In this paper we summarize the work conducted in our group in the area of E- and W-band optical high-capacity fiber-wireless links. We present performance evaluations of E- and W-band mm-wave signal generation using photonic frequency upconversion employing both VCSELs and ECLs, along with transmission over different type of optical fibers and for a number of values for the wireless link distance. Hybrid wireless-optical links can be composed of mature and resilient technology available off-the-shelf, and provide functionalities that can add value to optical access networks, specifically in mobile backhaul/fronthaul applications, dense distributed antenna systems and fiber-over-radio scenarios.

The past decade has witnessed a growing interest in vehicular networking. Initially motivated by traffic safety, vehicles equipped with computing, communication and sensing capabilities will be organized into ubiquitous and pervasive networks with a significant Internet presence while on the move. Large amount of data can be generated, collected, and processed on the vehicular networks. Big data on vehicular networks include useful and sensitive information which could be exploited by malicious intruders. But intrusion detection in vehicular networks is challenging because of its unique features of vehicular networks: short range wireless communication, large amount of nodes, and high mobility of nodes. Traditional methods are hard to detect intrusion in such sophisticated environment, especially when the attack pattern is unknown, therefore, it can result unacceptable false negative error rates. As a novel attempt, the main goal of this research is to apply data mining methodology to recognize known attacks and uncover unknown attacks in vehicular networks. We are the first to attempt to adapt data mining method for intrusion detection in vehicular networks. The main contributions include: 1) specially design a decentralized vehicle networks that provide scalable communication and data availability about network status; 2) applying two data mining models to show feasibility of automated intrusion detection system in vehicular networks; 3) find the detection patterns of unknown intrusions.

In recent years, computation offloading, through which applications on a mobile device can offload their computations onto more resource-rich clouds, has emerged as a promising technique to reduce battery consumption as well as augment the devices' limited computation and memory capabilities. In order for computation offloading to be energy-efficient, an accurate estimate of battery consumption is required to decide between local processing and computation offloading. In this paper, we propose a novel technique for estimating battery consumption without requiring detailed information about the mobile application's internal structure or its execution behavior. In our approach, the relationship is derived between variables that affect battery consumption (i.e., the input to the application, the transmitted data, and resource status) and the actual consumed energy from the application's past run history. We evaluated the performance of the proposed technique using two different types of mobile applications over different wireless network environments such as 3G, Wi-Fi, and LTE. The experimental results show that our technique can provide tolerable estimation accuracy and thus make correct decisions between local processing and computation offloading.

In this invited paper, software defined network (SDN)-based approaches for future cost-effective optical mobile backhaul (MBH) networks are discussed, focusing on key principles, throughput optimization and dynamic service provisioning as its use cases. We propose a novel physical-layer aware throughput optimization algorithm that confirms > 100Mb/s end-to-end per-cell throughputs with ≥2.5Gb/s optical links deployed at legacy cell sites. We also demonstrate the first optical line terminal (OLT)-side optical Nyquist filtering of legacy 10G on-off-keying (OOK) signals, enabling dynamic >10Gb/s Orthogonal Frequency Domain Multiple Access (OFDMA) λ-overlays for MBH over passive optical network (PON) with 40-km transmission distances and 1:128 splitting ratios, without any ONU-side equipment upgrades. The software defined flexible optical access network architecture described in this paper is thus highly promising for future MBH networks.

Mobile IPv6 is an IETF (Internet Engineering Task Force) standard which permits node mobility in IPv6. To manage mobility, it establishes a centralized mediator, Home Agent (HA), which inevitably introduces several penalties like triangular routing, single point of failure and limited scalability. Some later extensions such as Global HAHA, which employed multiple HAs, made to alleviate above shortcomings by introducing Distributed Mobility Management (DMM) approach. However, Multiple HA model will not be beneficial, unless the HAs are located finely. But, no major research paper has focused on locating HAs. This paper examines impact of single and multiple HA placements in data plane, by using an Autonomous System (AS) level topology consisting of 30,000 nodes with several evaluation criteria. All possible placements of HA(s) are analysed on a fair, random set of 30,000 node pairs of Mobile Nodes (MN) and Correspondent Nodes (CN). Ultimate result provides a concise account of different HA placements: i.e. cost centrality interprets performance variation better than degree centrality or betweenness. 30,000 ASs are classified into three groups in terms of Freeman's closeness index and betweenness centrality: 1) high range group, 2) mid range group, and 3) low range group. Considering dual HA placement, if one HA is placed in an AS in the high range group, then any subsequent HA placement gives worse results, thus single HA placement is adequate. With the mid range group, similar results are demonstrated by the upper portion of the group, but the rest yields better results when combined with another HA. Finally, from the perspective of low range group, if the subsequent HA is placed in the high range group, it gives better result. On the other hand, betweenness based grouping yields varying results. Consequently, this study reveals that the Freeman's closeness index is most appropriate in determining impacts of HA placements among considered indices.

