Network function virtualization (NFV) flexibly provides servoces by virtualizing network functions on a general-purpose server, and attracted research interest in recent years. In NFV environment, providing service chaining, which dynamically connects each network function (virtual network function: VNF), is critical issue. However, as it is challenging to select the optimal sequence of VNF services in the service chain in a decentralized manner, the distances between the VNFs tend to increase, leading to longer communication and processing delays. Furthermore, it has never considered that certain VNFs that can be exchange the order of services with one another. To address this problem, in this paper, we propose a distributed search method for ordered VNFs to reduce delays while considering the load on control server, by exploiting an in-network guidance technology, called Breadcrrmubs, for query messages.

What should be the ultimate form of the cloud computing environment? The solution should have two important features; “Fine-Granularity” and “Participation.” To realize an attractive and feasible solution with these features, we propose a “participating fine-grained cloud computing platform” that a large number of personal or small-company resource suppliers participate in, configure and provide cloud computing on. This enables users to be supplied with smaller units of resources such as computing, memory, content, and applications, in comparison with the traditional Infrastructure as a Service (IaaS). Furthermore, to search for nearby resources efficiently among the many available on the platform, we also propose Resource Breadcrumbs (RBC) as a key technology of our proposed platform to provide in-network guidance capability autonomously for users' queries. RBC allows supplier-nodes to distribute guidance information directed to themselves with dedicated control messages; in addition, the information can be logged along the trail of message from supplier to user. With this distributed information, users can to autonomously locate nearby resources. Distributed management also reduces computational load on the central database and enables a participating fine-grained cloud platform at lower cost.

Lately, access loads on servers are increasing due to larger content size and higher request frequency in content distribution networks. Breadcrumbs (BC), an architecture with guidance information for locating a content cache, is designed to reduce the server load and to form content-oriented network autonomously in cooperation with cached contents over IP network. We also proposed Breadcrumbs+ which solves BC's endless routing loop problem. However, Breadcrumbs takes only a passive approach; BC entries are created only when a content is downloaded and only at routers on the download path but not at any other routers. We expect that active and adaptive control of guidance information with simple complexity improves its performance with keeping scalability. In this paper, we propose Active Breadcrumbs which achieves efficient content retrieval and load-balancing through active and adaptive control of guidance information by cache-nodes themselves. In addition, we show the effectiveness of Active Breadcrumbs through the extensive computer simulation.

In conventional networks, service control function and network control function work independently. Therefore, stereotypical services are provided via fixed routes or selected routes in advance. Recently, advanced network services have been provided by assortment of distributed components at low cost. Furthermore, service platform, which unifies componentized network control and service control in order to provide advanced services with flexibility and stability, has attracted attention. In near future, network management system (NMS) is promising, which replies an answer quickly for such advanced service platforms when route setting is requested with some parameters: quality of service (QoS), source and destination addresses, cost (money) and so on. In addition, the NMS is required to provide routes exploiting functions such as path computation element (PCE) actually. This paper proposes scalable network architecture that can quickly reply an answer by pre-computing candidate routes when route setting is requested to a control unit like an Autonomous System (AS). Proposed architecture can manage network resources scalably, and answer the availability of the requested QoS-aware path settings instantaneously for the forthcoming service platform that finds an adequate combination of a server and a route. In the proposed method, hierarchical databases are established to manage the information related to optical network solution and their data are updated at fewer times by discretized states and their boundaries with some margin. Moreover, with multiple and overlapped overlay, it pre-computes multiple candidate routes with different characteristics like available bandwidth and the number of hops, latency, BER (bit error rate), before route set-up request comes. We present simulation results to verify the benefits of our proposed system. Then, we implement its prototype using OpenFlow, and evaluate its effectiveness in the experimental environment.

