第4章 无线信道容量.pdf

研究生《现代无线通信技术》课程 第四章无线信道容量 余 华 华南理工大学电子与信息学院 2012年4月19日星期四 Outline • Shannon Capacity • Capacity of Flat-Fading Channels – Fading Statistics (CDI) Known – Fading (CSI) Known at RX – Fading Known at TX and RX – Optimal Rate and Power Adaptation – Channel Inversion with Fixed Rate • Capacity of Freq.-Selective Fading Channels 2 Shannon Capacity • Defined as the maximum MI of channel AWGN: • Maximum error-free data rate a channel can support. • Theoretical limit (not achievable) • Channel characteristic – Not dependent on design techniques 3 Shannon Capacity 4 Capacity of Flat-Fading Channels • Capacity defines theoretical rate limit – Maximum error free rate a channel can support • Depends on what is known about channel • Fading Statistics Known (CDI known, but CSI-Channel gain g[i] at time i unknown) – Hard to find capacity 5 Fading Known at Receiver Only • The value of g [i] is known at the RX at time i • γ[i] is known at the RX at time i • Both the TX and RX know the distribution of g [i] • Shannon capacity (Ergodic capacity, 遍历容量, (4.4)) ∞ ( ) C B log 1+γ p (γ)dγ ≤B log (1+γ) ∫ 2 2 0 • Capacity with outage(带中断的容量) ( ) C (1−P )B log 1+γ , P P (γ γ ) out out 2 min out min γmin is the minimum received S