alcatel gprs edge capacity dimensioning guidelines v1 0

GPRS/EDGE Capacity Dimensioning Guidelines

Alcatel-Lucent Egypt ALU and Mobinil Confidential Page 1 (29)


April 2009

Provided by ALU GPRS Service Team

Mission Name Mobinil GPRS/EDGE Monitoring Service

Date 2 April 2009

Revision 1.0



Content

1. INTRODUCTION ....................................................................................................................................................................3 2. TRX/TCH CAPACITY PLANNING......................................................................................................................................4

2.1 Input data requirements.....................................................................................................................................................4 2.2 Dimensioning Rule ...........................................................................................................................................................4 2.3 Example............................................................................................................................................................................6

3. EXTRA ABIS TIMESLOT DIMENSIONING......................................................................................................................8 3.1 Input Data Requirements ..................................................................................................................................................9 3.2 Dimensioning Rule ...........................................................................................................................................................9 3.3 Example..........................................................................................................................................................................10

4. ATERMUX PS DIMENSIONING........................................................................................................................................12 4.1 Input Data Requirements ................................................................................................................................................14 4.2 Dimensioning Rule .........................................................................................................................................................14 4.3 Example..........................................................................................................................................................................15

5. GPU DIMENSIONING..........................................................................................................................................................18 5.1 Input Data Requirements ................................................................................................................................................18 5.2 Dimensioning Rule .........................................................................................................................................................18 5.3 Example..........................................................................................................................................................................19

6. GB DIMENSIONING ............................................................................................................................................................21 6.1 Gb Configuration............................................................................................................................................................21 6.2 Input Data Requirements ................................................................................................................................................22 6.3 Dimensioning Rule .........................................................................................................................................................22 6.4 Example..........................................................................................................................................................................24

7. GPRS SIGNALING LINK.....................................................................................................................................................26 7.1 Input Data Requirements ................................................................................................................................................26 7.2 GSL Dimensioning Rule.................................................................................................................................................27 7.3 Example..........................................................................................................................................................................27

8. CONCLUSION .......................................................................................................................................................................29



1. INTRODUCTION

The objective of this document is to guidelines on GPRS/EDGE capacity audit and dimensioning point of view in Alcatel-Lucent system to Mobinil capacity planning team during GPRS/EDGE monitoring service program. This document included main items are:

1. TRX/TCH capacity planning 2. Extra Abis timeslot dimensioning 3. Atermux PS dimensioning 4. GPU dimensioning 5. Gb capacity dimensioning 6. GPRS signaling link dimensioning



2. TRX/TCH CAPACITY PLANNING

The objective of this topic is for understanding how to calculating and planning TCH capacity to support GPRS cell priority concept and GSM cells as well. The target of TCH capacity planning is for balancing TRX resource between CS traffic (GSM) and PS traffic (GPRS/EDGE) sharing.

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

TRX#1 BCCH SDCCH TCH TCH TCH TCH TCH TCH

TRX#2 SDCCH TCH TCH TCH TCH TCH TCH TCH

TCH channel can use for PDCH to carried PS traffic. However, some parameters needed to check to make sure that which cells can use for GPRS are:

- EN_GPRS = enabled - TRX_PREF_MARK = 0

Input data requirements 2.1

2.2

Input data requirement is available in Alcatel-Lucent RNO tool are:

- TCH traffic BH o RTCH_Erlang_total (TCTRE) in GPRS BH for PS capacity planning o RTCH_Erlang_total (TCTRE) in GSM BH for CS capacity planning

- Number of TCH timeslots - Number of TRX - MIN_PDCH - MAX_PDCH_HIGH_LOAD - MAX_PDCH

Dimensioning Rule

Normally in GSM TCH capacity calculation as: TCH Timeslots = (TRX x 8) BCCH TS SDCCH TS [2.1]

TCH Capacity (Erl) = Erlang B (TCH Timeslots) [2.2]



However, now 2G network is always included with GPRS network also. So for TCH capacity calculation is a little difference from previous equation [2.2]. For TCH capacity calculation to support also for PS traffic needed to take number of PDCH need to reserve for PS traffic to consider for this calculation. So, will change to: TCH Capacity in PS BH = Erlang B (TCH timeslots PDCH reserve for PS traffic) [2.3] Number PDCH reserve for PS traffic setting is depends on Operator define. For this case high GPRS priority cells can take MAX_PDCH_HIGH_LOAD for calculation. So, finally TCH capacity is (from equation [2.2]): TCH Capacity (Erl) = Erlang B (TCH timeslots MAX_PDCH_HIGH_LOAD) [2.4]

%TCH Utilisation = (TCH Traffic BH / TCH Capacity) x 100% [2.5] TCH TS Needed = Inverse Erlang B (TCH Traffic BH) [2.6] Note

- If %utilisation more than 80% of the capacity, so TCH capacity expansion is required such as TRX upgrading, feature activating (HR, Directed Retry, Fast Traffic HO and ) and balance traffic loading (antenna tilt and or parameters tuning).

