2007 strategic bh erlang forecasting methodology rfpl-gsm-0007 v0.2

2007 Strategic BH Erlang Forecasting

Methodology

September 18, 2006 RFPL-GSM-0007 v0.2

Version 0.2


SunCom

2007 Strategic BH Erlang Forecasting Methodology

© 2006 SunCom All Rights reserved.


1100 Cassatt RoadBerwyn, PA 19312


Table of Contents

Preface............................................................................................................................................2Objectives..................................................................................................................................................................................................................2Background................................................................................................................................................................................................................2Target Groups............................................................................................................................................................................................................2Version History..........................................................................................................................................................................................................2Future Improvements.................................................................................................................................................................................................3

FORECAST VERSION SUMMARY........................................................................................................................................................................3

First Forecast - August 15, 2006...............................................................................................................................................................................3

GENERAL...................................................................................................................................................................................................................4

Eight Steps to Forecasting.........................................................................................................................................................................................4Eight Steps in Detail..................................................................................................................................................................................................4

Use, Objectives, Quantities, and Time..................................................................................................................................................................4Model.....................................................................................................................................................................................................................4Information Requirements.....................................................................................................................................................................................4Validation..............................................................................................................................................................................................................5Forecast.................................................................................................................................................................................................................5Implementation......................................................................................................................................................................................................5

Deliverables...............................................................................................................................................................................................................5

COLLABORATION...................................................................................................................................................................................................5

RESOURCES...............................................................................................................................................................................................................5

APPENDICES..............................................................................................................................................................................................................6

The Forecasting Tool.................................................................................................................................................................................................6Physical Assumptions............................................................................................................................................................................................6Utility Columns......................................................................................................................................................................................................7Historical Traffic...................................................................................................................................................................................................7Controls.................................................................................................................................................................................................................7Assumptions...........................................................................................................................................................................................................8

Glossary......................................................................................................................................................................................................................10


Preface

ObjectivesThe purpose of this paper is to document the method we will be using to conduct high level traffic forecasting for 2007. We want the forecast of BH Erlang to be as accurate as possible in order to facilitate decision making pertaining to network growth and budget creation. The forecast is the cornerstone of planning for many other functional areas.

The forecast shall be responsive to the guidance from higher echelons pertaining to the anticipated business climate for 2007: Outcollect, MOU/sub/month, Subscriber Growth.

The forecast shall be responsive to the desired operational results: grade of service (GOS) and hardware utilization.

BackgroundThe base forecast itself is (B10-T11) Busy Hour (BH) Combined Adjusted Erlang as reported in the monthly performance reports generated in Essent Infosource GSM. We have chosen to dimension the network to the performance of the floating busy hour instead of the more conservative approach of dimensioning to peak traffic or the more liberal approach of dimensioning to average traffic.

Combined Adjusted describes the Full Rate Erlang (FR) + Half Rate Erlang (HR)/2 condition. We chose this as it represents the Erlang as seen by the hardware and not the larger Combined Erlang of FR + HR which would result in over dimensioning the Um interface as well as the interfaces and nodes that follow.

Target Groups1. RF Performance and Design Engineers2. Network and RF Planning Engineers3. Sr. RF Managers4. Network Design

Version HistoryMajor changes aside from editorial corrections are summarized below:

Version 0.1: First Draft


Version 0.2: Pre-1st Pass Deliverables for September 21, 2006 added.

Version 1.0: TBD First Forecast – August 15, 2006

Future ImprovementsNo planned changes, however, this document will be revised with each reforecast and scenario performed during the 2007 budget cycle.

Forecast Version Summary

First Forecast - August 15, 2006This forecast is a high level brush over to produce a forecast on which to base tentative planning for 2007 to include GSM Expansions, BSC/TRC Expansions, and Abis DS1 growth. We will use the remaining strategic forecast for 2006: August – December and augment an 18% annual linear growth rate for 2007. The 18% comes from the sole strategic assumptions issued thus far. The conditions given for Domestic are as follows:

Gross Add Penetration

3.02%

Churn 2.70%

Population 14,371,290

Population Growth 1.0%

Beginning Subscribers

812,881

Gross Adds 433,294

Disconnects -286,688

Net Adds 146,607

Ending Subscribers 959,488

Average Subscribers 886,185

% Growth 17.2%

September 18, 2006 2 of 19 RFPL-GSM-0007 v0.2

Average MOU per Sub

1,341

On System MOUs (millions)

14,260.7

There are some known limitations of using this model. In reality not every sector grows and declines at the average rate of the network, in this case 18%. Some sectors grow faster and others grow slower or remain steady in traffic flow. In future forecast, as we refine the assumptions and get more detailed guidance, we will improve the accuracy of the forecast by applying more specific growth rates to each sector.

