Hopping Transmission Research Articles

Polymer-in-salt electrolyte enables ultrahigh ionic conductivity for advanced solid-state lithium metal batteries

Polymer solid-state electrolyte (SSE) still confronts low room-temperature ionic conductivity for broad application in solid-state batteries. Herein, an eye-catching polymer-in-salt PVDF-HFP/LiFSI/LLZTO composite SSE with ultrahigh ionic conductivity is elaborately designed. In this electrolyte system, poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix provides the electrolyte well mechanical property and Li salt solubility, high content of lithium bis(fluorosulfonyl) imide (LiFSI) with low dissociation energy contributes to extra Li+ hopping transmission path, and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) filler endows the SSE enhanced electrochemical stability. As a consequence, this polymer-in-salt composite SSE exhibits an ionic conductivity of 1.67 × 10−3 S cm−1 and superior critical current density (CCD) of 3.2 mA cm−2 at room temperature (25 °C). Moreover, Li||Li symmetric battery holds uniform polarization over 240 h at 0.3 mA cm−2 and 0.3 mAh cm−2. And Li||LiFePO4 full cell exhibited a high capacity retention ratio of 97.2% with Coulombic efficiency of 99.75% after 300 cycles.

High-Efficiency PCSK-CFFH System Design for IoT Networks

Industrial Internet of Things (IIoT) brings opportunities for innovation and upgrading to industrial production, but meanwhile, it poses unprecedented challenges on the physical layer of wireless communications. In this article, we propose a novel frequency hopping transmission scheme for IIoT, which owns much high efficiency and strong anti-jamming ability. This new scheme is built based on the combination of coherent fast frequency hopping (CFFH) and cyclic code shift key (CCSK), named phase cyclic shift-keying-based CFFH (PCSK-CFFH). For the proposed PCSK-CFFH system, the shift of orthogonal base sequence is adopted to modulate the phases among interhop, instead of transmitting each hop with the same phase as conventional CFFH. This scheme is able to further exploit the extra dimensions of CFFH signals and enables the CFFH system to transmit additional information at no extra cost on either bandwidth or power. Moreover, the bit error rate performance of the proposed PCSK-CFFH system is analyzed theoretically. To improve its ability against severe narrow-band jamming, the selection combining is introduced in our scheme. Furthermore, the anti-jamming performance of the proposed PCSK-CFFH system is also demonstrated. Finally, the simulation results are shown to demonstrate that: by introducing the interhop dimension to CFFH, PCSK-CFFH improves the power efficiency and spectrum efficiency by multiple times and simultaneously inherits the excellent anti-jamming performance of the conventional CFFH system. It can be concluded that the proposed PCSK-CFFH scheme has a great potential to be applied to low-power and highly reliable IIoT communications.

Research On LDPC-DFH Code Modulation And Demodulation System Based On Hard Decision Decoding

In order to reduce the bit error rate of differential hopping transmission, differential frequency hopping (DFH) is combined with low density parity check code (LDPC). On the basis of not adding more system complexity, the hard decision bit inversion algorithm (BF) and weighted error check based bit inversion algorithm (WVBF) are proposed to decode LDPC-DFH system. The check matrixes of different generation methods are used respectively. The BF decoding method and WVBF decoding method are used to simulate the Gaussian channel and Rician channel. The influence of different decoding methods on the bit error rate is discussed. The simulation results show that the BER of the DFH system with LDPC code is lower than that of DFH without LDPC, and the WVBF algorithm is better than the BF algorithm.

Anti - follower jamming analysis of multi - sequence frequency hopping in AWGN channel

The modulated signals sent by conventional frequency-hopping systems are easily affected by follower jamming. Multi-sequence frequency-hopping is a frequency hopping communication system that uses channels to represent messages. It has good anti-follower jamming performance.Compared with differential frequency hopping, which uses user data to determine the transmission frequency, increasing frequency hopping sequence as a constraint can better suppress out-of-band jamming. In order to further study the effect of multi-sequence frequency hopping under follower jamming, a new multi-sequence frequency hopping transmission model under AWGN channel is established, the principle of multi-sequence frequency hopping anti-jamming was analyzed, and the performance of multi-sequence frequency hopping under follower jamming with different parameters is studied. The oretical analysis and simulation results show that multi-sequence frequency hopping can gain about 2.47-2.7dB when the SNR is 13.35dB and the BER requirement is 10^(-4), compared with the conventional frequency hopping.

