Jianrong Bao

Improved Relay Selection Strategy for Hybrid Decode-Amplify Forward Protocol

—To improve the problems of noise amplification and error propagation of the fixed cooperation schemes in cooperative communications, a relay selection strategy is proposed based on the hybrid decode-amplify-forward protocol. It can adaptively determine cooperation schemes according to the Channel Status Information (CSI) of the source-relay. Then it selects the best relay from the candidate relay set of the two fixed cooperation schemes, for a maximum Signal-Noise Ratio (SNR) in the destination. The theoretical analyses and the simulation results all show that the proposed strategy can improve the performance of the Bit-Error-Rate (BER) and the outage probability significantly, when compared with the relay selection strategies of the fixed cooperation schemes. Also it performs excellent with the increased number of the relays.

Optimized Power Allocation and Relay Location Selection in Cooperative Relay Networks

An incremental selection hybrid decode-amplify forward (ISHDAF) scheme for the two-hop single relay systems and a relay selection strategy based on the hybrid decode-amplify-and-forward (HDAF) scheme for the multirelay systems are proposed along with an optimized power allocation for the Internet of Thing (IoT). Given total power as the constraint and outage probability as an objective function, the proposed scheme possesses good power efficiency better than the equal power allocation. By the ISHDAF scheme and HDAF relay selection strategy, an optimized power allocation for both the source and relay nodes is obtained, as well as an effective reduction of outage probability. In addition, the optimal relay location for maximizing the gain of the proposed algorithm is also investigated and designed. Simulation results show that, in both single relay and multirelay selection systems, some outage probability gains by the proposed scheme can be obtained. In the comparison of the optimized power allocation scheme with the equal power allocation one, nearly 0.1695 gains are obtained in the ISHDAF single relay network at a total power of 2 dB, and about 0.083 gains are obtained in the HDAF relay selection system with 2 relays at a total power of 2 dB.

Optimization of power allocation and outage probability of cooperative relay networks

In order to solve the extra power consumption caused by reducing complexity in cooperative relay networks, an optimized power allocation algorithm is proposed for the efficient incremental selection hybrid decode-amplify forward (ISHDAF) scheme. In the ISHDAF scheme, the transmission efficiency is improved by optimizing the power allocation, which is constrained by constant total power. And the outage probability is used as the objective function to optimize the whole power allocation. Then, rational allocation of the power of source and relay nodes can be obtained by the optimization of equal power allocation algorithm in the power limited wireless communication system. Simulation results show that the outage probability of a relay network is effectively reduced by the proposed scheme for the ISHDAF relay network. For an instance of a total power of 40W, there is a certain optimization of outage probability, when compared with that of the current HDAF scheme. Therefore, the proposed power allocation algorithm for the ISHDAF scheme can be effectively applied to optimize the power consumption in the relay network systems.

Low Rate QC LDPC Codes with Reconfigurable Structures for Space Information Networks

—This paper presents the construction of the efficient low rate Quasi-Cyclic (QC) Low-Density Parity-Check (LDPC) codes and their reconfigurable structures for space information networks. The code is firstly produced by a seed AccumulateRepeat-Accumulate (ARA) protograph and then extended to a QC generalized LDPC code, where a parity check node pair is replaced with a more powerful pre-coding Hamming node. The code matrix is optimized by both the Progressive Edge progressive (PEG) and the QC oriented modified approximate cycle extrinsic message degree (QC-MACE) algorithm. The QC form in the code saves much storage and reduces coding complexity greatly. The reconfigurable code structure is also given and it can be used in variable space channels. Simulation results show that the proposed code obtains 0.05 dB gain and has better error floor, when compared to the Turbo code in the Consultative Committee for Space Data Systems (CCSDS) with same parameters at a Bit-Error-Rate (BER) of 10. And the coding gain is also about 0.1 dB over that of the currently low rate and short QC LDPC codes at a BER of 10. Besides, it has good features of low decoding complexity and low latency and so on.

