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Friday, November 22, 2019

Unconscious mind

From Wikipedia, the free encyclopedia
 
The unconscious mind (or the unconscious) consists of the processes in the mind which occur automatically and are not available to introspection and include thought processes, memories, interests and motivations.

Even though these processes exist well under the surface of conscious awareness, they are theorized to exert an impact on behavior. The term was coined by the 18th-century German Romantic philosopher Friedrich Schelling and later introduced into English by the poet and essayist Samuel Taylor Coleridge.

Empirical evidence suggests that unconscious phenomena include repressed feelings, automatic skills, subliminal perceptions, and automatic reactions, and possibly also complexes, hidden phobias and desires.

The concept was popularized by the Austrian neurologist and psychoanalyst Sigmund Freud. In psychoanalytic theory, unconscious processes are understood to be directly represented in dreams, as well as in slips of the tongue and jokes.

Thus the unconscious mind can be seen as the source of dreams and automatic thoughts (those that appear without any apparent cause), the repository of forgotten memories (that may still be accessible to consciousness at some later time), and the locus of implicit knowledge (the things that we have learned so well that we do them without thinking).

It has been argued that consciousness is influenced by other parts of the mind. These include unconsciousness as a personal habit, being unaware and intuition. Phenomena related to semi-consciousness include awakening, implicit memory, subliminal messages, trances, hypnagogia and hypnosis. While sleep, sleepwalking, dreaming, delirium and comas may signal the presence of unconscious processes, these processes are seen as symptoms rather than the unconscious mind itself.
Some critics have doubted the existence of the unconscious.

Historical overview

The term "unconscious" (German: Unbewusste) was coined by the 18th-century German Romantic philosopher Friedrich Schelling (in his System of Transcendental Idealism, ch. 6, § 3) and later introduced into English by the poet and essayist Samuel Taylor Coleridge (in his Biographia Literaria). Some rare earlier instances of the term "unconsciousness" (Unbewußtseyn) can be found in the work of the 18th-century German physician and philosopher Ernst Platner.

Influences on thinking that originate from outside of an individual's consciousness were reflected in the ancient ideas of temptation, divine inspiration, and the predominant role of the gods in affecting motives and actions. The idea of internalised unconscious processes in the mind was also instigated in antiquity and has been explored across a wide variety of cultures. Unconscious aspects of mentality were referred to between 2,500 and 600 BC in the Hindu texts known as the Vedas, found today in Ayurvedic medicine.

Paracelsus is credited as the first to make mention of an unconscious aspect of cognition in his work Von den Krankheiten (translates as "About illnesses", 1567), and his clinical methodology created a cogent system that is regarded by some as the beginning of modern scientific psychology. William Shakespeare explored the role of the unconscious in many of his plays, without naming it as such. In addition, Western philosophers such as Arthur Schopenhauer, Baruch Spinoza, Gottfried Leibniz, Johann Gottlieb Fichte, Georg Wilhelm Friedrich Hegel, Eduard von Hartmann, Søren Kierkegaard, and Friedrich Nietzsche used the word unconscious.

In 1880, Edmond Colsenet supports at the Sorbonne, a philosophy thesis on the unconscious. Elie Rabier and Alfred Fouillee perform syntheses of the unconscious "at a time when Freud was not interested in the concept".

Psychology

Psychologist Jacques Van Rillaer points out that, "the unconscious was not discovered by Freud. In 1890, when psychoanalysis was still unheard of, William James, in his monumental treatise on psychology (The Principles of Psychology), examined the way Schopenhauer, von Hartmann, Janet, Binet and others had used the term 'unconscious' and 'subconscious'". Historian of psychology Mark Altschule observes that, "It is difficult—or perhaps impossible—to find a nineteenth-century psychologist or psychiatrist who did not recognize unconscious cerebration as not only real but of the highest importance."

Eduard von Hartmann published a book dedicated to the topic, Philosophy of the Unconscious, in 1869.

Furthermore, 19th century German psychologists, Gustav Fechner and Wilhelm Wundt, had begun to use the term in their experimental psychology, in the context of manifold, jumbled sense data that the mind organizes at an unconscious level before revealing it as a cogent totality in conscious form."[24]

Freud's view

An iceberg is often (though misleadingly) used to provide a visual representation of Freud's theory that most of the human mind operates unconsciously.
 
Sigmund Freud and his followers developed an account of the unconscious mind. It plays an important role in psychoanalysis.

Freud divided the mind into the conscious mind (or the ego) and the unconscious mind. The latter was then further divided into the id (or instincts and drive) and the superego (or conscience). In this theory, the unconscious refers to the mental processes of which individuals make themselves unaware. Freud proposed a vertical and hierarchical architecture of human consciousness: the conscious mind, the preconscious, and the unconscious mind—each lying beneath the other. He believed that significant psychic events take place "below the surface" in the unconscious mind, like hidden messages from the unconscious. He interpreted such events as having both symbolic and actual significance.

In psychoanalytic terms, the unconscious does not include all that is not conscious, but rather what is actively repressed from conscious thought or what a person is averse to knowing consciously. Freud viewed the unconscious as a repository for socially unacceptable ideas, wishes or desires, traumatic memories, and painful emotions put out of mind by the mechanism of psychological repression. However, the contents did not necessarily have to be solely negative. In the psychoanalytic view, the unconscious is a force that can only be recognized by its effects—it expresses itself in the symptom. In a sense, this view places the conscious self as an adversary to its unconscious, warring to keep the unconscious hidden. Unconscious thoughts are not directly accessible to ordinary introspection, but are supposed to be capable of being "tapped" and "interpreted" by special methods and techniques such as meditation, free association (a method largely introduced by Freud), dream analysis, and verbal slips (commonly known as a Freudian slip), examined and conducted during psychoanalysis. Seeing as these unconscious thoughts are normally cryptic, psychoanalysts are considered experts in interpreting their messages.

Freud based his concept of the unconscious on a variety of observations. For example, he considered "slips of the tongue" to be related to the unconscious in that they often appeared to show a person's true feelings on a subject. For example, "I decided to take a summer curse". This example shows a slip of the word "course" where the speaker accidentally used the word curse which would show that they have negative feelings about having to do this. Freud noticed that also his patient's dreams expressed important feelings they were unaware of. After these observations, he came to the conclusion that psychological disturbances are largely caused by personal conflicts existing at the unconscious level. His psychoanalytic theory acts to explain personality, motivation and mental disorders by focusing on unconscious determinants of behavior.

Freud later used his notion of the unconscious in order to explain certain kinds of neurotic behavior. The theory of the unconscious was substantially transformed by later psychiatrists, among them Carl Jung and Jacques Lacan.

In his 1932/1933 conferences, Freud "proposes to abandon the notion of the unconscious that ambiguous judge".

Jung's view

Carl Gustav Jung, a Swiss psychiatrist, developed the concept further. He agreed with Freud that the unconscious is a determinant of personality, but he proposed that the unconscious be divided into two layers: the personal unconscious and the collective unconscious. The personal unconscious is a reservoir of material that was once conscious but has been forgotten or suppressed, much like Freud's notion. The collective unconscious, however, is the deepest level of the psyche, containing the accumulation of inherited psychic structures and archetypal experiences. Archetypes are not memories but energy centers or psychological functions that are apparent in the culture's use of symbols. The collective unconscious is therefore said to be inherited and contain material of an entire species rather than of an individual. Every person shares the collective unconscious with the entire human species, as Jung puts it: "[the] whole spiritual heritage of mankind's evolution, born anew in the brain structure of every individual".

In addition to the structure of the unconscious, Jung differed from Freud in that he did not believe that sexuality was at the base of all unconscious thoughts.

Controversy

The notion that the unconscious mind exists at all has been disputed. 

Franz Brentano rejected the concept of the unconscious in his 1874 book Psychology from an Empirical Standpoint, although his rejection followed largely from his definitions of consciousness and unconsciousness.

Jean-Paul Sartre offers a critique of Freud's theory of the unconscious in Being and Nothingness, based on the claim that consciousness is essentially self-conscious. Sartre also argues that Freud's theory of repression is internally flawed. Philosopher Thomas Baldwin argues that Sartre's argument is based on a misunderstanding of Freud.

Erich Fromm contends that, "The term 'the unconscious' is actually a mystification (even though one might use it for reasons of convenience, as I am guilty of doing in these pages). There is no such thing as the unconscious; there are only experiences of which we are aware, and others of which we are not aware, that is, of which we are unconscious. If I hate a man because I am afraid of him, and if I am aware of my hate but not of my fear, we may say that my hate is conscious and that my fear is unconscious; still my fear does not lie in that mysterious place: 'the' unconscious."

