Showing papers in "IEICE Transactions on Communications in 2004"

Bit error rate analysis of DS-CDMA with joint frequency-domain equalization and antenna diversity combining

Abstract: To improve the DS-CDMA signal transmission performance in a frequency-selective fading channel, the frequency-domain equalization (FDE) can be applied, in which simple one-tap equalization is carried out on each subcarrier component obtained by fast Fourier transform (FFT). Equalization weights for joint FDE and antenna diversity combining based on maximal ratio combining (MRC), zero-forcing (ZF), and minimum mean square error (MMSE) are derived. The conditional bit error rate (BER) is derived for the given set of channel gains in a frequency-selective multipath fading channel. The theoretical average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Performance comparison between DS- and multi-carrier (MC)-CDMA both using FDE is also presented.

A Study on Performance of Hierarchical Mobile IPv6 in IP-Based Cellular Networks

Abstract: SUMMARY Next-generation wireless/mobile networks will be IPbased cellular networks integrating Internet with the existing cellular networks. Recently, Hierarchical Mobile IPv6 (HMIPv6) was proposed by the Internet Engineering Task Force (IETF) for efficient mobility management. HMIPv6 reduces the amount of signaling and improves the performance of MIPv6 in terms of handoff latency. Although HMIPv6 is an efficient scheme, the performance of wireless networks is highly dependent on various system parameters such as user mobility model, packet arrival pattern, etc. Therefore, it is essential to analyze the network performance when HMIPv6 is deployed in IP-based cellular networks. In this paper, we develop two analytic models for the performance analysis of HMIPv6 in IP-based cellular networks, which are based on the random-walk and the fluid-flow models. Based on these analytic models, we formulate the location update cost and the packet delivery cost. Then, we analyze the impact of cell residence time and user population on the location update cost and the packet delivery cost, respectively. In addition, we study the variation of the total cost as the session-to-mobility ratio is changed and the optimal MAP domain size to minimize the total cost is also investigated.

A Target Shape Estimation Algorithm for Pulse Radar Systems Based on Boundary Scattering Transform

Abstract: SUMMARY Environment measurement is an important issue for various applications including household robots. Pulse radars are promising candidates in a near future. Estimating target shapes using waveform data, which we obtain by scanning an omni-directional antenna, is known as one of ill-posed inverse problems. Parametric methods such as Model-fitting method have problems concerning calculation time and stability. We propose a non-parametric algorithm for high-resolution estimation of target

Joint use of frequency-domain equalization and transmit/receive antenna diversity for single-carrier transmissions

Abstract: SUMMARY The joint use of frequency-domain equalization and antenna diversity is presented for single-carrier (SC) transmission in a frequency-selective fading channel. Frequency-domain equalization techniques using minimum mean square error (MMSE), orthogonal restoration combining (ORC) and maximum ratio combining (MRC), those used in multi-carrier code division multiple access (MC-CDMA), are considered. As antenna diversity techniques, receive diversity and delay transmit diversity (DTD) are considered. Bit error rate (BER) performance achievable with the joint use of frequency-domain equalization and antenna diversity

An evaluation of multi-path Transmission Control Protocol (M/TCP) with robust acknowledgement schemes

Abstract: We propose a new end-to-end transport protocol called Multi-path Transmission Control Protocol (M/TCP) and its two robust acknowledgement (ACK) schemes. Our protocol is designed as an alternative TCP option to improve reliability and performance of the Internet. The M/TCP sender simultaneously transmits data via multiple controlled paths to the receiver. Our protocol requires no modification in IP layer. Two M/TCP endpoints establish multiple paths between them by subscribing to multiple ISPs. The two robust ACK schemes proposed in this paper aim at improving M/TCP performance over the Internet with high packet loss in ACK channels. Performances between our protocol and TCP Reno are compared in terms of throughput and fairness by using ns2 simulator. Simulation results indicate that M/TCP achieves higher throughput than TCP Reno in situation of random drop and burst traffic with small buffer size. When there is network congestion on reverse path, M/TCP with the proposed robust ACK schemes performs better than M/TCP with the conventional immediate ACK scheme.

