Study Of Adaptive Bit And Power Allocation In MIMO-OFDM Systems

According the increasing of different wireless businesses, it needs to enlarge the systemcapacity and get higher data rate for multimedia business. The combination of multiple-inputmultiple-output technology and orthogonal frequency division multiplexing technology make anew high data rate transmission technology. MIMO technology can significantly increase thechannel capacity of wireless communication systems and enhance the reliability of datatransmissions by using multiple transmitting antennas and receiving antennas. OFDMtechnology can decompose the frequency-selective fading channel into a group of orthogonal flatfading channel, therefore, it could be applied to the MIMO system for overcoming the impact ofmultipath fading. MIMO-OFDM wireless communication system not only has theanti-frequency-selective fading ability, but also has the great channel capacity. It is regarded thatMIMO-OFDM technology is the main physical layer technology of the fourth generation mobilecommunication system.Adaptive technology can take full advantage of the instant dynamic performance toallocate the transmitting data rate and power, so that we can optimize the system performance byit. The adaptive technology in MIMO-OFDM wireless communication system can greatlyimprove the system performance. The adaptive modulation technique in MIMO-OFDM systemchanges dynamically each subcarrier transmission parameters to optimize the overall systemperformance, based on the channel state information. Under such circumstances, adaptivemodulation is also known as adaptive bit and power allocation, which allocates the bitinformation and transmitting power dynamically to each subcarrier based on real-time statusinformation, so as to achieve the purpose of optimizing the system performance.In this paper, an adaptive modulation scheme is proposed in order to minimize the totaltransmission power subject to given BER and transmitting data rate in single-userMIMO-OFDM wireless communication systems, which is based on the precoding design. Thekey algorithm of the scheme is Campello algorithm which is used widely, meanwhile, it isimproved by various-step adaptive bit loading. The simulation results show that the presentedimproved algorithm has a similar system performance to Campello algorithm, but lesscomplexity than it, and both performances are much better than non-adaptive MIMO system.