5 Things to Consider When Choosing a Cloud Drive

A client of mine recently purchased a Samsung tablet and wanted to view files from two devices, the tablet and a Windows 8 laptop. In this case, accessibility to files from multiple devices when traveling was the highest priority requirement, but it got me thinking. There are many different cloud drive services to choose from, each with varying features. Add to that that any one person will have differing requirements and you get a bit of a recipe for complications. Want to set up a cloud drive that'll work the way you want it to? Here's a list of considerations to help you make the right choices. 

Security and Privacy

Keeping your data secure is important and each cloud offering has built-in security. With storage of any information, the key question to ask yourself is how sensitive the data is and what the impact would be (to your business or your family) if that data were compromised. For example, if someone gains unauthorized access to personal information, that's likely to pose a greater risk for you than if your stored music files are hacked.

Once you’ve answered that question, look at what features your shortlisted cloud drive suppliers offer:
  • Each will have some method of authentication, so follow best practice rules for passwords by choosing something that is not in a dictionary, keeping it to yourself only and changing it often.
  • Some cloud providers enable you to store your authentication details in a settings file for easier usage. If this is the case, consider adding additional security measures for your device (such as a screen-lock password) so that if someone else picked it up, they would not have immediate access to your cloud stored data.
  • Is the data transferred to and from your device using secure protocols such as https? If not, someone else may be able to "see" your information in transit.
  • Are the files stored in an encrypted form on the cloud drive? This makes it harder to get at your data in the event that someone gains unauthorized access to the cloud supplier’s infrastructure. There are also additional tools available that enable you to encrypt files before storing them in the cloud, such as BoxCryptor for Google Drive.

Accessibility

How do you want to access the data in your cloud drive and where do you want to access it from? There are two ways you could use the cloud storage from your device:

  • Use the cloud storage as a backup copy only and either manually copy or update the file in the cloud, or use desktop tools (if provided by the cloud drive supplier) to synchronize file changes you make on your device with those on the cloud.
  • Only work with the file in its cloud location, and avoid copying it to your local machine. This is useful to expand the storage available on your device. Check that you have the necessary tools on the device to support how you wish to view or work with them.
With new devices appearing all the time, you should also check that the specific ones that you are using are supported by the cloud drive supplier. In the case of my recent client, Sky Drive was already integrated with Office 2013 on the Windows 8 laptop, while Google Drive and Dropbox were already available on the Samsung tablet. What we needed to do was to consider which would best to support how my client wished to interact with the files being stored.

Cost

Think about how much storage you need now and also in a few months’ time. How will your data grow? All of the cloud drive suppliers provide a specific amount of storage for free, but check the price plans should you need to go beyond this, so that you understand the possible costs. Otherwise, you might find yourself looking to change suppliers because the costs have risen unexpectedly.

It's good practice also to periodically review what files you have in the cloud and remove those you no longer need. Be disciplined in doing this. It will cost you less money and it will reduce your risk if any data breach occurs.

Availability

Recent outages to cloud suppliers have attracted headline news. It’s possible that there will be outages to any service. But remember that your access to the cloud is granted via other services; Internet service providers and wireless access points may also suffer failures. Ask yourself what the impact will be if you can't access your cloud drive when you need it.

If the answer is "No big deal, I can wait and try again later," then that’s one end of the scale. But if the answer is "I absolutely need it when I need it," you'll have to take some steps to mitigate the risk that you won't be able to gain access. Make sure your files are available locally so that if your cloud drive is not accessible, you can still get to them. (This is just one drawback of cloud storage. Read about more in The Dark Side of the Cloud.)

Add-Ons, Features and Other Doo-Dads

A number of cloud drive suppliers include productivity tools to support working with stored files. For example, Google Drive includes a very functional office suite, removing the need to have other software licensed and installed on your device. Sky Drive access is provided within Windows 8 and Office 2013 to make file synchronization easy to set up. It also integrates with online versions of Microsoft Office (Office 365). 

Cross-check any included add-on features with your Availability and Accessibility considerations. While these may be convenient, make sure they also suit how and when you want to work with your information.

Cloud Storage, Here I Come?

As with many things in life, one feature or aspect of cloud storage can catch our eye and become the greater part of your decision making. In choosing a cloud drive, include the above considerations in your deliberations to determine which is the most important for you. It will help you select a solution that works the way you want it to.

