All digital baseband frequency hopping OFDM system

In this paper, an all digital baseband frequency-hopping orthogonal frequency division multiplexing (OFDM) system based on sampling rate conversion has been proposed. By changing the ratio of sampling rate conversion, the frequency hopping (FH) gain can be configured easily. Comparing with the conventional fixed carrier frequency OFDM, this system can achieve frequency diversity gain; while comparing with the analog frequency hopping OFDM (FH-OFDM) emerging recently, our proposed system has more flexibility, lower complexity, and better acquisition and synchronization performance for digital receiver. Superimposed sequence has been employed as the training sequence for synchronization and channel estimation, unlike preamble sequence inserted in time domain and pilot subcarriers inserted in frequency domain, this scheme can improve spectrum efficiency at the cost of a little bit SNR loss, moreover, it can perform joint FH pattern acquisition and frame synchronization for the proposed system simultaneously. Simulation results show that the proposed system has better performance than non-FH system, and achieves good SER performance over additive white Gaussian noise (AWGN) channels as well as multipath channels. The power ratio of superimposed signal to information signal provides a way of trade-off between SNR loss and synchronization performance. Changing the power ratio also affects the system performance.