John Searle has offered a critique of the Freudian unconscious. He argues that the Freudian cases of shallow, consciously held mental states would be best characterized as 'repressed consciousness,' while the idea of more deeply unconscious mental states is more problematic. He contends that the very notion of a collection of "thoughts" that exist in a privileged region of the mind such that they are in principle never accessible to conscious awareness, is incoherent. This is not to imply that there are not "nonconscious" processes that form the basis of much of conscious life. Rather, Searle simply claims that to posit the existence of something that is like a "thought" in every way except for the fact that no one can ever be aware of it (can never, indeed, "think" it) is an incoherent concept. To speak of "something" as a "thought" either implies that it is being thought by a thinker or that it could be thought by a thinker. Processes that are not causally related to the phenomenon called thinking are more appropriately called the nonconscious processes of the brain.

Other critics of the Freudian unconscious include David Stannard, Richard Webster, Ethan Watters, Richard Ofshe, and Eric Thomas Weber.

David Holmes examined sixty years of research about the Freudian concept of "repression", and concluded that there is no positive evidence for this concept. Given the lack of evidence for many Freudian hypotheses, some scientific researchers proposed the existence of unconscious mechanisms that are very different from the Freudian ones. They speak of a "cognitive unconscious" (John Kihlstrom), an "adaptive unconscious" (Timothy Wilson), or a "dumb unconscious" (Loftus and Klinger), which executes automatic processes but lacks the complex mechanisms of repression and symbolic return of the repressed, and Robert Langs deep unconscious wisdom system.

In modern cognitive psychology, many researchers have sought to strip the notion of the unconscious from its Freudian heritage, and alternative terms such as "implicit" or "automatic" have been used. These traditions emphasize the degree to which cognitive processing happens outside the scope of cognitive awareness, and show that things we are unaware of can nonetheless influence other cognitive processes as well as behavior. Active research traditions related to the unconscious include implicit memory (see priming, implicit attitudes), and nonconscious acquisition of knowledge (see Lewicki, see also the section on cognitive perspective below).

Dreams

Freud

In terms of the unconscious, the purpose of dreams, as stated by Freud, is to fulfill repressed wishes through the process of dreaming, since they cannot be fulfilled in real life. For example, if someone were to rob a store and to feel guilty about it, they might dream about a scenario in which their actions were justified and renders them blameless. Freud asserted that the wish-fulfilling aspect of the dream may be disguised due to the difficulty in distinguishing between manifest content and latent content. The manifest content consists of the plot of a dream at the surface level. The latent content refers to the hidden or disguised meaning of the events in the plot. The latent content of the dream is what supports the idea of wish fulfillment. It represents the intimate information in the dreamer's current issues and childhood conflict.

Opposing theories

In response to Freud's theory on dreams, other psychologists have come up with theories to counter his argument. Theorist Rosalind Cartwright proposed that dreams provide people with the opportunity to act out and work through everyday problems and emotional issues in a non-real setting with no consequences. According to her cognitive problem solving view, a large amount of continuity exists between our waking thought and the thoughts that exist in dreams. Proponents of this view believe that dreams allow participation in creative thinking and alternate ways to handle situations when dealing with personal issues because dreams are not restrained by logic or realism.

In addition to this, Allan Hobson and colleagues came up with the activation-synthesis hypothesis which proposes that dreams are simply the side effects of the neural activity in the brain that produces beta brain waves during REM sleep that are associated with wakefulness. According to this hypothesis, neurons fire periodically during sleep in the lower brain levels and thus send random signals to the cortex. The cortex then synthesizes a dream in reaction to these signals in order to try to make sense of why the brain is sending them. However, the hypothesis does not state that dreams are meaningless, it just downplays the role that emotional factors play in determining dreams.

Contemporary cognitive psychology

Research

While, historically, the psychoanalytic research tradition was the first to focus on the phenomenon of unconscious mental activity, there is an extensive body of conclusive research and knowledge in contemporary cognitive psychology devoted to the mental activity that is not mediated by conscious awareness.

Most of that (cognitive) research on unconscious processes has been done in the mainstream, academic tradition of the information processing paradigm. As opposed to the psychoanalytic tradition, driven by the relatively speculative (in the sense of being hard to empirically verify) theoretical concepts such as the Oedipus complex or Electra complex, the cognitive tradition of research on unconscious processes is based on relatively few theoretical assumptions and is very empirically oriented (i.e., it is mostly data driven). Cognitive research has revealed that automatically, and clearly outside of conscious awareness, individuals register and acquire more information than what they can experience through their conscious thoughts.

Unconscious processing of information about frequency

For example, an extensive line of research conducted by Hasher and Zacks has demonstrated that individuals register information about the frequency of events automatically (i.e., outside of conscious awareness and without engaging conscious information processing resources). Moreover, perceivers do this unintentionally, truly "automatically," regardless of the instructions they receive, and regardless of the information processing goals they have. The ability to unconsciously and relatively accurately tally the frequency of events appears to have little or no relation to the individual's age, education, intelligence, or personality, thus it may represent one of the fundamental building blocks of human orientation in the environment and possibly the acquisition of procedural knowledge and experience, in general.

Defence mechanism

From Wikipedia, the free encyclopedia
 
A defence mechanism is an unconscious psychological mechanism that reduces anxiety arising from unacceptable or potentially harmful stimuli.

Defence mechanisms may result in healthy or unhealthy consequences depending on the circumstances and frequency with which the mechanism is used. In psychoanalytic theory, defence mechanisms (German: Abwehrmechanismen) are psychological strategies brought into play by the unconscious mind to manipulate, deny, or distort reality in order to defend against feelings of anxiety and unacceptable impulses and to maintain one's self-schema or other schemas. These processes that manipulate, deny, or distort reality may include the following: repression, or the burying of a painful feeling or thought from one's awareness even though it may resurface in a symbolic form; identification, incorporating an object or thought into oneself; and rationalization, the justification of one's behaviour and motivations by substituting "good" acceptable reasons for the actual motivations. In psychoanalytic theory, repression is considered as the basis for other defence mechanisms.

Healthy persons normally use different defences throughout life. An ego defence mechanism becomes pathological only when its persistent use leads to maladaptive behaviour such that the physical or mental health of the individual is adversely affected. Among the purposes of ego defence mechanisms is to protect the mind/self/ego from anxiety or social sanctions or to provide a refuge from a situation with which one cannot currently cope.

One resource used to evaluate these mechanisms is the Defense Style Questionnaire (DSQ-40).

Structural model: id, ego, and superego

Sigmund Freud
 
The concept of id impulses comes from Sigmund Freud's structural model. According to this theory, id impulses are based on the pleasure principle: instant gratification of one's own desires and needs. Freud believed that the id represents biological instinctual impulses in humans, such as aggression (Thanatos or the death instinct) and sexuality (Eros or the life instinct).

For example, when the id impulses (e.g., desire to have sexual relations with a stranger) conflict with the superego (e.g., belief in societal conventions of not having sex with unknown persons), unsatisfied feelings of anxiousness or feelings of anxiety come to the surface. To reduce these unpleasant feelings, the ego might use defence mechanisms (conscious or unconscious blockage of the id impulses).

Freud believed that conflicts between these two structures resulted in conflicts associated with psychosexual stages.

Definitions of individual psyche structures

The iceberg metaphor is often used to explain the psyche's parts in relation to one another
 
Freud proposed three structures of the psyche or personality:
  • Id: The id is the unconscious reservoir of the libido, the psychic energy that fuels instincts and psychic processes. It is a selfish, childish, pleasure-oriented part of the personality with no ability to delay gratification.
  • Superego: The superego contains internalised societal and parental standards of "good" and "bad", "right" and "wrong" behaviour. They include conscious appreciations of rules and regulations as well as those incorporated unconsciously.
  • Ego: The ego acts as a moderator between the pleasure sought by the id and the morals of the superego, seeking compromises to pacify both. It can be viewed as the individual's "sense of time and place".

Primary and secondary processes

In the ego, there are two ongoing processes. First, there is the unconscious primary process, where the thoughts are not organised in a coherent way; the feelings can shift, contradictions are not in conflict or are just not perceived that way, and condensations arise. There is no logic and no time line. Lust is important for this process. By contrast, there is the conscious secondary process, where strong boundaries are set and thoughts must be organised in a coherent way. Most conscious thoughts originate here.

Reality principle

Id impulses are not appropriate in a civilised society, so there is societal pressure to modify the pleasure principle in favour of the reality principle; that is, the requirements of the external world.

Formation of the superego

The superego forms as the child grows and learns parental and social standards. The superego consists of two structures: the conscience, which stores information about what is "bad" and what has been punished, and the ego ideal, which stores information about what is "good" and what one "should" do or be.

The ego's use of defence mechanisms

When anxiety becomes overwhelming, it is the ego's place to protect the person by employing defence mechanisms. Guilt, embarrassment, and shame often accompany anxiety. In the first definitive book on defence mechanisms, The Ego and the Mechanisms of Defence (1936), Anna Freud introduced the concept of signal anxiety; she stated that it was "not directly a conflicted instinctual tension but a signal occurring in the ego of an anticipated instinctual tension".

