With the increasing demand for accurate indoor localization in smart homes, robotics, and commercial scenarios, achieving precise location using minimal infrastructure has become essential yet challenging. Traditional RSSI-based fingerprinting methods typically require multiple APs, limiting their practicality in single-AP scenarios commonly found in real-world home environments. To overcome this limitation, we propose a single-AP localization method that employs multi-directional beamforming to generate rich RSSI fingerprints. By sweeping the AP beamforming angle, the method captures directional RSSI features, significantly improving localization accuracy. Additionally, we introduce an angular embedding mechanism, explicitly encoding beamforming direction into neural network inputs to enhance robustness, especially under limited labeled data conditions. Extensive simulation and real-world experiments demonstrate that our proposed approach significantly outperforms conventional single-AP RSSI methods, consistently achieving sub-meter accuracy with small training datasets, thereby validating its effectiveness.

Platooning within autonomous vehicles has proven effective in addressing driver shortages and reducing fuel consumption. However, as platooning lengths increase, traditional C-V2X (cellular vehicle-to-everything) architectures are susceptible to end-to-end (E2E) latency increases. This is due to the necessity of relaying information through multiple hops from the leader vehicle to the last vehicle. To address this problem, this paper proposes a hybrid communication architecture and evaluates its end-to-end (E2E) delay through simulation in a multi-platoon scenario that integrates light fidelity (LiFi) and C-V2X. The proposed architecture introduces multiple-leader vehicles equipped with outdoor LiFi communication nodes in platoons to achieve high-speed and low-delay communication between leader vehicles, thereby reducing E2E delay.

With the increasing demand for indoor localization, received signal strength indicator (RSSI)-based fingerprint localization has gained widespread attention due to its low equipment costs. Traditional methods only use RSSI data collected from user devices to train localization models, but the coarse granularity of RSSI often limits accuracy. Additionally, changes in the environment, such as door movements or furniture rearrangements, can render these models ineffective. While resource-intensive and time-consuming, data re-collection and model retraining are essential for capturing updated signal characteristics after environment changes, ensuring the model remains accurate and effective. To enhance localization accuracy, we expand on traditional approaches by incorporating RSSI data measured between wireless routers as additional fingerprint features, achieving nearly a 20% accuracy improvement. Furthermore, we address the challenges of dynamic environments by introducing a multi-task domain-adversarial transfer learning method, which extracts consistent features before and after environment changes. Transfer learning allows us to leverage knowledge from the environment before the change, thereby reducing the need for data re-collection after the change. Experiment results from simulated, real-world, and open dataset environments confirm the effectiveness of the proposed method in dynamic indoor localization. Our approach reduced the mean error distance (MED) by 35%, 44%, and 28%, respectively, with only 16%, 20%, and 17% of the data re-collected.

Summary In previous work, we introduced a distributed collections library for the APGAS for Java programming model. This library makes it possible for programmers to develop complex distributed programs thanks to the many abstractions and computation patterns supported. In particular, programmers can fully and dynamically change the distribution of data entries through high‐level abstractions. However, the problem of balancing the load between processes remains, especially in cases where multiple processes may be concurrently executing on a single host, or when the performance of the hosts used differs. To address this issue and to relieve the burden of programming a load balancing strategy for a specific application, we created a dynamic load balancer integrated into our library. This load balancer operates within a specific context in a manner which does not interfere with the program legibility. Internally, we implement a scheme inspired by the lifeline‐based global load balancer scheme first introduced in 10. We evaluate the performance of our integrated load balancer on a small‐scale Beowulf cluster.

Summary Global load balancer libraries should be easy to use and allow users to easily obtain good performance for their applications on a variety of distributed systems. In this article, we introduce a new tuning mechanism to our Java implementation of the lifeline‐based global load balancer which automatically adjusts the task granularity to reach good performance based on some selected runtime metrics. We evaluate our system against four backtrack‐search problems on both a many‐core supercomputer environment and on a beowulf server, achieving ideal performance with our tuning mechanism on the supercomputer. We also identify the limits of our mechanism in handling situations with reduced imbalance.

