Yoji Kishi

Bio: Yoji Kishi is an academic researcher from KDDI. The author has contributed to research in topics: MIMO & Mesh networking. The author has an hindex of 12, co-authored 87 publications receiving 525 citations.

Area map build up system for making area map based on communication quality information

Abstract: PROBLEM TO BE SOLVED: To provide an area map build up system which does not apply a load to the whole network by reducing the number of times for transmitting communication quality information from a general wireless terminal as much as possible when a database server makes an area map based on the communication quality information. SOLUTION: A database server determines a measurement area range information specifying an area where the number of pieces of communication quality information becomes a predetermined threshold or less, and transmits a measurement request including the measurement area range information and measurement quality range information to a wireless terminal. The wireless terminal judges whether communication area information based on the position of the wireless terminal itself is included in the measurement area range information included in the received measurement request and/or weather the communication quality information is included in the measurement quality range information or not. If the judgment is true, a measurement response including current position information and communication quality information is answered to the database server. COPYRIGHT: (C)2009,JPO&INPIT

Multi-hop wireless communication system and its routing method

Abstract: PROBLEM TO BE SOLVED: To provide a multi-hop wireless communication system capable of establishing an optimal route while taking account of the link quality, and to provide its routing method. SOLUTION: A relay node receives an RREQ and determines the link quality metric of a route from a source node to its own node before transferring it while registering in the RREQ. A destination node receives the RREQ and determines the link quality metric of a route from the source node to its own node before sending it back while registering in the RREP. A destination node receiving the same RREQ on a different route sends back the RREP in response to an RREQ having an excellent link quality metric. A source node receiving the same RREQ on a different route generates route information based on an RREP having an excellent link quality metric. COPYRIGHT: (C)2005,JPO&NCIPI

A Cell-Planning Model for HetNet with CRE and TDM-ICIC in LTE-Advanced

Abstract: Heterogeneous Network (HetNet) in 3GPP is a technique to increase network capacity. In order to further increase network capacity, Cell Range Expansion (CRE) and Time Domain Multiplexing Inter-Cell Interference Coordination (TDM-ICIC) have been discussed for LTE-Advanced. Since the parameter values for CRE and TDM-ICIC have a huge effect on network capacity expansion, in this paper, a cell-planning model for the downlink in HetNet with CRE and TDM-ICIC is presented in order to find the minimum number of installed pico BSs under the constraint of covering all user data traffic. The constraint condition is formulated by using an overload indicator for the cases of between normal subframes and muted subframes, because different interference sources are considered for these subframes by adopting TDM-ICIC. The appropriate parameter values of not only CRE and TDM-ICIC but also the location, transmission power, and antenna tilt for each pico BS are determined. Cell planning is conducted for traffic distribution generated by reference to realistic traffic distribution by a greedy algorithm based on the proposed cell-planning model. The result shows that the solution algorithm finds a good approximate solution which covers all data traffic by installing one pico BS with CRE bias value = 8 dB and setting the muted subframe ratio = 0.2.

Method for controlling sequence of packet in multi-link communication system

Abstract: PROBLEM TO BE SOLVED: To enable an unarrived packet and an erased packet to be distinguished without monitoring the waiting states of all the packets under the sequence control of the packets and to enable a packet transfer delay due to waiting for an erased packet to be reduced. SOLUTION: The sequence number of the packet reached at present time point, the sequence number (expected - seqno) expected to reach next, the minimum sequence number of the packet existing in a buffer, the sequence number (arrived - seqno [i]) of the packet reached at last at a port of a transmission line i, and the minimum sequence number of the arrived - seqno [i] are managed. A sequence control algorithm judges erasure of the unarrived packet when the packets of a sequence number larger than the expected - seqno arrived from all the transmission lines A, B and C, and a transfer process of the packet in the buffer is advanced. If the packet exists in the buffer, a time-out algorithm is performed at each predetermined time. COPYRIGHT: (C)2004,JPO

Shared Remote Radio Head architecture to realize semi-dynamic clustering in CoMP cellular networks

Abstract: In conventional cellular systems, transmission rate degrades at cell-edge because of inter-cell interference and pathloss. This problem is called “cell-edge problem”. To solve this problem, Coordinated Multi-Point (CoMP) technique has been proposed recently. CoMP can convert inter-cell interference signals from neighbor base stations (BSs) to desired signals. However, CoMP requires accurate synchronization among cooperative BSs as well as Channel State Information (CSI) between target user and all cooperative BSs. For practical realization of CoMP, new BS architecture in which a BS unit is connected to multiple Remote Radio Heads (RRHs) located apart through optical fiber has been proposed. Even using this architecture, however, CoMP can only be realized within the predefined connected RRHs (CoMP cluster). Therefore, cluster-edge users cannot experience throughput improvement by means of CoMP. This paper proposes a novel BS architecture called shared RRH network, in which each RRH is additionally connected to multiple BS units. As flexible clustering is made possible by this architecture, semi-dynamic clustering using geometrically overlapped cluster patterns allocated with orthogonal resources can be achieved which alleviates the cluster-edge problem. Simulation with parameters based on the 3GPP is setup for performance evaluation of the proposed system. Numerical results show that semi-dynamic CoMP using shared RRHs can significantly improve the system performance both at cell-inner and cell-edge compared with the conventional RRH systems, which confirms the effectiveness of the proposed network.

Hybrid mesh routing protocol

Abstract: A method for selecting a route by a node between a source node and a destination node in a wireless mesh network by establishing the route between the source node and the destination node using media access control addresses is described. A method for a node to selecting a route to join a multicast group in a wireless mesh network using media access control addresses, is also described.

Hypertext Transfer Protocol (HTTP)

Abstract: In this report (written in Greek) are presented the basics of the hypertext transfer protocol.

Automated access, key, certificate, and credential management

Abstract: Certain embodiments provide means for managing automated access to computers, e.g., using SSH user keys and other kinds of trust relationships. Certain embodiments also provide for managing certificates, Kerberos credentials, and cryptographic keys. Certain embodiments provide for remediating legacy SSH key problems and for automating configuration of SSH keys, as well as for continuous monitoring.

Power control for a wireless communication system utilizing orthogonal multiplexing

Abstract: Techniques for adjusting transmit power to mitigate both intra-sector interference to a serving base station and inter-sector interference to neighbor base stations are described. The amount of inter-sector interference that a terminal may cause may be roughly estimated based on the total interference observed by each neighbor base station, channel gains for the serving and neighbor base stations, and the current transmit power level. The transmit power may be decreased if high interference is observed by a neighbor base station and increased otherwise. The transmit power may be adjusted by a larger amount and/or more frequently if the terminal is located closer to the neighbor base station observing high interference and/or if the current transmit power level is higher, and vice versa. The intra-sector interference is maintained within an acceptable level by limiting a received SNR for the terminal to be within a range of allowable SNRs.

Uplink pilot and signaling transmission in wireless communication systems

Abstract: Techniques to more efficiently transmit pilot and signaling on the uplink in an OFDM system. With subband multiplexing, M usable subbands in the system are partitioned into Q disjoint groups of subbands. Each subband group may be assigned to a different terminal for uplink pilot transmission. Multiple terminals may transmit simultaneously on their assigned subbands. The transmit power for the pilot may be scaled higher to attain the same total pilot energy even though S instead of M subbands are used for pilot transmission by each terminal. Pilot transmissions from the terminals are received, and a channel estimate is derived for each terminal based on the pilot received on the assigned subbands. The channel estimate comprises a response for additional subbands not included in the assigned group. Subband multiplexing may also be used for uplink signaling transmission.