- Use average TCH traffic busy hour at least 3 days average data. - %TCH assignment congestion needed use for consideration. - Erlang B table is use at GoS 2%. - For MAX_PDCH_HIGH_LOAD is the number of PDCH that guarantee to reserve for PS

traffic for cell having PS traffic during high CS loading situation. Table below is parameters setting for difference GPRS/EDGE cell categories.

GPRS/EDGE Cell Categories PS TRX MAX_PDCH

MAX_PDCH_HIGH_LOAD MIN_PDCH

VIP 3 12 4 2Golden 2 8 3 2Silver 2 8 2 1

Bronze 1 4 2 1



2.3 Example

Please do calculating TCH capacity planning for cells (high GPRS priority) below:

- QARON-PETROLEUM_G_S4_64430_1_S o Configuration is 2 TRX, HR enabled, 1 BCCH TS, 1 SDCCH TS o MAX_PDCH_HIGH_LOAD is 2 o Average TCH traffic at GPRS BH is 18.3 Erlang

- SS-NUWEIBA-NTH_G_S3_60427_1_N

o Configuration is 4 TRX, HR enabled, 1 BCCH TS, 2 SDCCH TS o MAX_PDCH_HIGH_LOAD is 2 o Average TCH traffic at GPRS BH is 16.1 Erlang

- SZ-SALAM-CTY_D_S6_57641_2_S

o Configuration is 4 TRX, 1 BCCH TS, 5 SDCCH TS o MAX_PDCH_HIGH_LOAD is 2 o Average TCH traffic at GPRS BH is 11.4 Erlang

Calculation: For QARON-PETROLEUM_G_S4_64430_1_S; TCH TS = (TRX x 8) BCCH TS SDCCH TS MAX_PDCH_HIGH_LOAD = (2 x 8) -1 - 1 - 2 = 12 timeslots TCH Capacity = Erlang B (TCH TS) = Erlang B (12 x 1.5); using 1.5 times to TCH TS for HR feature = Erlang B (18) = 11.49 Erlang %TCH Utilisation = (TCH Traffic BH / TCH Capacity) x 100% = (18.3 / 11.49) x 100% = 159.3%

TCH TS Needed = Inverse Erlang B (TCH Traffic BH) = Inverse Erlang B (18.3) = 26 FR TS or 17 HR TS So, this cell required additional 1 TRX with HR activation

For SS-NUWEIBA-NTH_G_S3_60427_1_N;

TCH TS = (TRX x 8) BCCH TS SDCCH TS MAX_PDCH_HIGH_LOAD = (4 x 8) -1 - 2 - 2 = 27 timeslots TCH Capacity = Erlang B (TCH TS) = Erlang B (27 x 1.5); using 1.5 times to TCH TS for HR feature = Erlang B (40) = 31.0 Erlang



%TCH Utilisation = (TCH Traffic BH / TCH Capacity) x 100% = (16.1 / 31.0) x 100% = 51.9%

TCH TS Needed = Inverse Erlang B (TCH Traffic BH) = Inverse Erlang B (16.1) = 24 FR TS or 16 HR TS So, this cell not require for expansion.

For SZ-SALAM-CTY_D_S6_57641_2_S;

TCH TS = (TRX x 8) BCCH TS SDCCH TS MAX_PDCH_HIGH_LOAD = (4 x 8) -1 - 5 - 2 = 24 timeslots TCH Capacity = Erlang B (TCH TS) = Erlang B (24) = 16.63 Erlang %TCH Utilisation = (TCH Traffic BH / TCH Capacity) x 100% = (11.4 / 16.63) x 100% = 68.6%

TCH TS Needed = Inverse Erlang B (TCH Traffic BH) = Inverse Erlang B (11.4) = 18 TS So, this cell not require for expansion.



3. EXTRA ABIS TIMESLOT DIMENSIONING

Dynamic Abis is new feature in B9 to reduce Abis resource and can share between sectors in same BTS. There are: Extra Abis Nibbles Extra Abis nibbles are shared at BTS level. They can be shared among all the TREs of the BTS to which they have been associated (by the OMC and the BSC). Bonus Abis nibbles (whose RTSs are currently used for BCCH or static SDCCH channels in the BTS). Bonus Abis nibbles are shared at BTS level, as for extra Abis nibbles. They can be shared among all the TREs of the BTS. The dynamic SDCCH channel supports TCH traffic. So, the corresponding basic Abis nibble cannot be used for PS traffic. Basic Abis Nibbles Basic Abis nibbles are mapped to an RTS currently available for PS traffic or mapped to an RTS currently used as an MPDCH. Basic Abis nibbles are shared at the level of the BTS sector. They can be shared among all the TREs of a same BTS sector (i.e., the BTS sector in which the basic Abis nibbles were initially mapped on an RTS).