Participatory sensing is an emerging system that allows the increasing number of smartphone users to share effectively the minute statistical information collected by themselves. This system relies on participants' active contribution including intentional input data. However, a number of privacy concerns will hinder the spread of participatory sensing applications. It is difficult for resource-constrained mobile phones to rely on complicated encryption schemes. We should prepare a privacy-preserving participatory sensing scheme with low computation complexity. Moreover, an environment that can reassure participants and encourage their participation in participatory sensing is strongly required because the quality of the statistical data is dependent on the active contribution of general users. In this article, we present MNS-RRT algorithms, which is the combination of negative surveys and randomized response techniques, for preserving privacy in participatory sensing, with high levels of data integrity. By using our method, participatory sensing applications can deal with a data having two selections in a dimension. We evaluated how this scheme can preserve the privacy while ensuring data integrity.

In this paper, we design an efficient P2P based mobile social network to facilitate contents search over mobile ad hoc networks. Social relation is established by considering both the locations and interests of mobile nodes. Mobile nodes with common interests and nearby locations are recommended as friends and are connected directly in a mobile social network. Contents search is handled by using social relationships of the mobile social network rather than those of the whole network. Since each mobile node manages only neighboring nodes that have common interests, network management overhead is reduced. Results of experiments have shown that our proposed method outperforms existing methods.

This paper reports on the image compression tolerability and high implementability of a novel proposed watermarking method that uses a morphological wavelet transform based on max-plus algebra. This algorithm is suitable for embedded low-power processors in mobile devices. For objective and unified evaluation of the capability of the proposed watermarking algorithm, we focus attention on a watermarking contest presented by the IHC, which belongs to the IEICE and investigate the image quality and tolerance against JPEG compression attack. During experiments for this contest, six benchmark images processed by the proposed watermarking is done to reduce the file size of original images to 1/10, 1/20, or less, and the error rate of embedding data is reduced to 0%. Thus, the embedded data can be completely extracted. The PSNR value is up to 54.66dB in these experiments. Furthermore, when the smallest image size is attained 0.49MB and the PSNR value become about 52dB, the proposed algorithm maintains very high quality with an error rate of 0%. Additionally, the processing time of the proposed watermarking can realize about 416.4 and 4.6 times faster than that of DCT and HWT on the ARM processor, respectively. As a result, the proposed watermarking method achieves effective processing capability for mobile processors.

We have already proposed a service discovery scheme using mobile agents for mobile ad hoc networks where node positions in the network and the network topology change frequently. Mobile agents autonomously migrate among nodes and then perform a given task at a node. In the service discovery scheme using mobile agents, mobile agents collect and disseminate services in the network so it is most important how the mobile agents migrate in the network. Therefore, we propose two types of mobile agent migration mechanisms in this paper. One is that mobile agents migrate to the nodes at which other mobile agents do not stay, the other is that mobile agents migrate to the nodes to which mobile agents can disseminate a lot of service information. Finally, we conducted simulation experiments to investigate the performance of the proposed migration mechanisms with respect to the service dissemination time and rate.

This study proposes an integrated technology based on Proxy Mobile IPv6, which is a network-based protocol with mobility support, and a mobile content delivery network (CDN) that provides efficient content delivery management. The proposed architecture offers several benefits, such as the conservation of network resources because of reduced total traffic between hops and a reduced hop count.

To facilitate the discovery of mobile apps in personal devices, we present the personalized live homescreen system. The system mines the usage patterns of mobile apps, generates personalized predictions, and then makes apps available at users' hands whenever they want them. Evaluations have verified the promising effectiveness of our system.