Recently, video streaming services using P2P (Peer-to-Peer) have attracted attention to solve the problem of load concentration on servers and to reduce large latency. Many P2P streaming systems, like Coolstreaming, however, take a complicated approach to control playback timing severely. This leads to less churn resiliency and less adaptability to fluctuation of network traffic. Therefore, we focus on a simple and robust approach to realize “pseudo” streaming with high quality, which is based on BitTorrent. In the existing methods with the simple approach, peers download pieces just closer to playback timing to decrease the playback discontinuity. However, these methods do not consider the constitution of video structure in sophisticated manner. P2P streaming system must consider several important metrics for high-quality and fair distribution. Therefore, in this paper, we propose a new P2P video streaming system considering the cooperation of three important metrics; video structure, playback timing, and piece dispersion on network. In this system, users vary three piece selections to suit the delivery status. Specifically, users preferentially download pieces which affect the video quality, which are closer to playback timing, and which improve the delivery efficiency. Moreover, we show the effectiveness of the proposed method by computer simulation.

Coexistence between ZigBee and Wi-Fi technologies, which operate within the same frequency band, is increasing with the widespread use of the IoT (Internet of Things). ZigBee devices suffer significant decreases in the sink arrival rate of packets in the presence of Wi-Fi interference. To overcome this problem, many channel control methods have been proposed. These methods switch only ZigBee channels to avoid interference with Wi-Fi. In contrast, we propose a cooperative channel control method for improving ZigBee packet arrival rate by controlling both the Wi-Fi and ZigBee channels. Specifically, the proposed method not only controls ZigBee devices and channels but also requests a temporary pause in the use of specific Wi-Fi channels. Finally, computer simulations show the effectiveness of the proposed method from the viewpoints of ZigBee's packet arrival rate and applications' satisfaction. In addition, the feasibility of the proposed method is also confirmed by experiments with prototyping.

Recently, network coding (NC) has been popularly applied to wireless networks in order to improve scarce wireless capacity. In wireless LANs, NC can be applied to packet retransmission in which multiple packets can be simultaneously transmitted by a single transmission trial at a base station (BS). In this paper, we assume wireless LANs with QoS functionality and propose adaptive cooperation between NC and IEEE 802.11e EDCA. In EDCA, when network load is high, QoS is significantly degraded even for high priority class. To solve this, existing methods improve backoff control, and decrease packet loss caused by collision. However, this cannot prevent packet loss caused by channel fading. In the proposed cooperation between NC and EDCA, QoS of all priority classes is improved from the aspect of efficient loss recovery. Unlike NC method with no QoS control, we encounter transmission scheduling problem among an NC packet, a single lost packet and a new packet. Moreover, in the constitution of packets encoded into NC packet, packet's intrinsic priority should be considered. Therefore, we propose how to schedule the packets to be transmitted in BS, and how to constitute NC packets to be encoded. Finally, we show the effectiveness of the proposed method by extensive computer simulations.

In recent years, wireless LANs (WLANs) are closely deployed which means they interfere with each other. Mobile stations (MSs) like smart phones that connect to such WLANs are also increasing. In such interfering environments, radio interference frequency depends on MS position. In addition, as MSs and their applications become diverse, frame generation rates from MSs are also becoming various. Thus, sufficient frame transmission opportunities should be assigned to MSs regardless of their radio interference frequencies and frame generation rates. One key technology to deal with this issue is uplink orthogonal frequency division multiple access (OFDMA) transmission introduced in IEEE 802.11ax. However, existing works do not consider the differences of the interference frequencies and frame generation rates among MSs in an integrated manner. This paper proposes an uplink frame transmission method for interfering WLAN environments that effectively uses the OFDMA transmission to assign enough transmission opportunities to MSs regardless of their own interference frequencies and frame generation rates, while efficiently using the channel resource. Considering the combined problem, this proposed method allocates resource units (RUs), created by dividing the channel, to MSs. In addition, based on a mathematical analysis of required frame transmission duration, the proposed method flexibly selects the OFDMA transmission or conventional frame transmission with CSMA/CA, which is also not considered in the existing works.

