Location Area Planning www.huawei.com Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Definition o
Views 81 Downloads 0 File size 509KB
Location Area Planning www.huawei.com
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved.
Definition of Location Area GSM mobile communication network is divided into multiple service areas according to the codes of location areas. Location area is the basic unit of paging areas in GSM system. The paging message of a subscriber is sent in all cells of a location area. A location area contains one or more BSCs, but it belongs to one MSC only.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page2
1
Definition of Location Area
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page3
Location Area Code
LAC
Definition To locate the location of MS, the whole area covered by each GSM PLMN is divided into different location areas. LAC is used to identify different location areas.
Format LAI contains LAC, which is composed of two bytes. LAC adopts hexadecimal coding. The available range is from 0001H to FFFEH. The code 0000H and FFFFH cannot be used (please refer to specification GSM0303, 0408, and 1111). One location area can contain one or more cells. Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page4
2
Location Update Purpose of location update: To inform the system the LA in which the MS is to facilitate paging
When need the MS perform location update Getting into a new LA Periodical location update
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page5
Size of location areas The size of a location area, plays a key role in a GSM system. If the size of location area is too big, the paging traffic will be higher, perhaps PCH will be congestion. If the size of location area is too small, the MS will occur more location update process. The signaling traffic is higher, SDCCH channel perhaps be congestion.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page6
3
Paging VS Location update Traffic signaling traffic
Paging
Location update optimum number of cells in Loc. area
# of cells in Loc. area
minimize signaling traffic optimum varies with network evolution
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page7
Division of location areas If two or more location areas are present in a big city of great traffic, the landforms, such as mountains and rivers within this city can be used as edges of the location areas. If no such landforms available within this city, the areas (such as streets and shopping centers) with great traffic cannot be used as edges of the location areas. In the intersected areas of urban areas and suburban areas, to avoid frequent location update, should design the edges of location areas near the outer base stations.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page8
4
Location Area Design For Dual-band If 1800 MHz cells and 900 MHz cells are under the control of two MSCs respectively, their location areas are different. Related parameters should be set to maintain the mobile stations stay in the 1800 MHz cells where the traffic is absorbed. In this case, the times for the mobile station to handover between the two bands and reselect cells will decrease. Designing signaling channels, fully consider the load resulted from location update.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page9
Location Area Design For Dual-band If 1800 MHz cells and 900 MHz cells share a MSC, at the early network construction stage, they are suggested to use the same location area without affecting the network capacity. If the restriction on paging capacity is present, two location areas must be divided for them either in terms of band or geographic location, as shown in Figure .
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page10
5
Location Area Design For Dual-band
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page11
Location Area Design For Dual-band
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page12
6
Location Area Design For Dual-band If the location is divided in terms of geographic location, the frequent location updates resulted from inter-band handover and cell reselection can be avoided. However, need to modify the related data of the original 900 MHz network. In addition, at the edges of the location areas, because the location updates caused by intra-band and inter-band handover and cell reselection is present simultaneously, the signaling flow is huge at these edges. As a result, carefully design the edges of the location areas.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page13
Physical Combination of Logical Channel 26-frame multi-frame TCH/F+SACCH/F (full-rate TCH) TCH/H+SACCH/H (half-rate TCH)
51-frames multi-frame FCCH+SCH+BCCH+CCCH (main BCCH) FCCH+SCH+BCCH+CCCH+SDCCH/4+SACCH/4 (combined BCCH) BCCH+CCCH (extended BCCH) SDCCH/8+SACCH/8 (main SDCCH)
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page14
