Increase System Capacity Research Articles

Using Social Network Analysis to Promote Schoolwide Instructional Innovation: A Case Study

Social network analysis (SNA), a methodological approach that enables the mathematical examination of interprofessional relationships, can be an important tool for understanding and leveraging the social relationships that support and restrain instructional innovation and the quality and pace of school reform initiatives. In this article, we explicate the conceptual underpinnings of SNA and summarize how it has been used in a range of preK–12 educational evaluation contexts. A school-based case study is presented in which school leaders examined formal and advice-seeking networks among teachers, staff, and administrators and used the findings to reduce teacher isolationism, promote efficient communication, and increase system capacity for instructional innovation. Challenges associated with SNA for educational evaluation and school improvement are also discussed.

Macrocell–femtocells resource allocation with hybrid access motivational model

Femtocell technology has emerged as an efficient cost-effective solution not only to solve the indoor coverage problem but also to cope with the growing demand requirements. This paper investigates two major design concerns in two tier networks: resource allocation and femtocell access. Base station selection together with dual bandwidth and power allocation among the two tiers is investigated under shared spectrum usage. To achieve fair and efficient resource optimization, our model assumes that the hybrid access mode is applied in the femtocells. The hybrid access mode is beneficial for system performance as (1) it lessens interference caused by nearby public users, (2) it allows public users to connect to near femtocells and get better Quality of Service (QoS) and (3) it increases system capacity as it allows the macrocell to serve more users. However, femtocells’ owners can behave selfishly by denying public access to avoid any performance reduction in subscribers’ transmissions. Such a problem needs a motivation scheme to assure the cooperation of femtocells’ owners. In this paper, we propose a game-theoretical hybrid access motivational model. The proposed model encourages femtocells’ owners to share resources with public users, thus, more efficient resource allocation can be obtained. We optimize the resource allocation by means of the Genetic Algorithm (GA). The objective of the formulated optimization problem is the maximization of network throughput that is calculated by means of Shannon’s Capacity Law. Simulations are conducted where a modified version of the Weighted Water Filling (WWF) algorithm is used as a benchmark. Our proposed model, compared to WWF, achieves more efficient resource allocation in terms of system throughput and resources utilization.

A Common Operator for Discrete Wavelet Transform and Viterbi Algorithm

In wireless communication systems, the use of convolutional code with Viterbi algorithm and discrete wavelet transform to decreases SNR in order to increases system capacity. And recently, when referred to multi-standard designs reconfiguration mechanisms, flexibility and parameterization techniques are becoming an important subject. Therefore, this paper takes advantage of the Common Operator approach (parameterization) to introduce a mutual butterfly/ lattice structure for the DWT and Viterbi algorithms. The main advantage of presenting common operators is the regular architecture which contributes in multi-standard designs when carried out in this parameterization approach. Because of the regularity in architecture, the presented approach can analyze half the power consumption that of the sum of power consumed by individual architectures of DWT and Viterbi. Also, one another achievement of the system is the image quality metric in terms of root mean square error is obtained in the range 0.2188to 0.2941.

Selection of Distribution Feeders for Implementing Distributed Generation and Renewable Energy Applications

Climate change concerns mandated renewable portfolio standards, lucrative government incentives, and accelerated cost reduction in renewables, and distributed energy applications are driving steep growth in system installations. Distributed energy resources (DERs) are not commonly connected to a bulk power transmission system but are interconnected near the load in the electric power distribution system. DER includes renewable energy such as wind and solar, fossil-fuel-based generation (microturbines and small gas turbines), and distributed energy storage. In this paper, a novel methodology is developed that ranks utility feeders for implementation of DER systems. This performance index is based on peak-load reduction, increased system capacity, load-generation correlation, and feeder load growth. This is based on a statistical measure that quantifies the relationship between loads and the stochastic nature of renewable resources. This allows the utility to gain insight into improved benefits from nondispatchable renewable resources such as solar and wind technologies as well as dispatchable DER technologies.

