Research On Techniques Of Variable-Rate Multiple Access In The Broad-Band Ground-Air Link And Its FPGA Design

As the developing of the broad-bank ground-air communication, the fixed-rate data transmission between aircrafts and earth stations has been far from satisfying the modern complex business requirements. Variable-rate communication, which can meet the requirements of voice and low-rate data communications as well as the high-rate multi-media communications, is becoming a very hot research topic. Simultaneously, variable-rate communication makes the transmitted signal have an unfixed bandwidth, which puts forward a serious challenge to frequency division de-multiplexer in a FDMA system. After thorough study of the basic principle of quasi-orthogonal time division multiplexing (QOTDM), the thesis proposes a novel variable-rate multiple access system in the broad-bank ground-air link and deeply researches on the techniques in de-multiplexing of variable-width FDMA signals, as well as its FPGA implementation. The author's main contributions are as follows:1. Basing on the studies of techniques in QOTDM transmission system, a variable-rate multiple access system is proposed. Then the argumentation about functions of each component and some simulation experiments about the structure scheme of the system above has been made.2. Via thorough analysis of conventional FFT de-multiplexer, a new method using FFT/IFFT algorithms for de-multiplexing of variable-bandwidth FDMA signals for the system above is proposed, which can split the FDMA signals that meet the system requirements and have any bandwidth under the command of control center. Since the adoption of efficient FFT/IFFT algorithm, the method has characteristics of high efficiency and low complexity. Some simulation results to validate the function of the method above are given.3. Based on the theoretical analysis above, the FPGA design and function simulation on the variable-bandwidth FFT de-multiplexer has been done based on the platform of ISE.