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There are many kinds of image processing application in the industry, to improve better performance of producing, Automatic Guide vehicles (AGV) solution have been driven in service, for instance, the expensive solution such as light detection and ranging (LIDAR), magnetic tape guided and RFID are used. In the industry which not only search for better delivery performance but also search for economic efficiency. Here we present an economic efficiency solution, Easy i-Move for AGVs guiding system to fulfill customers’ necessity. In this study, we focus on color tape image recognition technology based on HSI color model. The implementation of the system architecture and the technology of image recognition in the proposed system are described and validated in this paper.

Indoor positioning systems based on wireless local area networks are growing rapidly in importance and gaining commercial interest. Pedestrian dead reckoning (PDR) systems, which rely on inertial sensors, such as accelerometers, gyroscopes, or even magnetometers to estimate users' movement, have also been widely adopted for real-time indoor pedestrian location tracking. Since both kinds of systems have their own advantages and disadvantages, a maximum likelihood-based fusion algorithm that integrates a typical Wi-Fi indoor positioning system with a PDR system is proposed in this paper. The strength of the PDR system should eliminate the weakness of the Wi-Fi positioning system and vice versa. The intelligent fusion algorithm can retrieve the initial user location and moving direction information without requiring any user intervention. Experimental results show that the proposed positioning system has better positioning accuracy than the PDR system or Wi-Fi positioning system alone.

Building context-aware services in pervasive computing environments have enabled the wide development of wireless local area network-based indoor positioning systems. In fingerprint localization, radio frequency (RF) signal strengths from access points (APs) are annotated with location labels to build the map of RF fingerprints. However, the newly received signal strength (RSS) variation due to device heterogeneity, which may cause RSS pattern mismatch, could jeopardize positioning accuracy. Solutions based on extra manual calibrations of RSSs for new, individual devices could address the problem. However, they are laborious and unpractical for real-world deployment. In this paper, an indoor positioning algorithm that utilizes two homogeneous features of different devices is proposed to solve the problem of device heterogeneity in fingerprint localization. The features of RSS order and linear dependency between RSSs measured by different devices are extensively investigated. The experimental results show that the proposed positioning algorithm solves the device heterogeneity problem without requiring extra manual calibration for diverse devices.

Nowadays, Intelligent Transportation Systems (ITS) technologies are exploring a wide range of services such as freeway management, crash prevention & safety, driver assistance, and infotainment of drivers and/or passengers. In this paper, an agile urban parking recommendation service for vehicular intelligent guiding system is designed to facilitate city citizens with fully efficient, real-time and precise parking lot guiding suggestions for the sustainability of the future green city. The system offers drivers a friendly parking lot recommendation sequence and saves driver's time circling around by the accurate prediction of the successful parking probability in each parking lot. The proposed cost model constructs an optimal recommendation sequence considering successful parking probability and time to reach the parking lot. Through the collection and analysis of realistic records from parking lots in Taipei city, a prediction algorithm is developed to estimate the successful parking probability by using current available space counts. Extensive experiments are conducted to demonstrate the effectiveness of the prediction algorithm.

Vehicular ad hoc networks (VANETs) provide the communication framework for the dissemination of safety-critical messages such as beacons and emergency messages. The communication channel witnesses significant network load generated by frequently exchanged beacons. Under high-density situations, it leads to a serious scalability problem in VANETs. Moreover, contention-based medium access control (MAC) protocols suffer from a great number of packet collisions, and as a result, the reliability and latency of safety messages are severely affected. Because of the periodic nature of beacons, time-division multiple access (TDMA) can be a good choice over contention-based MAC. In this paper, we propose congestion-controlled-coordinator-based MAC (CCC-MAC), which is a time-slot-based medium access protocol that addresses beacons and emergency messages. Basically, the network is virtually partitioned into a number of segments. Within a segment, medium access is accomplished by using a time-slot-scheduling mechanism supervised by a local coordinator vehicle. A significant number of vehicles can be supported under the proposed configuration. In fact, the proposed scheduling mitigates channel congestion by reducing the transmission time of beacons through the use of multiple data rates. Bandwidth utilization is also improved by reusing the unoccupied time slots. Finally, CCC-MAC ensures fast and reliable propagation of emergency messages by employing a pulse-based reservation mechanism. In the simulations, we demonstrate the ability of CCC-MAC to scale well in different vehicular density scenarios. Moreover, it outperforms existing MAC-layer protocols with respect to packet reception probability and latency of safety messages.

In a distributed system, a portion of nodes are more critical than others, and named them articulation points, all paths between certain nodes have to pass through these points. Most of previous works try to detect the articulation point problem in static networks such as wireless sensor networks, P2P networks. In dynamic networks, as group moving behavior, it is a challenge to detect articulation points because these nodes are moving with time. Group moving in this paper means that a group of mobile members move from one place to another place with different directions and speeds. We aim to propose a distributed LDFS algorithm to check the articulation points in dynamic networks, such as a moving group. The algorithm sets the number of hops for traversing and multiple initiators to reduce message overhead and improve the accuracy rate. In simulations, we design several schemes to compare message overhead, and correctness. Simulation results show that our scheme is better than GlobalDFS and CUD scheme. The scheme could be applied on different applications and is efficient helping us to save and alarm loss on group moving.

