Showing papers by "NTT DoCoMo published in 2002"

Hierarchical ID-Based Cryptography

Abstract: We present hierarchical identity-based encryption schemes and signature schemes that have total collusion resistance on an arbitrary number of levels and that have chosen ciphertext security in the random oracle model assuming the difficulty of the Bilinear Diffie-Hellman problem.

Layout of platform specific graphical user interface widgets migrated between heterogeneous device platforms

Abstract: A scaleable graphical user interface system utilizes a device platform independent model to provide dynamic layout of graphical user interface widgets migrated between any of a plurality of heterogeneous device platforms. The device platform independent model includes at least one platform independent graphical user interface widget. Based on the device platform independent model, platform specific graphical user interface widgets that correspond to each of the platform independent graphical user interface widgets may be laid out on a page and compared to the size of a display screen of a heterogeneous device platform. Where the page does not fit within the display screen, the platform independent graphical user interface widgets may be dynamically rearranged within the page to fit the display screen. In addition, where designated as splitable, the platform independent graphical user interface widgets may be split among multiple pages of a presentation to fit within the display screen.

System for management of cacheable streaming content in a packet based communication network with mobile hosts

Abstract: A cache handoff system for managing cacheable streaming content requested by a mobile node within a network architecture is disclosed. The network architecture includes a first subnet and a second subnet. The cache handoff system includes a first caching proxy operable in the first subnet to supply a content stream in response to a request of the mobile node operable in the first subnet. In addition, the cache handoff system includes a second caching proxy operable in the second subnet. The first caching proxy may initiate a cache handoff of the request to the second caching proxy when the mobile node relocates to the second subnet. The second caching proxy may seamlessly continue to supply the requested content stream as a function of the cache handoff.

Context aware application level triggering mechanism for pre-authentication, service adaptation, pre-caching and handover in a heterogeneous network environment

Abstract: A network selection system that includes a mobile terminal in communication with a first network, a second network in communication with the first network and an application layer triggering mechanism that determines which one of a plurality of triggers is required in a certain set of circumstances to provide a particular application.

Variable Spreading Factor Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM)

Abstract: This paper proposes Variable Spreading Factor — Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) as the most promising forward link wireless access method in broadband packet wireless transmission using an approximate 50 – 100 MHz bandwidth. OFCDM is originally based on multicarrier CDMA where the spreading sequence is multiplied in the frequency domain, and OFCDM employing VSF can flexibly realize near optimum wireless access with higher link capacity by adaptively changing the appropriate spreading factor, SF, in the frequency domain based on the cell structure and radio link conditions such as the delay spread. Furthermore, by establishing the spreading factor of SF = 1, i.e., no spreading mode, VSF-OFCDM can be used as orthogonal frequency division multiplexing (OFDM). Simulation results demonstrate that, while SF = 1 (OFDM) achieves higher link capacity than SF > 1 in an isolated-cell environment, OFCDM with the optimized SF value over 1 achieves approximately 1.4 times higher capacity compared with OFDM in a multi-cell environment associated with the advantageous one-cell frequency reuse. Consequently, VSF-OFCDM can provide seamless deployment of broadband packet wireless access with high link capacity, that is, OFDM in an isolated-cell environment such as hot spot areas or indoor offices, and OFCDM with the adaptively optimized SF value over 1 in a multi-cell environment such as cellular systems according to the radio link conditions such as measured delay spread, by only changing the spreading factor.

Context aware search service

Abstract: A context-aware search service is provided to users requesting information. The context-aware search incorporates contextual information such as the context of the user making the request, the external context of the user or terminal that the user accesses, or the characteristics or context of the terminal. The contextualized request is processed through sets of analyses to customize the request including analyses to determine an exact nature of the request, analyses to limit a universe of reference to be examined to provide the result, and analyses to select the most appropriate content and format for presentation to the user once the result is obtained from separate service providers.

Low latency mobile initiated tunneling handoff

Abstract: The present invention provides a tunnel-based IP handoff process that can minimize the handoff latency associated with the standard Mobile IP registration. In the present invention, when neighboring nodes are detected, these detected nodes are identified as candidate nodes. Detection of just the existence of neighboring nodes should be possible even in situations where these neighboring nodes use different access technologies. For instance, pilot beacon signals may be taken as indication of the existence of candidate nodes although it may be impossible to compare them quantitatively if the beacon signals emanate from different access technologies. As soon as candidate nodes are identified, tunnels are established between the source node and the candidate nodes. The tunnels are used to forward data to the mobile node after a communication link between the mobile node and the source node goes down. As soon as the mobile node enters one of the neighboring networks and identifies a target node, the tunnels are torn down except the tunnel for the target node.

