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18 pages, 4756 KiB  
Article
GENES: An Efficient Recursive zk-SNARK and Its Novel Application in Blockchain
by Jiaxi Liu, Li Guo and Tianyu Kang
Electronics 2025, 14(3), 492; https://doi.org/10.3390/electronics14030492 - 25 Jan 2025
Viewed by 264
Abstract
The rapid development of blockchain has significantly promoted research on zero-knowledge proofs (ZKPs), especially zero-knowledge succinct noninteractive arguments of knowledge (zk-SNARK). As is well known, protocol proof and verification time, as well as proof size, are the main obstacles that restrict the implementation [...] Read more.
The rapid development of blockchain has significantly promoted research on zero-knowledge proofs (ZKPs), especially zero-knowledge succinct noninteractive arguments of knowledge (zk-SNARK). As is well known, protocol proof and verification time, as well as proof size, are the main obstacles that restrict the implementation of ZKPs in practical applications, so they have become the main concerns of researchers in recent years. This work achieves a new recursive zk-SNARK called GENES, which does not have a trusted setup and is secure under the standard discrete logarithm assumption. GENES is designed from the form of the rank-1 constraint system (R1CS) satisfiability problem. Recursive proof composition is achieved by merging multiple R1CS instances, which transforms the verification of numerous proofs into the verification of a single proof. Moreover, multi-helpers amortize proof commitments in this study, significantly reducing the computational pressure and time cost of proof generation. Compared with previous work, GENES effectively improves the proof time and verification time, but at the cost of larger proof sizes. We provide a blockchain Layer-1 scaling solution leveraging GENES to demonstrate its practicality. Full article
(This article belongs to the Special Issue Data Security and Privacy in Blockchain and the IoT)
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Figure 1
<p>Prover times for our scheme compared to two other schemes [<a href="#B20-electronics-14-00492" class="html-bibr">20</a>,<a href="#B21-electronics-14-00492" class="html-bibr">21</a>].</p>
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<p>Proof sizes for our scheme compared to two other schemes [<a href="#B20-electronics-14-00492" class="html-bibr">20</a>,<a href="#B21-electronics-14-00492" class="html-bibr">21</a>].</p>
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<p>Verifier times for our scheme compared to two other schemes [<a href="#B20-electronics-14-00492" class="html-bibr">20</a>,<a href="#B21-electronics-14-00492" class="html-bibr">21</a>].</p>
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<p>Prover times for GENES’s merge scheme and bulletproofs.</p>
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<p>Proof sizes for GENES’s merge scheme and bulletproofs.</p>
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<p>Verifier times for GENES’s merge scheme and bulletproofs.</p>
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<p>An example of a new Ethereum block structure based on GENES.</p>
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16 pages, 10610 KiB  
Article
Enhanced Wound Healing and Autogenesis Through Lentiviral Transfection of Adipose-Derived Stem Cells Combined with Dermal Substitute
by Shiqi Wang, Dinghui Gao, Mingyu Li, Qian Wang, Xuanyu Du and Siming Yuan
Biomedicines 2024, 12(12), 2844; https://doi.org/10.3390/biomedicines12122844 - 13 Dec 2024
Viewed by 2460
Abstract
Background: Burns and chronic ulcers may cause severe skin loss, leading to critical health issues like shock, infection, sepsis, and multiple organ failure. Effective healing of full-thickness wounds may be challenging, with traditional methods facing limitations due to tissue shortage, infection, and lack [...] Read more.
Background: Burns and chronic ulcers may cause severe skin loss, leading to critical health issues like shock, infection, sepsis, and multiple organ failure. Effective healing of full-thickness wounds may be challenging, with traditional methods facing limitations due to tissue shortage, infection, and lack of structural support. Methods: This study explored the combined use of gene transfection and dermal substitutes to improve wound healing. We used the DGTM (genes: DNP63A, GRHL2, TFAP2A, and MYC) factors to transfect adipose-derived stem cells (ADSCs), inducing their differentiation into keratinocytes. These transfected ADSCs were then incorporated into Pelnac® dermal substitutes to enhance vascularization and cellular proliferation for better healing outcomes. Results: Gene transfer using DGTM factors successfully induced keratinocyte differentiation in ADSCs. The application of these differentiated cells with Pelnac® dermal substitute to dermal wounds in mice resulted in the formation of skin tissue with a normal epidermal layer and proper collagen organization. This method alleviates the tediousness of the multiple transfection steps in previous protocols and the safety issues caused by using viral transfection reagents directly on the wound. Additionally, the inclusion of dermal substitutes addressed the lack of collagen and elastic fibers, promoting the formation of tissue resembling healthy skin rather than scar tissue. Conclusion: Integrating DGTM factor-transfected ADSCs with dermal substitutes represents a novel strategy for enhancing the healing of full-thickness wounds. Further research and clinical trials are warranted to optimize and validate this innovative approach for broader clinical applications. Full article
(This article belongs to the Section Biomedical Engineering and Materials)
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<p>Diagrammatic summary of this study.</p>
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<p>Identification of ADSCs. (<b>A</b>) A Morphology of human ADSCs at 12 h and 72 h; scale bar: 100 μm. (<b>B</b>) Flow cytometry detection of ADSCs. ADSCs were positive for the markers CD73, CD90, and CD105 (blue peaks) and negative for the markers CD34 and CD45 (red peaks). The table summarizes the percentage of cells expressing each marker (mean ± SEM). (<b>C</b>) ADSC lipogenicity assay; scale bar: 100 μm. (<b>D</b>) ADSC osteogenicity assay; scale bar: 100 μm.</p>
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<p>Identification of ADSCs<sup>DGTM+</sup>. (<b>A</b>) Statistical graph of RT-PCR detection of the expression of transfected genes <span class="html-italic">GRHL</span>, <span class="html-italic">TFAP2</span>, <span class="html-italic">MYC</span>, and <span class="html-italic">TP63</span> in ADSCs<sup>DGTM+</sup>, ***, <span class="html-italic">p</span> &lt; 0.001. (<b>B</b>) Representative graph of immunohistochemistry detection of the expression of the keratinocyte-specific marker KRT14 in ADSCs<sup>DGTM+</sup> and ADSCs<sup>DGTM−</sup>. (<b>C</b>) WB detection of keratinocyte-specific markers KRT14 and CDH1 expression in ADSC, ADSCs<sup>DGTM+</sup> and ADSCs<sup>DGTM-</sup>. (<b>D</b>) Representative fluorescent staining of expression of keratinocyte-specific markers KRT14, CY3 (Pelnac<sup>®</sup> staining), and DAPI in the ADSCs + Pelnac<sup>®</sup> group, ADSCs<sup>DGTM+</sup> + Pelnac<sup>®</sup> group and ADSCs<sup>DGTM-</sup> + Pelnac<sup>®</sup> group.</p>
