Research On OFDM-based Digital Frequency Hopping Communication Technology And Its Hardware Design

In recent years,with the development of wireless communication technology,the Mobile Ad Hoc Network(Mobile Ad Hoc Network,MANET)has developed rapidly.However,due to the complex and rapid changes in the topology of the MANET network,the multipath effect and the interference between the nodes are more significant.Frequency hopping technology can effectively improve the anti-interference ability of the communication system and reduce the interference between channels.Orthogonal frequency division multiplexing(OFDM)technology is to transform the input data sequence in time domain into parallel data in frequency domain,so it may be considered to map the time domain data to one or more of the frequency bands to achieve digital frequency hopping based on OFDM.The digital frequency hopping system based on OFDM has the advantages of fast hopping speed,easy digital integration,and low power dissipation.In OFDM-based frequency-hopping communication,the subcarrier mapping methods and frequency-hopping sequence have important impact on the Frequency Hopping OFDM(FH-OFDM)system.The main works of this article are as follows:(1)Firstly,analyze the performance about OFDM-based frequency-hopping communication;secondly,We analyze the characters of OFDM-based time-continuous FH and time-interval FH;finally,the construction methods of the m-sequence,RS sequence,Costas sequence,Latin Square sequence on the impact of FH performance are studied.(2)For OFDM-based time-continuous frequency-hopping communication system,we studied five-subcarrier mapping method on system performance which are single-subcarrier mapping,random multi-subcarrier mapping,packet-dispersed subcarrier mapping,packet-localized subcarrier mapping,and packet-random subcarrier mapping.(3)A time-interval frequency-hopping communication system based on OFDM was proposed,we studied the system performance of fixed time interval grouping distributed subcarrier mapping,fixed time interval grouping centralized subcarrier mapping,fixed time interval grouping random subcarrier mapping and random time interval system performance of grouping random sub-carrier mapping and four-seed carrier mapping.(4)For different frequency hopping communication systems,m-sequence discontinuous tap,RS sequence,Costas sequence,Latin Square sequence are constructed.The OFDM-based frequency hopping communication system under the nine-subcarrier mapping method incorporation with four frequency hopping sequences.Under the Gaussian channel,Rayleigh channel,single frequency interference,multi-frequency interference and partial frequency band interference was simulated and analyzed.The simulation results shown that the FH-OFDM system has better anti-multipath and anti-interference performance than the OFDM system.At the same time,it is found that the random time interval grouping random subcarrier mapping FH-OFDM incorporation with the RS sequence can get better performance than the other subcarrier mapping methods under the same communication conditions.(5)The hardware circuits design of the FH-OFDM system that adapt random sub-carrier mapping with RS sequence is completed,the hardware design and functional verification of the system are accomplished by hardware description language.The hardware verification and logic synthesis based on the FPGA platform of XILINX Virtex-7 VC707 Evaluation board.The synthesis results shown that the clock frequence of the Frequency Hopping Timing Hopping(FHTH)module can reach up to 333 MHz,the total power dissipation is0.619 W,which occupies 1503 slice LUTs and 1627 slice registers,the transmitter module occupies 523 IO resources,and the receiver module occupies 522 IO resources.