Forum
Please or Register to create posts and topics.

Pulsed Waterfall Block

The Pulsed Waterfall shows the entiry spectrum based on the selected signal duration. A perfect duration value will offer a view of the fitting signals only:

Pulsed Waterfall Block

Left hand side Input:

  • Spectra

 

With the PulsedWaterfall block you can identify the duration of any signal live within the frequency spectrum at a glance. It somehow works like an analog tv where you need to tune the sync till you get a stable picture otherwise the picture will scroll up or down the screen. The number of Samples, Persistance, Pulse Duaration, Jitter and Time Compression are adjustable. In addition you can use the "Auto Detect" feature which will try to finde the dominant signal duration within the spectrum with a single mouse click:

Pulsed Waterfall Block Settup

The following screenshot shows a WiFi 802.11 signal. The automatic detected a signal duration of 1024µs. This is the WiFi 802.11 beacon interval. You often read that beacon frames are sent, by default, every 100 ms, but this is only half of the story: Beacons are sent by the AP at a regular interval defined as the so called "Target Beacon Transmission Time" (TBTT). The TBTT is a time interval measured in time units (TUs). A TU is often mentioned with a duration of 1 ms but this is a bit wrong. The reality is seen in the definition of a time unit within the 802.11-2012 standard document, which reads, "A measurement of time equal to 1024 µs." and this is exacly what we can measure:

1ms WiFi 802.11 Beacon Signal

The next screenshots shows two channels with a dominant 80mS pulse duration package looking like a TTI from multiple GSM bases stations. One cluster package is marked with the help of cursor showing a 10ms overall cluster length. In LTE the TTI length is fixed to 1 ms so for sure this must be a UMTS/HSPA transmission which offers a TTI of 2 ms, 10 ms (or 20 ms, 40 ms, 80 ms for some channels), and fixed for a given channel. The Transmission Time Interval (TTI) from a UMTS/HSPA is an interval of time for transmission of one layer 2 data unit (PDU). The TTI comprises the group of blocks of resources for the transmission to which the same coding and modulation is applied:

Pulsed Waterfall Screenshot showing a 80ms pulse duration from GSM Basestations

A typical Mission:

Pulsed Waterfall Typical Mission