dimensioning rules b9
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Dimensioning Rules for CS and PS traffic
with BSS Software Release B9
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CONTENTS
1. REFERENCE DOCUMENTS...........................................................................................................4
2. INTRODUCTION .............................................................................................................................4
3. DEFINITIONS ..................................................................................................................................5
4. AIR INTERFACE..............................................................................................................................5
5. A-BIS INTERFACE ..........................................................................................................................5
5.1 Number of time-slots available per A-bis Multidrop link.........................................................5
5.2 Usage of A-bis timeslots........................................................................................................6
5.3
Transport of Signaling on the A-bis interface.........................................................................6
5.3.1 A-bis signaling modes...............................................................................................6
5.3.2 Rules of usage of signaling multiplexing...................................................................7
6. BSC DIMENSIONNING RULES ......................................................................................................8
6.1 BSC equipment overview.......................................................................................................8
6.2 BSC A-bis connectivity...........................................................................................................8
6.2.1 Maximum number of TRXs.......................................................................................8
6.2.2 Maximum number of BTSs and Cells .......................................................................9
6.2.3
Mix of Full Rate and Dual Rate TRX.........................................................................9
6.2.4 Maximum capacity of each A-bis TSU......................................................................9
6.2.5 The particular case of cell splitting..........................................................................10
6.2.6 Introduction of CS-3, CS-4 and EDGE....................................................................10
6.3 BSC A-ter connectivity .........................................................................................................11
6.4 CS traffic handling capability................................................................................................11
6.4.1 Maximum BSC capacity figures ..............................................................................11
6.4.2 The moderation factor.............................................................................................11
7. A-TER INTERFACE.......................................................................................................................12
7.1 Definitions ............................................................................................................................12
7.2 Mixed A-ter CS/PS links.......................................................................................................13
7.3 Specific cases......................................................................................................................14
7.4 Minimum number of A-ter links............................................................................................15
7.5 Number of SS7 channels.....................................................................................................15
7.6 Number of GSL channels ....................................................................................................15
7.7 A-ter interface configuration rules........................................................................................15
8. TRANSCODER DIMENSIONING RULES .....................................................................................16
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8.1 Connection to the EVOLIUM G2 TC ................................................................................16
8.2 Connection to the A9125 TC................................................................................................16
8.3 Minimum number of A links .................................................................................................16
9.
A9135 MFS DIMENSIONING RULES ...........................................................................................17
9.1 A9135 MFS configurations...................................................................................................17
9.2 GPU capacity.......................................................................................................................17
10.GB INTERFACE.............................................................................................................................18
10.1 Configuration rules...............................................................................................................18
10.2 General dimensioning rules.................................................................................................19
11.ANNEX 1: STANDARD TRAFFIC MODEL....................................................................................20
12.ANNEX 2: A-BIS INTERFACE CONFIGURATION........................................................................21
12.1
Number of time-slots required with the different Signaling Multiplexing schemes...............21
12.2 Typical cases where Signaling Multiplexing is very advantageous......................................21
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1. REFERENCE DOCUMENTS
[1] 3DC 21006 0003 TQZZA Use of Moderation Factor for BSS traffic assessment
[2] 3DC 21016 0003 TQZZA EVOLIUM G2 Base Station Controller Product Description
[4] 3DC 21016 0005 TQZZA A9135 MFS Product Description
[5] 3GPP Technical
Specification 05.02
Multiplexing and Multiple Access on the Radio Path
[6] 3DC 21034 0001 TQZZA G2 Transcoder Product Description
[7] 3DC 21016 0007 TQZZA A9125 Compact Transcoder Product Description
[8] 3DC 21144 0047 TQZZA GPRS Master Channels in Release B8
[9] 3DC 21144 0032 TQZZA GPRS Radio Resource Management in Release B7
[10] 3DC 21150 0315 TQZZA GSM/GPRS/EDGE Radio Network Design Process For Alcatel
BSS Release B9
2. INTRODUCTION
This document provides dimensioning rules of the G2 BSC and the A9135 MFS equipments with the
BSS release B9.
It also provides the rules to dimension the interfaces in the BSS Air interface, A-bis interface, A-ter
interface and Gb interface.
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3. DEFINITIONS
A 64 kb/s channel on the A-bis interface is called an A-bis timeslot.
A 16 kb/s channel on the A-bis interface is called an A-bis nibble.
