萬代 雅希

This paper proposes a new congestion control method based on a hop-by-hop rate control in named data networking (NDN). The proposed method suppresses the excessive reduction of Interest sending rate due to continuous negative acknowledgement (NACK) packets caused by the propagation delay. The proposed method limits the rate reduction to once per congestion. The point of our method is not to change Interest sending rate for NACK packets after the rate reduction for a congestion until the rate reduction becomes effective. Through the performance evaluation by computer simulations, we show that the proposed method improves the throughput performance compared to the conventional method.

Content Centric Networking (CCN) is one of the most promising content-oriented network architectures. In CCN, forwarding information base (FIB) is allowed to have multiple entries for a same content name prefix, which means CCN potentially supports multi-source download. When a content is obtained from multiple sources, the technical knowledge obtained for congestion control in the current Internet cannot be simply applied. This is because in the current Internet, FIB is restricted to have only one entry for each IP address prefix, which causes quite different path feature from CCN. This paper proposes a new congestion control for CCN with multi-source content retrieval. The proposed congestion control is composed of end-to-end window flow control and router assisted Interest forwarding control and enables transmission rate regulation only on a congested branch.

In this paper, we first investigate how a network works when multiple receivers download content simultaneously in content-centric networking (CCN). We are especially interested in the case that the receivers' downloading speeds differ. From our investigation, we show that the download completion time of a faster user degrades excessively due to the problem that there being different downloading speeds decreases the cache-hit rate. To solve this problem, we propose a novel cache management method for simultaneous downloading from multiple receivers for CCN. The concept of the proposed method is to keep cached data packets in a router until they are transferred to the receiver. The proposed method increases the cache-hit rate for a slower receiver, and prevents a slower user from directly downloading data from the content provider. Through computer simulations, we confirm that the proposed method can improve the download completion time performance in the situation that multiple receivers download content at different speeds in CCN.

In this paper, we propose a quality of experience (QoE) aware quality-level switching algorithm for adaptive video streaming. The proposed algorithm is a quality-level switching algorithm which works on the controller of dynamic adaptive streaming over HTTP (DASH) system. The proposed algorithm has two features: insertion of intermediate quality level and limitation of quality-level switching. The proposed algorithm uses these two features adaptively for improving QoE based on network-throughput estimations. We implement the proposed algorithm on a real DASH system and evaluate QoE via subjective evaluations of users. As a result, we show that the proposed algorithm is effective to improve QoE when network throughput fluctuates. Note that the proposed algorithm realizes a high applicability to the existing web-based streaming because the proposed algorithm works on the client computer, and does not need any modifications on the server side.

In this paper, we propose a location-based service (SmartLocService) using space dependent information. The space dependent information is defined as the unique information for a specific place such as set of service set identifier (SSID) from Wireless LAN (WLAN) access points (APs). Existing location-based services (LBSs) mainly use Global Positioning System (GPS) to identify a place. However, GPS cannot work well in an indoor environment. SmartLocService realizes exact place identifications in indoors by using space dependent information. SmartLocService can be applied to various sophisticated location-based services in indoor such as reminders, call bliss and geofencing. We implement SmartLocService on smartphones, and evaluate its performance about registration time and location accuracy. As a result, since the accuracy of location is within five meters, we show that SmartLocService is useful to realize location-based services even in indoors.

In this paper, we propose a routing protocol for directional full-duplex wireless (D-FDW) to reduce hidden terminal problems in multi-hop networks. The proposed routing protocol is an on-demand detour routing protocol, which reduces number of cross points among traffic flows. In general, the throughput of a detour route degrades excessively due to increase of the number of hops between source and destination nodes. However, D-FDW has a remarkable benefit that throughput does not degrade excessively as the number of hops between source and destination nodes becomes large. Thus, the proposed detour routing can bring out the potential of D-FDW effectively. We evaluate the performance of the proposed routing protocol via ns-3 computer simulations, and show that the proposed routing protocol can reduce hidden terminal problems and improve end-to-end throughput performance up to 86.4% compared with the conventional AODV in a grid multi-hop network. To the best of our knowledge, this is the first routing protocol for D-FDW.

Mobile Peer-to-peer (P2P) realizes communications between mobile nodes without any access points. In general, Mobile P2P utilizes IEEE 802.11 Wireless LANs. However, IEEE 802.11 Wireless LANs do not support intelligent energy management schemes. Therefore, nodes should appropriately switch on and off its WLAN interface for reducing energy consumptions. In this paper, we propose energy efficient mobile P2P communications based on context information of users. We propose two models: Server-based model and Client-based model. In both models, nodes collect their context information such as location acquired by GPS. Server-based model uses a server to handle users' context information. In Server-based model, mobile nodes transmit the acquired context information to the server periodically. The server determines if the user should wake up or sleep, and transmits the decision to the user. Client-based model does not use any server. In Client-based model, each node decides to wake up or sleep by itself. We evaluate the performance of the proposed models via Nexus S smartphone. As results, we confirm that the proposed models can reduce energy consumption compared with the conventional IEEE 802.11 WLANs without energy management. In addition, we implement an audio streaming application using the proposed mobile P2P communications.

