Yang Fan, Zeng Xiaoping, Mao Haiwei, Jian Xin, Tan Xiaoheng, Du Derong
College of Communication Engineering, Chongqing University, Chongqing 400044, China.
Chongqing Jinmei Communication Co. Ltd., Chongqing 400030, China.
Sensors (Basel). 2018 Jan 15;18(1):229. doi: 10.3390/s18010229.
The high demand for multimedia applications in environmental monitoring, invasion detection, and disaster aid has led to the rise of wireless sensor network (WSN). With the increase of reliability and diversity of information streams, the higher requirements on throughput and quality of service (QoS) have been put forward in data transmission between two sensor nodes. However, lower spectral efficiency becomes a bottleneck in non-line-of-sight (NLOS) transmission of WSN. This paper proposes a novel nondata-aided error vector magnitude based adaptive modulation (NDA-EVM-AM) to solve the problem. NDA-EVM is considered as a new metric to evaluate the quality of NLOS link for adaptive modulation in WSN. By modeling the NLOS scenario as the η - μ fading channel, a closed-form expression for the NDA-EVM of multilevel quadrature amplitude modulation (MQAM) signals over the η - μ fading channel is derived, and the relationship between SER and NDA-EVM is also formulated. Based on these results, NDA-EVM state machine is designed for adaptation strategy. The algorithmic complexity of NDA-EVM-AM is analyzed and the outage capacity of NDA-EVM-AM in an NLOS scenario is also given. The performances of NDA-EVM-AM are compared by simulation, and the results show that NDA-EVM-AM is an effective technique to be used in the NLOS scenarios of WSN. This technique can accurately reflect the channel variations and efficiently adjust modulation order to better match the channel conditions, hence, obtaining better performance in average spectral efficiency.
环境监测、入侵检测和灾难援助等领域对多媒体应用的高需求推动了无线传感器网络（WSN）的兴起。随着信息流可靠性和多样性的增加，对两个传感器节点之间数据传输的吞吐量和服务质量（QoS）提出了更高要求。然而，较低的频谱效率成为WSN非视距（NLOS）传输的瓶颈。本文提出了一种基于非数据辅助误差向量幅度的新型自适应调制（NDA-EVM-AM）来解决该问题。NDA-EVM被视为评估WSN中用于自适应调制的NLOS链路质量的新指标。通过将NLOS场景建模为η-μ衰落信道，推导了η-μ衰落信道上多级正交幅度调制（MQAM）信号的NDA-EVM的闭式表达式，并建立了误符号率（SER）与NDA-EVM之间的关系。基于这些结果，设计了NDA-EVM状态机用于自适应策略。分析了NDA-EVM-AM的算法复杂度，并给出了NDA-EVM-AM在NLOS场景下的中断容量。通过仿真比较了NDA-EVM-AM的性能，结果表明NDA-EVM-AM是一种适用于WSN的NLOS场景的有效技术。该技术能够准确反映信道变化并有效调整调制阶数，以更好地匹配信道条件，从而在平均频谱效率方面获得更好的性能。
