opportunisticCommunication - 6: Opportunistic Communication...

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Unformatted text preview: 6: Opportunistic Communication and Multiuser Diversity 1 6. Opportunistic Communication and Multiuser Diversity Fundamentals of Wireless Communication, Tse&Viswanath 6: Opportunistic Communication and Multiuser Diversity 2 Fundamental Feature of Wireless Channels: Time Variation multipath fading large-scale channel variations time-varying interference 6: Opportunistic Communication and Multiuser Diversity 3 Traditional Approach to Wireless System Design Compensates for channel fluctuations. 6: Opportunistic Communication and Multiuser Diversity 4 Example: CDMA Systems Two main compensating mechanisms: 1. Channel diversity: frequency diversity via Rake combining macro-diversity via soft handoff transmit/receive antenna diversity 2. Interference management: power control interference averaging 6: Opportunistic Communication and Multiuser Diversity 5 What Drives this Approach? Main application is voice , with very tight latency requirements. Needs a consistent channel. 6: Opportunistic Communication and Multiuser Diversity 6 Opportunistic Communication: A Different View Transmit more when and where the channel is good. Exploits fading to achieve higher long-term throughput, but no guarantee that the "channel is always there". Appropriate for data with non-real-time latency requirements (file downloads, video streaming). 6: Opportunistic Communication and Multiuser Diversity 7 Point-to-Point Fading Channels Capacity-achieving strategy is waterfilling over time. 6: Opportunistic Communication and Multiuser Diversity 8 Performance over Rayleigh Channel...
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This note was uploaded on 10/02/2011 for the course ECE 5670 taught by Professor Scaglione during the Spring '11 term at Cornell University (Engineering School).

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opportunisticCommunication - 6: Opportunistic Communication...

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