Adaptive Radio Technologies (ART) offers a new platform that could significantly improve the CubeSat’s downlink bandwidth, but is not without its limitations.

In this paper, the traditional methods of downlink are compared to the new method proposed by ART.

The Low Earth Orbit to ground radio link is highly dynamic. The traditional approach by which radios are designed assume the worst-case scenarios, which gives reliability but is inefficient because is not utilizing the full capacity of a given channel. Los Alamos National Laboratory has developed advanced technologies that can fully exploit the dynamic channels that are used, thus improving the efficiency of small satellite radios. By adaptively changing the data transmission rate during a LEO satellite pass the adaptive radio is capable of bit rates as low as 117 kbps and as high as 18.6 Mbps.

This is achieved by measuring the signal strength and then using a conventional bit rate uplink to command the satellite to change the downlink’s bit rate. It is not practical to adapt this bit rate continuously; instead it can be adjusted at discrete steps to optimize the results. Given identical power, weight, and volume using the adaptive radio method provides 10 times more improvement than using conventional methods. To obtain these results a 2.4 GHz downlink frequency was used.

While this new concept provided by Adaptive Radio Technologies gives the best results in the downlink bandwidth, it is by using the 2.4 GHz frequencies. This creates a limitation because past CubeSats have used the amateur frequencies, which are also used by the ground station and are the frequencies that we should focus on as stated on the previous post.

Reference: www.adaptiveradiotech.com/presentations/jmp_smallsat_2009.pdf

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