Communication Algorithm 7: Communication System Algorithm Design, bit rate, spread spectrum, modulation method algorithm selection, communication system modulation method

Communication Algorithm 7: Communication System Algorithm Design, bit rate, spread spectrum, modulation method algorithm selection, communication system modulation method

1. Rate Matching: Bit Rate Selection

Channel environment: AWGN

Signal-to-Noise Ratio: SNR

Bit Rate R: 1/2, 1/3, 1/4, 1/8

MATALB simulation architecture: Source bit + convolution code/Turbo (1/3) + Rate Matching (different R) + PSK modulation + AWGN + PSK demodulation + decoding rate matching + Viterbi/Turbo + BER

Note: The R bit rate is 1/2, 1/4, and 1/8, and the performance increases.

2. Selection of Spread Spectrum factor SF

Channel environment: AWGN

Signal-to-Noise Ratio: SNR

Spread Spectrum factor SF: 1, 2, 4, 8, 16, 32, 64, 128

MATALB simulation architecture: Source bit + convolution code/Turbo (1/3) + Rate Matching + PSK modulation + spread spectrum + AWGN + unspread spectrum + PSK demodulation + decoding rate matching + Viterbi/Turbo + BER

Note: The Spread Spectrum factor SF, 128, 4, and increases the performance by in turn.

3. modulation method selection

Channel environment: AWGN

Signal-to-Noise Ratio: SNR

Modulation method: BPSK, PSK, opsk, DQPSK, and 16QAM Performance

MATALB simulation architecture: Source bit + (PSK) modulation + AWGN + (PSK) demodulation + BER

Note: BPSK: EbNo = 9.6dB, EsNo = 9.6dB;

PSK: EbNo = 9.6dB, EsNo = 12.6dB ;.

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Research on Spread Spectrum Communication and Simulation of error rate in MATLAB environment

Abstract
This paper describes the theoretical basis and implementation methods of the Extended Spectrum Communication Technology, and simulates the direct expansion communication system through the simulation platform provided by MATLAB, detailing the design of each module. The simulation system is run under the given simulation conditions and expected simulation results are obtained. At the same time, the relationship between the signal-to-noise ratio and the bit error rate is studied using the established simulation system. The results show that increasing the signal-to-noise ratio can reduce the bit error rate.
Keywords direct expansion communication; signal-to-noise ratio; bit error rate;

Abstract
This paper expounds the spread spectrum communication technology and the method of realizing the theoretical basis, and provide simulink7.1 simulation platform through MATLAB for straight expansion communication system is simulated, and detailed design of each module tells the story. in a given simulation conditions, run the simulation system, and gained anticipative simulation results. at the same time, using the simulation system, established the system ber relationship with SNR, the results show that, improve signal-to-noise ratio, can reduce the system ber.
Keywords straight extender communication; Signal-to-noise ratio (SNR );

1. Introduction
According to the method of extended spectrum, the existing spread spectrum communication systems can be divided into direct sequence (DS) Spread Spectrum, Frequency Hopping (FH), Time Hopping (TH), linear frequency modulation (chirp) and the combination of the above methods.
This article mainly discusses the performance of Direct Sequence Spread Spectrum System. Direct Sequence Spread Spectrum refers to the spectrum of signals that are directly extended at the sending end using a high-Bit Rate Spread Spectrum Code sequence. At the receiving end, the same extension is used.
The frequency code sequence is deexpanded, and the extended spread spectrum signal is restored to the original information. Principle 1 of the direct expansion communication system is shown in. The information input at the sending end is first modulated by information to form a digital signal of frequency modulation or phase modulation, and then the Spread Spectrum Code sequence generated by the Spread Spectrum Code Generator to modulated digital signals to broaden the signal spectrum, then, the extended broadband signal is modulated to the RF transmission. At the receiving end, the receiver receives the broadband
After the RF signal is obtained, the frequency is first converted to the intermediate frequency, and then the accurate phase of the Spread Spectrum Code sent by the synchronous circuit is captured, this generates a pseudo-random code used for receiving exactly the same phase as the sent Pseudo-Random Code. It is used as the local Spread Spectrum Code sequence for the Spread Spectrum demodulation, and is finally restored to the original information output after the information demodulation.

Figure 1 principle of Spread Spectrum Communication
It can be seen that the direct expansion communication system requires three modulation and the corresponding demodulation, namely information modulation, spread spectrum modulation and RF modulation, and the corresponding information demodulation, decoding and RF demodulation. In comparison with general communication systems, spread-spectrum communication involves the addition of Spread-spectrum modulation and decoding.
2. Development Direction of CDMA spread spectrum communication systems
The Spread Spectrum Communication System was developed in the middle of 1950s. Its Anti-interference, anti-eavesdrop, and low interception capabilities have been greatly improved, but they are only partially developed. With the advent of microprocessor, ultra-large-scale integrated circuit, digital signal processor, and Special Spread Spectrum devices, the Spread Spectrum Technology has made significant breakthroughs and progresses in 1960s, and its superiority in practical applications has become more obvious, spread Spectrum Communication becomes a communication ...... remaining full text>
 
Anti-interference technology of Spread Spectrum Communication Systems

Simulation of Spread Spectrum Communication System Based on MATLAB
Fan wei-chuan runzhan xingqun
(School of electronic information and electrical engineering, Shanghai Jiao Tong University, Shanghai 200030, China)
Abstract: This paper expounds the theoretical basis and implementation methods of extended spectrum communication technology, and uses the visualization provided by MATLAB
The simulation model of the spread-spectrum communication system is established in the tool chain, the design of each module is described in detail, and the simulation modeling is pointed out.
. The simulation program is run under the given simulation conditions and expected simulation results are obtained. At the same time
The relationship between the Spread Spectrum gain and the signal-to-noise ratio at the output end is studied using the established simulation system. The results show that, at the same bit error rate,
Increasing the Spread Spectrum gain can improve the signal-to-noise ratio at the output end of the system and improve the anti-interference capability of the communication system.
Key words spread spectrum communication, signal-to-noise ratio, bit error rate, spread spectrum gain
Chinese map: TN914.42 Document ID:
Simulation of the Spread Spectrum Communication System
Based on MATLAB
FAN Wei, ZHAI Chuan-run, ZHAN Xing-qun
School of Electronic, Information and Electrical Engineering, Shanghai Jiaotong University, 200030, Shanghai)
Abstract: The theory base and realizing methods of the spread spectrum communication
Technology was presented in this study. The simulation model of the spread spectrum
Communication system was built by using SIMULINK, which is provided by MATLAB. In
Addition, each module of the simulation model was introduced in detail, and pointed out
Problems that must be pay attention to in the system simulation. On the basis of the designed
Simulation conditions, the simulation program was run and the anticipant results were gained.
Moreover, the relationship between the spread spectrum gain and the fan-out error rate was also
Studied by use of the simulation system. The results showed that on the base of the same error rate,
If the spread spectrum gain was enlarged, the Signal-to-Noise of the system fan-out wocould be
Enhanced and the anti-jamming capability of the communication system wocould also be enhanced.
Keywords: spread spectru ...... remaining full text>