General

Eight Steps to Forecasting1. Determine the use of the forecast: what objective are we trying to

obtain?2. Select the items of quantities to be forecasted.3. Determine the time horizon of the forecast.4. Select the forecasting model or models.5. Gather the data needed to make the forecast.6. Validate the forecasting model.7. Make the forecast.8. Implement the results.

Eight Steps in Detail

Use, Objectives, Quantities, and TimeAs discussed above the primary objective of this forecast is to project Busy Hour (BH) Erlang Combined Adjusted month over month by sector for 2007. The forecasted BH Erlang drives many other forecasts or derivatives. These include, but are not limited to, voice devices, radios (channel adds), Abis DS0’s, BSC DIPs, TRH, TRC, STP, and MSC.

ModelThere are several qualitative, time series, and causal methods to choose from. Traditionally, we have used trend projections, a time series model, as simple as a linear forecast and sometimes more complicated or even composite forecasts. Composite forecast in this case would be a


weighted application of multiple different forecast models. For example, we may decide to use create a forecast composed of a 50% linear trend projection from historical performance and a 50% strategic growth rate determined for the market. More complicated models are acceptable if the level of accuracy achieved is worth the increased complexity.

The selection of the model depends to a large extent upon the objective of the forecast as well as the assumptions or key drivers available for consideration.

Information RequirementsManagement:

1. Grade of Service assumptions by market. Currently 3%.2. Utilization assumption by market. Currently 95%.3. EDGE deployment strategy or any changes in the number of dedicated

data channels at site.4. Outcollect MOU projected per month by market.5. MOU/SUB per month by market. 6. Subscriber growth per month per market.

RF Engineering

1. List of projected new sites for the period and the sectors that are offloaded by each and to what extent.

2. SDCCH deployment pattern if changed. Currently 2 @ 7th TCH, 3 @ 29th TCH, and 3 @ 53rd TCH.

3. Cell Split triggers per market and FLP% assumptions.4. List of sectors whose historical traffic trend is abnormally high or low

due to creative optimization.

ValidationOnce the model is built and populated, it will be made available to each group for review and comment. The more eyes the better. Excel mistakes are easy to make.

ForecastWith each new course of action received we will run the forecast and produce deliverables. We expect to do the many times through out the budget planning cycle.


ImplementationThis is not really within the scope of this document as it infers that a course of action has been selected.

DeliverablesEach group should compile a template of the information out of the forecast it will need to conduct budget planning.

Current Deliverables in order of creation:

1. TRUs and Voice Devices by sector for Network Planning.2. DS0s by site for Network Planning and Network Design.3. List of sites which trigger cell splits for RF Engineering4. Channel add software and hardware projection for RF Planning.5. List of GSM expansion requirements for RF Planning and Site

Development.

CollaborationDerrick Bray, Nicole Michaels, Orlando Landron, Howard Sears, Allen Russell, Danielle Francis

Resources


Appendices

The Forecasting ToolFor description purposes we will break the tool up into segments for discussion.

Physical Assumptions Sheet = “Forecast”

The sheet “Forecast” is the workhorse of the tool as it is a list of all sectors in the network currently as well as those that are planned to go in service during the forecasted period. The first section of columns in light blue are the physical assumptions which include such things as:

1. Sector and Site ID

2. On Air Status – either On-Air or the date currently projected to be On-Air.

3. GSM Only – 1 = Yes; 0 = No

4. Two Sector Only – 1 = Yes; 0 = No

5. Total Antenna Ports

6. Antenna Ports available to GSM

7. MCPA UDA Shelf Installed (site level condition)

8. MCPA (sector level condition)

9. HCU

10. Site Type (2206, etc.)

11. # of GSM BTSs

12. Total Actual TRUs – As exported from an Infosource System Report for a 24 hour period.

13. Total Planning TRUs – Compensates for the sites coming on air so that the initial channels don’t count as channel adds for the year.