System for end user monitoring of network service conditions across heterogeneous networks

Abstract: A network monitoring system for monitoring network performance across heterogeneous networks with an end device is disclosed. The network monitoring system includes a network comprising a first heterogeneous network communicatively coupled with a second heterogeneous network. The first heterogeneous network may include the end device, an intermediate node and a gateway. The second heterogeneous network may include an application server. The end device and the application server may communicate over the network with a datastream. The end device may generate a tracer packet as part of the datastream. The datastream may travel through the intermediate node. The intermediate node may store network service information in the tracer packet. The gateway may operate as an interface to the second heterogeneous network. The gateway may intercept the tracer packet and store network condition information therein. In addition, the gateway may redirect the tracer packet back to the end device over the first heterogeneous network. The end device may process the information contained in the tracer packet to determine current network and application server operating conditions, and provide results of the processing to a user of the end device.

Selective fusion location estimation (SELFLOC) for wireless access technologies

Abstract: In an RF environment serviced by 802.11, Bluetooth (TM), or other network transmitters, or combinations, location-estimation methods and systems can advantageously use redundancy to refine an estimated location of an RF receiver. In one embodiment, a method for finding a receiver's location includes receiving signals from fixed transmitters, calculating preliminary location estimates, and combining the estimates using predetermined reference information on the RF environment. The reference information preferably includes minimum mean-squared error optimizing coefficients.

System for providing access control platform service for private networks

Abstract: A NSP network is disclosed for providing a platform service for providing data communication security in an IP-based communications network. The platform service includes connections to various private networks, a subscriber data management unit for managing information about the mobile terminals using the network, and a platform unit. The platform unit determines from the subscriber data management unit the status of the mobile terminals requesting connections to private networks and the status of the mobile terminals for which private networks target for connection. The platform unit includes applications for querying the subscriber data management unit for subscriber status, applications to command the transmission of authorization data, and applications to provide secure virtual private network communication lines for connecting the mobile terminals and the private networks.

Context-aware market-making service

Abstract: A mobile virtual network operators system is disclosed. The mobile virtual network operators system provides a single point of contact for wireless customers accessing a variety of services offered by a plurality of vendors. The mobile virtual network operators system may generate a sales proposal for a customer or a vendor and handle a proposal generated by a customer or a vendor. The mobile virtual network operators system may include a vendor database and a customer database. The mobile virtual network operators system receives, records and analyzes plurality of the customer's product search requests to form the customer's context aware purchase history. The customer database may store accumulated context aware purchase histories for a plurality of customers. The mobile virtual network operators system may generate a solicitation proposal for a customer based on the customer's context aware purchase history. The mobile virtual network operators system can anticipate customer's needs in advance and can generate a proposal accordingly.

Link manager and link management method

Abstract: There is disclosed a link manager comprises detecting unit for detecting what link is installed; managing unit for defining a plurality of link metrics indicating characteristics of each link detected and managing data corresponding to the respective link metrics on a table; and selecting unit for selecting a link having link metrics complying with a given condition.

Adaptive interpolation filter system for motion compensated predictive video coding

Abstract: An adaptive interpolation filter system for searching to obtain an optimized interpolation filter that minimizes prediction error in a video codec includes an interpolation module and a discrete search space. A plurality of discrete interpolation filters are positioned in a three dimensional grid within the search space. The interpolation module may select a current minimum filter. Based on the current minimum filter, a search region within the search space that includes a plurality of candidate filters located adjacent to the current minimum filter may be identified. The interpolation module may interpolate a reference image signal with each of the candidate filters. The candidate filter resulting in the smallest prediction error may be identified as the current minimum filter and the search repeated until the prediction error is minimized.

