Ryo Hamamoto

Throughput Characteristics Evaluation of Media Access Control Method Based on Synchronization Phenomena of Coupled Oscillators over WLAN Coexisting of CSMA/CA Terminals

Wireless local area networks, based on the distributed coordination function of the IEEE802.11 standard, usually use carrier sense multiple access with collision avoidance (CSMA/CA) for media access control. In the CSMA/CA method, if the number of wireless terminals increases, data frame collision often occurs among wireless terminals, which results in a decrease in the total throughput. Therefore, to improve the total throughput, a media access control method based on the synchronization phenomena of coupled oscillators, which we refer to as SP-MAC, is proposed. However, the performance of terminals based on SP-MAC, which coexist with CSMA/CA terminals, has not been sufficiently evaluated. Therefore, in this study, we evaluate the throughput performance in detail when terminals based on SP-MAC coexist with those based on CSMA/CA.

An access point selection mechanism based on cooperation of access points and users movement

Public areas, such as train stations and airports, providing wireless Local Area Network (WLAN) services are increasing and expanding because of the rapid development of WLANs based on IEEE 802.11 standard. Moreover, because of the advances in smartphone tethering technology, portable access points (APs) such as mobile Wi-Fi routers are being utilized more frequently. Consequently, there are increasing circumstances where a user needs to select and connect to one of the many APs. AP selection significantly determines the quality of service of the subsequent communication session. Existing AP selection algorithms consider user movement but not AP movement. We propose an AP selection method that handles both types of movement effectively. Moreover, we show that the proposed method improves the throughput significantly compared to the existing method.

Setting Radio Transmission Range Using Target Problem to Improve Communication Reachability and Power Saving

Ad hoc networks can be composed entirely of mobile wireless terminals, and do not require permanent network infrastructure such as access points. They are considered a useful network configuration technology for various situations. For example, they are used to construct sensor networks in which distributed, inexpensive sensors monitor environmental conditions such as temperature and humidity. Further, ad hoc networks can be implemented after severe disasters that have disabled other network infrastructures. In general, ad hoc network terminals are battery powered. Therefore, extending network lifetime by reducing terminal power consumption is an important issue in ad hoc network management. One method for reducing power consumption involves reducing the radio transmission range of each terminal. However, reducing the radio transmission range causes degradation in the reachability of each terminal. In this paper, we propose a method to set ad hoc network radio transmission ranges using a Target problem, to reduce power consumption and increase each terminal’s reachability. Next, we evaluate our method using various routing protocols, and define the applicability of our proposed method for each protocol. Simulation results show that the proposal improves communication reachability and power savings in ad hoc networks with normally distributed terminals, when the Destination-Sequenced Distance-Vector (DSDV) routing protocol is used.

Improvement of Throughput Prediction Method for Access Point in Multi-rate WLANs Considering Media Access Control and Frame Collision

Wireless Local Area Networks (WLANs) based on the IEEE 802.11 standard have been spreading rapidly. Access Points (AP) are being established in various public places, such as railway stations and airports, as well as private residences. Moreover, the rate of public WLAN services continues to increase. Here the throughput prediction of an AP in a multi-rate environment (amount of receipt data including retransmission packets at an AP) is an important issue for wireless network design, and it is important to solve AP placement and selection problems. To realize the prediction of throughput, the authors have proposed an AP throughput prediction method that considers terminal distribution. We compared the predicted throughput of the proposed method with a method that uses linear order computation and confirmed the performance of the proposed method. However, the results did not show the effectiveness of the proposed method in realistic network environments. Here we compare the throughput obtained from the network simulator NS2 with the prediction value calculated by the proposed method. Simulation results show that the maximum relative error of the proposed method is approximately 6%.

Guaranteeing Asymptotic Stability of Clustering by Autonomous Decentralized Structure Formation

Clustering mechanisms are used in ad hoc networks to achieve network load-balancing and/or battery power saving. We have proposed a framework for autonomous decentralized control that creates spatial structures with finite size by using back diffusion drift. We have also proposed its application to autonomous clustering in ad hoc networks. However problems with the stability of the resulting cluster structure remain. If the structure is unstable, it is difficult to keep the order of the structure in dynamic environments. This study examines the problems of realizing asymptotic cluster stability and proposes an effective solution.

Control method to guarantee throughput based on media access control method SP-MAC over WLAN

Wireless local area networks (WLAN) based on IEEE 802.11 usually employ carrier sense multiple access with collision avoidance (CSMA/CA) for media access control. In the CSMA/CA mechanism, data frame collisions often occur if the number of wireless terminals increases. This problem decreases the total throughput of terminals connected to the same access point. To address this problem, a media access control method based on the synchronization phenomena of coupled oscillators (SP-MAC) has been proposed. Previous studies have confirmed that SP-MAC can significantly decrease the number of data frame collisions and improve total throughput compared to CSMA/CA. However, the previous studies did not consider a QoS control based on SP-MAC. This study focuses on throughput as a QoS metric. This study proposes a control method to guarantee throughput based on SP-MAC. Furthermore, this study evaluates the effectiveness of the proposed method through simulation experiments. The simulation results demonstrate that the proposed method can control the throughput of each terminal without decreasing total throughput. Furthermore, this study shows that the proposed method can guarantee throughput for a specified terminal.

