15-Gprs Egprs Idle Mode

GPRS/EGPRS Idle Mode15/038 13-LZU 108 3704 Uae Rev G
Capabilities
Paging and control of the paging load
GSM Radio Network Features
High probability for communication
The MS will at all times try to camp on the cell which has the highest probability of successful communication on both up- and downlink when accessing the system. This is achieved by means of the cell selection and cell reselection algorithms.
MPDCH capabilities
With the MPDCH, a more advanced traffic steering, that is, a separate cell plan for GPRS/EGPRS can be achieved. An increased signalling capacity is also obtained in each cell where the MPDCH is present.
Low power consumption in the MS
In standby mode, the MS performs a number of various tasks among them, continuous monitoring of the Packet Paging Channel (PPCH) in order to detect the paging messages. The Discontinuous Reception (DRX) is a technique implemented in the GPRS/EGPRS system which 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. Paging and control of the paging load
The GPRS/EGPRS paging feature also supports the Circuit Switched (CS) paging through the GPRS/EGPRS system for IMSI and GPRS attached MS if the Gs-interface exists
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GSM/WCDMA GPRS Network
MSC Mobile Switching Center
RNC Radio Network Controler
SCP Service Control Point
SMS Short Message Service
BCCH
PDCH
PPCH, Packet Paging Channel
PNCH, Packet Notification Channel
PTCCH, Packet TA Control Channel DL
Uplink:
PTCCH, Packet TA Control Channel UL
Downlink/Uplink:
PTCCH, Packet TA Control Channel DL/UL
Note: PCCCH printed in bold/italic
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MPDCH – Description
PBCCH
With the MPDCH an advanced traffic steering and more signaling capacity may be obtained as compared to the BCCH.
The MPDCH carries the logical channel Packet broadcast control channel (PBCCH) and the Packet common control channel (PCCCH). The PCCCH consists of the Packet access grant channel (PAGCH) and the Packet paging channel (PPCH) in the downlink; and the Packet random access channel (PRACH) in the uplink. The MPDCH may also carry payload data in both downlink and uplink, that is the Packet data traffic channel (PDTCH) and it's Packet associated control channel (PACCH).
The indication of the existence of an MPDCH in a cell and the placement of it is signalled in System information (SI) 13 on the BCCH.
The frame structure used for the MPDCH channel is the 52 multiframe, which is divided into 12 radio blocks. See figure above as an example where the MPDCH is allocated on time slot number two.
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MPDCH Configuration parameters
MAXSBLK that determines the maximum number of blocks in a multiframe that can be used for the PBCCH
MAXSMSG that defines the maximum number of PSI messages that preferably shall be scheduled on one PBCCH block
TRAFBLK defines the number of blocks reserved for PAGCH, PDTCH and PACCH
The configuration of the MPDCH is controlled by a number of parameters which are broadcasted on the PBCCH. Some of the parameters may indirectly or directly be configured in the BSS.
The parameter BS_PBCCH_BLKS, which is broadcasted on the PBCCH, defines the number of blocks that are used for the PBCCH in a multiframe on the MPDCH. The value of BS_PBCCH_BLKS is dynamically determined by an algorithm in the BSS. There are two settable parameters used as input to the algorithm. Firstly, parameter MAXSBLK that determines the maximum number of blocks in a multiframe that can be used for the PBCCH. Secondly, the settable parameter MAXSMSG that defines the maximum number of PSI messages that preferably shall be scheduled on one PBCCH block.
The algorithm works in such a way that when MAXSMSG has been reached, more blocks are allocated to the PBCCH as long as not more than MAXSBLK blocks have been allocated.
Dependent on the number of blocks used for the PBCCH, the blocks B0, B6, B3 and B9 in that order, on the MPDCH are used.
