Okumura Model
Encyclopedia
The Okumura model for Urban Areas is a Radio propagation model
that was built using the data collected in the city of Tokyo
, Japan
. 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
.
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.
Mobile station antenna height: between 1 m and 10 m
Base station antenna height: between 30 m and 1000 m
Link distance: between 1 km and 100 km
where,
L = The median
path loss
. Unit: Decibel
(dB)
LFSL = The Free Space Loss
. Unit: Decibel
(dB)
AMU = Median
attenuation
. Unit: Decibel
(dB)
HMG = Mobile station
antenna
height gain
factor.
HBG = Base station
antenna
height gain
factor.
Kcorrection = Correction factor gain (such as type of environment, water surfaces, isolated obstacle etc.)
Okumura developed a set of curves giving the median attenuation relative to free space (Arnu), in an urban area over a quasi-smooth terrain with a base station effective antenna height (hte) 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 MHz to 1920 MHz and as a function of distance from the base station in the range 1 km to 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 Amu(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
L50(dB) = LF + Amu(f, d)- G(hte) — G(hre) — Garea
where L50 is the 50th percentile (i.e., median) value of propagation path loss, LF is the free space propagation loss, Amu is the median attenuation relative to free space, G(hte) is the base station antenna height gain factor, G(hre) is the mobile antenna height gain factor, and GAREA 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 Amu(f, d) and GAREA for a wide range of frequencies are shown in Figure 3,23 and Figure 3.24. Furthermore, Okumura found that G(hte) 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(hte) = 20 log(hte/200) 1000 m > hte > 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 [0ku68].
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 environmehts. 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.
Radio propagation model
A radio propagation model, also known as the Radio Wave Propagation Model or the Radio Frequency Propagation Model, is an empirical mathematical formulation for the characterization of radio wave propagation as a function of frequency, distance and other conditions...
that was built using the data collected in the city of Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. 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
Hata Model for Urban Areas
In wireless communication, the Hata Model for Urban Areas, also known as the Okumura-Hata model for being a developed version of the Okumura Model, is the most widely used radio frequency propagation model for predicting the behaviour of cellular transmissions in built up areas...
.
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 MHz to 1920 MHzMobile station antenna height: between 1 m and 10 m
Base station antenna height: between 30 m and 1000 m
Link distance: between 1 km and 100 km
Mathematical formulation
The Okumura model is formally expressed as:where,
L = The median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
path loss
Path loss
Path loss is the reduction in power density 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
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
(dB)
LFSL = The Free Space Loss
Free-space loss
In telecommunication, free-space path loss is the loss in signal strength of an electromagnetic wave that would result from a line-of-sight path through free space , with no obstacles nearby to cause reflection or diffraction...
. Unit: Decibel
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
(dB)
AMU = Median
Median
In probability theory and statistics, a median is described as the numerical value separating the higher half of a sample, a population, or a probability distribution, from the lower half. The median of a finite list of numbers can be found by arranging all the observations from lowest value to...
attenuation
Attenuation
In physics, attenuation is the gradual loss in intensity of any kind of flux through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.In electrical engineering and telecommunications, attenuation affects the...
. Unit: Decibel
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
(dB)
HMG = Mobile station
Mobile Station
The mobile station comprises all user equipment and software needed for communication with a mobile network.The mobile station refers to global system connected to the mobile network, i.e. mobile phone or mobile computer connected using a mobile broadband adapter. This is the terminology of 2G...
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...
height gain
Gain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
factor.
HBG = 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...
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...
height gain
Gain
In electronics, gain is a measure of the ability of a circuit to increase the power or amplitude of a signal from the input to the output. It is usually defined as the mean ratio of the signal output of a system to the signal input of the same system. It may also be defined on a logarithmic scale,...
factor.
Kcorrection = 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 MHz to 1920 MHz (although it is typically extrapolated up to 3000 MHz) and distances of 1 km to 100 km. It can be used for base station antenna heights ranging from 30 m to 1000 m.Okumura developed a set of curves giving the median attenuation relative to free space (Arnu), in an urban area over a quasi-smooth terrain with a base station effective antenna height (hte) 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 MHz to 1920 MHz and as a function of distance from the base station in the range 1 km to 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 Amu(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
L50(dB) = LF + Amu(f, d)- G(hte) — G(hre) — Garea
where L50 is the 50th percentile (i.e., median) value of propagation path loss, LF is the free space propagation loss, Amu is the median attenuation relative to free space, G(hte) is the base station antenna height gain factor, G(hre) is the mobile antenna height gain factor, and GAREA 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 Amu(f, d) and GAREA for a wide range of frequencies are shown in Figure 3,23 and Figure 3.24. Furthermore, Okumura found that G(hte) 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(hte) = 20 log(hte/200) 1000 m > hte > 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 [0ku68].
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 environmehts. 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 for Urban AreasHata Model for Urban AreasIn wireless communication, the Hata Model for Urban Areas, also known as the Okumura-Hata model for being a developed version of the Okumura Model, is the most widely used radio frequency propagation model for predicting the behaviour of cellular transmissions in built up areas...
- Hata Model for Suburban AreasHata Model for Suburban AreasThe Hata Model for Suburban Areas, also known as the Okumura-Hata model for being a developed version of the Okumura Model, is the most widely used model in radio frequency propagation for predicting the behavior of cellular transmissions in city outskirts and other rural areas...
- Hata Model for Open AreasHata Model for Open AreasThe Hata Model for Open Areas, also known as the Okumura-Hata model for being a developed version of the Okumura Model, is the most widely used model in radio frequency propagation for predicting the behavior of cellular transmissions in open areas. This model incorporates the graphical information...
- Young ModelYoung ModelYoung model is a radio propagation model that was built on the data collected on New York City. It typically models the behaviour of cellular communication systems in large cities.-Applicable to/under conditions:...
External links
- VOLCANO advanced radio propagation model including both direct-path and multi-path (ray-tracingRay tracing (physics)In physics, ray tracing is a method for calculating the path of waves or particles through a system with regions of varying propagation velocity, absorption characteristics, and reflecting surfaces. Under these circumstances, wavefronts may bend, change direction, or reflect off surfaces,...
) models