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To evaluate clinical outcomes of thoracic duct embolization (TDE) for the management of postoperative chylothorax with the aid of the bail-out retrograde approach for thoracic duct cannulation (TDC). Forty-five patients with postoperative chylothorax underwent Lipiodol lymphangiography (LLG) between February 2016 and November 2019. If targetable central lymphatic vessels were identified in LLG, TDC, a prerequisite for TDE, was attempted. While the conventional antegrade transabdominal approach was the standard TDC method, the retrograde approach was applied as a bail-out method. Embolization, the last step of TDE, was performed after confirming leakages in the trans-TDC catheter lymphangiography. Technical and clinical success rates were determined retrospectively. TDC was attempted in 40 among 45 patients based on LLG findings. The technical success rate of TDC with the conventional antegrade approach was 78% (31/40). In addition, six more patients were cannulated using the bail-out retrograde approach, which raised the technical success rate to 93% (37/40). While 35 patients underwent embolization (TDE group), ten patients did not (non-TDE group) for the following reasons: (1) lack of targetable lymphatics for TDC in LLG (n = 5), (2) technical failure of TDC (n = 3), and (3) lack of discernible leakages in the transcatheter lymphangiography (n = 2). The clinical success of the TDE group was 89% (31/35), compared with 50% (5/10) of the non-TDE group. One major procedure-related complication was bile peritonitis caused by the needle passage of the distended gallbladder. Bail-out retrograde approach for TDC could improve the overall technical success of TDC significantly. • Bail-out retrograde thoracic duct access may improve the overall technical success of thoracic duct access, thus improving the clinical success of thoracic duct embolization.

The convenience and energy efficiency of electric trams have resulted in their rapid adoption in many areas of the world. Despite trams’ many advantages, overhead lines installed along the track cause severe problems, such as safety issues, maintenance problems, and difficulty in renovating the urban road system. To solve these problems, a wireless charging electric tram system has been developed to replace the overhead lines, catenary, and pantograph. With wireless charging segments installed underground, a tram can operate freely without any support from overhead lines. In order to successfully commercialize a wireless charging tram system, it is essential to minimize the energy cost of the wireless charging tram system. In this article, a model of a wireless charging electric tram system and an energy cost minimization algorithm are proposed. The Manchester Metrolink tram network is modeled using the Google Maps API, the Google Transit API, and the Metrolink API to simulate the wireless charging system under massive public transportation network. To determine the minimum energy cost, an energy cost minimization algorithm for the wireless charging tram system is proposed based on decentralized multiagent reinforcement learning with feedback. The numerical results show that the proposed algorithm can reduce costs while ensuring stable operation.

An accurate and efficient path loss modeling method for millimeter wave communications plays a significant role in the large-scale deployment of a fifth-generation (5G) mobile communication system. Conventional path loss modeling methods such as deterministic methods, empirical methods, and machine learning-based methods, in practice, cannot achieve the desired level of performance in terms of accuracy. This paper proposes a novel path loss model for 5G communications in suburban scenarios using deep learning with dilated convolution and attention. Dilated convolution is used to alleviate the locality of feature extraction and capture the global information on input images. Attention rendered by global context blocks helps the attention-enhanced convolutional neural network (AE-CNN) model utilize the global information on inputs to extract essential features of propagation environments. A distance-embedded local area multi-scanning algorithm which generates input images that can improve learning the latent features with dependency on distance is proposed. The experimental results indicate that the AE-CNN model can outperform state-of-the-art deterministic and empirical methods in terms of root mean square error in test scenarios.

Path loss modeling of millimeter waves is regarded as one of the most challenging problems in the design of the fifth-generation (5G) mobile communication networks due to the high susceptibility to various environmental influences. We present a novel convolutional neural network (CNN)-based path loss modeling method based on a set of 28 GHz mmWave field measurements in suburban scenarios. Enhanced local area multi-scanning (E-LAMS) algorithm that provides a CNN with path loss environmental information is proposed. A new CNN structure with four subnetworks and feature-sharing layers added between convolutional layers is also proposed. The proposed methods demonstrate their superior performance over empirical models and deterministic models in terms of accuracy and complexity. The root-mean-square error of 8.59 dB has been achieved in path loss prediction in the test scenarios.

