Non-contact measurement of vital signs is an important issue in modern healthcare, aimed at enhancing patient comfort and convenience. Achieving sufficient measurement distance and adaptability to patient movement is essential for effectiveness. Current research covers measurement ranges between 1 and 3.5 meters. This study introduces a novel multifeature transformer-based super-resolution model. By inputting and encoding low-resolution sequences of distance, phase, and phase variation rates, the model upsamples these sequences, generating additional sample points and transforming the lowresolution data into high-resolution sequences. This process improves the quality and range of FMCW radar measurements by increasing the sample points, enabling the model to extract vital sign information from low-resolution sequences and produce accurate results. From the generated high-resolution sequences, vital signs such as heart rate and respiration are then extracted. Experimental results show that, at a distance of 5 meters, the system achieves 87.3 accuracy for heart rate and 89.1 accuracy for respiration in a walking scenario, outperforming existing solutions by 8.6 % and 6.5 %, respectively.

Semen analysis is the primary method for evaluating male infertility, with sperm morphology being a critical indicator. However, existing methods for classifying human sperm head morphology (HSHM) often lack cross-domain generalizability. To address this limitation, we propose an enhanced meta-learning algorithm that learns invariant features across tasks, improving generalization by transferring knowledge to new tasks. To mitigate gradient conflicts in multi-task learning, we separate meta-training tasks into primary and auxiliary tasks. This approach, in conjunction with auxiliary tasks, enhances the model’s generalization using diverse HSHM datasets. We introduce the Contrastive Meta-Learning with Auxiliary Tasks (HSHM-CMA) algorithm, which integrates localized contrastive learning in the outer loop of meta-learning to exploit invariant sperm morphology features across domains. This improves task convergence and adaptation to new categories. In our evaluation, we assess the model’s generalization performance using three testing objectives: the same dataset with different HSHM categories, different datasets with the same HSHM categories, and different datasets with different HSHM categories. Our evaluation across these objectives demonstrates that HSHM-CMA outperforms existing meta-learning approaches, achieving accuracies of 65.83%, 81.42%, and 60.13%, respectively.

Deep learning on graphs has shown to be powerful in modeling graph-structured data and learning representations for graphs, which involves aggregating information from graph neighborhoods to derive effective node representations. Although graph neural networks (GNNs) can be trained from scratch, pretraining GNNs to learn transferable knowledge for downstream tasks has been used recently to improve performance. However, using pre-training and fine-tuning to model each subtask can sometimes ignore the relationships, conflicts, and constraints between tasks, resulting in worse performance. In this paper, we propose a novel framework called Self-supervised Multi-Task Learning for Generative Graph Convolutional Network (SMT-GGCN) to enhance graph-based neural network models. SMT-GGCN combines self-supervised learning pretext tasks with supervised learning to train Graph Convolutional Networks (GCN) for graph structure understanding. We demonstrate that self-supervised multi-task learning can improve GCN’s generalization ability and enhance feature learning.

Radar-based human motion recognition (HMR) is gaining increasing attention, primarily due to its robust performance in various lighting conditions, especially in healthcare and safety applications, with a specific emphasis on personal privacy. This paper introduces a novel cross-modal bi-contrastive learning method, named BiCLR. Utilizing a Transformer-based network [1] for temporal modeling, BiCLR excels in discriminating instances across both single-modal and cross-modal settings through self-supervised learning. Additionally, the “Radar Combination Map (RCM)” is proposed to provide a comprehensive representation by seamlessly integrating the Range-Doppler Map (RDM), Range-Azimuth Map (RAM), and Range-Elevation Map (REM) into a unified map. The primary objective of this work is to address the inherent sparsity in radar data through cross-modality and the newly introduced RCM, presenting a transferable framework applicable to various downstream tasks. This contributes to a deeper understanding of radar-based recognition systems. Despite being trained on a smaller dataset, the pre-trained encoder demonstrates remarkable effectiveness in leveraging cross-modal and contrastive learning methods and the newly introduced radar data format in a HMR task using solely radar data, as substantiated by a thorough evaluation.

Doppler-radar-based continuous human motion recognition (CHMR) recently has attracted extensive attention, which is a favorable choice for privacy and personal security. Existing results of CHMR using mmWave FMCW Radar not consider the continuous human motion with the high similarity problem. In this paper, we proposed a new CHMR algorithm with the consideration of the high similarity (HS), is namely CHMR-HS, by using the modified Transformer-sequential-decoder model, such that our Transformer-sequential-decoder model can recognize the continuous human action with the high similarity. The experimental results show that the accuracy of our proposed CHMR-HS scheme is 94.5%, is better than that of existing CHMR schemes.

Due to the increasing severity of the COVID-19 pandemic, timely screening and diagnosis of infections are essential. Since cough is a common symptom of COVID-19, an AI-assisted cough classification scheme is designed in this paper to diagnose COVID-19 infection. To reduce the labeling efforts by human experts, a semi-supervised learning with voting scheme using a triple-classifier model is proposed for the COVID-19 cough classification. This work aims to improve the accuracy of the classification. Initially, the data pre-processing scheme is executed by performing data cleaning, resampling, and data enhancement so as to improve the audio quality before training. The pre-training scheme is then performed by using a few numbers of COVID-19 cough data with labeling. Then we modify a well-known self-supervised learning model, SimCLR, to a semi-supervised learning-based SimCLR-like model, which uses three different loss functions to fine-tune three training models for cough classification. Finally, a voting scheme is performed based on the classification results of the three cough classifiers so as to enhance the accuracy of the cough classification for COVID-19. The experiment results illustrate that the proposed scheme can achieve 85% accuracy, which outperforms the existing semi-supervised learning-based classification schemes.

