Zigbee

New Experiment

In the Simulation menu select Simulation New ZigBee Networks

Create Scenario

Adding Node -

• Click on the ZigBee icon in the toolbar and click and drop it inside the grid (i.e. Visibility Range - The systems can move and communicate in this range only).
• A Node cannot be placed on another Node. A Node cannot float outside the grid.

Adding PAN Coordinator - Click on the PAN Coordinator icon in the toolbarand click and drop inside the grid.

Set Environment Properties

Right click in side of the on the Environment and click Properties.

Modifying/Viewing/Accepting Properties

On opening an already configured properties of environment, the input fields will be frozen (i.e. the input cannot be changed).To modify these values click on the Modify button in the screen. Now the input value can be changed.Click on the Accept button, the modified values will be saved.

Set Node, Link and Application Properties

• Right click on the appropriate node or link and select Properties. Then modify the parameters according to the requirements. In Zigbee Node, Routing Protocol in Network Layer and all user editable properties in DataLink Layer, Physical Layer and Power are Global i.e. changing properties in one node will automatically reflect in the others in that network.
• Select the Application Button on the ribbon and click on the empty region between the Grid Environment and the ribbon. Now right click on Application and select Properties. Multiple applications can be generated by using add button in Application properties.
• Set the values according to requirement and click Accept.

Enable Packet Trace, Event Trace & Dynamic Metrics (Optional)

Click Packet Trace / Event Trace icon in the tool bar. To get detailed help, please refer section 6.5, 6.6 and 6.3 respectively. Select Dynamic Metrics icon for enabling Dynamic Metrics and click OK.

Run Simulation

Click on Run Simulation icon on the top toolbar.

Set the Simulation Time and click on Simulate.

Sample Experiment

A sample network is created in “Configuration.xml” file which is located inside<NetSim installed Path>\Docs\ Sample_Configuration\ Zigbee, which the user can open using NetSim and understand how devices are connected among themselves for that network and their default properties.

Furthermore, users can open this Configuration.xml file using Visual Studio 2010 and analyze how to write a designed network scenario manually. Further information is provided in “Understanding Configuration.xml file” under “Running NetSim via CLI” chapter 5.

SINR, BER and Propagation models for 802.15.4

SINR Calculation:

Analogous to the SNR used often in wired communications systems, the SINR is defined as the power of a certain signal of interest divided by the sum of the interferencepower (from all the other interfering signals) and the power of some background noise. The interference power is the difference between the total power received by the receiver and the power received from one particular transmitter.

The background thermal noise in dBm at room temperature is given by:

P (in dBm) =

where Δf is the Bandwidth in Hertz. For 802.15.4, Δf = 2 MHz

P (in mW) =

Therefore, SINR in dBm is calculated as:

SINR (in dBm) =

Bit Error Rate (BER) Calculation:

The bit error rate (BER) is the number of bit errors divided by the total number of transferred bits during a studied time interval. The BER results were obtained using the analytical model from IEEE standard 802.15.2-2003 [B9]. The calculation follows the approach outlined in 5.3.2 of that standard.

BER =

Where SINR = Signal-to-Interference-plus-Noise Ratio. BER should be between 0 and 1.

Propagation Loss:

Three different and mutually independent propagation phenomena influence the power of the received signal: path loss, shadowing and multipath fading.

Shadowing:

Slow shadowing in wireless network is the attenuation caused by buildings or any obstacles between a transmitter and a receiver. In the model with shadowing, the shadowing value Xσ, typically defined in dB, is added to (or subtracted from) the average received power. Xσ is a zero means Gaussian distributed random variable with standard deviation σ.

The Probability Density Function (PDF) of the lognormal distribution is:

The default value for standard deviation is chosen as 5 dB.

Path Loss:

Pathloss is the reduction in power density of an electromagnetic wave as it propagates through space. Path loss may be due to many effects, such as free-space loss, refraction, diffraction, reflection, aperture-medium coupling loss, and absorption.

Path loss can be represented by the path loss exponent, whose value is normally in the range of 2 to 4, where 2 is for propagation in free space and 4 is for relatively loss environments. In NetSim, the default value for path loss exponent is taken as 2.

Path loss is usually expressed in dB. In its simplest form, the path loss can be calculated using the formula

Where L is the path loss in decibels, is the path loss exponent, d is the distance between the transmitter and the receiver, usually measured in meters, and C is a constant which accounts for system losses.

A simplified formula for the path loss between two isotropic antennas in free space:

L (in dBm) =

Where L is the path loss in decibels, λ is the wavelength and d is the transmitter-receiver distance in the same units as the wavelength.

Calculation of Received Power:

In general,

The path loss model used is described in IEEE Standard 802.15.2-2003[B9], which stipulates a two-segment function with a path loss exponent of 2.0 for the first 8 m and then a path loss exponent of 3.3 thereafter. The formula given in IEEE Standard 802.15.2 is shown in Equation (E.1).

pl(d) =

Where, for 2.4 Ghz pl(1) = 40.2 dBm pl(8) = 58.5 dBm = 2, the path loss exponent for d ≤ 8m = 3.3, the path loss exponent for d > 8m

Reference: IEEE Standard 802.15.4 – 2006

Part 15.4: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (WPANs).