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<p>Construction of dermal substitute–ADSCs<sup>DGTM+</sup> complexes. (<b>A</b>) Observation of dermal substitute–ADSCs<sup>DGTM+</sup> complexes under inverted fluorescence microscope; scale bar: 200 μm. (<b>B</b>) Observation of dermal substitute–ADSCs<sup>DGTM+</sup> complexes under scanning electron microscope at different magnifications. The red arrow in the middle image points to the pore. (<b>C</b>,<b>D</b>) Observation of the proliferation of ADSCs<sup>DGTM+</sup> grown in Pelnac<sup>®</sup> by culturing ADSCs<sup>DGTM+</sup> alone within 9 days under an inverted fluorescence microscope and statistical graphs; scale bar: 200 μm.</p>
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<p>Dermal substitute–ADSCs<sup>DGTM+</sup> complexes fill full-thickness defective wounds. (<b>A</b>) Flowchart of animal experiments. (<b>B</b>) Representative images of skin regeneration. Mice wounds were divided into the following groups: blank, Pelnac<sup>®</sup> ADSCs + Pelnac<sup>®</sup>, and ADSCs<sup>DGTM+</sup> + Pelnac<sup>®</sup>. (<b>C</b>) Temporal variation of skin regeneration. (<b>D</b>) HE staining of mice in each group of the wound. (<b>E</b>) MASSON staining of mice in each group of the wound. (<b>F</b>) Statistical graph of the percentage of wound healing over time for each group. (<b>G</b>) Statistical graph of the thickness of re-epithelialization of the wound in each group. (<b>H</b>) Statistical graph of the proportion of wound collagen in each group. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, n = 4.</p>
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<p>Dermal substitute–ADSCs<sup>DGTM+</sup> complexes promote wound cell proliferation and revascularization. (<b>A</b>) Representative immunofluorescence staining of CD31, Ki67, and DAPI in the whole layer defect wounds of neoplastic skin of each wound group. (<b>B</b>) Immunofluorescence staining of CD31 in neoplastic whole skin defect wounds in each group. (<b>C</b>) Immunofluorescence staining of Ki67 in neoplastic whole skin defect wounds in each group; ** <span class="html-italic">p</span> &lt; 0.01, n = 4.</p>
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<p>Dermal substitute–ADSCs<sup>DGTM+</sup> complexes involved in the filling of full-thickness defective skin. (<b>A</b>) Representative fluorescent staining of KRT14, HLA-ABC, and DAPI in the wounds of mice in the ADSCs + Pelnac<sup>®</sup> and ADSCs<sup>DGTM+</sup> + Pelnac<sup>®</sup> groups. (<b>B</b>,<b>C</b>) Representative plots of average fluorescence intensity of different channels in the ADSCs<sup>DGTM+</sup> + Pelnac<sup>®</sup> group and ADSCs + Pelnac<sup>®</sup> group.</p>
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19 pages, 833 KiB  
Article
Secured Real-Time Machine Communication Protocol
by Yifei Ren, Lakmal Rupasinghe, Siavash Khaksar, Nasim Ferdosian and Iain Murray
Network 2024, 4(4), 567-585; https://doi.org/10.3390/network4040028 (registering DOI) - 12 Dec 2024
Viewed by 602
Abstract
In this paper, we introduce the Secured Real-Time Machine Communication Protocol (SRMCP), a novel industrial communication protocol designed to address the increasing demand for security and performance in Industry 4.0 environments. SRMCP integrates post-quantum cryptographic techniques, including the Kyber Key Encapsulation Mechanism (Kyber-KEM) [...] Read more.
In this paper, we introduce the Secured Real-Time Machine Communication Protocol (SRMCP), a novel industrial communication protocol designed to address the increasing demand for security and performance in Industry 4.0 environments. SRMCP integrates post-quantum cryptographic techniques, including the Kyber Key Encapsulation Mechanism (Kyber-KEM) and AES-GCM encryption, to ensure robust protection against both current and future cryptographic threats. We also present an innovative “Port Hopping” mechanism inspired by frequency hopping, enhancing security by distributing communication across multiple channels. Comparative performance analysis was conducted with widely-used protocols such as ModBus and the OPC UA, focusing on key metrics such as connection, reading, and writing times across local and remote networks. Results demonstrate that SRMCP outperforms ModBus in reading and writing operations while offering enhanced security, although it has a higher connection time due to its dual-layer encryption. The OPC UA, while secure, lags significantly in performance, making it less suitable for real-time applications. The findings suggest that SRMCP is a viable solution for secure and efficient machine communication in modern industrial settings, particularly where quantum-safe security is a concern. Full article
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<p>SRMCP communication procedures summary.</p>
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<p>The transaction procedure of client operation. Blue Arrows: Neutrual operations. Green Arrows: Operations when evaluation is true. Red Arrows: Operations when evaluation is false. Blue box: Objects. Yellow box: operations. Orange box: Evaluations. Red box: Critical Evaluations.</p>
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<p>SRMCP packet structure.</p>
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<p>Testing results for connecting the client and server over a local loopback address.</p>
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<p>Testing results for reading multiple variables over local loopback address.</p>
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<p>Testing results for writing a variable over a local loopback address.</p>
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<p>Testing results for local network connection time.</p>
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<p>Testing results for reading multiple variables over a local network.</p>
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<p>Testing results for writing a variable over a local network.</p>
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<p>Testing results for remote network connection time.</p>
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<p>Testing results for reading multiple variables over a remote network.</p>
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<p>Testing results for writing a variable over a remote network.</p>
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15 pages, 1935 KiB  
Article
Performance Characterization of Hardware/Software Communication Interfaces in End-to-End Power Management Solutions of High-Performance Computing Processors
by Antonio del Vecchio, Alessandro Ottaviano, Giovanni Bambini, Andrea Acquaviva and Andrea Bartolini
Energies 2024, 17(22), 5778; https://doi.org/10.3390/en17225778 - 19 Nov 2024
Viewed by 597
Abstract
Power management (PM) is cumbersome for today’s computing systems. Attainable performance is bounded by the architecture’s computing efficiency and capped in temperature, current, and power. PM is composed of multiple interacting layers. High-level controllers (HLCs) involve application-level policies, operating system agents (OSPMs), and [...] Read more.
