The Adaptive OFDM Technology Of Data Services Research Based On Cross-layer Control

With the rapid development and the increasing integration of network technology andwireless communication technology, the contradiction between the limited network resourcesand users’ increasing business needs is also becoming more prominent. How to use the channelspectrum resources more efficiently is one of the important research topics. With its outstandingadvantages, adaptive OFDM modulation system brought a turning point to the wirelessenvironment which has limited spectrum resources.Firstly, this thesis introduces the overview and summary of adaptive OFDM technologydevelopment and cross-layer control technology, and describes the principles and classicalalgorithm of adaptive OFDM modulation technology. With the guidance of the cross-layerdesign thinking, the thesis presents a design scheme about adaptive OFDM communicationsystem which is based on FPGA+MCU hardware platform and designs the implementationframework for adaptive OFDM modulation system. What’s more, we also develops MAC framestructure and the PPDU format. The adaptive algorithm used by the system is improved SBLA.Theoretically, the maximum data transfer rate can reach14Mbps.Particularly, this thesis analyzes the modulator of this system, formulates the overallimplementation framework and system parameters, and also designs detailed schemes for the keymodules such as channel encoding, constellation mapping, pilot modulated, sub-bandpre-equalization, preamble sequence constructor, configurable IFFT/FFT, interpolation filter.On Quartus II platform of Altera, we implemented the modulator of this system on CycloneIII series FPGA platform with Verilog HDL. And the simulation is conducted on ModelSim.Among this, we use the configurable IFFT/FFT soft-core to implement IFFT module. Thesoft-core adopts radix-22algorithm and SDF pipeline structure. It can be easily configured to2n(n [3,12]) points FFT or IFFT. The maximum operating frequency is up to306.30MHz. Themodulator of adaptive OFDM we implemented can use the adaptive parameters which isincluded in MAC frame to modulate. The MAC data frame can be received from MCU via thehigh-speed serial interface. In this way, we achieves the adaptive transmission in complexwireless environment. In practical applications, it has a great deal of flexibility and adaptability.