Multipath TCP Path Scheduling Optimization
Based on Q-Learning in Vehicular Heterogeneous
Networks
Haitao Zhao, Mengkang Zhang, Hongsu Yu, Tianqi Mao, Hongbo Zhu
College of Telecommunications and Information Engineering
Nanjing University of Posts and Telecommunications
Nanjing, China
email: zhaoht@njupt.edu.cn
Abstract—Nowadays, as a variety of network interfaces are
deployed in vehicles for a heterogeneous vehicular network,
the diversity of interfaces leads to a noticeable difference in
characteristics between transmission paths. When the
vehicular heterogeneous network uses multipath TCP for
transmission, the difference between the paths will cause the
receiving buffer to be blocked, resulting in poor multipath
TCP transmission performance. Aiming at the multipath TCP
receive buffer blocking problem, this paper proposes an QL-
MPS (Q-Learning Multipath Scheduling) optimization
algorithm based on Q-Learning. By using Q-Learning, the
multipath TCP node in the vehicular heterogeneous network
can continuously learn interactively with the surrounding
environment, and dynamically adjust the number of paths
used for transmission according to the learning result, so that
the node can always combine the data packets with the best
path set to transmit. After that, we predict the buffer blocking
problem by judging the number of out-of-ordered packets, and
use this algorithm to stop the data transmission on the bad
paths to improve the performance of multipath TCP. The
simulation results show that the algorithm can improve the
overall throughput of the system and improve the network
utilization.
Index Terms-Vehicular heterogeneous network; Q-
Learning; buffer blocking; optimization
I. INTRODUCTION
With the development of new network access
technologies, a variety of network interfaces are provided on
the vehicles. Therefore, the traditional internet of vehicles is
moving towards the trend of vehicular heterogeneous
networks. The vehicular heterogeneous network is a
communication system composed of a plurality of different
types of networks integrated into the vehicle environment,
the vehicle terminal has a variety of network interface
modules that can access any of the networks that make up
the heterogeneous vehicular networking system. The
cooperation and mutual assistance between multiple
networks largely meets the communication requirements in
the vehicle environment and the diversity of vehicle user
services.
The Multipath Transmission Control Protocol is a
protocol proposed by the Internet Engineering Group (IETF)
in 2009 [1-3]. It is an extension protocol of the Transmission
Control Protocol (TCP), allowing the simultaneous use of
multiple paths for data transmission. Using multipath TCP
can improve resource utilization. Multipath TCP uses TCP as
a subflow, with each path representing each TCP subflow.
multipath TCP can achieve higher throughput by increasing
the efficiency of network resource usage. Applying
Multipath TCP to a vehicular heterogeneous network can
improve transmission throughput.
One of the major challenges in using multipath TCP is
the receiver buffer blocking problem. The algorithm sends
data to each subflow in turn by polling, without considering
the differences between subflows. The delay, bandwidth,
load, and packet loss rate of the paths in the vehicular
heterogeneous network are different from each other. The
Round-Robin algorithm used in the conventional multipath
TCP will cause the packets to be out of order. These out-of-
orderd packets are accumulated in a limited receiving buffer,
which causes blocking and seriously affects the
communication performance between the vehicles. In this
case, it is very important to design an effective multi-path
scheduling optimization method to avoid the receiver buffer
blocking problem and improve the transmission performance
of the heterogeneous network.
II. R
ELATED RESEARCH
Multipath TCP is a research hotspot at home and abroad
in recent years. A large number of scholars and research
institutions have carried out related optimization research on
Multipath TCP in an attempt to improve the throughput of
heterogeneous networks when transmitting with multipath
TCP.
Authors of [4] explores the performance of multipath
TCP in an outdoor environment, focusing on the
transmission of two paths. The research results show that
multipath TCP can improve the overall throughput of the
system. Authors of [5] proposes a balanced link adaptation
mechanism and then performs congestion control of
multipath TCP based on this mechanism. This mechanism
guarantees fairness in the transmission process and can
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