paging is not

repeated.

1 Global paging is repeated with IMSI.


PAGNUMBERLA

Type: Numeral

Range: 1 to 3

Unit: -

Default: 1

Command: MGEPC , MGEPP.

O&M: -

Comments:Number of location areas in a paging message.

This parameter indicates the maximum permitted amount of location areas that can be included in a paging message.


A parameter with a value > 1 is only valid if all BSCs connected to an MSC/VLR support a paging message with a list of location areas.


PAGTIMEFRST1LA

Type: Numeral

Range: 2 to 10

Unit: s

Default: 4


O&M: -

Comments:Time supervision for the first paging in one location area.

This parameter defines the time supervision for the page response of the first paging attempt in one location area. After expiration of this timer the paging is repeated according to parameter PAGREP1LA. The parameter is optional.


PAGTIMEFRSTGLOB

Type: Numeral

Range: 2 to 10

Unit: s

Default: 4


O&M: -

Comments:Time supervision for the first global paging.

This parameter defines the time supervision for the page response of the first global paging attempt. After expiration of this timer the paging is repeated according to parameter PAGREPGLOB. The parameter is optional.

Note This parameter is only defined for

Ericsson MSCs.

PAGTIMEREP1LA

Type: Numeral

Range: 2 to 10

Unit: s

Default: 7


O&M: -

Comments:Time supervision for the repeated paging in one location area.


This parameter defines the time supervision for the page response of repeated paging in one location area. After expiration of this timer no new paging repetition for this call is done.


PAGTIMEREPGLOB

Type: Numeral

Range: 2 to 10

Unit: s

Default: 7


O&M: -

Comments:Time supervision for the repeated global paging.


This parameter defines the time supervision for page response of repeated global paging. After expiration of this timer no new paging repetition for this call is done.


LATAUSED

Type: Numeral

Range: 0, 1

Unit: -

Default: 0


O&M: -

Comments: Defines the usage of LATA administration.

0 LATA administration is not used.

1 LATA administration is used.



PAGLATA

Type: Numeral

Range: 0, 1

Unit: -

Default: 0

Command: DBTSP:TAB=AXEPARS,SETNAME=GSMMMSC.

O&M: -

Comments: Indicates if LATA paging is used for mobile terminating calls or not.

0 LATA paging is not used.

1 LATA paging is used.

This parameter is only valid if parameter LATAUSED = 1. The parameter is optional.


PAGREPCT1LA

Type: Numeral

Range: 0 to 3

Unit: -

Default: 2

Command: DBTSP:TAB=AXEPARS,SETNAME=GSMMMSC.

O&M: -

Comments: Defines how the paging is repeated in one location area.


is not repeated.

1 Paging in one location area is repeated with either TMSI or IMSI.


is repeated with TMSI.

3 Paging is repeated as call delivery LATA paging with IMSI.

This parameter is only valid if parameter PAGLATA = 1.



PAGTIMEREPLATA

Type: Numeral

Range: 2 to 10

Unit: s

Default: 7


O&M: -

Comments:Defines the time supervision for page response of repeated LATA paging. After expiration of this timer no new paging repetition for this call is done.

This parameter is only valid if parameter PAGLATA = 1. The parameter is optional.


PAGPRIO

Type: Numeral

Range: 0-5

Unit: -

Default: 5

Command: RLVGC, RLVGP

O&M: -

Comments: This parameter indicates the lowest paging priority that will cause a paging for a call in an ongoing group call.

AGBLK

Type: Numeral

Range:0 to 7 if non-combined BCCH is used.

0 to 2 if combined BCCH and SDCCH/4 is used

Unit: -

Default: 1

Command: RLDEC, RLDEP

O&M: The parameter is only allowed to be changed in cell state HALTED.

Comments:Number of reserved access grant blocks.

Number of CCCH blocks reserved for the access grant channel. The remaining CCCH blocks are used for the paging channel.

In each downlink non-combined SDCCH 51 frames multiframe there are 9 different CCCH blocks and in the combined BCCH/SDCCH there are 3 different blocks. They can be used to:

Send paging messages, i.e. used as a Paging Channel.

Send access granted messages, i.e. used as an Access Grant Channel.

After an MS tunes to the BCCH/CCCH channel and decodes the System Information, it performs an evaluation that, taking into account the MS's own IMSI (International Mobile Station Identity) number, determines to which particular CCCH block in the physical channel it should listen (Reference [7]). Every CCCH in the physical channel (Paging Subchannel) sends paging messages to a certain group of MSs that are called its paging group. The reason for the

existence of such paging groups is that the MSs can save batteries because it only needs to listen to its own Paging Subchannel messages.

The physical channel (Paging Subchannel) sends paging messages to a certain group of MSs. As mentioned before these very same CCCH blocks are also used to send Access Grant messages to the MSs, i.e. to answer a Random Access message that an MS wanting to access the system has sent to the system, and to send notifications on the NCH.

The structure of the BCCH regarding Paging messages and Access Grant messages can be controlled by the two parameters AGBLK and MFRMS.

AGBLK tells how many of the CCCH blocks that should be reserved for the Access Grant messages and NCH information. In Ericsson's GSM system, Access Grant messages are given priority over Paging messages. Together with MFRMS, AGBLK indicates how many paging groups there will be.

With a non-combined BCCH and AGBLK = 1, there are 8 CCCH blocks in each multiframe. This means that it is possible to have 16 to 72 different Paging Subchannels, i.e. Paging Groups. (Since MFRMS can take values between 2 and 9.)

With a combined BCCH/SDCCH and AGBLK = 1, there are 2 CCCH blocks in each multiframe. In this case it is possible to have 4 to 18 different Paging Groups.

Note AGBLK must not be 0 when SI 7 and 8 have to be sent, when short message service cell broadcast (SMSCB) is in use on a cell not using combined BCCH and SDCCH/4 (GSM05.02) or when Voice Group Call Service is used in the cell.

Note Only AGBLK = 0 and 1 is supported by the RBS 200 series BTS.

MFRMS

Type: Numeral

Range: 2 to 9

Unit: CCCH multiframes

Default: 6

Command: RLDEC, RLDEP

O&M: The parameter is only allowed to be changed in cell state HALTED.

Comments:Multiframes period. Defines period of transmission for PAGING REQUEST messages to the same paging subgroup.

Together with AGBLK, MFRMS determines the number of paging groups.

MFRMS is also used by the MS to determine downlink signalling failure in idle mode (Reference [8]). The downlink signalling failure criterion is based on the downlink signalling failure counter DSC. When the MS camps on a cell, DSC shall be initialised to a value equal to the nearest integer to 90/N where N is the MFRMS parameter for that cell. Thereafter, whenever the MS attempts to decode a message in its paging subchannel; if a message is successfully decoded DSC is increased by 1, (however never beyond the nearest integer to 90/N), otherwise DSC is decreased by 4. When DSC reaches 0, a downlink signalling failure shall be declared. A downlink signalling failure shall result in cell reselection.

MFRMS is also used by the MS to control monitoring of received BCCH carrier level (Reference [8]). Whilst in idle mode an MS shall continue to monitor all BCCH carriers as indicated in the BCCH allocation list (BA list). A running average of received level in the preceding 5 to

Max{5, ((5*N+6) div 7)*MFRMS/4}

seconds shall be maintained for each carrier in the BCCH allocation. N is the number of non-serving cell BCCH carriers

in BA.

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