Objective To compare the therapeutic efficacy between conventional transarterial chemoembolization (cTACE) and combined therapy using cTACE and radiofrequency ablation (RFA) in ultrasound (US)-invisible early stage hepatocellular carcinoma (HCC). Materials and Methods From January 2008 to June 2016, 167 patients with US-invisible early stage HCCs were treated with cTACE alone (cTACE group; n = 85) or cTACE followed by immediate fluoroscopy-guided RFA targeting intratumoral iodized oil retention (combined group; n = 82). Procedure-related complications, local tumor progression (LTP), time to progression (TTP), and overall survival (OS) were compared between the two groups. Multivariate analyses were performed to identify prognostic factors. Results There was no major complication in either group. The cTACE group showed higher 1-, 3-, and 5-year LTP rates than the combined group; i.e., 12.5%, 31.7%, and 37.0%, respectively, in the cTACE group; compared to 7.3%, 16.5%, and 16.5%, respectively, in the combined group; p = 0.013. The median TTP was 18 months in the cTACE group and 24 months in the combined group (p = 0.037). Cumulative 1-, 3-, and 5-year OS rates were 100%, 93.2%, and 87.7%, respectively, in the cTACE group and 100%, 96.6%, and 87.4%, respectively, in the combined group (p = 0.686). Tumor diameter > 20 mm and cTACE monotherapy were independent risk factors for LTP and TTP. Conclusion Combined therapy using cTACE followed by fluoroscopy-guided RFA is a safe and effective treatment in US-invisible early stage HCCs. It provides less LTP and longer TTP than cTACE alone.

Stent placement was performed in 10 patients with symptomatic spontaneous dissection of the superior mesenteric artery (SMA). A stent was placed as first-line treatment in 7 patients and as second-line treatment in 3 patients in whom conservative treatment had failed. Abdominal pain completely resolved within 2 days after stent placement, and follow-up (median 53 months; range, 11-99 months) CT angiography revealed complete obliteration of the false lumen and good stent patency in 9 patients. One patient showed asymptomatic stent occlusion at 99-month follow-up. Long-term patency of stent placement in patients with symptomatic SMA dissection seems to be acceptable.

Purpose To describe angiographic findings and assess safety and effectiveness of bronchial artery embolization (BAE) with N -butyl cyanoacrylate (NBCA) in patients with cryptogenic hemoptysis (CH). Materials and Methods Between May 2003 and March 2014, 26 patients who underwent BAE for CH were enrolled. A retrospective review was conducted for angiographic findings and clinical outcomes of BAE, including technical and clinical success, complications, and recurrent hemoptysis. Results Selective arteriograms were abnormal in 22 patients (85%), showing hypertrophied bronchial arteries (n = 19), parenchymal hypervascularity (n = 18), and bronchial-to-pulmonary shunting (n = 8). All abnormal bronchial and nonbronchial collateral arteries (n = 36) were successfully embolized with NBCA. Hemoptysis ceased within 24 hours in all patients. There were no procedure-related complications. During 11–117 months of follow-up (median, 60.2 mo), 1 patient (4%) experienced recurrent hemoptysis at 5 months after initial BAE, which was treated with repeat BAE. The 5-year hemoptysis-free survival rate was 96%. Conclusions Bronchial arteries were angiographically abnormal in most patients with CH (85%). BAE is a safe and effective treatment with excellent short- and long-term results in patients with CH. NBCA appears to be a useful embolic material for this application.

The most of sentiment analysis on the user reviews only aim to classify the review as overall positive, negative, and neutral sentiment in terms of the overall polarity score. Such overall sentiment score cannot provide detailed information. This study proposes a method of automatic extraction of features and their modifying sentiment words in user reviews, thus a recommendation system provide more detailed sentiment and information. To parse such sentiment and information, we propose a general method for extracting modification relations between nouns and adjectives in Korean sentences, which are corresponding to features and their modifying (sentiment) words, respectively.

The design of conventional electric vehicles (EVs) is affected by numerous limitations, such as a short travel distance and long charging time. As one of the first wireless charging systems, the Online Electric Vehicle (OLEV) was developed to overcome the limitations of the current generation of EVs. Using wireless charging, an electric vehicle can be charged by power cables embedded in the road. In this paper, a model and algorithm for the optimal design of a wireless charging electric bus system is proposed. The model is built using a Markov decision process and is used to verify the optimal number of power cables, as well as optimal pickup capacity and battery capacity. Using reinforcement learning, the optimization problem of a wireless charging electric bus system in a diverse traffic environment is then solved. The numerical results show that the proposed algorithm maximizes average reward and minimizes total cost. We show the effectiveness of the proposed algorithm compared with obtaining the exact solution via mixed integer programming (MIP).

