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Analysis of TwoLayer Performance Models by Using Generalized Approaches from Teletraffic Theory

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Proposal of a new unified analytical traffic model for a system with mixed services: ... difference between two models is. the system throughput utilization ... – PowerPoint PPT presentation

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Title: Analysis of TwoLayer Performance Models by Using Generalized Approaches from Teletraffic Theory


1
Analysis of Two-Layer Performance Models by
Using Generalized Approaches 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
2
Motivation
Multi-Service UMTS Network
  • 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

3
Capacity 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 doesnt occupy a channel
    continuously (on-off source ) produce
    interference only when it is actually
    transmitting

Inherent but uncontrolled Statistical Multiplexing
no fixed value of the maximal cell capacity
4
Conventional Traffic Models
  • Classical traffic models from fixed networks
    only deal with the system behavior at connection
    level (call arrival process)

5
Conventional Traffic Models
6
Conventional Traffic Models
7
Conventional Traffic Models
8
Conventional Traffic Models
Aggregated Traffic
9
Conventional Traffic Models
Adjusted according to the measured quality
Overbooking
10
Conventional Traffic Models
11
Conventional Traffic Models
12
Conventional Traffic Models
13
Connection Level Call Admission Control
Blocked-Call-Cleared
  • If not enough capacity
  • block call completely
  • Erlang BCC model
  • Hard blocking only

too pessimistic performance results
14
Problem Definition
  • Classical traffic models dont 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

15
Contribution
  • 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

16
Multi-Layer Traffic Model (recap)
17
Multi-Layer Traffic Model (recap)
18
Multi-Layer Traffic Model (recap)
19
Multi-Layer Traffic Model (recap)
20
Multi-Layer Traffic Model (recap)
Aggregated Traffic
21
Multi-Layer Traffic Model (recap)
Adjusted according to the measured quality
Overbooking
22
Multi-Layer Traffic Model (recap)
Blocked-Call-Held
  • 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

The same TTI during decoding all blocks are
affected
23
Modified Multi-Layer Traffic Model
Blocked-Call-Buffered
24
Modified Multi-Layer Traffic Model
Blocked-Call-Buffered
25
Modified Multi-Layer Traffic Model
Blocked-Call-Buffered
Congested Traffic
26
Modified Multi-Layer Traffic Model
Buffered Traffic
Carried Delayed Traffic
27
Advantages of Suggested Approach (1)
Blocked-Call-Held
Blocked-Call-Buffered
Main difference between two models is the system
throughput utilization
28
Advantages of Suggested Approach (2)
Key aspects of the algorithm
  • 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

29
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 BlockedCallBuffered model
  • On-off traffic with activity factor
  • State-dependent loss probability
  • Neighbor cell interference (log normal)

30
Numerical results (1)
Packet Handling Policy
  • Blocked-Call-Held model
  • 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 N128 channels

31
Numerical results (1)
Packet Handling Policy
  • Blocked-Call-Held model
  • Blocked-Call-Buffered model
  • 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 N128 channels

32
Modified Call Handling Policy
Packet Handling Policy
  • Blocked-Call-Held model
  • Blocked-Call-Buffered model
  • Blocked-Call-Buffered model
  • with wireless interference
  • 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
  • Other cell-interference factor0.55
  • Total cell capacity N128 channels

33
Conclusions
  • 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
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