Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
Wireless sensor nodes (WSNs) are widely used in the field of environmental detection;\nhowever, they face serious power supply problems caused by the complexity of the environmental\nlayout. In this study, a new ultra-low-power hybrid energy harvesting (HEH) system for two types\nof microenergy collection (photovoltaic (PV) and soil-temperature-difference thermoelectric (TE))\nwas designed to provide stable power to WSNs. The power supply capabilities of two microenergy\nsources were assessed by analyzing the electrical characteristics and performing continuous energy\ndata collection. The HEH system consisted of two separated power converters and an electronic\nmultiplexer circuit to avoid impedance mismatch and improve efficiency. The feasibility of the\nself-powered HEH system was verified by consumption analysis of the HEH system, the WSNs,\nand the data analysis of the collected microenergy. Taking the summation of PV and TEG input\npower of 1.26 mW (PPV:PTEG was about 3:1) as an example, the power loss of the HEH system\naccounted for 33.8% of the total input power. Furthermore, the ratio decreased as the value of the\ninput power increased....
High-order modulations are necessary to improve the bandwidth efficiency of the satellite\ncommunication system. However, the non-linear characteristic of satellite channels limits the\napplication of high-order modulations. In this paper, we propose a new 7-point constellation which\nis expected to be effectively applied to the satellite communication system, and combine it with\nnon-binary low-density parity-check (NB-LDPC) codes over Galois field GF(7) to guarantee the\nreliability of the data transmission. The exact expression for the average symbol error probability\n(SEP) of 7-order quadrature amplitude modulation (7-QAM) over the Additive White Gaussian Noise\n(AWGN) channel is derived, and the non-linear distortion over satellite channels is also analyzed.\nSimulation results reveal that, compared with the traditional 8-order phase-shift keying (8-PSK), the\n7-QAM method can achieve about 3 dB gain over the AWGN channel without channel coding at\nsymbol error rate (SER) of 10-6. Moreover, the proposed combined coded modulation scheme also\nhas better SER performance than the NB-LDPC coded 8-PSK modulation scheme over the non-linear\nsatellite channel....
Virtual network embedding (VNE) problem is a key issue in network virtualization technology, and much attention has been paid\nto the virtual network embedding. However, very little research work focuses on parallelized virtual network embedding problems\nwhich assumes that the substrate infrastructure supports parallel computing and allows one virtual node to be mapped to multiple\nsubstrate nodes. Based on the work of Liang and Zhang, we extend the well-known VNE to parallelizable virtual network\nembedding (PVNE) in this paper. Furthermore, to the best of our knowledge, we give the first formulation of the PVNE problem.\nA new heuristic algorithm named efficient parallelizable virtual network embedding (EPVNE) is proposed to reduce the cost of\nembedding the VN request and increase the VN request acceptance ratio. EPVNE is a two-stage mapping algorithm, which first\nperforms node mapping and then performs link mapping. In the node mapping phase, we present a simple and efficient virtual\nnode and physical node sorting formula and perform the virtual node mapping in order. When mapping virtual nodes, we map\nvirtual nodes to physical nodes that just meet the CPU requirements. Substrate nodes with more CPU resources will be retained\nfor subsequent virtual network mapping requests. In the link mapping phase, Dijkstraâ??s algorithm is used to find a substrate path\nfor each virtual link. Finally, simulations are carried out and simulation results show that our algorithm performs better than the\nexisting heuristic algorithms....
In this paper, a combination of energy harvesting (EH) and cooperative nonorthogonal multiple access (NOMA) has been\nproposed for full-duplex (FD) relaying vehicle-to-vehicle (V2V) networks with two destination nodes over a Rayleigh fading\nchannel. Different from previous studies, here both source and relay nodes are supplied with the energy from a power beacon (PB)\nvia RF signals, and then use the harvested energy for transmitting the information. For the extensive performance analysis, the\nclosed-form expressions for the performance indicators, including outage probability (OP) and ergodic capacity of both users,\nhave been derived rigorously. Additionally, the effect of various parameters, such as EH time duration, residual self-interference\n(RSI) level, and power allocation coefficients, on the system performance has also been investigated. Furthermore, all mathematical\nanalytical results are confirmed by Monte-Carlo simulations, which also demonstrate the optimal value of EH time\nduration to minimize the OP and maximize the ergodic capacity of the proposed system....
With the rapid development of cloud computing and big data, traditional Vehicular Ad hoc\nNetworks (VANETs) are evolving into the Internet of Vehicles (IoV). As an important communication\ntechnology in IoV, IEEE 802.11p protocols have been studied by many experts and scholars. In IEEE\n802.11p, a nodeâ??s backoff counter will be frozen when the channel is detected as busy. However,\nmost studies did not consider the possibility of continuous backoff freezing when calculating delay.\nThus, in this paper, we focus on the performance analysis of IEEE 802.11p for continuous backoff\nfreezing. Specifically, we establish an analytical model to analyze the broadcast performance in\nthe highway scene where vehicles can obtain traffic density from roadside units through Vehicle to\nInfrastructure (V2I) communications. We first calculate the relationship between vehicle density and\nthe number of vehicles. Then, we derive the relationship between the number of vehicles and packet\ndelay according to Markov chains. Next, we utilize the probability generating function (PGF) to\ntransform traditional Markov chains into z domain under the situation of non-saturation. Finally,\nwe employ the Mason formula to derive packet delay. As compared with the performance without\nconsidering the continuous backoff freezing, the simulation results have demonstrated that our\nanalytical model is more reasonable....
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