The signalling function of anxiety is thus seen as crucial, and biologically adapted to warn the organism of danger or a threat to its equilibrium. The anxiety is felt as an increase in bodily or mental tension, and the signal that the organism receives in this way allows for the possibility of taking defensive action regarding the perceived danger. Defence mechanisms work by distorting the id impulses into acceptable forms, or by unconscious or conscious blockage of these impulses.

Theories and classifications

The list of defence mechanisms, with no theoretical consensus on the exact number. Classifying defence mechanisms according to some of their properties (like underlying mechanisms, similarities or connections with personality) has been attempted. Different theorists have different categorizations and conceptualizations of defence mechanisms. Large reviews of theories of defence mechanisms are available from Paulhus, Fridhandler and Hayes (1997) and Cramer (1991). The Journal of Personality published a special issue on defence mechanisms (1998).

In 1936, Anna Freud enumerated the ten defence mechanisms that appear in the works of her father, Sigmund Freud: repression, regression, reaction formation, isolation, undoing, projection, introjection, turning against one's own person, reversal into the opposite, and sublimation or displacement.

A. Freud considered defense mechanisms as intellectual and motor automatisms of various degrees of complexity, that arose in the process of involuntary and voluntary learningRomanov, E.S. (1996). Mechanisms of psychological defense: genesis, functioning, diagnostics.
 
Both Freuds studied defence mechanisms, but Anna spent more of her time and research on five main mechanisms: repression, regression, projection, reaction formation, and sublimation. All defence mechanisms are responses to anxiety and how the consciousness and unconscious handle the stress of a social situation.
  • Repression: when a feeling is hidden and forced from the consciousness to the unconscious because it is seen as socially unacceptable
  • Regression: falling back into an early state of mental/physical development seen as "less demanding and safer"
  • Projection: possessing a feeling that is deigned as socially unacceptable and instead of facing it, that feeling or "unconscious urge" is seen in the actions of other people
  • Reaction formation: acting the opposite way that the unconscious instructs a person to behave, "often exaggerated and obsessive". For example, if a wife is infatuated with a man who is not her husband, reaction formation may cause her to – rather than cheat – become obsessed with showing her husband signs of love and affection.
  • Sublimation: seen as the most acceptable of the mechanisms, an expression of anxiety in socially acceptable ways
Otto F. Kernberg (1967) developed a theory of borderline personality organization of which one consequence may be borderline personality disorder. His theory is based on ego psychological object relations theory. Borderline personality organization develops when the child cannot integrate helpful and harmful mental objects together. Kernberg views the use of primitive defence mechanisms as central to this personality organization. Primitive psychological defences are projection, denial, dissociation or splitting and they are called borderline defence mechanisms. Also, devaluation and projective identification are seen as borderline defences.

In George Eman Vaillant's (1977) categorization, defences form a continuum related to their psychoanalytical developmental level. They are classified into pathological, immature, neurotic and "mature" defences. 

Robert Plutchik's (1979) theory views defences as derivatives of basic emotions, which in turn relate to particular diagnostic structures. According to his theory, reaction formation relates to joy (and manic features), denial relates to acceptance (and histrionic features), repression to fear (and passivity), regression to surprise (and borderline traits), compensation to sadness (and depression), projection to disgust (and paranoia), displacement to anger (and hostility) and intellectualization to anticipation (and obsessionality).

The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) published by the American Psychiatric Association (1994) includes a tentative diagnostic axis for defence mechanisms. This classification is largely based on Vaillant's hierarchical view of defences, but has some modifications. Examples include: denial, fantasy, rationalization, regression, isolation, projection, and displacement.

Vaillant's categorization

Psychiatrist George Eman Vaillant introduced a four-level classification of defence mechanisms:
  • Level I – pathological defences (psychotic denial, delusional projection)
  • Level II – immature defences (fantasy, projection, passive aggression, acting out)
  • Level III – neurotic defences (intellectualization, reaction formation, dissociation, displacement, repression)
  • Level IV – mature defences (humour, sublimation, suppression, altruism, anticipation)

Level 1: pathological

When predominant, the mechanisms on this level are almost always severely pathological. These six defences, in conjunction, permit one effectively to rearrange external experiences to eliminate the need to cope with reality. Pathological users of these mechanisms frequently appear irrational or insane to others. These are the "pathological" defences, common in overt psychosis. However, they are normally found in dreams and throughout childhood as well. They include:
  • Delusional projection: Delusions about external reality, usually of a persecutory nature
  • Denial: Refusal to accept external reality because it is too threatening; arguing against an anxiety-provoking stimulus by stating it does not exist; resolution of emotional conflict and reduction of anxiety by refusing to perceive or consciously acknowledge the more unpleasant aspects of external reality
  • Distortion: A gross reshaping of external reality to meet internal needs

Level 2: immature

These mechanisms are often present in adults. These mechanisms lessen distress and anxiety produced by threatening people or by an uncomfortable reality. Excessive use of such defences is seen as socially undesirable, in that they are immature, difficult to deal with and seriously out of touch with reality. These are the so-called "immature" defences and overuse almost always leads to serious problems in a person's ability to cope effectively. These defences are often seen in major depression and personality disorders. They include:
  • Acting out: Direct expression of an unconscious wish or impulse in action, without conscious awareness of the emotion that drives the expressive behavior
  • Hypochondriasis: An excessive preoccupation or worry about having a serious illness
  • Passive-aggressive behavior: Indirect expression of hostility
  • Projection: A primitive form of paranoia. Projection reduces anxiety by allowing the expression of the undesirable impulses or desires without becoming consciously aware of them; attributing one's own unacknowledged, unacceptable, or unwanted thoughts and emotions to another; includes severe prejudice and jealousy, hypervigilance to external danger, and "injustice collecting", all with the aim of shifting one's unacceptable thoughts, feelings and impulses onto someone else, such that those same thoughts, feelings, beliefs and motivations are perceived as being possessed by the other.
  • Schizoid fantasy: Tendency to retreat into fantasy in order to resolve inner and outer conflicts

Level 3: neurotic

These mechanisms are considered neurotic, but fairly common in adults. Such defences have short-term advantages in coping, but can often cause long-term problems in relationships, work and in enjoying life when used as one's primary style of coping with the world. They include:
  • Displacement: Defence mechanism that shifts sexual or aggressive impulses to a more acceptable or less threatening target; redirecting emotion to a safer outlet; separation of emotion from its real object and redirection of the intense emotion toward someone or something that is less offensive or threatening in order to avoid dealing directly with what is frightening or threatening.
  • Dissociation: Temporary drastic modification of one's personal identity or character to avoid emotional distress; separation or postponement of a feeling that normally would accompany a situation or thought
  • Intellectualization: A form of isolation; concentrating on the intellectual components of a situation so as to distance oneself from the associated anxiety-provoking emotions; separation of emotion from ideas; thinking about wishes in formal, affectively bland terms and not acting on them; avoiding unacceptable emotions by focusing on the intellectual aspects (isolation, rationalization, ritual, undoing, compensation, and magical thinking)
  • Reaction formation: Converting unconscious wishes or impulses that are perceived to be dangerous or unacceptable into their opposites; behaviour that is completely the opposite of what one really wants or feels; taking the opposite belief because the true belief causes anxiety
  • Repression: The process of attempting to repel desires towards pleasurable instincts, caused by a threat of suffering if the desire is satisfied; the desire is moved to the unconscious in the attempt to prevent it from entering consciousness; seemingly unexplainable naivety, memory lapse or lack of awareness of one's own situation and condition; the emotion is conscious, but the idea behind it is absent

Level 4: mature

These are commonly found among emotionally healthy adults and are considered mature, even though many have their origins in an immature stage of development. They have been adapted through the years in order to optimise success in human society and relationships. The use of these defences enhances pleasure and feelings of control. These defences help to integrate conflicting emotions and thoughts, whilst still remaining effective. Those who use these mechanisms are usually considered virtuous. Mature defences include:
  • Altruism: Constructive service to others that brings pleasure and personal satisfaction
  • Anticipation: Realistic planning for future discomfort
  • Humour: Overt expression of ideas and feelings (especially those that are unpleasant to focus on or too terrible to talk about directly) that gives pleasure to others. The thoughts retain a portion of their innate distress, but they are "skirted around" by witticism, for example self-deprecation.
  • Sublimation: Transformation of unhelpful emotions or instincts into healthy actions, behaviours, or emotions, for example, playing a heavy contact sport such as football or rugby can transform aggression into a game[24]
  • Suppression: The conscious decision to delay paying attention to a thought, emotion, or need in order to cope with the present reality; making it possible later to access uncomfortable or distressing emotions whilst accepting them

Other defence mechanisms

Diagram of selected ego defence mechanisms

Pathological

  • Conversion: The expression of an intrapsychic conflict as a physical symptom; some examples include blindness, deafness, paralysis, or numbness. This phenomenon is sometimes called hysteria.
  • Splitting: A primitive defence. Both harmful and helpful impulses are split off and unintegrated, frequently projected onto someone else. The defended individual segregates experiences into all-good and all-bad categories, with no room for ambiguity and ambivalence. When "splitting" is combined with "projecting", the undesirable qualities that one unconsciously perceives oneself as possessing, one consciously attributes to another.