Convolutional Neural Networks (CNNs) have shown surprisingly good performance in both classification and regression problems. Given a floor plan of a building and indoor measurement data of Wi-Fi received signal strength (RSS) at discrete locations, a CNN can be trained to approximate the underlying functions of path loss. In this article, we propose a novel CNN-based indoor path loss modeling approach. Based on a floor plan and measurement data, input images are generated for training a CNN, which can make predictions of the RSS of 5 GHz Wi-Fi in an indoor usage scenario. Experiment results show that CNNs can be used for indoor path loss modeling with the encouraging performance with the Root Mean Square Error (RMSE) of 3.9404 dBm and good generalization property.

Traditional low-cost GPS installed on vehicles and other equipment has a tolerance of tens of meters. With the help of auxiliary devices and/or methodologies such as Differential GPSs (DGPSs), Assisted GPSs (AG-PSs), Real-Time Kinematic (RTK), computer vision and etc., the positioning accuracy of GPS receivers increased a lot, but a certain amount of cost increased at the same time. In this paper, we propose a new cooperative vehicular localization scheme for improving the accuracy of GPS fixes based on Vehicle-to-vehicle (V2V) communication. The proposed scheme first estimates the distances between neighboring vehicles using WLS-DD scheme [1] and uses a machine learning technique called Constrained Self-Organizing Map (C-SOM) with a set of GPS fixes collected over time to generate the final estimates of GPS locations with much lower errors. We present simulation results that demonstrate the superior performance of the proposed Constrained-SOM.

The performance of traditional routing protocols for mesh networks can decrease significantly in disaster recovery situations due to dynamic changes to the network environment. A number of multi-path routing protocols have been proposed to address such issues. MMQR is a multi-path routing protocol for OFDM–TDMA mesh networks which use multiple paths that can be replaced immediately by one another in case of link failures. In this paper we extend the MMQR such that the alternative paths are reordered adaptively as the communication environment changes based on the heuristic model of attractor selection mechanism by which biological entities are known to adapt to dynamically changing environment. Simulation results show that the multi-path routing protocol with attractor selection mechanism outperforms existing multi-path routing protocols in terms of packet delivery ratio, throughput and QoS.

In this paper, we propose a joint resource allocation, routing, and connection admission control (CAC) scheme for uplink transmission in orthogonal frequency division multiple access (OFDMA) relay networks with cooperative relaying. For cooperative relaying, relay station can relay uplink data from mobile station (MS) to base station with cooperation of the MS using transmit diversity. Transmit diversity can be achieved by virtual MISO via distributed space---time coding. The proposed scheme jointly allocates OFDMA resources and selects path for each user with CAC to maximize the upink throughput of cooperative OFDMA relay networks. The basic OFDMA resource unit is considered as a resource element which is one subcarrier over one OFDMA symbol. An efficient multi-choice multi-dimensional knapsack (MMKP) algorithm is presented for the proposed scheme. The proposed MMKP algorithm provides a unified framework which is applicable to OFDMA networks with and without cooperative relaying. We evaluate the performance of the proposed scheme with and without cooperative relaying in a hilly terrain with heavy tree density by using OPNET-based simulation. We show that the cooperative relaying improve the uplink system throughput compared with non-cooperative relaying, and the proposed scheme outperforms the conventional link quality-based scheme in both cooperative and non-cooperative relay networks.

Three-dimensional (3D) video is expected to be a “killer app” for OFDMA-based broadband wireless systems. The main limitation of 3D video streaming over a wireless system is the shortage of radio resources due to the large size of the 3D traffic. This paper presents a novel resource allocation strategy to address this problem. In the paper, the video-plus-depth 3D traffic type is considered. The proposed resource allocation strategy focuses on the relationship between 2D video and the depth map, handling them with different priorities. It is formulated as an optimization problem and is solved using a suboptimal heuristic algorithm. Numerical results show that the proposed scheme provides a better quality of service compared to conventional schemes.

