Institute of Engineering and Technology

Subject: Wireless Communication (EC-305)

Submission of Lab-Assignment - X

Roll no: 131021

July 29, 2015

1 Problem definition

1. Calculating the mean path loss using Okumaras model for d=50 km,hte= 100 m, hre= 10 m and carrier frequency =900 MHz in a subur-ban environment.Writing a MATLAB code for the model and also deriving and inter-preting the result. Varying distance and height of the transmitterantenna and graphically showing the relationships for

(a) path loss and distance

(b) path loss and height of the transmitter antenna

2. Finding the median path loss under the Hata model assuming fc = 900MHz, transmitter antenna height = 40 m, receiver antenna height = 5m and d = 20 km for a large urban city, a small urban city, a suburb,and a rural area. Explaining qualitatively the path loss differencesfor these 4 environments. Also writing MATLAB code for the modeland deriving the useful result interpretation. Comparing the pathloss obtained by this model with Okumara model in suburban areahaving same system specifications. Varing distance and graphicallyshow relations between

(a) Path loss and distance for all the four environments of Hata model

(b) Path loss and distance for Okumura model

(c) Path loss and distance for COST-231

(d) Comparing the graphs obtained in different model

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2 Theory

Wireless Communications using wireless has becaming significant tools insustaning communications especially at home and workplaces due to com-munication models. Propagation models are of two types: fully empiricalmodels and Deterministic models.

Semi-empirical models are models which has the chareteristics of both types.Empirical models are based on practically measured data. Since few param-eters are used, these models are simple but not very accurate. The modelswhich are categorized as empirical models for macro cellular environment.These include Hata model, Okumura model, COST-231 Hata model.

On the other hand, deterministic models are very accurate. Some of theexamples include Ray Tracing and Ikegami model. As mentioned earlier,semiempirical models are based on both empirical data and deterministicaspects. Cost-231 Walfisch-Ikegami model is categorized as a semi empiricalmodel. All these models estimate the mean path loss based on parameterssuch as antenna heights of the transmitter and Receiver, distance betweenthem, etc. These models have been extensively validated for mobile net-works. Most of these models are based on a systematic interpretation ofmeasurement data obtained in the service area[1]

Okumura Model

this is the most popular model that is used widely for urban areas in radiopropagation that was originated in Japan/Tokyo. this model server as thebase of Hata model.this model is optimum to be used in cities with urbanstructure but not too many tall buildings. it can be applied to 3 areasnamely: Urban, Suburban and rural

Formula for Okumura Model is expressed below:Lm(dB) = LF(d)+ Amu(f,d) – G(hr) – G(ht) – GAREA

Where;Lm = (i.e., median) of path lossLF(d) = free space propagation path loss.Amu(f,d) = median attenuation relative to free spaceG(ht) = base station antenna height gain factorG(hr) = mobile antenna height gain factorG(ht) = 20log(ht/200) 1000m > ht > 30mG(hr) = 10log(hr/3) hr ≤ 3mG(hr) = 20log(hr/3) 10m > hr > 3mGAREA = gain due to type of environment

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we find GAREA from the graph given below :

and we find AMU from the graph below:

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Now, Lets look at an example:for a given Hte = 100m and Hre=10m,and transmitting frequency should be 900 MHz in a suburban area,we see from the graph of Garea, it is approximately 9 and AMU nearly 39.substituiting hte and hre in the equations:G(hr) = 20log(10/3) = 10.45G(ht) = 20log(100/200) = -6Now, Lambda = (3×108)/(900× 106) = 1/3

the free space path loss,Lf = 10log[(4× π × 50)2)/((1/3)2)] = 65.56

and finally, the propagation path loss:L50 = Lf+Amu-Ghte-Ghre-Garea;=65.56-39-6-10.45-9 = 91.05 {Answer}

Hata Model

Hata established empirical mathematical relationships to describe the graph-ical information given by Okumura. Hatas formulation is limited to certainranges of input parameters and is applicable only over quasi-smooth terrain.The mathematical expression and their ranges of applicability are as follows.