Characteristics Analysis of an AP Selection Method Based on Coordination Moving Both Users and APs

Recently, connecting to the Internet by using the wireless LAN has become familiar. In addition, the rapid growth of wireless LAN provides a lot of the wireless LAN Internet connection service areas such as hotels, cafes and airports. Moreover, the smart phones can be access point (AP) by tethering technology. These situations yields the case that there are multiple APs in the same area. In this case, users have to select an AP. Selection of an AP a ects the large impact on the overall both system throughput (the sum of the throughput of all APs in the system) and user throughput. We have proposed an AP selection method considering cooperative moving of user and AP and evaluated its performance. However, the evaluation of throughput was insufficient. This paper shows the performance evaluation over the more realistic situation considering the join and leave of user and the number of connectable AP in order to investigate the detail characteristics of the pRecently, connecting to the Internet by using the wireless LAN has become familiar. In addition, the rapid growth of wireless LAN provides a lot of the wireless LAN Internet connection service areas such as hotels, cafes and airports. Moreover, the smart phones can be access point (AP) by tethering technology. These situations yields the case that there are multiple APs in the same area. In this case, users have to select an AP. Selection of an AP affects the large impact on the overall both system throughput (the sum of the throughput of all APs in the system) and user throughput. We have proposed an AP selection method considering cooperative moving of user and AP and evaluated its performance. However, the evaluation of throughput was insufficient. This paper shows the performance evaluation over the more realistic situation considering the join and leave of user and the number of connectable AP in order to investigate the detail characteristics of the proposed method. We also indicate that the higher throughput can be obtained under the above considerations compared to the existing method which the new user only moves.

Performance Evaluation of Flow QoS Guarantee Method Based on TCP Congestion Control and MAC Frame Priority Control over Multi-rate WLAN Environment

In order to guarantee the bandwidth of a flow (flow QoS) in Wireless LANs (WLANs), a flow QoS guarantee method using both TCP Congestion Control for QoS (QoS-TCP) and MAC Frame Priority Control (QoS-MAC), which we refer to as a cross layer control method, has been proposed. This method tries to guarantee the bandwidth of a flow mainly by using QoS-TCP. And MAC Frame Priority Control assists with QoS-TCP to guarantee the bandwidth. This paper uses TCP-AV and Receive Opportunity Control in MAC Frame (ROC) as QoS-TCP and QoS-MAC, respectively. The previous study evaluates the cross layer control method in a single rate environment. In this environment, each terminal uses only one transmission rate in the physical layer. However, current wireless devices usually use multiple transmission rates. This study calls this environment as a multi-rate environment. Thus, the performance evaluation of the cross layer control method over the multi-rate environment is insufficient. This paper evaluates the throughput performance of the cross layer control method in the multi-rate environments. Moreover, this paper shows that the method can assure the target bandwidth in the multi-rate environment. From simulation results, we found that the method can guarantee the target bandwidth for a priority flow and improve the total throughput in the multi-rate environment.

Guaranteeing Asymptotic Stability of Clustering for MANET by Autonomous Decentralized Structure Formation Mechanism Based on Local Interaction

One useful tool in responding to wide-scale disasters is the MANET (Mobile Ad hoc Network), it is created by network terminals connecting directly to each other with no permanent network infrastructure. Clustering mechanisms for ad hoc networks have been proposed for power-saving and load-balancing. Moreover, maintenance (guaranteeing the stability) of cluster structure is an important issue in addition to realizing power-saving and load-balancing. We have proposed autonomous decentralized structure formation technology based on the local-interaction of terminals, and we have used the proposed structure formation technology to create an autonomous decentralized clustering method of ad hoc networks. However, although this technology can yield a cluster structure, it is not clear whether that structure is stable over long periods (guaranteed asymptotic stability). If asymptotic stability is missing, it is difficult to appropriately reconfigure the cluster structure in the face of the network topology changes caused by large-scale movement of node groups. In this paper, we propose a means of guaranteeing the asymptotic stability of the cluster structures created in autonomous decentralized manner. Finally, we evaluate the performance of the proposed solution in terms of guaranteeing asymptotic stability in MANET.

Redundancy Setting Method for TCP Congestion Control Based on FEC over Wireless LAN

With the rapid increase of mobile device users, the number of streaming services used over wireless LANs has increased. UDP is often used as a transport layer protocol in real-time communication. However, communication using UDP may be rejected by some network devices, thus, the number of streaming services that use TCP has increased. However, for TCP communication, throughput is unstable due to congestion control caused by packet loss. Thus, TCP control to secure a required transmission rate for streaming communications using forward error correction (FEC) technology (TCP-AFEC) has been proposed. TCP-AFEC can control the appropriate transmission rate according to network conditions using a combination of TCP congestion control and FEC. However, TCP-AFEC was not developed for wireless LAN environments, thus, it requires a certain time to set the appropriate redundancy and cannot obtain the required throughput. In this paper, we demonstrate the drawbacks of TCP-AFEC and propose a redundancy setting method that can secure the required throughput. Simulation results indicate that the proposed method can secure more stable throughput than TCP-AFEC.