Localization is a key issue in wireless sensor networks. The geographical location of sensors is important information that is required in sensor network operations such as target detection, monitoring, and rescue. These methods are classified into two categories, namely range-based and range-free. Range-based localizations achieve high location accuracy by using specific hardware or using absolute received signal strength indicator (RSSI) values, whereas range-free approaches obtain location estimates with lower accuracy. Because of the hardware and energy constraints in sensor networks, RSSI offers a convenient method to find the position of sensor nodes. However, in the presence of channel noise, fading, and attenuation, it is not possible to estimate the actual location. In this paper, we propose an RSSI-based localization scheme that considers the trend of RSSI values obtained from beacons to estimate the position of sensor nodes. Through applying polynomial modeling on the relationship between received RSSI and distance, we are able to locate the maximum RSSI point on the anchor trajectory. Using two such trajectories, the sensor position can be determined by calculating the intersection point of perpendiculars passing through the maximum RSSI point on each trajectory. In addition, we devised schemes to improve the localization method to perform under a variety of cases such as single trajectory, unavailability of RSSI trends, and so. The advantage of our scheme is that it does not rely on absolute RSSI values and hence, can be applied in dynamic environments. In simulations, we demonstrate that the proposed localization scheme achieves higher location accuracy compared with existing localization approaches.

Using advanced wireless local area network technologies, vehicular ad hoc networks (VANETs) have become viable and valuable for their wide variety of novel applications, such as road safety, multimedia content sharing, commerce on wheels, etc. Multihop information dissemination in VANETs is constrained by the high mobility of vehicles and the frequent disconnections. Currently, geographic routing protocols are widely adopted for VANETs as they do not require route construction and route maintenance phases. Again, with connectivity awareness, they perform well in terms of reliable delivery. To obtain destination position, some protocols use flooding, which can be detrimental in city environments. Further, in the case of sparse and void regions, frequent use of the recovery strategy elevates hop count. Some geographic routing protocols adopt the minimum weighted algorithm based on distance or connectivity to select intermediate intersections. However, the shortest path or the path with higher connectivity may include numerous intermediate intersections. As a result, these protocols yield routing paths with higher hop count. In this paper, we propose a hop greedy routing scheme that yields a routing path with the minimum number of intermediate intersection nodes while taking connectivity into consideration. Moreover, we introduce back-bone nodes that play a key role in providing connectivity status around an intersection. Apart from this, by tracking the movement of source as well as destination, the back-bone nodes enable a packet to be forwarded in the changed direction. Simulation results signify the benefits of the proposed routing strategy in terms of high packet delivery ratio and shorter end-to-end delay.

The problem of correlated data gathering in wireless sensor networks is studied in this paper. For the sake of efficiency, tree transmission structures are often used for data gathering. Previously, the problem of minimizing the total communication cost with a single-tree transmission structure was shown to be NP-hard. However, when the explicit communication approach is used, the total communication cost can be further reduced, provided a double-tree transmission structure is used and inverse links are allowed. This motivates us to devise a double-tree routing scheme in which two trees are used for data transmission, one carrying raw data and the other carrying encoded data. We show that with the double-tree routing scheme, the problem of minimizing the total communication cost remains NP-hard. A distributed algorithm for solving it is suggested. We show that under the simple correlation model, the algorithm has an approximation ratio of two. Extensive simulations are conducted to verify the effectiveness of the double-tree routing scheme.

Vehicular ad hoc networks (VANETs) have recently been considered as an attractive network architecture to provide various services ranging from road safety to entertainment applications. In this paper, we propose an IEEE-802.11-based multihop broadcast protocol to address the issue of emergency message dissemination in VANETs. The protocol adopts a binary-partition-based approach to repetitively divide the area inside the transmission range to obtain the furthest possible segment. The forwarding duty is then delegated to a vehicle chosen in that segment. Aside from accomplishing directional broadcast for highway scenario, the protocol also exhibits good adaptation to complex road structures. The main focus of the paper lies in reducing broadcast delay, which is an important factor for time-critical safety applications. Most importantly, the contention delay remains almost constant, irrespective of vehicle density. Mathematical analysis is performed to assess the effectiveness of the protocol. Simulation results demonstrate that the proposed protocol imparts greater performance in terms of latency and message progress when compared with contemporary multihop broadcast protocols for VANETs.

The emerging adoption of wireless communications on surface transportation systems has generated extensive interest among researchers over the last several years. Innovative inter-vehicular communications and vehicle-to-infrastructure communications achieve road traffic safety, ecstatic driving and delightful travelling experiences. Multi-hop information dissemination in vehicular ad hoc networks is challenged by high mobility and frequent disconnections of wireless nodes. This paper presents a new routing scheme for Highway/Freeway VANETs, which consists of a unicast destination discovery process, a robust forward node selection mechanism and a positional hello mechanism. In this paper, no dedicated path is framed in order to prevent frequent path maintenance. In addition, the avoidance of flooding and location services substantially reduces the control overhead. Positional hello scheme ensures connectivity and diminishes control overhead concurrently. Simulation results signify the benefits of the proposed routing strategy (i.e. DDOR) has higher packet delivery ratio, reduced routing overhead and shorter delay compared with previous works.