Immature

  • Idealization: Tending to perceive another individual as having more desirable qualities than he or she may actually have.
  • Introjection: Identifying with some idea or object so deeply that it becomes a part of that person. For example, introjection occurs when we take on attributes of other people who seem better able to cope with the situation than we do.
  • Passive aggression: Aggression towards others expressed indirectly or passively, often through procrastination.
  • Projective identification: The object of projection invokes in that person a version of the thoughts, feelings or behaviours projected.
  • Somatization: The transformation of uncomfortable feelings towards others into uncomfortable feelings toward oneself: pain, illness, and anxiety.
  • Wishful thinking: Making decisions according to what might be pleasing to imagine instead of by appealing to evidence, rationality, or reality.

Neurotic

  • Isolation: Separation of feelings from ideas and events, for example, describing a murder with graphic details with no emotional response.
  • Rationalization (making excuses): Convincing oneself that no wrong has been done and that all is or was all right through faulty and false reasoning. An indicator of this defence mechanism can be seen socially as the formulation of convenient excuses.
  • Regression: Temporary reversion of the ego to an earlier stage of development rather than handling unacceptable impulses in a more adult way, for example, using whining as a method of communicating despite already having acquired the ability to speak with an appropriate level of maturity.
  • Undoing: A person tries to 'undo' an unhealthy, destructive or otherwise threatening thought by acting out the reverse of the unacceptable. Involves symbolically nullifying an unacceptable or guilt provoking thought, idea, or feeling by confession or atonement.
  • Upward and downward social comparisons: A defensive tendency that is used as a means of self-evaluation. Individuals will look to another individual or comparison group who are considered to be worse off in order to dissociate themselves from perceived similarities and to make themselves feel better about themselves or their personal situation.
  • Withdrawal: Avoidance is a form of defence. It entails removing oneself from events, stimuli, and interactions under the threat of being reminded of painful thoughts and feelings.

Relation with coping

There are many different perspectives on how the construct of defence relates to the construct of coping; some writers differentiate the constructs in various ways, but "an important literature exists that does not make any difference between the two concepts". In at least one of his books, George Eman Vaillant stated that he "will use the terms adaptation, resilience, coping, and defense interchangeably".

Wi-Fi

From Wikipedia, the free encyclopedia
 
Wi-FI Alliance Logo.png
Wi-Fi Alliance
IntroducedSeptember 1998; 21 years ago
Compatible hardwarePersonal computers, gaming consoles, televisions, printers, mobile phones

Wi-Fi is a family of wireless networking technologies, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access. Wi‑Fi is a trademark of the non-profit Wi-Fi Alliance, which restricts the use of the term Wi-Fi Certified to products that successfully complete interoperability certification testing. As of 2010, the Wi-Fi Alliance consisted of more than 375 companies from around the world. As of 2009, Wi-Fi-integrated circuit chips shipped approximately 580 million units annually. Devices that can use Wi-Fi technologies include desktops and laptops, smartphones and tablets, smart TVs, printers, digital audio players, digital cameras, cars and drones.

Wi-Fi uses multiple parts of the IEEE 802 protocol family and is designed to seamlessly interwork with its wired sibling Ethernet. Compatible devices can network through a wireless access point to each other as well as to wired devices and the Internet. The different versions of Wi-Fi are specified by various IEEE 802.11 protocol standards, with the different radio technologies determining radio bands, and the maximum ranges, and speeds that may be achieved. Wi-Fi most commonly uses the 2.4 gigahertz (120 mm) UHF and 5 gigahertz (60 mm) SHF ISM radio bands; these bands are subdivided into multiple channels. Channels can be shared between networks but only one transmitter can locally transmit on a channel at any moment in time.

Wi-Fi's wavebands have relatively high absorption and work best for line-of-sight use. Many common obstructions such as walls, pillars, home appliances etc. may greatly reduce range, but this also helps minimize interference between different networks in crowded environments. An access point (or hotspot) often has a range of about 20 metres (66 feet) indoors while some modern access points claim up to a 150-metre (490-foot) range outdoors. Hotspot coverage can be as small as a single room with walls that block radio waves, or as large as many square kilometres using many overlapping access points with roaming permitted between them. Over time the speed and spectral efficiency of Wi-Fi has increased. As of 2019, at close range, some versions of Wi-Fi running on suitable hardware can achieve speeds of over 1 Gbit/s (gigabit per second).

Wi-Fi is potentially more vulnerable to attack than wired networks because anyone within range of a network with a wireless network interface controller can attempt access. Therefore to connect to a Wi-Fi network, a user typically needs the network name (the SSID) and a password. The password is used to encrypt Wi-Fi packets so as to block eavesdroppers. Wi-Fi Protected Access (WPA) is a family of technologies created to protect information moving across Wi-Fi networks and includes solutions for personal and enterprise networks. As the security landscape has changed over time security features of WPA have included stronger protections and new security practices.

History

In 1971, ALOHAnet connected the Great Hawaiian Islands with a UHF wireless packet network. ALOHAnet and the ALOHA protocol were early forerunners to Ethernet, and later the IEEE 802.11 protocols, respectively.

A 1985 ruling by the U.S. Federal Communications Commission released the ISM band for unlicensed use. These frequency bands are the same ones used by equipment such as microwave ovens and are subject to interference. 

In 1991, NCR Corporation with AT&T Corporation invented the precursor to 802.11, intended for use in cashier systems, under the name WaveLAN

The Australian radio-astronomer Dr John O'Sullivan with his colleagues Terence Percival, Graham Daniels, Diet Ostry, and John Deane developed a key patent used in Wi-Fi as a by-product of a Commonwealth Scientific and Industrial Research Organisation (CSIRO) research project, "a failed experiment to detect exploding mini black holes the size of an atomic particle". Dr O'Sullivan and his colleagues are credited with inventing Wi-Fi. In 1992 and 1996, CSIRO obtained patents for a method later used in Wi-Fi to "unsmear" the signal.

The first version of the 802.11 protocol was released in 1997, and provided up to 2 Mbit/s link speeds. This was updated in 1999 with 802.11b to permit 11 Mbit/s link speeds, and this proved popular.

In 1999, the Wi-Fi Alliance formed as a trade association to hold the Wi-Fi trademark under which most products are sold.

Wi-Fi uses a large number of patents held by many different organizations. In April 2009, 14 technology companies agreed to pay CSIRO $1 billion for infringements on CSIRO patents. This led to Australia labeling Wi-Fi as an Australian invention, though this has been the subject of some controversy. CSIRO won a further $220 million settlement for Wi-Fi patent-infringements in 2012, with global firms in the United States required to pay CSIRO licensing rights estimated at an additional $1 billion in royalties. In 2016, the wireless local area network Test Bed was chosen as Australia's contribution to the exhibition A History of the World in 100 Objects held in the National Museum of Australia.

Etymology and terminology

A Japanese sticker indicating to the public that a location is within range of a Wi-Fi network. A dot with curved lines radiating from it is a common symbol for Wi-Fi, representing a point transmitting a signal.
 
An example of a service set called "WiFi Wikipedia" consisting of two Basic Service Sets. Notebook_My is able to automatically roam between the two BSSs, without the user having to explicitly connect to the second network.
 
The name Wi-Fi, commercially used at least as early as August 1999, was coined by the brand-consulting firm Interbrand. The Wi-Fi Alliance had hired Interbrand to create a name that was "a little catchier than 'IEEE 802.11b Direct Sequence'." Phil Belanger, a founding member of the Wi-Fi Alliance who presided over the selection of the name "Wi-Fi", has stated that Interbrand invented Wi-Fi as a pun on the word hi-fi (high fidelity), a term for high-quality audio technology.

The name Wi-Fi has no further meaning, and was never officially a shortened form of "Wireless Fidelity". Nevertheless, the Wi-Fi Alliance used the advertising slogan "The Standard for Wireless Fidelity" for a short time after the brand name was created, and the Wi-Fi Alliance was also called the "Wireless Fidelity Alliance Inc" in some publications.

Interbrand also created the Wi-Fi logo. The yin-yang Wi-Fi logo indicates the certification of a product for interoperability.

Non-Wi-Fi technologies intended for fixed points, such as Motorola Canopy, are usually described as fixed wireless. Alternative wireless technologies include mobile phone standards, such as 2G, 3G, 4G, and LTE

The name is sometimes written as WiFi, Wifi, or wifi, but these are not approved by the Wi-Fi Alliance. IEEE is a separate, but related, organization and their website has stated "WiFi is a short name for Wireless Fidelity".

To connect to a Wi-Fi LAN, a computer must be equipped with a wireless network interface controller. The combination of a computer and an interface controller is called a station. Stations are identified by one or more MAC addresses.

Wi-Fi nodes often operate in infrastructure mode where all communications go through a base station. Ad-hoc mode refers to devices talking directly to each other without the need to first talk to an access point.