7
Structure of Main BCCH 1 multi-frame (51TDMA Frames) 235.38ms Downlink Group3,4
Group
Group1
Group2
Grpup5
(same as Group2)
Channel Frame Number
F
S
BX4
CX4
F
S
CX4
CX4
……
F
S
CX4
CX4
I
0
1
2-5
6-9
10
11
12-15
16-19
20-39
40
41
42-45
46-49
50
1 multi-frame (51TDMA Frames) 235.38ms Uplink Channel
R
R
R
R
R
R
R
R
R
R
R
R
R
R……R
R
R
R
R
0
1
2
3
4
5
6
7
8
9
10
11
12
13-46
47
48
49
50
Frame Number
F:FCCH; S:SCH; B:BCCH; C:CCCH; I:IDLE; R:RACH Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page15
Structure of Combined BCCH 1 multi-frame (51TDMA Frames) 235.38ms Downlink Group
Group1
Channel
F
S
Channel
F
S
0
1
Frame Number
B
Group2 C
4
B
4
C
C
F
S
F
S
11
4
4
2-5
6-9
10
4
C
Group3 C 4
C
4
4
12-
16-
15
19
F
S
F
S
20
21
Group4
D0
D1
4
4
D0
D1
4
4
22-
26-
25
29
F
S
F
S
30
31
1 multi-frame (51TDMA Frames) 235.38ms
Grpup5
D2
D3
4
4
D2
D3
4
4
32-
36-
35
39
F
S
F
S
40
41
A0
A1
4
4
A2
A3
4
4
42-
46-
45
49
I
I
50
Uplink
Channel
D3 4
R
R
A2 4
A3 4
R……R
D0 4
D1 4
R
R
D2 4
Channel
D0 4
R
R
A0 4
A1 4
R……R
D0 4
D1 4
R
R
D2 4
Frame Number
0-3
4
5
6-9
10-13
14-36
37-40
41-44
45
46
47-50
F:FCCH; S:SCH; B:BCCH; C:CCCH; D:SDCCH ;A:SACCH; I:IDLE; R:RACH Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page16
8
Structure of Logical Channel Combination Frame-Main SDCCH 1 multi-frame (51TDMA Frames) 235.38ms Downlink Channel
Channel Frame Number
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
A3
4
4
4
4
4
4
4
4
4
4
4
4
D0
D1
D2
D3
D4
D5
D6
D7
A4
A5
A6
A7
4
4
4
4
4
4
4
4
4
4
4
4
0-3
4-7
8-11
12-
16-
20-
24-
28-
32-
36-
40-
44-
15
19
23
27
31
35
39
43
47
I
I
I
I
I
I
48
49
50
1 multi-frame (51TDMA Frames) 235.38ms Uplink Channel
A5 4
A6 4
A7 4
I
I
I
D0 4
D1 4
D2 4
D3 4
D4 4
D5 4
D6 4
D7 4
A0 4
Channel
A1 4
A2 4
A3 4
I
I
I
D0 4
D1 4
D2 4
D3 4
D4 4
D5 4
D6 4
D7 4
A4 4
Frame Number
0-3
12
13
14
1518
1922
4-7
8-11
2326
2730
3134
3538
3942
4346
4750
D:SDCCH; A:SACCH; I:IDLE Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page17
ATT Value range: Yes, No Content It is used to inform MS whether IMSI attach-detach is allowed in this cell. If it is set to “Yes”, the network will not process the connection to the called mobile subscriber when MS is power-off. Thus network processing time and radio resources are saved. Otherwise the network will process the connection even though the MS has been powered off. Recommendation
Yes
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page18
9
CCCH_CONF Value range: 1 Non-Compounding CCCH, 1 Compounding CCCH, 2 Non-Compounding CCCHs, 3 Non-compounding CCCHs, 4 Noncompounding CCCHs. Content: It is “Common Control Channel Configuration”. CCCH configuration determines the capacity of PCH, AGCH and RACH. This parameter can be automatically configured by the BSC Data Auto Configuration System according to the TRX channel configuration. Recommendation: When there is one TRX in the cell, one combined CCCH is recommended (in a system with few paging messages in location area). For others, it is configured according to the number of TRX in the cell.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page19
BS_AG_BLKS_RES Value range: 0~2 (1 combined CCCH), 0~7 (others) Unit: Block Content: It is also called Access Granted Blocks Reserved. It is the number of CCCH channel message blocks that are reserved in one multi-frame for access granted channels (AGCH). Recommendation: 2 (non-combined CCCH)
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page20
10
BS_PA_MFRAMES Value range: 2 9 Unit: Multi-frame period (51 frames) Content: It is Paging Channel Multi-frames. It defines the number of multi-frames used as a cycle of paging subchannels. Recommendation: 2
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page21
T3212 Value range: 0~255 Unit: 6 minutes Content: It is the Periodic Location Update Timer. It defines the interval of periodic location update. Recommendation: 30 (for urban area), 20 (for suburban area)
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page22
11
CRH Value Range: 0~14, the step size is 2dB Unit: dB Default Value: 6 Description: Cell Reselection Hysteresis. It is the parameter used when cell reselection happens between two location areas. Location: Cell Attributes/Idle Mode/Basic Idle Parameters
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page23
TCH Immediate Assignment Value Range: Yes, No Default Value : No Description: Option "Yes" means that TCH channel can be immediately assigned as signaling and traffic channel when SDCCH has no available resource. The option "No" means that only SDCCH can be assigned. Location: Cell Attributes
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page24
12
Calculating For Location Area Generally, the capacity of a location area is calculated as follows: The number of paging blocks sent in each second
the
number of paging messages sent in each paging block = the maximum paging times in each second.
