Skip to main content Accessibility help
×
  1. Home
  2. Browse subjects
  3. Computer Science
  4. Distributed, Networked and Mobile Computing
  5. Content listing

Refine search

Refine search

Access:
Content type:
Publication date:
Apply   From and To filters
Subject: Show more
Journals Show more
Publishers: Show more
Societies Show more
Series: Show more
Collections: Show more

Actions for selected content:

Select all | Deselect all
  • View selected items
  • Export citations
  • Download PDF (zip)
  • Save to Kindle
  • Save to Dropbox
  • Save to Google Drive

Save Search

You can save your searches here and later view and run them again in "My saved searches".

Please provide a title, maximum of 40 characters.
Cancel
×

1983 results in Distributed, Networked and Mobile Computing

Page 24 of 100

  • 6 - Power Control in Cellular Wireless Networks

  • from Part III - Physical Layer Resource Allocation in Wireless Networks
  • Ekram Hossain, University of Manitoba, Canada, Mehdi Rasti, Long Bao Le, Université du Québec, Montréal
  • Book:
    Radio Resource Management in Wireless Networks
    Published online:
    11 May 2017
    Print publication:
    27 April 2017, pp 207-230

  • Summary

    For a wireless network, the transmit power is one of the main radio resources. Two major objectives of power control in a wireless network are to extend UEs’ battery life and to maintain an acceptable QoS (e.g., in terms of the SINR or throughput) for all UEs by minimizing interferences to UEs. Data services require a higher SINR (as a measure of QoS) as compared to the voice service, because the latter is more tolerant to bit errors. In contrast to the voice service for which the QoS is measured by a step function of the SINR [1], the commonly used QoS measure for the data service is, in general, an increasing function of the SINR.

    A distributed scheme for power control is preferred to a centralized one, because in the former, the transmit power level of a user is decided by that user by utilizing the locally available information and uses minimal feedback from the BS. In this way, the need for frequent power setting commands by the BS are avoided, and the processing capabilities at the BS needed to obtain the instantaneous uplink power levels of all UEs are substantially reduced. In contrast, a centralized approach needs to have information about path-gains and throughput requirements for all UEs at the BS.

    In this chapter, we first discuss why power control is needed and state the objectives of power control, followed by a discussion on conventional open/closed loop and centralized power control algorithms. Then various existing distributed power control algorithms are presented and evaluated according to different criteria.

    Objectives of Power Control

    In Chapter 5, we studied the relation between transmit power and SINR vectors. We know that the achieved SINRs by UEs at uplink or downlink determine their experienced QoS. Now the question is how the predetermined target QoS for users can be achieved. The transmit power cannot be set at random or at a fixed level by the UEs. For example, if the UEs served by the same cell transmit at the same fixed power level, the SINR for the UEs with good path-gains (e.g., those near the BS) are high, whereas for the far UEs it will be low. This is called the near-far problem, which can be addressed if the transmit power is dynamically controlled.

  • 2 - Wireless Networks and Resource Allocation

  • from Part I - Basics of Wireless Networks
  • Ekram Hossain, University of Manitoba, Canada, Mehdi Rasti, Long Bao Le, Université du Québec, Montréal
  • Book:
    Radio Resource Management in Wireless Networks
    Published online:
    11 May 2017
    Print publication:
    27 April 2017, pp 49-114

  • Summary

    Protocol Layers for Data Communication

    Data communication between two processes (or applications) can be implemented by performing several tasks (i.e., modules) in a hierarchical manner. These modules, when arranged in a vertical stack, form a layered protocol stack. Each layer performs a subset of functions (related to transmission and/or reception) required for communication between the two processes. Such a layer depends on more primitive functions performed by its lower layer, and it also provides services to the upper layers. During the communication process between two processes, the peer layers in the corresponding devices communicate by using a defined set of rules or conventions. This set of rules or conventions is referred to as a protocol at the corresponding layer.