Traveling Electromagnetic Waves on Linear Periodic Arrays of Lossless Penetrable Spheres

Abstract: Traveling electromagnetic waves on infinite linear periodic arrays of lossless penetrable spheres can be conveniently analyzed using the source scattering-matrix framework and vector spherical wave functions. It is assumed that either the spheres are sufficiently small, or the frequency such, that the sphere scattering can be treated using only electric and magnetic dipole vector spherical waves, the electric and magnetic dipoles being orthogonal to each other and to the array axis. The analysis simplifies because there is no cross-coupling of the modes in the scattering matrix equations. However, the electric and magnetic dipoles in the array are coupled through the fields scattered by the spheres. The assumption that a dipolar traveling wave along the array axis can be supported by the array of spheres yields a pair of equations for determining the traveling wave propagation constant as a function of the sphere size, inter-sphere separation distance, the sphere permittivity and permeability, and the free-space wave number. These equations are obtained by equating the electric (magnetic) field incident on any sphere of the array with the sum of the electric (magnetic) fields scattered from all the other spheres in the array. Both equations include a parameter equal to the ratio of the unknown normalized coefficients of the electric and magnetic dipole fields. By eliminating this parameter between the two equations, a single transcendental equation is obtained that can be easily solved numerically for the traveling wave propagation constant. Plots of the k - β diagram for different types and sizes of spheres are shown. Interestingly, for certain spheres and separations it is possible to have multiple traveling waves supported by the array. Backward traveling waves are also shown to exist in narrow frequency bands for arrays of spheres with suitable permittivity and permeability.

A phase compensation algorithm for high-resolution pulse radar systems

Abstract: Imaging techniques for robots are important and meaningful in the near future. Pulse radar systems have a great potential for shape estimation and locationing of targets. They have an advantage that they can be used even in critical situations where optical techniques cannot be used. It is thus required to develop high-resolution imaging algorithms for pulse radar systems. High-resolution imaging algorithms utilize the carrier phase of received signals. However, their estimation accuracy suffers degradation due to phase rotation of the received signal because the phase depends on the shape of the target. In this paper, we propose a phase compensation algorithm for high-resolution pulse radar systems. The proposed algorithm works well with SEABED algorithm, which is a non-parametric algorithm of estimating target shapes based on a reversible transform. The theory is presented first and numerical simulation results follow. We show the estimation accuracy is remarkably improved without sacrificing the resolution using the proposed algorithm.

AODV-Based Multipath Routing Protocol for Mobile Ad Hoc Networks

Abstract: The single path routing protocol, known as the Ad Hoc On-demand Distance Vector, has been widely studied for use in mobile ad hoc networks. AODV requires a new route discovery whenever a path breaks. Such frequent route discoveries cause a delay due to route discovery latency. To avoid such inefficiency, a multipath routing protocol has been proposed that attempts to find link-disjoint paths in a route discovery. However, when there are two or more common intermediate nodes on the path, the protocol can not find a pair of link-disjoint paths even if the paths actually exist. To reduce this route discovery latency, it is necessary to increase the opportunities for finding a pair of link-disjoint paths. In this paper, we focus on AODV and propose an AODV-based new multipath routing protocol for mobile ad hoc networks. The proposed routing protocol uses a new method to find a pair of link-disjoint paths by selecting a route having a small number of common intermediate nodes on its path. Using simulation models, we evaluate the proposed routing protocol and compare it with AODV and the existing multipath routing protocol. Results show that the proposed routing protocol achieves better performance in terms of delay than other protocols because it increases the number of cases where a pair of link-disjoint paths can be established.

A Lantern-Tree-Based QoS On-Demand Multicast Protocol for a Wireless Mobile Ad Hoc Network

Abstract: SUMMARY The multimedia applications have recently generated much interest in wireless network infrastructure with supporting the quality-of-service (QoS) communications In this paper, we propose a lantern-tree-based QoS on-demand multicast protocol for wireless ad hoc networks Our proposed scheme offers a bandwidth routing protocol for QoS support in a multihop mobile network, where the MAC sub-layer adopts the CDMA-over-TDMA channel model The QoS on-demand multicast protocol determines the end-to-end bandwidth calculation and bandwidth allocation from a source to a group of destinations In this paper, we identify a lantern-tree for developing the QoS multicast protocol to satisfy certain bandwidth requirement, while the lantern-tree is served as the multicast-tree Our lantern-tree-based scheme offers a higher success rate to construct the QoS multicast tree due to using the lantern-tree The lantern-tree is a tree whose sub-path is constituted by the lantern-path, where the lantern-path is a kind of multi-path structure This obviously improves the success rate by means of multi-path routing In particular, our proposed scheme can be easily applied to most existing on-demand multicast protocols Performance analysis results demonstrate the achievements

The Reliability Performance of Wireless Sensor Networks Configured by Power-Law and Other Forms of Stochastic Node Placement

Abstract: SUMMARY Sensor nodes are prone to failure and have limited powercapacity, so the evaluation of fault tolerance and the creation of technologyfor improved tolerance are among the most important issues for wirelesssensor networks. The placement of sensor nodes is also important, sincethis affects the availability of nodes within sensing range of a target in agiven location and of routes to the base station. However, there has beenlittle research on the placement of sensor nodes. Furthermore, all researchto date has been based on deterministic node placement, which is not suit-able when a great many sensor nodes are to be placed over a large area. Insuch a situation, we require stochastic node placement, where the sensor-positions are in accord with a probability density function. In this paper,we examine how fault tolerance can be improved by stochastic node place-ment that produces scale-free characteristics, that is, where the degree ofthe nodes follows a power law. key words: sensor network, node placement, fault tolerance, power law

Password authentication without the server public key

Abstract: In 2002, Hwang and Yeh showed that Peyravian-Zunic's password authentication schemes are not secure and proposed an improvement by using the server public key. Since applying the server public key results in the additional burden, we propose secure password authentication schemes without using the server public key in this paper.