In this paper, a semi-supervised transfer learning with dynamic associate domain adaptation is proposed for human activity recognition by using the channel state information (CSI) of the WiFi signal. We propose a dynamic associate domain adaptation (DADA), by modifying the existing associate domain adaptation algorithm, while the target domain can dynamically provide a different ratio of labelled data set/unlabelled data set. The advantage of DADA is that it provides a dynamic strategy to eliminate different effects under the different environments. We designed an attention-based DenseNet model (AD) as our training network, so our proposed scheme is simplified as DADAAD scheme. The experimental results illustrate that the accuracy of human activity recognition of the DADA-AD scheme is 97.4%. It also shows that DADA-AD has advantages over existing semi-supervised learning schemes.

Mobile data offloading has become an important issue for mobile cellular network in recent years. Existing energy-aware data offloading scheme for mobile cellular network makes the offloading decision only according to the current local information of the user equipment (UE) and thus the UE cannot switch to a more efficient way to offload even other UEs have released their transmission resources later on. Hence, in this paper, a centralized offloading scheme based on cloud radio access networks (C-RAN) is proposed so as to make the offloading more efficient. The C-RAN based centralized offloading scheme considers all the situation of UEs of a baseband unit (BBU) at the same time and thus the BBU can do a better offloading decision for those UEs. At the beginning, each UE, who needs offloading, sends an offloading request to the BBU. When there is any UE released the transmission resource, the corresponding BBU will try to fulfill the pending offloading requests of the UEs. The corresponding BBU considers the pending UEs' transmission rate and energy consumption of the cellular network as well as the Wi-Fi network, and then makes offloading decisions for those UEs so as to save more energy and achieve higher throughput at the macroscopic level. Extensive simulations have been conducted to illustrate that the proposed energy-aware data offloading scheme can reduce the energy consumption and turnaround time, and enhance the transmission throughput.

In vehicular ad hoc networks, vehicles may use a routing protocol to inform emergent events, for example, car accidents or traffic jams. Hence, many of the researchers are focused on minimizing the end-to-end delay of the routing protocol. However, some applications, for example, email or ftp, are not time critical, and radio spectrum is a limited resource. Hence, delay-bounded routing protocol, whose goal is to deliver messages to the destination within user-defined delay and minimize the usage of radio, has become an important issue. The delay-bounded routing protocols deliver message to the destination by the hybrid of data muling carried by the vehicle and forwarding transmitted through radio. When the available time is enough, the message will be delivered by muling; otherwise, it will be delivered by forwarding. However, in an urban area, there are many traffic lights, which may greatly affect the performance of the delay-bounded routing protocols. Existing works do not consider the effect of traffic lights, and hence, it may adopt an improper delivery strategy and thus wastes much available time. To improve previous works, we propose a novel delay-bounded routing protocol, which has considered the effect of traffic lights. Whenever a vehicle passes an intersection, it will gather the information of the traffic light and traffic load of the next road section, and thus, it can make a more accurate prediction and adopt a more proper strategy to deliver message. Simulation results show that the proposed protocol can make a better usage of the available time and uses less radio resource to deliver the message in time. Copyright © 2013 John Wiley & Sons, Ltd.

A new non-IP networking technology, called as named data networking (NDN), is an emerging research topic for the future Internet. In this paper, we propose a pipe-assisted mobility protocol in NDN networks. The proposed mobility protocol is constructed based on a new proposed name-based routing scheme by utilizing a pipe technique. A new name-based routing protocol is developed by constructing a pipe from a consumer to a producer in NDN networks. With the assistance of the constructed pipe, a pipe-assisted producer mobility protocol is proposed. When a mobile producer enters a new domain, a pipe-based pre-route with the maximum popular levels is built to increase the successful probability of discovering a new path from the producer to the consumer. Extensive simulations illustrate that the proposed pipe-assisted mobility protocol significantly reduces the packet loss rate.

Most of the researches pay attention to minimize the end-to-end delay rather than reduce the usage of radio. However, some information is not urgent and radio is a valuable and limited resource. Recently, delay-bounded routing protocol has become a popular issue, whose goal is to deliver messages to the destination within user-defined delay and minimize the usage of radio. To decrease the burden on the environment and save energy, the hybrid-solar vehicle is one of the most prominent solutions. The existing delay-bounded routing protocols do not consider the charge and the energy expenditure factors and only choose the path with the least forwarding times. To improve previous works, we propose a mechanism based on a cost function, which includes forwarding times and power gain, to choose a minimum cost path. Besides, we propose a novel mechanism to deliver message to the destination by the hybrid of data muling (carried by the vehicle) and forwarding (transmitted through radio). In the existing protocol, when the remaining time is not enough the vehicle should forward the message by radio and when the remaining time is enough the vehicle should carry the message by itself. However, forwarding message by radio consumes more energy and hence the energy factor should be added into the consideration. The proposed protocol contains two schemes: the greedy and centralized schemes. In the centralized scheme, the information such as the solar illumination, length of each road segment, and the average velocity of the vehicles on each road segment are collected and then the dynamic programming is used to find the least cost routing path. In the greedy scheme, it only has the knowledge of the average velocity, the solar illumination and the length of all the possible next road segments to choose the next road segment with the least cost. Simulation results illustrate that the proposed routing protocol can save more energy than existing protocols.