Localization using low-power wireless devices is one of the promising methods even in outdoor environments because the Global Navigation Satellite System (GNSS) devices generally consume much power to result in frequent battery replacements. Received Signal Strength Indicator (RSSI) is often utilized in such methods due to availability in most wireless devices. Even in outdoor open space, however, various factors such as path-loss characteristics and antenna directivity possibly cause difficulty in RSSI-based localization. This paper investigates the error factors of Deep Neural Network (DNN)-based fingerprinting localization in terms of antenna directivity. Most existing studies have analyzed the error factor in localization algorithms or methods to improve accuracy. On the other hand, the error factors on the environments had not been paid attention yet at all. In this paper, we investigate distance errors of the DNN-based fingerprinting method in terms of antenna directivity as one of the environmental factors using virtual space reproduced in a computer. Through experiments where an actual Bluetooth Low Energy (BLE) tag system was emulated, we found that the tag antenna directivity could be the factor to worsen the localization accuracy while receiver antenna directivity to better.

The importance of real-time notification has been growing for social services and Intelligent Transporting System (ITS). As an advanced version of Pub/Sub systems, publish-process-subscribe systems, where published messages are spooled and processed on edge servers, have been proposed to achieve data-driven intelligent notifications. In this paper, we present a system that allows a topic to be managed on multiple edge servers so that messages are processed near publishers and subscribers, even when publishers are spread over a wide area. However, permitting a topic to use multiple edge servers can cause exhaustion of resources as the number of topics and consumed resources by each topic increase. We formulate the delay caused by the depletion of edge server resources to find the optimal allocation of topics on limited edge server resources. As the optimization problem is NP-hard, we propose heuristics leveraging the given locality and the pub/sub relationships observed between clients to use the edge server resources efficiently while delivering realtime notifications. The experimental results demonstrate that the proposed method reduces the delay to deliver notifications and the effectiveness of the strategy exploiting the relationships between clients.

In recent years, wireless mesh networks (WMNs) have become popular because of their wide coverage areas and high fault tolerance. Although unlicensed-band off-the-shelf wireless devices based on IEEE 802.11 are widely deployed, WMNs based on IEEE 802.11 suffer from degradation of throughput owing to the hidden node problem. To mitigate this problem, in this study, we developed a new routing metric called the “Asymmetric Hidden node problem Aware routing Metric (AHAM).” AHAM enables a new flow to establish a source-destination path that largely avoids not only interference with hidden nodes of existing flows but also making hidden nodes on that path interfere with existing flows. This is because the hidden node problem can asymmetrically impact throughput between flows when new flows are established. As a response, AHAM aims to estimate the influence of hidden nodes accurately and compensate for how both the new and existing flows influence each other. Simulation results showed that AHAM realizes high throughput while maintaining network fairness compared with other metrics.

Network traffic for sharing contents is significantly increasing. The cache network is a desirable architecture to reduce traffic and to improve reliability of contents retrieval. “Breadcrumbs” is one of the promising techniques to find cached contents in a distributed manner. Thanks to Breadcrumbs, users can retrieve a content without managing where the cache exists. This demo shows a contents sharing application among mobile users in the Breadcrumbs-enabled cache network.

In severe disaster environments, wireless sensor networks (WSNs) need to be tolerant to spatial node failure due to external factors such as bomb attack and river overflow. The aim of this paper is to realize data-gathering WSNs that keep the data collection ratio as high as possible while keeping system lifetime as long as possible. This paper proposes not only a multipath data gathering protocol called “Side Trip (ST)” scheme to enhance spatial node-failure tolerance, but also an improved version of ST scheme called “Side Trip with Network Coding (STNC)” scheme which utilizes inter-flow XOR network coding to reduce redundant packets without affecting the system lifetime significantly. In data-gathering WSNs, nodes further from a sink node tend to relay fewer packets. In the ST scheme, a node establishes another secondary path which, for some distance, passes through nodes the same hop count away from the sink in order to spatially separate the path from the primary path. In the STNC scheme, redundant packets from different source nodes are network-coded into an encoded packet in order to reduce the number of redundant packets. We compare the ST scheme, STNC scheme, and two existing multipath protocols, i.e., H-SPREAD (hybrid-secure protocol for reliable data delivery) scheme and Sub-branch Multipath Routing Protocol (SMRP) scheme, by means of a self-developed simulator. The results show that STNC scheme and ST scheme offer enhanced tolerance to node-failure compared to H-SPREAD scheme and SMRP scheme with no significant impact on system lifetime.

