You are here: Manual / PropagationModels / IEEE 802.11 Model C modified plug-in

---

IEEE 802.11 Model C (modified) plug-in

Introduction

The IEEE 802.11 (Model C) [1] was used in the developemnt of the ECC Report 131Annex 2 [2] to characterise all TS-TS radio propagation in the Monte Carlo studies.

The SEAMCAT plugin can be found here (revised 27 Sept. 2010 - change 32.44 by 32.4 in the equations)(it contains the .class and .java files).

Note: the “modified” term to the plugin refers to the fact that the algorithm has been implemented to ensure the user to set most of the input parameters.

Assumptions

Measurements results reported in the literature indicate that the presence of people across the propagation link between a transmitter and a receiver could cause additional loss (of up to 20 to 30dB), as a result of body loss or multi-path interference due to body scattering.

In circumstances where the spatial density of TSs is high (as in the geometries investigated in ECC Report 131), the probability of TS-TS path blocking is also high, and hence the TS-TS path can no longer be treated as line-of-sight. Consequently, a path loss model with a greater exponent is more suitable than the free space path loss model for the characterisation of TS-TS links in dense hotspots.

In ECC Report 131, the mean path loss is characterised by a dual-slope model with a break point at 5 m. The proposed plugin as the flexibility to allow the user to set the distance break point as input to Parameter 1.

In addition, the log-normal distributed shadowing with standard deviations of 3 dB and 4 dB is assumed in ECC Report 131 for separations of less than 5 metres and greater than 5 metres respectively. The proposed plugin as the flexibility to allow the user to set the lognormal value before and after the breakpoint as Parameter 2 and Parameter 3 respectively.

Where the calculated path loss is less than free space attenuation for the same distance, the free space attenuation is used instead.

Equation

The mean path loss is characterised by a dual-slope model with a break point d_BP, an exponent of 2 for all distances less than dBP, and an exponent of 3.5 otherwise. In short, the mean path loss, L, in dB is



where d is the separation between the transmitter and receiver in kilometres, d_BP = 0.005 is the break-point in km (i.e. 5 m), and L_FS is free space path loss.



where h_Tx and h_Rx are the height of the transmitter (Tx) and receiver (Rx) respectively and are expressed in m. d is the distance between the Tx and Rx and is expressed in km. f is the frequency and is expressed in MHz.

The log-normal distributed shadowing with standard deviations as defined by the user is applied to the pathloss calculated.

This propagation model is used to calculate terminal-terminal interference and takes account of shadowing losses due to objects between the two terminals, but does not explicitly account for any loss from near-field objects, such as the person carrying the equipment.

To use the Propagation plugin:

1. Select “plugin” from the propagation model selection (contrary from a built in model)
2. Select the plugin to use (i.e. IEEE_802_11_Model_C_modified)
3. Select the environment: Rural/suburban/urban (not in use)
4. Parameter 1: distance break point, d_BP (in km)
5. Parameter 2: log-normal shadowing standard deviation before the d_BP (in dB)
6. Parameter 3: log-normal shadowing standard deviation after the d_BP (in dB)

References

[1] “TGn Channel Models (IEEE 802.11-03/940r2),” High Throughput Task Group, IEEE P802.11, 15 March 2004.
[2] ECC Report 131, Derivation of a Block Edge Mask (BEM) for terminal stations in the 2.6 GHz frequency band (2500-2690 MHz)  www.ecodocdb.dk