Adaptive Modulation Algorithms In Block-wised System

Multipath fading is the basic character of broadband wireless communication. Block-wised transmission techniques have become a hot research field featuring robustness to multipath fading and high frequency efficiency ,which will be the key techniques for the forth generation communication. There are two CP-aided block-wised transmission techniques: Orthogonal Frequency Domain Multiplexing (OFDM)[1] and Single Carrier with Frequency Domain Equalization (SC-FDE)[2]. As two block-wised transmission techniques, OFDM and SC-FDE has duality[3].In order to get high data rate communication, we must enhance frequency efficiency because mat frequency resource is limited. Adaptive modulation is an effect way to enhance frequency efficiency. Most work in the thesis focus on the research of adaptive modulation algorithms. The thesis introduces the basic principle of OFDM and SC-FDE at first. Then it gives the comparisons between them. In chapter three, the principle and application of adaptive modulation are introduced in brief. After mat we give the introduction and analysis to the algorithms that have been proposed.The last chapter is the most important part of the thesis, which introduces three new adaptive modulation algorithms. The adaptive modulation algorithm research in SC-FDE is in its infancy compared with OFDM. Optimal signal subspace is the foundation for our adaptive modulation algorithms in SC-FDE. Another new concept is introduced called sequenced optimal signal subspaces. The new algorithm is aimed to get the maximum date rate with constant bit error ratio under power constraint The main idea is determining sequenced optimal signal subspaces at first, and men power is allocated according to water-filling principle. After that bits can be allocated to subspaces according to constraint condition. This algorithm has higher spectral efficiency compared with present one. According to the character of sequenced optimal signal space in SC-FDE, we propose an algorithm called minimum power algorithm. The new algorithm has low complexity and good performance. After several years research, adaptive modulation in OFDM is mature. At the end of chapter four, we propose a high performance adaptive modulation algorithm with lower complexity, which has better performance than Fischer' s algorithm, though it is not suitable for fast changing channels.At the end of this thesis, we summarize the major results and point out problems need to be further discussed and researched.