Military robot swarm becomes more and more important for contemporary military application. In order to satisfy sophisticated application scenarios, novel communication architecture for military robot swarm has to be conceived. In this paper, we propose a multi-carrier intelligent covert satellite communication (MCICSC) architecture based on electromagnetic environment sensing technology, in where the ability of dynamically adapting the system configuration to the holistic requirements of covertness, performance, and complexity can be considerably improved. Additionally, in order to solve the carrier synchronization problem in very low signal noise ratio (SNR) for each data stream of MCICSC, polar code (PC) is incorporated into the proposed MCICSC system. With the aid of the proposed polar code-aided multi-stream parallel feedback (PAMSPF) carrier synchronization scheme, the MCICSC system is capable of realizing high-precise carrier synchronization even in very low SNR region. Moreover, in order to further decrease the complexity of our MCICSC system, we also propose a polar code-based diversity combining (PBDC) scheme, which is capable of efficiently combing all the data streams without the aid of channel state information (CSI) estimation. Numerical simulations demonstrate that for MCICSC system the performance of the PAMSPF carrier synchronization and PBDC combining schemes can get extremely close to that of an ideally synchronized system. Complexity analysis of the proposed algorithms is given as well.

Polar codes (PCs) have attracted significant attention in the last decade, especially after their adoption in the forthcoming 5G wireless networks. However, previous studies focused on coherent polar codes, which always rely on the strong assumption of available perfect channel state information. Instead, in this paper, we investigate the use of PCs in noncoherent systems. First, a binary differential phase shift keying (BDPSK) demodulator is concatenated with a polar decoder to form the noncoherent detector, where successive cancellation (SC) is applied. The simulation results demonstrate that the SC-based PCs for noncoherent detection have approximately a discrepancy of only 3 dB compared with the coherent counterpart in noncoherent channels. Furthermore, in order to further decrease this discrepancy, we replace the BDPSK demodulator with a soft-input soft-output (SISO) multiple symbol differential sphere decoding demodulator. Similarly, the SC-based PC decoder is replaced by the SISO belief propagationbased PC decoder, and by using this novel architecture, an iterative noncoherent detector is constructed. Benefiting from further invoking extrinsic information transfer chart tool and the dynamic window-size detection scheme, the performance of the proposed iterative noncoherent detector becomes competitive with its coherent one in practical applications, since the performance degradation is reduced to 1 dB.

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