Table below show coding scheme and GCHs needed for each scheme.

System Scheme Modulation Maximum data rate per timeslot (Kbit/s)Nbr of GCH

neededCS-1 GMSK 8 0.73CS-2 GMSK 12 1.00CS-3 GMSK 14.4 1.25CS-4 GMSK 20 1.64

MCS-1 GMSK 8.8 0.89MCS-2 GMSK 11.2 1.00MCS-3 GMSK 14.8 1.33MCS-4 GMSK 17.6 1.50MCS-5 8PSK 22.4 1.86MCS-6 8PSK 29.6 2.86MCS-7 8PSK 44.8 3.49MCS-8 8PSK 54.4 4.14MCS-9 8PSK 59.2 4.49

GPRS

EGPRS

3.1

3.2

Input Data Requirements

- Parameters setting o EN_GPRS o EN_EGPRS o MAX_GPRS_CS o MAX_EGPRS_MCS

- Number of sectors per BTS - Number of bonus Abis nibbles (BCCH + Static SDCCH) - Number of PDCH assumption per cell (basic Abis nibbles) - Current extra Abis timeslots

Dimensioning Rule

GCH Requirement = Number of GCH needed x Number of PDCH assumption [3.1] GCH Total = Sum of GCH Requirement for all sector in the BTS [3.2]

Extra Abis nibbles = GCH Total - Basic Abis nibbles - Bonus Abis nibbles [3.3] Extra Abis TS = Extra Abis nibbles / 4 [3.4]



Note that for sharing factor of bonus and Abis nibbles will consider to take in to account. But for the value is depends on Operator setting and consideration but should not more than 60% sharing. Table below is sharing factor assumption that summary for this Extra Abis TS dimensioning. However, this factor depends on Operator preferred, but should not less than 0.4.

#Sector per BTS Factor1 1.02 0.63 0.54 0.45 0.46 0.4

050500

3.3 Example

Please do Extra Abis timeslots planning for new GPRS/EDGE sites as follow:

- Site A; 3 sectors o A_1: EDGE enabled, MAX_EGPRS_MCS = MCS-9, 2 SDCCH o A_2: EDGE enabled, MAX_EGPRS_MCS = MCS-9, 2 SDCCH o A_3: EDGE enabled, MAX_EGPRS_MCS = MCS-9, 2 SDCCH

- Site B; 3 sectors

o B_1: EDGE enabled, MAX_EGPRS_MCS = MCS-9, 4 SDCCH o B_2: EDGE enabled, MAX_EGPRS_MCS = MCS-6, 2 SDCCH o B_3: EDGE disable, MAX_GPRS_CS = MCS-4, 1 SDCCH

- Site C; 2 sectors

o C_1: EDGE enabled, MAX_EGPRS_MCS = MCS-9, 1 SDCCH o C_2: EDGE enabled, MAX_EGPRS_MCS = MCS-9, 1 SDCCH

Special team: all cells enabled GPRS and number of PDCH assumption is 4. Calculation: For site A;

GCH Total = GCH needed x PDCH assumption (for A_1 + A_2 + A_3) = (4.49 x 4) + (4.49 x 4) + (4.49 x 4) = 17.96 + 17.96 + 17.96 = 53.88 54 GCHs



Extra Abis nibbles = GCH Total - Basic Abis nibbles - Bonus Abis nibbles = 54 (4 + 4 + 4) (2 + 2 + 2) = 36 nibbles Extra Abis TS = Extra Abis nibbles / 4 = 36 / 4 = 9 Timeslots (64 Kbit/s TS) Sharing factor consider for calculation to reduce number of Extra Abis TS. So that, Extra Abis TS = (Extra Abis nibbles x Sharing Factor) / 4 [3.5] = (36 x 0.5) / 4 = 4.5 5 Timeslots (64 Kbit/s TS) For site B;

GCH Total = GCH needed x PDCH assumption (for B_1 + B_2 + B_3) = (4.49 x 4) + (2.86 x 4) + (1.64 x 4) = 17.96 + 11.44 + 6.56 = 35.96 36 GCHs

Extra Abis nibbles = GCH Total - Basic Abis nibbles - Bonus Abis nibbles = 36 (4 + 4 + 4) (4 + 2 + 1) = 17 nibbles

Extra Abis TS = (Extra Abis nibbles x Sharing Factor) / 4 = (17 x 0.5) / 4 = 8.5 3 Timeslots (64 Kbit/s TS) For site C;

GCH Total = GCH needed x PDCH assumption (for C_1 + C_2) = (4.49 x 4) + (2.86 x 4) = 17.96 + 11.43 = 35.96 36 GCHs

Extra Abis nibbles = GCH Total - Basic Abis nibbles - Bonus Abis nibbles = 36 (4 + 4 + 4) (4 + 2 + 1) = 17 nibbles

Extra Abis TS = (Extra Abis nibbles x Sharing Factor) / 4 = (17 x 0.5) / 4 = 8.5 3 Timeslots (64 Kbit/s TS) However, sharing factor depends on Operator prefer to use or not. You can calculate without this factor and will get bigger extra Abis timeslots. Without factor will be good to support throughput for user but it will impact to BSC capacity by increasing Abis capacity.



