Showing papers by "NTT DoCoMo published in 2008"

Base station apparatus and communication control method

Abstract: The object is achieved by providing a base station apparatus for performing time and frequency scheduling in uplink packet access with: an interference amount measurement part configured to measure an uplink interference amount for each interference amount measurement unit which comprises a predetermined period and a predetermined number of frequency blocks; an interference amount determination part configured to determine whether the uplink interference amount satisfies a predetermined condition; and an overload indicator reporting part configured to report an overload indicator to a neighboring cell when the predetermined condition is satisfied.

NLOS identification and weighted least-squares localization for UWB systems using multipath channel statistics

Abstract: Non-line-of-sight (NLOS) identification and mitigation carry significant importance in wireless localization systems. In this paper, we propose a novel NLOS identification technique based on the multipath channel statistics such as the kurtosis, the mean excess delay spread, and the root-mean-square delay spread. In particular, the IEEE 802.15.4a ultrawideband channel models are used as examples and the above statistics are found to be well modeled by log-normal random variables. Subsequently, a joint likelihood ratio test is developed for line-of-sight (LOS) or NLOS identification. Three different weighted least-squares (WLSs) localization techniques that exploit the statistics of multipath components (MPCs) are analyzed. The basic idea behind the proposed WLS approaches is that smaller weights are given to the measurements which are likely to be biased (based on the MPC information), as opposed to variance-based WLS techniques in the literature. Accuracy gains with respect to the conventional least-squares algorithm are demonstrated via Monte-Carlo simulations and verified by theoretical derivations.

Base station device and communication control method

Abstract: A base station device which performs communication with a mobile station by using a downlink shared channel includes: reception means for receiving transmission acknowledgement information for a downlink shared channel from the mobile station by a control channel which is frequency-multiplexed with an uplink shared channel; measurement means for measuring radio quality of the control channel; and judgment means for judging the reliability of the downlink radio quality information according to the radio quality. Moreover, a communication control method in the base station device which performs communication with the mobile station by using the downlink shared channel includes: a step of receiving transmission acknowledgement information for the downlink shared channel from the mobile station by the control channel which is frequency-multiplexed with the uplink shared channel; a step of measuring radio quality of the control channel; and a step of judging whether the mobile station has transmitted the downlink radio quality information according to the radio quality.

A hybrid frequency assignment for femtocells and coverage area analysis for co-channel operation

Abstract: Successful deployment of femtocells requires intelligent cell planning and introduces some unique challenges. In this letter, an efficient frequency assignment technique is proposed for femtocells considering practical issues such as hand-off, coverage, and interference. Moreover, interference-limited coverage area (ILCA) of a co-channel femtocell base station is calculated based on parameters such as the distance to the macrocell BS, path loss exponents, and transmission power levels.

Automated test input generation for web applications

Abstract: A method and apparatus is disclosed herein for automated test input generation for web applications. In one embodiment, the method comprises performing a source-to-source transformation of the program; performing interpretation on the program based on a set of test input values; symbolically executing the program; recording a symbolic constraint for each of one or more conditional expressions encountered during execution of the program, including analyzing a string operation in the program to identify one or more possible execution paths, and generating symbolic inputs representing values of variables in each of the conditional expressions as a numeric expression and a string constraint including generating constraints on string values by modeling string operations using finite state transducers (FSTs) and supplying values from the program's execution in place of intractable sub-expressions; and generating new inputs to drive the program during a subsequent iteration based on results of solving the recorded string constraints.

Efficient broadcasting using network coding

Abstract: We consider the problem of broadcasting in an ad hoc wireless network, where all nodes of the network are sources that want to transmit information to all other nodes. Our figure of merit is energy efficiency, a critical design parameter for wireless networks since it directly affects battery life and thus network lifetime. We prove that applying ideas from network coding allows to realize significant benefits in terms of energy efficiency for the problem of broadcasting, and propose very simple algorithms that allow to realize these benefits in practice. In particular, our theoretical analysis shows that network coding improves performance by a constant factor in fixed networks. We calculate this factor exactly for some canonical configurations. We then show that in networks where the topology dynamically changes, for example due to mobility, and where operations are restricted to simple distributed algorithms, network coding can offer improvements of a factor of log n, where n is the number of nodes in the network. We use the insights gained from the theoretical analysis to propose low-complexity distributed algorithms for realistic wireless ad hoc scenarios, discuss a number of practical considerations, and evaluate our algorithms through packet level simulation.