A transmission channel established for carrying (E)GPRS traffic is called a GCH (GPRS channel).
One GCH uses one A-bis and one A-ter nibble.
In this document, EDGE may be used instead of E-GPRS, for wording simplification purpose.
4. AIR INTERFACE
The maximum number of TRX per cell is 16. This figure can be achieved thanks to the feature Cell
split over two BTS (as the maximum number of TRX per BTS is 12).
Radio configuration of GSM cells :
There is one timeslot devoted to CCCH per cell.
The maximum number of SDCCH channels per cell is 88.These SDCCH channels may be static or
dynamic. At least one static SDCCH (SDCCH/4 or SDCCH/8) must be positioned on the BCCH TRX,
for recovery.
The maximum number of SDCCH per TRX on an EVOLIUM BTS is 24.
In a multiband cell, all SDCCH are in the primary band of the cell.
In a concentric cell, all SDCCH are in the outer zone.
All TRX can be declared as Full rate or Dual Rate TRX. Mixtures of DR TRX and FR TRX are
supported.
Packet configuration:
The maximum number of PDCH in one cell is 60.
There may be one primary master channel (PBCCH) and up to 3 secondary master channels
(PCCH) in one cell.
In a multiband cell, all packet traffic is in the primary band of the cell.
In a concentric cell, all packet traffic is in the outer zone.
5. A-BIS INTERFACE
5.1 Number of time-slots available per A-bis Multidrop link
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This number depends on :
- The type of the multidrop link : Closed Loop or Open Chain,
- whether time-slot zero (TS0) transparency is used or not,
- the BTS generation.
The table below indicates the number of time-slots available per PCM link according to the possible
choices:
OPEN CHAIN MULTIDROP CLOSED LOOP MULTIDROP
G1 or G2 BTS A9100 BTS (*) G1 BTS (**) G2 or
EVOLIUM BTS
WITH TS0 TRANSPARENCY 30 31 28 29
TS0 USAGE 31 31 30 30
(*) Improvement with EVOLIUM BTS: In case all BTSs of a Multidrop are EVOLIUM BTSs,
and if TS0 transparency is used, then the time-slot used for transmission supervision can be
saved (because the OML of EVOLIUM BTS supports also the transmission supervision
information)
(**) This column applies as soon as there is one G1 BTS in a closed multidrop.
5.2 Usage of A-bis timeslots
On the A-bis interface, there are basic timeslots, extra timeslots and timeslots devoted to signalling.
One timeslot on the air interface is mapped on one basic 16kb/s nibble on the A-bis interface.
As a consequence, each TRX corresponds to two A-bis basic timeslots.
Additional extra timeslots can be added for transport of packet. This makes sense when CS3/CS4 or
EDGE have been activated. If the cell transports voice only, or GPRS up to CS-2, there is no reason
to add extra-timeslots.
The number of extra timeslots per BTS is determined by the Operator.
In case one E1 link is not sufficient for transporting the packet traffic on the A-bis interface, a second
incoming A-bis link can be defined for a BTS. The second A-bis link transports only extra timeslots.
5.3 Transport of Signaling on the A-bis interface
In addition to data, signalling has to be transported on the A-bis interface. There are two types of
information to be conveyed :
- RSL : Radio Signaling Link. There is one RSL per TRX
- OML : O&M link. There is one OML per BTS.
5.3.1 A-bis signaling modes
There are three types of Signaling Multiplexing :
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Static Signaling Multiplexing consists of multiplexing on one A-bis time-slot (64 kb/s) up to 4
RSLs (Radio Signaling Link) of 16 kb/s each belonging to the same BTS. The OML uses an
additional A-bis time-slot (64 kb/s).
Statistical Signaling Multiplexing 64k consists in multiplexing on one A-bis time-slot (64kb/s) up to 4 RSLs (Radio Signaling Link) of a BTS plus the OML. Each RSL has a transfer
rate of maximum 64 kb/s.
Statistical Signaling Multiplexing 16k : the basic nibble corresponding to the radio timeslot 0
of each TRX encompasses the RSL of this TRX and eventually the OML of the BTS. This
feature requires that no traffic, but only signaling (BCCH or SDCCH) is affected on timeslot 0
of each TRX. In this case no additional timeslot is required on the A-bis for signaling.