Routing protocols for vehicular ad hoc networks (VANETs) have attracted a lot of attention recently. Most of the researches emphasize on minimizing the end-to-end delay without paying attention to reducing the usage of radio. This paper focuses on delay-bounded routing, whose goal is to deliver messages to the destination within user-defined delay and to minimize the usage of radio because radio spectrum is a limited resource. The messages can be delivered to the destination by the hybrid of data muling (carried by the vehicle) and forwarding (transmitted through radio). In the existing protocol, a vehicle may only switch the delivery strategy (muling or forwarding) at an intersection according to the available time of the next road segment, which is between the current intersection and the next intersection. To improve previous works, our protocol uses linear regression to predict the available time and the traveling distance, and thus, the vehicle can switch to a proper delivery strategy at a proper moment and can reduce the number of relays by radio. Our protocol contains two schemes: the greedy and centralized schemes. The greedy scheme uses only the current sampling data to predict the available time and decide when to switch the delivery strategy, whereas the centralized scheme uses the global statistical information to choose a minimum-cost path. Simulation results justify the efficiency of the proposed protocol. Copyright © 2011 John Wiley & Sons, Ltd.

The IPv6 over Low power Wireless Personal Area Network (6LoWPAN) has attracted lots of attention recently because it can be used for the communications of Internet of things (IoT). In this paper, the concept of group-based network roaming in Proxy Mobile IPv6 (PMIPv6) domain is considered in the 6LoWPAN-based wireless body area networks. PMIPv6 is a standard to manage the network-based mobility in all-IP wireless network. However, it does not perform well in group-based body area networks. To further reduce the handoff delay and signaling cost, an enhanced group mobility scheme is proposed in this paper to reduce the number of control messages, including Router Solicitation (RS) and Router Advertisement (RA) messages as opposed to the group-based PMIPv6 protocol. Simulation results illustrate that the proposed handoff scheme can reduce the handoff delay and signaling cost. The packet loss ratio and the overhead can also be reduced.

A mobicast, or called as mobile geocast, problem in three-dimensional (3D) underwater sensor networks (USNs) is investigated in this paper, which aims to overcome the hole problem and minimizes the energy consumption of the sensor nodes while maximizing the data collection. In this work, all underwater sensor nodes are randomly distributed in a 3D underwater environment in the sea to form a 3D USN. Considered a mobile sink or an AUV (autonomous underwater vehicle), all possible sensor nodes near to the AUV form a 3D geographic zone (called as 3D zone of reference or 3D ZOR). The AUV travels a user-defined route and continuously collects data form sensor nodes within a series of 3D ZORs at different time. The main problem is how to efficiently collect data from sensor nodes within a 3D ZOR while those sensor nodes are usually in sleep mode for a long period of time. The routing protocol relies on two phases; the first phase is to collect data form sensor nodes within a 3D ZOR, and the second phase is to wake up those sensor nodes in the next 3D ZOR to be queried while trying to avoid topology holes. To save power, only sensor nodes in a 3D ZOR are notified to enter the active mode in order to deliver sensed results to the AUV. To consider the characteristics of USNs, a new mobicast routing protocol is developed in 3D USNs. The key design challenge is to develop a power-saving mobicast protocol in 3D USNs to overcome the unpredictable 3D hole problem. An ”apple slice” technique is used to build multiple segments to surround a hole and to assure routing path continuity. Finally, performance analysis is derived and simulation results illustrate the performance improvement in successful delivery rate and power consumption.

Abstract The design of the seamless handoff is the key issue in the next‐generation mobile networks. A new broadband wireless access, called WiMAX, has been specified in the IEEE 802.16e standard document, to provide the high bandwidth and the large coverage area than the IEEE 802.11‐based wireless networks. In the IP‐based mobile network, mobile IPv6 (MIPv6) protocol provides the binding update message to update the mobile station's IP information for supporting the layer 3 mobility. Hierarchical mobile IPv6 (HMIPv6) protocol is proposed by employing a hierarchical network structure to reduce handoff latency. HMIPv6 protocol suffers the long handoff delay and the high packet lost in the macro mobility. This paper presents a new cross‐layer partner‐assisted handoff mechanism based on HMIPv6, termed as P_HMIPv6 protocol. The P_HMIPv6 protocol is a cross‐layer approach by the combination of layer 2 and layer 3. The partner station (PS) is a new component with relay ability and adopted by our protocol. With the assistance of the PS, care‐of address (CoA) is pre‐acquired and DAD operation is pre‐executed by the PS before the MS initiates the layer 2 handoff. The simulation results show that P_HMIPv6 protocol actually achieves the performance improvements in handoff delay time, packet loss rate, and handoff delay jitter. Copyright © 2009 John Wiley & Sons, Ltd.

