6:Opportunistic Communication and Multiuser EECS Diversity ireless oundations 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). Fundamentals of Wireless Communication,Tse&Viswanath 6
6: Opportunistic Communication and Multiuser Diversity Fundamentals of Wireless Communication, Tse&Viswanath 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 EECS Diversity Wireless F oundations Point-to-Point Fading Channels P[m]=0 P(m Time m Capacity-achieving strategy is waterfilling over time. Fundamentals of Wireless Communication,Tse&Viswanath
6: Opportunistic Communication and Multiuser Diversity Fundamentals of Wireless Communication, Tse&Viswanath 7 Point-to-Point Fading Channels Capacity-achieving strategy is waterfilling over time
6:Opportunistic Communication and Multiuser ECS Diversity ireless oundations Performance over Rayleigh Channel 7 6 5 AWGN 4 Full CSI CSIR 3 2 1 0 -20 -15 -10 -5 0 10 15 20 SNR (dB) Fundamentals of Wireless Communication,Tse&Viswanath 8
6: Opportunistic Communication and Multiuser Diversity Fundamentals of Wireless Communication, Tse&Viswanath 8 Performance over Rayleigh Channel
6:Opportunistic Communication and Multiuser ECS Diversity Wireless F oundations Performance:Low SNR 3 2.5 2 CSIR Full CSI.. 1.5 1 050 -15 -10 -5 0 5 10 SNR [dB] At low SNR,capacity can be greater when there is fading. Fundamentals of Wireless Communication,Tse&Viswanath 9
6: Opportunistic Communication and Multiuser Diversity Fundamentals of Wireless Communication, Tse&Viswanath 9 Performance: Low SNR At low SNR, capacity can be greater when there is fading
6:Opportunistic Communication and Multiuser EECS Diversity Nireless oundations Hitting the Peaks Near Optimal All Optimal Allocation Time (】 P(m] (b At low SNR,one can transmit only when the channel is at its peak. Primarily a power gain. In practice,hard to realize such gains due to difficulty in tracking the channel when transmitting so infrequently. Fundamentals of Wireless Communication,Tse&Viswanath 10
6: Opportunistic Communication and Multiuser Diversity Fundamentals of Wireless Communication, Tse&Viswanath 10 Hitting the Peaks At low SNR, one can transmit only when the channel is at its peak. Primarily a power gain. In practice, hard to realize such gains due to difficulty in tracking the channel when transmitting so infrequently