Mobility issues in cognitive satellite communication systems

The natural aging process is impossible to avoid, but its effects go beyond fine lines and wrinkles on our skin. Our cognitive abilities tend to decline with age, which is why it is difficult to spot signs of major cognitive issues in elderly as they often interpreted as natural part of life. What are the signs of cognitive decline in older adults? Scroll down to find out how to spot these issues in your loved ones.

Cognitive impairment in the elderly has a number of causes ranging from medication side effects to depression and neurodegenerative disorders. There is no consensus regarding the age of onset of cognitive decline.

While some studies show that we experience a decline in cognitive skills after the age of 60, there is also evidence showing that women can show signs of cognitive decline age Cognitive impairment in the elderly has a number of signs and symptoms. Learning to recognize them allows you to address these problems effectively and prevent or delay more severe problems. Here are 10 symptoms to remember:. No, we are not talking about a processing speed of a computer or your smartphone, but a cognitive ability.

You see, processing speed refers to the time it takes a person to perform some mental task. Completing assignments, following instructions, and other forms of mental work or the time it takes for you to complete them shows whether processing speed is fast or slow.

Many of the cognitive changes in elderly occur due to slow processing speed. Attention is the ability to focus and concentrate on specific stimuli. Elderly with cognitive impairment and age-related dementia experience problems with selective and divided attention.

On the other hand, divided attention is your ability to focus on multiple things simultaneously. A sign of cognitive problems in elderly is the difficulty to retain attention both divided and selective i. While we forget things from time to time in youth, memory problems are more frequent in the elderly.

Cognitive Impairment

A growing body of evidence confirms that change in memory is one of the most common cognitive complaints among older adults. Age-related memory changes occur due to a number of reasons including slower processing speed, reduced use of strategies to improve memory and learning and decreased the ability to ignore irrelevant information.

When it comes to language, in most cases it remains intact as we age. For example, your vocabulary remains the same or even improves over the years. However, one of the frequently overlooked cognitive issues in the elderly is decreased verbal fluency.

Verbal fluency is a cognitive function that serves to facilitate information retrieval from memory and refers to the ability to perform a word search and generate words for a certain category.

Problems with verbal fluency usually make it more difficult for a person to find the right words e. While losing the house or car keys and finding them in your bag or between sofa cushions is not a big deal, locating them in the freezer is a sign for concern.The demand for precious radio spectrum is continuously increasing while the available radio frequency resource has become scarce due to spectrum segmentation and the dedicated frequency allocation of standardized wireless systems.

This scarcity has led to the concept of cognitive radio communication which comprises a variety of techniques capable of allowing the coexistence of licensed and unlicensed systems over the same spectrum. In this context, this thesis focuses on interweave and underlay cognitive radio paradigms which are widely considered as important enablers for realizing cognitive radio technology.

In the interweave paradigm, an unlicensed user explores the spectral holes by means of some spectrum awareness methods and utilizes the available spectral availabilities opportunistically while in the underlay paradigm, an unlicensed user is allowed to coexist with the licensed user only if sufficient protection to the licensed user can be guaranteed. Starting with a detailed overview of the existing techniques, this thesis provides contributions in both theoretical and the practical aspects of these paradigms.

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This thesis is structured into two main parts as described below. One of the important capabilities required for a cognitive radio transceiver is to be able to acquire the knowledge of its surrounding radio environment in order to utilize the available spectral opportunities efficiently. The higher the level of information it can acquire, the better becomes the spectrum utilization.

In this context, the first part of this thesis focuses on spectrum awareness techniques such as spectrum sensing, signal to noise ratio estimation and sparsity order estimation which are useful for realizing interweave and underlay based cognitive transceivers as well as a hybrid cognitive transceiver, which overcomes the drawbacks of both the above approaches.

The effects of noise and channel correlations, which are often neglected in the existing literature, are considered in our analysis. In the above context, firstly, we propose new sensing thresholds for the eigenvalue based sensing approach using recent results from random matrix theory in order to achieve the improved sensing in correlated scenarios. Then we study the signal to noise ratio estimation problem for both narrowband and wideband transceivers with the help of a detailed theoretical analysis under the signal plus noise hypothesis for a range of correlated scenarios.

