HARQ Transmission Technology In The Short-wave Channel

The short-wave communication can communication far distance, and it is free fromthe influence of terrain and the destruction. So the short-wave communication has beenan important means of communication. As fading and multipath effect is thecharacteristic of short-wave channel, the performance of the short-wave communicationsystem will be affected, so we need to predict the maximum usable frequency toimprove the performance of the communication system. The HARQ (Hybrid Automaticrepeat Request) technology can further improve the performance of the system, which isthe key technology in the third generation of short-wave communication protocols. Inthis paper, we mainly research the method of MUF (Maximum Usable Frequency)prediction of the short-wave and HARQ technology of the short-wave communicationprotocols.First, the paper researches the method of MUF prediction of the short-wave. MUFprediction is based on the distance between the transmitter and the receiver, the sunspotnumbers and the time and other parameters. Then calculate the MUF using the differentcomputing model. This paper uses the REC533and VOACAP to predict the MUF in thetypical time and typical places. The data show that the longer the distance, the greaterthe MUF. The MUF reaches max in the day due to the electron is most dense, and theMUF dropped to the lowest point in the evening.Secondly, this paper researches the HARQ technology in the third generation ofshort-wave communication protocol. Through studying the behavior and the transferprocess of the different states, we use OPNET building the short-wave communicationsystem, and simulation the various transition states of the system. Then we study thetransmission of long packet waveform in the third generation of short-wavecommunication system. Building the transmitter side includes the channel encoding, theGray encoding, the scrambling encoding and the modulation. And building thereceiving side, which includes the channel estimated, the channel equalization and thedemodulation descrambling and solving the Gray mapping. Then we combine thesystem with HARQ technology. The simulation proved the effectiveness of the key technologies, and the data show that the retransmission reduces the error rate of thesystem.Lastly, this paper compares the advantages and disadvantages of the differentHARQ protocol type between the short-wave system and the3G LTE(Long TermEvolution) system. Using N-channel stop-and-wait protocol can send the data in the idletime continually. According to the idle time and the data transmitting time of eachframe, we can determine the number of N reasonably. Then this scheme can make fulluse of the channel, and simulation results show that the system throughput is improved.Moreover, this paper analyzes the design and the transmission mechanism of thefeedback information of the HARQ protocol in the3G LTE system. We can add1bitredundant information in both the transmitter and the receiver in the short-wavecommunication system. The receiver can detect ACK (Acknowledgement)/NACKerrors during transmission. The theoretical analysis and simulation results show that thisscheme can reduce the packet loss rate of the system. Then, this paper researches thepart of the incremental redundancy coding techniques of Turbo coding in the3G LTEsystem. We use it in the short-wave communication system. Then we can reduce theerror rate of the system and the number of retransmissions through increasing mergingand decoding complexity at the receiver. What’s more, this paper analyzes thecombined rearranged algorithm. The algorithm change the constellation points of theretransmission, then exchange the imaginary part of the first transmission data and theretransmission data, so that high-order modulation is converted into a low-ordermodulation. The theoretical derivation and simulation prove that the algorithm canimprove the performance of the HARQ system effectively in a single path channel.In summary, due to the characteristic of short-wave channel will affect theperformance of the short-wave communication, this paper researches the MUF ofshort-wave transmission system, and use the REC533and VOACAP test the MUF ofthe typical time and place. Moreover, this paper studies the HARQ technique of thethird generation short-wave communication protocol, improve the key technologies ofthe HARQ technology based on the short-wave communication system, theperformance of the system improve effectively.