Carrier Frequency: 150 MHz≤ fc ≤ 1500 MHzBase Station/transmitter Antenna Height: 30 m ≤ ht ≤200 mMobile Station/reciever Antenna Height: 1 m ≤hr ≤10 mTransmission Distance: 1 km ≤d ≤20 km

Hence,L50 (dB) =A + B log10 (d) for urban areasL50 (dB) =A + B log10 (d) C for suburban areaL50 (dB) =A + B log10 (d) D for open area

Where:A = 69.55 +26.161log10(fc)–13.82 log10(ht)–a(hr)B = 44.9–6.55log10(ht) C = 5.4 + 2 [log10(fc/28)]2

D = 40.94 + 4.78 [log10 (fc)]2 18.33log2(fc)

Where,a(hr) = [1.1log10 (fc) 0.7] ht [1.56log10 (fc) 0.8]for medium or small cities

8.29[log10 (1.54ht)]2–1.1 for large city and fc ≤ 200 MHz3.2 [log10 (11.75ht)]2–4.97 for large city and fc ≤ 400 MHz

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COST-231 MODEL

Most future PCS systems are expected to operate in the 18002000 MHzfrequency band. It has been shown that path loss can be more dramaticat these frequencies than those in the 900 MHz range. Some studies havesuggested that the path loss experienced at 1845 MHz is approximately 10dB larger than those experienced at 955 MHz, all other parameters beingkept constant. The COST231-Hata model extends Hata’s model for use inthe 1500-2000 MHz frequency range, where it is known to underestimatepath loss. The model is expressed in terms of the following parameters.

Carrier Frequency (fc) 1500–2000 MHzAntenna Height (ht) 30–200 mAntenna Height (hr) 1–10 mTransmission Distance(d) 1–20 km

The path loss according to the COST-231-Hata model is expressed as:L50(dB) = A + B log10(d) +CWhere; A = 46.3+ 33.910(fc)–13.28 log10(ht)– a(hr)B = 44.9–6.55 log10(ht)C= 0 for medium city and suburban areasC=3 for metropolitan areas

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3 Block diagram/program

1. Okumura Model

figure-1: matlab code for finding propagation path loss insuburban region

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figure-2: matlab code for showing the effect of varying thedistance from the base station on propagation path loss in

suburban region

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figure-3:matlab code for showing the effect of varying theheight of transmitter antennae at base station on

propagation path loss in suburban region

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2. Hata Model

figure-4:matlab code for finding median path loss for all theenvironments for a specific value of frequency and antennae

heights

figure-5:matlab code for plotting median path loss vsdistance (0m-20m) for 4 different areas

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3. Cost-231 Model

figure-6:matlab code for plotting median path loss vsdistance (0m-20m) for medium and metropolitan areas

4 Results

1. Okumura Model

figure-7: propagation path loss for 50 Km distance frombase station Hte=100m, Hre=10m and frequency =

900MHz

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figure-8: propagation path loss vs distance from basestation for Hte=100m, Hre=10m, d=50Km and frequency

= 900MHz

figure-9:propagation path loss vs height of transmittingantennae for Hte=100m, d=50Km and frequency =

900MHz

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2. Hata Model

figure-10:median path loss for all the four environments forHte=40m, Hre=5m, d=20Km and frequency = 900MHz

figure-11:median path loss vs distance (0m-20m) for all 4environments Hte=40m, Hre=5m, d=20Km and frequency

= 900MHz

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3. Cost-231 Model

figure-12:Path loss vs distance from the base station atfrequency 1500 Hz(at border limit) for same system

configuration

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4. Comparisions of models

figure-13:graphs comparing Hata and Okumura model withsame system specifications in suburban area with

frequency=900Mhz

figure-14:Comparing the hata model and Cost-231 modelwith same system specifications- frequency = 1500Mhz and

suburban area

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5 Result Interpretation

1. Okumura Model

(a) from figur 8, we can interpret that propagation path loss increaseswhen we increase the distance of transmission in suburban areafor a given system configuration. the path loss change in dB re-duces slightly when we keep on increasing the distance.this is obvious that when we increase the distance, the path willhave more obstacles, eventually resulting in more path loss, weak-ening the signal.

(b) from figure 9, we can easily interpret that the path loss has aninverse relationship with height of the transmitter antennae insuburban area with the same system specifications, the change iscoming to a saturation when it gets to large heights.the reason behind this is that the power transmission is directlyproportional to Height of the transmitting antennae. So thatthere is lower path loss in propagation.As line of sight commu-nication quality increases with increasing antennae height, pathloss decreases.

2. Hata Model

(a) figure 10 shows the path losses calculated by MATLAB for fourdifferent environments at same system configurations, frequencyand distance. we interpret that path loss in large urban areawhere density of tall buildings and chances of disturbances tosignals are very high, the path loss is highest (164dB). Now, whenwe move to small urban areas, relative obstacles decreases slightlyand so the distance, which will slightly decrease the path loss(4 dB) but is still high. Moderate change in path loss- 10 dB- is seen in the suburban regions as the tall buildings are lessand is mainly covered by open areas, therefore, less path loss insuburban regions. And, there is a significant change when wemove to rural areas, as there are no tall buildings here and areonly covered by low rise buildings and slums, no disturbance tosignals is observed and hence, very less path loss in the rural areas(132 dB) - but which is still to be taken care of.