Dynamic test input generation for web applications

Abstract: Web applications routinely handle sensitive data, and many people rely on them to support various daily activities, so errors can have severe and broad-reaching consequences. Unlike most desktop applications, many web applications are written in scripting languages, such as PHP. The dynamic features commonly supported by these languages significantly inhibit static analysis and existing static analysis of these languages can fail to produce meaningful results on realworld web applications.Automated test input generation using the concolic testing framework has proven useful for finding bugs and improving test coverage on C and Java programs, which generally emphasize numeric values and pointer-based data structures. However, scripting languages, such as PHP, promote a style of programming for developing web applications that emphasizes string values, objects, and arrays.In this paper, we propose an automated input test generation algorithm that uses runtime values to analyze dynamic code, models the semantics of string operations, and handles operations whose argument and return values may not share a common type. As in the standard concolic testing framework, our algorithm gathers constraints during symbolic execution. Our algorithm resolves constraints over multiple types by considering each variable instance individually, so that it only needs to invert each operation. By recording constraints selectively, our implementation successfully finds bugs in real-world web applications which state-of-the-art static analysis tools fail to analyze.

Impact of denial of service attacks on ad hoc networks

Abstract: Significant progress has been made towards making ad hoc networks secure and DoS resilient. However, little attention has been focused on quantifying DoS resilience: Do ad hoc networks have sufficiently redundant paths and counter-DoS mechanisms to make DoS attacks largely ineffective? Or are there attack and system factors that can lead to devastating effects? In this paper, we design and study DoS attacks in order to assess the damage that difficult-to-detect attackers can cause. The first attack we study, called the JellyFish attack, is targeted against closed-loop flows such as TCP; although protocol compliant, it has devastating effects. The second is the black hole attack, which has effects similar to the JellyFish, but on open-loop flows. We quantify via simulations and analytical modeling the scalability of DoS attacks as a function of key performance parameters such as mobility, system size, node density, and counter-DoS strategy. One perhaps surprising result is that such DoS attacks can increase the capacity of ad hoc networks, as they starve multi-hop flows and only allow one-hop communication, a capacity-maximizing, yet clearly undesirable situation.

Base station device, user device and method used in mobile communication system

Abstract: A base station apparatus is disclosed that is capable of communicating with user equipment used in a mobile communication system. The base station apparatus includes a determination unit determining whether a path loss value reported from the user equipment satisfies a predetermined condition, an instruction signal generation unit, based on a result of the determination made by the determination unit, generating an instruction signal indicating whether the user equipment should reduce a transmission power value in response to a request from an other cell to reduce the transmission power value, and a transmission unit transmitting the instruction signal to the user equipment. Further, the path loss value is derived based on an average receiving quality value and a target quality value.

Energy Consumption Issues on Mobile Network Systems

Abstract: This paper describes energy consumption demographic data in operating real mobile networks. We examine published data from NTT DoCoMo, which is the largest mobile telecommunication operator in Japan and operating nationwide 3G networks, and identify the most power consuming part is of radio access networks including base tranciever stations. We also investigate power consumption of terminals, and find that the consumption ratio of terminal v.s. networks is about 1:150. Our daily energy consumption per a customer is 0.83 Wh/day for a terminal and 120 Wh/day for the mobile network. The terminal side energy consumption is negligible in view of total CO2 emission though, limitation of its battery performance raises another issue called "energy starvation of mobile devices." The demographic data leads our discussion to (1) radio-on-fiber access network architecture as green networks and (2) thin client models as the key to sustain the evolution toward the future.

Performance Analysis of Power Saving Mechanism with Adjustable DRX Cycles in 3GPP LTE

Abstract: Long-term evolution (LTE) of the UMTS terrestrial radio access and radio access network is considered to ensure the competitiveness of 3GPP radio-access technology in a longer time frame. To minimize/optimize the user equipment (UE) power consumption, and further to support various services and large amount of data transmissions, a discontinuous reception (DRX) mechanism with adjustable DRX cycles has been adopted in LTE RRC_CONNECTED mode. In this paper, we take an overview of the DRX cycle adjustable feature of the LTE power saving mechanism and further modeling the mechanism with bursty packet data traffic using a semi-Markov process. The analytical results, which are validated against simulation experiments, show that LTE DRX achieves power saving gains over UMTS DRX at the price of prolonging wake-up delay. Based on the analytical model, effects of the DRX parameters on the power saving and wake-up delay performance are also investigated, and the results verify a trade-off relationship between the power saving and wake-up delay performance.