The section looks like the below printscreen:


It is critical to be as accurate in this portion of the tool as possible as the physical assumptions will be key in determining the correct expansions and scopes of work.

Utility ColumnsSheet = “Forecast”

The next section of the tool changes somewhat depending on the current objectives. The section in used mostly for RF Planning to evaluate sectors for expansion. Based on the physical assumptions in the prior section, the Max TRX Capable for each section is hand populated due to the complexity of the configurations we have. The Max TRX Capable is the first purple headed column “U” below. The next column is a simple check to see if the Actual TRX’s from Essent are greater than the max capable which could indicate an incorrect physical assumption. The next 3 columns are Max TRXs forecasted during the period, the month that the max occurs, and max voice devices. In orange the most recent releases are detailed for differentiation for the needs that are triggered in the green columns: review and solution.

Historical TrafficSheet = “Forecast”

In gray we maintain a brief BH Erlang Combined Adjusted history in order to build forecast. Additionally, the information can be


enlightening when evaluating the behavior of individual sectors and determining whether a certain type of forecast works for a given sector.

ControlsSheet = “Controls”

The purpose of this sheet is to have a central location where the most popular variables of a forecast can be changed and a new forecast run simply.

This sheet walks the user through steps that will produce a new forecast:

1. Select GOS.

2. Select # of Primary Dedicated Data Channels.

3. Select # of Dedicate EDGE channels.

4. Provide Outcollect assumptions. This is simply a hyperlink to the area of the workbook where those assumptions are input.

5. Provide MOU/Sub/Month Assumptions. Again, this is only a hyperlink.

6. Provide Subs/Month/Market. Again, this is only a hyperlink.


AssumptionsSheet = “Assumptions”

The first component of this sheet is Outcollect which comes from Intercarrier Services via Finance.

The actual layout of this data depends in part on how we receive the assumptions from above. Generally, we get Outcollect numbers at the network level, not market, by month. So these most be spread out across the markets according to their average % of total Outcollect.

The Home Mou/Sub/Month is similar.

The Total Subscriber numbers.


We use these to formulate strategic growth rates of total MOU per market. Assuming that the % of BH Erlang of Total BH Erlang stays relatively stable, these growth rates are applied to the historical Erlang to produce a forecast or a composite component to a forecast.

GlossaryBCC Base Station Color Code

BCCH Broadcast Control Channel

BSIC Base Station Identity Code

BSC Base Station Controller

B-TCH

BTS Ericsson RBS 200 GSM family member Base Transceiver Stations

CHAP Channel Allocation Profile


DCP In Ericsson network nomenclature the Digital Connection Point (DCP) refers to a time slot on a T1 or the termination point in the BTS for the Abis path.

DIP Digital Path

DS0 Digital Signal Level 0: 64 kbps

DT Data Transcript

DTCP Distance to Cell Border

EDGE Enhanced Data rate for Global Evolution

E-TCH EDGE Traffic Channel also referred to as a EDGE 64k Packet Data Channel (PDCH)

GPRS General Packet Radio Services

GSM Global System for Mobile communications

HSCSD High Speed Circuit Switched Data

ICDM Inter Cell Dependency Matrix

LAPD Link Access Protocol - Channel D (Procedures sometimes inserted instead of Protocol)

MRR Measurement Result Recording

OL Overlay subcell

PDCH Packet Data Channel

RBLT Abis Interface Line Terminal. In Ericsson network nomenclature the RBLT device is a 64 kbps channel on the link between the Base Station Controller (BSC) and Base Transceiver


Station (BTS)

SACCH Slow Associated Control Channel

SCLD Subcell load distribution. SCLD moves traffice between the subcells according to planned traffic load limits in the UL subcell.

SDCCH Stand alone Dedicated Control Channel

T1 Transmission standard, G.703, a 1544 kbit/s PCM link

TA Timing Advance

TCH Traffic Channel

TEMS Ericsson GSM Measurement and System Optimization Tool

TG Transceiver Group

TRU Transceiver Unit

TRX Transceiver

TSC Training Sequence Code

UL Underlay subcell

Um GSM air interface from BTS to MS


2007 strategic bh erlang forecasting methodology rfpl-gsm-0007 v0.2

Documents

forecast of bh erlang

base forecast

forecast version summary

remaining strategic

adjusted erlang

network growth

forecasting tool

high level traffic forecasting