Providing qos in ad hoc networks with distributed resource reservation ieee802 11e and extensions
Download
1 / 37

Providing QoS in Ad Hoc Networks with Distributed Resource Reservation IEEE802.11e and extensions - PowerPoint PPT Presentation


  • 87 Views
  • Uploaded on

Providing QoS in Ad Hoc Networks with Distributed Resource Reservation IEEE802.11e and extensions. Ulf Körner and Ali Hamidian. The Goal. To provide QoS guarantees to WLANs operating in ad hoc mode by allowing stations to reserve resources (medium time)

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Providing QoS in Ad Hoc Networks with Distributed Resource Reservation IEEE802.11e and extensions' - satin


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Providing qos in ad hoc networks with distributed resource reservation ieee802 11e and extensions

Providing QoS in Ad Hoc Networks with Distributed Resource ReservationIEEE802.11e and extensions

Ulf Körner and Ali Hamidian


The goal
The Goal Reservation

  • To provide QoS guarantees to WLANs operating in ad hoc mode

    • by allowing stations to reserve resources (medium time)

    • by distributing the existing admission control and scheduling algorithms

  • Example of application area: gaming


No qos in ieee 802 11
No QoS in IEEE 802.11 Reservation

  • Today’s WLANsdo not offer any QoS

    • usually not a big problem if you just surf the Internet

    • bad voice/video quality if you use e.g. Skype or MSN messenger


802 11 mac its qos limitations
802.11 MAC & its QoS Limitations Reservation

  • 802.11 has two medium access methods:

    • distributed coordination function (DCF)

      • All data flows have the same priority

    • point coordination function (PCF)

      • Not possible for stations to send QoS requirements to the AP

      • Unknown transmission time of the polled stations

  • 802.11e introduces:

    • hybrid coordination function (HCF)

      • enhanced distributed channel access (EDCA)

      • HCF controlled channel access (HCCA)


Hybrid coordination function hcf
Hybrid Coordination Function (HCF) Reservation

  • transmission opportunity (TXOP): A bounded time interval during which a station may transmit multiple frames

    • Solves the PCF problem with unknown transmission times

  • traffic specification (TSPEC): Contains information about the QoS expectation of a traffic stream (frame size, service interval, data rate, burst size, delay bound, etc.)

    • Solves the PCF problem with the inability to send QoS needs


Enhanced distributed channel access edca

mapping to AC Reservation

Background [1]

Best effort [2]

Video [3]

Voice [4]

AIFSN[1]

CWmin[1]

CWmax[1]

TXOPlimit[1]

AIFSN[2]

CWmin[2]

CWmax[2]

TXOPlimit[2]

AIFSN[4]

CWmin[4]

CWmax[4]

TXOPlimit[4]

AIFSN[3]

CWmin[3]

CWmax[3]

TXOPlimit[3]

virtual collision handler

Enhanced Distributed Channel Access (EDCA)

  • Contention-based

  • “Enhanced DCF”

  • access category (AC): Each station has four ACs (”transmission queues”). Each AC contends for TXOPs independently of the other ACs

  • Service differentiation is realized by varying

    • Different parameters


Hcf controlled channel access hcca
HCF Controlled ReservationChannel Access (HCCA)

  • Contention-free

  • “Enhanced PCF”

  • Medium access controlled by a QoS access point (QAP)

  • HCCA allows stations with QoS traffic to reserve TXOPs using TSPECs


Motivation of our work qos limitations in 802 11e
Motivation of our Work: ReservationQoS Limitations in 802.11e

  • Problem with EDCA

    • Random medium access & no distributed admission control => not possible to guarantee QoS

  • Problem with HCCA

    • Centralized infrastructure requirement => HCCA not useful in ad hoc networks

  • We need a solution which is

    • Deterministic (unlike EDCA)

      • Remove the random medium access delays

    • Distributed (unlike HCCA)

      • Remove the need of an access point


Edca with resource reservation edca rr
EDCA with Resource Reservation (EDCA/RR) Reservation

  • distributed admission control and scheduling

  • possibility to reserve TXOPs for deterministic and contention-free medium access


Edca rr operation
EDCA/RR Operation Reservation

Similar to EDCA as long as LP frames (AC_Background and AC_BestEffort) are sent


Edca rr operation1
EDCA/RR Operation Reservation

When a HP frame (AC_Video and AC_Voice) reaches the MAC sublayer, the source checks whether its new stream can be admitted


Edca rr operation2
EDCA/RR Operation Reservation

  • If admission control OK:

  • schedule the new stream

  • broadcast ADDTS request containing TSPEC

  • wait for ADDTS response

ADDTS request


Edca rr operation3
EDCA/RR Operation Reservation

Once all ADDTS responses are received by the source, it waits until its first reserved TXOP at service start time & starts transmitting

ADDTS response


Edca rr operation4
EDCA/RR Operation Reservation

deterministic and contention-free medium access: the source has now reserved TXOPs every scheduled service interval (SI)

HP data frames


Results
Results Reservation

  • EDCA/RR implementation in ns-2 based on an enhanced 802.11/802.11e implementation

  • EDCA vs. EDCA/RR

  • Stationary behaviour: How is the average end-to-end delay of a HP-stream affected whenthe number of LP streams increases?


Throughput edca

ad hoc network Reservation

Throughput: EDCA

1 LP-stream and 4 HP-streams each started 10 s apart.


Throughput edca1
Throughput: EDCA Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream


Throughput edca2
Throughput: EDCA Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 1 HP stream


Throughput edca3
Throughput: EDCA Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 2 HP streams


Throughput edca4
Throughput: EDCA Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 3 HP streams


Throughput edca5
Throughput: EDCA Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 4 HP streams


Throughput edca rr
Throughput: EDCA/RR Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network


Throughput edca rr1
Throughput: EDCA/RR Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream


Throughput edca rr2
Throughput: EDCA/RR Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 1 admitted HP stream


Throughput edca rr3
Throughput: EDCA/RR Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 2 admitted HP streams


Throughput edca rr4
Throughput: EDCA/RR Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 3 admitted HP streams


Throughput edca rr5
Throughput: EDCA/RR Reservation

1 LP-stream and 4 HP-streams each started 10 s apart.

ad hoc network

1 LP stream + 3 admitted HP streams +

1 rejected HP stream


Throughput: ReservationEDCA vs. EDCA/RR

EDCA

EDCA/RR


End Reservation


Average end to end delay
Average End-to-End Delay Reservation

- 1 HP source

- 150 simulation runs!

- simulation time: 200 s


Problem due to hidden stations
Problem due to Hidden Stations Reservation

  • The hidden station C doesn’t receive A’s ADDTS request so it can start sending just before A’s TXOP starts! ==> no QoS guarantees!


Solving the hidden station problem
Solving the Hidden Station Problem Reservation

  • The TSPEC is included in the ADDTS response so when B sends an ADDTS response to A, C hears that message and learns about A’s reservation

  • In addition:

    Send RTS_TSPEC and CTS_TSPEC in the beginning of each TXOP





Multi hop resource reservation
Multi-hop Resource Reservation Reservation

  • A: if traffic is admitted, send RREQ-ADDTSRequest

  • B: if traffic is admitted, send RREQ-ADDTSRequest

  • C: if traffic is admitted, schedule traffic and send RREP-ADDTSResponse

  • B: schedule traffic and send RREP-ADDTSResponse

  • A: schedule traffic and send data

AODV + EDCA/RR


Summary
Summary Reservation

  • EDCA/RR

    • is a MAC scheme with distributed admission control and scheduling

    • allows stations to reserve TXOPs for deterministic and contention-free medium access


ad