With the advent of multiple radio interfaces on modern smart phones, simultaneous transmission and reception of data through via both mobile networks and WiFi networks has gained a considerable attention as a cost-effective means for mobile data offloading. In this paper, we present a practical SDN-based data offloading framework based on a Femto-WiFi Integrated network. The proposed framework take advantage of the flow handling and analysis capability of SDN controllers to make decisions on how to distribute data flows between mobile core networks and broadband IP networks. It follows the device-initiated, network-assisted approach, where a User Equipment (UE) make selection on the radio interfaces to be used based on the network traffic flow information provided by an Access Network Selection Information (ANSI) server.

In this paper, we propose a joint bandwidth allocation and path selection scheme for IEEE 802.16j networks in uplink with cooperative relaying, and we evaluate the performance of the proposed scheme by using OPNET based simulation in hilly terrain with heavy tree density. The proposed scheme maximizes the system throughput in uplink with cooperative relaying in IEEE 802.16j networks. Then, we transform the proposed scheme into multi-dimensional multiple choice knapsack problem (MMKP) based scheme. We also propose uplink throughput maximization scheme and MMKP based scheme without cooperative relaying. We show that the system throughput of the proposed MMKP based scheme is higher than that of link quality based scheme, and cooperative relaying provides higher system throughput than the conventional case without cooperative relaying in uplink.

In many nations of Europe, tram is still used as main public transportation system. Despite of its many advantages, overhead lines installed along the track line cause severe problems, such as safety issue, maintenance and difficulty in renewing road system. To solve these problems, wireless charging segment is developed to replace the overhead lines, catenary, and pantograph. With wireless charging segment installed underground, tram can operate freely without any support from overhead lines. In this paper, a model of wireless charging tram system is suggested considering all main parts, such as tractive effort, battery modeling, and driving cycle. In order to find out the minimum cost, optimization of battery capacity, power track allocation and pickup capacity of wireless charging tram system is conducted using heuristic algorithm. Moreover, the optimized result and location of power track installation based on Prague tram line are derived. Lastly, initial installation cost between conventional and proposed tram system is evaluated.

This paper presents a location-based interactive model for Internet of Things (IoT) and cloud integration (IoT-cloud). In the model, IoT-cloud provides sensing service on demand based on interest and location of mobile users. Cloud plays a role as a virtual sink which makes schedule for physical sensor networks on-demand based on locations of mobile users. Through extensive analysis results, we show that the model scheme achieve a significant improvement compared to traditional wireless sensor networks (WSNs).

Today, although most bluetooth hands-free devices within a vehicle provide telephone service functions such as voice communication, caller id display and SMS message display and so on, they do not provide a function that displays Internet-based text data. We need to develop a scheme that displays the internet-based text data including existing hands-free function because the request for using the Internet service is increasing within a vehicle recently. The proposed bluetooth device application includes advanced function such as SNS message arrival notification, the message display function and we chose Android as the implementation mobile platform giving consideration to the fact that most SNS applications operate on Android and the platform is easily embedded into small embedded device. Smartphone or tablet PC connected with the proposed bluetooth device is an Android-based device and we designed a form of Android app for the function implementation of the devices. When the audio-text gateway app receives SNS text data, it extracts title and sender information from the message header information in a form of text data and sends them via ACL (Asynchronous Connection-Oriented) link to the bluetooth device showing the data on the screen. Android-based bluetooth devices are not possible to play voice through speaker because the bluetooth hands-free or headset profile ported within Android platform normally only includes audio gateway`s function. The proposed bluetooth device application, therefore, applies the streaming scheme that sends data via ACL link instead of the way that sending them via SCO (Synchronous Connection-Oriented) link.

Multimedia services need macrodiversity handoff to guarantee real-time property and quality of service (QoS). Therefore, it is important to consider macrodiversity effect in calculating forward link capacity. In this paper, a novel analytic model of forward link capacity with integrated voice/data/multimedia services is developed with taking into account the effect of macrodiversity. In our analytic model, we define capacity of a system as the available peak load while maintaining a desired service quality. From the numerical results, we can see the quantitative effects of macrodiversity in system capacity. Numerical results show that forward link capacity is affected by the power distribution ratio of multipath signal, the ratio of handoff region and the combining method. Our analytic model can be extended to various environments by adjusting given parameters.