To leverage the scalability limits of traditional routing/multicasting for mobile ad hoc networks, a typical approach adopts two-tier architectures by selecting a fraction of the network hosts as backbone hosts (BHs). BHs are responsible for managing the architectures and performing routing/multicasting; thus, the proper way of selecting BHs is crucial to two-tier architectures. Once a host with low stability (i.e., high mobility) to the neighborhood hosts is selected as a BH, the architecture may become fragile, and the performance may dramatically decline. In this paper, a distinct strategy is proposed to select stable BHs. The global positioning system (GPS) is used to estimate the amount of remaining connection time for two neighboring hosts, and with its aid, stable BHs with longer remaining connection time to the other hosts are selected. In addition, a new multicast protocol is proposed based on the selected stable BHs to select stable multicast routes. A stable route is a route that is available for a longer time. Simulation results show that the proposed protocol has shorter transmission latency, shorter more stable multicast routes, lower overhead, more stable attachment of multicast members to BHs, and higher receiving data packet ratios than other existing two-tier multicast protocols.

In 802.11-based wireless local area networks (WLANs), it is difficult to simultaneously attain both high throughput and fairness for multirate traffic. There is a performance anomaly when there are stations whose data rates are much lower than the other stations, in which the aggregate throughput of the high-rate stations drastically degrades. The problem of maximizing the total throughput while maintaining time fairness among the competing stations was studied previously by the same authors. However, our previous solution sacrificed the throughput of low-rate stations. In this paper, we extend our previous work by solving the same optimization problem while maintaining both time fairness and throughput fairness. The optimization problem is formulated as a mixed-integer nonlinear programming problem. The two fairness constraints are maintained by means of changing the channel access probability and transmission time among the competing stations, which can be realized by adjusting their minimum contention window sizes and medium access control (MAC) frame sizes, respectively. A penalty function accompanied with a gradient-based approach is used to solve the problem, and its effectiveness is verified by computational experiments. The proposed solution is also compared with our previous solution in terms of convergence speed and total throughput.

Purpose – Emerging real‐time multimedia services over IP have penetrated into the daily lives of normal people with the advent of advanced broadband communications and innovated interconnection technologies. To protect shared Internet from unfairness and further congestion collapse, rate control plays a crucial role for many multimedia services such as streaming applications. Streaming applications such as video on demand (VoD) or voice over IP (VoIP) services face some critical problems such as insufficient bandwidth and improper performance of transmission protocols. Besides, the new generation networks are anticipated to integrate all heterogeneous wired and wireless networks and offer seamless customized multimedia services anywhere, anytime. However, wireless networks usually with low and variable bandwidth, and non‐congestion related loss do bring the challenge to the existing transport protocol, such as TCP, TFRC etc.Design/methodology/approach – The paper uses simulations and compares other method...

The bandwidth-constrained routing problem (BCRP) asks for a route that has sufficient bandwidth for data transmission. When BCRP is defined for wired networks, it can be solved in polynomial time. On the other hand, when it is defined for wireless ad hoc networks, it is NP-complete if the underlying MAC protocol is TDMA-based or CDMA-over-TDMA-based. In this paper, we show that BCRP is still NP-complete, even if CSMA-based or contention-based CDMA MAC prot.ocols are used. Besides, we show that BCRP is polynomial-time solvable if the channel model is collision-free and the scheduling policy is FIFO. In wireless ad hoc networks, no MAC protocol was designed before, which would lead to a polynomial-time solution to BCRP. The results of this paper suggest a design for MAC protocols that can support QoS routing well.

The importance of location prediction is rapidly increasing with the current trend of database applications in mobile computing environment. However, current personal communication services network could only provide currently maintained location information of non-idle mobile terminals. Pertinent researches predict the future location based on tangent velocity approaches, which require mobile terminals to spend lots of precious electronic power to sense and then measure a sequence of positions for predicting the future tangent velocity, and the prediction is effective only within a short range of time. In this study, we propose an approach to predict future locations of mobile terminals based on the moving behaviors mined from their long-term moving history. Location prediction based on moving behavior requires no power consumption for position measurement, and the prediction results are effective for a long time without requiring the queried clients to be non-idle. With the help of moving behavior, we propose several location prediction operators for location query. Finally, we demonstrate the accuracy of the location query operators through simulation statistics. The experimental results show that the predictions are accurate enough for regular moving mobile terminals.

IEEE 802.15.3, an emerging wireless technology, was designed to provide high-quality multimedia services at home. Dynamic bandwidth allocation for a multimedia connection should be considered in order to achieve higher channel utilization, less buffer and less delay, especially for variable bit rate (VBR) multimedia connections. For real-time VBR videos, the bandwidth requirement should be predicted adaptively for effective channel-time requests. Previously, the adaptive least-mean square (LMS) algorithm with fixed step size was applied to predict channel time requirements due to its simplicity and relatively good performance. However, the performance might degrade when scene changes occurred. In this paper, we modify the variable step-size LMS algorithm and apply it as our predictor (VSSNLMS) so that the prediction errors on scene changes can be effectively reduced. Using the prediction results of VSSNLMS, we propose a dynamic bandwidth-allocation scheme that is scene-change aware and can guarantee the delay bound of real-time VBR videos. Simulation results show that the VSSNLMS predictor is superior to previous LMS-type predictors in performance, and the proposed scheme has better performance in channel utilization, buffer usage, and packet loss

