Internal Use Only ▲
1 Paging 1.1
Paging Principle Radio paging is a communication process in which MSC finds out MS through paging. Only when the mobile subscriber has been found out can MSC carry out next call connection.
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Internal Use Only ▲
Fig. 4-1 Schematic Diagram of Sending Paging Message
1.2
Basic Signaling Flow of Radio Paging
Fig. 4-2 Basic Signaling Flow of Radio Paging
From Fig. 4-2, it is known that MSC will send, after getting the current LAC information of MS from VLR, paging messages to all BSCs in the LAC. After receiving the paging message, BSC will send out Paging Command to all cells within it under this LA. After BTS received the Paging Command, it will send out, on the paging subchannel of the paging group the IMSI is in, Paging Request, which carries IMSI or TMSI number of the paged subscriber. After receiving the Paging Request, MS will request through RACH for SDCCH allocation. And BSC will assign this SDCCH to MS through Immediate Assignment message in AGCH after it confirmed the activation of the needed SDCCH by BTS. And MS will use this SDCCH to send Paging Response. BSC will then forward this Paging Response to MSC, finishing a radio paging successfully. Now, the switch in GSM network usually adopts second paging with a paging interval of 5 seconds. After MSC obtains the current LAC information of the MS from VLR, it will send out paging message for the first time to all BSCs under the LAC the MS is in, if no paging response is received within 5 seconds, MSC will send out paging message again to all BSCs under the LAC the MS is in. If there is still no paging response within 5 seconds, this radio paging fails, and MSC will send a voice notification “the subscriber you dialed cannot be connected for the moment” to the MOC subscriber.
1.3
Paging Group After MS succeeds in decoding BCCH and system information, it could work out the paging channel it should monitor. The size of a paging group could be defined in
This document contains proprietary information of ZTE Corporation and is not to be disclosed or used except in accordance with applicable agreements.
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Internal Use Only ▲ OMC. It defines that how many paging sub-channels the paging channels in a cell could be divided into. In actual network, MS monitors only the paging sub-channel it belongs to and ignores the contents in other paging sub-channels. The larger the paging group, i.e. the more the paging sub-channels in a cell, the fewer the subscribers in each paging sub-channel. Thus, the average service time of the MS battery could be extended. By large paging groups, the paging capacity in system could be increased; but the average time delay of paging messages on radio channel will be extended, lowering system service performance. By small paging groups, the paging response could be speeded up, but the MS battery will be used up quickly and the system paging capacity will also be small. The number of paging groups is determined by BS-AG-BLKS-RES and BS-PAMFRMS.
1.4
BS-AG-BLKS-RES BS-AG-BLKS-RES indicates the number of message blocks in CCCH reserved for Access Granted Channel. After CCCH configuration is finished, this parameter actually shows the proportion of AGCH and PCH allocated on CCCH. The setting of this parameter will affect both the time for MS to respond to paging and the system service performance. If PCH is idle when all AGCHs are fully occupied, it could be used for sending Immediate Assignment Command. If BS-AG-BLKS-RES is set as 0, Immediate Assignment will have to be sent on idle paging channels.
1.5
BS-PA-MFRMS BS-PA-MFRMS refers to the number of multi-frames that could form a period of paging sub-channel. This parameter actually defines how many sub-channels the paging channels in a cell could be divided into. The larger the BS-PA-MFRMS, the more the paging sub-channels in a cell; this parameter should be set to the minimum value, provided no paging channel overload occurs. The running networks should be measured regularly about whether overload occurs on paging channels. Based on this, the value of BS-PA-MFRMS could be adjusted moderately. Any paging messages in the same LA (the same LAC) should be sent simultaneously in all cells under the LA, so the paging channel capacity in a cell should be the same as or close to that of other cells under the same LA (the number of paging sub-channels in each cell finally calculated). If BS-PA-MFRMS = 9, the MS belonging to a paging group will be paged every nine multi-frames, with an interval of 2.1 seconds (235.4ms*9).