Subsequently, we study the problem of compressive sparsity order estimation in order to estimate the sparsity order of the carrier occupancy over the wide spectrum using a compressive sensing approach. In addition, we carry out the performance analysis of a hybrid cognitive transceiver which combines the spectrum sensing approach with a power control-based underlay approach.

The second part of this thesis introduces the concept of cognitive satellite communications which is a rather unexplored area in the literature despite its significant benefits to both satellite and terrestrial operators. This concept has been motivated due to the limited availability of the satellite spectrum as well as the continuously increasing demand of broadband multimedia, broadcast and interactive satellite services.

Subsequently, we study the applications of various cognitive radio techniques in satellite communication systems focusing on the following two scenarios: i Hybrid cognitive satellite communication which deals with the spectral coexistence of satellite systems with the terrestrial systems, and ii Dual cognitive satellite communication which deals with the spectral coexistence of two satellite systems operating over the same coverage area. Understanding the characteristics of coexisting systems is of great importance while applying a suitable cognitive radio technique.

In this context, this thesis exploits the specific characteristics of satellite systems in order to map a suitable cognitive radio technique to a specific scenario. For hybrid cognitive scenarios, we propose the following enabling techniques: a Interference modeling, b Harmful interference detection, c Cognitive beamforming including both transmit and receive beamforming, and d Dual-polarized spectrum sensing.

Similarly, for dual cognitive scenarios, we propose the following techniques: i Cognitive interference alignment, ii Cognitive beamhopping, and iii Dual-polarized spectrum sensing.

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Finally, we provide interesting open research issues in the considered domain. Location of Repository. OAI identifier: oai:orbilu. Provided by: Open Repository and Bibliography - Luxembourg. Suggested articles.Maybe your parent has seemed more confused recently.

The answer to the last question is this: if you are worried about memory or thinking, then you should seek out some kind of medical evaluation. Those need to be detected, and treated if at all possible. It may or may not keep getting slowly worse; it all depends on the underlying cause or causes. Toxins are another potential cause of cognitive impairment. Research is ongoing as to the cognitive effects of toxins people may be exposed to, such as heavy metals, air pollutants, contaminants in our drinking water, pesticides, and others.

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Here are ten specific things the clinician should ask about, check on, or do, as part of an initial evaluation for cognitive impairment in an older adult. The following list reflects my own practice and that of most geriatricians. It is in line with most syntheses of guidelines and best practices, including the UpToDate. This is in of itself worth noting, especially if family or others have voiced concerns. If the older person does have concerns or observations, these should be explored.

Older adults with cognitive impairment are often unaware of — or reluctant to reveal — the difficulties they are experiencing. For this reason, a health provider who has been alerted to the possibility of cognitive impairment should make an effort to get information from a family member or other knowledgeable informant.

The best is to ask a family member to complete a validated questionnaire, such as the AD-8 informant interview. Be sure to include information on when the problems started and whether they seem to be getting worse.

The ideal is to for the health provider to ask both the patient and the family about this. The provider should also ask about ADLs, which are the more fundamental self-care tasks such as walking around, feeding oneself, getting dressed, managing continence, and so forth. Functional impairments may correspond with safety issues that need to be addressed; if an older person is having difficulty with finances, it may be a good idea to check for signs of financial exploitation, or otherwise take steps to protect the person financially.

Last but not least, impairment in daily functioning is also a criterion that separates mild cognitive impairment MCI from more significant impairment including dementia. In MCI, a person may be experiencing some cognitive impairment, but it should not be bad enough to significantly interfere with performing their usual daily life tasks.

Cognitive Security of Wireless Communication Systems in the Physical Layer

Check for the presence of other behavioral, mood, and thinking symptoms that may be related to certain causes of cognitive impairment. Checking for tremor and stiffness both of which are associated with Parkinsonism is also recommended. Excessive use of alcohol, certain prescription drugs such as tranquilizersor of illicit drugs can affect cognitive function.

