Emerging IoT applications are transitioning from battery-powered to grid-powered nodes. DRP, a contention-based data dissemination protocol, was developed for these applications. Traditional contention-based protocols resolve collisions through control packet exchanges, significantly reducing goodput. DRP mitigates this issue by employing a distributed delay timer mechanism that assigns transmission-start delays based on the average link quality between a sender and its children, prioritizing highly connected nodes for early transmission. However, our in-field experiments reveal that DRP is unable to accommodate real-world link quality fluctuations, leading to overlapping transmissions from multiple senders. This overlap triggers CSMA’s random back-off delays, ultimately degrading the goodput performance. To address these shortcomings, we first conduct a theoretical analysis that characterizes the design requirements induced by real-world link quality fluctuations and DRP’s passive acknowledgments. Guided by this analysis, we design EDRP, which integrates two novel components: (i) Link-Quality Aware CSMA (LQ-CSMA) and (ii) a Machine Learning-based Block Size Selection (ML-BSS) algorithm for rateless codes. LQ-CSMA dynamically restricts the back-off delay range based on real-time link quality estimates, ensuring that nodes with stronger connectivity experience shorter delays. ML-BSS algorithm predicts future link quality conditions and optimally adjusts the block size for rateless coding, reducing overhead and enhancing goodput. In-field evaluations of EDRP demonstrate an average goodput improvement of 39.43% than the competing protocols.

As the number of wireless devices supporting multiple communication interfaces increases, the connection redundancy is being considered for efficient bandwidth utilization and QoS improvement. Accordingly, network technologies must adapt to emerging multi-interface devices to improve network performance. Multipath TCP (MPTCP) is default multipath transport protocol desired for networks with multi-interface devices and has achieved success in computer networks. However, it has not been well studied for wireless networks, especially for carrier sense multiple access (CSMA) based wireless networks, which present great challenges to round trip time (RTT) computation and multipath scheduling. This paper introduces MPTCP techniques for heterogeneous WiFi and 5G networks. We first model a proposed 5-state congestion control algorithm and WiFi CSMA function. We then present an innovative RTT computation method and a novel loss-ware multipath scheduling mechanism. We evaluated the proposed MPTCP techniques under varying network configurations. Our MPTCP can significantly outperform conventional MPTCP.

This paper explores the transformative potential of the IoT paradigm in promoting smart agriculture. Key challenges lie in how to connect agriculture sensors to remote cloud servers in the absence of feasible communication infrastructure and the unreliable wireless links in rural areas. To address these issues, we propose an innovative two-tier smart agriculture architecture: an Unmanned Aerial Vehicle (UAV) aided agriculture network model, which leverages UAVs as intermediaries to collect and route data from agriculture sensors to cloud servers. This novel architecture leads to two particular problems, i.e., data packet scheduling in the first-tier networks and multi-hop routing in the second-tier UAV mesh network. To that end, we present formal Markov decision process (MDP) based problem formulations for both tiers, with a primary focus on the more challenging multi-hop routing problem in the second-tier network. This problem is approached as a multi-agent reinforcement learning (MARL) framework, for which we introduce a novel distributed algorithm - Focus Coordination: attention-guided Multi-Agent Deep Deterministic Policy Gradient (FC-MADDPG). This algorithm reduces communication overhead and mitigates the risks associated with single-node failures. We evaluated the performance of the proposed FC-MADDPG algorithm, demonstrating its efficacy in enhancing data transmission reliability and efficiency.

