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Mathematical model of multi-user power control and resource allocation in cognitive OFDM system is investigated. Multi-user resource allocation with the target of maximizing the cognitive user's transmission rate and satisfying the proportional rate constraint between cognitive users is proposed in the condition of primary user's interference constraint. The paper supposes that cognitive transmitter...
Multi-user cognitive orthogonal frequency division multiplexing (MU-COFDM) is a promising technique for achieving high transmission capacity in future cellular and wireless local area network (WLAN) systems. Multi-user resource allocation with the target of maximizing the transmit capacity of cognitive users and satisfying the proportional rate constraint between cognitive users is proposed under...
The problem of resource allocation in multiuser OFDM system is a combinatorial optimization problem, difficult to solve in polynomial time. For the sake of reducing complexity, it can be solved either by relaxing constraints and making use of linear algorithms or by metaheuristic methods. In this paper, ant colony optimization, a typical algorithm of metaheuristic methods, is applied to solve the...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
This paper investigates effects of pilot assisted channel estimation on dynamic resource allocation in a multiuser orthogonal frequency division multiplexing (OFDM) system. The channel estimation is done in each OFDM symbol through least-squared error (LSE) or minimum mean-squared error (MMSE) algorithm. The performance of each of these algorithms is evaluated through computer simulations. The maximal...
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