Bandai Masaki

Wireless LAN has been dramatically evolving in performance and coming into wide use. Mesh network, which access points are deployed in mesh structure, extends the coverage of the networks. That has a lot of benefits, simplicity of building network, wide coverage, load balancing of access points and so forth. The paper proposes a new mesh network structure, which consists of access points with longer wireless range and terminal nodes with shorter one. We also define a zone from a viewpoint of asymmetry of wireless range. In order to save battery consumption, a new algorithm of routing for ad hoc mesh network is proposed and discussed.

Wireless LAN has been dramatically evolving in performance and coming into wide use. Mesh network, which access points are deployed in mesh structure, extends the coverage of the networks. That has a lot of benefits, simplicity of building network, wide coverage, load balancing of access points and so forth. The paper proposes a new mesh network structure, which consists of access points with longer wireless range and terminal nodes with shorter one. We also define a zone from a viewpoint of asymmetry of wireless range. In order to save battery consumption, a new algorithm of routing for ad hoc mesh network is proposed and discussed.

When sensing data generation is disproportionate geographically, battery depletion partially occurs. As a result, network lifetime degrades significantly. In order to improve network lifetime we have proposed a scheme with data dispersal transmission for wireless sensor networks with multiple-sinks, and have improved network lifetime. In this paper, in order to improve network lifetime more, we improve the dispersal rate of node for each sink in our proposed. We evaluate the performance of the proposed scheme for several pattern of data generation is by using computer simulations. We show that the improvement of proposed scheme is effective to improve network lifetime more.

In the conventional multi-channel Medium Access Control protocols of ad-hoc networks, a channel allocation problem for collision avoidance occurs if nodes cannot make carrier sensing for different channels simultaneously. In this paper, a novel multi-channel MAC protocol with dynamic channel allocation is proposed to solve the problem. Specifically, in the proposed protocol, nodes make carrier sensing by channel-hopping method. With the information of channel usage, the protocol can allocate a channel to the nodes dynamically. Furthermore, by adjusting the data transmission probability enables. the proposed protocol to also realize high throughput for different number of nodes and data sizes. A theoretical protocol analysis is also described.

We propose Media Access Control (MAC) protocol that applies the transmission power control and the bit-rate control to improve the electric power efficiency in the data transmission. In the proposal protocol, An appropriate sequence is selected according to the received power obtained by exchanging the control frames. Moreover, each node makes a table for the transmission power and the bit-rate in own wireless interface. The data is transmitted with high power efficiency by acquiring appropriate transmission power and the bit-rate corresponding to the change in a peripheral wireless situation. The performance of the proposal protocol is shown by the computer simulation.

RFID systems with plural readers have a problem that communications of readers and tags collide when they are located physically near positions. For this problem, Waldrop, Engels, Sarm proposed DCS and VDCS and showed that they achieve higher probability of communication than slotted aloha in case of high probability between readers and tags through simulation. However, the mathematical structure of the protocols are still unclear. This paper analyses the performance of RFID systems with plural readers. First of all, the paper formals DCS and analyzes state transition probabilities, stationary state probabilities, and communication success rates. The theoretical result shows that there is an optimal load which maximizes the communication success rate, and so forth. We also points out the defects of DCS.

In this paper, we propose a novel routing algorithm constructing a power efficient route called PERFECT (Power-efficient routing based on the Function of Energy Computing Time) in ad hoc networks. In PERFECT, the standby time to forward RREQ (Route REQest) is calculated by the received power of RREQ. PERFECT does not need additional control packets such as position information etc.. Even if some nodes equipped with different characteristic antenna exist together, PERFECT can construct a power efficient route. In addition, we also propose the extended version of PERFECT called D-PERFECT (Discrete-PERFECT) for discrete power control environment. Theoretical and Simulated results show the effectiveness of PERFECT and D-PERFECT.

In conventional multi-channel Medium Access Control protocol of ad-hoc networks, there is a channel allocation problem for collision avoidance because node cannot make carrier sensing for different channels simultaneously. In this paper a novel multi-channel MAC protocol with dynamic channel allocation is proposed to solve the problem. Specifically, in the protocol, nodes make carrier sensing by channel-hopping methods. With the information of channel usage, we can allocate a channel to the nodes dynamically. Furthermore, by adjusting the data transmission probability, proposed protocol can also realize high performance throughput n different number of nodes and data sizes. A theoretically protocol analysis is also described.

Smart antennas are expected to enhance scalability in ad hoc networks. This paper at first evaluates three directional MAC protocols, DMAC, MMAC and SWAMP as well as the omni-directional protocol IEEE 802.11 DCF in multi-hop transmission environment. The evaluations address the problem that the performance strongly depends on the topology of routes between sources and destinations, referred to as a directional hidden terminal problem. After analyzing the problem, we propose three solutions. The solutions are NAV indicators which are high gain CTS (HCTS), backward RTS (BRTS) and relayed CTS (RCTS) indicating on-going communications to a directional hidden terminal to set NAV. Among those we show that the solutions have the improvement of the throughput.

