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Infrastructure Mesh Broadband Wireless System: Example of Cooperative Wireless

Infrastructure Mesh Broadband Wireless System: Example of Cooperative Wireless. Byoung-Jo Kim, N. K. Shankaranarayanan AT&T Labs April 2007 (This is work done jointly with: Amit Saha, Rice University ). An operator perspective.

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Infrastructure Mesh Broadband Wireless System: Example of Cooperative Wireless

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  1. Infrastructure Mesh Broadband Wireless System: Example of Cooperative Wireless Byoung-Jo Kim, N. K. Shankaranarayanan AT&T Labs April 2007 (This is work done jointly with: Amit Saha, Rice University )

  2. An operator perspective • Operators seek to apply wireless technology/network advances to aid deployment (control costs) and/or improve performance (additional capacity, revenue) • Areas where cooperative wireless could help in cellular systems: • Improve coverage/outage, especially at cell edge • Improve capacity / spectral efficiency • Improve interference avoidance • Some examples: • Use of infrastructure mesh Base Stations (mBS) a.k.a. Relay Repeaters • Inter-Base Station cooperation • Cooperation at radio as well as network level

  3. Infrastructure Mesh example • Mesh Base Stations (mBS) are strategically deployed and controlled by the operator to forward user traffic between Base Stations (BS) and user terminals (SS) • Similar to Relay Repeater • Mesh BS and BS are good examples of cooperative wireless nodes: • PHY/MAC level • Network level • Dynamic resource sharing

  4. Why Infrastructure Mesh ? • Mesh BS can be installed closer to cell edge and mitigate coverage and outage issues • Mesh BS avoids cost and complexity of wired backhaul provision to a new BS • Mesh/relay architecture aggregates traffic at the main BS which has wired backhaul • Lower $/bit for fatter wired pipes • Changes the economics of achieving “smaller cells” where needed

  5. Technical Issues for Infrastructure Mesh • Radio Capacity exhaustion at Wired Base Station for Access Applications • Optimization problem over depth of mesh, cost, management • Radio Resource Sharing between Client Traffic & Forwarding Traffic • Self-Organization and Adaptation • Routes, Load, QoS, Latency, Channel Adaptation • Consideration for MIMO & Directivity • Minimum installation effort • Unique Security issue • Trust Relationship Management • Standards Support • 802.11s: Near Completion • 802.16j Multihop Relay: Infrastructure focus

  6. Assumptions in this Analysis • Mesh BS can be lower complexity/cost • Smaller and lower antenna height than BS • Single radio communicating with both SS and BS • Omni-directional antenna to serve SS • Similar complexity as SS except • Directional antenna for backhaul • Alternate between antennas using simple switch • Time-shared “centralized MAC” packet radio system • Examples: 802.16/WiMAX, UMTS HSDPA • Equal time per SS under uniform infinite offered traffic load

  7. Analysis approach: Take 6-sector cell ..

  8. Add mBS at cell edge BS 600 mBS mBS

  9. A Analysis on pair of opposing sectors BS1 • 6-sector cell • 1 mBS per sector per cell • 2 mBS at cell-edge boundary of each sector • mBS1 belonging to & cooperating with BS1 • mBS2 belonging to & cooperating with BS2 mBS1 mBS2 BS2

  10. Time Intra-Sector Scheduling Approach • Compatible with 802.16 structure • A possible downlink frame structure Simultaneous Scheduling Dedicated Scheduling Backhaul BS to SS BS to mBS BS to SS mBS to SS mBS to SS

  11. Simulation Parameters

  12. Simulation Parameters - Rates • 6 MHz effective channel • Representative values from 802.16/WiMAX • Discrete levels • Continous capacity curves with no SNR limits exaggerate the benefits of mesh

  13. Multi-Cell Scenario without mBS • No log normalfading

  14. Multi-Cell Scenario without mBS • With log normal fading

  15. Multi-Cell Scenario with mBS

  16. Multi-Cell Scenario with mBS • No log-normal fading for illustration • Simultaneousscheduling regions

  17. Multi-Cell Scenario with mBS • No log-normal fading • Dedicated scheduling regions

  18. 21.25 20.44 16.22 16.02 Throughput Comparison Sector Throughput (Mbps)

  19. 24.32 22.36 5.16 4.17 QPSK ½ Outage Comparison Percentage of SS below QPSK ½

  20. SS Data Rate Comparison

  21. Conclusions and Future Work • (1,6,6) system with 6 mBS per cell shows: • Outage improvement around 80 % • Overall sector throughput improves from 16 Mbps to 21 Mbps • Uplink and (1,3,6) system shows similar trends • Capacity improvement in mesh system more than compensates for radio resources diverted towards mBS - BS backhaul • Power control, measurement/scheduling scheme, technology-specific issues

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