4. ATERMUX PS DIMENSIONING

The Atermux interface is a set of 2 Mbit/s PCM links, i.e. a PCM is made of 32 timeslots of 64 Kbit/s carrying either only PS traffic or a mix of PS traffic and CS traffic. The CS timeslots are made up of:

- Speech timeslots composed of 4 speech nibbles at 16 Kbit/s. A speech nibble carried the voice for a transaction or data in circuit mode. A speech nibble is also called CIC. Four 16 Kbit/s nibbles from 64 Kbit/s timeslot of the PCM link.

- Speech signaling N7. - Other specific O&M timeslots not related to speech (X25, Qmux, Alarm octet).

The PS timeslots on the Atermux contain:

- The timeslots devoted to the transport of PS data composed of 4 PS nibbles at 16 Kbit/s. A PS nibble on the Atermux is called GIC. The content of the GIC is called GCH. Four of 16 Kbit/s nibbles from a 64 Kbit/s timeslot of the PCM link.

- The PS LapD link at 64 Kbit/s supports the signaling channel. There is one LapD link per Atermux PCM. The signaling channel shares the traffic over LapD links. The content of a GPRS signaling channel is called GSL.

Pictures below are show Atermux configuration and mapping.



4.1 Input Data Requirements

- Number of Atermux PS links dedicated per GPU/BSC - Number of GCH capacity per GPU/BSC (taken for RNO)

o GPRS_GPU_GCH_available (AAGCHAVN) - GCH transmission busy time (use calculating for GCH traffic) in GPRS busy hour

o GPRS_transmission_GCH_busy_time (AAGCHUST) - Erlang C table (use at 0.1% blocking probability and delay time is 0 sec)

Table below is summary of Erlang C table use for Atermux dimensioning.

Atermux PS Link Dedicated

GCH Available GSL Link

Capacity in Erlang

0.25 28 1 15.180.50 56 1 37.460.75 84 1 61.271.00 112 1 85.851.00 116 1 89.401.25 140 1 110.901.50 168 1 136.301.75 196 1 161.942.00 224 2 187.782.00 228 1 191.492.25 253 2 214.712.50 282 2 241.792.75 311 2 268.983.00 340 2 296.263.25 369 2 323.643.50 398 2 351.103.75 427 2 378.624.00 456 2 406.20

4.2 Dimensioning Rule

GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 [4.1] Atermux GCH Capacity = Erlang C (GCH Available) [4.2] %Atermux Utilisation = (GCH Traffic Load / Atermux GCH Capacity) x 100% [4.3]



For future plan of Atermux capacity, 15% is considered to add for traffic growth after expansion.

Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin [4.4] GCH Required = Inverse Erlang C (Required GCH Traffic) [4.5]

Required Atermux link = GCH Required / 112 [4.6]

4.3 Example

Please do analysis Atermux utilisation and dimensioning follow as data:

- RODA_1 o Current configuration: 1 Atermux PS dedicated o GCH available (AAGCHAVN) = 112 GCHs o transmission GCH busy time BH (AAGCHUST_BH) = 325,471 sec

- MAADI_5

o Current configuration: 1 Atermux PS dedicated o GCH available (AAGCHAVN) = 112 GCHs o transmission GCH busy time BH (AAGCHUST_BH) = 331,532 sec

- CAIRO16


- SOHAG_1


Calculation: For RODA_1; GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 = 325,471 / 3600 = 90.41 Erlang Atermux GCH Capacity = Erlang C (GCH Available) = Erlang C (112) = 85.85 Erlang Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin = 90.41 + (90.41 x 15) / 100 = 103.97 Erlang



GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (103.97) = 133 GCHs %Atermux Utilisation = (GCH Traffic Load / Atermux GCH Capacity) x 100% = (90.41 / 85.85) x 100% = 105.31%

Required Atermux link = GCH Required / 112

= 133 / 112 = 1.19 2 Atemux Links So, for RODA_1 additional 1 Atermux link is required. For MAADI_5;

GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 = 331,532 / 3600 = 92.09 Erlang Atermux GCH Capacity = Erlang C (GCH Available) = Erlang C (112) = 85.85 Erlang Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin = 92.09 + (92.09 x 15) / 100 = 105.91 Erlang GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (105.91) = 135 GCHs %Atermux Utilisation = (GCH Traffic Load / Atermux GCH Capacity) x 100% = (92.09 / 85.85) x 100% = 107.28% Required Atermux link = GCH Required / 112 = 135 / 112 = 1.21 2 Atemux Links So, for MAADI_5 additional 1 Atermux link is required. For CAIRO16;

GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 = 221,741 / 3600 = 61.59 Erlang Atermux GCH Capacity = Erlang C (GCH Available) = Erlang C (112) = 85.85 Erlang Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin = 61.59 + (61.59 x 15) / 100 = 70.83 Erlang



GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (70.83) = 95 GCHs %Atermux Utilisation = (GCH Traffic Load / Atermux GCH Capacity) x 100% = (61.59 / 85.85) x 100% = 71.75% Required Atermux link = GCH Required / 112 = 95 / 112 = 0.85 1 Atemux Links For CAIRO16 not require for Atermux expansion. But if consider about %Atermux utilisation that CAIRO16 has 71.75% if set %utilisation at 70% for expansion. So, this case Atermux expansion is required. For SOHAG_1;

GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 = 331,532 / 3600 = 92.09 Erlang Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin = 92.09 + (92.09 x 15) / 100 = 105.91 Erlang GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (105.91) = 135 GCHs GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (58.83) = 82 GCHs %Atermux Utilisation = (GCH Traffic Load / Atermux GCH Capacity) x 100% = (51.16 / 89.40) x 100% = 57.22% Required Atermux link = GCH Required / 112 = 82 / 112 = 0.73 1 Atemux Links So, for SOHAG_1 no require to expansion.



5. GPU DIMENSIONING

GPU stand for GPRS Processing Unit. The GPU supports the Packet Control Unit (PCU), as defined by GSM. The PCU handles Gb-related functions, Radio Resource Allocation functions and protocol exchanges with the Mobile Stations. Each GPU consists of 4 DSPs, which are in charge of the RLC/MAC functions as well as the EGCH protocol exchanges with the BTSs. Each DSP supports 120 GCH but the GPU should handle less than 480 (120 GCHs x 4 DSPs) GCH to avoid blocking the DSP. 5 Atermux are needed to support 480 GCHs. However, Alcatel-Lucent recommend to dimensioning maximum 4 Atermux per GPU. A GPU board is linked to one BSC. There are a maximum of 16 PCM links (Atermux & Gb) per GPU board.

5.1

5.2


- Current number of GPU per BSC - GCH transmission busy time (use calculating for GCH traffic) in GPRS busy hour

o GPRS_transmission_GCH_busy_time (AAGCHUST) - Erlang C table (use at 0.1% blocking probability and delay time is 0 sec)

Dimensioning Rule

For calculation of GPU dimensioning is similar to Atermux and many input data requirement is same. So, normally we will do calculation and dimensioning together with Atermux.

GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 [4.1]



Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin [4.4] GCH Required = Inverse Erlang C (Required GCH Traffic) [4.5]

Required Atermux Link = GCH Required / 112 [4.6] GPU Capacity (Erl) = Erlang C (480) = 429.07 Erlang [5.1] %GPU Utilisation = (GCH Traffic Load / GPU Capacity) x 100% [5.2] %GPU GCH Loading = (GCH Required / Total GCH Capacity) x 100% [5.3] Required GPU = Required Atermux Link / 4 [5.4]

5.3 Example

Please analyse and dimensioning GPU as per information below:

- RODA_1 o Current configuration: 1 GPU per BSC o transmission GCH busy time BH (AAGCHUST_BH) = 325,471 sec

- MAADI_5

o Current configuration: 1 GPU per BSC o transmission GCH busy time BH (AAGCHUST_BH) = 331,532 sec

Calculation: For RODA_1; GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 = 325,471 / 3600 = 90.41 Erlang Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin = 90.41 + (90.41 x 15) / 100 = 103.97 Erlang GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (103.97) = 133 GCHs

Required Atermux link = GCH Required / 112 = 133 / 112 = 1.19 2 Atemux Links %GPU Utilisation = (GCH Traffic Load / GPU Capacity) x 100% = (90.41 / 429.07) x 100% = 21.07%



%GPU GCH Loading = (GCH Required / Total GCH Capacity) x 100% = (133 / 480) x 100% = 27.71% Required GPU = Required Atermux Link / 4 = 2 / 4 = 0.5 1 GPU So, for RODA_1 no need GPU additional. For MAADI_5;

GCH Traffic Load (Erl) = GPRS_transmission_GCH_busy_time (sec) / 3600 = 331,532 / 3600 = 92.09 Erlang Required GCH Traffic (Erl) = GCH Traffic Load (Erl) + 15% margin = 92.09 + (92.09 x 15) / 100 = 105.91 Erlang GCH Required = Inverse Erlang C (Required GCH Traffic) = Inverse Erlang C (105.91) = 135 GCHs

Required Atermux link = GCH Required / 112

= 135 / 112 = 1.21 2 Atemux Links %GPU Utilisation = (GCH Traffic Load / GPU Capacity) x 100% = (92.09 / 429.07) x 100% = 21.46% %GPU GCH Loading = (GCH Required / Total GCH Capacity) x 100% = (135 / 480) x 100% = 28.13% Required GPU = Required Atermux Link / 4 = 2 / 4 = 0.5 1 GPU So, for MAADI_5 no need GPU additional.