Cryptanalysis of the Revised NTRU Signature Scheme

Abstract: In this paper, we describe a three-stage attack against Revised NSS, an NTRU-based signature scheme proposed at the Eurocrypt 2001 conference as an enhancement of the (broken) proceedings version of the scheme. The first stage, which typically uses a transcript of only 4 signatures, effectively cuts the key length in half while completely avoiding the intended hard lattice problem. After an empirically fast second stage, the third stage of the attack combines lattice-based and congruence-based methods in a novel way to recover the private key in polynomial time. This cryptanalysis shows that a passive adversary observing only a few valid signatures can recover the signer's entire private key. We also briefly address the security of NTRUSign, another NTRUbased signature scheme that was recently proposed at the rump session of Asiacrypt 2001. As we explain, some of our attacks on Revised NSS may be extended to NTRUSign, but a much longer transcript is necessary. We also indicate how the security of NTRUSign is based on the hardness of several problems, not solely on the hardness of the usual NTRU lattice problem.

Radio communication system, base station, relay station, mobile station, and packet transmission control method

Abstract: The object is to control interference in a permissible range by applying the CDMA system to signal collision in the conventional CSMA and TDMA base multihop systems and to relax the hidden terminal problem and others to enhance the throughput of the entire system by grouping of channel groups in multihop transmission and by control of transmission based on an interference level from another station A multihop relay station calculate a desired signal level, for example, from an interference level at its own station of a packet sent from a mobile station, and notifies the mobile station of the desired signal level; and the mobile station calculates a transmission power amount of a packet from the desired signal level, determines whether the packet is transmissible to the station as a source of the desired signal level, on the basis of the transmission power amount, and transmits the packet by a power of the transmission power amount to the source station determined as a packet-transmissible station On this occasion, an interference signal is weakened by assignment of channel groups 1,2 for transmission of signals

Geographically adjacent access router discovery and caching for mobile nodes

Abstract: A geographically adjacent access router discovery system discovers geographically adjacent access routers through a distributed process in which mobile node(s) associated with a current access router may receive beacon signals from geographically adjacent access points. A link layer ID included in the beacon signals may be used by the system to identify corresponding geographically adjacent access routers. Network layer addresses of geographically adjacent access routers may be mapped to corresponding link layer IDs and cached by the system. The cache may be used to identify a network layer address from the link layer ID received in a beacon signal.

Receiver, transmitter, communication system, and method of communication

Abstract: A receiver, comprising a plurality of antennas configured to receive signals that are obtained by multiplying a plurality of data symbols transmitted over a plurality of data channels using spreading codes for each of the data channels, the data symbol being transmitted over a plurality of sub-carriers having different frequencies; a spreading code multiplier configured to multiply reception signals received by the plurality of antennas using spreading codes for the data channels corresponding to the reception signals; a weight controller configured to adjust antenna weights by which a reception signal received by each antenna is to be multiplied, and sub-carrier weights by which a reception signal received over each sub-carrier is to be multiplied; a weight multiplier configured to multiply the reception signals by the antenna weights and the sub-carrier weights adjusted by the weight controller; and a combining unit configured to combine the reception signals multiplied by the antenna weights and the sub-carrier weights at the weight multiplier among the antennas and over spreading code duration of the spreading codes.

Broadband packet wireless access based on VSF-OFCDM and MC/DS-CDMA

Abstract: This paper proposes broadband packet wireless access employing Variable Spreading Factor-Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) with two-dimensional spreading that prioritizes time domain spreading in the forward link and multi-carrier/DS-CDMA (MC/DS-CDMA) in the reverse link for the system beyond IMT-2000. Based on the wireless access scheme, we propose major radio air interfaces in the physical layer to achieve our target maximum throughput beyond 100 Mbps and 20 Mbps in the forward and reverse links, respectively. Furthermore, we present key technologies such as the adaptive radio link parameter control coupled with link adaptation, pilot channel assisted coherent detection in both links, adaptive antenna array beam forming transmitter and receiver, cell search, and channel coding. Finally, simulation results elucidate that VSF-OFCDM using die proposed radio link parameters achieves a throughput above 100 Mbps at the average received signal energy per symbol-to-background noise power spectrum density ratio (Ea/No) of approximately 13 dB (101.5 MHz bandwidth, without antenna diversity reception, 12-path Rayleigh fading channel). Furthermore, MC/DS-CDMA realizes a throughput above 20 Mbps at the average received Ea/No of approximately 8 dB (40 MHz bandwidth, with antenna diversity reception, 6-path Rayleigh fading channel).