Abstract The requirement for in‐vehicle passengers to access Internet multimedia services has risen recently. As a consequence, Vehicle Ad hoc NETwork (VANET) has gained much attention, and is regarded as a promising solution for providing in‐vehicle Internet service through inter‐vehicle and infrastructure communication. A new developed wireless network technique, termed WiMAX Mobile Multihop Relay (MMR), provides a good communication framework for a VANET formed from vehicles on high‐speed freeways. Applying MMR WiMAX allows some public transportation vehicles to act as relay vehicles (RVs) to provide Internet access to passenger vehicles. However, the standard handover procedure of mobile or MMR WiMAX suffers long delay due to the lack of information about the next RV. This study presents a cross‐layer fast handover scheme, called vehicular fast handover scheme (VFHS), where the physical layer information is shared with the MAC layer, to reduce the handover delay. The key idea of VFHS is to utilize oncoming side vehicles (OSVs) to accumulate physical and MAC layers information of passing through RVs and broadcast the information to vehicles that are temporarily disconnected, referred to as disconnected vehicles (DVs). A DV can thus perform a rapid handover when it enters the transmission range of one of approaching RVs. The effectiveness of VFHS is verified using ns2 simulations. Simulation results indicate that VFHS significantly decreases handover latency and packet loss. Copyright © 2009 John Wiley & Sons, Ltd.

Recently, wireless and mobile communication networks have become increasingly popular and the huge number of smart mobile devices and applications has brought the mobile operators with challenges from various aspects. This trend will continue to affect the way in which we live, work, and play with many smart and innovative services, and the intensive mobility control messages and data will give great impact on the traditional wireless and mobile communication networks. For this reason, the mobility management support is one of very important issues for the future generation of wireless and mobile networks and services, and the design of efficient and robust mobility management is one of the most challenging research tasks. Observing the great need for an in-depth research of the mobility management in both academia and industry, we have put together this special issue through an open call for papers. More than 10 high-quality papers from all around the world were submitted. Although many of them were of high quality, we had room for only three papers that best fit the theme. To guarantee higher quality of this special issue, we also have selectively collected four expanded papers from the proceedings of MobiWorld 2008 workshop while inviting two comprehensive surveys. Accordingly, this special issue brings together nine papers. The first two papers are devoted to review and survey recent developments and methods of mobility management, and the others propose and analyze some of the most interesting and innovative solutions dealing with the mobility management in wireless mobile networks. The paper “Next generation mobility management: an introduction” by F. Richard Yu, Vincent W. S. Wong, Joo-Han Song, Victor C. M. Leung, and Henry C. B. Chan reviews recent research trend and developments in location management, and surveys methods for inter-system handover management between heterogeneous systems. It classifies the inter-system handover management schemes according to the protocol layer, so that the readers can gain in-depth insight into the topic. It also provides open problems and research direction for the next negation mobility management. Recently, communication devices are being installed in more and more vehicles and roadside infrastructure. In the near future, traveling vehicles will be able to communicate while forming rapidly changing ad hoc networks. The paper “Mobility and Handoff Management in Vehicular Networks: A Survey” by Kun Zhu, Dusit Niyato, Ping Wang, Ekram Hossain, and Dong In Kim presents a good comprehensive survey on existing mobility management works for both vehicle-to-vehicle and vehicle-to-infrastructure communications in vehicular networks, and also provides several open research issues of the topic. The following four papers refer to the proxy mobile IPv6 (PMIPv6) which is a famous mobility management protocol recently standardized by IETF. PMIPv6 is a representative network-based localized mobility management protocol and has been of great interest to both academia and industry. Unlike host-based IP mobility management protocols, PMIPv6 does not require the participation of mobile nodes in mobility signaling. The paper “Implementation and analysis of proxy MIPv6” by Jianfeng Guan, Huachun Zhou, Zhiwei Yan, Yajuan Qin, and Hongke Zhang analyzes the singling cost of PMIPv6, provides their test-bed implement to evaluate its performance, and shows that its performance is better than the other mobility management protocols. The paper “Smart Buffering for seamless handover in Proxy Mobile IPv6” by Hyon-Young Choi, Kwang-Ryoul Kim, Hyo-Beom Lee, Sung-Gi Min, and Youn-Hee Han presents a PMIPv6 buffering scheme using only network-side information to prevent packet loss by proactively buffering packets that will be lost during handover, and also provides redundant packet elimination and packet reordering methods to minimize duplicate packet delivery and disruption of connection-oriented data flows. The paper “The applicability of virtual interface for inter-technology handovers in Proxy Mobile IPv6” by Ryuji Wakikawa, Sawako Kiriyama, and Sri Gundavelli analyzes the required software function on the mobile node for performing inter-technology handovers and investigates the applicability of virtual interface support available in Linux for implementing the PMIPv6-based inter-technology handover. The paper “QoS aware dynamic route optimization for Proxy Mobile IPv6 networks” by A. Dev Pragad, Vasilis Friderikos, Paul Pangalos, and A. Hamid Aghvami provides a QoS aware dynamic route optimization scheme where the network identifies the lower QoS sessions, and establishes a binding update with the correspondent node (CN) rather than with the LMA. The paper “A Cross-Layer Partner-Assisted Handoff Scheme for Hierarchical Mobile IPv6 in IEEE 802.16e Systems” by Yuh-Shyan Chen and Kun-Lin Wu presents a new partner-assisted handoff mechanism based on cross-layer approach by the combination of layer 2 and layer 3 in hierarchical mobile IPv6 which is a protocol standardized by IETF. The paper “Soft handoff support for SIP-NEMO: design, implementation, and performance evaluation” by Shun-Ren Yang, Ya-Jun Huang, and Chun-Wei Chiu provides a soft handoff mechanism to effectively reduce the handoff disruption time which may be long in thesession initiation protocol and network mobility (SIP-NEMO). The paper “An end-to-end framework of transport layer mobility management” by Yi Wu, Yanqun Le, and Dongmei Zhang extends the TCP migrate work by resolving the simultaneous mobility issue that the existing transport layer mobility schemes do not support and proposes an improved end-to-end framework of TCP migrate scheme through handover redirection and transmission resuming. We would like to thank all the authors for their great work and for considering this special issue for submitting their papers. We would like to extend our gratitude to the anonymous reviewers who spent much of their precious time reviewing all the papers and providing substantive comments on paper improvements. We also would like to thank the devoted staff of Wiley for their high level of professionalism, and particularly express our sincere thanks to the Editor-in-Chief of WCMC, Professor Mohsen Guizani, for inviting us to edit this special issue and for their continuing keen interest. It has been a pleasure to put together this special issue on this very timely topic and we hope you enjoy it.