Power Optimized Single Relay Selection with an Improved Link-Adaptive-Regenerative Protocol

To improve the reliability and efficiency in cooperative communications, a power optimized single relay selection scheme is proposed by increasing the diversity effort with an improved link-adaptive-regenerative (ILAR) protocol. The protocol determines the forwarding power of a relay node by comparing the signal-to-noise ratio (SNR) at both sides of the node; thus it improves the power efficiency. Moreover, it also proposes a single relay selection strategy to maximize the instantaneous SNR product, which ensures the approximate best channel link quality for good relay forwarding. And the system adjusts the forwarding power in real time and also selects the best relay node participated in the cooperative forwarding. In addition, the cooperation in the protocol is analyzed and the approximate expression of the bit-error-rate (BER) and the outage probability at high SNRs are also derived. Simulation results indicate that the BER and outage probability of the relay selection scheme by the ILAR protocol outperform other contrast schemes of current existing protocols. At BER of 10−2, the proposed scheme with ILAR protocol outperforms those of the decoded-and-forward (DF), the selected DF (SDF), and the amplify-and-forward (AF) protocols by 3.5, 3.5 and 7 dB, respectively. Moreover, the outage probability of the relay system decreases with the growth of the relay number. Therefore, the proposed relay selection scheme with ILAR strategies can be properly used in cooperative communications for good reliability and high power efficiency.

A Primary User Emulation Attack Countermeasure Strategy and Energy-Efficiency Analysis in Cognitive Radio Networks

Due to the fact that security and energy efficiency are investigated separately in the conventional Primary User Emulation Attack (PUEA) countermeasure strategy in Cooperative Spectrum Sensing (CSS) process, the tradeoff between security and energy efficiency is discussed in this paper. CSS can improve detection performance whereas energy consumption will dramatically boost up with the increasing of cooperative users. To tackle this problem, we set CSS energy efficiency in the presence of PUEA as optimal objective, whereas secure detection performance and secure false alarm threshold as the constraint conditions. The optimal problem is resolved to achieve a trade-off between energy efficiency and security in the presence of PUEA attack. The optimal fusion threshold K and optimal cooperative user numbers can be obtained in secure CSS with energy efficiency maximization, which guarantees energy efficiency as well as secure CSS detection performance. The proposed PUEA countermeasure strategy detection performance is presented and compared with traditional Maximum Ratio Combining (MRC) fusion rule. Simulation results show that, the proposed strategy is immune to PUE interference power, and it provides high robustness to PUEA attack, which implements the trade-off between security and energy efficiency in Cognitive Radio Network (CRN) effectively.

A spectrum sensing data falsification countermeasure strategy in energy-efficient CRN

In cooperative detection, many secondary users (SUs) collaborate to sense spectrum holes, in order to enhance the reliability of spectrum sensing. However, some malicious SUs may interfere with cooperative spectrum sensing (CSS) performance by inducing false observation bits for fusion. An improved spectrum sensing data falsification (SSDF) countermeasure strategy is proposed. The strategy considers both energy-efficiency and security in cooperative detection phase. The optimal legitimate/malicious SU numbers can be determined with the objective of energy-efficiency maximization, under the constraints of message authentication code (MAC), CSS report distance and report error rate in the reporting sub-phase. In the proposed strategy, the tradeoff between security and energy-efficiency is investigated to guarantee secure CSS. Numerical results reveal that the proposed strategy outperforms a conventional SSDF defensive strategy with the same MAC security bits scenario. The improved SSDF countermeasure scheme provides significant enhancement of energy-efficiency and security performance in CRN secure CSS.

High Rate QC-LDPC Codes with Optimization of Maximum Average Girth

Nowadays, modern digital communication systems develop rapidly with larger capacity and high data rate to fulfill the requirement of mass multimedia information transmission and so on. One of such systems, the optical communication system, has several advantages, such as ultra larger capacity and better transmission channel, when compared with wireless and even the traditional cable communications. And it has been widely used for the long-haul transmission all over the world. But the reliability and effectiveness are still crucial for the optical communications. And effective measures are needed to

Joint iterative decoding and MMSE-SIC VBLAST detection of LDPC coded MIMO systems

A joint iterative low-density parity-check (LDPC) decoding and minimum mean square error with successive interference cancel (MMSE-SIC) vertical-Bell laboratories layered space-time (VBLAST) detection of LDPC coded multiple input multiple output (MIMO) system is proposed in an additive white Gaussian noise (AWGN) channel. It combines the LDPC decoding with VBLAST detection into a unified iterative framework by integrity and united method. It adopts the joint iterative message processing through the VBALST detector and the variable and check nodes of LDPC decoder. So it reduces the unnecessary information loss, which usually happens in separated coding and detection MIMO systems. Simulation results show that the proposed joint LDPC coded binary phase shift keying (BPSK) MIMO schemes outperforms the contrast scheme of simple concatenation about 0.3~0.5 dB at a bit-error-ratio (BER) of 10-5 in an AWGN channel. In addition, it only requires some rational coding and detection complexity, because it employs the sparse check matrices for encoding and applies joint processing for detection too. Therefore, the proposed joint LDPC decoding and MMSE-SIC VBLAST detection of an LDPC coded MIMO system can be efficiently applied in modern wireless digital communications for high performance.