Showing papers in "IEICE Transactions on Communications in 2008"

Multi-Constrained QoS Geographic Routing for Heterogeneous Traffic in Sensor Networks

Abstract: Sensor networks that carry heterogeneous traffics and are responsible for reporting very time-critical important events necessitate an efficient and robust data dissemination framework. Designing such a framework, that can achieve both the reliability and delay guarantee while preserving the energy efficiency, namely multi-constrained QoS (MCQoS), is a challenging problem. Although there have been many research works on QoS routing for sensor networks, to the best of our knowledge, no one addresses the above three service parameters all together. In this paper, we propose a new aggregate routing model and a distributed aggregate routing algorithm (DARA) that implements the model for achieving MCQoS. DARA is designed for multi-sink, multipath and location aware network architecture. We develop probabilistic models for multipath reliability constraint, sojourn time of a packet at an intermediary node and node energy consumption. Delay-differentiated multi-speed packet forwarding and in-node packet scheduling mechanisms are also incorporated with DARA. The results of the simulations demonstrate that DARA effectively improves the reliability, delay guarantee and energy efficiency.

Optical Cross-Connect Switch Architectures for Hierarchical Optical Path Networks

Abstract: SUMMARY This paper proposes new switch architectures for hierarchical optical path cross-connect (HOXC) systems. The architectures allow incremental expansion of system scale in terms of the number of input/output fiber ports, wavebands, and optical paths per waveband. These features assure the cost-effective introduction of HOXCs even at the outset when traffic volume is not so large. Furthermore the effectiveness of the proposed switch architectures is demonstrated in a comparison with singlelayer OXCs (conventional OXCs). The results provide useful criteria for the introduction of HOXCs in terms of hardware scale. Broadband access including ADSL and FTTH is being rapidly adopted throughout the world and, as a result, traffic is continually increasing. The maximum number of WDM wavelengths per fiber now exceeds one hundred, and wavelength routing using ROADMs (Reconfigurable OADMs) is being widely adopted to develop cost-effective networks [1]. GMPLS controlled OXCs have also been used to create nation-wide testbeds [2]. Further traffic expansion is expected in the near future with the introduction of new broadband services including IP TV and high definition TV. This will result in a significant increase in the number of wavelength paths that are to be cross-connected at nodes, and hence optical node throughput needs to be greatly enhanced. To resolve this problem, the hierarchical optical path crossconnect (HOXC) [3]–[5] is being investigated; it can handle hierarchical bandwidth optical paths, wavelength paths and wavebands (WBs) which consist of multiple wavelength paths. Indeed, several studies have targeted the development of hierarchical optical path network design algorithms [6]– [9], these algorithms were shown to greatly lower network cost compared to conventional single-layer optical path networks for a wide range of traffic demand. Most of the works evaluated the effectiveness in terms of the total number of OXC and HOXC ports compared to those of single-layer OXCs. Another study [10] showed that an HOXC with nonuniform WB size can not only improve node throughput but also reduce cross-connect node cost. The key components needed to develop HOXCs are waveband multi/demultiplexers (WB MUX/DEMUX),

DEMOCO: Energy-Efficient Detection and Monitoring for Continuous Objects in Wireless Sensor Networks

Abstract: The proliferation of research on target detection and tracking in wireless sensor networks has kindled development of monitoring continuous objects such as fires and hazardous bio-chemical material diffusion. In this paper, we propose an energy-efficient algorithm that monitors a moving event region by selecting only a subset of nodes near object boundaries. The paper also shows that we can effectively reduce report message size. It is verified with performance analysis and simulation results that total average report message size as well as the number of nodes which transmit the report messages to the sink can be greatly reduced, especially when the density of nodes over the network field is high.