Welcome to MobiSys 2013: The Eleventh International Conference on Mobile Systems, Applications, and Services. As the premier forum for presenting the latest research in mobile and wireless systems, this year's conference attracted a record number of 211 submissions, a sign of continuing vibrancy and increasing maturity of our community. In addition to the strong technical program covering virtually every major topic of mobile systems research, we've incorporated a new video program showcasing innovative ideas selected from submissions, and have continued the tradition of having an interactive demo and poster fest. The Technical Program Committee and Industrial Reviewer Panel are to be lauded for their extraordinary effort in vetting each paper with care during the rigorous review process. Each paper was assigned to three Program Committee members for a first round of reviews. Each of the 211 papers with at least one positive review (weak accept) was assigned two additional reviewers from the Program Committee in the second round. A paper with potential industrial applications was further assigned to an Industrial Reviewer Committee member. In all, the Program Committee members and industrial reviewers generated 866 reviews and the top 60 papers received at least 5 reviews. The Program Committee met for a full day at Jekyll Island, Georgia, USA. The Committee discussed the top 60 papers and accepted 33 papers for the program. Each of these 33 papers was shepherded by a member of the Program Committee, to ensure that recommendations made by the reviewers and during the Program Committee meeting were satisfactorily addressed. The resulting technical program is the fruit of labor by many. We want to thank all the authors of submitted papers. We are indebted to the Technical Program Committee and Industry Reviewer Panel for their extraordinary work in reviewing papers and providing feedback for the authors, and the Video Program Committee for reviewing and selecting the short videos. We hope you will find the program interesting and thought-provoking, and you will take this opportunity to share your ideas while also networking with other researchers and practitioners from around the world.

Wireless full-duplexing enables a transmission and a reception on the same frequency channel at the same time, and has the potential to improve the end-to-end throughput of wireless multi-hop networks. In the present paper, we propose a media access control (MAC) protocol for wireless full-duplex and multi-hop networks called Relay Full-Duplex MAC (RFD-MAC). The RFD-MAC is an asynchronous full-duplex MAC protocol, which consists of a primary transmission and a secondary transmission. The RFD-MAC increases the full-duplex links by overhearing frames, which include 1-bit information concerning the existence of a successive frame, and selecting a secondary transmission node using the gathered information. The gathered information is also used to avoid a collision between the primary and secondary transmission. Simulation results reveal that the proposed RFD-MAC improves up to 68%, 49% and 56% of end-to-end throughput compared to CSMA/CA, FD-MAC and MFD-MAC, respectively.

In this paper, we propose a novel node architecture introducing directional antennas into full duplex wireless (FDW) technology. In the proposed architecture, each element of switched-beam antenna is connected to a software switch for directional antenna selection. A node needs only one set of digital and analog cancellation circuits, which is almost the same circuit scale and complexity of the conventional omnidirectional FDW node. In addition, we propose a MAC protocol for the proposed node architecture with FDW and directional antennas for avoiding collisions and obtaining the advantages of both techniques. We evaluate the performance of the proposed protocol via computer simulations, and show that the proposed protocol can improve end-to-end throughput performance up to 114 percent in a line-type multihop network. Moreover, we extend the proposed MAC protocol for mitigating the performance degradation in two-way traffic in line-type multihop networks, and confirm its effectiveness. To the best of our knowledge, this is the first work that attempts to use directional antennas in FDW networks.

Multi-view video consists of multiple video sequences captured simultaneously by multiple closely spaced cameras from different angles. It allows the users to change their viewpoints by playing different video sequence. However, the transmission of multi-view video is much larger than conventional media and increases with increasing number of views, which brings much more increment in the bandwidth requirement. In our previous works, we have proposed a live-encoding scheme call UDMVT [1][2] to reduce the transmission bitrate for multi-view video transmission. In UDMVT, the periodic feedback containing the position and switching speed of user is used to predict a triangle area. Frames in this triangle area are possible to be displayed in next period of time. Only these specific frames are transmitted instead of all the frames to reduce the transmission bitrate. Even though, UDMVT hasn't effectively solve the "out of triangle" problem in which the user may switch to the outside of the triangle during the playback in the triangle area. In this paper, we propose a layered scheme called Layered User dependent Multi-view video Streaming (LUMS) to solve the "out of triangle" problem for UDMVT. In LUMS each triangle is layered into several layers according to the minimum and maximum switching speed. The corresponding layers are transmitted according to the current switching speed each time received from feedback. If the "out of triangle" occurs, the higher layers will be retransmitted. All the frames in high layers are encoded into B-frame predicted from the basic and lower layers, so the retransmission bitrate is low. Performance evaluation proves that LUMS reduce transmission bitrate by 44.9% compared to UDMVT.

