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Network diversity in broadband wireless system

Flexible and scalable wide area network using satellite backhauls and configurable wireless ground access. Supports broadband multimedia applications and all-IP based mobility management. | Network diversity in broadband wireless system ONR workshop 2003 Hui Liu Department of Electrical Engineering University of Washington Outline Multiuser/network diversity Applications OFDMA network Rapidly deployable, self-configurable WAN Concluding Remarks Multiuser/network diversity Wireless users’ characteristics are heterogeneous. Dynamic channels (space/frequency/time) Diverse QoS requirements. Varying mutual interference. Multi-user/network diversity: diversity exploited by the MAC layer for efficient resource sharing Example: spatial multiuser diversity User 5 User 1 User 2 User 3 User 4 User 1 User 2 User 4 User 5 User 3 time space SDMA: random assignment User 1 User 3 User 4 User 5 User 2 time space SDMA: channel-aware assignment spatial correlation: orthogonal coherent intelligent SDMA: near-orthogonal users in one time slot significant gain without undue PHY cost Spatial signatures Example: frequency multiuser diversity frequency-selective broadband channels spontaneous | Network diversity in broadband wireless system ONR workshop 2003 Hui Liu Department of Electrical Engineering University of Washington Outline Multiuser/network diversity Applications OFDMA network Rapidly deployable, self-configurable WAN Concluding Remarks Multiuser/network diversity Wireless users’ characteristics are heterogeneous. Dynamic channels (space/frequency/time) Diverse QoS requirements. Varying mutual interference. Multi-user/network diversity: diversity exploited by the MAC layer for efficient resource sharing Example: spatial multiuser diversity User 5 User 1 User 2 User 3 User 4 User 1 User 2 User 4 User 5 User 3 time space SDMA: random assignment User 1 User 3 User 4 User 5 User 2 time space SDMA: channel-aware assignment spatial correlation: orthogonal coherent intelligent SDMA: near-orthogonal users in one time slot significant gain without undue PHY cost Spatial signatures Example: frequency multiuser diversity frequency-selective broadband channels spontaneous packet interference each narrowband resource likely to be a very good channel for some users capacity maximized when channel to the best user (fairness ignored) Example: traffic multiuser diversity diverse QoS (e.g., delay and throughput) instantaneous resource unit (time-frequency-space) bears different significance cross-layer designs enable maximum gain Challenge is to exploit multiuser diversity while sharing the benefits fairly and timely to users Outline Multiuser/network diversity Applications OFDMA network Rapidly deployable, self-configurable WAN Concluding Remarks The trend Generic OFDMA broadband wireless network IFFT Serial To Parallel Parallel To Serial OFDM User signal Coding COFDM MC-CDMA OFDMA Spread spectrum 1 -1 1 -1 FH-OFDM t IFFT Serial To Parallel User signal Coding Spread spectrum 1 1 -1 -1 f No intracell interference Finest granularity Simple, low cost PHY Capacity achieving Exploiting multiuser diversity in OFDMA Maximizing the total throughput (easy) while .