    The open system interconnection (OSI) model proposed by the International Organization for Standardization (ISO) [2] defines a generic protocol stack for a data communication network. The OSI model consists of the following seven layers depicted in Figure 2.1: physical, data link, network, transport, session, presentation, and application layers. The lower layers are closer to hardware-based physical data transmission procedures, while the higher layers mostly perform software-based operations. Each layer communicates with its own counterpart; for example, the network layer in the transmitter communicates with the network layer in the receiver. This independently layered structure enables very versatile and reliable networks such as the Internet. In this section, we briefly discuss each of the layers in the OSI protocol stack.

    Physical Layer

    The physical layer is concerned with the transmission of individual bits over the transmission medium. That is, it is responsible for the modulation and demodulation of the signals at the transmitter and receiver, respectively. The modulation and demodulation techniques depend on the physical medium (e.g., whether it is a “wireline” or a “wireless” medium). For wireless communications, modulation techniques such as PSK, PAM, and QAM and their variants can be used (which were briefly discussed in Chapter 1). For communications over fiber optic cables, typical transmitters are laser diodes that can be modulated to switch between ON and OFF states, which correspond to transmission of 1 and 0, respectively.

  • 1 - Introduction

  • from Part I - Basics of Wireless Networks
  • Ekram Hossain, University of Manitoba, Canada, Mehdi Rasti, Long Bao Le, Université du Québec, Montréal
  • Book:
    Radio Resource Management in Wireless Networks
    Published online:
    11 May 2017
    Print publication:
    27 April 2017, pp 3-48

  • Summary

    Basics of a Wireless Communication System

    Wireless connectivity is one of the most prominent features of modern communications. A basic wireless communication system consists of three main components: transmitter, wireless medium, and receiver. The transmitter transforms the information into physical signals and transmits it over a transmission medium. The wireless medium, which is also called the communication channel, carries the signal, e.g., the free space carries the electromagnetic waves. The receiver receives physical signals from the medium and converts them into information. Usually, the medium corrupts and distorts the transmitted signal. The aim of any communication system is to obtain the transmitted information at the receiver with the lowest possible error rate. Figure 1.1 depicts the block diagram of a digital communication system. For successful multiuser communication, specific network structures and protocols need to be employed.

    Electromagnetic Spectrum and Frequency Range

    To transmit information over free space, electromagnetic waves are used. The properties of electromagnetic waves vary with frequency, and each frequency band is suitable for certain applications. The natural electromagnetic spectrum consists of a wide range of frequencies, starting from a few Hz up to 1022 Hz. Figure 1.2 lists the frequency bands in the electromagnetic spectrum along with the corresponding applications.

    Wireless communication is usually possible in a specific frequency range called the radio frequency (RF) band. The RF band consists of frequencies as low as 30 MHz up to 30 GHz. One advantage of RF band is, for most of the part of this band, relatively small antennas can be used to receive and transmit electromagnetic signals. When impinging on the earth's atmosphere, the RF signals penetrate the ionosphere and the earth's curvature does not hinder the transmission. The low-frequency RF signals, i.e., shortwave signals, are reflected by the ionosphere and thus can be used to broadcast signals.

    While military use of the RF spectrum may vary in different countries, the International Telecommunications Union (ITU) allocates and standardizes the commercial spectrum worldwide. The commercial spectrum bands can be divided into licensed and unlicensed bands.

  • 12 - Channel Allocation for Infrastructure-Based 802.11 WLANs

  • from Part IV - Link Layer Resource Allocation in Wireless Networks
  • Ekram Hossain, University of Manitoba, Canada, Mehdi Rasti, Long Bao Le, Université du Québec, Montréal
  • Book:
    Radio Resource Management in Wireless Networks
    Published online:
    11 May 2017
    Print publication:
    27 April 2017, pp 352-376

  • Summary

    Introduction

    Due primarily to its unlicensed frequency band of operation and low-cost equipment, the IEEE 802.11-based wireless access technology, also known as WiFi, has been widely deployed in local area networks (LANs). A typical deployment of this technology is shown in Figure 12.1. Based on how they are managed, wireless LANs (WLANs) can be categorized into one of the following: (1) Centrally managed or (2) Uncoordinated [2]. Centrally managed deployments are usually seen in places such as university campuses, offices, or airports where all access points (APs) and associated clients are managed by a central entity. On the other hand, uncoordinated WLANs operate in the absence of a central control and are typical in places such as residential neighborhoods or private hotspots managed by different service providers (e.g., restaurants, coffee shops, etc.).