Two-dimensional communication system (2DCS) is a novel communication system which utilizes surface of sheet as communication medium. 2DCS provides wireless power supply as well as safely and high-speed data transmission to sensor devices. However, how to suppress the standing wave effect to a minimum is still an open issue for 2DCS. In this study, we explore how the power distribution on sheet medium changes by the location of input coupler, and then compose a scheme of the power provision with multiple single or compound couplers where shadowing effect is considered to suppress the standing wave effect. Through simulation experiments, we evaluate the performance of proposed scheme to improve the power provision efficiency over 2DCS.

Public WLANs based on IEEE802.11 standard are now widely deployed. In an environment offering several APs (Access Points), a UTE (User Terminal Equipment) needs to choose which AP to associate with. Conventionally, the UTE associates with the AP with the strongest RSSI (Received Signal Strength Indicator). This simple approach, however, can degrade the efficiency of network utilization since the UTE is likely choose a heavily loaded AP, even though choosing a more lightly loaded AP would be more effective. So far, some AP association schemes have been proposed. To the best of our knowledge, however, these existing schemes do not take into account of individual difference among UTEs in terms of user utility, physical data rate, traffic characteristics such as traffic demand and frame length. In this paper, we propose a distributed user association control scheme that does considering such UTE characteristics. The proposed scheme needs to estimate uplink and downlink throughput, so that we introduce a throughput estimation method that considers UTE diversities. Through numerical simulations, we confirm that our distributed control scheme can improve user utility and fairness.

Femtocell is an emerging technology that promises increased network capacity and enhanced indoor coverage at a low capital and operational cost. However, macrocell network performance depreciates when macrocell users (mUEs) are located indoors with femtocell base stations (FBSs), and these users are not allowed access to the FBSs (closed access). This is a critical issue that needs to be addressed in order to successfully deploy femtocell tier over existing macrocell networks. This paper proposes a macrocell proportional fair-based batch resource allocation strategy that enables FBS to be aware of macrocell resource usage schedule. In this context, batch means multiple time-slots. The knowledge of macrocell resource usage schedule enables the FBS to effectively mitigate interference caused to mUEs in its neighborhood. We show by simulation results that our proposed cross-layer interference coordination approach significantly increases the total macrocell throughput through interference reduction.

IEEE 802.11e medium access control (MAC) is a supplement to the IEEE 802.11 wireless network (WLAN) standard to support quality of service (QoS). The 802.11e MAC defines a new coordination function, namely hybrid coordination function (HCF), which takes the QoS requirements of flows into account and allocates transmission opportunity (TXOP) to stations. On the basis of mean sending rate, delay of variable bit rate (VBR) traffic cannot be bounded with the reference HCF scheduling algorithm proposed in this supplement. In this paper, the authors propose a new scheduling algorithm that utilizes the token bucket and a modified latency-rate (LR) scheduling algorithm to guarantee a bounded delay for HCF controlled channel access (HCCA). The new service interval (SI) is calculated to optimize the number of stations accommodated and takes into account delay bound and token bucket parameters. The authors show that is possible to obtain worst-case performance guarantees on delay. First, the authors analyze the behavior of the proposed scheduler with a loss free wireless channel model and after this, with a burst loss model and the authors explain how it is possible to extend this scheduler for a multi-rate scheme. Properties of the proposal are investigated both theoretically and using ns-2 simulations. The authors present a set of simulations with both constant bit rate (CBR) and VBR flows and performance comparisons with HCF scheduling algorithm. The results show that the delay upper bound can be achieved for a large range of networks load with bandwidth optimization.