Routing protocols for vehicular ad hoc networks (VANETs) have attracted a lot of attention recently. Most of the researches emphasize on minimizing the end-to-end delay without paying attention to reducing the usage of radio. This paper focuses on delay-bounded routing, whose goal is to deliver messages to the destination within user-defined delay and minimize the usage of radio. The messages can be delivered to the destination by the hybrid of data muling (carried by the vehicle) and forwarding (transmitted through radio). In the existing protocol, a vehicle may only switch the delivery strategy (muling or forwarding) at an intersection according to the available time of the next block. To improve previous works, our protocol uses linear regression to predict the available time and the travel distance and thus the vehicle can switch to a proper delivery strategy at a proper moment and can reduce the number of relays by radio. Our protocol contains two schemes: the greedy and centralized schemes. The greedy scheme uses only the local vehicle's speed to predict the available time and decide when to switch the delivery strategy; while the centralized scheme uses the global statistical information to make the decision. Simulation results justify the efficiency of the proposed protocol.

You-Chiun Wang, Tomoaki Ohtsuki, Athanasios (Thanos) Vasilakos, Ashutosh Sabharwal, Yuh-Shyan Chen, Yu-Chee Tseng; Algorithms, Protocols and Future Applica

In this paper, we present a spatiotemporal multicast, called a mobicast, protocol for supporting applications which require spatiotemporal coordination in VANETs. The spatiotemporal character of a mobicast is to forward a mobicast message to vehicles located in some geographic zone at time t, where the geographic zone is denoted as zone of relevance (ZOR). Vehicles located in ZOR at the time t must keep the connectivity to maintain the real-time data communication between all vehicles in ZOR. The temporal network fragmentation problem is occurred if the connectivity of ZOR is lost such that vehicles in ZOR cannot successfully receive the mobicast messages. To solve the problem, a new mobicast protocol is presented in this work to successfully disseminate mobicast messages to all vehicles in ZOR via a special geographic zone, called as zone of forwarding (ZOF). The main contribution of this work is to develop a new mobicast routing protocol to dynamically estimate the accurate ZOF to successfully disseminate mobicast messages to all vehicles in ZOR. To illustrate the performance achievement, simulation results are examined in terms of dissemination successful rate, packet overhead multiplication, and packet delivery delay.

This study presents a cross-layer fast handover scheme for VANET, called vehicular fast handover scheme (VFHS), where the physical layer information is shared with the MAC layer, to reduce the handover delay. The key idea of VFHS is to utilize oncoming side vehicles (OSVs) to collect physical and MAC layers information of passing through RVs and broadcast the information to vehicles that are temporarily disconnected, referred to as broken vehicles (BVs). A BV can thus perform a rapid handover when it enters the transmission range of the approaching RVs. The effectiveness of VFHS is verified using ns2 simulations. Simulation results indicate that VFHS significantly decreases handover latency and packet loss.

The goal of the network mobility (NEMO) management is to effectively reduce the complexity of handoff procedure and keep the mobile devices connected to the Internet. Vehicle is moving so fast that it may cause the handoff and packet loss problems. Both of the problems will lower down the throughput of the network. To overcome these problems, we propose a novel NEMO protocol for vehicular ad hoc network (VANET). In freeway, since every car is moving in a fixed direction with high moving speed, the car adopting our protocol can acquire IP address from the VANET through vehicle to vehicle communications. The vehicle can rely on the assistance of the front vehicle to execute the pre-handoff procedure or it may acquire its new IP address through multi-hop relays from the car on the lanes of the same or opposite direction and thus reduces the handoff delay and maintain the connectivity to the Internet. Simulation results have shown that the proposed scheme is able to reduce both handoff delay and packet loss rate.

In this paper, a new approach is proposed to reduce handoff operation in IEEE 802.16e network. Traditional mobile approaches, such as mobile IPv6 (MIPv6) and hierarchical MIPv6 (HMIPv6), can support smoothly handoff. These approach, ,unfortunately, suffer large handoff delay and packet lost in macro mobility for mobile users. With the aid of the partner node, DAD operation can be pre-executed by the partner node before the mobile node initialize the handoff request, we propose a cross-layer partner based fast handoff mechanism based on HMIPv6 in IEEE 802.16e network, called as P_HMIPv6 protocol. The P_HMIPv6 protocol is a cross-layer, layer 2 and layer 3, approach. The partner station (PS), which is a new component with relay ability and adopted by our protocol, is a static mobile station (MS). With the aid of the PSs, care-of address (CoA) can be pre-acquired and DAD operation can be pre-executed by the PS before the MS initials the layer 2 handoff. The simulation results show that P_HMIPv6 protocol actually achieves the performance improvements in the handoff delay time and the packet loss.

