Recent years, various services using Cloud computing are involving in people's life. However, when techniques and devices of Internet of Things (IoT) are getting more involved in people's life, current Cloud computing can hardly satisfy the requirement of low latency. To address the above problem, new distributed computing called Fog computing is proposed by Cisco System, Inc. Fog computing has a simple three-tiered hierarchy: Edge device, Fog and Cloud. The Fog tier is put between the Edge device tier and the Cloud tier to play the same or part of roles of the Cloud tier by its proximity to Edge device. The Fog tier consists of some fog nodes. The fog node receives jobs from the Edge device tier. Then, according to the jobs, the fog node decides to either process the jobs or assign it Cloud tier immediately. We call this process “Job assignment”. However, the division of roles between the Fog tier and the cloud tier is not clear and it must be decided depending on the system. In this paper, we express the Fog computing with VCHS (Various Customers, Heterogeneous Servers) queueing model. We then evaluate this model and study on an effective Job assignment strategy.

We have introduced pair works to university-level computer literacy education as opposed to the traditional one, standalone teaching. In this paper, in order to extract the learner characteristics factors that influence the pair work effects such as test-score improvement level, pair-work activity level and pair-work satisfaction level, we conducted two experimental pair work classes in computer literacy exercise courses. For the investigation, we used two main questionnaire surveys, TEGⅡ and GAMI as personality indexes. The result showed that the personality index has clear strong correlation with the degree of activity and degree of satisfaction in TEGⅡ and also to the degree of score elevation in GAMI. The personality score, obtained from the result, is useful for more effective pair combination.

We have proposed pair work in university-level computer literacy education as opposed to traditional, standalone teaching. In this paper, in order to extract the factors affecting the number of utterances, known to be important to improve the pair work effect, we conducted two experimental pair work classes. The participants were approximately 280 students who participated in computer literacy exercise courses. The results indicated that performing several utterances during pair work improved assignment achievement and pair work effect, thus also enhancing the satisfaction level of the pair work. In addition, there was little difference between the individuals within a pair in terms of the number of utterances, but the difference was significant between pairs. Participants in a pair with high basic academic ability and high differences in computer experiences before university-level education tended to have a smaller number of utterances, which is a characteristic of pair work conversation.

In this paper, we propose a novel MAC scheme that dynamically optimizes each active node's backoff process. Through theoretical analysis, we find that the average channel idle interval can represent current network traffic load and then can used together with estimated number of nodes for setting optimal CW. Since necessary indexes can be obtained through direct measurement, our scheme will not increase any added load to networks, which makes our schemes simpler and more reliable when network traffic reaches saturated. Through simulation comparison with previous schemes, we show that our scheme can greatly improve the throughput no matter the network is in saturated or non-saturated case, while maintaining good fairness.

In this paper, firstly we have proposed the free charged local community network service system with ad hoc networking technology and secondly then presented the performance evaluation model of the service with multi agent systems by using the prospect theory, and finally evaluated the service system. The proposed method is expected to contribute to the application of ubiquitous network and the optimum design of mobile ad hoc communication systems.

Ad-hoc networks do not need infrastructures such as base stations and they are an interested technology. One of the important subjects of ad-hoc networks is a radio media access control method. A control channel is usually used with a TDMA based method. There is a big influence on the performance of ad-hoc networks when a frequency channel zone is used as a TDMA based method. We have already proposed an access control method that is called the two division back off algorithm (TDBA). This algorithm can solve collisions with few overheads. But, this method has the problem that the success probability that a node will acquire a channel decreases when the number of collision-nodes increases. This work introduces a variable retransmission probability instead of a fixed retransmission probability, and the performance characteristics are compared and evaluated.

Major types of data for multimedia with mobile communications are voice, WWW and FTP. Different regimes for quality of service (QoS) exist for each with reference to delay sensitivity. Sharing available radio resource has been inherently based on the characteristics of data types and their associated QoSs. To satisfy each QoSs, the Delay of Voice End-User (DOVE) protocol has been presented. However, when evaluating the performance of DOVE protocol, there was one problem which requires much calculation time. In this paper, introducing the steady state equations for the Markov chain of DOVE protocol and solving them, we present a simplified method for evaluating the performance of DOVE protocol. The proposed method can be carried out in a less computer time.

Cascade, single and multi-bit, /spl Sigma//spl Delta/ architectures provide stable, high order quantization noise shaping used in high resolution A/D conversion. One major disadvantage of cascaded /spl Sigma//spl Delta/ topologies is the extreme SNDR sensitivity to gain mismatch between the analog modulator and the digital error correction logic. This paper will investigate this SNDR sensitivity phenomenon for a 6th order, 1-bit quantizer and 4th order, 5-bit quantizer cascaded /spl Sigma//spl Delta/ A/D system. Circuit parameters of the switched capacitor integrator such as amplifier open loop gain, integrator gain, and amplifier offsets and layout parasitics are characterized.

The ISDN has been developed to provide a variety of communication services. As a next step, the broadband ISDN with the asynchronous transfer mode is expected to contribute to the social infrastructure in the 21st century. For the optimum traffic and network designs of the ISDN and the BISDN, it is necessary to evaluate the GI/G/s general traffic (queuing) systems. The notation GI/G/s means s homogeneous parallel switching servers with the general independently distributed interarrival times and the general service time distribution. The exact analytical solution for the GI/G/s model has not yet been obtained. Until now, in order to evaluate the performance indexes of the GI/G/s traffic systems, we have presented the artificial neural method. The method uses a simple three layer feedfoward neural network trained with the backpropagation training algorithm. As a result of the training, the connective weight of the neural network accumulate a lot of information and knowledge relative to the behavior of the GI/G/s system. In this paper, the connective weight is analyzed and interpreted to find important traffic rules of the GI/G/s system. The discovery method is expected to contribute to the designs of 21st networks.

In broadband ISDN with ATM, various kinds of traffic, such as voice, data and video, share the common transmission resource. For such multiclass traffic systems, it is necessary to evaluate the grade of service (GOS) for individual traffic. In particular, for the ATM networks integrating voice and video which are of bursty property and delay sensitive, the individual performance evaluation for the mixed bursty traffic an important problem. The authors propose a simplified evaluation of the individual mean waiting time for the bursty multiclass systems appearing in the ATM network and show numerical examples for voice/video system.>

The single-server general queuing model G1/G/1 is studied for a modified Erlangian input that covers a wide range of bursty and nonbursty input processes. The E/sub k//G/1 model is analyzed using spectral factorization, and explicit form performance is evaluated in terms of the mean and variance of the waiting time.>