Tetsuo Ideguchi

Ad-Hoc Routing Protocol Avoiding Route Breaks Based on AODV

Many routing protocols in mobile ad-hoc networks have been developed by many researchers. One of ad-hoc routing protocol types is the on-demand routing that establishes a route to a destination node only when required. But it is necessary to re-establish a new route when its route breaks down. However, most of on-demand routing protocols re-establish a new route after a route break. In this paper, we propose a new route maintenance algorithm to avoid route breaks because each intermediate node on an active route detects a danger of a link break to an upstream node and re-establishes a new route before a route break. We propose this algorithm based on AODV (Ad-hoc On-demand Distance Vector routing protocol) that is one of the routing protocols under study by the IETF MANET Working Group. Then, we evaluate the performance of our proposal by computer simulations.

Improving Throughput and Fairness in WLANs through Dynamically Optimizing Backoff

Given the limited channel capacity in wireless LANs, it is important to achieve high throughput and good fairness through medium access control (MAC) schemes. Although many schemes have been proposed to enhance throughput or fairness of the original IEEE 802.11 standard, they either fail to consider both throughput and fairness, or to do so with complicated algorithms. In this paper, we propose a new MAC scheme that dynamically optimizes each active nodes backoff process. The key idea is to enable each node to adjust its Contention Window (CW) to approach the optimal one that will maximize the throughput. Meanwhile, when the network enters into steady state in saturated case, i.e., under heavy traffic load, all the nodes will maintain approximately identical CWs, which guarantees fair share of the channel among all nodes. A distinguishing feature of this scheme is the use of an index called average channel idle interval for optimizing the backoff process without estimating the number of active nodes in networks. We show through theoretical analysis that the average channel ideal interval can represent current network traffic load and indicate the optimal CW. Moreover, since it can be obtained through direct measurement, our scheme eliminates the need for complicated estimation of the number of active nodes as required in previous schemes, which makes our schemes simpler and more reliable when network traffic changes frequently. Through simulation comparison with previous schemes, we show that our scheme can greatly improve the throughput no matter the network is in saturated or non-saturated case, while maintaining good fairness.

A Design Method of Local Community Network Service Systems with Ad-Hoc Network Technology

In this paper, firstly we have proposed the free charged local community network service system with ad hoc networking technology and secondly then presented the performance evaluation model of the service with multi agent systems by using the prospect theory, and finally evaluated the service system. The proposed method is expected to contribute to the application of ubiquitous network and the optimum design of mobile ad hoc communication systems.

A simplified performance evaluation for delay of voice end-user in TDMA integrated voice/data cellular mobile communications systems

Major types of data for multimedia with mobile communications are voice, WWW and FTP. Different regimes for quality of service (QoS) exist for each with reference to delay sensitivity. Sharing available radio resource has been inherently based on the characteristics of data types and their associated QoSs. To satisfy each QoSs, the Delay of Voice End-User (DOVE) protocol has been presented. However, when evaluating the performance of DOVE protocol, there was one problem which requires much calculation time. In this paper, introducing the steady state equations for the Markov chain of DOVE protocol and solving them, we present a simplified method for evaluating the performance of DOVE protocol. The proposed method can be carried out in a less computer time.

Traffic Evaluation of Group Communication Mechanism among Vehicles

In recent years, much work has been done on ITS, which is proved to be an effect method to improve transport system. In this paper, we focus on improving the safety of driving vehicles by a novel effective communication system. We consider a consensus formation on vehicle group. We propose WDDP (Wireless Direct Distribution Protocol) that has a group communication mechanism among vehicles. After comparing several methods with the proposal of group communication mechanism among vehicles in this paper, we discuss the characteristics of packet traffic and number of group nodes as comparison items. We define a simulation model using the communication network simulator, OPNET Modeler. Then, we analyze network traffic on the simulation model and evaluate basic properties.

Multichannel time-spread scheduling: a new approach to handling heavy traffic loads in ad hoc networks

Wireless mobile networks that do not have infrastructure or centralized administration, known as the ad hoc networks, have received considerable attention in the last few years. The salient characteristics of such networks - time-varying topology and lack of centralized control design - have made medium access control design more complicated and challenging, which is particularly when multiple channels are employed. Recently, many multichannel transmission protocols, such as collision-avoidance transmission scheduling (CATS), have been investigated for their higher efficiency although their problems are abundant. In this paper, we propose a new protocol, namely, multichannel time-spread scheduling (MATS), to improve the throughput performance under heavy traffic loads. In MATS, nodes with transmission requests are divided into three groups, and carry out channel reservations in parallel with a short overhead. We carry out simulation study and the results show that the performance of this protocol under high traffic loads is significantly improved.