Power management (PM) is cumbersome for today’s computing systems. Attainable performance is bounded by the architecture’s computing efficiency and capped in temperature, current, and power. PM is composed of multiple interacting layers. High-level controllers (HLCs) involve application-level policies, operating system agents (OSPMs), and PM governors and interfaces. The application of high-level control decisions is currently delegated to an on-chip power management unit executing tailored PM firmware routines. The complexity of this structure arises from the scale of the interaction, which pervades the whole system architecture. This paper aims to characterize the cost of the communication backbone between high-level OSPM agents and the on-chip power management unit (PMU) in high performance computing (HPC) processors. For this purpose, we target the System Control and Management Interface (SCMI), which is an open standard proposed by Arm. We enhance a fully open-source, end-to-end FPGA-based HW/SW framework to simulate the interaction between a HLC, a HPC system, and a PMU. This includes the application-level PM policies, the drivers of the operating system-directed configuration and power management (OSPM) governor, and the hardware and firmware of the PMU, allowing us to evaluate the impact of the communication backbone on the overall control scheme. With this framework, we first conduct an in-depth latency study of the communication interface across the whole PM hardware (HW) and software (SW) stack. Finally, we studied the impact of latency in terms of the quality of the end-to-end control, showing that the SCMI protocol can sustain reactive power management policies. Full article
(This article belongs to the Section F1: Electrical Power System)
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<p>Overview of the main PM components of modern HPC SoCs. This work focuses on the PMIs linking HLCs to the LLC from a HW and SW perspective in Arm-based server-class CPUs. (<b>a</b>) Architecture of the power management scheme in an application-class processor, (<b>b</b>) Block diagram of a state-of-the-art HIL platform for power management systems emulation, (<b>c</b>) Block diagram of the extended HIL platform proposed in this work.</p>
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<p>Sequence of function calls within the Linux CPUFreq stack, for a perf_level_set SCMI request.</p>
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<p>Delay time distribution for (<b>a</b>) transmission window, (<b>b</b>) decode window, and (<b>c</b>) reception window.</p>
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<p>Control Delay distribution for different HLC configurations and interfaces: (<b>a</b>) periodic HLC with shared memory, (<b>b</b>) periodic HLC with SCMI mailbox, (<b>c</b>) event-driven HLC with shared memory, (<b>d</b>) event-driven HLC with SCMI mailbox.</p>
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42 pages, 1312 KiB  
Article
Mobility–Multihoming Duality
by Ryo Yanagida and Saleem Noel Bhatti
Future Internet 2024, 16(10), 358; https://doi.org/10.3390/fi16100358 - 1 Oct 2024
Viewed by 953
Abstract
In modern Internet-based communication, especially mobile systems, a mobile node (MN) will commonly have more than one possibility for Internet Protocol (IP) connectivity. For example, an MN such as a smartphone may be associated with an IEEE 802.11 network at a site while [...] Read more.
In modern Internet-based communication, especially mobile systems, a mobile node (MN) will commonly have more than one possibility for Internet Protocol (IP) connectivity. For example, an MN such as a smartphone may be associated with an IEEE 802.11 network at a site while also connected to a cellular base station for 5G. In such a scenario, the smartphone might only be able to utilise the IEEE 802.11 network, not making use of the cellular connectivity simultaneously. Currently, IP does not allow applications and devices to easily utilise multiple IP connectivity opportunities—multihoming for the MN—without implementing special mechanisms to manage them. We demonstrate how the use of the Identifier Locator Network Protocol (ILNP), realised as an extension to IPv6, can enable mobility with multihoming using a duality mechanism that treats mobility and multihoming as the same logical concept. We present a network layer solution that does not require any modification to transport protocols, can be implemented using existing application programming interfaces (APIs), and can work for any application. We have evaluated our approach using an implementation in Linux and a testbed. The testbed consisted of commercial equipment to demonstrate that our approach can be used over existing network infrastructure requiring only normal unicast routing for IPv6. Full article
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Figure 1
<p>Comparison of the IPv6 unicast address format with the ILNP unicast addressing format. The L64 value has the same syntax and semantics as the IPv6 routing prefix. The NID value has the same syntax as the IPv6 Interface Identifier, but it has different semantics. The NID-L64 pairing is an Identifier Locator Vector (IL-V), which can be used the same way as an IPv6 address.</p>
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<p>An example of a Locator Update (LU) handshake for a Mobile Node (MN). The MN discovers a new L64 value via an IPv6 Router Advertisement (RA) message. It updates its local ILNP Communication Cache (ILCC) and sends an LU message to the Correspondent Node (CN). The CN updates its own ILCC and sends a LU-ack (acknowledgement) to the MN.</p>
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<p>The ILNP IPv6 extension header as in RFC6744.</p>
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<p>The ILNP LU message structure based on the message format from RFC6743.</p>
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<p>A flowchart describing UDP/TCP packet processing with ILNP mobility–multihoming duality mechanism with Deficit Round-Robin (DRR) load sharing. Overall, the existing IPv6 packet processing code path has been re-used and modified effectively. Grey boxes indicate unmodified processes with respect to IPv6 packet processing. Orange boxes indicate modifications of existing IPv6 packet processing logic. Green boxes are the additional logic and processing for ILNP.</p>
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<p>A scenario diagram describing host movement for the mobility–multihoming duality evaluation. There are four IPv6 networks, aa–dd, connected via the 4 routers, R1–R4, scenario. Network dd is used connect R1, R2, and R3 to R4, and it represents connectivity on over the Internet between MN and CN. The arrow labelled 1 is the first movement the MN carries out: moving from network aa on R1 to network cc on R3. The arrow labelled 2 shows the second set of movement, where the MN returns from network cc back to network aa.</p>
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<p>A timeline diagram showing an example of a mobility–multihoming duality scenario. The MN has three interfaces, and the CN has one interface. The MN starts communication only on network aa. The MN and the CN begin a communication session using a single interface on both sides. The MN activates interface 2, receives L64 (IPv6 prefix) <tt>bb</tt>, sends an LU, and sets the new L64 as ACTIVE. The CN responds with an LU-Ack, acknowledging the new set of L64 values that the MN now has. The MN continues to activate another interface, which is also signalled to the CN. The MN then lists the first interface in the <tt>net.ilnp6.disabled_interface</tt> <tt>sysctl</tt> list, triggering another LU and state changes in the ILCC. After the CN acknowledges the removal of the first interface, the MN removes the interface.</p>
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<p>The procedure for a data collection run. Both CN and MN initially have only a single interface (i/f) enabled. <tt>iperf2</tt> is started with bi-directional data transfer. Additional interfaces are enabled at the MN until all interfaces are enabled. Then, interfaces are disabled at the MN until only a single interface remains enabled. This is repeated so that all additional interfaces have been enabled/disabled twice.</p>
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<p>Plots showing packet delivery statistics of TCP and UDP over ILNP. Note that the y axis is in the range of 0.00–0.01, i.e., 0.00–1.00%. The box around the median value is invisible, as the results were consistent across the runs, and the rate remained near zero. In all cases, both the misorder and loss were very low and very consistent across multiple runs. Note that the different transmission characteristics and behaviours for TCP and UDP mean these metrics are not directly comparable. (<b>a</b>) TCP misordering ratio based on sequence numbers (data packets) and acknowledgement numbers received. Negligible misordering was observed. (<b>b</b>) TCP duplicate ratio based on sequence numbers (data packets) and acknowledgement numbers sent and received.No significant numbers of duplicate packets were observed in the sequence numbers or the acknowledgement numbers. (<b>c</b>) UDP packet statistics observed in mobility–multihoming duality scenarios with <tt>iperf2</tt> UDP over ILNP. With all scenarios, both misordering and loss ratio remained low or nil. The small size of the box indicates that there was little to no variation across different runs.</p>
