Signal Strength In Telecommunications
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In
telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
, particularly in
radio frequency engineering Radio-frequency (RF) engineering is a subset of electronic engineering involving the application of transmission line, Waveguide (electromagnetism), waveguide, Antenna (radio), antenna and Electromagnetic radiation, electromagnetic field princip ...
, signal strength refers to the
transmitter power output In radio transmission, transmitter power output (TPO) is the actual amount of power (in watts) of radio frequency (RF) energy that a transmitter produces at its output. This is not the amount of power that a radio station reports as its power, as i ...
as received by a reference antenna at a distance from the transmitting antenna. High-powered transmissions, such as those used in
broadcasting Broadcasting is the distribution (business), distribution of sound, audio or video content to a dispersed audience via any electronic medium (communication), mass communications medium, but typically one using the electromagnetic spectrum (radio ...
, are expressed in dB-
millivolt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defini ...
s per metre (dBmV/m). For very low-power systems, such as
mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...
s, signal strength is usually expressed in dB-
microvolt The volt (symbol: V) is the unit of electric potential, electric potential difference (voltage), and electromotive force in the International System of Units (SI). It is named after the Italian physicist Alessandro Volta (1745–1827). Defi ...
s per metre (dBμV/m) or in
decibel The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a po ...
s above a reference level of one
milliwatt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
(
dBm DBM or dbm may refer to: Science and technology * dBm, a unit for power measurement * DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB * Database Manager (DBM), a component of 1987's ''Extended Edi ...
). In broadcasting terminology, 1 mV/m is 1000 μV/m or 60 dBμ (often written dBu). ;Examples: *100 dBμ or 100 mV/m: blanketing interference may occur on some receivers *60 dBμ or 1.0 mV/m: frequently considered the edge of a
radio station Radio broadcasting is transmission of audio (sound), sometimes with related metadata, by radio waves to radio receivers belonging to a public audience. In terrestrial radio broadcasting the radio waves are broadcast by a land-based radio ...
's protected area in North America *40 dBμ or 0.1 mV/m: the minimum strength at which a station can be received with acceptable quality on most receivers


Relationship to average radiated power

The electric
field strength In physics, field strength means the ''magnitude'' of a vector-valued field (e.g., in volts per meter, V/m, for an electric field ''E''). For example, an electromagnetic field results in both electric field strength and magnetic field strength ...
at a specific point can be determined from the power delivered to the transmitting antenna, its geometry and radiation resistance. Consider the case of a center-fed half-wave
dipole antenna In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole w ...
in
free space A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists often dis ...
, where the total length L is equal to one half wavelength (λ/2). If constructed from thin conductors, the current distribution is essentially sinusoidal and the radiating electric field is given by : E_\theta (r) = e^ where \scriptstyle is the angle between the antenna axis and the vector to the observation point, \scriptstyle is the peak current at the feed-point, \scriptstyle is the permittivity of free-space, \scriptstyle is the speed of light in a vacuum, and \scriptstyle is the distance to the antenna in meters. When the antenna is viewed broadside (\scriptstyle) the electric field is maximum and given by : \vert E_(r) \vert = \, . Solving this formula for the peak current yields : I_\circ = 2\pi\varepsilon_0 c \, r\vert E_(r) \vert \, . The average power to the antenna is : where \scriptstyle is the center-fed half-wave antenna's radiation resistance. Substituting the formula for \scriptstyle into the one for \scriptstyle and solving for the maximum electric field yields : \vert E_(r)\vert \, = \, \sqrt \, = \, \sqrt \quad (L = \lambda /2) \, . Therefore, if the average power to a half-wave dipole antenna is 1 mW, then the maximum electric field at 313 m (1027 ft) is 1 mV/m (60 dBμ). For a short dipole (\scriptstyle) the current distribution is nearly triangular. In this case, the electric field and radiation resistance are : E_\theta (r) = \left ( \right ) e^ \, , \quad R_a = 20\pi^2 \left ( \right )^2 . Using a procedure similar to that above, the maximum electric field for a center-fed short dipole is : \vert E_(r)\vert \, = \, \sqrt \, = \, \sqrt \quad (L \ll \lambda /2)\, .