Sub-1 GHz (920 MHz) frequency bands for LPWAN (Low Power Wide Area Network) wireless communications systems are attracting attention from various IoT applications. Environmental and infrastructure monitoring systems, such as smart meter, ground inclinometer, and bridge sensor, are widely deployed. AsLPWAN systems operating on Sub-1 GHz bands can provide long distance communications,, a large number of network devices can connect to networks. Although these networks can be configured in a star configuration for a relatively small area, the mesh configuration has been emerging recently. IEEE 802.15.4g-FSK PHY/OFDM PHY is a typical PHY technology in mesh networks for the purpose of transferring IoT application data over a wider area. To distribute the same data such as firmware to LPWAN devices during network operation, improving distribution efficiency becomes critical. On the one hand, using broadcast transmission, the delivery confirmation cannot be performed. On the other hand, unicast transmission is very time consuming if the number of IoT devices is large. Therefore, we proposed a novel firmware distribution method using erasure code for large scale IoT networks. Our ns-3 simulations demonstrate that the proposed method can improve the distribution efficiency by up to 1.8 times compared to conventional methods and achieve higher spectrum efficiency for IEEE 802.15.4g-OFDM PHY.

With the advent of 5G and beyond communication technologies, the consumer IoT devices are evolving from current generation to next generation. Next generation IoT devices can support multiple communication interfaces and perform more functions. Accordingly, IoT network technologies must adapt to the emerging multi-link devices to improve network performance. Multipath TCP (MPTCP) is desired for networks with multi-link devices and has achieved success in computer networks. However, MPTCP has not been well studied for wireless networks. To that end, this paper presents MPTCP techniques for heterogeneous wireless IoT networks consisting of IEEE 802.15.4 nodes and 5G nodes. We propose a path builder, an adaptive congestion controller and an innovative path scheduler. We evaluated our MPTCP techniques under varying network configurations. Compared with conventional MPTCP, the proposed MPTCP can significantly reduce the number of packet transmissions, shorten packet delivery time, improve network throughput and packet delivery rate.

Sub-1 GHz Wireless Communications of LPWAN (Low Power Wide Area Network) are attracting attention in IoT applications. In addition to battery-powered devices, the number of grid-powered and solar-powered sensor devices using LPWAN are also rapidly increasing for various IoT applications. We aim to improve reliability and efficiency of IEEE 802.15.4 CSMA/CA mechanism in the network consisting of devices without power constraint. We propose Suspendable Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) algorithms for IEEE 802.15.4 to mitigate packet loss by channel access failure while maintaining compatibility with conventional IEEE 802.15.4 CSMA/CA. We have performed extensive simulations to valid the Suspendable CSMA/CA mechanism. Simulation results show that the proposed Suspendable CSMA/CA improves Packet Delivery Rate (PDR) by 9.7 points (89.9 % to 99.6 %) compared to the conventional IEEE 802.15.4g CSMA/CA and therefore, can lead higher spectrum efficiency for IoT applications operate in the limited Sub-l G Hz wireless bandwidth. The proposed Suspendable CSMA/CA mechanism has been also approved and adopted for the next IEEE 802.15.4 amendment by IEEE 802.15 Working Group.

Highly accurate time synchronization is increasingly required in many Industrial IoT devices, including synchronization among mobile base stations for 5G network system, video distribution, factory automation, and automotive in-vehicle networks. IEEE 802.1AS-2020, a profile for industrial and automotive networks that enables network synchronization on the order of microseconds or less, has attracted much attention. This standard, however, is specified with software processing in mind, and makes it difficult to build systems with very high accuracy. This paper presents the performance evaluation of IEEE 802.1AS-2020 using our hardware prototype implemented on Industrial IoT devices. Our proposed hardware method achieves highly accurate time synchronization for precision time protocol with a target of 50 ns and a fluctuation within±20 ns.

With the advent of 5G and beyond communication technologies, the consumer IoT devices are evolving from current generation to next generation. The next generation IoT devices are capable of supporting multiple communication modes and performing more functions. During the migration phase, it is impractical to completely remove the deployed current generation devices. Accordingly, the next generation IoT networks will consist of the mixed current and next generation devices. To that end, how to efficiently route diverse data in next generation IoT networks needs to be addressed. This paper presents a two-topology routing architecture for next generation IoT networks, one topology for regular data delivery and another topology for priority data delivery. The priority routes are discovered to minimize route overlap. We evaluated our route discovery algorithms under varying network configurations. Compared with standard RPL baseline, the proposed routing algorithms can simultaneously reduce route overlap, route transmission time and route length.

