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35-461: The purpose of the guard interval is to introduce immunity to propagation delays , echoes and reflections, to which digital data is normally very sensitive. In OFDM , the beginning of each symbol is preceded by a guard interval. As long as the echoes fall within this interval, they will not affect the receiver's ability to safely decode the actual data, as data is only interpreted outside the guard interval. In TDMA , each user's timeslot ends with

70-400: A 0.4 μs guard interval. This provides an 11% increase in data rate. To increase coverage area, IEEE 802.11ax (Wi-Fi 6) provides optional support for 0.8 μs , 1.6 μs , and 3.2 μs guard intervals. The shorter guard interval results in a higher packet error rate when the delay spread of the channel exceeds the guard interval or if timing synchronization between the transmitter and receiver

105-430: A race condition between two signals derived from a common source but with different delays. In some cases, such as a well-timed synchronous circuit , this could be a harmless and well-tolerated effect that occurs normally in a design. In other contexts, a glitch can represent an undesirable result of a fault or design error that can produce a malfunction. Some electronic components, such as flip-flops , are triggered by

140-912: A water filtration plant in New Canaan, 2010, failures in the Computer Aided Dispatch system used by the police in Austin, resulting in unresponded 911 calls, and an unexpected bit flip causing the Cassini spacecraft to enter "safe mode" in November 2010. Glitches can also be costly: in 2015, a bank was unable to raise interest rates for weeks resulting in losses of more than a million dollars per day. Glitches in video games may include graphical and sound errors, collision detection problems, game crashes, and other issues. Quality assurance (QA) testers are commonly employed throughout

175-412: A 'muff,' 'fluff,' 'bust,' or 'glitch'?" And in a 1948 book called The Advertising and Business Side of Radio , Ned Midgley explained how a radio station's "traffic department" was responsible for properly scheduling items in a broadcast. "Usually most 'glitches,' as on-the-air mistakes are called, can be traced to a mistake on the part of the traffic department", Midgley wrote. In the 1950s, glitch made

210-469: A Wall Street Journal article written by Ben Zimmer, The Yale law librarian Fred Shapiro came up with the new earliest use of the word yet found: May 19, 1940. That was when the novelist Katharine Brush wrote about glitch in her column "Out of My Mind" (syndicated in The Washington Post , The Boston Globe , and other papers). Brush corroborated Tony Randall's radio recollection: When

245-467: A game for fun, using methods such as cartridge tilting to disrupt the data flow. "Glitch hunters" are fans of a game who search for beneficial glitches that will allow them to speedrun the game faster, usually by skipping portions of a level, or quickly defeating enemies. One example of a speedrunning scene with large amounts of glitch hunters is the Souls series . The use of glitches during speedruns

280-634: A guard interval. Thus, the guard interval protects against data loss within the same timeslot, and protects the following user's timeslot from interference caused by propagation delay. It is a common misconception that TDMA timeslots begin with the guard interval, as with OFDM. However, in specifications for TDMA systems such as GSM , the guard period is defined as being at the end of the timeslot. Longer guard periods allow more distant echoes to be tolerated but reduce channel efficiency. For example, in DVB-T , guard intervals are available as 1/32, 1/16, 1/8 or 1/4 of

315-463: A low frequency interference which appears as a narrow horizontal bar moving vertically through the picture". A 1959 article in Sponsor , a trade magazine for television and radio advertisers, gave another technical usage in an article about editing TV commercials by splicing tape. " 'Glitch' is slang for the 'momentary jiggle' that occurs at the editing point if the sync pulses don't match exactly in

350-462: A means to break the fourth wall and either scare the player or put the player at unease, or otherwise as part of the game's narrative. Games like Eternal Darkness and Batman: Arkham Asylum include segments with intentional glitches where it appears that the player's game system has failed. The Animus interface in the Assassin's Creed series, which allows the player-character to experience

385-416: A more serious bug which is a genuine functionality-breaking problem. Alex Pieschel, writing for Arcade Review , said: " 'bug' is often cast as the weightier and more blameworthy pejorative, while 'glitch' suggests something more mysterious and unknowable inflicted by surprise inputs or stuff outside the realm of code". The word itself is sometimes humorously described as being short for "gremlins lurking in