With the widespread diffusion of Internet of Things (IoT), the number of applications using wireless sensor devices are increasing, and Quality of Service (QoS) required for these applications is diversifying. Thus, it becomes difficult to satisfy a variety of QoS with a single wireless system, and many kinds of wireless systems are working in the same domains; time, frequency, and place. This paper considers coexistence environments of ZigBee and Wi-Fi networks, which use the same frequency band channels, in the same place. In such coexistence environments,ZigBee devices suffer radio interference from Wi-Fi networks, which results in severe ZigBee packet losses because the transmission power of Wi-Fi is much higher than that of ZigBee. Many existing methods to avoid interference from Wi-Fi networks focus on only one of time, frequency, or space domain. However, such avoidance in one domain is insufficient particularly in near future IoT environments where more ZigBee devices and Wi-Fi stations transfer more amount of data. Therefore, in this paper, we propose joint channel allocation and routing in both frequency and space domains. Finally, we show the effectiveness of the proposed method by computer simulation.

Multi-Channel MAC protocols increase network throughput because multiple data transmissions can take place simultaneously. However, existing Multi-Channel MAC protocols do not take full advantage of the multi-channel environment, because they lack a mechanism allowing wireless stations to acquire vacant channel and time resources. In this paper, we first establish the basic model of existing Multi-Channel MAC protocols to know the capability of the most important existing protocols. Next, under the condition that each station can use only two transceivers, we propose Multi-Channel MAC protocols that effectively utilize idle channels and potentially available time resources of stations by employing bursts and interrupted frame transfers. We assume a transceiver can behave as either a transmitter or a receiver but not both at the same time. Moreover, we show the effectiveness of our proposal by computer simulation. Furthermore, through the evaluation in the case that each station can use more than two transceivers, we confirm two transceivers' case is best solution in terms of both attained throughput and hardware complexity.

This paper deals with the inefficient channel utilization of wireless LANs that use rate adaptation. Recently, wireless LANs are being utilized in various environments. However, inefficient channel utilization is still a serious problem. The effective solutions include to decrease the frequency of packet loss and to transmit packets at a higher rate. While the backoff algorithm in IEEE 802.11 avoids only the packet loss caused by collision, other previous works tackle the packet loss caused by channel fading by means of transmission at a lower rate. This approach is called rate adaptation and a simple rate adaptation scheme is widely diffused in commercial 802.11 wireless LAN devices. However, utilizing lower transmission rate degrades transmission efficiency because the channel is occupied for a longer time. In this paper, decreasing transmission rate is avoided with novel transmission scheduling. Specifically, the proposed scheduling interrupts packet transmission to receiver stations under fading channel condition until the condition improves. Instead, other packets to other stations are transmitted in advance. To implement this proposed scheduling, only access points (APs) need to be modified. Hence, legacy wireless stations can benefit from higher communication bandwidth simply by introducing the modified APs. Moreover, although wireless stations must also be modified, an extended RTS/CTS handshake is also proposed to quickly detect the improvement of channel condition and to minimize the wasted time even if fading loss occurs. Here, wireless stations must also be modified to adopt the extended RTS/CTS handshake but further bandwidth increase is achievable. Evaluation results demonstrate that network throughput is improved without degrading the throughput fairness among receiver stations and packet transfer delay of interrupted stations.

These days, in addition to host-to-host communication, Information-Centric Network (ICN) has emerged to reflect current content-centric network usage, based on the fact that many users are now interested not in where contents are but in acquired contents themselves. However, current IP network must still remain, at least from deployment perspective, as one of near future network architectures. This is because ICN has various scalability and feasibility challenges, and host-to-host communication is also diffused like remote login, VoIP, and so on. Therefore, the authors aim to establish the feature of ICN on conventional IP network to achieve feasible and efficient architecture. We consider that, as a feasible and efficient architecture, only user-edges keep some contents' caches within their computational and bandwidth limitations and contents should be replicated also on some replica servers dispersedly to assure contents' distribution even if user caches are not found. To achieve this, in this paper, we propose to operate Content Delivery Network (CDN) and Breadcrumbs (BC) frameworks coordinately on IP network. Both CDN and BC are important as a content-centric technique. In CDN, replica servers called surrogates are placed dispersedly in all over the Internet. Although this provides users with contents from nearer surrogate servers, the surrogate servers have higher workload to distribute contents to many users. In the proposed method, in cooperation with BC method that is proposed to implement ICN on IP network, the surrogate server workload is drastically reduced without largely increasing hop count for content delivery. Although it needs some functions to implement our approach such as adopting BC architecture to routers, calculating and reporting information required for cooperation of BC method with CDN, the cost for the functions in our solution is not so significant. Finally, we evaluate the proposed method with CDN we carefully modeled through simulation.

