Cognitive Group Power Assignment in Low-Power Regime
To improve the spectrum utilization efficiency by using cognitive radio (CR), the efficient use of power resource is essential. For low-power underlay systems such as ultra wideband (UWB), extremely low transmit power is mandatory for the purpose of primary users’ (PU) protection, which however significantly impedes the use of UWB’s spectrum. In this paper, for UWB based CR systems, we propose an cognitive group power assignment algorithm to maximize the CR-UWB’s spectral efficiency while conforming to the PUs protection requirements. We formulate the spectral efficiency maximization problem as an multidimensional knapsack problem which is generally NP-Hard, and approximate the optimal solution by developing a greedy based algorithm considering the low-power feature of the CR-UWB system. A power grouping technique is derived to limit the proposed algorithm’s order-of-growth. Compared with the traditional water-filling based power allocation algorithms, the proposed algorithm can attain the highest spectral efficiency which is close to the optimality in extremely low-power regime.
KeywordsPower allocation Cognitive radio Low-Power regime
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