Suddenly stopping or reducing the use of alcohol or other substances can also occasionally cause or worsen cognitive function. Review all medications, with a focus on identifying those known to worsen cognitive function.

Certain types of medications tend to dampen brain function, and may cause a noticeable worsening in cognitive abilities.Handbook of Cognitive Radio pp Cite as. Cognitive radio CR is one of the most intensively researched paradigms in recent wireless communication systems. The great deal of attention that CR has attracted can be ascribed to its demonstrated capability to increase spectrum efficiency and overall network capacity through interference-free spectrum sharing among several wireless communication systems.

CR provides intelligence to wireless networks, enabling users to access multiple air interfaces and select the most appropriate alternative under varying communication needs and operation conditions. The potential benefits of CR have not gone unnoticed to many wireless communication systems, which nowadays have effectively benefited from the adoption of CR techniques and operating principles.

This chapter provides an overview on the introduction of CR principles into two prominent wireless communication systems, namely, mobile and satellite communication networks. A detailed discussion is provided on the background and motivation for the adoption of the CR technology and how CR techniques have been introduced in these two systems.

A brief discussion is also provided on the adoption of the CR technology in other wireless communication systems, including military communications, public safety and emergency networks, aeronautical communications, and wireless-based Internet of Things. This chapter is aimed at illustrating the practical implementation of the theoretical CR principles widely discussed in the literature.

While the concept of cognitive radio CR [ 39 ] in its broadest sense can find a wide range of applications in wireless communications, dynamic spectrum access DSA [ 3 ] is certainly the most popular one as a matter of fact, the term CR is often used to refer to DSA.

Cognitive radio scenarios for satellite communications: The CoRaSat approach

This spectrum access paradigm allows several wireless communication systems to coexist in the same region of the spectrum, thus enabling a more efficient exploitation of the available spectrum resources. The potential benefits that the CR technology can bring into a broad variety of wireless communication systems have not gone unnoticed by academia, industry, and regulatory bodies, which over the last years have constantly explored new ways to introduce the principles of CR and DSA into existing wireless communication networks.

This chapter provides an overview of how CR principles and techniques have been adopted in wireless communication systems. This chapter discusses the background and motivation for the introduction of CR in these systems and how CR techniques have been adopted by different standardized technologies, which illustrates the practical implementation in real deployments of the theoretical CR principles widely discussed in the literature [ 34 ].

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Mobile communication systems have always experienced an ever-increasing capacity demand since the early days [ 30 ]. The replacement of the first generation 1G of analogic devices with digital handsets based on the second-generation 2G global system for mobile communication GSM standard [ 15 ] unleashed a worldwide expansion of mobile communications to the general public and the creation of a mass market for mobile communications.

The decade following the deployment of GSM networks witnessed an astonishing increase in the number of subscribers to the mobile service that has never decreased.

mobility issues in cognitive satellite communication systems

The third-generation 3G universal mobile telecommunications service UMTS standard [ 16 ] introduced true data services in mobile networks for the first time and represented the beginning of a race to increase the network capacity in response to the sustained increase in the number of subscribers as well as the introduction of more demanding data-hungry services.

This continuous increase in traffic demand has strained mobile operators, which have been forced to find new ways to increase the network capacity. More spectrum efficiency. This approach is aimed at increasing the number of bits transmitted per time and spectrum unit i. This includes new modulation and coding schemes such as orthogonal frequency-division multiplexing OFDM or filter bank multicarrier FBMC which can reduce the space between modulated subcarriers [ 938 ], multiple antenna techniques such as massive MIMO multiple-input multiple-output [ 22 ], full-duplex radios [ 3241 ] which can transmit and receive simultaneously in the same time and frequency thus potentially enabling in theory an increase in the spectrum efficiency by a factor of 2, non-orthogonal multiple access techniques [ 7 ] which use the power domain to separate signals from each other high-power signals can be isolated to be detected and then cancelled out to leave the low-power signalsor orthogonal polarizations used to transmit different data streams however, the radio propagation environment can modify the polarization of the signal components and cause mutual interference.

