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The Hata-SRD variation was developed in CEPT within the Project Team SE24 for studies of Short Range Devices (SRD). The basis for modification was an assumption that although SRD devices are usually operated at low antenna heights (typically person-carried devices, i.e. with antenna height of ca. 1.5 m), but the interference would usually occur at relatively short distances (up to 100 m or so) when direct-Line-of-Sight (LoS) or near-direct-LoS might be assumed. Therefore the Hata-SRD model includes adjusted expression of the parameter b(Hb), which in the standard Hata model would introduce significant additional path loss when transmitter antenna height is much less than 30 m. It was found that this additional loss is not justified in the considered SRD scenarios of short range & direct-LoS communication/coupling. In the SEAMCAT propagation library, the user will find the model under the name “Extend Hata - SRD”
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Figure 473: SEAMCAT Interface to the Extended Hata propagation model (general model on the left) and its adapted version for SRDs (on the right)Anchor F473 F473
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Table 7879: Description of the Extended Hata and Extended Hata (SRD) modelsAnchor T078T079T078 T079
Description | Symbol | Type | Unit | Comments |
Variation | Variation in path loss takes into account the uncertainty of building design, furniture, room size, etc. | |||
General environment | Environment of the propagation: urban, rural, suburban | |||
Propagation environment | Environment of the propagation: Below roof, Above roof (used for standard deviation calculations) ONLY USED IF VARIATION OPTION IS CHECKED | |||
Wall loss(indoor - indoor) | Scalar | dB | ||
Wall loss std dev (indoor - indoor) | Scalar | dB | ||
Loss between adjacent floor | Scalar | dB | ||
Empirical parameters: | b | This parameter is used for the necessary corrections to be performed in the local environments if the transmitter and receiver are located in the same building in order to apply the correct wall attenuation between them. The snippet of code below this table indicates the exact calculation performed within SEAMCAT. | ||
Size of the room | droom | Scalar | m | |
Height of each floor | hfloor | Scalar | m |
Method in SEAMCAT to perform corrections to the local environments, depending on the location of the transmitter and receiver (i.e. within the same building or in different buildings):
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protected static LocalEnvCorrections localEnvCorrections(LocalEnvCorrections localEnvironmentCorrections,LinkResult linkResult,
double floorHeight,double roomSize, double wiLoss, double floorLoss, double empiricalParam, double wiStdDev) {
//LocalEnvCorrections result = new LocalEnvCorrections(0, localEnvironmentCorrections.rStdDev);
LocalEnvironmentResult rxEnv = linkResult.rxAntenna().getLocalEnvironment();
LocalEnvironmentResult txEnv = linkResult.txAntenna().getLocalEnvironment();
// CAUTION : do NOT permute the order of the tests
if ( rxEnv.getEnvironment() == Indoor && txEnv.getEnvironment() == Indoor) {
if ( linkResult.isTxRxInSameBuilding() ) {
// Transmitter and receiver are located in the same building
// specific calculation : replaces standard calculation
double rK;
rK = Math.abs(
Math.floor(linkResult.txAntenna().getHeight()/ floorHeight) -
Math.floor(linkResult.rxAntenna().getHeight()/ floorHeight)
);
double d1 = linkResult.txAntenna().getHeight() - linkResult.rxAntenna().getHeight();
double realDistance = Math.sqrt( (d1*d1) + (linkResult.getTxRxDistance()*linkResult.getTxRxDistance()) );
localEnvironmentCorrections.rMedianLoss = -27.6
+ 20.0
* Math.log10(1000 * realDistance)
+ 20.0
* Math.log10(linkResult.getFrequency())
+ Math.floor(1000 * linkResult.getTxRxDistance() / roomSize)
* wiLoss
+ Math.pow(rK,
((rK + 2.0) / (rK + 1.0) - empiricalParam))
* floorLoss;
localEnvironmentCorrections.rStdDev = wiStdDev;
} else {
// Transmitter and receiver are located in different buildings
// Calculation is similar to indoor-outdoor case with doubled
// corrections
localEnvironmentCorrections.rMedianLoss += rxEnv.getWallLoss() + txEnv.getWallLoss();
localEnvironmentCorrections.rStdDev = Math
.sqrt(
localEnvironmentCorrections.rStdDev * localEnvironmentCorrections.rStdDev +
((txEnv.getWallLossStdDev() * txEnv.getWallLossStdDev()) +
(rxEnv.getWallLossStdDev() * rxEnv.getWallLossStdDev())));
}
} else if (rxEnv.getEnvironment() == Indoor && txEnv.getEnvironment() == Outdoor) {
localEnvironmentCorrections.rMedianLoss += rxEnv.getWallLoss();
localEnvironmentCorrections.rStdDev = Math.sqrt(localEnvironmentCorrections.rStdDev * localEnvironmentCorrections.rStdDev +
rxEnv.getWallLossStdDev() * rxEnv.getWallLossStdDev());
} else if (rxEnv.getEnvironment() == Outdoor && txEnv.getEnvironment() == Indoor) {
localEnvironmentCorrections.rMedianLoss += txEnv.getWallLoss();
localEnvironmentCorrections.rStdDev = Math.sqrt(localEnvironmentCorrections.rStdDev * localEnvironmentCorrections.rStdDev +
txEnv.getWallLossStdDev()*txEnv.getWallLossStdDev());
}
// outdoor outdoor => no correction
return localEnvironmentCorrections;
}
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