Techopedia explains Public Cloud Storage

Public cloud storage generally enables the sourcing of massive amounts of storage space on demand over the Internet, and is built over storage virtualization, which logically distributes large storage arrays into a multi-tenant architecture shared among various users and applications. Public cloud storage capacity is made possible through two different sourcing models:

  • Web services APIs
  • Thin client applications

 Public cloud storage enabled through APIs is designed to be used for Web applications that require access to scalable storage at run time, whereas thin client applications provide end users with a way to back up and store their local data on remote cloud storage. Amazon S3, Mezeo and Windows Azure are popular examples of public cloud storage.

Definition - What does Public Cloud Storage mean?

Public cloud storage is a cloud storage model that enables individuals and organizations alike to store, edit and manage data. This type of storage exists on a remote cloud server and is accessible over the Internet under a subscription-based utility billing method where the users pay only for the storage capacity being used.

Public cloud storage is provided by a storage service provider that hosts, manages and sources the storage infrastructure publicly to many different users.

Public cloud storage service is also known as storage as a service, utility storage and online storage.

Techopedia explains Managed Cloud Hosting

Managed cloud hosting includes the safety and dependability of private cloud hosting but is as cost effective as a public cloud.
Advantages of managed cloud hosting are as follows:
  • Consistent availability: Designed on a high availability and private-cloud structure, it uses effective redundancy via its various servers, storage area network (SAN) and storage protection for reliable failover protection.
  • Automated resource balancing and failover: If a host stops working, cloud servers are at an advantages due to their consistently available infrastructure. Failover and resource balancing between hardware hosts is automatically managed at the virtualization level, and it has the capability to manage and update software and hardware.
  • Network security: Virtual local area networks (VLAN), protected firewalls and Intrusion Detection System (IDS)/Intrusion Prevention System (IPS) may be used in cloud servers to deliver a highly protected environment.
  • Creates a hybrid of virtual and physical servers: Applications and database engines can share a dedicated network with cloud servers, resulting in the creation of virtual and physical servers on the same system.
  • Affordable: The costs of a managed cloud are as effective as most public clouds. The resources and also the services are billed per usage.

 Managed cloud computing offers organizations the same security and provisions of a dedicated private cloud with a better and more cost-effective package. Organizations that use managed cloud computing can focus on business operations, rather than addressing server glitches and downtime.

Definition - What does Managed Cloud Hosting mean?

Managed cloud hosting is a process in which organizations share and access resources, including databases, hardware and software tools, across a remote network via multiple servers in another location.
In managed cloud hosting, servers are purchased in slices or as a virtual server. However, before considering costs, the key focus of managed cloud hosting is on security and consistent availability. In contrast to servers that are acquired on an hourly basis, managed cloud hosting is delivered in the form of monthly (or longer) contracts for businesses, which run enterprise-critical apps over long periods.

Managed cloud hosting is also known as managed cloud computing.

Why Mobile Cloud Computing (MCC)?

Mobile devices face many resource challenges such as battery life, storage and bandwidth. Mobile Cloud Computing offers advantages to users by allowing them to utilize infrastructure, platforms and software by cloud providers at low cost and elastically in an on-demand fashion. Mobile cloud computing provides mobile users with data storage and processing services in the cloud, eliminating the need to have a powerful device configuration (e.g. CPU speed, memory capacity etc.), as all resource-intensive computing can be performed within the cloud.

MCC Architecture

CloudComputing
















Advantages of MCC
  • Mobile applications leverage remote processing, extending battery lifetime
  • MCC enables mobile users to store and access large data on the cloud. Mobile applications are no longer constrained by the storage capacity of the device.
  • Keeping data and applications in the cloud reduces the potential for loss of data in the event of a hardware failure, improving reliability and availability
  • MCC can be designed with a comprehensive data security model for both service providers and users by allowing protected copyrighted digital contents in the cloud. MCC providers have security services in place such as virus scanning, malicious code detection and authentication for mobile users
  • The data and services in the cloud are always available even when the users are moving from place to place
  • Sharing data in the Cloud provides the user with access to the latest documentation even while ‘on the go’
  • Mobile applications can be scaled to meet the growing user demands
  • Service providers can easily add and expand their service offerings
  • Multiple services from different providers can be integrated easily through the cloud to meet today’s complex user demands

