Earticle

The current paper proposes fast distributed constrained power control (FDCPC) with a non‐stationary relaxation factor as the next power update for CDMA cellular power control systems. A review is also given of unconstrained control algorithms: distributed power control (DPC), unconstrained second‐order power control (USOPC), and DPC with a stationary relaxation factor (DPCSRF). To improve the performance of outage probability convergence, DCPC with a non‐stationary relaxation factor (FDCPC) is proposed. Under constrained conditions, the convergence rate of FDCPC is shown to outperform that of DCPC and constrained second order power control(CSOPC).

전술데이터 링크는 다양한 정보 교환을 위한 핵심 군통신 시스템이며 대한민국은 자체 전술데이터 링크 를 개발 및 구축하기 위한 계획을 진행 중이다. 본 논문에서는 유무인 비행체가 지상국과 통신하는 지상-공중 데 이터링크 시스템을 고려한다. 이러한 데이터링크를 구축할 때 일반적으로 지상국은 하나를 두고 분산안테나를 이 용하여 넓은 면적에서 비행체와 통신이 가능하도록 구성한다. 지상국에서 송신 시 분산안테나는 동일한 신호를 송 신하며 비행체는 이 신호를 수신한다. 비행체가 두 개의 분산안테나 중간지점을 지나가는 상황에서는 두 안테나로 부터의 송신신호가 동일한 크기, 동일한 시간 지연을 가지고 도착하기 때문에 서로 간섭으로 영향을 미치게 된다. 따라서 안테나와 안테나 사이의 특정 영역에서는 통신이 두절되는 상황이 발생할 수 있다. 본 논문은 주파수 도약 에 기반한 송수신 모뎀설계 안을 제시하고 분산안테나 환경에서 수신성능에 대해 분석한다. 이를 통해 분산안테나를 적용한 지상국 환경에서 통신이 불가능한 상황을 정확하게 확인하는 것이 본 논문의 목적이다. 컴퓨터 모의실 험에 따르면 두 안테나에서 수신되는 신호의 크기가 같고, 시간지연 역시 유사한 상황에서 통신이 제대로 수행되 지 않는다. 하지만 두 조건 중 하나만 만족하면 원활한 통신이 가능함을 확인하고, 분산안테나에서 송신하는 전력 의 크기를 조절하면 통신이 불가능한 영역을 줄일 수 있음을 제안한다.

The tactical data link is a key military communication system for exchanging various information, and South Korea is in the process of developing and constructing its own tactical data link. This paper considers the ground-to-air data link system that communicates with unmanned and manned aircraft. When constructing such a data link, the ground station typically installs a distributed antenna to enable communication with aircraft over a wide area, using one ground station. When the ground station transmits, the distributed antenna transmits the same signal, and the aircraft receives the signal. However, when the aircraft pass through the midpoint between the two distributed antennas, the signals from the two antennas interfere with each other because they arrive with the same power and time delay. Therefore, communication may be interrupted in a specific area between the antennas. This paper presents a frequency-hopping modem design and performs a receiver performance analysis in a distributed antenna environment. The purpose of this paper is to accurately identify areas where communication is impossible in a ground station environment using a distributed antenna. According to computer simulations, when the signal powers and time delays received from the two antennas are similar, communication does not work properly. Confirming that good communication is possible when only one of the two conditionas is satisfied, we propose that adjusting the transmission power from the distributed antenna can reduce the areas where communication is impossible.

Distributed Systems remained one of the most recent development fields in computing research. The parallel applications development faced enormous hindrance in QoS delivery due to resource hungry queuing models and complex memory patterns. Being a collection of multiple autonomous systems, a distributed system's efficiency lies in best coordination of its middle ware and coordinating modular layers. The concurrency is maintained by implementing Integrity constraint rules. The paper assesses various coherence addressing schemes for QoS delivery in Distributed Network environment.

Middleware facilitates the development of distributed systems by accommodating heterogeneity, hiding distribution details and providing a set of common and domain specific services. It plays a central and essential role for developing distributed systems. However, middleware is considered a mean rather than core elements of development process in the existing distributed systems software process. This paper explains the concept of middleware by categorizes middleware and analysis the problems of current middleware architectures. It also extracts three essential non-functional requirements of middleware and proposes a middleware-based distributed systems software process. The proposed software process consists in five phases: requirements analysis, design, validation, development and testing. The characteristics of middleware are considered in the entire software process. Component- Based Software Engineering, Separation of Concerns, Model-Driven Architecture, formal methods and Aspect Oriented Programming are five active research areas that have been around for several years now. In this paper, we present how these five paradigms can be put together in the context of a new software development method and we show how they can complement each other at different stages in the development life-cycle of middlewaremediated applications.

