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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. 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

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  1. 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

  2. Outline • Overview of IEEE 802.11e • EDCA with Resource Reservation (EDCA/RR) • Multi-hop resource reservation in EDCA/RR • Summary

  3. 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.)

  4. EDCA HCCA • Contention-based • “Enhanced DCF” • Distributed • Service differentiation • Contention-free • “Enhanced PCF” • Centralized • Resource reservation

  5. 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

  6. Outline • Overview of IEEE 802.11e • EDCA with Resource Reservation (EDCA/RR) • Multi-hop resource reservation in EDCA/RR • Summary

  7. 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

  8. 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

  9. EDCA/RR Operation • If admission control OK: • schedule the new stream • broadcast ADDTS request containing TSPEC • wait for ADDTS response destination source ADDTS request

  10. 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

  11. EDCA/RR Operation Now the source has periodic and contention-free access to the medium. destination source HP data frames

  12. 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

  13. Average End-to-End Delay - 0 % packet error

  14. Outline • Overview of IEEE 802.11e • EDCA with Resource Reservation (EDCA/RR) • Multi-hop resource reservation in EDCA/RR • Summary

  15. 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

  16. 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

  17. 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

  18. 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).

  19. 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

  20. 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

  21. Multi-hop Resource Reservation in EDCA/RR Schedule traffic and forward RRP A B C

  22. Multi-hop Resource Reservation in EDCA/RR Schedule traffic; TXOP reservation done A B C

  23. 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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