Mobile Cloud Computing: Architectures, Algorithms and Applications

Features

  • Provides the first book on the field of MCC
  • Introduces sensor MCC, vehicular MCC, and femtocell-based MCC
  • Addresses security and privacy concerns, the business aspects of MCC models, and resource allocation and management schemes
  • Explores open research problems and future research directions to improve the strength of MCC and enrich mobile user experience
  • Offers code for various algorithms on the book’s CRC Press web page

Summary

Minimize Power Consumption and Enhance User Experience
Essential for high-speed fifth-generation mobile networks, mobile cloud computing (MCC) integrates the power of cloud data centers with the portability of mobile computing devices. Mobile Cloud Computing: Architectures, Algorithms and Applications covers the latest technological and architectural advances in MCC. It also shows how MCC is used in health monitoring, gaming, learning, and commerce.
The book examines computation within a mobile device; the evolution, architecture, and applications of cloud computing; the integration of mobile computing and cloud computing; offloading strategies that address constraints such as poor battery life; and green technologies to optimize mobile power consumption. It also presents various resource allocation schemes of MCC, the architecture and applications of sensor MCC, the new concept of mobile social cloud, security and privacy issues in MCC, and different types of trust in MCC.
In addition, the book explains how to integrate MCC with vehicular networks, compares economic models, and explores the application of MCC to mobile learning, vehicle monitoring, digital forensic analysis, health monitoring, and other areas. The book concludes with a discussion of possible solutions to challenges such as energy efficiency, latency minimization, efficient resource management, billing, and security.

Mobile Cloud Applications

A mobile cloud application is a software program that is designed to be accessed over the Internet by many types of portable computing devices.
Mobile cloud apps and mobile Web apps are similar. They both run on servers external to the mobile device, they both store data externally and they are both accessed over the Internet with a browser. However, it is often said that while all cloud apps are Web apps -- not all Web apps are cloud apps. Simply put, not all mobile Web apps can run in a virtual environmentwithout being re-engineered. This is because a Web app may have originally been written to run and store data on a dedicated physical server in a data center. A cloud app, on the other hand, will always be written to live on virtual servers in a distributed, multi-tenant architecture and store data in the cloud.

Native Cloud Application (NCA)

A native cloud application (NCA) could be a program that's designed specifically for a cloud computing design.

NCAs ar designed to require advantage of cloud computing frameworks, that ar composed of loosely-coupled cloud services. which means that developers should break down tasks into separate services which will run on many servers in several locations. as a result of the infrastructure that supports a native cloud app doesn't run regionally, NCAs should be planned with redundancy in mind that the application will stand up to breakdown and be ready to re-map scientific discipline addresses mechanically ought to hardware fail.

The design paradigm is efficient, however, as a result of services and resources for computation and storage are often scaled out horizontally PRN, that negates the necessity for overprovisioning hardware and having to set up for load equalisation. Virtual servers will quickly be value-added for testing and, in theory, AN NCA are often dropped at market on identical day it's created.

In general, a native app is AN computer programme that has been developed to be used on a selected platform or device.

Cloud Collaboration

Cloud collaboration is a type of enterprise collaboration that allows employees to work together on documents and other data types, which are stored off-premises and outside of the company firewall. Employees use a cloud-based collaboration platform to share, edit and work together on projects. Cloud collaboration enables two or more people to work on a project at once.

A cloud collaboration project begins when one user creates the file or document and then gives access to certain individuals; for example, the project creator may share a link to the project that allows others to view and edit it. Users can make changes to the document at any time, including when employees are viewing and working simultaneously. All changes are saved and synced so every user sees the same version of the project.
Cloud collaboration has become more sophisticated as vendors try to attract customers. It is common for a collaboration tool to include a way for project participants to see who else is viewing the document and to communicate with each other while working, such as through comments or a chat function. Tools also often allow users to set up email alerts for when a file is changed. These and other functions help increase worker efficiency and productivity.
Employee's motivations for using cloud collaboration tools vary, but the impetus is often that workers find the cloud tool to be better in some way than an old tool. Employees may think the cloud collaboration tool is faster, looks nicer, is easier to use and more.
Desire for a better collaboration tool can lead employees to choose and use a tool without prior approval of IT, a practice known as shadow IT. IT departments should be on the lookout for this, but they should also be open to the positive impact a cloud collaboration tool can have on group communication and teamwork.