A service set is the set of all the devices associated with a particular Wi-Fi network. Devices in a service set need not be on the same wavebands or channels. A service set can be local, independent, extended or mesh or a combination.

Each service set has an associated identifier, the 32-byte Service Set Identifier (SSID), which identifies the particular network. The SSID is configured within the devices that are considered part of the network.

A Basic Service Set (BSS) is a group of stations that all share the same wireless channel, SSID, and other wireless settings that have wirelessly connected (usually to the same access point). Each BSS is identified by a MAC address which is called the BSSID.

Certification

The IEEE does not test equipment for compliance with their standards. The non-profit Wi-Fi Alliance was formed in 1999 to fill this void—to establish and enforce standards for interoperability and backward compatibility, and to promote wireless local-area-network technology. As of 2010, the Wi-Fi Alliance consists of more than 375 companies and includes 3Com (now owned by HPE/Hewlett-Packard Enterprise), Aironet (now owned by Cisco), Harris Semiconductor (now owned by Intersil), Lucent (now owned by Nokia), Nokia and Symbol Technologies (now owned by Zebra Technologies). The Wi-Fi Alliance enforces the use of the Wi-Fi brand to technologies based on the IEEE 802.11 standards from the IEEE. This includes wireless local area network (WLAN) connections, device to device connectivity (such as Wi-Fi Peer to Peer aka Wi-Fi Direct), Personal area network (PAN), local area network (LAN) and even some limited wide area network (WAN) connections. Manufacturers with membership in the Wi-Fi Alliance, whose products pass the certification process, gain the right to mark those products with the Wi-Fi logo.

Specifically, the certification process requires conformance to the IEEE 802.11 radio standards, the WPA and WPA2 security standards, and the EAP authentication standard. Certification may optionally include tests of IEEE 802.11 draft standards, interaction with cellular-phone technology in converged devices, and features relating to security set-up, multimedia, and power-saving.

Not every Wi-Fi device is submitted for certification. The lack of Wi-Fi certification does not necessarily imply that a device is incompatible with other Wi-Fi devices. The Wi-Fi Alliance may or may not sanction derivative terms, such as Super Wi-Fi, coined by the US Federal Communications Commission (FCC) to describe proposed networking in the UHF TV band in the US.

Versions

Generation/IEEE Standard Maximum Linkrate
Wi‑Fi 6 (802.11ax) 600–9608 Mbit/s
Wi‑Fi 5 (802.11ac) 433–6933 Mbit/s
Wi‑Fi 4 (802.11n) 72–600 Mbit/s
802.11g 3–54 Mbit/s
802.11a 1.5 to 54 Mbit/s
802.11b 1 to 11 Mbit/s
(Wi-Fi 1, Wi-Fi 2, Wi-Fi 3 are unbranded but have unofficial assignments)
Equipment frequently support multiple versions of Wi-Fi. To communicate, devices must use a common Wi-Fi version. The versions differ between the radio wavebands they operate on, the radio bandwidth they occupy, the maximum data rates they can support and other details. Some versions permit the use of multiple antennas, which permits greater speeds as well as reduced interference. 

Historically, equipment has simply listed the versions of Wi-Fi using the name of the IEEE standard that it supports. In 2018, the Wi-Fi alliance standardized generational numbering so that equipment can indicate that it supports Wi-Fi 4 (if the equipment supports 802.11n), Wi-Fi 5 (802.11ac) and Wi-Fi 6 (802.11ax). These generations have a high degree of backward compatibility with previous versions. The alliance have stated that the generational level 4, 5, or 6 can be indicated in the user interface when connected, along with the signal strength.

The full list of versions of Wi-Fi is: 802.11a, 802.11b, 802.11g, 802.11n (Wi-Fi 4), 802.11h, 802.11i, 802.11-2007, 802.11-2012, 802.11ac (Wi-Fi 5), 802.11ad, 802.11af, 802.11-2016, 802.11ah, 802.11ai, 802.11aj, 802.11aq, 802.11ax (Wi-Fi 6), 802.11ay.

Uses

Internet access

Wi-Fi technology may be used to provide local network and Internet access to devices that are within Wi-Fi range of one or more routers that are connected to the Internet. The coverage of one or more interconnected access points (hotspots) can extend from an area as small as a few rooms to as large as many square kilometres. Coverage in the larger area may require a group of access points with overlapping coverage. For example, public outdoor Wi-Fi technology has been used successfully in wireless mesh networks in London. An international example is Fon.

Wi-Fi provides service in private homes, businesses, as well as in public spaces. Wi-Fi hotspots may be set up either free-of-charge or commercially, often using a captive portal webpage for access. Organizations, enthusiasts, authorities and businesses, such as airports, hotels, and restaurants, often provide free or paid-use hotspots to attract customers, to provide services to promote business in selected areas.

Routers often incorporate a digital subscriber line modem or a cable modem and a Wi-Fi access point, are frequently set up in homes and other buildings, to provide Internet access and internetworking for the structure.

Similarly, battery-powered routers may include a cellular Internet radio modem and Wi-Fi access point. When subscribed to a cellular data carrier, they allow nearby Wi-Fi stations to access the Internet over 2G, 3G, or 4G networks using the tethering technique. Many smartphones have a built-in capability of this sort, including those based on Android, BlackBerry, Bada, iOS (iPhone), Windows Phone and Symbian, though carriers often disable the feature, or charge a separate fee to enable it, especially for customers with unlimited data plans. "Internet packs" provide standalone facilities of this type as well, without use of a smartphone; examples include the MiFi- and WiBro-branded devices. Some laptops that have a cellular modem card can also act as mobile Internet Wi-Fi access points.

Many traditional university campuses in the developed world provide at least partial Wi-Fi coverage. Carnegie Mellon University built the first campus-wide wireless Internet network, called Wireless Andrew, at its Pittsburgh campus in 1993 before Wi-Fi branding originated. By February 1997, the CMU Wi-Fi zone was fully operational. Many universities collaborate in providing Wi-Fi access to students and staff through the Eduroam international authentication infrastructure.

City-wide

An outdoor Wi-Fi access point
 
In the early 2000s, many cities around the world announced plans to construct citywide Wi-Fi networks. There are many successful examples; in 2004, Mysore (Mysuru) became India's first Wi-Fi-enabled city. A company called WiFiyNet has set up hotspots in Mysore, covering the complete city and a few nearby villages.

In 2005, St. Cloud, Florida and Sunnyvale, California, became the first cities in the United States to offer citywide free Wi-Fi (from MetroFi). Minneapolis has generated $1.2 million in profit annually for its provider.

In May 2010, London mayor Boris Johnson pledged to have London-wide Wi-Fi by 2012. Several boroughs including Westminster and Islington  already had extensive outdoor Wi-Fi coverage at that point. 

Officials in South Korea's capital Seoul are moving to provide free Internet access at more than 10,000 locations around the city, including outdoor public spaces, major streets and densely populated residential areas. Seoul will grant leases to KT, LG Telecom, and SK Telecom. The companies will invest $44 million in the project, which was to be completed in 2015.

Geolocation

Wi-Fi positioning systems use the positions of Wi-Fi hotspots to identify a device's location.

Operational principles

Wi-Fi stations communicate by sending each other data packets: blocks of data individually sent and delivered over radio. As with all radio, this is done by the modulating and demodulation of carrier waves. Different versions of Wi-Fi use different techniques, 802.11b uses DSSS on a single carrier, whereas 802.11a, Wi-Fi 4, 5 and 6 use multiple carriers on slightly different frequencies within the channel (OFDM).

As with other IEEE 802 LANs, stations come programmed with a globally unique 48-bit MAC address (often printed on the equipment) so that each Wi-Fi station has a unique address. The MAC addresses are used to specify both the destination and the source of each data packet. Wi-Fi establishes link-level connections, which can be defined using both the destination and source addresses. On reception of a transmission, the receiver uses the destination address to determine whether the transmission is relevant to the station or should be ignored. A network interface normally does not accept packets addressed to other Wi-Fi stations.

Due to the ubiquity of Wi-Fi and the ever-decreasing cost of the hardware needed to support it, most manufacturers now build Wi-Fi interfaces directly into PC motherboards, eliminating the need for installation of a separate network card.

Channels are used half duplex and can be time-shared by multiple networks. When communication happens on the same channel, any information sent by one computer is locally received by all, even if that information is intended for just one destination. The network interface card interrupts the CPU only when applicable packets are received: the card ignores information not addressed to it. Use of the same channel also means that the data bandwidth is shared, such that, for example, available data bandwidth to each device is halved when two stations are actively transmitting.

A collision happens when two stations attempt to transmit at the same time. They corrupt transmitted data and require stations to re-transmit. The lost data and re-transmission reduces throughput. In the worst case, where multiple active hosts connected with maximum allowed cable length attempt to transmit many short frames, excessive collisions can reduce throughput dramatically. A scheme known as carrier sense multiple access with collision avoidance (CSMA/CA) governs the way the computers share the channel.