Adaptive Routing Protocol with Energy Efficiency and Event Clustering for Wireless Sensor Networks

Abstract: Wireless sensor network (WSN) is a promising approach for a variety of applications. Routing protocol for WSNs is very challenging because it should be simple, scalable, energy-efficient, and robust to deal with a very large number of nodes, and also self-configurable to node failures and changes of the network topology dynamically. Recently, many researchers have focused on developing hierarchical protocols for WSNs. However, most protocols in the literatures cannot scale well to large sensor networks and difficult to apply in the real applications. In this paper, we propose a novel adaptive routing protocol for WSNs called ARPEES. The main design features of the proposed method are: energy efficiency, dynamic event clustering, and multi-hop relay considering the trade-off relationship between the residual energy available of relay nodes and distance from the relay node to the base station. With a distributed and light overhead traffic approach, we spread energy consumption required for aggregating data and relaying them to different sensor nodes to prolong the lifetime of the whole network. In this method, we consider energy and distance as the parameters in the proposed function to select relay nodes and finally select the optimal path among cluster heads, relay nodes and the base station. The simulation results show that our routing protocol achieves better performance than other previous routing protocols.

Efficient Flexible Macroblock Ordering Technique

Abstract: The H.264/AVC standard provides several new error-resilient features to enable the reliable transmission of compressed video signals over lossy packet networks. Flexible Macroblock Ordering (FMO) is one of the most interesting resilient features within the H.264/AVC standard. Unlike former standards, in which slices were constructed out of consecutive raster scan macroblocks, FMO suggests new slices composed of spatially distributed Macroblocks (MBs), and organized in a mixed-up fashion. H.264/AVC specifies seven types of FMO. The standard defines also an explicit FMO type (Type 6), which allows explicitly assignment of each MB within the frame to any available slice groups. Therefore new FMO types can be used and integrated into H264/AVC without violating the standard. In this paper we propose a new Explicit Chessboard-Wipe (ECW) Flexible Macroblocks Ordering (FMO) technique, which outperforms all other FMO types. The new ECW ordering results in effective error scattering which maximizes the number of correctly received macroblocks located around corrupted macroblocks, leading to better error concealment. Performance evaluations demonstrate that the proposed Explicit FMO approach outperforms all the FMO types. Both subjective and objective visual quality comparative study has been also carried out in order to validate the proposed approach.

Introduction to IEEE P1900.4 Activities

Abstract: The Project Authorization Request (PAR) for the IEEE P1900.4 Working Group (WG), under the IEEE Standards Coordinating Committee 41 (SCC41) was approved in December 2006, leading to this WG being officially launched in February 2007 [1]. The scope of this standard is to devise a functional architecture comprising building blocks to enable coordinated network-device distributed decision making, with the goal of aiding the optimization of radio resource usage, including spectrum access control, in heterogeneous wireless access networks. This paper introduces the activities and work under progress in IEEE P1900.4, including its scope and purpose in Sects. 1 and 2, the reference usage scenarios where the standard would be applicable in Sect. 4, and its current system architecture in Sect. 5.

A Network Selection Algorithm Considering Power Consumption in Hybrid Wireless Networks

Abstract: In this paper, we propose a novel network selection algorithm considering power consumption in hybrid wireless networks for vertical handover. CDMA, WiBro, WLAN networks are candidate networks for this selection algorithm. This algorithm is composed of the power consumption prediction algorithm and the final network selection algorithm. The power consumption prediction algorithm estimates the expected lifetime of the mobile station based on the current battery level, traffic class and power consumption for each network interface card of the mobile station. If the expected lifetime of the mobile station in a certain network is not long enough compared the handover delay, this particular network will be removed from the candidate network list, thereby preventing unnecessary handovers in the preprocessing procedure. On the other hand, the final network selection algorithm consists of AHP (Analytic Hierarchical Process) and GRA (Grey Relational Analysis). The global factors of the network selection structure are QoS, cost and lifetime. If user preference is lifetime, our selection algorithm selects the network that offers longest service duration due to low power consumption. Also, we conduct some simulations using the OPNET simulation tool. The simulation results show that the proposed algorithm provides longer lifetime in the hybrid wireless network environment.