Common Cloud

The lines between local computing and cloud computing sometimes get very, very blurry. That's because the cloud is part of almost everything on our computers these days. You can easily have a local piece of software (for instance, Microsoft Office 365) that utilizes a form of cloud computing for storage (Microsoft One Drive).
That said, Microsoft also offers a set of Web apps, now called Office Online, that are online-only versions of Word, Excel, PowerPoint, and One Note accessed via your Web browser without installing anything. That makes them a version of cloud computing (Web-based=cloud).
Some other major examples of cloud computing you're probably using:
Asus ChromebitGoogle Drive: This is a pure cloud computing service, with all the storage found online so it can work with the cloud apps: Google Docs, Google Sheets, and Google Slides. Drive is also available on more than just desktop computers; you can use it on tablets like the iPad$349.00 at Amazon or on smartphones, and there are separate apps for Docs and Sheets, as well. In fact, most of Google's services could be considered cloud computing: Gmail, Google Calendar, Google Maps, and so on.
Apple iCloud: Apple's cloud service is primarily used for online storage, backup, and synchronization of your mail, contacts, calendar, and more. All the data you need is available to you on your iOS, Mac OS, or Windows device (Windows users have to install the iCloud control panel). Naturally, Apple won't be outdone by rivals: it offers cloud-based versions of its word processor (Pages), spreadsheet (Numbers), and presentations (Keynote) for use by any iCloud subscriber. iCloud is also the place iPhone users go to utilze the Find My iPhone feature that's all important when the phone goes missing.
Amazon Cloud Drive: Storage at the big retailer is mainly for music, preferably MP3s that you purchase from Amazon, and images—if you have Amazon Prime, you get unlimited image storage. The Cloud Drive also holds anything you buy for the Kindle. It's essentially storage for anything digital you'd buy from Amazon, baked into all its products and services.
Hybrid services like Box, Dropbox, and Sugar Sync all say they work in the cloud because they store a synced version of your files online, but most also sync those files with local storage. Synchronization to allow all your devices to access the same data is a cornerstone of the cloud computing experience, even if you do access the file locally.
Likewise, it's considered cloud computing if you have a community of people with separate devices that need the same data synched, be it for work collaboration projects or just to keep the family in sync. For more, check out the The Best Cloud Storage Services for 2015.
Cloud HardwareRight now, the primary example of a device that is completely cloud-centric is the Chromebook. These are laptops that have just enough local storage and power to run the Chrome OS, which is essentially turning theGoogle Chrome Web browser into an operating system. With a Chromebook, most everything you do is online: apps, media, and storage are all in the cloud. Coming soon are Chrome Bits, smaller-than-a-candy-bar drives (pictured) that turn any display with an HDMI port into a usable computer running Chrome OS.
Of course, you may be wondering what happens if you're somewhere without a connection and you need to access your data. This is currently one of the biggest complaints about Chrome OS, although its offline functionality is expanding.
The Chromebook isn't the first product to try this approach. So-called "dumb-terminals" that lack local storage and connect to a local server or mainframe go back decades. The first Internet-only product attempts included the old NIC (New Internet Computer), the Netpliance iOpener, and the disastrous 3Com Audrey. You could argue they all debuted well before their time—dial-up speeds of the 1990s had training wheels compared to the accelerated broadband Internet connections of today. That's why many would argue that cloud computing works at all: the connection to the Internet is as fast as the connection to the hard drive. Or is it?