Background In recent years, the population structure in Taiwan has changed so dramatically. Based on concerns of social welfare issues, Taiwanese government began to seek principles for assessment of disability. After seven years of carefully evaluation, the World Health Organization’s International Classification of Functioning, Disability, and Health (Abbreviated to ICF) is officially adopted as Taiwan’s assessment standard while most of the assessment procedures of ICF are sophisticated, and time consuming. In this paper, we propose a sensor based decision supporting system for ICF. Our prototype system aims to reduce the burden of medical staffs, and to assist subjects to perform the assessments. Methods This paper integrate multiple devices including ASUS XtionTM, temperature/acceleration/gyro sensors on Arduino, and Zigbee to measure the mobility of limbs and joints. The subject’s log of assessments is then recorded in the database so that the medical staffs can remote-monitor the co ndition of subjects immediately, and analyze the results later. Additionally, in our system, a user-friendly interface is implemented for the detection of dementia. Results In this paper, three experiments have been conducted for different purpose. The experiment was conducted to compare the variation between thermometer and our device. Moreover, we invited 20 elders aged for 65 to 80 to use our system and all of them gave positive feedback. Two elders were invited to perform full assessment for dementia and the results show that both of them didn’t have sign of dementia. Also, the assessment of joint movement was performed by a 67 year-old elder and the result shows that the elder had well physical function and could take care of daily life. Conclusions The proposed system has potential for aiding users to perform the ICF testing better and provide benefits to medical staffs and society. With current technology, integration between sensor network systems and artificial intelligence approaches will more and more important. We develop a simple interface for user to manipulate and perform the ICF assessment. In addition, the early detection of dementia likely has the potential to provide patients with an increased level of precaution, which may improve quality of life.

Recent advances in pervasive computing and wireless technologies have enabled novel multicast services anywhere, anytime, such as mobile auctions, advertisement, and e-coupons. Routing/multicast protocols in large-scale ad-hoc networks adopt two-tier infrastructures to accommodate the effectiveness of the flooding scheme and the efficiency of the tree-based scheme. In these protocols, hosts with a maximal number of neighbors are chosen as backbone hosts (BHs) to forward packets. Most likely, these BHs will be traffic concentrations or bottlenecks of the network and spend significant amount of time forwarding packets. In this paper, a distinct strategy is proposed for constructing a two-tier infrastructure in a large-scale ad-hoc network. Hosts with a minimal number of hops to the other hosts rather than those with a maximal number of neighbors will be adopted as BHs in order to obtain shorter multicast routes. The problem of determining BHs can be formulated with linear programming. BHs thus found have the advantages of shorter relay and less concentration. Besides, BHs are selected on-demand and can be globally reused for different multicast groups without flooding again. Simulation results show that the proposed protocol has shorter transmission latency, fewer control/data packets and higher receiving data packet ratios than other existing multicast protocols. Besides, the two-tier infrastructure constructed by the proposed protocol is more stable.

Adequate bandwidth allocations and strict delay requirements are required for real time flows, such as streaming audio and video data. Most of commonly known packet scheduling algorithms like Weighted Fair Queueing (WFQ) and Start-Time Fair Queueing (SFQ) were mainly designed to ensure the bandwidth reservation function. They only guarantee the queueing delay under a certain threshold. It may cause unsteady packet latencies and introduces extra handling overheads for streaming applications. A few packet scheduling algorithms were proposed in recent years to address this problem like Low Latency Queueing (LLQ) which may suffer from low priority traffic starvation problem. In this paper, we will show the unsteady queueing delay problem, 'The buffer underrun problem' for most well known packet scheduling algorithms. We propose a novel packet scheduling algorithm with history support, LLEPS, to ensure low latency and efficient packet scheduling for streaming applications via monitoring the behavior of queues and traffics.

Driven by the growing number of the mobile subscribers, efficient channel resource management plays a key role for provisioning multimedia service in the next generation personal communication systems. To reuse limited channel resources, diminishing the coverage areas of cells seems to be the ultimate solution. Thus, however, causes more handover events. To provide seamless connection environment for mobile terminals and applications, this article presents a novel handover scheme called the intelligent channel reservation (ICR) scheme, which exploits the location prediction technologies to accurately reserve channel resources for handover connections. Considering the fact that each mobile terminal has its individual mobility characteristic, the ICR scheme utilizes a channel reserving notification procedure (CRNP) to collect adequate parameters for predicting the future location of individual mobile terminals. These parameters will be utilized by the handover prediction function to estimate the expected handover blocking rate and the expected number of idle channels. Based on the handover prediction estimations, a cost function for calculating the damages from blocking the handover connections and idling channel resources, and a corresponding algorithm for minimizing the cost function are proposed. In addition, a guard channel decision maker (GCDM) determines the appropriate number of guard channels. The experimental results show that the ICR scheme does reduce the handover-blocking rate while keeping the number of idle channels small.

Due to insufficient available bandwidth resources and the continuously growing demand for cellular communication services, the channel assignment problem has become increasingly important. To trace the optimal assignment, several heuristic strategies have been proposed. So far, most of them focus on the small-scale systems containing no more than 25 cells and they use an anachronistic cost model, which does not satisfy the requirements of most existing cellular operators, to measure the solution quality. Solving the small-scale channel assignment problems could not be applied into existing large scale cellular networks' practice. This article proposes a decomposition approach to solve the fixed channel assignment problem (FCAP) for large-scale cellular networks through partitioning the whole cellular network into several smaller sub-networks and then designing a sequential branch-and-bound algorithm that is made to solve the FCAP for them sequentially. The key issue of partition is to minimize the dependences of the sub-networks so that the proposed heuristics for solving smaller problems will suffer fewer constraints in searching for better assignments. The proposed algorithms perform well based on experimental results and they were applied to the Taiwan Cellular Cooperation (TCC) in ChungLi city to find better assignments for its network.