Experimental Study of Non-specular Wave Scattering from Building Surface Roughness for the Mobile Propagation Modeling

Abstract: SUMMARY In the urban area, buildings are the main scatterer which dominate the mobile propagation characteristics. However, reflection, diffraction, and scattering on the building surfaces in the radio environment induce undesirable multipath propagation. Multipath prediction with respect to a building surface has been conventionally based on an assumption that reflection from the surface has a substantial specular direction. However non-specular scattering from the building surface can affect the channel characteristics as well as specular scattering. This paper presents multipath characteristics of non-specular wave scattering from building surface roughness based on the experimental results. Superresolution method was applied as an approach to handle the signal parameters (DoA, ToA) of the individual incoming waves reflected from building surface roughness. The results show that the multipaths can be detected at many scatterers, such as ground, window’s glass, window’s frames and bricks surface, as well as directly from the transmitter. Most of the scattered waves are arriving closely from specular directions. The measured reflection coefficients were well bounded by reflection coefficients of the theoretically smooth and random rough surface. The Fresnel reflection coefficient formula, considering the finite thickness of the building surface and Gaussian scattering correction, give better prediction for glass and bricks reflection coefficient

Technical Trends in P2P-Based Communications

Abstract: This paper outlines and analyses major P2P technologies currently being actively studied at various research organisations or already in use in both business and personal environments. Various technical features of P2P as well as its history and market trends are shown. P2P principles focussing on discovery and network-organisational mechanisms of major P2P systems such as JXTA, SIONet, Freenet, and Chord are first summarised. Also, other technical issues related to delivery, network control, security, digital rights management, and distributed computing are described. Then, P2P technologies to promote next-generation community networks with autonomous and intelligent characteristics are addressed. Based on these, P2P applications are analysed and some examples are shown. Studies of P2P traffic measurement, which is difficult by using traditional evaluation methods, are taken up to consider total network design in the P2P era.

Transport Layer Mobility Support Utilizing Link Signal Strength Information

Abstract: SUMMARY Recently, mobile SCTP (mSCTP) has been proposed as a transport layer approach for supporting mobility. mSCTP is based on the ‘multi-homing’ feature of Stream Control Transmission Protocol (SCTP), and utilizes the functions to dynamically add or delete IP addresses of end points to or from the existing connection in order to support mobility. In this paper, we propose a transport layer mobility supporting scheme, which is based on mSCTP and utilizes the link layer signal strength information in order to determine when to add or delete end-point IP addresses of mobile node and how to change data delivery paths when handover happens. Exploiting the fact that the transport layer is aware of the mobility in the proposed scheme, we also propose error and congestion control enhancement to cope with handover efficiently. The simulation results show that the performance of proposed scheme is competitive compared to the traditional network layer mobility supporting approach. Especially, when the moving speed of mobile node is fast or new path acquisition takes long, it shows better performance than the traditional network layer approach.

Joint Space-Time Transmit Diversity and Minimum Mean Square Error Equalization for MC-CDMA with Antenna Diversity Reception

Abstract: SUMMARY In this paper, the space time transmit diversity (STTD) decoding combined with minimum mean square error (MMSE) equalization is presented for MC-CDMA downlink and uplink in the presence of multiple receive antennas. The equalization weights that minimize the MSE for each subcarrier are derived. From computer simulation, it was found that the BER performance of STTD decoding combined with MMSE equalization and Mr-antenna diversity reception using the weights derived in this paper provides the same diversity order as 2Mr-antenna receive diversity with MMSE equalization but with 3 dB performance penalty and is always better than that with no diversity. The uplink BER performance can also be improved with STTD, but the error floor still exists. However, with 2-receive antennas in addition to 2-antenna STTD, the BER floor can be reduced to around 10 −5 even for the uplink.

Location Management Using Mobile History for Hierarchical Mobile IPv6 Networks

Abstract: Hierarchical Mobile IPv6 (HMIPv6) has been proposed to improve the performance capability of Mobile IPv6 at handover. In HMIPv6, local entities named Mobility Anchor Points (MAPs) are distributed throughout a network to localize the management of intra-domain mobility. In particular, multi-layered MAP has been proposed to improve performance. MAPs reduce the number of Binding Updates to the Home Agent and improve the communication quality at handover. These conventional methods that manage a multi-layered MAP cannot, however, select an appropriate MAP because they use the virtual mobility speed. As a result, they increase the signaling traffic in a multi-layered MAP. Moreover, they may cause the load to concentrate at a specific MAP. In this paper, we propose a location management method for Hierarchical Mobile IPv6 using the MN's mobile history. In this method, when a MN performs a handover, the Access Router calculates the area-covered rate of each upper MAP from the MN's mobile history and selects the MAP that best manages the MN in accordance with its rate. Thus, the proposed method reduces both the number of Binding Updates to the Home Agent and the signaling traffic because it reduces the frequency of changing the MAP. We evaluate the performance of the proposed method by simulation.