A Dynamic Resource Allocation Scheme for the Downlink Heterogeneous Traffic of Internet Protocol (IP) Based OFDM networks

Radio Resource management mechanisms such as physical-centric radio resource allocation and medium access control (MAC)--centric packet scheduling are expected to play a substantial role in the performance of orthogonal frequency division multiplexing (OFDM) based wireless networks. OFDM provide fine granularity for resource allocation since they are capable of dynamically assigning sub-carriers to multiple users and adaptively allocating transmit power. The current layered networking architecture, in which each layer is designed and operated independently, results in inefficient resource use in wireless networks due to the nature of the wireless medium, such as time-varying channel fading. Thus, we need an integrated adaptive design across different layers, allowing for a cross-layer design. In this paper, a scheduling scheme is proposed to dynamically allocate resources for the downlink data transmission of internet protocol based OFDM networks. Generally to maximize the capacity and user satisfaction improvements in packet data admission, scheduling and policing are necessary. Of the three, efficient scheduling has the greatest impact on increased system capacity or effective spectrum usage. In addition, proper scheduling can greatly improve user satisfaction. The contribution of this work is twofold: first we evaluate current allocation schemes by exploiting the knowledge of channel sate information (CSI) and traffic characteristics in terms of queue state information (QSI) to acquire the system performance on a real time network. Second, the resource allocation scheme is extended by incorporating MAC layer information as well as opportunistic packet scheduling in the time-domain-based on minimum weight cost function. The key factors that affect the overall system performance in terms of system average throughput and delay are identified, evaluated and discussed.

Sorted QR-Decomposition Based Parallel Detection Algorithm for MIMO Systems

Multiple input multiple output (MIMO) wireless communication system can increase system capacity enormously. Maximum likelihood (ML) detection algorithm can obtain the optimal detection performance with exponential computational complexity that results it difficulty to use in practice. Classical ordered successive interference cancellation (SIC) algorithm suffers from error propagation and high complexity, so an improved parallel SIC algorithm based on Maximum likelihood (ML) detection is proposed, in which signal detection is performed at two stages. ML detections for one layer is carried out firstly, and redundancy of candidate sequences are selected to perform parallel detection for improving detection performance for next step. Sorted QR decomposition based SIC algorithm are performed in second step in order to reduce calculating complexity. By adjusting the number of candidate sequences, tradeoff between detection performance and calculating complexity can be obtained properly.

Femto Cells-A New Generation Cellular Stations

This paper provides a cost effective method for cellular telecommunications base stations that can be installed in residential or business environments either as single stand-alone items or in clusters to provide improved cellular coverage within a building. Data transmission, good signal strengths within buildings, increase in system capacity and data rates are some of the issues been discussed in this review work. The increasing demand for higher data rates in cellular networks has resulted in a trend to smaller cell sizes (Femto cells) and Pico-cellular hot spot coverage. As a result the user can have the advantage of better coverage for additional services, cost benefits and also the network operator, the use of Femto cells provides a very cost effective means of improving coverage, along with linking users to the network, and providing additional revenue from the provision of additional services. Femto cells deployed in the macro cell significantly improve the indoor coverage and provide better user experience. This article summarizes about the network architecture of Femto cells and the issues involved with it. Also it describes about the methods to overcome the issues

Cross‐layer channel selection and reward‐based power allocation for increasing system capacity and reward in multiple‐input–multiple‐output wireless communications

For increasing network bandwidth and guaranteeing quality of service in WiMAX, IEEE 802.16 m proposes the multiple-input–multiple-output (MIMO) technique that offers compatible specifications with the existing IEEE 802.16 family specifications. However, the performance of the IEEE 802.16 MIMO specification is significantly degraded in the high-mobility environment and high communication interference. As a result, a sender easily uses inaccurate modulation and coding scheme (MCS) and improper power allocation for different-priority users having different received signal-to-noise ratios. The system capacity is thus affected significantly. Additionally, the multiuser MIMO systems seldom consider that different-priority users and different-class traffic bring different rewards to the system. This study thus proposes a cross-layer reward-based approach (namely CLR) that consists of three schemes: adaptive modulation and coding determination, cross-layer dynamic channel selection, and reward-based weighting power allocation. The proposed CLR approach achieves accurate channel state information determination, optimal channel selection, and adaptive reward power allocation. Numerical results demonstrate that the proposed approach significantly outperforms the other approaches in system reward, system capacity, and the accuracy of the MCS determination.