We propose a concept allowing disabled patient taking their rehabilitation treatment without going to the hospital. We design a portable device of rehabilitation and it can be lightweight in an advanced version. Particularly, we select PhoneGap to be a mobile development framework and to build the specific application for mobile devices using JavaScript, HTML5, and CSS3 instead of using device-specific language in our system. The great advantage is cross-platform that represent write once and run anywhere. In our software, we lead the patient to do the exercise of rehabilitation step-by-step and then store recovery status in database. Finally, the system will play restful music when patient do exercise. According to the mentioned above, we developed the Mobility Rehabilitation that combines mobility, entertainment, and storing ability.

In recent years, several kinds of wireless network have been widely deployed. In this work, we focus on the e-bus-system for movements of buses. Passengers can get the bus information through the intelligent bus stop when they are waiting for the bus. In today’s environment of Taiwan, the transportation information is provided through some specific Mobile network operators. In this case, it costs a huge expenditure every month for the charge of data transmission. Therefore, we propose a new network system with Digital Mobile Radio (DMR) and Super Wi-Fi to replace the mobile network operator. Furthermore, when the catastrophe happened, the proposed system can also change to be used for the rescues. The implementation of the system architecture, the application of DMR and super WiFi in the proposed system, and the operation scenario are described in this paper.

Our team proposes a concept allowing patients taking health check anytime everywhere, which can increase patients’ attention to their own health condition. To improve the user experience and convenience, the system must be designed to simply operate and easily connect with the medical devices. Moreover, the system must have the ability to communicate between the patients and doctor or medical personnel. In this paper, we illustrate our system, such as user interface, storage, display and cloud system. The user interface is designed with standards-based Web technologies. We use PhoneGap to build cross-platform mobile apps with HTML, JavaScript, and CSS. Because patients need to keep their record of health check, we use SQLite database for storage. Moreover, for the patients’ health check report which shall be easily understood, we design line charts to display the data. In this paper, we implement the Personal Health Assistant system.

Since mobile hosts suffer from burst and location-dependent channel errors in wireless networks, packet fair queueing algorithm in wireline networks cannot be applied directly to wireless networks. Generally, a fair scheduler in a wireless network retains the virtual time of flow when the flow encounters channel errors. This results to the flow having higher priority when it exits from errors, and the system can compensate the lost service for the flow. This causes the lagging flows to capture the shared channel and affects the queueing delay of flows perceiving a clean channel. In this paper, we present a channel condition self-clocked packet scheduling scheme. This algorithm can address the problem and achieve the following goals: (1) steady delay and jitter for flows perceiving an error-free environment, (2) delay and throughput guarantees in an error-free environment, (3) short-term fairness among flows perceiving an error-free environment, and (4) long-term fairness for error system. Our algorithm is based on start-time fair queueing, and the virtual time of flows is reset to contend for forwarding its packet the next time when errors happen for the flow.

Maintaining connectivity among nodes is one of the critical issues for reliable communications in wireless sensor networks. Unfortunately, the mobility and failure of nodes in wireless sensor networks (WSNs) have made this issue complicated and challenging. To prevent the network from partitioning, prior works focused on identifying articulation points (AP) in a WSN. However, these approaches either produce low AP identification accuracy or introduce expensive communications overhead. In this paper, we propose a novel algorithm, namely, APs collaborative exploration (ACE). The basic idea of ACE is for nodes to identify the loops by locally broadcasting the exploration packets. By examining the exploration packets, each node can efficiently and accurately identify if it is an AP without much communications overhead. Simulation results using both real and synthesized data sets illustrate that ACE not only achieves a high AP identification accuracy comparable with the state of the arts but only incurs a significant 50% lower communication overhead. Consequently, the proposed ACE is energy-efficient and saves up to 160% of energy compared with existing schemes.

EIMS is a stable and safe communication system. It integrates the communication of citizen patrols and police units. When unexpected emergency happens, the system can enhance the citizen patrols' communications capabilities, decrease the time in communication and response, and reduce the loss of life and property. There are five citizen patrols implemented EIMS in northern Taiwan. They have enhanced the capacity of community citizen patrols. And, there are more than 1,500 residents to enjoy the efficient of its system.

The number of real-time applications are growing dramatically at an unprecedented rate. Efficient bandwidth allocations and strict delay requirements are indispensable for real-time flows such as audio streaming. Unfortunately, most of the well-known packet scheduling algorithms like Weighted Fair Queueing (WFQ) and Start-time Fair Queueing (SFQ) can not guarantee low and stable latencies for real-time flows due to the ‘unsteady queueing delay problem’ that we will explain later. Only a few scheduling algorithms address this problem in recent years like Low Latency Queueing (LLQ) and Low Latency and Efficient Packet Scheduling algorithm (LLEPS). However, LLQ has unfair and starvation problems. The queueing delay of LLEPS is not steady enough in existing networks. Thus, in this paper, we propose a novel credit-based low latency packet scheduling algorithm (CBLLPS) that is well-suited for real-time applications. The performance of CBLLPS is validated by ns-2 simulations. The simulation results show that CBLLPS guarantees low and steady queueing delay for real-time flows and outperforms any of the existing scheduling algorithms in terms of queueing delay. Moreover, the functionalities of bandwidth sharing and bandwidth reservation of this new scheduling mechanism are still preserved.