Cross-Dimensional Perceptual Quality Assessment for Low Bit-Rate Videos

Abstract: Most studies in the literature for video quality assessment have been focused on the evaluation of quantized video sequences at fixed and high spatial and temporal resolutions. Only limited work has been reported for assessing video quality under different spatial and temporal resolutions. In this paper, we consider a wider scope of video quality assessment in the sense of considering multiple dimensions. In particular, we address the problem of evaluating perceptual visual quality of low bit-rate videos under different settings and requirements. Extensive subjective view tests for assessing the perceptual quality of low bit-rate videos have been conducted, which cover 150 test scenarios and include five distinctive dimensions: encoder type, video content, bit rate, frame size, and frame rate. Based on the obtained subjective testing results, we perform thorough statistical analysis to study the influence of different dimensions on the perceptual quality and some interesting observations are pointed out. We believe such a study brings new knowledge into the topic of cross-dimensional video quality assessment and it has immediate applications in perceptual video adaptation for scalable video over mobile networks.

Information processing device and program

Abstract: The present invention provides an information processing device for estimating usage of contents and properly limiting functions realized through use of the contents in accordance with the estimation. Usage of contents is estimated by determining in which of cache memory means and content storage means the contents are stored. When the contents are processed or executed, it is determined whether to limit functions realized through processing or execution of the contents, on the basis of the estimated usage of the contents and function limit information showing a rule regarding limits on functions realized through processing or execution. On the basis of the determination, the functions realized through processing or execution of the contents are limited.

System for managing program applications storable in a mobile terminal

Abstract: Management server 16 may obtain application programs from content server 20 in response to requests of mobile terminal 11. Management server 16 may transmit the obtained application programs to mobile terminal 11 with information concerning reliabilities of the application programs. After mobile terminal 11 receives the application programs from management server 16, mobile terminal 11 manages operations of the application programs. Operations of the application programs are coordinated with operations of other programs using the information concerning the reliabilities corresponding to the application programs. Management of the coordinated operations of the application programs avoids problems concerning information security, where valuable information may be distributed unexpectedly because of operations of low reliable application programs. As a result, convenience of users of mobile terminals 11 can be improved without deteriorating the information security of mobile terminals 11.

OFCDM: a promising broadband wireless access technique

Abstract: Future mobile communication systems aim to provide extremely high-speed data transmission, especially in the downlink. The broadband orthogonal frequency- and code-division multiplexing system with two-dimensional spreading (time and frequency domain spreading) is becoming a very promising technique for highspeed wireless communications due to its advantages over OFDM. This article presents the basic structure and main functions of the OFCDM system. A nonsequential code assignment scheme is introduced. The novel detection method for the OFCDM, called hybrid multi-code interference cancellation and minimum mean square error detection, is described. The application of advanced techniques to the OFCDM, such as turbo coding and MIMO, is also discussed. It is shown in this article that OFCDM is superior to OFDM.

Image prediction/encoding device, image prediction/encoding method, image prediction/encoding program, image prediction/decoding device, image prediction/decoding method, and image prediction decoding program

Abstract: Disclosed are an image prediction encoding device, an image prediction encoding method, an image prediction encoding program, an image prediction decoding device, an image prediction decoding method, and an image prediction decoding program wherein an encoding area within an image is divided into a plurality of prediction regions. Candidates for motion information to be used in the generation of prediction signals for a target prediction region that is the next prediction region are selected from encoded motion information for the region adjacent to the target prediction region, based on prediction information for an adjacent region which is adjacent to the target region, the number of encoded prediction regions within the target region, and the encoded prediction information for the target region. Merge block information, which instructs the generation of prediction signals for the target prediction area that has used the selected candidates for motion information, and motion information detected by a prediction information estimation means, or one of either said merge block information or said movement information is encoded, and motion information used to generate prediction signals for the target prediction area is saved by a prediction information saving means.

