ECE/MAE 7750: Distributed Control Systems FISP: Focused Independent Study and Presentation Topic: Integrated congestion control and scheduling in wireless local area networks - PowerPoint PPT Presentation

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ECE/MAE 7750: Distributed Control Systems FISP: Focused Independent Study and Presentation Topic: Integrated congestion control and scheduling in wireless local area networks

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Title: ECE7750 Distributed Control Systems Subject: FISP template Author: YangQuan Chen Last modified by: Yashodhan Created Date: 12/2/2003 5:03:49 PM – PowerPoint PPT presentation

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Title: ECE/MAE 7750: Distributed Control Systems FISP: Focused Independent Study and Presentation Topic: Integrated congestion control and scheduling in wireless local area networks


1
ECE/MAE 7750 Distributed Control SystemsFISP
Focused Independent Study and PresentationTopic
Integrated congestion control and scheduling in
wireless local area networks
  • Presenter
  • Yashodhan Tarte
  • Dept. of Electrical and Computer Engineering
  • Utah State University
  • E yashodhan_at_cc.usu.edu T (435)797-2845

02/28/2005
2
Presentation Outline
  • References
  • QoS contract
  • Problems with the present architecture
  • Proposed solution
  • Traffic control module
  • MT i scheduler
  • MT i buffer controller
  • Simulation results
  • Authors conclusions
  • Readers comment

3
References
  • Francesco Delli Priscoli Alberto Isidori
    (2004). A control engineering approach to
    integrated congestion control and scheduling in
    wireless local area networks. Control Engineering
    Practice 13 (2005) 541-558
  • Arindam Paul. QoS in Data Networks Standards and
    Protocols. Department of Computer Science and
    Engineering, Ohio State University

4
QoS contract
  • A Service Class is defined as the set of
    connections whose QoS contract is characterized
    by the same parameters
  • A Quality of Service contract is agreed
    establishing
  • The characteristics (e.g. minimum bit rate etc.)
    of the so-called Compliant Traffic, i.e. the
    traffic which has to be admitted in the network
    in whatever traffic condition
  • The delay and jitter do not exceed maximum
    tolerable values for a given service class
  • The Non-Compliant Traffic is admitted into the
    wireless network as long as this admittance does
    not affect QoS requirements of Compliant Traffic

5
Problems with the present architecture
  • Internet protocol only provides best-effort
    packet delivery service and may consequently be
    inadequate to allow the respect of the QoS
    contracts.
  • Inefficient use of available bandwidth because
    various underlying networks (e.g. IEEE 802.11,
    GPRS etc.) use different mechanisms to respect
    the QoS contracts.
  • Because of established standards, there is little
    flexibility in both the IP and the UN layers for
    improved IP with wireless.

6
Proposed solution
  • Wireless adaptation layer (WAL) A layer that
    works between IP and UN layers and is transparent
    to both.
  • Components of WAL
  • a. Traffic control module (TCM) It includes
    both the congestion control and scheduling
    roles.
  • b. Logical link control translator (LLCT)
    Interface between the WAL and the considered UN.
  • c. WAL coordinator For coordination between
    various WAL modules.

7
Traffic control module
  • A TCM consists of the following building blocks
  • A Classifier in charge of sorting the IP
    datagrams arriving at the TCM according to the
    associations (i,j) they belong to.
  • A Capacity-to-MT Assigner whose role is to select
    the mobile terminal which has to transmit an IP
    datagram towards the LLCT whenever it is
    possible.
  • The MT i Scheduler ( i 1,., N ) which handles
    the IP datagrams directed to the ith mobile
    terminal.

8
Traffic control module (contd.)
9
MT i Scheduler
  • The MT i scheduler consists of the following
    blocks
  • one FIFO buffer for each association
  • an MT i Buffer Controller which is in charge of
    deciding the admittance/discarding of the
    incoming IP datagrams
  • one Admittance Handler for each association,
    implementing the decisions taken by the buffer
    controller.

10
MT i Scheduler (contd.)
11
MT i Scheduler (contd.)
12
MT i Buffer Controller
  • The decisions of the MT i Buffer Controller are
    based on
  • the information about the IP datagrams arrived at
    the MT i Scheduler
  • the information about the decisions performed by
    the Capacity-to-MT Assigner
  • the FIFO Buffer (i,j) (j 1,., C(i))
    occupancies.

13
MT i Buffer Controller (contd.)
  • The aim of the buffer controller is increasing
    the (properly weighted) admitted traffic, while
    respecting the QoS constraints
  • The adopted approach is based on the idea of
    periodically computing an ideal equilibrium and
    then using proportional feedback control in order
    to steer the state of the system towards such an
    ideal equilibrium

14
Simulation Results
  • QoS contracts associated to the connections
    relevant to the four considered services

Parameter Voice FTP Web Video
Minimum bit rate 29 kbps 200 kbps 40 kbps 1350 kbps
Maximum delay 0.1 s 4 s 1.5 s 0.5 s
Maximum jitter 0.09 s 3.8 s 1.45 s 0.48 s
15
Simulation Results (contd.)
  • The number of bits discarded during the
    simulation time period (20 min. for the graph
    shown below )is given by
  • Bloss

16
Simulation Results (contd.)
  • The Link Efficiency is given as the ratio of bits
    passed towards the LLCT during the simulation
    time period (20 min for the graph shown below) to
    the bits which the LLCT would have been able to
    accept during that period.

17
Simulation Results (contd.)
  • The above results clearly show the advantages, at
    high traffic loads, of the closed loop option
    with respect to open loop option both in terms of
    higher Link Efficiency and in terms of lower
    number of discarded bits.

18
Authors Conclusions
  • The proposed Traffic Control Module performs
    better than the present arrangements because of
    the presence of a single controller which
  • integrates congestion control and scheduling
    tasks
  • performs these tasks in a real time closed loop
    fashion
  • performs these tasks in a centralized way for all
    the connections involving the considered access
    point (or base station).

19
Readers Comment
  • The proposed scheme can only be used in the
    wireless networks where cost of implementing such
    a complex system can be justified (e.g. in
    real-time applications)

20
  • Questions?
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