A novel MAC protocol of wireless LAN with high throughput and fairness

In this paper, we propose a novel MAC scheme that dynamically optimizes each active nodes backoff process. Through theoretical analysis, we find that the average channel idle interval can represent current network traffic load and then can used together with estimated number of nodes for setting optimal CW. Since necessary indexes can be obtained through direct measurement, our scheme will not increase any added load to networks, which makes our schemes simpler and more reliable when network traffic reaches saturated. Through simulation comparison with previous schemes, we show that our scheme can greatly improve the throughput no matter the network is in saturated or non-saturated case, while maintaining good fairness.

Improving protocol capacity by scheduling random access on WLANs

The MAC protocol is important, especially for wireless LAN because of limited bandwidth. A great deal of research has been carried out and some of proposed schemes are effective. Specifically, considerable effort has been devoted to improving the IEEE 802.11 standard which is utilized widely. Previous theoretical analysis gave the upper bound of IEEE 802.11 DCF throughput which is far below the channel capacity and corresponding algorithm was proposed, which can achieve the throughput close to the upper bound. It seems that we cannot expect to enhance the throughput much more in a usual way. In the meantime, besides throughput, there are some other issues for DCF such as fairness and QoS support. However, except for several hybrid protocols, most proposals were either based on contention mode or schedule mode and neither of the two modes has possessed the good characters of the other.In this paper, we propose a new MAC scheme used for DCF (with no control node) that dynamically adapts to traffic changes without degradation of delay in the case of low traffic load and achieves high throughput which is close to transmission capacity in saturated case. The key idea is to divide the virtual frame into two parts, i.e., schedule part and contention part, and to enable each node to reserve a slot in schedule part. Unlike conventional hybrid protocols, every node does not have to intentionally reset any parameter according to the changing traffic load except its queue length. A distinguishing feature of this scheme is the novel way of allowing WLANs to work with low delay as in the contention-based mode and achieve high throughput as in the schedule-based mode without complicated on-line estimation required in previous schemes. This makes our scheme simpler and more reliable. Through an analysis of simulation results, we show that our scheme can greatly improve the throughput with low delay.

MATS: multichannel time-spread scheduling in mobile ad hoc networks

Wireless mobile ad hoc networks (MANETs) have received considerable attention in the last few years. Most research works focus on single-channel MANETs with a single power-level in order to simplify the network design and analysis. How to take advantage of multiple channels and multiple power levels in MANETs poses a serious challenging problem. Recently, a few multichannel transmission protocols such as collision-avoidance transmission scheduling (CATS) have been proposed to harvest the advantage of high transmission efficiency when multiple channels are deployed. Although such protocols do provide ways to coordinate the use of multiple channels, there exist some serious problems such as the throughput fast drop-off under heavy traffic loads. In this paper, we propose a new protocol, namely, multichannel time-spread scheduling (MATS), which attempts to tackle these problems. In MATS, nodes with transmission requests are divided into three groups, which carry out channel reservations in parallel and can simultaneously support unicasting, multicasting and broadcasting at the link level. MATS ensures successful and collision-free data transmissions using the reserved channels and allows multicasting and broadcasting high priorities over unicasting. Both theoretical analysis and extensive simulation studies are carried out which show that the performance of MATS under high traffic loads significantly outperforms the existing schemes.

Multiple paths protocol for a cluster type network

We can access Internet by carrying a portable computer and using the wireless communication. The wireless network with PHS (Personal Handy phone System) and portable cellular telephone has only rates of tens of Kbps to a few Mbps. Compared with the cable network, the transfer rate cannot generally satisfy a highly developed communication services such as large file transfer and real-time communications. This paper proposes a protocol, SHAKE, for sharing multiple paths in cluster type network that is a kind of LAN in which some mobile hosts temporarily connect mutually. SHAKE provides the functions for composing cluster type network, and dispersing traffic efficiently by measuring transfer rate and round-trip time. As a mobile host has only low transfer capacity in individual to communicate with outside, if whole capacities of other hosts which compose cluster type network are shared, we can get larger transfer capacity and satisfy the required communication services.