UWB Direct Chaotic Communication Technology for Low-Rate WPAN Applications

Abstract: The goal of this paper is to describe the design of an ultrawideband (UWB) system that is optimized for low-complexity, low-power, low-cost, and low-rate wireless personal area network applications. To this aim, we propose a system based on novel direct chaotic communication (DCC) technology, in which a 2-GHz-wide chaotic signal is directly generated into the lower band of the UWB spectrum. Based on this system, two simple modulation schemes, namely, chaotic on-off keying and differential chaos-shift keying, are studied, and the performance of both noncoherent and differential-coherent transceiver architectures is evaluated. Various system design parameters and tradeoffs are discussed throughout the paper, including frequency band plans, data throughput, and system scalability. In particular, the frequency-division multiplexing technique is proposed as a low-cost alternative to achieving simultaneous operating piconets for short-distance applications. The average power consumption for various operating data rates and the technical feasibility of implementing the DCC system as a low-cost integrated circuit are also addressed. Finally, Monte Carlo simulations are performed based on the IEEE 802.15.4a standard channel models to evaluate the performance of the two modulation schemes. In general, both schemes experience little degradation under multipath environments due to the self-inherent wideband characteristic of the chaotic signal.

Media streaming with online caching and peer-to-peer forwarding

Abstract: A system, method and apparatus are disclosed herein for media streaming. In one embodiment, the system comprises one or more media servers to serve media content and a plurality of peers communicably coupled to one or more other peers of the plurality of peers and at least one of the one or more media servers to receive segments of media content, where at least one of peers allocates a set of resources for serving the segments of media content including cache memory to store the segments and media files and uplink bandwidth to send the segments of media content to the one or more peers to which the one peer is communicably coupled. The system also includes a first control server to track media content demand and the allocated resources of the plurality of peers to determine which peer should cache which segment of the media file and to return peer location information specifying the one or more peer locations from which each peer is to receive each segment of each media content requested. The control server is operable to send the location information to each peer. In one embodiment, the one control server is also operable to calculate a utility of each caching option and enforce it by sending triggers to the peers to initiate the caching at those peers.

Dyser: towards a real-time search engine for the web of things

Abstract: The increasing penetration of the real world with embedded and globally networked sensors enables the formation of a Web of Things (WoT), where high-level state information derived from sensors is embedded into Web representations of real-world entities (e.g. places, objects, creatures). A key service for the WoT is searching for entities which exhibit a certain dynamic state at the time of the query, which is a challenging problem due to the dynamic nature of the sought state information and due to the potentially huge scale of the WoT. Below we report on our initial efforts to construct such a search engine and the underlying WoT.

Positioning system, positioning method, and positioning program

Abstract: An object of the present invention is to implement accurate positioning of a mobile communication terminal even in an environment in which delay waves are included in radio waves arriving at the mobile communication terminal from radio wave sources A positioning server 10 forming a positioning system for estimating a location of a cellular terminal 20 has a distance information acquisition unit 13 for acquiring information indicating distances calculated based on radio waves transmitted and received between a plurality of cellular base stations 30 and the cellular terminal 20; a direction information acquisition unit 14 for acquiring a plurality of pieces of information indicating directions of radio waves received by the cellular terminal 20; a virtual sector calculation unit 15 for calculating for each of the cellular base stations, a range of directions from the cellular base station 30 to the cellular terminal 20 from the information indicating the directions of the radio waves, based on a range calculation rule stored in advance; and a location calculation unit 16 for calculating the location of the cellular terminal 20, based on the distances and the range of directions

Method and apparatus for prioritized information delivery with network coding over time-varying network topologies

Abstract: A method and apparatus is disclosed herein for information delivery with network coding over time-varying network topologies. In one embodiment, the method comprises decomposing a sequence of topology graphs that model a time-varying network topology into a plurality of virtual graphs, where each virtual graph of the plurality of virtual graphs corresponds to a distinct traffic class, and the virtual topology graph representing a partial topology of a time-varying network. The method also includes selecting a network code for each virtual graph in the plurality of the virtual graphs to meet requirements of the distinct traffic class corresponding to said each topology graph, where the network code is used to encode packets of the associated traffic class, and processing packets of each traffic class using the network code determined by its corresponding virtual topology and the requirements of said each traffic class, including using a virtual buffer system to implement the network code corresponding to each traffic class over the physical network topology. The method also includes using a scheduler to determine the transmission schedules for each output packet from the virtual buffer system of each traffic class where the scheduling decisions are based, at least in part, on the QoS requirements of each class.