Opportunistic spectrum access (OSA) is a suitable approach to increase spectrum efficiency for the current spectrum management. This paper considers the secondary user (SU) multi-rate multi-hop impact under the temporal dynamic aspect of OSA. Firstly, we investigate the SU multi-rate transmission and number of hops impact under the temporal dynamic aspect of OSA. The observed metrics include both SU and PU performance. Numerical analysis and simulation results show the existence of multi-rate and multi-hop diversity. To obtain the optimal performance, the balance between high enough transmission rate and few enough number of hops is essential. Secondly, according to the multi-rate multi-hop investigation, we propose a rate adaption scheme with PU activity consideration, called Auto Rate Increase (ARI). ARI is based on the Auto Rate Fallback (ARF) scheme with the aims to select the best transmission rate under limited PU idle duration. ARI also adopts ARF simplicity, hence, there is no need for any prior nor additional knowledge of the networks environment. Simulation results show, under tight OSA environment, ARI scheme can increase the SU performance up to 37% compared with the original ARF scheme. © 2011 IEEE.

Energy harvesting has been studied as a candidate for powering next generation wireless sensor networks. The technologies that can harvest electric power from ambient energy sources include solar, vibration, heat and wind. However, sensor nodes powered by energy harvesting devices cannot always communicate with other nodes because the energy harvesting devices cannot provide a stable supply power. A node cannot know whether its neighboring nodes have enough energy to receive a data packet that it has transmitted. During the process of relaying the packet, each additional hop increases the overall probability of losing the packet. In this paper, we propose two data collection protocols for the energy harvesting wireless sensor networks called Probabilistic ReTransmission protocol (PRT) and PRT with Collision Consideration (PRT-CC). The idea is to derive the number of times to retransmit a packet based on the reception probability and the active intervals computed by the receivers themselves. In PRT-CC, each node computes the reception probability with packet collision consideration. The simulation results show that the proposed protocols achieve higher delivery ratio than the previous works (GR-DD and GR-DD-RT).

Opportunistic spectrum access (OSA) is a suitable approach to increase spectrum efficiency for the current spectrum management. This paper considers the temporal aspect of 802.11-based OSA scenario. Firstly, we investigate the secondary users (SU) multi-rate transmission and number of hops effects to the SU performance when exploiting primary users (PU) idle duration. Numerical analysis and simulation results show that, during limited PU idle duration, higher data rate transmission is essential even though it results in more hops but as the SU source traffic is getting busier, the balance between the data rate and number of hops is required. Secondly, according to the multi-rate multi-hop investigation, we propose a rate adaption scheme with PU activity consideration, called Auto Rate Increase (ARI). ARI is based on the Auto Rate Fallback (ARF) scheme with the difference that ARI aims to increase the SU data rate whenever it detects PU interruption failure. ARI also adopts ARF simplicity, hence, there is no need for any prior nor additional knowledge of the networks environment. Simulation results show, under tight OSA environment, ARI scheme can increase the SU performance up to 56% compared with the original ARF scheme.

The traffic of multi-view video is several times larger than traditional multimedia, which brings much more increment in the bandwidth requirement. To overcome this problem, Simulcast and MVC (Multi-view Video Coding) can be used to decrease the traffic for multi-view video. However, although Simulcast removes redundant information within each view, it still contains a large amount of inter-view redundant information. MVC further removes the correlation between the views, but all the views should be encoded and transmitted. So the bit-rates are still too high in these schemes. We have already proposed a system with the basic conception. In this paper, the basic conception is extended to support the 3D multi-view video transmission. The scheme called UDMVT (User Dependent Multi-view Video Transmission) makes use the periodically fed back information to encode and transmit only those frames which are possible to be displayed instead of all the frames. So it is able to decrease the bit-rate for multi-view video transmission. Performance evaluation proves that UDMVT reduces the average bit-rate for the transmission of multi-view video.

The traffic of multi-view video is several times larger than traditional multimedia, which brings much more increment in the bandwidth requirement. To overcome this problem, Simulcast and MVC (Multi-view Video Coding) can be used to decrease the traffic for multi-view video. However, although Simulcast removes redundant information within each view, it still contains a large amount of inter-view redundant information. MVC further removes the correlation between the views, but all the views should be encoded and transmitted. So the bit-rates are still too high in these schemes. We have already proposed a system with the basic conception. In this paper, the basic conception is extended to support the 3D multi-view video transmission. The scheme called UDMVT (User Dependent Multi-view Video Transmission) makes use the periodically fed back information to encode and transmit only those frames which are possible to be displayed instead of all the frames. So it is able to decrease the bit-rate for multi-view video transmission. Performance evaluation proves that UDMVT reduces the average bit-rate for the transmission of multi-view video.

Multi-view video allows user to watch 3D video and select desired viewpoint. In order to reduce the switching delay, many researches tend to transmit all the views, which brings much more increment in the bandwidth requirement. And the traffic increase as the increase of the number of the views in the multi-view video. In order to overcome these problems, we have proposed a user dependent scheme called UDMVT for the transmission of multi-view video in [1]. And we further improved this scheme to support the 3D multi-view video in the [2]. The evaluation results proved that UDMVT is efficient to reduce the bit-rate of the transmission of the multi-view video in the successive motion model especially when the number of view is larger. In this paper, we will simply introduce the UDMVT and discuss the application of the UDMVT in the Free Viewpoint TV.