Personal data storage on mobile cloud

One of the key concerns for people about using a mobile cloud is that their personal data on mobile device could be stored on, or accessed by the cloud. A mobile device contains contact lists, text messages, personal photos and videos, calendars, location information, and these data can reveal many things about someone’s personal life. However, a personal computer also stores many such personal data such as photos and other multimedia, chat logs, emails, passwords, financial records or access to such records, calendar and contact lists. Today, thousands of monetary transactions are being done in online shopping sites such as eBay, and Amazon. Therefore, the risks involved in mobile cloud are not necessarily greater than those involved in traditional clouds. However, the issue here is whether the means of handling those risks have been properly implemented in the mobile cloud. Despite reservations, people do tend to use their mobile devices with the cloud. Some recent examples of mobile cloud storage are Apple’s iCloud, Google Drive and Dropbox. Apple iCloud enables users of iOS devices to synchronize their application data such as photos, iTunes music, calendars, email, and messages. An initial 5 GB of iCloud storage is free for an Apple user, with additional storage available for a monthly fee. Although iCloud offers an Apple user an impressive user friendly feature suite (such as Find my Phone), it is only for data related to Apple devices. In contrast, Dropbox is less specialized, but works across heterogeneous platforms including Microsoft Windows, Linux, Mac OS, iOS, Android, and Blackberry. Dropbox also allows sharing stored data with friends, and file revisions.

Data management

For many cloud users and providers, managing data on the cloud raises many complications. In mobile cloud computing, as the name itself suggests, data that would traditionally be only accessible only to the mobile device’s owner, would now be stored on, accessible to, shared with external devices or users. For many mobile users, this raises privacy and security questions. Also, data representation in mobile devices vary, and in a heterogeneous mobile cloud, this would lead to problems with portability and interoperability. Computations in a mobile cloud would be spread across a distributed file system, where multiple devices may need to access and modify files.

Furthermore, special considerations must be given to accessing files from mobiles over wireless networks. In a mobile cloud, users geographical locations are not fixed, and bandwidth must be conserved because of data access costs. However, it is also vital that mobile databases contain policies to safeguard against data loss while ensuring it conforms to mobility constraints. We discuss these issues in the following subsections. Issues regarding data privacy and security are not discussed here, since they have already been explained at length in Section 4.4: Privacy, Security and Trust.

Energy awareness

Because a mobile device operates on a finite supply of energy contained in its battery, energy is one of the key resources that needs to be used carefully [99]. In the context of mobile clouds, the cost of participation (such as power consumption) should be less than the benefit gained [100]. Also, it will enable the mobile device to take appropriate component level action to minimize unnecessary energy consumption, and hence, lengthen the system’s life span by unloading unneeded software components, redeploying energy intensive components to more resourceful hosts, and collocating frequently communicating hosts, as suggested in [101]. For these reasons, being aware of a device’s energy usage is vital.
In the following we discuss the research on energy consumption, mainly focusing on work on energy profiling and energy usage estimation.
Energy profiling. In PowerScope  [102] the authors present a profiling tool for mobile applications. The tool maps power usage to specific code components in applications and the operating system, allowing an analysis of power draining procedures. Using this analysis, the developers can modify their software to be more energy efficient. The authors report a 46% energy saving by using PowerScope to profile an adaptive video application run on the Odyssey platform [44]. Experiments were carried out with several laptops and pocket computers. Profiling is done offline after collecting data, to ensure no overheads are added to the analysis. A digital multimeter measures the electric current used by the profiling computer and the energy profile is generated using these correlated current measurements. The apps can only be profiled on an open source operating system however, as small modifications to the kernel are required.
In [103], Rice and Hay present a power consumption measurement framework, specifically for mobile phones. In particular, they explore the effect of message size and send buffer size when transmitting data on two Android 1.5-based phones. Power usage during connection to a WiFi network and idle power costs for WiFi, 3G and 2G are also discussed. Power consumption is measured by sampling the voltage drop across the phone battery and a high precision resistor. The mobile device first downloads the test script from a central server and uploads the results to the same server. The central server aligns the test results with the traces and logs. Their findings can be summarized as follows:
1.
When connecting to a WiFi network through DHCP, a significant portion of the time and therefore power, are taken by the ARP Probe packets and the delay between them.
2.
In the case of idle power, WiFi has the lowest energy cost, followed by 3G and 2G respectively. However, it should be noted that the locations of the base stations will also affect radio transmission.
3.
Although it would be logical to expect that the energy cost per byte will decrease as the message size increases, results show that this is not the case. There appears to be a sharp increase of power cost from sending a 7 kB message to 8 kB. However, the reason for this is not clear.
4.
The choice of buffer size can significantly affect the power consumption.
The work discussed previously measures the energy via hardware. A different approach is to take the measurements via software to query battery levels as done in PowerSpy [104], implemented in the Windows operating system. PowerSpy operated in two stages; event tracking and analysis. In the event tracking stage, the application is run and tracked for CPU time, I/O activity and energy consumption. In the analysis stage, the data acquired in the previous stage is processed. To filter out the energy consumed by I/O activities, an estimation of energy usage by various devices to run particular tasks (such as energy used by the disk to read 1 kB) as specified by the devices manufacturer, is used. This estimation is subtracted from the total of recorded energy use, and the remainder is taken as the energy taken up by CPU threads. Next, energy consumption is drilled down to individual threads, on the assumption that CPU power usage is proportional to the number of CPU cycles spent on a thread.
Work done by Cano et al. [105] and [106] provides insight into the energy consumption of the Bluetooth protocol. The focus of their work is on the different states of Bluetooth such as Startup, Standby, Inquiry, Connection and especially the low power modes provided by the protocol.
Energy usage estimation. Work done by Chiyoung et al.  [101] and Seo et al. [107]focused on the energy (electrical) consumption estimation of Java based pervasive systems at the level of its system level components. The initial estimation in [101] is done prior to runtime—during construction time. Then the estimation is refined during runtime automatically depending on certain system parameters such as size of data exchanged over the network, inputs to the components’ interfaces, and invocation frequency of components’ interfaces. The exact formulas for calculating the estimation are given in [107]. Their methodology gives an Energy Cost Framework as follows:
•
Overall Energy cost = Computational energy cost + Communicational energy.
•
System Energy cost = Overall Energy cost + Overall infrastructure energy cost
where infrastructure cost is the cost incurred by the operating system. The computational cost is determined by the level of its public interfaces and the computational cost of an jth invocation of an ith interface on a given JVM is modeled in terms of byte codes, native methods and monitor operations. Communication cost due to the jth invocation of component c1’s interface I1 on host H1 is calculated in terms of the size of the transmitted and received data and the energy consumption of transmission/receive cost of H1. The authors claim that based on their evaluations in which they ran distributed applications on Kaffe 1.15 JVM on Compaq iPAQ PDAs, their estimations are within 5% of the actual power consumption.

