Cross-layer design for tree-type routing and
level-based centralised scheduling in IEEE
802.16 based wireless mesh networks
M. Peng, Y. Wang and W. Wang
Abstract: Infrastructure wireless mesh network, also named as mesh router, is one key topology for
the next generation wireless networking. In this work, the performance optimisation for the infra-
structure wireless mesh network is presented and the sub-optimum solution mechanism is investi-
gated. A cross-layer design for tree-type routing, level-based centralised scheduling and distributed
power control theme is proposed as the sub-optimum solution strategy. The cross-layer design
relies on the channel information and the distributed transmission power control in the physical
layer, and the wireless scheduling in the medium access control (MAC) layer, as well as the
routing selection mechanism in the MAC upper layer. In this work, a modified distributed
power control algorithm is proposed first. In addition, a tree-type routing construction algorithm
for centralised scheduling is presented to improve the network throughput by jointly considering
interference and hop-count to construct the routing tree. Simulation results show that the proposed
cross-layer design strategy can effectively improve the network throughput performance, decrease
the power consumption and achieve better performances.
1 Introduction
The mesh-type fixed broadband wireless access system
defined by the IEEE 802.16-2004 standard [1], is an attrac-
tive way of providing proprietary commercial solutions. It
serves as an access network which can be dynamically self-
organised and self-configured, with the nodes in the network
automatically establishing an ad hoc alike network and
maintaining the mesh connectivity. In IEEE 802.16-based
wireless mesh networks (WMNs), there are three kinds of
scheduling mechanisms: coordinated centralised schedul-
ing, coordinated distributed scheduling and uncoordinated
distributed scheduling. For the centralised scheduling, the
mesh base station (MBS) works like a cluster head and
determines how the mesh subscriber stations (MSS)
should share the same channel in different time slots. The
TDMA-based scheduling in the mesh system provides the
fine gra nularity radio resource control and allows centra-
lised slot allocation, which provi des overall efficient
resource utilisation. Although the architecture of mesh can
provide high data rate to fulfil the Quality of Service
(QoS), how to achieve such a target in multi-hop mesh
network is still challenging.
The cross-layer design introduces wide layer interdepen-
dencies to optimise the overall network performance and
improves the performance of wireless communication and
mobile networks [2]. In this work, we propose a cross-layer
design scheme for the wireless mesh router topology,
which is named as CL-JTRLSDPC (cross-layer-joint
tree-type routing, level-based centralised scheduling and dis-
tributed power control). The cross-layer design relies on the
routing selection mechanism in medium access control
(MAC) upper layer, and the transmission power control in
physical layer, as well as the level-based scheduling mechan-
ism in MAC layer. Interference in wireless systems is one of
the most significant factors that limit the capacity and scal-
ability, and it can be overcome by the power control algor-
ithm. Meanwhile, the consideration of the path loss, the
interference conditions and the power consumption con-
ditions impacts the design of routing tree formation
schemes, while limiting the mutual interference and maxi-
mising the network throughput with better spectral utilis-
ation. The level-based centralised scheduling theme, based
on the proposed tree-type routing topology, is aimed to
improve the spectrum efficiency as much as possible.
2 Related work
In IEEE 802.16 mesh mode, the MBS provides backhaul
connectivity of the mesh network and controls one or
more MSSs. This work only focuses on the centralised
mesh topology to establish the high-speed broadband
mesh connections, where the MBS coordinates the radio
resource allocation within the mesh network. In the centra-
lized scheme, each MSS estimates and sends its resource
allocation request to the MBS through the established
routing tree, and the MBS determines the amount of
granted resources for each link. The request and grant
process uses the mesh centralised scheduling (MSH-
CSCH) message. The MSS’s resource request messages
are forwarded via the MSH-CSCH:Request message to
the MSS’s par ent node. After the MBS determines the
resource allocation results, the MSH-CSCH:Grant is propa-
gated along the routing tree from MBS. To disseminate the
# The Institution of Engineering and Technology 2007
doi:10.1049/iet-com:20060519
Paper first received 23rd August and in revised form 29th November 2006
M. Peng and Y. Wang are with the Wireless Signal Processing & Network Lab,
Beijing University of Posts and Telecommunications, Beijing, China
W. Wang is with the Key Laboratory of Universal Wireless Communication
(BUPT), Ministry of Education, PO Box 93, No. 10 Xi Tu Cheng Road,
Beijing 100876, China
E-mail: pmg@bupt.edu.cn
IET Commun., 2007, 1, (5), pp. 999 –1006
999
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