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






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







6.2.2.2 When all TRX are configured in Dual Rate mode

BSC G2 EQUIPMENT max. nb. of BTSs max. nb. of Cells







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






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







8 TCH TCH TCH GCH GCH







1516

17 TCH TCH GCH GCH GCH







24 TCH GCH GCH GCH GCH




28 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:


High signaling load:



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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

dimensioning rules b9

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