Recently, OSGi has been used in many areas of smart phones, software applications, and home network. However, it cannot be used for enterprise distributed systems because it does not have auto-managing schema for them and does not provide a backup strategy. A service location protocol which is a dynamic configurations protocol can be used to auto-manage the distributed systems, but the protocol cannot ensure the stability of distributed systems. In this paper, we present a technique of automated service discovery in distributed systems based on OSGi. The proposed technique defines four components and four type profiles to achieve automated service discovery and backup functions. By using the technique, OSGi could be widely used for developing enterprise distributed systems.

Cloud computing has based on on-demand access to potentially significant amounts of remote datacenter capabilities in distributed systems environment. By propagation data centers in clouds, computers should have a lower energy consumption. Hence, a good prediction about the amount of needed resources is very helpful for correct decision on energy consumption management. In this paper the Fuzzy Logic approach has been used for decision making about the performance of processors to obtain the estimated amounts of energy consumed by them and have been applied Auto Regressive and Neural Network approaches to predict the future workload. In prediction operation, three modes On, Off and Idle are considered for each server. At times of peak demand all servers must be turned on but when consumption is low, an estimated number of servers that must be turned on is obtained, 10% of remaining servers are idle and others are off. In this case a significant amount of energy is saved compared to the case that all servers are clear. The result show that Neural Network approach has more accurate prediction and better performance than Auto Regressive model.

In the past decades, plenty scheduling policies have been proposed for improving the execution performance of workflow applications. However, few of them have addressed the issue of energy conservation. In this paper, a novel scheduling metric, namely Minimal Energy Consumption Path, is introduced to reducing the energy consumption when scheduling large-scale workflows. The proposed scheduling metric can be incorporated into current schedulers so as to enhance their capability of energy conservation as well as maintain their scheduling performance. A lot of experiments are performed by using different scheduler and experimental settings to evaluate the proposed scheduling metric and the results indicate it is effective for reducing the storage-related energy consumption, especially when the target workflows are data-intensive.

In order to successfully monitor a large-scale distributed system, it is an important issue that the monitoring function fully covers all the entities in the system. To this end, a key challenge is to efficiently transmit state information of the entities in the system. This paper solves this challenge from two aspects. First, in virtue of the idea of self-organizing networks, this paper proposes a neighborhood organization algorithm, which self-organizes the nodes into several monitoring neighborhoods based on the t distance between nodes. The second aspect focuses on message transmission. There are three common message transmission methods in network, i.e., flooding, multicast and unicast. Flooding may cause high network overhead, while unicast may pose high system delay. Based on the idea of Gossip protocol, this paper proposes a directional message dissemination algorithm (D-Gossip), which is a kind of probabilistic multicast. D-Gossip reduces message dissemination uncertainty of traditional Gossip protocols. It effectively improves the efficiency and coverage of message dissemination, while reducing redundant information in the system due to Gossip protocol. The experimental results show that the neighborhood organization algorithm and the D-Gossip can effectively solve the above challenge.

With the development of wireless communication technologies and popularity of smart phones, many people are using location-based services (LBSs). However, since users continuously request LBS queries to LBS server by sending their exact location data, their privacy information is in danger. Therefore, cloaking area creation schemes have been proposed to protect the user’s location privacy. However, because the existing techniques generate a cloaking area in a centralized manner, an anonymizer suffers from performance degradation and security problem. Therefore, a cloaking area creation scheme based on distributed system is required for the safe and comfortable use of mobile users. In this paper, we propose a grid-based cloaking area creation scheme for continuous LBS queries in distributed systems. The proposed scheme stores information and performs operations in a distributed manner to create a cloaking area. In addition, the proposed scheme uses aggregate nodes to prevent query issuers' bottleneck. Finally, we show from a performance analysis that our cloaking area creation scheme shows better performance than the existing centralized cloaking area creation schemes.