When sensing data generation disproportinates geographically, battery depletion occurs partially. As a result, network lifetime degrades significantly. In this paper, in order to improve network lifetime we propose a scheme with data dispersal transmission for wireless sensor networks with multiple sinks. In the proposed scheme, when sensing data generation disproportionates geographically, each node transmits data to plural sinks according to probability calculated by number of hops and remaining batterys. We evaluate the performance of the proposed scheme by using computer simulations. We show that the proposed scheme is effective to improve network lifetime by 20%.

Using directional antennas to sensor nodes is effective for power saving. However, because of its narrow beamwidth the number of links decrease. We propose a sensor node composition and control of method that applies multiple directional antennas to solve this problem. First, a variety of antenna models composed by the proposed method are evaluated by computer simulation under the environment that considers collisions in the MAC layer. Next, it evaluates to this environment when the data transfer to the sink is considered. We show the effectiveness of two or more the proposed method with directional.

In recent years, various communication systems for ITS (Intelligent Transport Systems) have been proposed. The Inter-Vehicle Communication(IVC) is one of the ITS communication methods. IVC should be available to prevent accidents and to achieve automatic driving. Therefore, it requires high reliability. However, the frequent collision of data packets results in the low reliability. This paper proposes a vehicle grouping communication protocol called R-VGMP and evaluates it. R-VGMP is TDMA-based and achieves high reliability by building a vehicle group with the master car, which control the group network. Simulation study shows that reachability rate of the control packet in vehicle grouping phase is relatively higher than a simple protocol of IEEE802.11 due to suppression of data collision.

This paper proposes an routing algorithm, called PERFECT (Power Efficient Routing based on Function of Energy Computing Time) which constructs a power efficient route in wireless ad hoc networks. After receiving RREQ, each node defers forwarding RREQ transmission for the standby time derived from the predefined delay function from the signal strength of received RREQ. Therefore, shorter links result to be chosen rather than longer links. We show that PERFECT can build a more efficient route at less cost than PCDC and DPER. We also develop the delay function according to the actual devices which enable some discrete power levels.

In order to realize low handoff latency without increasing overhead, we propose a handoff scheme using positional information for Mobile IP based networks. In the proposed scheme, to reduce overhead in wired channel, when a foreign agent (FA) detect a handoff, old FA estimates the next FA by using the positional information of mobile node (MN) and neighbor FAs. The old FA copies and forwards packets to the estimated next FA. In addition, to shorten handoff latency, old FA informs a handoff to the estimated next FA, and the estimated next FAs shorten its Agent Advertisement (ADV) message interval. Moreover, to alleviate overhead in wireless channel, old FA informs to all neighbor FAs except the actual next FA that the estimation is failed. The informed FAs cancel to shorten ADV message transmission interval. By performance evaluation using theoretical analysis and computer simulations, we show that the proposed scheme can realize low handoff latency without increasing overhead in both wired and wireless channel.

In this paper, to avoid disconnecting multicast path, we propose a multicast protocol for reducing disconnected time due to routechange via MMG hi Mobile IP environment. When MH, which recieves multicast packet via MMG from CH, hands off to other network, MMG changes the multicast route to avoid disconnecting multicast path in the proposed protocol. The simulation results show that the proposed protocol can reduce both the usage rate of bandwidth and disconnected time compared with the conventional protocols.

We propose to A Wireless Sensor Networking Architecture for Lifesaving in a Disaster. In this research, system has a division-by-class structure by role. At our Sensor Network, the kind of node is different from the communication ranges. We propose to manage power consumption to reduce by three modes. In the communication system is combined various MAC protocols. This paper examines the construction of the sensor network which collects information for damage assessment of a building or the rescue of the persons confined in a building at a disaster. We describe the composition of a sensor network and the function of a node and examine the communication system for disaster. Moreover, we examine the MAC protocol which raises communicative reliability for the power-saving of a sensor and the communicates at the time of a calamity.

In this paper, we propose an effective multicast routing protocol in ad-hoc network with asymmetric links. In the proposed protocol the node receiving Join Query in ODMRP(On-Demand Multicast Routing Protocol) transmits ACK packet, and the proposed protocol can detect asymmetric links by using Join Query and ACK packet. And the node detecting asymmetric links researches the forwarding route for Join Reply by using surrounding nodes. Thus, in the proposed protocol multicast source can use the shortest route to receivers in ad-hoc network with asymmetric links. We evaluate the performance of average number of hops and the probability that the route between multicast source and receivers does not exist in the proposed protocol and ODMRP by using computer simulations. It is found that the proposed protocol improves these performances and the proposed protocol is an effective multicast routing protocol for ad-hoc network with asymmetric links.

In order to realize low handoff latency without increasing overhead in wired channel extremely, we propose a low latency handoff scheme using positional information for mobile IP based networks. In the proposed scheme, mobile host (MH) and foreign agent (FA) can get own positional information by using a device such as global positioning system (GPS) . FAs exchange IP address and positional information among their neighbor FAs. When a distance between FA and MH exeeds a threshold, the FA anticipates the MH's next FA. The FA copies data packets and begins to forward them to the MH's next FA. Moreover, in the MH's next FA, the transmission interval of advertisement message is shortened. By shortening the interval, MH can receive advertisement message from a new FA. In addition, when a new FA receives a registration request message from MH, the FA replies tentative registration message to the MH to minimize the handoff latency. By performance evaluation using both theoretical analysis and computer simulations, we show that the proposed scheme can realize low handoff latency without increasing overhead in both wired and wireless channel extremely.

