Cognitive radio network (CRN) is designed to improve the low resource utilization problem caused by the fixed spectrum allocation policy used today. In CRNs, secondary users (SUs) sense spectrum holes and adaptively use the frequency band. In this paper, we tackle the Quality of Service (QoS) routing problem in wireless ad hoc CRNs. We consider such factors as available time, frequency bands, transmission range, error rate, primary user (PU) interruption rate and transmission range, and design a new QoS routing metric for wireless ad hoc CRNs. We then evaluate the performance via simulations in terms of the average and maximum end-to-end delays. The results show that our proposed metric outperforms existing solutions, including probability based, bit-rate based, and hop-count based methods.

We explored mined block temporarily holding (MBTH), MBTH with enforce fork (MBTH-EF), and intermittent MBTH-EF (iMBTH-EF) attacks to understand the effect of selfish mining on winning rate and fairness from the pool operation perspective. The temporary holding time of the current mined block provides a pool additional time to begin mining the next block early with MBTH attack. In this situation, the winning probability increases for the next block, but the pool may risk losing the mined block. One enhanced method to maintain the winning probability of the held block is to ensure the holding pool sends out the mined block once it receives the mined block message from the other pools with the MBTH-EF attack. The explored MBTH attacks differ from the existing selfish miner and pool attacks. The operations and effects of the MBTH-EF attack are different from stubborn mining strategies and a self-holding attack integrates selfish and stubborn mining attacks. We propose a mining competition solution that does not involve actual hash calculation. It entails using one stochastic target hash value for batch racing simulation to evaluate the holding threshold, holding periods, mining time, mining difficulty, pool sizes, and the rate of fork occurrences according to the operation data of the Bitcoin system. Accordingly, the dynamic time-by-time, block-by-block, and pool-by-pool simulations are adopted to study these attacks. We analyzed MBTH and MBTH-EF attacks as well as evaluated the effects of the win rate on when and how long a block is held. Because the periodic adjustment of mining difficulty reduces the holding effect, we further evaluated how an intermittent MBTH-EF (iMBTH-EF) attack model balance the average mining time and mining difficulty according to the mining difficulty adjustment of a stage. The effect of intermittent holding is examined on the mining game win rate for a long-term competition. We also identified suitable attack detection methods for the future work according to the simulation results.

Purpose: The purpose of this study is to review the levels of open government data (OGD) among various countries that are not consistent with the development levels of those countries. This study evaluates the associativity between OGD Index (OGD) and the characteristics of those countries as well as to compare the degree of OGD among countries. Accordingly, an advanced discussion to explore how a country’s characteristics affect how that country’s government opens data was presented.Design/methodology/approach: The stakeholder relationships of OGD is analysed with the characteristics of a country. The usage data are compared with the data availability according to nine indicators. These data collected from the statistics and OGDI websites are grouped for comparative statistical analyses based on basic descriptive statistics, one-way analysis of variance and a regression model with variance inflation faction.Findings: The results 1) revealed the reasons some countries have high-ranking indexes and 2) verified the high index values of countries in terms of their degrees of development. This study, thus, attempted to derive a balanced appraisal of national development and OGD.Research limitations/implications: The study sample is limited only to countries 1) which open the statistical data; and 2) are of uneven population density and development degree. The OGDI is limited to expert evaluation. The score might be vary to experts and users with diverse countries at different evaluation period. The limitations can be attributed to the differences between OGDI and real open levels. These differences might influence the reliability and validity.Practical implications: Government departments with OGD policies provide raw data in various formats and with application interfaces for user access. This study, thus, attempts to derive a balanced appraisal of national development and OGD. The factors that evaluate which types of countries open the level of data are explored.Originality/value: This study establishes stakeholder relationships of OGD and extends to analyse the characteristics of a country and OGD that affect the government data open level. The relationships are evaluated through the OGDI with design score scheme. The measurement results indicated that a country possesses high relation to open data with high DI and nature resource.

The network lifetime for wireless sensor network plays an important role to survivability, Thus, we indicate the importance of routing protocol to network lifetime, and model the expected retransmission time as a convex function with respect to aggregate jlow on each sensor node. Thus we formulate the optimal energy-eficient routing as a non-linear min-max programming problem with convex productform, which can be optimally solved by optimal routing framework. Based on the optimal routing framework, we propose Lagrangean-based algorithm and primal optimal algorithm. By the combination of these two algorithms, we can optimally and efficiently get the routing assignment to maximize the network life in the sensor network. From experiments,we observe that when the optimal network lifetime increases as the number of sensor nodes increase. While the shortest path-based heuristic algorithm can only achieve about 48% network lifetime compared to our solution approach.

In heterogeneous wireless networks, coordinated multipoint technology facilitates coordination and mutual cooperation among various types of networks and applications. The resource requirements of various applications differ considerably under the constraint of limited resources so that the allowable delay is considered. This study considered a centralized management scheme involving fourth-generation (4G) mobile networks Evolved Node B, access points, and back-end coordinated servers. The operator controls the flow and performs routing selection procedures through long-term evolution advanced and Wi-Fi in accordance with the 5G wireless networks. The problem was constructed as a mathematical programming model. A Lagrangian relaxation (LR) approach was adopted to maximize the revenue minus the penalty costs as objective to evaluate the resource allocation, tolerable delay, and multisession routing algorithm. The primal problem was decomposed into seven independent subproblems through LR procedures, and the combination of a subgradient method and a routing algorithm was used to obtain approximate solutions. A novel algorithm for flow control involving multisession routing is proposed for handling resource allocation. The algorithm involving a near-optimal approach was designed to solve the insufficient resource problem. The solution can be used by operators for improving resource utilization in next-generation wireless networks.