In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is...In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.展开更多
Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous rese...Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).展开更多
为探讨智能网联车混入人工驾驶车交通流后对信号控制的影响,提高交叉口车辆通过效率,对智能网联异质交通流在交叉口中的运动状态进行刻画,确定不同场景下的跟驰模型,基于D3QN(Dueling Double Deep Q Network)算法,结合LSTM(Long Short-T...为探讨智能网联车混入人工驾驶车交通流后对信号控制的影响,提高交叉口车辆通过效率,对智能网联异质交通流在交叉口中的运动状态进行刻画,确定不同场景下的跟驰模型,基于D3QN(Dueling Double Deep Q Network)算法,结合LSTM(Long Short-Term Memory)进行交通流预测,构建单点信号控制模型,通过SUMO(Simulation of Urban Mobility)软件的Traci(Traffic Control Interface)接口开展仿真实验。结果表明,智能网联车渗透率越高,交叉口平均排队长度越短,平均车速越快;当智能网联车渗透率达到0.6时,平均排队长度的降幅和平均车速的增幅较为显著,渗透率为1时,幅度最大;对比其他算法,研究提出的结合LSTM进行交通流预测的D3QN算法平均排队长度最短,平均车速最快,信号控制效果更佳,收敛速度更快。展开更多
物理信息深度学习(physics-informed deep learning, PIDL)是一种将深度学习与物理学先验知识相结合的新兴范式,该范式在智能交通领域,尤其在交通状态估计应用中,展现出了巨大潜力。为进一步优化物理信息深度学习模型在交通状态估计问...物理信息深度学习(physics-informed deep learning, PIDL)是一种将深度学习与物理学先验知识相结合的新兴范式,该范式在智能交通领域,尤其在交通状态估计应用中,展现出了巨大潜力。为进一步优化物理信息深度学习模型在交通状态估计问题上的准确度与收敛速度,构建了一个结合Aw-Rascle宏观交通流模型的物理信息自适应深度学习模型(physics-informed adaptive deep learning with Aw-Rascle, PIAdapDL-AR),依据有限与局部的交通检测数据,实时准确估计全局交通流状态。主要的改进包括两部分,一是在PIDL框架中的物理部分引入高阶Aw-Rascle交通流模型作为物理约束条件,引导并规范神经网络的训练过程;二是在神经网络部分融合自适应激活函数,替代固定的非线性激活函数,以动态优化神经网络性能。基于NGSIM数据集生成模拟的固定检测器数据和移动检测器数据,进行实验以验证模型有效性。实验结果表明:在不同覆盖率的固定检测数据场景下,PIAdapDL-AR的相对误差相比于基线模型PIDL-LWR降低了34.38%~45.24%;在不同渗透率的移动检测数据场景下,PIAdapDL-AR的相对误差相比于PIDL-LWR降低了18.33%~34.95%;融合自适应激活函数的PIAdapDL-AR的收敛速度优于配置固定激活函数的PIDL-AR,且收敛速度和估计精度均随着自适应激活函数中比例因子的增大而提升。展开更多
为深入挖掘交通流数据的复杂时空特征并建立其依赖关系,提高交通流参数的预测精度,本文提出一种新的交通流量预测模型——基于注意力机制和残差网络的时空关系图卷积网络(TSARGCN)。TSARGCN对输入数据进行切片,实现多分支建模,挖掘数据...为深入挖掘交通流数据的复杂时空特征并建立其依赖关系,提高交通流参数的预测精度,本文提出一种新的交通流量预测模型——基于注意力机制和残差网络的时空关系图卷积网络(TSARGCN)。TSARGCN对输入数据进行切片,实现多分支建模,挖掘数据的时间周期性特征;引入残差网络保证网络中信息传递的完整性;利用DTW (Dynamic Time Warping)算法计算路网中节点之间交通流量序列在时间维度的相似程度大小,提出时间图的概念,结合路网结构中各节点的邻近关系,提出时空关系图的概念;基于时空关系图,在每个分支结合注意力机制分别进行图卷积和时间维度卷积,捕获交通流的时空特征及其依赖关系,实现对路网交通流量数据时空关系的建模。经过在公开数据集PEMSD4上进行实验,结果表明:TSARGCN在交通流量预测中的平均绝对误差(MAE)达到19.24,均方根误差(RMSE)达到27.09,比ARIMA(Autoregressive Integrated Moving Average model),Conv-LSTM(Convolution Long short-term memory)及ASTGCN(Attention based Spatial-temporal Graph Convolutional Network)等知名交通流量预测算法具有更高的预测精度。展开更多
实时、准确的交通流短期预测是交通诱导、管理的前提.为了提高预测精度,结合交通流数据中的历史时间相关性与网络空间断面相关性,构建了一种基于皮尔森相关系数法(Pearson Correlation Coefficient,PCC)与双向长短时记忆(Bidirectional ...实时、准确的交通流短期预测是交通诱导、管理的前提.为了提高预测精度,结合交通流数据中的历史时间相关性与网络空间断面相关性,构建了一种基于皮尔森相关系数法(Pearson Correlation Coefficient,PCC)与双向长短时记忆(Bidirectional Long Short Term Memory,BLSTM)架构的交通流短时预测模型.该模型可以通过PCC筛选路网中与目标路段空间相关的路段,并将其重构为新数据集,作为BLSTM预测模型的输入,以实现交通流短期预测.通过美国加州交通流数据对模型预测性能进行评价,实验结果表明:该模型可以融合交通流数据中的时空相关性,相对于其他主流预测模型精度平均可提高4.83%.展开更多
基金ACKNOWLEDGEMENT This work was supported by National Natural Science Foundation of China （Grant No. 61231008）, National Basic Research Program of China （973 Program） （Grant No. 2009CB320404）, Program for Changjiang Scholars and Innovative Research Team in University （Grant No. IRT0852）, and the 111 Project （Grant No. B08038）.