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<p>Plots showing the throughput for TCP and UDP over ILNP. Note that, due to the different protocols and their characteristics, these are not directly comparable to each other. (<b>a</b>) Throughput observed in the mobility–multihoming duality scenarios with <tt>iperf2</tt> TCP flows over ILNP. Across all delay scenarios, the throughput remained near the 10 Mbps target with little variation, as shown by barely visible 25th and 75th percentile line of the box plot. Note that the <span class="html-italic">y</span> axis is in the range of 9.0–11.0 Mbps. The box around the median value is invisible, as the results were consistent across the runs, and the value remained near 10.2 Mbps. (<b>b</b>) Throughput observed in mobility–multihoming duality scenarios with <tt>iperf2</tt> UDP flows over ILNP. The throughput remained consistent at around the 10 Mbps target with very few exceptions. Note that the <span class="html-italic">y</span> axis is in the range of 9.0–11.0 Mbps. The box around the median value is invisible, as the results were consistent across the runs, and the value remained near 10.1 Mbps.</p>
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<p>Plots showing the throughput and sequence numbers observed in typical mobility–multihoming duality <tt>iperf2</tt> TCP scenario evaluations received at the CN. In each column, the top graph is throughput (faceted top to bottom as network aa, bb, cc, and aggregate). There was consistent aggregate throughput (bottom facet), with the expected throughput observed at the respective source/destination IL-V on each network (aa, bb, cc) as expected. The vertical dashed line shows the Locator Update (LU) message event. In each column, the lower graph is the TCP sequence number progression. This also showed consistent increase, indicating a consistent flow and delivery of packets.</p>
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<p>Plots showing the throughput and sequence numbers observed in typical mobility–multihoming duality <tt>iperf2</tt> TCP scenario evaluations received at the MN. In each column, the top graph is throughput (faceted top to bottom as network aa, bb, cc, and aggregate). There was consistent aggregate throughput (bottom facet), with the expected throughput observed at the respective source/destination IL-V on each network (aa, bb, cc) as expected. The vertical dashed line shows the Locator Update (LU) message event. In each column, the lower graph is the TCP sequence number progression. This also showed consistent increase, indicating a consistent flow and delivery of packets.</p>
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<p>Plots showing the throughput and sequence numbers observed in typical mobility–multihoming duality <tt>iperf2</tt> UDP scenario evaluations received at the CN. In each column, the top graph is throughput (faceted top to bottom as network aa, bb, cc, and aggregate). There was consistent aggregate throughput (bottom facet), with the expected throughput observed at the respective source/destination IL-V on each network (aa, bb, cc) as expected. The vertical dashed line shows the Locator Update (LU) message event. In each column, the lower graph is the <tt>iperf2</tt> sequence number progression. This also showed consistent increase, indicating a consistent flow and delivery of packets.</p>
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<p>Plots showing the throughput and sequence numbers observed in typical mobility–multihoming duality <tt>iperf2</tt> UDP scenario evaluations received at the MN. In each column, the top graph is throughput (faceted top to bottom as network aa, bb, cc, and aggregate). There was consistent aggregate throughput (bottom facet), with the expected throughput observed at the respective source/destination IL-V on each network (aa, bb, cc) as expected. The vertical dashed line shows the Locator Update (LU) message event. In each column, the lower graph is the <tt>iperf2</tt> sequence number progression. This also showed consistent increase, indicating a consistent flow and delivery of packets.</p>
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<p>Box plot showing MP-TCP flow for 20 runs with no added delay on path. While the individual interfaces may exhibit ‘bursty’ behaviour due to the way multipath congestion control algorithm distributes traffic, it satisfies the target load requirement of 10 Mbps.</p>
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<p>MP-TCP typical behaviour on the same testbed as for the ILNP evaluation. The distribution of the throughput is uneven, and changes to throughput on the individual interfaces are ‘bursty’. The vertical line shows the protocol level signalling (MP-TCP-specific multipath control plane protocol) to add or remove connectivity received at the respective IPv6 addresses. (<b>a</b>) Throughput facet plot of MP-TCP flow received at the MN. The top three plots show the throughput received at the addresses of the respective three interfaces at the MN, and the bottom plot shows the aggregate throughput. (<b>b</b>) Throughput facet plot of MP-TCP flow received at the CN. The top three plots show the throughputs received from the addresses of the respective three interfaces at the MN, and the bottom plot shows the aggregate throughput.</p>
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<p>MP-TCP typical behaviour on the same testbed as for the ILNP evaluation. The distribution of the throughput is uneven, and changes to throughput on the individual interfaces are ‘bursty’. The vertical line shows the protocol level signalling (MP-TCP-specific multipath control plane protocol) to add or remove connectivity received at the respective IPv6 addresses. (<b>a</b>) Throughput facet plot of MP-TCP flow received at the MN. The top three plots show the throughput received at the addresses of the respective three interfaces at the MN, and the bottom plot shows the aggregate throughput. (<b>b</b>) Throughput facet plot of MP-TCP flow received at the CN. The top three plots show the throughputs received from the addresses of the respective three interfaces at the MN, and the bottom plot shows the aggregate throughput.</p>
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6 pages, 3115 KiB  
Proceeding Paper
Medium Access Control Layer for Internet of Things Edge-Side Network Using Carrier-Sense Multiple Access Protocol
by Selahattin Kosunalp and Sami Acik
Eng. Proc. 2024, 70(1), 1; https://doi.org/10.3390/engproc2024070001 - 23 Jul 2024
Viewed by 638
Abstract
The Internet of Things (IoT) has recently received a great deal of research interest due to its broad range of applications. One of the important layers in IoT applications is known as edge computing where resource-constrained devices at the edge form a simple [...] Read more.
The Internet of Things (IoT) has recently received a great deal of research interest due to its broad range of applications. One of the important layers in IoT applications is known as edge computing where resource-constrained devices at the edge form a simple type of network to sense required data. A more powerful edge device is responsible for collecting all sensed data to be transferred to the upper layers. A critical focus is therefore placed on maximum rate of data collection, requiring effective and intelligent solutions to coordinate the channel access of the devices. Medium access control (MAC) protocols take this responsibility as their design mission. Carrier-sense multiple access (CSMA) has been a baseline MAC scheme and many previous traditional networks utilized a CSMA-based solution. The motivation of this paper is to study the performance of a typical network at the edge through the CSMA theme. A practical network is constructed to assess the channel throughput performance via a commercially available radio transceiver. The practical performance observations indicate the suitability of the proposed CSMA-based solution. Full article
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<p>IoT architecture with common layers.</p>
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<p>ALOHA throughput with an infinite number of objects.</p>
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<p>CSMA throughput with respect to varying parameter α.</p>
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<p>A view of the transceiver module.</p>
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<p>The deployed single-hop topology.</p>
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<p>Throughput of ALOHA and CSMA on realistic topology.</p>
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21 pages, 2475 KiB  
Article
Addressing Vulnerabilities in CAN-FD: An Exploration and Security Enhancement Approach
by Naseeruddin Lodge, Nahush Tambe and Fareena Saqib
IoT 2024, 5(2), 290-310; https://doi.org/10.3390/iot5020015 - 30 May 2024
Cited by 1 | Viewed by 1469
Abstract
The rapid advancement of technology, alongside state-of-the-art techniques is at an all-time high. However, this unprecedented growth of technological prowess also brings forth potential threats, as oftentimes the security encompassing these technologies is imperfect. Particularly within the automobile industry, the recent strides in [...] Read more.