Call-Level Performance Modelling of Elastic and Adaptive Service-Classes with Finite Population

Abstract: The call-level performance modelling is a challenge in the highly heterogeneous environment of modern telecom networks, due to the presence of elastic traffic. In this paper, we review existing teletraffic loss models and propose a model for elastic traffic of service-classes with finite population (quasi-random call arrival process). Upon arrival, calls have contingency alternative bandwidth requirements that depend on thresholds which indicate the available/occupied link bandwidth (state dependent model). Calls are admitted under the complete sharing policy, and can tolerate bandwidth compression, while in-service. We prove a recurrent formula for the efficient calculation of the link occupancy distribution and consequently the call blocking probabilities and link utilization. The accuracy of the proposed model is verified by simulation and is found to be quite satisfactory. Comparative results with other existing models show the necessity and the effectiveness of the proposed model. Its potential applications are mainly in the environment of wireless networks.

MIMO Spatial Spectrum Sharing for High Efficiency Mesh Network

Abstract: In this paper, an architecture of MIMO mesh network which avoids co-channel interference and supplies link multiplexing simultaneously, namely MIMO spatial spectrum sharing, is proposed. As a MIMO transmission scheme, linear (such as zero-forcing) and nonlinear (such as dirty paper coding and successive interference cancellation) MIMO algorithm are developed for the proposed mesh network. It is found from numerical analysis that the proposed MIMO mesh network achieves significantly higher channel capacity than that of conventional mesh networks.

Study on Soft Decision Based Cooperative Sensing for Cognitive Radio Networks

Abstract: SUMMARY In this paper, we propose a soft decision based cooperative sensing method for cognitive radio (CR) networks for opportunistic frequency usage To identify unused frequency, CR should exploit sensing technique to detect presence or absence of primary user and use this information to opportunistically provide communication among secondary users while performance of primary user should not be deteriorated by the secondary users Because of multipath fading or shadowing, the detection of primary users may be significantly difficult For this problem, cooperative sensing (CS), where gathered observations obtained by multiple secondary users is utilized to achieve higher performance of detection, has been investigated We design a soft decision based CS analytically and analyze the detector in several situations, ie, signal model where single-carrier case and multi-carrier case are assumed and two scenarios; in the first scenario, SNR values of secondary users are totally equal and in the second scenario, a certain SNR difference between secondary users is assumed We present numerical results as follows The first scenario shows that there is little difference between the signal models in terms of detection performance The second scenario shows that CS is superior to non-cooperative sensing In addition, we presents that detection performance of soft decision based CS outperform detection performance of hard decision based CS

Measuring Video Quality on Full Scalability of H.264/AVC Scalable Video Coding

Abstract: In heterogeneous network environments, it is mandatory to measure the grade of the video quality in order to guarantee the optimal quality of the video streaming service. Quality of Service (QoS) has become a key issue for service acceptability and user satisfaction. Although there have been many recent works regarding video quality, most of them have been limited to measuring quality within temporal and Signal-to-Noise Ratio (SNR) scalability. H.264/AVC Scalable Video Coding (SVC) has emerged and has been developed to support full scalability. This includes spatial, temporal, and SNR scalability, each of which shows different visual effects. The aim of this paper is to define and develop a novel video quality metric allowing full scalability. It focuses on the effect of frame rate, SNR, the change of spatial resolution, and motion characteristics using subjective quality assessment. Experimental results show the proposed quality metric has a high correlation to subjective quality and that it is useful in determining the video quality of SVC.