The fingerprint-based techniques are commonly used for indoor location estimation, in which a radio map is built by calibrating signal-strength values at several training locations in the offline phase. However, the signal-strength values change as the environment changes, and hence the radio map built may be out of date. Further, the recalibration of signal-strength values for each environment change is laborious and time consuming. Therefore, in this paper, an efficient radio map management method is proposed in response to the environment changes. We first demonstrate that different features of signal propagation are obtained in different regions of the indoor environment. According to the different features of signal propagation, the environment is divided into several regions and the signal-strength values collected at the training locations in different regions can be updated accurately and individually using proper propagation features. The experimental results show the usefulness of the proposed method and the accuracy of the localization can be improved.

TCP-Friendly Rate Control (TFRC) has been widely adopted for advanced streaming applications over wired-wireless networks. TFRC applies an equation-based rate control scheme to provide smooth sending rate and perceptual quality in streaming applications. However, TFRC tends to malfunction in wireless environment if packet lost event was introduced by poor channel quality but network congestion. Therefore, TFRC cannot provide high quality-of-service for streaming applications over wired-wireless networks. In this paper, we proposed a novel one-way delay jitter based TFRC with end-to-end semantic over wired-wireless networks. This scheme not only provide smooth sending rate and TCP-friendly characteristics like standard TFRC, but also considerable increase the throughput by accurately estimating the available bandwidth in wired-wireless networks with bursty nature of background traffic. Simulation results show that our scheme conducts performance improvement without intrusiveness issue and even if background traffic is bursty over wired-wireless networks.

In this paper, we introduce the concept of ceased areas for enhancing the spatial reuse in CSMA/CA based wireless ad hoc networks. Intuitively, a ceased area is created by a transmitter-receiver pair where all other nodes are required to keep silent. The size of a ceased area depends on the transmission power and the transmitter-receiver distance. A new transmission power control (TPC) scheme that can minimize the induced ceased area is proposed. And it is superior to previous TPC schemes in throughput.

With the advances of wireless communication technologies, wireless networks gradually become the most adopted communication networks in the new generation Internet. Computing devices and mobile devices may be equipped with multiple wired and/or wireless network interfaces. Stream Control Transmission Protocol (SCTP) has been proposed for reliable data transport and its multihoming feature makes use of network interfaces effectively to improve performance and reliability. However, like TCP, SCTP suffers unnecessary performance degradation over wired-wireless heterogeneous networks. The main reason is that the original congestion control scheme of SCTP cannot differentiate loss events so that SCTP reduces the congestion window inappropriately. In order to solve this problem and improve performance, we propose a jitter-based congestion control scheme with end-to-end semantics over wired-wireless networks. Besides, we solved ineffective jitter ratio problem which may cause original jitter-based congestion control scheme to misjudge congestion loss as wireless loss. Available bandwidth estimation scheme will be integrated into our congestion control mechanism to make the bottleneck more stabilized. Simulation experiments reveal that our scheme (JSCTP) gives prominence to improve performance effectively over wired-wireless networks.

In the recent years, researches focus on decay of TCP throughput over wireless links, and many wireless TCP solutions are proposed to deal with this issue. On the other hand, followed by the improvement of hardware technology, new network structures and mechanisms are proposed to enhance wireless communications, for example, the Cognitive Radio (CR) networks. However this new network architecture causes a new problem, which is not solved in wireless TCPs. In this paper, we identify a new issue that impacts the TCP performance over CR networks, which we call Bandwidth Variation. A cross layer solution is proposed to deal with this new issue. Both numerical and simulation results are resented to demonstrate the effectiveness of the proposed solution.

The innovative exploitation of network coding technology could bring great design advantages to MANETs. First, wireless links are inherently lossy due to channel fading or interference. Second, the delivery condition of the route from the source to each receiver in a multicast transmission might be significantly distinct. Trying to satisfy the reliability requirement for the poorly-connected receivers may affect the performance of the rest of the receivers. In this paper, we present a tree-based multicast protocol, which exploits the characteristics of network coding to provide efficient and reliable multicast. A metric, named Receiving Probability (RP), is proposed to represent the probability for a node in a multicast tree to successfully receive a packet sent by the multicast source. To mitigate the distinctions among the receivers, the proposed multicast protocol aims to construct multiple trees such that the RP of each receiver satisfies a predefined threshold. Besides, since seldom redundant packets are generated with random network coding, by applying random network coding to these constructed multiple trees, differently coded packets can be transmitted on multiple trees, and the throughput of the reliable multicast can be improved. Simulation results show that the average throughput can be enhanced 30% and the throughput of the poorly-connected receivers can be enhanced 100% with our protocol, compared to a recent work.

Vehicular Ad Hoc Network has recently been considered as attractive network architecture to provide various services ranging from road safety to entertainment applications. In this paper, we propose an IEEE 802.11 based multihop broadcast protocol to address the issue of safety message dissemination in Vehicular Ad Hoc Networks. This position- based protocol adopts a repetitive 2-partition method to divide the area inside transmission range resulting in a furthest narrow segment and delegates the forwarding duty to a vehicle chosen in the furthest segment. The main focus of the paper lies in reducing broadcast delay which is an important factor in time critical safety applications. We attempt to attain consistent performance irrespective of node density and different VANET scenarios. In addition to this, the protocol also solves the hidden terminal problem of multihop broadcasting. Simulation results show that our protocol achieves greater performance in terms of latency and message progress when compared with other well known multihop broadcast protocols for Vehicular Ad Hoc Networks

Event detection and environment surveillance are the important issues in wireless sensor networks. However,using the non-renewable power source leads to the short lifetime of the networks. For this reason the scheduling process is to determine the time sensor node wakes up and goes sleeping to conserve energy, so the delay time and the working interval would become trade-off. In this article, we introduce the two ranked aware phase surveillance to lower the delay time, and we use the sensed data to make the scheduling policy.We consider the event happening in two phase, so we propose two surveillance models to cope with these two phases,although this model is simple to create it can achieve the goal of reducing the delay time of detection and delivery. Finally, we show our performance in the simulation section and then describe the improvement of our approach in the future work section.