5.3.2 Rules of usage of signaling multiplexing
Static Signaling Submultiplexing can only be used if all the following conditions are met:- Full rate only (no Dual Rate).
- Each TRX carries 8 SDCCH channels maximum
Statistical Signaling Submultiplexing 16 k can only be used if all the following conditions are met:
- EVOLIUM BTS and Micro-BTS,
- Full rate only TRX (no Dual Rate).
- Each TRX carries 8 SDCCH channels maximum
- The Time-Slot 0 of each TRX must not be assigned to traffic (but to BCCH/CCCH or SDCCH)
Statistical Signaling Submultiplexing 64 k can only be used on EVOLIUM BTS and Micro-BTS.
The multiplexing ratio depends on the signaling load and on the configuration of the TRX (Dual Rate
or Full Rate).
It is not possible to mix the RSL of Full-Rate TRX and Dual-Rate TRX in the same 64 kb/s timeslot.
Multiplexing ratio :
Full Rate TRX Dual rate TRX
Normal
signaling load
High signaling
load
Normal
signaling load
High signaling
load
4:1 2:1 2:1 1:1
The signalling load is entered by the OMC-operator when choosing the multiplexing scheme. The
high signalling load is recommended in the case where several TRX in a cell are configured with
more than 8 SDCCH, which may be the case with multiband or concentric cells.
In other cases the normal signalling load option should be advised.
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6. BSC DIMENSIONNING RULES
6.1 BSC equipment overview
The G2 BSC range available with the BSS Software Release B9 is:
Configurationnumber
BSC G2 EQUIPMENT nb of cabinets
1 32 TRX-FR; 16A, 6 A-bis-ITF 1
2 128 TRX-FR; 24A,24 A-bis -ITF 1
3 192 TRX-FR; 40A,36 A-bis -ITF 2
4 288 TRX-FR; 48A, 54 A-bis -ITF 2
5 352 TRX-FR; 64A, 66 A-bis -ITF 3
6 448 TRX-FR; 72A, 84 A-bis -ITF 3
For more details on BSC HW, please refer to the BSC product description [2].
6.2 BSC A-bis connectivity
There is a set of rules to be respected to determine the maximum amount of TRXs and BTSs that
can be connected to a G2 BSC. Some rules refer to the BSC equipment as a whole, others to the
A-bis Terminal Sub-Unit (A-bis TSU) capacity.
6.2.1 Maximum number of TRXs
The following table gives the maximum TRX connectivity.
BSC G2 EQUIPMENT Max. Nb. of TRX-FR
Max. Nb. of TRX-DR
Configuration 1 32 14
Configuration 2 128 62
Configuration 3 192 92
Configuration 4 288 140
Configuration 5 352 170
Configuration 6 448 218
Note : At least one TCU in each BSC rack must be allocated in Full Rate.
That is the reason why it is not possible to have more than 218 DR TRX in configuration #6.
When the maximum number of DR TRX is reached, there are still up to 4 potential FR TRX for
configurations (1) & (2), 8 FR TRX for configurations (3) & (4), and 8 FR TRX for configurations (5) &
(6).
It is not possible to mix FR TRX and DR TRX in a single TCU.
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6.2.2 Maximum number of BTSs and Cells
One must distinguish whether the TRX is configured in Full Rate or in Dual Rate mode.
6.2.2.1 When all TRX are configured in Full Rate mode
BSC G2 EQUIPMENT max. nb. of BTSs max. nb. of Cells
Configuration 1 23 32
Configuration 2 95 120
Configuration 3 142 192
Configuration 4 214 240
Configuration 5 255 264
Configuration 6 255 264
6.2.2.2 When all TRX are configured in Dual Rate mode
BSC G2 EQUIPMENT max. nb. of BTSs max. nb. of Cells
Configuration 1 14 14
Configuration 2 62 62
Configuration 3 92 92
Configuration 4 140 140
Configuration 5 170 170
Configuration 6 218 218
6.2.3 Mix of Full Rate and Dual Rate TRX
The Half-Rate Flexibility feature allows defining the number of Dual Rate TRX in each BTS sector.
6.2.4 Maximum capacity of each A-bis TSU
Each A-bis TSU includes 8 TCUs (Terminal Control Unit) and six G.703 A-bis interfaces, which allow
connecting six A-bis PCM trunks.
The table below indicates the number of A-bis TSU for each G2 BSC configuration.