Waveband

In the 2.5 GHz wavebands as well as others, transmitters straddle multiple channels. Overlapping channels can suffer from interference unless this is a small portion of the total received power.
 
A keychain-size Wi-Fi detector
 
The 802.11 standard provides several distinct radio frequency ranges for use in Wi-Fi communications: 900 MHz, 2.4 GHz, 5 GHz, 5.9 GHz, and 60 GHz bands. Each range is divided into a multitude of channels. Countries apply their own regulations to the allowable channels, allowed users and maximum power levels within these frequency ranges. The ISM band ranges are also often used.

802.11b/g/n can use the 2.4 GHz ISM band, operating in the United States under Part 15 Rules and Regulations. In this frequency band equipment may occasionally suffer interference from microwave ovens, cordless telephones, USB 3.0 hubs, and Bluetooth devices.

Spectrum assignments and operational limitations are not consistent worldwide: Australia and Europe allow for an additional two channels (12, 13) beyond the 11 permitted in the United States for the 2.4 GHz band, while Japan has three more (12–14). In the US and other countries, 802.11a and 802.11g devices may be operated without a license, as allowed in Part 15 of the FCC Rules and Regulations. 

802.11a/h/j/n/ac/ax can use the 5 GHz U-NII band, which, for much of the world, offers at least 23 non-overlapping 20 MHz channels rather than the 2.4 GHz ISM frequency band, where the channels are only 5 MHz wide. In general, lower frequencies have better range but have less capacity. The 5 GHz bands are absorbed to a greater degree by common building materials than the 2.4 GHz bands, and usually give shorter range.

As 802.11 specifications evolved to support higher throughput, the protocols have become much more efficient in their use of bandwidth. Additionally they have gained the ability to 'bond' channels together to gain still more throughput where the bandwidth is available. 802.11n allows for double radio spectrum/bandwidth (40 MHz- 8 channels) compared to 802.11a or 802.11g (20 MHz). 802.11n can also be set to limit itself to 20 MHz bandwidth to prevent interference in dense communities. In the 5 GHz band, 20, 40, 80 and 160 MHz bandwidth signals are permitted with some restrictions, giving much faster connections.

Communication stack


Wi-Fi is part of the IEEE 802 protocol family. The data is organized into 802.11 frames that are very similar to Ethernet frames at the data link layer, but with extra address fields. MAC addresses are used as network addresses for routing over the LAN.

Wi-Fi's MAC and physical layer (PHY) specifications are defined by IEEE 802.11 for modulating and receiving one or more carrier waves to transmit the data in the infrared, and 2.4, 3.6, 5, or 60 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). The base version of the standard was released in 1997, and has had many subsequent amendments. The standard and amendments provide the basis for wireless network products using the Wi-Fi brand. While each amendment is officially revoked when it is incorporated in the latest version of the standard, the corporate world tends to market to the revisions because they concisely denote capabilities of their products. As a result, in the market place, each revision tends to become its own standard.

In addition to 802.11 the IEEE 802 protocol family has specific provisions for Wi-Fi. These are required because Ethernet's cable-based media are not usually shared, whereas with wireless all transmissions are received by all stations within range that employ that radio channel. While Ethernet has essentially negligible error rates, wireless communication media are subject to significant interference. Therefore, accurate transmission is not guaranteed so delivery is therefore a best-effort delivery mechanism. Because of this, for Wi-Fi, the Logical Link Control (LLC) specified by IEEE 802.2 employs Wi-Fi's media access control (MAC) protocols to manage retries without relying on higher levels of the protocol stack.

For internetworking purposes Wi-Fi is usually layered as a link layer (equivalent to the physical and data link layers of the OSI model) below the internet layer of the Internet Protocol. This means that nodes have an associated internet address and, with suitable connectivity, this allows full Internet access.

Modes

Infrastructure

Depiction of a Wi-Fi network in infrastructure mode. The device sends information wirelessly to another device, both connected to the local network, in order to print a document
 
In infrastructure mode, which is the most common mode used, all communications goes through a base station. For communications within the network, this introduces an extra use of the airwaves, but has the advantage that any two stations that can communicate with the base station can also communicate through the base station, which enormously simplifies the protocols.

Ad hoc and Wi-Fi direct

Wi-Fi also allows communications directly from one computer to another without an access point intermediary. This is called ad hoc Wi-Fi transmission. Different types of ad hoc network exist. In the simplest case network nodes must talk directly to each other. In more complex protocols nodes may forward packets, and nodes keep track of how to reach other nodes, even if they move around.

Ad-hoc mode was first invented and realized by Chai Keong Toh in his 1996 invention of Wi-Fi ad-hoc routing, implemented on Lucent WaveLAN 802.11a wireless on IBM ThinkPads over a size nodes scenario spanning a region of over a mile. The success was recorded in Mobile Computing magazine (1999) and later published formally in IEEE Transactions on Wireless Communications, 2002 and ACM SIGMETRICS Performance Evaluation Review, 2001.

This wireless ad hoc network mode has proven popular with multiplayer handheld game consoles, such as the Nintendo DS, PlayStation Portable, digital cameras, and other consumer electronics devices. Some devices can also share their Internet connection using ad hoc, becoming hotspots or "virtual routers".

Similarly, the Wi-Fi Alliance promotes the specification Wi-Fi Direct for file transfers and media sharing through a new discovery- and security-methodology. Wi-Fi Direct launched in October 2010.

Another mode of direct communication over Wi-Fi is Tunneled Direct Link Setup (TDLS), which enables two devices on the same Wi-Fi network to communicate directly, instead of via the access point.

Multiple access points

Access points send out beacon frames to announce the presence of networks.
 
An Extended Service Set may be formed by deploying multiple access points that are configured with the same SSID and security settings. Wi-Fi client devices typically connect to the access point that can provide the strongest signal within that service set.

Increasing the number of Wi-Fi access points for a network provides redundancy, better range, support for fast roaming and increased overall network-capacity by using more channels or by defining smaller cells. Except for the smallest implementations (such as home or small office networks), Wi-Fi implementations have moved toward "thin" access points, with more of the network intelligence housed in a centralized network appliance, relegating individual access points to the role of "dumb" transceivers. Outdoor applications may use mesh topologies.

Performance

Parabolic dishes transmit and receive the radio waves only in particular directions and can give much greater range than omnidirection antennas
 
Yagi-Uda antennas, widely used for television reception, are relatively compact at Wi-Fi wavelengths
 
Antenna of wireless network interface controller Gigabyte GC-WB867D-I. Simple stick-like antennas like these have unidrectional reception and relatively low range of 20m or so.

Wi-Fi operational range depends on factors such as the frequency band, radio power output, receiver sensitivity, antenna gain and antenna type as well as the modulation technique. In addition, propagation characteristics of the signals can have a big impact.

At longer distances, and with greater signal absorption, speed is usually reduced.

Transmitter power

Compared to cell phones and similar technology, Wi-Fi transmitters are low power devices. In general, the maximum amount of power that a Wi-Fi device can transmit is limited by local regulations, such as FCC Part 15 in the US. Equivalent isotropically radiated power (EIRP) in the European Union is limited to 20 dBm (100 mW).

To reach requirements for wireless LAN applications, Wi-Fi has higher power consumption compared to some other standards designed to support wireless personal area network (PAN) applications. For example, Bluetooth provides a much shorter propagation range between 1 and 100m and so in general have a lower power consumption. Other low-power technologies such as ZigBee have fairly long range, but much lower data rate. The high power consumption of Wi-Fi makes battery life in some mobile devices a concern.

Antenna

An access point compliant with either 802.11b or 802.11g, using the stock omnidirectional antenna might have a range of 100 m (0.062 mi). The same radio with an external semi parabolic antenna (15 dB gain) with a similarly equipped receiver at the far end might have a range over 20 miles.

Higher gain rating (dBi) indicates further deviation (generally toward the horizontal) from a theoretical, perfect isotropic radiator, and therefore the antenna can project or accept a usable signal further in particular directions, as compared to a similar output power on a more isotropic antenna. For example, an 8 dBi antenna used with a 100 mW driver has a similar horizontal range to a 6 dBi antenna being driven at 500 mW. Note that this assumes that radiation in the vertical is lost; this may not be the case in some situations, especially in large buildings or within a waveguide. In the above example, a directional waveguide could cause the low power 6 dBi antenna to project much further in a single direction than the 8 dBi antenna, which is not in a waveguide, even if they are both driven at 100 mW.

On wireless routers with detachable antennas, it is possible to improve range by fitting upgraded antennas that provide higher gain in particular directions. Outdoor ranges can be improved to many kilometres through the use of high gain directional antennas at the router and remote device(s).

MIMO (multiple-input and multiple-output)

This Netgear Wi-Fi router contains dual bands for transmitting the 802.11 standard across the 2.4 and 5 GHz spectrums and supports MIMO.

