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43-453: (Redirected from Dead Zone ) [REDACTED] Look up dead zone in Wiktionary, the free dictionary. Dead zone may refer to: Science and technology [ edit ] Dead zone (cell phone) , an area where cell phones cannot transmit to a nearby cell site Dead zone (ecology) , low-oxygen areas in the world's oceans Dead band ,

86-510: A wireless carrier offers coverage, due to limitations in cellular network architecture (the locations of antennas), limited network density, interference with other mobile sites, and topography. Since cell phones rely on radio waves , which travel through the air and are easily attenuated (particularly at higher frequencies), mobile phones may be unreliable at times. Like other radio transmissions, mobile phone calls can be interrupted by large buildings , terrain, trees, or other objects between

129-455: A call is abruptly cut-off (disconnected) during midconversation. This happens less often today than it would have in the early 1990s. The termination occurs unexpectedly and is influenced by a number of different reasons such as "Dead Zones." In technical circles, it is called an abnormal release . One reason for a call to be "dropped" is if the mobile phone subscriber travels outside the coverage area—the cellular network radio tower(s). After

172-478: A common cause of dropped calls. Another problem may be a faulty transceiver inside the base station. Calls can also be dropped if a mobile phone at the other end of the call loses battery power and stops transmitting abruptly. Sunspots and solar flares are rarely blamed for causing interference leading to dropped calls, as it would take a major geomagnetic storm to cause such a disruption (except for satellite phones ). Experiencing too many dropped calls

215-440: A delay. In radar processing, multipath causes ghost targets to appear, deceiving the radar receiver . These ghosts are particularly bothersome since they move and behave like the normal targets (which they echo), and so the receiver has difficulty in isolating the correct target echo. These problems can be minimized by incorporating a ground map of the radar's surroundings and eliminating all echoes which appear to originate below

258-527: A film based on the Stephen King novel starring Christopher Walken Dragon Ball Z: Dead Zone , the first of thirteen Dragon Ball Z films Whisper of Dead Zone , the translated English title of the 2012 Turkish film Ölü Bölgeden Fısıltılar . Television [ edit ] The Dead Zone (TV series) , a television series based on the Stephen King novel, starring Anthony Michael Hall Sports [ edit ] Dead zone (gridiron football) ,

301-441: A foreign cell site that is known to frequently cause such issues for their customers. The volume of network traffic can also cause calls to be blocked or dropped due to a disaster or other mass call event which overloads the number of available radio channels in an area, or the number of telephone circuits connecting to and from the general public switched telephone network . Areas where mobile phones cannot transmit to

344-481: A nearby mobile site , base station , or repeater are known as dead zones . In these areas, the mobile phone is said to be in a state of outage. Dead zones are usually areas where mobile phone service is not available because the signal between the handset and mobile site antennas is blocked or severely reduced , usually by hilly terrain , dense foliage , or physical distance. A number of factors can create dead zones, which may exist even in locations in which

387-517: A stationary receiver's output to indicate as if it were randomly jumping about or creeping. When the unit is moving the jumping or creeping may be hidden, but it still degrades the displayed accuracy of location and speed. Multipath propagation is similar in power line communication and in telephone local loops . In either case, impedance mismatch causes signal reflection . High-speed power line communication systems usually employ multi-carrier modulations (such as OFDM or wavelet OFDM) to avoid

430-456: A technical term in American and Canadian football Other uses [ edit ] Death zone , high altitudes where the amount of oxygen is insufficient to sustain human life Dead zone (military) , a blind spot in a fortification 's field of fire which is relatively sheltered from defensive fire. See also [ edit ] The Dead Zone (disambiguation) Topics referred to by

473-417: A telephone connection between two subscribers has been completed, both the tower and the mobile phone must remain within range of that subscribers network provider or that connection will be lost (dropped). Not all cellular telephone radio towers are owned by the same telephone company (though this is not true to all locations) be maintained across a different company's network (as calls cannot be re-routed over

