Adaptive Modulation Algorithms Research For Next Genearation Communication Systems

Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) system can be one of the nominated systems for beyond the third generation (B3G) mobile communication systems because of its high capacity. Adaptive modulation (AM) technology is also paid more attention by many scholars for its high data transmission rate. So we do some research work about AM algorithm for MIMO-OFDM systems in theory and practical applications.In this thesis, we firstly introduce the knowledge about MIMO and OFDM simply, and then the basic knowledge of adaptive technology is depicted later. The traditional algorithm Greedy which is well known for good performance is introduced. The AM algorithms with low complexity under some constraints are proposed to minimize the transmit power and maximize the transmission rate, respectively. Besides that, the AM algorithm using Quadrature Rectangle (QR) decomposition is given and the performance analysis in theory is deduced too. The innovations about the thesis are given as following:Firstly, the adaptive algorithm with the goal of minimizing the transmit power under the constraint of certain bit error ratio (BER) and transmission rate is proposed in the thesis. Comparing with the Greedy algorithm, the new AM algorithm can achieve almost the same performance but with much lower complexity.Secondly, we give out one new AM algorithm to maximize the transmission rate under the constraint of BER and transmit power with in this thesis. The AM algorithm can lower the complexity and the performance is almost the same performance with that of using Greedy algorithm to maximize the data transmission rate. Lastly, we propose one AM algorithm to maximize the transmission rate and give out the performance analysis result in theory. The system performance can be improved greatly (in the field of data transmission rate and BER) with the AM algorithm. The theorical result and the simulation result are almost the same, so the theorical deduction is correct.The first two AM algorithm proposed in the thesis can lower the complexity greatly, so they can be widely used in practical systems. The last AM algorithm can improve the system performance effectively, and the performance analysis result is of important theorical guide in AM design field.