The rapid advancement of technology, alongside state-of-the-art techniques is at an all-time high. However, this unprecedented growth of technological prowess also brings forth potential threats, as oftentimes the security encompassing these technologies is imperfect. Particularly within the automobile industry, the recent strides in technology have brought about increased complexity. A notable flaw lies in the CAN-FD protocol, which lacks robust security measures, making it vulnerable to data theft, injection, replay, and flood data attacks. With the rising complexity of in-vehicular networks and the widespread adoption of CAN-FD, the imperative to safeguard the protocol has never been more crucial. This paper aims to provide a comprehensive review of the existing in-vehicle communication protocol, CAN-FD. It explores existing security approaches designed to fortify CAN-FD, demonstrating multiple multi-layer solutions that leverage modern techniques including Physical Unclonable Function (PUF), Elliptical Curve Cryptography (ECC), Ethereum Blockchain, and Smart contracts. The paper highlights existing multi-layer security measures that offer minimal overhead, optimal performance, and robust security. Moreover, it identifies areas where these security measures fall short and discusses ongoing research along with suggestions for implementing software and hardware-level modifications. These proposed changes aim to streamline complexity, reduce overhead while ensuring forward compatibility. In essence, the methods outlined in this study are poised to excel in real-world applications, offering robust protection for the evolving landscape of in-vehicular communication systems. Full article
(This article belongs to the Special Issue Cloud and Edge Computing Systems for IoT)
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<p>CAN vs. CAN-FD Dataframes [<a href="#B6-IoT-05-00015" class="html-bibr">6</a>].</p>
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<p>Comparison of Message Size with Varying Payload for CAN vs. CAN-FD [<a href="#B8-IoT-05-00015" class="html-bibr">8</a>].</p>
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<p>Comparison of Message Overhead with Varying Payload for CAN vs. CAN-FD [<a href="#B8-IoT-05-00015" class="html-bibr">8</a>].</p>
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<p>Secure Block Implementation at Each Client Node [<a href="#B1-IoT-05-00015" class="html-bibr">1</a>].</p>
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<p>Sender Preparing to send the encrypted message along with MAC Tag and sender public key to help receiver decrypt the message.</p>
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<p>Decrypting a Message from the Sender.</p>
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<p>CAN-FD Blockchain Integration Architecture [<a href="#B6-IoT-05-00015" class="html-bibr">6</a>].</p>
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<p>CAN-FD Communication via Blockchain [<a href="#B6-IoT-05-00015" class="html-bibr">6</a>].</p>
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21 pages, 4943 KiB  
Article
Cross-Layer Optimization for Enhanced IoT Connectivity: A Novel Routing Protocol for Opportunistic Networks
by Ayman Khalil and Besma Zeddini
Future Internet 2024, 16(6), 183; https://doi.org/10.3390/fi16060183 - 22 May 2024
Cited by 3 | Viewed by 1415
Abstract
Opportunistic networks, an evolution of mobile Ad Hoc networks (MANETs), offer decentralized communication without relying on preinstalled infrastructure, enabling nodes to route packets through different mobile nodes dynamically. However, due to the absence of complete paths and rapidly changing connectivity, routing in opportunistic [...] Read more.
Opportunistic networks, an evolution of mobile Ad Hoc networks (MANETs), offer decentralized communication without relying on preinstalled infrastructure, enabling nodes to route packets through different mobile nodes dynamically. However, due to the absence of complete paths and rapidly changing connectivity, routing in opportunistic networks presents unique challenges. This paper proposes a novel probabilistic routing model for opportunistic networks, leveraging nodes’ meeting probabilities to route packets towards their destinations. Thismodel dynamically builds routes based on the likelihood of encountering the destination node, considering factors such as the last meeting time and acknowledgment tables to manage network overload. Additionally, an efficient message detection scheme is introduced to alleviate high overhead by selectively deleting messages from buffers during congestion. Furthermore, the proposed model incorporates cross-layer optimization techniques, integrating optimization strategies across multiple protocol layers to maximize energy efficiency, adaptability, and message delivery reliability. Through extensive simulations, the effectiveness of the proposed model is demonstrated, showing improved message delivery probability while maintaining reasonable overhead and latency. This research contributes to the advancement of opportunistic networks, particularly in enhancing connectivity and efficiency for Internet of Things (IoT) applications deployed in challenging environments. Full article
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<p>Schematic of two required tables.</p>
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<p>Flowchart process of the AckedMessagesTable.</p>
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<p>Message overhead.</p>
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<p>Delivery probability with respect to number of messages.</p>
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<p>Latency with respect to number of messages.</p>
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<p>Overhead ratio with respect to number of messages.</p>
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<p>Delivery probability with respect to number of users.</p>
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<p>Overhead ratio with respect to number of users.</p>
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<p>Latency with respect to number of users.</p>
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<p>Delivery probability with respect to number of copies (DakNet scenario).</p>
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<p>Overhead ratio with respect to number of copies.</p>
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<p>Latency with respect to number of copies.</p>
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<p>Delivery probability case, WiFi-direct.</p>
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<p>Overhead ratio case, WiFi-direct.</p>
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<p>Latency case, WiFi-direct.</p>
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45 pages, 2604 KiB  
Systematic Review
Biomechanics of the Human Osteochondral Unit: A Systematic Review
by Matteo Berni, Gregorio Marchiori, Massimiliano Baleani, Gianluca Giavaresi and Nicola Francesco Lopomo
Materials 2024, 17(7), 1698; https://doi.org/10.3390/ma17071698 - 8 Apr 2024
Cited by 2 | Viewed by 2135
Abstract
The damping system ensured by the osteochondral (OC) unit is essential to deploy the forces generated within load-bearing joints during locomotion, allowing furthermore low-friction sliding motion between bone segments. The OC unit is a multi-layer structure including articular cartilage, as well as subchondral [...] Read more.
