QoS Provisioning in Wireless Mesh Networks Ali Hamidian and Ulf Körner In this talk I’ll present our latest work (still in progress) with EDCA/RR, which is our proposed extension to 802.11e 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

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 Contention-based “Enhanced DCF” Distributed Service differentiation Contention-free “Enhanced PCF” Centralized Resource reservation

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

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

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 Operation If admission control OK: schedule the new stream broadcast ADDTS request containing TSPEC wait for ADDTS response destination source ADDTS request

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

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

Average End-to-End Delay - 0 % packet error no. of LP-streams average end-to-end delay (ms) 99 % confidence interval (ms) EDCA EDCA/RR 0.69 12.33 (0.69,0.69) (12.13,12.53) 1 6.21 12.22 (6.20,6.22) (12.02,12.42) 2 11.17 12.27 (11.14,11.19) (12.08,12.47) 3 13.93 (13.90,13.96) (12.01,12.42) 4 17.12 12.38 (17.08,17.16) (12.19,12.57) 5 20.51 12.25 (20.46,20.56) (12.06,12.45)

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)? 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 (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 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/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 The routing protocol copies the TSPEC from the packet into a route and reservation request (RRQ) and sends it down to the MAC sublayer (EDCA/RR). EDCA/RR does admission control. If OK, broadcast RRQ. An HP-packet is sent down the protocol stack and reaches the routing protocol (AODV).

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/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/RR Schedule traffic and forward RRP A B C

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

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