We consider a multiple-input, multiple-output (MIMO) wideband Rayleigh blockfading channel where the channel state is unknown to both the transmitter andthe receiver and there is only an average power constraint on the input. Wecompute the capacity and analyze its dependence on coherence length, number ofantennas and receive signal-to-noise ratio (SNR) per degree of freedom. Weestablish conditions on the coherence length and number of antennas for thenon-coherent channel to have a "near coherent" performance in the widebandregime. We also propose a signaling scheme that is near-capacity achieving inthis regime. We compute the error probability for this wideband non-coherent MIMO channeland study its dependence on SNR, number of transmit and receive antennas andcoherence length. We show that error probability decays inversely withcoherence length and exponentially with the product of the number of transmitand receive antennas. Moreover, channel outage dominates error probability inthe wideband regime. We also show that the critical as well as cut-off ratesare much smaller than channel capacity in this regime.
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