Electrical Power Processing

Software architecture plays an important role in determining software quality characteristics, such as maintainability, reliability, reusability, and performance. Performance effects of architectural decisions can be evaluated at an early stage by constructing and analyzing quantitative performance models, which capture the interactions between the main components of the system as well as the performance attributes of the components themselves. The paper proposes a systematic approach to building Layered Queueing Network (LQN) performance models from a UML description of the high-level architecture of a system, and more exactly from the architectural patterns used for the system. The performance model structure retains a clear relationship with the system architecture, which simplifies the task of converting performance analysis results into conclusions and recommendations related to the software architecture. In the second part of the paper, the proposed approach is applied to a telecommunication product for which a LQN model is built and analyzed. The analysis shows how the performance bottleneck is moving from component to component (hardware or software) under different loads and configurations, and exposes some weaknesses in the original software architecture, which prevent the system from using the available processing power at full capacity due to excessive serialization.

The necessity for employing various location management procedures, in conjunction with the millions of users expected to subscribe to third generation mobile telecommunication systems, will generate a huge amount of signalling load. In this paper, we propose a method which aims at the significant reduction of the signalling overhead on the radio link produced by the paging procedure compared to the approach followed in second generation systems like GSM. The key idea here is the application of a multiple step paging strategy which operates as follows: At the instance of a call terminating to a mobile user which roams within a certain location area, paging is initially performed in a portion of the location area (this location area portion constitutes the paging area) that the so-called "paging related information"

Cellular positioning has been a very active research area for the last decade. Large improvement in accuracy has been made to support, for example, e-call and other location-based services. Traditionally, cellular positioning has been limited to cellular operators equipped with expensive synchronization hardware in order to achieve good accuracy. Lately, third parties have employed fingerprinting methods to enable positioning systems independent from the cellular operators. With improved available processing power, denser cellular networks, cheaper data collection and efficient pattern matching algorithms, the fingerprinting positioning methods have also gained popularity. In this paper, we analyzed the potential of using System Frame Number (SFN)-SFN observed time differences, which are traditionally used in Time Difference of Arrival (TDOA) positioning, for fingerprinting-based positioning. A field test was performed using measurements from TEMS (Telecommunication Management System) Investigation. By combining SFN-SFN observed time differences with Received Signal Code Power (RSCP) measurements, we demonstrated an improved accuracy of the fingerprinting method by 20% compared to only using RSCP measurements. The results are promising and show good potential in using SFN-SFN observed time differences for positioning based on fingerprinting.

Small-cell systems based on cloud radio access network (cloud-RAN) architecture have been proposed as promising solutions to meet the ever-increasing capacity demand of the next-generation wireless access networks. By centralizing the processing power to reduce the complexity of conventional cell sites, the cloud-RAN architecture is ideal for large-scale small-cell system at reduced capital and operational expenses. However, high-speed, flexible, and scalable backhaul links between the centralized baseband processing unit (BBU) and the remote antenna units (RAUs) are required to support the high throughput of the small-cell cloud-RANs, and the conventional approaches are based on digital baseband signal transmission in the backhaul links. In this paper, we propose a novel multi-service small-cell wireless access architecture based on radio-over-fiber (RoF) technologies. By utilizing analog radio frequency (RF) signal transmission in the optical backhaul links, the design of RAUs can be further simplified. In addition, by combing RoF with optical wavelength division multiplexing (WDM) techniques, multiple bands, multiple services and multiple operators can coexist in a shared optical infrastructure without interference. To demonstrate the proposed system, two-operator coexistence in a shared small-cell cloud-RoF access network is implemented in an in-building testbed by using off-the-shelf optoelectronic components and commercialized WiMAX base stations and clients. In addition, the feasibility of delivering both conventional wireless services and future-proof high-RF-band services (millimeter-wave band) is also demonstrated in the proposed multi-service small-cell cloud-RoF access systems.

Orthogonal space-time block coding (STBC) is an open-loop transmit diversity scheme that decouples the multiple-input multiple-output (MIMO) channel, thereby reducing the space-time decoding into a scalar detection process. This characteristic of STBC makes it a powerful tool, achieving full diversity over MIMO fading channels, and requiring little computational cost for both the encoding and decoding processes. In this paper, we exploit the single-input single-output equivalency of STBC in order to analyze its performance over nonselective Nakagami fading channels in the presence of spatial fading correlation. More specifically, we derive exact closed-form expressions for the outage probability and ergodic capacity of STBC, when the latter is employed over spatially correlated MIMO Nakagami fading channels. Moreover, we derive the exact symbol error probability of coherent M-PSK and M-QAM, when these modulation schemes are used along with STBC over such fading channels. The derived formulae are then used to assess the robustness of STBC to spatial correlation by considering general MIMO correlation models and analyzing their effects on the outage probability, ergodic capacity, and symbol error probability achieved by STBC.

Software architecture plays an important role in determining software quality characteristics, such as maintainability, reliability, reusability, and performance. Performance effects of architectural decisions can be evaluated at an early stage by constructing and analyzing quantitative performance models, which capture the interactions between the main components of the system as well as the performance attributes of the components themselves. The paper proposes a systematic approach to building Layered Queueing Network (LQN) performance models from a UML description of the high-level architecture of a system, and more exactly from the architectural patterns used for the system. The performance model structure retains a clear relationship with the system architecture, which simplifies the task of converting performance analysis results into conclusions and recommendations related to the software architecture. In the second part of the paper, the proposed approach is applied to a telecommunication product for which a LQN model is built and analyzed. The analysis shows how the performance bottleneck is moving from component to component (hardware or software) under different loads and configurations, and exposes some weaknesses in the original software architecture, which prevent the system from using the available processing power at full capacity due to excessive serialization.