The software distribution in advanced IoT networks is inevitable. However, distributing software in multi-hop wireless networks consumes enormous communication bandwidth and can also suffer from reliability challenge. This paper proposes an innovative dynamic relay point (DRP) protocol to reduce the number of software packet transmissions. It also introduces a network condition based rateless coding scheme to improve the packet transmission reliability. The NS3 simulator is employed for performance evaluation. The proposed DRP protocol outperforms multi-point relay (MPR) baseline by reducing the software packet transmissions and improving the effective throughput.

While privacy concerns entice connected and automated vehicles to incorporate on-board federated learning (FL) solutions, an integrated vehicle-to-everything communication with heterogeneous computation power aware learning platform is urgently necessary to make it a reality. Motivated by this, we propose a novel mobility, communication and computation aware online FL platform that uses on-road vehicles as learning agents. Thanks to the advanced features of modern vehicles, the on-board sensors can collect data as vehicles travel along their trajectories, while the on-board processors can train machine learning models using the collected data. To take the high mobility of vehicles into account, we consider the delay as a learning parameter and restrict it to be less than a tolerable threshold. To satisfy this threshold, the central server accepts partially trained models, the distributed roadside units (a) perform downlink multicast beamforming to minimize global model distribution delay and (b) allocate optimal uplink radio resources to minimize local model offloading delay, and the vehicle agents conduct heterogeneous local model training. Using real-world vehicle trace datasets, we validate our FL solutions. Simulation shows that the proposed integrated FL platform is robust and outperforms baseline models. With reasonable local training episodes, it can effectively satisfy all constraints and deliver near ground truth multi-horizon velocity and vehicle-specific power predictions.

With the explosive proliferation of wireless devices, our lives are improved by various applications supported by heterogeneous wireless technologies, such as WiFi and ZigBee. However, the coexistence of WiFi and ZigBee also results in the degradation of the network performance, which cannot be avoided if the WiFi devices are even unaware of the ambient ZigBee devices. To better accommodate the heterogeneous wireless devices, this paper presents X-Disco, the first cross-technology neighbor discovery mechanism, for a WiFi device to detect ZigBee neighbors, without modification to hardware or firmware. With the help of the recently proposed cross-technology communication, X-Disco enables a commodity WiFi device to trigger responses, containing ZigBee neighbor information, from the ambient ZigBee coordinators (including routers). Through exploring the WiFi PHY-layer information accessible by WiFi driver, X-Disco decodes the responded ZigBee messages and obtains the ZigBee neighbor information. To improve X-Disco's reliability, we also propose ZigBee neighbor validation and interruption mitigation to exclude hidden node terminals and mitigate the interference caused by the ambient WiFi traffic respectively. The evaluation of X-Disco is performed on the commodity devices (TP-Link WDR 4300 WiFi router, TelosB motes) and USRP B210. The results demonstrate X-Disco successfully detects nine ZigBee neighbors within 70ms in the office.

In this paper, a multiple cluster-based transmission diversity scheme is proposed for asynchronous joint transmissions (JT) in private networks. The use of multiple clusters or small cells is adopted to reduce the transmission distance to users thereby increasing data-rates and reducing latency. To further increase the spectral efficiency and achieve flexible spatial degrees of freedom, we consider that a distributed remote radio unit system (dRRUS) is installed in each of the clusters. A key characteristic of deploying the dRRUS in private networks is the associated multipath-rich and asynchronous delay propagation environment. Therefore, we consider asynchronous multiple signal reception at the remote radio units and propose an intersymbol interference free distributed cyclic delay diversity (dCDD) scheme for JT to achieve the full transmit diversity gain without requiring full channel state information of the private network. The spectral efficiency of the proposed dCDD-based JT is analyzed by deriving a new closed-form expression, and then compared with link-level simulations for non-identically distributed frequency selective fading over the entire network. Due to its distributed structure, the dRRUS relies on backhaul communications between the private network server and cluster master (CM), which is the main backhaul connection, and between the CM to remote radio units, which are the secondary backhaul connections. Thus, it is important for us to investigate the impact of reliability of main and secondary backhaul connections on the system. Our results show that the resulting composite backhaul connections can be accurately modeled by our proposed product of independent Bernoulli processes.