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516-615: Is a signalling message used in handover procedures of UMTS and CDMA mobile telephony standards. On Android phones, the acronym ASU has nothing to do with Active Set Update. It has not been declared precisely by Google developers. Multipath interference In radio communication , multipath is the propagation phenomenon that results in radio signals reaching the receiving antenna by two or more paths. Causes of multipath include atmospheric ducting , ionospheric reflection and refraction , and reflection from water bodies and terrestrial objects such as mountains and buildings. When

559-817: Is also common in other VHF radio bands including FM broadcasting , may also cause other anomalies, such as a person in San Diego "roaming" on a Mexican tower from just over the border in Tijuana , or someone in Detroit "roaming" on a Canadian tower located within sight across the Detroit River in Windsor, Ontario . These events may cause the user to be billed for "international" usage despite being in their own country, though mobile phone companies can program their billing systems to re-rate these as domestic usage when it occurs on

602-701: Is an integer value indicating the received signal strength measured by the mobile phone. It is possible to calculate the real signal strength measured in dBm (and thereby power in Watts) by a formula. However, there are different formulas for 2G, 3G and 4G networks. In GSM networks, ASU maps to RSSI (received signal strength indicator, see TS 27.007 sub clause 8.5). In UMTS networks, ASU maps to RSCP level (received signal code power, see TS 27.007 sub clause 8.69 and TS 25.133 sub clause 9.1.1.3). In LTE networks, ASU maps to RSRP (reference signal received power, see TS 36.133, sub-clause 9.1.4). The valid range of ASU

645-403: Is different from Wikidata All article disambiguation pages All disambiguation pages Dead zone (cell phone) Generally, a strong mobile phone signal is more likely in an urban area, though these areas can also have some "dead zones", where no reception can be obtained. Cellular signals are designed to be resistant to multipath reception, which is most likely to be caused by

688-410: Is from 0 to 97. For the range 1 to 96, ASU maps to The value of 0 maps to RSRP below -140 dBm and the value of 97 maps to RSRP above -44 dBm. On Android devices however, the original GSM formula may prevail for UMTS. Tools like Network Signal Info can directly show the signal strength (in dBm), as well as the underlying ASU. ASU shouldn't be confused with "Active Set Update". The Active Set Update

731-564: Is normally prohibited or strictly regulated, and is often difficult to arrange. In areas where signal reception would normally be strong, other factors can have an effect on reception or may cause complete failure (see RF interference). From inside a building with thick walls or of mostly metal construction (or with dense rebar in concrete ), signal attenuation may prevent a mobile phone from being used. Underground areas, such as tunnels and subway stations , will lack reception unless they are wired for cell signals. There may also be gaps where

774-462: Is not "aware" of the cell to which the phone is trying to handoff. If the phone cannot find an alternative cell to which to move that can take over the call, the call is lost. Co-channel and adjacent-channel interference can also be responsible for dropped calls in a wireless network. Neighbouring cells with the same frequencies interfere with each other, deteriorating the quality of service and producing dropped calls. Transmission problems are also

817-520: Is one of the most common customer complaints received by wireless service providers . They have attempted to address the complaint in various ways, including expansion of their home network coverage, increased cell capacity, and offering refunds for individual dropped calls. Various signal booster systems are manufactured to reduce problems due to dropped calls and dead zones. Many options, such as wireless units and antennas, are intended to aid in strengthening weak signals. Arbitrary Strength Unit (ASU)

860-441: Is that the components of the wave remain coherent throughout the whole extent of their travel. The interference will arise owing to the two (or more) components of the wave having, in general, travelled a different length (as measured by optical path length – geometric length and refraction (differing optical speed)), and thus arriving at the detector out of phase with each other. The signal due to indirect paths interferes with

903-425: Is time varying, and as such we have Very often, just one parameter is used to denote the severity of multipath conditions: it is called the multipath time , T M {\displaystyle T_{M}} , and it is defined as the time delay existing between the first and the last received impulses In practical conditions and measurement, the multipath time is computed by considering as last impulse