With fast proliferation of QoS-enabled wireless packet networks, need for effective QoS control is increasing. In this paper, we focus on QoS provisioning in Mobile WiMAX access service network (ASN). We investigate a dynamic bandwidth provisioning method that can help to increase resource utilization. Our approach consists of two stages: traffic forecasting, followed by bandwidth provisioning. For the first stage, we use auto-regressive integrated moving average (ARIMA) model to forecast traffic based on online measurement. For the second stage, we use a bandwidth provisioning scheme that allocates bandwidths depending on the traffic forecasting. We modeled our problem as a Fractional Knapsack Problem for which we used a greedy algorithm in order to find an approximate solution. Through simulation studies with real-world data sets, we found that our approach could increase the bandwidth for the real-time traffic class and guarantee adequate service quality for the nonreal-time traffic class as well, while maximizing resource utilization.

Energy efficiency is a very important requirement in designing a MAC protocol for wireless sensor networks (WSNs) using battery-operated sensor nodes. We proposed a new energy-efficient MAC protocol, RIX-MAC, based on asynchronous duty cycling and receiver-initiated scheme. In this paper, we analyze the performance such as throughput, delay, and energy consumption of RIX-MAC with modeling and simulation. Our modeling is validated by comparing it with the simulation results in NS-2. As the result, we obtain average 95% confidence interval of the simulation results of this paper.

Due to excessive endeavor to reduce greenhouse gas caused by internal combustion engine-powered vehicles, battery-powered electric vehicles (EV) are arising as a solution. However, EV possess numerous limitations, such as short travel distance and long charging time. The On-Line Electric Vehicle (OLEV) is developed to overcome the limitations that the current generations of the EV have. The OLEV is battery-powered electric vehicle which can be charged wirelessly from the transmitter embedded under the road. The cost of the OLEV system is dependent on battery capacity, pickup capacity and cable length. To investigate the key factors of optimizing the cost of OLEV system, it is necessary to know the interrelations among above three main variables. This paper derives the cost function of the OLEV system, considering the three main components, such as battery, pickup and power cable. Also, it shows the change of the vehicle cost and infra cost with varying the capacity or length of OLEV system's components.

We study flow control and routing in a network of parallel links, in which competitive users make independent decisions to optimize their performance measures. The model we adopt in this paper differs from previously considered ones in that a user performs both flow control and routing, its performance measure is assumed to be a simple concave type function, and its service requirement is restricted by, e.g., a minimum demand or a system capacity. Adopting this extended model for parallel link networks, we prove that there exists a unique equilibrium which is a network operating point that attains user optimality.

This paper presents a location-based interactive model of Internet of Things (IoT) and cloud integration (IoT-cloud) for mobile cloud computing applications, in comparison with the periodic sensing model. In the latter, sensing collections are performed without awareness of sensing demands. Sensors are required to report their sensing data periodically regardless of whether or not there are demands for their sensing services. This leads to unnecessary energy loss due to redundant transmission. In the proposed model, IoT-cloud provides sensing services on demand based on interest and location of mobile users. By taking advantages of the cloud as a coordinator, sensing scheduling of sensors is controlled by the cloud, which knows when and where mobile users request for sensing services. Therefore, when there is no demand, sensors are put into an inactive mode to save energy. Through extensive analysis and experimental results, we show that the location-based model achieves a significant improvement in terms of network lifetime compared to the periodic model.

The IEEE Wireless Access for Vehicular Environment (WAVE) standard consists of the IEEE 802.11p and the IEEE 1609 specifications supporting fast link establishment as well as broadband data communication in vehicular environment. Although the standard has been widely accepted by industry as well as highway authorities in many countries to be used for the radio communication infrastructure of the next-generation Intelligent Transport System (ITS), it remains open for further enhancements such as seamless handover support. This paper presents two proactive caching and forwarding schemes for seamless handover in IEEE WAVE networks: one for straight highway sections and the other for crossroads and junctions. Practical and efficient handover procedures, based on the proposed schemes, are also presented. Specifically, an on-board unit (OBU) informs the old road-side unit (RSU) about its departure from the coverage area such that the old RSU can forward the buffered packets to candidate RSUs for proactive caching. In handover scenarios around crossroads and junctions, the IEEE 802.11f Move-notify message is used by the new RSU to request the rest of candidate RSUs to purge the cached packets in order to prevent the waste of radio resource. Simulation results show that the proposed schemes outperform conventional schemes.

