CN 321: TELE-TRAFFIC ENGINEERING

INTRODUCTION TO TELE-TRAFFIC
ENGINEERING
Lecture outline:

 Introduction to Network performance

 Network Performance measures
 Tele-traffic tools for performance analysis
 Introduction

A telecommunications network consists of

expensive hardware (trunks, switch, etc.) with
the function of carrying telecommunications
traffic (phone call, data packets, etc.).

The physical network is fixed, but the traffic

that it is designed to carry is random.
 Introduction

That is, the time at which calls are generated

are unpredictable (except in a statistical
sense), and similarly, the lengths of time that
the calls will last are unpredictable;

Yet, the network designers must decide how

many resources to provide to accommodate
this random demand.
 Introduction

If the resources are provided economically,

then the quality of service will be low (e.g.,
Too may calls will be lost because the
required resources are not available when
needed);

But, if the resources are provided too

generously, then the cost will be too high.
 Introduction

Tele-traffic theory deals with the mathematical

analysis of models of telecommunications
systems and with the interrelationships among
the provision of resources, the random
demand, and the quality of service;

Tele-traffic engineering addresses the art and

science of the application of this theory to the
design of real telecommunication systems.
Introduction to Network
performance
A telecommunication system is a
system consisting of the necessary
equipment for seamless transfer of
information
user electromagnetic transmission of information user
A B
(wire pair, coaxial cable, fiber optics and radio)
Introduction to Network
performance

A telecommunication system is a system

consisting of the necessary equipment for
seamless transfer of information

user user
A underlying network B
Performance is the ability of a system to
provide the resources needed to deliver its
service

user user
A Network: Collection of network
underlying systems that B
exchange data among themselves
Performance is the ability of a system to
provide the resources needed to deliver its
service

user Network: Collection Electronic

that trading user
Information servicesof systems
A exchange data among themselves B
Communication services
Real-time communication
The users do not care what the underlying
network is. They only care about the quality
of the service

Real-time communication
Performance will be tightly linked to
the network’s capabilities of:

user user
Traffic handling
A Dependability B
Security
Performance will be tightly linked to
the network’s capabilities of

user user
Traffic handling
A B
Traffic handling

limited network user demand

capacity

Links, routers,,
switches etc…

Performance
Traffic handling Cont..

 Traffic handling in the network is much

the same as traffic handling in the road
system.
 Picture yourself going by the car to work.
The time it takes from home to work will
depend on the traffic situation. It is a limit
on how many cars can be on the road
before queues build up.
Performance and network capacity

Performance

Network Capacity
 Performance and network capacity

Performance

Requirement

Network Capacity
Performance and network capacity
 For a given traffic load, performance will
improve as capacity is increased, however
there will be a point where more capacity
is simply a waste. Performance will no
longer improve.
 Performance and network capacity

Performance

Requirement
Over provisioning and poor
utilization of resources

Network Capacity
The use of network capacity should be optimized

Net
Traffic
(stochastic
user demand)

Net Net
Network
Network
capacity
Performance
Performance and Network capacity
 Understanding the functional relationship
is important for network planning and
dimensioning.
 One thing is capture the current traffic
demand. Also traffic forecasting is
important.
To say something about network
performance we need well-
defined performance measures.
 Network Performance measures

Two fundamental information transfer modes

Packet switched
networks
(wired and wireless)

Circuit switched networks

(mobile and fixed)B Next generation
Internet ?

1876: 1969 Internet 1991 www 2010 time

A. G. Bell Arpanet
Circuit Switched network (e.g PSTN): a circuit lasts for
the duration of the call
Circuit Switched network (e.g PSTN): a circuit lasts for
the duration of the call
Circuit Switched network (e.g PSTN): a circuit lasts for the
duration of the call
Call set-up and release delay

Mobile:
handover

Probability of blocking

 Call level performance measures are directly

mapped to end user satisfaction.
 The packet level performance measures are
more vague. How much packet loss,delay and
delay variation an application can handle will
depend on application type.
Circuit Switched network (e.g PSTN): a circuit lasts for the
duration of the call
Call set-up and release delay

Mobile:
handover

Probability of blocking
Packet switched network (Internet), traffic is segmented into
packets. No dedicated circuit and capacity is shared.
Circuit Switched network (e.g PSTN): a circuit lasts for the
duration of the call
Call set-up and release delay
delay
Mobile:
handover

Probability of blocking

Packet switched network (Internet), traffic is segmented into

packets. No dedicated circuit and capacity is shared.