The parameter BS_PAG_BLKS_RES, which is broadcasted on the PBCCH, indicates the number of blocks on the MPDCH where neither PPCH nor PBCCH should appear, that is, blocks that may be used for payload data. This number corresponds therefore to the number of blocks reserved for PAGCH, PDTCH and PACCH. BS_PAG_BLKS_RES is given the value of the settable parameter TRAFBLK.
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Example
No radio blocks reserved for only PAGCH, PDTCH or PACCH
MAXSBLK=2 (BS_PBCCH_BLKS)
TRAFBLK=2 (BS_PAG_BLKS_RES)
Note that the following has to be fulfilled in order to always leave at least one block on the MPDCH for the PPCH: (12 - MAXSBLK - TRAFBLK ) > 1
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Allocation of the Master PDCH
“MPDCH allocated?” means that a Master PDCH will be allocated if there is (at least) one dedicated PDCH in the cell.
Parameter: GPRSNWMODE
Parameter: MPDCH
A Master PDCH may be allocated in a cell to carry the packet broadcast channel and the packet common control channel, the PBCCH and the PCCCH. The Master PDCH may also carry packet data traffic. The Master PDCH can only be set up if there are dedicated PDCHs in the cell.
Whether the Master PDCH is allocated or not when at least one dedicated PDCH is configured, is dependent on the cell parameter MPDCH (default value = NO) and also on the chosen GPRS network operation mode, set per BSC by parameter GPRSNWMODE. The GPRS network operation mode I requires the optional Gs interface between the MSC and the SGSN, while the GPRS network mode II or III should be chosen when the Gs interface is not present.
If a Master PDCH is allocated in the cell, one of the dedicated PDCHs allocated in the primary dedicated PSET becomes the Master PDCH in the cell. The parameter PRIMPLIM restricts the number of PDCHs that can be allocated in the primary dedicated PSET. Because of this, it will be possible to place the MPDCH in another CHGR than the rest of the dedicated PDCHs.
The MPDCH is placed in the primary dedicated PSET in reverse TN priority order compared with ordinary PDCH allocation.
By setting parameter PRIMPLIM to 1, only one dedicated PDCH (the master PDCH) will be placed in the primary dedicated PSET. The rest of the dedicated or semi-dedicated PDCHs will reside in a secondary dedicated PSET. The secondary dedicated PSET will then contain the E-PDCHs according to the allocation algorithm.
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GPRS Mobility Management State Model
IDLE
READY
STANDBY
IDLE
READY
STANDBY
Idle state
The MS is turned on but not GPRS attached. The MS is “invisible” to GPRS. MS invisible in SGSN.
The MS is not attached to GPRS MM.
To enter the Standby State, it has to perform GPRS attach procedure.
Used when outside of GPRS coverage area or for class C mobiles when used for CS.
No TBF exists, only in packet transfer mode.
Standby state
The MS is GPRS attached and sends Routing Area Updates to the SGSN every time it changes Routing Area. The MS has performed GPRS Attached procedure.
The location of the MS is known (Routing Area Identity = Location Area in R8).
The MS may receive paging (CS and PS)
Ready state
A packet transfer is ongoing or has recently ended. A READY timer defines how long time the MS shall remain in the ready state after a transfer. The time is decided by the SGSN and can take values from zero to infinity, i.e. the MS shall never go back to the Standby state. The MS sends cell update to SGSN every time it changes cell. In ready state there is no need to send a page to the MS. SGSN sends the LLC frames to the PCU and the PCU sends an assignment immediately to the MS since the location is known on cell level.
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Routing Area Update
when it changes Routing Area
in periodic intervals (T3312)
To make it possible for the GPRS attached mobile subscriber to be paged for GPRS/EGPRS services, the network must know where the MS is located. To keep the network updated of the location of the MS, the network is informed by the MS on a regular basis. This is called Routing Area Updating. There are three different types of routing area updating defined:
Normal routing area updating
Periodic routing area updating
Combined routing and location area updating
The MS may also use the routing area update procedure in order to:
Make an IMSI attach for non-GPRS/EGPRS services
To resume the GPRS/EGPRS service if a resumption failure occured when leaving dedicated CS mode.