This paper investigates a new TDMA-based MAC, called C-MAC (MAC using Chinese remainder theorem), protocol with low power consumption while maintaining low packet latency for large-scale cluster-based WSNs. To offer low power consumption, each node and coordinator to be active and sleep states based on the time-slot schedule of Chinese remainder theorem. To provide low packet latency, our C-MAC protocol provides an adaptive time-slot scheme to distributively and dynamically wake up time slots for the burst data transmission in a duty cycle. Finally, simulation results illustrate our performance achievements to verify that C-MAC performs better than existing TDMA-based MAC protocols, BMA and EMAC, in terms of power consumption and average packet latency.

In this paper, we propose a cross-layer partner- based fast handoff mechanism based on HMIPv6, called as PHMIPv6 protocol. Our PHMIPv6 protocol is a cross-layer, layer-2 + layer-3, approach. A new node, called partner node, is adopted in PHMIPv6 protocol. A new layer-2 trigger scheme used in PHMIPv6 protocol is to accurately predict the next AP (access point) and then to invite a possible partner node in the area of the next AP. With the aid of the partner node, CoA can be pre-acquired and DAD operation can be pre-executed by the partner node before the mobile node initialize the handoff request. By the way, PHMIPv6 protocol can significantly reduce the handoff delay time and packet losses. In the mathematical analysis, we verify that our PHMIPv6 protocol offers a better handoff latency than MIPv6, HMIPv6, and SHMIPv6. Finally, the experimental results also illustrate that PHMIPv6 protocol actually achieves the performance improvements in the handoff delay time, and the packet loss rate.

In this paper, a new cross-layer protocol was developed, called as SmSCTP protocol, for session mobility over WLAN and 3G UMTS heterogeneous networks. Two key issues investigated in this work are the connection broken problem and fleeting-location-collapse problem. The connection broken problem indicates that a connection is broken when a mobile device is roaming to a different network. The connection broken problem incurs the long handoff delay time and cannot provide the seamlessly handoff result for session mobility. Traditional session mobility schemes, such as SIP (layer-7 solution) and MSCTP (layer-4 solution) protocols, only provide non-real time registration when third party user is calling up mobile user. The non-real time registration incurs the well-known fleeting-location-collapse problem and causes additional location update overhead. This paper presents a SIP-based MSCTP (SmSCTP) protocol which is a cross-layer, combination of layer-4 and layer-7, approach. The SmSCTP protocol utilizes the multi-homing mechanism to reduce hand-off delay time and to provide the more seamless handoff scheme. In the SmSCTP protocol, two new SIP signalings for the SmSCTP protocol are designed to simplify the initial handoff procedure and solve fleeting-location-collapse problem. Finally, simulation results are conducted to illustrate the performance achievements of the proposed SmSCTP protocol by improving the signaling cost, the hand-off delay time.

WLANs will become a major portion of the fourth generation (4G) cellular system. The seamless handoff problem in WLANs is a very important design issue to support the new astounding amazing applications in wireless networks. The entire delay time of a handoff is divided into probe, authentication, and reassociation delay times. Because the probe delay occupies most of the handoff delay time, efforts have focused mainly on reducing the probe delay to develop faster handoff schemes. This paper presents a new fast handoff scheme, called the DeuceScan scheme, to further reduce the probe delay for 802.11- based WLANs. A spatiotemporal approach is developed in this work to utilize a spatiotemporal graph to provide spatiotemporal information for making accurate handoff decisions by correctly searching for the next AP (access point). The DeuceScan scheme is a pre-scan approach which efficiently reduces the MAC layer handoff latency. Two factors of stable signal strength and variable of signal strength are both used in our developed DeuceScan scheme. Finally, the simulation results illustrate the performance achievements of the DeuceScan scheme in reducing the handoff delay time and packet loss rate.

In this paper, we propose a new mobicast routing protocol, called the HVE-mobicast (hierarchical-variant-egg-based mobicast) routing protocol, in wireless sensor networks (WSNs). Existing protocols for a spatiotemporal variant of the multicast protocol called a "mobicast" were designed to support a forwarding zone that moves at a constant velocity, vrarr, through sensornets. The spatiotemporal characteristic of a mobicast is to forward a mobicast message to all sensor nodes that are present at time t in some geographic zone (called the forwarding zone), Z, where both the location and shape of the forwarding zone are a function of time over some interval (tstart, tend). Mobicast routing protocols aim to provide reliable and just-in-time message delivery for mobile sink nodes. The new HVE-mobicast routing protocol is a cluster-based VE-mobicast routing protocol. The message delivery of nodes in the forwarding zone of the HVE-mobicast routing protocol is transmitted by two phase: cluster-to-cluster and cluster-to-node phases. In the cluster-to-cluster phase, the cluster-head and relay nodes are distributively notified to wake them up. In the cluster-to-node phase, all member nodes are then notified to wake up by cluster-head nodes according to the estimated arrival time of the delivery zone. The key contribution of the HVE-mobicast routing protocol is that it is more power efficient. This effect is mainly achieved by improving the predicted accuracy, especially by considering different moving speeds and directions. Finally, simulation results illustrate performance enhancements in message overhead, power consumption, and predicted accuracy, compared to existing mobicast routing protocols