Queue of packets
Circuit Switched network (e.g PSTN): a circuit lasts for the
duration of the call
Call set-up and reales delay

Mobile:
handover

Probability of blocking

Packet switched network (Internet), traffic is segmented into

packets. No dedicated circuit and capacity is shared.

Throughput
Packet loss

Queue of packets Packet loss pattern

Packet delay Packet delay variation

Packet Switched Network
 If the incoming rate is smaller than
capacity, it will be as if the users have
dedicated lines.
 When the incoming rate exceeds the link
capacity queues will build up and packets
must wait in line. The packets will undergo
varying delay (delay variation), which is of
special concern to real-time application
that have little tolerance for delay
variations.
Performance measures related to traffic
handling:

Circuit switched network Packet switched network

(call-level) (packet-level)
• Packet delay and delay
• Call set up and release delay
variation
• Probability of end-to-end
• packet loss rate and packet loss
blocking
pattern
• Probability of unsuccessful
• Throughput
handover(mobile)
 Tele-traffic tools for performance
analysis

Teletraffic tools are used to analyse

performance related to traffic in a
telecommunication system
Three categories of Teletraffic tools
 Measurement tools
 Simulation tools
 Mathematical tools
Three categories of Teletraffic tools
 Measurement tools
 Simulation tools
 Mathematical tools

15
Measurement tools are used to carry out
measurements on real systems or
prototypes

Software
or
hardware
Drive testing: measurement tool for wireless and
mobile network performance measurements

Performance measures:
coverage, capacity, hand-over, call-setup, blocking
probability in mobile networks
Measurement Tools Cont..
 Drive testing is a method of measuring and assessing the
coverage, capacity and Quality of Service (QoS) of a
mobile radio network.

 The technique consists of using a motor vehicle containing

mobile radio network air interface measurement
equipment that can detect and record a wide variety of
the physical and virtual parameters of mobile cellular
service in a given geographical area.

 By measuring what a wireless network subscriber would

experience in any specific area, wireless carriers can make
directed changes to their networks that provide better
coverage and service to their customers.
Measurement tools are the only means of
verifying that performance is according to
the specifications
 What is the quality of the measurements?
 There may be large stochastic uncertainties
and these must be considered
 Measurements may be collected from
large-scale systems (e.g. Internet). Are we
even measuring what we think we are
measuring?
 What is the quality of the analysis of the
data?
Three categories of Teletraffic tools
 Measurement tools
 Simulation tools
 Mathematical tools
A simulation tool is used to analyse the
performance of a simulation model

Traffic
User demands Data generated
from real traffic
Artifical data

Structure Strategy
Hardware Software
Priorities?
Topology, Scheduling
capacity Admission Control
Wireless, wired
Transfer mode
Simulation tools make performance
analysis flexible
 A good simulation model can be quite detailed
and realistic and provides control on all
underlying parameters.
 The significance of the individual parameters may
be difficult to grasp
 A simulation model is not general. Every scenario
must be simulated.
 Both stochastic uncertainies and quality of data
analysis must be considered.
 The simulation model must be verified using a real
network
Three categories of Teletraffic tools
 Measurement tools
 Simulation tools
 Mathematical Analysis tools
Mathematical performance analysis is carried out using a
mathematical representation of the system

O r
N Traffic Parameter
Characterist exampels: Poisson
a b ics are Mean
modeled Variance
OF
F Distribution

Topology, Structure Strategy

Hardware Software Priorities?
capacity Scheduling
Wireless, wired Admission
Transfer mode Control

a mathematical model 25
Mathematical analysis tool
 Describe the stochastic behavior of the
traffic with some model.
 The model must be very simple so to be
mathematically tractable.
 Typically is call arrivals modeled by a poisson
process.
 When doing a mathematical analysis, the
mathematical models are the tools
 accurate mathematical model is invaluable
for network dimensining and planning.
Mathematical models give an exact
functional relationship between
performance measures.
• If the system changes the model may no
longer hold.
• There is a trade-off between simplicity
and accuracy of the model (closeness to
the real system).
 Teletraffic tools are used to quantify
performance related to traffic in a
telecommunication system.
Validate and estimate
Measurement parameters
tools

Simulation Mathematical
tools analysis
tools
Flexible, understand Exact relations
behavior, validation accuracy issues
 The choice of the most appropriate method
depends on what the system is and
performance measures.

 Reading Assignment(Revision)
➢ Probability theory
➢ Exponential
➢ Poisson and Binomial Distributions