Recently, wireless LAN is achieving remarkable growth and maturity. On the other hand, by the advance of the Internet, the demand for multimedia communication services which include video and voice will be expected to grow. Therefore, in the future, the mechanism of QoS guarantee must be realized even in wireless LAN environment. So far, IEEE 802.11e EDCF has been proposed, which is a contention based channel access method to achieve the QoS guarantee in wireless LAN. However, this cannot realize the desired throughput ratio or deterministic target throughput in principle. In this paper, we expand the EDCF to solve such QoS issues and enable more flexible QoS control. Moreover, we show the effectiveness of our proposal by computer simulation.

With the rapid increase in IoT (Internet of Things) applications, more sensor devices, generating periodic data flows whose packets are transmitted at regular intervals, are being incorporated into WSNs (Wireless Sensor Networks). However, packet collision caused by the hidden node problem is becoming serious, particularly in large-scale multi-hop WSNs. Moreover, focusing on periodic data flows, continuous packet collisions among periodic data flows occur if the periodic packet transmission phases become synchronized. In this paper, we tackle the compounded negative effect of the hidden node problem and the continuous collision problem among periodic data flows. As this is a complex variant of the hidden node problem, there is no simple and well-studied solution. To solve this problem, we propose a new MAC layer mechanism. The proposed method predicts a future risky duration during which a collision can be caused by hidden nodes by taking into account the periodic characteristics of data packet generation. In the risky duration, each sensor node stops transmitting data packets in order to avoid collisions. To the best of our knowledge, this is the first paper that considers the compounded effect of hidden nodes and continuous collisions among periodic data flows. Other advantages of the proposed method include eliminating the need for any new control packets and it can be implemented in widely-diffused IEEE 802.11 and IEEE 802.15.4 devices.

Nowadays, in various wireless sensor networks, both aperiodically generated packets like event detections and periodically generated ones for environmental, machinery, vital monitoring, etc. are transferred. Thus, packet loss caused by collision should be suppressed among aperiodic and periodic packets. In addition, some packets for wireless applications such as factory IoT must be transferred within permissible end-to-end delays, in addition to improving packet loss. In this paper, we propose transmission timing control of both aperiodic and periodic packets at an upper layer of medium access control (MAC). First, to suppress packet loss caused by collision, transmission timings of aperiodic and periodic packets are distributed on the time axis. Then, transmission timings of delay-bounded packets with permissible delays are assigned within the bounded periods so that transfer within their permissible delays is possible to maximally satisfy their permissible delays. Such control at an upper layer has advantages of no modification to the MAC layer standardized by IEEE 802.11, 802.15.4, etc. and low sensor node cost, whereas existing approaches at the MAC layer rely on MAC modifications and time synchronization among all sensor nodes. Performance evaluation verifies that the proposed transmission timing control improves packet loss rate regardless of the presence or absence of packet's periodicity and permissible delay, and restricts average transfer delay of delay-bounded packets within their permissible delays comparably to a greedy approach that transmits delay-bounded packets to the MAC layer immediately when they are generated at an upper layer.

To cope with the drastic increase in traffic, space division multiplexing elastic optical networks (SDM-EONs) have been investigated. In multicore fiber environments that realize SDM-EONs, crosstalk (XT) occurs between optical paths transmitted in the same frequency slots of adjacent cores, and the quality of the optical paths is degraded by the mutual influence of XT. To solve this problem, we propose a core and spectrum assignment method that introduces the concept of prohibited frequency slots to protect the degraded optical paths. First-fit-based spectrum resource allocation algorithms, including our previous study, have the problem that only some frequency slots are used at low loads, and XT occurs even though sufficient frequency slots are available. In this study, we propose a core and spectrum assignment method that introduces the concepts of “adjacency criterion” and “XT budget” to suppress XT at low and middle loads without worsening the path blocking rate at high loads. We demonstrate the effectiveness of the proposed method in terms of the path blocking rate using computer simulations.

