Covert Communication with Finite Blocklength in AWGN Channels
This work addresses secure communication for scenarios requiring undetectability, providing analytical insights for finite blocklength regimes, though it is incremental as it builds on existing covert communication theory.
The paper tackles the problem of covert communication in AWGN channels with finite blocklength, proving that using all available channel uses maximizes effective throughput under covertness constraints, with results showing throughput increases with blocklength despite per-use power limits decreasing.
Covert communication is to achieve a reliable transmission from a transmitter to a receiver while guaranteeing an arbitrarily small probability of this transmission being detected by a warden. In this work, we study the covert communication in AWGN channels with finite blocklength, in which the number of channel uses is finite. Specifically, we analytically prove that the entire block (all available channel uses) should be utilized to maximize the effective throughput of the transmission subject to a predetermined covert requirement. This is a nontrivial result because more channel uses results in more observations at the warden for detecting the transmission. We also determine the maximum allowable transmit power per channel use, which is shown to decrease as the blocklength increases. Despite the decrease in the maximum allowable transmit power per channel use, the maximum allowable total power over the entire block is proved to increase with the blocklength, which leads to the fact that the effective throughput increases with the blocklength.