Research in this area has been intensive, and the current state of the art has closely approached the well-known Shannon limit [ 43 ], which represents an upper bound on the maximum attainable spectrum efficiency.

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This suggests that this approach has almost hit the performance wall and the room for further improvements appears to be limited [ 8 ]. More dense network deployments.New waveforms approaches exploiting the complementary features of multi-dimensional resources emerge to be a tempting solution to break the bottleneck in the physical layer toward heterogeneous networks. In this context, novel waveform designs to fulfill the requirements of heterogeneous networks constitute our main research interests.

Toward this ultimate point, our scope ranges from the fundamental properties of the waveforms e. We investigate not only waveform itself in time-frequency in terms of channel adaptation and flexibility, but also cross relations between waveforms like signal separability regarding to the their suitability to next generation networks.

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Additionally, considering practical systems, we focus on their impacts on the other topics in physical layer e. Related last projects can be found here. Go to the top Digital baseband signal processing algorithm development for future wireless communication systems Advanced digital baseband algorithm designs can improve the performance of the communication system, reduce the computational complexity and power consumption, extend the range of communication, and increase the data rates.

Actually, the enabling factors for current developments and future projections in wireless communications are the flexibility and capability in digital signal processing DSP. In other words, the requirement for the efficient design can vary depending on the application and type of the network. Therefore, adaptive, channel aware, and user aware algorithm designs are critical for the next generation systems that will mostly be possible with digital baseband processing advances.

Go to the top Cognitive Radio and Software Defined Radio Demands for more bandwidth requiring applications and increasing number of wireless devices caused inevitable evolution of wireless systems. However, the spectrum is still limited and spectral crowd pushes more efficient spectrum usage. This brought the idea of cognitive radio CR which has spectrum sensing, awareness of its surroundings, learning and self-adapting capabilities to maintain communication in an opportunistic manner.

As WCSP Group, we are interested in developing CR and software defined radio SDR algorithms to enable future radios to have advanced capabilities and designing CR test beds in our well equipped laboratory to test performance of the proposed techniques in practical cases. Related links can be found here. Go to the top Testing, measurements, and modeling Testing, measuring, and verification of next generation wireless devices, sub-systems, and networks are very challenging.

The next generation tools should have the ability to process wide variety of waveforms and should be equipped with autonomous synchronization and detection capabilities. In addition, understanding the transient behaviors of the transmitted and received signals is crucial.

We are interested in testing, measuring, and modeling the components, devices, wireless channel, RF front-end subsystem, interference, network of radios, etc. Go to the top Interference Interference is a limiting factor for the capacity of wireless services and might occur as a result of loose planning of wireless networks, mobile device hardware impairments and impacts of wireless channel.

Accordingly, increasing demand for more bandwidth consuming applications and lack of spectrum availability with the introduction of heterogeneous network HetNet nodes leads to denser frequency reuse and coexistence of different technologies. This leads future wireless networks to observe interference from even a larger number of sources. As WCSP Group, we believe that interference is a significantly important issue for both commercial and public safety communication systems.

mobility issues in cognitive satellite communication systems

Therefore, first we focus on understanding and modeling the interference scenario to exploit unique characteristics for interference suppression, and accordingly develop novel techniques based on the most suitable interference avoidance, coordination or cancellation approaches considering the available resources, e. Go to the top Heterogeneous Network With the urge to be always-connected to network along with data-hungry applications traditional homogeneous large scale network deployments are not sufficient to address emerging throughput demands of broadband wireless users.

Especially, the new applications e. Satisfaction of these recent trends constitutes the main driving force for heterogeneous networks that allow various types of cells at different scales e. Recently, significant effort has been devoted to maximize the spectral efficiency and network flexibility for heterogeneous deployments. However, interference between cells utilizing the same spectrum resources still constitutes the main problem of heterogeneous networks.

Our current research areas include but not limited to load balancing, mobility and interference management in heterogeneous networks.However, the problems associated with satellites are:. This type of delay is not acceptable particularly for voice communication, because it results in echo and talker overlap. Special protocols need to be designed for data communication networks that use satellites.