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420-410: A pulse that must not be shorter than a specified minimum duration in order to function correctly; a pulse shorter than the specified minimum may be called a glitch. A related concept is the runt pulse , a pulse whose amplitude is smaller than the minimum level specified for correct operation, and a spike , a short pulse similar to a glitch but often caused by ringing or crosstalk . A computer glitch

455-410: A slight glitch". The astronaut John Glenn explained the term in his section of the book Into Orbit , writing that Another term we adopted to describe some of our problems was "glitch". Literally, a glitch is a spike or change in voltage in an electrical circuit which takes place when the circuit suddenly has a new load put on it. You have probably noticed a dimming of lights in your home when you turn

490-564: A switch or start the dryer or the television set. Normally, these changes in voltage are protected by fuses. A glitch, however, is such a minute change in voltage that no fuse could protect against it. John Daly further defined the word on the July 4, 1965, episode of What's My Line , saying that it's a term used by the Air Force at Cape Kennedy, in the process of launching rockets, "it means something's gone wrong and you can't figure out what it

525-459: A symbol period. The shortest interval (1/32) provides the lowest protection and the highest data rate; the longest interval (1/4) provides the highest protection but the lowest data rate. Ideally, the guard interval is set to just above the delay spread of the channel. The standard symbol guard interval used in IEEE 802.11 OFDM is 0.8 μs . To increase data rate, 802.11n added optional support for

560-435: Is a controversial topic, with some frowning upon their use as subverting the intent of the developers. Those in favor of glitch use believe that using the glitches can in itself take a great deal of skill. Multiple categories of speedruns exist, with "any%" allowing the use of any type of glitch, while "glitchless" indicates the speedrun was performed without them. Some games purposely include effects that look like glitches as

595-427: Is a short-lived technical fault , such as a transient one that corrects itself, making it difficult to troubleshoot. The term is particularly common in the computing and electronics industries, in circuit bending , as well as among players of video games . More generally, all types of systems including human organizations and nature experience glitches. A glitch, which is slight and often temporary, differs from

630-520: Is not precise. A scheme could be developed to work out whether a short guard interval would be of benefit to a particular link. To reduce complexity, manufacturers typically only implement a short guard interval as a final rate adaptation step when the device is running at its highest data rate. Propagation delay Propagation delay is the time duration taken for a signal to reach its destination. It can relate to networking , electronics or physics . In computer networks , propagation delay

665-501: Is so you call it a 'glitch'". Later, on July 23, 1965, Time magazine felt it necessary to define it in an article: "Glitches—a spaceman's word for irritating disturbances". In relation to the reference by Time , the term has been believed to enter common usage during the American Space Race of the 1950s, where it was used to describe minor faults in the rocket hardware that were difficult to pinpoint. According to

700-459: Is the amount of time it takes for the head of the signal to travel from the sender to the receiver. It can be computed as the ratio between the link length and the propagation speed over the specific medium. Propagation delay is equal to d / s where d is the distance and s is the wave propagation speed . In wireless communication, s = c , i.e. the speed of light . In copper wire , the speed s generally ranges from .59c to .77c. This delay

735-403: Is the failure of a system, usually containing a computing device, to complete its functions or to perform them properly. It frequently refers to an error which is not detected at the time it occurs but shows up later in data errors or incorrect human decisions. Situations which are frequently called computer glitches are incorrectly written software ( software bugs ), incorrect instructions given by

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770-511: Is the major obstacle in the development of high-speed computers and is called the interconnect bottleneck in IC systems. In electronics , digital circuits and digital electronics , the propagation delay, or gate delay , is the length of time which starts when the input to a logic gate becomes stable and valid to change, to the time that the output of that logic gate is stable and valid to change. Often on manufacturers' datasheets this refers to

805-470: The R factor, and supply threshold voltage increases will affect whether more than one time constants are required to reach the threshold. If the output of a logic gate is connected to a long trace or used to drive many other gates (high fanout ) the propagation delay increases substantially. Wires have an approximate propagation delay of 1 ns for every 6 inches (15 cm) of length. Logic gates can have propagation delays ranging from more than 10 ns down to

