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Upper bounds on the capacity of discrete-time blockwise white Gaussian channels with feedback

2000; Institute of Electrical and Electronics Engineers; Volume: 46; Issue: 3 Linguagem: Inglês

10.1109/18.841195

1557-9654

Han Wu Chen, Kenjiro Yanagi,

graph theory and CDMA systems

Although it is well known that feedback does not increase the capacity of an additive white Gaussian channel, Yanagi (1992) gave the necessary and sufficient condition under which the capacity C/sub n,FB/(P) of a discrete time nonwhite Gaussian channel is increased by feedback. In this correspondence we show that the capacity C/sub n,FB/(P) of the Gaussian channel with feedback is a concave function of P, and give two types of inequalities: both 1//spl alpha/ C/sub n,FB/(/spl alpha/P) and C/sub n,FB/(/spl alpha/P)+ 1/2 ln 1//spl alpha/ are decreasing functions of /spl alpha/>0. As their application we can obtain two upper bounds on the capacity of the discrete-time blockwise white Gaussian channel with feedback. The results are quite useful when power constraint P is relatively not large.