    Successful deployment in either case requires efficient mechanisms for addressing performance issues such as excessive interference, which usually translates into low throughputs. In the literature, several techniques have been proposed to address such performance issues. In particular, association control (or load balancing), in which a central entity associates (respectively, disassociates) clients with (respectively, from) APs in order to balance traffic in a network, is usually proposed for the centrally managed deployments [3]. Proposed for the uncoordinated deployments, on the other hand, are such techniques as power control [4] and careful carrier-sensing [5], in which transmission power is dynamically tuned and unnecessary carrier sensing is avoided, respectively. One other technique that is extensively considered and applicable to both centrally managed and uncoordinated environments is channel assignment, in which a frequency channel is assigned to each AP for use for a certain duration of time. In this chapter, we present a survey of such channel assignment techniques. We identify and discuss several major approaches applicable to the different deployment scenarios. Subsequently, a qualitative comparison is made among these approaches. Some comments on current practice in channel assignment are also presented. Finally, several important future research directions are outlined.

  • Preface

  • Ekram Hossain, University of Manitoba, Canada, Mehdi Rasti, Long Bao Le, Université du Québec, Montréal
  • Book:
    Radio Resource Management in Wireless Networks
    Published online:
    11 May 2017
    Print publication:
    27 April 2017, pp xiii-xvi

  • Summary

    Wireless communications and networking technology are advancing at a very rapid pace. Newer technologies and standards are evolving to serve the ever-increasing number of users demanding different types of mobile applications and services. Research and development activities on wireless technology constitute one of the most important segments of research and development in the telecommunications area today. Radio resources such as the radio spectrum and transmission power are the fundamental ingredients for any wireless system. Radio resource management is a fundamental problem in wireless networks. Efficient allocation and management of radio resources to serve the mobile users with different requirements is essential for practical deployment and operation of wireless communications systems and networks.

    Radio resource allocation is a very broad topic that cannot be fully covered in a single book. This book with the title Radio Resource Management in Wireless Networks: An Engineering Approach particularly focuses on resource management issues related to power control, interference management, joint power control and cell association, channel assignment, and multiple access control in traditional as well as emerging wireless networks such as multi-tier cellular, relay-based cellular, and cognitive radio networks (CRNs). This book intends to provide background knowledge on resource allocation in wireless networks from a system-centric or engineering point of view, review the existing related literature, discuss the research challenges, present different techniques to model and analyze the resource allocation problems, and develop both centralized or distributed resource allocation algorithms. This book includes the classical as well as recently developed models and analyses for allocation of different resources (e.g., spectrum and transmission power) in cellular wireless networks. It will be useful for graduate students (M.Sc. and junior Ph.D. students) to understand different resource allocation problems and algorithms in different types of wireless networks (i.e., both infrastructure-based and infrastructure-less wireless networks). It can be used as a textbook for a graduate course on “Wireless Networks” as well as a reference book for researchers and engineers working in the area of wireless communications and networks.

  • Appendix I - Hot Research Topics

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 384-387

  • Summary

    A lot of research is happening in and around the field of cloud computing in order to achieve more efficient solutions to different issues and to gain optimal results from them. This section introduces a few, among many, hot research topics related to the wide domain of cloud computing.

    OPTIMAL MANAGEMENT OF CLOUD RESOURCE

    Resource management in cloud computing is the prime responsibility of the IaaS cloud service providers who build and manage the data centers. IaaS cloud provider has two major resource management objectives. First, to make the environment reliable as well as robust for optimal and efficient utilization of the data center infrastructure. The second is related to the SLA, which defines the relation with the consumer party.

    The first objective deals with issues like load balancing, fault tolerance, energy conservation etc. Here, the load should be distributed in a way that in a data center, the utilization rate remains in balance among resources of a similar type. To make a system fault tolerant, the allocation of the resources should happen in a way that the effect of the failure of some resource component remains insignificant. Energy conservation is another important issue while managing resources at a data center. Optimal energy use reduces computing cost and it should also be minimized to reduce the carbon footprint.

