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.

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%.

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 propose an improved data embedding and extraction method for information retrieval considering the use of mobile devices. Although the conventional method has demonstrated good results for images captured by cellular phones, some problems remain with this method. One problem is the lack of consideration of the construction of the code grouping in the code grouping method. In this paper, a new construction method for code grouping is proposed, and it is shown that a suitable grouping of the codes can be found. Another problem is the correction method of lens distortion, which is time-consuming. Therefore, to improve the processing speed, the golden section search method is adopted to estimate the distortion coefficients. In addition, a new tuning algorithm for the gain coefficient in the embedding process is also proposed. Experimental results show an increase in the detection rate for embedding data and a reduction of the processing time.

In this paper, we introduce the concept of a multi-operator mobile relay node (RN) for cellular networks on buses or trains. The installation of RNs improves spectral efficiency because an antenna with a higher gain than that of user equipment (UE) can be installed in an RN. However, installing different RNs for different operators is not efficient because of the large amount of space needed to install multiple RNs in a bus. Thus, sharing one RN among multiple operators is a more practical approach. When we use a multi-operator mobile RN, the required amount of resource for each operator varies independently as the RN moves. Consequently, we propose a system of shared-spectrum allocation among operators for RN-UEs communication. Shared bandwidth can be allocated to operators according to link quality in order to achieve effective utilization of radio resources. However, to introduce shared-spectrum allocation, fairness among the operators and the total efficiency of the system should be taken into consideration. Using computer simulations, we evaluate shared-spectrum allocation based on the Nash bargaining solution (NBS). The results, in terms of both fairness and efficiency, indicate that total throughput can be improved by approximately 20% compared with the situation where multiple operators install different RNs individually.

The Open Mobile Alliance (OMA) Order of Rights Object Evaluation algorithm causes the loss of rights on contents under certain circumstances. By identifying the cases that cause this loss we suggest an algebraic characterization, as well as an ordering of OMA licenses. These allow us to redesign the algorithm so as to minimize the losses, in a way suitable for the low computational powers of mobile devices. In addition we provide a formal proof that the proposed algorithm fulfills its intent. The proof is conducted using the OTS/CafeOBJ method for verifying invariant properties.

The gathering problem of anonymous and oblivious mobile robots is one of the fundamental problems in the theoretical mobile robotics. We consider the gathering problem in unoriented and anonymous rings, which requires that all robots eventually keep their positions at a common non-predefined node. Since the gathering problem cannot be solved without any additional capability to robots, all the previous results assume some capability of robots, such as the agreement of local view. In this paper, we focus on the multiplicity detection capability. This paper presents a deterministic gathering algorithm with local-weak multiplicity detection, which provides a robot with information about whether its current node has more than one robot or not. This assumption is strictly weaker than that in previous works. Our algorithm achieves the gathering from an aperiodic and asymmetric configuration with 2 < k < n/2 robots, where n is the number of nodes. We also show that our algorithm is asymptotically time-optimal one, i.e., the time complexity of our algorithm is O(n). Interestingly, despite the weaker assumption, it achieves significant improvement compared to the previous algorithm, which takes O(kn) time for k robots.

Existing MANET routing protocols may not be efficient for mobile sensor networks (MSNs) since they generate too much control traffic by relying on flooding or route maintenance messages. Furthermore, peer-to-peer communication patterns assumed in MANET would exacerbate the traffic around sink nodes in MSNs. In this paper we propose traffic adaptive routing (TAR) for MSNs; it can reduce the control packets by analyzing and predicting the source, volume, and the patterns of both traffic and mobility. Through its analysis and the prediction of mobility, TAR also copes with dynamic topology changes by carrying out a fast route recovery process. Our theoretical analysis shows that TAR can effectively reduce unnecessary control packet flooding by 53% on average when compared to AODV. We implement TAR on NS-2. Our experimental evaluation confirms that TAR can not only improve the network and energy performance for MSNs but also can be a practical routing solution for MANET and WSNs compared to the existing ad hoc routing protocols.

The performance of a mobile database management system (DBMS) in which most queries are made up of random data accesses if the NAND flash memory is used as storage media of the DBMS is degraded. The reason for this is that the performance of NAND flash memory is good for writing sequentially but poor when writing randomly. Thus, a new storage structure and querying policies are needed in mobile DBMS when flash memory is used as the storage media. In this letter, we propose a new policy of database page management to enhance the frequent random update performance, and then evaluate the performance experimentally.

Automatic modulation classification (AMC) involves extracting a set of unique features from the received signal. Accuracy and uniqueness of the features along with the appropriate classification algorithm determine the overall performance of AMC systems. Accuracy of any modulation feature is usually limited by the blindness of the signal information such as carrier frequency, symbol rate etc. Most papers do not sufficiently consider these impairments and so do not directly target practical applications. The AMC system proposed herein is trained with probable input signals, and the appropriate decision tree should be chosen to achieve robust classification. Six unique features are used to classify eight analog and digital modulation schemes which are widely used by low frequency mobile emergency radios around the globe. The Proposed algorithm improves the classification performance of AMC especially for the low SNR regime.

This letter proposes a new mechanism that supports adaptive sending control using Real-Time Streaming Protocol (RTSP) and Transmission Control Protocol (TCP) for IPTV service over heterogeneous networks. The proposed mechanism is implemented on a mobile IPTV device and its performance is verified for providing seamless television watching in heterogeneous networks, even when in motion.

