With an increasing number of collocated personal, local and cellular wireless communication systems, the question of optimum coexistence and internetworking are raised. Although some mitigation techniques, like DAA, LDC, Frequency band notching etc. are being widely studied by industries, regulation bodies and standardization authorities, none of them show good performance in terms of detection and energy consumption without having a priori knowledge about the primary system which is not usually available. Cognitive radios and networks with cognitive signaling and dataaided mitigation techniques can become then key enablers for true heterogeneous communication environment with optimal sharing of the spectrum and coexistence. Cognitive pilot channel (CPC) is a novel, recently proposed approach which could guarantee a conflict-free coexistence. In this paper we show a generic scheme to achieve better coexistence between UWB and WIMAX through enhancing existing mitigation techniques.

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Recent effort related to cognitive radio systems\ud has lead to an in-depth analysis of context\ud information management and exploitation\ud based on a cognitive control channel for\ud enhancement of management needed for, say,\ud suitable link selection in a heterogeneous radio\ud framework, dynamic radio resource management,\ud and distributed sensing. Concerning the\ud actual implementation of such a CCC, the focus\ud was recently moved toward an in-band solution,\ud where the information is transported building\ud on existing radio access technologies. In this\ud scope, this article illustrates relevant technical\ud scenarios in which CCCs can be exploited and\ud outlines a set of derived system requirements.\ud The article provides an overview of various possible\ud RAT independent and dependent implementation\ud options, such as Diameter,\ud distributed agents, 3GPP radio resource control(RRC) mechanisms, IEEE 802.21, IEEE 802.11,\ud WiMedia UWB, and Bluetooth. The advantages\ud and drawbacks of the various options are\ud discussed.Peer ReviewedPostprint (published version