Recently, network coding (NC) has been popularly applied to wireless networks in order to improve scarce wireless capacity. In wireless LANs, NC can be applied to packet retransmission, and a base station can simultaneously retransmit multiple packets destined to different wireless stations by a single retransmission trial. On the other hand, NC creates additional packet delay at both base station and wireless stations, and hence, packet transfer delay may increase seriously. However, existing NC-based retransmission methods do not consider this additional delay explicitly. In addition, when the number of flows is small, NC exhibits less benefit because the chances of NC-based retransmission are highly reduced. Therefore, in this paper, we propose a novel NC-based retransmission method in order to improve packet transfer delay and jitter of received packets. Moreover, to achieve further improvement of delay, jitter and retransmission efficiency even when there exist a small number of traffic flows, we propose a retransmission method in which NC-based retransmission cooperates with the typical ARQ method. We overcome the disadvantage of NC-based retransmission by combining with ARQ cooperatively. Finally, we show the effectiveness of the proposed methods by extensive computer simulation.

This paper addresses power saving for STAs (Wireless Stations) in WLANs (Wireless LANs). Mobile devices are increasingly used in situations in which they access WLANs. However, mobile devices consume large amounts of power when they communicate through a WLAN, and this shortens their battery lifetime. IEEE 802.11 specifies PSM (Power-Saving Mode) as the power-saving method for standard WLANs. However, the sleep conditions specified by PSM for STAs are not optimal in terms of power saving, except when the number of STAs is small, and this increases packet transfer delay. In this paper, we propose a power-saving method in which STAs reduce power consumption by sleeping for a period specified by the NAV (Network Allocation Vector) duration, which is set by an RTS/CTS handshake, and the duration of the NAV is extended by bidirectional burst transmission. To suppress the transfer delay caused by the bidirectional burst transmission, an AP (Access Point) manages the transmission deadline of each downlink packet on the basis of its acceptable value of delay and adapts the number of packets transferred in the bidirectional burst transmission. Although another existing method also uses the NAV duration to manage STA sleeping, the bidirectional burst transmission can only be initiated by the STAs themselves and the NAV is of an extremely limited duration. On the other hand, the proposed method specifies generalized bidirectional burst transmission without the limitations of the transmission initiator and the burst length within acceptable packet transfer delay. Moreover, we investigate the combination of the proposed method with PSM in order to improve the performance in situations in which the number of STAs is small by taking advantage of the combined properties of PSM and the proposed method. The evaluation results demonstrate that these proposed methods can reduce the power consumption of wireless stations and suppress packet transfer delay.

Recently, ZigBee has been attracting attention as a low-power and short-range wireless communication standard. In ZigBee networks, it is necessary to suppress frame transfer load because ZigBee needs to operate within severe capacity constraints and with low power consumption. However, in the typical environments in which ZigBee is used, such as smart home networks, WLAN (Wireless LAN) generally coexists, and radio interference occurs between the two networks. Existing studies focused on only interference avoidance. On the other hand, in this paper, we focus on adaptive cooperation between ZigBee network and WLAN. Specifically, from the viewpoints of WLANs that have wider communication range but have many idle periods in some environments like homes, we propose and study a hop count reduction method of ZigBee frame transfer by partially employing WLAN communication to transfer ZigBee frames. To the best of our knowledge, this is the first paper that considers the adaptive cooperation between ZigBee network and WLAN, where some ZigBee frames are transferred via WLAN to the sink. This is a completely new approach different from existing interference avoidance approaches. Then, we evaluate the hop count reduction by considering the number and the positions of relay points to transfer ZigBee frames to WLAN, and ZigBee tree topology for frame transfer routes. Through the evaluation, two realistic deployment policies of the relay points are derived. Finally, as specific advantages from the hop count reduction, we demonstrate the performance improvement about sink arrival ratio and end-to-end transfer delay of ZigBee frames, and energy consumption.