为降低自由空间光(FSO:Free Space Optical)通信系统中由大气湍流引起的误码率影响,提出基于低密度奇偶校验(LDPC:Low-Density Parity-Check)码的编码多级调制方式,该方式将LDPC码与二进制相移键控(BPSK:Binary Phase-Shift Keying)和脉冲位置调制(PPM:Pulse Position Modulation)复用的调制方式相结合,以提升FSO系统的性能。设计了基于PPM-BPSK-LDPC编码多级调制方式的发射机以及接收机系统模型。通过在弱湍流信道和平均功率约束下的仿真证明,所提的PPM-BPSK-LDPC编码多级调制方式与基础的PPM-LDPC编码调制方式相比,其频带利用率更高,平均误码率性能更好。
A hybrid polarization division multiplexed-differential phase shift keying-multipulse pulse position modulation(PDM-DPSK-MPPM) scheme for multi-hop free-space optical(FSO) communication is investigated. The analytical bit error rate(BER) of the proposed system in Gamma-Gamma turbulence channels is derived and verified using computer simulation. The results show that both multi-hop and hybrid modulation schemes are efficient techniques to improve the performance of FSO links. Compared with the traditional binary phase shift keying(BPSK) and MPPM, the hybrid scheme can improve the bandwidth-utilization efficiency and reliability of the system. Compared with the coherent demodulation of PDM-QPSK-MPPM, the system complexity is reduced at the cost of the degradation of BER performance, which can improve the practicality of hybrid modulation technology in FSO system.
The key techniques in indoor positioning based on visible light communication and the state of the art of this research were surveyed. First, the significance of indoor positioning based on visible light communication from two aspects of the limitations of current indoor positioning technology and the advantages of visible light communication was discussed; And then, the main four technology of indoor positioning based on visible light communication were summarized and the triangulation of RSS method and the principle of image positioning were introduced in detail; Next, the performance characteristics of various typical algorithms were compared and analyzed; In the end, several suggestions on future research of indoor positioning based on visible light communication were given.
WANG ChunyueWANG LangCHI XuefenLIU ShuangxingSHI WenxiaoDENG Jing
为解决所构建的联合资源分配模型的资源分配问题,提出一种面向拥塞控制的联合功率控制与信道分配算法(CCJPCA:Congestion Control oriented Joint Power control and Channel assignment Algorithm)。CCJPCA算法通过混合编码策略实现了链路功率与信道变量的共同进化,利用Q-Learning算法的回报机制实现变异策略的自适应选择,从而保证网络资源的合理配置。NS-3(Network Simulator-3)仿真结果表明,CCJPCA算法能优先为网络瓶颈链路分配网络资源,提高算法收敛速度,减少网络排队和重传时延,降低网络平均丢包率。