Battery life and outdoor visibility are two of the most important features for mobile applications today. It is desirable to achieve both low power consumption and excellent outdoor visibility on the display device at the same time. We have previously reported a new RGBW method to realize low power consumption and high luminance with high image quality. In this paper, the basic concept of a new RGBW calculation utilizing an “Extended HSV color space” model is described, and also its performance, such as low power consumption, color image reproducibility and outdoor visibility is presented. The new method focuses on the luminance-increase ratio by means of a White signal for the display image data, and derives the appropriate RGBW signal and backlight PWM signal for every frame period. This dynamically controlled system solves the problems of conventional RGBW systems, and realizes the same image quality as a corresponding RGB display. In order to quantify its color image reproducibility, a spectroscopic measurement has been completed using the Macbeth Color Chart. In addition, the advantages of high luminance by the new RGBW method is described. The converted tone curve with an RGBW method provides very high luminance, such as 1,000cd/m2, and improved outdoor visibility. Finally, a newly developed 4.38-inch full-HD (1,080 × 1,920) 503ppi prototype LCD utilizing this new RGBW technology is described.

A mobile hotspot is a moving vehicle that hosts an Access Point (AP) such as train, bus and subway where users in these vehicles connect to external cellular network through AP to access their internet services. To meet Quality of Service (QoS) requirements, typically throughput and/or delay, a Call Admission Control (CAC) is needed to restrict the number of users accepted by the AP. In this paper, we analyze a modified guard channel scheme as CAC for mobile hotspot as follows: During a mobile hotspot is in the stop-state, we adopt a guard channel scheme where the optimal number of resource units is reserved for vertical handoff users from cellular network to WLAN. During a mobile hotspot is in the move-state, there are no handoff calls and so no resources for handoff calls are reserved in order to maximize the utility of the WLAN capacity. We model call's arrival and departure processes by Markov Modulated Poisson Process (MMPP) and then we model our CAC by 2-dimensional continuous time Markov chain (CTMC) for single traffic and 3-dimensional CTMC for two types of traffic. We solve steady-state probabilities by the Quasi-Birth and Death (QBD) method and we get various performance measures such as the new call blocking probabilities, the handoff call dropping probabilities and the channel utilizations. We compare our CAC with the conventional guard channel scheme which the number of guard resources is fixed all the time regardless of states of the mobile hotspot. Finally, we find the optimal threshold value on the amount of resources to be reserved for the handoff call subject to a strict constraint on the handoff call dropping probability.

In information retrieval from printed images considering the use of mobile devices, the correction of geometrical deformation and lens distortion is required, posing a heavy computational burden. In this paper, we propose a method of reducing the computational burden for such corrections. This method consists of improved extraction to find a line segment of a frame, the reconsideration of the interpolation method for image correction, and the optimization of image resolution in the correction process. The proposed method can reduce the number of computations significantly. The experimental result shows the effectiveness of the proposed method.

In order to employ Multiple-Input-Multiple-Output (MIMO) techniques, multiple antenna branches are necessary and as a consequence the installation space requirements are increased. Since the installation space is limited, much attention is now focused on utilizing polarization characteristics in MIMO configurations to relax the requirements. This is called Orthogonal Polarization-MIMO in this paper. To evaluate accurately the performance of Orthogonal Polarization-MIMO, a channel model that can handle the polarization dispersion characteristics of propagation paths is essential. Up to now, the spatial-temporal dispersion characteristics of paths have been investigated in detail. However, there are only a few reports on the polarization dispersion characteristics. In this paper, we propose a new power profile for the rotational polarized angle as an evaluation model for polarization dispersion, and clarify the analyzed power profile based on measurement data in an urban macrocell environment.