Low bandwidth: As compared to the terrestrial media, particularly the optical fiber, the bandwidth supported by satellites is much less. Though present satellites provide much more bandwidth than the satellites of the s and s, the bandwidth is nowhere comparable to the optical fiber bandwidth.

Noise: Satellite channels are affected by rain, atmospheric disturbances, etc. As a result, the performance of satellite links is generally poor as compared to terrestrial links. If data is received with errors, the data has to be retransmitted by the sender. To reduce retransmissions, forward error correcting FEC codes are implemented.

The problems associated with satellite communication are: high propagation delay, low bandwidths as compared to terrestrial media, and noise due to the effect of rain and atmospheric disturbances.

The large propagation delay in satellite networks poses problems for voice communication. High delay causes echo and talker overlap. Echo cancellers need to be used to overcome this problem. The stack is suitably modified to overcome the problems due to propagation delay.

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Privacy policy. This website uses cookies. Click here to find out more. Accept cookies.While the wireless communication systems provide the means of connectivity nearly everywhere and all the time, communication security requires more attention.

Even though current efforts provide solutions to specific problems under given circumstances, these methods are neither adaptive nor flexible enough to provide security under the dynamic conditions which make the security breaches an important concern. In this paper, a cognitive security CS concept for wireless communication systems in the physical layer is proposed with the aim of providing a comprehensive solution to wireless security problems.

The proposed method will enable the comprehensive security to ensure a robust and reliable communication in the existence of adversaries by providing adaptive security solutions in the communication systems by exploiting the physical layer security from different perspective.

The adaptiveness relies on the fact that radio adapts its propagation characteristics to satisfy secure communication based on specific conditions which are given as user density, application specific adaptation, and location within CS concept. Thus, instead of providing any type of new security mechanism, it is proposed that radio can take the necessary precautions based on these conditions before the attacks occur. Various access scenarios are investigated to enable the CS while considering these conditions.

The proliferation of wireless technologies in our daily life leads to an increasing demand for these technologies. While the prevalence of wireless communication systems presents indisputable advantages to the users, due to the open broadcast nature of the wireless signals, the communication exchanges are exposed to the attacks of adversaries.

As opposed to its wired counterparts, the enhanced mobility support of the wireless communication systems comes with the handicap of serious security vulnerabilities from the physical layer to the application layer. To protect the wireless signals from malicious attacks, security measures should be provided to the user.

In the existing wireless communication systems, security concerns are addressed in the upper layers by means of various encryption techniques.

Encryption is achieved in such a way that the message is encrypted with a key generated by using cipher, that is, an encryption algorithm, before the signal is transmitted. The receiver can decrypt the message by using the same key.

mobility issues in cognitive satellite communication systems

However, since encryption is a way of protecting the message in the upper layers, it does not prevent the signal from being detected by adversaries in the medium. Additionally, encryption increases the infrastructural overhead and power consumption to enable the authentication, which may not be feasible in some applications such as wireless sensor networks [ 1 ]. Data security in wireless domain has to adapt itself to the new wireless communications paradigm by becoming more adaptive and flexible.

To this end, implementation of communication security in the physical layer has recently become a field of interest. Existing security threats in the physical layer can be categorized into three groups: eavesdropping, jamming, and spoofing as depicted in Figure 1. In the physical layer security studies, legitimate transmitter, legitimate receiver, and passive attacker are symbolized, respectively, as Alice, Bob, and Eve.

Cognitive Radio Techniques for Satellite Communication Systems

The attacker might be considered as either a jammer or a spoofer if attacker is active. Eavesdropping refers to a situation where Eve can receive the message transmitted by Alice. The message needs to be protected against the eavesdroppers. When Bob receives both signals at the same time, legitimate signal would be received as meaningless signal. Therefore, the signal would not be decoded. This type of attack is named as jamming. When the attack is held, it needs to be identified by legitimate users, and the signal needs to be protected accordingly.

Spoofing can be carried out in two ways. Similar to the jamming case, this attack needs to be identified and necessary precautions should be taken.

In the literature, studies on physical layer security mainly focus on spread spectrum SS techniques and channel and power based solutions.