In this paper, a multiple cluster-based transmission diversity scheme is proposed for asynchronous joint transmissions (JT) in private networks, in which the use of multiple clusters or small cells is preferable to increase transmission speeds, reduce latency, and bring transmissions closer to the users. To increase the spectral efficiency and coverage, and to achieve flexible spatial degrees of freedom, a distributed remote radio unit system (dRRUS) is installed in each of the clusters. When the dRRUS is disposed in the private environments, it will be associated with multipath-rich and asynchronous delay propagation. Taking into account of this unique environment of private networks, asynchronous multiple signal reception is considered in the development of operation at the remote radio units to make an intersymbol interference free distributed cyclic delay diversity (dCDD) scheme for JT to achieve a full transmit diversity gain without full channel state information. A spectral efficiency of the proposed dCDD-based JT is analyzed by deriving the closed- form expression, and then compared with link-level simulations for non-identically distributed frequency selective fading over the entire private network.

Motivated by an increasing interest in wireless networking in mission-critical applications, and a recent amendment of the time slotted channel hopping to IEEE 802.15.4, the multichannel delay sensitive scheduling is investigated in the many-to-one network, which is also known as the convergecast network. In such a network, each node has data to be transmitted to a gateway through multi-hop communications. As a realistic setting, packet release time at each node is not assumed to be uniform. Under this assumption, the goal of this work is to design a scheduling scheme that minimizes the schedule length and maximum end-to-end delay, in which the former is essential for repetitive data acquisition, whereas the later improves the freshness of the acquired data. To achieve the scheduling goal, the problem is formulated as a multi-objective integer programming. To obtain a feasible solution and gain an insight into the problem, a lower bound on the schedule length is derived. Based on that, a new scheduling scheme is designed to minimize the two objectives simultaneously. Link level simulations verify the performance improvement of the proposed scheme over the existing schemes.

IEEE 802.11ah and IEEE 802.15.4g are two wireless technologies designed for outdoor IoT applications. Both technologies have communication range up to 1000 meters. Therefore, 802.11ah network and 802.15.4g network are likely to coexist. Our simulation results show that using standard defined coexistence mechanisms, 802.11ah network can severely interfere with 802.15.4g network and lead to significant packet loss in 802.15.4g network. As a result, additional coexistence control mechanisms are needed. Due to asymmetrical features such as modulation scheme and frame structure, 802.11ah devices and 802.15.4g devices cannot perform automatic cooperation. Thus, self-coexistence control techniques are preferred. This paper proposes learning based self-coexistence control techniques for 802.11ah devices to mitigate the interference impact of 802.11ah network on 802.15.4g network. We first present a α-Fairness based energy detection clear channel assessment (ED-CCA) method that enables 802.11ah devices to detect more ongoing 802.15.4g packet transmissions. We then introduce a Q-Learning based backoff mechanism for 802.11ah devices to avoid interfering with 802.15.4g packet transmission process. The proposed coexistence techniques can achieve fair spectrum sharing between 802.11ah network and 802.15.4g network.

