BSSDIM: Dimensioning strategies and rulesBSS DIM Module 03
Module Objectives
At the end of the module, the participant will be able to:
Define the basic dimensioning strategies and rules to be applied in the different BSS interfaces
Identify the specific information needed in planning and dimensioning a network
Know the most important input parameters to be considered
Identify how different features and services have to be taken into account
* BSSDIM-BSS Dimensioning strategies and rules
Content
TCSM & Ater interface
BSS Dimensioning Principles
BSS Dimensioning can be defined as the process of calculating and/or estimating the required equipments, resources and parameters in order to achieve agreed performance targets (in terms of QoS, GoS, KPI) for three main aspects:
Coverage
Quality
Capacity
sector by sector,
while considering different cellular criteria;
* BSSDIM-BSS Dimensioning strategies and rules
BSS Dimensioning Principles
REQUIRED INFORMATION
Available transmission methods
FEATURES & SERVICES INFLUENCE
Approximately doubles voice traffic carrying capacity
Introduction of EDGE air interface
Higher data rates requiring higher transmission capacity
Dynamic Abis feature
DIMENSIONING PROCESS BEGINS AT
* BSSDIM-BSS Dimensioning strategies and rules
Guidelines & Rules
Air interface
Air interface, defined between the MS and BTS, is a scarce resource that has to be carefully dimensioned
Output of dimensioning will be the number of TRXs required to support a given CS + PS traffic fulfilling provided QoS criteria
FACTORS TO BE CONSIDERED IN Air DIMENSIONING
Both CS and PS traffic supported in the network
QoS criteria to be fulfilled in the system (CS blocking, average and minimum PS throughput)
Frequency planning (layer and number of frequencies)
Technology used (GPRS or EGPRS)
Features activated (DTX, DL PC)
Types of mobiles in the system (timeslot capability)
* BSSDIM-BSS Dimensioning strategies and rules
Guidelines & Rules
Abis interface
Abis interface is situated between BSC and BTS, being used for both circuit and packet switched services
Introduction of EDGE traffic implies new requirements in the Abis interface EGPRS Dynamic Abis Pool (EDAP)
Output of dimensioning exercise will be size of EDAP pool, blocking rate and throughput supported
FACTORS TO BE CONSIDERED IN Abis DIMENSIONING
Transmission requirements of (E)GPRS MCS in Abis
Limitations when implementing Abis pool (e.g. max pool size, sharing of EDAP between TRXs, distribution of pools within PCM frames)
Non usage of EDAP in retransmissions
Dimensioning shall be based both in Radio and Transmission Network Planning aspects
* BSSDIM-BSS Dimensioning strategies and rules
Guidelines & Rules
PCU & BSC
Base Station Controller (BSC) is the entity that provides the connection between the MCS, the BTSs and the SGSN
Packet Control Unit (PCU) is the entity within the BSC controlling transmission of data through the radio interface and the link point with the core network
Output of dimensioning exercise will be number of required PCUs per BSC for a certain network configuration, and once this is calculated, number of required BSCs
FACTORS TO BE CONSIDERED
Number of DAPs per PCU
Number of data radio resources (dedicated + default ) per PCU
Number of TRXs per PCU
Number of BTSs per PCU
PCU processing capacity
Max Erlang_CS per BSC
HR Support
Guidelines & Rules
TCSM
Speech transmission rate in the air interface is different from the transmission rate in the A interface
Transcoder Units are in charge of transforming from one rate to the other and vice versa
TCSM dimension also includes Ater interface (between BSC and TCSM)
Output of the dimensioning exercise will be number of TCSM units needed for a given traffic load
FACTORS TO BE CONSIDERED IN TCSM DIMENSIONING
Um, Abis and A interfaces need to be dimensioned in advanced for a given voice & data traffic
Speech channel types supported
Guidelines & Rules
Gb interface
Gb interface dimensioning consists of:
BSC dimensioning
SGSN dimensioning
Output of dimensioning exercise will be capacity of Gb interface (number of Frame Relay links) for a certain BSC configuration (number of PCUs + supported traffic)
FACTORS TO BE CONSIDERED IN Gb DIMENSIONING
BSC Capacity in number of PCU cards implemented
Maximum Gb throughput supported per BSC
Knowledge of Gb interface, in terms of expected traffic and characteristics of such traffic
* BSSDIM-BSS Dimensioning strategies and rules
Guidelines & Rules
Special Features
New features introduced in different Nokia releases shall be considered when performing network dimensioning
MultiBCF & Common BCCH allow to gather BTSs of different technologies (frequency band, family) into one logical BTS (segment)
Only one BCCH is required to control all the BTSs
Dynamic Frequency & Channel Allocation (DFCA) performs intelligent channel allocation based on control of interference levels
Multi BCF & Common BCCH
influence in dimensioning
Only one BCCH per segment, not necessary one BCCH per TRX
Possible existence of different GPRS and EGPRS territories
DFCA
New inter-BSC interface is required, with new transmitted messages
Its frequency to be calculated in order to check if capacity is required
* BSSDIM-BSS Dimensioning strategies and rules
Conclusions
This module summarizes the most important aspects related to network dimensioning in the different equipments and interfaces of a system
Air interface
Abis interface
Influences of new features over dimensioning exercising are also depicted