Design Of An Index Modulation Technique And A Rateless Coded Vector OFDM System

In recent years, the rapid development of wireless communication brings great convenience to our daily life. OFDM scheme has been extensively adopted by many wireless communica-tion systems. Inspired by the OFDM scheme, people start to research other schemes which have higher spectrum efficiency than OFDM. To improve the throughput of OFDM system further more, the OFDM with index modulation is proposed, in which not all the subcarriers are selected to carry constellation symbols while the indices of the active subcarriers also carry information. It has been shown that the OFDM-IM scheme achieves significantly better BER performance than traditional OFDM at high SNR region. In another field, it has been a difficult problem to achieve reliable and high-spectrum-efficiency communication in the high speed mobile environ-ment. From the view of coding, rateless code has the channel adaptive characteristics. From the view of modulation, Vector OFDM scheme is a modulation between single carrier modula-tion and multi-carrier modulation, which has a better performance in the doubly selective fading channels than OFDM scheme. In this paper, firstly, a more efficient scheme called OFDM in-dex modulation with improved mapping algorithm is proposed. Secondly, combined with the characteristic of high speed mobile communication, a transmission system which is based on the rateless encoding and Vector OFDM modulating is designed. Related studies are as follows:A more efficient scheme called OFDM index modulation with improved mapping algorithm is proposed. At the transmitter, the structure of the subblock is redesigned, and two vectors k and M are introduced for the design of the Tx table, respectively denote all the allowed number of active subcarriers and mapping methods. At the receiver, we redesign the detection structure. By calculating LLR value and ML value to decide the mode of the subblock, we can recover the original bits. The simulation results show that the proposed system achieves a higher spectrum efficiency and better BER performance compared with the existing OFDM-IM schemes.A transmission system based on the rateless encoding and Vector OFDM modulating is designed for the high speed mobile communication. We propose the transmitter and receiver structure of the system, then we focus on the design of the physical layer frame, which contains short preamble, long preamble, signal and data. At the receiver, we design an adaptive energy detection module and an auto gain control module. The details of the parameters used in adaptive energy detection and the operational flowchart are given. At last, we design the pilot of the Vector OFDM symbol block.Based on the Sora platform which is a software radio system in commodity PC architec- ture developed by Microsoft Research Asia, we design and implement the rateless encoding and Vector OFDM modulating system. In this paper, the system parameters are shown and the con-stellations of the transmitter and receiver are also presented. As for the aspect of decoding, we derive the LLR formula for QPSK mapping. In order to simulate the characteristics of the high speed mobile communication, we add the BEM channel parameters. Fort the purpose of finding the best encoding parameter, two encoding plans are proposed. Finally, we calculate the theo-retical transmission throughput and give out throughput that our designed system achieves under the different system parameters.