Rate and robustness control with RTP monitoring agent for mobile multimedia streaming

Abstract: We propose a of control architecture for mobile multimedia streaming in which RTP monitoring agents report QoS information to media servers. The RTP monitoring agents lie midway between wired networks and radio links, monitor RTP packets sent from media servers to mobile terminals, and report quality information to media servers so that the servers can realize network-adaptive QoS control. By analyzing the information sent from the agents, the servers can distinguish quality degradation caused by network congestion from that caused by radio link errors, and can improve service quality by controlling the transmission rate and robustness against packet loss. Simulation results show our implemented QoS control schemes that use the feedbacks from the agent and control transmission rate and robustness provide better video quality than a simple rate control mechanism.

Proactive deployment of decision mechanisms for optimal handover

Abstract: To achieve optimal selection of new access points for mobile devices (10) being located in a mobile communication environment (14), according to the present invention there is provided a method of assisting handovers for a mobile device in a mobile communication environment. It is proposed to proactively deploy a handover decision mechanism in relation to a handover and in view of the operational context of the mobile device (10). This proactively deployed handover decision mechanism is then used to determine a new access point for the mobile device (10).

Method and system for location management and location information providing system

Abstract: In an information providing system, a user inputs desired mobile ID number to a client terminal. The client terminal transmits a request for location information on the mobile station including the mobile ID number to a location server via a location information server. The location server transmits a request for object movement information corresponding to the mobile station to an object information server. The location information server obtains the information from a traffic control device. Location information on the mobile station obtained by the location information server is transmitted to the terminal.

Measuring device, method for correcting measured outcomes, program and recording media

Abstract: A measuring device, with a display mode able to display separately map elements specified by a user selected from a list of map elements existing within the error span of the measured distance of a location by the help of which, the user can determine his/her own location and correct the measured distance of the location.

Access network dynamic firewall

Abstract: A network system includes a network edge point configured to provide a terminal with access to a network. The network edge point includes a security policy associated with the terminal, and controls communications between the network and the terminal according to the security policy. The security policy may include a personal filter downloaded from the terminal, a service filter downloaded from a service policy server, and/or a domain filter downloaded from a domain policy server. The terminal may access the network through a second network edge point. The second network edge point may download one or more of the filters from the first network edge point, and control communications between the network and the terminal according to the security policy.

Resource control system, resource control method, and base station and mobile station suitable for use in the same

Abstract: An object of the present invention is to enable the improvement of Qos and efficient use of resources with regard to the entire system by performing resource control of an own cell in cooperation with that of peripheral cells. The present invention provides a resource control system used for packet communication between a mobile station and each of a first and a second base stations. The first base station includes the judgment unit for judging whether or not the Qos of a packet to be communicated with the mobile station is ensured in the packet communication with the mobile station, or judging whether or not the resources necessary for a packet to be communicated with the mobile station are secured; and the second base station interface for requesting the second base station to suppress the use of resources when the Qos is judged not to be ensured, or the necessary resources are judged not to be secured. The second base station includes a resource use suppression unit, which suppresses the use of resources for the packet communication with the mobile station in accordance with the request from the first base station.

Multipath interference canceller for high-speed packet transmission with adaptive modulation and coding scheme in W-CDMA forward link

Abstract: This paper proposes a multipath interference canceller (MPIC) associated with orthogonal code-multiplexing that achieves much higher peak throughput than 2 Mbit/s with adaptive data modulation for high-speed packet transmission in the wideband direct sequence-code division multiple access (W-CDMA) forward link, and evaluates its throughput performance by computer simulation. The simulation results elucidate that sufficient multipath interference (MPI) suppression is achieved by a four-stage MPIC with 6-12 orthogonal code-multiplexing using one iterative channel estimation with pilot and decision feedback data symbols and further that the interference rejection weight control according to the number of observed multipaths is effective in improving the throughput. It is also demonstrated that MPIC exhibits a superior MPI suppression effect to a chip equalizer in the lower received signal energy per bit-to-background noise spectrum density (E/sub b//N/sub 0/) channel around 0-3 dB owing to the successive channel estimation at each stage. We show that the maximum peak throughput using MPIC is approximately 2.1 fold that without MPIC in a two-path and three-path Rayleigh fading channel and that the peak throughput of 8.0 Mbit/s is achieved using 64 QAM data modulation in a two-path fading channel within a 5 MHz bandwidth. Furthermore, the required average E/sub b//N/sub 0/ for satisfying the same throughput with MPIC is decreased by more than 2.0 dB.

