03-05-2011, 05:00 PM
Abstract—
In this paper, we propose a bandwidth-efficient multicast mechanism for heterogeneous wireless networks. We reduce the
bandwidth cost of an Internet Protocol (IP) multicast tree by adaptively selecting the cell and the wireless technology for each mobile
host to join the multicast group. Our mechanism enables more mobile hosts to cluster together and leads to the use of fewer cells to
save the scarce wireless bandwidth. Besides, the paths in the multicast tree connecting to the selected cells share more common links
to save the wireline bandwidth. Our mechanism supports the dynamic group membership and offers mobility of group members.
Moreover, our mechanism requires no modification to the current IP multicast routing protocols. We formulate the selection of the cell
and the wireless technology for each mobile host in the heterogeneous wireless networks as an optimization problem. We use Integer
Linear Programming to model the problem and show that the problem is NP-hard. To solve the problem, we propose a distributed
algorithm based on Lagrangean relaxation and a network protocol based on the algorithm. The simulation results show that our
mechanism can effectively save the wireless and wireline bandwidth as compared to the traditional IP multicast.
Index Terms—Heterogeneous wireless networks, multicast.
1 INTRODUCTION
THE success of wireless and mobile communications in
the 21st century has resulted in a large variety of
wireless technologies such as second and third-generation
cellulars, satellite, Wi-Fi, and Bluetooth. The heterogeneous
wireless networks combine various wireless networks and
provide universal wireless access. The leading wireless
companies in some countries have operated networks with
multiple wireless technologies, such as T-Mobile in the
United States, British Telecom in the United Kingdom,
Orange Telecom in France, NTT DoCoMo in Japan, and
Chunghwa Telecom in Taiwan. The number of such
companies would increase because the standards for
operators to provide seamless services in networks with
multiple wireless technologies have been proposed by the
Third-Generation Partnership Project (3GPP) [1] and Unlicensed
Mobile Access (UMA) [2]. In addition, users in the
heterogeneous wireless networks are usually covered by
more than one cell to avoid connection drop and service
disruption. More mobile terminals in the wireless networks
are likely to own multiple wireless technologies. Therefore,
the heterogeneous wireless networks provide the mobile
hosts with many choices for the cells and wireless
technologies to access the Internet.
Multicast is an efficient way for one-to-many and manyto-
many communications. Each multicast group owns a set
of members, and each member can be a sender or a receiver
of the group. The sender in a multicast group delivers data
in a multicast tree to all receivers of the group. Current
Internet Protocol (IP) multicast routing protocols adopt the
shortest path trees for data delivery [3], [4], [5], [6], [7]. The
path from the root of the shortest path tree to each member
must be the shortest path in the network. In other words,
the routing of the shortest path tree is fixed once the root
and all group members have been determined. As a
consequence, the bandwidth consumption in an IP multicast
tree will not be able to be reduced in wired networks.
In this paper, we first comment that the bandwidth
consumption in the shortest path tree can be reduced in the
heterogeneous wireless networks because the routing of the
shortest path tree here is more flexible. The shortest path
tree in the heterogeneous wireless networks consists of two
parts. The first one is composed of the cell and the wireless
technology chosen by each mobile host. The second one is
comprised of the wired links that connect the root of the tree
and the chosen cells. Therefore, we can change the routing
of the shortest path tree by selecting different cells and
wireless technologies for the mobile hosts to reduce the
bandwidth consumption. Consider the scenario in Fig. 1 as
an example, where mobile hosts A, B, C, and D are the
members of the multicast group. The example presents
three different shortest path trees to serve the four mobile
hosts. The first one uses a WiMax cell to serve the four
mobile hosts. The second one uses a Universal Mobile
Telecommunications System (UMTS) cell to serve mobile
hosts A and B and two Wi-Fi cells to serve mobile hosts C
and D. The third one uses four Wi-Fi cells to serve the four
mobile hosts. Therefore, this example shows that the
routing of the shortest path tree in the heterogeneous
wireless networks is not unique.
Download full report
http://inrg.csie.ntu.edu.tw/web2008/pape...ireles.pdf