IEEE 802.11n (Wi-Fi 4) and IEEE 802.11ac (Wi-Fi 5) allow devices to have multiple antennas. Multiple antennas enable the equipment to focus on the far end device, reducing interference in other directions, and giving a stronger useful signal. This greatly increases range and network speed without exceeding the legal power limits. 

IEEE 802.11n can more than double the range. Range also varies with frequency band. Wi-Fi in the 2.4 GHz frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block used by 802.11a (and optionally by 802.11n).

The 802.11ac standard, uses the 5 GHz band exclusively and is capable of multi-station WLAN throughput of at least 1 gigabit per second, and a single station throughput of at least 500 Mbit/s. In the first quarter of 2016, The Wi-Fi Alliance certifies devices compliant with the 802.11ac standard as "Wi-Fi CERTIFIED ac". This standard uses several signal processing techniques such as multi-user MIMO and 4X4 Spatial Multiplexing streams, and large channel bandwidth (160 MHz) to achieve the Gigabit throughput. According to a study by IHS Technology, 70% of all access point sales revenue In the first quarter of 2016 came from 802.11ac devices.

Radio propagation

With Wi-Fi signals line-of-sight usually works best, but signals can transmit, absorb, reflect, and diffract through and around structures, both man made, and natural.

Due to the complex nature of radio propagation at typical Wi-Fi frequencies, particularly around trees and buildings, algorithms can only approximately predict Wi-Fi signal strength for any given area in relation to a transmitter. This effect does not apply equally to long-range Wi-Fi, since longer links typically operate from towers that transmit above the surrounding foliage.

Mobile use of Wi-Fi over wider ranges is limited, for instance, to uses such as in an automobile moving from one hotspot to another. Other wireless technologies are more suitable for communicating with moving vehicles.
Distance records
Distance records (using non-standard devices) include 382 km (237 mi) in June 2007, held by Ermanno Pietrosemoli and EsLaRed of Venezuela, transferring about 3 MB of data between the mountain-tops of El Águila and Platillon. The Swedish Space Agency transferred data 420 km (260 mi), using 6 watt amplifiers to reach an overhead stratospheric balloon.

Interference

Network planning frequency allocations for North America and Europe. Using these types of frequency allocations can help minimize co-channel and adjacent-channel interference.

Wi-Fi connections can be blocked or the Internet speed lowered by having other devices in the same area. Wi-Fi protocols are designed to share the wavebands reasonably fairly, and this often works with little to no disruption. To minimize collisions with Wi-Fi and non Wi-Fi devices, Wi-Fi employs Carrier-sense multiple access with collision avoidance (CSMA/CA), where transmitters listen before transmitting, and delay transmission of packets if they detect that other devices are active on the channel, or if noise is detected from adjacent channels or from non Wi-Fi sources. Nevertheless, Wi-Fi networks are still susceptible to the hidden node and exposed node problem.

A standard speed Wi-Fi signal occupies five channels in the 2.4 GHz band. Interference can be caused by overlapping channels. Any two channel numbers that differ by five or more, such as 2 and 7, do not overlap (no adjacent-channel interference). The oft-repeated adage that channels 1, 6, and 11 are the only non-overlapping channels is, therefore, not accurate. Channels 1, 6, and 11 are the only group of three non-overlapping channels in North America. However, whether the overlap is significant depends on physical spacing. Channels that are four apart interfere a negligible amount-much less than reusing channels (which causes co-channel interference)-if transmitters are at least a few metres apart. In Europe and Japan where channel 13 is available, using Channels 1, 5, 9, and 13 for 802.11g and 802.11n is recommended

However, many 2.4 GHz 802.11b and 802.11g access-points default to the same channel on initial startup, contributing to congestion on certain channels. Wi-Fi pollution, or an excessive number of access points in the area, can prevent access and interfere with other devices' use of other access points as well as with decreased signal-to-noise ratio (SNR) between access points. These issues can become a problem in high-density areas, such as large apartment complexes or office buildings with many Wi-Fi access points. Wi-Fi 6 has greatly improved power control, and suffers less from interference in congested areas.

Other devices use the 2.4 GHz band: microwave ovens, ISM band devices, security cameras, ZigBee devices, Bluetooth devices, video senders, cordless phones, baby monitors, and, in some countries, amateur radio, all of which can cause significant additional interference. It is also an issue when municipalities or other large entities (such as universities) seek to provide large area coverage. On some 5GHz bands interference from radar systems can occur in some places. For base stations that support those bands they employ Dynamic Frequency Selection which listens for radar, and if it is found, will not permit a network on that band.

These bands are can be used by low power transmitters without a license, and with few restrictions. However, while unintended interference is common, users that have been found to cause deliberate interference (particularly for attempting to locally monopolize these bands for commercial purposes) have been issued large fines.

Throughput

Graphical representation of Wi-Fi application specific (UDP) performance envelope 2.4 GHz band, with 802.11g
 
Graphical representation of Wi-Fi application specific (UDP) performance envelope 2.4 GHz band, with 802.11n with 40 MHz
 
Various layer 2 variants of IEEE 802.11 have different characteristics. Across all flavours of 802.11, maximum achievable throughputs are either given based on measurements under ideal conditions or in the layer 2 data rates. This, however, does not apply to typical deployments in which data are transferred between two endpoints of which at least one is typically connected to a wired infrastructure, and the other is connected to an infrastructure via a wireless link.

This means that typically data frames pass an 802.11 (WLAN) medium and are being converted to 802.3 (Ethernet) or vice versa.

Due to the difference in the frame (header) lengths of these two media, the packet size of an application determines the speed of the data transfer. This means that an application that uses small packets (e.g., VoIP) creates a data flow with a high overhead traffic (e.g., a low goodput).

Other factors that contribute to the overall application data rate are the speed with which the application transmits the packets (i.e., the data rate) and the energy with which the wireless signal is received. The latter is determined by distance and by the configured output power of the communicating devices.

The same references apply to the attached throughput graphs, which show measurements of UDP throughput measurements. Each represents an average throughput of 25 measurements (the error bars are there, but barely visible due to the small variation), is with a specific packet size (small or large), and with a specific data rate (10 kbit/s – 100 Mbit/s). Markers for traffic profiles of common applications are included as well. This text and measurements do not cover packet errors but information about this can be found at the above references. The table below shows the maximum achievable (application specific) UDP throughput in the same scenarios (same references again) with various different WLAN (802.11) flavours. The measurement hosts have been 25 metres apart from each other; loss is again ignored.

Hardware

An embedded RouterBoard 112 with U.FL-RSMA pigtail and R52 mini PCI Wi-Fi card widely used by wireless Internet service providers (WISPs) in the Czech Republic
 
OSBRiDGE 3GN – 802.11n Access Point and UMTS/GSM Gateway in one device
 
Wi-Fi allows wireless deployment of local area networks (LANs). Also, spaces where cables cannot be run, such as outdoor areas and historical buildings, can host wireless LANs. However, building walls of certain materials, such as stone with high metal content, can block Wi-Fi signals.

A Wi-Fi device is a short-range wireless device. Wi-Fi devices are fabricated on RF CMOS integrated circuit (RF circuit) chips.

Since the early 2000s, manufacturers are building wireless network adapters into most laptops. The price of chipsets for Wi-Fi continues to drop, making it an economical networking option included in ever more devices.

Different competitive brands of access points and client network-interfaces can inter-operate at a basic level of service. Products designated as "Wi-Fi Certified" by the Wi-Fi Alliance are backward compatible. Unlike mobile phones, any standard Wi-Fi device works anywhere in the world.

Access point

An AirPort wireless G Wi-Fi adapter from an Apple MacBook.
 
A wireless access point (WAP) connects a group of wireless devices to an adjacent wired LAN. An access point resembles a network hub, relaying data between connected wireless devices in addition to a (usually) single connected wired device, most often an Ethernet hub or switch, allowing wireless devices to communicate with other wired devices.

Wireless adapter

Wireless network interface controller Gigabyte GC-WB867D-I.
 
Wireless adapters allow devices to connect to a wireless network. These adapters connect to devices using various external or internal interconnects such as PCI, miniPCI, USB, ExpressCard, Cardbus and PC Card. As of 2010, most newer laptop computers come equipped with built in internal adapters.

Router

Wireless routers integrate a Wireless Access Point, Ethernet switch, and internal router firmware application that provides IP routing, NAT, and DNS forwarding through an integrated WAN-interface. A wireless router allows wired and wireless Ethernet LAN devices to connect to a (usually) single WAN device such as a cable modem, DSL modem or optical modem. A wireless router allows all three devices, mainly the access point and router, to be configured through one central utility. This utility is usually an integrated web server that is accessible to wired and wireless LAN clients and often optionally to WAN clients. This utility may also be an application that is run on a computer, as is the case with as Apple's AirPort, which is managed with the AirPort Utility on macOS and iOS.

Bridge

Wireless network bridges can act to connect two networks to form a single network at the data-link layer over Wi-Fi. The main standard is the wireless distribution system (WDS).

