Performance Study Of Diversity Differential Frequency Hopping Systems In Jamming And Fading Channels

Differential Frequency Hopping (DFH) is a new generation of remote military radio communication system. It can provide reliable HF communication at high data rate and demonstrate improved anti-jamming and low detection probability performance. Unlike the conventional FH technique which need keep frequency synchronization between transmitter and receiver, DFH takes advantage of the correlation of transmitted frequency and function G to control new output frequency. On the condition of no error correcting code, DFH can correct partial missed hop by itself. Just because the excellent performance, differential frequency hopping technique has become one of the most active research aspects of HF radio communication in the recent decade.Interference and channel fade is a vital point that can influence the reliability of the radio communication system. DFH is applied so frequently to shortwave military communication that manmade interference is the important factor which must be considered especially. Partial-band interference can be treated as a specific fade form which has two discrete fade levels, it had be widely noticed that diversity is a very effective way that can overcome the disadvantage that fade brings to radio system, so the author of this dissertation decided to choose anti-jam and anti-fade in DFH to be the research direction. It is the final goal of this dissertation to analyze the bit error rate performance of DFH in the different diversity technique and fade channels.The main work of this dissertation includes the following three aspects. Firstly, a new time diversity differential frequency system is proposed by this project which has designed in detail the model of the transmitter and receiver and described its operational principle. We use an address code system to realize the time and frequency diversity of transmitted signal, an information symbol reaches the receiver by different fading transmission path. In this scheme, a class of dual-k codes with the best distance properties is acted as the function G of DFH, and receiver introduces the noncoherent energy detection to received frequency signal, the output of the detection is used to make maximum likelihood sequence decoding. Combining the trellis code transfer function with Chernoff bound, we derive concretely the pairwise error probability of DFFH and theoretical formula on BER Unino-Chernoff bound of system, moreover we research the BER system performance on the condition of gaussian noise channel, rayleigh fading channel and rician fading channel and analyze the effect on bit error rate that diversity order, jammer factor and jammer state information make.Secondly, we propose a new DFH scheme which has space-time function G in multiple input and multip output (MIMO) channel, and give the precise mathematical model and working theory about it. According to correlation of partial-band noise jamming (PBNJ) on different transmitting antenna, we consider two schemes. One of them is that the PBNJ on different antennas is independent with each other. In this situation, Chernoff parameter is correlated with output encoded symbol and is uncorrelated with the branch label, and this system can provide space diversity gain by multiple receive antennas. Unlike SISO system, we use modified decoding metric to derive detailed BER union-chernoff which is based on MIMO PBNJ channel. The other scheme is the PBNJ on different transmitting antenna is correlated, we present a new branch label gain based on M-ary orthogonal signal. Jointing this branch label gain and Pair-state transition diagram, we analyze mathematically pairwise error probability and union bound of non-uniform error probability code under the partial-band noise jamming channel. In this method, multiple chernoff parameter is brought into M-ary orthogonal signal and space-time trellis system and it is somewhat complex to implement it completely.Finally, we research the concrete implementation of shortwave wideband channel simulator based on ITS channel model. According to quasi-stationary time-invariant theory, the delay power profile function, deterministic phase function, stochastic modulating function and noise and interference function are formulated as discrete rather than continuous ones so as to be processed by digital filter. We also study the filter implementation of the stochastic modulating function which causes gaussian and lorentzian shape spectral smearing. In order to satisfy the actual demand, a RF shortwave wideband channel simulator is designed. Simulator structure and RF subsystem are described in detail. On the basis of the specific shortwave channel parameter, we analyze the channel impulse response and scattering function of shortwave wideband simulator proposed in this dissertation, and design the delay and power spectrum characteristic of simulator tap coefficient. In order to studying the BER performance DFH system in frequency-selective fading channel, we derive mathematically discrete time equivalent baseband model of shortwave wideband channel simulator. Applying this equivalent model combined with shortwave RAKE and MLSE equalization technique, we use computer simulation to test BER performance of DFH in shortwave intersymbol interference channel...