Priority based Dynamic Packet Assignment for
Multipath Routing in Multihop Networks
Zheng Wan
School of Information Technology, Jiangxi University of Finance and Economics, Nanchang, China
Email: cloudcity66@yahoo.com.cn
Abstract—With the prevalence of wireless video applications,
QoS of wireless video transmission in resource-limited
wireless networks attract more and more researchers’
attention. In network layer, how to perform video packet
assignment in multipath routing is a key issue. In this paper,
we develop a simple but efficient, priority based dynamic
assignment algorithm for multipath routing. The idea of this
algorithm is to assign packet to a suitable path dynamically
based on the priority of a video packet, quality difference
between different paths and coding structure of the
streaming video sequence. Simulation results show that our
novel algorithm outperforms single path routing algorithm
and other multipath routing algorithms significantly in
packet receiving and average PSNR performance.
Index Terms—Wireless video transmission, multipath
routing, IEEE 802.11e, packet assignment
I. INTRODUCTION
With the increase of wireless bandwidth, more and
more video applications emerged. To ensure wireless
video transmission, mechanisms in each level of
hierarchical network architecture had been proposed,
among which mechanisms in link layer and network layer
attracted more attention.
In link layer, a milestone is the emergence of standard
IEEE 802.11e [1] which provides differentiated
guarantees for different kinds of services by assigning
packets of different service kinds to their matching access
categories (ACs). Many enhancement of IEEE 802.11e
had been proposed in the last decade.
As for mechanisms in network layer many novel
routing metrics were suggested, including single metric
and combined metric. Since most video applications run
in multihop wireless networks, single path and multipath
routing are studied to verify whether they are suitable for
wireless video transmission. Niculescu [2] measured the
performance of both routing mechanisms and find that
multipath routing will not only alleviate the heavy load of
single path but also incur inter-path interference. Thus
how to assign video packets to different paths becomes a
key issue. Existing multipath routing mechanisms for
video transmission were discussed in section II.
In this paper we propose a simple but efficient, priority
based dynamic assignment algorithm (PDAA) for
multipath routing. Characteristics of this work are
summarized in the following.
(1) Priority of a video packet is recognized by the
frame type that the packet belongs to.
(2) Quality of a path could be recognized by its hop
count, available bandwidth and other parameters.
(3) Packet assignment is dynamically performed,
according to the priority of a video packet, quality
difference between different paths and coding structure of
the streaming video sequence.
The rest of the paper is organized as follows. Section II
introduces related work. Idea and details of PDAA are
described in Section III. Performance comparison
between PDAA and other routing algorithms based on
evaluation is provided in section IV. Section V concludes
the paper and points out future work.
II.
RELATED WORK
In this section related studies are discussed, including
MAC layer solutions (IEEE 802.11e standard and its
modifications), network layer solutions (multipath
routing is the key issue), and cross-layer solutions.
A. IEEE 802.11e and its Modifications
IEEE 802.11e standard includes a contention-based
channel access method, called Enhanced Distributed
Channel Access (EDCA) and a centrally controlled
channel access method, known as HCF Controlled
Channel Access (HCCA). QoS support in EDCA is
achieved with the introduction of four access categories
(ACs). Each AC has a transmission queue and a set of
channel access parameters to contend for transmission
opportunities. If an AC has a smaller AIFS, CW
min
, or
CW
max
, traffic of this AC has a better chance to access the
channel earlier. Generally, AC3 and AC2 are reserved for
voice and video applications respectively, while AC1 and
AC0 are for best effort and background traffic. Streams
that fall in the same AC are effectively given identical
priority to access the channel. Another parameter called
TXOP
limit
is defined as an interval of time during which a
node has the right to initiate transmissions. Depending on
TXOP
limit
, a node may transmit one or more frames.
There are existing works on improving video
transmission performance over IEEE 802.11e networks.
On one hand, a lot of papers proposed enhanced
scheduling mechanisms to reduce video frame dropping
probability [3-5]. Scheduling enhancements can be
further classified into two categories. The first category
focused on priority based scheduling [3-4]. The second
JOURNAL OF NETWORKS, VOL. 7, NO. 11, NOVEMBER 2012
doi:10.4304/jnw.7.11.1876-1883