6. GB DIMENSIONING

The Gb interface connects between the MFS and the SGSN or between the MSC and the SGSN, in order to exchange the PS signaling and traffic data. The Gb interface is based on Frame Relay protocol, whether or not an actual Frame Relay network is set. On the physical layer, the Gb interface is supported by 2 Mbit/s PCM links of 32 TS at 64 Kbit/s.

Gb Configuration 6.1

There are 3 possible ways to connect the MFS and the SGSN via the Gb interface:

Through a Frame Relay network Direct MFS-SGSN connections: this is the most chosen case of Gb connections. Through NSS transmission network

The figure below displays the different types of Gb connections between the MFS and the SGSN.

The maximum number of E1 links handled by a GPU/GP board is 16. These links have to be shared between Atermux and Gb interfaces.



The maximum number of Gb links from one GPU/GP board to the SGSN is 8. The minimum number of Gb links from one GPU/GP board to the SGSN is 2. At least 2 Gb links per GPU/GP is recommended for security reason.

6.2

6.3


- Number of Gb timeslot per GPU - LLC data traffic (Kbytes) minimum 3 days data on GPRS busy hour

o GPRS_DL_LLC_bytes (TGBVCDLN) for LLC traffic on DL o GPRS_UL_LLC_bytes (TGBVCULN) for LLC traffic on UL

- Erlang C table (use at 0.1% blocking probability and delay time is 0 sec)

However, for %blocking probability is Erlang C table is depends on Operator accepted %blocking probability in the Gb interface. It is possible to take this value from 0.1% to 2.0%.

Dimensioning Rule

The target is to estimate the number of Gb timeslot for each Gb link. There are:

Gb Traffic (Erl) = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / 28,800 [6.1] Note 1 Erlang = [Gb TS speed (64Kbits/s) x 3600] / 8 = 28,800 KB

Required Gb Traffic (Erl) = Gb traffic + 15% margin [6.2] Note a 15% margin is added to the required traffic Gb TS per link = Inverse Erlang C (Required Gb Traffic) [6.3] %Gb Loading = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / Gb Capacity [6.4] Note Gb capacity is number of Gb timeslot multiply by 64 Kbit/s in 1 hour Gb Capacity = Gb TS x 64 x 3600 [6.5]



The other input is Grade of Service (GoS), which is defined by %Quintile of x delay second (pGb). Since the MFS always tries to assign TBFs as soon as the request is received, we usually dimension for 0 sec delay. Normally GoS should be given or agreed by the Mobile Operator. At high network element level Gb interface, the recommended value is 99.9% quintile of 0 delay sec. Notes:

- Minimum 2 Gb links are required for one GPU/GP due to security reason - Maximum 31 Gb TS (TS no. 1 to 31) can be configured per one Gb link. TS0 cannot be

used as it is reserved for specific usages e.g. frame synchronisation. - In general, around 4 to 8 Gb TS are configured per one Gb link.

Table below is Erlang C table for Gb calculation with difference %blocking probability.

Timeslot 0.10% 0.20% 0.50% 1.00% 2.00% 5.00%0 0.000 0.000 0.000 0.000 0.000 0.0001 0.001 0.002 0.005 0.010 0.020 0.0522 0.045 0.064 0.104 0.152 0.223 0.3813 0.193 0.248 0.349 0.455 0.602 0.8994 0.438 0.534 0.701 0.869 1.092 1.5245 0.762 0.900 1.132 1.360 1.657 2.2186 1.146 1.325 1.622 1.909 2.276 2.9607 1.578 1.798 2.157 2.500 2.935 3.7388 2.051 2.311 2.729 3.127 3.627 4.5439 2.557 2.855 3.332 3.782 4.345 5.37010 3.092 3.427 3.961 4.461 5.083 6.21511 3.651 4.021 4.610 5.160 5.841 7.07612 4.231 4.636 5.279 5.875 6.615 7.95013 4.830 5.269 5.964 6.607 7.401 8.83514 5.446 5.918 6.662 7.351 8.200 9.72915 6.076 6.582 7.375 8.108 9.009 10.63216 6.721 7.258 8.099 8.875 9.828 11.54317 7.378 7.945 8.834 9.651 10.656 12.46118 8.046 8.643 9.578 10.436 11.491 13.38419 8.724 9.351 10.331 11.230 12.333 14.31420 9.411 10.068 11.091 12.030 13.181 15.24921 10.107 10.792 11.859 12.837 14.036 16.18822 10.812 11.525 12.634 13.651 14.896 17.13223 11.524 12.264 13.416 14.470 15.760 18.07924 12.243 13.011 14.203 15.295 16.630 19.03125 12.969 13.763 14.997 16.124 17.505 19.98526 13.700 14.521 15.795 16.959 18.383 20.94327 14.438 15.285 16.598 17.797 19.265 21.90328 15.182 16.054 17.406 18.640 20.150 22.86729 15.930 16.827 18.218 19.487 21.039 23.83330 16.684 17.606 19.033 20.337 21.931 24.80131 17.442 18.389 19.854 21.190 22.827 25.773



