Spectral Efficiency in the Wideband Regime：（宽带频谱效率的制度）.pdfVIP

IEEE TRANSACTIONS ON INFORMATION THEORY, VOL. 48, NO. 6, JUNE 2002 1319 Spectral Efficiency in the Wideband Regime Sergio Verdú, Fellow, IEEE Invited Paper Abstract— The tradeoff of spectral efficiency (b/s/Hz) versus en- as a synonym of asymptotic optimality in the low-power ergy-per-information bit is the key measure of channel capacity in regime. Using this criterion, Golay [3] showed that (1) can the wideband power-limited regime. This paper finds the funda- be approached by on–off keying (pulse position modulation) mental bandwidth–power tradeoff of a general class of channels in the wideband regime characterized by low, but nonzero, spectral with very low duty cycle, a signaling strategy whose error efficiency and energy per bit close to the minimum value required probability was analyzed in [4]. for reliable communication. A new criterion for optimality of sig- Enter fading. Jacobs [5] and Pierce [6] noticed not only that naling in the wideband regime is proposed, which, in contrast to (1) is achieved if all the energy is concentrated in one message- the traditional criterion, is meaningful for finite-bandwidth com- dependent frequency slot, but also that the limiting rate in (1) munication. is unexpectedly robust: it is achievable even if the orthogonal Index Terms—Antenna arrays, channel capacity, fading chan- signaling undergoes fading which is unknown to the receiver (a nels, noisy channels, spectral efficiency, wideband regime.