This paper proposes T-CROM (Time-delayed Collaborative ROuting and MAC) protocol, that allows collaboration between network and MAC layers in order to extend the lifetime of MANETs in a resources-limited environment. T-CROM increases the probability of preventing energy-poor nodes from joining routes by using a time delay function that is inversely proportional to the residual battery capacity of intermediate nodes, making a delay in the route request (RREQ) packets transmission. The route along which the first-arrived RREQ packet traveled has the smallest time delay, and thus the destination node identifies the route with the maximum residual battery capacity. This protocol leads to a high probability of avoiding energy-poor nodes and promotes energy-rich nodes to join routes in the route establishment phase. In addition, T-CROM controls the congestion between neighbors and reduces the energy dissipation by providing an energy-efficient backoff time by considering both the residual battery capacity of the host itself and the total number of neighbor nodes. The energy-rich node with few neighbors has a short backoff time, and the energy-poor node with many neighbors gets assigned a large backoff time. Thus, T-CROM controls the channel access priority of each node in order to prohibit the energy-poor nodes from contending with the energy-rich nodes. T-CROM fairly distributes the energy consumption of each node, and thus extends the network lifetime collaboratively. Simulation results show that T-CROM reduces the number of total collisions, extends the network lifetime, decreases the energy consumption, and increases the packet delivery ratio, compared with AOMDV with IEEE 802.11 DCF and BLAM, a battery-aware energy efficient MAC protocol.

Proxy Mobile IPv6 (PMIPv6) is a network-based localized mobility management protocol that is independent of global mobility management protocols. In a single local mobility domain, the mobile node (MN) is not involved in any IP mobility-related signaling, but when the MN moves into another local mobility domain, the MN must change its PMIPv6 home address. In this case, host-based mobility signaling is activated, and PMIPv6's network-based mobility cannot be retained. Additionally, if the MN does not support global mobility, it cannot maintain its communication sessions with its correspondent node. In this paper, we propose a solution for network-based global mobility support in PMIPv6 networks, which allows the MN to maintain active communication sessions without mobility protocol stacks when the MN moves into another local mobility domain. In the proposed mechanism, the MN remains unaware of its movement when it moves to another local mobility domain, and it is forced to use only its MIPv6 home address for all its communication. Thus, the MN is not involved in any IP mobility-related signaling, despite its movement. The proposed protocol provides for global mobility while retaining the advantages of the network-based localized mobility in the Proxy Mobile IPv6 protocol. In this paper, we propose a solution for global mobility support in PMIPv6 networks by which the MAG (Mobile Access Gateway) can maintain the MN's communication sessions during inter-domain handover. In the proposed mechanism, the MN remains unaware of its movement when it moves to another local mobility domain, and it is forced to use only its MIPv6 home address for all its communication. Thus, the MN is not involved in any IP mobility-related signaling, despite its movement. We evaluate and compare network performance between our proposed solution and PMIPv6 and the main host-based mobility protocol. We evaluate and compare handover delays, and packet loss cost of the two protocols.

In this paper, we proposed that an area- and speed-effective fixed-point pipelined divider be used for reducing the bit-width of a division unit to fit a mobile rendering processor. To decide the bit-width of a division unit, error analysis has been carried out in various ways. As a result, when the original bit-width was 31-bit, the proposed method reduced the bit-width to 24-bit and reduced the area by 42% with a maximum error of 0.00001%.

The capacity of general mobile ad hoc networks (MANETs) remains largely unknown up to now, which significantly hinders the development and commercialization of such networks. Available throughput capacity studies of MANETs mainly focus on either the order sense capacity scaling laws, the exact throughput capacity under a specific algorithm, or the exact throughput capacity without a careful consideration of critical wireless interference and transmission range issues. In this paper, we explore the exact throughput capacity for a class of MANETs, where we adopt group-based scheduling to schedule simultaneous link transmissions for interference avoidance and allow the transmission range of each node to be adjusted. We first determine a general throughput capacity upper bound for the concerned MANETs, which holds for any feasible packet delivery algorithm in such networks. We then prove that the upper bound we determined is just the exact throughput capacity for this class of MANETs by showing that for any traffic input rate within the throughput capacity upper bound, there exists a corresponding two-hop relay algorithm to stabilize such networks. A closed-form upper bound for packet delay is further derived under any traffic input rate within the throughput capacity. Finally, based on the network capacity result, we examine the impacts of transmission range and node density upon network capacity.

A new path loss model of interference between mobile terminals in a residential area is proposed. The model uses invertible formulas and considers the effects on path loss characteristics produced by paths having many corners or corners with various angles. Angular profile and height pattern measurements clarify three paths that are dominant in terms of their effect on the accurate modeling of path loss characteristics in residential areas: paths along a road, paths between houses, and over-roof propagation paths. Measurements taken in a residential area to verify the model's validity show that the model is able to predict path loss with greater accuracy than conventional models.