Data Acquisition and Statistical Characterization

There are four closely related parameters that will be measured by the link experiment for the W band uplink and V band downlink: bit error rate (BER), availability, signal to noise ratio (SNR), and link margin.

BER Measurement and Availability:

BER measurements will be taken continuously on the satellite transponder and the earth station receiver. BER from the transponder will be relayed back to earth on the satellite’s telemetry link, and all the data will be stored for later statistical analysis.

For availability, the link is defined as being available when the BER below a threshold. For the purposes of this experiment, we will define the BER threshold for availability as 10^-6.

SNR and Link Margin:

Each receiver will also measure and store SNR in addition to the BER data for later statistical analysis. The SNR depends on the received power and the receiver noise power, and it is a good indication of the condition of the link (see the W Band Link Budget section for more details).

Link margin is defined as the amount of additional received power above the threshold required for the link to meet the minimum BER requirement. A theoretical SNR threshold can be calculated based on the theoretical error probability of each modulation constellation and the coding gain, however the actual value will vary slightly from the theoretical based on the receiver implementation and performance.

Statistical Analysis:

The same platform as was used for the beacon experiment will be used to store and analyze data for the W-band communications link (see V-band Experiment Plan).

Once a sufficient amount of data is collected, statistical analyses can be done to obtain curves for these parameters (BER, SNR, availability, and link margin) vs. percentage of time over time periods such as one month or one year. Further, the results obtained here can be correlated with the weather and atmospheric data collected for the beacon experiment to draw curves such as rainfall rate vs. BER or link margin. It will also be useful to look at the collected data vs. time of day and seasons. Once the collected data is correlated against rainfall rate, it will be possible to extrapolate the data to other ITU zones within the range of rainfall rates observed. The data will also be used to evaluate the performance of the coding and modulation in real world conditions compared to the theoretical values, and having the flexibility to do this is a good asset to investigate the feasibility of broadband transmissions in the W-band in the future.