    A cloud provider may opt for a number of approaches to handle these issues. It can optimize these parameters by taking a combined approach, or it can work on every metric individually. The cloud provider may use some consistent set of combinations and/or may also decide to employ varied performance goals for individual operational situations. For instance, energy minimization may be a higher priority during low-load conditions, while the service performance may be the higher priority during high load. A balance should be maintained among all these choices without affecting the user expectations. Finding out an optimal balancing point between performance and energy conservation is a critical concern of the research in such cases.

    For resource management objectives related to the Service Level Agreements (SLA), the cloud providers generally adopt an approach called service differentiation. In this approach, different levels of service performances are delivered to different consumers depending on the service level agreements made with them.

  • 1 - Introduction

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 1-18

  • Summary

    The catchword Cloud Computing may sound new to the arena of computing as well as information technology; although the concept behind it is not completely new. In a broad sense, it is a step (forward) to access the web-based services through Internet; or in general terms, cloud computing represents an advance in the field of computing technology where management of computing services is outsourced to greater extents and in multiple dimensions. To be specific, computing facilities are being made available as services offered by reputed vendors.

    Computing technology has been evolved over the years. There have been steady developments in the field of computing hardware, software architecture, web technology and network communications over the last decade. The speed of internetworks has increased day by day and it has also become cheaper. All these developments contributed in settinging the stage for the initiation of the revolutionary concept of ‘cloud computing’.

    Cloud computing has changed the way computation happens. It provides the means for smarter ways to do business and accordingly it makes life simpler. This chapter tries to highlight the shortcomings in the traditional computing approaches and it attempts to iterate how the stage was ready for the arrival of this new model of computing.

    Cloud computing has evolved over the years and has changed the way people live and do business over the World Wide Web.

    WHAT IS THE BUZZ ABOUT

    Cloud computing provides the means for users to easily avail computing facilities whenever and wherever required. They need not worry about setting up infrastructure, purchasing new equipment or investing in the procurement of licensed software. Rather they can access any volume, large or small, of computing facilities in exchange for some nominal payment. It is a new model of computing which has become possible through integration of advanced computing models, sophisticated web technologies and modern network communication technologies (especially high-speed Internet).

    Cloud computing became a hot topic for large computing vendors (companies like Amazon, Google, Microsoft etc.) only from mid-2008, but the concept itself is quite old. People have different perceptions regarding this new computing model. To some, it is a new and radical innovation.

  • 5 - Cloud Computing Services

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 76-94

  • Summary

    As discussed in the previous chapter, the NIST model of cloud computing treats the computing methodology from two perspectives as deployment and as service. While cloud can be deployed in four possible ways, the services it offers can be categorized primarily into three different types.

    Apart from three primary cloud services, computing vendors deliver a number of specialized cloud services which are considered as special services under these three primary cloud services. In order to understand how cloud computing can be of value to consumers, it is important to understand the services it offers. This chapter focusses on all of these service delivery models.

    There are many vendors who provide different cloud services in the market today. Along with proprietary public cloud services, many open-source initiatives are also available which mainly focus on to create private as well as hybrid cloud environments. Few among those open-source initiatives have also been discussed in this chapter.

    SERVICE DELIVERY MODELS

    Three categories of computing services that people consume from the days of traditional computing have been already mentioned in the first chapter. They are:

  • ▪ Infrastructure Service

  • ▪ Platform Service

  • ▪ Software Application Service

    • Cloud computing talks about delivering these facilities to consumers as computing services through network/internetwork. The benefit for the consumers is that they can avail these facilities over Internet anytime, as much as required, sitting at their own locations in a cost-effective manner. They only need to have a simple and suitable access device (like PC, laptop, tablet, mobile etc.) to access these services. Using these simple devices anyone can access any kind of computing infrastructure, platform or software application on payment-as-per-actual-usage basis.