Dynamic-cost-reward connection admission control for maximizing system reward in 4G wireless multihop relaying networks

The 3GPP Long Term Evolution (LTE) Advanced and IEEE 802.16j specifications adopt the mobile multi-hop relaying (MMR) mechanism for enlarging service area and improving wireless transmission quality simultaneously. By deploying different types of Relay Stations (RSs), MMR can bring some advantages: (1) the signal fading and wireless interference of a single long wireless link is improved obviously; (2) the ranges of wireless access and relay area are extended, etc. MMR can offer a high data rate transmission for packet services and can increase system capacity. Note that MMR can be applied to the public transportation system, e.g., equipped a mobile RS on a high-speed train. A mobile RS handoff initializes a multiple handoff requests of different types of traffics. It becomes as a critical handoff issue in 4G MMR. Thus, the MMR handoff needs a new efficient Connection Admission Control (CAC) to guarantee qualities for various types of traffics and to increase system revenue. However, traditional CACs are difficult to fulfill the objectives. This paper thus proposes the Dynamic Cost-Reward-based (DCR) CAC that consists of two key mechanisms: (1) adopting a Markov decision process-based (MDP) cost function and (2) providing different reward functions for different types of nodes and various types of connection. Additionally, a mathematical analytical Markov chain is modeled for DCR. The simulation results are very close to the analysis results, which justifies the correctness of the analytical model. Numerical results demonstrate that DCA outperforms the compared CACs in the probabilities of new blocking, MS-handoff, and RS-handoff dropping, FRL, GoS, and system reward.

Influencia de una cultura organizativa orientada hacia la calidad en los beneficios de la implantación de un sistema de gestión de recursos ERP

Purpose: Organizational culture focused on quality management aims to meet customer needs and enhance teamwork, being oriented toward a dynamic process of continuous improvement. The purpose of this paper is to analyze whether, indeed, the quality-oriented culture has an effect on the management of business processes. In doing so, we analyze their relationship with the benefits of a resource management system or ERP. Design/methodology/approach: A survey is used to collect data, with valid questionnaires obtained for 200 Spain based respondents. Empirical analysis utilises Structural Equation Modelling (SEM). Findings: The results confirm that firm's commitment with quality management, customer focus, and confidence of workers has a positive effect on the results of operational, strategic and managerial benefits derived from an ERP system implementation. However, there is not relationship between customer focus and organizational benefits, neither to increase system capacity. Originality/value: The present study analyzes the relationship between quality-oriented culture and the resource management systems of the firm clarifying their strengths and limitations. In this sense, the customer orientation may limit the flexibility of business as require a lot of resources, and generate dissatisfaction among workers resulting from the attention to customer complaints.

Uplink Power Control via Adaptive Hidden-Markov-Model-Based Pathloss Estimation

Dynamic variations in channel behavior is considered in transmission power control design for cellular radio systems. It is well known that power control increases system capacity, improves Quality of Service (QoS), and reduces multiuser interference. In this paper, an adaptive power control design based on the identification of the underlying pathloss dynamics of the fading channel is presented. Formulating power control decisions based on the measured received power levels allows modeling the fading channel pathloss dynamics in terms of a Hidden Markov Model (HMM). Applying the online HMM identification algorithm enables accurate estimation of the real pathloss ensuring efficient performance of the suggested power control scheme.

Optimal Channel Allocation with Hot-Spot Technique in Wireless Network

In wireless mobile communication systems, proper channel allocation scheme is required. Due to the limitation of available frequency spectrum, channels must be reused as much as possible to increase system capacity. Complication arises in channel allocation, when more than one cell become “hot-spot” in the network of one BSC. The cells become “hot-spot” when bandwidth resources currently available in those cells are not sufficient to sustain any more call. In hybrid channel allocation, cells send a multilevel hot-spot notification to the dynamic pool of BSC on each channel request that cannot be satisfied locally at the base station. Proportional to the current hot-spot level of the cell, this hot-spot notification will request more than one channel to assign to the requesting cell. Severe complication arises, when not even one channel available in the dynamic pool of BSC in order to assign to requesting cells. This is the situation, when call starts dropping or blocking. This paper presents a new scheme in which BSC will fetch those ideal channels, which are borrowed to requesting cell from the dynamic pool in the time of hot spot but become ideal in the temporary pool of BTS for some period of time. BTS make use of these channels in order to sustain new incoming call .The proposed algorithm in this paper will reduce the call dropping probability comparatively more than the simple hybrid channel allocation algorithm.