Wireless bridging can connect a wired network to a wireless network. A bridge differs from an access point: an access point typically connects wireless devices to one wired network. Two wireless bridge devices may be used to connect two wired networks over a wireless link, useful in situations where a wired connection may be unavailable, such as between two separate homes or for devices that have no wireless networking capability (but have wired networking capability), such as consumer entertainment devices; alternatively, a wireless bridge can be used to enable a device that supports a wired connection to operate at a wireless networking standard that is faster than supported by the wireless network connectivity feature (external dongle or inbuilt) supported by the device (e.g., enabling Wireless-N speeds (up to the maximum supported speed on the wired Ethernet port on both the bridge and connected devices including the wireless access point) for a device that only supports Wireless-G). A dual-band wireless bridge can also be used to enable 5 GHz wireless network operation on a device that only supports 2.4 GHz wireless and has a wired Ethernet port.

Wireless range-extenders or wireless repeaters can extend the range of an existing wireless network. Strategically placed range-extenders can elongate a signal area or allow for the signal area to reach around barriers such as those pertaining in L-shaped corridors. Wireless devices connected through repeaters suffer from an increased latency for each hop, and there may be a reduction in the maximum available data throughput. In addition, the effect of additional users using a network employing wireless range-extenders is to consume the available bandwidth faster than would be the case whereby a single user migrates around a network employing extenders. For this reason, wireless range-extenders work best in networks supporting low traffic throughput requirements, such as for cases whereby a single user with a Wi-Fi equipped tablet migrates around the combined extended and non-extended portions of the total connected network. Also, a wireless device connected to any of the repeaters in the chain has data throughput limited by the "weakest link" in the chain between the connection origin and connection end. Networks using wireless extenders are more prone to degradation from interference from neighboring access points that border portions of the extended network and that happen to occupy the same channel as the extended network.

Embedded systems

Embedded serial-to-Wi-Fi module
 
The security standard, Wi-Fi Protected Setup, allows embedded devices with limited graphical user interface to connect to the Internet with ease. Wi-Fi Protected Setup has 2 configurations: The Push Button configuration and the PIN configuration. These embedded devices are also called The Internet of Things and are low-power, battery-operated embedded systems. A number of Wi-Fi manufacturers design chips and modules for embedded Wi-Fi, such as GainSpan.

Increasingly in the last few years (particularly as of 2007), embedded Wi-Fi modules have become available that incorporate a real-time operating system and provide a simple means of wirelessly enabling any device that can communicate via a serial port. This allows the design of simple monitoring devices. An example is a portable ECG device monitoring a patient at home. This Wi-Fi-enabled device can communicate via the Internet.

These Wi-Fi modules are designed by OEMs so that implementers need only minimal Wi-Fi knowledge to provide Wi-Fi connectivity for their products.

In June 2014, Texas Instruments introduced the first ARM Cortex-M4 microcontroller with an onboard dedicated Wi-Fi MCU, the SimpleLink CC3200. It makes embedded systems with Wi-Fi connectivity possible to build as single-chip devices, which reduces their cost and minimum size, making it more practical to build wireless-networked controllers into inexpensive ordinary objects.

Network security

The main issue with wireless network security is its simplified access to the network compared to traditional wired networks such as Ethernet. With wired networking, one must either gain access to a building (physically connecting into the internal network), or break through an external firewall. To access Wi-Fi, one must merely be within the range of the Wi-Fi network. Most business networks protect sensitive data and systems by attempting to disallow external access. Enabling wireless connectivity reduces security if the network uses inadequate or no encryption.

An attacker who has gained access to a Wi-Fi network router can initiate a DNS spoofing attack against any other user of the network by forging a response before the queried DNS server has a chance to reply.

Securing methods

A common measure to deter unauthorized users involves hiding the access point's name by disabling the SSID broadcast. While effective against the casual user, it is ineffective as a security method because the SSID is broadcast in the clear in response to a client SSID query. Another method is to only allow computers with known MAC addresses to join the network, but determined eavesdroppers may be able to join the network by spoofing an authorized address.

Wired Equivalent Privacy (WEP) encryption was designed to protect against casual snooping but it is no longer considered secure. Tools such as AirSnort or Aircrack-ng can quickly recover WEP encryption keys. Because of WEP's weakness the Wi-Fi Alliance approved Wi-Fi Protected Access (WPA) which uses TKIP. WPA was specifically designed to work with older equipment usually through a firmware upgrade. Though more secure than WEP, WPA has known vulnerabilities.

The more secure WPA2 using Advanced Encryption Standard was introduced in 2004 and is supported by most new Wi-Fi devices. WPA2 is fully compatible with WPA. In 2017, a flaw in the WPA2 protocol was discovered, allowing a key replay attack, known as KRACK.

A flaw in a feature added to Wi-Fi in 2007, called Wi-Fi Protected Setup (WPS), let WPA and WPA2 security be bypassed, and effectively broken in many situations. The only remedy as of late 2011 was to turn off Wi-Fi Protected Setup, which is not always possible.

Virtual Private Networks can be used to improve the confidentiality of data carried through Wi-Fi networks, especially public Wi-Fi networks.

Data security risks

The older wireless encryption-standard, Wired Equivalent Privacy (WEP), has been shown easily breakable even when correctly configured. Wi-Fi Protected Access (WPA and WPA2) encryption, which became available in devices in 2003, aimed to solve this problem. Wi-Fi access points typically default to an encryption-free (open) mode. Novice users benefit from a zero-configuration device that works out-of-the-box, but this default does not enable any wireless security, providing open wireless access to a LAN. To turn security on requires the user to configure the device, usually via a software graphical user interface (GUI). On unencrypted Wi-Fi networks connecting devices can monitor and record data (including personal information). Such networks can only be secured by using other means of protection, such as a VPN or secure Hypertext Transfer Protocol over Transport Layer Security (HTTPS). 

Wi-Fi Protected Access encryption (WPA2) is considered secure, provided a strong passphrase is used. In 2018, WPA3 was announced as a replacement for WPA2, increasing security; it rolled out on June 26.

Piggybacking

Piggybacking refers to access to a wireless Internet connection by bringing one's own computer within the range of another's wireless connection, and using that service without the subscriber's explicit permission or knowledge.

During the early popular adoption of 802.11, providing open access points for anyone within range to use was encouraged to cultivate wireless community networks, particularly since people on average use only a fraction of their downstream bandwidth at any given time. 

Recreational logging and mapping of other people's access points has become known as wardriving. Indeed, many access points are intentionally installed without security turned on so that they can be used as a free service. Providing access to one's Internet connection in this fashion may breach the Terms of Service or contract with the ISP. These activities do not result in sanctions in most jurisdictions; however, legislation and case law differ considerably across the world. A proposal to leave graffiti describing available services was called warchalking.

Piggybacking often occurs unintentionally – a technically unfamiliar user might not change the default "unsecured" settings to their access point and operating systems can be configured to connect automatically to any available wireless network. A user who happens to start up a laptop in the vicinity of an access point may find the computer has joined the network without any visible indication. Moreover, a user intending to join one network may instead end up on another one if the latter has a stronger signal. In combination with automatic discovery of other network resources (see DHCP and Zeroconf) this could possibly lead wireless users to send sensitive data to the wrong middle-man when seeking a destination (see man-in-the-middle attack). For example, a user could inadvertently use an unsecure network to log into a website, thereby making the login credentials available to anyone listening, if the website uses an unsecure protocol such as plain HTTP without TLS

An unauthorized user can obtain security information (factory preset passphrase and/or Wi-Fi Protected Setup PIN) from a label on a wireless access point can use this information (or connect by the Wi-Fi Protected Setup pushbutton method) to commit unauthorized and/or unlawful activities.

Health concerns

The World Health Organization (WHO) says, "no health effects are expected from exposure to RF fields from base stations and wireless networks", but notes that they promote research into effects from other RF sources. Although the WHO's International Agency for Research on Cancer (IARC) later classified radio-frequency electromagnetic fields (EMFs) as "possibly carcinogenic to humans (Group 2B)" (a category used when "a causal association is considered credible, but when chance, bias or confounding cannot be ruled out with reasonable confidence"), this classification was based on risks associated with wireless phone use rather than Wi-Fi networks.

The United Kingdom's Health Protection Agency reported in 2007 that exposure to Wi-Fi for a year results in the "same amount of radiation from a 20-minute mobile phone call".

A review of studies involving 725 people who claimed electromagnetic hypersensitivity, "...suggests that 'electromagnetic hypersensitivity' is unrelated to the presence of an EMF, although more research into this phenomenon is required."

Alternatives

A number of other "wireless" technologies provide alternatives to Wi-Fi in some cases:
  • Bluetooth, short distance network
  • Bluetooth Low Energy, a low-power variant
  • Zigbee, low-power, low data rate, and close proximity
  • Cellular networks, as used by smartphones
  • WiMax, provide wireless internet connection from outside individual homes
Some alternatives are "no new wires", re-using existing cable:
Several wired technologies for computer networking provide, in some cases, viable alternatives—in particular:

Spinal disc herniation

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