Risk assessment using context-awareness

In MobiCloud [37], context information is used to facilitate risk assessment and routing decisions. MobiCloud introduces Virtual Trusted and Provisioning Domains (VTaPDs), which is a service that can isolate different information flows in in different domains by way of programmable router technologies. VTaPDs identify these separate flows and create virtual domains. By doing this, a user is able to securely run multiple applications on different security domains, and to separate services for different settings based on context. The MANET’s contextual information such as device sensing values, location, and neighboring device status are recorded by the VTaPD manager, and used for risk management and intrusion detection procedures. Parameter values related to devices, network, content, and security such as battery level, connectivity, predefined goals, and privacy, are used to provide context-aware service migrations. Risk management is aided through context information because the status of the entire system (end-to-end communication delay, reachability of the destination, security status of each mobile node, etc.) is available. From this centralized data collection and processing, knowledge of the full MANET system is gained, and MobiCloud can easily identify malicious nodes.

4.5.3. Identifying potential resources and common activities using context-awareness

In [12], a Context Manager component is deployed to sense context information and store it to be used for other components such as Application Manager, which launches, intercepts and modifies an application according to the current context. Location and number of nearby devices in the vicinity are the key contexts, with location information used for mobility traces, and number of devices used to aid the forming of the mobile cloud. Thus, the system is made aware if a new device enters the resource pool, or leaves it, thereby leading to better scalability and content distribution. Furthermore, this information is used to infer if a particular device is ‘stable’ or not, which is essential to decide if it is following a common movement pattern with the other devices, leading to common activities.