BER Analysis of Dual-Hop AMplify-and-Forward MIMO Relaying with Best Antenna Selection in Rayleigh Fading Channels

Abstract: Combining relaying and multi-input multi-output (MIMO) transmission is a generic way to overcome the channel-fading impairments. Best antenna selection is a simple but efficient MIMO method that achieves the full diversity and also serves as a lower bound reference of MIMO performance. For a dual-hop MIMO system with an ideal amplify-and-forward (AF) relaying gain and best antenna selection, we provide a probability density function (PDF) of received signal-to-noise ratio (SNR) and an analytic BER equation when using M-ary PSK in Rayleigh fading channels. The analytic result is shown to exactly match with simulated one. Furthermore, the effect of link unbalance between the first hop and the second hop, due to differences in the number of antennas deployed in both hops as well as in the average power of channel coefficients, on the BER performance is numerically investigated and the results show that the links with better balance give better performance.

Soft versus Hard Cooperative Energy Detection under Low SNR

Abstract: Amidst conflicting views about whether soft cooperative energy detection scheme (SCEDS) outperforms hard cooperative energy detection scheme (HCEDS) greatly in cognitive radio, we establish the bridge that mathematically connects SCEDS and HCEDS by closed approximations. Through this bridge, it is demonstrate that, if the number of detectors of HCEDS is 1.6 times as that of SCEDS, they have nearly the same performance which is confirmed by numerical simulations, enabling a quantitative evaluation of the relation between them and a resolution of the conflicting views.

Isosceles-Trapezoidal-Distribution Edge Tapered Array Antenna with Unequal Element Spacing for Solar Power Satellite

Abstract: SUMMARY The Earth will require sustainable electricity sources equivalent to 3 to 5 times the commercial power presently produced by 2050. Solar Power Satellite (SPS) is one option for meeting the huge future energy demand. SPS can send enormous amounts of power to the Earth as the form of microwave (MW). A highly efficient microwave power transmission (MPT) system is needed for SPS. A critical goal of SPS is to maintain highest Beam Efficiency (BE) because the microwaves from SPS will be converted to utility power unlike the MW from communication satellites. Another critical goal of SPS is to maintain Side Lobe Levels (SLL) as small as possible to reduce interference to other communication systems. One way to decrease SLL and increase BE is the edge tapering of a phased array antenna. However, tapering the excitation requires a technically complicated system. Another way of achieving minimum SLL is with randomly spaced element position but it does not guarantee higher BE and the determination of random element position is also a difficult task. Isosceles Trapezoidal Distribution (ITD) edge tapered antenna was studied for SPS as an optimization between full edge tapering and uniform amplitude distribution. The highest Beam Collection Efficiency (BCE) and lowest SLL (except maximum SLL) are possible to achieve in ITD edge tapering and ITD edge tapered antenna is technically better. The performance of ITD is further improved from the perspective of both Maximum Side Lobe Level (MSLL) and BE by using unequal spacing of the antenna elements. A remarkable reduction in MSLL is achieved with ITD edge tapering with Unequal element spacing (ITDU). BE was also highest in ITDU. Determination of unequal element position for ITDU is very easy. ITDU is a newer concept that is experimented for the first time. The merits of ITDU over ITD and Gaussian edge tapering are discussed.

QR-LRL Signal Detection for Spatially Multiplexed MIMO Systems

Abstract: The performance of the ordered successive interference cancellation (OSIC) signal detection method is well known to depend on the successful detection of the first layer. In a previous work, in an effort to mitigate the error propagation effect, all the constellation points were tried as the first layer symbol, thereby achieving a better performance. In this letter, we show that the selection of the first layer impacts the error performance significantly, and based on the observation, we propose a novel signal detection method QR-LRL. In the proposed work, the least reliable layer (LRL) is chosen to be the first layer, which is shown to be the best choice in terms of noise enhancement in detecting the other layers. Also, we discuss Log Likelihood Ratio (LLR) computation when the proposed method is used. Computer simulations confirm the efficacy of the proposed method.

Joint Tomlinson-Harashima Precoding and Frequency-Domain Equalization for Broadband Single-Carrier Transmission

Abstract: The performance of single-carrier (SC) transmission in a frequency-selective fading channel degrades due to a severe inter-symbol interference (ISI). Using frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can improve the bit error rate (BER) performance of SC transmission. However, the residual ISI after FDE limits the performance improvement. In this paper, we propose a joint use of Tomlinson-Harashima precoding (THP) and FDE to remove the residual ISI. An approximate conditional BER analysis is presented for the given channel condition. The achievable average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER. The BER analysis is confirmed by computer simulation of the signal transmission.

