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Cluster-based Multihop Networking with controlled Quality of Service

Cluster-based Multihop Networking with controlled Quality of Service. Joerg Habetha, Wolfgang O. Budde Philips Research, Aachen, Germany joerg.habetha@philips.com. Outline. The need for multi-cluster multi-hop communication in QBSSs Coverage area extension of a QBSS:  forwarding mechanisms

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Cluster-based Multihop Networking with controlled Quality of Service

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  1. Cluster-based Multihop Networking with controlled Quality of Service Joerg Habetha, Wolfgang O. Budde Philips Research, Aachen, Germany joerg.habetha@philips.com

  2. Outline • The need for multi-cluster multi-hop communication in QBSSs • Coverage area extension of a QBSS:forwarding mechanisms • Interconnection of QBSSsmulti-hop ad hoc networking • Conclusions • Next steps

  3. The need for multi-cluster multi-hop QoS-controlled W-LANs • QBSSs’ coverage area is limited to the radio range of the Hybrid Coordinator (HC) • Overall capacity for QoS-controlled traffic is given by the capacity of a single channel • Multi-cluster multi-hop communication is a necessity for QoS-enhanced wireless networks • Standardization needs to be started now!

  4. Benefits of multi-cluster multi-hop QoS-controlled W-LANs • Coverage Extension of QBSSs • Capacity Increase due to clustering • Wireless interconnection of QBSSs • More efficient use of spectrum in case of multi-hop connections (no collisions) • Builds upon existing IEEE802.11 extensions • 802.11e: QoS enhancements • 802.11h: Frequency agility

  5. Problem: Limited coverage area of QBSSs • The higher the frequency • the more ray-like the propagation, • the higher the free-space loss, • the higher the attenuation due to walls and other obstacles • thus, the smaller the coverage area

  6. FN FN HC Solution: Extension of coverage area by means of forwarding • Coverage area of HC’s QoS management increased through forwarding of control information • QBSS coverage area increased through forwarding of user traffic City scenario: FN: Forwarding Node

  7. Problem: Interconnection of QBSSs • As of today, QBSSs can only be connected through wired infrastructure • A-priori network planning required • Rather limited ad-hoc capabilities • No multi-hop mode defined for QBSSs

  8. Solution: Multi-channel Cluster Bridges • A cluster bridge (CB) associates with overlapping QBSSs operating in different channels • Part-time presence in either of the two BSSs • Throughput optimization by predefined medium access opportunities • Requires some buffer space for transportation of packets from one BSS into the other

  9. Properties of clustered wireless networks • The smaller the clusters, the more channels can be used in a given area (re-use). • Advantage: offered traffic per channel decreases • Option: spatial diversity improves re-use factor • The smaller the cluster, the higher modulation/coding can be used. • Advantage: increased channel capacity • The smaller the cluster, the more hops needed • Dynamic clustering helps to maintain efficiency

  10. Capacity increase over # clusters = Number of Clusters

  11. Clustering in 802.11 • Applicable diversity techniques • Frequency (channel) • Space • Code • Compliant with latest extensions • 802.11h: frequency agility • 802.11e: QoS enhancements (periodic beacons, reserved TXOPs)

  12. Coverage extension • FQSTA is transparent representative of HC. • Selection and hand-off of FQSTA and HC. • QoS is guaranteed. • Bandwidth-efficient. FQSTA HC

  13. Wireless Inter-connection of BSSs Cluster 1 (frequency 1) HC CB HC Cluster 2 (frequency 2) CB: Cluster Bridge HC: Hybrid Coordinator

  14. Proposal for extended MAC frame structure with additional TXOP Sub-MAC frame structure CFP CP TXOP for FQSTAand CBs Cont. free per. (CFP) CP Beacon CFP/CP, CFBs Beacon

  15. Multi-frequency forwarding solution • PCs/HCs operate on different frequencies • FQSTAs/CBs switch from one frequency to the other • FQSTAs/CBs switch during (E)DCF-phase • Switching Times TS and Waiting Times TW will occur f1 f2 f2 f1 f1 FQSTA/CB T T T T S W S W

  16. T7 T8 T9 T11 T10 T12 T13 T16 T15 T14 Work items to be tackled T4 T5 T6 HC1 T3 • Dynamic clustering • Signalling procedures • Membership management • Interconnection of clusters • Forwarding procedure • Choice of forwarding stations • CB-installation and hand-off • Routing of packets • Type of algorithm • Address resolution T2 T1 HC2 HC3

  17. Conclusions • Multi-cluster multi-hop communication is a necessity for QoS-enhanced wireless networks. • Centralized solutions based on PC/HC and Forwarding Stations / Cluster Bridges have been sketched • Compliance with current 802.11 features and extensions shown • Coverage extension and capacity increase for QoS-controlled networks is feasible

  18. Next steps • Discussion and standardization has to be started now • 802.11a is in initial deployment • 802.11e/h are settling these days • The road towards coverage extension and capacity increase must be presented in short term • Experience from simulation exists • Partners needed!

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