analysis of two-layer performance models by using generalized approaches from teletraffic theory l....

Analysis of Two-Layer Performance Analysis of Two-Layer Performance Models by Using Generalized Models by Using Generalized

Approaches from Teletraffic TheoryApproaches from Teletraffic Theory

L. N. Popova Institute for Mobile Communications,

University of Erlangen-Nürnberg, Germany

V. B. Iversen COM - DTU,

Technical University of Denmark, Lyngby, Denmark

Larissa Popova and Villy Iversen: Analysis of Two-Level Performance Models2

MotivationMotivation

Simultaneous support for a wide range of services with different characteristics on a common carrier

Universal frequency reuse High spectrum efficiency

Flexible service bit rate

Statistical Multiplexing among services Higher resource utilization

Problem:

Diversity of service requirements difficult to ensure sufficient QoS for all services

Multi-Service UMTS Network:


Capacity of UMTSCapacity of UMTS UMTC cell capacity is power based capacity Each new user increases the total power level in the

frequency channel Capacity is limited by the amount of interference in the air

interface Packet user doesn’t occupy a channel continuously (on-off

source ) produce interference only when it is actually transmitting

no fixed value of the maximal cell capacity

Inherent but uncontrolled Inherent but uncontrolled Statistical MultiplexingStatistical Multiplexing


Conventional Traffic ModelsConventional Traffic Models

Classical traffic models from fixed networks only deal with the system behavior at connection level (call arrival process)


Aggregated Traffic



OverbookingAdjusted according to the measured quality



Connection Level Call Admission ControlConnection Level Call Admission Control

If not enough capacity

block call completely Erlang BCC model Hard blocking only

Blocked-Call-Cleared:

too pessimistic performance resultstoo pessimistic performance results


Classical traffic models don’t take into account diversity of service requirements on packet-oriented wireless networks

Just a rough approximation for network performance Don’ t ensure sufficient QoS for all services

Important features of WCDMA radio interface are neglected:

– Variable on –off user transmission rate

– Packet buffering/delay

– Dynamic cell capacity (wireless interference)

Handover strategies are not included

Problem DefinitionProblem Definition


ContributionContribution Proposal of a new unified analytical traffic model for a system

with mixed services:

– Analysis of interaction between the two performance levels:

• Connection level call admission procedure

• Packet level call handling process

– Individual performance assessment for each service class

Proposal of an extended call handling policy buffer scheme

Analysis of impact of buffer on:

– The average system performance

– Individual users’ throughput


Multi-Layer Traffic Model (recap)Multi-Layer Traffic Model (recap)


Aggregated Traffic



OverbookingAdjusted according to the measured quality



In case of overbooking, there is loss for the period of congestion

Fry-Molina BCH model

Loss sharing between simultaneously transmitted blocks of distinct users

Soft Capacity


Blocked-Call-Held:

The same TTI during decoding: all blocks are affected


Modified Modified Multi-Layer Traffic ModelMulti-Layer Traffic Model

Blocked-Call-Buffered


Modified Modified Multi-Layer Traffic ModelMulti-Layer Traffic Model



ModifiedModified Multi-Layer Traffic Model Multi-Layer Traffic Model

Congested Traffic



ModifiedModified Multi-Layer Traffic Model Multi-Layer Traffic Model

Carried Delayed TrafficBuffered Traffic


Advantages of Advantages of Suggested Suggested Approach (1)Approach (1)

Main difference between two models is

the system throughput utilization

Blocked-Call-Held: Blocked-Call-Buffered:


Fast and stable algorithm

Supports the coupling between connection and packet-level QoS characteristics.

Individual performance measure for each traffic stream

More realistic model for analysing behaviour of multiple traffic flows

Supports all classical loss/delay models.

Applicable to performance prediction and the optimum design of virtually arbitrary networks

Key aspects of the algorithm:

Advantages of Advantages of Suggested Suggested Approach (2)Approach (2)


Traffic Model and Assumptions Traffic Model and Assumptions Radio interface of W-CDMA, Perfect Power control, Uplink Multiple service classes with different QoS-parameters:

Binomial – Poisson – Pascal (BPP) multi-rate traffic Connection - Level: Blocked-Call-Cleared (Erlang) model:

– Each traffic stream is characterized by:• Mean offered traffic

• Peakedness

• Data rate required by stream

Packet – Level: Blocked–Call–Buffered model – On-off traffic with activity factor

– State-dependent loss probability • Neighbor cell interference (log normal)


Numerical results (1)Numerical results (1)

Blocked-Call-Held modelPacket Handling Policy:

Setup: mixed services:

Radio stream (Poisson);

= 4(8)128 (Erl.)

Web browsing (Engset);

= 40 (Erl.)

Email (Pascal);

= 37(Erl.) Activity factor: 0.5; 0.3; 0.7 FIFO-principle No trunk reservation Total cell capacity N=128 channels


Numerical results (1)Numerical results (1)

Blocked-Call-Held model Blocked-Call-Buffered model

Packet Handling Policy:



= 4(8)128 (Erl.)


= 40 (Erl.)

Email (Pascal);

= 37(Erl.) Activity factor: 0.5; 0.3; 0.7 FIFO-principle No trunk reservation Total cell capacity N=128 channels


Modified Call Handling PolicyModified Call Handling PolicyPacket Handling Policy: Blocked-Call-Held model Blocked-Call-Buffered model Blocked-Call-Buffered model with wireless interference



= 4(8)128 (Erl.)


= 40 (Erl.)

Email (Pascal);

= 37(Erl.) Activity factor: 0.5; 0.3; 0.7 Other cell-interference factor=0.55 Total cell capacity N=128 channels


ConclusionsConclusions Goal: Analysis of resource allocation scheme for large-scale queuing

networks with WCDMA radio interface Proposal of an extended call handling policy (introducing of buffer scheme) How: by using a novel generalized algorithm from extended teletraffic

theory:

– Combines properties of both loss and queuing systems

– Addresses connection and packet-level QoS metrics simultaneously.

– Allows explicit theoretical analysis of complex multimedia traffic behavior

– Generalizes scheduling policy and service priority discipline for performance evaluation of traffic streams with different QoS provisioning problems.

Findings: Comparison of Blocked-Call-Held scheme with Blocked-Call-Buffered traffic model:– Blocked-Call-Buffered traffic model is a more realistic approach for

modelling system processes on the complex network packet-level– Applicable to performance prediction and the optimum design of virtually

arbitrary networks

analysis of two-layer performance models by using generalized approaches from teletraffic theory l....

Documents

layer performance models

larissa popova

villy iversen

classical traffic models

denmark slide

popova institute

iversen com dtu

arrival process slide