The damping system ensured by the osteochondral (OC) unit is essential to deploy the forces generated within load-bearing joints during locomotion, allowing furthermore low-friction sliding motion between bone segments. The OC unit is a multi-layer structure including articular cartilage, as well as subchondral and trabecular bone. The interplay between the OC tissues is essential in maintaining the joint functionality; altered loading patterns can trigger biological processes that could lead to degenerative joint diseases like osteoarthritis. Currently, no effective treatments are available to avoid degeneration beyond tissues’ recovery capabilities. A thorough comprehension on the mechanical behaviour of the OC unit is essential to (i) soundly elucidate its overall response to intra-articular loads for developing diagnostic tools capable of detecting non-physiological strain levels, (ii) properly evaluate the efficacy of innovative treatments in restoring physiological strain levels, and (iii) optimize regenerative medicine approaches as potential and less-invasive alternatives to arthroplasty when irreversible damage has occurred. Therefore, the leading aim of this review was to provide an overview of the state-of-the-art—up to 2022—about the mechanical behaviour of the OC unit. A systematic search is performed, according to PRISMA standards, by focusing on studies that experimentally assess the human lower-limb joints’ OC tissues. A multi-criteria decision-making method is proposed to quantitatively evaluate eligible studies, in order to highlight only the insights retrieved through sound and robust approaches. This review revealed that studies on human lower limbs are focusing on the knee and articular cartilage, while hip and trabecular bone studies are declining, and the ankle and subchondral bone are poorly investigated. Compression and indentation are the most common experimental techniques studying the mechanical behaviour of the OC tissues, with indentation also being able to provide information at the micro- and nanoscales. While a certain comparability among studies was highlighted, none of the identified testing protocols are currently recognised as standard for any of the OC tissues. The fibril-network-reinforced poro-viscoelastic constitutive model has become common for describing the response of the articular cartilage, while the models describing the mechanical behaviour of mineralised tissues are usually simpler (i.e., linear elastic, elasto-plastic). Most advanced studies have tested and modelled multiple tissues of the same OC unit but have done so individually rather than through integrated approaches. Therefore, efforts should be made in simultaneously evaluating the comprehensive response of the OC unit to intra-articular loads and the interplay between the OC tissues. In this regard, a multidisciplinary approach combining complementary techniques, e.g., full-field imaging, mechanical testing, and computational approaches, should be implemented and validated. Furthermore, the next challenge entails transferring this assessment to a non-invasive approach, allowing its application in vivo, in order to increase its diagnostic and prognostic potential. Full article
(This article belongs to the Special Issue The 15th Anniversary of Materials—Recent Advances in Biomaterials)
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<p>Scheme of the osteochondral unit structure, with particular focus on the knee joint, i.e., proximal tibia.</p>
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<p>PRISMA flowchart for the eligibility of studies.</p>
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<p>Distribution of eligible studies (total) over time. Studies are further clustered by considering the investigated tissue (<b>top graph</b>) and the joint from which samples are retrieved (<b>bottom graph</b>). A discontinuity in the line means that there are no eligible studies in a range of three years, centred on the year for which the point is missing.</p>
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<p>Distribution, over the years, of the Aggregate Quality Score of eligible studies, clustered by tissue (<b>top graph</b>) and joint (<b>bottom graph</b>). A discontinuity in the line means that there are no eligible studies in a range of three years, centred on the year for which the point is missing.</p>
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31 pages, 3700 KiB  
Review
Cross-Layer Methods for Ad Hoc Networks—Review and Classification
by Valeriy Ivanov and Maxim Tereshonok
Future Internet 2024, 16(1), 29; https://doi.org/10.3390/fi16010029 - 16 Jan 2024
Cited by 3 | Viewed by 2399
Abstract
The OSI model used to be a common network model for years. In the case of ad hoc networks with dynamic topology and difficult radio communications conditions, gradual departure is happening from the classical kind of OSI network model with a clear delineation [...] Read more.
The OSI model used to be a common network model for years. In the case of ad hoc networks with dynamic topology and difficult radio communications conditions, gradual departure is happening from the classical kind of OSI network model with a clear delineation of layers (physical, channel, network, transport, application) to the cross-layer approach. The layers of the network model in ad hoc networks strongly influence each other. Thus, the cross-layer approach can improve the performance of an ad hoc network by jointly developing protocols using interaction and collaborative optimization of multiple layers. The existing cross-layer methods classification is too complicated because it is based on the whole manifold of network model layer combinations, regardless of their importance. In this work, we review ad hoc network cross-layer methods, propose a new useful classification of cross-layer methods, and show future research directions in the development of ad hoc network cross-layer methods. The proposed classification can help to simplify the goal-oriented cross-layer protocol development. Full article
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<p>Network classification.</p>
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<p>Ad hoc network.</p>
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<p>The interdependence of OSI layers in an ad hoc network.</p>
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<p>Two main cross-layer architectures: “MobileMan” and “Crosstalk”.</p>
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<p>Cross-layer methods as the iterative optimization of multiple-layer configuration.</p>
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<p>Cross-layer methods for ad hoc networks publication activity.</p>
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<p>Cross-layer methods for ad hoc network classification.</p>
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26 pages, 11010 KiB  
Article
Knowledge Development Trajectory of the Internet of Vehicles Domain Based on Main Path Analysis
by Tang-Min Hsieh and Kai-Ying Chen
Sensors 2023, 23(13), 6120; https://doi.org/10.3390/s23136120 - 3 Jul 2023
Cited by 5 | Viewed by 2468
Abstract
The Internet of vehicles (IoV) is an Internet-of-things-based network in the area of transportation. It comprises sensors, network communication, automation control, and data processing and enables connectivity between vehicles and other objects. This study performed main path analysis (MPA) to investigate the trajectory [...] Read more.
The Internet of vehicles (IoV) is an Internet-of-things-based network in the area of transportation. It comprises sensors, network communication, automation control, and data processing and enables connectivity between vehicles and other objects. This study performed main path analysis (MPA) to investigate the trajectory of research regarding the IoV. Studies were extracted from the Web of Science database, and citation networks among these studies were generated. MPA revealed that research in this field has mainly covered media access control, vehicle-to-vehicle channels, device-to-device communications, layers, non-orthogonal multiple access, and sixth-generation communications. Cluster analysis and data mining revealed that the main research topics related to the IoV included wireless channels, communication protocols, vehicular ad hoc networks, security and privacy, resource allocation and optimization, autonomous cruise control, deep learning, and edge computing. By using data mining and statistical analysis, we identified emerging research topics related to the IoV, namely blockchains, deep learning, edge computing, cloud computing, vehicular dynamics, and fifth- and sixth-generation mobile communications. These topics are likely to help drive innovation and the further development of IoV technologies and contribute to smart transportation, smart cities, and other applications. On the basis of the present results, this paper offers several predictions regarding the future of research regarding the IoV. Full article
(This article belongs to the Section Vehicular Sensing)
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<p>Example of the SPLC algorithm.</p>
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<p>The results of SPLC algorithm final main path.</p>
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<p>Cumulative number of IoV papers on WOS database.</p>
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<p>Global main path.</p>
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<p>Key-route main path.</p>
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<p>Analysis of Cluster 1: wireless channels.</p>
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<p>Analysis of Cluster 2: communication protocols and control techniques.</p>
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<p>Analysis of Cluster 3: VANETs.</p>
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<p>Analysis of Cluster 4: security and privacy protection protocols.</p>
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<p>Analysis of Cluster 5: resource allocation and optimization.</p>
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<p>Analysis of Cluster 6: vehicle ACC.</p>
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<p>Analysis of Cluster 7: deep learning and edge computing.</p>
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<p>Trajectory of research regarding the IoV.</p>
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20 pages, 8425 KiB  
Article
Formalizing the Semantics of DDS QoS Policies for Improved Communications in Distributed Smart Grid Applications
by Alaa Alaerjan
Electronics 2023, 12(10), 2246; https://doi.org/10.3390/electronics12102246 - 15 May 2023
Cited by 1 | Viewed by 1465
Abstract
Quality communication is a major challenges in large-scale and distributed smart grid applications. Several protocols and middleware have been proposed to address communication quality issues in those applications. DDS is a standard data-centric middleware for publish/subscribe communication. It has been proposed for smart [...] Read more.
