Kodialam and Lakshman, 2000; Suri et al., 2003; Ricciato and
Monaco, 2005). In these literatures, the common solution is to
find a feasible path on the constructed topology by removing all
links that do not meet the bandwidth requirement. Although this
method could work well in wired model, it is not applicable in
wireless multi-hop networks due to interference.
In the past few years, a lot of research efforts have been made
on QoS guarantee issues in wireless multi-hop networks. Some of
them (e.g., Lin and Liu, 1999; Hanzo-II and Tafazolli, 2007; Chiu
et al., 2009; Khoukhi and Cherkaoui, 2010; Hanzo-II and Tafazolli,
2011; Kajioka et al., 2011) have been especially dedicated for
mobile ad hoc networks (MANET). In Lin and Liu (1999), the paper
proposed a bandwidth-based routing protocol for QoS support in
multi-hop mobile network, by which the source was informed of
the bandwidth and QoS available to any destination. In Hanzo-II
and Tafazolli (2007), the authors offered a survey QoS routing
solutions for MANETs published in the period 1997–2006. This
article provided the academic with insight into the differences
and allowed them to highlight trends in protocol design and
identify areas for future research. In Chiu et al. (2009), the authors
introduced an efficient distributed joint channel assignment and
routing protocol in multi-channel multi-radio ad hoc networks,
which allowed a data interface to dynamically change its working
mode on a call-by-call basis. In Khoukhi and Cherkaoui (2010),
Khoukhi et al. proposed a new intelligent cross-layer QoS scheme
for MANETs. The solution adopted fuzzy logic for improving traffic
regulation and the control of congestion to support both real-time
multimedia (audio/video) services and non-real-time traffic ser-
vices. Lajos Hanzo et al. designed a QoS-aware routing protocol
and admission control mechanism in shadow-fading environ-
ments for Multi-rate MANETs in Hanzo-II and Tafazolli (2011),
which could enhance system performance in situation of mobi-
lity, shadowing, and varying SINR. In Kajioka et al. (2011), the
authors proposed a new QoS-aware routing protocol to support
real-time multimedia communication by efficiently exploiting the
limited wireless network capacity in MANETs.
In addition, there are also some research papers (Cobo et al.,
2010; Kandris et al., 2011; Lin et al., 2011) aiming to solving QoS
issues in the field of wireless sensor networks (WSNs). In Cobo
et al. (2010), Cobo et al. built a hierarchical structure on the
network before choosing suitable routes to meet various QoS
requirements, thus maximizing network utilization. In Kandris
et al. (2011), the article proposed a novel scheme for video
communication, which incorporated an energy aware hierarchical
routing protocol with an intelligent video packet scheduling
algorithm to achieve energy saving and high QoS attainment. In
Lin et al. (2011), the literature systemically analyzed the similar-
ity between social network and wireless multimedia sensor net-
work (WMSN), and designed a QoS trust estimation model based
on social network analysis. Furthermore, it proposed an energy
efficient QoS assurance routing based on cluster hierarchy to
achieve energy efficiency and meet the QoS requirement.
However, the above QoS guarantee mechanisms dedicated for
MANETs and WSNs are not very effective and efficient in WMNs.
The designing baseline of QoS routing in MANETs is to deal with
the mobility of nodes and availability of routing satisfying some
weight measures, while the main point of designing QoS control
mechanism for WSNs is to consider both the energy efficiency
constrain of node characteristic and QoS guarantee for real-time
traffic. As a contrast, the mesh backbone has static topology,
meanwhile mesh nodes without power limit are often plug in.
Therefore the focus of QoS routing designing in WMNs is on how
to offer high-speed broadband services to maximize throughput
capacity of networks with QoS assurance.
In recent years, there are also some exploration literatures for
QoS routing in WMNs. In Ergin et al. (2008), the article presented
an integrated admission control and routing mechanism for
multi-rate WMNs. The authors also introduced a packet
probing-based bandwidth estimation method, suitable for legacy
device implementations, and verified it experimentally. In Liu and
Liao (2009), Liu et al. proposed an on-demand bandwidth-con-
strained routing protocol for multi-radio multi-rate multi-
channel WMNs with the IEEE 802.11 DCF MAC protocol. Basing
on a distributed threshold-triggered bandwidth estimation
scheme, they proposed a novel routing metric which struck a
balance between the routing cost and the path bandwidth. In
Rezgui et al. (2010), the paper introduced a distributed admission
control scheme for WMNs, and proposed an analytical model to
compute the appropriate acceptance ratio. This scheme guaran-
teed that the packet loss probability did not exceed a threshold
value. In Bakhshi and Khorsandi (2011), the paper studied the
problem of QoS provisioning in term of end-to-end bandwidth
allocation in WMNs. Then the authors proposed a k-shortest path
based algorithmic framework to solve this problem by on-line
dynamic routing. In Hou et al. (2012), Hou et al. studied the
problem of identifying the maximum available bandwidth path in
WMNs, and proved that the proposed hop-by-hop routing proto-
col could satisfy the consistency and loop-freeness requirements.
However, some of the above references need to modify MAC to
adapt these protocols and are not easy to implement, while others
do not consider integration of multiple channels to accommodate
the high volume traffic of real-time multimedia applications.
Contrary to those mentioned mechanisms, our protocol intro-
duces cross-layer idea and multi-radio multi-channel technique
over 802.11 MAC, thus overcomes the disadvantages and has
good adaptability.
3. System model
We consider the multi-radio multi-channel WMNs with the
IEEE 802.11 DCF MAC protocol. In our model, there are N nodes
which are all stationary and act as traffic aggregation access
points, providing network connectivity to mobile end-users
within their coverage ranges. Packets are forwarded via multi-
hop relaying manner. Each node i is equipped with R
i
hetero-
geneous radios, and the number of radios on each node may be
different. By heterogeneous radios, we mean that the wireless
capability, power level, and working spectrum, etc., on these
radios may be different. Each radio serves as a transmitter or a
receiver on a channel at any given time, i.e., half duplex mode. We
assume that there are a total of L orthogonal channels in the
system, numbered CH
1
, CH
2
,y,CH
L
, exhibiting no inter-channel
interference. For the sake of efficiency, all radios of each node are
tuned to non-overlapping channels. We consider a random traffic
model and adopt dynamic channel assignment strategy, which
assigns the radio with the best channel greedily in neighboring
areas. Two nodes are said to be neighbors on channel k if they
both have a radio operating on the common channel k and
simultaneously fall within the transmission range of each other.
The multi-rate capability in the physical layer is also taken into
account in our model, i.e., nodes in the network may commu-
nicate at different data rates, depending on the distance between
them, the radio signal quality, and the set of modulation and
coding schemes available in the system. Note that here we can
use radio and interface alternatively without confusion through-
out this article. Without loss of generality, we number radios and
channels from 0 to R
i
1. When network initializes, we need to
assign identifications for radios and channels. For simplicity, the
assignment method is the same among all nodes: channel 0
is assigned to match radio 0, channel 1 is assigned to match
radio 1 and so on. In our proposal, one channel numbered 0, called
Y. Peng et al. / Journal of Network and Computer Applications 36 (2013) 843–857 845