Orthogonal variable spreading factor (OVSF) channelization codes are widely used to provide variable data rates for supporting different bandwidth requirements in wideband code division multiple access (WCDMA) systems. Many novel works in the literature have intensively investigated code placement and replacement schemes in OVSF code trees to reduce the code blocking probability and the code reassignment cost. In this paper, we introduce a new code tree structure, namely, a rotated-orthogonal variable spreading factor (ROVSF) code tree, whose code capacity is the same as that of the traditional OVSF code tree. This work addresses both code placement and replacement schemes in the ROVSF code tree system, where ROVSF codes can be used at the forward link of WCDMA systems. Some valuable properties of the developed ROVSF code tree are presented to develop code placement/replacement schemes with lower code blocking probability and less code reassignment cost. The main contribution of our scheme is to identify linear-code chains (LCCs) and nonlinear-code trees (NCTs) in the ROVSF code tree. This work exploits the unsequence property of linear-code chains to design a new code placement and replacement mechanism. Our code placement/ replacement schemes initially attempt to allocate request codes on LCCs and, then, to allocate them to NCTs. Using LCCs with the unsequence property allows us to efficiently reduce the code blocking probability and the code reassignment cost. Extensive simulations are conducted to illustrate that our code placement/replacement results based on the ROVSF code tree actually improve the code blocking probability and the code reassignment cost.

The IPv6-enabled network architecture has recently attracted much attention. In this paper, we address the issue of connecting MANETs to global IPv6 networks while supporting IPv6 mobility. Specifically, we propose a self-organizing, self-addressing, self-routing IPv6-enabled MANET infrastructure, referred to as IPv6-based MANET. The proposed self-organization addressing protocol automatically organizes nodes into tree architecture and configures their global IPv6 addresses. Novel unicast and multicast routing protocols, based on longest prefix matching and soft state routing cache, are specially designed for the IPv6-based MANET. Mobile IPv6 is also supported such that a mobile node can move from one MANET to another. Moreover, a P2P information sharing system is also designed over the proposed IPv6-based MANET. We have implemented a prototyping system to demonstrate the feasibility and efficiently of the IPv6-based MANET and the P2P information sharing system. Simulations are also conducted to show the efficiency of the proposed routing protocol and the P2P file sharing system.

In this paper, we present a new "spatiotemporal multicast" protocol for supporting applications which require spatiotemporal coordination in sensornets. To simultaneously consider the factors of moving speed and direction, this work mainly investigates a new mobicast routing protocol, called variant-egg-based mobicast (VE-mobicast), by utilizing the variant-egg shape of the forwarding zone to achieve a high predicted accuracy. The contributions of our protocol are summarized as follows: (1) it builds a new shape of a forwarding zone, called the variant-egg, to adaptively and efficiently determine the location and shape of the forwarding zone to maintain the same number of wake-up sensor nodes; (2) it is a fully distributed algorithm which reduces the communication overhead of determining the forwarding zone and the mobicast message forwarding overhead; (3) it can improve the predicted accuracy of the forwarding zone by considering the factors of moving speed and direction. Finally, the simulation results illustrate the performance achievements, compared to existing mobicast routing protocols.

The quality-of-service (QoS) communication that supports mobile applications to guarantee bandwidth utilization is an important issue for Bluetooth wireless personal area networks (WPANs). In this paper, we address the problem of on-demand QoS routing with interpiconet scheduling in Bluetooth WPANs. A credit-based QoS (CQ) routing protocol is developed which considers different Bluetooth packet types because of different types of Bluetooth packets have different bandwidth utilization levels. This work improves the bandwidth utilization of Bluetooth scatternets by providing a new interpiconet scheduling scheme. Centralized and distributed algorithms are investigated in this work to improve the bandwidth utilization for the on-demand QoS routing protocol The performance analysis illustrates that our credit-based QoS routing protocol achieves enhanced performances, compared to existing QoS routing protocols.

The Internet protocol version 6 (IPv6)-enabled network architecture has recently attracted much attention. In this paper, we address the issue of connecting mobile ad hoc networks (MANETs) to global IPv6 networks, while supporting IPv6 mobility. Specifically, we propose a self-organizing, self-addressing, self-routing IPv6-enabled MANET infrastructure, referred to as IPv6-based MANET. The proposed self-organization addressing protocol automatically organizes nodes into tree architecture and configures their global IPv6 addresses. Novel unicast and multicast routing protocols, based on longest prefix matching and soft state routing cache, are specially designed for the IPv6-based MANET. Mobile IPv6 is also supported such that a mobile node can move from one MANET to another. Moreover, a peer-to-peer (P2P) information sharing system is also designed over the proposed IPv6-based MANET. We have implemented a prototyping system to demonstrate the feasibility and efficiency of the IPv6-based MANET and the P2P information sharing system. Simulations are also conducted to show the efficiency of the proposed routing protocols.

We devote to provide teachers and students with short-range wireless learning environment. The wireless learning platform consists of wireless handheld devices (PDA, notebook, etc.) carried by the guide and learners. A content-based image retrieval system (CBIR) is constructed to provide learner with required information using image recognition and wireless transmission technologies, such that the objective of outdoor ecology learning can be achieved. A firefly database is used as an instance to illustrate the operations of CBIR system. Instead of learning from textbook, a real firefly in natural environment can be observed and learned through digital camera and image recognition system. During the learning activity, the teacher can use this CBIR system to control the learning progress, evaluate the learning effects and provide necessary assistances to students in order to have a flourish learning environment.