Vehicle-to-Pedestrian (V2P) communication using wireless LAN (Local Area Network) has issues. Fast Device Discovery is one of them. In this paper, we proposed two novel methods to solve this issue. The methods are Collective Scanning and Collective Scanning + Extension Receiving. Collective Scanning improves the scanning time by a vehicle which operates in one channel receives responses from all pedestrians which operate in available channels. Collective Scanning + Extension Receiving, is an extension method of Collective Scanning, improves the scanning time and prevents the detection leakage of pedestrians by a vehicle that extends waiting of responses depending on the number of responses from pedestrians. We evaluated two proposal methods compared with conventional Active Scanning of IEEE 802.11 about the scanning time and the detection rate of pedestrians using Network Simulator-3 (NS-3). In the result, by Collective Scanning, the scanning time improved 24.51 millisecond (ms) from 114.74 ms with the same detection rate in the environment that has one vehicle and within 50 pedestrians when comparing with Active Scanning of IEEE 802.11. By Collective Scanning + Extension Receiving, the scanning time improved 42.52 ms from 114.65 ms with the same detection rate in the environment that has one vehicle and more than 50 pedestrians when comparing with Active Scanning of IEEE 802.11.

We propose a new cooperation mechanism, denoted by cooperative channel segmentation (CCS), between IEEE 802.11 WLANs and Bluetooth based WPANs, which operate in the 2.4 GHz ISM band. The CCS avoids false detection of WLAN carrier sense, which usually happens when WLAN and Bluetooth antenna are nearly deployed. In CCS, WLAN and Bluetooth system share the mutual interference channel information and devices operation channels between Bluetooth and WLAN. We evaluated the performance of CCS by simulation, and the simulation result showed that the performance of CCS is better than legacy cooperation mechanisms.

This paper proposes four schedulers using location information and side information in telematics applications for vehicular networks. The scheduler algorithms consider peak traffic and link reliability, achieving savings of channel resources and reducing the number of retransmissions. A key feature of the proposed schedulers is the use side information in the form of a coverage map, which provides a map of link quality for the area covered by the radio access networks. In this paper, the total offered load and average excess delay are considered as two metrics for measuring the proposed schedulers, which are evaluated by simulation results. The performance of schedulers is reported and compared.

Increasing demand on the broadband wireless communication over Gigabits has focused renewed attention on 60 GHz millimeter wave. We developed a novel point-to-multipoint (P2MP) gigabit WLAN System on 60 GHz millimeter wave. The proposed system employed wide angle beams antenna overcomes the usability of the conventional system, covers larger areas. Maximum transmission rate was designed to be 1.2 Gigabit/sec. Orthogonal frequency division multiplex (OFDM) using 1024 points FFT and convolutional code were implemented with PHY layer of the WLAN equipments. Superframe for multiple beams and frame aggregation for high throughput were designed for MAC layer. All control channels for downlink such as broadcast, frame control and access feedback were aggregated to reduce overhead in addition to aggregation of data frame. Evaluated throughput using proposed frame aggregation was confirmed to be more than 800 Mbit/sec with developed prototype in the case of aggregation size of 10 × 1500 byte.

Increasing demand on the broadband wireless communication over Gigabits has focused renewed attention on 60 GHz millimeter wave. We developed a novel point-to-multipoint (P2MP) Gigabit WLAN System on 60 GHz millimeter wave. The proposed system employed wide angle beams antenna overcomes the usability of the conventional system, covers larger areas. Maximum transmission rate was designed to be 1.2 Gigabit/sec. Orthogonal frequency division multiplex (OFDM) using 1024 points FFT, and convolutional code were implemented with PHY layer of the WLAN equipments. Superframe for multiple beams and frame aggregation for high throughput were designed for MAC layer. All control channels for downlink such as broadcast, frame control and access feedback were aggregated to reduce overhead in addition to aggregation of data frame. Maximum improvement of throughput due to control channel aggregation was evaluated to be 200% compared with individual transmission. Evaluated throughput using proposed frame aggregation was confirmed to be more than 852 Mbit/sec in the case of aggregation size of 16 times 1500byte.

We developed a high speed wireless LAN prototype in 5 GHz frequency band. Maximum transmission rate of the developed WLAN system is 324 Mbit/sec using 6 multi-channels of the IEEE802.11a. We propose a SINR estimation scheme using the correlation of long training fields, and implemented it in closed-loop link adaptation. We compared the proposed link adaptation schemes with the legacy ACK-based link adaptation schemes by computerized simulation. It was found that the performances of legacy ACK-based link adaptation schemes depended largely on the parameter choices. The proposed link adaptation scheme achieved higher throughput than the legacy ACK-based link adaptation schemes. We also found that the proposed link adaptation scheme selected the optimal MCS on the developed WLAN system in both AWGN and fading conditions.