The specification of IEEE 802.16j defines the operation of multi-hop relay stations (RSs) with cooperative communication as an optional functionality to achieve space diversity gain. One of the key issues in cooperative communication using RSs is to determine which RSs should be used as cooperative nodes, i.e., cooperative relay selection. In this paper, we investigate the conditions that should be tested for RSs to operate as cooperative nodes based on the signal intensity data. We also propose two cooperative RS selection schemes for determining a group of cooperative RSs out of all candidate RSs: max-min-max cooperative RS selection and joint cooperative RS-path selection. The first scheme selects a group of RSs with the highest diversity gain, whereas the second scheme selects the cooperative RSs and paths simultaneously that could yield the highest system throughput. Simulation results are presented to evaluate and compare the performance of the two schemes.

This paper presents a seamless handover scheme for the IEEE WAVE (Wireless Access for Vehicular Environment) networks based on proactive caching of data packets. In the proposed scheme an On-broad Unit (OBU) uses the IEEE 802.11 disassociation message to inform the old Road-Side Unit (RSU) about its departure from the coverage area such that the old RSU can forward the buffered packets to candidate RSUs for caching. A multicast-based forwarding scheme is used to forward the buffered packets when there are multiple candidate new RSUs around crossroads or diverging roadways. One of the candidate RSUs becomes the new RSU which transmits the cached packets to the OBU upon its entry into the radio coverage. The IEEE 802.11f Move-notify message is used by the new RSU to request the rest of candidate RSUs to purge the cached packets in order to prevent the waste of radio resource. Simulation results show the proposed scheme outperforms a simple multicast-based scheme.

This paper presents general software optimization techniques to improve software performance and energy consumption in embedded systems. Software optimization can be categorized into three levels: algorithmic, source code-level. Then these techniques are applied to optimize our tactical message processing software, which is a message encoder-decoder for tactical communication equipped on weapon systems. The optimized software achieved performance increase of about 12%, memory access decrease of 72% and memory usage decrease of 35% over the original software.

The ad-hoc network is a collection of wireless mobile nodes without any support of a stationary infrastructure. Due to the node's mobility and the network topology changes to be kinetic, the network disconnection occur frequently. This paper proposes a variation of the AODV protocol, which selects CORE nodes using path's accumulation information, and then establishes multi paths based on CORE-node's information. When network is disconnected, our proposed protocol saves path reset time and reduces the reset control messages by using the information held by the CORE-node.

The cooperative communication makes wireless transmission reliable utilizing special diversity, where the relay selection is one of important issues. In this paper, we propose a relay selection scheme exploiting SNR and success probability of the link between nodes in network, especially focus in the link between the source and the relay. Proposed scheme is compared with previous schemes by the simulation. The simulation results show that our scheme perform better than other schemes in terms of BER and throughput.

The IEEE 802.11p-based wireless access networks are about to be deployed by major highways around the world as one of the main information hauling infrastructure for ITS safety applications. As the most applications of the IEEE 802.11p standard require the delivery of short text-based messages, the standard does not support handover between adjacent Road-side Units (RSUs). However, demand for seamless real-time services such as short video clips of CCTVs on a highway gives rise to support for handover in the IEE 802.11p-based wireless access systems. In this paper, we describe a seamless handover scheme for an IEEE 802.11p-based wireless access system that takes advantage of the fixed-order placement of the RSUs and unidirectional movement of the vehicles along the highways. More specifically, this handover scheme utilizes the IEEE 802.11 disassociation message as to signal the old RSU of an On-broad Unit's (OBU) departure from its coverage area. The subsequent downstream data frames can be proactively forwarded to the new RSU for delivery to the OBU after its link establishment with the new RSU. Simulation results show superior performance of the proposed scheme compared to a poll-based scheme.

As an emerging technology, wireless mesh networks are making significant progress in the area of wireless networks in recent years. However, the nature of sharing transmission medium makes it challenging to fully exploit these networks. In an attempt to improve the radio resource utilization, several routing metrics have been specifically designed for wireless mesh networks. However none of these routing metrics efficiently tackles interference issues. In this paper, we propose a routing metric for wireless mesh networks, which takes account of the amount of interference by considering the traffic situation of adjacent nodes and selects less interfered path for transmission. The aim of this metric is to route the traffic through interference areas and balance the load amongst the network nodes. Simulation results show that the proposed routing metric reduces the end-to-end delay when compared to the MIC, ETT and hop-count routing metrics.