文摘In the paper,we propose a framework to investigate how to effectively perform traffic flow splitting in heterogeneous wireless networks from a queue point.The average packet delay in heterogeneous wireless networks is derived in a probabilistic manner.The basic idea can be understood via treating the integrated heterogeneous wireless networks as different coupled and parallel queuing systems.The integrated network performance can approach that of one queue with maximal the multiplexing gain.For the purpose of illustrating the effectively of our proposed model,the Cellular/WLAN interworking is exploited.To minimize the average delay,a heuristic search algorithm is used to get the optimal probability of splitting traffic flow.Further,a Markov process is applied to evaluate the performance of the proposed scheme and compare with that of selecting the best network to access in terms of packet mean delay and blocking probability.Numerical results illustrate our proposed framework is effective and the flow splitting transmission can obtain more performance gain in heterogeneous wireless networks.
基金Supported by the Support Program of the National 12th Five Year-Plan of China(2015BAK25B03)
文摘Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).
文摘为探讨智能网联车混入人工驾驶车交通流后对信号控制的影响,提高交叉口车辆通过效率,对智能网联异质交通流在交叉口中的运动状态进行刻画,确定不同场景下的跟驰模型,基于D3QN(Dueling Double Deep Q Network)算法,结合LSTM(Long Short-Term Memory)进行交通流预测,构建单点信号控制模型,通过SUMO(Simulation of Urban Mobility)软件的Traci(Traffic Control Interface)接口开展仿真实验。结果表明,智能网联车渗透率越高,交叉口平均排队长度越短,平均车速越快;当智能网联车渗透率达到0.6时,平均排队长度的降幅和平均车速的增幅较为显著,渗透率为1时,幅度最大;对比其他算法,研究提出的结合LSTM进行交通流预测的D3QN算法平均排队长度最短,平均车速最快,信号控制效果更佳,收敛速度更快。
文摘物理信息深度学习(physics-informed deep learning, PIDL)是一种将深度学习与物理学先验知识相结合的新兴范式,该范式在智能交通领域,尤其在交通状态估计应用中,展现出了巨大潜力。为进一步优化物理信息深度学习模型在交通状态估计问题上的准确度与收敛速度,构建了一个结合Aw-Rascle宏观交通流模型的物理信息自适应深度学习模型(physics-informed adaptive deep learning with Aw-Rascle, PIAdapDL-AR),依据有限与局部的交通检测数据,实时准确估计全局交通流状态。主要的改进包括两部分,一是在PIDL框架中的物理部分引入高阶Aw-Rascle交通流模型作为物理约束条件,引导并规范神经网络的训练过程;二是在神经网络部分融合自适应激活函数,替代固定的非线性激活函数,以动态优化神经网络性能。基于NGSIM数据集生成模拟的固定检测器数据和移动检测器数据,进行实验以验证模型有效性。实验结果表明:在不同覆盖率的固定检测数据场景下,PIAdapDL-AR的相对误差相比于基线模型PIDL-LWR降低了34.38%~45.24%;在不同渗透率的移动检测数据场景下,PIAdapDL-AR的相对误差相比于PIDL-LWR降低了18.33%~34.95%;融合自适应激活函数的PIAdapDL-AR的收敛速度优于配置固定激活函数的PIDL-AR,且收敛速度和估计精度均随着自适应激活函数中比例因子的增大而提升。
文摘为深入挖掘交通流数据的复杂时空特征并建立其依赖关系,提高交通流参数的预测精度,本文提出一种新的交通流量预测模型——基于注意力机制和残差网络的时空关系图卷积网络(TSARGCN)。TSARGCN对输入数据进行切片,实现多分支建模,挖掘数据的时间周期性特征;引入残差网络保证网络中信息传递的完整性;利用DTW (Dynamic Time Warping)算法计算路网中节点之间交通流量序列在时间维度的相似程度大小,提出时间图的概念,结合路网结构中各节点的邻近关系,提出时空关系图的概念;基于时空关系图,在每个分支结合注意力机制分别进行图卷积和时间维度卷积,捕获交通流的时空特征及其依赖关系,实现对路网交通流量数据时空关系的建模。经过在公开数据集PEMSD4上进行实验,结果表明:TSARGCN在交通流量预测中的平均绝对误差(MAE)达到19.24,均方根误差(RMSE)达到27.09,比ARIMA(Autoregressive Integrated Moving Average model),Conv-LSTM(Convolution Long short-term memory)及ASTGCN(Attention based Spatial-temporal Graph Convolutional Network)等知名交通流量预测算法具有更高的预测精度。
文摘实时、准确的交通流短期预测是交通诱导、管理的前提.为了提高预测精度,结合交通流数据中的历史时间相关性与网络空间断面相关性,构建了一种基于皮尔森相关系数法(Pearson Correlation Coefficient,PCC)与双向长短时记忆(Bidirectional Long Short Term Memory,BLSTM)架构的交通流短时预测模型.该模型可以通过PCC筛选路网中与目标路段空间相关的路段,并将其重构为新数据集,作为BLSTM预测模型的输入,以实现交通流短期预测.通过美国加州交通流数据对模型预测性能进行评价,实验结果表明:该模型可以融合交通流数据中的时空相关性,相对于其他主流预测模型精度平均可提高4.83%.