To update the network with new MS Radio Access Capability or new DRX parameter.
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PS Paging
SGSN
The PS paging procedure is initiated when SGSN receives a request to transfer a packet to a GPRS/EGPRS MS which is in MM Standby state. The SGSN sends a paging request to all BSSs serving the RA where the MS is currently located. The timer T3313 is started. Upon expiry of the timer, if no paging response is received, the SGSN repeats the procedure up to five times before the procedure is considered to be unsuccessful and stopped.
The PS paging procedure is considered to be successful when the paging response, which could be any valid LLC PDU, is received from the MS.
BSS
The MS is paged in all cells within the paging area. The PPCH is used if the MPDCH channel exists in these cells. For those cells not having an MPDCH, the PCH is used instead. This is under condition that the cell supports GPRS/EGPRS.
For DTM capable mobiles with a speech call ongoing the PS page is sent out as a PAGING NOTIFICATION on the FACCH instead, if the cell supports DTM.
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CS Paging (I)
In order to support CS Paging coordination, three network operation modes are defined:
Network operation mode I: The network sends a CS paging message for a GPRS attached MS, either on the same channel as the paging channel or on the PACCH if the MS is in Packet transfer mode.
Network operation mode II: The network sends a CS paging message for a GPRS attached MS on the PCH of CCCH. The MS only monitors the CCCH paging channel.
Network operation mode III: The network sends a CS paging message for a GPRS attached MS on the PCH of CCCH, and sends a PS paging message on the PPCH channel (if MPDCH is allocated in the cell). The MS needs to monitor both paging channels.
The BSC indicates in the system information which network operation mode is supported. This is done with the BSC exchange parameter GPRSNWMODE. If the Gs-interface exists, the network should operate in mode I, otherwise the network operation mode should be set to II or III.
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CS Paging (II)
For the GPRS-attached mobile, the first paging attempt for the circuit- switched services is always made via the Gs-interface. The procedure is initiated and supervised by MSC/VLR.
The mobile is paged in the LA if it is known, otherwise a Global paging is performed. The CS paging procedure is time supervised. Upon expiry of the timer TIMPAGINGM, a second paging may be performed where different strategies are applied if the first paging was LA or Global paging. The paging is repeated only once.
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CS Paging (III)
Paging request to a LA:
If the LA has been changed while waiting for the page response, the following procedures are applied based on the GPRS state of the MS:
If the MS is still GPRS-attached, the second paging is performed in one LA via the Gs-interface. If the state of the MS is change to GPRS-detached, the second paging is performed in one LA via the A-interface. See the User Description, Idle Mode Behavior.
If the LA has not been changed, the path of the second paging is determined by the application parameter SECPAGEPATH:
No paging.
The second paging may be performed via the A-interface, see the User Description, Idle Mode Behavior.
The second paging may be performed via the Gs-interface.
In the case of paging via Gs-interface, if the MS is still GPRS-attached, the application parameter PAGREP1LA determines which procedure is applied:
No second paging.
Global paging via the Gs-interface by IMSI.
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CS Paging (IV)
Upon expiry of timer TIMPAGINGM, a second paging may be performed depending on the application parameter SECPAGEPATH. The following are the options:
No second paging.
The second paging may be performed via the A-interface, see the User Description, Idle Mode Behavior.
The second paging may be performed via the Gs-interface.
In the case of the second paging via the Gs-interface, if the MS is still GPRS-attached, the application parameter PAGREPGLOB determines which procedure is applied:
No second paging.
Global paging via the Gs-interface with IMSI
Otherwise, if the state of the MS has been changed to GPRS-detached, the second paging may be performed via the A-interface, see the User Description, Idle Mode Behavior.
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Paging groups and DRX
The number of paging blocks available on the PCCCH is determined according to the following formula:
N = (12 - BS_PBCCH_BLKS - TRAFBLK) * 64
The formula below is used to calculate the paging groups of MS with above setting of parameters in the system.
