| Popis: |
Cognitive Radio (CR) has been proposed as one of the most promising technologies to provide efficient utilization of the limited wireless spectrum. In this paper, we investigate the power allocation for CR system based on orthogonal frequency division multiplexing (OFDM), and an improved allocation algorithm called power-weight algorithm is proposed. This algorithm performs initial allocation via Lagrange multiplier method, and then accomplishes second allocation based on power weight obtained in initial allocation. The analytical results reveal that the total transmission rate of all subcarriers is much closer to the optimal algorithm (i.e. the greedy algorithm) than the water-level algorithm, the Krongold algorithm and adaptive water-filling algorithm, subject to transmit power constraint and bit error rate (BER) constraint. These algorithms are all based on water-filling thought. Finally, simulation results verify our analysis. |
