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QoS Provisioning in Wireless Mesh Networks. Ali Hamidian and Ulf Körner. Fourth EuroNGI/FGI Workshop on Wireless and Mobility January 16-18 2008, Barcelona, Spain. Outline. Overview of IEEE 802.11e EDCA with Resource Reservation (EDCA/RR) Multi-hop resource reservation in EDCA/RR Summary.

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qos provisioning in wireless mesh networks

QoS Provisioning in Wireless Mesh Networks

Ali Hamidian and Ulf Körner

Fourth EuroNGI/FGI Workshop on Wireless and Mobility

January 16-18 2008, Barcelona, Spain

outline
Outline
  • Overview of IEEE 802.11e
  • EDCA with Resource Reservation (EDCA/RR)
  • Multi-hop resource reservation in EDCA/RR
  • Summary
ieee 802 11e and hcf
IEEE 802.11e and HCF
  • 802.11e introduces hybrid coordination function (HCF), which has 2 medium access methods:
    • enhanced distributed channel access (EDCA)
    • HCF controlled channel access (HCCA)
  • HCF introduces 2 new concepts:
    • transmission opportunity (TXOP): A bounded time interval during which a station may transmit multiple frames
    • traffic specification (TSPEC): Contains information about the QoS expectation of a traffic stream (frame size, service interval, data rate, burst size, delay bound, etc.)
edca hcca
EDCA HCCA
  • Contention-based
  • “Enhanced DCF”
  • Distributed
  • Service differentiation
  • Contention-free
  • “Enhanced PCF”
  • Centralized
  • Resource reservation
motivation of edca rr qos limitations in 802 11e
Motivation of EDCA/RR: QoS Limitations in 802.11e
  • Problem with EDCA
    • Contention-based medium access & no distributed admission control ==> not possible to guarantee QoS
  • Problem with HCCA
    • Centralized infrastructure requirement ==> HCCA not useful in ad hoc/mesh networks
  • We need a solution which is
    • Contention-free (unlike EDCA)
      • Remove the random medium access delays
    • Distributed (unlike HCCA)
      • Remove the need of an access point
outline1
Outline
  • Overview of IEEE 802.11e
  • EDCA with Resource Reservation (EDCA/RR)
  • Multi-hop resource reservation in EDCA/RR
  • Summary
edca rr operation
EDCA/RR Operation

EDCA/RR is similar to EDCA as long as the stations are sending LP-frames (which do not need resource reservation).

destination

source

edca rr operation1
EDCA/RR Operation

When an HP-stream needs to reserve resources, EDCA/RR in the source checks whether its own new stream can be admitted.

destination

source

edca rr operation2
EDCA/RR Operation
  • If admission control OK:
  • schedule the new stream
  • broadcast ADDTS request containing TSPEC
  • wait for ADDTS response

destination

source

ADDTS request

edca rr operation3
EDCA/RR Operation

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

destination

source

ADDTS response

edca rr operation4
EDCA/RR Operation

Now the source has periodic and contention-free access to the medium.

destination

source

HP data frames

simulation setup
Simulation Setup
  • EDCA/RR implementation in ns-2.26 based on Mike Moreton’s enhanced 802.11/802.11e implementation
  • EDCA vs. EDCA/RR
  • The impact of (hidden) LP-streams on an HP-stream
  • HP stream (AC_VO): G.711, 180 B, UDP datagrams every 20 ms
  • LP stream (AC_BE): FTP, 1000 B, TCP segments
outline2
Outline
  • Overview of IEEE 802.11e
  • EDCA with Resource Reservation (EDCA/RR)
  • Multi-hop resource reservation in EDCA/RR
  • Summary
motivation why edca rr for wireless mesh networks wmns
Motivation: Why EDCA/RR for Wireless Mesh Networks (WMNs)?
  • EDCA/RR (with multi-hop capability) is especially well-suited for static wireless networks, like WMNs
  • IEEE 802.11s for mesh networks is based on EDCA, so it is not too difficult/unrealistic extending 802.11s to support EDCA/RR
motivation why edca rr for wireless mesh networks wmns1
Motivation: Why EDCA/RR for Wireless Mesh Networks (WMNs)?
  • Results from a 4-hop 802.11g WMN

CS = Counter Strike

server to clients: (50.4+6.15×n) B every 60 ms

clients to server: 42 B every 50 ms

multi hop resource reservation in edca rr
Multi-hop Resource Reservation in EDCA/RR
  • Combined route discovery (AODV) and resource reservation (EDCA/RR)
    • search for route fulfilling the QoS requirements
    • faster route discovery/resource reservation
  • Why AODV? Because it will be part of HWMP (Hybrid Wireless Mesh Protocol), which is the default routing protocol suggested in 802.11s
    • reactive part: RM-AODV (Radio Metric AODV)
    • proactive part: tree-based routing
multi hop resource reservation in edca rr1
Multi-hop Resource Reservation in EDCA/RR
  • Copy TSPEC from HP-packet to RRQ
  • Do admission control
  • Temporarily mark resources as reserved and broadcast RRQ

RRQ (route and reservation request) is a RREQ extended with some TSPEC fields.

A

B

C

An HP-packet is sent down the protocol stack and reaches the routing protocol (AODV).

multi hop resource reservation in edca rr2
Multi-hop Resource Reservation in EDCA/RR
  • Copy TSPEC from RRQ
  • Do admission control
  • Temporarily mark resources as reserved and rebroadcast RRQ

A

B

C

multi hop resource reservation in edca rr3
Multi-hop Resource Reservation in EDCA/RR
  • Copy TSPEC from RRQ
  • Do admission control
  • Schedule the traffic request and send a RRP

A

B

C

multi hop resource reservation in edca rr4
Multi-hop Resource Reservation in EDCA/RR

Schedule traffic and forward RRP

A

B

C

multi hop resource reservation in edca rr5
Multi-hop Resource Reservation in EDCA/RR

Schedule traffic; TXOP reservation done

A

B

C

summary
Summary
  • EDCA/RR
    • is a MAC scheme with distributed admission control and scheduling
    • allows stations to reserve TXOPs for periodic and contention-free medium access
    • suites well for WMNs
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