BSC G2 EQUIPMENT Nb. Of A-bisTSU
Configuration 1 1
Configuration 2 4
Configuration 3 6
Configuration 4 9
Configuration 5 11
Configuration 6 14
The following rules, relative to the A-bis TSU, must be respected:
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- All TRXs of all BTSs of a same A-bis multidrop are handled by a single A-bis TSU.
- Each TCU can handle 6 signaling links (LAPD), i.e. typically: (4 RSLs + 2 OMLs for 4 TRXs+ 2
BTSs ) or (3 RSLs + 3 OMLs for 3 TRXs+ 3 BTSs).
- Each TCU can handle either Full Rate or Dual Rate traffic (but not both).
- Each TCU can handle 32 Traffic Channels, i.e. 4 Full-Rate TRXs or 2 Half-Rate TRXs.
- The traffic channels and the RSL of a given TRX are handled by the same TCU.
- In case of Signaling Multiplexing, all RSLs of a given 64 kb/s A-bis time-slot are handled by the
same TCU (this rule applies for both Static and Statistical Signaling Multiplexing)
- 6 A-bis open chain multidrop links can be connected to one A-bis TSU. In case of closed loop
multidrop links, both ends of an A-bis multidrop loop must be connected to the same A-bis-
TSU. Hence up to 3 A-bis closed loop multidrop links can be connected to 1 A-bis-TSU.
-In each cabinet, there is at least one TCU configured in Full Rate.
Remarks:
- It is possible to mix within a same TCU, RSLs which are multiplexed (static and/or statistical)
and RSLs which are not multiplexed.
Recommendations:
- If the detailed A-bis topology is not known, it is not always possible to predict the applicability of
all the above rules. It is thus recommended not to dimension a BSC over 90% of its maximum
connectivity.
- Leaving free some spare capacity in all A-bis TSUs will simplify further extensions.
6.2.5 The particular case of cell splitting
Cell splitting is available from release B7 onwards. This feature enables to share a cell between 2
BTSs. This feature enables for example to extend a site, adding a new BTS without modifying the
arrangement of the already existing BTS(s).
The connection to the BSC of the A-bis links coming from these BTSs shall not follow any specific
rule. The BTS can be connected to the same or to different A-bis TSUs.
However, in the particular case of Multi-band Cell usage, one must be aware that all radio signalling
is concentrated on the primary band. Thus it is recommended to mix the 900 MHz BTSs and the1800 MHz BTSs in each A-bis TSU, so as to enable a better signalling load distribution at TCU level.
6.2.6 Introduction of CS-3, CS-4 and EDGE
Introduction of CS-3, CS-4 and EDGE has impacts on A-bis dimensioning and on the BSC TRX
connectivity.
Extra-timeslots defined on the A-bis links are cross-connected inside the BSC and consume some
BSC connectivity.
Two A-bis extra timeslots are equivalent to one Full Rate TRX in terms of connectivity in the BSC.
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In other words, one extra timeslot is equivalent to FR TRX.
Note : the system maps extra-timeslots on any FR TCU of the A-bis TSU to which the A-bis link is
connected.
6.3 BSC A-ter connectivity
The maximum number of A-ter interfaces is given in the table below:
BSC G2 EQUIPMENT Max. Nb. ofA-ter itf
Configuration 1 4
Configuration 2 6
Configuration 3 10
Configuration 4 12
Configuration 5 16
Configuration 6 18
6.4 CS traffic handling capability
The maximum traffic handling capacity is mainly limited by the number of A-ter interface channels
available for traffic
6.4.1 Maximum BSC capacity figures
These figures are guaranteed with respect to the call mix specified in annex 1.
BSC capacity
Configuration 1 160 Erlang
Configuration 2 620 Erlang
Configuration 3 1050 Erlang
Configuration 4 1300 Erlang
Configuration 5 1700 Erlang
Configuration 6 1900 Erlang
These figures correspond to a blocking probability on the A-ter interface of 0.1%.
Note that a conf. 6 BSC can reach a 2000 Erlangs capacity with a less constraining traffic model.Also in that case, the blocking rate will reach 0.24%, instead of 0.1%.
6.4.2 The moderation factor
When dimensioning a network, one must check that the nominal traffic generated by the different
BTSs does not exceed the maximum traffic handling capacity of the BSC to which they are
connected.
