Mobile phone signal - AbsoluteAstronomy.com

A mobile phone signal is the strength

Signal strength

In telecommunications, particularly in radio, signal strength refers to the magnitude of the electric field at a reference point that is a significant distance from the transmitting antenna. It may also be referred to as received signal level or field strength. Typically, it is expressed in...

(measured in dBm) of the connection to the mobile phone

Mobile phone

A mobile phone is a device which can make and receive telephone calls over a radio link whilst moving around a wide geographic area. It does so by connecting to a cellular network provided by a mobile network operator...

with its network. Depending on various factors, such as proximity to a tower

Cell site

A cell site is a term used to describe a site where antennas and electronic communications equipment are placed, usually on a radio mast, tower or other high place, to create a cell in a cellular network...

, obstructions such as buildings or trees, etc, the signal may vary. Most mobile devices use a set of bars of varying heights to display the strength of the signal where the device is located. Traditionally five bars are used; see five by five

Five by five

Five by five is the best of 25 possible subjective responses used to describe the quality of communications, specifically the signal-to-noise ratio. As receiving stations move away from an analog radio transmitting site, the signal strength decreases gradually while noise levels increase...

.

Generally, a stronger mobile phone signal is easier to obtain in an urban area, though urban areas do have some "dead zones" where a reception cannot be obtained. On the contrary, many rural or minimally inhabited areas lack a signal or have a very weak reception, but many mobile phone providers are attempting to set up towers in parts of these areas most likely to be occupied by users, such as along major highways. Even some national park

National park

A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or owns. Although individual nations designate their own national parks differently A national park is a reserve of natural, semi-natural, or developed land that a sovereign state declares or...

s and other popular tourist destinations away from urban areas now have cell phone receptions.

In an area where the signal would normally be strong, certain other factors may have an effect on the reception, thereby making it either stronger or weaker, or may cause complete interference. For example, a building with thick walls may prevent a mobile phone from being used. Many underground areas, such as tunnel

Tunnel

A tunnel is an underground passageway, completely enclosed except for openings for egress, commonly at each end.A tunnel may be for foot or vehicular road traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers...

s and subway stations

Metro station

A metro station or subway station is a railway station for a rapid transit system, often known by names such as "metro", "underground" and "subway". It is often underground or elevated. At crossings of metro lines, they are multi-level....

, lack a reception. Additionally, the weather

Weather

Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

and volume of network traffic may impact the strength.

Dead zones

Areas where cell phones cannot transmit to a nearby cell site

Cell site

, base station

Base station

The term base station can be used in the context of land surveying and wireless communications.- Land surveying :In the context of external land surveying, a base station is a GPS receiver at an accurately-known fixed location which is used to derive correction information for nearby portable GPS...

, or repeater

Repeater

A repeater is an electronic device that receives asignal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances.-Description:...

are known as dead zones. In these areas, the cell phone is said to be in a state of outage

Outage

Outage may refer to:* Network outage* Sun outage* Power outage* Outing...

. Dead zones are usually areas where cell phone service is not available because the signal between the handset

Handset

On a telephone, the handset is a device the user holds to the ear to hear the audio sound. Modern-day handsets usually contain the phone's microphone as well, but in early telephones the microphone was mounted directly on the telephone itself, which often was attached to a wall at a convenient...

and the cell site antenna

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

is blocked, usually by hilly terrain, excessive foliage, physical distance, or tall buildings.

A number of factors can create dead zones which may exist even in locations in which a wireless carrier offers coverage, due to limitations in cellular network

Cellular network

A cellular network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver known as a cell site or base station. When joined together these cells provide radio coverage over a wide geographic area...

architecture (the locations of antennas

Antenna (radio)

An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...

), limited network density, interference with other cell sites, and topography. Since cell phones rely on radio waves

Radio waves

Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Radio waves have frequencies from 300 GHz to as low as 3 kHz, and corresponding wavelengths from 1 millimeter to 100 kilometers. Like all other electromagnetic waves,...

, and radio waves travel though the air and are easily attenuated, cell phones may be unreliable at times. Like other radio transmissions, cell phone calls can be interrupted by large buildings, terrain, trees, or other objects between the phone and the nearest base station antennas.

Many wireless service 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").

Dropped calls

Dropped call is the common term for a wireless

Wireless

Wireless telecommunications is the transfer of information between two or more points that are not physically connected. Distances can be short, such as a few meters for television remote control, or as far as thousands or even millions of kilometers for deep-space radio communications...

mobile phone

Mobile phone

call

Telephone call

A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...

that is terminated unexpectedly as a result of technical reasons, including presence in a dead zone.

One reason for a dropped call is when the mobile phone moves out of range of a wireless network

Cellular network

. An active call cannot usually be maintained across a different company's network (as calls cannot be re-routed over the traditional phone network while in progress), 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 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 site

Cell site

s' 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. Neighbour 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 (XCVR) inside the base station.

Calls can also be dropped if a mobile phone at the other end of the call loses battery

Battery (electricity)

An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...

power and stops transmitting abruptly.

Sun spots and solar flares are rarely blamed for causing interference leading to dropped calls.

Experiencing too many dropped calls is one of the most common customer complaints received by wireless service providers

Mobile network operator

A mobile network operator , also known as mobile phone operator , carrier service provider , wireless service provider, wireless carrier, or cellular company, or mobile network carrier is a telephone company that provides services for mobile phone subscribers.One essential...

. 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

Cellular repeater

A cellular repeater, cell phone repeater, or wireless cellular signal booster, a type of bi-directional amplifier as commonly named in the wireless telecommunications industry, is a device used for boosting the cell phone reception to the local area by the usage of a reception antenna, a signal...

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

ASU or Active Set Update is an integer value proportional to 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 and 3G networks.

In GSM networks, ASU is equal to the RSSI

RSSI

In telecommunications, received signal strength indicator is a measurement of the power present in a received radio signal.RSSI is a generic radio receiver technology metric, which is usually invisible to the user of the device containing the receiver, but is directly known to users of wireless...

(received signal strength indicator, see TS 27.007).
dBm = 2*ASU - 113, ASU in the range of 0..31 and 99
In UMTS networks, ASU is equal the RSCP

RSCP

In the UMTS cellular communication system, received signal code power denotes the power measured by a receiver on a particular physical communication channel. It is used as an indication of signal strength, as a handover criterion, in downlink power control, and to calculate path loss...

level (received signal control power, see TS 25.125)
dBm = ASU - 116, ASU in the range of -5..91
Although the mobile standards define an ASU message ("Active Set Update") used in handover procedures, on Android phones the acronym ASU has nothing to do with Active Set Update. It has not been declared precisely by Google developers, but it is believed to mean "Arbitrary Scale Unit" or "Android Signal Unit". (see NeighboringCellInfo)

Dead zones

Dropped calls

ASU

See also