840-706: The computer hardware". Some reference books, including Random House's American Slang , claim that the term comes from the German word glitschen ' to slip ' and the Yiddish word glitshn ' to slide, to skid ' . Either way, it is a relatively new term. It was first widely defined for the American people by Bennett Cerf on the June 20, 1965, episode of What's My Line as "a kink ... when anything goes wrong down there [Cape Kennedy], they say there's been

875-457: The development process to find and report glitches to the programmers to be fixed, then potentially start over with a new build of the game. If insufficient bug fixes are performed, numerous glitches and bugs can make their way to the final product. Bethesda Softworks , for example, is notorious for the amount of glitches in their games, though some players even prefer them to a glitch-free experience. Some players may seek to induce glitches in

910-399: The memories of an ancestor though their genetic heritage, includes occasional glitches as to enforce the idea that the game is what the player-character is witnessing through a computer-aided system. In broadcasting, a corrupted signal may glitch in the form of jagged lines on the screen, misplaced squares, static looking effects, freezing problems, or inverted colors. The glitches may affect

945-621: The operator ( operator errors , and a failure to account for this possibility might also be considered a software bug), undetected invalid input data (this might also be considered a software bug), undetected communications errors, computer viruses , Trojan attacks and computer exploiting (sometimes called "hacking"). Such glitches could produce problems such as keyboard malfunction, number key failures, screen abnormalities (turned left, right or upside-down), random program malfunctions, and abnormal program registering. Examples of computer glitches causing disruption include an unexpected shutdown of

980-412: The picosecond range, depending on the technology being used. In physics , particularly in the electromagnetic field, the propagation delay is the length of time it takes for a signal to travel to its destination. For example, in the case of an electric signal, it is the time taken for the signal to travel through a wire. See also velocity factor and radio propagation . Glitch A glitch

1015-431: The propagation delay of a combined circuit requires identifying the longest path of propagation delays from input to output and by adding each propagation delay along this path. The difference in propagation delays of logic elements is the major contributor to glitches in asynchronous circuits as a result of race conditions . The principle of logical effort utilizes propagation delays to compare designs implementing

1050-439: The radio talkers make a little mistake in diction they call it a "fluff," and when they make a bad one they call it a "glitch," and I love it. Other examples from the world of radio can be found in the 1940s. The April 11, 1943, issue of The Washington Post carried a review of Helen Sioussat 's book about radio broadcasting, Mikes Don't Bite . The reviewer noted an error and wrote, "In the lingo of radio, has Miss Sioussat pulled

1085-439: The same logical statement. Propagation delay may increases/decrease with operating temperature depending the device type. For FinFET transistors for example due Inverse Temperature Depedance, gate delay decreases as the temperature increases however for metal wires the delay increases as resistance of conductive materials tends to increase with temperature. Marginal increases in supply voltage can increase propagation delay since

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1120-428: The splice". It also provided one of the earliest etymologies of the word, noting that, " 'Glitch' probably comes from a German or Yiddish word meaning a slide, a glide or a slip". An electronics glitch or logic hazard is a transition that occurs on a signal before the signal settles to its intended value, particularly in a digital circuit . Generally, this implies an electrical pulse of short duration, often due to

1155-426: The time required for the output to reach 50% of its final output level from when the input changes to 50% of its final input level. This may depend on the direction of the level change, in which case separate fall and rise delays t PHL and t PLH or t f and t r are given. Reducing gate delays in digital circuits allows them to process data at a faster rate and improve overall performance. The determination of

1190-510: The transition from radio to television. In a 1953 ad in Broadcasting magazine, RCA boasted that their TV camera has "no more a-c power line 'glitches' (horizontal-bar interference)". And Bell Telephone ran an ad in a 1955 issue of Billboard showing two technicians monitoring the TV signals that were broadcast on Bell System lines: "When he talks of 'glitch' with a fellow technician, he means

1225-425: The upper switching threshold voltage, V IH (often expressed as a percentage of the high-voltage supply rail), naturally increases proportionately. Increases in output load capacitance, often from placing increased fan-out loads on a wire, will also increase propagation delay. All of these factors influence each other through an RC time constant : any increase in load capacitance increases C, heat-induced resistance

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