Asymptotic Performance Analysis of Multihop Relayed Transmissions over Nakagami-m Fading Channels

Abstract: This letter studies the asymptotic bit error rate (BER) performance of multihop communication systems with amplify-and-forward relaying over Nakagami-m fading channels. Since it is difficult to find the exact probability density function (PDF) of the output signal-to-noise ratio (SNR) at the destination, we resort to the series expansion of this PDF in the neighborhood of zero. Building upon this result, a closed-form expression for the average BER in the high SNR region is derived. Numeric results show that the derived asymptotic BER expression is accurate at medium and high SNR for both independent identically distributed (i.i.d.) and independent non-identically distributed (i.n.i.d.) channels.

Resource Allocation Scheme in MIMO-OFDMA System for User's Different Data Throughput Requirements

Abstract: In the subcarrier and power allocation schemes in Multi-Input Multi-Output and Orthogonal Frequency Division Multiple Access (MIMO-OFDMA) systems, only equal fairness among users has been considered and no scheme for proportional data rate fairness has been considered. In this paper, a subcarrier, bit and power allocation scheme is proposed to maximize the total throughput under the constraints of total power and proportional data rate fairness among users. In the proposed scheme, joint subchannel allocation and adaptive bit loading is firstly performed by using singular value decomposition (SVD) of channel matrix under the constraint of users' data throughput requirements, and then adaptive power loading is applied. Simulation results show that effective performance of the system has been improved as well as each throughput is proportionally distributed among users in MIMO-OFDMA systems.

Fast and Accurate 3-D Imaging Algorithm with Linear Array Antennas for UWB Pulse Radars

Abstract: Pulse radars with UWB signals are promising as a high-resolution imaging technique that can be used for the non-destructive measurement of surface details in industrial products such as antennas and aircraft. We have already proposed a fast 3-D imaging algorithm, SEABED, that utilizes a reversible transform between the time delay and the target boundary. However, data acquisition is time-consuming when obtaining an accurate image because it assumes a mono-static radar with 2-D scanning of an antenna. In this paper, we utilize linear array antennas and propose a fast and accurate imaging algorithm. We extend the reversible transform for mono-static radars to apply to bi-static radars to reduce the data acquisition time. The effectiveness of the proposed method is verified with numerical simulations and experiments.

An adaptive RFID anti-collision algorithm based on dynamic framed ALOHA

Abstract: The collision of ID signals from a large number of colocated passive RFID tags is a serious problem; to realize a practical RFID systems we need an effective anti-collision algorithm. This letter presents an adaptive algorithm to minimize the total time slots and the number of rounds required for identifying the tags within the RFID reader's interrogation zone. The proposed algorithm is based on the framed ALOHA protocol, and the frame size is adaptively updated each round. Simulation results show that our proposed algorithm is more efficient than the conventional algorithms based on the framed ALOHA.

A Stopping Criterion for Low-Density Parity-Check Codes

Abstract: We propose a new stopping criterion for decoding LDPC codes which consists of a measure of decoder behaviors and a decision rule to predict decoding failure. We will show that the proposed measure, the number of satisfied check nodes, does not need (or minimizes) additional complexity, and the decision rule is efficient and more importantly channel independent, which was not possible in the previous work.