Context-aware service provisioning

It has been suggested that, mobile clouds can utilize the sensing abilities of their mobile devices such as location, acceleration, etc. and act as providers of context awareness/information. In [95] the authors suggest utilizing the sensing capabilities of mobile Internet devices to provide such context-aware service provisioning. Consider a mobile device connected to a remote cloud service through the Internet. As the context of the user changes, this prompts invocation of different cloud services based on the current context. With this kind of context-awareness, a service would not be bound to a user. Instead, when a mobile user invokes a cloud service, the request is accompanied by his/her context information, and the most suitable service is selected based on that information. Therefore, context is used to provide personalized services, and also as fault tolerant mechanisms such as rectifying low quality of service problems. Here, the authors identify a model consisting of four layers of context elements:
1.
Monitored context: refers to current monitored context consisting of: device context which includes the environmental and device settings, user preference for user-specific preference settings, such as those regarding services selection and invocation, situational context relating to monitored data on user location, time etc., and Service Context information such as QoS.
2.
Types of gaps: refers to gaps that happen as a result of content changes. For example, when the user’s service is changed from Service1 to Service2 owing to a context change, there is a gap between the two services. Mainly, two types of gaps are identified: gap on functionality that relates to an available service and the needed service, and gap on nonfunctionality relating to differences in QoS values between the previous service and the current one.
3.
Types of causes: refers to the factors that can cause the aforementioned gaps. A service may have multiple interfaces, and an interface may have different implementations. Similarly, there can be different component instantiations for the same service component. The gaps arise because of the mismatches between these: Service-level Unmatched, Service Interface-level Unmatched, Service Component-level Unmatched, and Component Instance-level Unmatched.
4.
Adapters: refers to the remedial actions that should be taken to remove the aforementioned causes.
Based on this model, the authors propose a context aware service provisioning architecture consisting of three tiers: User Layer that is made up by the mobile devices where the applications run on, Agent Layer that adapts the services according to context, and Service Layer that deploys the services.
Volare [96] introduces a middleware for monitoring the context of a mobile device that is connected to a cloud service, and dynamically adapts the services so as to make them more resource efficient, reliable and cost efficient. Acting as an intermediary, VOLARE intercepts service discovery requests from applications while monitoring mobile device’s context such as battery consumption, CPU usage, network bandwidth, user preferences like low power operation etc. Depending on this contextual information, VOLARE tries to adapt each service request by comparing the current QoS level with predefined thresholds. Instead of modifying the applications, a declarative language has been created to describe the adaptation policies. If at any time, the QoS level and the cost changes beyond the predefined values, VOLARE will automatically rebind to another service that can satisfy the requirements.
In MoCA [59], a proxy can register an ‘interest expression’ on a mobile, i.e., “FreeMem <10 kB” for a particular client, which would result in the proxy getting notified if and when the client’s free memory drops below 10 kB. These context specific “interests” depend on those specific applications requirements. For example, if the proxy gets an update that a client’s wireless connectivity has gone down a certain point, it could take certain actions such as compressing the data.
Using ‘Intelligent access’ for Mobile Cloud Computing is discussed in [97], where use of context information provided by terminals, network nodes, or sensors deployed in the users environment enables efficient network access management across different Radio Access Technologies (RATs) such as GPRS, WCDMA/HSPA, LTE, WiMAX, cdma2000 and WLAN. Conventional intelligent access schemes assume that all categories of dynamic context information such as user profiles, terminal status and sensor information and external sensor networks would aid in improving mobile access. However, mobile cloud computing requires a wireless connection with a set of different necessities than classical heterogeneous access scenarios: connectivity for long periods, scalable bandwidth, network selection and usage based on energy costs. To satisfy these requirements, the paper proposes Intelligent Radio Network Access (IRNA). The status and attributes of each RAT is considered, while at the same time effort is taken to entertain the user requirements based on environmental factors. Their proposed context management architecture (CMA), based on the producer–consumer role model such as given in [98], is responsible for acquiring, processing, managing, and delivering context information. To control the supply of context information according to the mobile cloud’s requirements, the framework has a Context Quality Enabler (CQE). The CMA is made up of three components:
1.
Context Provider (CP): this is where the context information originates from and is provided to other components of the architecture. The communication between CPs and other components are done through context requests.
2.
Context Broker (CB): acting as a middleman, the CB keeps a registry of available CPs and their capabilities, and provides a CP look-up service. Also, the CB itself is able to forward the data it receives from CPs.
3.
Context Consumer: these are the entities that take context data as inputs for their actual functionality, e.g.: network services, applications for end users, and service enablers.
In MiPeG [25], a middleware for integrating mobile devices into grid environments, several mechanisms for providing and using context awareness are discussed. Context information such as location, resources and environment conditions is used to adapt the services provided by the grid, using Semantic Web technologies, thus supporting the ‘pervasive grid’ concept. The ‘Context Reasoning Engine’ forms the main component of the context service. Its responsibilities include handling the context, information gathering from sensing devices, and forming higher level semantic rules depending on the context information received.
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