In last decades, the demand of wireless spectrum has increased rapidly with the development of mobile communication services. Recent studies recognize that traditional fixed spectrum assignment does not use spectrum efficiently. Such a wasting phenomenon could be amended after the present of cognitive radio. Cognitive radio is a new type of technology that enables secondary usage to unlicensed user. This paper presents an opportunistic cognitive MAC protocol (OC-MAC) for cognitive radios to access unoccupied resource opportunistically and coexist with wireless local area network (WLAN). By a primary traffic predication model and transmission etiquette, OC-MAC avoids producing fatal damage to licensed users. Then a ns2 simulation model is developed to evaluate its performance in scenarios with coexisting WLAN and cognitive network.

In this paper, we design a novel transmission structure called a double-tree for correlated data gathering problem for wireless sensor networks, where the goal is to minimize the total transmission cost of information collected by all sensor nodes, to the sink node. It is well-known that a tree structure is often adopted for network routing problems. However, the traditional tree transmission structure for network routing may not be an optimal structure while data correlation factors are being considered. For a given wireless sensor network, some nodes send their raw data directly to the sink, and some nodes send their encoded data based on information received from other nodes; therefore, there are two types of data in the network. Without the help of decoding/re-coding at the intermediate node, the purpose of encoded data routing is to directly send to the sink, but the purpose of raw data routing is not only to send to the sink, but also to spread raw data to other nodes as side information in encoding operations. The difference from one data type makes traditional tree structure unsuitable for the correlated data gathering problem. Therefore according to our observations, we propose a new transmission double-tree structure, which uses one tree for raw data routing, and uses another tree for encoded data routing. By employing the double-tree structure, the network can achieve lower transmission cost of gathering sensing data. Furthermore the adoption of double-tree structure always outperforms the traditional tree structure in correlated data gathering problem. We first formulate the optimization problem with a double-tree transmission structure in the general case, and prove NP-Hardness of simplified version of this problem. Then we present a 2-approximation algorithm MST+SPT that guarantees the upper bound of total transmission cost compared to the optimal solution.

Internet and multimedia services are widely-provided in All-IP based networks. There has been growing demand for mobile users to get those services. The Wireless Mesh Network (WMN) extends communication range and provides Internet connectivity to mobile users with low upfront investment. In WMN, the traffic usually passes through the gateway and makes it become the common destination of the traffic. Conventional multipath routing protocols in the ad hoc networks do not allow intermediate nodes to reply the route request messages, so the flooding messages make the area near the gateway become congested and degrade the performance. In this paper, we proposed Gateway Zone Multi-path Routing (GZMR) protocol. GZMR uses node around the gateway to form a Gateway Cooperative Zone and ceases the routing control messages flooding from outside the zone. Border nodes in the zone can help replying gateway information to reduce route discovery delay. Our simulation results show that by lowering routing overheads and utilizing multiple paths from source to gateway, GZMR can shorten average end-to-end delay and improve the packet delivery in WMNs.

Wireless mesh networks provide an easy deployed and extensible solution to access Internet or communicate with each other for both enterprises and individuals. With the help of multi-channel and multi-radio, wireless mesh network can support more traffic load to meet higher and higher bandwidth requirement in this modern time. There have been researches that focus on channel assignment and routing algorithm for IEEE 802.11 multi-channel environment to achieve better network throughout. However, the data rate and transmission range of 802.11 is limited and is not suitable for a large area metropolitan mesh network deployment. This paper presents a rate-adaption channel assignment and routing algorithm for IEEE 802.16 multi-channel multiradio network in mesh mode which is expected as the last-mile wireless broadband connectivity. We takes 802.16 TDMA characteristic and modulation/ rate adaption into consideration. The Simulation results show that our channel assignment procedure uses fewer channels and better channel utilization than the migrated 802.11 greedy approach. Among the three comparing routing protocols, our protocol performs better in multi-rate 802.16 mesh network and results in higher aggregate throughput.

In the existing mobile ad hoc network (MANET) QoS routing and multicasting protocols, the methods of bandwidth calculation and allocation were proposed to determine routes with bandwidth guaranteed for QoS applications. As our observations, two bandwidth-violation problems is incurred in the above protocols. First: When a new bandwidth-requirement flow starts, the existing methods determine a bandwidth-satisfied route and reserve the bandwidth for the flow accordingly by considering the nodes' status on the route and network configuration. However, the reservation might violate the bandwidth capacities of other ongoing bandwidth-consuming flows. Second: Another bandwidth-violation problem would mislead the bandwidth reservation for QoS multicast applications when the multiple routes from a server to all clients were determined concurrently. Our simulation results exhibit that the two problems have high possibilities to be incurred so as to cause serious performance declination while the network traffic is heavy. In this paper, the problem of determining a bandwidth-satisfied tree is formulated as a 0/1 integer linear programming (ILP) for the theoretical studies. We minimize the number of forwarders for reducing the number of hosts participating in packet forwarding so as to lower bandwidth and power consumption that are crucial to MANET performance.