High speed wireless LAN prototype of 324 Mbit/sec has been developed. Six channel binding of 802.11 a signal on frequency domain was employed for increasing PHY data rate. Frame aggregation was employed to improve MAC-SAP throughput. Individual adaptive data rate setting on each channel, so called adaptive dynamic channel assign was implemented in order to achieve maximum MAC-SAP throughput at any channel condition. In this paper, multiple channel interleaving over all frequency channels for randomization of burst error was presented. Interleaving can be carried out over all channels or inside individual channel. Bit and packet error rate were measured using implemented WLAN equipements with/without multiple channel interleaving. It was confirmed that improvement using multiple channel interleaving were measured to be 2 dB.

We developed a high speed wireless LAN prototype in the 5GHz band. Maximum transmission rate of the developed WLAN equipment was 324Mbit/sec using 6 multi-channels of 802.11a (1). We implemented a frame aggregation scheme to improve MAC efficiency (2-3). The evaluated system throughput was achieved more than 170Mbit/sec using the implemented frame aggregation. The HDTV transmission using 324Mbit/sec WLAN equipment was demonstrated. We compared the developed prototype and the conventional 802.11g (4).

We developed a high speed wireless LAN prototype in the 5 GHz band. Maximum transmission rate of the developed WLAN system is 324 Mbit/sec using 6 multi-channels of 802.11a. We propose a closed-loop link adaptation scheme to improve MAC efficiency. The proposed scheme inserts MCS (Modulation and Coding Scheme) feedback information into Data frame and ACK frame. The MCS is calculated based on the estimated SNR. We compared the proposed link adaptation scheme with the legacy ACK-based link adaptation schemes by computerized simulation. The proposed link adaptation scheme achieved higher throughput than the legacy ACK-based link adaptation scheme. We also found that the proposed link adaptation scheme selected the optimal MCS on the developed WLAN system.

We developed a high speed wireless LAN prototype in the 5GHz band that is backward compatible with legacy IEEE802.11a. The developed WLAN equipment has a data rate of 324Mbit/sec using 6 PHY transmission channels of 802.11a. We propose frame aggregation to improve MAC efficiency. The proposed frame aggregation features an adaptive aggregation size selection depending on wireless channel conditions and application requirements. The optimal frame aggregation size for the PHY data rate is evaluated by using computer simulation. MAC throughput as a function of aggregation size was simulated and measured. We find that high throughput of more than 170Mbit/sec was achieved using the proposed frame aggregation.

We developed a high speed wireless LAN prototype in the 5 GHz band. Maximum transmission rate of the developed WLAN equipment was 324 Mbit/sec using 6 multi-channels of 802.11a. We proposed a novel frame aggregation scheme to improve MAC efficiency. The proposed frame aggregation scheme had a feature of an adaptive aggregation size selection depending on wireless channel conditions and application requirements. Throughput performance was simulated in the case of multiple stations with the proposed frame aggregation. The evaluated system throughput was achieved more than 150 Mbit/sec in the case of 10 STAs. It is found that throughput of the developed equipment was measured to be more than 170 Mbit/sec using the proposed frame aggregation

We developed a high speed wireless LAN prototype in the 5 GHz band. The developed WLAN equipment had a data rate of 324 Mbit/sec using 6 PHY transmission channels of IEEE 802.11a. We presented the system of 324 Mbit/sec WLAN equipment focus on PHY layer using high grade FPGA devices. In this system, we proposed channels-interleave to improve characteristics of the equipment under multi-path environment. We confirmed that the effect of channels-interleave was about 2-4 dBm under a wireless condition of 324 Mbit/sec