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However it has been noticed that the actual traffic encountered in a BSC is generally significantly
lower than the sum of traffic capacities of all connected BTS. This comes from the fact that the
nominal traffic is not reached simultaneously in each cell and that all TRXs or all traffic channels are
not all necessary to handle the actual traffic.
To account for this and avoid over-estimating the number of BSCs necessary for a given network,
the notion of Moderation Factor has been introduced. The Moderation Factor is defined as the ratio
between the actual traffic encountered in the BSC at its busy hour and the theoretical traffic figure.
The value of the Moderation Factor can vary very significantly depending on the network context.
Except for very dense urban areas, a maximum value of 0.8 may be used. Significantly lower values
may even be used in many cases.
It must be noted that using the Moderation Factor is also recommended for the assessment of the
number of A-ter Interfaces and of transcoders.
More details on the Moderation Factor can be found in document [1].
7. A-TER INTERFACE
7.1 Definitions
The A-ter1 interface is both the interface between the BSC and the TC, and between the BSC and
the MFS.
The A-ter interface may transport pure circuit, it is then called A-ter CS.
When it transports packet traffic, it is called A-ter PS.
It is possible to mix PS and CS traffic on one single A-ter link, it is then called A-ter CS/PS.
On the A-ter CS interface, a 64 kb/s timeslot transmits information for 4 Circuit Switch calls
(whatever they use FR or HR codecs).
On the A-ter PS interface, a 64 kb/s timeslot supports 4 GCHs.
1 Strictly speaking, the A-ter interface is an internal G2 BSC interface : it is the interface between the
DTC and the ASMB boards. On this interface, a 64 kb/s timeslot transmits information for a single
CS call (FR or HR).
The actual interface between the BSC and the TC is the Atermux interface.
However, in order to simplify the wording, the Atermux interface is simply called A-ter interface.
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7.2 Mixed A-ter CS/PS links
The number of 64 kb/s time-slots assigned to PS traffic (and PS signalling) is configured by the
Operator at the OMC-R, with the following granularity: 4, 8, 15, 22, and 29 timeslots (full PS) per
PCM, as depicted in the following table:
PS TS 4 8 15 22 29
0
1 TCH TCH TCH TCH GCH
2 TCH TCH TCH TCH GCH
3 TCH TCH TCH TCH GCH
4 TCH TCH TCH TCH GCH
5 TCH TCH TCH TCH GCH
6 TCH TCH TCH TCH GCH
7 TCH TCH TCH TCH GCH
8 TCH TCH TCH GCH GCH
9 TCH TCH TCH GCH GCH
10 TCH TCH TCH GCH GCH
11 TCH TCH TCH GCH GCH
12 TCH TCH TCH GCH GCH
13 TCH TCH TCH GCH GCH
14 TCH TCH TCH GCH GCH
1516
17 TCH TCH GCH GCH GCH
18 TCH TCH GCH GCH GCH
19 TCH TCH GCH GCH GCH
20 TCH TCH GCH GCH GCH
21 TCH TCH GCH GCH GCH
22 TCH TCH GCH GCH GCH
23 TCH TCH GCH GCH GCH
24 TCH GCH GCH GCH GCH
25 TCH GCH GCH GCH GCH
26 TCH GCH GCH GCH GCH
27 TCH GCH GCH GCH GCH
28 GCH GCH GCH GCH GCH
29 GCH GCH GCH GCH GCH
30 GCH GCH GCH GCH GCH
31 GCH GCH GCH GCH GCH
A-ter CS/PS configurations
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The A9135 MFS transparently routes the 64 kb/s timeslots used for voice towards the transcoder.
The MFS has the possibility to split the traffic on a link to the transcoder for the CS traffic and a link
to the SGSN for PS traffic.
It is also possible to route both CS and packet traffic (Gb) to the transcoder. The same granularity
between CS & PS is kept.
The figure below displays the different types of links between the MFS and the SGSN.