With the fast development of mobile communication technologies, mobile multimedia services like mobile Video on Demand (VOD) are becoming prevalent. However, VOD streaming requires dedicated bandwidth to satisfy Quality of Service (QoS), and the limited wireless bandwidth will become insufficient to support the increasing number of mobile VOD users. In order to solve the problem, this paper proposes a Call Admission Control (CAC) approach which can accept new users even when the system bandwidth is insufficient. Our approach also guarantees continuous playback for subscribers by taking into account the service end time and the delay bound of the users. Simulation results demonstrate that the proposed scheme can increase the number of concurrent users and reduce the connection blocking probability significantly without playback interruption.

This letter proposes a new mechanism for network configuration on a mobile device that provides Point of Attachment (PoA) specific information using IEEE 802.21 and DHCP before moving to a new PoA. This allows the mobile device to prepare for intelligent handover decision either stateless address configuration or stateful address configuration when entering an IPv6 network. It allows the mobile device to reduce time delay for IP address configuration in the new PoA. Implementation and evaluation results show that the proposed mechanism can be an acceptable network configuration mechanism for providing seamless television watching in IPv6 mobile networks, even when in motion.

This paper describes mobile backhaul optical access network designs for future cellular systems, in particular, for those systems that exploit coordinated multipoints (CoMP) transmission/reception techniques. Wavelength-division-multiplexing passive optical networks (WDM-PON) are primarily considered and two proposals to enhance mobile backhaul capability of WDM-PONs for CoMP are presented. One is physical X2 links that support dedicated low latency and high capacity data exchange between base stations (BSs). The other is multicasting in WDM-PONs. It effectively reduces data/control transmission time from central node to multiple BSs joining CoMP. Evaluation results verify that the proposed X2 links and the multicasting enable more BSs to join CoMP by enhancing the mobile backhaul capability, which results in improved service quality for users.

The recent increase in mobile data traffic has resulted in service quality problems. Although an economic approach to control congestion can be achieved by pricing, the current pricing schedule of mobile data services instead causes smartphone users to create more traffic. We establish a pricing model based on the distribution of demand types among heterogeneous users to improve the current tariff structure; our method mixes usage-based and fixed-fee pricing schemes. The results derived from the application of this model to survey data on willingness-to-pay for mobile data service demonstrate that the provider can decrease the amount of data traffic and increase the expected revenue by lowering the price for a unit of data and raising the fixed-fee level for unlimited service. The model also explains the changing weight of usage-based and fixed-fee pricing schemes by considering shifts in the type distribution through service evolution and proposes pricing strategies for future communications services.

The paper presents capability of signal detection for realizing coexistence between broadband wireless access (BWA) systems and ultra wideband (UWB) devices. The capability is experimentally evaluated for baseband signals of downlink (DL) in both mobile WiMAX and 3GPP LTE. An UWB receiver based on fast Fourier transform (FFT) compliant with MB-OFDM standard is implemented as a detector of the BWA signals. The capability is evaluated in terms of elapsed time required to achieve signal detection with probability of 99% by the implemented FFT-based UWB receiver at different conditions of the receiver. Decisions on the signal detection are made by the simplest method which is by setting a threshold which is determined by noise floor of the receiver as reference. The experiments have been conducted though baseband signals for both AWGN and multipath fading channels without any synchronization between the DL signals and UWB receiver. In AWGN environment, results show that the elapsed time depends on the duty ratio of the DL signal to be detected, however, the correlation between the required time and duty ratio is not linear since their envelopes of the DL signals are not constant. In multipath fading environments based on channel models commonly employed as mobile radio environments, the required time for the signal detection becomes as 17 times longer than that in AWGN due to its signal attenuation. For robust signal detection in multipath fading environments, it has been revealed that the number of quantization bits at ADC is crucial through the experiments.

This paper presents an algorithmic approach to acquiring the influencing relationships among users by discovering implicit influencing group structure from smartphone usage. The method assumes that a time series of users' application downloads and activations can be represented by individual inter-personal influence factors. To achieve better predictive performance and also to avoid over-fitting, a latent feature model is employed. The method tries to extract the latent structures by monitoring cross validating predictive performances on approximated influence matrices with reduced ranks, which are generated based on an initial influence matrix obtained from a training set. The method adopts Nonnegative Matrix Factorization (NMF) to reduce the influence matrix dimension and thus to extract the latent features. To validate and demonstrate its ability, about 160 university students voluntarily participated in a mobile application usage monitoring experiment. An empirical study on real collected data reveals that the influencing structure consisted of six influencing groups with two types of mutual influence, i.e. intra-group influence and inter-group influence. The results also highlight the importance of sparseness control on NMF for discovering latent influencing groups. The obtained influencing structure provides better predictive performance than state-of-the-art collaborative filtering methods as well as conventional methods such as user-based collaborative filtering techniques and simple popularity.

In this letter, for offloading traffic to Wireless Local Area Network (WLAN) with transport layer mobility where WLAN service is intermittently available, we propose a novel scheme to freeze and melt the timeout handling procedure of SCTP. Simulation results show that the proposed scheme significantly improves the performance in terms of file transfer completion time.

It is well known that satellite communications systems are effective and essential communication infrastructure for disaster relief. NICT sent researchers to Tsunami stricken area in March right after the Great East Japan Earthquake and provided broadband satellite communications link to support rescue activities. Through this experience, we learned many kinds of requirements of communications for such purposes. In this paper, we list up the requirements and report what kind of satellite communications technologies are needed, and research and development issues.

In this letter, we propose a new 4-dimensional constellation-rotation (CR) modulation method that achieves diversity gain of 4 in Rayleigh fading channels. The proposed scheme consists of two consecutive CR operations for QAM symbols unlike the conventional 2-dimensional CR method based on only one CR operation. Computer simulation results show that the new method exhibits much better performance than the conventional one in terms of code rate and channel erasure ratio.