Quality communication is a major challenges in large-scale and distributed smart grid applications. Several protocols and middleware have been proposed to address communication quality issues in those applications. DDS is a standard data-centric middleware for publish/subscribe communication. It has been proposed for smart grid to address both connectivity and communication quality issues. DDS provides multiple quality of service (QoS) policies to address reliability, latency, and data availability. One of the main challenges in adopting the standard in smart grids is the complexity of adopting and tailoring its QoS policies. This is because those policies are described informally introducing ambiguities, which hinders the precise implementation of DDS. To address this, we formalize the descriptions of DDS QoS policies using the object constraint language (OCL). We also clearly defined the design structural relations among DDS entities and QoS policies. In the process, we analyzed the dependencies among QoS policies and we built clear and concise structural relations. We then proposed feature modeling and a management layer to facilitate QoS tuning and to reduce development and configuration complexity. We implemented the proposed approach in a simulated power consumption domain. The results show that the approach improves the development process. They also show that the approach significantly improves the performance of DDS-enabled applications. Full article
(This article belongs to the Special Issue Internet of Things for Smart Grid)
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<p>Different categories of DDS QoS policies.</p>
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<p>Class diagram of the service configuration.</p>
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<p>Class diagram of data delivery QoS policies.</p>
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<p>Class diagram of data availability QoS policies.</p>
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<p>Class diagram of data timeliness QoS policies.</p>
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<p>Class diagram of resource control QoS policies.</p>
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<p>Feature model of DDS QoS policies based on defined categories.</p>
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<p>Implementation of <span class="html-italic">DataDelivery</span> and <span class="html-italic">ResourceControl</span> in FeatureIDE.</p>
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<p>Different layers in DDS and placement of QoSML.</p>
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<p>Communication scenarios in consumption domain using DDS.</p>
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<p>Structure of the implemented approach on sensor nodes.</p>
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<p>CPU load on the DDS publisher (wireless communication).</p>
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<p>CPU load on the DDS publisher (wired communication).</p>
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<p>CPU load on DDS subscriber (wireless communication).</p>
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<p>CPU load on DDS subscriber (wired communication).</p>
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<p>Illustration of CPU load (wireless communication).</p>
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<p>Illustration of the CPU load on wired communication.</p>
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18 pages, 5202 KiB  
Article
Optimization of Drone Base Station Location for the Next-Generation Internet-of-Things Using a Pre-Trained Deep Learning Algorithm and NOMA
by Hadeel Alsolai, Wafa Mtouaa, Mashael S. Maashi, Mahmoud Othman, Ishfaq Yaseen, Amani A. Alneil, Azza Elneil Osman and Mohamed Ibrahim Alsaid
Mathematics 2023, 11(8), 1947; https://doi.org/10.3390/math11081947 - 20 Apr 2023
Cited by 2 | Viewed by 1577
Abstract
Next-generation Internet-of-Things applications pose challenges for sixth-generation (6G) mobile networks, involving large bandwidth, increased network capabilities, and remarkably low latency. The possibility of using ultra-dense connectivity to address the existing problem was previously well-acknowledged. Therefore, placing base stations (BSs) is economically challenging. Drone-based [...] Read more.
Next-generation Internet-of-Things applications pose challenges for sixth-generation (6G) mobile networks, involving large bandwidth, increased network capabilities, and remarkably low latency. The possibility of using ultra-dense connectivity to address the existing problem was previously well-acknowledged. Therefore, placing base stations (BSs) is economically challenging. Drone-based stations can efficiently address Next-generation Internet-of-Things requirements while accelerating growth and expansion. Due to their versatility, they can also manage brief network development or offer on-demand connectivity in emergency scenarios. On the other hand, identifying a drone stations are a complex procedure due to the limited energy supply and rapid signal quality degradation in air-to-ground links. The proposed method uses a two-layer optimizer based on a pre-trained VGG-19 model to overcome these issues. The non-orthogonal multiple access protocol improves network performance. Initially, it uses a powerful two-layer optimizer that employs a population of micro-swarms. Next, it automatically develops a lightweight deep model with a few VGG-19 convolutional filters. Finally, non-orthogonal multiple access is used to schedule radio and power resources to devices, which improves network performance. We specifically examine how three scenarios execute when various Cuckoo Search, Grey Wolf Optimization, and Particle Swarm Optimization techniques are used. To measure the various methodologies, we also run non-parametric statistical tests, such as the Friedman and Wilcoxon tests. The proposed method also evaluates the accuracy level for network performance of DBSs using number of Devices. The proposed method achieves better performance of 98.44% compared with other methods. Full article
(This article belongs to the Section E1: Mathematics and Computer Science)
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<p>Architecture diagram of the proposed method.</p>
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<p>Working flow of the two-layer optimizer.</p>
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<p>Two-layer optimizer based on the VGG19 network.</p>
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<p>Average pathloss with search agents for Scenario 1.</p>
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<p>Average pathloss with number of generations for Scenario 1.</p>
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<p>Average pathloss with various environments for Scenario 1.</p>
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<p>(<b>a</b>) Average pathloss for the urban environment; (<b>b</b>) Average pathloss for the suburban environment; (<b>c</b>) Average pathloss for the dense urban environment; (<b>d</b>) Average pathloss for the high-rise urban environment.</p>
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<p>(<b>a</b>) Average pathloss for the urban environment; (<b>b</b>) Average pathloss for the suburban environment; (<b>c</b>) Average pathloss for the dense urban environment; (<b>d</b>) Average pathloss for the high-rise urban environment.</p>
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<p>Coverage probability for the urban environment using a threshold of T = 90.</p>
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<p>Coverage probability for the sub-urban environment using a threshold of T = 100.</p>
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<p>Coverage probability for the dense urban environment using a threshold of T = 110.</p>
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<p>Coverage probability for the high-rise urban environment using a threshold T = 120.</p>
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<p>Accuracy of various optimizers compared to the proposed model.</p>
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19 pages, 2158 KiB  
Article
Application-Layer Time Synchronization and Data Alignment Method for Multichannel Biosignal Sensors Using BLE Protocol
by Jianan Li, Eric Quintin, He Wang, Benjamin E. McDonald, Todd R. Farrell, Xinming Huang and Edward A. Clancy
Sensors 2023, 23(8), 3954; https://doi.org/10.3390/s23083954 - 13 Apr 2023
Cited by 3 | Viewed by 3049
Abstract
Wearable wireless biomedical sensors have emerged as a rapidly growing research field. For many biomedical signals, multiple sensors distributed about the body without local wired connections are required. However, designing multisite systems at low cost with low latency and high precision time synchronization [...] Read more.