Data link transmission control methods, mobile communication systems, data link transmission control apparatus, base stations, mobile stations, mobile station control programs, and computer-readable recording media

Abstract: A data link transmission control method performs data link transmission control comprising automatic repeat request control for transmission/reception of a packet between a mobile station (131, 231) and a plurality of base stations (102, 112, 122, 202, 212, 222), wherein a first base station (102, 202) stores (S322) and makes (S322) a copy of packet in which identification information specifying the packet has been added to packet addressed to said mobile station (131, 231), wherein said first base station (102, 202) delivers (S323) said packet copy to a second base station (112, 212), wherein said second base station stores (S324) said delivered packet copy, and wherein one or more base stations (102, 112, 202, 212) comprising said first base station (102, 202) transmit (S328) to said mobile station (131, 231) the packet accompanied by said identification information, or said delivered packet copy; wherein said mobile station (231) measures (S461) receiving qualities of signals transmitted from a plurality of base stations (202, 212, 222), and wherein, based (S462) on the receiving qualities for the respective base stations (202, 212, 222), said mobile station (231) or each base station (202, 212, 222) sends (S463) a request for a transition of a communication state to a base station (202, 212, 222) desired to make the transition of the communication state into another communication state, wherein said communication states comprise: a first state in which no packet transmission/reception is carried out to or from the mobile station (231); a second state in which a packet addressed to said mobile station (231) is provided with identification information for specifying said packet and in which the packet accompanied by the identification information can be transmitted to the mobile station (231); a third state in which a packet addressed to said mobile station (231) is provided with identification information for specifying said packet, a copy is made from the packet accompanied by the identification information, the packet copy is delivered, and the packet accompanied by the identification information can be transmitted; and a fourth state in which the packet copy is received from a base station (202, 212, 222) working in said third state and in which the packet copy can be transmitted to the mobile station (231).

Secure network access method

Abstract: The present invention provides network-layer authentication protocols for authenticating mobile client and access router to each other. The present invention uses Router Discovery as a carrier to implement the authentication protocols. In an embodiment of the present invention, a mobile client sends out a solicitation message to request connectivity service. The solicitation message contains a proof of identity of the mobile client. An access router that receives the solicitation message will not respond to it until the proof of the identity is verified. Only when the proof of identity of the mobile client is verified, will the access router respond and return an advertising message to the mobile client, thereby preventing unauthorized mobile clients from obtaining network access.

Method and system for server load balancing

Abstract: In one aspect of the invention, a method for load balancing a plurality of servers is provided. The method comprises intercepting a request from a requestor client forming part of a client group for a service provided by the plurality of servers, determining wait times for servicing prior requests from at least one member client of the client group by at least one of the plurality of servers, and selecting an execution server from among the plurality of servers for responding to the request dynamically based on a computation of the wait times.

Packet transmission method and system, and packet transmitting apparatus, packet receiving apparatus, and packet transmitting/receiving apparatus

Abstract: A packet transmission method for transmitting packets classified according to a quality of service (QoS) requirement from a transmitting node to a receiving node is provided. In the transmitting node, the steps of: selecting sequentially a QoS class; dividing a queued packet to be transmitted belonging to the selected class into a plurality of predetermined data units, and transmitting one of the obtained predetermined data units; and applying a transmitter-side retransmission control process to the data unit to be transmitted when the selected class is a QoS class specified for data type packets are provided. In the receiving node, the steps of: receiving sequentially the data units transmitted from the transmitting node; assembling a plurality of received data units to decompress the original packet for each QoS class; and applying a receiver-side retransmission control process to the received data units to be assembled when the received data unit belongs to one of the QoS classes specified for the data type packets are provided.

Multi-hop radio access cellular concept for fourth-generation mobile communications system

Abstract: This paper proposes a multi-hop radio access cellular (MRAC) scheme for achieving both high speed and high capacity and good area coverage in fourth generation mobile communications systems. In this scheme, we assume two kinds of hop stations, one is a dedicated repeater station installed at a good propagation location such as a rooftop, and the other is a user terminal that temporarily experiences good propagation conditions. For both cases, the path diversity effect can be obtained between single-hop and multi-hop paths. Four propagation models were studied representing the paths among the base station, hop stations, and mobile station. Based on the propagation models, suitable MRAC operation conditions are discussed. For mobile stations located at the cell edge area, MRAC operation is effective in reducing the transmit power. Consequently, MRAC reduces the interference in cellular systems and enhances the area coverage.