New Stochastic Algorithm for Optimization of Both Side Lobes and Grating Lobes in Large Antenna Arrays for MPT

Abstract: The concept of placing enormous Solar Power Satellite (SPS) systems in space represents one of a handful of new technological options that might provide large scale, environmentally clean base load power to terrestrial markets. Recent advances in space exploration have shown a great need for antennas with high resolution, high gain and low side lobe level (SLL). The last characteristic is of paramount importance especially for the Microwave Power Transmission (MPT) in order to achieve higher transmitting efficiency (TE) and higher beam collection efficiency (BCE). In order to achieve low side lobe levels, statistical methods play an important role. Various interesting properties of a large antenna arrays with randomly, uniformly and combined spacing of elements have been studied, especially the relationship between the required number of elements and their appropriate spacing from one viewpoint and the desired SLL, the aperture dimension, the beamwidth and TE from the other. We propose a new unified approach in searching for reducing SLL by exploiting the interaction of deterministic and stochastic workspaces of proposed algorithms. Our models indicate the side lobe levels in a large area around the main beam and strongly reduce SLL in the entire visible range. A new concept of designing a large antenna array system is proposed. Our theoretic study and simulation results clarify how to deal with the problems of side lobes in designing a large antenna array, which seems to be an important step toward the realization of future SPS/MPT systems.

Optimal Sensor Deployment for Wireless Surveillance Sensor Networks by a Hybrid Steady-State Genetic Algorithm

Abstract: An important objective of surveillance sensor networks is to effectively monitor the environment, and detect, localize, and classify targets of interest. The optimal sensor placement enables us to minimize manpower and time, to acquire accurate information on target situation and movement, and to rapidly change tactics in the dynamic field. Most of previous researches regarding the sensor deployment have been conducted without considering practical input factors. Thus in this paper, we apply more real-world input factors such as sensor capabilities, terrain features, target identification, and direction of target movements to the sensor placement problem. We propose a novel and efficient hybrid steady-state genetic algorithm giving low computational overhead as well as optimal sensor placement for enhancing surveillance capability to monitor and locate target vehicles. The proposed algorithm introduces new two-dimensional geographic crossover and mutation. By using a new simulator adopting the proposed genetic algorithm developed in this paper, we demonstrate successful applications to the wireless real-world surveillance sensor placement problem giving very high detection and classification rates, 97.5% and 87.4%, respectively.

Multiple Sink Positioning and Routing to Maximize the Lifetime of Sensor Networks

Abstract: In wireless sensor networks, the sensor nodes collect data, which are routed to a sink node. Most of the existing proposals address the routing problem to maximize network lifetime in the case of a single sink node. In this paper, we extend this problem into the case of multiple sink nodes. To maximize network lifetime, we consider the two problems: (i) how to position multiple sink nodes in the area, and (ii) how to route traffic flows from sensor nodes to sink nodes. In this paper, the solutions to these problems are formulated into a Mixed Integer Linear Programming (MILP) model. However, it is computationally difficult to solve the MILP formulation as the size of sensor network grows because MILP is NP-hard. Thus, we propose a heuristic algorithm, which produces a solution in polynomial time. From our experiments, we found out that the proposed heuristic algorithm provides a near-optimal solution for maximizing network lifetime in dense sensor networks.

A Secure and Efficient Handover Authentication Based on Light-Weight Diffie-Hellman on Mobile Node in FMIPv6

Abstract: This letter proposes a secure and efficient handover authentication scheme that requires a light-weight Diffie-Hellman operation at mobile nodes. Our scheme provides more enhanced securities like the PFS, PBS, and so on than the existing security-context-transfer schemes. Also, the mobile node delegates the exponent operation for the DH to the access router to reduce computational cost on it.

Design of the Cross-Layer QoS Framework for the IEEE 802.16 PMP Networks

Abstract: As one of the promising techniques in Broadband Wireless Access (BWA), IEEE 802.16 also namely WiMax provides wide-area, high-speed, and non-line-of-sight wireless transmission to support multimedia services. Four service types are defined in the specification of IEEE 802.16 for QoS support. In order to achieve end-to-end multimedia services, 802.16 QoS must be well integrated with IP QoS. In this paper, we propose a framework of cross-layer QoS support in the IEEE 802.16 network. Two novel mechanisms are proposed in the framework for performance improvement: Fragment Control and Remapping. Fragment Control handles the data frames that belong to the same IP datagram in an atomic manner to reduce useless transmission. Remapping is concerned with the mapping rules from IP QoS to 802.16 QoS and is designed to reduce the impact of traffic burstiness on buffer management. Simulation study has shown that the proposed scheme has higher goodput and throughput, and lower delay than the contrast.