To create constantly evolving software, the upgrading is an essential factor. There are two ways to upgrade, pushing and polling. Polling has the advantage of keeping the latest versions of all the clients, but can cause heavy server load by simultaneously connections to many clients and unnecessary network traffics. On the other hand, push causes much less because push can upgrade the specific clients, but there is cumbersome monitoring to keep stopped clients on latest version. The Half-Push/Half-Polling pattern mixes these two different ways, keeping their advantages, eliminating their disadvantages.

In the VANET, where the duration of communication is extremely short, the large amount of control overheads associated with discovering and maintaining end-to-end path information may not be tolerable. This paper presents a new multi-hop forwarding protocol which does not use explicit path information, but instead, uses reachability information towards the destinations in determining next-hop nodes. The reachability information for a particular node merely indicates that the node is reachable. At each hop, one of the neighbor nodes which hold the reachability information towards the same destination is selected as the next-hop node by contention based on some priority values. The proposed protocol is designed to be integrated with the IEEE 802.11 MAC protocol in order to achieve higher efficiency and accuracy in its time-critical operations. It is shown through simulations that the proposed protocol outperforms the AODV in a realistic the VANET scenario in terms of both the end-to-end delay and packet delivery ratio.

With the fast proliferation of mobile Internet, the wireless community has been increasingly looking for a framework that can provide seamless mobility. In this paper, we propose a fast cross-layer handover scheme based on movement prediction in mobile WiMAX environment. Prediction is achieved by linear regression model with keeping track of the signal strength of mobile users. With the help of the prediction, layer-3 handover activities are able to occur prior to layer-2 handover, and therefore, total handover latency can be reduced. The experiments conducted with system parameters and propagation model defined by WiMAX Forum demonstrate that the proposed method predicts the future signal level accurately and reduces the total handover latency.

Although the Distributed Coordination Function is the fundamental access protocol of IEEE 802.11, it cannot meet the quality of service (QoS) requirements in general. So, the Point Coordinate Function is provided to support QoS related services. However, it has inherent problems. Access point (AP) has no knowledge of the queue status and instantaneous channel condition of stations in the system. In this paper we propose an efficient and versatile polling scheduler that shows excel-lent throughput and fairness performance. Comparison with well known polling schemes is provided through computer simulation under various channel situations including error prone environments.

Conventional topology-based routing protocols such as AODV, DSR and ZRP are not suitable for highly mobile ad hoc network, where frequent route re-establishment may cause high end-to-end delay and packet loss. This paper presents a new ad hoc routing protocol called the multi-hop MAC forwarding protocol (MMFP). The MMFP avoids explicit path setup in order to reduce the control overhead associated with it, but instead uses the reachability information towards the destination at each hop. Next-hop nodes are determined on-the-fly by contention based on a priority value. The basic operations of the MMFP are conceptually similar to that of MAC bridges and position-based ad-hoc routing protocols. The MMFP is designed to be integrated with the IEEE 802.11 MAC protocol in order to achieve higher efficiency and accuracy in its time-critical operations. Simulation results show that the MMFP outperforms the AODV in a practical ad hoc network scenario in terms of both the end-to-end delay and packet delivery ratio.

Conventional topology-based routing protocols such as AODV, DSR and ZRP are not suitable for inter-vehicular communication, where the duration of communication lasts extremely shortly. This paper presents a new inter-vehicular communication protocol called the Multi-hop MAC Forwarding Protocol (MMFP). The MMFP avoids explicit path setup in order to reduce the control overhead associated with it, but instead uses the reachability information towards the destination at each hop. Next-hop nodes are determined on-the-fly by contention based on a priority value. The basic operations of the MMFP are conceptually similar to that of MAC bridges and position-based ad-hoc routing protocols. The MMFP is designed to be integrated with the IEEE 802.11 MAC protocol in order to achieve higher efficiency and accuracy in its time-critical operations. It is shown through simulations that the MMFP outperforms the AODV in a realistic inter-vehicular communication scenario in terms of both the end-to-end delay and packet delivery ratio.

Self-organizing hierarchical ad hoc network (SOHAN) is a new network architecture that has been proposed to increase the scalability property of flat ad hoc networks. This paper describes how SOHAN interoperates efficiently with the Internet based on IPv6. Procedures for the autoconfiguration of a globally-routable address, routing and gateway discovery are presented. The amount of control overheads is reduced by taking advantage of cross-layer interaction and limited-scope broadcast (LSBC) techniques. Simulation results display SOHAN with the proposed interworking procedures outperforms conventional flat ad hoc networks in interworking with the Internet in terms of throughput capacity and scalability.