In this paper, we compare two basic approaches towards providing peer-to-peer file-sharing (or more generally, information search) in mobile ad-hoc networks (MANET). The flooding approach broadcasts a query (e.g., to locate a node holding a given file) to all network nodes. The index-server approach adds additional servers (known as index servers) that cache directory information about which nodes have which files. With index servers, a node wishing to locate a file first queries its local index server, which then queries other index servers, as needed. The use of index servers presents the possibility of locating a file index quickly in an index server cache, but requires additional overhead to maintain cache consistency. We compare the performance of the flooding approach to two index-server caching approaches: consistent caching and local caching. We quantify the reduction in search overhead using the index-server scheme rather than flooding in MANET, and study how the optimal number of index servers varies according to network size, query rate, and index generation rate. We compare the flooding scheme and the consistent caching and local caching schemes, for two types of queries: history queries and latest queries. Numerical results show how one can choose between the alternatives of consistent caching and local caching depending on network size, index generation rate and query rate.

This paper proposes a new feedback picture sequence control (FPSC) for providing better QOS and more effective usage of network resource in ATM networks. The FPSC utilizes the feedback mechanism of the ABR service and the flexibility of MPEG video coding in order to resolve the collision of I-pictures at switches. The FPSC requires only a very little modification of usage of RM cell in the ABR service. We also describe the MPEG encoder which can change the number of pictures in a GOP. Simulation results show that the FPSC can improve the QOS such as the cell loss ratio and mean buffering delay in the cell buffer of the switch.

Our study aims to construct the framework to accommodate periodic and bursty sources into ATM networks effectively. For this purpose, we develop two effective algorithms which can find a good combination of the initial phases of periodic sources in a short time. We then consider a call admission control (CAC) scheme which controls phase combinations of the periodic sources and decides whether a new call is accepted or not by taking account of the controlled phase combinations. Our CAC scheme is applicable to real-time MPEG video traffic which will be the major traffic in ATM networks. Simulation results show that our algorithms can find a better combination of initial phases than those chosen randomly in any our trials under both homogeneous and heterogeneous traffic environments.

This paper proposes a novel phase assignment algorithm "silent wave algorithm (SWA)" for periodic VBR traffic in ATM networks. Our algorithm decides when a new periodic VBR connection should begin to transmit based on its notification parameters and traffic measurement of going connections. Simulation results showed that it is difficult to accommodate pseudo periodic VBR traffic effectively without any phase allocation but the SWA can provide better QOS and improve the network utilization.

Using the rate control to restrict the peak cell rate of traffic is addressed. The asynchronous transfer mode (ATM) environment is considered as a discrete-time environment in which one slot is equal to one cell transmission time. A rate control that can restrict the number of cells during any fixed-length time interval in a discrete-time environment is studied. The scheme is realized by means of simple counter accumulation per slot, and it is easy to synchronize with slots. The simplicity of this scheme may make possible the flexible restriction of the peak cell rate according to network conditions. The scheme is analyzed, using matrix analytic techniques, in order to investigate the smoothing effect of bursty traffic and the queue length required to satisfy a certain quality of cell loss probability. Numerical results show the effect of restricting the peak cell rate of bursty traffic and the tradeoff between the smoothing effect and the required queue length.>

A traffic control scheme for FDDI (fiber distributed data interface) interconnection through an ATM (asynchronous transfer mode) network is presented. The scheme consists of two parts, a VP (virtual path) bandwidth allocation algorithm and a feedback type buffer protection flow control. Both use the acknowledge for the frame of FDDI as a control unit. Simulation results show that VP bandwidth allocated by the scheme increases according to arrival traffic when the destination FDDI has enough capacity and allocated bandwidth is not increased when its capacity is less than arrival traffic. Thus, the scheme has desirable VP bandwidth allocation characteristics. Simulation results also show that the scheme prevents cell loss at a destination gateway completely.>