Wearable wireless biomedical sensors have emerged as a rapidly growing research field. For many biomedical signals, multiple sensors distributed about the body without local wired connections are required. However, designing multisite systems at low cost with low latency and high precision time synchronization of acquired data is an unsolved problem. Current solutions use custom wireless protocols or extra hardware for synchronization, forming custom systems with high power consumption that prohibit migration between commercial microcontrollers. We aimed to develop a better solution. We successfully developed a low-latency, Bluetooth low energy (BLE)-based data alignment method, implemented in the BLE application layer, making it transferable between manufacturer devices. The time synchronization method was tested on two commercial BLE platforms by inputting common sinusoidal input signals (over a range of frequencies) to evaluate time alignment performance between two independent peripheral nodes. Our best time synchronization and data alignment method achieved absolute time differences of 69 ± 71 μs for a Texas Instruments (TI) platform and 477 ± 490 μs for a Nordic platform. Their 95th percentile absolute errors were more comparable—under 1.8 ms for each. Our method is transferable between commercial microcontrollers and is sufficient for many biomedical applications. Full article
(This article belongs to the Special Issue Wearable Sensors for Human Movement)
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<p>System diagram for both TI and Nordic platforms.</p>
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<p>Flowchart of time synchronization method, using <math display="inline"><semantics> <mrow> <mi>N</mi> <mo> </mo> </mrow> </semantics></math>= 10 as an example. Variables <math display="inline"><semantics> <mi>N</mi> </semantics></math>, <math display="inline"><semantics> <mrow> <mi>T</mi> <msub> <mi>S</mi> <mi>C</mi> </msub> </mrow> </semantics></math>, <math display="inline"><semantics> <mrow> <mi>T</mi> <msub> <mi>S</mi> <mi>P</mi> </msub> </mrow> </semantics></math>, and <math display="inline"><semantics> <mrow> <mi>T</mi> <msub> <mi>S</mi> <mrow> <mi>A</mi> <mi>D</mi> <mi>C</mi> </mrow> </msub> </mrow> </semantics></math> are defined in the text.</p>
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<p>Illustration of ADC stream deletion and insertion of a sample, as needed, to maintain data alignment. The sample time corresponding to each peripheral 1 ADC sample is adjusted to the estimated central node time using its respective linear regression time synchronization model (which is based on paired timestamps—see <a href="#sensors-23-03954-f002" class="html-fig">Figure 2</a>). ADC samples from peripheral 2 are similarly time-synchronized, using its respective model. Whenever too few ADC samples arrive from peripheral 2, an extra peripheral 2 sample is inserted (shown above). Whenever too many ADC samples arrive from peripheral 2, a peripheral 2 sample is deleted (also shown above). Note: ADC arrival time variations in peripheral 2 are exaggerated above to illustrate both an insertion and a deletion. In practice, at most one correction was made per packet.</p>
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<p>TI platform (<b>left</b>) and Nordic platform (<b>right</b>).</p>
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<p>Histogram, scaled as a probability density function estimate, showing Nordic platform time differences between two peripheral nodes. Results are combined from all number of timestamp pairs (<math display="inline"><semantics> <mi>N</mi> </semantics></math> = 2, 4, 8, 16, 32, 64, and 128) and update intervals (100, 200, 500, and 1000 ms).</p>
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19 pages, 2049 KiB  
Article
Comparison between Two Time Synchronization and Data Alignment Methods for Multi-Channel Wearable Biosensor Systems Using BLE Protocol
by He Wang, Jianan Li, Benjamin E. McDonald, Todd R. Farrell, Xinming Huang and Edward A. Clancy
Sensors 2023, 23(5), 2465; https://doi.org/10.3390/s23052465 - 23 Feb 2023
Cited by 5 | Viewed by 2630
Abstract
Wireless wearable sensor systems for biomedical signal acquisition have developed rapidly in recent years. Multiple sensors are often deployed for monitoring common bioelectric signals, such as EEG (electroencephalogram), ECG (electrocardiogram), and EMG (electromyogram). Compared with ZigBee and low-power Wi-Fi, Bluetooth Low Energy (BLE) [...] Read more.
Wireless wearable sensor systems for biomedical signal acquisition have developed rapidly in recent years. Multiple sensors are often deployed for monitoring common bioelectric signals, such as EEG (electroencephalogram), ECG (electrocardiogram), and EMG (electromyogram). Compared with ZigBee and low-power Wi-Fi, Bluetooth Low Energy (BLE) can be a more suitable wireless protocol for such systems. However, current time synchronization methods for BLE multi-channel systems, via either BLE beacon transmissions or additional hardware, cannot satisfy the requirements of high throughput with low latency, transferability between commercial devices, and low energy consumption. We developed a time synchronization and simple data alignment (SDA) algorithm, which was implemented in the BLE application layer without the need for additional hardware. We further developed a linear interpolation data alignment (LIDA) algorithm to improve upon SDA. We tested our algorithms using sinusoidal input signals at different frequencies (10 to 210 Hz in increments of 20 Hz—frequencies spanning much of the relevant range of EEG, ECG, and EMG signals) on Texas Instruments (TI) CC26XX family devices, with two peripheral nodes communicating with one central node. The analysis was performed offline. The lowest average (±standard deviation) absolute time alignment error between the two peripheral nodes achieved by the SDA algorithm was 384.3 ± 386.5 μs, while that of the LIDA algorithm was 189.9 ± 204.7 μs. For all sinusoidal frequencies tested, the performance of LIDA was always statistically better than that of SDA. These average alignment errors were quite low—well below one sample period for commonly acquired bioelectric signals. Full article
(This article belongs to the Special Issue Wearable Sensors for Human Movement)
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<p>Aligning the <math display="inline"><semantics> <mi>M</mi> </semantics></math> peripheral nodes at startup. Red blocks represent the data packet streams. The black dashed line marks the arrival of the last peripheral into the configuration, signifying the start time of the whole system. Blue dashed lines mark discarded ADC data samples.</p>
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<p>TI platform (one central node and two peripheral nodes) and the Hewlett Packard 33120A signal generator. The signal generator sine wave output is simultaneously connected to the ADC input of both peripheral nodes.</p>
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<p>Example time-series plots from one trial (10 s to 11 s time range) of 10 Hz input frequency. (<b>a</b>) Input signals from two peripheral nodes without alignment; (<b>b</b>) same signals after applying LIDA.</p>
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<p>Histogram plot generated from absolute time alignment errors using input frequencies of 10 Hz, 110 Hz, and 210 Hz (<b>a</b>–<b>c</b>) and all input frequencies (<b>d</b>). The red bins were generated using LIDA and the white bins were generated using SDA, with the overlapped parts colored pink.</p>
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<p>(<b>a</b>,<b>b</b>) Cross-plots (one per peripheral node, as labeled) of time differences between successive central node timestamps on the <span class="html-italic">x</span>-axis vs. time differences between paired successive peripheral node timestamps on the <span class="html-italic">y</span>-axis. Inset plots show expanded view of points clustered around the nominal time differences of 1050 ms. Line of agreement drawn in each cross-plot. (<b>c</b>,<b>d</b>) Corresponding histograms of the distances from each x–y timestamp location and the closest point on the line of agreement. Scales differ in all plots.</p>
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