Interference Management in Femtocells

Increase in system capacity and data rates can be achieved efficiently in a wireless system by getting the transmitter and receiver closer to each other. Femtocells deployed in the macrocell significantly improve the indoor coverage and provide better user experience. The femtocell base station called as Femtocell Access Point (FAP) is fully user deployed and hence reduces the infrastructure, maintenance and operational cost of the operator while at the same time providing good Quality of Service (QoS) to the end user and high network capacity gains. However, the mass deployment of femtocell faces a number of challenges, among which interference management is of much importance, as the fundamental limits of capacity and achievable data rates mainly depends on the interference faced by the femtocell network. To cope with the technical challenges including interference management faced by the femtocells, researchers have suggested a variety of solutions. These solutions vary depending on the physical layer technology and the specific scenarios considered. Furthermore, the cognitive capabilities, as a functionality of femtocell have also been discussed in this survey. This article summarises the main concepts of femtocells that are covered in literature and the major challenges faced in its large scale deployment. The main challenge of interference management is discussed in detail with its types in femtocells and the solutions proposed over the years to manage interference have been summarised. In addition an overview of the current femtocell standardisation and the future research direction of femtocells have also been provided.

A Multi-Head Clustering Algorithm in Vehicular Ad Hoc Networks

Clustering is an important research topic in wireless networks, because cluster structures can facilitate resource reuse and increase system capacity. In this paper, we present a new clustering algorithm that considers both node position and node mobility in vehicular ad hoc environments. The proposed algorithm intends to create stable clusters by reducing reclustering overhead, prolonging cluster lifetime, and shortening the average distance between cluster heads and their cluster members. Most important, this algorithm supports single and multiple cluster heads. Simulation results show the superiority of our clustering algorithm over the other three well-known algorithms.

High Speed Data Transmission Using Coding

The relible and fast data transmission over noisy band limitted channels is the basic requirment of digital communication and transmission system. Reliability considerations require that forward error correction techniques be used. This techniques find and correct limitted erros caused by a transport or storage systems. Such coding technique is therefore used to help compensate for signal degradation and provide increase in system capacity and reliability. In this paper, we analyze the performance of three codes which are the Reed Soloman Code, the convolutional code, and turbo code for the same signal that is corrupted by transmission channel. The type of channel considered in this work is the AWGN. For the same message length, the turbo code gives the best performance and the Reed Soloman Code gave the poorest performance when the signal is corrupted by AWGN channel.

Time‐reversal techniques for MISO and MIMO wireless communication systems

We consider the application of different time‐reversal (TR) signal processing and beamforming techniques to multiple‐input single‐output (MISO) and multiple‐input multiple‐output (MIMO) wireless communication systems. Conventional TR beamforming provides spatial focusing at the intended receiver; however, it does not yield perfect channel equalization. Time‐reversed pilot can be normalized to provide perfect equalization at the expense of power level. This equalization is particularly important for high data rates where the bit error rate performance is dominated by internal noise due to intersymbol interference. To increase physical layer covertness, TR beamforming is combined with the multiple‐signal‐classification (MUSIC) technique to produce null fields at eavesdroppers. This technique is also applied to MIMO setups to eliminate interuser interference and hence increase system capacity. Differential TR is used to obtain and update pilot signals for passive moving receivers, i.e., those that cannot (or do not) transmit pilot signals. Time‐reversed differential backscattered signal is able to provide satisfactory spatial and temporal focusing at the moving receiver.

Interference reduction through femto-relays

Femtocell, also known as home base station is one of the promising cost-effective technologies that ensure a steady increase in system capacity, improvement in service quality and a better data rate for users mainly in the indoor environment. However massive rollout of femtocells cause severe interference to the existing macrocell network and drive users into outage. Moreover, though femtocells can provide improved home coverage and capacity for indoor users, many a times, these femtocells are under-utilised when they do not serve any voice or data request. In this paper a novel idea to extend the coverage of femtocells beyond the home environment through multiple hops is proposed. The idea is to exploit the under-utilised femtocells to serve the high data rate requests of many outdoor user equipments and reduce the probability of their outage. This will not only extend the coverage of femtocell and relax the burden on the macrocell base station, but also helps in reducing the interference to the co-existing macrocell network, because of reduced transmission power and path loss, achieved through relaying.