Alcatel
9135MFS
T
C
MSC
BSC
SGSN
A-ter CS
+PS
Gb
A/Gb
Alcatel
9135MFS
T
C
T
C
MSC
BSCBSC
SGSN
A-ter CS
+PS
Gb
A-ter CS
+ Gb
A/Gb
Alcatel
9135MFS
T
C
MSC
BSC
SGSN
A-ter CS
+PS
Gb
A/Gb
Alcatel
9135MFS
T
C
T
C
MSC
BSCBSC
SGSN
A-ter CS
+PS
Gb
A-ter CS
+ Gb
A/Gb
Alcatel 9135
MFS
T
C
MSC
BSC
SGSN
A-ter CS +PS
Gb
A-ter CS
Alcatel 9135
MFS
T
C
MSC
BSC
SGSN
A-ter CS +PS
Gb
A-ter CS
Alcatel 9135
MFS
T
C
T
C
MSC
BSCBSC
SGSN
A-ter CS +PS
Gb
A-ter CS
7.3 Specific cases
Specific A-ter timeslots are not usable for traffic. It is the case for:
Timeslot 15 of each A-ter interface : it is used by an O&M internal channel, and cannot
be used for traffic. 2 additional timeslots must be dedicated to the O&M link from the BSC to the OMC-R if
this connection is performed through the A-ter Interface, and not using an other X25
network. In this case timeslot 31 is used on A-ter links N1 & 2.
In each G2 BSC rack, there is one subchannel (on timeslot 14) on the first two A-ter
links1 that is dedicated to the Qmux protocol (Transmission equipment supervision).
The three other subchannels are used for TCH.
1 The involved links are A-ter links N 1, 2, 7, 8, 13 & 14.
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In addition, timeslots are reserved for transport of signalling
One timeslot per A-ter link for transport of SS7, generally on timeslot 16.
On A-ter PS, one GSL may be configured. It is then transported on timeslot 28.
7.4 Minimum number of A-ter links
The minimum number of A-ter links connected to a BSS is 2.
7.5 Number of SS7 channels
The number of SS7 64 kb/s channels required depends on the traffic mix.
There is a maximum of one SS7 64 kb/s channel par A-ter link.
In total, there may be up to 16 SS7 channels per BSS.
- With the Alcatel traffic mix presented in Annex 1, it is recommended to have one SS7
channel per A-ter link.
- With a different traffic mix than the one presented in Annex 1, with a mean call duration higher
than 80 seconds, the rule is the following:
The recommended number of SS7 links is: 1 + 0.5 x N, where N is the total number of
A-ter interfaces.
7.6 Number of GSL channels
Each GPU requires at least one GSL channel.
There can be 0 or 1 GSL per A-ter link.
The number of GSL channels depends on the traffic. The different parameters to calculate it are
given in document [10].
For security reason it is recommended to have 2 GSL channels per GPU.
7.7 A-ter interface configuration rules
On the A-ter interface, from one up to 8 PCM can be connected to each GPU board. Each PCM link
can be dedicated to packet traffic or shared between CS and PS traffic.
For security reasons, the time-slots assigned to PS traffic should be spread among different A-ter
PCMs. However, when there is enough PS traffic to fill 2 or more PCMs, there is an advantage to
dedicate complete PCMs to PS rather than mixing PS with CS traffic. Indeed, doing so avoids
connecting the A9135 MFS to the Transcoder, with A-ter PCMs not fully devoted to circuit-switched
traffic, and thus avoids wasting transcoder resource.
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It is possible to set PS time-slots on all A-ter PCMs; indeed, this can be useful in the case of
configurations with only 2 A-ter PCMs in order to ensure better security.
However, it is recommended not to carry PS traffic on the first A-ter PCM so that it can be connected
directly to the transcoder in order to enable MFS installation without O&M interruption on the BSC.
8. TRANSCODER DIMENSIONING RULES
8.1 Connection to the EVOLIUM G2 TC
Each BSC rack must be connected to only one TC G2 rack. But one TC rack can be connected to
several BSC racks.
(Please refer to the EVOLIUM G2 TC product description [6] for more details.)
8.2 Connection to the A9125 TC
It is possible to connect up to 24 BSCs on one A9125 Compact TC.
At least 2 A-ter links per BSC are required.
It is also possible to connect one BSC to different TC racks.
(Please refer to the A9125 TC product description [7] for more details.)
8.3 Minimum number of A links
The minimum number of A-ter links connected to a BSS is 2.
- If the O&M link to the OMC-R is not conveyed by the A-ter interface, each A-ter link needs to
be connected to a minimum of one A interface link (total 2 A links).
- If the O&M link to the OMC-R is conveyed by the A-ter interface, each A-ter link needs to be
connected to 2 A interface links (total 4 A links).