    Cloud computing offers computing infrastructure, platform and application delivered ‘as-a-service’. Those services are considered as primary cloud computing services and are referred to as:

  • ▪ Infrastructure-as-a-Service (IaaS)

  • ▪ Platform-as-a-Service (PaaS)

  • ▪ Software-as-a-Service (SaaS)

    • These services are generally pronounced as ‘i-a-a-s’, ‘pass’, and ‘saas’ respectively. They are the driving forces behind the growth of cloud computing. Clubbed together these three service models are commonly referred as SPI (Service-Platform-Infrastructure) model. Cloud service providers arrange these services for the cloud consumers. The NIST reference architecture represents these services under ‘service orchestration’ component of the providers (Figure 5.1).

  • 17 - Privacy and Compliance Issues

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 293-306

  • Summary

    Security and privacy are often mentioned in the same breath, but they are not similar. It is a fact that both of them are important for trustworthiness of a system. However, when it comes to cloud computing, security tends to draw more attention and concern. But that does not mean that privacy can be compromised in anyway. Privacy maintenance in cloud is mainly the responsibility of service providers but consumers should also be conscious about their own privacy while drafting the service-level agreement (SLA).

    Regulatory compliance is another issue that has taken a complicated shape in the context of public cloud computing facility. It often becomes difficult to fulfill all legal compliance requirements in a cloud environment where data centers of a service provider are spread across the globe and more often consumers do not know where (in which country or region) their data are being stored. Cloud consumers must be aware about their responsibilities regarding the information privacy and regulatory compliance maintenance, apart from checking service provider's reputation and approach towards maintenance of these issues.

    Apart from these, this chapter discusses GRC (governance, risk and compliance) issue as another important concern of any business and how the issue becomes more prominent with adoption of cloud computing services for businesses. Regular auditing of these issues may help identify any violation. Standard audit frameworks exist, which when adopted for auditing cloud services can help build trust among the consumers.

    A common misconception is that data privacy is a subset of information security. But, security and privacy do not mean the same.

    WHAT IS PRIVACY?

    Both security and privacy are interrelated but it is a misconception that privacy is a part of information security. Rather, privacy brings its own set of concerns. Privacy of personal kind of information may be very sensitive and needs special attention.

    In line with the concerns about the security of a cloud system, consumers need to be careful about the privacy of their data before they use services or enter into a contract with any cloud vendor. Who owns the data? Who has access to it? How many copies are being maintained? Will the data be erased in the event the customer changes the service provider?

  • 20 - Popular Cloud Services

  • Sandeep Bhowmik
  • Book:
    Cloud Computing
    Published online:
    31 August 2020
    Print publication:
    17 April 2017, pp 351-374

  • Summary

    Computing as a utility service has been a long desired dream in the field of computing. Although the basic idea about cloud computing was introduced many years back, it could not become a reality due to several technological constraints. Later on, technologists succeeded in overcome these technical constraints one after another, and with time computing technology started advancing at a steady pace. The economical and other advantages of cloud computing were visible to everyone including business houses and once all of the required technologies were in place, the computing vendors jumped into the development of cloud services.

    In last ten years, many companies have been successful in offering cloud services in different types, sizes and shapes. List of such companies include the major technology vendors like Microsoft, Amazon and Google whose cloud services have gained a major share in the market. These providers along with many other large and middle size vendors and research institutes have developed and offered a number of service plans suitable for both individual consumers and businesses.

    Cloud computing is the future of computing in forthcoming years. Cloud services are rapidly gaining more and more appreciation globally and the expansion of cloud service industry is evident. It provides swift availability of enterprise-quality resource and high-performance computing services that can significantly improve business productivity. This chapter focuses on some very popular public cloud services presented by computing majors who also have contributed immensely in the development of IaaS, PaaS and SaaS.

    AMAZON WEB SERVICES

    Amazon.com, Inc. is an American electronic-commerce company with headquarters in Washington, United States. The company started as an online bookstore but later expanded its business in different domains. Amazon has emerged as a front-runner among the providers of public cloud services. Among the business domain of different cloud services, Amazon is considered as a market leader in Infrastructure-as-a-Service. The suite of cloud computing services offered by Amazon is known as Amazon web services (AWS).

    Amazon Web Services is currently the leading IaaS offering in the market. AWS is offered through the web and has been built strictly based on SOA standards following SOAP, HTTP, REST protocols. It also uses open-source operating system and application servers.

Page 24 of 100