Abstract
Low-Power Wide-Area Network (LPWAN) is the technology that the Internet-of-Things (IoT) uses in long-distance, wide-coverage scenarios. As one of the ultra-narrowband (UNB) modulation techniques, M-ary position phase shift keying (MPPSK) modulation can provide high coverage and high reliability for LPWAN. This paper proposes a multipath separation method based on MPPSK modulation, which aims to eliminate the influence of multipath on the main path without increasing the spectrum overhead and system complexity. Specifically, the modulation parameter of the system is adjusted according to the delay value, so that the phase jump of the multipath signal falls outside the phase jump of the main path symbol to achieve separation of the multipath from the main path. Moreover, a normalized symbol joint decision method is proposed in order to reduce the introduced noise while using multipath information for decisions. The simulation results indicate that the multipath separation conditions given in this paper can meet the requirements of multipath separation of MPPSK signals. Compared with the existing mainstream decision scheme, the normalized symbol joint decision improves the demodulation performance of the system.
Highlights
The Internet-of-Things is a new concept that is increasingly attracting the attention of researchers and industries [1]
In order to meet the requirements of different application indicators, different modulation signal bandwidths, transmission rates, and system demodulation performance can be obtained by adjusting the values of modulation parameters A, B, M, N, K, θ and r g
The effectiveness of the least mean square time delay estimation method for the estimation of M-ary position phase shift keying (MPPSK)-modulated signal delay in a multipath environment is verified by experiments
Summary
The Internet-of-Things is a new concept that is increasingly attracting the attention of researchers and industries [1]. Compared with traditional modulation methods, MPPSK has the advantages of high bandwidth efficiency and line spectrum elimination. It has important theoretical and practical significance. In [17], a multipath separation method based on the EBPSK modulation system is proposed This scheme is only applicable to binary EBPSK modulation, and there are fewer scenarios available. When sub-path information is used to participate in the decision, the multipath separation scheme based on EBPSK modulation introduces all sub-path noise. By using the normalized symbol joint decision proposed in this paper, the receiver reduces the introduced noise while utilizing multipath information, thereby reducing the bit error rate of the system.
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