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946-422: The complex amplitude (i.e., magnitude and phase) of the generic received pulse. As a consequence, y ( t ) {\displaystyle y(t)} also represents the impulse response function h ( t ) {\displaystyle h(t)} of the equivalent multipath model. More in general, in presence of time variation of the geometrical reflection conditions, this impulse response

989-622: The intersymbol interference that multipath propagation would cause. The ITU-T G.hn standard provides a way to create a high-speed (up to 1 gigabit per second) local area network using existing home wiring ( power lines , phone lines, and coaxial cables ). G.hn uses OFDM with a cyclic prefix to avoid ISI. Because multipath propagation behaves differently in each kind of wire, G.hn uses different OFDM parameters (OFDM symbol duration, guard interval duration) for each media. DSL modems also use orthogonal frequency-division multiplexing to communicate with their DSLAM despite multipath. In this case

1032-426: The service contours of the individual base stations (Cell towers) of the mobile provider (and/or its roaming partners) do not completely overlap. In addition, the weather may affect the strength of a signal, due to the changes in radio propagation caused by clouds (particularly tall and dense thunderclouds which cause signal reflection ), precipitation , and temperature inversions . This phenomenon, which

1075-510: The blocking of a direct signal path by large buildings, such as high-rise towers. By contrast, many rural or sparsely inhabited areas lack any signal or have very weak fringe reception ; many mobile phone providers are attempting to set up towers in those areas most likely to be occupied by users, such as along major highways . Even some national parks and other popular tourist destinations away from urban areas now have cell phone reception, though location of radio towers within these areas

1118-418: The coverage area. Occasionally, calls are dropped upon handoff between cells within the same provider's network. This may be due to an imbalance of traffic between the two cell sites ' areas of coverage. If the new cell site is at capacity, it cannot accept the additional traffic of the call trying to "hand in." It may also be due to the network configuration not being set up properly, such that one cell site

1161-588: The distance (in Hz) between two consecutive valleys (or two consecutive peaks), is roughly inversely proportional to the multipath time. The so-called coherence bandwidth is thus defined as For example, with a multipath time of 3 μs (corresponding to a 1 km of added on-air travel for the last received impulse), there is a coherence bandwidth of about 330 kHz. [REDACTED]  This article incorporates public domain material from Federal Standard 1037C . General Services Administration . Archived from

1204-413: The first one which allows receiving a determined amount of the total transmitted power (scaled by the atmospheric and propagation losses), e.g. 99%. Keeping our aim at linear, time invariant systems, we can also characterize the multipath phenomenon by the channel transfer function H ( f ) {\displaystyle H(f)} , which is defined as the continuous time Fourier transform of

1247-501: The ground or above a certain height (altitude). In digital radio communications (such as GSM ) multipath can cause errors and affect the quality of communications. The errors are due to intersymbol interference (ISI). Equalizers are often used to correct the ISI. Alternatively, techniques such as orthogonal frequency division modulation and rake receivers may be used. In a Global Positioning System receiver , multipath effects can cause

1290-514: The impulse response h ( t ) {\displaystyle h(t)} where the last right-hand term of the previous equation is easily obtained by remembering that the Fourier transform of a Dirac pulse is a complex exponential function, an eigenfunction of every linear system. The obtained channel transfer characteristic has a typical appearance of a sequence of peaks and valleys (also called notches ); it can be shown that, on average,

1333-534: The larger network. Personal microcells, such as those for a home , are called femtocells , and generally have the range of a cordless phone , but may not be usable for an MVNO phone. A similar system can be set up to perform inmate call capture, which prevents cellphones smuggled into a prison from being used. These still complete calls to or from pre-authorized users such as prison staff, while not violating laws against jamming . These systems must be carefully designed so as to avoid capturing calls from outside

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1376-600: The light takes 3 μs to cross a 1 km span). Thus, the received signal will be expressed by where N {\displaystyle N} is the number of received impulses (equivalent to the number of electromagnetic paths, and possibly very large), τ n {\displaystyle \tau _{n}} is the time delay of the generic n t h {\displaystyle n^{th}} impulse, and ρ n e j ϕ n {\displaystyle \rho _{n}e^{j\phi _{n}}} represent