RF signals

Although there are cell phone base station tower networks across many nations globally, there are still many areas within those nations that do not have good reception. Some rural areas are unlikely to ever be covered effectively since the cost of erecting a cell tower is too high for only a few customers. Even in areas with high signal strength, basements and the interiors of large buildings often have poor reception. Weak signal strength can also be caused by
destructive interference In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive ...
of the signals from local towers in urban areas, or by the construction materials used in some buildings causing significant attenuation of signal strength. Large buildings such as warehouses, hospitals and factories often have no usable signal further than a few metres from the outside walls. This is particularly true for the networks which operate at higher
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
since these are attenuated more by intervening obstacles, although they are able to use
reflection Reflection or reflexion may refer to: Science and technology * Reflection (physics), a common wave phenomenon ** Specular reflection, reflection from a smooth surface *** Mirror image, a reflection in a mirror or in water ** Signal reflection, in ...
and
diffraction Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...
to circumvent obstacles.


Estimated received signal strength

The estimated received signal strength in an active
RFID tag Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver and transmitter. When triggered by an electromagn ...
can be estimated as follows: :\mathrm = -43.0 - 40.0\ \log_\left( \frac\right) In general, you can take the path loss exponent into account: :\mathrm = -43.0 - 10.0 \ \gamma \ \log_\left( \frac\right) The effective
path loss Path loss, or path attenuation, is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. Path loss is a major component in the analysis and design of the link budget of a telecommunication system. ...
depends on
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...
,
topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...
, and environmental conditions. Actually, one could use any known ''signal power'' dBm0 at any distance r0 as a reference: :\mathrm = \mathrm_0 - 10.0 \ \gamma \ \log_\left( \frac \right)


Number of decades

:\log_ ( R / r ) would give an estimate of the number of decades, which coincides with an average path loss of 40 dB/decade.


Estimate the cell radius

When we measure cell distance ''r'' and received power pairs, we can estimate the mean cell radius as follows: :R_e = \operatorname \ r \ 10 ^ \ /math> Specialized calculation models exist to plan the location of a new cell tower, taking into account local conditions and
radio equipment Radio-frequency (RF) engineering is a subset of electronic engineering involving the application of transmission line, waveguide, antenna and electromagnetic field principles to the design and application of devices that produce or use signals ...
parameters, as well as consideration that mobile radio signals have
line-of-sight propagation Line-of-sight propagation is a characteristic of electromagnetic radiation or acoustic wave propagation which means waves travel in a direct path from the source to the receiver. Electromagnetic transmission includes light emissions travelin ...
, unless reflection occurs.


See also

* Cel-Fi *
Cell network Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
*
Cell phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...
*
Cellular repeater A cellular repeater (also known as cell phone signal booster or cell phone signal amplifier) is a type of bi-directional amplifier used to improve cell phone reception. A cellular repeater system commonly consists of a donor antenna that receive ...
*
Dropped call A mobile phone signal (also known as reception and service) is the signal strength (measured in dBm) received by a mobile phone from a cellular network (on the downlink). Depending on various factors, such as proximity to a tower, any obstruction ...
*
Dead zone (cell phone) A mobile phone signal (also known as reception and service) is the signal strength (measured in dBm) received by a mobile phone from a cellular network (on the downlink). Depending on various factors, such as proximity to a tower, any obstructi ...
* Field strength in free space *
Field strength meter In telecommunications, a field strength meter is an instrument that measures the electric field strength emanating from a transmitter. The relation between the electric field and the transmitted power In ideal free space, the electric field stre ...
*
Received signal strength indication In telecommunications, received signal strength indicator (RSSI) is a measurement of the power present in a received radio signal. RSSI is usually invisible to a user of a receiving device. However, because signal strength can vary greatly and af ...
*
S meter An S meter (signal strength meter) is an indicator often provided on communications receivers, such as amateur radio or shortwave broadcast receivers. The scale markings are derived from a system of reporting signal strength from S1 to S9 as par ...
*
Signal (electrical engineering) In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The ''IEEE Transactions on Signal Processing'' ...
*
Mobile phone signal A mobile phone signal (also known as reception and service) is the signal strength (measured in dBm) received by a mobile phone from a cellular network (on the downlink). Depending on various factors, such as proximity to a cell site, tower, any o ...
* Mobile coverage


References


External links


Global map of cell phone signal by network. Based on crowdsourced data.

Crowd sourced map of cell and wifi signals. Data release under the Open Database License.
{{Refend Radio electronics Mobile technology es:Repetidor celular id:Penguat sinyal selular