For physical-layer secrecy performance, existing studies only focus on coding schemes that can achieve the secrecy capacity. However, finite blocklength penalty could be fatal for security of private message. In this paper, we explore the impact of finite blocklength on secrecy for the wiretap channel model. We propose secrecy performance matrices for finite blocklength analysis and provide analytical expressions to evaluate the secrecy performance. We demonstrate trade-off between secrecy and reliability, and also provide an upper bound of secret information rate in finite blocklength case. The results are also applied to indicate asymptotic performance.

We investigate a wireless energy harvesting and information transfer protocol in cognitive relay networks, where an energy harvesting secondary network shares the spectrum as well as harvests energy by assisting the primary transmission. In particular, the secondary transmitter scavenges energy from the received primary signal and then forwards the resulting signals along with the secondary signal. The secondary receiver can also harvest the ambient energy, and use the remaining signal to remove the primary interference. We analytically derive the exact expressions of the outage probabilities for both primary and secondary networks. Based on the proposed protocol, we analyze the rate-energy trade-off between the maximum ergodic capacity and the maximum harvested energy in the secondary network. Our results demonstrate that the proposed protocol not only achieves both the primary and secondary transmissions but also harvests the ambient energy without the performance loss.

In this paper, we propose a multi-level physical-layer network coding (MPLNC) scheme that optimizes the relay performance for both symmetric and asymmetric traffic in a Gaussian two-way relay channel. The proposed MPLNC scheme enables each source to employ multiple linear binary codes for encoding, one per modulation level, and the relay node to decode superimposed network codewords at each modulation level. We first derive the achievable rate for the transmission of arbitrary constellations and then prove that MPLNC with multistage decoding (MPLNC/MSD) can achieve the achievable rate if binary code rates are properly chosen for both sources. Furthermore, the design criteria for the proposed MPLNC scheme is investigated, which includes the rate design rule and the labeling strategy. Moreover, we derive the error exponent and an upper bound of the overall error probability for MPLNC. Our analysis and simulation results show that MPLNC/MSD has a significant performance advantage in comparison to the existing bit-interleaved coded modulation (BICM)-based PLNC scheme.

In this paper, we present a structured LDPC decoding algorithm for hierarchical QAM modulation systems. Unlike the traditional hierarchical demodulation approaches which suffer from serious inter-layer interference (ILI), the proposed method exploits structure information of the secondary layer to mitigate the ILI impairment, thereby offers significant gains in reception performance. An achievable rate analysis is performed to calculate the theoretical limit of the basic layer in HM reception, which in certain cases is 8 dB better than the required SINR threshold for QAM detection with all Gaussian interference. The new algorithm has been implemented on a broadband in-band on-channel (IBOC) digital radio broadcasting system. Numerical results from both simulations and experiments are provided to quantify the performance advantages of the new algorithm against the DVB-T benchmark.

In this paper, we present an in-band on-channel (IBOC) broadcasting system suitable for digital audio and data broadcasting in FM and AM channels. The new system utilizes a combination of frequency hopping, LDPC coding, hierarchical modulation and band aggregation techniques to increase the data rate, improve spectrum efficiency, and at the same time, provide spectrum flexibility to meet the requirements of high quality audio and multimedia services. A prototype has been developed on a personal computer (PC) based software defined radio (SDR) platform. Numerical results and initial laboratory tests demonstrate significant performance advantages of the new design over existing systems such as the Digital Radio Mondiale (DRM) and Hybrid Digital (HD) radio.