Mobile phone signal

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A display of bars on a mobile phone screen

A mobile phone signal (also known as reception and service) is the

five by five)[1]

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

radio towers
within these areas 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 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

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 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

telephone circuits connecting to and from the general public switched telephone network

Dead zones

Areas where

foliage
, or physical distance.

A number of factors can create dead zones, which may exist even in locations in which a

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

cordless phone, but may not be usable for an MVNO phone. A similar system can be set up to perform inmate call capture,[2] 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 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.

Dropped calls

A dropped call is a common term used and expressed by wireless mobile phone call subscribers when 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

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.[clarification needed
]

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 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 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 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 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.

ASU

Arbitrary Strength Unit (ASU) 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

RSSI (received signal strength indicator, see TS 27.007[3]
sub clause 8.5).

dBm = 2 × ASU - 113, ASU in the range of 0.31 and 99 (for not known or not detectable).

In

RSCP level (received signal code power, see TS 27.007[3]
sub clause 8.69 and TS 25.133 sub clause 9.1.1.3).

dBm = ASU - 115, ASU in the range of 0.90 and 255 (for not known or not detectable).

In

RSRP
(reference signal received power, see TS 36.133, sub-clause 9.1.4). The valid range of ASU is from 0 to 97. For the range 1 to 96, ASU maps to

(ASU - 143) < dBm ≤ (ASU - 140).

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.[4] Tools like Network Signal Info[5] 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 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.[6]

See also

References

  1. ^ Reardon, Marguerite. "5-bar phone signal: What's it get you? (FAQ)". CNet. CNet. Retrieved 19 June 2021.
  2. ^ Putting an end to illegal cell phone use in prisons
  3. ^ a b "3GPP TS 27.007 version 8.5.0 Release 8" (PDF). etsi.org. ETSI. Retrieved 11 June 2014.
  4. ^ "ASU Wert - Signalstärke messen und interpretieren" [ASU parameter - measure and interpret signal strength] (in German). Retrieved 2016-06-29.
  5. ^ "Network Signal Info - Android Apps on Google Play". Retrieved 2016-06-29.
  6. ^ "NeighboringCellInfo - Android Developers". Android Developers.
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