Switched Phased-Array Transmission Architecture for Secure Millimeter-Wave Wireless Communication

In this paper, we propose a new wireless communication transmission architecture called switched phased-array (SPA), to enhance physical layer security. SPA works as a platform for three different transmission techniques: 1) conventional phased-array transmission; 2) antenna subset transmission (AST) technique; and 3) silent antenna hopping (SAH) transmission technique. SPA consists of a conventional phased-array blacktransmitter followed by antennas with an on–off switching circuit. The proposed solution maintains the objective of scrambling the constellation points in both amplitude and phase in undesired directions, while preserving a clear constellation in the target direction. The proposed solution—SPA—is different from previously used methods in the following ways: 1) SPA is not restricted to the use of phase modulation, and can accept any modulation type including QAM; 2) it does not need to modulate the signal in the radio frequency (RF) domain, where the conventional phased-array transmitter circuits remain unchanged; 3) in the far field, SPA scrambles the signal constellation by randomly switching- off some of the transmitting antennas (AST), or only one of them (SAH); 4) SPA can be easily integrated with the current infrastructure of phased-array transmitters; 5) SPA breaks up the correlation between the data rates and the switching speed; and 6) SPA performs a variety of DM transmission techniques. We present the potential transmission techniques including PA, AST, and SAH. We analyze the performance for all cases and derive an exact expression of the bit error probability, and also we analyze the secrecy capacity. The results show that SPA, and its variants AST and SAH, are simple and very efficient solutions to improve the physical layer security of mm-wave communication.

Learning-Based Opportunistic Spectrum Access with Adaptive Hopping Transmission Strategy

This paper presents an adaptive hopping transmission strategy for secondary users (SUs) to access temporarily idle frequency-slots of a licensed frequency band in consideration of the random return of primary users (PUs), aiming to maximize the overall SU throughput. A SU dynamically hops over multiple idle frequency-slots, each with an adaptive activity factor to avoid high-risk data loss due to possible PU return. SU activity factor optimization problems are formulated to develop the optimal opportunistic spectrum access (OSA) algorithms for SUs based on the Lagrange dual decomposition method. Subsequently, a fully distributed learning-based OSA algorithm is developed in which each SU independently adapts its activity factors to the optimal values over time by learning other SUs' behavior from locally available information. The convergence and convergence rate that characterize its asymptotic behavior and efficiency are analyzed. It is shown that the proposed learning-based OSA algorithm converges with probability of 1 to the optimal solution. Illustrative results confirm its effectiveness and performance gain as compared to existing OSA schemes.

저속 주파수 도약 방식 위성 데이터링크에서 송수신 신호중첩 및 주파수 다이버시티 적용

본 논문에서는 주파수 도약방식에서는 적용이 어려운 송수신 중첩통신 방식을 DSM형 중계기를 사용하는 위성 데이터링크에 적용하고 항재밍 성능 개선을 위해 잔여 주파수 자원을 주파수 다이버시티에 활용하는 방안을 제안 한다. 시뮬레이션을 통해 제안한 방식에 대한 항재밍 성능과 탐지회피 성능을 분석하였다. 항재밍 성능 분석 결과, 주파수 다이버시티 적용으로 데이터 통신시 18.5dB의 처리이득을 얻을 수 있으며, 500MHz 도약 방식에서 통신단말형태의 재머에 대해 4.8Mbps의 데이터 전송이 가능함을 확인하였다. 또한, 주파수 중첩에 의해 주파수 자원을 최대 2배까지 재사용 가능하며, 데이터 속도를 추정 할 수 있는 D&M 검출기를 대상으로 중첩을 하지 않았을 때 보다 2.5dB LPI 성능이 개선됨을 확인하였다. In this paper, we propose a possibility of usage of carrier superpositioning scheme for a specific slow frequency hopping(SFH) transmission method for the satellite data link in which all of hopping carriers have to be synchronized to DSM transponder of our previous work and usage of frequency diversity in the saved frequency to overcome the SFH disadvantage against jammer. We have analyzed anti-jamming performance and LPI performance and confirmed that the proposed scheme can support data service with 18.5dB processing gain against the worst case partial band jamming and give 2.5dB gain in the LPI performance against D&M detector which can estimate the data rate of unknown signals.

주기적 모니터링 센서 네트워크에서 핫 스팟 문제 해결을 위한 호핑 라우팅 기법

Abstract In this paper we proposed a hopping routing scheme to resolve the hot spot problem for periodic monitoring services in wireless sensor networks. Our hopping routing scheme constructs load balanced routing path, where an amount of energy consumption of all nodes in the sensor networks is predictable. Load balanced routing paths can be obtained from horizontal hopping transmission scheme which balances the load of the sensor nodes in the same area, and also from vertical hopping transmission scheme which balances the load of the sensor nodes in the other area. The direct transmission count numbers as load balancing parameter for vertical hopping transmission are derived using the energy consumption model of the sensor nodes. The experimental results show that the proposed hopping scheme resolves the hot spot problem effectively. The efficiency of hopping routing scheme is also shown by comparison with other routing scheme such as multi-hop, direct transmission and clustering.Key Words : Hot Spot Problem, Hopping Routing, Load Balanced Routing Path