The Okumura model is a
radio propagation model
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere.
As a form of electromagnetic radiation, like light waves, radio waves are affected ...
that was built using the data collected in the city of
Tokyo
Tokyo (; ja, 東京, , ), officially the Tokyo Metropolis ( ja, 東京都, label=none, ), is the capital and largest city of Japan. Formerly known as Edo, its metropolitan area () is the most populous in the world, with an estimated 37.468 ...
,
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
. The model is ideal for using in cities with many urban structures but not many tall blocking structures. The model served as a base for the
Hata model
The Hata model is a radio propagation model for predicting the path loss of cellular transmissions in exterior environments, valid for microwave frequencies from 150 to 1500 MHz. It is an empirical formulation based on the data from the Okumura mo ...
.
Okumura model was built into three modes. The ones for urban, suburban and open areas. The model for urban areas was built first and used as the base for others.
Coverage
Frequency = 150–1920 MHz
Mobile station antenna height: between 1 m and 3 m
Base station antenna height: between 30 m and 100 m
Link distance: between 1 km and 100 km
Mathematical formulation
The Okumura model is formally expressed as:
where,
L = The
median
In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value. The basic fe ...
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. ...
. Unit:
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 ...
(dB)
L
FSL = The
free space loss
In telecommunication, the free-space path loss (FSPL) (also known as Free Space Loss, FSL) is the attenuation of radio energy between the feedpoints of two antennas that results from the combination of the receiving antenna's capture area plus the ...
. Unit:
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 ...
(dB)
A
MU =
Median
In statistics and probability theory, the median is the value separating the higher half from the lower half of a data sample, a population, or a probability distribution. For a data set, it may be thought of as "the middle" value. The basic fe ...
attenuation
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable att ...
. Unit:
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 ...
(dB)
H
MG =
Mobile station
A mobile station (MS) comprises all user equipment and computer software, software needed for communication with a Cellular network, mobile network.
The term refers to the global system connected to the mobile network, i.e. a mobile phone or mob ...
antenna
Antenna ( antennas or antennae) may refer to:
Science and engineering
* Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves
* Antennae Galaxies, the name of two collid ...
height
gain
Gain or GAIN may refer to:
Science and technology
* Gain (electronics), an electronics and signal processing term
* Antenna gain
* Gain (laser), the amplification involved in laser emission
* Gain (projection screens)
* Information gain in de ...
factor.
H
BG =
Base station
Base station (or base radio station) is – according to the International Telecommunication Union's (ITU) Radio Regulations (RR) – a "land station in the land mobile service."
The term is used in the context of mobile telephony, wireless com ...
antenna
Antenna ( antennas or antennae) may refer to:
Science and engineering
* Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves
* Antennae Galaxies, the name of two collid ...
height
gain
Gain or GAIN may refer to:
Science and technology
* Gain (electronics), an electronics and signal processing term
* Antenna gain
* Gain (laser), the amplification involved in laser emission
* Gain (projection screens)
* Information gain in de ...
factor.
K
correction = Correction factor gain (such as type of environment, water surfaces, isolated obstacle etc.)
Points to note
Okumura's model is one of the most widely used models for signal prediction in urban areas. This model is applicable for frequencies in the range 150–1920 MHz (although it is typically extrapolated up to 3000 MHz) and distances of 1–100 km. It can be used for base-station antenna heights ranging from 30–1000 m.
Okumura developed a set of curves giving the median attenuation relative to free space (A
mu), in an urban area over a quasi-smooth terrain with a base station effective antenna height () of 200 m and a mobile antenna height (hre) of 3 m. These curves were developed from extensive measurements using vertical omni-directional antennas at both the base and mobile, and are plotted as a function of frequency in the range 100–1920 MHz and as a function of distance from the base station in the range 1–100 km. To determine path
loss using Okumura's model, the free space path loss between the points of interest is first determined, and then the value of A
mu(f, d) (as read from the curves) is added to it along with correction factors to account for the type of terrain. The model can be expressed as
where L50 is the 50th percentile (i.e., median) value of propagation path loss, LF is the free space propagation loss, A
mu is the median attenuation relative to free space, G() is the base station antenna height gain factor, G(hre) is the mobile antenna height gain factor, and G
AREA is the gain due to the type of environment.
Note that the antenna height gains are strictly a function of height and have nothing to do with antenna patterns.
Plots of A
mu(f, d) and G
AREA for a wide range of frequencies are shown in Figure 3,23 and Figure 3.24. Furthermore, Okumura found that G() varies at a rate of 20 dB/decade and G(hre) varies at a rate of 10 dB/decade for heights less than 3 m.
G() = 20 log(/200) 1000 m > > 30 m
G(hre) = 10 log(hre/3) hre <= 3 m
G(hre) = 20 log (hre/3) 10 m > hre > 3 m
Other corrections may also be applied to Okumura's model. Some of the important terrain related parameters are the terrain undulation height (A/i), isolated ridge height, average slope of the terrain and the mixed land-sea parameter.
Once the terrain related parameters are calculated, the necessary correction
factors can be added or subtracted as required. All these correction factors are
also available as Okumura curves
ku68
In irregular terrain, one frequently encounters non-line-of-sight paths caused by terrain obstacles. Okumura's model includes a correction factor called the "Isolated Ridge" factor to account for obstacles. However, the applicability of this correction is only to obstacles conforming to that description; i.e. an isolated ridge. More complex terrain cannot be modeled by the Isolated Ridge correction factor. A number of more general models exist
[López Giovaneli, Carlos, "An analysis of simplified solutions for multiple knife-edge diffraction”, ''IEEE Trans Ant Prop'', 32(3), Mar 1984, pp 297-301.] for calculating diffraction loss. However, none of these can be applied directly to Okumura's basic mean attenuation. Proprietary methods of doing so have been developed; however, none are known to be in the public domain.
Okumura's model is wholly based on measured data and does not provide
any analytical explanation. For many situations, extrapolations of the derived
curves can be made to obtain values outside the measurement range, although
the validity of such extrapolations depends on the circumstances and the
smoothness of the curve in question.
Okumura's model is considered to be among the simplest and best in terms of accuracy in path loss prediction for mature cellular and land mobile radio systems
in cluttered environments. It is very practical and has become a standard for system planning in modern land mobile radio systems in Japan. The major
disadvantage with the model is its slow response to rapid changes in terrain, therefore the model is fairly good in urban and suburban areas, but not as good
in rural areas. Common standard deviations between predicted and measured path loss values are around 10 dB to 14 dB.
See also
*
Hata model
The Hata model is a radio propagation model for predicting the path loss of cellular transmissions in exterior environments, valid for microwave frequencies from 150 to 1500 MHz. It is an empirical formulation based on the data from the Okumura mo ...
*
Young model
*
Yoshihisa Okumura
Dr. Yoshihisa Okumura (born 1926, in Isikawa Prefecture) is a Japanese engineer, known for development of cellular telephone networks.
His radio survey of signal strength as a function of distance as measured in drive tests in automobiles was cri ...
References
Further reading
* ''Introduction to RF propagation'', John S. Seybold, 2005, Wiley.
* ''Wireless Communications: Principles and Practice'', (2nd Edition), Theodore S. Rappaport, 2002, Prentice Hall.
* ''The Mobile Radio Propagation Channel'', 2nd Edition, J. D. Parsons, 2000, Wiley.
* ''Radio Propagation in Cellular Networks'', N. Blaunstein, 2000, Artech.
External links
VOLCANO advanced radio propagation modelincluding both direct-path and multi-path (
ray-tracing) models
{{Radio frequency propagation models
Radio frequency propagation model