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- 저자 : ( Dazhuan Xu ) (검색결과 3 건)
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Cross-Layer Resource Allocation Scheme for WLANs with Multipacket Reception
Lei Xu,Dazhuan Xu,Xiaofei Zhang,Shufang Xu 한국전자통신연구원 2011 ETRI Journal Vol.33 No.2
Tailored for wireless local area networks, the present paper proposes a cross-layer resource allocation scheme for multiple-input multiple-output orthogonal frequency-division multiplexing systems. Our cross-layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets’ lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets’ lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.
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Design and Optimization for Distributed Compress-and-Forward System based on Multi-Relay Network
( Junwei Bao ),( Dazhuan Xu ),( Hao Luo ),( Ruidan Zhang ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.6
A novel distributed compress-and-forward (CF) system based on multi-relay network is presented. In this system, as the direct link between the source and destination is invalid due to some reasons, such as the limited power, special working environment, or even economic factors, relays are employed to receive analog signals and carry on distributed compressed encoding. Subsequently, the digital signals are transmitted to the destination via wireless channel. Moreover, a theoretical analysis for the system is provided by utilizing the Chief Executive Officer (CEO) theory and Shannon channel capacity theory, and the rate-distortion function as well as the connection between the transmission rate and the channel capacity are constructed. In addition, an optimal signal-to-noise ratio (SNR) -based power allocation method is proposed to maximize the quantization SNR under the limited total power. Simulation result shows that the proposed CF system outperforms the amplify-and-forward (AF) system versus the SNR performance.
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Low‐complexity de‐mapping algorithms for 64‐APSK signals
Junwei Bao,Dazhuan Xu,Xiaofei Zhang,Hao Luo 한국전자통신연구원 2019 ETRI Journal Vol.41 No.3
Due to its high spectrum efficiency, 64‐amplitude phase‐shift keying (64‐APSK) is one of the primary technologies used in deep space communications and digital video broadcasting through satellite‐second generation. However, 64‐APSK suffers from considerable computational complexity because of the de‐mapping method that it employs. In this study, a low‐complexity de‐mapping method for (4 + 12 + 20 + 28) 64‐APSK is proposed in which we take full advantage of the symmetric characteristics of each symbol mapping. Moreover, we map the detected symbol to the first quadrant and then divide the region in this first quadrant into several partitions to simplify the formula. Theoretical analysis shows that the proposed method requires no operation of exponents and logarithms and involves only multiplication, addition, subtraction, and judgment. Simulation results validate that the time consumption is dramatically decreased with limited degradation of bit error rate performance.
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