An efficient functionality of any distributed database system “DDBS” is highly dependent on its proper design in terms of the adopted fragmentation and allocation methods. However, an optimal fragmentation and allocation design techniques could be very complex and requires good experiences and knowledge to reach. Fragmentation of a large, global databases are performed by dividing the database relations horizontally, vertically or as a combination of both. In order to enable distributed database systems to work efficiently, these fragments have to be allocated across the available sites in such a way that reduces communication cost i.e. to minimize the total volume of data transmitted during queries execution over sites. This paper presents a new data re-allocation model for replicated and non-replicated constrained DDBSs by bringing a change to data access pattern. This approach assumes that the distribution of fragments over network sites was initially performed according to a properly forecasted set of query frequency values that could be employed over sites. Our model takes sites constraints into account in the re-allocation phase. It proposes an efficient plan to re-allocate data fragments across sites based on communication and update cost values for each fragment individually. The re-allocation process will be performed by selecting the maximal update cost value for each fragment and making the re-allocation accordingly. Experimental results confirmed that the proposed technique will effectively contribute in solving fragments re-allocation problem in a dynamic distributed relational databases environment.

Distributed renewable energy generation is lack of intelligent information processing and decision-making section. The above problems can be solved effectively by the means of intelligent information processing technology based on the dynamic structure of multi-agent for distributed renewable energy. In order to solve the problems of less data and poor information, this paper puts forward fuzzy hyperbolic model and attempts to use dynamic intelligent information processing technology based on multi-agent to change the unreliable, inaccurate information into be full, reliable and accurate. And then the information we have obtained could be intelligent fitted, filtered and decided. The self-organizing self-learning and reasoning ability of multi-agent are considered when the information processing. The intelligent information processing section is comprised of three layers and two kinds of agents. The two kinds of agents are Bus Agents and Coordination Agents, and the three structural layers are the data layer, the filter layer and the policy making layer. Moreover the information have been processed could be utilized.

In this paper, we propose a cooperative protocol of relay-based WUSB/DRD and WLP device in the WSS of WiMedia environment. For this, we investigate a RNT table configuration and algorithm of RNS relay node to be used in relay-based cooperative communication. Then, we describe the feature of the device to configure the WLP network and propose a cooperative protocol for WUSB/DRD/WLP device communication. The proposed cooperative protocol can communicate with WUSB/DRD/WLP devices by using the standard DRP reservation and WUSB DRP reservation.

Single-phase grid-connected inverters play an important role in small distributed generation (DG) systems. This paper illustrates the circuit configuration and operation principle of a novel single-phase, single-stage, three-switch, fly-back, buck-boost inverter. The equivalent circuits associated with the four operation modes are established for the charging and discharging process. The inverter can operate in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). Most importantly, a new pulse generation method called pulse energy modulation (PEM) is proposed and applied to the three-switch buck-boost inverter in this paper. PEM signals for controlling the power switches are generated by meeting the output energy demand in each switching period with the stored energy in the coupled fly-back inductors. The duty ratio of PEM is thus determined by the energy demand and dc input voltage. The efficiency of the inverter used PEM is analyzed. A 400W experimental prototype is built in the laboratory to verify the operation of the proposed pulse energy modulation method. The inverter controller employs DSP dsPIC33FJ64MC506 for controlling, detecting and protecting functions. Experimental results have shown that PEM provides a new modulation mechanism for controlling the three-switch buck-boost inverter to inject a sinusoidal current into the grid under a wide range of operating conditions.

This paper theoretically analyzes the performance of distributed-antenna orthogonal frequency division multiplexing (OFDM) systems with multiple carrier frequency offsets (CFO) using zero-forcing (ZF) detection. Considering both the large-scale fading and the multipath fading of the wireless channel, we derive the average power of the inter-carrier interference (ICI) due to the CFOs and thus obtain the expression for the signal to interference and noise ratio (SINR). By analyzing the underlying characteristics of the ZF detection, we address the reason for the inaccuracy of the conventional SINR expression and propose a novel modified SINR expression with better precision, and hence obtain a closed-form expression for the bit error rate (BER) performance with the presence of multiple CFOs. It is shown by the analytical and simulation results that the analytical SINR obtained by the conventional expression appears lower than actually while the analytical SINR and BER obtained by the expressions presented in this paper are more accurate and closer to the corresponding simulation results.