Beacon Frame Receiver Example (Obsolete)

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In this section, we will show an IEEE 802.11b beacon frame receiver example. In this example, FMCOMMS2 is used as RF front-end, which captures the WiFi signals over the air. These signals are then streamed from target to Simulink via the iio_sys_obj block. The Simulink model is shown in the figure below, where the Receiver and PLCP Display are from an existing Simulink example IEEE 802.11 WLAN - Beacon Frame Receiver with USRP Hardware. This Simulink model will decode the received WiFi signals, and display all the information from the beacon frame.

In order to run this example, your MATLAB version should be 2014b or higher, and your license needs to include the following components:

• Communications System Toolbox

• DSP System Toolbox

• Signal Processing Toolbox

The model can be found here:

• IEEE 802.11 Beacon Frame Receiver Model

Its initialization functions are based on the ones of IEEE 802.11 WLAN - Beacon Frame Receiver with USRP Hardware.

Figure 1 Beacon Frame Receiver Simulink model

In this example, we set up the target using iio_sys_obj block. One of the most important parameters is the RX_LO_FREQ. It should be set as the center frequency of the incoming WiFi signal channel. In this case, since the incoming WiFi signal is at Channel 11, this frequency is set at 2462 MHz. (The TX LO Frequency on your target should be set at least 50 MHz away from the RX_LO_FREQ in order to avoid interference.)

One other tip: In order to avoid saturation of the RX channel, use the manual gain control mode to adjust the received signal strength, so RX1_GAIN_MODE is set as uint8('manual').

With everything set up properly, we can run the model and get the results below:

Figure 2 Beacon Frame Receiver output

Figure 3 Decoded beacon frame information