The IEEE 802.16e WMAN (Wireless Metropolitan Area Networks), which has been designed for fixed or mobile broadband wireless access, is getting into the spotlight as the base technology for the mobile Internet As most mobile stations are battery-powered in wireless environment, energy efficient protocols are essential for their practical use Although many systems, including the IEEE 802.16e, adopt the sleep mode, little attention has been paid to the traffic characteristics or status of the mobile station In this paper, we propose a new scheme called Cumulative-TIM, in which BS(base station) does not wake up a mobile station until a sufficient amount of data for the station is stored, thus guaranteeing mobile stations sleep enough amount of time In this way, mobile stations can use their energy more efficiently than the standard sleep mode: Our simulation result shows that proposed scheme has a better performance compare with the current standard of the WMAN.

Self-organizing hierarchical ad hoc network (SOHAN) is a new ad-hoc network architecture designed to improve the scalability properties of conventional “flat” ad hoc networks. This network architecture consists of three tiers of ad-hoc nodes, i.e., access points, forwarding nodes and mobile nodes. This paper presents a joint topology discovery and routing protocol for the self-organization of SOHAN. We propose a cross-layer path metric based on link quality and MAC delay which plays a key role in producing an optimal cluster-based hierarchical topology with high throughput capacity. The topology discovery protocol provides the basis for routing which takes place in layer 2.5 using MAC addresses. The routing protocol is based on AODV with appropriate modifications to take advantage of the hierarchical topology and interact with the discovery protocol. Simulation results are presented which show the improved performance as well as scalability properties of SOHAN in terms of throughput capacity, end-to-end delay, packet delivery ratio and control overhead.

Simulcast Technique can be used to diminish handoff rate and share resources among multiple relays in MMR system. Using dynamic grouping, simulcast technique can also rearrange traffic load. In this paper, we analyze group handoff generated by dynamic grouping in MMR system. Performance is evaluated in view of blocking and handoff call dropping probability.

Packet losses are bursty in nature since the dominant reason is temporary overload situations in the shared resources over networks. To increase the effectiveness of forward error correction (FEC) schemes, adaptive FEC schemes have been suggested, where the amount of redundancy is controlled according to current network status. In this paper, we propose a gap- based adaptive FEC scheme, which is motivated by the Markov gap model for packet losses, and show that the gap-based adaptive FEC scheme performs better than the adaptive FEC scheme based on the Gilbert model.

Several Bluetooth piconets can be interconnected using an inter-piconet unit called a bridge node to form a Bluetooth scatternet. The bridge node can make its presence in each piconet on a time division basis by switching its frequency hopping sequence. Without a careful coordination among nodes, piconet switching can result in conflicts and idle time in communication, which impact the throughput of the entire scatternet. In this paper we present an efficient inter-piconet scheduling scheme called LSRR (Limited Sniff Round Robin). LSRR is a locally coordinated scheduling scheme that assigns presence points in round robin fashion among different piconets. LSRR uses the sniff mode as the inter-piconet switching mechanism and dynamically adjusts the duration of communication events based on the past history of transmissions. Simulation results show LSRR outperforms the pure round robin scheme in terms of throughput and delay.

The communication network is in a transition toward the NGN (Next Generation Networks), which can support both of voice and data at the same time, according to the explosive demand of new services. The NGN allows the third-party application provisioning by defining the networks as layers of Services, Distributed Processing Environment and Transport. The Service layer can further be divided into Application and Service Component layer. In order to realize the third-party application provisioning, the Parlay Group has adopted an open Parlay API approach as an interface between the Application and the Service Component layer. Using Parlay API, the third parties may build and deploy the new applications at the Application layer exploiting the service components within network operators’ domain. In this paper, we presents the implementation details about the two-party call setup and release using the third party service logic based on Parlay API Rel. 3.0., where SIP is used as a signaling protocol in Transport layer.

Traditional neural network training techniques do not work well on problems with many discontinuities, such as those that arise in multicomputer communication cost modeling. We develop a new algorithm to solve this problem. This algorithm incrementally adds modules to the network, successively expanding the 'window' in the data space where the current module works well. The need for a new module is automatically recognized by the system. This algorithm performs very well on problems with many discontinuities, and requires fewer computations than traditional backpropagation. >