1419-799: The phone and the nearest base. Cellular network providers work continually to improve and upgrade their networks in order to minimize dropped calls , access failures, and dead zones (which they call "coverage holes" or "no-service areas"). For mobile virtual network operators , the network quality depends entirely on the host network for the particular handset in question. Some MVNOs use more than one host, which may even have different technologies (for example, different Starlink , Spectrum (brand) and TracFone handsets use either CDMA and 1xRTT on Verizon Wireless , or GSM and UMTS on AT&T Mobility or GSM and UMTS on T-Mobile US ). Dead zones can be filled-in with microcells , while picocells can handle even smaller areas without causing interference to

1462-449: The prison, which would in effect create a dead zone for any passersby outside. In the event of a disaster causing temporary dead zones, a cell on wheels may be brought in until the local telecom infrastructure can be restored. These portable units are also used where large gatherings are expected, in order to handle the extra load. A dropped call is a common term used and expressed by wireless mobile phone call subscribers when

1505-406: The receiver, due to the presence of the multiple electromagnetic paths, more than one pulse will be received, and each one of them will arrive at different times. In fact, since the electromagnetic signals travel at the speed of light , and since every path has a geometrical length possibly different from that of the other ones, there are different air travelling times (consider that, in free space ,

1548-434: The reflections may be caused by mixed wire gauges , but those from bridge taps are usually more intense and complex. Where OFDM training is unsatisfactory, bridge taps may be removed. The mathematical model of the multipath can be presented using the method of the impulse response used for studying linear systems . Suppose you want to transmit a single, ideal Dirac pulse of electromagnetic power at time 0, i.e. At

1591-454: The region of insensitivity of a system Arts and entertainment [ edit ] Games [ edit ] Dead Zone (video game) , a video game produced by SunSoft Dead zone (video gaming) , term for a region of the screen in video gaming Deadzone (Skirmish Game) , by Mantic Games Literature [ edit ] The Dead Zone (novel) , a novel by Stephen King Film [ edit ] The Dead Zone (film) ,

1634-438: The required signal in amplitude as well as phase which is called multipath fading. In analog facsimile and television transmission , multipath causes jitter and ghosting, seen as a faded duplicate image to the right of the main image. Ghosts occur when transmissions bounce off a mountain or other large object, while also arriving at the antenna by a shorter, direct route, with the receiver picking up two signals separated by

1677-400: The same signal is received over more than one path, it can create interference and phase shifting of the signal. Destructive interference causes fading ; this may cause a radio signal to become too weak in certain areas to be received adequately. For this reason, this effect is also known as multipath interference or multipath distortion . Where the magnitudes of the signals arriving by

1720-415: The same term [REDACTED] This disambiguation page lists articles associated with the title Dead zone . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Dead_zone&oldid=1257185428 " Category : Disambiguation pages Hidden categories: Short description

1763-404: The traditional phone network while in progress), also resulting in the termination of the call once a signal cannot be maintained between the phone and the original network. Another common reason is when a phone is taken into an area where wireless communication is unavailable, interrupted, interfered with, or jammed . From the network's perspective, this is the same as the mobile moving out of

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1806-399: The underlying physics. Multipath interference is a phenomenon in the physics of waves whereby a wave from a source travels to a detector via two or more paths and the two (or more) components of the wave interfere constructively or destructively. Multipath interference is a common cause of " ghosting " in analog television broadcasts and of fading of radio waves . The condition necessary

1849-598: The various paths have a distribution known as the Rayleigh distribution , this is known as Rayleigh fading . Where one component (often, but not necessarily, a line of sight component) dominates, a Rician distribution provides a more accurate model, and this is known as Rician fading . Where two components dominate, the behavior is best modeled with the two-wave with diffuse power (TWDP) distribution. All of these descriptions are commonly used and accepted and lead to results. However, they are generic and abstract/hide/approximate

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