In this paper, in order to reduce the communication overhead and the location search overhead, we propose the multi-level zone-based hierarchical link state (ZHLS) routing with the new location search technique for mobile ad-hoc networks. The proposed protocol can reduce the communication overhead by hierarchizing the network into multi-level zones. Moreover, the location search is not performed by unicasting one location request to each zone, but performed by each higher-level gateway node searching own lower-level zones in the proposed protocol. So the location search overhead is reduced. We compare the performance by the mathematical analysis and the computer simulations. The mathematical analysis and the simulation results show that the proposed protocol can reduce the communication overhead and the location search overhead.

The idle bandwidth arises in the isochronous area when bit rate of video data does not attain the peak rate. In this paper, to decrease idle bandwidth, we propose VBR video transmission scheme with isochronous and asynchronous transfer mode over Wireless 1394. In the proposed scheme, the video node which uses isochronous transfer mode is assigned bandwidth equivalent to average rate of the video stream. It is found that the proposed scheme can improve the channel utilization performace.

We propose a medium access control protocol for broadcast and unicast transmission with deadlock avoidance and tolerance for network topology changes in wireless ad-hoc networks. In the proposed sheme, the terminals trarnsmit the transmission request packet through one minislot from pluralities to avoid the confliction of the packet and to solve the reservation deadlock. To reduce the access delay and to be tolerant for the topology changes by movement of the terminals, the proposed scheme makes reservation at every slot. By the performance evaluation using computer simulation, we show that proposed scheme can improve the throughput performance, and reduce the access delay compared to the conventional schemes.

We propose a medium access protocol with token passing and retransmission by the hub station in the asynchronous transfer mode of Wireless 1394 in high data rate home network. In the proposed protocol, to improve the waiting time performance, the token passing is adopted. Moreover, when the data packets are received incorrectly because of the shadowing, the hub station transmits the corresponding data packets instead of transmitting from the same station to improve the recovery rate performance. By the performance evaluation using computer simulations, we show that the proposed protocol can improve the waiting time performance and the recovery rate performance comparing to the conventional Wireless 1394.

To realize high throughput performance in wireless ad hoc networks, we propose a media access control protocol with tone signals. In the proposed protocol, two tone signals are adopted in addition to the RTS/CTS handshaking. The prohibition transmitting tone (PTt) signal is used in order to prohibit neighbor nodes from transmitting a packet. The prohibition receiving tone (PTr) signal is also used in order to prohibit neighbor nodes from receiving a packet. Adopting PTt signal, since hidden nodes from the receiver can sense the PTt signal, hidden nodes postpone its RTS packet transmission. Adapting PTr signal, since exposed nodes can sense no PTr signal, exposed nodes can send its RTS packet. Moreover, in order to alleviate the collisions among RTS packets, when a node transmits RTS packets, the PTr signal is adopted. The performance of the proposed protocol is analyzed theoretically in the single area situation. By means of computer simulations, we evaluate the performance of the proposed protocol. As the result, we show that the proposed protocol is useful to improve the throughput performance.

To improve the message delay performance without degrading the voice packet loss probability, two modified DRMA protocols are proposed. The DRMA with multiple slots reservation is proposed as the proposed-1 scheme. The proposed-1 DRMA with retransmission algorithm using exponential backoff scheme is proposed as the proposed-2 scheme. By the performance evaluation using computer simulations, we show that comparing to the conventional DRMA, the proposed-1 and the proposed-2 scheme reduce the data message delay without degrading the voice packet loss probability.

This paper proposes two protocols which can reduce the mean delay for variable-sized messages in a single-hop network based on wavelength division multiplexing (WDM). The first protocol makes reserved short length messages prior to long length messages, and the second protocol introduces the priority for long delay messages. We show the simulation results that first protocol can reduce the mean delay compared with the protocol which reserves messages randomly, and that second protocol reduces the mean delay of long length messages by introducing the priority for long delay messages.

The shared concentration output queueing (SCOQ) with middle buffer at input of Batcher-Banyan network is proposed. In the proposed model, when multiple packets distined for a output port at the same time, one packet call be routed to output buffer and rest of packets are waiting in the head-of-the-line of middle buffer. We evaluate the packet loss probability and the mean waiting time by theoretical calculation and computer simulation. As the results, it is shown that the proposed model is useful to decrease the packet loss probability.

A packet switching protocol in a WDM-based optical network using a passive star topology is proposed. In the proposed protocol, one time slot is divided into minislots and a message is organized with short-length Packets. Packets are transmitted simultaneous1y within one time slot. We evaluate throughput and the average system delay under uniform traffic by computer simulation. As the results, it is shown that the proposed protocol is useful to support variable-sized messages efficiently without degrading throughput and delay performance.