tailieunhanh - Advanced Trends in Wireless Communications Part 7

Tham khảo tài liệu 'advanced trends in wireless communications part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 200 Advanced Trends in Wireless Communications significantly BER compared to without FH at same level of SNR. From Figure 12 it can be seen that applying FH with GFSK modulation reduces dramatically BER compared to without FH at same level of SNR and lead to a much higher performance. In overall based on the evaluation results it can be concluded that applying the designed FH schemes with certain modulations can improve their communication performances especially at weak SNR levels as most cases of short range wireless communications have. 6. Conclusion As a result of the work it can be concluded that adaptive frequency hopping is a powerful technique to deal with interference and Gilbert-Elliot channel model is a good technique to analyze the situations of channels by categorizing the channel conditions based on their performance as Good or Bad and then apply adaptive frequency hopping which hops frequencies adaptively by analyzing the state of the channel in case of environmental problems such as interferences and noises to improve the communication performance. Frequency hopping spread spectrum is modelled with MATLAB and three different modulations . QAM QPSK and GFSK are studied to investigate which of these modulations are good to apply with FHSS model. The simulation results show that applying FHSS with QAM modulation dose not lead to a remarkable reduction of BER but with QPSK modulation gives a good result and reduces BER at lower SNR while in GFSK modulation shows a significant reduction of BER and lead to a high performance. Fig. 10. QAM modulation 201 Frequency Hopping Spread Spectrum An Effective way tO improve Wireless Communication Performance Fig. 11. QPSK modulation Fig. 12. GFSK .