Friday, December 13, 2013

Network Statistics/ Quality of Service (QoS)

Categories  of  QoS  are  shown  in  the  following  Figure:  QoS  Categories.  All  the  services provided to the subscribers through network are associated with the quality of service of  the network.

There are expected values, designed values of QoS and we need to measure QoS parameters. Those QoS statistics are connected in a chain as shown in the Figure: QoS Cycle.

Network Efficiency is also a measure of QoS. And it is measured as follows.
  •   Network Efficiency = (Carried Traffic at Busy Hour) / (Capacity at 2% GOS)
 Definition  for  Grade  of  Service  (GOS):   Percentage  of  attempts  which  are  allowed  to  be blocked in the network when considering the availability of circuits  (CICs)  when calls are to be  made.  The  capacity  for  a  particular  GOS,  with  the  presence  of  particu lar  number  of circuits can be found from the Erlang B table.  Considering the Key Performance Indicators (KPIs),  it  can  be  defined  as  KPIs  related  to  successful  initiation  of  a  call  and  successful termination of a call. Here are some KPIs;
  • SDCCH (Standard Dedicated Control Channel) Accessibility:  successful capture of a SDCCH time slot by the subscriber.
  • SDCCH Drop Rate :  successful completion of the SDCCH phase and  then  releasing (loosing) the SDCCH channel.
  • TCH  (Traffic  Channel)  Accessibility :  successful  capture  of  a  TCH  time  slot  by  the subscriber in a call attempt.
  • TCH drop rate :  successful completion of the TCH phase and  then  releasing  (loosing) the TCH.
To keep the performance of the network at a higher level it is required to maintain QoS of the network. It is the responsibility of RAN team. They have defined some threshold values for KPIs.  Using  them  they  continuously  monitor  the  whole  network  every  day.  There  are  few
  • methods where they can measure QoS of the network mentioned below.Analyzing Daily Traffic Data
  • Analyze Drive Test Results
  • Observing  the  daily  quality  of  service   parameters  using  Network  Performance Optimizer (NPO) tool
  • Monitoring network using OMC-R