(b) the same interpretation we can see in the figure 11, which showsthe path loss in 4 areas in range of 20 km of radius from the basestation. it obvious that the path loss of all the areas will increaseas the distance increases as we saw in 1(a). it can also be seenthat, all 4 environments maintains the similar difference in pathloss in dBs for every value in distance from the base station.

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Note: the graphs for suburban regions are for the urban areaswhich are small.

3. COST-231 Modelfigure 12 gives a similar interpretation of Hata model which signifiesthat this model is the extension of Hata Model. there is a very highpath loss at lower distace itself and increases rapidly when we increasethe distance. as this has been plotted for 1500 Hz, the path loss hasto be higher. we can also interpret that this model has the highestpath loss among the three. the two lines maintains the distance of 3dB on the graph which conveys the C factor of the model accordingto the area. apart from this, rapid increase in path loss is seen withthe increase in distance.

4. Comparision of different Models

(a) there is a vast difference between Hata and Okumura model inpath loss, approximately 70 dB of more path loss in Hata modelthen in Okumura model with the same systems specifications.And as usual, with the distance, the loss increases

(b) the same thing is observed in comparison in Hata and COST -231 models, except for the difference being small but at higherfrequency of 1500 MHz instead of 900 MHz in above Comparisongraph. Also with distance, the increase of path loss is seen to belarger than in above comparison.

6 Conclusion

The path loss of Okumura, Hata and Cost 231 models shows decreasingtrend with respect to transmitter antenna height and increasing trend withrespect to transmission distance.

In Hata and Cost-231 models, with increasing urbanization, the path Lossis also seen to increase.

Among the communication models Okumura model shows the least pathloss and Cost-231 model shows the largest path loss.Among the three mod-els Hata model shows intermediate results for path loss.

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7 Lab Report

1. Programs

figure-15: MATLAB code for Okumura model - varying thefrequency with same system specifications

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figure-16: MATLAB code for Okumura model- varying thedistance with same system specifications

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figure-17: MATLAB code for varying the Hte with samesystem specifications

Note: changin the variable has been done with the same code, soscreenshot has not been shown.

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2. Results

figure-18: Okumura Model: Path Loss vs frequency

figure-19: Okumura Model: Path Loss vs distance

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figure-20: Okumura Model: Path Loss vs Transmitterantennae height

figure-21: Hata Model: Path Loss vs distance

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figure-22: Hata Model: Path Loss vs Frequency

figure-23: Hata Model: Path Loss vs Transmiter antennaeHeight

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figure-24: summary of outputs of all the varying terms forOkumura Model

figure-25: summary of outputs of all the varying terms forHata Model

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figure-26: summarizes all environments with differentfrequencies for Hata Model

3. Result interpretationNote: Both the graphs are for suburban region

(a) Okumura ModelFrom Results, we can interpret that with frequency, path lossIncreases as more power transmitted and hence, more power dis-sipated.As we already saw, with distance, path loss shows increasingtrend.And with transmitter antennae height, there is an inverse rela-tionship. the reasons for this has been described earlier. As line ofsight communication quality increases with increasing antennaeheight, path loss decreases

(b) Hata Modelfrom results of figure 21, 22, 23, we can see that with distanceof transmission, the propagation path loss shows increasing trendas explained earlier.the same happens with frequency too, as it happens with distancedue to power strength loss.it shows a decreasing trend with transmitter antennae height asline of sight communication quality increases.

the quantitative interpretations has been summarized in figure24 and 25 which implies the same trends as explained above.

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Figure 26 summarizes almost every effect of variables of HataModel. you can see that the triplets of urban region varies withdifferent frequencies. the highest frequency (900MHz) experi-ences the highest path loss and it decreases with the frequency.the same happens with every region with respect to frequency.we can also interpret from the graph that with urbanization, pathloss increases. no matter what the frequency is (it is significantbut not when comared to the area), path loss increases signifi-cantly with the urbanization, and the frequency affects it moder-ately.and distance affects every graph with increasing trend of pathloss.

4. Conclusion

With frequency and distance, in both the models, the path loss in-creases.the transmitter height has the inverse relationship with path loss inboth the models.with urbanization, again the path loss shows an increasing trend.and hata Model always has a higher path loss than Okumura Model.

8 References

1. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.303.4057rep=rep1type=pdf

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