A Class of Hierarchical Routing Protocols Based on Autonomous Clustering for Large Mobile Ad Hoc Networks

Abstract: Along with expansion of utilization of mobile ad hoc networks, it is expected that the network size becomes large. However, design of current typical routing protocols supposes at most several hop routes between source and destination nodes. When messages are delivered along long hop routes in the networks, such routing protocols tend to degrade performance. Previously, we have proposed an autonomous clustering scheme for constructing and maintaining hierarchical structure in mobile ad hoc networks, which are adaptive to node movement. This paper proposes a class of hierarchical routing protocols Hi-TORA, Hi-DSR and Hi-AODV, all of which are based on the autonomous clustering scheme, compares them with their corresponding flat routing protocols TORA, DSR and AODV, respectively, and shows effectiveness of these hierarchical routing protocols by simulation experiments.

Multi-Path Transmission Algorithm for End-to-End Seamless Handover across Heterogeneous Wireless Access Networks

Abstract: In mobile networks, new technologies are needed to enable mobile hosts to move across various kinds of wireless access networks. In the past, many researchers have studied handover in IP networks. In almost all cases, special network devices are needed to maintain the host’s mobility. However, in these technologies, mobile hosts cannot move across different wireless access networks without closing the connection and degrading the goodput. To overcome these, we propose here a multi-path transmission algorithm for end-to-end seamless handover. The main purpose of this algorithm is to improve the goodput during handover by sending the same packets along multiple paths, reducing unnecessary consumption of network resources. We evaluate our algorithm through simulations and show that mobile hosts gain a better goodput.

Analysis of Multi-Server Round Robin Scheduling Disciplines

Abstract: With the need and adoption of link aggregation where multiple links exist between two adjacent nodes in order to increase transmission capacity between them, there arise the problems of service guarantee and fair sharing of multiple servers. Although a lot of significant work has been done for single-server scheduling disciplines in the past years, not much work is available for multi-server scheduling disciplines. In this paper, we present and investigate two round robin based multi-server scheduling disciplines, which are Multi-Server Uniform Round Robin (MS-URR) and Multi-Server Deficit Round Robin (MS-DRR). In particular, we analyze their service guarantees and fairness bounds. In addition, we discuss the misordering problem with MS-DRR and present a bound for its misordering probability.

Performance Analysis of MIMO Eigenmode Transmission System under Realistic Channel and System Conditions

Abstract: The performance of the MIMO eigenmode transmission system (EMTS) is very sensitive to the accuracy of channel state information and thus it is of practical importance to analyzing its performance when channel state information is corrupted under realistic system and propagation conditions. We lower bound the mutual information of MIMO EMTS with imperfect channel estimation and delayed quantized feedback in a spatially correlated continuous fading channel. Our results show that this lower bound is tight and can serve as a comprehensive guide to the actual performance of MIMO EMTS under practical operating conditions.

Fitting Self-Similar Traffic by a Superposition of MMPPs Modeling the Distribution at Multiple Time Scales

Abstract: Measuring and modeling network traffic is of key importance for the traffic engineering of IP networks, due to the growing diversity of multimedia applications and the need to efficiently support QoS differentiation in the network. Several recent measurements have shown that Internet traffic may incorporate long-range dependence and self-similar characteristics, which can have significant impact on network performance. Selfsimilar traffic shows variability over many time scales, and this behavior must be taken into account for accurate prediction of network performance. In this paper, we propose a new parameter fitting procedure for a superposition of Markov Modulated Poisson Processes (MMPPs), which is able to capture self-similarity over a range of time scales. The fitting procedure matches the complete distribution of the arrival process at each time scale of interest. We evaluate the procedure by comparing the Hurst parameter, the probability mass function at each time scale, and the queuing behavior (as assessed by the loss probability and average waiting time), corresponding to measured traffic traces and to traces synthesized according to the proposed model. We consider three measured traffic traces, all exhibiting self-similar behavior: the well-known pOct Bellcore trace, a trace of aggregated IP WAN traffic, and a trace corresponding to the popular file sharing application Kazaa. Our results show that the proposed fitting procedure is able to match closely the distribution over the time scales present in data, leading to an accurate prediction of the queuing behavior. key words: Traffic modeling, self-similar, time scale, Markov Modulated Poisson Process.