Network Modulation Technique Based On Relay Using In Deep Space Communication

Network modulation technique offers protection mechanism according to their relative importance of transmitting messages, the system model of network modulation is based on relay with three points network topology. In this paper, it’s the first time network modulation technology is used in deep space communication, which is based on relay network topology. The main purpose is to compromise reliability and validity of deep space communication. That is, improving effectiveness of system on the premise of guaranteeing reliability of system. The main content includes three parts: constellations mapping rule of network modulation, different mapping rules and demodulation methods which may affect system performance, calculation principle and derivation of BER and throughput which are two important indicators to measure the reliability and validity.Firstly, the system model of network modulation technology is established, and then the transmission mechanism and the constellations mapping rules are introduced in detail. Different constellations mapping rules and different demodulation methods can lead to different system performance. In this paper, we take a three-hop link using Gray mapping 8PSK modulation technology as an example, proposing the overall demodulation and bit-by-bit demodulation method, then use Matlab to simulate these two different demodulation methods. The conclusion is that using bit-by-bit demodulation method can reduce system error rate through the analysis of simulation results.Secondly, formulas of bit error rate(BER) and throughput are derivated and simulated. BER and throughput are the main manifestations of reliability and effectiveness, we propose the recursive method to derive generic hierarchical PAM error rate formula in additive white Gaussian noise channel condition, and then we analyze and compare different constellation points mapping rules of network modulation techniques through Matlab simulation. For solving throughput method, we use network modulation model based on Shannon limit theorem to derive the formula of throughput of system. At last, we analyze and compare throughput using network modulation with different modulations by Matlab simulation.Lastly, numerical results verify that the network modulation technology can improve system performance used in deep space communication link by simulation. Taking the communication link from the Moon to the Earth as an example, we set the Lagrangian L1 point as the relay satellite’s position between the Moon and the Earth. By Matlab simulation we plot a graph including three throughput curves of different transmission ways: network modulation technique, direct link modulation and two-hop link modulation with one relay node. By comparing the results of curves we can get the conclusion: network modulation technology used in deep space communication can effectively improve system throughput, thereby it effectively solves the problem of low effectiveness in deep space communications.