Small-cell systems based on cloud radio access network (cloud-RAN) architecture have been proposed as promising solutions to meet the ever-increasing capacity demand of the next-generation wireless access networks. By centralizing the processing power to reduce the complexity of conventional cell sites, the cloud-RAN architecture is ideal for large-scale small-cell system at reduced capital and operational expenses. However, high-speed, flexible, and scalable backhaul links between the centralized baseband processing unit (BBU) and the remote antenna units (RAUs) are required to support the high throughput of the small-cell cloud-RANs, and the conventional approaches are based on digital baseband signal transmission in the backhaul links. In this paper, we propose a novel multi-service small-cell wireless access architecture based on radio-over-fiber (RoF) technologies. By utilizing analog radio frequency (RF) signal transmission in the optical backhaul links, the design of RAUs can...

Recent advances in digital imaging technology combined with the next generation digital wireless communication has great potential to transform the paradigm for how humans will communicate visual information with one another in the next century. The first major change is that the model of one message from a single source to many clients (mass broadcasting) will be replaced by a model of many messages from multiple sources to many receivers (peer to peer). A second major change is that the model will move from a passive client, which only receives messages to an interactive client able to respond and even direct the information content to itself. This will have great impact in the experience of visual communication in the next decade. In this paper, we shall outline some of the key technological challenges in terms of bandwidth, processing power, data rate, data sizes and human factors required to influence this paradigm shift resulting from the merger of digital imaging and digital ...

Cellular positioning has been a very active research area for the last decade. Large improvement in accuracy has been made to support, for example, e-call and other location-based services. Traditionally, cellular positioning has been limited to cellular operators equipped with expensive synchronization hardware in order to achieve good accuracy. Lately, third parties have employed fingerprinting methods to enable positioning systems independent from the cellular operators. With improved available processing power, denser cellular networks, cheaper data collection and efficient pattern matching algorithms, the fingerprinting positioning methods have also gained popularity. In this paper, we analyzed the potential of using System Frame Number (SFN)- SFN observed time differences, which are traditionally used in Time Difference of Arrival (TDOA) positioning, for fingerprinting-based positioning. A field test was performed using measurements from TEMS (Telecommunication Management Syst...

With the emergence of utility computing and the continuous search for reducing the cost of running Information Technology (IT) infrastructures, we will soon experience an important change on the way these infrastructures are assembled, configured and managed. In this paper we consider the problem of managing a hybrid high-performance computing infrastructure whose processing elements comprise in-house dedicated machines, a utility computing service provider, and idle machines from a best-effort peer-to-peer grid. This infrastructure supports the execution of both best-effort and real-time applications. Realtime applications use primarily computing power from the inhouse machines and any processing power that can be attained from the best-effort grid. Extra capacity required to meet deadlines is purchased from the utility computing service provider. This extra capacity is reserved for future use through short term contracts which are negotiated with no human intervention. We take a business-driven approach for the management of this hybrid infrastructure and propose heuristics that can be used by a contract planner agent to reduce the cost of running the applications at the same time that guarantees that deadlines are met. In particular, we show that constructing an estimation for the behavior of the grid is essential for making contracts that lead to high efficiency in the use of the hybrid infrastructure.

A smart space is typically composed of heterogeneous networks of communicating and collaborating nodes with varying capacities of resources such as processing power, memory and energy. Recent developments in wireless communication technology and miniaturization of Consumer Electronics (CE) hardware have made Low Capacity Networks (LCN) such as Wireless Sensor and Actuator Networks (WSAN) an important element of smart spaces. However, resource and service management in LCNs that interoperate with resource-rich nodes of a smart space is still a challenge. We propose and implement an architecture for lightweight resource and service management in LCNs. Furthermore, we present a validation of the proposed architecture through performance analysis in comparison to an existing interoperability architecture. 1 .

Growth and usage trends for large decision support databases indicate that there is a need for architectures that scale the processing power as the dataset grows. To meet this need, several researchers have recently proposed Active Disk architectures which integrate substantial processing power and memory into disk units. In this paper, we evaluate Active Disks for decision support databases. First, we compare the performance of Active Disks with that of existing scalable server architectures: SMP-based conventional disk farms and commodity clusters of PCs. Second, we evaluate the impact of several design choices on the performance of Active Disks. We focus on the performance impact of interconnect bandwidth, amount of disk memory and disk-to-disk communication architecture on decision support workloads. Our results show that for identical disks, number of processors and I/O interconnect, Active Disks provide better price/performance than both SMPbased conventional disk farms and commodity clusters. Experiments evaluating the impact of design alternatives in Active Disk architectures indicate that: (1) for configurations up to 64 disks, a dual fibre channel arbitrated loop interconnect is sufficient even for the most communicationintensive decision support tasks; (2) most decision support tasks do not require a large amount of memory; and (3) direct disk-to-disk communication is necessary for achieving good performance on tasks that repartition all (or a large fraction of) their dataset.