The existing physical layer security schemes, which are based on the key generation model and the wire-tap channel model, achieve security by utilizing channel reciprocity entropy and noise entropy, respectively. In contrast, we propose a novel secure transmission framework that combines noise entropy with reciprocity entropy, achieved by inserting reciprocity entropy into the frozen bits of polar codes. Note that in real-world scenarios, when eavesdroppers employ polynomial-time attacks, the bit error rate (BER) increases due to the introduction of computational entropy. To achieve indistinguishability security, we convert the practical physical layer security metric, BER, into the average min-entropy, a widely accepted concept in cryptography. The simulation results demonstrate that the eavesdropper’s BER can be significantly increased without compromising the communication performance of the legitimate receiver. Under concrete parameters we selected, when compared to the joint scheme of physical layer key generation and one time pad, the modular semantically-secure scheme based on the wire-tap channel model, and the simple channel entropy combination scheme, our scheme achieves a message rate approximately 1.2 times, 3.8 times, and 1.4 times better, respectively. Experimental testing validates the feasibility of our scheme.

This letter proposes a key exchange scheme for the untrusted relay system, where the relay not only assists in message transmission but also tries to recover messages. Terminal users initiate the process by transmitting a local key and utilize constellation overlapping techniques to create an overlapped constellation at the relay nodes, which increases the decoding error rate for relay eavesdropping but still poses a risk of key leakage. To address this, we propose a fine-grained entropy extraction algorithm that quantifies the overlapped constellation points into key bits, which are uniformly random bits from the relay’s perspective. In the constellation overlapping scenario, we can estimate the number of instances where the relay cannot distinguish. Leveraging this, our algorithm achieves remarkable levels of entropy utilization. QPSK enables perfect lossless entropy extraction, while other QAM modulation schemes can achieve a utilization rate of up to 96%.

Polar codes are the first provably capacity-achieving novel channel codes. Successive cancellation list (SCL) decoding algorithm has a performance close to maximum-likelihood decoding when code length is finite, though the complexity is high. To reduce the complexity of SCL, a partial path expansion with segmented check and pruning SCL (PPE-SCP-SCL) algorithm is proposed in this paper. Based on the successive decoding structure, if the decoding result of a bit is judged to be reliable enough, then a hard decision is made directly and no path expansion is necessary. Moreover, several parity-check points are introduced to perform segmented parity-check during the decoding process, and if the check fails, the current path is directly abandoned. The rationality of the operations is theoretically verified, and numerical simulations also verify that the proposed algorithm can significantly reduce the complexity of decoding with trivial loss of error performance.

The sparse code multiple access technology and polar code technology can meet the functional requirements of the three major scenarios of 5G. A SCMA system receiver can combine a multi-user detector with a polar code decoder, but it requires high computational complexity to obtain the ideal bit error rate (BER) performance. This paper proposes a joint iterative detection and decoding receiver (VJDD) scheme for transmitting verified messages based on a serial structure. This solution improves the iterative convergence speed of the receiver by transmitting verified messages to each node in the factor graph in time. Simulation results show that the VJDD scheme can reduce the computational complexity of the receiver on the premise of ensuring the performance of the receiver.

Joint detection and decoding (JDD) algorithm has recently received extensive attention due to its excellent performance. Responding to the requirements of the 5thgeneration communication system with high rate and low latency, a low complexity joint detection and decoding (LCJDD) algorithm for MIMO-LDPC system has been proposed. The computational complexity of the proposed algorithm is significantly lower than that of systems using JDD blocks, and the performance loss can be controlled to be within about 0.5 dB.

With end-to-end latency constantly emphasized in next generation wireless communication, we present a novel low latency polar coded modulation scheme for noncoherent multiple-input multiple-output (MIMO) channel. Parallel demodulation structure is utilized in our scheme in order to reduce the latency of noncoherent MIMO demodulation. Moreover, by splitting a whole polar code into several component codes, we increase the parallelism of polar decoding to further reduce latency. Besides, an efficient and practical polar code construction method is provided. Complexity analysis and numerical simulation show that system latency is significantly reduced with a trivial error performance loss.