Paging group (0..N-1) = ((IMSI mod 1000) + Max{(m*N) div SPLIT_PG_CYCLE, m}) mod N
where N = (12 - BS_PBCCH_BLKS - TRAFBLK) * 64
and m = 0, ...., (Min{N, SPLIT_PG_CYCLE}-1)
The number of paging blocks available on the PCCCH is determined according to the following formula:
N = (12 - BS_PAG_BLKS_RES - BS_PBCCH_BLKS - 1) * 64
The total number blocks available for the PPCH is 704. The paging groups of an individual MS is allocated on these paging blocks. The allocation is based on the IMSI and the DRX parameter SPLIT PG CYCLE received from the SGSN. The DRX parameter gives the possibility to each mobile to choose its own DRX period in the fraction of the paging block cycle (i.e., 704 paging blocks). The maximum DRX period is 64 * 52 multiframe period, that is 15,360 seconds. The minimum DRX period is indicated by "no DRX" which means that the MS monitors all paging groups.
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Example of Paging groups and DRX
In the example above BS_PBCCH_BLKS is one, meaning that the block B0 is always reserved for the PBCCH and parameter TRAFBLK is set to 0 leaving 704 blocks for paging ((12-1-0)*64). The value of SPLIT_PG_CYCLE is set to 176 by the MS. The paging block cycle is split into 176 periods, that is the occurrence of the paging groups for this MS will be reduced to every fourth radio block of those which are available for paging.
The DRX parameter includes also the Non-DRX timer. The timer indicates the period of time during which the MS will be in "Non-DRX" mode after leaving the packet transfer mode. This is to shorten the delay of subsequent packet transfer to the MS. The maximum allowed value for this timer is set by the system information parameter DRX_TIMER_MAX which is given the value of 64 seconds.
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GPRS/EGPRS System Information
GPRS system information parameters are distributed in the SI13 message on the BCCH
When the MPDCH is allocated in the cell, the SI13 message is still sent continuously on the BCCH carrying the information about the MPDCH position
The PSI1 message contains global power control parameters, parameters for control of the PRACH and PCCCH organization parameters and cell options related to GPRS like information if GPRS/EGPRS Quality of Service is supported in the BSC, EGPRS capability for the cell and if NACC is supported in the cell or not.
The PSI2 message includes cell identification, cell options related to GSM, cell allocation, reference frequency lists, GPRS mobile allocations and a description for the PCCCH.
The PSI3 message includes the GPRS BA-list and cell reselection parameters in defined neighbouring cells with GPRS available. If there is no room for the list in the PSI3 message, the PSI3bis message is used, in addition to PSI3 message.
The PSI3quater message is optional and carries information for 3G neighbour cells (that is UTRAN cells). The existence of PSI3quater is indicated in the PSI2 message. If the BSS parameter COEXUMTS is set to ON and 3G neighbours exists, PSI3quater messages are distributed.
The PSI14 message contains the PBCCH frequency description and in DTM cells also CCCH access information.
The information of where the CBCH is located is sent in PSI8.
For further details on the PSI messages, see 3GPP TS 44.060.
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Sheet1
TIMPAGINGM
9
9
Short message service cell broadcast
Short message service cell broadcast provides an operator with the capability to distribute short messages to idle subscribers
When a GPRS/EGPRS MS is listening to the PBCCH, it will need to know where the CBCH on the BCCH is configured in order to receive the messages sent on the CBCH.
The information of where the CBCH is located is sent in PSI8. It is possible to enable or disable the distribution of PSI8 in a cell with the parameter CBCHD.
Parameters
Sheet1
TIMPAGINGM
9
9
Packet System
Information message
PSI1YesOptional
PSI2YesOptional
PSI3YesYes
PSI3bisYesYes
PSI3quaterOptionalNo
PSI8OptionalNo
PSI14NoOptional

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15-Gprs Egprs Idle Mode