| 摘要 |
Communications systems and/or methods are disclosed that can provide extreme privacy, cognitive radio capability, robustness to fading and interference, communications performance associated with M-ary orthonormal signaling and/or high multiple-access capacity. Embodiments can use spread-spectrum waveforms that are featureless, devoid of chipping and devoid of cyclostationary signatures, statistically indistinguishable from thermal noise and able to cognitively fit within any available frequency space (narrow-band, broad-band, contiguous, non-contiguous). Some embodiments maintain all desirable features of classical direct-sequence spread-spectrum communications while providing new dimensions that are important to communications systems. Embodiments of the invention can provide M-ary orthonormal signaling with chipless spread-spectrum waveforms to provide extreme covertness and privacy. Moreover, embodiments of the invention may be used to cognitively and covertly utilize spectrum resources at minimal impact to incumbent users. Further embodiments may be used to provide minimum interference, opportunistic, "white space spectrum" communications.
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