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9. A9135 MFS DIMENSIONING RULES
9.1 A9135 MFS configurations
The A9135 MFS can accommodate from 1 to 2 telecommunication sub-racks.
One GPU board per sub-rack is always dedicated to the n+1 redundancy feature.
MFS based on DS10 systems :
From the B8 release onwards, the MFS based on DS10 systems can house up to 32 GPU boards.
Hence each A9135 MFS sub-rack can include up to 15 GPU boards plus 1 GPU board for
redundancy. The granularity is 1 GPU board.
MFS based on AS800 systems :
The MFS based on AS800 systems can house up to 24 GPU boards.
Hence each A9135 MFS sub-rack can include up to 11 GPU boards plus 1 GPU board for
redundancy. The granularity is 1 GPU board.
Each GPU board is connected to only one BSC.
But one BSC can be connected to several GPU (up to 6 from B7 Release onwards), depending on
packet traffic. These GPUs can belong to different MFS subracks.
All the BSCs connected to a given MFS must be connected to the same OMC-R as the MFS.
There can be more than one A9135 MFS per MSC, and one A9135 MFS can be connected to BSCsof several MSCs.
One MFS can be connected to several SGSN units. One GPU is connected to only one SGSN.
One A9135 MFS can control up to 22 BSCs.
One MFS can manage up to 2000 cells.
The maximum number of cell adjacencies handled by the MFS is 40000.
9.2 GPU capacity
One GPU board can support up to 16 external links (A-ter + Gb).
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GPRS PDCH
Max CS Max nb of PDCH per GPUCS2 240
CS3 220CS4 204
EDGE PDCH
Max EGPRS MCS Max nb of PDCH per GPUMCS 2 228MCS 3 212MCS 4 200MCS 5 180MCS 6 172
MCS 7 140MCS 8 116MCS 9 108
10. GB INTERFACE
The links between the A9135 MFS and the SGSN or between the MSC and the SGSN can be direct
point to point physical connections or an intermediate Frame Relay Network can be traversed.
The maximum number of links from one GPU board to the SGSN is 8.
10.1 Configuration rules
There are 2 ways to connect the MFS and the SGSN via the Gb interface:
- Through the Transcoder and the MSC.
- Bypassing the Transcoder and going either directly to the SGSN (through the MSC or not).
This is the recommended solution when the traffic is sufficient to justify A-ter PCMs completely
devoted to GPRS traffic. However, depending on the hardware and software versions, this is
not always possible, because of the GPU synchronisation issues1.
The figure below displays the different types of links between the MFS and the SGSN.
1 For synchronisation issues, please refer to the A9135 MFS product description [4].
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BTS
BTS
BTS
BSC
MFS
TC
SGSN
MSC FRDN
A bis A ter A ter A
FrameRelay
Data
Network
BTS
BTS
BTS
BSC
MFS
TC
SGSN
MSC FRDN
A bis A ter A ter A
FrameRelay
Data
Network
Remarks:
- The links going through the MSC can benefit from the multiplexing capability of the MSC in
order to reduce the number of ports required to the frame relay network towards the SGSN.
10.2 General dimensioning rules
The peak throughput of the Gb interface is equal to the peak LLC throughput multiplied by an
overhead factor which takes into account the Gb interface overheads.
- This overhead factor depends on the mean frame size.
- The maximum number of Frame Relay bearer channels is 120 per GPU board (theoretical
value). It is however interesting to reduce the number of bearer channels to 2 (for redundancy
reason) in order to take benefit from the statistical effect of using larger bearer channels.
For more information on the method to determine the Gb peak throughput according to the traffic mix
expected within the BSC area and the Gb interface overheads, please refer to [10].
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11. ANNEX 1: STANDARD TRAFFIC MODEL
For comparison reasons, the following models are standardized with: BHCA = MOC + MTC = 1
BHCA : Busy Hour Call Attempt
MOC : Mobile Originating CallMTC : Mobile Terminating Call
Events No. of Occurrences per
Call Attempt
Mean holding time (s)
on DTCA (ie A interface) SDCCH (s) TCH (s) SCCP (s)
Mean call duration 4s 50s 54s
Internal Handover 2 - -
External Handover 1 - 4s
Location Update 3 3s 3s
IMSI Attach 0.50 3s 3s
IMSI Detach 0.50 3s 3s
Originating SMS (PtP) 0.3 3s 3s
Terminating SMS (PtP) 0.7 3s 3s
Paging (as occurred in
the A-ter itf )
70 per second
Location request 0,1 (1)
- The G2-BSC can handle different call mixes. If a Customers traffic mix is significantly different
from the above Standard Traffic Model, Alcatel is prepared to study the possibility for the G2-
BSC to cope with it.