6.4 Example

Please do analysis and dimensioning Gb capacity for BSCs below:

- AGHAKHAN_1 o Current configuration: 5 timeslots per Gb link o GPRS_DL_LLC_bytes (GPRS_BH) = 15,072 KB o GPRS_UL_LLC_bytes (GPRS_BH) = 4,279 KB

- MAADI_5

o Current configuration: 5 timeslots per Gb link o GPRS_DL_LLC_bytes (GPRS_BH) = 11,914 KB o GPRS_UL_LLC_bytes (GPRS_BH) = 3,355 KB

- RODA_1 o Current configuration: 5 timeslots per Gb link o GPRS_DL_LLC_bytes (GPRS_BH) = 8,446 KB o GPRS_UL_LLC_bytes (GPRS_BH) = 80,109 KB

Calculation: For AGHAKHAN_1; Gb Traffic (Erl) = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / 28,800 = Max (15072 , 4279) / 28800 = 15,072 / 28,800 = 0.52 Erlang Required Gb Traffic (Erl) = Gb traffic + 15% margin = 0.52 + (0.52 x 15)/100 = 0.52 + 0.08 = 0.60 Erlang Gb TS per link = Inverse Erlang C (Required Gb Traffic) = Inverse Erlang C (0.60) = 5 timeslots %Gb Loading = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / Gb Capacity

= Max (15072 , 4279) / (5 x 64 x 3600) = 15,072 / 144,000 = 10.47%

So, for AGHAKHAN_1 no need to do Gb expansion. For MAADI_5;

Gb Traffic (Erl) = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / 28,800 = Max (11914 , 3355) / 28800 = 11,914 / 28,800 = 0.42 Erlang



Required Gb Traffic (Erl) = Gb traffic + 15% margin = 0.42 + (0.41 x 15)/100 = 0.42 + 0.06 = 0.48 Erlang Gb TS per link = Inverse Erlang C (Required Gb Traffic) = Inverse Erlang C (0.48) = 5 timeslots %Gb Loading = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / Gb Capacity

= Max (11914 , 3355) / (5 x 64 x 3600) = 11,914 / 144,000 = 8.27%

So, for MAADI_5 no need to do Gb expansion. For RODA_1;

Gb Traffic (Erl) = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / 28,800 = Max (8446 , 80109) / 28800 = 80,109 / 28,800 = 2.78 Erlang Required Gb Traffic (Erl) = Gb traffic + 15% margin = 2.78 + (3.20 x 15)/100 = 2.78 + 0.42 = 3.20 Erlang Gb TS per link = Inverse Erlang C (Required Gb Traffic) = Inverse Erlang C (3.20) = 11 timeslots %Gb Loading = Max (GPRS_DL_LLC_bytes, GPRS_UL_LLC_bytes) / Gb Capacity

= Max (8446 , 80109) / (5 x 64 x 3600) = 80,109 / 144,000 = 55.63%

So, for RODA_1 6 timeslots required to expansion for each Gb link in this GPU. However, before expansion Gb timeslot, need to be sure that Gb link without any degradation or Alarm.



7. GPRS SIGNALING LINK

GPRS signaling link called PS LapD link or GSL is link between BSC and MFS for GPRS signaling.

Note maximum 1 GSL is possible for 1 Atermux PS link (TS28).

7.1 Input Data Requirements

- GPRS_LAPD_DL_traffic_sent_to_BSC (TALAPDLN) at GPRS BH - GPRS_LAPD_UL_traffic_received_from_BSC (TALAPULN) at GPRS BH - Number of Atermux link per GPU - Number of GSL link per GPU - Erlang C table (use at 0.1% blocking probability and delay time is 0 sec)



7.2

7.3

GSL Dimensioning Rule

The target is to estimate the number of Atermux PS link needed per GPU, according to signaling traffic.

