Research On Frequency Mapping And Collision For The Baseband FH-OFDM

The basic transmission and multiple access techniques of broadband wireless access and broadband mobile communications are both based on OFDM technology. The uplink used single carrier frequency division multiple access (SC-FDMA) which is realized by the extended discrete Fourier transform OFDM (DFT-S-OFDM) technology, and the downlink uses orthogonal frequency division multiple access (OFDMA) technology in LTE. As OFDM uses multiple parallel transmission technology, it can improve the information transfer rate, moreover, the sub-carriers are orthogonal to each other, so that it can partially overlap, which can improve spectral efficiency. Because of different frequencies, the fading of poles are not the same, and the frequency hopping technology can avoid frequency hit at the fading poles for a long time which can achieve frequency diversity.The combination of frequency hopping and OFDM technology can not only play advantages of the both, but also reduce the frequency hopping implementation complexity by selecting the appropriate combination. As the development of communication technology, the uplink shared channel (PUSCH) in LTE has been used frequency hopping scheme, the IEEE802.20also uses OFDMA based on scheduling or frequency hopping, frequency hopping OFDM will be gradually taken seriously.Firstly, the implementation process of multi-carrier frequency-hopping OFDM and RF frequency hopping OFDM include baseband frequency hopping OFDM are studied and analyzed in this thesis. In the RF frequency hopping OFDM system, OFDM modulation and frequency hopping modulation can be regarded as two separate modules, although combines the advantages of both, the implementation complexity is not reducing. And the realization of the frequency hopping OFDM in baseband is equivalent to precode with information, let the subcarriers to jump, need not produce new frequency, it’s easy to achieve.Secondly, the key lies in the baseband frequency hopping OFDM is sub-carrier frequency hopping mapping, so the thesis focused on frequency-hopping mapping method and the frequency collision problems. In the study of cycle frequency hopping mechanism, two ways of realizing frequency hopping are given, one is DFT matrix transform, the other is zero-padding method, and Matlab simulation and analysis are done. As cycle frequency hopping and DFT matrix transformation frequency hopping is not easy to achieve in a distributed implementation of FH-OFDMA, the thesis refers to the packet frequency hopping and independent random hopping sub-carrier mapping, conducting a theoretical analysis of the collisions of frequency and simulating by Matlab, the simulation results shown that the collision probability of the two hopping style are equal to the theoretical result, and the number of error symbols generated by the two hopping are equal.