representation because the spatiotemporal graph structure in-
herently has the complex coupling in both spatial and tempo-
ral dimensions. To our knowledge, existing methods hardly
take into account each of the important conditions mentioned
above simultaneously because of the consideration of com-
putational complexity or inference speed or even modelling
ability.
To overcome these shortages, the Combined Dynamic Vir-
tual spatiotemporal Graph Mapping (CDVGM) is proposed.
In this work, we explore capturing dynamic correlations be-
tween spatial and temporal dimensions without any topolog-
ical additions and the stability of the prediction. The work
draws on cross-entropy theory and uses it as the basis for the
asymmetric study of node correlations in the construction of
dynamic Laplacian. In this work, all traffic nodes are located
in the same quantifying space to compute the differences by
cross-entropy of history flow data. We treat the result as the
expression of correlations of each two nodes in the case of
incorporating temporal features. Therefore, the direction is
also addressed as there are up-streams and down-streams ob-
jectively in the road of the real. Unlike existing methods, CD-
VGM efficiently generates adaptive Laplacian through his-
tory flows in a series of states even if the road network is
changing, e.g. some interactions might be unavailable due to
the crash. Finally, we find that the graph Laplacian operators
with different order of magnitude scales can better represent
the key nodes in the spatial network and find the high-energy
regions existing in the corresponding road network, which is
more conducive to the transmission of induced graph signals.
Besides, the stability of the mid-range forecasting problem
also got relief by the way of LT 2Smodule, which takes the
trend as the key of the prediction task and improves the whole
accuracy even in complex couplings of spatiotemporal depen-
dencies.
1) The first topological-structure-free framework with dy-
namic dependencies modelling is proposed, which com-
bined both synchronous and asynchronous advantages
within fast convergence speed and excellent prediction
accuracy.
2) The Laplacian is carefully designed by a dynamic vir-
tual graph for graph signal passing, which considers the
temporal correlations and spatial connections simultane-
ously in a time-series-based way by similarity theory.
3) A Long-Term Temporal Strengthen (LT 2S) module is
proposed to enhance the perception of long-range de-
pendencies with flexibility. It gives a simple but effec-
tive way to the series prediction task.
4) Extensive experiments on four benchmarks demonstrate
that the proposed framework outperforms many recent
state-of-the-art methods, implying that CDVGM has the
best predictive ability and application value so far.
2 Related works
2.1 Traffic Prediction
Traffic forecasting has many application values in smart city
construction. Traffic data is often viewed as a spatiotemporal
graph. Due to the limited modelling ability of the early sta-
tistical methods [Junior et al., 2014], they only consider the
temporal dimension for modelling, ignoring the geographic
effect of the spatial dimension, which leads to the funda-
mental defects of such methods. Subsequently, STGCN [Yu
et al., 2017a]and DCRNN [Li et al., 2017]model the spa-
tial dimension through a deep learning method with GLU or
RNN for temporal prediction asynchronously while methods
such as STSGCN [Song et al., 2020]and STFGNN [Li and
Zhu, 2021]use a local graph to represent spatiotemporal cor-
relation synchronously. S2TAT [Wang et al., 2022b]uses a
time-oriented graph convolution network to improve the abil-
ity of spatiotemporal perception. Owing to the challenges
of spatiotemporal modelling, attention mechanism is adopted
such as ASTGCN [Guo et al., 2019a]and DGCN [Guo et al.,
2022]etc. Except this, STGODE [Fang et al., 2021]uses
spatial-based adjacency matrices and semantic-based adja-
cency matrices to reflect spatial dependencies, and perceive
high-dimensional spatiotemporal correlations through ordi-
nary differential equations. ST-3DNet [Guo et al., 2019b]
first utilizes a 3D-convolution operator for spatiotemporal
graph modelling and ST-ResNet [Zhang et al., 2017]consid-
ers the fact of temporal characteristics of crowd movement to
fit the real-world situation better.
In a word, existing methods normally either consider the
complex coupling as a separate modelling problem wrongly
within the IID assumption or ignore the direct or indirect en-
tanglement that exists between potential spatiotemporal de-
pendencies, which leads to the drawbacks of low general-
izability. Unlike prior works, our novelty is that propos-
ing a topological-free virtual graph designed by combining
spatiotemporal dimensions and equipped with a temporal
strengthen strategy asynchronously to boost performance for
the prediction task.
2.2 Graph convolutional neural network
The graph convolutional neural network realizes the opera-
tion of convolution of non-Euclidean graph data, and GNN
has had a significant impact in the fields of social relation-
ship mining and chemical biology. It can be roughly divided
into two categories, one is a spectral graph neural network
based on spectral graph theory, and the other is a graph net-
work based on the spatial method. Among them, ChebyNet
[Defferrard et al., 2016]uses Chebyshev polynomials to ap-
proximate the Laplacian operator of spectral graph decompo-
sition, which greatly reduces the computational complexity
and is a typical representative of spectral graph neural net-
works. Then graph convolution neural network (GCN) [Kipf
and Welling, 2016]simplifies ChebyNet with a first-order
polynomial, which removes the hyperparameter of K-level
adjacent and becomes the cornerstone of spatial graph neu-
ral network. Space-based GCN generalizes convolution in
Euclidean space to work on graph data. For example, Graph-
SAGE [Hamilton et al., 2017]transmits the neighbour node’s
signal through an adjacency matrix before aggregating fea-
tures, and Graph Attention Network (GAT) [Velickovic et al.,
2017]weight node signals by attention mechanism. Simpli-
fied Graph Convolution Network (SGC) [Wu et al., 2019]re-
moves the non-linear activations in hidden layers for local av-