[問題] 一個通訊的問題

看板comm_and_RF作者 (蹂躪之爪牙)時間16年前 (2007/11/20 21:33), 編輯推噓1(106)
留言7則, 3人參與, 最新討論串1/1
The capacity of a waveform channel can be approximated with a summation of the capacities of parallel sub-channels which partition the original shaped K channel, i.e., C=△WΣlog [1+(sk/nk)] k=1 2 where sk and nk are the signal and noise power at the k-th sub-channel respectively. Assume that sk is known, and you want to “jam” the transmission by arranging a noise distribution with total power of N, that is, nk satisfies the constraint . What is the “best” noise distribution that minimizes the channel capacity? (Note: When derive your results, assume two extreme situations: the first is to assume that the noise budget is far less than the signal power. And the second is to assume a much greater noise power than the signal.) 請指教Orz -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.113.123.1

11/20 21:54, , 1F
Inverse Water-Filling....
11/20 21:54, 1F

11/21 03:39, , 2F
當N很小,用log(1+sk/nk)=log(sk/nk)
11/21 03:39, 2F

11/21 03:41, , 3F
N很大時, log(1+sk/nk)=sk/nk
11/21 03:41, 3F

11/21 03:43, , 4F
之後就可以用Lagrange multiplier去解
11/21 03:43, 4F

11/21 03:49, , 5F
I don't think it's a good idea to ask
11/21 03:49, 5F

11/21 03:50, , 6F
your HW on bbs, at least, you should
11/21 03:50, 6F

11/21 03:52, , 7F
post your thoughts first
11/21 03:52, 7F
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