Peak-To-Average Power Reduction In Mimo-Ofdm Systems Using Sub-Optimal Algorithm

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology is one of the most attractive candidates for fourth generation (4G) mobile radio communication. It effectively combats the multipath fading channel and improves the bandwidth efficiency. At the same time, it also increases system capacity so as to provide a reliable transmission. However, the main drawback of MIMO-OFDM system is high peak-to-average power ratio (PAPR) for large number of sub-carriers, which result in many restrictions for practical applications. Coding, phase rotation and clipping are among many PAPR reduction schemes that have been proposed to overcome this problem. In this paper, we mainly investigate the PAPR reduction performance with two different PAPR reduction methods: partial transmit sequence (PTS) and selective mapping (SLM). These two methods are sub-entities of phase rotation scheme. We propose an algorithm, Sub-Optimal algorithm that shows better PAPR reduction compared to the existing algorithms. Results are verified using MATLAB software.

다수의 부스트림을 이용한 분산 비디오 스트리밍 시스템을 위한 공정하고 효율적인 부스트림 할당 기법

비디오 소스를 다수의 부스트림으로 인코딩하는 향상된 코딩 기법을 이용하는 분산 비디오 스트리밍 시스템의 경우 시스템의 용량 증대를 위해서는 피어들이 자발적으로 많은 양의 부스트림을 재전송할 수 있는 장려책이 필요하다. 또한 참여 피어들은 자원 제공자인 동시에 서비스 소비자인 특성을 가지므로 시스템의 전체 용량은 참여 피어들의 부스트림 제공량에 따라 공정하게 할당되어야 하며 시스템의 효율성 측면에서는 참여 피어들의 전체 서비스 인지 품질이 최대화 되도록 할당되어야 한다. 본 논문에서는 이와 같은 문제 해결을 위해 최적화기법을 이용한 부스트림 할당 기법을 제안한다. 제안 기법은 자원 제공자이자 소비자인 피어의 특성을 고려하여 참여 피어의 자발적 자원 제공을 장려함으로써 기존 최적화 기법과 달리 분산 비디오 스트리밍 시스템 자원의 효율적 이용과 공정한 배분을 보장한다는 것을 모의실험을 통해 정량적으로 검증하였다. In a distributed streaming system using an advanced coding scheme that encodes a video into multiple substreams, the capacity of the system depends on the amount of contribution of participating peers. Thus, an incentive mechanism for peers to contribute voluntarily is needed to increase system capacity. In addition, since peers are not only a provider but also a consumer in the system (i.e. prosumer), the overall capacity of the system must be allocated fairly among the peers while it must be allocated in a way that can maximize the net quality of experience of peers to increase system efficiency. In this paper, we propose a substream allocation method to solve the problems taking an optimization approach. Unlike the other optimization approaches, the proposed method is verified quantitatively in a simulation study that it can use the capacity of video streaming system efficiently while allocating fair amount of substreams among peers because it considers explicitly the prosumer characteristics of peers.

Advances in cooperative wireless networking: Part II

Over the last few years, fundamental research has demonstrated the great potential of cooperative wireless networking in increasing system capacity and enlarging the coverage area as well as enhancing quality of service (QoS) by taking advantage of cooperative diversity and multiplexing. Consequently, cooperative wireless networking has become one of the widely recognized features for the future wireless communication systems. While the conventional research mainly focuses on relatively simple cooperative relay topologies or the cooperation schemes under the existing infrastructure networks, cooperative networking for future wireless systems has its own unique spectrum of features. Specifically, frequent user cooperation and interaction empower mobile users with a new role as mobile service providers, comparing with their traditional role as only the consumers. In this sense, mobile users? cooperation strategy and decisions are sensitive to not only the QoS requirements of the end users? applications but also their own benefits as rewards for providing mobile services. Moreover, the cooperation provided by mobile users does not have to rely heavily on the infrastructure networks.