Sparse orthonormal transforms for image compression

Abstract: We propose a block-based transform optimization and associated image compression technique that exploits regularity along directional image singularities. Unlike established work, directionality comes about as a byproduct of the proposed optimization rather than a built in constraint. Our work classifies image blocks and uses transforms that are optimal for each class, thereby decomposing image information into classification and transform coefficient information. The transforms are optimized using a set of training images. Our algebraic framework allows straightforward extension to non-block transforms, allowing us to also design sparse lapped transforms that exploit geometric regularity. We use an EZW/SPIHT like entropy coder to encode the transform coefficients to show that our block and lapped designs have competitive rate-distortion performance. Our work can be seen as nonlinear approximation optimized transform coding of images subject to structural constraints on transform basis functions.

Base station apparatus and method in mobile communication system

Abstract: A base station apparatus used in a mobile communication system where user terminals with various numbers of reception antennas may be situated includes a providing unit configured to provide plural reference signals according to the number of transmission antennas; a precoding unit configured to replicate each of a predetermined number of input signal sequences according to the number of transmission antennas, apply a predetermined precoding vector to each of the replicated sequences, and generate output signal sequences corresponding to the number of transmission antennas; and a transmitting unit configured to transmit transmission signals including the output signal sequences from plural transmission antennas; wherein at least one of the input signal sequences includes a control signal and one of the plural reference signals.

Mobile communications system, base station apparatus, user apparatus, and method

Abstract: A user apparatus which wirelessly communicates with a base station apparatus within a mobile communications system is disclosed. The user apparatus includes a receive unit which receives control information in downlink; and a transmit unit which transmits a first channel in uplink, wherein the transmit unit, based on the control information, makes a value of a maximum transmit power of the first channel smaller than that of a nominal power specified for the mobile communications system.

Usage Control Enforcement: Present and Future

Abstract: Both personal data and intellectual property must be protected for various reasons. The authors explore the state of the art in usage control, which is about controlling the use of such data after it has been given away, and identify room for improvement.

Multiuser MIMO downlink with limited inter-cell cooperation: Approximate interference alignment in time, frequency and space

Abstract: We consider a realistic albeit simplified scenario for wireless cellular systems of the next generation (4G and beyond), where MIMO-OFDM, opportunistic scheduling, channel state information at the transmitter and limited base-station cooperation are envisaged. We propose two strategies with limited base-station cooperation that can be easily implemented with today's technology and achieve an approximate form of inter-cell interference alignment. The first strategy consists of imposing a ldquopower maskrdquo in frequency such that adjacent cooperative clusters of base stations generate different interference levels in different frequency subchannels. The second strategy consists of switching between different cooperative clusters such that no user is in a permanently disadvantaged location.We compare single-user and multiuser MIMO systems in terms of average throughput as a function of the user location.

Prototype of pedestrian-to-vehicle communication system for the prevention of pedestrian accidents using both 3G wireless and WLAN communication

Abstract: For the realization of a safe road traffic environment a wireless communication system which makes an information network between pedestrians and vehicles has been needed. A prototype of pedestrian-to-vehicle communication system was developed by using a cellular phone and a car navigation system equipped with GPS and wireless communication function. By interoperation of 3G wireless network and wireless LAN, it was possible to communicate in a wide area and with little delay time in a local area. The system can exchange the necessary information between pedestrians and vehicles, inform of the location of the ones that have an accident risk, and give an alarm by employing the developed algorithm for estimating the collision risk between each pedestrian and vehicle. The effectiveness of the system was shown by simulation of traffic situations.

A method and apparatus for constructing security policies for web content instrumentation against browser-based attacks

Abstract: A method and apparatus is disclosed herein for constructing security policies for content instrumentation against attacks. In one embodiment, the method comprises constructing one or more security policies for web content using at least one rewriting template, at least one edit automata policy, or at least one policy template; and rewriting a script program in a document to cause behavior resulting from execution of the script to conform to the one or more policies.

System and method for generating a graphical user interface

Abstract: A communications terminal comprises a display, a first storage for storing data, a second storage unit that stores a first and a second information set, the first information set including a first communications address and a communications recipient's name, and the second information set includes a second communications address and a communications recipient's name, a first display controller displays a text string expressed by data stored in the first storage unit; and a second display controller that identifies a name from the second storage unit included in the text string being displayed. When the name is associated with the first communications address, a screen prompts communications to the first communications address, or when the name is associated with the second communications address, a screen prompts communications to the second communications address.