Satellite communication is a communication method between two terminals on the ground through artificial earth satellite relay. Since 1960, when American researchers completed the first satellite relay communication through “Echo I”, after more than 70 years of development, satellite communication has penetrated into people’s daily work and life. At present, satellite communication resources (frequency band, power, etc.) are still very important communication resources.
How to efficiently use satellite communication resources has always been one of the important research directions in this field. In 1998, Mark Dankberg, an engineer at ViaSat in the United States, proposed a new technology for two-way satellite communication: PCMA: Paired Carrier Multiple Access.
This technology enables both communication parties to transmit their respective signals on the same frequency band, and the signal processing at the receiving end makes it have the same reception sensitivity as the traditional communication method; However, the utilization rate of spectrum resources is more than double higher than that of traditional multi-access methods. Therefore, PCMA technology has a unique advantage in terms of the interest rate of spectrum resources.
The basic principle of PCMA is that the signals of terminals A and B are transmitted simultaneously on the same transponder band r(t) = sA(t) + sB(t) + n(t). If it is a third party, it is impossible to recover the corresponding transmission bitstream, but as one of the two parties to the communication, the A terminal subtracts its own transmit signal when receiving the signal, so that it can receive the transmitted signal of the other terminal B: rA(t) = r(t) - sA(t) = sB(t) + n(t), thereby restoring the bitstream sent by the opposite.
As we can see from the above technology, since the transmitted signals of the two sides of the communication are superimposed, this will also increase the difficulty of receiving third parties. Therefore, PCMA technology has a natural ability to resist interception. At present, the technology has been applied in some special areas.
In today’s world where frequency resources are still scarce, more efficient and more discreet PCMA technology will play a bigger role.
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