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page25
Calculating For Location Area The number of paging blocks sent in each second 1 frame = 4.61ms, 1 multiframe = 51 frames = 0.2354s;
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page26
13
Calculating For Location Area suppose the number of access grant blocks is AGB, the number of blocks, the number of paging blocks sent in each second is calculated by the following formulas: For non-combined BCCH, the number of paging blocks sent in each second = (9 – AGB)/0.2345 (paging block/second). For non-combined BCCH, the AGB is 2 according to Huawei BSC. Therefore, the number of paging blocks sent in each second is 29.7 (paging block/second).
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page27
Calculating For Location Area suppose the number of access grant blocks is AGB, the number of blocks, the number of paging blocks sent in each second is calculated by the following formulas: For combined BCCH, the number of paging blocks sent in each second = (3 – AGB)/0.2345 (paging block/second). For combined-BCCH, the AGB is 1, so the number of paging blocks sent in each second is 8.5 (paging blocks/second).
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page28
14
Calculating For Location Area The number of paging messages sent in each paging block (X) According to protocols, each paging block has 23 bytes, and can send 2 IMSI pages, or 2 TMSI and 1 IMSI pages, or 4 TMSI pages. According to the paging strategies of Huawei MSC, if the IMSI paging mechanism is adopted, the number of paging messages sent in each paging blocks is 2 (paging times/paging block); if the TMSI paging mechanism is adopted, it is 4 (paging times/paging block) Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page29
Calculating For Location Area If the IMSI paging mechanism is adopted, for non-combined BCCH when AGB = 2, P = 59.47 (paging times/second); For combined-BCCH when AGB = 1, P = 16.99 (paging times/second);
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page30
15
Calculating For Location Area If the TMSI paging mechanism is adopted, for non-combined BCCH, when AGB = 2, P = 118.95 (paging times/second); For combined BCCH, when AGB = 1, P = 33.98 (paging times/second);
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page31
Calculating For Location Area Paging Capability (Hour)= [(CCCH CONF-BS AG BLKS RES) Paging Strategy 3600] / [51 TDMA period (1+Sencond Paging Ratio)]
Paging Strategy: IMSI paging or TMSI paging
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page32
16
Calculating For Location Area LAC Capability (ERL)= [(CCCH CONF-BS AG BLKS RES) Paging Strategy
Average Holding Time Average
Paging Load at BTS ] / [51 TDMA period (1+Sencond Paging Ratio)
MTC Ratio]
Paging Strategy: IMSI paging or TMSI paging
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page33
Calculating For Location Area LAC Capability (TRX)= LAC Capability (ERL) / Average Traffic Volume per TRX
(1+TCHH Ratio) ]
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page34
17
Calculating For Location Area CCCH CONF
Main BCCH 5
BS AG BLKS RES
15%
Sencond Paging Ratio Paging Strategy
TMSI
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page35
Calculating For Location Area CCCH CONF
9
BS AG BLKS RES
2
BS PA MFRMS
2
Sencond Paging Ratio
15%
MTC Ratio
50%
Average Paging Load at BTS
50%
TCHH Ratio
70%
Average Holding Time Paging Strategy Average Traffic Volume per TRX
58 TMSI 4.8
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page36
18
Calculating For Location Area Paging Capability (Hour) =
LAC Capability (ERL) =
[(9 - 2) × 2 × 4 × 3600] = 372813 51× 0.00461× 2 × (1 + 0.15)
[(9 - 2) × 4 × 58] × 0.5 = 6006 51× 0.00461× (1 + 0.15)× 0.5
LAC Capability (TRX)= 6006 / 4.8
(1+ 0.7) ] =736
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page37
Copyright © 2009 Huawei Technologies Co., Ltd. All rights reserved. Page38
19
Thank you www.huawei.com
20