Recently, ultra-wideband (UWB) technologies have attracted considerable attention for its capability, high data rate to achieve 480 Mbps, to wireless personal communications. In this paper, the problem of TCP and energy efficient transmission in IEEE 802.15.3 WPAN based on UWB technologies are addressed. Also, a simple power-efficient scheme for TCP transmission in accordance with IEEE 802.15.3 WPAN standard is proposed and NS2 is used for evaluating the performance of this proposal. The scheme design is driven by two major factors. The first one is that the scheme should provide high TCP throughput in a piconet and low end-to-end delay for TCP packets. The second one is that the scheme should be energy efficient since most mobile devices typically are powered by battery and have limited power capacity. In order to meet these requirements, the energy efficient design at the MAC layer and transport layer is taken into account by the proposed schema

Due to varying wireless channel conditions, the IEEE 802.11 wireless local area network (WLAN) standard supports multiple modulation types to accommodate the tradeoff between data rate and bit error rate. In Heusse(2003), Rousseau, Berger-Sabbatel and Duda theoretically analyzed a performance anomaly when multi-rate stations with different modulation types exist in IEEE 802.11 WLANs. The performance anomaly is: the aggregate throughput of those stations transmitting at a higher data rate will dramatically degrade below the same level as that of those stations transmitting at a lower data rate. In this paper, we address the anomaly problem and formulate a nonlinear mixed integer programming problem to maximize the total aggregate throughput of all stations subject to that the channel occupancy times among the stations transmitting at different data rates are kept at a fairness ratio. With its aid, a single-hop WLAN can dynamically accommodate the resource access usage to maximize the system throughput in varying fading environments. We prove that the optimization problem is intractable and propose a heuristic solution based on a penalty function with gradient-based approach to solve it. We show the effectiveness of the approach via computational experiments and provide some useful guidelines to regulate the parameters needed for the approach.

This paper proposes a new real-time video traffic predictor to meet increasing consumer demand for a high speed high performance wireless broadband network. It analyzes the behaviors and the problems of previous adaptive LMS-type predictors using fixed step size in detail and then proposes an adaptive predictor using variable step size for predicting bandwidth requirement of real-time VBR videos. The proposed adaptive predictor has better ability for handling scene changes and needs not change its parameters for different VBR videos. The simulation shows that the performance of the proposed adaptive predictor is better or near the optimal performance of previous adaptive LMS-type predictors using fixed step size.

This paper proposes a QoS routing protocol (RP) for multimedia services in mobile ad hoc networks (MANETs). We adopt a new distributed MAC protocol, called enhanced distributed coordination function (EDCF), to support service differentiation. It requires a QoS RP to find routes with QoS guarantees. The proposed QoS RP discovers routes for source-destination transmission pairs with bandwidth and end-to-end delay guarantees. The procedures of neighborhood maintenance, QoS violation detection, and route maintenance are also presented in this paper. Furthermore, we introduce a new problem called hidden route problem, which arises because of existing routes that are hidden from the current route discovery procedure. This problem is also solved in the proposed QoS RP. We use the ns-2 simulation to evaluate the performance of the proposed QoS RP and compare it with other ad hoc QoS RPs. Simulation results show that the performance criteria, such as packet delivery ratio and average end-to-end delay, outperform other existing QoS RPs with the sacrifice of routing overhead under light load conditions.

Broadcast/multicast is a key service for mobile ad hoc networks. A great number of applications rely on a reliable and efficient MAC layer broadcast. The IEEE 802.11 broadcast protocol, which is based on carrier sense multiple access with collision avoidance (CSMA/CA), does not offer any MAC layer recovery on broadcast frames. Consequently, the increasing probability of lost frames may deteriorate the quality of broadcast/multicast services offered at upper layers. In this paper, we first formulate the broadcast problem as an optimization problem and show that it is NP-hard, even if the upper layer service is periodical beacons. An approximation algorithm with a guaranteed approximation ratio is also suggested. Then, a reliable and efficient MAC layer broadcast protocol, named broadcast protocol with busy tone (BPBT), is proposed. BPBT applies a busy tone to solve the hidden terminal problem. Finally, BPBT is compared with previous protocols for performance evaluation by simulation.

The session initiation protocol (SIP) provides advanced signaling and control functionality for a wide variety of multimedia services. This paper introduces an extension of session initiation protocol (SIP) to support multipoint conference. via functions, a multipoint conference could be constructed by mobile hosts (user agents, UAs), It requires no server side or network structure modifications. Considering the network performance and end-to-end delay, we propose a new multipoint mobile multicast location management mechanism using SIP. In this mechanism, each data packet is sent out using multicast and routed in a shortest path between any two members of a conference. This paper also introduces the analytical model and performs simulation experiments using network simulator 2 (NS2). The experiment results demonstrate that this extension of SIP carries advantages in end-to-end packet delay and the processing time for a new participant to join a multipoint conference.

TCP is a widely used transport protocol constructed from the wired links that performs well over the traditional network. Since the wireless network is growing rapidly particularly in the wired/wireless mixed inter-network, a heterogeneous environment is expected to be deployed in the next generation all-IP wireless networks. The TCP that detects the losses as congestion events could not suit the heterogeneous network in which the losses are introduced by the higher bit error rates or handoffs. There exist some unsolved challenges for applying TCP over the wireless links. End-to-end congestion control and fairness issues are two significant factors. To satisfy these two criteria, we propose a jitter-based scheme to adapt the sending rates by the packet losses and jitter ratios. The experiment results have shown that our jitter-based TCP (JTCP) has a good performance over the heterogeneous network.