Research On Adaptive Bit And Power Algorithms For OFDM-MIMO System

According the increasing of different wireless businesses, it needs to enlarge the system capacity and get higher data rate for multimedia business. The combination of multiple-input multiple-output technology and orthogonal frequency division multiplexing technology make a new high data rate transmission technology. MIMO technology can significantly increase the channel capacity of wireless communication systems and enhance the reliability of data transmissions by using multiple transmitting antennas and receiving antennas. OFDM technology can decompose the frequency-selective fading channel into a group of orthogonal flat fading channel, therefore, it could be applied to the MIMO system for overcoming the impact of multipath fading. OFDM-MIMO wireless communication system not only has the anti-frequency-selective fading ability, but also has the great channel capacity. It is regarded that OFDM-MIMO technology is the main physical layer technology of the fourth generation mobile communication system.Adaptive technology can take full advantage of the instant dynamic performance to allocate the transmitting data rate and power, so that we can optimize the system performance by it. The adaptive technology in OFDM-MIMO wireless communication system can greatly improve the system performance. The adaptive modulation technique in OFDM-MIMO system changes dynamically each subcarrier transmission parameters to optimize the overall system performance, based on the channel state information. Under such circumstances, adaptive modulation is also known as adaptive bit and power allocation, which allocates the bit information and transmitting power dynamically to each subcarrier based on real-time status information, so as to achieve the purpose of optimizing the system performance.The multiple antenna Orthogonal Frequency Division Multiplexing (OFDM) system model is analyzed in this paper. Considering that Multiple-Input Multiple Output (MIMO) channel can be separated into parallel subchannels by means of the singular value decomposition, and deep faded subcarriers may degrade the OFDM system performance. the adaptive bit and power allocation for MIMO-OFDM system are proposed. The analysis and simulation results show that the proposed adaptive MIMO-OFDM improves bit error rate performance and spectral efficiency of the system.