- For the largest BSC configuration (BSC G2 FOR 448 TRX-FR; 72A, 84A-BIS-ITF), used at a
capacity of 1900 Erlangs, the above traffic mix corresponds to:
- Total BHCA (=MOC+ MTC) : 136 800 per hour
- Total Handovers : 410 400 per hour
- Total SMS : 136 800 per hour
- Total Pagings : 252 000 per hour
- (1): SDCCH holding time depends on the mix of LCS positioning method.
- Performances versus traffic mix are committed upon BSC load test completion.
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12. ANNEX 2: A-BIS INTERFACE CONFIGURATION
12.1 Number of time-slots required with the different Signaling Multiplexing
schemes
The table below gives the number of 64 kb/s time-slots required with the different Signaling
Multiplexing schemes. The BTS is assumed to have n TRXs in total all working in Full-Rate mode,
and we shall use the notation roundup(x) when a value x is to be rounded up to the next higher
integer. For G2 sectored BTS, we shall note i, j and k the number of TRXs in sector 1,2,and 3.
WithoutSignalingMultiplexing
Static-SignalingMultiplexing
Statistical-SignalingMultiplexing-64k
Statistical-SignalingMultiplexing-16k
Trafic (n TRX) 2n (2 per TRX) 2n (2 per TRX) 2n (2 per TRX) 2n (2 per TRX)
OML if EVOLIUM BTS 1 per BTS 1 per BTS 0 0
OML if non EVOLIUM BTS(previous generation)
1 per Sector 1 per Sector Not applicable Not applicable
RSL if EVOLIUM BTS 1 per TRX Roundup (n/4) Roundup ( n/4)or Roundup(n/2)(*)
0
RSL if non EVOLIUM BTS( G2-BTS)
1 per TRX Roundup(i/4)+Roundup(j/4)+Roundup(k/4)
Not applicable Not applicable
Number of A-bis time-slots required according to the different Signaling Multiplexing schemes
(*) Depends on signalling load: 4 for normal signalling load, 2 for high signalling load.
12.2 Typical cases where Signaling Multiplexing is very advantageous
- With Static Multiplexing, a sectored site with 3 x G2 BTS having 4 TRXs requires:
3x[ 1+ 4x2+ roundup ( 4 / 4 )] = 30 time-slots . Hence, it is possible to connect this site
with only one A-bis PCM (except if Closed Loop with TS0 transparency)
- With Statistical Multiplexing 64k, one EVOLIUM A9100 BTS having 3x4 TRXs requires
Normal signaling load:3x4x2 + roundup ( 3x4/4 ) = 27 time-slots.
(However under High Signaling load, 30 A-bis TS remain needed)
3x4x2 + roundup ( 3x4/2 ) = 30 time-slots.
- With Statistical Multiplexing 64k, one EVOLIUM BTS A9100 having 3x2 TRXs requires:
Normal signaling load:
3x2x2 + roundup ( 3x2/4 ) = 14 time-slots.
High signaling load:
3x2x2 + roundup ( 3x2/2 ) = 15 time-slots.
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Hence, it is possible to connect 2 such sites with only one A-bis PCM.
- With Statistical Multiplexing 16k, one EVOLIUM Micro-BTS A9110 with 2 TRX in full Rate
mode requires:
2x2 = 4 time-slots. Hence, it is possible to connect 7 of such BTSs with only one A-bis
PCM.
- With Statistical Multiplexing 16k, one EVOLIUM BTS A9100 with 3x1 TRX requires:
3x2 = 6 time-slots. Hence, it is possible to connect 5 such sites with only one A-bis PCM
(if open chain or closed loop with TS0 usage).
- With Statistical Multiplexing 16k, one EVOLIUM BTS A9100 with 3x2 TRXs in full-rate mode
offering CS3/CS4 and EDGE thanks to one TRX Class 4 per sector requires:
3 x (1x2 + 4x2) = 30 time-slots. Hence it is possible to connect 1 such site with only one
A-bis PCM link.
End of Document
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