1.6
Relation between Paging Group, BS-PA-MFRMS, and BS-AG-BLKS-RES (AGB） Number of paging groups for combined BCCH/SDCCH = (3-AGB)*BS-PA-MFRMS
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Internal Use Only ▲ Number of paging groups for Non-combined BCCH/SDCCH = MFRMS
(9-AGB)*BS-PA-
The relation between paging group, BS-PA-MFRMS, and BS-AG-BLKS-RES is as follows:
BS-PA-MF RMS
1.7
Time between
Number of paging groups
Number of paging groups
Combined BCCH/SDCCH
Non-Combined BCCH/SDCCH
transmission of
3 paging blocks
2 paging blocks
9 paging blocks
8 paging blocks
each paging group
per multi-frame
per multi-frame
per multi-frame
per multi-frame
AGB=0
AGB=1
AGB=0
AGB=1
2
0.47
6
4
18
16
3
0.71
9
6
27
24
4
0.94
12
8
36
32
5
1.18
15
10
45
40
6
1.41
18
12
54
48
7
1.65
21
14
63
56
8
1.89
24
16
72
64
9
2.12
27
18
81
72
Paging Strategies If the LA of an MS is already known in VLR, the first paging message will be broadcasted only in the LA the MS registered, i.e. local paging. If the MS does not respond to the first paging, MSC will initiate the second paging, which is usually broadcasted also in the original LA; however, for devices from some manufacturers, the second paging could be sent to all cells within the MSC, i.e. global paging. The latter will increase the paging success rate. In the paging process, TMSI or IMSI could be used to differentiate MSs.
This document contains proprietary information of ZTE Corporation and is not to be disclosed or used except in accordance with applicable agreements.
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Internal Use Only ▲
2 Calculation of LA Capacity 2.1
Calculation of LA Capacity The method to calculate LA capacity is as follows: Number of paging blocks per second X Number of paging messages per paging block = Maximum number of sending paging messages per second( Each hour support paging number of times) Maximum number of sending paging messages allowed in an hour Traffic allowed in an LA
Number of paging blocks per second
1 multi-frame = 51 frames = 0.2354s. If the number of BS_AG_BLK_RES is AGB, the formula to calculate the number of paging blocks per second is as follows：
Non-combined BCCH: the number of paging blocks/s = （ 9AGB）/0.2354 (paging blocks/s)
Non-combined BCCH: when AGB=2, the number of paging blocks/s = 27.9 paging blocks/s. When AGB = 0, the number of paging blocks/s= 38.2 paging blocks/s.
Number of Sending Paging Messages per Paging Block
There are 23 octets in each paging block, which could send two IMSI paging messages (a); or two TMSI paging and one IMSI paging messages (b); or four TMSI paging messages (c). If IMSI paging mechanism is adopted, each paging block could send paging messages for X times in average, X＝2
Number of Sending Paging Messages/paging blocks
If TMSI paging mechanism is adopted, then, X=4
Number of Sending Paging Messages/paging blocks
Maximum Number of Sending Paging Messages per Second (P)
This could be calculated through the following formula,
Non-combined BCCH: P =（9-AGB）/0.2354 (paging blocks/s) × X (number of sending paging messages/paging blocks)
IMSI paging mechanism: to non-combined BCCH, when AGB=2, P=59.47 times of sending paging messages/s; TMSI paging mechanism: to non-combined BCCH, if AGB=2, P=118.95 times of sending paging messages/s Therefore, the paging capacity in IMSI paging is half that in TMSI paging. This document contains proprietary information of ZTE Corporation and is not to be disclosed or used except in accordance with applicable agreements.
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Internal Use Only ▲
Traffic allowed in an LA (T)
An important principle in planning LA capacity is that the size of the LA shall not exceed the maximum capacity it could bear. As to expanded network, the number of sending paging commands in busy hour forwarded by BSC could be collected in OMC, and then converted into the number of paging commands per second. This number shall not exceed the value calculated above. If there is no traffic statistics could be referred to, e.g. newly established networks, the calculation should be based on a hypothetical traffic model:
Average call duration：90s
The proportion of the number of successful MTC calls (cause paging and generate TCH traffics) in the total number of call attempts: 50%
Then, the call duration for 90 seconds is corresponding to 1/90 times of call attempts/(second.Erl), in which, 50% is caused by MTC calls, therefore, 50% of successful MTC calls are corresponding to: 1/90*50% = 0.0056 times of successful MTC calls/(second.Erl). Given that 75% of MSs respond in the first paging, that 25% respond in the second paging, and that those respond in the third paging are ignored (this is the basis for the hypothesis, and the actual network data should be used in practical calculation), it needs 1.25 times of paging for each MTC call (25% of paging need to be sent for the second time), thus, Y=0.0056*(1+25%)=0.007 （second.Erl）
times
of
sending
paging
messages/
If IMSI paging mechanism is adopted, the traffic allowed in an LA is: T=P*50%/Y = 4247.86 Erl
(AGB=2，non-combined BCCH)
This document contains proprietary information of ZTE Corporation and is not to be disclosed or used except in accordance with applicable agreements.
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