Due to their spectrum shaping capability and high adaptability, the multi-carrier systems are considered as prime candidates for use in the Cognitive Radio (CR) networks. In these structures, the deactivation of the p...Due to their spectrum shaping capability and high adaptability, the multi-carrier systems are considered as prime candidates for use in the Cognitive Radio (CR) networks. In these structures, the deactivation of the primary users’ (PUs) bands makes the secondary users (SUs) use a limited number of sub-carriers, so the total capacity of CR networks is reduced. However, multiple transmit antennas can be applied to OFDM- based CR to compensate for such a low capacity. The present study investigates the problem of power allo-cation in MIMO-OFDM based CR Networks. The objective is maximizing the total capacity of CR systems in the downlink path under both interference on the PUs’ bands and maximum power of the CR transmitter constraints. It is shown that the optimal solution has high computational complexity, and therefore, an effi-cient sub-optimal algorithm is suggested for this application. As simulation results show, the suggested algo-rithm in the present paper is more enhanced and efficient than the previous algorithms.展开更多
In this paper, Multiband-OFDM UWB system based on IEEE 802.15.3a standard is studied and simulated with spatial, time and frequency (STF)coding scheme. The using of STF coding method can guarantee both full symbol rat...In this paper, Multiband-OFDM UWB system based on IEEE 802.15.3a standard is studied and simulated with spatial, time and frequency (STF)coding scheme. The using of STF coding method can guarantee both full symbol rate and full diversity advantages. The simulation results show that the STF code uses multi- path-rich and random-clustering characteristics of UWB channel environment on the performance of MB- OFDM system.展开更多
文摘Due to their spectrum shaping capability and high adaptability, the multi-carrier systems are considered as prime candidates for use in the Cognitive Radio (CR) networks. In these structures, the deactivation of the primary users’ (PUs) bands makes the secondary users (SUs) use a limited number of sub-carriers, so the total capacity of CR networks is reduced. However, multiple transmit antennas can be applied to OFDM- based CR to compensate for such a low capacity. The present study investigates the problem of power allo-cation in MIMO-OFDM based CR Networks. The objective is maximizing the total capacity of CR systems in the downlink path under both interference on the PUs’ bands and maximum power of the CR transmitter constraints. It is shown that the optimal solution has high computational complexity, and therefore, an effi-cient sub-optimal algorithm is suggested for this application. As simulation results show, the suggested algo-rithm in the present paper is more enhanced and efficient than the previous algorithms.
文摘In this paper, Multiband-OFDM UWB system based on IEEE 802.15.3a standard is studied and simulated with spatial, time and frequency (STF)coding scheme. The using of STF coding method can guarantee both full symbol rate and full diversity advantages. The simulation results show that the STF code uses multi- path-rich and random-clustering characteristics of UWB channel environment on the performance of MB- OFDM system.