In this paper, we propose a lantern-tree-based QoS multicast protocol with a reliable mechanism for wireless ad-hoc networks, where the MAC sublayer adopts the CDMA-over-TDMA channel model. In this paper, we identify a lantern-tree for developing an on-demand QoS multicast protocol to satisfy certain bandwidth requirements from a source to a set of destination nodes. The lantern-tree serves as the multicast-tree. Our lantern-tree-based scheme offers a higher success rate to construct the QoS multicast tree due to using the lantern-tree. The lantern-tree is a tree whose sub-path is constituted by the lantern-path, where the lantern-path is a special multi-path structure. This greatly improves the success rate by means of multi-path routing. In particular, our proposed scheme can be easily applied to most existing on-demand multicast protocols. Performance analysis results demonstrate the QoS achievements of our proposed protocol.

We present a new energy-efficient directed diffusion protocol by using the proposed diagonal-based hexagonal-mesh scheme for a wireless sensor network. The wireless sensor network is more reasonable to build a fixed-topological wireless network environment than the conventional MANET due to the low mobility. Therefore, all sensor nodes are arranged into a fixed-topological wireless network structure, namely the hexagonal-mesh, while the MAC protocol is adopted using the periodic active-and-sleep model. The wireless sensor networks use battery-operated computing and sensing devices. The directed diffusion is mainly operated on the diagonal-paths of the hexagonal-mesh under the energy-efficient consideration. To achieve the energy-efficient purpose, our diagonal-based directed diffusion scheme has the following main contributions: (1) a periodic active-and-sleep MAC protocol on TDMA channel model is designed; (2) a periodic backbone-path-exchange scheme is periodically performed on the diagonal-mesh to consider the per-node fairness problem; and (3) a directed diffusion communication application is developed based on the diagonal-based scheme. Finally, the performance analysis result is demonstrated to illustrate the energy-efficient achievement of our proposed scheme.

A mobile ad hoc network (MANET) is a characterized by multi-hop wireless links, absence of any cellular infrastructure, and frequent host mobility. Existing MANET routing protocols are divided into location-aware and non-location-aware routing protocols. In a location-aware routing protocol, location information can be exploited to facilitate routing. Our protocol, namely the multi-eye spiral-hopping (MESH) routing protocol, is a location-aware routing protocol. Most promising routing protocols are constructed by the route-discovery, route-reply, and route-maintenance phases. Our MESH protocol utilizes the location information to confine the blind-flooding region in the route-discovery phase, minimize route-reply packets in the route-reply phase, and promote routing robustness in the route-maintenance phase. Two major contributions of this paper are introduced: (1) a multi-eye scheme is presented to confine the route-discovery region for reducing redundant packets; and (2) a highly robust path, called the spiral-hopping path, is introduced to provide on-line route-recovery capability. Extensive simulations are conducted to evaluate the protocol.

The arrangement graph A/sub n,k/ is not only a generalization of the star graph (n-k=1), but is also more flexible. Designing an efficient routing algorithm on a regular interconnection network is a fundamental issue for parallel processing techniques. We elucidate the multi-node broadcasting problem in an all-port communication model on the arrangement graph. Our routing strategy is proposed by construction of 2(n-k) spanning trees, where the height of each spanning tree is 2k-1. We also extend the routing strategy to a one-to-all broadcasting algorithm. Using 2(n-k) spanning trees allows us to present efficient (one/multi)- node broadcasting algorithms in the arrangement graph. The arrangement graph is assumed to use one-port and all-port models and packet-switching (or store-and forward) technique. Moreover we show that our (one/multi)-node broadcasting algorithms outperform previous results in the literature. This is justified by our performance analysis.

Broadcasting is a common operation in a network to resolve many issues.In a mobile ad hoc network (MANET) in particular, due to host mobility, such operations are expected to be executed more frequently (such as finding a route to a particular host, paging a particular host, and sending an alarm signal).Because radio signals are likely to overlap with others in a geographical area, a straightforward broadcasting by flooding is usually very costly and will result in serious redundancy, contention, and collision, to which we refer as the broadcast storm problem.In this paper, we identify this problem by showing how serious it is through analyses and simulations.We propose several schemes to reduce redundant rebroadcasts and differentiate timing of rebroadcasts to alleviate this problem.Simulation results are presented, which show different levels of improvement over the basic flooding approach.

Trees are a common structure to represent the inter-task communication pattern of a parallel algorithm. In this paper, we consider the embedding a complete binary tree in a star graph with the objective of minimizing congestion and dilation. We develop two embeddings: i) a congestion-free, dilation-2, load-1 embedding of a level- p binary tree, and ii) a congestion-free, dilation-2, load-2 k embedding of a level-(p+k) binary tree, into an n-dimensional star graph, where p = \\Sigma n i=2 blog ic = \\Omega\\Gamma n log n) and k is any positive integer. The first result offers a tree of size comparable or superior to existing results, but with less congestion and dilation. The second result provides more flexibility in the embeddable tree sizes compared to existing results. Keywords: Graph embedding, interconnection network, complete binary tree, star graph, parallel processing. This research was supported in part by the National Science Council, R.O.C., under grant numbers NS...

The arrangement graph A/sub n,k/ is a generalization of star graph (n-k=1) and more flexible than the star graph. In this paper we consider the embedding of multiple spanning trees in an arrangement graph with the objective of being congestion-free. This is first result to exploit multiple spanning trees in the arrangement graphs. We develop a congestion-free embedding of n-k spanning trees with height 2k-1 in an (n, k)-dimensional arrangement graph.