Broadcasting with Randomized Network Coding in Dense Wireless Ad Hoc Networks

Abstract: In this paper, we consider the broadcast storm problem in dense wireless ad hoc networks where interference among densely populated wireless nodes causes significant packet loss. To resolve the problem, we apply randomized network coding (RNC) to the networks. RNC is a completely different approach from existing techniques to resolve the problem, and it reduces the number of outstanding packets in the networks by encoding several packets into a single packet. RNC is a kind of linear network coding, and it is suited to wireless ad hoc networks because it can be implemented in a completely distributed manner. We describe a procedure for implementing the wireless ad hoc broadcasting with RNC. Further, with several simulation scenarios, we provide some insights on the relationship between the system parameters and performance and find that there is the optimal length of coding vectors for RNC in terms of packet loss probability. We also show a guideline for the parameter setting to resolve the broadcast storm problem successfully.

Restorability of Rayleigh Backscatter Traces Measured by Coherent OTDR with Precisely Frequency-Controlled Light Source

Abstract: This letter presents the first experimental results that confirm the restorability of Rayleigh backscatter traces from a single-mode fiber measured by using a coherent optical time domain reflectometer (OTDR) with a precisely frequency-controlled light source. Based on this restorability, we can measure the distributed strain and temperature along the fiber with a very high measurand resolution that is one to two orders of magnitude better than that provided by Brillouin-based techniques for a long length of fiber.

Multiple Tree Multicast Ad Hoc On-Demand Distance Vector (MT-MAODV) Routing Protocol for Video Multicast over Mobile Ad Hoc Networks

Abstract: Video multicast over wireless medium has gained increasing popularity in a wide range of applications, such as video-on-demand and group video conferencing. With mobile ad hoc networks emerging as a promising solution for future ubiquitous communications, supporting reliable video multicast over mobile ad hoc networks is a timely research topic. In this paper we tackle this issue by using multiple tree multicast routing protocol. Specifically, we introduce an extension to the Multicast Ad Hoc On-demand Distance Vector (MAODV) routing protocol to construct two optimally disjoint trees in a single routine. The extended protocol is called Multiple Tree Multicast Ad Hoc On-demand Distance Vector (MT MAODV) routing protocol. In order to distribute the video evenly and independently between these disjoint trees, the Multiple Description Coding (MDC) scheme is used for video coding. Simulation shows that the proposed protocol demonstrates video multicast with better quality than the conventional video multicast using a single tree only.

The Development of BCI Using Alpha Waves for Controlling the Robot Arm

Abstract: SUMMARY The highly accurate BCI using alpha waves was developed for controlling the robot arm, and real-time operation was succeeded by using noninvasive electrodes. The significant components of the alpha wave were identified by spectral analysis and confirmation of the amplitude of the alpha wave. When the alpha wave was observed in the subject, the subjects were instructed to select the multiple decision branches, concerning 7 motions (including “STOP”) of a robot arm. As a result, high accuracy (70–95%) was obtained, and the subject succeeded in transferring a small box by controlling the robot arm. Since high accuracy was obtained by use of this method, it can be applied to control equipments such as a robot arm. Since the alpha wave can be easily generated, the BCI using alpha waves does not need more training than that using other signals. Moreover, we tried to reduce the false positive errors by effectively detecting artifacts using spectral analysis and detecting signals of 50µ Vo r more. As a result, the false positive errors could be reduced from 25% to 0%. Therefore, this technique shows great promise in the area of communication and the control of other external equipments, and will make great contribution in the improvement of Quality of Life (QOL) of mobility dis