GSL Traffic (Erl) = Max (GPRS_LAPD_DL_traffic_sent_to_BSC,

GPRS_LAPD_UL_traffic_received_from_BSC) / 28,800 [7.1]

Note: 1 Erlang = [GSL TS speed (64 Kbit/s) x 3600] / 8 = 28,800 Kbytes GSL capacity is number of GSL x 4 (x16 Kbit/s)

GSL Capacity (Erl) = Erlang C (GSL link) [7.2] GSL Capacity (Erl) = Erlang C (4) = 0.44 Erlang (for 1 GSL) %GSL Loading = (GSL Traffic / GSL Capacity) x 100% [7.3]

Note: GSL load on a given GPU should not exceed 80%

It is recommended to increase the number of GSL per GPU if GSL load is greater than 70%

The number of GSL equals to the number of Atermux link, as only one GSL can be defined per Atermux link. Up to 4 GSLs can be defined per GPU.

At least 2 GSLs are recommended to be defined per GPU due to security reason.

Example

Please analyse GSL loading as per details below: - AGHAKHAN_1

o GPRS_LAPD_DL_traffic_sent_to_BSC = 2,195 KB in GPRS BH o GPRS_LAPD_UL_traffic_received_from_BSC = 1,109 KB in GPRS BH o Current configuration: 1 Atermux link per GPU and 1 GSL per GPU

- BOULAK_3

o GPRS_LAPD_DL_traffic_sent_to_BSC = 3,288 KB in GPRS BH o GPRS_LAPD_UL_traffic_received_from_BSC = 1,806 KB in GPRS BH o Current configuration: 1 Atermux link per GPU and 1 GSL per GPU

- RODA_1 o GPRS_LAPD_DL_traffic_sent_to_BSC = 2,782 KB in GPRS BH



o GPRS_LAPD_UL_traffic_received_from_BSC = 1,204 KB in GPRS BH o Current configuration: 1 Atermux link per GPU and 1 GSL per GPU

Calculation:

For AGHAKHAN_1;

GSL Traffic (Erl) = Max (GPRS_LAPD_DL_traffic_sent_to_BSC,

GPRS_LAPD_UL_traffic_received_from_BSC) / 28,800 = Max (2195 , 1109) / 28800 = 2,195 / 28,800 = 0.08 Erlang %GSL Loading = (GSL Traffic / GSL Capacity) x 100% = (0.08 / 0.44) x 100% = 17.38%

GSL capacity for AGHAKHAN_1 is 0.44 Erlang as details in equation 7.2

So, for AGHAKHAN GSL loading is normal and 1 GSL is enough to handle signaling traffic.

For BOULAK_3;

GSL Traffic (Erl) = Max (GPRS_LAPD_DL_traffic_sent_to_BSC, GPRS_LAPD_UL_traffic_received_from_BSC) / 28,800

= Max (3288 , 1806) / 28800 = 3,288 / 28,800 = 0.11 Erlang %GSL Loading = (GSL Traffic / GSL Capacity) x 100% = (0.11 / 0.44) x 100% = 26.04%

So, for BOULAK_3 GSL loading is normal and 1 GSL is enough to handle signaling traffic.

For RODA_1;

GSL Traffic (Erl) = Max (GPRS_LAPD_DL_traffic_sent_to_BSC, GPRS_LAPD_UL_traffic_received_from_BSC) / 28,800

= Max (2782 , 1204) / 28800 = 2,782 / 28,800 = 0.10 Erlang %GSL Loading = (GSL Traffic / GSL Capacity) x 100% = (0.10 / 0.44) x 100% = 22.03%

So, for RODA_1 GSL loading is normal and 1 GSL is enough to handle signaling traffic.



8. CONCLUSION

For dimensioning point of view, network planner or capacity planner need to consider some additional information such as congestion percentage for last 7 days (at least needed minimum high congestion 3 days continuous with high utilisation) and alarm. Normally, before dimensioning each element in dimensioning part performance must stable without any hardware degradation.

For all traffic or payload data, before using for dimensioning needed to take average data at busy hour for 7 days or at least 3 days data average value.

Finally, for dimensioning criterion and capacity calculation such as %blocking probability in Erlang B or Erlang C, loading and utilisation are depends on Operator defined and acceptable in blocking rate can be happen in the network.

1. INTRODUCTION2. TRX/TCH CAPACITY PLANNING2.1 Input data requirements2.2 Dimensioning Rule2.3 Example

3. EXTRA ABIS TIMESLOT DIMENSIONING3.1 Input Data Requirements3.2 Dimensioning Rule3.3 Example

4. ATERMUX PS DIMENSIONING4.1 Input Data Requirements4.2 Dimensioning Rule4.3 Example

5. GPU DIMENSIONING5.1 Input Data Requirements5.2 Dimensioning Rule5.3 Example

6. GB DIMENSIONING6.1 Gb Configuration6.2 Input Data Requirements6.3 Dimensioning Rule6.4 Example

7. GPRS SIGNALING LINK7.1 Input Data Requirements7.2 GSL Dimensioning Rule7.3 Example

8. CONCLUSION

alcatel gprs edge capacity dimensioning guidelines v1 0

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