Beacon Test Plan

Signal Attenuation

Measurement of Signal Attenuation is to be characterized by comparing the signal amplitude received and logged by the DSP on the receiver at the ground station during a Clear-Day condition and comparing this value to the measurements taken with varying weather conditions at all locations. By doing this many times for both clear day and conditions and for the different weather conditions a table of attenuations can be generated.

Phase Distortion

Phase distortion measurements will be completed by monitoring the In Phase and Quadrature components of the signal going into the DSP block of the receiver and comparing them to those generated at the transmitter. Both of the software defined radio of the transmitter and the DSP block of the receiver are to be locked to GPS timing and time stamped. By doing so, the difference in phase and compensating for the phase difference created by the signal having travelled from the transmitter to the receiver, the phase distortion of the channel can be found. In order for this testing scheme to work, the full gain and phase behavior of both the transmitter and the receiver must be characterized for all frequencies tested.

Depolarization

Measurement of depolarization is to be completed by taking advantage of the ground station receiver having two antennas; one polarized for vertical polarization while the other one is horizontal. By switching between the two antennas and monitoring the amplitude and phase of the signal received for both states, it is proposed that the amount of depolarization of the original vertically polarized signal can be found. This process is to be completed for Clear-day conditions to calculate a baseline depolarization and then repeated for various weather conditions.

Testing

As many of the procedures to test these characteristics can be done simultaneously, a rigorous Design of Experiments (DoE) analysis will be completed to define the minimum number of tests that can be completed that will fully characterize the atmospheric effects of a wide range of weather conditions on the link. Tests will be repeated will similar weather, polarization, and signal level as necessary to rigorously test the validity of data. This data proposed to then by used in modeling software created to predict results of future testing; the results of this software simulation is to be compared with the aforementioned test results for accuracy.

Modulation Schemes/Coding

Initial proposed modulation scheme is Binary Phase Shift Keying (BPSK) with a variable data rate based on the testing required. It is proposed that as more characterization of the atmosphere is completed, or if it is found during development that more complexity is needed, that other modulation schemes and coding is to be added to the system.

Bit Error Rate

Bit Error Rate (BER) is to be characterized at various data rates, frequencies and atmospheric conditions. The BER assumed in all link budget calculations for this proposal is 0.0001; an ideal goal for communications. Characterizing the BER of the system for BPSK will be completed by sending identical messages to the DSP of the receiver, either on the satellite or the base station, on both the channel under test and on the auxiliary channel for command and control mentioned in the BAA. These received messages will then be compared bit by bit for errors, which will be reported to the tester.

Link Margin

Link Margin is to be measured by varying the amplitude output of the transmitter at various data rates, frequencies, and atmospheric conditions until the BER measured by the system becomes unacceptable to the tester. By doing so, the difference between maximum output power and the output of the transmitter at the point of crossover into bad BERs, will be used as the link margin.

Availability

It is proposed that availability tables are to be constructed, for various data rates and a defined maximum BER, of frequency versus percentage of time available. This is to be completed by tests that span various whether conditions at each location. By logging the amount of time that the BER of the link is higher than that desired for availability (0.001 has been the baseline for this proposal), and comparing that to the length of the test, the availability percentage can be found.

Testing

As many of the procedures to test these characteristics can be done simultaneously, a rigorous Design of Experiments (DoE) analysis will be completed to define the minimum number of tests that can be completed that will fully characterize the atmospheric effects of a wide range of weather conditions on the link. This data proposed to then by used in modeling software created to predict results of future testing; the results of this software simulation is to be compared with the aforementioned test results for accuracy.